Display device

Abstract

To provide a semiconductor device in which the variation in threshold voltage of a transistor is suppressed, a semiconductor device in which the decrease in on-state current of the transistor is suppressed, and a manufacturing method for the semiconductor device.SOLUTION: A manufacturing method for a transistor 410 includes forming a gate electrode layer 401 on a substrate 400, forming a gate insulating film 402 on the gate electrode layer, forming an oxide semiconductor film 403 on the gate insulating film, forming a metal oxide film 404 and a conductive film 405 with the higher reducing property than the oxide semiconductor film on the oxide semiconductor film, forming a metal film 406 by performing a thermal process with the metal oxide film and the oxide semiconductor film in contact so as to reduce the metal oxide film, forming a resist mask on the conductive film 405 through a photolithography step, forming metal films 406a and 406b and conductive films 405a and 405b by selective etching, and forming a source electrode layer 407a and a drain electrode layer 407b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.

[0002] In this specification, a semiconductor device is a device that can function by utilizing semiconductor characteristics. Generally, electro-optical devices, semiconductor circuits, and electronic devices are all semiconductor devices. [Background technology]

[0003] A technology for constructing transistors using semiconductor thin films formed on substrates with insulating surfaces is The transistor is used in integrated circuits (ICs) and image display devices (also known simply as display devices). These are widely used in electronic devices such as semiconductors that can be applied to transistors. Silicon-based semiconductor materials are widely known as thin film semiconductors, but other materials include oxide semiconductors. Conductors are attracting attention.

[0004] For example, amorphous silicon containing indium (In), gallium (Ga), and zinc (Zn) A transistor using a semiconductor layer made of oxide (IGZO-based amorphous oxide) is disclosed. In addition, a semiconductor device provided in contact with such an oxide semiconductor film has been proposed (see Patent Document 1). Titanium, tungsten, molybdenum, etc. are used for the source electrode layer and the drain electrode layer. (See Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-181801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-129926 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-270313 Summary of the Invention [Problem to be solved by the invention]

[0006] Titanium is used for the source electrode layer and the drain electrode layer provided in contact with the oxide semiconductor film. In this case, when heat treatment is performed in a state where the oxide semiconductor film and the titanium layer are in contact with each other, the titanium layer is oxidized. The reaction with oxygen in the oxide semiconductor film causes titanium oxide to form at the interface with the oxide semiconductor film. At this time, the oxide semiconductor film is reduced, oxygen vacancies are formed, and oxidation Majority carriers are generated in the semiconductor film. As a result, the threshold voltage of the transistor increases. This causes a problem of shifting in the negative direction.

[0007] When tungsten or molybdenum is used for the source electrode layer and the drain electrode layer, and performing high-temperature heat treatment while the oxide semiconductor film is in contact with the tungsten layer or the molybdenum layer. If titanium is used, the oxide semiconductor film may be reduced. Similarly, the threshold voltage of the transistor may shift in the negative direction.

[0008] Further, when the oxide semiconductor film is in contact with the tungsten layer or the molybdenum layer, high-temperature heat treatment is performed. When the oxide semiconductor film is heated, oxygen may diffuse from the oxide semiconductor film to the tungsten layer or the molybdenum layer. As a result, high resistance components are formed in the source electrode layer and the drain electrode layer, This causes a problem of a decrease in the on-state current of the transistor.

[0009] In the case of a channel or back channel of an oxide semiconductor film, the source electrode layer and the drain electrode layer Even after the formation of the oxide film, oxygen can be supplied to reduce the oxygen vacancies. Therefore, oxygen vacancies are formed at the interfaces between the oxide semiconductor film and the source and drain electrode layers. If the oxide semiconductor film is formed, oxygen is trapped at the interfaces between the oxide semiconductor film and the source and drain electrode layers. It becomes difficult to supply oxygen to the source electrode layer and the drain electrode layer and reduce oxygen vacancies. If high resistance components are formed in the silicon electrode layer due to oxygen diffusion, it is necessary to remove the high resistance components. This requires additional steps to achieve this.

[0010] In view of the above problems, in one embodiment of the present invention, reduction of an oxide semiconductor film is suppressed, and By reducing oxygen vacancies in the oxide semiconductor film, the threshold voltage of the transistor can be decreased toward the negative side. Another object of the present invention is to provide a semiconductor device in which a shift in the direction of the oxide is suppressed. By reducing the resistance caused by the oxide semiconductor film, the source electrode layer, and the drain electrode layer, An object is to provide a semiconductor device in which a decrease in on-state current of a transistor is suppressed. The present invention solves at least one of the above problems. [Means for solving the problem]

[0011] A semiconductor device according to one embodiment of the present invention includes a source electrode layer and a drain electrode layer in contact with an oxide semiconductor film. As an electrode layer, an oxide semiconductor is used to prevent oxygen from being extracted from the oxide semiconductor film. A metal film having higher oxidation resistance than the metal element contained in the film is used. The drain electrode layer may have a stacked structure of the metal film and a conductive film.

[0012] In this specification and the like, a metal having higher oxidation resistance than a metal element contained in an oxide semiconductor film is is more oxidation resistant than indium, gallium, zinc, and tin (at least indium (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) Specific examples include copper, silver, ruthenium, and iridium.

[0013] In addition, the conductive film is preferably formed from a material that does not form an oxide film at the interface with the metal film. For example, gold, platinum, copper, silver, ruthenium, iridium, titanium, tungsten, nitride Examples include titanium, molybdenum nitride, tungsten nitride, and tantalum nitride.

[0014] Copper, silver, ruthenium, iridium, or the like may be used as the metal film in contact with the oxide semiconductor film. This can prevent oxygen from being extracted from the oxide semiconductor film. The oxide semiconductor film can be prevented from increasing in oxidation vacancies, and the threshold voltage of the transistor can be reduced. It is possible to suppress a shift in the negative direction.

[0015] Furthermore, the above-mentioned metal film can suppress the diffusion of oxygen into the metal film, so that a high concentration of oxygen is present in the metal film. Therefore, the oxide semiconductor film, the source voltage, and the like can be prevented from being formed. The resistance due to the electrode layer and the drain electrode layer can be reduced, The decrease in on-current can be suppressed.

[0016] In addition, a metal film ( For example, copper, silver, ruthenium, etc.) can be selected to form an oxide semiconductor film and a source This is preferable because the contact resistance with the electrode layer and the drain electrode layer can be reduced. This also reduces the resistance caused by the oxide semiconductor film, the source electrode layer, and the drain electrode layer. Since the on-state current of the transistor can be reduced, a decrease in the on-state current of the transistor can be suppressed.

[0017] Specifically, one embodiment of the present invention is a semiconductor device including an oxide semiconductor film and a solder paste provided in contact with the oxide semiconductor film. a source electrode layer and a drain electrode layer, a gate electrode layer overlapping the oxide semiconductor film, and an oxide semiconductor film. and a gate insulating film provided between the body film and the gate electrode layer, and The metal oxide semiconductor layer and the drain electrode layer are in contact with the oxide semiconductor film. This is a semiconductor device that uses a metal that has higher oxidation resistance than elements.

[0018] Another embodiment of the present invention is a semiconductor device including a gate electrode layer provided over a substrate and a gate electrode layer provided over the gate electrode layer. a gate insulating film formed on the gate insulating film and an oxide film formed on the gate insulating film in a region overlapping the gate electrode layer; a semiconductor film, and a source electrode layer and a drain electrode layer provided in contact with the oxide semiconductor film; at least a portion where the source electrode layer and the drain electrode layer are in contact with the oxide semiconductor film The metal element is a semiconductor element containing a metal having higher oxidation resistance than a metal element contained in an oxide semiconductor film. It is a body device.

[0019] Another embodiment of the present invention is a semiconductor device including a gate electrode layer provided over a substrate and a gate electrode layer provided over the gate electrode layer. and an oxide film formed on the gate insulating film in a region overlapping the gate electrode layer. a source electrode layer and a drain electrode layer provided in contact with the oxide semiconductor film; The source electrode layer and the drain electrode layer have a stacked structure of a metal film and a conductive film. The metal film is made of a metal having higher oxidation resistance than a metal element contained in the oxide semiconductor film. It is a semiconductor device that can be used.

[0020] Another embodiment of the present invention is a semiconductor device including a gate electrode layer provided over a substrate and a gate electrode layer provided over the gate electrode layer. and an oxide film formed on the gate insulating film in a region overlapping the gate electrode layer. an insulating film provided on the oxide semiconductor film in a region overlapping with the gate electrode layer; a source electrode layer and a drain electrode layer provided in contact with the oxide semiconductor film and the insulating film; and the source electrode layer and the drain electrode layer are formed with a stacked structure of a metal film and a conductive film. The metal film is formed of a metal having higher oxidation resistance than a metal element contained in the oxide semiconductor film. This is a semiconductor device that is used.

[0021] Another embodiment of the present invention is a semiconductor device including a gate electrode layer provided over a substrate and a gate electrode layer provided over the gate electrode layer. a gate insulating film formed on the gate electrode layer; and a source electrode layer and a drain electrode layer formed on the gate insulating film. an oxide semiconductor film provided over a gate insulating film, a source electrode layer, and a drain electrode layer; the source electrode layer and the drain electrode layer have a stacked structure of a conductive film and a metal film, The metal film is made of a metal having higher oxidation resistance than a metal element contained in the oxide semiconductor film. It is a semiconductor device.

[0022] Another embodiment of the present invention is a method for manufacturing a semiconductor device including an oxide semiconductor film provided over a substrate and a gate insulating film provided over the oxide semiconductor film. a gate insulating film formed on the gate electrode layer; and a side insulating film provided to contact the side surfaces of the gate electrode layer and the insulating film. The wall insulating film and the oxide semiconductor film, the gate insulating film and the sidewall insulating film are in contact with each other. a source electrode layer and a drain electrode layer, and the oxide semiconductor film overlaps with the gate electrode layer. A channel forming region is provided in the region, and dopant regions are provided on both sides of the channel forming region. and at least a source electrode layer and a drain electrode layer are formed of an oxide semiconductor film. The contact portion is a metal film having higher oxidation resistance than a metal element contained in the oxide semiconductor film. , a semiconductor device.

[0023] One embodiment of the present invention is a method for manufacturing a semiconductor device including an oxide semiconductor film provided over a substrate and a gate insulating film provided over the oxide semiconductor film. a gate insulating film formed on the gate electrode layer; and a sidewall formed in contact with the side surfaces of the gate electrode layer and the insulating film. a source electrode contacting the oxide semiconductor film, the gate insulating film, and the sidewall insulating film; a gate electrode layer and a drain electrode layer, and the oxide semiconductor film is formed in a region overlapping with the gate electrode layer. and a dopant provided on either side of the channel forming region. a source electrode layer and a drain electrode layer in contact with the oxide semiconductor film, The metal film has a laminated structure with a conductive film and a metal film that is more oxidation-resistant than the metal element contained in the semiconductor film. It is a semiconductor device.

[0024] Another embodiment of the present invention is a semiconductor device including a source electrode layer and a drain electrode layer provided over a substrate. an oxide semiconductor film provided over the source electrode layer and the drain electrode layer; a gate insulating film formed on the gate electrode layer; the oxide semiconductor film is provided in a region overlapping with the gate electrode layer. a channel forming region formed by the dopant and a region including the dopant provided on both sides of the channel forming region; a source electrode layer and a drain electrode layer in contact with the oxide semiconductor film, The semiconductor film has a laminated structure with a metal film that has higher oxidation resistance than the metal element contained in the semiconductor film. It is a conductor device.

[0025] In each of the above configurations, the thickness of the metal film is preferably 1 nm or more and 50 nm or less.

[0026] In each of the above structures, the oxide semiconductor film has higher oxidation resistance than the metal element contained in the oxide semiconductor film. The metal is preferably one having a Gibbs free energy higher than that of the oxidation reaction of molybdenum. Specifically, one or more of copper, silver, ruthenium, and iridium are used. It is preferable that

[0027] In each of the above structures, the conductive film may be made of gold, platinum, copper, silver, ruthenium, or iridium. , titanium, tungsten, titanium nitride, molybdenum nitride, tungsten nitride, tantalum nitride It is preferable to use one or more of the following:

[0028] In addition, the oxide semiconductor film disclosed in this specification and the like has an energy gap of 2.8 eV or more. The energy gap is 3.2 eV, which is larger than that of silicon, which is 1.1 eV. The minority carriers in the oxide semiconductor film are 10 -9 cm -3 and the intrinsic carrier density of silicon is 10 degrees 11 cm -3 is extremely small compared to

[0029] The majority carriers (electrons) in the oxide semiconductor film only flow from the source of the transistor. In addition, since the channel formation region can be completely depleted, the transistor can be turned off. The current can be made extremely small. The current is 10yA / μm or less at room temperature, and 1zA / μm even at 85℃ to 95℃. is as follows, which is extremely small.

[0030] Therefore, the S value of a transistor using an oxide semiconductor film is small, and the ideal electrical Furthermore, the transistor has high reliability.

[0031] A method for manufacturing a semiconductor device according to one embodiment of the present invention includes: A metal oxide film having a higher reducing property than the film is formed, and then a heat treatment is performed. Therefore, the metal oxide film, which has higher reduction ability than the oxide semiconductor film, is reduced to form a metal film. do.

[0032] In this specification and the like, a metal oxide film having a higher reduction property than an oxide semiconductor film is an indium oxide film. , gallium, zinc, and tin (at least indium, gallium, zinc , and the Gibbs free energy of the oxidation reaction of tin is higher than that of the metal oxide. , copper oxide, silver oxide, ruthenium oxide, iridium oxide, etc.

[0033] A metal oxide film which is in contact with an oxide semiconductor film and has a higher reducing property than the oxide semiconductor film is subjected to heat treatment. By carrying out the above process, the metal oxide film is reduced, and oxygen is released from the metal oxide film. The oxygen vacancies in the oxide semiconductor film are reduced by the release of the oxygen and the supply of the oxygen to the oxide semiconductor film. This allows the threshold voltage of the transistor to shift in the negative direction. can be suppressed.

[0034] In addition, the metal film formed by reducing the metal oxide film is included in the oxide semiconductor film. The film has higher oxidation resistance than the metal element contained in it. In other words, oxygen is less likely to diffuse into the metal film. By using the metal film as the source electrode layer and the drain electrode layer, Therefore, the formation of a high-resistance component in the oxide semiconductor film can be suppressed. Since the resistance due to the source electrode layer and the drain electrode layer can be reduced, This can suppress a decrease in the on-state current of the transistor.

[0035] In addition, a metal film ( For example, copper, silver, ruthenium, etc.) can be selected to form an oxide semiconductor film and a source This is preferable because the contact resistance with the electrode layer and the drain electrode layer can be reduced. This also reduces the resistance caused by the oxide semiconductor film, the source electrode layer, and the drain electrode layer. Since the on-state current of the transistor can be reduced, a decrease in the on-state current of the transistor can be suppressed.

[0036] Alternatively, a conductive film may be formed in contact with a metal oxide film having a higher reducing property than an oxide semiconductor film. The conductive film has an oxide film at the interface with a metal oxide film having a higher reducing property than an oxide semiconductor film. It is preferable to form the conductive layer from a material that does not form the conductive layer, for example, copper, silver, ruthenium, iridium , titanium, tungsten, tantalum nitride, etc.

[0037] In the case where a conductive film is formed after a metal oxide film is formed over an oxide semiconductor film, the heat treatment is For example, a metal oxide film is formed over an oxide semiconductor film, and then the metal oxide film is heated. After the heat treatment, a conductive film may be formed. Alternatively, after the conductive film is formed on the metal oxide film, Alternatively, a conductive film may be formed on the metal oxide film to form a source electrode layer and a drain electrode layer. After being processed into a rain electrode layer, a heat treatment may be carried out.

[0038] Alternatively, in the case where a metal oxide film is formed over a conductive film and then an oxide semiconductor film is formed, heating The treatment may be performed after the oxide semiconductor film is formed, or after the oxide semiconductor film is processed into an island shape. You can go there.

[0039] Specifically, one embodiment of the present invention is a method for forming a gate electrode layer over a substrate, and forming a gate electrode on the gate electrode layer. An insulating film is formed, an oxide semiconductor film is formed over the gate insulating film, and an oxide semiconductor film is formed over the oxide semiconductor film. A metal oxide film having a higher reducing property than the oxide semiconductor film is formed, and the metal oxide film and the oxide semiconductor film are By performing heat treatment in a state of contact, oxygen is supplied from the metal oxide film to the oxide semiconductor film. The metal oxide film is reduced to a metal film, and the metal film is processed to obtain a source voltage. The method for manufacturing a semiconductor device includes forming a gate electrode layer and a drain electrode layer.

[0040] In one embodiment of the present invention, a gate electrode layer is formed over a substrate, and a gate insulating film is formed over the gate electrode layer. an insulating film is formed on the gate insulating film, an oxide semiconductor film is formed on the gate insulating film, and an oxide A metal oxide film having a higher reducing property than a semiconductor film and a conductive film are stacked to form a metal oxide film. By performing heat treatment in a state where the metal oxide film is in contact with the oxide semiconductor film, the oxide Oxygen is supplied to the semiconductor film, and the metal oxide film is reduced to a metal film, and the metal film and the conductive A method for manufacturing a semiconductor device, in which a source electrode layer and a drain electrode layer are formed by processing a film It is the law.

[0041] In one embodiment of the present invention, a gate electrode layer is formed over a substrate, and a gate insulating film is formed over the gate electrode layer. an insulating film is formed, an oxide semiconductor film is formed on the gate insulating film, and an insulating film is formed on the oxide semiconductor film a metal oxide having a higher reducing property than the oxide semiconductor film is formed on the oxide semiconductor film and the insulating film; A metal oxide film and a conductive film are stacked, and the metal oxide film and the oxide semiconductor film are heated in a state where they are in contact with each other. By performing the treatment, oxygen is supplied from the metal oxide film to the oxide semiconductor film, and the metal oxide The conductive film is reduced to a metal film, and the source electrode layer and the conductive film are processed. The method for manufacturing a semiconductor device includes forming a drain electrode layer.

[0042] In one embodiment of the present invention, a gate electrode layer is formed over a substrate, and a gate insulating film is formed over the gate electrode layer. A conductive film and a metal oxide film are laminated on the gate insulating film. The source electrode layer and the drain electrode layer are formed by processing the metal oxide film. An oxide semiconductor film having a lower reducing property than a metal oxide film is formed on the electrode layer and the drain electrode layer. The metal oxide film is heated in a state where the metal oxide film and the oxide semiconductor film are in contact with each other. oxygen is supplied from the metal oxide film to the oxide semiconductor film, and the metal oxide film is reduced to a metal film; This is a method for manufacturing a semiconductor device, in which a metal film is formed.

[0043] Further, according to one embodiment of the present invention, an oxide semiconductor film is formed over a substrate, and a gate insulating film is formed over the oxide semiconductor film. A gate insulating film is formed, and a gate electrode layer and an insulating film are laminated on the gate insulating film. A dopant is added to the oxide semiconductor film using the gate electrode layer and the insulating film as a mask, and a gate insulating film is formed. A sidewall insulating film is formed on the film to contact the side surfaces of the gate electrode layer and the insulating film, and an oxide A metal oxide film having a higher reducing property than the oxide semiconductor film is formed so as to be in contact with the semiconductor film. The metal oxide film is heated while the metal oxide film and the oxide semiconductor film are in contact with each other. Oxygen is supplied to the oxide semiconductor film from the metal oxide film, and the metal oxide film is reduced to a metal film. An interlayer insulating film is formed on the film, and the metal film and the interlayer insulating film are polished until the insulating film is exposed. In this method for manufacturing a semiconductor device, a source electrode layer and a drain electrode layer are formed by performing the above steps.

[0044] Further, according to one embodiment of the present invention, an oxide semiconductor film is formed over a substrate, and a gate insulating film is formed over the oxide semiconductor film. A gate insulating film is formed, and a gate electrode layer and an insulating film are laminated on the gate insulating film. A dopant is added to the oxide semiconductor film using the gate electrode layer and the insulating film as a mask, and a gate insulating film is formed. A sidewall insulating film is formed on the film to contact the side surfaces of the gate electrode layer and the insulating film, and an oxide A metal oxide film having a higher reducing property than an oxide semiconductor film and a conductive film are formed so as to be in contact with the semiconductor film. The metal oxide film and the oxide semiconductor film are stacked and then heat treatment is performed while the metal oxide film and the oxide semiconductor film are in contact with each other. As a result, oxygen is supplied from the metal oxide film to the oxide semiconductor film, and the metal oxide film is reduced. A metal film is formed, and an interlayer insulating film is formed on the conductive film. The metal film, the conductive film, and the interlayer insulating film are combined into an insulating film. By polishing the semiconductor layer to expose the source and drain electrode layers, A method for making a body device.

[0045] In one embodiment of the present invention, an island-shaped insulating film is formed over a substrate, and a conductive film is formed over the island-shaped insulating film. and a metal oxide film are laminated to form the conductive film and the metal oxide film, and the conductive film and the metal oxide film are exposed by the island-shaped insulating film. By polishing the source electrode layer and the drain electrode layer, an oxide semiconductor film is formed over the metal oxide film and the drain electrode layer; By performing heat treatment in a state of contact, oxygen is supplied from the metal oxide film to the oxide semiconductor film. The metal oxide film is reduced to a metal film, and a gate insulating film is formed on the oxide semiconductor film. A gate electrode layer is formed on the gate insulating film, and the gate electrode layer is used as a mask to perform oxidation. This is a method for manufacturing a semiconductor device by adding a dopant to a compound semiconductor film.

[0046] In each of the above manufacturing methods, a metal oxide film having a higher reducing property than an oxide semiconductor film is formed by depositing a metal oxide film having a thickness of 1 nm or more. It is preferable to form the film with a thickness of 50 nm or less.

[0047] In the above-mentioned manufacturing methods, the metal oxide film may be formed of copper oxide, silver oxide, ruthenium oxide, or oxide. It is preferable that the conductive film is formed using one or more of iridium nitride. , gold, platinum, copper, silver, ruthenium, iridium, titanium, tungsten, titanium nitride, The insulating layer is formed using one or more of molybdenum nitride, tungsten nitride, and tantalum nitride. It is preferable that [Effects of the Invention]

[0048] According to one embodiment of the present invention, reduction of an oxide semiconductor film is suppressed, and the oxide semiconductor The oxygen vacancies in the film can be reduced, so the threshold voltage of the transistor is shifted to the negative direction. In addition, a semiconductor device in which the oxide semiconductor is By reducing the resistance caused by the film, the source electrode layer, and the drain electrode layer, It is possible to provide a semiconductor device in which a decrease in on-current is suppressed. [Brief explanation of the drawings]

[0049] [Figure 1] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 2] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 3] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 4] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 5] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 6] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 7] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 8] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 9] A diagram showing the Gibbs free energy of the oxidation reaction of each metal. [Figure 10] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 11] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 12] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 13] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 14] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 15] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 16] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 17] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 18] FIG. 1 is a plan view illustrating one embodiment of a semiconductor device. [Figure 19] 1A and 1B are a plan view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 20] 1A and 1B are cross-sectional views illustrating one embodiment of a semiconductor device. [Figure 21] 1A and 1B are a circuit diagram and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 22] 1A to 1C are a cross-sectional view, a plan view, and a circuit diagram illustrating one embodiment of a semiconductor device. [Figure 23]1A and 1B are a circuit diagram and a perspective view illustrating one embodiment of a semiconductor device. [Figure 24] 1A and 1B are a cross-sectional view and a plan view illustrating one embodiment of a semiconductor device. [Figure 25] SRAM and DRAM circuit diagrams. [Figure 26] FIG. 1 is a block diagram illustrating one embodiment of a semiconductor device. [Figure 27] FIG. 1 is a block diagram illustrating one embodiment of a semiconductor device. [Figure 28] FIG. 1 is a block diagram illustrating one embodiment of a semiconductor device. [Figure 29] 1A to 1C illustrate electronic devices. [Figure 30] 1A and 1B are diagrams illustrating an electronic device and a block diagram of a charge / discharge control circuit. [Figure 31] 1A to 1C illustrate electronic devices. [Figure 32] 1A and 1B are a top view and a cross-sectional view of a transistor used for evaluation. [Figure 33] A diagram showing the results of TDS analysis. [Figure 34] FIG. 1 shows the results of SIMS measurement. DETAILED DESCRIPTION OF THE INVENTION

[0050] Hereinafter, embodiments of the invention disclosed in this specification will be described in detail with reference to the accompanying drawings. However, the invention disclosed in this specification is not limited to the following description, and various forms and details may be used. It will be readily understood by those skilled in the art that the invention disclosed in this specification can be modified in any manner. The present invention is not limited to the following embodiments. The ordinal numbers such as 2 are used for convenience and do not indicate the order of processes or stacking. Furthermore, the present specification does not indicate specific names as matters for identifying the invention. do not have.

[0051] (Embodiment 1) In this embodiment, one mode of a semiconductor device will be described with reference to FIGS. 1, 2, and 9. In this embodiment, a transistor including an oxide semiconductor film is used as an example of a semiconductor device. Indicates the data.

[0052] In the semiconductor device according to one embodiment of the present invention, the structure of the transistor is not particularly limited. For example, a top gate structure or a staggered or planar type of bottom gate structure may be applied. The transistor can be a single gate transistor in which one channel forming region is formed. In the gate structure, there are two gates in the double gate structure and three gates in the triple gate structure. Alternatively, two gate insulating films may be arranged above and below the channel forming region. The gate electrode may have a dual gate structure having two gate electrode layers.

[0053] The transistor 410 shown in FIGS. 1A, 1B, and 1C has a bottom-gate structure (inverted). FIG. 1A shows an example of a transistor (also called a staggered transistor). 1(B) is a plan view of the transistor 410, and FIG. 1(B) is a cross-sectional view taken along line A1-A2 in FIG. 1(A). (Cross-sectional view in the channel length direction), and FIG. 1(C) is a cross-sectional view taken along B1-B2 in FIG. 1(A). 1(A) is a cross-sectional view (cross-sectional view in the channel width direction). Therefore, some of the components of the transistor 410 (for example, the gate insulating film 402) can be omitted. It is illustrated in simplified form.

[0054] The transistor 410 shown in FIGS. 1A, 1B, and 1C includes a substrate 400 having an insulating surface. a gate electrode layer 401 provided on the gate electrode layer 401; and a gate insulating film provided on the gate electrode layer 401. 402, and an oxide film provided on the gate insulating film 402 in a region overlapping the gate electrode layer 401. a source electrode layer 407a provided in contact with the oxide semiconductor film 403; The transistor 410 has an insulating layer 407b and a drain electrode layer 407c. A film 408 and a planarization insulating film 409 are provided.

[0055] As shown in FIGS. 1A, 1B, and 1C, the transistor 410 includes an oxide semiconductor film 40 The source electrode layer 407a and the drain electrode layer 407b in contact with the semiconductor substrate 3 have a stacked structure. The source electrode layer 407a has a stacked structure of a metal film 406a and a conductive film 405a, and the drain electrode layer 407b has a stacked structure of a metal film 406a and a conductive film 405a. The electrode layer 407b has a laminated structure of a metal film 406b and a conductive film 405b. It may also be referred to as a conductive film.

[0056] As shown in FIGS. 1A, 1B, and 1C, the metal film 406 in contact with the oxide semiconductor film 403 a and 406b are oxide films that prevent oxygen from being extracted from the oxide semiconductor film 403. The metal used is more oxidation-resistant than the metal element contained in the compound semiconductor film 403.

[0057] Here, a metal having higher oxidation resistance than a metal element contained in the oxide semiconductor film 403 is , will be described with reference to FIG.

[0058] First, the standard enthalpy of formation ΔH and standard entropy S for each substance are shown in Table 1. The standard enthalpy of formation ΔH and standard entropy S for each substance are shown in Table 1. The values ​​are mainly taken from "Chemical Handbook, Basics II, Revised 4th Edition, Maruzen Co., Ltd." compiled by the Chemical Society of Japan. In addition, the standard enthalpy of formation ΔH and standard enthalpy of formation of each substance shown in Table 1 are By substituting the entropy S value into the equation for each oxidation reaction, the standard The values ​​of the enthalpy of formation ΔH and the standard entropy of formation ΔS were calculated. The values ​​of the standard enthalpy of formation ΔH and the standard entropy of formation ΔS in the reaction are shown in Table 2. .

[0059] [Table 1]

[0060] [Table 2]

[0061] Next, the values ​​of the standard formation enthalpy ΔH and the standard formation entropy ΔS shown in Table 2 are calculated as follows: Substituting into equation (1), the Gibbs equations for each oxidation reaction in the temperature range of 0°C to 900°C are The free energy value was calculated. Note that T in equation (1) is temperature [K].

[0062] ΔG=ΔH-TΔS×10 -3 (1)

[0063] Figure 9 shows the Gibbs free energy distributions of the oxidation reactions of various metals in the temperature range of 0°C to 900°C. The horizontal axis is the temperature [℃] and the vertical axis is the Gibbs free energy. Geometry ΔG [kJ / mol].

[0064] From the graph in Figure 9, the reactions at the bottom of Figure 9 are more likely to cause oxidation reactions, i.e., oxidation The reactions at the top of Figure 9 are more likely to cause reduction reactions, meaning that reduction reactions are more likely to occur. Therefore, the metal oxide contained in the oxide semiconductor film 403 is easily The metals that are more oxidation resistant than the group elements may be any of the metals listed in the upper part of FIG.

[0065] For example, when the oxide semiconductor film 403 is an In-Ga-Zn-based oxide, indium, gallium, It has better oxidation resistance than indium, gallium, and zinc (at least the oxidation resistance of indium, gallium, and zinc). It can be seen that any metal with a Gibbs free energy higher than the oxidation reaction is sufficient. When the semiconductor film 403 is an In-Sn-Zn oxide, the oxide is formed of indium, tin, and zinc. It also has oxidation resistance (at least Gibbs free energy of the oxidation reaction of indium, tin, and zinc). Any metal (higher in energy than the metal) will suffice.

[0066] However, tungsten and molybdenum, which are metals that are more resistant to oxidation than indium, Even if the film is tungsten or molybdenum, oxygen in the film increases when the heat treatment temperature becomes high. This can lead to high resistance formation in the tungsten or molybdenum film. This causes a problem that the on-current of the transistor is reduced. The metal films 406a and 406b are made of silicon, which has higher oxidation resistance than molybdenum (molybdenum It is more preferable to use a metal having a Gibbs free energy higher than the Gibbs free energy of the oxidation reaction of the metal. Typical examples include copper, silver, ruthenium, and iridium, as shown in FIG.

[0067] The metal films 406a and 406b may be made of copper, silver, ruthenium, iridium, or the like. Therefore, oxygen can be prevented from being extracted from the oxide semiconductor film 403. The increase in oxygen vacancies in the compound semiconductor film 403 is suppressed, and the threshold voltage of the transistor 410 is reduced. This can prevent the pressure from shifting in the negative direction.

[0068] Furthermore, the metal films 406a and 406b are resistant to oxidation, and no oxidation is present in the metal films 406a and 406b. Since the diffusion of elements can be suppressed, high resistance components are not formed in the metal films 406a and 406b. Therefore, the oxide semiconductor film 403 and the source electrode layer 407 can be prevented from being broken. Since the resistance due to the drain electrode layer 407a and the drain electrode layer 407b can be reduced, Therefore, the decrease in the on-current of the gate 410 can be suppressed.

[0069] In addition, a gold film having a work function of ±0.2 eV with respect to the electron affinity of the oxide semiconductor film 403 is used. By selecting metal films 406a, 406b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 403 is in contact with the source electrode layer 407a and the drain electrode layer 407b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0070] For example, if the electron affinity of an In-Ga-Zn oxide semiconductor is 4.6 eV, the work It is preferable to use ruthenium, which has a valence function of 4.71 eV. By using the compound semiconductor film 403 and the metal films 406a and 406b, the contact resistance can be reduced.

[0071] Below, metals are listed in descending order of Gibbs free energy of oxidation reaction of metals shown in Figure 9.

[0072] Au,Pt,Ag,Ir,Ru,Cu,Mo,W,Sn,In,Zn,Ga,Si,Ti ,Al,Hf

[0073] The conductive films 405a and 405b stacked with the metal films 406a and 406b are made of gold. It is preferable that the material does not form an oxide film at the interface with the metal films 406a and 406b. The conductive films 405a and 405b can be made of a metal film 406a. In addition to the materials that can be used in 406b, gold, platinum, titanium, tungsten, nitride Examples of the conductive film include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 405a and 405b are configured in a single layer structure or a laminated structure. In the case of a laminated structure, for example, It can be made up of a tantalum nitride film and a tungsten film.

[0074] In the transistor 410 illustrated in FIGS. 1A, 1B, and 1C, the source electrode layer 407a and The drain electrode layer 407b is formed by using metal films 406a and 406b and conductive films 405a and 405b. Therefore, the metal film 406a is made of the same material. The interfaces between the conductive films 405a and 405b and the conductive films 406a and 406b are indicated by dotted lines. In the case of the transistor 410, for example, ruthenium is used as the metal films 406a and 406b, The conductive films 405a and 405b can be formed using ruthenium.

[0075] In the transistor 410, metal oxide is formed in part of the metal films 406a and 406b. For example, when the metal films 406a and 406b are made of ruthenium, they may be partially oxidized. Ruthenium may be formed. Ruthenium oxide may be formed in part of the metal film. Even so, the resistivity of ruthenium oxide is 3.5 × 10 -5 [cmΩ](300K) This is preferable because high resistance components are not formed in the source electrode layer and the drain electrode layer.

[0076] The oxide semiconductor film 403 has an energy gap of 2.8 eV to 3.2 eV. , which is larger than the energy gap of silicon, 1.1 eV. 03 minority carriers are 10 -9 cm -3 is 10 times the intrinsic carrier density of silicon. 1 1 cm -3 is extremely small compared to

[0077] The majority carriers (electrons) in the oxide semiconductor film 403 flow only from the source of the transistor. In addition, since the channel formation region can be completely depleted, The off-state current of the transistor using the oxide semiconductor film 403 can be made extremely small. The off-state current of the transistor is 10 yA / μm or less at room temperature, and It is extremely small, less than 1zA / μm.

[0078] Therefore, the transistor including the oxide semiconductor film 403 has a small S value and is not ideal. Moreover, the transistor has high reliability.

[0079] Next, referring to FIG. 2, a transistor that is partially different from the transistor 410 shown in FIG. I will explain.

[0080] 2A is a plan view of the transistor 420, and FIG. 2B is a plan view of C1- 2(A) is a cross-sectional view at C2 (cross-sectional view in the channel length direction). In order to avoid this, some of the components of the transistor 420 (for example, the gate insulating film 4 The illustration omits the numbers 02, 03, etc.

[0081] In the transistor 420 shown in FIGS. 2A and 2B, the source electrode layer 417a and the drain electrode layer 417b are The inner electrode layer 417b is made up of metal films 406a and 406b and conductive films 415a and 415b. Therefore, the metal films 406a and 406b and the conductive film The interfaces with the conductive films 415a and 415b are indicated by solid lines. The conductive films 405a and 405b are formed using a material similar to that of the conductive films 405a and 405b, and have a single-layer structure or a stacked-layer structure. In the case of the transistor 420 shown in FIG. 2, for example, the metal films 406a and 406b are For example, tantalum nitride can be used for the conductive films 415a and 415b.

[0082] Note that in the transistor 420, the source electrode layer 417a and the drain electrode layer 417b Other than the above, the configuration is the same as that of the transistor 410. Please take this into consideration.

[0083] As described above, the metal films 406a and 406b in contact with the oxide semiconductor film 403 are The oxide semiconductor film 403 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 403 (at least indium). (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) This prevents oxygen from being extracted from the oxide semiconductor film 403. As a result, the source electrode layer 417a, the drain electrode layer 417b, and the oxide semiconductor film 403 This suppresses the increase in oxygen vacancies at the interface with the semiconductor, thereby minimizing the threshold voltage of the transistor. It is possible to suppress a shift in the negative direction.

[0084] In addition, the metal films 406a and 406b are less likely to be oxidized than the oxide semiconductor film 403. Since oxygen diffusion into the metal films 406a and 406b can be suppressed, Therefore, the formation of a high-resistance component in the oxide semiconductor film b can be suppressed. Since the resistance due to the source electrode layer and the drain electrode layer can be reduced, Therefore, the decrease in the on-state current of the transistor can be suppressed.

[0085] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0086] (Embodiment 2) In this embodiment, an example of a method for manufacturing a semiconductor device including the transistor 410 shown in FIGS. This will be described with reference to FIG.

[0087] There is no significant limitation on the substrate that can be used for the substrate 400 having an insulating surface, but at least In either case, it is necessary for the material to have heat resistance sufficient to withstand the subsequent heat treatment. Glass substrates such as borosilicate glass and aluminoborosilicate glass, ceramic substrates, stone A silicon substrate, a sapphire substrate, etc. can be used. Also, silicon, silicon carbide, etc. Single crystal semiconductor substrates, polycrystalline semiconductor substrates, and compound semiconductor substrates such as silicon germanium , SOI substrates, etc. can also be applied, and semiconductor elements are provided on these substrates. may be used as the substrate 400.

[0088] Alternatively, a semiconductor device may be manufactured using a flexible substrate as the substrate 400. In order to manufacture such a semiconductor device, a transistor including an oxide semiconductor film 403 is formed over a flexible substrate. Alternatively, a transistor including the oxide semiconductor film 403 may be formed on another substrate. The substrate 410 may be fabricated, and then peeled off and transferred to a flexible substrate. In order to separate and transfer the transistor to a flexible substrate, It is advisable to provide a release layer between the substrate 410 and the heat sink 410.

[0089] Next, an insulating film that functions as a base film may be formed over the substrate 400. , silicon oxide, silicon oxynitride, Oxides such as aluminum oxide, aluminum oxynitride, hafnium oxide, and gallium oxide Insulating films, silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxide nitride, etc. The insulating film can be formed using any of nitride insulating films or a mixture of these materials. For example, by using a laminated structure of a silicon nitride film and a silicon oxynitride film, This can prevent metals, hydrogen, and the like from penetrating from the plate into the oxide semiconductor film that will be formed later. Therefore, it is preferable.

[0090] An insulating film serving as a base film (a film in contact with the oxide semiconductor film 403 in the case of a stacked structure) It is preferable that oxygen exists in the film (bulk) in an amount exceeding at least the stoichiometric composition. For example, when a silicon oxide film is used as the insulating film, the amount of oxygen is set to SiO2 +α (However, it is preferable that α>0).

[0091] An insulating film containing a large amount (excessive amount) of oxygen, which serves as an oxygen supply source, is provided in contact with the oxide semiconductor film 403. By this, oxygen can be supplied from the insulating film to the oxide semiconductor film 403. Further, heat treatment is performed in a state where the oxide semiconductor film 403 is in contact with at least part of the insulating film. Oxygen may be supplied to the oxide semiconductor film 403 by using an insulating film containing a large amount of oxygen. By using the oxide semiconductor film, oxygen can be supplied to the oxide semiconductor film 403. Therefore, oxygen deficiency in the compound semiconductor film 403 can be reduced.

[0092] Next, a conductive layer that will become a gate electrode layer (including wiring formed in the same layer) is formed on the substrate 400. The conductive film is made of molybdenum, titanium, tantalum, tungsten, and aluminum. Metallic materials such as aluminum, copper, chromium, neodymium, scandium, etc., or materials containing these as their main components The conductive film can be formed using an alloy material. can be.

[0093] The conductive film may be made of indium oxide containing indium tin oxide or tungsten oxide. , indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, Indium tin oxide containing titanium oxide, indium oxide zinc oxide, silicon oxide added Conductive materials such as indium tin oxide can also be used. Alternatively, the metal material may be laminated.

[0094] In addition, a metal oxide containing nitrogen is used as a conductive film in contact with the gate insulating film 402 to be formed later. Specifically, a nitrogen-containing In-Ga-Zn-O film, a nitrogen-containing In-Sn-O film, Nitrogen-containing In-Ga-O film, nitrogen-containing In-Zn-O film, nitrogen-containing Sn-O film In-O films containing nitrogen and metal nitride films (InN, SnN, etc.) can be used. These films have a specific resistance of 5 eV (electron volts), preferably 5.5 eV (electron volts) or more. Since the gate electrode layer has a gate insulating film, the threshold voltage of the transistor is lowered. The value voltage can be made positive, and a so-called normally-off switching element can be realized. .

[0095] Next, a resist mask is formed over the conductive film by a photolithography process. Then, etching is performed to form a gate electrode layer 401. After the gate electrode layer 401 is formed, a resist The conductive film can be etched by either dry etching or wet etching. Either one or both may be used.

[0096] After the gate electrode layer 401 is formed, the substrate 400 and the gate electrode layer 401 are subjected to heat treatment. For example, a heat treatment may be performed at 650°C for 1 to 5 minutes using a GRTA device. Alternatively, heat treatment may be carried out in an electric furnace at 500°C for 30 minutes to 1 hour. By performing the heat treatment, hydrogen, water, and the like contained in the substrate 400 and the gate electrode layer 401 are removed. can be removed.

[0097] Next, a gate insulating film 402 is formed on the gate electrode layer 401 .

[0098] In order to improve the coverage of the gate insulating film 402, a flat surface is formed on the surface of the gate electrode layer 401. In particular, when a thin insulating film is used as the gate insulating film 402, It is preferable that the surface of the gate electrode layer 401 has good flatness.

[0099] The thickness of the gate insulating film 402 is set to 1 nm or more and 20 nm or less, and is formed by sputtering or MBE. The deposition method, CVD method, PECVD method, pulsed laser deposition method, ALD method, etc. can be used as appropriate. The gate insulating film 402 is formed in a multi-layer structure approximately perpendicular to the surface of the sputtering target. Alternatively, the film may be formed using a sputtering apparatus that performs film formation with multiple substrate surfaces set thereon.

[0100] The material of the gate insulating film 402 may be silicon oxide, gallium oxide, aluminum oxide, Silicon nitride, silicon oxynitride, aluminum oxynitride, or silicon nitride oxide is used. The gate insulating film 402 can be formed using hafnium oxide, oxide, or the like. Yttrium silicate, hafnium silicate (HfSi x O y (x>0, y>0)), nitrogen Doped hafnium silicate (HfSiO x N y (x>0, y>0)), hafnium Aluminate (HfAl x O y (x>0, y>0)), high-k oxide such as lanthanum oxide By using the above material, the gate leakage current can be reduced. The insulating film 100 can be formed to have a single layer structure or a laminated structure using the above materials.

[0101] The gate insulating film 402 has an oxygen-containing layer in a portion in contact with an oxide semiconductor film 403 to be formed later. In particular, the gate insulating film 402 preferably contains at least one oxide in the film (bulk). It is preferable that the amount of oxygen present exceeds the stoichiometric ratio. For example, When a silicon oxide film is used, SiO 2+α (where α>0).

[0102] The gate insulating film 402 containing a large amount (excessive amount) of oxygen, which serves as an oxygen supply source, is then By providing the gate insulating film 402 in contact with the oxide semiconductor film 403, the oxide semiconductor Oxygen can be supplied to the oxide semiconductor film 403. 402 is at least partially in contact with the gate insulating film 4 Oxygen may be supplied from the oxygen source 2 to the oxide semiconductor film 403.

[0103] By supplying oxygen to the oxide semiconductor film 403, oxygen vacancies in the oxide semiconductor film 403 are reduced. Furthermore, the gate insulating film 402 can reduce the size of the transistor to be manufactured. It is preferable to form the insulating film 402 in consideration of the step coverage of the gate insulating film 402 and the size of the insulating film 402 .

[0104] After the gate insulating film 402 is formed, the substrate 400, the gate electrode layer 401, and the gate insulating film 402 are The film 402 may be subjected to a heat treatment. For example, the film 402 may be heated at 650°C for 1 to 5 minutes using a GRTA device. Alternatively, the heat treatment may be performed in an electric furnace at 500°C for 30 minutes to 1 hour. By performing heat treatment, hydrogen and water contained in the gate insulating film 402 are removed. etc. can be removed.

[0105] Next, an oxide semiconductor film is formed over the gate insulating film 402. A resist mask is formed over the oxide semiconductor film by a process, and selective etching is performed to form an island. The oxide semiconductor film 403 is formed (see FIG. 3A). The oxide semiconductor film 403 is etched by dry etching. Either etching or wet etching may be used, or both may be used.

[0106] In addition, a resist mask for forming the island-shaped oxide semiconductor film 403 was formed by an ink-jet method. If the resist mask is formed by the ink-jet method, a photomask can be used. Since no external wiring is used, manufacturing costs can be reduced.

[0107] Note that the etching of the oxide semiconductor film may be dry etching or wet etching. For example, an etching method used for wet etching of an oxide semiconductor film may be used. The cleaning solution can be a mixture of phosphoric acid, acetic acid, and nitric acid. O-07N (manufactured by Kanto Chemical Co., Ltd.) may also be used. Dry etching using the Inductively Coupled Plasma (Inductively Coupled Plasma) etching method The etching process may be performed by etching.

[0108] The oxide semiconductor used for the oxide semiconductor film 403 contains at least indium (In). It is particularly preferable that the oxide contains indium (In) and zinc (Zn). As a stabilizer to reduce the variation in the electrical characteristics of transistors using semiconductor films, In addition to these, it is preferable to have gallium (Ga). Tin (Sn), hafnium (Hf), aluminum (Al), zirconium (Zr) It is preferable to have one or more of the following:

[0109] Other stabilizers include lanthanides such as lanthanum (La) and cerium ( Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), hol Mium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Ru It may contain one or more of tetraethion (Te) and tetraethion (Tb).

[0110] For example, oxide semiconductors include indium oxide, tin oxide, zinc oxide, and oxides of binary metals. In-Zn oxides, In-Mg oxides, In-Ga oxides, and ternary metal oxides In-Ga-Zn oxide (also written as IGZO), In-Al-Zn oxide Oxides, In-Sn-Zn oxides, In-Hf-Zn oxides, In-La-Zn oxides oxides, In-Ce-Zn oxides, In-Pr-Zn oxides, In-Nd-Zn oxides In-Sm-Zn oxides, In-Eu-Zn oxides, In-Gd-Zn oxides , In-Tb-Zn oxide, In-Dy-Zn oxide, In-Ho-Zn oxide, In-Er-Zn oxide, In-Tm-Zn oxide, In-Yb-Zn oxide, I n-Lu-Zn ​​oxide, In-Sn-Ga-Zn oxide, which is an oxide of a quaternary metal, In-Hf-Ga-Zn oxide, In-Al-Ga-Zn oxide, In-Sn-Al -Zn-based oxides, In-Sn-Hf-Zn-based oxides, In-Hf-Al-Zn-based oxides It can be used.

[0111] For example, an In-Ga-Zn oxide is an oxide having In, Ga, and Zn as its main components. The ratio of In, Ga, and Zn is not important. Metal elements may also be included.

[0112] In addition, as an oxide semiconductor, InMO3(ZnO) m (m>0 and m is not an integer) It is also possible to use a material represented by the formula: where M is selected from Ga, Fe, Mn, and Co. It refers to one or more metal elements. In addition, as an oxide semiconductor, In2SnO5 (ZnO) nA material expressed as (n>0 and n is an integer) may be used.

[0113] For example, In:Ga:Zn=1:1:1 (=1 / 3:1 / 3:1 / 3), In:Ga:Z n=2:2:1 (=2 / 5:2 / 5:1 / 5), or In:Ga:Zn=3:1:2 In-Ga-Zn oxides with atomic ratios of (=1 / 2:1 / 6:1 / 3) and their neighboring compositions Alternatively, an oxide of In:Sn:Zn=1:1:1 (=1 / 3: 1 / 3:1 / 3), In:Sn:Zn=2:1:3(=1 / 3:1 / 6:1 / 2) or is In-Sn with an atomic ratio of In:Sn:Zn=2:1:5 (=1 / 4:1 / 8:5 / 8). It is preferable to use a -Zn-based oxide or an oxide having a composition close to that.

[0114] However, oxide semiconductors containing indium are not limited to these, and may have the required semiconductor properties ( It is sufficient to use an appropriate composition depending on the characteristics (mobility, threshold, variation, etc.). In order to obtain the desired semiconductor characteristics, the carrier concentration, impurity concentration, defect density, metal element and oxygen It is preferable to make the atomic ratio, interatomic distance, density, etc., appropriate.

[0115] For example, high mobility can be obtained relatively easily with In-Sn-Zn oxides. Therefore, even in In-Ga-Zn oxides, the mobility can be increased by reducing the defect density in the bulk. It can be done.

[0116] For example, when the atomic ratio of In, Ga, and Zn is In:Ga:Zn=a:b:c(a+b+ The composition of the oxide with c=1) is In:Ga:Zn=A:B:C (A+B+C = 1), the oxide composition is close to (aA) 2 +(bB)2 + (cC) 2 ≦r 2 The value of r can be set to, for example, 0.05. The same applies to other oxides.

[0117] The oxide semiconductor film 403 may be single-crystalline, polycrystalline (also referred to as polycrystalline), or amorphous. Which state to take?

[0118] The oxide semiconductor film 403 is preferably a CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor) film.

[0119] The CAAC-OS film is neither completely single crystalline nor completely amorphous. The oxide semiconductor film has a crystalline-amorphous mixed phase structure in which a crystalline portion is included in an amorphous phase. The crystal portion is often sized to fit within a cube with one side less than 100 nm. Transmission Electron Microscope (TEM) In the observation image using a microscope, the boundary between the amorphous and crystalline parts in the CAAC-OS film was The grain boundaries in the CAAC-OS film were not clearly observed by TEM. Therefore, the CAAC-OS film is not affected by electron transfer due to grain boundaries. The decrease in mobility is suppressed.

[0120] The crystal part included in the CAAC-OS film has a c-axis that is the normal vector of the surface on which the CAAC-OS film is formed. The triangle is aligned parallel to the normal vector of the sphere or surface and perpendicular to the ab plane. The metal atoms are arranged in a layered or hexagonal shape when viewed perpendicular to the c-axis. Metal atoms and oxygen atoms are arranged in layers. The orientation of the a and b axes may be different. The range of 5° to 95° is also included. This also includes the range of 10° to 5°.

[0121] In the CAAC-OS film, the distribution of the crystal parts may not be uniform. In the process of forming the C-OS film, when crystal growth is performed from the surface side of the oxide semiconductor film, The proportion of crystalline parts may be higher near the surface than near the growth surface. By adding impurities to the AC-OS film, the crystalline part in the impurity-doped region becomes amorphous. It may also be pawned.

[0122] The c-axis of the crystalline part in the CAAC-OS film is the normal vector of the surface on which the CAAC-OS film is formed. The CAAC-OS film shape (on which the film is formed) is Depending on the cross-sectional shape of the surface or the cross-sectional shape of the surface, they may face in different directions. The direction of the c-axis of the crystal is the normal vector of the surface on which the CAAC-OS film is formed. The direction of the crystal is parallel to the normal vector of the film or surface. is formed by carrying out a crystallization treatment such as a heat treatment after the film formation.

[0123] The electrical characteristics of a transistor using a CAAC-OS film change when irradiated with visible or ultraviolet light. Therefore, the transistor has high reliability.

[0124] Note that part of oxygen contained in the oxide semiconductor film may be substituted with nitrogen.

[0125] In addition, in oxide semiconductors with crystalline parts such as CAAC-OS, defects in the bulk can be further reduced. By improving the surface flatness, the movement can be reduced more than that of an amorphous oxide semiconductor. To improve the flatness of the surface, it is necessary to deposit an oxide semiconductor on a flat surface. Specifically, it is preferable to form a surface having an average surface roughness (Ra) of 1 nm or less, preferably 0 It is preferable to form it on the surface with a thickness of 0.3 nm or less, more preferably 0.1 nm or less.

[0126] Note that Ra is defined in JIS B 0601:2001 (ISO4287:1997). It is a three-dimensional extension of the arithmetic mean roughness that is currently used to measure surface roughness, and is applicable to curved surfaces. It can be expressed as the "average of the absolute values ​​of the deviation from the reference surface to the specified surface" and is defined by the following formula (2): will be done.

[0127]

number

[0128] Here, the specified surface is the surface to be measured for roughness, and has coordinates (x1, y1, f(x1, y 1))(x1,y2,f(x1,y2))(x2,y1,f(x2,y1))(x2,y 2, f(x2, y2)) and project the specified surface onto the xy plane. The area of ​​the rectangle is S0, and the height of the reference plane (average height of the specified plane) is Z0. Measurement possible with AFM (Atomic Force Microscope) is.

[0129] In order to improve the flatness of the surface of the oxide semiconductor film 403, the oxide semiconductor film 403 is formed on the gate insulating film 402. It is preferable to perform planarization treatment on the region where the compound semiconductor film 403 is formed. The treatment is not particularly limited, but may be a polishing treatment (for example, a chemical mechanical polishing method). Mechanical Polishing (CMP), dry etching Alternatively, plasma treatment can be used.

[0130] The plasma treatment may be, for example, a reverse plasma treatment in which argon gas is introduced to generate plasma. Reverse sputtering is a process in which RF is applied to the substrate side in an argon atmosphere. This method involves applying voltage using a power supply to generate plasma near the substrate, thereby modifying the surface. Instead of the argon atmosphere, nitrogen, helium, oxygen, etc. may be used. When the cleaning is performed, powdery substances (particles, dust, etc.) adhering to the surface of the gate insulating film 402 are removed. (also called) can be removed.

[0131] As a planarization process, polishing, dry etching, and plasma treatment may be performed multiple times. In addition, when the steps are combined, there is no particular limitation on the order of the steps. It is not limited to this value, and may be set appropriately according to the unevenness of the surface of the gate insulating film 402.

[0132] The thickness of the oxide semiconductor film 403 is 1 nm to 200 nm, preferably 5 nm to 50 nm. nm or less, and sputtering method, MBE (Molecular Beam Epita xy) method, CVD method, pulsed laser deposition method, ALD (Atomic Layer Deposition The oxide semiconductor film 403 can be formed by a spat Film deposition is performed with multiple substrate surfaces set approximately perpendicular to the target surface. Alternatively, the film may be formed using a sputtering apparatus that performs the above steps.

[0133] The concentration of hydrogen or water in the oxide semiconductor film 403 is preferably as low as possible. When the hydrogen concentration is high, the hydrogen atoms bond with the elements contained in the oxide semiconductor, and the hydrogen atoms are separated. This is because the part acts as a donor, generating electrons as carriers.

[0134] Therefore, in the step of forming the oxide semiconductor film 403, hydrogen, Alternatively, in order to minimize the inclusion of water, the oxide semiconductor film 403 may be subjected to pretreatment and Then, the substrate on which the gate insulating film 402 is formed is preheated in the preheating chamber of the sputtering device. The substrate and gate insulating film 402 are heated to remove impurities such as hydrogen and moisture adsorbed thereon, and the gas is exhausted. It is preferable that the exhaust means provided in the preheating chamber is a cryopump.

[0135] Note that the oxide semiconductor film 403 is formed under conditions in which a large amount of oxygen is contained (for example, under conditions in which oxygen (e.g., sputtering under a 100% oxygen atmosphere) (preferably, the oxide semiconductor has a stoichiometric composition in a crystalline state, and the content of oxygen is It is preferable to use a membrane containing regions in which the metal is in excess.

[0136] In this embodiment, the oxide semiconductor film 403 is formed by a spa Using a sputtering method with a sputtering device, a 35 nm thick In-Ga-Zn system oxide film was deposited. In this embodiment, an In:Ga:Zn=3:1: An In-Ga-Zn oxide target with an atomic ratio of 2 is used. Under an argon atmosphere (oxygen flow rate 50%), pressure 0.4 Pa, power supply power 0.5 kW, The plate temperature is 200°C.

[0137] The oxide semiconductor film 403 is formed using a sputtering gas containing hydrogen, water, a hydroxyl group, or It is preferable to use a high-purity gas from which impurities such as hydrides have been removed.

[0138] The substrate is held in a film-forming chamber that is kept in a reduced pressure state, and the remaining moisture in the film-forming chamber is removed. The sputtering gas from which hydrogen and moisture have been removed is introduced, and the substrate 40 is sputtered using the target. In order to remove residual moisture in the deposition chamber, an oxide semiconductor film 403 is formed on the substrate. type vacuum pumps, such as cryopumps, ion pumps, titanium sublimation pumps It is preferable to use a turbo molecular pump with a cold trap as the exhaust means. The deposition chamber evacuated using a cryopump may be, for example, Hydrogen atoms, compounds containing hydrogen atoms such as water (H2O) (preferably compounds containing carbon atoms) Since the gases such as hydrogen and oxygen are exhausted, the hydrogen contained in the oxide semiconductor film 403 formed in the deposition chamber is , the concentration of impurities such as water, hydroxyl groups or hydrides can be reduced.

[0139] In addition, the gate insulating film 402 and the oxide semiconductor film 40 are not exposed to the atmosphere. It is preferable to form the gate insulating film 402 continuously without exposing it to the atmosphere. When the insulating film 402 and the oxide semiconductor film 403 are formed in succession, water is deposited on the surface of the gate insulating film 402. This can prevent impurities such as oxygen and moisture from being adsorbed.

[0140] Further, excess hydrogen (including water and a hydroxyl group) is removed (dehydrated or The temperature for the heat treatment is 300°C or higher and 700°C or lower. The temperature should be below ℃ or below the distortion point of the substrate. The heat treatment should be carried out under reduced pressure or in a nitrogen atmosphere. It is possible.

[0141] In addition, when a crystalline oxide semiconductor film is used as the oxide semiconductor film 403, Heat treatment may be carried out.

[0142] In this embodiment, the substrate is placed in an electric furnace, which is a type of heat treatment apparatus, and the oxide semiconductor film 4 03 at 450°C for 1 hour in a nitrogen atmosphere, and then at 450°C in a nitrogen and oxygen atmosphere. Heat treatment is carried out at ℃ for 1 hour.

[0143] The heat treatment device is not limited to an electric furnace, and may be a heat treatment device using heat conduction or heat from a heat source such as a resistance heating element. A device that heats the object to be treated by radiation may be used. For example, a lamp-driven thermal analyzer (LRTA) Rapid Thermal Anneal (GRTA) equipment, RTA (Rapid Thermal Anneal) equipment, etc. The LRTA device can be used with halogen lamps, metal halide lamps, etc. lamp, xenon arc lamp, carbon arc lamp, high-pressure sodium lamp, high-pressure mercury lamp It is a device that heats the object to be treated by radiating light (electromagnetic waves) emitted from a lamp or other lamp. The GRTA device is a device that uses high-temperature gas to perform heat treatment. Inert gases such as argon or nitrogen that do not react with the material to be treated by heat treatment An active gas is used.

[0144] For example, as a heat treatment, the substrate is placed in an inert gas heated to a high temperature of 650 to 700°C. After heating for several minutes, GRTA may be performed in which the substrate is taken out of the inert gas.

[0145] In the heat treatment, nitrogen or a rare gas such as helium, neon, or argon is used. It is preferable that the nitrogen or hydrogen introduced into the heat treatment device is not contained. The purity of rare gases such as sodium, neon, and argon is preferably 6N (99.9999%) or higher. is 7N (99.99999%) or more (i.e., impurity concentration is 1 ppm or less, preferably 0.1 It is preferable to set the concentration to less than 1 ppm.

[0146] After the oxide semiconductor film 403 was heated by the heat treatment, high-purity oxygen gas and high-purity SiO 2 were added to the same furnace. nitrous oxide gas or ultra dry air (CRDS (cavity ring down laser separation) When measured using a dew point meter using the optical method, the moisture content is 20 ppm (-55°C in dew point equivalent). air, preferably 1 ppm or less, more preferably 10 ppb or less, may be introduced. It is preferable that the oxygen gas or nitrous oxide gas does not contain water, hydrogen, etc. Alternatively, the purity of the oxygen gas or nitrous oxide gas introduced into the heat treatment device is preferably 6N or more. or 7N or more (i.e., impurity concentration in oxygen gas or nitrous oxide gas is 1 ppm or less, Preferably, the concentration is 0.1 ppm or less. This action simultaneously reduces impurities through the removal process of dehydration or dehydrogenation treatment. By supplying oxygen, which is the main component of oxide semiconductors, Oxygen vacancies in the semiconductor film 403 can be reduced.

[0147] Note that the heat treatment for dehydration or dehydrogenation may be performed before or after processing the oxide semiconductor film into an island shape. Alternatively, this may be done after processing into an island shape.

[0148] The heat treatment for dehydration or dehydrogenation may be carried out multiple times, or may be carried out in combination with other heat treatments. You can sleep.

[0149] The heat treatment for dehydration or dehydrogenation is performed to form the oxide semiconductor film 403 into an island shape. If the oxide semiconductor film is formed on the gate insulating film 402, the gate insulating film 4 This prevents the oxygen contained in O2 from being released to the outside due to the heat treatment.

[0150] Next, a thin film of a metal oxide is formed over the gate electrode layer 401, the gate insulating film 402, and the oxide semiconductor film 403. A metal oxide film that will become the source electrode layer and the drain electrode layer (including wiring formed in the same layer) Then, a nitride film 404 and a conductive film 405 are formed (see FIG. 3B).

[0151] The metal oxide film 404 is a metal oxide film having a higher reduction property than the oxide semiconductor film 403. The metal oxide film having a higher reduction property than the oxide semiconductor film 403 is a metal oxide film having a higher reduction property than the oxide semiconductor film 403, as shown in FIG. It is more reducing than indium oxide, gallium oxide, zinc oxide, and tin oxide (i.e., (higher than the Gibbs free energy of oxidation reactions of indium, gallium, zinc, and tin) Any oxide may be used. Specifically, copper oxide, silver oxide, ruthenium oxide, iridium oxide, etc. The metal oxide film 404 is formed to have a single layer structure or a multilayer structure.

[0152] The thickness of the metal oxide film 404 is 1 nm or more and 50 nm or less, preferably 1 nm or more and 30 nm or less. The thickness of the metal oxide film 404 is preferably 5 nm or more and 10 nm or less. The film can be formed by appropriately using a sputtering method, a CVD method, or the like.

[0153] In this embodiment, the metal oxide film 404 is formed by sputtering to a thickness of 10 nm. A film of ruthenium oxide is formed.

[0154] The conductive film 405 may be formed using a material that can withstand subsequent heat treatment. Therefore, it is preferable to form the metal oxide film 404 using a material that does not form an oxide film at the interface with the metal oxide film 404. The conductive film 405 may be made of, for example, gold, platinum, copper, silver, ruthenium, iridium, or titanium. Tantalum, tungsten, titanium nitride, molybdenum nitride, tungsten nitride, tantalum nitride, etc. The conductive film 405 is preferably formed to be thicker than the metal oxide film 404. The tantalum nitride film is formed in a single layer structure or a laminated structure. A tungsten film may also be formed.

[0155] The thickness of the conductive film 405 is set to 50 nm or more and 600 nm or less. The film can be formed by appropriately using a sputtering method, a CVD method, or the like.

[0156] In this embodiment, the conductive film 405 is formed by a sputtering method. A film of ruthenium is formed.

[0157] Next, the oxide semiconductor film 403, the metal oxide film 404, and the conductive film 405 are subjected to heat treatment (see FIG. 3(C)). Heat treatment is performed while the metal oxide film 404 and the oxide semiconductor film 403 are in contact with each other. By this, oxygen is released from the metal oxide film 404 and supplied to the oxide semiconductor film 403. When oxygen is supplied to the oxide semiconductor film 403, the oxide semiconductor film 403 In addition, the oxide semiconductor film 403 has a higher reducing property than the oxide semiconductor film 403. The metal oxide film 404 is reduced to form a metal film 406 .

[0158] In FIG. 3C, when the metal oxide film 404 is entirely reduced to the metal film 406, However, only the vicinity of the interface between the metal oxide film 404 and the oxide semiconductor film 403 is reduced. The metal oxide film 404 may remain in areas other than the interface. For example, when ruthenium oxide is used as the metal oxide film 404, only the vicinity of the interface is reduced. Ruthenium oxide may remain in areas other than the interface. Even if ruthenium oxide remains outside, the resistivity of ruthenium oxide is 3.5 × 10 - 5 [cmΩ] (300K), and no high resistance components are formed in the source and drain electrode layers. This is preferable because it does not

[0159] The metal film 406 formed by reducing the metal oxide film 404 is an oxide film. The metal film 403 has higher oxidation resistance than the metal element contained in the semiconductor film 403. 06, a film that makes it difficult for oxygen to diffuse into the

[0160] As shown in this embodiment, when the metal oxide film 404 covers the oxide semiconductor film 403, Because of the heat treatment, oxygen is supplied to the channel formation region, which will be formed later, This is preferable because defects are reduced.

[0161] Further, a conductive film 405 is provided over the metal oxide film 404, and heat treatment is performed to form a metal oxide film. The oxygen contained in the oxide film 404 is not released to the outside but is supplied to the oxide semiconductor film 403. Therefore, it is preferable.

[0162] Heat treatment is carried out in an inert gas (nitrogen, or helium, neon, argon, krypton, xenon) atmosphere, oxidizing gas is 10 ppm or more, preferably 1% or more, Preferably, the atmosphere contains 10% or more of oxygen, or the atmosphere is under reduced pressure (10 Pa or less, preferably 1 Pa or less). At a temperature of 150°C or higher and 650°C or lower, preferably 0.1 Pa or lower The heating is carried out at a temperature of 200°C or higher and 450°C or lower.

[0163] In this embodiment, the heat treatment is performed at 650° C. for 1 to 5 minutes using a GRTA device. Alternatively, heat treatment may be carried out in an electric furnace at 500° C. for 30 minutes to 1 hour.

[0164] Next, a resist mask is formed over the conductive film 405 by a photolithography process. Then, etching is performed to form metal films 406a and 406b and conductive films 405a and 405b. The metal film 406a and the conductive film 405a are formed as the source electrode layer 407. a, and the metal film 406b and the conductive film 405b function as the drain electrode layer 407b. After the source electrode layer 407a and the drain electrode layer 407b are formed, a resist mask is formed. Remove the mask.

[0165] When forming a resist mask, ultraviolet light, KrF laser light, or ArF laser light is used for exposure. The bottom end of the source electrode layer 407a and the bottom end of the drain electrode layer 407b adjacent to each other over the oxide semiconductor film 403 are preferably The channel length of the transistor 410 to be formed later is determined by the gap width between the bottom end of the layer 407b and the When performing exposure with a channel length L of less than 25 nm, the value of L is determined. Extreme ultraviolet light with an extremely short wavelength of 10 nm is used. It is recommended to use extreme ultraviolet light for exposure when forming a resist mask. Therefore, the channel length L of the transistor to be formed later is set to 10 nm or more. It is also possible to achieve a thickness of 0.000 nm or less, which allows for faster circuit operation speeds.

[0166] In addition, in order to reduce the number of photomasks and steps used in the photolithography process, The resist mask is formed by a multi-tone mask, which is an exposure mask that allows the incident light to have multiple intensities. The etching process may be performed using a resist mask formed using a multi-tone mask. The mask has a shape with multiple film thicknesses, and the shape can be further deformed by etching. Therefore, it can be used in multiple etching processes to process different patterns. Therefore, one multi-tone mask can handle at least two different patterns. Therefore, the number of exposure masks can be reduced. Since the corresponding photolithography process can also be eliminated, the process can be simplified.

[0167] The etching gas for etching the conductive film 405 and the metal film 406 is halogen. The halogen-containing gas may be a chlorine-containing gas, for example. For example, chlorine (Cl2), boron trichloride (BCl3), silicon tetrachloride (SiCl4), carbon tetrachloride Gases containing halogen such as (CCl4) can be used. Fluorine-containing gases, such as carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), and nitrogen trifluoride Gases containing NF3, trifluoromethane (CHF3), etc. can be used. In addition, gases in which rare gases such as helium (He) and argon (Ar) are added to these gases, etc. can be used.

[0168] As described above, the film in contact with the oxide semiconductor film 403 is etched using a halogen-containing etching agent. However, a plasma treatment using an etching gas containing an acid can be suitably used. When a halogen-containing semiconductor film is exposed to an etching gas containing a halogen element, the halogen-containing The halogen element contained in the oxide semiconductor film extracts oxygen from the oxide semiconductor film, There is a risk of oxygen vacancies being formed near the surface of the conductor film.

[0169] For example, if the metal film 406 is made of ruthenium, the etching gas may be oxygen or A mixed gas of oxygen and a rare gas such as argon can be used. It is not necessary to use etching gas containing halogen elements when etching the film on top. In this case, oxygen in the oxide semiconductor film can be prevented from being extracted. Oxygen can be supplied into the oxide semiconductor film 403. More preferably, 405 is formed of ruthenium.

[0170] The etching method is parallel plate RIE (Reactive Ion Etching) ) method and ICP (Inductively Coupled Plasma) Plasma etching can be used. The etching conditions (the amount of power applied to the coil-type electrode, the amount of power applied to the electrode on the substrate side) The welding conditions (power, electrode temperature on the substrate, etc.) are adjusted appropriately.

[0171] Note that the oxide semiconductor film 403 is etched during the etching process of the conductive film 405 and the metal film 406. The conductive film 405 and the metal film 406 are etched so as not to be lost or divided. It is desirable to optimize the etching conditions. The oxide semiconductor film 402 is not etched at all. Therefore, the oxide semiconductor film 4 is not etched when the conductive film 405 and the metal film 406 are etched. By removing a part of the oxide semiconductor film 403, the oxide semiconductor film 403 has a groove (depression). There is.

[0172] Through the above steps, a transistor 410 according to one embodiment of the present invention is manufactured (see FIG. 3E). ).

[0173] In this embodiment, an oxide semiconductor is formed over the source electrode layer 407a and the drain electrode layer 407b. An insulating film 408 is formed in contact with the inorganic film 403 to serve as an inorganic insulating film.

[0174] The insulating film 408 has a thickness of at least 1 nm. The insulating film 408 is formed by using an appropriate method that prevents impurities such as water and hydrogen from being mixed into the insulating film 408. When hydrogen is contained in the oxide semiconductor film 403, the hydrogen penetrates into the oxide semiconductor film 403, or the oxide semiconductor Oxygen is extracted from the film, and the back channel of the oxide semiconductor film 403 becomes low resistance (n-type). ) and there is a risk of forming a parasitic channel. It is important that the deposition method be hydrogen-free so that the resulting film is hydrogen-free.

[0175] The insulating film 408 is typically made of silicon oxide, silicon oxynitride, or aluminum oxide. , aluminum oxide nitride, hafnium oxide, or gallium oxide, silicon nitride, aluminum nitride A single layer or multilayer structure of inorganic insulating films such as silicon nitride oxide, aluminum nitride oxide, etc. A layer structure can be used.

[0176] When a heating step is performed as the dehydration or dehydrogenation treatment, oxygen is added to the oxide semiconductor film 403. By supplying oxygen to the oxide semiconductor film 403, the oxygen in the film is The element deficiency can be further reduced.

[0177] In this embodiment, oxygen is supplied to the oxide semiconductor film 403 from the insulating film 408. The insulating film 408 may be an oxide insulating film containing oxygen (for example, a silicon oxide film When the insulating film 408 is used as an oxygen source, the insulating film 40 8 is a film containing a large amount (excess) of oxygen (preferably containing a large amount of oxygen relative to the stoichiometric composition in the crystalline state). If the film contains a region with an excessive amount of oxygen, it will function favorably as an oxygen source. It is possible.

[0178] In this embodiment, a silicon oxide film having a thickness of 300 nm is deposited as the insulating film 408 by sputtering. The substrate temperature during film formation should be between room temperature and 300°C. In the embodiment, the temperature is set to 100° C. The silicon oxide film is formed by sputtering. In a gas (typically argon) atmosphere, in an oxygen atmosphere, or in a mixed atmosphere of rare gas and oxygen The target may be a silicon oxide target or a silicon target. For example, a silicon target can be used to The silicon oxide film can be formed by sputtering in an atmosphere containing SiO 2 .

[0179] Similar to the formation of the oxide semiconductor film 403, moisture remaining in the deposition chamber for the insulating film 408 is removed. To achieve this, it is preferable to use an adsorption type vacuum pump (such as a cryopump). The concentration of impurities contained in the insulating film 408 formed in a deposition chamber evacuated using an opto-pump was reduced. In addition, the exhaust means for removing the residual moisture in the film forming chamber of the insulating film 408 may be: A turbomolecular pump with a cold trap added may also be used.

[0180] The sputtering gas used in forming the insulating film 408 is a gas containing no impurities such as hydrogen and water. It is preferable to use high purity gases that have been removed.

[0181] Next, a state in which a part (a channel formation region) of the oxide semiconductor film 403 is in contact with the insulating film 408 The heating step is carried out.

[0182] The temperature of the heating process is between 250°C and 700°C, or between 400°C and 700°C, or For example, the substrate is introduced into an electric furnace, which is a type of heat treatment device, and The oxide semiconductor film is subjected to a heating step at 250° C. for 1 hour in a nitrogen atmosphere.

[0183] This heating step is carried out using the same heating method and heating device as in the heating step for dehydration or dehydrogenation treatment. can be used.

[0184] The heating process can be carried out under reduced pressure or with nitrogen, oxygen, or ultra-dry air (CRDS (Cavity Ring Down System)). When measured using a laser spectroscopic dew point meter, the moisture content was 20 ppm (dew point equivalent). -55°C or less, preferably 1 ppm or less, preferably 10 ppb or less air), or The above-mentioned treatment can be carried out under an atmosphere of nitrogen, oxygen, or ultra-dry gas (argon, helium, etc.). It is preferable that the dry air or rare gas atmosphere does not contain water, hydrogen, etc. The purity of nitrogen, oxygen, or rare gas introduced into the heat treatment equipment must be 6N (99.9999%) or higher. Preferably, the impurity concentration is 7N (99.99999%) or more (i.e., the impurity concentration is 1 ppm or less, preferably It is preferable to keep the concentration below 0.1 ppm.

[0185] Further, a heat treatment is performed while the oxide semiconductor film 403 and the insulating film 408 containing oxygen are in contact with each other. Therefore, the oxygen that is simultaneously reduced by the impurity removal process is removed by the insulating film 408 containing oxygen. This allows the oxygen to be supplied to the oxide semiconductor film 403 (channel formation region).

[0186] Furthermore, a highly dense inorganic insulating film may be provided over the insulating film 408. For example, An aluminum oxide film is formed on 408 by sputtering. High density (film density 3.2 g / cm 3 or more, preferably 3.6 g / cm 3 (or more) This allows the transistor 410 to have stable electrical characteristics. Rutherford Backscattering (RBS) Spectrometry and X-ray Reflectometry (XRR) It can be measured by tmetry.

[0187] An aluminum oxide film that can be used as an inorganic insulating film provided on the transistor 410 The membrane has a blocking effect ( High blocking effect.

[0188] Therefore, the aluminum oxide film is free from hydrogen, which is a factor of fluctuation during and after the manufacturing process. The inclusion of impurities such as moisture in the oxide semiconductor film 403 and the inclusion of a main component constituting the oxide semiconductor The oxide semiconductor film 403 functions as a protective film for preventing oxygen, which is a material, from being released from the oxide semiconductor film 403.

[0189] In this embodiment, oxygen is supplied to the oxide semiconductor film 403 from the insulating film 408. However, the oxide semiconductor film 403 may be formed by adding oxygen (at least oxygen radicals). Oxygen may be supplied to the film by introducing oxygen atoms, oxygen ions, or oxygen atoms. Alternatively, oxygen may be supplied to the oxide semiconductor film 403 by a combination of these methods.

[0190] The oxygen introduction method includes ion implantation, ion doping, and plasma immersion. This can be done by implantation, plasma treatment, or a combination of both. can.

[0191] In the step of introducing oxygen, oxygen may be introduced into the oxide semiconductor film 403 through the insulating film 408. Oxygen may be directly introduced into the exposed oxide semiconductor film 403. When introducing, ion implantation, ion doping, plasma immersion ion implantation, The oxide semiconductor film 403 may be directly exposed to oxygen. When introducing the metal oxide, plasma treatment or the like can also be used.

[0192] Further, oxygen may be introduced into the oxide semiconductor film 403 after the insulating film 408 is formed. For example, it is advisable to perform the treatment after the gate insulating film is formed or after the gate insulating film is heated. During the transistor manufacturing process, if a process of introducing oxygen is performed before removing hydrogen and water, During the heat treatment, oxygen is extracted from the oxide semiconductor film, which causes oxygen vacancies. Therefore, if a step of supplying oxygen is performed after the heat treatment for removing hydrogen and water, the oxide semiconductor This is preferable because oxygen can be efficiently supplied to the film 403 .

[0193] In addition, a planarization insulating film 409 is formed to reduce surface irregularities caused by the transistor 410. The planarization insulating film 409 may be made of a material such as a polyimide resin, an acrylic resin, or a benzosilane. Organic materials such as clobutene-based resins can be used. In addition, insulating materials formed from these materials can be used. The planarization insulating film 409 may be formed by stacking a plurality of insulating films.

[0194] For example, an acrylic resin film having a thickness of 1500 nm may be formed as the planarization insulating film 409. After applying the acrylic resin film by coating, it is baked (for example, in a nitrogen atmosphere at 250°C for 1 hour). It can be formed as follows.

[0195] After the planarization insulating film 409 is formed, heat treatment may be performed. Heat treatment is carried out for 1 hour.

[0196] In this way, heat treatment may be performed after forming the transistor 410. You may do this several times.

[0197] Through the above steps, a semiconductor device including the transistor 410 shown in FIG. 1B is manufactured. .

[0198] The oxide semiconductor film 403 contains almost no impurities such as copper, aluminum, or chlorine. It is desirable that the material be highly purified so that it does not contain any traces of fluorine. A process in which there is no risk of these impurities being mixed into the oxide semiconductor film or being attached to the surface of the oxide semiconductor film. In addition, when the oxide semiconductor film is attached to the surface of the oxide semiconductor film, the oxide semiconductor film is easily adhered to the surface of the oxide semiconductor film. Exposure to acid or dilute hydrofluoric acid, or plasma treatment (such as N2O plasma treatment) Therefore, it is preferable to remove impurities from the surface of the oxide semiconductor film. The copper concentration in membrane 403 is 1×10 18 atoms / cm 3 Less than 1 × 10 17 a toms / cm 3 The aluminum concentration in the oxide semiconductor film is 1×10 or less. 18 atoms / cm 3 The chlorine concentration in the oxide semiconductor film is 2×10 18 ato ms / cm 3 The following applies.

[0199] In addition, immediately after the deposition, the oxide semiconductor film is in a supersaturated state with more oxygen than in the stoichiometric composition. For example, when an oxide semiconductor film is formed by a sputtering method, In this case, it is preferable to form the film under conditions where the proportion of oxygen in the film forming gas is high, and particularly in an oxygen atmosphere. It is preferable to form the film using 100% oxygen gas. The proportion of oxygen in the film formation gas is high. When film formation is performed under conditions, particularly in an atmosphere of 100% oxygen gas, for example, when the film formation temperature is 300°C or higher, Even if the film is heated, the release of Zn from the film is suppressed.

[0200] Further, the oxide semiconductor film can be formed by sufficiently removing impurities such as hydrogen or by sufficiently removing impurities such as hydrogen. By supplying oxygen in a supersaturated state, the water is highly purified. Specifically, the hydrogen concentration in the oxide semiconductor film is preferably 5×10 19 atoms / c m 3 Below 5×10 18 atoms / cm 3 Less than or equal to 5×10 1 7 atoms / cm 3 Note that the hydrogen concentration in the oxide semiconductor film is determined by the secondary electron Secondary Ion Mass Spectrometry (SIMS) It is measured by the oxygen saturation test. To achieve this, an insulating film (such as SiOx) containing excess oxygen is formed to enclose the oxide semiconductor film. Install adjacently.

[0201] The hydrogen concentration in the insulating film containing excess oxygen is also important because it affects the characteristics of the transistor. be.

[0202] The following describes the influence of the hydrogen concentration in an insulating film containing excess oxygen on the characteristics of a transistor. I will explain.

[0203] First, hydrogen is intentionally added to an insulating film containing excess oxygen, and the hydrogen concentration is measured by SIMS. Evaluated.

[0204] In this embodiment, four types of samples were prepared.

[0205] A glass substrate was prepared, and a silicon oxide film was formed on the glass substrate by sputtering to a thickness of 3 mm. The silicon oxide film was formed using a quartz target at a pressure of 0.4 Pa and a power of 0. The film was formed at a power of 1.5 kW (13.56 MHz) and a substrate temperature of 100°C during film formation. Oxygen gas (O2) and deuterium gas (D2) are the deposition gases used to deposit silicon oxide films. Four different conditions were tested for the flow rate ratio of argon gas (Ar).

[0206] Table 3 shows the sample name, the flow rate of each deposition gas used to deposit the silicon oxide film, and the data obtained by SIMS. The average D (deuterium atom) concentration and H (hydrogen) concentration in the 30 nm thick silicon oxide film The D2 ratio (D2 / (O2+Ar+D2)) in the deposition gas for each sample was Sample 1 was 0% by volume, sample 2 was 0.005% by volume, sample 3 was 0.50% by volume, and sample 4 was 2.5% by volume. It was set to 0% by volume.

[0207] [Table 3]

[0208] From Table 3, it can be seen that the higher the D2 ratio in the deposition gas, the higher the D concentration in the silicon oxide film. I found out that...

[0209] Next, transistors were manufactured using Samples 1 to 4 shown in Table 3.

[0210] 32A is a top view of a transistor used for evaluation. A cross-sectional view corresponding to AB is shown in FIG. 32(B). For simplicity, in FIG. 32(A), In this figure, the protective insulating film 718, the gate insulating film 712, the insulating film 702, and the like are omitted.

[0211] The transistor shown in FIG. 32B includes a substrate 700 and an insulating film 7 702, an oxide semiconductor film 706 provided over the insulating film 702, and a a pair of electrode layers 716 provided between the oxide semiconductor film 706 and the pair of electrode layers 716; The gate insulating film 712 is provided to cover the oxide semiconductor film 7 06, and the gate electrode layer 704 and the gate insulating layer and a protective insulating film 718 provided on the film 712. The channel length (L) is 10 μm, a channel width (W) of 10 μm, and a pair of the gate electrode layer 704 in the channel length direction. The overlapping (Lov) of the electrode layers 716 is 1 μm (total 2 μm). A gyroscope was created.

[0212] In addition, a transistor formed under the film formation conditions of Sample 1 was used as the insulating film 702 in Sample 5. The transistors fabricated under the film deposition conditions of Sample 2 were fabricated under the film deposition conditions of Samples 6 and 3. The transistor fabricated under the same conditions as Sample 4 was designated Sample 7, and the transistor fabricated under the same conditions as Sample 4 was designated Sample 8. The thickness of the insulating film 702 was set to 300 nm.

[0213] Samples 5 to 8 were fabricated under the same conditions except for the conditions for forming the insulating film 702. The substrate 700 is a glass substrate, and the oxide semiconductor film 706 is made of IGZO (In:Ga: Zn=1:1:1 [atomic ratio] target) was used to form a film with a thickness of 20 nm. The electrode layer 716 is made of tungsten with a thickness of 100 nm, and the gate insulating film 712 is made of silicon oxynitride. The gate electrode layer 704 is made of tantalum nitride from the gate insulating film 712 side. The protective insulating film 718 is silicon oxynitride. The thickness of the film was set to 300 nm.

[0214] For each of the transistors (samples 5 to 8) having the above structure, a BT strip was The BT stress test method used is as follows:

[0215] First, at a substrate temperature of 25°C, the drain voltage (Vd) of the transistor is set to 3 V, and the gate The drain current (Id) was evaluated when the gate voltage (Vg) was swept from -6V to 6V. The characteristics of the transistor at this time are called the characteristics of the transistor before the BT stress test.

[0216] Next, Vd was set to 0.1 V, Vg was set to -6 V, and the substrate temperature was kept at 150°C for 1 hour.

[0217] Next, Vd, Vg, and temperature were stopped, and Vd was set to 3 V at a substrate temperature of 25°C. The Id was evaluated when Vg was swept from -6V to 6V. The characteristics of the transistor after the BT stress test are called the characteristics of the transistor after the BT stress test.

[0218] Threshold voltage (Vth) and Field-effect mobility (μ FE ) are shown in Table 4.

[0219] [Table 4]

[0220] From Table 4, sample 8 shows μ FE was found to have decreased significantly .

[0221] Moreover, sample 8 had a larger variation in Vth in the negative direction than the other samples.

[0222] As described above, in a transistor having a structure in which a silicon oxide film and an oxide semiconductor are in contact with each other, The D concentration in the silicon oxide film is 7.2 × 10 20 atoms / cm 3 When It was found that the characteristics of the transistors were abnormal.

[0223] Thus, the deuterium concentration of the insulating film containing excess oxygen is 7.2 × 10 20 atoms / cm 3 If this is the case, the initial characteristics of the transistor will vary, the L length will increase, and Furthermore, the deuterium concentration of the insulating film containing excess oxygen is significantly increased due to the large deterioration in the BT stress test. Degrees are 7.2 x 10 20 atoms / cm 3 That is, the hydrogen concentration of the oxide semiconductor film is less than Degrees are 5 x 10 19 atoms / cm 3 The deuterium concentration of the insulating film containing excess oxygen is , 7.2 × 10 20 atoms / cm 3 It is preferable that it is less than 1000 kJ / s.

[0224] Further, the insulating film containing excess oxygen is formed so as to surround the oxide semiconductor film and to be disposed outside the insulating film containing excess oxygen. It is preferable to provide a blocking film (such as AlOx) that suppresses oxygen release from the oxide semiconductor film. stomach.

[0225] The oxide semiconductor film is surrounded by an insulating film or a blocking film containing excess oxygen. In a semiconductor film, the state where the composition is almost the same as the stoichiometric ratio, or the composition is different from the stoichiometric ratio. For example, if the oxide semiconductor film is IGZO, it can be made into a supersaturated state with a large amount of oxygen. An example of the stoichiometric composition is In:Ga:Zn:O=1:1:1:4 [atomic ratio]. Therefore, the atomic ratio of oxygen is 4 or more.

[0226] Although the explanation has been given in FIG. 32 using a transistor with a top gate structure, a transistor with a bottom gate structure may also be used. The same can be said for a gate structure transistor. The insulating film 402 and the insulating film 408 are insulating films in which the hydrogen concentration is reduced to the above concentration. By doing so, abnormalities in the characteristics of the transistor can be suppressed. 402, an insulating film containing excess oxygen is used as the insulating film 408, and the insulating film containing excess oxygen By providing a blocking film on the outside, the oxide semiconductor film has a nearly stoichiometric composition. The state can be such that the oxygen content is almost equal to the stoichiometric composition, or the state can be supersaturated with more oxygen than the stoichiometric composition. can.

[0227] In this embodiment, after the conductive film 405 is formed over the metal oxide film 404, heat treatment is performed. However, one embodiment of the present invention is not limited thereto. After the metal oxide film 404 is formed on the film 403, heat treatment may be performed. A conductive film 405 is formed over the film 404 and processed into source and drain electrode layers. Heat treatment may be carried out.

[0228] In addition, by selecting materials so that the metal film 406 and the conductive film 405 are made of different materials, Therefore, the transistor 420 shown in FIG. 2 can be manufactured. For example, a metal oxide film Ruthenium oxide is used as the conductive film 404, and tantalum nitride is used as the conductive film 405. By performing this process, a layered structure of ruthenium and tantalum nitride is formed. The metal film can be used as the source electrode layer 417a and the drain electrode layer 417b. An oxide film is formed at the interface between the conductive films 406a and 406b and the conductive films 415a and 415b. The conductive films 415a and 415b are preferably made of tantalum nitride and tungsten. Alternatively, the insulating film 10 may be formed in a laminated structure.

[0229] The metal films 406a and 406b and the conductive films 405a and 405b are made of the same material. Even if the material is selected as the metal oxide film 404, the metal films 406a and 406b are The conductive films 405a and 405b are formed by reduction. Therefore, when the metal films 406a and 406b and the conductive films 405a and 405b have different physical properties, For example, the metal films 406a and 406b may have a larger thickness than the conductive films 405a and 405b. The density may be low. The film density can be measured, for example, by X-ray reflectivity (XRR). It can be measured by the endoscopic method.

[0230] In this embodiment, the source electrode layer 407a and the drain electrode layer 407b are formed of a metal film. Although the case where the insulating film 406a and the insulating film 406b are formed by the conductive films 405a and 405b has been described, However, one embodiment of the present invention is not limited thereto. It's good to

[0231] In the channel and back channel of the oxide semiconductor film 403, the source electrode layer 407a and Even after the formation of the insulating film 408 or the oxygen introduction step, the insulating film 408 and the drain electrode layer 407b are removed. However, the source electrode layer When an easily oxidizable material is used for the source electrode layer 407a and the drain electrode layer 407b, Oxygen vacancies are formed at the interface between the electrode layer 407a and the drain electrode layer 407b. If the thickness is too small, it becomes difficult to supply oxygen to the interface and reduce oxygen vacancies. Oxygen diffuses into the source electrode layer 407a and the drain electrode layer 407b, forming high resistance components. Once formed, an additional step is required to remove the high resistance component.

[0232] According to this embodiment, the metal oxide film 404 in contact with the oxide semiconductor film 403 is subjected to heat treatment. By reducing the metal oxide film 404 with oxygen, oxygen is released from the metal oxide film 404, and the oxide semiconductor film 40 3. As a result, the source electrode layer 407a and the drain electrode layer 40 Oxygen vacancies at the interface between 7b and the oxide semiconductor film 403 can be reduced. This prevents the threshold voltage of the transistor 410 from shifting in the negative direction. This can be done.

[0233] The metal film 406 formed by reducing the metal oxide film 404 is an oxide film. The metal film 403 has higher oxidation resistance than the metal element contained in the semiconductor film 403. The metal films 406a and 406b are formed on the source electrode layer 40. By using the metal films 406a and 406b as the drain electrode layer 407a and the drain electrode layer 407b, Therefore, the formation of a high-resistance component in the oxide semiconductor film 403 can be suppressed. Therefore, the resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor 410 can be suppressed.

[0234] In addition, a gold film having a work function of ±0.2 eV with respect to the electron affinity of the oxide semiconductor film 403 is used. By selecting a metal film 406 (e.g., copper, silver, ruthenium, etc.), an oxide semiconductor The contact resistance between the film 403 and the source electrode layer 407a and the drain electrode layer 407b is reduced. This is also preferable because the oxide semiconductor film 403, the source electrode Since the resistance due to the drain electrode layer 407a and the drain electrode layer 407b can be reduced, A decrease in the on-state current of the transistor can be suppressed.

[0235] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0236] (Embodiment 3) In this embodiment, another mode of a semiconductor device will be described with reference to FIGS. 4 and 5. Note that the same parts as those in the above embodiment modes or parts having similar functions and parts manufactured in similar steps may be used. Therefore, repeated explanation will be omitted.

[0237] The transistor 430 shown in FIG. 4 is an example of a bottom-gate transistor. 4A is a plan view of the transistor 430, and FIG. 4B is a diagram of the D1-D2 4(A) is a cross-sectional view (cross-sectional view in the channel length direction) at (A). To avoid this, some of the components of the transistor 430 (for example, the gate insulating film 402 etc.) are omitted in the illustration.

[0238] The transistor 430 shown in FIGS. 4A and 4B is provided over a substrate 400 having an insulating surface. a gate electrode layer 401 formed on the gate electrode layer 401; and a gate insulating film 402 formed on the gate electrode layer 401. An oxide semiconductor layer is provided on the gate insulating film 402 in a region overlapping with the gate electrode layer 401. a gate electrode layer 401 provided over the oxide semiconductor film 403; the insulating film 411, which is formed on the oxide semiconductor film 403, and the insulating film 411. The transistor has a source electrode layer 407a and a drain electrode layer 407b. An insulating film 408 and a planarizing insulating film 409 are provided to cover 430 .

[0239] As shown in FIG. 4B, the transistor 430 has a source The electrode layer 407a and the drain electrode layer 407b have a stacked structure. The drain electrode layer 407b is a layered structure of a metal film 406a and a conductive film 405a. It has a laminated structure of a metal film 406b and a conductive film 405b.

[0240] The transistor 430 shown in FIG. 4B has the same structure as the transistor 410 shown in FIG. The difference is that the region ( An insulating film 411 is provided in a region overlapping with a channel formation region of the oxide semiconductor film 403. In FIG. 4B, the oxide semiconductor film 403 overlaps with the channel formation region. By providing the insulating film 411 in the region, during the manufacturing process of the transistor 430, Hydrogen, water, elements contained in an etching gas, and the like are mixed into the oxide semiconductor film 403. This can prevent the following.

[0241] The insulating film 411 is made of, for example, silicon oxide, silicon oxynitride, aluminum oxide, or silicon oxynitride. Aluminum oxide, hafnium oxide, gallium oxide, silicon nitride, aluminum nitride, nitride Inorganic insulating materials such as silicon oxide nitride or aluminum oxide nitride are used to form single-layer structures or is formed in a laminated structure.

[0242] In addition, the insulating film 411 (when the insulating film 411 has a stacked structure, the insulating film 411 is in contact with the oxide semiconductor film 403) When the oxide semiconductor film 403 is made to contain a large amount of oxygen (excessive oxygen), oxygen is supplied to the oxide semiconductor film 403. It can be suitably used as a supply source of

[0243] The insulating film 411 is formed by forming an insulating film over the oxide semiconductor film 403 and then performing a photolithography process. By forming a resist mask on the insulating film and selectively etching it, The insulating film formed over the oxide semiconductor film 403 is appropriately etched, An island-shaped insulating film 411 can be formed as shown in FIG. 4(B).

[0244] The source electrode layer 407a and the drain electrode layer 407b are in contact with the oxide semiconductor film 403 and the insulating film 411. The source electrode layer 407a is formed by a conductive metal film 406a. The drain electrode layer 407b is a laminated structure of the metal film 406b and the conductive film 405b. It is a laminated structure.

[0245] The metal films 406a and 406b in contact with the oxide semiconductor film 403 and the insulating film 411 are made of an oxide semiconductor. In order to prevent oxygen from being extracted from the conductive film 403, It has higher oxidation resistance than other metal elements (the Gibbs free energy of the oxidation reaction of molybdenum is Specifically, copper, silver, ruthenium, iridium, etc. The metal films 406a and 406b contain a metal element selected from a group consisting of fluorine and fluorine atoms, and a metal element selected from a group consisting of fluorine atoms and fluorine atoms, which is different from the metal element contained in the oxide semiconductor film 403. By using a metal having oxidation resistance, oxygen vacancies in the oxide semiconductor film 403 increase. This can be suppressed.

[0246] In addition, the metal films 406a and 406b are less likely to be oxidized than the oxide semiconductor film 403. Since oxygen diffusion into the metal films 406a and 406b can be suppressed, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 4 3. Resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0247] In addition, a gold film having a work function of ±0.2 eV with respect to the electron affinity of the oxide semiconductor film 403 is used. By selecting metal films 406a, 406b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 403 is in contact with the source electrode layer 407a and the drain electrode layer 407b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0248] The conductive films 405a and 405b stacked with the metal films 406a and 406b are made of gold. It is preferable that the material does not form an oxide film at the interface with the metal films 406a and 406b. The conductive films 405a and 405b can be made of a metal film 406a. In addition to the materials that can be used in 406b, gold, platinum, titanium, tungsten, nitride Examples of the conductive film include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 405a and 405b are configured in a single layer structure or a laminated structure. In the case of a laminated structure, for example, It can be made up of a tantalum nitride film and a tungsten film.

[0249] In the transistor 430 shown in FIG. 4, the source electrode layer 407a and the drain electrode layer 40 7b is formed so that the metal films 406a and 406b and the conductive films 405a and 405b are made of the same material. The case where the metal films 406a and 406b and the conductive films 405a and 406b are formed as shown in FIG. 05b may be made of a different material.

[0250] In the transistor 430 shown in FIG. 4, the metal films 406a and 406b are partially For example, the metal films 406a and 406b may be made of ruthenium. In this case, ruthenium oxide may be formed in a part of the metal film. Even if formed, the resistivity of ruthenium oxide is 3.5 × 10 -5 [cmΩ](30 0K), and high resistance components are not formed in the source electrode layer and the drain electrode layer. It's nice.

[0251] Next, referring to FIG. 5, a transistor that is partially different from the transistor 430 shown in FIG. I will explain.

[0252] 5A is a plan view of the transistor 440, and FIG. 5B is a plan view of the transistor 440. 5(A) is a cross-sectional view at E2 (cross-sectional view in the channel length direction). In order to avoid this, some of the components of the transistor 420 (for example, the gate insulating film 4 The illustration omits the numbers 02, 03, etc.

[0253] The transistor 440 shown in FIG. 5 differs from the transistor 430 shown in FIG. 4 in the following points: An insulating film 411 is provided to cover the oxide semiconductor film 403. The oxide semiconductor film 403, the source electrode layer 407a, and the drain electrode layer 407b are exposed through the openings. The insulating film 411 is in contact with the oxide semiconductor film 403. By providing the oxide semiconductor film 40, the oxide semiconductor film 40 can be formed in a state where the oxide semiconductor film 40 is thin. 3) To better prevent the inclusion of hydrogen, water, and elements contained in etching gases It is possible.

[0254] Note that the transistor 440 is the same as the transistor 430 except for the shape of the insulating film 411. Since the transistors are similar, the description of the transistor 430 can be referred to.

[0255] As described above, the metal films 406a and 406b in contact with the oxide semiconductor film 403 are The oxide semiconductor film 403 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 403 (at least indium). (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) This prevents oxygen from being extracted from the oxide semiconductor film 403. As a result, the source electrode layer 407a, the drain electrode layer 407b, and the oxide semiconductor film 403 This suppresses the increase in oxygen vacancies at the interface between the semiconductor and the transistor, thereby reducing the fluctuation in the threshold voltage of the transistor. It can be suppressed.

[0256] In addition, the metal films 406a and 406b are less likely to be oxidized than the oxide semiconductor film 403. Since oxygen diffusion into the metal films 406a and 406b can be suppressed, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 4 3. Resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0257] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0258] (Fourth embodiment) In this embodiment, another mode of a semiconductor device will be described with reference to FIGS. 6 and 7. It should be noted that the same parts as those in the above embodiments or parts having similar functions will be omitted. The explanation will be omitted.

[0259] The transistor 450 shown in FIG. 6 is an example of a bottom-gate transistor. 6A is a plan view of the transistor 450, and FIG. 6B is a plan view of F1-F2 in FIG. 6A. 6(A) is a cross-sectional view (cross-sectional view in the channel length direction) at (A). To avoid this, some of the components of the transistor 450 (for example, the gate insulating film 402 etc.) are omitted in the illustration.

[0260] The transistor 450 shown in FIGS. 6A and 6B is provided over a substrate 400 having an insulating surface. a gate electrode layer 401 formed on the gate electrode layer 401; and a gate insulating film 402 formed on the gate electrode layer 401. , a source electrode layer 407a and a drain electrode layer 407b provided over the gate insulating film 402. and a gate insulating film 402, a source electrode layer 407a, and a drain electrode layer 407b. The transistor 450 has an oxide semiconductor film 403 formed thereon. An insulating film 408 and a planarizing insulating film 409 are provided.

[0261] As shown in FIGS. 6A and 6B, the transistor 450 has a first insulating film in contact with the oxide semiconductor film 403. The source electrode layer 407a and the drain electrode layer 407b have a stacked structure. The source electrode layer 407a has a laminated structure of a conductive film 405a and a metal film 406a, and the drain electrode layer 40 7b is a laminated structure of a conductive film 405b and a metal film 406b.

[0262] The transistor 450 shown in FIG. 6B has the same structure as the transistor 410 shown in FIG. The difference is that the oxide semiconductor film 403 is formed between the source electrode layer 407a and the drain electrode layer 407b. In FIG. 1B, the source electrode layer 407a and the drain electrode layer 407 6B, the source electrode layer 403 is in contact with the oxide semiconductor film 403. The drain electrode layer 407a and the drain electrode layer 407b are in contact with the bottom surface of the oxide semiconductor film 403.

[0263] In the structure shown in FIG. 6B, the metal films 406a and 406b are made of copper, silver, ruthenium, or the like. By using titanium, iridium, or the like, oxygen can be extracted from the oxide semiconductor film 403. Therefore, an increase in oxygen vacancies in the oxide semiconductor film 403 can be suppressed. Therefore, the threshold voltage of the transistor 410 can be prevented from shifting in the negative direction. can.

[0264] In addition, the metal films 406a and 406b are less likely to be oxidized than the oxide semiconductor film 403. Since oxygen diffusion into the metal films 406a and 406b can be suppressed, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 4 3. Resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0265] In addition, a gold film having a work function of ±0.2 eV with respect to the electron affinity of the oxide semiconductor film 403 is used. By selecting metal films 406a, 406b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 403 is in contact with the source electrode layer 407a and the drain electrode layer 407b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0266] In addition, the conductive films 405a and 405b are oxidized at the interfaces with the metal films 406a and 406b. It is preferable that the conductive films 405a and 405b are made of a material that does not form a conductive film. In addition to the materials that can be used for the metal films 406a and 406b, Gold, platinum, titanium, tungsten, titanium nitride, molybdenum nitride, tungsten nitride, nitride As shown in FIG. 6B, the conductive films 405a and 405b are In order to be in contact with the oxide semiconductor film 403 on the surface, gold, platinum, titanium nitride, molybdenum nitride, or the like is used. It is more preferable to use tantalum nitride.

[0267] In this embodiment, in the transistor 450 shown in FIGS. 6A and 6B, The layer 407a and the drain electrode layer 407b are formed by the metal films 406a and 406b and the conductive film 405 This shows the case where 405a and 405b are made of the same material. The interfaces between the metal films 406a and 406b and the conductive films 405a and 405b are indicated by dotted lines. In the case of the transistor 450 shown in FIG. 6, for example, the metal films 406a and 406b are The conductive films 405a and 405b can be made of ruthenium.

[0268] In the transistor 450 shown in FIGS. 6A and 6B, the metal films 406a and 406 For example, metal oxide may be formed in part of the metal films 406a and 406b. When the metal film is made of ruthenium, ruthenium oxide may be formed in part of the metal film. Even if ruthenium oxide is formed, the resistivity of ruthenium oxide is 3.5 × 10 -5 [ cmΩ] (300K), and no high resistance components were formed in the source and drain electrode layers. Therefore, it is preferable.

[0269] Next, referring to FIG. 7, a transistor that is partially different from the transistor 450 shown in FIG. I will explain.

[0270] 7A is a plan view of the transistor 460, and FIG. 7B is a plan view of the G1- 7(A) is a cross-sectional view at G2 (cross-sectional view in the channel length direction). In order to avoid this, some of the components of the transistor 460 (for example, the gate insulating film 4 The illustration omits the numbers 02, 03, etc.

[0271] In the transistor 460 shown in FIGS. 7A and 7B, the source electrode layer 417a and the drain electrode layer The inner electrode layer 417b is made up of metal films 406a and 406b and conductive films 415a and 415b. Therefore, the metal films 406a and 406b and the conductive film The interfaces with the conductive films 415a and 415b are indicated by solid lines. The conductive films 405a and 405b are formed using a material similar to that of the conductive films 405a and 405b, and have a single-layer structure or a stacked-layer structure. 6B, in FIG. 7B, the conductive films 415a and 415b are also formed on the side surfaces thereof. In order to be in contact with the oxide semiconductor film 403, gold, platinum, titanium nitride, molybdenum nitride, It is more preferable to use tantalum nitride. For example, in the case of transistor 460 shown in FIG. For example, ruthenium is used for the metal films 406a and 406b, and the conductive films 415a and 415b are made of ruthenium. For example, tantalum nitride can be used.

[0272] Note that in the transistor 460, the source electrode layer 417a and the drain electrode layer 417b Other than the above, the configuration is the same as that of the transistor 450. Please take this into consideration.

[0273] As described above, the metal films 406a and 406b in contact with the oxide semiconductor film 403 are The oxide semiconductor film 403 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 403 (at least indium). The Gibbs free energy of oxidation reaction of aluminum, gallium, and zinc is higher than that of the metals This can prevent oxygen from being extracted from the oxide semiconductor film 403. As a result, an increase in oxygen vacancies in the oxide semiconductor film 403 can be suppressed, and the threshold of the transistor can be improved. This can prevent the low voltage from shifting in the negative direction.

[0274] Furthermore, the metal films 406a and 406b are resistant to oxidation, and no oxidation is present in the metal films 406a and 406b. Since the diffusion of elements can be suppressed, high resistance components are not formed in the metal films 406a and 406b. Therefore, the oxide semiconductor film 403 and the source electrode layer 417 can be prevented from being broken. Since the resistance due to the drain electrode layer 417a and the drain electrode layer 417b can be reduced, This can suppress a decrease in the on-state current of the transistor.

[0275] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0276] (Embodiment 5) In this embodiment, an example of a method for manufacturing a semiconductor device including the transistor 450 shown in FIGS. This will be described with reference to FIG.

[0277] First, a gate electrode layer 401 and a gate electrode layer 402 are formed on a substrate 400 according to the process described with reference to FIG. A gate insulating film 402 is formed (see FIG. 8(A)).

[0278] Next, a source electrode layer and a drain electrode layer (which will be formed later in the same layer) are formed on the gate insulating film 402. A conductive film 405 and a metal oxide film 404 are formed (including the wiring to be formed) (FIG. 8( See B).

[0279] The conductive film 405 may be formed using a material that can withstand heat treatment to be performed later. It is preferable that the conductive film be made of a material that does not form an oxide film at the interface with the metal oxide film. Examples of 405 include gold, platinum, copper, silver, ruthenium, iridium, titanium, and tungsten. Examples include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. However, it is more preferable to use copper, silver, ruthenium, or iridium. It is preferable that the thickness of the metal oxide film 404 is larger than that of the metal oxide film 404, and the metal oxide film 404 is formed in a single layer structure or a laminated structure. can be.

[0280] The thickness of the conductive film 405 is set to 50 nm or more and 600 nm or less. The film can be formed by appropriately using a sputtering method, a CVD method, or the like.

[0281] In addition, the metal oxide film 404 may be a metal oxide film having a higher reducing property than the oxide semiconductor film 403. The metal oxide film having a higher reduction property than the oxide semiconductor film 403 is a metal oxide film as shown in FIG. It is more reducing than indium oxide, gallium oxide, zinc oxide, and tin oxide (i.e. and higher than the Gibbs free energies of the oxidation reactions of indium, gallium, zinc, and tin. ) Any metal oxide may be used. Specifically, copper oxide, silver oxide, ruthenium oxide, iridium oxide, The metal oxide film 404 is formed to have a single layer structure or a multilayer structure.

[0282] The thickness of the metal oxide film 404 is 1 nm or more and 50 nm or less, preferably 1 nm or more and 30 nm or less. The thickness of the metal oxide film 404 is preferably 5 nm or more and 10 nm or less. The film can be formed by appropriately using a sputtering method, a CVD method, or the like.

[0283] Next, a resist mask is formed on the metal oxide film 404 by a photolithography process. Selective etching is performed to remove the metal oxide films 404a and 404b, the conductive film 405a, and The metal oxide films 404a and 404b and the conductive film 405b are formed (see FIG. 8B). After forming 405a and 405b, the resist mask is removed.

[0284] Next, an oxide semiconductor film 404a, 404b, and the gate insulating film 402 are formed on the metal oxide films 404a, 404b, and the gate insulating film 402. The oxide semiconductor film 413 is formed on the metal oxide film 4 (see FIG. 8C). It can also be said that it has lower reducing properties than 04a and 404b.

[0285] Next, the conductive films 405a and 405b, the metal oxide films 404a and 404b, and the oxide semiconductor Heat treatment is performed on the film 413. The material and deposition method of the oxide semiconductor film 413 are shown in FIG. The description of the oxide semiconductor film 403 shown in 2. can be referred to.

[0286] By performing heat treatment while the metal oxide film 404 and the oxide semiconductor film 413 are in contact with each other, Oxygen is released from the metal oxide films 404a and 404b and supplied to the oxide semiconductor film 413. When oxygen is supplied to the oxide semiconductor film 413, In addition, the metal oxide film 412 has a higher reducing property than the oxide semiconductor film 413. The oxide films 404a and 404b are reduced to form metal films 406a and 406b.

[0287] In FIG. 8D, the metal oxide films 404a and 404b are all metal films 406a and 406b. The case where the metal oxide films 404a and 404b are reduced to oxide 406b has been described. Only the vicinity of the interface with the semiconductor film 413 is reduced to form metal films 406a and 406b. For example, the metal oxide film 404a, 404b may remain in the other areas. When ruthenium oxide is used, only the area near the interface is reduced to ruthenium, and the interface adhesion Ruthenium oxide may remain in areas other than the interface. Even if the resistivity of ruthenium oxide is 3.5×10 -5 [cmΩ](300K) This is preferable because high resistance components are not formed in the source electrode layer and the drain electrode layer.

[0288] In addition, the metal oxide films 404a and 404b are reduced to form a metal film 40 The oxide semiconductor film 413 is made of a metal element. In other words, the metal films 406a and 406b are films in which oxygen is less likely to diffuse.

[0289] Next, a resist mask is formed over the oxide semiconductor film 413 by a photolithography process. Then, selective etching is performed to form an island-shaped oxide semiconductor film 403. After the semiconductor film 403 is formed, the resist mask is removed.

[0290] Through the above steps, a transistor 450 according to one embodiment of the present invention is manufactured (see FIG. 8E). ).

[0291] Next, an insulating film 408 and a planarization insulating film 409 are formed to cover the transistor 450. The materials and forming methods of the insulating film 408 and the planarizing insulating film 409 are shown in FIG. Since this is understandable, detailed explanations will be omitted.

[0292] Through the above steps, a semiconductor device including the transistor 450 shown in FIG. 6B is manufactured. .

[0293] In this embodiment, the conductive films 405a and 405b and the metal oxide films 404a and 404b are In the above description, the case where heat treatment is performed after the oxide semiconductor film 413 is formed is described. One embodiment is not limited to this. After processing into the oxide semiconductor film 403, heat treatment may be performed. In the films 404a and 404b, the oxide semiconductor film 403 is in contact with the oxide semiconductor film 403. However, reduction may not occur in a region that is not in contact with the oxide semiconductor film 403. It is only necessary that the metal oxide film be reduced in a region in contact with the oxide semiconductor film 403.

[0294] In addition, the metal films 406a and 406b and the conductive films 405a and 405b are made of different materials. By selecting materials in this manner, the transistor 460 shown in FIG. 7 can be fabricated. For example, ruthenium oxide is used as the metal oxide film 404, and nitrogen oxide is used as the conductive film 405. By using tantalum nitride and performing heat treatment, a laminated structure of ruthenium and tantalum nitride is formed. These are used as the source electrode layer 417a and the drain electrode layer 417b. In addition, at the interfaces between the metal films 406a and 406b and the conductive films 415a and 415b, In this case, an oxide film is not formed, which is preferable. At the interface between the surface and the oxide semiconductor film 403, oxygen is extracted from the oxide semiconductor film 403. This is more preferable because it can prevent the material from being damaged.

[0295] The metal films 406a and 406b and the conductive films 405a and 405b are made of the same material. Even if the material is selected as the metal oxide film 404, the metal films 406a and 406b are The conductive films 405a and 405b are formed by reduction. Therefore, when the metal films 406a and 406b and the conductive films 405a and 405b have different physical properties, For example, the metal films 406a and 406b may have a larger thickness than the conductive films 405a and 405b. The density may be low. The film density can be measured, for example, by X-ray reflectivity (XRR). It can be measured by the endoscopic method.

[0296] In this embodiment, the source electrode layer 407a and the drain electrode layer 407b are formed of a metal film. Although the case where the insulating film 406a and the insulating film 406b are formed by the conductive films 405a and 405b has been described, However, one embodiment of the present invention is not limited to this. For example, the conductive film 405 does not necessarily have to be formed.

[0297] According to this embodiment, the metal oxide film 404 in contact with the oxide semiconductor film 403 is subjected to heat treatment. By reducing the metal oxide film 404 with oxygen, oxygen is released from the metal oxide film 404, and the oxide semiconductor film 40 3. As a result, the source electrode layer 407a and the drain electrode layer 40 Oxygen vacancies at the interface between 7b and the oxide semiconductor film 403 can be reduced. This suppresses the negative shift of the threshold voltage of the transistor 450. This can be done.

[0298] The metal film 406 formed by reducing the metal oxide film 404 is an oxide film. The metal film 403 has higher oxidation resistance than the metal element contained in the semiconductor film 403. The metal films 406a and 406b are formed on the source electrode layer 40. By using the metal films 406a and 406b as the drain electrode layer 407a and the drain electrode layer 407b, Therefore, the formation of a high-resistance component in the oxide semiconductor film 403 can be suppressed. Therefore, the resistance due to the source electrode layer 407a and the drain electrode layer 407b can be reduced. Therefore, a decrease in the on-state current of the transistor 410 can be suppressed.

[0299] In addition, a gold film having a work function of ±0.2 eV with respect to the electron affinity of the oxide semiconductor film 403 is used. By selecting a metal film 406 (e.g., copper, silver, ruthenium, etc.), an oxide semiconductor The contact resistance between the film 403 and the source electrode layer 407a and the drain electrode layer 407b is reduced. This is also preferable because the oxide semiconductor film 403, the source electrode Since the resistance due to the drain electrode layer 407a and the drain electrode layer 407b can be reduced, A decrease in the on-state current of the transistor can be suppressed.

[0300] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0301] (Embodiment 6) In this embodiment, one mode of a semiconductor device will be described with reference to FIGS. 1 illustrates a transistor including an oxide semiconductor film as an example of a semiconductor device.

[0302] The transistor 110 shown in FIG. 10 is an example of a top-gate transistor. 10(A) is a plan view of the transistor 110, and FIG. 10(B) is a plan view of the H of FIG. 10(A). 1-H2 (cross-sectional view in the channel length direction). For simplicity, some of the components of transistor 110 (e.g., gate insulator) are 1, the insulating film 111, the insulating film 106, etc. are omitted from the illustration.

[0303] The transistor 110 shown in FIGS. 10A and 10B is provided over a substrate 100 having an insulating surface. The oxide semiconductor film 103 is covered with a gate insulating film 104. 11, a gate electrode layer 105 provided on the gate insulating film 111, and the gate electrode layer 105 The insulating film 106 is formed on the gate electrode layer 105 and the insulating film 106. The oxide semiconductor film 103 and the gate insulating film 104 are formed on the gate insulating film 104. The source electrode layer 11 is in contact with the gate insulating film 111 and the sidewall insulating films 109a and 109b. 6a and the drain electrode layer 116b. An insulating film 101 serving as a base film is provided between the transistor 110 and the insulating film 101. An interlayer insulating film 115 is provided.

[0304] The oxide semiconductor film 103 has a channel forming region provided in a region overlapping with the gate electrode layer 105. A region 108 and a region 107 containing a dopant provided on either side of the channel forming region 108 The dopant-containing regions 107a and 107b are channel forming regions. This is a region with a lower resistance than 108. The metal film may also be referred to as a conductive film.

[0305] The transistor 110 shown in FIGS. 10A and 10B has a source electrode in contact with the oxide semiconductor film 103. The source electrode layer 116a and the drain electrode layer 116b are configured in a stacked structure. The layer 116a has a laminated structure of a metal film 114a and a conductive film 113a, and the drain electrode layer 116b has a , a laminated structure of a metal film 114b and a conductive film 113b.

[0306] The metal films 114a and 114b in contact with the oxide semiconductor film 103 shown in FIG. In order to prevent oxygen from being extracted from the oxide semiconductor film 103, Metals that are more oxidation-resistant than the metal elements used are used.

[0307] The metal films 114a and 114b in contact with the oxide semiconductor film 103 are In order to prevent oxygen from being extracted, a metal element contained in the oxide semiconductor film 103 is Metals with oxidation resistance (higher than the Gibbs free energy of the oxidation reaction of molybdenum) are used. Specifically, copper, silver, ruthenium, iridium, etc. are used. a and 114b have higher oxidation resistance than the metal element contained in the oxide semiconductor film 103. By using a metal, an increase in oxygen vacancies in the oxide semiconductor film 103 can be suppressed. This can be done.

[0308] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor 110 can be suppressed.

[0309] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting metal films 114a, 114b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 103 is in contact with the source electrode layer 116a and the drain electrode layer 116b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 116a and the drain electrode layer 116b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0310] For example, if the electron affinity of an In-Ga-Zn oxide semiconductor is 4.6 eV, the work It is preferable to use ruthenium, which has a valence function of 4.71 eV. By using the compound semiconductor film 103 and the metal films 114a and 114b, the contact resistance can be reduced.

[0311] The conductive films 113a and 113b stacked on the metal films 114a and 114b are made of gold. It is preferable that the material does not form an oxide film at the interface with the metal films 114a and 114b. The conductive films 113a and 113b can be made of a material such as a metal film 114a. In addition to the materials that can be used for 114b, gold, platinum, titanium, tungsten, nitride Examples of conductive film include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 13a and 113b are configured with a single layer structure or a laminated structure. In the case of a laminated structure, for example, It can be made up of a tantalum nitride film and a tungsten film.

[0312] In the transistor 110 shown in FIGS. 10A and 10B, the source electrode layer 116a and the drain electrode layer The conductive layer 116b is made of the same metal films 114a and 114b as the conductive films 113a and 113b. Therefore, the metal films 114a and 11 The interfaces between the transistor 4b and the conductive films 113a and 113b are indicated by dotted lines. In the case of the sintered body 110, for example, ruthenium is used as the metal films 114a and 114b, and the conductive Ruthenium can be used for the films 113a and 113b. The drain electrode layer 116a and the drain electrode layer 116b are formed by metal films 114a and 114b, conductive films 113a, 113b may be made of a different material. In this case, for example, Ruthenium is used for the metal films 114a and 114b, and ruthenium is used for the conductive films 113a and 113b. Tantalum nitride can be used.

[0313] In the transistor 110, metal oxide is formed in part of the metal films 114a and 114b. For example, when the metal films 114a and 114b are made of ruthenium, they may be partially oxidized. Ruthenium may be formed. Ruthenium oxide may be formed in part of the metal film. Even so, the resistivity of ruthenium oxide is 3.5 × 10 -5 [cmΩ](300K) This is preferable because high resistance components are not formed in the source electrode layer 116a and the drain electrode layer 116b. It's nice.

[0314] The oxide semiconductor film 103 has an energy gap of 2.8 eV to 3.2 eV. , which is larger than the energy gap of silicon, 1.1 eV. 03 minority carriers are 10 -9 cm -3 is 10 times the intrinsic carrier density of silicon. 1 1 cm -3 is extremely small compared to

[0315] The majority carriers (electrons) in the oxide semiconductor film 103 flow only from the source of the transistor. In addition, since the channel formation region can be completely depleted, The off-state current of the transistor using the oxide semiconductor film 103 can be made extremely small. The off-state current of the transistor is 10 yA / μm or less at room temperature, and It is extremely small, less than 1zA / μm.

[0316] Therefore, the transistor including the oxide semiconductor film 103 has a small S value and is not ideal. Moreover, the transistor has high reliability.

[0317] As described above, the metal films 114a and 114b in contact with the oxide semiconductor film 103 are The oxide semiconductor film 103 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 103 (at least indium). (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) This prevents oxygen from being extracted from the oxide semiconductor film 103. As a result, the source electrode layer 116a, the drain electrode layer 116b, and the oxide semiconductor film 103 This suppresses the increase in oxygen vacancies at the interface with the semiconductor, thereby minimizing the threshold voltage of the transistor. It is possible to suppress a shift in the negative direction.

[0318] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0319] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0320] (Embodiment 7) In this embodiment, one method for manufacturing a semiconductor device including the transistor 110 shown in FIGS. An example will be described with reference to FIGS.

[0321] There is no significant limitation on the substrate that can be used for the substrate 100 having an insulating surface. In either case, it is necessary for the material to have heat resistance sufficient to withstand the subsequent heat treatment. Glass substrates such as borosilicate glass and aluminoborosilicate glass, ceramic substrates, stone A silicon substrate, a sapphire substrate, etc. can be used. Also, silicon, silicon carbide, etc. Single crystal semiconductor substrates, polycrystalline semiconductor substrates, and compound semiconductor substrates such as silicon germanium , SOI substrates, etc. can also be applied, and semiconductor elements are provided on these substrates. may be used as the substrate 100.

[0322] Alternatively, a semiconductor device may be manufactured using a flexible substrate as the substrate 100. In order to manufacture such a semiconductor device, a transistor including an oxide semiconductor film 103 is formed on a flexible substrate. Alternatively, a transistor including the oxide semiconductor film 103 may be formed on another substrate. The substrate 110 may be fabricated, and then peeled off and transferred to a flexible substrate. In order to separate and transfer the transistor including the formation substrate and the oxide semiconductor film 103 to a flexible substrate, It is advisable to provide a release layer between the substrate and the heater 110.

[0323] Next, an insulating film 101 that functions as a base film is formed over the substrate 100. For example, silicon oxide and silicon oxynitride are deposited by plasma CVD or sputtering. aluminum oxide, aluminum oxide nitride, hafnium oxide, gallium oxide, etc. Oxide insulating film, silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxynitride It is formed in a single layer structure or a laminated structure using a nitride insulating film such as silicon or a mixture of these materials. It can be achieved.

[0324] In the insulating film 101 (in the case of a stacked structure, a film in contact with the oxide semiconductor film 103), ) preferably contains at least an amount of oxygen exceeding the stoichiometric composition. For example, When a silicon oxide film is used as the insulating film 101, the amount of oxygen is set to SiO 2+α (just It is preferable that α>0.

[0325] The insulating film 101 containing a large amount (excessive amount) of oxygen, which serves as an oxygen supply source, is in contact with the oxide semiconductor film 103. By providing the insulating film 101 as the insulating layer, oxygen can be supplied to the oxide semiconductor film 103. In addition, when the oxide semiconductor film 103 is in contact with at least a part of the insulating film 101, Oxygen may be supplied to the oxide semiconductor film 103 by performing heat treatment in a low-temperature state. By using the insulating film 101 containing a large amount of oxygen, oxygen is supplied to the oxide semiconductor film 103. Therefore, oxygen vacancies in the oxide semiconductor film 103 can be reduced.

[0326] In this embodiment, the insulating film 101 is formed by sputtering an acid film having a thickness of 300 nm. A silicon dioxide film is formed.

[0327] Before forming the insulating film 101 that functions as a base film, the substrate 100 is subjected to plasma As the plasma treatment, for example, argon gas is introduced to generate plasma. Inverse sputtering can be performed by generating a In an atmosphere, a voltage is applied to the substrate side using an RF power supply to form plasma near the substrate, and the surface is This is a method of modifying the surface. Note that nitrogen, helium, oxygen, etc. can be used instead of the argon atmosphere. When reverse sputtering is performed, the powdery material (particulate matter) adhering to the surface of the substrate 100 is removed. It is possible to remove dust (also called dirt or garbage).

[0328] Here, in order to improve the flatness of the surface of the oxide semiconductor film 102 to be formed later, the insulating film 10 In the method of manufacturing the semiconductor device according to the present invention, a region in contact with the oxide semiconductor film 102 is subjected to planarization treatment. The planarization treatment is not particularly limited, but may be a polishing treatment (for example, chemical mechanical polishing). Chemical Mechanical Polishing (CMP), Dry etching and plasma treatment can be used.

[0329] The plasma treatment may be, for example, a reverse plasma treatment in which argon gas is introduced to generate plasma. Reverse sputtering is a process in which RF is applied to the substrate side in an argon atmosphere. This method involves applying voltage using a power supply to generate plasma near the substrate, thereby modifying the surface. Instead of the argon atmosphere, nitrogen, helium, oxygen, etc. may be used. When cleaning is performed, powdery substances (also called particles or dust) adhering to the surface of the insulating film 101 are removed. (U) can be removed.

[0330] As a planarization process, polishing, dry etching, and plasma treatment may be performed multiple times. In addition, when the steps are combined, there is no particular limitation on the order of the steps. It is not limited to this value, and may be set appropriately according to the unevenness of the surface of the insulating film 101.

[0331] By performing a planarization process on the insulating film 101, the average surface roughness (R a) is set to 1 nm or less, preferably 0.3 nm or less, and more preferably 0.1 nm or less. It is possible.

[0332] Next, the oxide semiconductor film 102 is formed over the insulating film 101 (see FIG. 11A).

[0333] The oxide semiconductor used for the oxide semiconductor film 102 is the oxide semiconductor film shown in FIG. Detailed explanation is omitted here, as the description in 403 can be taken into consideration.

[0334] The oxide semiconductor film 102 may be single-crystalline, polycrystalline (also referred to as polycrystalline), or amorphous. Which state to take?

[0335] The oxide semiconductor film 102 is preferably a CAAC-OS film.

[0336] The thickness of the oxide semiconductor film 102 is 1 nm to 30 nm (preferably 5 nm to 10 nm). m or less), and sputtering method, MBE (Molecular Beam Epita xy method, plasma CVD method, pulsed laser deposition method, ALD (Atomic Layer Deposition A deposition method or the like can be used as appropriate. In this case, multiple substrate surfaces are set approximately perpendicular to the sputtering target surface. Alternatively, the film may be formed using a sputtering apparatus that forms a film in this state.

[0337] The concentration of hydrogen or water in the oxide semiconductor film 103 is preferably as low as possible. When the hydrogen concentration is high, the hydrogen atoms bond with the elements contained in the oxide semiconductor, and the hydrogen atoms are separated. This is because the part acts as a donor, generating electrons as carriers.

[0338] Therefore, in the process of forming the oxide semiconductor film 102, hydrogen, Alternatively, in order to minimize the inclusion of water, pretreatment before the formation of the oxide semiconductor film 102 may be performed. Then, the substrate on which the insulating film 101 is formed is preheated in a preheating chamber of the sputtering device. It is preferable to desorb and exhaust impurities such as hydrogen and moisture adsorbed on the substrate and insulating film 101. It is preferable that the exhaust means provided in the preheating chamber is a cryopump.

[0339] Note that the oxide semiconductor film 102 is formed under conditions in which a large amount of oxygen is contained (for example, under conditions in which oxygen (e.g., sputtering under a 100% oxygen atmosphere) (preferably, the oxide semiconductor has a stoichiometric composition in a crystalline state, and the content of oxygen is It is preferable to use a membrane containing regions in which the metal is in excess.

[0340] In this embodiment, the oxide semiconductor film 102 is formed by a sputtering device having a DC power supply. A 10 nm thick In-Ga-Zn oxide film was deposited using a sputtering method with a laser scanning device. In this embodiment, an IGZO film is formed using a material of In:Ga:Zn=3:1:2. An In-Ga-Zn oxide target with a molecular ratio of 1000 nm is used.

[0341] The oxide semiconductor film 102 is formed using a sputtering gas containing hydrogen, water, a hydroxyl group, or It is preferable to use a high-purity gas from which impurities such as hydrides have been removed.

[0342] The substrate is held in a film-forming chamber that is kept in a reduced pressure state, and the remaining moisture in the film-forming chamber is removed. The sputtering gas from which hydrogen and moisture have been removed is introduced, and the substrate 10 is sputtered using the target. In order to remove residual moisture in the deposition chamber, an oxide semiconductor film 102 is formed on the substrate. type vacuum pumps, such as cryopumps, ion pumps, titanium sublimation pumps It is preferable to use a turbo molecular pump with a cold trap as the exhaust means. The deposition chamber evacuated using a cryopump may be, for example, Hydrogen atoms, compounds containing hydrogen atoms such as water (H2O) (preferably compounds containing carbon atoms) Since the gases (e.g., gases) are exhausted, hydrogen contained in the oxide semiconductor film 102 formed in the deposition chamber is , the concentration of impurities such as water, hydroxyl groups or hydrides can be reduced.

[0343] In addition, the insulating film 101 and the oxide semiconductor film 102 are continuously formed without exposing the insulating film 101 to the air. It is preferable to form the insulating film 101 and the oxide semiconductor layer without exposing the insulating film 101 to the air. When the film 102 is formed continuously, impurities such as hydrogen and moisture are adsorbed on the surface of the insulating film 101. This can prevent this.

[0344] Next, a resist mask is formed over the oxide semiconductor film by a photolithography process. Then, etching is performed to form an island-shaped oxide semiconductor film 103 (see FIG. 11B). After the island-shaped oxide semiconductor film 103 is formed, the resist mask is removed.

[0345] In addition, a resist mask for forming the island-shaped oxide semiconductor film 103 was formed by an ink-jet method. If the resist mask is formed by the inkjet method, a photomask can be used. Therefore, the manufacturing cost can be reduced.

[0346] Note that the oxide semiconductor film 102 can be etched by either dry etching or wet etching. For example, when the oxide semiconductor film 102 is wet-etched, The etching solution used may be a mixture of phosphoric acid, acetic acid, and nitric acid. ITO-07N (manufactured by Kanto Chemical Co., Ltd.) may also be used. Inductively Coupled Plasma Etching Method The etching process may be performed by dry etching.

[0347] Further, excess hydrogen (including water and a hydroxyl group) is removed (dehydrated or The temperature for the heat treatment is 300°C or higher and 700°C or lower. The temperature should be below ℃ or below the distortion point of the substrate. The heat treatment should be carried out under reduced pressure or in a nitrogen atmosphere. It is possible.

[0348] In addition, when a crystalline oxide semiconductor film is used as the oxide semiconductor film 103, Heat treatment may be carried out.

[0349] In this embodiment, the substrate is placed in an electric furnace, which is a type of heat treatment apparatus, and the oxide semiconductor film 1 03 at 450°C for 1 hour in a nitrogen atmosphere, and then at 450°C in a nitrogen and oxygen atmosphere. Heat treatment is carried out at ℃ for 1 hour.

[0350] The heat treatment device is not limited to an electric furnace, and may be a heat treatment device using heat conduction or heat from a heat source such as a resistance heating element. A device that heats the object to be treated by radiation may be used. For example, a lamp-driven thermal analyzer (LRTA) Rapid Thermal Anneal (GRTA) equipment, RTA (Rapid Thermal Anneal) equipment, etc. The LRTA device can be used with halogen lamps, metal halide lamps, etc. lamp, xenon arc lamp, carbon arc lamp, high-pressure sodium lamp, high-pressure mercury lamp It is a device that heats the object to be treated by radiating light (electromagnetic waves) emitted from a lamp or other lamp. The GRTA device is a device that uses high-temperature gas to perform heat treatment. Inert gases such as argon or nitrogen that do not react with the material to be treated by heat treatment An active gas is used.

[0351] For example, as a heat treatment, the substrate is placed in an inert gas heated to a high temperature of 650 to 700°C. After heating for several minutes, GRTA may be performed in which the substrate is taken out of the inert gas.

[0352] In the heat treatment, nitrogen or a rare gas such as helium, neon, or argon is used. It is preferable that the nitrogen or hydrogen introduced into the heat treatment device is not contained. The purity of rare gases such as sodium, neon, and argon is preferably 6N (99.9999%) or higher. is 7N (99.99999%) or more (i.e., impurity concentration is 1 ppm or less, preferably 0.1 It is preferable to set the concentration to less than 1 ppm.

[0353] After the oxide semiconductor film 103 is heated by the heat treatment, high-purity oxygen gas and high-purity SiO 2 are introduced into the same furnace. nitrous oxide gas or ultra dry air (CRDS (cavity ring down laser separation) When measured using a dew point meter using the optical method, the moisture content is 20 ppm (-55°C in dew point equivalent). air, preferably 1 ppm or less, more preferably 10 ppb or less, may be introduced. It is preferable that the oxygen gas or nitrous oxide gas does not contain water, hydrogen, etc. Alternatively, the purity of the oxygen gas or nitrous oxide gas introduced into the heat treatment device is preferably 6N or more. or 7N or more (i.e., impurity concentration in oxygen gas or nitrous oxide gas is 1 ppm or less, Preferably, the concentration is 0.1 ppm or less. This action simultaneously reduces impurities through the removal process of dehydration or dehydrogenation treatment. By supplying oxygen, which is the main component of oxide semiconductors, Oxygen vacancies in the semiconductor film 103 can be reduced.

[0354] Note that the timing of heat treatment for dehydration or dehydrogenation is determined based on the time when the oxide semiconductor film is heated. The step may be performed after the formation of the oxide semiconductor film 102 or after the formation of the island-shaped oxide semiconductor film 103.

[0355] The heat treatment for dehydration or dehydrogenation may be carried out multiple times, or may be carried out in combination with other heat treatments. You can sleep.

[0356] The heat treatment for dehydration or dehydrogenation is performed to form the oxide semiconductor film 103 into an island shape. If the oxide semiconductor film 102 covers the insulating film 101, the insulating film 101 This can prevent the contained oxygen from being released to the outside due to the heat treatment.

[0357] Next, an insulating film 101 which will later become a gate insulating film is formed on the insulating film 101 and the oxide semiconductor film 103. 4 is formed (see FIG. 11(C)).

[0358] In order to improve the coverage of the insulating film 104, the surface of the oxide semiconductor film 103 is subjected to a planarization treatment. In particular, when a thin insulating film is used as the insulating film 104, the oxide semiconductor It is preferable that the surface of the conductor film 103 has good flatness.

[0359] The thickness of the insulating film 104 is set to 1 nm or more and 20 nm or less, and the insulating film 104 is formed by a sputtering method, an MBE method, or a plasma method. The plasma CVD method, pulsed laser deposition method, ALD method, etc. can be used as appropriate. The coating film 104 is formed by setting a plurality of substrate surfaces approximately perpendicular to the sputtering target surface. Alternatively, the film may be formed using a sputtering device that forms a film in a cooled state.

[0360] The insulating film 104 may be made of silicon oxide, gallium oxide, aluminum oxide, silicon nitride, or the like. Silicon, silicon oxynitride, aluminum oxynitride, or silicon nitride oxide The insulating film 104 can be made of hafnium oxide, yttrium oxide, or the like. Hafnium silicate (HfSi x O y(x>0, y>0)), nitrogen-added ha HfSiO x N y (x>0, y>0)), hafnium aluminate (HfAl x O y (x>0, y>0)), using high-k materials such as lanthanum oxide The insulating film 104 is formed by simply using the above-mentioned material. It can be formed to have a layered structure or a laminated structure.

[0361] In this embodiment, a silicon oxynitride film is formed to a thickness of 20 nm by plasma CVD.

[0362] Next, a gate electrode layer (including wiring formed in the same layer) is formed on the insulating film 104. After forming the conductive film, an insulating film is formed. Then, the insulating film is formed by a photolithography process. A resist mask is formed on the film, and selective etching is performed to remove the gate electrode layer 105 and the insulating film. The insulating film 106 is formed by laminating (see FIG. 11(D)).

[0363] The material of the gate electrode layer 105 is molybdenum, titanium, tantalum, tungsten, aluminum, or the like. Metallic materials such as aluminum, copper, chromium, neodymium, scandium, etc., or alloys containing these as their main components The gate electrode layer 105 can be formed using a gold material. Semiconductor films such as element-doped polycrystalline silicon films, nickel silicide, etc. The gate electrode layer 105 may be formed to have a single layer structure or a stacked layer structure. will be done.

[0364] The gate electrode layer 105 is made of an indium tin oxide or tungsten oxide. Indium oxide, indium zinc oxide with tungsten oxide, indium zinc oxide with titanium oxide Indium oxide, indium tin oxide with titanium oxide, indium oxide zinc oxide, silicon oxide Conductive materials such as indium tin oxide doped with silicon can also be used. A laminated structure of a conductive material and the above-mentioned metal material may also be used.

[0365] The gate electrode layer 105 in contact with the insulating film 104 is made of a metal oxide containing nitrogen, specifically These include nitrogen-containing In-Ga-Zn-O films, nitrogen-containing In-Sn-O films, and nitrogen-containing In-Ga-O films containing nitrogen, In-Zn-O films containing nitrogen, Sn-O films containing nitrogen, In-O films containing InN and SnN, etc., can be used. The film has a work function of 5 eV (electron volts), preferably 5.5 eV (electron volts) or more. Therefore, when the gate electrode layer is used, the threshold voltage of the transistor can be reduced. This can be made positive, and a so-called normally-off switching element can be realized.

[0366] The insulating film 106 may be formed of silicon oxide, silicon oxynitride, aluminum oxide, or silicon oxynitride. Aluminum, silicon nitride, aluminum nitride, silicon nitride oxide, aluminum nitride oxide The insulating film 106 can be formed by a plasma CVD method or The film can be formed by sputtering or the like.

[0367] Next, using the gate electrode layer 105 and the insulating film 106 as a mask, an acid A dopant is added to the nitride semiconductor film 103, and regions 107a and 107b containing the dopant are formed. (See FIG. 11(E)).

[0368] The dopant is an element that changes the electrical conductivity of the oxide semiconductor film 103. Examples include group 15 elements (e.g., nitrogen (N), phosphorus (P), arsenic (As), and antimony). (Sb)), boron (B), aluminum (Al), argon (Ar), helium (He ), neon (Ne), indium (In), fluorine (F), chlorine (Cl), titanium (Ti ), and zinc (Zn).

[0369] Depending on the doping method, the dopant passes through another film (the insulating film 104 in this embodiment) and The dopant can be added to the oxide semiconductor film 103. Ion implantation, ion doping, plasma immersion ion implantation, etc. In this case, the dopant may be a simple ion, a fluoride, or a salt. It is preferable to use ions of chlorides.

[0370] The dopant introduction process involves various injection conditions such as acceleration voltage and dose amount, as well as the thickness of the film through which the dopant is passed. In this embodiment, phosphorus is used as the dopant, and in Phosphorus ions are implanted by the ion implantation method. The dopant dose is 1×10 13 io ns / cm 2 5x10 or more 16 ions / cm 2 The following would suffice.

[0371] By adding a dopant to the oxide semiconductor film 103, a region 107 containing the dopant is formed. a, 107b, the dopant concentration is 5 × 10 18 / cm 3 More than 1×10 22 / cm 3 Below Preferably it is below.

[0372] When dopants are added to the oxide semiconductor film 103, the substrate 100 may be heated. The treatment of introducing a dopant into the oxide semiconductor film 103 may be performed multiple times. A plurality of types of dopants may be used.

[0373] After the dopant is added, a heat treatment may be carried out. or higher and 700°C or lower, preferably 300°C or higher and 450°C or lower, for 1 hour in an oxygen atmosphere. It is also preferable to carry out the heat treatment under a nitrogen atmosphere, under reduced pressure, or in the air (ultra-dry air). That's fine.

[0374] In this embodiment, phosphorus (P) ions are implanted into the oxide semiconductor film 103 by an ion implantation method. The implantation conditions for phosphorus (P) ions are an acceleration voltage of 25 kV and a dose of 1.0 × 1 0 15 ions / cm 2 Let's say.

[0375] When the oxide semiconductor film 103 is a CAAC-OS film, the addition of a dopant partially In this case, by performing a heat treatment after the introduction of the dopant, The crystallinity of the oxide semiconductor film 103 can be restored.

[0376] By the dopant addition step, the dopant-containing regions 108 are formed on both sides of the channel forming region 108. The oxide semiconductor film 103 provided with the gate electrodes 07a and 107b is formed.

[0377] Next, an insulating film is formed on the gate electrode layer 105 and the insulating film 106, and the insulating film is etched. Then, sidewall insulating films 109a and 109b are formed. The insulating film 104 is etched using the sidewall insulating films 109a and 109b as a mask. Then, a gate insulating film 111 is formed (see FIG. 12(A)).

[0378] The sidewall insulating films 109a and 109b are formed using the same material and method as the insulating film 106. In this embodiment, the sidewall insulating films 109a and 109b A silicon oxynitride film formed by a CVD method is used as the insulating film.

[0379] Next, the oxide semiconductor film 103, the gate insulating film 111, the sidewall insulating film 109a, The source electrode layer and the drain electrode layer (and the A metal oxide film 112 and a conductive film 113 are formed to form wirings (including wirings formed in the same layer). (See Figure 12(B)).

[0380] The metal oxide film 112 is a metal oxide film having a higher reduction property than the oxide semiconductor film 103. The metal oxide film having a higher reduction property than the oxide semiconductor film 103 is a metal oxide film having a higher reduction property than the oxide semiconductor film 103, as shown in FIG. It is more reducing than indium oxide, gallium oxide, zinc oxide, and tin oxide (i.e., (higher than the Gibbs free energy of oxidation reactions of indium, gallium, zinc, and tin) Any oxide may be used. Specifically, copper oxide, silver oxide, ruthenium oxide, iridium oxide, etc. The metal oxide film 112 is formed to have a single layer structure or a multilayer structure.

[0381] The thickness of the metal oxide film 112 is 1 nm or more and 50 nm or less, preferably 1 nm or more and 30 nm or less. The thickness of the metal oxide film 112 is preferably 5 nm or more and 10 nm or less. The film can be formed by appropriately using a sputtering method, a plasma CVD method, or the like.

[0382] In this embodiment, the metal oxide film 112 is formed by sputtering to a thickness of 10 nm. A film of ruthenium oxide is formed.

[0383] The conductive film 113 may be formed using a material that can withstand subsequent heat treatment. Therefore, it is preferable to form the metal oxide film 112 using a material that does not form an oxide film at the interface with the metal oxide film 112. The conductive film 113 may be made of, for example, gold, platinum, copper, silver, ruthenium, iridium, or titanium. Tantalum, tungsten, titanium nitride, molybdenum nitride, tungsten nitride, tantalum nitride, etc. The conductive film 113 is preferably formed to be thicker than the metal oxide film 112. The tantalum nitride film is formed in a single layer structure or a laminated structure. A tungsten film may also be formed.

[0384] The thickness of the conductive film 113 is set to 50 nm or more and 600 nm or less. The film can be formed by appropriately using a sputtering method, a plasma CVD method, or the like.

[0385] In this embodiment, the conductive film 113 is formed by sputtering. A film of ruthenium is formed.

[0386] Next, the oxide semiconductor film 103, the metal oxide film 112, and the conductive film 113 are subjected to heat treatment (see FIG. 12(C)). Heat treatment is performed while the metal oxide film 112 and the oxide semiconductor film 103 are in contact with each other. By this treatment, oxygen is released from the metal oxide film 112 and transferred to the oxide semiconductor film 103. The supply of oxygen to the oxide semiconductor film 103 causes the oxide semiconductor film 10 In addition, the oxide semiconductor film 103 has a higher reducing property than the oxide semiconductor film 103. The thin metal oxide film 112 is reduced to form a metal film 114 .

[0387] In FIG. 12C, when the metal oxide film 112 is entirely reduced to the metal film 114, However, only the vicinity of the interface between the metal oxide film 112 and the oxide semiconductor film 103 is reduced. The metal oxide film 112 may remain except near the interface. For example, when ruthenium oxide is used as the metal oxide film 112, only the vicinity of the interface is reduced. Ruthenium oxide may remain in areas other than the interface. Even if ruthenium oxide remains outside of this range, the resistivity of ruthenium oxide is 3.5 x 10 -5 [cmΩ] (300K), and no high resistance components are formed in the source and drain electrode layers. This is preferable because it does not

[0388] The metal film 114 formed by reducing the metal oxide film 112 is an oxide film. The metal film 103 has higher oxidation resistance than the metal element contained in the semiconductor film 103. 14, a film through which oxygen is less likely to diffuse.

[0389] 12C, the oxide semiconductor film 103 is formed by the metal film 114 and the conductive film 1 13. As a result, the oxide semiconductor film 103, the gate insulating film 111, The oxygen contained in the sidewall insulating films 109a and 109b is not released to the outside. In addition, the gate insulating film 111 and the sidewall insulating films 109a and 109b The oxygen contained in the oxygen gas can be supplied to the oxide semiconductor film 103.

[0390] Further, the conductive film 113 is provided over the metal oxide film 112 and subjected to heat treatment. The oxygen contained in the oxide film 112 is not released to the outside but is supplied to the oxide semiconductor film 103. Therefore, it is preferable.

[0391] In this embodiment, the heat treatment is performed at 650° C. for 1 to 5 minutes using a GRTA device. In addition, heat treatment is carried out in an electric furnace at 500°C for 30 minutes to 1 hour.

[0392] Next, an interlayer insulating film 115 is formed over the conductive film 113 (see FIG. 12D).

[0393] The interlayer insulating film 115 is formed by sputtering or the like in a manner that does not allow impurities such as hydrogen to be mixed in. The method is appropriately used to form the film.

[0394] The interlayer insulating film 115 is typically made of silicon oxide, silicon oxynitride, aluminum oxide, Aluminum oxide nitride, hafnium oxide, gallium oxide, silicon nitride, aluminum nitride A single layer or multilayer structure of inorganic insulating films such as silicon nitride oxide, silicon nitride oxide, or aluminum nitride oxide. The structure can be used.

[0395] As the interlayer insulating film 115, a highly dense inorganic insulating film is preferably provided in contact with the conductive film 113. For example, an aluminum oxide film is formed by sputtering. High density (film density 3.2 g / cm 3 or more, preferably 3.6 g / cm 3 (or more) This allows the transistor 110 to have stable electrical characteristics. Rutherford Backscattering (RBS) Spectrometry and X-ray Reflectometry (XRR) It can be measured by tmetry.

[0396] In this embodiment, the source electrode layer 116a and the drain electrode layer 116b are formed of a metal film. The case where the conductive films 114a and 114b are formed on the conductive films 113a and 113b has been described. However, one embodiment of the present invention is not limited thereto. For example, when the conductive films 113a and 113b are not formed, It's good to

[0397] An aluminum oxide film that can be used as an inorganic insulating film provided on the transistor 110 The membrane has a blocking effect ( High blocking effect.

[0398] Therefore, the aluminum oxide film is free from hydrogen, which is a factor of fluctuation during and after the manufacturing process. The inclusion of impurities such as moisture in the oxide semiconductor film 103 and the inclusion of a main component constituting the oxide semiconductor The oxide semiconductor film 103 functions as a protective film for preventing oxygen, which is a material, from being released from the oxide semiconductor film 103.

[0399] Next, a resist mask is formed over the conductive film 113 by a photolithography process. By selectively etching the film 113 and the metal film 114, the source electrode layer and the drain electrode layer are formed. The inner electrode layer is processed in the channel width direction.

[0400] Next, the insulating film 106 is exposed to the interlayer insulating film 115, the conductive film 113, and the metal film 114. This polishing process removes the interlayer insulating film 115, the conductive film 113, and the metal film 11. 4 is removed to form the source electrode layer 116a and the drain electrode layer 116b. do.

[0401] As a polishing process, chemical mechanical polishing (CPM) Although the CMP (Chemical Polishing) method can be used, other cutting (grinding, polishing) methods can also be used. After the polishing process, dry etching or plasma treatment (reverse plasma treatment) may be performed. By performing the above-mentioned treatment, the flatness of the polished surface can be improved.

[0402] In this embodiment, the insulating film 106 is provided on the gate electrode layer 105, and therefore, the insulating film 106 is an interlayer insulating film. Even if the insulating film 115, the conductive film 113, and the metal film 114 are polished, the gate electrode layer 105 and Therefore, it is possible to prevent the source electrode layer 116a and the drain electrode layer 116b from being short-circuited. Cut.

[0403] Through the above steps, the transistor 110 of one embodiment of the present invention is manufactured (see FIG. 12E). (see).

[0404] The oxide semiconductor film 103 contains almost no impurities such as copper, aluminum, or chlorine. It is desirable that the material be highly purified so that it does not contain any traces of fluorine. A process in which there is no risk of these impurities being mixed into the oxide semiconductor film or being attached to the surface of the oxide semiconductor film. In addition, when the oxide semiconductor film is attached to the surface of the oxide semiconductor film, the oxide semiconductor film is easily adhered to the surface of the oxide semiconductor film. Exposure to acid or dilute hydrofluoric acid, or plasma treatment (such as N2O plasma treatment) Therefore, it is preferable to remove impurities from the surface of the oxide semiconductor film. The copper concentration in the membrane 103 is 1×10 18 atoms / cm 3 Less than 1 × 10 17 a toms / cm 3 The aluminum concentration in the oxide semiconductor film is 1×10 or less. 18 atoms / cm 3The chlorine concentration in the oxide semiconductor film is 2×10 18 ato ms / cm 3 The following applies.

[0405] In addition, immediately after the deposition, the oxide semiconductor film is in a supersaturated state with more oxygen than in the stoichiometric composition. For example, when an oxide semiconductor film is formed by a sputtering method, In this case, it is preferable to form the film under conditions where the proportion of oxygen in the film forming gas is high, and particularly in an oxygen atmosphere. It is preferable to form the film using 100% oxygen gas. The proportion of oxygen in the film formation gas is high. When film formation is performed under conditions, particularly in an atmosphere of 100% oxygen gas, for example, when the film formation temperature is 300°C or higher, Even if the film is heated, the release of Zn from the film is suppressed.

[0406] Further, the oxide semiconductor film can be formed by sufficiently removing impurities such as hydrogen or by sufficiently removing impurities such as hydrogen. By supplying oxygen in a supersaturated state, the water is highly purified. Specifically, the hydrogen concentration in the oxide semiconductor film is preferably 5×10 19 atoms / c m 3 Below 5×10 18 atoms / cm 3 Less than or equal to 5×10 1 7 atoms / cm 3 Note that the hydrogen concentration in the oxide semiconductor film is determined by the secondary electron Secondary Ion Mass Spectrometry (SIMS) It is measured by the oxygen saturation test. To achieve this, an insulating film (such as SiOx) containing excess oxygen is formed to enclose the oxide semiconductor film. Install adjacently.

[0407] In addition, the deuterium concentration of the insulating film containing excess oxygen is 7.2 × 10 20 atoms / cm 3 End In this case, the variation in the initial characteristics of the transistor increases, the L length dependency increases, and The deuterium concentration of the insulating film containing excess oxygen is 7.2×10 20 atoms / cm 3 That is, the hydrogen concentration in the oxide semiconductor film is set to be less than 5 x10 19 atoms / cm 3 The deuterium concentration of the insulating film containing excess oxygen is 7. 2×10 20 atoms / cm 3 It is preferable that it is less than 1000 kJ / s.

[0408] Further, the insulating film containing excess oxygen is formed so as to surround the oxide semiconductor film and to be disposed outside the insulating film containing excess oxygen. It is preferable to provide a blocking film (such as AlOx) that suppresses oxygen release from the oxide semiconductor film. stomach.

[0409] The oxide semiconductor film is surrounded by an insulating film or a blocking film containing excess oxygen. In a semiconductor film, the state where the composition is almost the same as the stoichiometric ratio, or the composition is different from the stoichiometric ratio. For example, if the oxide semiconductor film is IGZO, it can be made into a supersaturated state with a large amount of oxygen. An example of the stoichiometric composition is In:Ga:Zn:O=1:1:1:4 [atomic ratio]. Therefore, the atomic ratio of oxygen is 4 or more.

[0410] In this embodiment, after the conductive film 113 is formed over the metal oxide film 112, heat treatment is performed. However, one embodiment of the present invention is not limited thereto. After the metal oxide film 112 is formed on the film 103, heat treatment may be performed. A conductive film 113 is formed on the film 112, an interlayer insulating film 115 is formed, and then heat treatment is performed. That's fine.

[0411] In this embodiment, the metal films 114a and 114b and the conductive films 113a and 113b are The materials were selected so that they would be the same, but the metal films 114a and 114b and the conductive film 113a , 113b may be made of a different material. For example, Ruthenium oxide is used as the conductive film 12, and tantalum nitride is used as the conductive film 113. By carrying out this process, a laminated structure of ruthenium and tantalum nitride is formed. No oxide film is formed at the interfaces between the conductive films 113a and 113b and the conductive films 114a and 114b. The conductive films 113a and 113b are made of tantalum nitride and tungsten. It may be formed in a laminated structure.

[0412] The metal films 114a and 114b and the conductive films 113a and 113b are made of the same material. Even if the material is selected, the metal films 114a and 114b are formed by the metal oxide film 112. The conductive films 113a and 113b are formed films. Therefore, when the metal films 114a and 114b and the conductive films 113a and 113b have different physical properties, For example, the metal films 114a and 114b may have a larger thickness than the conductive films 113a and 113b. The density may be low. The film density can be measured, for example, by X-ray reflectivity (XRR). It can be measured by the endoscopic method.

[0413] According to this embodiment, the metal oxide film 112 in contact with the oxide semiconductor film 103 is subjected to heat treatment. By reducing the metal oxide film 112 with oxygen, oxygen is released from the metal oxide film 112, and the oxide semiconductor film 10 3. As a result, the source electrode layer 116a and the drain electrode layer 11 Oxygen vacancies at the interface between the oxide semiconductor film 6b and the oxide semiconductor film 103 can be reduced. This prevents the threshold voltage of the transistor 110 from shifting in the negative direction. This can be done.

[0414] The metal film 114 formed by reducing the metal oxide film 112 is an oxide film. The metal film 103 has higher oxidation resistance than the metal element contained in the semiconductor film 103. The metal films 114a and 114b are formed on the source electrode layer 11. By using the metal films 114a and 114b as the drain electrode layer 116a and the drain electrode layer 116b, Therefore, it is possible to prevent a high-resistance component from being formed in the oxide semiconductor film 103. Therefore, the resistance due to the source electrode layer 116a and the drain electrode layer 116b can be reduced. Therefore, a decrease in the on-state current of the transistor 110 can be suppressed.

[0415] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting a metal film 114 (e.g., copper, silver, ruthenium, etc.), an oxide semiconductor The contact resistance between the film 103 and the source electrode layer 116a and the drain electrode layer 116b is reduced. This is also preferable because the oxide semiconductor film 103, the source electrode Since the resistance due to the drain electrode layer 116a and the drain electrode layer 116b can be reduced, A decrease in the on-state current of the transistor can be suppressed.

[0416] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0417] (Embodiment 8) In this embodiment mode, another mode of a semiconductor device will be described with reference to FIG. The same parts as those in the above-described embodiments or parts having similar functions will not be described repeatedly. Further, detailed explanations of the same parts will be omitted.

[0418] The transistor 120 illustrated in FIG. 13 is an example of a top-gate transistor. 13(A) is a plan view of the transistor 120, and FIG. 13(B) is a plan view of the transistor 120 in FIG. 13(A). 1-I2 cross-sectional view (cross-sectional view in the channel length direction). For simplicity, some of the components of transistor 120 (e.g., gate insulator) are omitted. The illustration omits the velum 111 and other components.

[0419] The transistor 120 shown in FIGS. 13A and 13B is provided on a substrate 100 having an insulating surface. The source electrode layer 116a and the drain electrode layer 116b are formed by the The oxide semiconductor film 103 is formed on the drain electrode layer 116b. 3, and a gate electrode provided on the gate insulating film 111. The gate electrode layer 105 and the insulating film 106 are provided on the gate electrode layer 105. An interlayer insulating film 115 is provided to cover the transistor 120 .

[0420] The oxide semiconductor film 103 has a channel forming region provided in a region overlapping with the gate electrode layer 105. A region 108 and a region 107 containing a dopant provided on either side of the channel forming region 108 The dopant-containing regions 107a and 107b are channel forming regions. This is a region with lower resistance than 108.

[0421] As shown in FIG. 13B, the transistor 120 has a source electrode in contact with the oxide semiconductor film 103. The source electrode layer 116a and the drain electrode layer 116b are provided in a stacked structure. The layer 116a has a laminated structure of a conductive film 113a and a metal film 114a, and the drain electrode layer 116b has a , a laminated structure of a conductive film 113b and a metal film 114b.

[0422] The transistor 120 shown in FIG. 13 differs from the transistor 110 shown in FIG. 10 in the following respects: In this case, the oxide semiconductor film 103 is in contact with the source electrode layer 116a and the drain electrode layer 116b. That is, in the transistor 110 shown in FIG. The source electrode layer 116a and the drain electrode layer 116b are in contact with each other on the upper surface of the In the transistor 120, the source electrode layer 116a and the drain electrode layer 116b are formed on the lower surface of the oxide semiconductor film 103. The electrode layer 116b is in contact with it.

[0423] The metal films 114a and 114b in contact with the oxide semiconductor film 103 are In order to prevent oxygen from being extracted, a metal element contained in the oxide semiconductor film 103 is Metals with oxidation resistance (higher than the Gibbs free energy of the oxidation reaction of molybdenum) are used. Specifically, copper, silver, ruthenium, iridium, etc. are used. a and 114b have higher oxidation resistance than the metal element contained in the oxide semiconductor film 103. By using a metal, an increase in oxygen vacancies in the oxide semiconductor film 103 can be suppressed. This can be done.

[0424] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0425] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting metal films 114a, 114b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 103 is in contact with the source electrode layer 116a and the drain electrode layer 116b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 116a and the drain electrode layer 116b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0426] The conductive films 113a and 113b stacked on the metal films 114a and 114b are made of gold. It is preferable that the material does not form an oxide film at the interface with the metal films 114a and 114b. The conductive films 113a and 113b can be made of a material such as a metal film 114a. In addition to the materials that can be used for 114b, gold, platinum, titanium, tungsten, nitride Examples of conductive film include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 13a and 113b are configured with a single layer structure or a laminated structure. In the case of a laminated structure, for example, It can be made up of a tantalum nitride film and a tungsten film.

[0427] In the transistor 120 shown in FIG. 13, the source electrode layer 116a and the drain electrode layer 1 In the case of 16b, the metal films 114a and 114b and the conductive films 113a and 113b are made of the same material. The case where the metal films 114a and 114b and the conductive films 113a and 113b are configured as above will be described. 113b may be made of a different material.

[0428] In the transistor 120 shown in FIG. 13, the metal films 114a and 114b are partially For example, if the metal films 114a and 114b are made of ruthenium, a metal oxide may be formed on the metal films 114a and 114b. In this case, ruthenium oxide may be formed in a part of the metal films 114a and 114b. Even if ruthenium oxide is formed in the region, the resistivity of ruthenium oxide is 3.5×10 -5 [cmΩ] (300K), and the source electrode layer 116a and the drain electrode layer 116b This is preferable because no high resistance component is formed in the

[0429] On the substrate 100, between the source electrode layer 116a and the drain electrode layer 116b The insulating film 121 is made of an oxide semiconductor. It is provided in a region overlapping with the channel forming region 108 of the film 103 .

[0430] The insulating film 121 is made of, for example, silicon oxide, silicon oxynitride, aluminum oxide, or oxynitride. Aluminum oxide, hafnium oxide, gallium oxide, silicon nitride, aluminum nitride, nitride Inorganic insulating materials such as silicon oxide nitride or aluminum oxide nitride are used to form single-layer structures or is formed in a laminated structure.

[0431] In addition, the insulating film 121 (when the insulating film 121 has a stacked structure, the insulating film 121 is in contact with the oxide semiconductor film 103) When the oxide semiconductor film 103 is made to contain a large amount of oxygen, oxygen is supplied to the oxide semiconductor film 103. It can suitably function as a source of

[0432] As described above, the metal films 114a and 114b in contact with the oxide semiconductor film 103 are The oxide semiconductor film 103 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 103 (at least indium). (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) This prevents oxygen from being extracted from the oxide semiconductor film 103. As a result, the source electrode layer 116a, the drain electrode layer 116b, and the oxide semiconductor film 103 This suppresses the increase in oxygen vacancies at the interface between the semiconductor and the transistor, thereby reducing the fluctuation in the threshold voltage of the transistor. It can be suppressed.

[0433] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0434] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0435] (Embodiment 9) In this embodiment, one method for manufacturing a semiconductor device including the transistor 120 shown in FIGS. An example will be described with reference to FIG. 14. Note that the transistor 110 described in Embodiment 7 The difference from the method of forming the insulating film 121 is the formation of the source electrode layer 116a and the drain electrode layer 116. Therefore, detailed explanation of the same steps as those in the seventh embodiment will be omitted.

[0436] First, an insulating film that will become the island-shaped insulating film 121 is formed on the substrate 100 .

[0437] The insulating film can be formed using a material and a method similar to those of the insulating film 101 which functions as a base film. The thickness of the insulating film is determined based on the thickness of the source electrode layer 116a and the drain electrode layer 116b to be formed later. It can be set according to the film thickness of 16b.

[0438] Next, a resist mask is formed on the insulating film by a photolithography process, and selective etching is performed. After the island-shaped insulating film 121 is formed, a resist pattern is formed. Remove the mask.

[0439] Next, a source electrode layer and a drain electrode layer (which will be formed later) are formed on the substrate 100 and the insulating film 121. The conductive film 113 and the metal oxide film 112 are formed to become wirings (including wirings formed in the same layer). (See Figure 14(A)).

[0440] The conductive film 113 may be formed using a material that can withstand subsequent heat treatment. Therefore, it is preferable to form the metal oxide film 112 using a material that does not form an oxide film at the interface with the metal oxide film 112. The conductive film 113 may be made of, for example, gold, platinum, copper, silver, ruthenium, iridium, or titanium. Tantalum, tungsten, titanium nitride, molybdenum nitride, tungsten nitride, tantalum nitride, etc. The conductive film 113 is preferably formed thicker than a metal oxide film, and is preferably formed as a single layer. In the case of a laminated structure, a tungsten nitride film is formed on the tungsten film. Alternatively, a tantalum film may be formed.

[0441] The thickness of the conductive film 113 is set to 50 nm or more and 600 nm or less. The film can be formed by appropriately using a sputtering method, a plasma CVD method, or the like.

[0442] In this embodiment, the conductive film 113 is formed by sputtering. A film of ruthenium is formed.

[0443] As the metal oxide film, a metal oxide film having a higher reduction property than the oxide semiconductor film 103 is used. The metal oxide film having higher reduction property than the oxide semiconductor film 103 is a metal oxide film having an oxide semiconductor layer as shown in FIG. It is more reducing than indium, gallium oxide, zinc oxide, and tin oxide (i.e., indium Metal oxides with Gibbs free energies higher than those of the oxidation reactions of aluminum, gallium, zinc, and tin. Specifically, copper oxide, silver oxide, ruthenium oxide, iridium oxide, etc. The metal oxide film 112 is formed to have a single layer structure or a multilayer structure.

[0444] The thickness of the metal oxide film 112 is 1 nm or more and 50 nm or less, preferably 1 nm or more and 30 nm or less. The thickness of the metal oxide film 112 is preferably 5 nm or more and 10 nm or less. The film can be formed by appropriately using a sputtering method, a plasma CVD method, or the like.

[0445] In this embodiment, the metal oxide film 112 is formed by sputtering to a thickness of 10 nm. A film of ruthenium oxide is formed.

[0446] Next, a resist mask is formed over the conductive film 113 by a photolithography process. By selectively etching the film 113 and the metal film 114, the source electrode layer and the drain electrode layer are formed. The inner electrode layer is processed in the channel width direction.

[0447] Next, the conductive film 113 and the metal oxide film 112 are polished until the insulating film 121 is exposed. As a result, the conductive film 113 and the metal oxide film 112 are partially removed, and the conductive film 113 and the metal oxide film 112 are partially removed. The conductive films 113a and 113b and the metal oxide films 112a and 112b are formed (FIG. 14(B) )reference).

[0448] As a polishing process, chemical mechanical polishing (CPM) Although the CMP (Chemical Polishing) method can be used, other cutting (grinding, polishing) methods can also be used. After the polishing process, dry etching or plasma treatment (reverse plasma treatment) may be performed. By performing the above-mentioned treatment, the flatness of the polished surface can be improved.

[0449] At this time, the average surface roughness (R a) is 1 nm or less, preferably 0.3 nm or less, more preferably 0.1 nm or less. It is preferable to keep

[0450] Next, the oxide semiconductor film 102 is formed on the insulating film 121 and the metal oxide films 112a and 112b. (See FIG. 14(C)).

[0451] In this embodiment, the oxide semiconductor film 102 is formed by a sputtering A 10 nm thick In-Ga-Zn oxide film was deposited using a sputtering method with a laser scanning device. (IGZO film) is deposited.

[0452] Next, the oxide semiconductor film 103 and the metal oxide films 112a and 112b are subjected to heat treatment (FIG. 1 4(D)). Heat treatment is performed while the metal oxide film 112 and the oxide semiconductor film 103 are in contact with each other. By performing this, oxygen is released from the metal oxide film 112 and supplied to the oxide semiconductor film 103. When oxygen is supplied to the oxide semiconductor film 103, the oxide semiconductor film 103 In addition, the oxide semiconductor film 103 has a higher reducing property than the oxide semiconductor film 103. The metal oxide film 112 is reduced to form a metal film 114 .

[0453] In FIG. 14C, the metal oxide films 112a and 112b are all metal films 114a and 114b. The case where the metal oxide films 112a and 112b are reduced to 114b has been described. Only the vicinity of the interface with the compound semiconductor film 103 is reduced to form metal films 114a and 114b. The metal oxide films 112a and 112b may remain in areas other than the vicinity. When ruthenium oxide is used as 112a and 112b, only the area near the interface is reduced. Ruthenium oxide may remain in areas other than the interface. Even if ruthenium oxide remains, the resistivity of ruthenium oxide is 3.5 × 10 -5 [c mΩ] (300K), and no high resistance components are formed in the source and drain electrode layers. Therefore, it is preferable.

[0454] In addition, the metal oxide films 112a and 112b are reduced to form the metal film 11 The oxide semiconductor film 103 is made of a metal element. In other words, the metal films 114a and 114b are films in which oxygen is less likely to diffuse.

[0455] In this embodiment, the heat treatment is performed at 650° C. for 1 to 5 minutes using a GRTA device. In addition, heat treatment is carried out in an electric furnace at 500°C for 30 minutes to 1 hour.

[0456] Next, according to the steps of FIG. 11(B) to FIG. 11(E) shown in the seventh embodiment, an island-shaped oxide A semiconductor film 103 is formed, an insulating film is formed over the oxide semiconductor film 103, and a gate insulating film is formed over the insulating film. Next, the gate electrode layer 105 and the insulating film 106 are laminated. By adding a dopant to the oxide semiconductor film 103 using the insulating film 106 as a mask, The semiconductor film 103 has a channel formation region 1 provided in a region overlapping with the gate electrode layer 105. and dopant-containing regions 107a and 107b sandwiching the channel forming region 108. Form 07b.

[0457] After that, the oxide semiconductor film 103, the insulating film 106, and the like are removed according to the process shown in FIG. An insulating film is formed to cover the insulating film 109a. , 109b are formed. Furthermore, the gate electrode layer 105 and the sidewall insulating film 109a are formed. The insulating film 101 is etched using the mask 109b to form a gate insulating film 111. That's fine.

[0458] Next, an insulating film is formed so as to cover the oxide semiconductor film 103, the insulating film 106, etc., and a polishing process is performed. By carrying out this process, an interlayer insulating film 115 is formed (see FIG. 14(F)).

[0459] Through the above steps, the transistor 120 can be manufactured.

[0460] According to this embodiment, the metal oxide film 112 in contact with the oxide semiconductor film 103 is subjected to heat treatment. By reducing the metal oxide film 112 with oxygen, oxygen is released from the metal oxide film 112, and the oxide semiconductor film 10 3. As a result, the source electrode layer 116a and the drain electrode layer 11 Oxygen vacancies at the interface between the oxide semiconductor film 6b and the oxide semiconductor film 103 can be reduced. This prevents the threshold voltage of the transistor 110 from shifting in the negative direction. This can be done.

[0461] The metal film 114 formed by reducing the metal oxide film 112 is an oxide film. The metal film 103 has higher oxidation resistance than the metal element contained in the semiconductor film 103. The metal films 114a and 114b are formed on the source electrode layer 11. By using the metal films 114a and 114b as the drain electrode layer 116a and the drain electrode layer 116b, Therefore, it is possible to prevent a high-resistance component from being formed in the oxide semiconductor film 103. Therefore, the resistance due to the source electrode layer 116a and the drain electrode layer 116b can be reduced. Therefore, a decrease in the on-state current of the transistor 110 can be suppressed.

[0462] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting a metal film 114 (e.g., copper, silver, ruthenium, etc.), an oxide semiconductor The contact resistance between the film 103 and the source electrode layer 116a and the drain electrode layer 116b is reduced. This is also preferable because the oxide semiconductor film 103, the source electrode Since the resistance due to the drain electrode layer 116a and the drain electrode layer 116b can be reduced, A decrease in the on-state current of the transistor can be suppressed.

[0463] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0464] (Embodiment 10) In this embodiment, another mode of a semiconductor device will be described with reference to FIG. The same parts as those in the above-described embodiments or parts having similar functions will not be described repeatedly. Omitted.

[0465] The transistor 130 shown in FIG. 15 is an example of a top-gate transistor. 15(A) is a plan view of the transistor 130, and FIG. 15(B) is a plan view of the J 15(A) is a cross-sectional view taken along the line 1-J2 (cross-sectional view in the channel length direction). For simplicity, some of the components of transistor 120 (e.g., gate insulator) are omitted. The illustration omits the velum 111 and other components.

[0466] The transistor 130 shown in FIGS. 15A and 15B is provided on a substrate 100 having an insulating surface. The oxide semiconductor film 103 and the source electrode layer 116a in contact with the oxide semiconductor film 103 the drain electrode layer 116b, the oxide semiconductor film 103, the source electrode layer 116a, and the drain electrode layer 116b. A gate insulating film 111 is provided on the inner electrode layer 116b, and an oxide film is provided on the gate insulating film 111. and a gate electrode layer 105 provided in a region overlapping with the compound semiconductor film 103. An insulating film 101 serving as a base film is provided between a substrate 100 and an oxide semiconductor film 103. An interlayer insulating film 115 is provided to cover the transistor 130 .

[0467] The transistor 130 shown in FIGS. 15A and 15B has a source electrode in contact with the oxide semiconductor film 103. The source electrode layer 116a and the drain electrode layer 116b are configured in a stacked structure. The layer 116a has a laminated structure of a metal film 114a and a conductive film 113a, and the drain electrode layer 116b has a , a laminated structure of a metal film 114b and a conductive film 113b.

[0468] The metal films 114a and 114b in contact with the oxide semiconductor film 103 are In order to prevent oxygen from being extracted, a metal element contained in the oxide semiconductor film 103 is Metals with oxidation resistance (higher than the Gibbs free energy of the oxidation reaction of molybdenum) are used. Specifically, copper, silver, ruthenium, iridium, etc. are used. a and 114b have higher oxidation resistance than the metal element contained in the oxide semiconductor film 103. By using a metal, an increase in oxygen vacancies in the oxide semiconductor film 103 can be suppressed. This can be done.

[0469] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0470] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting metal films 114a, 114b (e.g., copper, silver, ruthenium, etc.), The oxide semiconductor film 103 is in contact with the source electrode layer 116a and the drain electrode layer 116b. This is also preferable because the contact resistance can be reduced. Therefore, the resistance due to the source electrode layer 116a and the drain electrode layer 116b can be reduced. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0471] The conductive films 113a and 113b, which are stacked on the metal films 114a and 114b, are made of gold. It is preferable that the material does not form an oxide film at the interface with the metal films 114a and 114b. The conductive films 113a and 113b can be made of a material such as a metal film 114a. In addition to the materials that can be used for 114b, gold, platinum, titanium, tungsten, nitride Examples of conductive film include titanium nitride, molybdenum nitride, tungsten nitride, and tantalum nitride. 13a and 113b are configured with a single layer structure or a laminated structure. In the case of a laminated structure, for example, It can be made up of a tantalum nitride film and a tungsten film.

[0472] In the transistor 130 shown in FIG. 15, the source electrode layer 116a and the drain electrode layer 1 In the case of 16b, the metal films 114a and 114b and the conductive films 113a and 113b are made of the same material. The case where the metal films 114a and 114b and the conductive films 113a and 113b are configured as above will be described. 113b may be made of a different material.

[0473] In the transistor 130 shown in FIG. 15, the metal films 114a and 114b are partially For example, if the metal films 114a and 114b are made of ruthenium, a metal oxide may be formed on the metal films 114a and 114b. In this case, ruthenium oxide may be formed in a part of the metal film. Even if ruthenium oxide is formed, the resistivity is 3.5×10 -5 [cmΩ](3 00K), and no high resistance components are formed in the source electrode layer 116a and the drain electrode layer 116b. This is preferable because it does not

[0474] Next, referring to FIG. 16, a transistor that is partially different from the transistor 130 shown in FIG. This will be explained in light of the above.

[0475] 16A is a plan view of the transistor 140, and FIG. 16B is a plan view of the transistor 140 of FIG. 16A. 16A is a cross-sectional view taken along the line K1-K2 (cross-sectional view in the channel length direction). To avoid clutter, some of the components of the transistor 140 (e.g., the gate The insulating film 111 and the like are omitted from the illustration.

[0476] As shown in FIG. 16B, the transistor 140 has a source electrode in contact with the oxide semiconductor film 103. The source electrode layer 116a and the drain electrode layer 116b are provided in a stacked structure. The layer 116a has a laminated structure of a conductive film 113a and a metal film 114a, and the drain electrode layer 116b has a , a laminated structure of a conductive film 113b and a metal film 114b.

[0477] The transistor 140 shown in FIG. 16 differs from the transistor 130 shown in FIG. 15 in the following respects: In this case, the oxide semiconductor film 103 is in contact with the source electrode layer 116a and the drain electrode layer 116b. That is, in the transistor 130 shown in FIG. The source electrode layer 116a and the drain electrode layer 116b are in contact with each other on the upper surface of the In the transistor 140, the source electrode layer 116a and the drain electrode layer 116b are formed on the lower surface of the oxide semiconductor film 103. The electrode layer 116b is in contact with it.

[0478] As shown in FIG. 16B, the side surfaces of the conductive films 113a and 113b are formed on the oxide semiconductor film. Therefore, the conductive films 113a and 113b are made of gold, platinum, titanium nitride, It is more preferable to use molybdenum nitride or tantalum nitride.

[0479] As described above, the metal films 114a and 114b in contact with the oxide semiconductor film 103 are The oxide semiconductor film 103 has higher oxidation resistance than the metal element contained in the oxide semiconductor film 103 (at least indium). (higher than the Gibbs free energy of oxidation reaction of aluminum, gallium, zinc, and tin) This prevents oxygen from being extracted from the oxide semiconductor film 103. As a result, the source electrode layer 116a, the drain electrode layer 116b, and the oxide semiconductor film 103 This suppresses the increase in oxygen vacancies at the interface between the semiconductor and the transistor, thereby reducing the fluctuation in the threshold voltage of the transistor. It can be suppressed.

[0480] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0481] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0482] (Embodiment 11) In this embodiment, one method for manufacturing a semiconductor device including the transistor 140 shown in FIGS. An example will be described with reference to Fig. 17. Note that the detailed description of the same steps as in the seventh embodiment will be omitted. is omitted.

[0483] First, an insulating film 101 is formed on a substrate 100, and a source electrode layer and a drain electrode layer are formed on the insulating film 101. The conductive film 113 that will become the inner electrode layer (including wiring formed in the same layer) and the metal oxide film 112 are laminated (see FIG. 17(A)).

[0484] Next, a resist mask is formed on the metal oxide film 112 by a photolithography process. , the metal oxide films 112a and 112b and the conductive films 113a and 113b are removed by etching. (See FIG. 17(B)).

[0485] Next, the oxide semiconductor film 102 is formed on the metal oxide films 112a and 112b (FIG. 17( See C).

[0486] Next, the oxide semiconductor film 102, the metal oxide films 112a and 112b, the conductive films 113a and 113b, and the conductive films 113a and 113b are The metal oxide films 112a and 112b and the oxide film 3b are subjected to heat treatment (see FIG. 17D). By performing heat treatment while the semiconductor film 102 is in contact with the metal oxide film 112a, Oxygen is released from 12b and supplied to the oxide semiconductor film 102. By supplying oxygen to the oxide semiconductor film 102, oxygen vacancies in the oxide semiconductor film 102 can be reduced. In addition, the metal oxide films 112a and 112b have a higher reduction property than the oxide semiconductor film 102. is reduced to form a metal film 114.

[0487] In FIG. 17(D), the metal oxide films 112a and 112b are all metal films 114a and 114b. The case where the metal oxide films 112a and 112b are reduced to 114b has been described. Only the vicinity of the interface with the compound semiconductor film 102 is reduced to form metal films 114a and 114b. The metal oxide films 112a and 112b may remain in areas other than the vicinity. When ruthenium oxide is used as 112a and 112b, only the area near the interface is reduced. Ruthenium oxide may remain in areas other than the interface. Even if ruthenium oxide remains, the resistivity of ruthenium oxide is 3.5 × 10 -5 [c mΩ] (300K), and no high resistance components are formed in the source and drain electrode layers. Therefore, it is preferable.

[0488] In addition, the metal oxide films 112a and 112b are reduced to form the metal film 11 The oxide semiconductor film 102 is made of a metal element. In other words, the metal films 114a and 114b are films in which oxygen is less likely to diffuse.

[0489] Next, a resist mask is formed over the oxide semiconductor film 102 by a photolithography process. Then, etching is performed to form the oxide semiconductor film 103. 116a, a drain electrode layer 116b, and a gate insulating film 111 formed on the oxide semiconductor film 103. (See FIG. 17(E)).

[0490] Next, a gate electrode layer (including wiring formed in the same layer) is formed on the gate insulating film 111. Then, a resist is formed on the conductive film by a photolithography process. A mask is formed and etching is performed to form the gate electrode layer 105. An interlayer insulating film 115 is formed on the gate insulating film 111 and the gate electrode layer 105 .

[0491] Through the above steps, the transistor 140 can be manufactured (see FIG. 17F).

[0492] In this embodiment, heat treatment is performed before processing the oxide semiconductor film into an island shape. However, one embodiment of the present invention is not limited thereto. After the application, a heat treatment may be carried out.

[0493] In this embodiment, the metal films 114a and 114b and the conductive films 113a and 113b are The materials were selected so that they would be the same, but the metal films 114a and 114b and the conductive film 113a , 113b may be made of a different material. Ruthenium oxide is used as the conductive film 12, and tantalum nitride is used as the conductive film 113. By carrying out this process, a laminated structure of ruthenium and tantalum nitride is formed. No oxide film is formed at the interfaces between the conductive films 113a and 113b and the conductive films 114a and 114b. The conductive films 113a and 113b are made of tungsten and tantalum nitride. It may be formed in a laminated structure.

[0494] The metal films 114a and 114b and the conductive films 113a and 113b are made of the same material. Even if the material is selected, the metal films 114a and 114b are formed by the metal oxide film 112. The conductive films 113a and 113b are formed films. Therefore, when the metal films 114a and 114b and the conductive films 113a and 113b have different physical properties, For example, the metal films 114a and 114b may have a larger thickness than the conductive films 113a and 113b. The density may be low. The film density can be measured, for example, by X-ray reflectivity (XRR). It can be measured by the endoscopic method.

[0495] In this embodiment, the source electrode layer 116a and the drain electrode layer 116b are formed of a metal film. The case where the conductive films 114a and 114b are formed on the conductive films 113a and 113b has been described. However, one embodiment of the present invention is not limited thereto. For example, when the conductive films 113a and 113b are not formed, It's good to

[0496] According to this embodiment, the metal oxide films 112a and 112b in contact with the oxide semiconductor film 103 By reducing the metal oxide films 112a and 112b by heat treatment, oxygen is released from the metal oxide films 112a and 112b. The source electrode layer 116 can be supplied to the oxide semiconductor film 103. The oxygen vacancies at the interfaces between the a and drain electrode layers 116a and 116b and the oxide semiconductor film 103 are reduced. This allows the threshold voltage of the transistor 140 to shift in the negative direction. This can prevent the device from becoming soft.

[0497] In addition, the metal oxide films 112a and 112b are reduced to form the metal film 11 The oxide semiconductor film 103 is made of a metal element. In other words, the metal films 114a and 114b are films in which oxygen is less likely to diffuse. 14a and 114b are used as a source electrode layer 116a and a drain electrode layer 116b. This makes it possible to prevent high resistance components from being formed in the metal films 114a and 114b. Therefore, the oxide semiconductor film 103, the source electrode layer 116a, and the drain electrode layer 116b can be formed. Since the resistance caused by 16b can be reduced, the on-current of the transistor 140 can be reduced. The bottom can be suppressed.

[0498] In addition, a gold film having a work function of ±0.2 eV relative to the electron affinity of the oxide semiconductor film 103 is used. By selecting a metal film 114 (e.g., copper, silver, ruthenium, etc.), an oxide semiconductor The contact resistance between the film 103 and the source electrode layer 116a and the drain electrode layer 116b is reduced. This is also preferable because the oxide semiconductor film 103, the source electrode Since the resistance due to the drain electrode layer 116a and the drain electrode layer 116b can be reduced, A decrease in the on-state current of the transistor can be suppressed.

[0499] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0500] (Embodiment 12) In this embodiment, a display function is realized using the transistor described in any of the above embodiments. A semiconductor device (also called a display device) having a transistor can be manufactured. A part or the whole of the driver circuit including the pixel portion is formed on the same substrate as the system-on-panel can be formed.

[0501] In FIG. 18A, a pixel portion 4002 provided on a first substrate 4001 is surrounded by a A sealant 4005 is provided on the substrate 4001, and the substrate 4001 is sealed with a second substrate 4006. In FIG. 8(A), the area surrounded by the sealing material 4005 on the first substrate 4001 is A single crystal semiconductor film or a polycrystalline semiconductor film is formed on a separately prepared substrate in a region different from the region. A scanning line driver circuit 4004 and a signal line driver circuit 4003 are mounted on the substrate. A signal line driver circuit 4003 and a scanning line driver circuit 4004 or a pixel portion 4002 are provided. Various signals and potentials are transmitted via FPC (Flexible Printed Circuit). t) Powered by 4018a and 4018b.

[0502] In FIG. 18(B) and FIG. 18(C), the pixel portion 4 provided on the first substrate 4001 A sealant 4005 is provided so as to surround the gate electrode 4002 and the scanning line driver circuit 4004. In addition, a second substrate 4006 is provided on the pixel portion 4002 and the scanning line driver circuit 4004. Therefore, the pixel section 4002 and the scanning line driving circuit 4004 are connected to the first substrate 4 The display element is sealed by the 001, the sealant 4005, and the second substrate 4006. In FIG. 18(B) and FIG. 18(C), the sealing material 4 on the first substrate 4001 In a region different from the region surrounded by 005, a single crystal semiconductor is formed on a separately prepared substrate. A signal line driver circuit 4003 formed of a thin film or a polycrystalline semiconductor film is mounted on the substrate. In FIG. 18B and FIG. 18C, a signal line driver circuit 4003 and a scanning Various signals and potentials given to the line driver circuit 4004 or the pixel portion 4002 are transmitted through the FPC 401 It is supplied by 8.

[0503] In addition, in FIG. 18(B) and FIG. 18(C), a signal line driver circuit 4003 is separately formed. Although an example in which the first substrate 4001 is mounted is shown, the present invention is not limited to this configuration. The scanning line driver circuit may be formed separately and mounted, or a part of the signal line driver circuit or the scanning line driver circuit may be mounted. Only a part of the path may be formed separately and mounted.

[0504] The method of connecting the separately formed drive circuit is not particularly limited, and may be any method such as COG (C Hip On Glass method, wire bonding method, or TAB (Tape On Glass) method Automated Bonding (ABA) method can be used. 4003 and a scanning line driver circuit 4004 are mounted by the COG method. FIG. 18B shows an example in which a signal line driver circuit 4003 is mounted by the COG method. 18(C) is an example in which the signal line driver circuit 4003 is mounted by the TAB method.

[0505] The display device also includes a panel in which a display element is sealed, and a controller for the panel. and modules in which ICs, etc., including the above are mounted.

[0506] The display device also includes a panel in which a display element is sealed, and a controller for the panel. and modules in which ICs, etc., including the above are mounted.

[0507] In this specification, the term "display device" refers to an image display device, a display device, or an optical device. Also refers to connectors, such as FPC or TAB tape. or a module with TCP attached, a printed wiring board at the end of TAB tape or TCP or a module in which an IC (integrated circuit) is directly mounted on the display element using the COG method. All such modules are also included in the display device.

[0508] In addition, the pixel portion and the scanning line driver circuit provided on the first substrate have a plurality of transistors. The transistor described in the above embodiment can be applied to this.

[0509] The display element provided in the display device may be a liquid crystal element (also called a liquid crystal display element), a light-emitting element ( A light-emitting element can be used. It includes elements whose intensity can be controlled, specifically inorganic EL (Electro L Also, electronic ink and other electrically-activated A display medium whose contrast changes depending on the light source can also be applied.

[0510] Further, one mode of a semiconductor device will be described with reference to FIGS. 18(B) along the dashed line MN.

[0511] As shown in FIG. 20, the semiconductor device has a connection terminal electrode 4015 and a terminal electrode 4016. The connection terminal electrodes 4015 and the terminal electrodes 4016 are anisotropic with the terminals of the FPC 4018. The electrodes are electrically connected via a transparent conductive film 4019 .

[0512] The connection terminal electrode 4015 is formed from the same conductive film as the first electrode layer 4030. 016 is the same metal as the source electrode layer and the drain electrode layer of the transistors 4040 and 4011. It is made of a metal film and a conductive film.

[0513] In addition, a pixel portion 4002 and a scanning line driver circuit 4004 are provided on a first substrate 4001. 20, the transistors included in the pixel portion 4002 are 4040 and a transistor 4011 included in the scanning line driver circuit 4004. In FIG. 20A, an insulating film 4020 is provided over the transistors 4040 and 4011. In FIG. 20(B), an insulating film 4021 is further provided.

[0514] The transistors 4010 and 4011 are the transistors described in the above embodiment. In this embodiment, the transistor 410 described in Embodiment 1 can be An example of application of a transistor obtained by the above structure and manufacturing method will be described.

[0515] A transistor having a structure and a manufacturing method similar to those of the transistor 410 described in Embodiment 1 The oxide semiconductor films 4010 and 4011 are formed with a gold film having a higher reducing property than the oxide semiconductor film. After the metal oxide film and the conductive film are formed, a heat treatment is performed to reduce the metal oxide film. At this time, the metal oxide film, which has a higher reducing property than the oxide semiconductor film, is converted into an oxide film. The source electrode layer and the oxide semiconductor film are then supplied with the released electrons. The oxygen vacancies at the interface between the drain electrode layer and the oxide semiconductor film are reduced, and the transistor 40 10, 4011 threshold voltage shift in the negative direction can be suppressed. .

[0516] Furthermore, since high resistance components can be prevented from being formed in the metal film, it is possible to This reduces the resistance caused by the source electrode layer and the drain electrode layer. The decrease in the on-current of the transistors 4010 and 4011 can be suppressed.

[0517] Therefore, the stable electrical characteristics using the oxide semiconductor film of this embodiment shown in FIGS. The semiconductor device includes transistors 4010 and 4011 having high reliability. An apparatus can be provided.

[0518] In addition, the oxide semiconductor film overlaps with the channel formation region of the transistor 4011 for the driver circuit. A conductive layer may be further provided at a position overlapping with the channel formation region of the oxide semiconductor film. By placing it in a position where The amount of change in the threshold voltage of the transistor 4011 can be further reduced. The potential of the gate electrode layer of the transistor 4011 may be the same as or different from that of the gate electrode layer of the transistor 4011. The conductive layer may also function as a second gate electrode layer. V, or may be floating.

[0519] The conductive layer also shields external electric fields, i.e., prevents external electric fields from reaching the internal It also has a function to prevent the influence of static electricity on the circuitry (particularly, an electrostatic shielding function against static electricity). The shielding function of the conductive layer prevents the electrical conductivity of the transistor from being affected by external electric fields such as static electricity. This can prevent fluctuations in the characteristics.

[0520] The transistor 4010 provided in the pixel portion 4002 is electrically connected to a display element. The display element is not particularly limited as long as it can display, and various display elements can be used. can be used.

[0521] FIG. 20(A) shows an example of a liquid crystal display device using a liquid crystal element as a display element. In the figure, a liquid crystal element 4013, which is a display element, has a first electrode layer 4030 and a second electrode layer 4040. 031 and a liquid crystal layer 4008. The liquid crystal layer 4008 is sandwiched between alignment films. The second electrode layer 4031 is provided with insulating films 4032 and 4033 that function as a second The first electrode layer 4030 and the second electrode layer 4031 are disposed on the substrate 4006 side. The structure is stacked via 008.

[0522] The spacers 4035 are columnar spacers obtained by selectively etching the insulating film. It is provided to control the film thickness (cell gap) of the liquid crystal layer 4008. A spherical spacer may also be used.

[0523] When liquid crystal elements are used as display elements, thermotropic liquid crystals, low molecular weight liquid crystals, polymer liquid crystals, etc. The liquid crystals that can be used include polymer dispersed liquid crystals, ferroelectric liquid crystals, and antiferroelectric liquid crystals. The liquid crystal material (liquid crystal composition) can be in a cholesteric phase, a smectic phase, or a cubic phase depending on the conditions. The phases shown are nematic, chiral, isotropic, etc.

[0524] In addition, a liquid crystal composition that exhibits a blue phase without using an alignment film may be used for the liquid crystal layer 4008. In this case, the liquid crystal layer 4008, the first electrode layer 4030, and the second electrode layer 4031 The blue phase is one of the liquid crystal phases, and when the temperature of the cholesteric liquid crystal is increased, The blue phase is the phase that appears just before the transition from the cholesteric phase to the isotropic phase. It can be expressed by using a liquid crystal composition in which a chiral agent and a blue colorant are mixed. In order to widen the temperature range in which the blue phase appears, a polymerizable monomer is added to the liquid crystal composition that appears the blue phase. A polymerization initiator may also be added to form a liquid crystal layer by carrying out a polymer stabilization process. The liquid crystal composition exhibiting the blue phase has a short response time and is optically isotropic, so Since alignment treatment is not required, the viewing angle dependency is small. This eliminates the need for rubbing, preventing electrostatic damage caused by rubbing. This makes it possible to reduce defects and damage to the liquid crystal display device during the manufacturing process. The productivity of the display device can be improved. The influence of static electricity can cause the electrical characteristics of transistors to fluctuate significantly, resulting in deviation from the design range. Therefore, there is a risk that a blue light may be emitted from a liquid crystal display device including a transistor including an oxide semiconductor film. It is more effective to use a liquid crystal composition that exhibits a phase.

[0525] The specific resistance of the liquid crystal material is 1×10 9 Ω·cm or more, preferably 1×10 11 Ω·cm or more, and more preferably 1×10 12 Ω·cm or more. The resistivity values ​​in this document are those measured at 20°C.

[0526] The size of the storage capacitor provided in the liquid crystal display device is determined by the lead of the transistor arranged in the pixel portion. It is set so that the charge can be held for a predetermined period, taking into consideration the current and other factors. The size of the oxide film may be set in consideration of the off-state current of the transistor. By using a transistor with a semiconductor film, the liquid crystal capacitance in each pixel It is sufficient to provide a storage volume having a size of 1 / 3 or less, preferably 1 / 5 or less, of the capacity of the do.

[0527] The transistor including the oxide semiconductor film disclosed in this specification has a current value ( Therefore, the retention time of electrical signals such as image signals can be controlled to be low. The write interval can be set to a long value when the power is on. This reduces the frequency of flash operations, thereby reducing power consumption.

[0528] In addition, the transistor including the oxide semiconductor film disclosed in this specification has a relatively high field effect For example, a transistor capable of such high speed driving can be By using a transistor in a liquid crystal display device, the switching transistor in the pixel portion and the driving transistor The driver transistors used in the circuit section can be formed on the same substrate. That is, it is necessary to use a semiconductor device formed from a silicon wafer or the like as a separate driving circuit. Therefore, the number of components in the semiconductor device can be reduced. By using a transistor that can be driven at high speed, it is possible to provide a high-quality image.

[0529] There are two types of LCD displays: TN (Twisted Nematic) mode, IPS (In-P lane-Switching) mode, FFS(Fringe Field Switching) mode, ching) mode, ASM(Axially Symmetric aligned) Micro-cell mode, OCB (Optical Compensated B) refrigeration mode, FLC (Ferroelectric Liquid d Crystal) mode, AFLC (AntiFerroelectric Liq. uid Crystal) mode can be used.

[0530] Furthermore, normally black type liquid crystal display devices, for example, those employing vertical alignment (VA) mode The liquid crystal display device may be a transmission type. For example, MVA (Multi-Domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode , ASV (Advanced Super View) mode, etc. can be used. It can also be applied to VA type liquid crystal display devices. VA type liquid crystal display devices are: It is a type of method for controlling the alignment of liquid crystal molecules in a liquid crystal display panel. VA type liquid crystal display devices are When no voltage is applied, the liquid crystal molecules are oriented perpendicular to the panel surface. In addition, a pixel is divided into several regions (subpixels), each of which is oriented in a different direction. This is called multi-domain or multi-domain design, which is designed to knock down molecules. The following method can be used.

[0531] In addition, in display devices, black matrices (light-shielding layers), polarizing members, phase difference members, reflecting members, Optical members (optical substrates) such as a protection member are provided as appropriate. For example, a polarizing substrate and a retardation substrate are provided as appropriate. Alternatively, a backlight or a sidelight may be used as the light source. It's fine.

[0532] In addition, the display method in the pixel section uses the progressive method, interlace method, etc. In addition, the color elements controlled by pixels when displaying colors are RGB (R is It is not limited to the three colors (red, green, and blue). For example, RGBW (W stands for white). , or RGB plus one or more colors such as yellow, cyan, magenta, etc. The size of the display area may be different for each dot of the color element. is not limited to color display devices, but also applies to monochrome display devices. It is also possible.

[0533] Furthermore, a light-emitting element that utilizes electroluminescence is used as a display element included in the display device. The light-emitting element using electroluminescence can be applied to a light-emitting material They are distinguished by whether they are organic or inorganic compounds, and generally, the former are organic E The latter is called an inorganic EL element.

[0534] In an organic EL element, electrons and holes are released from a pair of electrodes by applying a voltage to the light-emitting element. are injected into the layers containing the light-emitting organic compounds, causing a current to flow. The recombination of the electrons and holes creates an excited state in the light-emitting organic compound. The excited state is then converted to the ground state, at which point light is emitted. Such a light-emitting element is called a current-excited light-emitting element. An example using an organic EL element is shown below.

[0535] Inorganic EL elements are divided into dispersion-type inorganic EL elements and thin-film-type inorganic EL elements depending on the element structure. Dispersion-type inorganic EL elements have a light-emitting layer in which particles of a light-emitting material are dispersed in a binder. The emission mechanism is a donor-acceptor interaction that utilizes the donor and acceptor levels. Thin-film inorganic EL devices sandwich the light-emitting layer between dielectric layers. Furthermore, this structure is sandwiched between electrodes, and the light emission mechanism utilizes the inner-shell electron transition of metal ions. In this example, the light-emitting element is an organic EL element. do.

[0536] In order to extract light emitted from the light-emitting element, at least one of the pair of electrodes needs to be light-transmitting. Then, a transistor and a light emitting element are formed on the substrate, and light is extracted from the surface opposite to the substrate. There are various types of light sources, including top emission, bottom emission, and light emission from the substrate side and the opposite side of the substrate. There are light emitting elements with a double-sided emission structure that emits light from both sides, and light emitting elements of any emission structure can be applied. It is possible.

[0537] 19(A), (B) and 20(B) show examples of light-emitting devices using light-emitting elements as display elements. show.

[0538] FIG. 19(A) is a plan view of the light emitting device, and the dashed lines V1-W1 and V2- The cross section taken along lines W2 and V3-W3 corresponds to FIG. 19(B). In the plan view, the electroluminescent layer 542 and the second electrode layer 543 are omitted and not shown. do not have.

[0539] The light-emitting device shown in FIG. 19 includes a transistor 510, a capacitor 520, and wirings on a substrate 500. The transistor 510 has a layer intersection 530, and is electrically connected to the light emitting element 540. 19 shows a bottom emission light source that extracts light from the light emitting element 540 through the substrate 500. This is a light emitting device with a molded structure.

[0540] The transistor described in the above embodiment can be used as the transistor 510. In this embodiment, a transistor having a structure and operation similar to that of the transistor 410 described in Embodiment 1 is used. An example of application of a transistor obtained by the manufacturing method will be described below.

[0541] The transistor 510 includes gate electrode layers 511a and 511b, a gate insulating film 502, an oxide semiconductor The conductive film 512, the conductive layers 513a and 513b functioning as source and drain electrode layers, and the conductive film 513c functioning as source and drain electrode layers. Contains b.

[0542] A transistor having a structure and a manufacturing method similar to those of the transistor 410 described in Embodiment 1 The substrate 510 is a metal oxide film and a metal oxide film having a higher reducing property than the oxide semiconductor film. After forming the conductive film, a heat treatment is performed to reduce the metal oxide film to a metal film. At this time, oxygen is released from the metal oxide film, which has a higher reducing property than the oxide semiconductor film. The source electrode layer and the drain electrode layer can be supplied with the oxide semiconductor film. oxygen vacancies at the interface between the oxide semiconductor film and the oxide semiconductor film, and This can prevent the voltage from shifting in the negative direction.

[0543] Furthermore, since high resistance components can be prevented from being formed in the metal film, it is possible to This reduces the resistance caused by the source electrode layer and the drain electrode layer. The decrease in the on-current of the transistor 510 can be suppressed.

[0544] Therefore, stable electrical characteristics can be obtained using the oxide semiconductor film 512 of this embodiment shown in FIG. A highly reliable semiconductor device including a transistor 510 having the same is provided. This can be done.

[0545] The capacitor element 520 includes conductive layers 521a and 521b, a gate insulating film 502, and an oxide semiconductor film 5 22, including a conductive layer 523, and the conductive layers 521a, 521b and the conductive layer 523 form a gate insulating film. A capacitor is formed by sandwiching the film 502 and the oxide semiconductor film 522.

[0546] The wiring layer intersection 530 is an intersection between the gate electrode layers 511a and 511b and the conductive layer 533. The gate electrode layers 511a and 511b and the conductive layer 533 are provided with a gate insulating film 502 therebetween. Intersect via.

[0547] In this embodiment, the gate electrode layer 511a and the conductive layer 521a are formed to a thickness of 30 nm. A titanium film of 200 nm thick was used as the gate electrode layer 511b and the conductive layer 521b. Therefore, the gate electrode layer has a laminated structure of a titanium film and a copper thin film.

[0548] The oxide semiconductor films 512 and 522 are IGZO films with a thickness of 25 nm.

[0549] An interlayer insulating film 504 is formed on the transistor 510, the capacitor element 520, and the wiring layer intersection 530. A color filter is formed on the interlayer insulating film 504 in an area overlapping the light emitting element 540. A flat insulating film 504 is formed on the interlayer insulating film 504 and the color filter layer 505. An insulating film 506 that functions as a photo-insulating film is provided.

[0550] A first electrode layer 541, an electroluminescent layer 542, and a second electrode layer 543 are stacked in this order on an insulating film 506. The light emitting element 540 includes a stacked structure. 510 is an opening formed in the insulating film 506 and the interlayer insulating film 504 that reaches the conductive layer 513a. At this point, the first electrode layer 541 and the conductive layer 513a are electrically connected by being in contact with each other. A partition wall 507 is provided to cover a part of the first electrode layer 541 and the opening. It is being used.

[0551] The interlayer insulating film 504 is formed by a plasma CVD method using an oxide film having a thickness of 200 nm to 600 nm. The insulating film 506 may be a silicon nitride film. The partition 507 is made of a photosensitive acrylic film and a photosensitive polyimide film with a thickness of 1500 nm. This can be done.

[0552] The color filter layer 505 may be made of, for example, a chromatic translucent resin. As the chromatic translucent resin, photosensitive or non-photosensitive organic resins can be used. Using a photosensitive organic resin layer reduces the number of resist masks required, simplifying the process. It is preferable.

[0553] Chromatic colors are colors other than achromatic colors such as black, gray, and white. It is made of materials that transmit only colored light. Chromatic colors include red, green, and blue. Also, cyan, magenta, yellow, etc. may be used. The color filter layer transmits only light of the selected chromatic color. The color filter layer has a peak at the wavelength of light of It is advisable to appropriately control the optimum film thickness taking into consideration the relationship between the concentration of the color and the light transmittance. The thickness of the filter layer 505 may be set to 1500 nm or more and 2000 nm or less.

[0554] In the light-emitting device shown in FIG. 20B, a light-emitting element 4513 which is a display element is a pixel portion 4 The light-emitting element 451 is electrically connected to the transistor 4010 provided in the light-emitting element 451. The third configuration is a stack of a first electrode layer 4030, an electroluminescent layer 4511, and a second electrode layer 4031. The structure is not limited to the configuration shown in the figure. The structure of the light-emitting element 4513 can be changed accordingly.

[0555] The partition walls 4510 and 507 are formed using an organic insulating material or an inorganic insulating material. An opening is formed on the first electrode layer 4030, 541 using a flexible resin material, and the opening It is preferable that the sidewall be formed as an inclined surface having a continuous curvature.

[0556] The electroluminescent layers 4511 and 542 may be formed of a single layer or a plurality of layers stacked. It doesn't matter whether it's configured as follows:

[0557] To prevent oxygen, hydrogen, moisture, carbon dioxide, etc. from entering the light emitting elements 4513 and 540, A protective film may be formed over the electrode layers 4031 and 543 and the partition walls 4510 and 507. As the film, a silicon nitride film, a silicon nitride oxide film, a DLC film, etc. can be formed. .

[0558] In addition, oxygen, hydrogen, moisture, carbon dioxide, etc. must be prevented from entering the light emitting elements 4513 and 540. A layer containing an organic compound that covers the light-emitting elements 4513 and 540 may be formed by evaporation.

[0559] The first substrate 4001, the second substrate 4006, and the sealing material 4005 seal the The space is sealed with a filler 4514. Highly airtight and low outgassing protective film (lamination film, UV curable resin) It is preferable to package (enclose) the product in a film or a cover material.

[0560] Filler 4514 can be inert gas such as nitrogen or argon, or ultraviolet curing resin or Thermosetting resins can be used, such as PVC (polyvinyl chloride), acrylic, and polyimide. resin, epoxy resin, silicone resin, PVB (Polyvinyl Butyral) or EVA (Ethylene Vinyl For example, nitrogen may be used as a filler.

[0561] If necessary, a polarizing plate or a circular polarizing plate (including an elliptical polarizing plate) may be provided on the light-emitting surface of the light-emitting element. Optical films such as retardation plates (λ / 4 plates, λ / 2 plates) and color filters may be provided as appropriate. In addition, an anti-reflection film may be provided on the polarizing plate or the circular polarizing plate. Anti-glare treatment can be applied to diffuse reflected light and reduce glare.

[0562] It is also possible to provide electronic paper that drives electronic ink as a display device. Electronic paper is also called an electrophoretic display (electrophoretic display), and is a paper It is possible to make it as easy to read as a digital camera, consume less power than other display devices, and have a thinner and lighter form factor. This has the advantage that

[0563] The electrophoretic display device may have various forms, but it has a structure in which first particles having a positive charge and The microcapsules containing the negatively charged second particles are dispersed in a solvent or solute. By applying an electric field to the microcapsules, The particles in the tube are moved in opposite directions to display only the color of the particles that have gathered on one side. The first particles or the second particles contain a dye and do not move in the absence of an electric field. In addition, the color of the first particle and the color of the second particle are different (including colorless). do.

[0564] In this way, the electrophoretic display device moves materials with high dielectric constants to areas with high electric fields, so-called This is a display that utilizes the dielectrophoretic effect.

[0565] The microcapsules dispersed in a solvent are called electronic ink. The electronic ink can be printed on surfaces such as glass, plastic, fabric, and paper. Color display is also possible by using color filters or particles containing pigments.

[0566] The first particles and the second particles in the microcapsules may be made of a conductive material, an insulating material, Semiconductor materials, magnetic materials, liquid crystal materials, ferroelectric materials, electroluminescent materials, A material selected from magnetochromic materials, magnetophoretic materials, or a composite material of these is used. That's good enough.

[0567] In addition, a display device using a twist ball display method can also be applied as electronic paper. The twist ball display method uses spherical particles painted in black and white on the display element. The electrode layer is disposed between the first electrode layer and the second electrode layer. This is a method of displaying information by controlling the orientation of spherical particles by generating a potential difference between the electrode layers. be.

[0568] 18 to 20, the first substrates 4001 and 500, the second substrate 4006, As the substrate, in addition to a glass substrate, a flexible substrate can also be used. For example, a transparent substrate can be used. As for plastic, FRP (Fibre Reinforced Plastic) can be used. Glass-Reinforced Plastics) plate, PVF (Polyvinyl Fluoride film, polyester film or acrylic resin film can be used. If transparency is not required, metal substrates such as aluminum and stainless steel can be used. For example, aluminum foil can be covered with PVF film or polyester film. A sheet sandwiched between two polyester films can also be used.

[0569] In this embodiment, an aluminum oxide film is used as the insulating film 4020. can be formed by sputtering or plasma CVD.

[0570] The aluminum oxide film provided as the insulating film 4020 over the oxide semiconductor film is resistant to hydrogen, moisture, and It has a high blocking effect that prevents impurities such as urea and oxygen from passing through the membrane. stomach.

[0571] Therefore, the aluminum oxide film is free from hydrogen, which is a factor of fluctuation during and after the manufacturing process. The intrusion of impurities such as moisture into the oxide semiconductor film and the intrusion of the main component material of the oxide semiconductor The oxide semiconductor film functions as a protective film that prevents oxygen from being released from the oxide semiconductor film.

[0572] The insulating films 4021 and 506 functioning as planarizing insulating films are made of acrylic resin, polyimide, or the like. Heat-resistant resins such as amide resins, benzocyclobutene resins, polyamide resins, and epoxy resins In addition to the above organic materials, low dielectric constant materials (L low-k materials), siloxane resin, PSG (phosphor glass), BPSG (phosphor boron glass) In addition, a plurality of insulating films made of these materials can be stacked. In this way, an insulating film may be formed.

[0573] The method for forming the insulating films 4021 and 506 is not particularly limited. Depending on the material, sputtering may be used. coating method, SOG method, spin coating, dip coating, spray coating, droplet ejection method (inkjet printing methods (screen printing, offset printing, etc.), doctor knife, roll coater A coater, curtain coater, knife coater, etc. can be used.

[0574] A display device transmits light from a light source or a display element to display an image. All thin films such as the substrate, insulating film, and conductive film provided in the part are resistant to light in the visible light wavelength range. It shall be translucent.

[0575] A first electrode layer and a second electrode layer (a pixel electrode layer, a common electrode layer, a pair of electrodes) that apply a voltage to the display element In the case of a light-emitting diode (also called a counter electrode layer), the direction of the light to be extracted, the location of the electrode layer, and The light transmission property or reflectivity can be selected depending on the pattern structure of the electrode layer.

[0576] The first electrode layers 4030 and 541 and the second electrode layers 4031 and 543 are made of tungsten oxide. Indium oxide containing tungsten oxide, indium zinc oxide containing titanium oxide Indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium tin oxide (hereinafter , denoted as ITO), indium zinc oxide, indium tin oxide doped with silicon oxide A light-transmitting conductive material such as graphene can be used.

[0577] The first electrode layers 4030 and 541 and the second electrode layers 4031 and 543 are made of tungsten ( W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium ( V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel Ni (Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), silver ( Using one or more of metals such as Ag, their alloys, or their metal nitrides It can be formed.

[0578] In this embodiment, the light emitting device shown in FIG. 19 is a bottom emission type, so the first electrode layer 54 The first electrode layer 541 has a light-transmitting property, and the second electrode layer 543 has a reflective property. When a film is used, the film thickness is thin enough to maintain light-transmitting properties, and the second electrode layer 543 has light-transmitting properties. In the case of using a conductive film, a conductive film having reflectivity may be stacked.

[0579] The first electrode layers 4030 and 541 and the second electrode layers 4031 and 543 are made of highly conductive The conductive layer can be formed using a conductive composition containing conductive molecules (also called a conductive polymer). As the conductive polymer, a so-called π-electron conjugated conductive polymer can be used. For example, , polyaniline or a derivative thereof, polypyrrole or a derivative thereof, polythiophene or a derivative thereof derivatives, or copolymers of two or more of aniline, pyrrole and thiophene Examples include hydroxybenzoates and their derivatives.

[0580] In addition, since transistors are easily damaged by static electricity, a protection circuit for protecting the drive circuit is required. It is preferable that the protection circuit is configured using a non-linear element.

[0581] As described above, by using the transistor described in Embodiment 1 or 2, various It is possible to provide semiconductor devices having various functions.

[0582] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0583] (Embodiment 13) Information on an object is read using the transistor described in Embodiment 1 or 2. A semiconductor device having an image sensor function can be manufactured.

[0584] FIG. 21A shows an example of a semiconductor device having an image sensor function. FIG. 21(B) is a cross-sectional view showing a part of the photosensor. .

[0585] The photodiode 602 has one electrode connected to a photodiode reset signal line 658 and the other One electrode is electrically connected to the gate of transistor 640. One of the source and drain is connected to the photosensor reference signal line 672, and the other of the source and drain is connected to the photosensor reference signal line 673. The other terminal is electrically connected to one of the source and drain terminals of the transistor 656. The transistor 656 has a gate connected to a gate signal line 659 and a source or drain connected to a photodiode. The signal line 671 is electrically connected to the sensor output signal line 671.

[0586] Note that in the circuit diagrams in this specification, a transistor including an oxide semiconductor film is not clearly shown. To make it easy to identify, the symbol for a transistor using an oxide semiconductor film is written as “OS.” In FIG. 21A, the transistor 640 and the transistor 656 are the same as those in the previous embodiment. The transistor shown in the embodiment can be applied to the transistor including an oxide semiconductor film. In this embodiment, a transistor having a structure and a manufacturing method similar to those of the transistor 410 described in Embodiment 1 is used. An example of applying a transistor that can be used in a semiconductor device will be shown below.

[0587] FIG. 21B shows a photodiode 602 and a transistor 640 in the photosensor. 6 is a cross-sectional view showing a substrate 601 (TFT substrate) having an insulating surface, on which a sensor function is provided. A photodiode 602 and a transistor 640 are provided. A substrate 613 is provided on the board 602 and the transistor 640 using an adhesive layer 608. There are.

[0588] An insulating film 631, an interlayer insulating film 633, and an interlayer insulating film 634 are provided on the transistor 640. The photodiode 602 is provided on the interlayer insulating film 633. Electrode layers 641a and 641b formed on the interlayer insulating film 634 and an electrode layer 641a formed on the interlayer insulating film 634. 42, a first semiconductor film 606a and a second semiconductor film 606 are formed between the first semiconductor film 606a and the second semiconductor film 606b in this order from the interlayer insulating film 633 side. The second semiconductor film 606b and the third semiconductor film 606c are stacked.

[0589] The electrode layer 641b is electrically connected to the conductive layer 643 formed on the interlayer insulating film 634. The layer 642 is electrically connected to the conductive layer 645 via the electrode layer 641a. is electrically connected to the gate electrode layer of the transistor 640, and 2 is electrically connected to transistor 640.

[0590] Here, the first semiconductor film 606a is a semiconductor film having a p-type conductivity, and the second semiconductor film 606b is a high resistance semiconductor film (i-type semiconductor film), and the third semiconductor film 606c is an n-type A pin-type photodiode in which semiconductor films having different conductivity types are stacked is shown as an example.

[0591] The first semiconductor film 606a is a p-type semiconductor film, and is an amorphous film containing an impurity element that imparts p-type. The first semiconductor film 606a can be formed from a group 13 silicon film. Using semiconductor material gas containing impurity elements (e.g., boron (B)), plasma CVD is used. Silane (SiH4) can be used as the semiconductor material gas. Alternatively, i2H6, SiH2Cl2, SiHCl3, SiCl4, SiF4, etc. may be used. In addition, after forming an amorphous silicon film that does not contain impurity elements, the film is formed by diffusion or ion implantation. Impurity elements may be introduced into the amorphous silicon film by using a method such as ion implantation. It is preferable to diffuse the impurity element by heating or the like after introducing the impurity element. In this case, the amorphous silicon film can be formed by LPCVD, vapor phase growth, Alternatively, sputtering or the like may be used. The thickness of the first semiconductor film 606a is 10 nm or more and 5 nm or less. It is preferable to form it so that the thickness is 0 nm or less.

[0592] The second semiconductor film 606b is an i-type semiconductor film (intrinsic semiconductor film) and is made of amorphous silicon. The second semiconductor film 606b is formed by amorphous silicon using a semiconductor material gas. A thick silicon film is formed by plasma CVD. The semiconductor material gas is silane. (SiH4) can be used. Alternatively, Si2H6, SiH2Cl2, SiHCl3, S The second semiconductor film 606b may be formed by LPCVD. The second semiconductor film 606b may be formed by vapor deposition, sputtering, or the like. It is preferable to form the film so that the thickness is 00 nm or more and 1000 nm or less.

[0593] The third semiconductor film 606c is an n-type semiconductor film and is an amorphous film containing an impurity element that imparts n-type. The third semiconductor film 606c is formed of a thick silicon film. It is formed by the plasma CVD method using a semiconductor material gas containing silicon (e.g., phosphorus (P)). Silane (SiH4) can be used as the semiconductor material gas. SiH2Cl2, SiHCl3, SiCl4, SiF4, etc. may also be used. After forming an amorphous silicon film that does not contain elements, the film is then doped with silicon using diffusion or ion implantation. An impurity element may be introduced into the amorphous silicon film by ion implantation or the like. After the element is introduced, the impurity element may be diffused by heating or the like. The amorphous silicon film can be formed by LPCVD, vapor phase growth, or sputtering. The thickness of the third semiconductor film 606c is 20 nm or more and 200 nm or less. It is preferable to form it so that it faces downward.

[0594] The first semiconductor film 606a, the second semiconductor film 606b, and the third semiconductor film 606c are Instead of an amorphous semiconductor, it may be formed using a polycrystalline semiconductor, or a microcrystalline (semi-amorphous) semiconductor. Rufus (Semi Amorphous Semiconductor: SAS) Semiconductor It may also be formed using a conductor.

[0595] In addition, the mobility of holes generated by the photoelectric effect is smaller than that of electrons, so the pin-type The photodiode exhibits better characteristics when the p-type semiconductor film side is used as the light receiving surface. From the surface of the substrate 601 on which the in-type photodiode is formed to the photodiode 602 The example shows how the light 622 received by the semiconductor film is converted into an electrical signal. Since light from the semiconductor film side having the conductivity type of the conductive type becomes disturbance light, the electrode layer is made of a conductive material having a light-shielding property. It is also possible to use the n-type semiconductor film side as the light receiving surface.

[0596] The insulating film 631, the interlayer insulating film 633, and the interlayer insulating film 634 are made of insulating materials. Depending on the material, sputtering, plasma CVD, SOG, spin coating, Spray coating, droplet ejection method (inkjet method, etc.), printing method (screen printing, It can be formed using techniques such as offset printing.

[0597] The insulating film 631 may be made of an inorganic insulating material such as a silicon oxide layer, a silicon oxynitride layer, An oxide insulating film such as an aluminum oxide layer or an aluminum oxynitride layer, or a silicon nitride layer , a nitride such as a silicon nitride oxide layer, an aluminum nitride layer, or an aluminum nitride oxide layer A single layer or a stacked layer of insulating films can be used.

[0598] In this embodiment, an aluminum oxide film is used as the insulating film 631. It can be formed by sputtering or plasma CVD.

[0599] The aluminum oxide film provided as the insulating film 631 over the oxide semiconductor film is resistant to hydrogen, moisture, and the like. High blocking effect that prevents both impurities and oxygen from passing through the membrane .

[0600] Therefore, the aluminum oxide film is free from hydrogen, which is a factor of fluctuation during and after the manufacturing process. The intrusion of impurities such as moisture into the oxide semiconductor film and the intrusion of the main component material of the oxide semiconductor The oxide semiconductor film functions as a protective film that prevents oxygen from being released from the oxide semiconductor film.

[0601] The interlayer insulating films 633 and 634 function as planarizing insulating films to reduce surface irregularities. The interlayer insulating films 633 and 634 are preferably made of, for example, polyimide resin, aluminum, or the like. Resin-resistant materials such as acrylic resin, benzocyclobutene resin, polyamide resin, and epoxy resin In addition to the above organic insulating materials, low dielectric constant organic insulating materials can be used. low-k materials, siloxane resins, PSG (phosphor glass), BPSG (phosphor A single layer or a multilayer of a material such as boron glass can be used.

[0602] By detecting the light incident on the photodiode 602, information on the detected object is read. It is possible to read the information of the detected object using a light source such as a backlight. It is possible.

[0603] A transistor having a structure and a manufacturing method similar to those of the transistor 410 described in Embodiment 1 The metal oxide film and the metal oxide film having a higher reducing property than the oxide semiconductor are formed on the oxide semiconductor film. After the conductive film is formed, a heat treatment is performed to reduce the metal oxide film to a metal film. At this time, oxygen is released from the metal oxide film, which has a higher reducing property than the oxide semiconductor, and the oxide This allows the source electrode layer and the drain electrode layer to be formed on the semiconductor film. The oxygen vacancies at the interface with the oxide semiconductor film are reduced, and the threshold voltage of the transistor 640 is can be prevented from shifting in the negative direction.

[0604] Furthermore, since high resistance components can be prevented from being formed in the metal film, it is possible to This reduces the resistance caused by the source electrode layer and the drain electrode layer. The decrease in the on-current of the transistor 640 can be suppressed.

[0605] Therefore, the transistor using the oxide semiconductor film of this embodiment and having stable electrical characteristics 640, a highly reliable semiconductor device can be provided.

[0606] The structures, methods, and the like described in this embodiment may be combined as appropriate with the structures, methods, and the like described in other embodiments. They can be used in combination.

[0607] (Embodiment 14) In this embodiment, a transistor according to one embodiment of the present invention is used, and a transistor is used in a state where power is not supplied. Here is an example of a semiconductor device that can retain memory contents even under certain conditions and has no limit on the number of times it can be written. This will be explained using the drawings.

[0608] 22A and 22B are examples of the structure of a semiconductor device. FIG. 22A is a cross-sectional view of the semiconductor device. 22(B) shows a plan view of the semiconductor device, and FIG. 22(C) shows a circuit diagram of the semiconductor device. Here, FIG. 22(A) corresponds to the cross section taken along line E1-E2 in FIG. 22(B).

[0609] The semiconductor device (memory cell 514) shown in FIGS. 22A and 22B has a first A transistor 210 made of a semiconductor material is provided on top of a transistor made of a second semiconductor material. The transistor 550 may be the transistor described in Embodiment 6. The structure of 110 is applied.

[0610] Here, the first semiconductor material and the second semiconductor material may be materials having different forbidden band widths. For example, the first semiconductor material may be a semiconductor material other than an oxide semiconductor (such as silicon). The second semiconductor material can be an oxide semiconductor. The transistors used in this method can easily operate at high speed. The properties of the charge storage capacitor allow it to retain charge for a long period of time.

[0611] The semiconductor material used for the transistor 210 may be, for example, silicon, germanium, silicon dioxide, or silicon dioxide. Congenerium germanium, silicon carbide, or gallium arsenide can be used. It is preferable to use a conductor. Alternatively, an organic semiconductor material may be used. Transistors using conductive materials are capable of operating at sufficiently high speeds.

[0612] The transistor 210 and the transistor 550 are both n-channel transistors. However, a p-channel transistor can also be used. It goes without saying that the semiconductor memory device shown in Embodiment 6, which uses an oxide semiconductor for storing data, The transistor 110 is used as the transistor 210 and is also used in semiconductor devices. It is not necessary to limit the specific configuration of the semiconductor device, such as the materials and structure of the semiconductor device, to those shown here. There's no need.

[0613] The transistor 210 in FIG. 22(A) includes a semiconductor material (e.g., silicon). A channel forming region 216 is provided on the substrate 200, and the channel forming region 216 is sandwiched between the substrate 200 and the channel forming region 216. The impurity regions 220a and 220b are provided as shown in FIG. The intermetallic compound regions 224a and 224b are formed on the channel forming region 216. a gate insulating film 208 and a gate electrode layer 209 provided on the gate insulating film 208. In the drawings, the source electrode layer and the drain electrode layer may not be explicitly shown. For convenience, this state may also be called a transistor. To explain the connection relationship of the transistor, the source electrode including the source and drain regions is In other words, in this specification, the source electrode layer and the drain electrode layer are sometimes referred to as a source electrode layer and a drain electrode layer. The description of may include a source region.

[0614] An element isolation insulating film 206 is provided on the substrate 200 so as to surround the transistor 210. The insulating film 228 contacts the transistor 210, and the insulating film 230 contacts the insulating film 228. In the transistor 210, a side surface of the gate electrode layer 209 is provided with a surface. A sidewall insulating film is provided to form impurity region 2 including regions with different impurity concentrations. 20a, 220b may also be used.

[0615] The transistor 210 using a single crystal semiconductor substrate can operate at high speed. By using this transistor as a readout transistor, it is possible to read out information at high speed. In this embodiment, the insulating film in contact with the transistor 210 is The insulating film 228 has a two-layer structure made up of an insulating film 230 in contact with the insulating film 228. The insulating film in contact with the transistor 210 may be a single layer or a laminate of three or more layers. As a process before forming the transistor 550 and the capacitor element 551, The insulating film formed on the substrate is subjected to CMP processing to form planarized insulating films 228 and 230. At the same time, the upper surface of the gate electrode layer 209 is exposed.

[0616] The insulating film 228 and the insulating film 230 are respectively a silicon oxide film, a silicon oxynitride film, and an alumina oxide film. Aluminum film, aluminum oxynitride film, silicon nitride film, aluminum nitride film, nitriding acid An inorganic insulating film such as a silicon nitride film or an aluminum nitride oxide film can be used. The insulating film 228 and the insulating film 230 are formed by using a plasma CVD method, a sputtering method, or the like. This can be done.

[0617] In addition, organic materials such as polyimide resin, acrylic resin, and benzocyclobutene resin are also used. In addition to the above organic materials, low dielectric constant materials (low-k materials) can also be used. When organic materials are used, they can be formed by wet methods such as spin coating and printing. The insulating films 228 and 230 may be formed by the above process.

[0618] In this embodiment, the insulating film 228 is a silicon nitride film, and the insulating film 230 is a silicon nitride film. A silicon oxide film is used.

[0619] On the surface of the insulating film 230, a planarization treatment is performed on a region where the oxide semiconductor film 103 is to be formed. In this embodiment, the surface is sufficiently planarized by a polishing process (for example, a CMP process). Preferably, the average surface roughness of the insulating film 230 is 0.15 nm or less. A semiconductor film 103 is formed.

[0620] The transistor 550 includes an oxide semiconductor film 103 provided over an insulating film 230 and an oxide semiconductor film 104. A gate insulating film 111 is provided on the conductor film 103, and a gate insulating film 112 is provided on the gate insulating film 111. A gate electrode layer 105, an insulating film 106 provided on the gate electrode layer 105, and a gate electrode A sidewall insulating film 109a is provided to cover the side surfaces of the layer 105 and the insulating film 106. , 109b, the oxide semiconductor film 103, the gate insulating film 111, and the sidewall insulating film 1 a source electrode layer 116a and a drain electrode layer 116b in contact with the gate electrodes 109a and 109b, respectively. In addition, an insulating film 117 and an interlayer insulating film 115 are provided to cover the transistor 550. do.

[0621] The oxide semiconductor film 103 is formed between the channel formation region 108 and the oxide semiconductor film 103. The dopant-containing regions 107a and 107b are formed by the dopant-containing region 1. Regions 07a and 107b have a lower resistance than the channel formation region 108.

[0622] The transistor 550 includes a source electrode layer 116a and a drain electrode layer 116b in contact with the oxide semiconductor film 103. The source electrode layer 116a is formed of a metal film 114. The drain electrode layer 116b is a laminated structure of the metal film 114b and the conductive film 113a. 13b is a laminated structure.

[0623] The metal films 114a and 114b in contact with the oxide semiconductor film 103 are It has higher oxidation resistance than the metallic elements contained in By using metals with a Gibbs free energy higher than that of the oxidation reaction of lead, oxide semiconductors can be This prevents oxygen from being extracted from the source electrode layer 103. Oxygen vacancies at the interfaces between the drain electrode layer 116a and the oxide semiconductor film 103 and the drain electrode layer 116b The increase in the threshold voltage of the transistor is suppressed, and the threshold voltage of the transistor is shifted in the negative direction. can be suppressed.

[0624] In addition, the metal films 114a and 114b are less susceptible to oxidation than the oxide semiconductor film 103. Since oxygen can be prevented from diffusing into the metal films 114a and 114b, Therefore, it is possible to prevent a high resistance component from being formed in the oxide semiconductor film 1 3. To reduce the resistance caused by the source electrode layer 116a and the drain electrode layer 116b. Therefore, a decrease in the on-state current of the transistor can be suppressed.

[0625] The transistor 550 is a transistor in which an oxide semiconductor is used for a channel formation region. Here, the oxide semiconductor film 103 included in the transistor 550 is oxidized by hydrogen, water, or the like. The impurities are reduced and oxygen vacancies are reduced. As a result, the transistor 550 can have excellent off-state characteristics.

[0626] The off-state current of the transistor 550 is extremely small; therefore, by using the transistor 550, In other words, no refresh operation is required. Alternatively, it is possible to provide a semiconductor memory device in which the frequency of refresh operations is extremely low. Therefore, power consumption can be reduced sufficiently.

[0627] In addition, the insulating film 117, the interlayer insulating film 115, and the insulating film 111 are formed so as to cover the transistor 210. The insulating film 117 and the insulating film 118 are made of the same material as the interlayer insulating film 115. The interlayer insulating film 115, the insulating film 117, and the insulating film 11 can be formed by the above method. The insulating film 117 and the interlayer insulating film 115 are formed in a single layer structure or a multilayer structure. After forming the insulating film 117 and the interlayer insulating film 115 so as to cover the transistor 550, The insulating film 117 and the interlayer insulating film 115 are polished until the surface of the film 106 is exposed. The surface of the insulating film 117 and the interlayer insulating film 11 are planarized. An insulating film 118 is formed on the substrate 5 .

[0628] In this embodiment, the insulating film 117 is made of aluminum oxide formed by sputtering. The interlayer insulating film 115 is a silicon oxynitride film formed by plasma CVD. As the silicon oxide film and the insulating film 118, a silicon oxynitride film formed by the plasma CVD method is used. It is said.

[0629] The insulating film 117 is preferably a dense inorganic insulating film. An aluminum oxide film is formed by sputtering so as to cover the capacitor 550. High density aluminum film (film density 3.2g / cm 3 or more, preferably 3.6 g / cm 3 (End) By doing so, stable electrical characteristics can be imparted to the transistor 550. The density was measured by Rutherford Backscattering (RBS). ring spectrometry, X-ray reflectometry (XRR), It can be measured by reflection spectroscopy (RFS).

[0630] An aluminum oxide film that can be used as an inorganic insulating film provided on the transistor 550 The membrane has a blocking effect ( High blocking effect.

[0631] Therefore, the aluminum oxide film is free from hydrogen, which is a factor of fluctuation during and after the manufacturing process. The inclusion of impurities such as moisture in the oxide semiconductor film 103 and the inclusion of a main component constituting the oxide semiconductor The oxide semiconductor film 103 functions as a protective film for preventing oxygen, which is a material, from being released from the oxide semiconductor film 103.

[0632] On the insulating film 118, a transistor 210 and a wiring layer 1 for connecting other transistors are formed. The wiring layer 119a is provided between the insulating film 118 and the interlayer insulating film 11 5, and is electrically connected to the source electrode layer 116a through an opening formed in the insulating film 117. The wiring layer 119b is formed on the insulating film 118, the interlayer insulating film 115, and the insulating film 117. Electrical connection to the drain electrode layer 116b is made through the formed opening.

[0633] The wiring layer 119a and the wiring layer 119b are formed using the same material and method as the gate electrode layer 105. For example, the wiring layer 119a and the wiring layer 119b can be formed of aluminum ( Al), chromium (Cr), copper (Cu), tantalum (Ta), titanium (Ti), molybdenum (Mo), tungsten (W), or a metal film containing the above elements. Metal nitride films (titanium nitride film, molybdenum nitride film, tungsten nitride film) In addition, a small amount of aluminum, copper, or other metal film may be used to form the insulating film. At least one of the layers is made of a high melting point metal film such as titanium, molybdenum, or tungsten, or A structure in which metal nitride films (titanium nitride film, molybdenum nitride film, tungsten nitride film) are stacked It may also be composed.

[0634] Furthermore, the wiring layer 119a and the wiring layer 119b may be made of a conductive metal oxide. Conductive metal oxides include indium oxide (In2O3) and tin oxide (S nO2), zinc oxide (ZnO), indium tin oxide (In2O3-SnO2, ITO and abbreviated), indium oxide zinc oxide (In2O3-ZnO) or these metal oxide materials The conductive material may contain silicon oxide. It may also be a laminated structure of metal oxide materials.

[0635] For example, the wiring layer 119a and the wiring layer 119b may be a single layer of molybdenum film or a tantalum nitride film. A laminate of a tantalum nitride film and a copper film, or a laminate of a tantalum nitride film and a tungsten film, etc., can be used. Cut.

[0636] An insulating film 121 is formed to cover the wiring layers 119a and 119b. An electrode layer 122 is formed on the wiring layer 121 in a region overlapping with the wiring layer 119b. The insulating film 121 and the electrode layer 122 function as a capacitor 551.

[0637] The insulating film 121 can be formed using the same material and method as the interlayer insulating film 115 and the like. Cut.

[0638] In FIG. 22(A) and FIG. 22(B), the transistor 210 and the transistor 550 are provided so as to overlap at least partially, and the source region of the transistor 210 Alternatively, the drain region and the oxide semiconductor film 103 may be provided so as to partly overlap each other. By adopting such a planar layout, the occupied area of ​​the semiconductor device can be reduced. This allows for a reduction in the number of elements required, thereby enabling higher integration.

[0639] Next, an example of a circuit configuration corresponding to FIGS. 22(A) and 22(B) is shown in FIG. 22(C).

[0640] In FIG. 22C, the first wiring (1st Line) and the source of the transistor 210 The electrode layer is electrically connected to the second wiring (2nd Line) and the transistor 210. The drain electrode layer is electrically connected to the third wiring (3rd Line ) is electrically connected to the source electrode layer or the drain electrode layer of the transistor 550, The fourth wiring (4th Line) and the gate electrode layer of the transistor 550 are electrically connected to each other. The gate electrode layer of the transistor 210 and the gate electrode layer of the transistor 550 are connected. The source or drain electrode layer is electrically connected to one of the electrodes of the capacitor 551. The fifth wiring (5th Line) and the other electrode of the capacitor 551 are electrically connected. are.

[0641] In the semiconductor device shown in FIG. 22C, the potential of the gate electrode layer of the transistor 210 can be held. By taking advantage of this feature, it is possible to write, store, and read information as follows: do.

[0642] The writing and retention of data will be explained. First, the potential of the fourth wiring is applied to the transistor 550 is set to a potential at which the transistor 550 is turned on, thereby turning the transistor 550 on. The potential of the third wiring is applied to the gate electrode layer of the transistor 210 and the capacitor 551. That is, a predetermined charge is applied to the gate electrode layer of the transistor 210. (Write). Here, charges that give two different potential levels (hereinafter referred to as Low-level charges) , High level charge) is given. Then, the fourth wiring The potential of the transistor 550 is set to a potential at which the transistor 550 is turned off. By setting the transistor 210 in this state, the charge applied to the gate electrode layer of the transistor 210 is held. (hold).

[0643] Since the off-state current of the transistor 550 is extremely small, the gate electrode layer of the transistor 210 The charge is retained for a long time.

[0644] Next, we will explain how to read information. When a predetermined potential (constant potential) is applied to the first wiring, When an appropriate potential (read potential) is applied to the fifth wiring, the gate of the transistor 210 The second wiring has a different potential depending on the amount of charge held in the electrode layer. If the transistor 210 is an n-channel type, a high level is applied to the gate electrode layer of the transistor 210. The apparent threshold voltage V for a given charge th_H The gate of transistor 210 The apparent threshold voltage V when a low-level charge is applied to the gate electrode layer th_L twist Here, the apparent threshold voltage is the voltage at which the transistor 210 is turned on. This refers to the potential of the fifth wiring required to achieve the "state." The potential of V th_H and V th_L By setting the potential V0 between For example, in writing, the charge given to the gate electrode layer can be determined. If a Bell charge is applied, the potential of the fifth wire is V0 (>V th_H ) then When a low level charge is applied, the transistor 210 is in the "on state." The potential of the fifth wire is V0( <V th_L ), transistor 210 remains "off" Therefore, by observing th...

Claims

[Claim 1] an oxide semiconductor film; a source electrode layer and a drain electrode layer provided in contact with the oxide semiconductor film; a gate electrode layer overlapping the oxide semiconductor film; a gate insulating film provided between the oxide semiconductor film and the gate electrode layer, A semiconductor device in which a metal having higher oxidation resistance than a metal element contained in the oxide semiconductor film is used in at least portions of a source electrode layer and a drain electrode layer in contact with the oxide semiconductor film.

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