Semiconductor device

Abstract

To provide a semiconductor device capable of reducing oxygen deficiency in a metal oxide, and of stabilizing electrical characteristics.SOLUTION: A semiconductor device comprises: a gate electrode; a gate insulating film provided on the gate electrode; a first metal oxide film provided on the gate insulating film; a source electrode and a drain electrode provided so as to be contacted with the first metal oxide film; and a passivation film provided on the source electrode and the drain electrode. The passivation film is configured by sequentially laminating a first insulating film, a second metal oxide film, and a second insulating film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device using an oxide semiconductor.

[0002] In this specification, a semiconductor device is a device that can function by utilizing semiconductor characteristics. In this specification, a transistor refers to a semiconductor device, and an electric device including the transistor Optical devices, semiconductor circuits, and electronic devices are all included in the category of semiconductor devices. [Background technology]

[0003] It is used in many flat panel displays, such as liquid crystal displays and light-emitting displays. The transistors used are made of amorphous silicon and single crystal silicon formed on a glass substrate. The silicon semiconductor is made of silicon semiconductor such as polycrystalline silicon or polysilicon. Transistors using silicon semiconductors are also used in integrated circuits (ICs).

[0004] A technology that uses metal oxides that exhibit semiconducting properties in transistors instead of the silicon semiconductors mentioned above. In this specification, metal oxides that exhibit semiconducting properties are referred to as "oxide semiconductors." For example, Zn-O oxides or In-Ga-Z A transistor is manufactured using an nO-based oxide, and the transistor is used as a switch for pixels of a display device. Techniques for use in etching elements and the like have been disclosed (see Patent Documents 1 and 2). ).

[0005] By the way, it has been pointed out that hydrogen is a carrier source in oxide semiconductors. Therefore, it is necessary to take measures to prevent hydrogen from being mixed in during the formation of the oxide semiconductor. In addition, hydrogen in the oxide semiconductor and the gate insulating film in contact with the oxide semiconductor can be reduced. By reducing the number of gates, the fluctuation in the threshold voltage is reduced (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-123861 A [Patent Document 2] JP 2007-96055 A [Patent Document 3] JP 2009-224479 A Summary of the Invention [Problem to be solved by the invention]

[0007] In addition, in metal oxides, the source of carriers is oxygen vacancies in the metal oxide in addition to hydrogen. Some of the oxygen vacancies in the metal oxide become donors, and oxygen is released into the metal oxide. The electrons that are carriers are generated by oxygen in the metal oxide that contains the channel formation region of the transistor. If there are many defects, electrons are generated in the channel formation region, and the transistor This causes the threshold voltage to shift in the negative direction.

[0008] In addition, an insulating film provided in contact with the metal oxide film including the channel formation region can also The threshold voltage of a transistor is affected by negative charges such as oxygen ions of unbonded oxygen. The inclusion of fixed charges in the insulating film causes a positive shift in the threshold voltage of the transistor. However, if oxygen is released from the insulating film to the outside, The negative fixed charge is reduced, and the threshold voltage of the transistor shifts in the negative direction. There is a risk of this happening.

[0009] In view of this, one embodiment of the present invention is to reduce oxygen vacancies in a metal oxide including a channel formation region, In addition, the oxygen contained in the insulating film in contact with the metal oxide is prevented from being released to the outside. Therefore, an object of the present invention is to provide a semiconductor device having good and stable electrical characteristics. It shall be one of the following. [Means for solving the problem]

[0010] In a transistor using a metal oxide, in order to reduce oxygen vacancies in the metal oxide, In one embodiment of the present invention, the channel is provided with oxygen. An insulating film from which oxygen is released by heat treatment is provided in contact with the metal oxide film including the hole formation region. As a result, oxygen released during heat treatment is supplied to the metal oxide, filling the oxygen vacancies. can be reduced.

[0011] In addition, the insulating film from which oxygen is released by heat treatment (also referred to as the first insulating film) is Because the oxygen diffuses outward, it may not be possible to supply enough oxygen to the metal oxide. In view of the above, in one embodiment of the present invention, a chalcogenide film is provided in contact with an insulating film from which oxygen is released by heat treatment. A metal oxide film other than the metal oxide film (also referred to as the first metal oxide film) including the panel-forming region. The second metal oxide film is a thin film that is permeable to oxygen. By providing the second metal oxide film, it is possible to prevent overheating during heat treatment. The outward diffusion of the desorbed oxygen can be prevented. It is possible to supply sufficient oxygen to the film, and the oxygen contained in the insulating film is prevented from being desorbed to the outside. This can prevent the following from happening:

[0012] In addition, oxygen deficiencies may occur in the second metal oxide film that prevents oxygen from passing through. However, in one embodiment of the present invention, the second metal oxide film is subjected to a heat treatment to remove oxygen. Since the insulating film is sandwiched between the insulating films (the first insulating film and the second insulating film), Therefore, oxygen vacancies in the second metal oxide film can be compensated for.

[0013] One aspect of the present invention is a gate electrode, a gate insulating film provided on the gate electrode, and a gate insulating film. A first metal oxide film is provided on the insulating film, and a solenoid is provided in contact with the first metal oxide film. A passivation film is provided on the source electrode and the drain electrode. and a passivation film, the passivation film being made of a first insulating film, a second metal oxide film, and a second insulating The semiconductor device is formed by laminating a first insulating film and a second insulating film in this order.

[0014] Another aspect of the present invention is a gate electrode, a gate insulating film provided on the gate electrode, and a gate A first metal oxide film is provided on the insulating film, and a second metal oxide film is provided in contact with the first metal oxide film. A source electrode and a drain electrode, and a passivation layer provided on the source electrode and the drain electrode. The gate insulating film includes a second insulating film, a second metal oxide film, and a first The semiconductor device is formed by laminating a first insulating film and a second insulating film in this order.

[0015] In each of the above configurations, the first insulating film is thicker than the second insulating film in the semiconductor device.

[0016] In another embodiment of the present invention, a semiconductor device includes a base insulating film and a A first metal oxide film, and a source electrode and a drain electrode provided in contact with the first metal oxide film. an electrode, a gate insulator provided on the first metal oxide film, the source electrode, and the drain electrode; a gate electrode provided on the first metal oxide film via a gate insulating film; The base insulating film is a laminate of a first insulating film, a second metal oxide film, and a second insulating film in this order. do.

[0017] In another embodiment of the present invention, a semiconductor device includes a base insulating film and a A first metal oxide film, and a source electrode and a drain electrode provided in contact with the first metal oxide film. an electrode, a gate insulator provided on the first metal oxide film, the source electrode, and the drain electrode; a gate electrode provided on the first metal oxide film via a gate insulating film; The gate insulating film is formed by stacking a second insulating film, a second metal oxide film, and a first insulating film in this order. There are.

[0018] In each of the above structures, the first insulating film is preferably thinner than the second insulating film.

[0019] In each of the above structures, the first metal oxide film is a semiconductor film thicker than the second metal oxide film. The metal oxide film is capable of preventing oxygen transmission if it is about 5 nm thick. In addition, since the metal oxide film has a high relative dielectric constant, the metal oxide film including the channel formation region is When using a metal oxide film in addition, if the film is too thick, there is a risk of parasitic capacitance increasing. Therefore, the thickness of the second metal oxide film is preferably 5 nm or more and 15 nm or less. I wish.

[0020] In each of the above-described structures, the first insulating film and the second insulating film are insulating films from which oxygen is released by heat treatment. It is preferred to use a velum.

[0021] In each of the above structures, the first metal oxide film and the second metal oxide film are made of In, Ga, Sn and Zn. In the above, an element contained in the first metal oxide film and an element contained in the second metal oxide film are For example, the first metal oxide film and the second metal oxide film may be the same or different. As the metal oxide film, an In-Ga-Zn-O-based material may be used. The first metal oxide film is made of In-Ga-Zn-O. Ga-Zn-ON based materials may also be used.

[0022] In addition, metal oxide films can be either conductive or semiconducting depending on the amount of hydrogen and oxygen vacancies. For example, the resistivity of a metal oxide film is determined by the amount of metal oxide contained in the film. It changes depending on the amount of hydrogen and oxygen vacancies.

[0023] The insulating films sandwiching the metal oxide film are made of insulating films that do not release oxygen when heat treated. When the metal oxide film is processed, it becomes an electrical conductor. When an insulating film that releases oxygen by heat treatment is used for both, the metal oxide film It becomes an electrical insulator. In terms of the resistivity of a metal oxide film, the resistivity is 10 [Ω cm] or less. It becomes a conductor with a resistivity of 1×10 8 If it is more than [Ω·cm], it becomes an insulator.

[0024] In order to make the first metal oxide film a semiconductor, the resistivity must be such that it becomes a conductor and the resistivity must be such that it becomes an insulator. The resistivity of the first metal oxide film is set to a value between 10[Ω·cm]. Exceeding 1×10 8 It is sufficient to form it so that the electrical resistance is less than [Ω·cm].

[0025] The first metal oxide film and the second metal oxide film may be amorphous or crystalline. For example, the first metal oxide film may be non-single crystalline. When viewed perpendicular to the ab plane of the crystal, the atomic arrangement is triangular, hexagonal, equilateral triangular, or equilateral hexagonal. When viewed from a direction perpendicular to the c-axis, the metal atoms are in a layered form, or the metal atoms and oxygen atoms are in a layered form. It is preferable that the metal oxide contains a phase in which the metals are arranged in a layered form. CAAC-OS film: C Axis Aligned Crystallin We will call it e Oxide Semiconductor.

[0026] By using a CAAC-OS film as the first metal oxide film, the This suppresses the fluctuation of the electrical characteristics of transistors caused by the application of heat, bias, etc., and The reliability of the device can be improved. Effect of the Invention

[0027] According to one embodiment of the present invention, oxygen vacancies in a metal oxide are reduced, and a metal oxide that is in contact with the metal oxide is By preventing the oxygen contained in the insulating film from being released to the outside, good electrical properties and Furthermore, it is possible to provide a semiconductor device having stable electrical characteristics. [Brief description of the drawings]

[0028] [Figure 1] 1A and 1B are a top view and a cross-sectional view illustrating an example of a semiconductor device of one embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating a semiconductor device according to one embodiment of the present invention. [Diagram 3] 1A to 1C illustrate a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 4]1A and 1B are a top view and a cross-sectional view illustrating an example of a semiconductor device of one embodiment of the present invention. [Diagram 5] 1A and 1B are diagrams illustrating a semiconductor device according to one embodiment of the present invention. [Figure 6] 1A and 1B are a cross-sectional view and a circuit diagram illustrating an example of a semiconductor device of one embodiment of the present invention. [Figure 7] FIG. 1 is a circuit diagram of a semiconductor device according to one embodiment of the present invention. [Figure 8] 1A to 1C illustrate a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] FIG. 1 shows the results of CV measurement. [Figure 14] FIG. 1 shows the results of CV measurement. [Figure 15] FIG. 1 shows the results of CV measurement. [Figure 16] A diagram showing the results of TDS. [Figure 17] FIG. 13 is a diagram showing the structure of a sample according to Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The present invention will be described in detail with reference to the drawings. and the like, without departing from the spirit and scope of the present invention, It will be readily understood by those skilled in the art that the above may be modified in various ways. The present invention described below should not be construed as being limited to the description of the embodiment. In the configuration of the present invention, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings. These are commonly used between the different surfaces, and their repeated explanation will be omitted.

[0030] In each figure described in this specification, the size, thickness, or area of ​​each component is not clearly indicated. may be exaggerated for clarity and are not necessarily limited to scale .

[0031] In addition, the terms "first," "second," "third," etc., used in this specification are used in order to avoid confusion of components. The number is added for convenience and is not intended to be a numerical limit. The terms can be replaced with "second" or "third" as appropriate for explanation.

[0032] The function of the "source" and "drain" is to change the direction of current flow during circuit operation. For this reason, in this specification and the like, the terms "source" and "drain" are used interchangeably. The terms may be used interchangeably.

[0033] (Embodiment 1) In this embodiment, a semiconductor device and a manufacturing method thereof according to one embodiment of the present invention will be described with reference to FIGS. This will be explained with reference to FIG.

[0034] <Configuration Example of Semiconductor Device> FIG. 1 illustrates a plan view and a schematic diagram of a transistor 200 as an example of a semiconductor device according to one embodiment of the present invention. Here, FIG. 1(A) is a plan view, and FIG. 1(B) and FIG. 1(C) are cross-sectional views. These are cross-sectional views taken along the lines A1-A2 and B1-B2 in FIG. In FIG. 1(A), in order to avoid clutter, some of the components of the transistor 200 (e.g. For example, gate insulating film 104 and the like are omitted.

[0035] The transistor 200 shown in FIG. 1 includes a gate electrode 102 and a gate electrode 103 on a substrate 100. A gate insulating film 104 is provided on the gate insulating film 102, and a metal oxide film is provided on the gate insulating film 104. A metal oxide film 106a and a source electrode or a drain electrode provided in contact with the metal oxide film 106a. The metal oxide film 106a has a semiconductor characteristic. Therefore, it is also referred to as an oxide semiconductor.

[0036] The transistor 200 shown in FIG. 1 is a bottom-gate transistor. The top and drain electrodes 108a and 108b are in contact with the upper surface of the metal oxide film 106a. The source and drain electrodes 108a and 108b are made of gold. Alternatively, the metal oxide film 106 may have a bottom contact structure in contact with the lower surface of the metal oxide film 106a.

[0037] The region where the metal oxide film 106a and the gate electrode 102 overlap is a channel formation region. It works.

[0038] The metal oxide film 106a contains two or more elements selected from the group consisting of In, Ga, Sn, and Zn. The metal oxide has a band gap of 2 eV or more and less than 6 eV. Preferably, the value is 2.5 eV or more and 5.5 eV or less, and more preferably, 3 eV or more and 5 eV or less. In this way, by using metal oxides with a wide band gap, 00 off current can be reduced.

[0039] In addition, on the metal oxide film 106a and the source or drain electrodes 108a and 108b, A passivation film 110 is provided. The passivation film 110 is a metal oxide In the transistor 200 shown in FIG. The oxidization film 110 includes an insulating film 112, a metal oxide film 114, and an insulating film 116. Here, the insulating film 112 and the insulating film 116 are insulating films from which oxygen is released by heat treatment. It is used.

[0040] In this specification, the term "oxygen is released by heat treatment" refers to TDS (Thermal Desorption Desorption Spectroscopy: Temperature Programmed Desorption Spectroscopy The amount of oxygen released (or desorbed) converted to elementary atoms is 1.0 x 10 18 cm -3 Above, I prefer 3.0×10 20 cm -3 In addition, "oxygen is eliminated by heat treatment" means that "Does not desorb" means that the amount of oxygen released (or desorbed) converted to oxygen atoms in TDS analysis is 1. 0×10 18 cm -3 It means that it is less than.

[0041] The method for quantifying the amount of released oxygen by converting it into oxygen atoms using TDS analysis will be described below.

[0042] The amount of gas released during TDS analysis is proportional to the integral value of the ion intensity. The amount of desorbed gas is calculated based on the ratio of the integral value of the ion intensity measured to the reference value of the standard sample. The reference value of a standard sample is the value of the atomic density of the sample. is the ratio of the atomic density to the integral value of the ion intensity corresponding to

[0043] For example, the results of a TDS analysis of a silicon wafer containing a standard sample of hydrogen with a given density, From the results of TDS analysis of the insulating film, the amount of oxygen molecules desorbed from the insulating film (N O2 ) is calculated using formula 1. Here, all of the gases detected at mass number 32 in the TDS analysis are acids. Assume it is derived from an elementary molecule. There is CH3OH, which has a mass number of 32, but the possibility of it existing is The mass number of the oxygen atom is 17, which is an isotope of the oxygen atom. The abundance ratio of oxygen molecules containing oxygen atoms with mass number 18 and oxygen atoms with mass number 18 in nature is extremely small. It is not taken into account because it is a quantity.

[0044] N O2 =N H2 / S H2 ×S O2 ×α (Formula 1)

[0045] N H2 is the density of hydrogen molecules desorbed from the standard sample. H2 is a standard test The integral value of the ion intensity when the sample is subjected to TDS analysis. Here, the reference value of the standard sample is N H2 / S H2 Let us assume that S O2 is the integral value of the ion intensity when the insulating film is analyzed by TDS. α is a coefficient that affects the ion intensity in TDS analysis. For details of Equation 1, For details, see Japanese Patent Application Laid-Open No. 6-275697. The numerical values ​​of the amount of oxygen released are as follows: A thermal desorption analyzer EMD-WA1000S / W manufactured by Electron Science Corporation was used to measure the standard sample and 1×10 16 cm -3 This is a value measured using a silicon wafer containing hydrogen atoms. .

[0046] In addition, some of the oxygen is detected as oxygen atoms in the TDS analysis. The ratio of the oxygen molecules can be calculated from the ionization rate of the oxygen molecules. Since the ionization rate of oxygen molecules is included in the calculation, the amount of oxygen atoms released can be obtained by evaluating the amount of oxygen molecules released. It is possible to estimate even if

[0047] In addition, N O2 is the amount of oxygen molecules released. In the case of an insulating film, when converted to oxygen atoms, The amount of oxygen released is twice the amount of oxygen molecules released.

[0048] One example of a film from which oxygen is released by heat treatment is silicon oxide (SiOx(x Silicon oxide with excess oxygen (SiOx(x>2)) is a type of silicon It contains more than twice the number of oxygen atoms per unit volume. The numbers of nitrogen atoms and oxygen atoms are values ​​measured by the Rutherford backscattering method.

[0049] The metal oxide film 106 a is provided between the gate insulating film 104 and the insulating film 112 . The insulating film 112 is an insulating film from which oxygen is released by heat treatment, and the gate insulating film 104 is In the present embodiment, an insulating film that does not release oxygen due to heat treatment is used. Oxygen is released from 112 and supplied to the metal oxide film 106a.

[0050] In addition, the insulating film from which oxygen is released by heat treatment contains negatively charged oxygen ions such as oxygen ions of unbonded oxygen. It contains a large amount of constant charge. It is in contact with the metal oxide film including the channel formation region and is heated. By providing an insulating film from which oxygen is released, the threshold voltage of a transistor can be shifted positively. This is preferable because it allows

[0051] However, oxygen released from the insulating film during heat treatment diffuses outward, and the metal oxide In some cases, oxygen cannot be supplied sufficiently to the film 106a. By doing so, the negative fixed charges in the insulating film are reduced. As a result, the threshold voltage of the transistor may shift negatively.

[0052] In view of this, in one embodiment of the present invention, a metal oxide film 106a is provided on and in contact with the insulating film 112. A metal oxide film 114 is provided. The metal oxide film has the ability to prevent oxygen from passing through. Therefore, oxygen contained in the insulating film 112 is released during the heat treatment and diffuses outward. This can prevent the following:

[0053] In addition, oxygen vacancies may occur in the metal oxide film 114. The metal oxide film 114 is treated with an insulating film (insulating film 112 and insulating film 11) from which oxygen is released by heat treatment. 6) shall be used to sandwich the

[0054] Metal oxide films can prevent oxygen from passing through even when they are extremely thin, about 5 nm thick. In addition, since the metal oxide film has a high relative dielectric constant (for example, 15), When using a metal oxide film other than the metal oxide film containing There is a risk of the parasitic capacitance increasing. Therefore, the thickness of the metal oxide film 114 is set to 5 The thickness of the metal oxide film 114 is preferably from 1 nm to 15 nm. By making the metal oxide film 114 extremely thin, the metal oxide film 114 may not be used in part of the passivation film. In comparison with the case where the parasitic capacitance is increased, a significant increase in the parasitic capacitance can be prevented.

[0055] The metal oxide film 114 provided to prevent outward diffusion of oxygen is desorbed by heat treatment. By sandwiching the insulating film 1 between the insulating film 112 and the insulating film 116, the insulating film 1 Oxygen is released from the insulating film 116 and supplied to the metal oxide film 114, thereby filling the oxygen vacancies. As a result, the metal oxide film 114 becomes insulating (exhibits insulating properties). Even if it is used as a part of the passivation film 110, the transistor 200 Therefore, the electrical characteristics of the device are not affected.

[0056] In order to efficiently supply oxygen to the metal oxide film 106a, The thickness of the insulating film 112 in contact with the metal oxide film 114 is thicker than the thickness of the insulating film 116 in contact with the metal oxide film 114. The thickness of the insulating film 112 and the insulating film 116 is preferably equal to or larger than the thickness of the passivation film 110. This can be appropriately set depending on the film thickness.

[0057] When the insulating film 112 is a film from which oxygen is released by heat treatment, Oxygen is supplied to the metal oxide film 106a, and the interface between the insulating film 112 and the metal oxide film 106a is heated. Therefore, the charge generated due to the operation of the transistor 200 can be reduced. This can prevent the metal oxide film 106a from being trapped at the interface between the insulating film 112 and the metal oxide film 106a. The transistor 200 can be one with little degradation in electrical characteristics.

[0058] In addition, by providing the metal oxide film 114 in contact with the insulating film 112, outward diffusion of oxygen is suppressed. Therefore, oxygen vacancies in the metal oxide film 106a including the channel formation region can be prevented. This allows the threshold voltage of the transistor to be negatively shifted. In addition, the negative fixed charges in the insulating film 112 can be reduced. This prevents the threshold voltage of the transistor from increasing as the negative fixed charge decreases. Therefore, it is possible to suppress a negative shift of the low voltage.

[0059] The hydrogen concentration in the metal oxide film 106a and the metal oxide film 114 is 1×10 20 at oms / cm 3 Less than or equal to 1×10 19 atoms / cm 3 More preferably, 1×10 18 atoms / cm 3 The metal oxide film 106a is a channel-shaped In the formation region, the hydrogen concentration is reduced, and the BT (thermal The threshold voltage does not change much before and after the bias stress test, so a stable voltage is obtained. In addition, a transistor that is not a semiconductor but has excellent thermal properties and high reliability can be obtained. The hydrogen concentration of the metal oxide film 114 used as an insulator is preferably as low as possible. stomach.

[0060] The metal oxide film 114 is made of In, Ga, Sn, and Zn, similarly to the metal oxide film 106a. The metal oxide film 114 is a metal oxide containing two or more elements selected from the above. The element to be added may be the same as the element contained in the metal oxide film 106a, or may be different. For example, the metal oxide film 106a and the metal oxide film 114 may be In-Ga Alternatively, a material based on In-Ga-Zn may be used as the metal oxide film 106a. As the metal oxide film 114, an In-Ga-Zn-ON material is used. It may be used.

[0061] <Applications of semiconductor devices> 2A to 2C are cross-sectional views of transistors having different configurations from the transistor 200. The structure is shown.

[0062] The transistor 210 shown in FIG. 2A includes a gate electrode 102, a gate electrode 103, a gate electrode 104, a gate electrode 105, a gate electrode 106, a gate electrode 107, a gate electrode 108, a gate electrode 109 ... A gate insulating film 120 is provided on the electrode 102, and a metal film is provided on the gate insulating film 120. The oxide film 106a and the source electrode or drain electrode provided in contact with the metal oxide film 106a The electrode 108a and the electrode 108b are provided.

[0063] The difference between the transistor 200 and the transistor 210 is that the gate insulating film 120 has a The metal oxide film is provided to prevent the outward diffusion of oxygen. The insulating film 120 has a three-layer structure consisting of an insulating film 122, a metal oxide film 124, and an insulating film 126. In addition, the metal oxide film 106a and the source and drain electrodes 108a and 108b are An insulating film 118 is provided on the insulating film 12 as a passivation film. 2. The insulating film 126 is made of an insulating film that releases oxygen by heat treatment. The film 118 is made of an insulating film that does not release oxygen when subjected to heat treatment.

[0064] In order to efficiently supply oxygen to the metal oxide film 106a, The insulating film 122 in contact with the metal oxide film 124 is preferably thicker than the insulating film 126 in contact with the metal oxide film 124. The thicknesses of the insulating film 122 and the insulating film 126 are appropriately set depending on the thickness of the gate insulating film 120. In addition, if the metal oxide film 124 is at least 5 nm thick, oxygen can pass through it. Therefore, it is possible to prevent the gate insulating film 120 from being damaged by the heat treatment. That's good.

[0065] The transistor 220 shown in FIG. 2B includes a gate electrode 102, a gate electrode 103, a gate electrode 104, a gate electrode 105, a gate electrode 106, a gate electrode 107, a gate electrode 108, a gate electrode 109 ... A gate insulating film 120 is provided on the electrode 102, and a metal film is provided on the gate insulating film 120. The oxide film 106a and the source electrode or drain electrode provided in contact with the metal oxide film 106a The metal oxide film 106a and the source electrode or drain electrode 108b are also included. A passivation film 110 is provided on the drain electrodes 108a and 108b.

[0066] In the transistor 220, the gate insulating film 120 and the passivation film 110 For this reason, the description of the transistor 200 and the transistor 210 can be taken into consideration. Detailed explanation will be omitted.

[0067] In addition, in the transistor 200, the transistor 210, and the transistor 220, The source or drain electrodes 108a and 108b are in contact with the upper surface of the metal oxide film 106a. The top contact structure has been described. The source and drain electrodes 108a and 108b are in contact with the bottom surface of the metal oxide film 106a. A top contact structure can also be used. An example of a bottom contact structure is shown in FIG. 2(C). As shown in.

[0068] The transistor 230 shown in FIG. 2C includes a gate electrode 102 and a gate A gate insulating film 104 is provided on the electrode 102, and a semiconductor layer is provided on the gate insulating film 104. Source or drain electrodes 108a, 108b and source or drain electrodes 108a The metal oxide film 106a is provided in contact with the metal oxide film 108b. A passivation film 110 is provided on the transistor 106a in the same manner as the transistor 200. do.

[0069] The passivation film 110 is provided so as to cover the entire metal oxide film 106a. Therefore, oxygen can be efficiently supplied to the metal oxide film 106a.

[0070] In addition, even in a bottom-contact transistor, the gate insulating film contains oxygen and other impurities. A metal oxide film may be provided to prevent lateral diffusion. A metal oxide film for preventing outward diffusion of oxygen may be provided on a part of the insulation film.

[0071] As described above, in one embodiment of the present invention, a metal oxide film (first In order to reduce oxygen vacancies in the second metal oxide film, the second metal oxide film is heat-treated in contact with the first metal oxide film. In addition, the insulating film (first insulating film) from which oxygen is released is provided by heat treatment. A metal oxide film (a second metal oxide film) different from the first metal oxide film is in contact with the insulating film (a first insulating film) that is connected to the first metal oxide film. The second metal oxide film is then heat-treated to remove oxygen. The insulating film is sandwiched between insulating films (a first insulating film and a second insulating film) that are spaced apart from each other.

[0072] The insulating film 112 (or insulating film 122) from which oxygen is released by heating is treated with a metal oxide film 106 a and the metal oxide film 114 (or the metal oxide film 124). Oxygen desorbed from the insulating film 112 (or insulating film 122) during processing is released to the outside. This can prevent the oxygen deficiency in the metal oxide film 106a from occurring, and can sufficiently compensate for the oxygen deficiency in the metal oxide film 106a. In addition, the negative fixed charges contained in the insulating film 112 (or the insulating film 122) are prevented from decreasing. That is, according to one embodiment of the present invention, oxygen vacancies in the metal oxide film 106a can be eliminated. In addition, the insulating film 112 (or the insulating film 122) in contact with the metal oxide film 106a is By preventing the oxygen contained in the material from being released to the outside, it provides good electrical properties and Therefore, it is possible to provide a semiconductor device having stable thermal characteristics.

[0073] <Method for Manufacturing Semiconductor Device> Next, as an example of a method for manufacturing a semiconductor device according to one embodiment of the present invention, The manufacturing method will be described with reference to FIG.

[0074] First, a conductive film applicable to a gate electrode is formed on a substrate 100, and then the conductive film is formed by photolithography. A resist mask is formed on the conductive film, and the conductive film is formed using the resist mask. The gate electrode 102 is then etched into a desired shape. A gate insulating film 104 is formed on the silicon substrate 102 (see FIG. 3(A)).

[0075] The substrate 100 may be a substrate having an insulating surface. For example, a glass substrate, Substrates such as ceramic substrates, quartz substrates, and sapphire substrates can be used. If the substrate has a circumferential surface, it may be a single crystal semiconductor substrate such as silicon or silicon carbide, or a polycrystalline semiconductor substrate. Substrates, compound semiconductor substrates such as silicon germanium, and SOI substrates can also be used. It is possible to provide a semiconductor element on the substrate. There is no particular restriction on the substrate that can be used, but it must be heat-resistant enough to withstand the subsequent heat treatment. In this embodiment, a glass substrate is used as the substrate 100.

[0076] A flexible substrate can also be used as the substrate 100. When using a flexible substrate, the transistors may be directly fabricated on the flexible substrate, or may be fabricated on another substrate. The transistor 200 may be manufactured, and then peeled off and transferred. In order to peel and transfer the semiconductor device to a flexible substrate, a peeling layer and an insulating film are provided on the substrate. All you need to do is create a dial 200.

[0077] Conductive materials that can be used for the gate electrode 102 include aluminum, titanium, chromium, nickel, and the like. Ru, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten The gate electrode may be a single metal or an alloy mainly composed of the single metal. The conductive film that can be applied to the electrode 102 is formed of the above-mentioned conductive material and has a single layer structure or a laminated structure. For example, a single layer structure of an aluminum film containing silicon is formed. Two-layer structure with titanium film laminated, two-layer structure with titanium film laminated on tungsten film, copper-ma A two-layer structure in which a copper film is laminated on a magnesium-aluminum alloy film, a titanium film, and the titanium For example, a three-layer structure is formed by layering an aluminum film on top of a titanium film. In addition, transparent indium oxide and indium oxide containing tin oxide or zinc oxide are also available. A conductive material may also be used.

[0078] A conductive film that can be applied to the gate electrode 102 is formed by sputtering, plasma CVD, or the like. The film thickness is then set to 50 nm or more and 300 nm or less. A resist mask is formed on the conductive film, and the conductive film is then subjected to a desired treatment using the resist mask. The resist mask is then etched into a desired shape to form the gate electrode 102. In addition to the photolithography process, inkjet methods, printing methods, etc. can be used as appropriate. The etching process may be dry etching, wet etching, or Dry etching and wet etching can be combined. In this embodiment, tungsten is formed as a conductive film with a film thickness of 150 nm by sputtering. do.

[0079] The gate insulating film 104 is made of silicon oxide, gallium oxide, aluminum oxide, or the like. Any oxide insulating film or nitride insulating film such as silicon nitride or aluminum nitride or silicon oxynitride, aluminum oxynitride, silicon nitride oxide, or the like. In addition to the above materials, hafnium oxide, yttrium oxide, Thorium, hafnium silicate (HfSi x O y x>0, y>0), nitrogen is added Hafnium silicate (HfSiO x N y (x>0, y>0)), hafnium aluminate (HfAl x O y (x>0, y>0)) and other high-k materials can be used. The gate insulating film 104 may be formed in a single layer structure using the high-k material. Alternatively, the insulating film may be formed in a laminated structure with the insulating film made of the above-mentioned materials.

[0080] The gate insulating film 104 is formed to a thickness of 5 nm or more by a sputtering method, a plasma CVD method, or the like. The gate insulating film 104 is formed to a thickness of 300 nm or less using the above-mentioned high-k material. By using this, the thickness of the gate insulating film (e.g., silicon oxide film equivalent) can be changed. The physical gate insulating film can be made thicker without affecting the gate leakage current. It can be reduced.

[0081] In this embodiment, the gate insulating film 104 is formed by a silicon oxynitride film by a plasma CVD method. The silicon oxide film formed by the plasma CVD method is then heated to This is a film from which oxygen does not desorb.

[0082] Next, a metal oxide film 106 is formed on the gate insulating film 104 (see FIG. 3(B)).

[0083] The material of the metal oxide film 106 is at least two selected from the group consisting of In, Ga, Zn, and Sn. For example, a metal oxide material containing In-Sn, which is a quaternary metal oxide, can be used. -Ga-Zn-O based materials and In-Ga-Zn-O based materials, which are ternary metal oxides, In-Sn-Zn-O based materials, In-Al-Zn-O based materials, Sn-Ga-Zn-O Materials based on Al-Ga-Zn-O, materials based on Sn-Al-Zn-O, and binary alloys Metal oxides such as In-Zn-O, Sn-Zn-O, and Al-Zn-O Materials, Zn-Mg-O-based materials, Sn-Mg-O-based materials, In-Mg-O-based materials, I n-Ga-O based materials, In-O based materials, Sn-O based materials, Zn-O based materials, etc. Here, for example, the In-Ga-Zn-O material is indium (I n), gallium (Ga), and zinc (Zn), and their composition ratios In addition, elements other than In, Ga, and Zn may be included. It is preferable to have an excess of oxygen with respect to the stoichiometric ratio of the metal oxide film. This makes it possible to suppress the generation of carriers caused by oxygen deficiency in the metal oxide film.

[0084] When an In-Ga-Zn-O-based material is used as the material for the metal oxide film 106, the target As an example of a composite, the composition of In2O3:Ga2O3:ZnO=1:1:1 [molar ratio] is Furthermore, there are some with a ratio of In2O3:Ga2O3:ZnO=1:1:2 [mol A target with a composition ratio of In2O3:Ga2O3:ZnO=1:1:4[m or a target having a composition ratio of In2O3:Ga2O3:ZnO=2: A target having a composition ratio of 1:8 [molar ratio] can also be used.

[0085] Alternatively, when an In-Zn-O-based material is used as the material of the metal oxide film 106, the number of atoms is The ratio is In:Zn=0.5 to 50:1, preferably In:Zn=1 to 20: 1, and more preferably In:Zn=3 to 30:2. The atomic ratio of Zn is as described above. By setting the range, the field effect mobility of the transistor 200 can be improved. Here, when the atomic ratio of a compound is In:Zn:O=X:Y:Z, Z>1.5X+Y. This is preferable.

[0086] The metal oxide film 106 is formed of a metal oxide having the chemical formula InMO3(ZnO). m Materials expressed as (m>0) Here, M is one or more selected from Ga, Al, Mn, and Co. For example, M is Ga, Ga and Al, Ga and Mn, or G a and Co may also be used.

[0087] The metal oxide film 106 is formed by sputtering, molecular beam epitaxy, atomic layer deposition, or The metal oxide film 106 can be formed by a pulsed laser deposition method. The thickness is 5 nm or more and 100 nm or less, preferably 10 nm or more and 30 nm or less. Metal oxide films are semiconductors immediately after deposition.

[0088] The metal oxide film 106 may be amorphous or crystalline. For example, the metal oxide film 106 is non-single crystal, and more specifically, the direction perpendicular to the ab plane of the non-single crystal is When viewed from the opposite direction, the atomic arrangement is a triangle, a hexagon, an equilateral triangle, or a regular hexagon, and the c-axis is When viewed from the vertical direction, it contains a phase in which metal atoms are arranged in layers, or metal atoms and oxygen atoms are arranged in layers. In this specification, the metal oxide film is referred to as a CAAC-OS film. In addition, a CAAC-OS film is used as a film including a channel formation region of the transistor 200. This prevents damage caused by irradiation with visible or ultraviolet light, heat, bias, etc. The fluctuation of the electrical characteristics of the transistor 200 can be suppressed, and the reliability of the semiconductor device can be improved. do.

[0089] There are, for example, the following two methods for forming the metal oxide film 106 into a CAAC-OS film. In one method, the metal oxide film 106 is formed while the substrate is heated. One method is to deposit the metal oxide film 106 in two steps, and deposit the first film and then deposit the second film. This method involves performing a heat treatment on each of the films.

[0090] When the metal oxide film 106 is formed in one step while heating the substrate, the substrate temperature is, for example, For example, the substrate temperature is 150° C. or higher and 450° C. or lower, and preferably 250° C. or higher and 350° C. or lower. In addition, when the metal oxide film 106 is formed, the temperature to which the substrate 100 is heated is increased. It is possible to obtain a CAAC-OS film in which the ratio of crystalline portions to amorphous portions is high. .

[0091] In addition, when the metal oxide film 106 is formed in two steps, the substrate 100 is heated to a substrate temperature of 100 While maintaining the temperature at 450° C. or higher, a first metal oxide film is formed on the gate insulating film 104. The substrate is then heated to 550°C or higher under an atmosphere of nitrogen, oxygen, rare gas, or dry air, without reaching the distortion point. The heat treatment is continued for 10 minutes. The heat treatment forms a crystalline region in the area including the surface of the first metal oxide film. The second metal oxide film is then formed on the first metal oxide film. Then, heat treatment is performed again at a temperature of 550°C or higher but below the distortion point of the substrate. The first layer of the metal oxide film is formed with a crystalline region (including plate-like crystals) in the region including the surface. This acts as a seed for crystal growth, causing crystals to grow upward, crystallizing the entire second metal oxide film. Note that the first oxide semiconductor film is preferably formed to a thickness of 1 nm to 10 nm.

[0092] When the metal oxide film 106 is formed by sputtering, the metal oxide film 106 is preferably formed by sputtering as thin as possible. It is preferable to reduce the hydrogen concentration in the catalyst 106. The atmospheric gas supplied to the processing chamber of the sputtering device is a compound containing hydrogen, water, and a hydroxyl group. High-purity rare gas (typically argon) from which impurities such as nitrates or hydrides have been removed, The treatment chamber is exhausted with a mixture of oxygen and rare gas. It combines a cryopump with high pumping capacity and a sputter ion pump with high hydrogen pumping capacity. They can be used together.

[0093] By doing as described above, it is possible to form the metal oxide film 106 with reduced hydrogen contamination. Even if the above sputtering apparatus is used, the metal oxide film 106 may have some defects. It is formed by containing nitrogen. For example, secondary ion mass spectrometry (SIMS) of metal oxide film 106 measured by y Ion Mass Spectrometry The nitrogen concentration is 5 x 10 18 cm -3 It will be less than.

[0094] During or after the formation of the metal oxide film 106, oxygen deficiency in the metal oxide film 106 Generally, oxygen vacancies in metal oxide films occur when the oxygen Some of the defects become donors and generate electrons as carriers. In the case of the metal oxide film 106, some of the oxygen vacancies become donors, and electrons, which are carriers, This causes the threshold voltage of the transistor 200 to shift in the negative direction. In the metal oxide film 106, the generation of the electrons occurs between the metal oxide film 106 and the gate insulator. This is particularly noticeable in the oxygen vacancies occurring near the interface with the film 104 .

[0095] Therefore, after the metal oxide film 106 is formed, a first heat treatment is performed.

[0096] The first heat treatment is for releasing hydrogen (water, compounds containing hydroxyl groups) from the metal oxide film. That is, the first heat treatment is performed to remove hydrogen, which is an unstable carrier source, from the metal oxide film 106. By removing the charge, the threshold voltage of the transistor 200 shifts in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. This can be done.

[0097] The temperature of the first heat treatment is, for example, 150° C. or higher and lower than the substrate strain point temperature, preferably 250° C. and more preferably, 300°C to 450°C. The treatment is carried out in an inert atmosphere. The oxidizing atmosphere is an oxidizing atmosphere such as oxygen, ozone, or nitrogen oxide. An inert atmosphere is an atmosphere containing oxidizing gases at 10 ppm or more. The atmosphere contains less than 10 ppm of nitrogen or rare gas. The heat treatment time is 3 minutes to 24 hours. Heat treatment for more than 24 hours is not recommended because it reduces productivity. Not like that.

[0098] There is no particular limitation on the heating device used for the first heat treatment. The apparatus may be equipped with a device for heating the workpiece by thermal induction or thermal radiation. For example, an electric furnace , LRTA (Lamp Rapid Thermal Anneal) equipment, GRTA RTA (Rapid Thermal Anneal) equipment, etc. The LRTA device is a halogen-free thermal annealing device. Lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high pressure na The radiation of light (electromagnetic waves) emitted from lamps such as thorium lamps and high-pressure mercury lamps can cause damage to the body. This is a device that heats the material being treated. The GRTA device is a device that uses high-temperature gas to perform heat treatment. be.

[0099] Next, a resist mask is formed on the metal oxide film 106 by a photolithography process. Using the resist mask, the metal oxide film 106 is etched into a desired shape to form island-shaped metal A metal oxide film 106a is formed (see FIG. 3(C)). In addition to the lithography process, an inkjet method, a printing method, etc. can be appropriately used. The etching is performed so that the end of the metal oxide film 106a has a tapered shape. It is preferable that the end of the island-shaped metal oxide film 106a is tapered. In the manufacture of the transistor 200, the coverage of the formed film can be improved. The tapered shape allows the resist mask to be recessed while the etching is performed. It can be formed by etching.

[0100] The etching process may be performed using dry etching or wet etching. The etching solution used for wet etching is phosphoric acid. A solution of acetic acid and nitric acid, ammonia hydrogen peroxide (31% by weight hydrogen peroxide solution: 28% by weight ammonium peroxide solution) A 5:2:2 (volume ratio) of monia water: water can be used. N (manufactured by Kanto Chemical Co., Ltd.) may also be used.

[0101] The etching gas used in dry etching is a gas containing chlorine (chlorine-based gas, e.g. For example, chlorine (Cl2), boron trichloride (BCl3), silicon tetrachloride (SiCl4), carbon tetrachloride ( CCl4) and the like) are preferred. In addition, a gas containing fluorine (a fluorine-based gas, for example, carbon tetrafluoride) is preferred. Carbon fluoride (CF4), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), trifluoromethane (C HF3), hydrogen bromide (HBr), oxygen (O2), and helium (He) or a gas containing a rare gas such as argon (Ar), etc. can be used.

[0102] As dry etching, parallel plate type RIE (Reactive Ion Etch) ng) method and ICP (Inductively Coupled Plasma) A combined plasma etching method can be used. Etching conditions (power applied to the coil-type electrode, power applied to the substrate-side electrode, The temperature of the electrode on the substrate side, etc. are adjusted appropriately.

[0103] Next, a conductive film applicable to a source electrode and a drain electrode is formed on the metal oxide film 106a. Then, a resist mask is formed on the conductive film by a photolithography process. The conductive film is etched into a desired shape using a mask, and a source electrode or a drain electrode 1 is formed. 3D, the source electrode or drain electrode 108a is formed. The conductive material applicable to the gate electrode 102 may be the same as that applicable to the gate electrode 108b. The following conductive materials can be used.

[0104] In this embodiment, the source and drain electrodes 108a and 108b are formed by sputtering. By the etching method, a titanium film with a thickness of 50 nm, an aluminum film with a thickness of 100 nm, and a After forming a titanium film having a thickness of 100 nm, a photolithography process and an etching process are performed. It is formed.

[0105] Next, pads are formed on the metal oxide film 106a and the source and drain electrodes 108a and 108b. In the present embodiment, a passivation film 110 is formed (see FIG. 3(E)). As the insulating film 110, an insulating film 112, a metal oxide film 114, and an insulating film 116 are formed in this order. .

[0106] The insulating film 112 and the insulating film 116 are made of silicon oxide, gallium oxide, or aluminum oxide. The insulating film may be selected from silicon oxide nitride, silicon oxynitride, aluminum oxide nitride, etc. The insulating film 112 and the insulating film 116 can be formed in the same manner as the gate insulating film 104. The film forming method may be applied.

[0107] The metal oxide film 114 can be formed using the same material and film formation method as the metal oxide film 106. Therefore, detailed description will be omitted.

[0108] The thickness of the passivation film 110 is 50 nm or more and 1000 nm or less, preferably 100 The thickness may be set to 300 nm or more.

[0109] In this embodiment, the insulating film 112 is formed by sputtering an oxide film having a thickness of 200 nm. A silicon oxide film was formed as the metal oxide film 114 by sputtering to a thickness of 5 nm. A metal oxide film of In-Ga-Zn-O system was formed as the insulating film 116 with a thickness of 50 A silicon oxide film is formed by sputtering at 300 nm.

[0110] When the insulating film 112 and the insulating film 116 are formed by a sputtering method, As long as the concentration of hydrogen in the insulating film 112 and the insulating film 116 is low, it is preferable to reduce the concentration of hydrogen in the insulating film 112 and the insulating film 116. In order to reduce the concentration, water is used as the atmospheric gas supplied to the processing chamber of the sputtering device. A high-purity rare gas (typically Al) from which impurities such as nitrogen, water, and compounds containing hydroxyl groups have been removed. Gases such as argon, oxygen, and a mixture of rare gas and oxygen are appropriately used. The gas is pumped by a cryopump with high pumping capacity for water and a sputter ion pump with high pumping capacity for hydrogen. A combination of pumps may be used.

[0111] During the first heat treatment, hydrogen is released from the metal oxide film 106a and the metal oxide film 106b is There is a risk that oxygen may escape from the top surface of 06a to the outside. Oxygen vacancies may occur in the film 106a. For this reason, it is preferable to perform a second heat treatment after forming the passivation film 110.

[0112] The conditions and equipment for the second heat treatment may be the same as those for the first heat treatment. Detailed explanation will be omitted.

[0113] By performing the second heat treatment, oxygen is released from the insulating film 112, and the metal oxide film 106a In addition, a metal oxide film is provided on the insulating film 112 to prevent outward diffusion of oxygen. Since the film 114 is provided, oxygen contained in the insulating film 112 is evaporatively oxidized to the outside during the second heat treatment. This makes it possible to prevent diffusion and efficiently supply oxygen to the metal oxide film 106a. The metal oxide film 114 receives oxygen from the insulating films 112 and 116. This compensates for the oxygen deficiency and increases the resistance, making the material an insulator (insulating As a result, the metal oxide film 114 is used as a part of the passivation film 110. Even if the above-mentioned second insulating layer 240 is used, the electrical characteristics of the transistor 200 are not affected.

[0114] By performing the first heat treatment and the second heat treatment, the metal oxide film 106a and the metal oxide The hydrogen concentration in the metal film 114 is reduced, and the metal oxide is highly purified. The hydrogen concentration in the oxide film 106a and the metal oxide film 114 is 1×10 20 atoms / cm 3 Less than or equal to 1×10 19atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 The following is the case. Metal oxides are used as insulators rather than semiconductors. It is preferable that the hydrogen concentration of the film 114 is lower. a and the hydrogen concentration in the metal oxide film 114 are measured by SIMS analysis.

[0115] The hydrogen concentration is sufficiently reduced and the resulting product is highly purified by the first heat treatment and the second heat treatment, At the same time, sufficient oxygen is supplied to reduce the defect level in the energy gap caused by oxygen vacancies. The off-state current of the transistor 200 is reduced by using the metal oxide film 106a. Specifically, the off-state current (here, unit channel width ( The value per 1 μm is 100 zA (1 zA (zeptoampere) is 1 × 10 -21 A) Below The current should be below 10zA, preferably below 10zA.

[0116] In addition, alkali metals such as lithium (Li) and sodium (Na) are oxidized in the metal oxide film 10. Since the content of the impurities in the metal oxide film 6a and the metal oxide film 114 is low, it is preferable to reduce the content of the impurities. The concentration of the alkali metal contained in the metal oxide film 106a and the metal oxide film 114 is preferably , 2×10 16 cm -3 Less than 1×10 15 cm -3 It is preferable to do the following: Furthermore, since alkaline earth metals are also impurities, it is preferable to reduce their content. .

[0117] In addition, metal oxide films can be either conductive or semiconducting depending on the amount of hydrogen and oxygen vacancies. For example, the resistivity of a metal oxide film is determined by the amount of metal oxide contained in the film. It changes depending on the amount of hydrogen and oxygen vacancies.

[0118] The insulating films sandwiching the metal oxide film are made of insulating films that do not release oxygen when heat treated. When the metal oxide film is treated (e.g., at 350°C), its resistivity drops to 10 Ω cm or less. Therefore, the metal oxide film becomes a conductor. When a heat treatment (e.g., 350°C) is performed using an insulating film from which oxygen is desorbed due to the phenomenon, the resistivity is 1×10 8 [Ω·cm] or more, the metal oxide film becomes an insulator (indicating insulating properties). Therefore, in order for the metal oxide film 114 to be an insulator, the resistivity must be less than 1×10 8 [ It is sufficient to form it so that the resistivity is equal to or greater than [Ω·cm].

[0119] In order for the metal oxide film 106a to be a semiconductor, it must have a resistivity that makes it a conductor and a resistivity that makes it an insulator. Since the resistivity can be set to a value between 10[Ω·cm ] beyond 1×10 8 It is sufficient to form it so that the electrical resistance is less than [Ω·cm].

[0120] Through the above steps, the transistor 200 can be manufactured (see FIG. 3E).

[0121] In contact with the metal oxide film (oxide semiconductor) including the channel formation region, oxygen is removed by heat treatment. A metal oxide film is provided in contact with the insulating film to prevent outward diffusion of oxygen. By providing the insulating film, outward diffusion of oxygen from the insulating film is suppressed, and the metal Oxygen can be efficiently supplied to the oxide film. It is possible to reduce oxygen vacancies in the metal oxide film, thereby suppressing the generation of electrons, which act as carriers. This suppresses the negative shift of the threshold voltage of the transistor. do.

[0122] In addition, the metal oxide film for preventing the outward diffusion of oxygen is an insulating film from which oxygen is released by heat treatment. The metal oxide film is sandwiched between two insulating films and heat treated to prevent the outward diffusion of oxygen. Even if the temperature is low, oxygen vacancies are reduced and insulation is possible.

[0123] <Method of Manufacturing Application of Semiconductor Device> The transistor 210 illustrated in FIG. 2A can be manufactured as follows.

[0124] After forming a gate electrode 102 on a substrate 100, a gate insulating film 120 is formed. The insulating film 120 is formed by depositing an insulating film 126, a metal oxide film 124, and an insulating film 122 in this order.

[0125] The materials and film formation methods of the insulating films 126 and 122 are the same as those of the insulating films 116 and 112. The material and the deposition method of the metal oxide film 124 are the same as those of the metal oxide film 124. This is similar to the oxide film 114 .

[0126] Next, after the gate insulating film 120 is formed, a first heat treatment is preferably performed. The metal oxide film 124 is sandwiched between the insulating film 126 and the insulating film 122, from which oxygen is released by heat treatment. Since the metal oxide film 124 is covered with the metal oxide film 124, the metal oxide film 124 becomes an insulator (has insulating properties). A metal oxide film is formed on the insulating film 120, and the metal oxide film is subjected to a photolithography process and An etching process is performed to form the metal oxide film 106a.

[0127] Next, a conductive film is formed on the metal oxide film 106a, and then the conductive film is subjected to photolithography. By performing the step of etching, the source electrode or the drain electrode 108a, 108b is Form b.

[0128] Next, an insulating layer is formed on the metal oxide film 106a and the source or drain electrodes 108a and 108b. The insulating film 118 is formed using the same material and method as the insulating film 112. After that, a second heat treatment may be performed.

[0129] In this manner, the transistor 210 can be manufactured.

[0130] The transistor 220 shown in FIG. 2B can be manufactured as follows.

[0131] After the gate electrode 102 is formed on the substrate 100, the gate insulating film 120 is formed.

[0132] Next, a metal oxide film is formed on the gate insulating film 120, and then the metal oxide film is subjected to photolithography. A metal oxide film 106a is formed by performing a lithography process and an etching process. Thereafter, a first heat treatment is performed, whereby oxygen desorbed from the insulating film 126 is converted into metal oxide. The oxygen supplied to the metal oxide film 124 and desorbed from the insulating film 122 is transferred to the metal oxide film 124 and the insulating film 122. In addition, hydrogen and water contained in the metal oxide film 106a are reduced. can be done.

[0133] Next, source or drain electrodes 108a, 108b, and a conductive film 108a are formed on the metal oxide film 106a. A passivation film 110 is formed, and then a second heat treatment is performed.

[0134] In this manner, the transistor 220 can be manufactured.

[0135] This embodiment mode can be implemented in appropriate combination with the configurations described in other embodiments. It is.

[0136] (Embodiment 2) In this embodiment mode, a transistor having a structure different from that of the transistor described in the previous embodiment mode is used. We will explain about this.

[0137] FIG. 4 illustrates a plan view and a schematic diagram of a transistor 400 as an example of a semiconductor device according to one embodiment of the present invention. 4(A) is a plan view, and FIG. 4(B) and FIG. 4(C) are cross-sectional views. These are cross-sectional views taken along the lines A1-A2 and B1-B2 in FIG. 4(A), in order to avoid clutter, some of the components of transistor 400 (e.g. For example, gate insulating film 304 and the like are omitted.

[0138] The transistor 400 shown in FIG. 4A is a metal film formed on a substrate 300 with a base insulating film 310 interposed therebetween. A metal oxide film 306a and a source electrode or a drain electrode provided in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b, the metal oxide film 306a, and the source and drain electrodes 30 A gate insulating film 304 is provided on the gate insulating film 304. and a gate electrode 302 provided so as to overlap the thin film 306a.

[0139] The substrate 300 may be the same as the substrate 100. The metal oxide film 6a is made of the same material and is formed by the same method as the metal oxide film 106a. The source or drain electrodes 308a and 308b may be The electrodes 108a and 108b are made of the same material and are formed by the same method. The gate insulating film 304 may be made of the same material and in the same manner as the gate insulating film 104. The gate electrode 302 may be formed by the same method as the gate electrode 102. The same material and method as those used in the above may be used.

[0140] The transistor 400 shown in FIG. 4 is a transistor having a top gate structure. The source or drain electrodes 308a and 308b are in contact with the upper surface of the metal oxide film 306a. The source and drain electrodes 308a and 308b are It may have a bottom contact structure in contact with the lower surface of the metal oxide film 306a.

[0141] The region where the metal oxide film 306a and the gate electrode 302 overlap is a channel formation region. It works like this.

[0142] In addition, a base insulating film 310 is provided on the substrate 300. The base insulating film 310 is made of gold. In the transistor 400 shown in FIG. The base insulating film 310 includes an insulating film 312, a metal oxide film 314, and an insulating film 316. Here, the insulating film 312 and the insulating film 316 are insulating films from which oxygen is released by heat treatment. The gate insulating film 304 is made of a material that does not release oxygen during heat treatment. An insulating film is used.

[0143] The metal oxide film 306 a is provided between the gate insulating film 304 and the insulating film 312 . The insulating film 312 is an insulating film from which oxygen is released by heat treatment. As a result, oxygen is released from the insulating film 312 and supplied to the metal oxide film 306a.

[0144] In one embodiment of the present invention, in addition to oxygen, A metal oxide film 314 is provided to prevent unilateral diffusion. This can prevent oxygen contained in the insulating film 312 from being released and diffusing outward.

[0145] In addition, in one embodiment of the present invention, a metal oxide film 31 is provided to prevent outward diffusion of oxygen. 4 is sandwiched between insulating films 312 and 316 from which oxygen is released by heat treatment. As a result, oxygen is released from the insulating film 316 during the heat treatment and is supplied to the metal oxide film 314. The metal oxide film 314 is supplied with oxygen from the insulating films 312 and 316. This compensates for the oxygen deficiency and makes the material an insulator (exhibits insulating properties). Even if the oxide film 314 is used as a part of the base insulating film 310, Therefore, the electrical characteristics of the capacitor 400 are not affected.

[0146] In order to efficiently supply oxygen to the metal oxide film 306a, The insulating film 312 in contact with the metal oxide film 314 is preferably thicker than the insulating film 316 in contact with the metal oxide film 314. The thicknesses of the insulating films 312 and 316 are appropriately set depending on the thickness of the base insulating film 310. Just do that.

[0147] The insulating film 312 is formed of the same material and by the same method as the insulating film 112. The metal oxide film 314 may be made of the same material as the metal oxide film 114. The insulating film 316 may be formed by the same method as the insulating film 116. The same materials and the same methods may be used.

[0148] By using a film from which oxygen is released by heat treatment as the insulating film 312, Oxygen is supplied to the metal oxide film 306a, and the interface between the insulating film 312 and the metal oxide film 306a is heated. Therefore, the charge generated due to the operation of the transistor 400 can be reduced. Therefore, the trapping at the interface between the insulating film 312 and the metal oxide film 306a can be suppressed, and the transistor The transistor 400 can be one with little degradation in electrical characteristics.

[0149] The metal oxide film 314 is made of In, Ga, Sn, and Zn, similarly to the metal oxide film 306a. The metal oxide film 314 is a metal oxide containing two or more elements selected from the above. The element contained in the metal oxide film 306a may be the same as or different from the element contained in the metal oxide film 306a. For example, the metal oxide film 306a and the metal oxide film 314 may be In-Ga For the metal oxide film 306a, a material based on In-Ga-Zn As the metal oxide film 314, an In-Ga-Zn-ON material is used. It may be used.

[0150] <Applications of semiconductor devices> 5A to 5C are cross-sectional views of transistors having different configurations from the transistor 400. The structure is shown.

[0151] The transistor 410 shown in FIG. 5A includes an insulating film 31 over a substrate 300 as a base insulating film. 8 is provided, and the metal oxide film 306a on the insulating film 318 is in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b and the metal oxide film 306a are provided. A gate insulating film 320 provided on the source or drain electrodes 308a and 308b; A metal oxide film 306a is provided on the gate insulating film 320 so as to overlap with the channel forming region of the metal oxide film 306a. and a gate electrode 302 .

[0152] The difference between the transistor 400 and the transistor 410 is that the gate insulating film 320 has a The metal oxide film is provided to prevent the outward diffusion of oxygen. The insulating film 320 has a three-layer structure consisting of an insulating film 322, a metal oxide film 324, and an insulating film 326. In addition, an insulating film 318 is provided as a base insulating film. , 322 and the insulating film 318 are made of an insulating film from which oxygen is released by heat treatment.

[0153] In order to efficiently supply oxygen to the metal oxide film 306a, The insulating film 322 in contact with the metal oxide film 324 is preferably thicker than the insulating film 326 in contact with the metal oxide film 324. The thicknesses of the insulating films 322 and 326 are appropriately set depending on the thickness of the gate insulating film 320. In addition, if the metal oxide film 324 is at least 5 nm thick, oxygen can pass through it. This can be prevented by setting the thickness appropriately according to the thickness of the gate insulating film 320.

[0154] The transistor 420 shown in FIG. 5B is a transistor including a gold layer and a base insulating film 310 disposed on the substrate 300. A metal oxide film 306a and a source electrode or a drain electrode provided in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b, the metal oxide film 306a, and the source and drain electrodes 30 A gate insulating film 320 is provided on the gate electrodes 8a and 308b. A metal oxide film is provided on the gate insulating film 320. A gate electrode 302 is provided so as to overlap a channel forming region of the semiconductor film 306a. do.

[0155] In the transistor 420, the base insulating film 310 and the gate insulating film 320 are The description of the transistor 400 and the transistor 410 can be taken into consideration, so a detailed description will be given. The details are omitted.

[0156] In addition, in the transistor 400, the transistor 410, and the transistor 420, The source or drain electrodes 308a and 308b are in contact with the upper surface of the metal oxide film 306a. The top contact structure has been described. The source and drain electrodes 308a and 308b are in contact with the bottom surface of the metal oxide film 306a. A top contact structure can also be used. An example of a bottom contact structure is shown in FIG. As shown in.

[0157] The transistor 430 shown in FIG. 5C includes a base insulating film 310 provided over a substrate 300. and source and drain electrodes 308a and 308b provided on the base insulating film 310. , the metal oxide film 30 provided in contact with the source electrode or drain electrode 308a, 308b 6a, the source or drain electrodes 308a, 308b, and the metal oxide film 306a The gate insulating film 304 is provided on the metal oxide film 306a. The gate insulating film 304 overlaps with a channel formation region of the metal oxide film 306a. and a gate electrode 302 provided so as to contact the gate electrode 302 .

[0158] As described above, the transistor according to one embodiment of the present invention can be implemented in various forms. do.

[0159] In addition, the configurations, methods, etc. described in this embodiment may be used in conjunction with the configurations, methods, etc. described in other embodiments. They can be used in any suitable combination.

[0160] (Embodiment 3) In this embodiment, a semiconductor device including the transistor described in the above embodiment and a manufacturing method thereof will be described. Examples of the method, as well as circuit configurations and operations, are described with reference to Figures 6 to 8. In this embodiment, a so-called DRAM (Dynamic Random Access Memory) is used. An example of a semiconductor device having a structure equivalent to a memory (not shown) will be described. In the following, the symbol OS is used to indicate that the transistor is formed using an oxide semiconductor. In some cases, it may be added together.

[0161] <Cross-sectional structure of semiconductor device> First, an example of a cross-sectional structure of a semiconductor device will be described with reference to FIG. The semiconductor device shown in FIG.

[0162] A transistor according to one embodiment of the present invention is used as a transistor 400 in FIG. The transistor 400 is formed on a substrate 300 with a metal oxide film 310 interposed therebetween. 306a, source or drain electrodes 308a and 308b, and a gate insulating film 304. The base insulating film 310 includes an insulating film 312 and a metal oxide The insulating film 314 and the insulating film 316 are provided.

[0163] The capacitor 402 in FIG. 6A includes a gate insulating film 304, a source electrode or a drain electrode, The source or drain electrode 308a is a capacitance. The electrode 302b functions as one electrode of the capacitor 402. It functions as such.

[0164] In addition, an insulating film 330 is provided so as to cover the transistor 400 and the capacitor 402. Then, the source electrode or the drain electrode 30 is formed through an opening provided in the insulating film 330. 8b and the wiring 332 are connected.

[0165] <Basic circuit> Next, the basic circuit configuration and operation of the semiconductor device shown in FIG. In the semiconductor device shown in FIG. 6B, the first wiring Line) and the source electrode or drain electrode of the transistor 400 are electrically connected. The second wiring (2nd Line) and the gate electrode of the transistor 400 are electrically connected 402 and one of the electrodes of the capacitor 402 and the drain electrode or The third line and the capacitor are electrically connected to each other. The other electrode of the element 402 is electrically connected.

[0166] Here, the transistor 400 is, for example, a transistor including an oxide semiconductor. A transistor including an oxide semiconductor has a feature of having an extremely low off-state current. Therefore, when the transistor 400 is turned off, the capacitance element 402 is The applied potential can be maintained for a very long period of time.

[0167] The semiconductor device shown in FIG. 6B has a feature that a potential applied to the capacitor 402 can be held. By utilizing this characteristic, it is possible to write, retain, and read information as follows.

[0168] Next, we will explain how to write and hold information. For simplicity, we will use the third wiring. The potential of the second wiring is fixed. The transistor 400 is turned on by applying a potential to the first transistor 400 so that the first The potential of the line is applied to one of the electrodes of the capacitor 402. Then, a predetermined charge is applied (written). Then, the potential of the second wiring is applied to the transistor 4 00 is set to a potential at which the transistor 400 is turned off, The charge applied to the capacitance element 402 is held (retained). Since the off-state current is extremely small, charges can be retained for a long period of time.

[0169] Next, the reading of information will be described. In this state, when the potential of the second wiring is set to a potential at which the transistor 400 is turned on, The first wiring has a different potential depending on the amount of charge held in the capacitor 402. By detecting the potential of the first wiring, the stored data can be read out.

[0170] Next, the rewriting of information will be described. The rewriting of information includes the above-mentioned writing of information and That is, the potential of the second wiring is held in the same manner as when the transistor 400 is turned on. This causes the transistor 400 to be turned on. (a potential related to new data) is applied to one electrode of the capacitor 402. The potential of the wiring is set to a potential at which the transistor 400 is turned off. By turning off the capacitor 402, the capacitor 402 is turned on in a state where a charge related to new data is provided. It becomes a state of mind.

[0171] In this manner, the semiconductor device according to one embodiment of the present invention can directly store data by rewriting the data. This allows the semiconductor device to operate at high speed.

[0172] The above explanation is for n-type transistors (n-channel transistors) that use electrons as carriers. ) is used, but instead of n-type transistors, Needless to say, a p-type transistor can be used.

[0173] FIG. 7 shows an example of a circuit diagram of a semiconductor device having (m×n) memory cells 450. The configuration of the memory cell 450 in FIG. 7 is the same as that in FIG. 6. That is, the first arrangement in FIG. 6 corresponds to the bit line BL in FIG. 7, and the second wiring in FIG. 6 corresponds to the word 6 corresponds to the line WL, and the third wiring in FIG. 6 corresponds to the source line SL in FIG. 7 (FIG. 7 reference).

[0174] The semiconductor device shown in FIG. 7 includes n bit lines BL, m word lines WL, and memory cells 4 50, a memory cell array arranged in a matrix of m rows by n columns, A first driver circuit 461 connected to m bit lines BL and a second driver circuit 462 connected to m word lines WL. 2 and a driving circuit 462.

[0175] The memory cell 450 includes a transistor 400 and a capacitor 402 . The gate electrode of the transistor 400 is connected to the word line WL. One of the source electrode and the drain electrode of the transistor 400 is connected to the bit line BL. The other of the source electrode and the drain electrode of the transistor 400 is connected to one of the electrodes of the capacitor element 402. The other electrode of the capacitor 402 is connected to the source line SL. A constant potential is applied to the transistor 400. The data is applied.

[0176] A semiconductor device according to one embodiment of the present invention includes a transistor having a channel formation region formed of an oxide semiconductor. Therefore, compared to transistors that use single crystal silicon for the channel formation region, It has the characteristic of small current. For this reason, it is recognized as a so-called DRAM. When the transistor is applied to the semiconductor device shown in FIG. 7, the refresh period can be extremely long. It is possible to obtain a large memory.

[0177] <Method for Manufacturing Semiconductor Device> Next, a manufacturing method of the semiconductor device shown in FIG. 6 will be described with reference to FIG.

[0178] First, an insulating film 312 functioning as a base insulating film 310 and a metal oxide film 3 14, and an insulating film 316 are formed in this order (see FIG. 8(A)). Since the same materials as those of the insulating film 312 and the insulating film 313 can be used, detailed description thereof will be omitted. The insulating film 316 can be described in the same manner as the insulating film 112 and the insulating film 116. do.

[0179] Next, a metal oxide film 306a is formed over the base insulating film 310 (see FIG. 8B). For the metal oxide film 306a, the description of the metal oxide film 106a can be referred to.

[0180] Next, the source and drain electrodes 308a and 308b in contact with the metal oxide film 306a are After the formation, the metal oxide film 306a is formed on the source electrode or drain electrode 308a, 308b. A gate insulating film 304 is then formed on the gate insulating film 304. A gate electrode 302a is formed in a region overlapping with the channel forming region of 6a, and a source The electrode 302b is formed in a region overlapping with the drain electrode 308a (see FIG. 8C). The source and drain electrodes 308a and 308b are The descriptions in 108a and 108b may be taken into consideration.

[0181] Next, an interlayer insulating film is formed to cover the gate insulating film 304, the gate electrode 302a, and the electrode 302b. Then, the insulating film 330 and the gate insulating film 330 are formed. An opening is formed in the insulating film 330, and a wiring 332 is formed on the insulating film 330. The rain electrode 308b and the wiring 332 are electrically connected.

[0182] The insulating film 330 that functions as an interlayer insulating film is made of an inorganic material (silicon oxide, silicon nitride, etc.). , silicon oxynitride, etc.), photosensitive or non-photosensitive organic materials (polyimide, acrylic, polyimide, etc.), polyimide, polyimide amide, resist or benzocyclobutene), silicon (Si) and oxygen The skeleton is formed by bonds with (O), and the substituents contain at least hydrogen or the substituents contain fluorine. Materials containing at least one of fluorine, alkyl groups, and aromatic hydrocarbons, so-called silicides Polyoxanes and their laminated structures can be used.

[0183] The wiring 332 is formed by forming a conductive film using a sputtering method, a plasma CVD method, or the like. Then, the conductive film is subjected to a photolithography process and an etching process to form a The conductive film is made of aluminum, chromium, copper, tantalum, titanium, molybdenum, etc. The element selected from the group consisting of tungsten, tungsten, and alloys containing the above elements can be used. Yes, manganese, magnesium, zirconium, beryllium, neodymium, and scandium. The gate electrode may be made of any one of the following materials or a combination of these materials. Similar to 102 etc.

[0184] Through the above steps, a semiconductor device including a transistor 400 and a capacitor 402 is manufactured. (See FIG. 8(D)).

[0185] As described above, the configurations, methods, etc. described in this embodiment may be used in conjunction with the configurations, methods, etc. described in other embodiments. They can be used in any suitable combination.

[0186] (Embodiment 4) A semiconductor device according to one embodiment of the present invention can be applied to various electronic devices (including game machines). The electronic device can be, for example, a television device (television or television (also called digital receivers), computer monitors, digital cameras, digital video cameras, etc. Cameras such as digital cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices) (c) Portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Examples of electronic devices including the semiconductor device described in the above embodiment include explain.

[0187] FIG. 9A shows a notebook personal computer, which includes a main body 3001 and a housing 3002. , a display unit 3003, a keyboard 3004, etc. The semiconductor device shown in Embodiment 2 can be applied to the display portion 3003. The semiconductor device can be applied to a memory circuit included inside the housing 3002. The semiconductor device according to the first to third embodiments has high reliability because the fluctuation of electrical characteristics is suppressed. The computer may be a high performance notebook type personal computer.

[0188] FIG. 9B shows a portable digital assistant (PDA), which has a main body 3021 including a display unit 3023 and an external The external interface 3025 and the operation button 3024 are also provided. The stylus 3022 is included as an accessory. The semiconductor device shown in the third embodiment can be applied to the main body 302. The present invention can be applied to the memory circuit included in the semiconductor device according to the first to third embodiments. The device is highly reliable because the fluctuation of electrical characteristics is suppressed. ) can be used.

[0189] FIG. 9C shows an example of an electronic book. For example, the electronic book has a housing 2701 and The housing 2701 and the housing 2703 are made up of two housings. The handle 2711 is an integral part of the handle 2710, and can be opened and closed with the handle 2711 as an axis. With this configuration, it becomes possible to operate like a paper book.

[0190] A display unit 2705 is incorporated in the housing 2701, and a display unit 2707 is incorporated in the housing 2703. The display unit 2705 and the display unit 2707 are configured to display a continuous screen. Alternatively, a different screen may be displayed. For example, a text is displayed on the right display unit (display unit 2705 in FIG. 9C) and An image can be displayed on the display unit (display unit 2707 in FIG. 9C). The semiconductor device shown in FIG. 2 can be applied to the display portion 2705 and the display portion 2707. The semiconductor device shown in Embodiment 3 is a memory circuit included in the housings 2701 and 2703. The semiconductor device according to the first to third embodiments can be applied to a circuit. Since the above-mentioned problem is solved, it is possible to make the e-book highly reliable.

[0191] FIG. 9C shows an example in which an operation unit and the like are provided in the housing 2701. The body 2701 includes a power source 2721, operation keys 2723, a speaker 2725, etc. The operation keys 2723 can be used to turn pages. A keyboard and a pointing device may be provided on the rear of the housing. On the front and sides, there are external connection terminals (earphone terminal, USB terminal, etc.), a recording medium insertion part, etc. Furthermore, the electronic book may be configured to have a function as an electronic dictionary. You may do so.

[0192] The electronic book may be configured to transmit and receive information wirelessly. It is also possible to purchase and download desired book data from the server. be.

[0193] FIG. 9D shows a mobile phone, which is composed of two housings, a housing 2800 and a housing 2801. The housing 2801 includes a display panel 2802, a speaker 2803, a microphone, and a 2804, pointing device 2806, camera lens 2807, external connection terminal 2 808. The housing 2800 also includes a solar cell for charging the mobile phone. 2810, an external memory slot 2811, etc. The semiconductor device shown in the first and second embodiments is incorporated in the display panel 2802. The semiconductor device shown in the third embodiment can be applied to the housings 2800 and 280 The present invention can be applied to the memory circuit included in the semiconductor device according to the first to third embodiments. The device has suppressed fluctuations in electrical characteristics, making it a highly reliable mobile phone. can.

[0194] The display panel 2802 is equipped with a touch panel, and in FIG. The multiple operation keys 2805 are indicated by dotted lines. It also implements a boost circuit to boost the voltage supplied to each circuit to the voltage required.

[0195] The display direction of the display panel 2802 changes appropriately depending on the usage mode. Since it has a camera lens 2807 on the same surface as 2802, video telephony is possible. The speaker 2803 and the microphone 2804 are not limited to voice calls, but can also be used for video calls, Recording and playback are possible. Furthermore, the housing 2800 and the housing 2801 can be slid. It can be folded from the unfolded state as shown in 9(D) to the overlapped state, making it convenient to carry. It is possible to reduce the size.

[0196] The external connection terminal 2808 can be connected to various cables such as AC adapters and USB cables. It is capable of charging and data communication with a personal computer, etc. A recording medium can be inserted into the memory slot 2811 to accommodate larger amounts of data storage and transfer. do.

[0197] In addition to the above functions, even if the device has infrared communication function, TV reception function, etc. good.

[0198] FIG. 9(E) shows a digital video camera, which includes a main body 3051, a display unit (A) 3057, and a connection Eye unit 3053, operation switch 3054, display unit (B) 3055, battery 3056, etc. The semiconductor device shown in the first and second embodiments is configured as the display portion (A) 3057. The semiconductor device shown in Embodiment 3 can be applied to the display portion (B) 3055. The above can be applied to the memory circuit included inside the main body 3051. The semiconductor device according to any one of claims 1 to 3 has a highly reliable digital signal because the fluctuation of electrical characteristics is suppressed. The camera may be a portable video camera.

[0199] FIG. 9F shows an example of a television device. The television device 9600 is A display unit 9603 is built into the body 9601. The display unit 9603 displays images. In this embodiment, the housing 9601 is supported by a stand 9605. The semiconductor device shown in Embodiments 1 and 2 can be applied to the display portion 9603. The semiconductor device described in Embodiment 3 can be mounted on a metal substrate included in the housing 9601. The semiconductor device according to the first to third embodiments can be applied to a memory circuit. Since the fluctuation in the signal level is suppressed, a highly reliable television set can be obtained.

[0200] The television device 9600 can be operated using an operation switch on the housing 9601 or a separate remote control. The remote control can also be operated by the remote control. A display unit for displaying the output information may be provided.

[0201] The television device 9600 includes a receiver and a modem. It can receive more general television broadcasts, and can also be connected to a modem via wired or wireless connection. By connecting to a network, communication can be one-way (sender to receiver) or two-way. It is also possible to communicate information (between a sender and a receiver, or between receivers).

[0202] This embodiment mode can be implemented in appropriate combination with the configurations described in other embodiments. It is. EXAMPLES

[0203] In this embodiment, a MOS (Metal Oxide Semiconductor) substrate is The device was fabricated and subjected to withstand voltage and capacitance-voltage (CV) measurements. The results will be explained with reference to FIGS.

[0204] First, a method for preparing the samples used in this embodiment will be described.

[0205] As sample A, a first insulating film was formed on a silicon substrate by sputtering. A silicon oxide film was formed to a thickness of 50 nm. Next, a metal oxide film was formed on the silicon oxide film. Then, a metal oxide film of In-Ga-Zn-ON system with a thickness of 10 nm was formed by sputtering. Next, a second insulating film was formed on the In-Ga-Zn-O-N metal oxide film. As the substrate, a silicon oxide film was formed to a thickness of 50 nm by sputtering.

[0206] Sample B is an In-Ga-Zn-ON metal oxide film, which is the same as sample A. Instead of the metal film, a 10 nm thick In-Ga-Zn-O metal film was deposited by sputtering. The other configurations and manufacturing methods were the same as those of sample A.

[0207] As sample C, a first insulating film was formed on a silicon substrate by plasma CVD. A silicon oxynitride film was formed to a thickness of 50 nm. Next, a sputtering process was performed on the silicon oxynitride film. A 10 nm thick In-Ga-Zn-O metal oxide film was formed by the ring method. After that, a second insulating film is formed on the In-Ga-Zn-O metal oxide film by plasma C. A silicon oxynitride film was formed to a thickness of 50 nm by the VD method.

[0208] In the sample D, instead of the silicon oxide film (the first insulating film and the second insulating film) in the sample A, A silicon oxynitride film was formed to a thickness of 50 nm by plasma CVD. The preparation method is the same as that of sample A.

[0209] For sample E, a silicon oxide film with a thickness of 100 nm was deposited on a silicon substrate by sputtering. A cone film was formed.

[0210] Next, heat treatment was performed on Samples A to E. The heat treatment was performed under the conditions of a nitrogen atmosphere and a temperature of The reaction was carried out at 300°C for 1 hour.

[0211] Next, for each of Samples A to E, a thin film was formed on the second insulating film by a sputtering method. The electrode was made of an aluminum-titanium alloy film with a thickness of 400 nm (electrode area 0.785 mm 2 ) was formed.

[0212] Finally, samples A to E were subjected to a heat treatment in a nitrogen atmosphere at a temperature of 250° C. for 1 hour. I did.

[0213] The structures of the MOS substrates of samples A to E obtained as described above are shown in Table 1.

[0214] [Table 1]

[0215] Next, the current-voltage (IV) characteristics of samples A to E were measured. Measurements were taken at 13 points each.

[0216] The results of the withstand voltage measurement are shown in Figs. 10 to 12. Fig. 10(A) shows the results for sample A, and Fig. 1 11(B) shows the results for sample B, FIG. 11(A) shows the results for sample C, and FIG. 11(B) shows the results for sample B. 10 to 12, the horizontal axis indicates the voltage Vcc of sample D, and FIG. 12 indicates the voltage Vcc of sample E. The vertical axis indicates voltage, and the vertical axis indicates current.

[0217] In the sample C shown in FIG. 11(A) and the sample D shown in FIG. 11(B), the current rise In contrast, sample A shown in FIG. 10(A) and sample B shown in FIG. In sample B shown in (B), the current rise is slower than in samples C and D. In addition, sample E shown in FIG. 12 has the same breakdown voltage as samples A and B. It was found that it had pressure resistance.

[0218] Next, CV measurements were performed on samples A to E. Four measurements were performed on each sample. went.

[0219] The results of the CV measurements are shown in Figs. 13 to 15. Fig. 13(A) shows the results for sample A. FIG. 13(B) shows the results for sample B, FIG. 14(A) shows the results for sample C, and FIG. FIG. 13 shows the results for sample D, and FIG. 15 shows the results for sample E. In FIGS. indicates voltage, and the vertical axis indicates capacitance value.

[0220] For sample C shown in Fig. 14(A) and sample D shown in Fig. 14(B), CV curves were obtained. As can be seen from the results in Figure 11, the results were not satisfactory for samples C and D. This is thought to be because the insulation film in the In contrast, sample A shown in FIG. 13(A), sample B shown in FIG. 13(B), and sample C shown in FIG. In the case of sample E, a good CV curve was obtained.

[0221] Furthermore, the CV curves of samples A and B are positively polarized compared to the CV curve of sample E. This is because the negative shift in the α-H bands in samples A and B is greater than that in sample E. This is because there is a large amount of fixed charge, and such an insulating film is called a transistor channel type. By forming the metal oxide film including the metal oxide film having the insulating layer, the threshold voltage of the transistor can be reduced. It was suggested that it is possible to shift the

[0222] Samples C and D are made of an insulating film sandwiching a metal oxide film, and a nitriding agent formed by plasma CVD. Silicon oxide nitride film is used. In the case of the metal oxide film, oxygen is not released by the heat treatment. Therefore, oxygen is supplied from the insulating film to the metal oxide film. It is considered that the metal oxide film could not be insulated. In the conventional semiconductor device, silicon oxide films are used as insulating films sandwiching the metal oxide films. The silicon oxide film formed by the sputtering method loses oxygen when heat treated, It is believed that sufficient oxygen was supplied to the metal oxide film, making it insulating. It is believed that this is why the withstand voltage of Samples A and B has improved.

[0223] From the above results, when a metal oxide film is provided between insulating films from which oxygen is released by heat treatment, It was shown that the metal oxide film functions as an insulating film. EXAMPLES

[0224] In this example, a metal oxide film was formed on an insulating film that releases oxygen by heat treatment, using TDS analysis. In the structure to be formed, the amount of oxygen that diffuses outward from the insulating film through the metal oxide film is The results of the investigation will be explained below.

[0225] First, Samples F to I used in this embodiment will be described.

[0226] Sample F was prepared by sputtering a silicon oxide film with a thickness of 100 nm on a glass substrate. Next, a 5 nm thick silicon oxide film was formed on the silicon oxide film by sputtering. An In-Ga-Zn-O metal oxide film was formed.

[0227] As sample G, a silicon oxide film with a thickness of 100 nm was deposited on a glass substrate by sputtering. Next, a 10 nm thick silicon oxide film was formed on the silicon oxide film by sputtering. An In-Ga-Zn-O metal oxide film was formed.

[0228] Sample H was prepared by sputtering a silicon oxide film with a thickness of 100 nm on a glass substrate. Next, a 15 nm thick silicon oxide film was formed on the silicon oxide film by sputtering. An In-Ga-Zn-O metal oxide film was formed.

[0229] Sample I was prepared by depositing a silicon oxide film with a thickness of 100 nm on a glass substrate by sputtering. A thin film was formed.

[0230] Next, TDS analysis was performed on Samples F to I. In this example, the amount of oxygen desorbed was The values ​​were measured using a thermal desorption analyzer EMD-WA1000S / W manufactured by Electron Science Corporation.

[0231] FIG. 16 shows the TDS analysis results of Samples F to I.

[0232] As shown in FIG. 16, in the case of Sample I in which only a silicon oxide film was formed, the temperature was increased to about 200° C. In contrast, the peak was higher at the sample with a metal oxide film formed on a silicon oxide film. For samples F to H, almost no peaks were detected.

[0233] From the results of FIG. 16, it is clear that the formation of a metal oxide film on a silicon oxide film reduces the amount of oxidation. It was found that the oxygen contained in the silicon oxide film was not released to the outside. If the film is at least 5 nm thick, the oxygen contained in the silicon oxide film will not be released to the outside. These results prove that metal oxide films can prevent oxygen from passing through. It was done. EXAMPLES

[0234] In this embodiment, the resistivity of the metal oxide film is examined. The results are shown in FIG. explain.

[0235] First, the sample used in this example will be described with reference to FIG.

[0236] (Condition 1) The insulating films sandwiching the metal oxide film 506 are made of insulating films that do not release oxygen by heat treatment. This is considered to be condition 1.

[0237] First, a 10 mm thick insulating film 502 is formed on a glass substrate 500 by plasma CVD. A silicon oxynitride film was formed at 0 nm.

[0238] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0239] Next, as the metal oxide film 506, an In-Ga-Zn-O system was deposited by sputtering. A metal oxide film was formed. The film formation conditions for the metal oxide film were a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2=30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450° C. for 1 hour.

[0240] Next, a silicon oxynitride film is formed as an insulating film 508 by plasma CVD to a thickness of 100 nm. A silicon film was formed.

[0241] Next, the insulating film 508 and the metal oxide film 506 are subjected to a photolithography process and an etching process. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0242] Finally, the sample was subjected to heat treatment at 350° C. for 1 hour in a nitrogen atmosphere.

[0243] (Condition 2) The insulating films sandwiching the metal oxide film 506 are made of insulating films that release oxygen by heat treatment. This case is called condition 2.

[0244] First, a 10 mm thick insulating film 502 was formed on a glass substrate 500 by a sputtering method. A silicon oxide film was formed at a thickness of 0 nm.

[0245] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0246] Next, as the metal oxide film 506, an In-Ga-Zn-O system was deposited by sputtering. A metal oxide film was formed. The film formation conditions for the metal oxide film were a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2=30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450° C. for 1 hour.

[0247] Next, a silicon oxide film is formed as an insulating film 508 by sputtering to a thickness of 100 nm. A film was formed.

[0248] Next, the insulating film 508 and the metal oxide film 506 are subjected to a photolithography process and an etching process. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0249] Finally, the sample was subjected to heat treatment at 350° C. for 1 hour in a nitrogen atmosphere.

[0250] (Condition 3) The insulating film 502 is an insulating film from which oxygen is released by heat treatment, and the insulating film 508 is an insulating film from which oxygen is released by heat treatment. Therefore, the case where an insulating film from which oxygen is not released is used is defined as condition 3.

[0251] First, a 10 mm thick insulating film 502 was formed on a glass substrate 500 by a sputtering method. A silicon oxide film was formed at a thickness of 0 nm.

[0252] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0253] Next, as the metal oxide film 506, an In-Ga-Zn-O system was deposited by sputtering. A metal oxide film was formed. The film formation conditions for the metal oxide film were a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2=30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450° C. for 1 hour.

[0254] Next, a silicon oxynitride film is formed as an insulating film 508 by plasma CVD to a thickness of 100 nm. A silicon film was formed.

[0255] Next, the insulating film 508 and the metal oxide film 506 are subjected to a photolithography process and an etching process. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0256] Finally, the sample was subjected to heat treatment at 350° C. for 1 hour in a nitrogen atmosphere.

[0257] (Condition 4) The insulating film 502 is an insulating film from which oxygen is not released by heat treatment. Condition 4 is a case where an insulating film from which oxygen is released by heat treatment is used.

[0258] First, a 10 mm thick insulating film 502 is formed on a glass substrate 500 by plasma CVD. A silicon oxynitride film was formed at 0 nm.

[0259] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0260] Next, as the metal oxide film 506, an In-Ga-Zn-O system was deposited by sputtering. A metal oxide film was formed. The film formation conditions for the metal oxide film were a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2=30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450° C. for 1 hour.

[0261] Next, a silicon oxide film is formed as an insulating film 508 by sputtering to a thickness of 100 nm. A film was formed.

[0262] Next, the insulating film 508 and the metal oxide film 506 are subjected to a photolithography process and an etching process. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0263] Finally, the sample was subjected to heat treatment at 350° C. for 1 hour in a nitrogen atmosphere.

[0264] Next, the electrical conductivity σ was measured at four points for each of the samples described under Conditions 1 to 4. The resistivity ρ was calculated from the measured conductivity σ and the average value of the four points was calculated. , as shown in Table 2.

[0265] [Table 2]

[0266] As shown in Table 2, the resistivity ρ of the metal oxide film under condition 1 is 1.4×10 ―2 [Ω· The resistivity ρ of the metal oxide film under condition 2 was found to be 7.4 ×10 9 In addition, the resistance of the metal oxide film under condition 3 was calculated as [Ω·cm]. The rate ρ is 8.6×10 3 In addition, the metal in condition 4 was calculated as The resistivity of the oxide film is 8.5×10 6 It was possible to calculate the value as [Ω·cm].

[0267] From the results of Condition 1, the metal oxide film 506 was reduced by the heat treatment after the film formation. The resistance of 506 does not change and remains low even if a heat treatment is performed after the formation of the insulating film 508. As a result, it was found that the metal oxide film 506 has conductive properties.

[0268] In addition, the results of condition 2 show that the metal oxide film 506 was reduced by the heat treatment after deposition. It has been found that the resistance of the insulating film 506 increases by performing a heat treatment after the formation of the insulating film 508. This is because oxygen is supplied from the insulating film 502 and the insulating film 508 to the metal oxide film. This is believed to be because the oxygen vacancies that were generated are compensated for. As a result, the metal oxide film 506 It was found that the material becomes an insulator (exhibits insulating properties).

[0269] In addition, the results of Conditions 3 and 4 show that the heat treatment after the formation of the insulating film 508 causes the metal oxide The resistance of the metal oxide film 506 is higher than that of condition 1 and lower than that of condition 2. It was found that the oxide film 506 became a semiconductor.

[0270] From the above results, the type of insulating film in contact with the metal oxide film (or the amount of oxygen released from the insulating film) It was shown that the resistance of metal oxide films can be adjusted by changing the amount of [Explanation of symbols]

[0271] 100 Substrates 102 Gate electrode 104 Gate insulating film 106 Metal oxide film 106a Metal oxide film 108a source electrode or drain electrode 108b Source electrode or drain electrode 110 Passivation film 112 Insulating film 114 Metal oxide film 116 Insulating film 118 Insulating film 120 Gate insulating film 122 Insulating film 124 Metal oxide film 126 Insulating Film 200 Transistors 210 Transistor 220 Transistor 230 Transistor 300 Substrates 302 Gate electrode 304 Gate insulating film 306a Metal oxide film 308a Source electrode or drain electrode 308b Source electrode or drain electrode 310 Undercoat insulating film 312 Insulating film 314 Metal oxide film 316 Insulating Film 318 Insulating Film 320 Gate insulating film 322 Insulating film 324 Metal oxide film 326 Insulating Film 330 Insulating Film 332 Wiring 400 Transistors 402 Capacitive element 410 Transistor 420 Transistor 430 Transistor 450 memory cells 461 Drive Circuit 462 Drive circuit 500 Glass Substrate 502 Insulating film 504a electrode 504b electrode 506 Metal oxide film 508 Insulating film 2701 Case 2703 Case 2705 ​​Display section 2707 Display section 2711 Shaft 2721 Power supply 2723 Operation key 2725 Speaker 2800 Chassis 2801 Case 2802 Display Panel 2803 Speaker 2804 Microphone 2805 Operation key 2806 Pointing Device 2807 Camera lenses 2808 External connection terminal 2810 Solar Cell 2811 External memory slot 3001 Main unit 3002 Case 3003 Display section 3004 Keyboard 3021 Main unit 3022 Stylus 3023 Display section 3024 Operation button 3025 External Interface 302a Gate electrode 302b electrode 3051 Main unit 3053 Eyepiece 3054 Operation switch 3055 Display section (B) 3056 Battery 3057 Display section (A) 9600 Television Equipment 9601 Case 9603 Display section 9605 Stand

Claims

1. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having a region in contact with each of a side surface and an upper surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, the second insulating film including silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second insulating film has a region that is thicker than the third insulating film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; the first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film overlaps with a channel formation region of the first metal oxide film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film; Semiconductor device.

2. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having a region in contact with each of a side surface and an upper surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, the second insulating film including silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second insulating film has a region that is thicker than the third insulating film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; the first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers when viewed in a direction perpendicular to the c-axis, the second metal oxide film overlaps with a channel formation region of the first metal oxide film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film; Semiconductor device.

3. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having a region in contact with each of a side surface and an upper surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, the second insulating film including silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second conductive film and the third conductive film each include a metal oxide; the second insulating film has a region that is thicker than the third insulating film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; the first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film overlaps with a channel formation region of the first metal oxide film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film; Semiconductor device.

4. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having a region in contact with each of a side surface and an upper surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, the second insulating film including silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second conductive film and the third conductive film each include a metal oxide; the second insulating film has a region that is thicker than the third insulating film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; the first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; the first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers when viewed in a direction perpendicular to the c-axis, the second metal oxide film overlaps with a channel formation region of the first metal oxide film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film; Semiconductor device.

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