Semiconductor device

Abstract

To suppress variation in electrical characteristics and to improve reliability in a semiconductor device including an oxide semiconductor.SOLUTION: The semiconductor device includes a first insulating film, an oxide semiconductor film over the first insulating film, a second insulating film over the oxide semiconductor film, and a third insulating film over the second insulating film, the second insulating film includes oxygen and silicon, the third insulating film includes nitrogen and silicon, and indium is included in the vicinity of an interface between the second insulating film and the third insulating film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention is a semiconductor device including an oxide semiconductor film and a display device including the semiconductor device. This relates to a display device.

[0002] Note that one embodiment of the present invention is not limited to the above technical fields. The technical field of one aspect of the present invention relates to a product, a method, or a manufacturing method. Process, Machine, Manufacture, or Composition of Matter In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, The present invention relates to a device, a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] A transistor (field-effect transistor) is made using a semiconductor thin film formed on a substrate with an insulating surface. The technology that makes up the field-effect transistor (FET) or thin-film transistor (TFT) is attracting attention. The transistor is used in integrated circuits (ICs) and image display devices (display devices). It is widely used in electronic devices. Silicon is a semiconductor thin film that can be used in transistors. Semiconductor materials, such as silicon, are widely known, but oxide semiconductors are also attracting attention. This has been attracting attention (for example, Patent Document 1).

[0004] In addition, a base insulating layer of the oxide semiconductor layer in which a channel is formed is heated to release oxygen. A semiconductor device is disclosed in which an insulating layer is used to reduce oxygen vacancies in the oxide semiconductor layer (e.g., For example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-165529 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-9836 Summary of the Invention [Problem to be solved by the invention]

[0006] When a transistor is manufactured using an oxide semiconductor film for a channel region, Oxygen vacancies formed in the channel region during the process are problematic because they affect transistor characteristics. For example, when oxygen vacancies are formed in the channel region of the oxide semiconductor film, the oxygen vacancies Hydrogen bonds to the oxide semiconductor film and becomes a carrier supply source. When a source is generated, the electrical characteristics of a transistor including an oxide semiconductor film change, typically In addition, the electrical characteristics of each transistor vary. Therefore, in the channel region of the oxide semiconductor film, there is a problem that oxygen vacancies are small. The more the better.

[0007] In view of the above problems, one embodiment of the present invention is to provide a semiconductor device including an oxide semiconductor, One of the objectives is to suppress fluctuations in characteristics and improve reliability. An object of one embodiment of the present invention is to provide a semiconductor device with reduced power consumption. Another object of one embodiment of the present invention is to provide a novel semiconductor device. An object of one embodiment of the present invention is to provide a novel display device.

[0008] The above description of the problem does not preclude the existence of other problems. The embodiment does not necessarily have to solve all of these problems. Problems other than those mentioned above can be solved by the specification. It is clear from the description of the specification, etc. that the problems other than those mentioned above cannot be extracted from the description of the specification, etc. It is possible to issue it. [Means for solving the problem]

[0009] One embodiment of the present invention is a semiconductor device including an oxide semiconductor film, an insulating film, an oxide semiconductor film on the first insulating film, and a second insulating film on the oxide semiconductor film; and a third insulating film on the second insulating film, the second insulating film containing oxygen and silicon. The third insulating film contains nitrogen and silicon, and the second insulating film and the third insulating film The semiconductor device is characterized by having indium near the interface.

[0010] Another embodiment of the present invention is a semiconductor device including an oxide semiconductor film, The device includes a gate electrode, a first insulating film on the gate electrode, and an oxide semiconductor film on the first insulating film. a source electrode electrically connected to the oxide semiconductor film; a drain electrode formed on the oxide semiconductor film, a source electrode, and a second insulating film on the drain electrode; a third insulating film on the second insulating film, the second insulating film being composed of oxygen, silicon, and , and the third insulating film has nitrogen and silicon, and the second insulating film and the third insulating film The semiconductor device is characterized by having indium near the interface with the film.

[0011] In each of the above configurations, indium is preferably detected by secondary ion mass spectrometry.

[0012] In each of the above structures, the oxide semiconductor film contains oxygen, In, Zn, and M (M is It is preferable that the metal oxide has at least one of Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf. In each of the above structures, the oxide semiconductor film has a crystalline portion, and the crystalline portion has a c-axis It is preferable that the oxide semiconductor film have a portion parallel to a normal vector of a surface on which the oxide semiconductor film is formed.

[0013] Another embodiment of the present invention is a semiconductor device and a display element according to any one of the above structures. Another embodiment of the present invention is a display device including the display device and a touch sensor. Another embodiment of the present invention is a display module having any one of the above structures. a semiconductor device, the display device, or the display module according to one of the above; and an operation key or and a battery. [Effects of the Invention]

[0014] According to one embodiment of the present invention, fluctuations in electrical characteristics of a semiconductor device including an oxide semiconductor can be reduced. According to one embodiment of the present invention, the power consumption can be reduced and the reliability can be improved. A semiconductor device with reduced power consumption can be provided. According to one embodiment of the present invention, a novel semiconductor device can be provided. A display device can be provided.

[0015] The description of these effects does not preclude the existence of other effects. An embodiment does not necessarily have to have all of these effects. The above will be made clear from the description, drawings, claims, etc. It is possible to extract other effects from the descriptions in the aspects and claims. [Brief explanation of the drawings]

[0016] [Figure 1] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 2] 1A to 1C are cross-sectional views illustrating one embodiment of a semiconductor device and an example of a manufacturing process of the semiconductor device. [Figure 3] FIG. 1 is a diagram illustrating the results of SIMS analysis. [Figure 4] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 5] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 6] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 7] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 8] FIG. 1 is a diagram illustrating a band structure. [Figure 9] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 10] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 11] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 12] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 13] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 14] 1A to 1C are cross-sectional views illustrating an example of a manufacturing process of a semiconductor device. [Figure 15] FIG. 1 is a top view illustrating one embodiment of a display device. [Figure 16] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 17] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 18] 1A and 1B are a block diagram and a circuit diagram illustrating a display device. [Figure 19] FIG. 2 is a diagram illustrating a display module. [Figure 20] 1A to 1C illustrate electronic devices. [Figure 21] 1A to 1C are cross-sectional views illustrating a sample for analysis and a transistor structure in an example. [Figure 22] 10A to 10C are diagrams illustrating SIMS analysis results in the examples. [Figure 23] 10A and 10B are graphs showing electrical characteristics of transistors in Examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments will be described with reference to the drawings. It is possible to implement the present invention in various ways without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments.

[0018] Also, in the drawings, the size, thickness of layers, or areas are exaggerated for clarity. Therefore, the scale is not necessarily limited to that shown. The drawings are merely schematic illustrations and are not limited to the shapes or values ​​shown in the drawings.

[0019] In addition, in this specification and the like, ordinal numbers such as 1st, 2nd, etc. are used for convenience. It does not indicate the order of processes or stacking. For example, "first" may be changed to "second" "the" or "third" can be used as appropriate for explanation. The ordinal numbers listed in the specification do not match the ordinal numbers used to identify an aspect of the present invention. There are cases where this happens.

[0020] In addition, in this specification, the terms "above" and "below" that indicate the position of components are used to indicate the position of components. The positional relationship is used for convenience in describing the structure with reference to the drawings. The relationship between the two components changes depending on the direction in which each component is depicted. The terms are not limited to those used above, but can be rephrased appropriately depending on the situation.

[0021] In this specification and the like, a semiconductor device is a device that can function by utilizing semiconductor characteristics. Refers to devices in general, including semiconductor elements such as transistors, semiconductor circuits, arithmetic units, and memory The device is one aspect of a semiconductor device. Optical devices, power generation devices (including thin-film solar cells, organic thin-film solar cells, etc.), and electronic devices The device may include a semiconductor device.

[0022] In this specification, a transistor includes a gate, a drain, and a source. It is an element having at least three terminals including a drain (drain terminal, drain Between the drain electrode and the source terminal The semiconductor device has a channel region therein, and a current flows through the drain, the channel region, and the source. In this specification and the like, the channel region is a region where a current mainly flows. The flow area.

[0023] The functions of the source and drain may differ depending on whether transistors with different polarities are used or whether the circuit This may happen when the direction of the current changes during operation. In the specification, the terms source and drain may be used interchangeably. do.

[0024] In addition, in this specification, "electrically connected" means "something that has some kind of electrical effect." This includes cases where the device is connected via a "of" is not subject to any particular restrictions as long as it allows the transmission and reception of electrical signals between connected objects. For example, "things that have some kind of electrical action" include electrodes, wiring, and transistors. It has various functions such as switching elements, resistors, inductors, capacitors, etc. This includes elements such as:

[0025] In this specification and the like, a silicon oxynitride film is a film containing more oxygen than nitrogen as a component. A silicon nitride film is a film that contains more nitrogen than oxygen. This refers to a film with a high content of

[0026] In addition, in this specification and the like, the terms "film" and "layer" are interchangeable. For example, the term "conductive layer" can be changed to the term "conductive film." Alternatively, for example, the term "insulating film" may be changed to "insulating layer" It may be possible to change the term to

[0027] In this specification, "parallel" means that two straight lines are at an angle of -10° or more and 10° or less. Therefore, it includes the case where the angle is between -5° and 5°. "Almost parallel" means that two straight lines are arranged at an angle of between -30° and 30°. "Perpendicular" means that two straight lines are arranged at an angle of 80° or more and 100° or less. Therefore, it also includes the case where the angle is between 85° and 95°. This refers to a state in which two straight lines are arranged at an angle of 60° or more and 120° or less.

[0028] In this specification, the vicinity of the interface refers to a range of ±5 nm from the interface. In a state where different films are stacked in the vertical direction, a compound is applied near the interface where the different films contact each other. In this case, the vicinity of the interface refers to the compound and the area 5 nm above the compound. This refers to the combined range of the region above the compound and the region 5 nm below the compound.

[0029] (Embodiment 1) In this embodiment, a semiconductor device of one embodiment of the present invention will be described with reference to FIGS. explain.

[0030] <Configuration Example 1 of Semiconductor Device> FIG. 1A is a top view of a transistor 100 which is a semiconductor device of one embodiment of the present invention. 1(B) corresponds to a cross-sectional view of the cut surface taken along the dashed line X1-X2 shown in FIG. 1(A). 1(C) is a cross-sectional view taken along the dashed line Y1-Y2 in FIG. 1(A). In FIG. 1A, in order to avoid complication, the transistor 100 Some of the components (such as the insulating film that functions as the gate insulating film) are omitted in the illustration. The dashed line X1-X2 direction is the channel length direction, and the dashed line Y1-Y2 direction is the channel width direction. In the top view of the transistor, 1(A), some of the components may be omitted.

[0031] The transistor 100 includes a conductive film 104 over a substrate 102, which functions as a first gate electrode. an insulating film 106 on the substrate 102 and the conductive film 104; and an insulating film 107 on the insulating film 106. The oxide semiconductor film 108 on the insulating film 107 and the insulating film 108 electrically connected to the oxide semiconductor film 108 The conductive film 112a serving as a source electrode and the oxide semiconductor film 108 and a conductive film 112b which functions as a drain electrode connected to the conductive film 112a. Insulating films 114, 116, and 118 are provided on the oxide semiconductor film 112b and the oxide semiconductor film 108. The insulating films 114, 116, and 118 serve as protective insulating films for the transistor 100. It has a function.

[0032] The transistor 100 also includes an indium layer near the interface between the insulating film 116 and the insulating film 118. In other words, indium is detected near the interface between the insulating film 116 and the insulating film 118. The reason why indium is detected will be explained later.

[0033] The insulating film 106 and the insulating film 107 serve as the gate insulating film of the transistor 100. The insulating films 106 and 107 are referred to as a first insulating film, and the insulating films 114 and In the case where the insulating film 116 is referred to as a second insulating film and the insulating film 118 is referred to as a third insulating film, There is a match.

[0034] When oxygen vacancies are formed in the oxide semiconductor film 108 of the transistor 100, carriers Therefore, the oxide semiconductor film 1 tends to have a normally-on characteristic. Reducing oxygen vacancies in O8 is also important for obtaining stable transistor characteristics. In the structure of the transistor according to one embodiment of the present invention, the insulating film over the oxide semiconductor film 108 In this example, excess oxygen is introduced into the insulating film 114 over the oxide semiconductor film 108, thereby Oxygen is transferred from the oxide semiconductor film 114 to the oxide semiconductor film 108, and oxygen vacancies in the oxide semiconductor film 108 are formed. Alternatively, the insulating film 116 over the oxide semiconductor film 108 is formed with an excess amount of By introducing oxygen, the insulating film 116 and the oxide semiconductor film 108 are The oxide semiconductor film 108 is characterized in that oxygen is transferred thereinto to fill oxygen vacancies therein. Alternatively, excess oxygen may be introduced into the insulating film 114 and the insulating film 116 over the oxide semiconductor film 108. By this, oxygen is transferred from both the insulating film 114 and the insulating film 116 into the oxide semiconductor film 108. The oxide semiconductor film 108 is heated to 1000 K, and oxygen vacancies in the oxide semiconductor film 108 are filled.

[0035] Therefore, the insulating films 114 and 116 contain oxygen. More specifically, the insulating films 114 and 116 preferably contain oxygen and silicon. In other words, there is a region (oxygen excess region) that contains oxygen in excess of the stoichiometric composition. In this case, the insulating films 114 and 116 are insulating films that can release oxygen. To provide an oxygen excess region in the insulating films 114 and 116, for example, Oxygen is introduced into the silicon dioxide film 6 to form an oxygen-excess region. The oxygen introduction method is an ion implantation method. ion doping, plasma immersion ion implantation, plasma treatment, etc. The plasma treatment is carried out by converting oxygen gas into plasma using high frequency power. Plasma etching equipment or plasma ashing equipment is used. This is preferable.

[0036] The amount of oxygen molecules released from the insulating film capable of releasing oxygen is determined by the temperature-promoted desorption. Thermal Desorption Spectroscopy (TDS) For example, the insulating films 114 and 116 can be measured by TDS. When measured, the amount of released oxygen molecules was 1 × 10 19 pieces / cm 3 It is preferable that it is more than this. The substrate temperature in TDS is 100°C or higher and 700°C or lower, or 100°C or higher and 500°C or lower. A range of 00°C or less is preferred.

[0037] In one embodiment of the present invention, in order to form an oxygen excess region in the insulating films 114 and 116, Therefore, a film capable of suppressing oxygen release is formed on the insulating film 116, and The feature is that oxygen is introduced into the insulating films 114 and 116. The release of the oxygen can be suppressed. As the film having the function, a conductive film containing indium or a semiconductor film containing indium is used. It is also preferable that the film having the function of suppressing the release of oxygen is removed after the introduction of oxygen. It is preferable to do so.

[0038] As a film having a function of suppressing the release of oxygen, for example, a film containing indium (In) and zinc (Ni) is used. Lead (Zn), tin (Sn), tungsten (W), titanium (Ti), or silicon (Si ) can be used. In particular, it is possible to suppress the release of oxygen. Examples of films that have the function of being able to do this include indium oxide containing tungsten oxide, tungsten oxide, Indium zinc oxide containing titanium dioxide, indium oxide containing titanium dioxide, Indium Tin Oxide (IT O), indium zinc oxide, indium tin oxide with silicon oxide (Indium Conductive materials with transparency such as Tin SiO2 Doped Oxide (ITSO) Fees can be used.

[0039] In addition, a film capable of suppressing oxygen release is formed over the insulating film 116. When oxygen is introduced into the insulating films 114 and 116, the vicinity of the surface of the insulating film 116, in other words, Indium is detected near the interface between the insulating film 116 and the insulating film 118. This is because of the presence of oxygen. The film having the function of suppressing the emission contains indium, and the insulating films 114 and 11 This is because when oxygen is introduced into the insulating film 116, indium is implanted near the surface of the insulating film 116. do.

[0040] Here, regarding indium detected near the surface of the insulating film 116, using FIGS. 2 and 3, The details are explained below.

[0041] 2A is a cross-sectional view of the semiconductor device 200, and FIGS. 2B, 2C, and 2D are cross-sectional views of the semiconductor device 200. 1A is a cross-sectional view showing an example of a manufacturing process of the semiconductor device 200 shown in FIG.

[0042] The semiconductor device 200 shown in FIG. 2A includes an insulating film 204 on a substrate 202 and a and an insulating film 206 thereon.

[0043] The semiconductor device 200 shown in FIG. 2A has a detection region near the surface of the insulating film 116 shown in FIG. This is an analytical sample prepared to evaluate the indium emitted from the insulating The film 204 corresponds to the insulating film 116 shown in FIG.

[0044] The substrate 202 is a glass substrate, and the insulating film 204 is an acid film having a thickness of 400 nm. A silicon oxynitride film is used, and a silicon oxynitride film having a thickness of 200 nm is used as the insulating film 206. was used.

[0045] The semiconductor device 200 shown in FIG. 2A is a semiconductor device according to Sample A1, which is one embodiment of the present invention. and comparative sample A2 were fabricated, and the indium oxide near the interface between the insulating film 204 and the insulating film 206 was measured. The method for preparing Sample A1 and Sample A2 is as follows: do.

[0046] <Sample A1> An insulating film 204 is formed on the substrate 202, and a film having a function of suppressing oxygen release is formed on the insulating film 204. A film 230 was formed (see FIG. 2(B)).

[0047] The insulating film 204 was formed by a silane gas having a flow rate of 160 sccm at a substrate temperature of 220°C. Nitrous oxide gas at a flow rate of 4000 sccm was introduced into the chamber, and the pressure was set to 200 Pa. An RF power of 1500 W was supplied between the parallel plate electrodes installed in the PECVD device. The film 230 having the function of suppressing oxygen release was formed by using an IT film having a thickness of 5 nm. The ITSO film was formed using a sputtering system. The composition of the target used for the ITSO film was The ratio was In2O3:SnO2:SiO2 = 85:10:5 [wt %].

[0048] Next, oxygen 239 was added from above the film 230, which has the function of suppressing oxygen release ( See Figure 2(C)).

[0049] The oxygen 239 was added using an ashing device with a flow rate of 250 sccm. The pressure was set to 15 Pa and a bias was applied to the substrate side. The ashing was performed by supplying 4500 W of RF power between parallel plate electrodes installed in the ashing device. It was.

[0050] Next, the film 230 having the function of suppressing the release of oxygen is removed by an etchant 242. (See Figure 2(D)).

[0051] Etchant 242 was a 5% oxalic acid solution, and the treatment was carried out for 300 seconds. Then, the sample was treated with 0.5% hydrofluoric acid for 15 seconds.

[0052] Next, an insulating film 206 is formed on the insulating film 204, and the semiconductor device 200 shown in FIG. The insulating film 206 was fabricated by depositing silane at a flow rate of 75 sccm at a substrate temperature of 330°C. Nitrous oxide gas at a flow rate of 1200 sccm was introduced into the chamber, and the pressure was set at 70 Pa, and 120 W of RF power was supplied between the parallel plate electrodes installed in the PECVD device. The film was formed.

[0053] <Sample A2> Compared with the previously described sample A1, the sample A2 has not been subjected to the oxygen addition treatment shown in FIG. 2(C). That is, the sample A2 has a film 204 formed on the insulating film 204, which has a function of suppressing the release of oxygen. After forming 30, there is no need to perform oxygen addition treatment, and the film has the function of suppressing oxygen release. This is a sample in which the insulating film 230 is removed and the insulating film 206 is formed.

[0054] Next, the inclusions in the insulating films 204 and 206 of the samples A1 and A2 prepared above were measured. To measure the indium concentration, secondary ion mass spectrometry (SIMS) was used. Analysis was carried out using Ion Mass Spectrometry. The analysis results of sample A1 and sample A2 are shown in FIG. 3(A) and FIG. 3(B), respectively. In (A) and (B), the horizontal axis represents the depth (nm) and the vertical axis represents the indium concentration (atoms / cm m 3 ) respectively.

[0055] From the results shown in FIGS. 3(A) and 3(B), it is clear that the sample A1 has a high thermal conductivity at the interface between the insulating film 204 and the insulating film 206. There are 5×10 indium atoms nearby. 16 atoms / cm 3 This was confirmed at concentrations above 100. In the sample A2, indium was present in the vicinity of the interface between the insulating film 204 and the insulating film 206.16 a toms / cm 3 In the above SIMS analysis, the detection of indium was The lower limit is 1 x 10 15 atoms / cm 3 is.

[0056] In addition, due to the measurement principle, SIMS analysis can only collect data near the sample surface or near the stacking interface. However, when comparing sample A1 and sample A2, The amount of indium detected near the interface between the insulating film 204 and the insulating film 206 of the sample A1 is The amount of indium detected near the interface between the insulating film 204 and the insulating film 206 in Example 2 is larger than that detected near the interface between the insulating film 204 and the insulating film 206 in Example 2.

[0057] From the results shown in Figures 3(A) and 3(B), it can be seen that Sample A1 has the function of suppressing oxygen release. Indium in the ITSO film used as the film having the insulating film 204 On the other hand, in sample A2, the release of oxygen could not be suppressed. Since a film having the function of being able to be used is formed on the insulating film 204 and no oxygen addition treatment is performed, The result is that no indium is implanted into the film 204, or the amount of indium implanted is very small. It suggests.

[0058] As described above, a film having a function of suppressing oxygen release is formed on an insulating film, and the film is When oxygen is introduced into the insulating film, the constituent elements of the film that have the function of suppressing the release of oxygen are Indium, which is the indium atom, is implanted into the insulating film.

[0059] In the semiconductor device of one embodiment of the present invention, the insulating films 114 and 115 are formed over the oxide semiconductor film 108. Then, a film having a function of suppressing oxygen release is formed on the insulating film 116. By supplying oxygen to the insulating films 114 and 116 through the film, The insulating films 114 and 116 can contain excess oxygen. The oxygen compensates for oxygen vacancies formed in the oxide semiconductor film 108. By filling the oxygen vacancies in the silicon dioxide, a highly reliable semiconductor device can be provided. Cut.

[0060] Other components included in the semiconductor device of this embodiment will be described in detail below. do.

[0061] <Substrate> There is no particular restriction on the material of the substrate 102, but it should be strong enough to withstand the subsequent heat treatment. For example, glass substrates, ceramic substrates, quartz substrates, and A fire substrate or the like may be used as the substrate 102. Also, silicon or silicon carbide may be used as the material. Single crystal semiconductor substrates, polycrystalline semiconductor substrates, compound semiconductors such as silicon germanium, etc. It is also possible to apply a substrate, an SOI substrate, etc., and a semiconductor element is provided on these substrates. The substrate 102 may be a glass substrate. If you are using 6th generation (1500mm x 1850mm), 7th generation (1870mm x 220 0mm), 8th generation (2200mm x 2400mm), 9th generation (2400mm x 280 By using large area substrates such as 10th generation (2950mm x 3400mm), Larger display devices can be fabricated.

[0062] In addition, a flexible substrate is used as the substrate 102, and the transistor 10 is directly formed on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate 102 and the transistor 100. The release layer is preferably removed from the substrate 102 after a semiconductor device is partially or completely completed thereon. The transistor 100 can be separated and transferred to another substrate. It can also be transferred to substrates with poor thermal properties or flexible substrates.

[0063] <Conductive film> The conductive film 104 functions as a first gate electrode, and the conductive film 105 functions as a source electrode and a drain electrode. The conductive films 112a and 112b that function as a conductive film include chromium (Cr), copper (Cu), aluminum (Al), and the like. Al (Al), gold (Au), silver (Ag), zinc (Zn), molybdenum (Mo), tantalum (Ta), titanium (Ti), tungsten (W), manganese (Mn), nickel (Ni) , iron (Fe), cobalt (Co), or a metal element selected from the group consisting of the above metal elements. The alloys may be formed by using the above-mentioned metal elements or alloys combining the above-mentioned metal elements. can.

[0064] The conductive films 104, 112a, and 112b may have a single-layer structure or a stacked structure of two or more layers. For example, a single layer structure of an aluminum film containing silicon, a titanium film on an aluminum film, Two-layer structure with titanium film laminated on titanium nitride film, two-layer structure with titanium film laminated on titanium nitride film, titanium nitride film Two-layer structure with tungsten film laminated on top, tantalum nitride film or tungsten nitride film Two-layer structure with tungsten film stacked, titanium film, and aluminum film stacked on the titanium film. There are also three-layer structures, such as a titanium film on top of an aluminum film. Select from tantalum, tungsten, molybdenum, chromium, neodymium, and scandium. Alternatively, an alloy film or a nitride film made by combining one or more of these may be used.

[0065] The conductive films 104, 112a, and 112b are made of indium tin oxide or tungsten oxide. Indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, titanium oxide Indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide A conductive material having light-transmitting properties, such as indium tin oxide doped with silicon oxide, is used. It is also possible.

[0066] The conductive films 104, 112a, and 112b are made of a Cu-X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) may be applied. This allows for processing using a wet etching process, which reduces manufacturing costs. It becomes possible.

[0067] <Gate insulating film> The insulating films 106 and 107 functioning as the first gate insulating film of the transistor 100 are Plasma Enhanced Chemical Vapor Deposition (PECVD) Oxidation is performed by the ical vapor deposition method, sputtering method, etc. Silicon film, silicon oxynitride film, silicon nitride oxide film, silicon nitride film, aluminum oxide hafnium oxide film, yttrium oxide film, zirconium oxide film, gallium oxide film , tantalum oxide film, magnesium oxide film, lanthanum oxide film, cerium oxide film and ne oxide film The insulating film 106 and the insulating film 107 may be formed of an oxynitride film or an oxynitride film. Instead of the laminated structure of 107, a single insulating film selected from the above materials or three or more layers An insulating film may also be used.

[0068] Note that the oxide semiconductor film 108, which functions as a channel region of the transistor 100, is in contact with the oxide semiconductor film 108. The insulating film 107 is preferably an oxide insulating film, and the oxide content is in excess of the stoichiometric composition. It is more preferable that the insulating film 1 has a region containing oxygen (an oxygen-excess region). The insulating film 107 is an insulating film capable of releasing oxygen. To provide the insulating film 107, for example, the insulating film 107 may be formed in an oxygen atmosphere. Oxygen may be introduced into the insulating film 107 later to form an oxygen-excess region. These include ion implantation, ion doping, plasma immersion ion implantation, and plasma Zuma processing or the like can be used.

[0069] Furthermore, when hafnium oxide is used as the insulating film 107, the following effects are achieved. Hafnium has a higher dielectric constant than silicon oxide and silicon oxynitride. Compared to the case where silicon oxide is used, the thickness of the insulating film 107 can be made larger, so that the tunnel This reduces the leakage current due to the current flowing through the transistor. Furthermore, hafnium oxide, which has a crystalline structure, can be used to form amorphous structures. Therefore, the off-state current is small. To form a transistor, it is preferable to use hafnium oxide having a crystalline structure. Examples of the crystal structure include monoclinic and cubic crystals. The types are not limited to these.

[0070] In this embodiment, a silicon nitride film is formed as the insulating film 106, and the insulating film 107 The silicon nitride film has a lower dielectric constant than the silicon oxide film. The film thickness required to obtain the same capacitance as a silicon oxide film is large, so The gate insulating film of the transistor 100 contains a silicon nitride film, which makes the insulating film physically thick. Therefore, the decrease in the dielectric strength voltage of the transistor 100 can be suppressed, and further, the dielectric strength can be improved. The edge breakdown voltage can be improved, and electrostatic breakdown of the transistor 100 can be suppressed.

[0071] <Oxide semiconductor film> The oxide semiconductor film 108 is made of oxygen, In, Zn, and M (M is Ti, Ga, Sn, Y). , Zr, La, Ce, Nd, or Hf). 8 can be In-Ga oxide, In-Zn oxide, or In-Mn-Zn oxide. In particular, it is preferable to use In-M-Zn oxide as the oxide semiconductor film 108. .

[0072] When the oxide semiconductor film 108 is an In-M-Zn oxide, the In-M-Zn oxide is deposited. The atomic ratio of the metal elements in the sputtering target used for this purpose is In≧M, Zn≧M. It is preferable that the atomic ratio of the metal elements in such a sputtering target and In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn In:M:Zn=2:1:3, In:M:Zn=3:1:2, In:M:Zn=4:2:4.1 are preferred. Note that the atomic ratio of the oxide semiconductor film 108 to be formed is determined by taking the above-mentioned steps as an error. The atomic ratio of metal elements contained in the sputtering target can be varied by ±40%. For example, a sputtering target with an atomic ratio of In:Ga:Zn=4:2 When the oxide semiconductor film 108 is formed using In:Ga:Z, the atomic ratio of the oxide semiconductor film 108 is In:Ga:Z. In some cases, the ratio is around n=4:2:3.

[0073] When the oxide semiconductor film 108 is an In-M-Zn oxide, the The atomic ratio of In to M is preferably higher than 25 atomic % and higher than 75 atomic %. more preferably, In is greater than 34 atomic % and M is 66 atomic % or less. Less than omic%.

[0074] The oxide semiconductor film 108 has an energy gap of 2 eV or more, preferably 2.5 eV or more. eV or more, more preferably 3 eV or more. By using a nitride semiconductor, the off-state current of the transistor 100 can be reduced.

[0075] The thickness of the oxide semiconductor film 108 is greater than or equal to 3 nm and less than or equal to 200 nm, preferably less than or equal to 3 nm. The thickness is set to 100 nm or more, and more preferably 3 nm or more and 50 nm or less.

[0076] In addition, as the oxide semiconductor film 108, an oxide semiconductor film with low carrier density is used. For example, the oxide semiconductor film 108 has a carrier density of 1×10 17 pieces / cm 3 The following is preferred: 1×10 15 pieces / cm 3 or less, more preferably 1 × 10 13 pieces / cm 3 More information below: Preferably 1 x 10 11 pieces / cm 3 The following applies.

[0077] However, the semiconductor characteristics and electrical characteristics (field effect) of the required transistors are not limited to these. It is sufficient to use an appropriate composition depending on the required properties (e.g., the mobility, threshold voltage, etc.). In order to obtain semiconductor characteristics of a transistor, the carrier density and impurity of the oxide semiconductor film 108 are controlled. The material concentration, defect density, atomic ratio of metal elements to oxygen, interatomic distance, density, etc. are set appropriately. It is preferable.

[0078] Note that the oxide semiconductor film 108 is formed of an oxide semiconductor having a low impurity concentration and a low density of defect states. By using a conductive film, it is possible to fabricate a transistor with even better electrical characteristics. Here, it is preferable that the impurity concentration is low and the defect level density is low (there is little oxygen vacancy). High purity authentic or substantially high purity authentic High purity authentic or substantially high purity authentic Since the oxide semiconductor film has few carrier generation sources, the carrier density can be reduced. Therefore, a transistor in which a channel region is formed in the oxide semiconductor film can have a threshold voltage of 100 V. The electrical characteristics where the voltage is negative (also called normally on) are rare. In addition, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states. Therefore, the trap level density may also be low. The intrinsic oxide semiconductor film has a significantly small off-state current and a channel width W of 1×10 6 μm Even if the channel length L of the device is 10 μm, the voltage between the source electrode and the drain electrode (drain The off-state current is measured in the range of 1V to 10V. below the measurement limit, i.e., 1×10 -13 It can achieve a characteristic of A or below.

[0079] Therefore, the high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor film is provided with a channel. The transistors in which the regions are formed have small fluctuations in electrical characteristics and are highly reliable. Note that charges trapped in the trap states of the oxide semiconductor film are lost. It takes a long time for the charge to dissipate, and it can behave as if it were a fixed charge. A transistor in which a channel region is formed in an oxide semiconductor film with a high density of trap states has Impurities include hydrogen, nitrogen, alkali metals, or Alkaline earth metals, etc.

[0080] Hydrogen contained in the oxide semiconductor film 108 reacts with oxygen that is bonded to metal atoms to form water. At the same time, oxygen vacancies are formed in the lattice from which oxygen has been desorbed (or in the portion from which oxygen has been desorbed). When hydrogen enters an electron vacancy, a carrier electron may be generated. Some of them may combine with oxygen, which bonds with metal atoms, to generate electrons, which act as carriers. Therefore, a transistor using an oxide semiconductor film containing hydrogen has normally-on characteristics. Therefore, it is important to reduce hydrogen as much as possible in the oxide semiconductor film 108. Specifically, in the oxide semiconductor film 108, The hydrogen concentration is 2 x 10 20 atoms / cm 3 Less than or equal to 5 x 10 19 atoms / cm 3 Less than or equal to 1×10 19 atoms / cm 3 Less than or equal to 5, more preferably x10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 Below or less, more preferably 5 × 10 17 atoms / cm 3 or less, more preferably 1 × 10 1 6 atoms / cm 3 The following applies.

[0081] The oxide semiconductor film 108 contains silicon or carbon, which is one of the Group 14 elements. As a result, oxygen vacancies increase in the oxide semiconductor film 108, causing the oxide semiconductor film 108 to become n-type. The concentrations of silicon and carbon in the nitride semiconductor film 108 and the concentration of silicon and carbon in the oxide semiconductor film 108 near the interface with the oxide semiconductor film 108 are The concentration of silicon and carbon in the vicinity (obtained by SIMS analysis) is 2 × 10 18 ato ms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0082] In addition, in the oxide semiconductor film 108, alkali metal or is the concentration of alkaline earth metals, 1×10 18 atoms / cm 3 Below, preferably 2 x 1 0 16 atoms / cm 3 Alkali metals and alkaline earth metals are oxide semiconductors. When they bond with a conductor, carriers may be generated, increasing the off-state current of the transistor. For this reason, the alkali metal or alkaline earth metal in the oxide semiconductor film 108 It is preferable to reduce the concentration of the genus.

[0083] When nitrogen is contained in the oxide semiconductor film 108, electrons serving as carriers are generated, and As a result, the oxide semiconductor film containing nitrogen is easily converted to n-type. The transistor using the oxide semiconductor film tends to be normally on. In this case, it is preferable that the nitrogen content is reduced as much as possible. For example, The nitrogen concentration is 5×1018 atoms / cm 3 It is preferable to do the following:

[0084] The oxide semiconductor film 108 may have a non-single-crystal structure, for example. For example, CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor), polycrystalline structure, microcrystalline structure (described later), or Among non-single crystal structures, the amorphous structure has the highest defect level density, C AAC-OS has the lowest defect state density.

[0085] The oxide semiconductor film 108 may have, for example, an amorphous structure. For example, the atomic arrangement is disordered and does not have crystalline components. Or, an oxide with an amorphous structure The film has, for example, a completely amorphous structure and does not have any crystalline portions.

[0086] Note that the oxide semiconductor film 108 may have an amorphous structure, a microcrystalline structure, or a polycrystalline structure. The film may be a mixed film having two or more of the following: a CAAC-OS region, a CAAC-OS region, and a single crystal structure region. The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CA In the case of a single-layer structure having two or more regions, either an AC-OS region or a single-crystal structure region The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, and the like. A stack having two or more regions of a single crystal structure, a CAAC-OS region, or a single crystal structure region. It may have a structure.

[0087] <Protective insulating film> The insulating films 114, 116, and 118 function as protective insulating films. The insulating film 116 contains oxygen. The insulating film 114 is an insulating film that can transmit oxygen. The insulating film 114 is formed by using an oxide semiconductor when forming the insulating film 116 to be formed later. It also functions as a film for mitigating damage to the film 108 .

[0088] The insulating film 114 has a thickness of 5 nm to 150 nm, preferably 5 nm to 50 Silicon oxide, silicon oxynitride, etc., having a thickness of 1 nm or less can be used.

[0089] Furthermore, it is preferable that the insulating film 114 has a small number of defects. (ESR) measurement shows that the g value is 2.001, which is due to the silicon dangling bond. The spin density of the signal is 3×10 17 spins / cm 3 It is preferable that the following is true: If the density of defects in the insulating film 114 is high, oxygen will bond to the defects, and the insulating film The amount of oxygen permeated through 114 decreases.

[0090] In the insulating film 114, all the oxygen that has entered the insulating film 114 from the outside is Some oxygen does not move to the outside of the insulating film 114 and remains in the insulating film 114. At the same time, oxygen contained in the insulating film 114 moves to the outside of the insulating film 114, Oxygen may move in the film 114. When the oxide insulating film capable of forming the insulating film 114 is formed, the insulating film 116 and the insulating film 116 are formed on the insulating film 114. The desorbed oxygen can be transferred to the oxide semiconductor film 108 through the insulating film 114. .

[0091] The insulating film 114 is formed using an oxide insulating film with a low density of states due to nitrogen oxides. Note that the density of states due to the nitrogen oxide can be increased by increasing the valence charge of the oxide semiconductor film. The energy at the top of the nucleus (E v_os ) and the energy of the bottom of the conduction band of the oxide semiconductor film ( E c_os ) may be formed between the insulating film and the insulating layer. Silicon oxynitride film with low nitrogen oxide emission or aluminum oxynitride film with low nitrogen oxide emission A film such as a cellulose nitrate film can be used.

[0092] In addition, silicon oxynitride films that emit a small amount of nitrogen oxides have a low nitrogen oxide content in TDS. This is a membrane that releases more ammonia than other substances, and typically releases ammonia at 1 x10 18 pieces / cm 3 5x10 or more 19 pieces / cm 3 The following is a list of ammonia release rates. The amount is set so that the surface temperature of the film is 50°C or higher and 650°C or lower, preferably 50°C or higher and 550°C or lower. This is the amount released by heat treatment.

[0093] Nitrogen oxides (NO x , x is 0 or more and 2 or less, preferably 1 or more and 2 or less), typically NO 2 or NO forms a level in the insulating film 114 or the like. Therefore, the nitrogen oxide is located within the energy gap of the insulating film 114 and the oxide film. When the electrons diffuse to the interface of the compound semiconductor film 108, the level traps electrons on the insulating film 114 side. As a result, the trapped electrons may be trapped in the insulating film 114 and the oxide semiconductor. Since the electrons remain near the interface of the semiconductor film 108, the threshold voltage of the transistor is shifted in the positive direction. It makes me feel unwell.

[0094] Nitrogen oxide reacts with ammonia and oxygen during heat treatment. The nitrogen oxide contained in the insulating film 116 reacts with the ammonia contained in the insulating film 116 during the heat treatment. Therefore, the nitrogen oxide contained in the insulating film 114 is reduced. Therefore, electrons are less likely to be trapped in the vicinity of the interface between the oxide semiconductor film 106 and the oxide semiconductor film 108.

[0095] By using the oxide insulating film as the insulating film 114, the threshold voltage of the transistor can be shifted. It is possible to reduce the fluctuation of the electrical characteristics of the transistor. do.

[0096] The heat treatment in the manufacturing process of a transistor is typically performed at a temperature of 300° C. or higher but below the substrate distortion point. The insulating film 114 is subjected to the heat treatment, and the spectrum obtained by measuring the ESR at 100 K or less is The first signal has a g value of 2.037 to 2.039, and the second signal has a g value of 2.001 or more. A second signal with a g value of 2.003 or less and a third signal with a g value of 1.964 to 1.966 or less. The split width of the first signal and the second signal, The split width of the second and third signals is approximately 1 / 2 in the X-band ESR measurement. 5mT. Also, the first signal with a g value of 2.037 or more and 2.039 or less, and the g value of 2. A second signal between 0.001 and 2.003, and a g value between 1.964 and 1.966 The total spin density of the third signal is 1×10 18 spins / cm 3 Less than Typically, it is 1×10 17 spins / cm 3 More than 1×10 18 spins / cm 3 Not yet It is full.

[0097] In addition, the g value is between 2.037 and 2.039 in the ESR spectrum below 100K. The first signal has a g value of 2.001 or more and 2.003 or less, and the second signal has a g value of 1 The third signal, between 0.964 and 1.966, is nitrogen oxide (NO x , x is between 0 and 2 Representative examples of nitrogen oxides include: , nitrogen monoxide, nitrogen dioxide, etc. That is, the first signal, a second signal with a g-value between 2.001 and 2.003, and a g-value between 1.96 The smaller the sum of the spin densities of the third signals, which is between 4 and 1.966, the more oxide It can be said that the content of nitrogen oxides contained in the insulating film is low.

[0098] The oxide insulating film has a nitrogen concentration of 6×10 as measured by SIMS analysis. 20 ato ms / cm 3 The following is the result.

[0099] The substrate temperature is 220°C or higher, or 280°C or higher, or 350°C or higher, and silane and The oxide insulating film is formed by the PECVD method using nitrous oxide and silicon dioxide. A dense and hard film can be formed.

[0100] The insulating film 116 is an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition. The oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition is formed using When heated, some of the oxygen is released. The oxygen content is greater than the stoichiometric value. The oxide insulating film has a TDS analysis result of 1.0 x 10 oxygen atoms. 1 9atoms / cm 3 or more, preferably 3.0 × 10 20 atoms / cm 3 That's all The surface temperature of the film during the TDS analysis was 100°C or higher. The temperature range is preferably from 100°C to 500°C.

[0101] The insulating film 116 has a thickness of 30 nm to 500 nm, preferably 50 nm or more. Silicon oxide, silicon oxynitride, etc., of 400 nm or less can be used.

[0102] Furthermore, it is preferable that the insulating film 116 has a small number of defects. The spin density of the signal at g=2.001 originating from the silicon dangling bond is 1.5 x 10 18 spins / cm 3 Less than, or even 1×10 18 spins / cm 3 It is preferable that the insulating film 116 has a higher oxide semiconductor content than the insulating film 114. Since it is separated from the insulating film 108, it may have a higher defect density than the insulating film 114.

[0103] Indium is also detected near the surface of the insulating film 116 .

[0104] In addition, the insulating films 114 and 116 can be made of the same material, so that the insulating film In some cases, the interface between the film 114 and the insulating film 116 cannot be clearly seen. In this embodiment, the interface between the insulating film 114 and the insulating film 116 is shown by a broken line. In the embodiment, the two-layer structure of the insulating film 114 and the insulating film 116 has been described. For example, the insulating film 114 may have a single-layer structure.

[0105] The insulating film 118 contains nitrogen and silicon. The insulating film 118 also contains blockers such as oxygen, hydrogen, water, alkali metals, and alkaline earth metals. By providing the insulating film 118, the oxide semiconductor film 108 can be prevented from being oxidized. The diffusion of oxygen from the insulating films 114 and 116 to the outside. This can prevent hydrogen, water, and the like from entering the oxide semiconductor film 108. For example, a nitride insulating film can be used. Silicon nitride, silicon oxide nitride, aluminum nitride, aluminum oxide nitride, etc. Nitride insulating material with blocking effect against hydrogen, water, alkali metals, alkaline earth metals, etc. Instead of the insulating film, an oxide insulating film having a blocking effect on oxygen, hydrogen, water, etc. may be provided. As an oxide insulating film having a blocking effect against oxygen, hydrogen, water, etc., aluminum oxide is preferable. aluminum oxide nitride, gallium oxide, gallium oxide nitride, yttrium oxide, Examples include yttrium oxide nitride, hafnium oxide, and hafnium oxide nitride.

[0106] Note that the various films described above, such as the conductive film, insulating film, and oxide semiconductor film, are formed by sputtering. It can be formed by a coating method or a PECVD method, but other methods, such as thermal CVD (Ch It may be formed by thermal vapor deposition (CVD). As an example of the method, MOCVD (Metal Organic Chemical Vapor Deposition) Deposition method may also be used.

[0107] The thermal CVD method is a film formation method that does not use plasma, so defects can occur due to plasma damage. This has the advantage that no further processing is required.

[0108] In the thermal CVD method, the source gas and oxidant are simultaneously fed into a chamber, and the chamber is heated to atmospheric pressure. Alternatively, a film is formed by reacting the material near or on the substrate under reduced pressure and depositing the material on the substrate. You may go.

[0109] In addition, in the ALD method, the pressure inside the chamber is atmospheric or reduced, and the source gas for the reaction is The gases may be introduced into the chamber in sequence, and the film may be formed by repeating this gas introduction sequence. For example, by switching each switching valve (also called high-speed valve), two or more types of The above source gases are supplied to the chamber in order, and the first An inert gas (argon, nitrogen, etc.) is introduced simultaneously with or after the raw material gas. The second source gas is introduced. When an inert gas is introduced at the same time, the inert gas is It acts as a carrier gas, and even if an inert gas is introduced at the same time as the second source gas is introduced, Alternatively, instead of introducing an inert gas, the first source gas may be discharged by vacuum evacuation. After that, a second source gas may be introduced. The first source gas is adsorbed on the surface of the substrate to form a first layer. The first layer is deposited on the second layer by reacting with the second source gas introduced later. This process is repeated several times while controlling the gas introduction order until the desired thickness is achieved. By doing so, a thin film with excellent step coverage can be formed. The thickness can be precisely adjusted by changing the number of times the sequence is repeated. It is suitable for fabricating miniaturized FETs.

[0110] Thermal CVD methods such as MOCVD can be used to form the conductive film, insulating film, oxide semiconductor film, It is possible to form various films such as metal oxide films, for example, In-Ga-ZnO films. In this case, trimethylindium, trimethylgallium, and dimethylzinc are used. The chemical formula of trimethylindium is In(CH3)3. The chemical formula of gallium is Ga(CH3)3. The chemical formula of dimethylzinc is Zn( CH3)2. In addition, the combination is not limited to these, and instead of trimethylgallium, Triethylgallium (chemical formula Ga(C2H5)3) can also be used, and dimethylzinc Alternatively, diethylzinc (chemical formula Zn(C2H5)2) can be used.

[0111] For example, when forming a hafnium oxide film using a film forming apparatus that uses ALD, the solvent and liquids containing hafnium precursor compounds (hafnium alkoxides, tetrakisdimethyl The raw material gas is vaporized hafnium amide (such as TDMAH) and acid Two types of gases are used: tetrakisdimethylamide (TDMA) and ozone (O3) as a chlorine gas. The chemical formula for Hf is Hf[N(CH3)2]4. Other materials include tetrahydrofuran, Examples include rakis(ethylmethylamido) hafnium.

[0112] For example, when forming an aluminum oxide film using an ALD film forming device, A liquid containing a catalyst and an aluminum precursor compound (e.g., trimethylaluminum (TMA)) is added. Two types of gases are used: vaporized source gas and H2O as an oxidizing agent. The chemical formula for aluminum is Al(CH3)3. Other liquid materials include Tris( dimethylamido)aluminum, triisobutylaluminum, aluminum tris(2 ,2,6,6-tetramethyl-3,5-heptanedionate).

[0113] For example, when forming a silicon oxide film using a film forming device that uses ALD, Chlorodisilane is adsorbed onto the surface to be coated, removing the chlorine contained in the adsorbed material, and the oxidizing gas (O 2. Nitrous oxide (NO) radicals are supplied to react with the adsorbed material.

[0114] For example, when forming a tungsten film using an ALD deposition system, WF6 The initial tungsten film was formed by sequentially introducing BH gas and BH gas. The tungsten film is formed by repeatedly introducing B2H6 gas and H2 gas in sequence. SiH4 gas may be used instead of gas.

[0115] For example, an oxide semiconductor film, such as In-Ga-ZnO, can be formed using a film formation device that uses ALD. When forming a film, In(CH3)3 gas and O3 gas are introduced in sequence and repeatedly to form InO Then, Ga(CH3)3 gas and O3 gas are introduced repeatedly to form a GaO layer. Then, Zn(CH3)2 gas and O3 gas are introduced repeatedly to form a ZnO layer. The order of these layers is not limited to this example. Mixed compound layers such as In-Ga-O, In-Zn-O, and Ga-Zn-O layers are formed. It is also possible to use H2O gas obtained by bubbling an inert gas such as Ar instead of O3 gas. However, it is preferable to use O3 gas that does not contain H. In(CH3 In place of In(C2H5)3 gas, Ga(CH3)3 gas may be used. Instead of gas, Ga(C2H5)3 gas may be used. It's okay to be there.

[0116] <Configuration Example 2 of Semiconductor Device> Next, examples of structures different from those of the transistor 100 shown in FIGS. 4(A)(B)(C) will be used for the explanation. Note that the functions described above are the same as those described above. In some cases, the hatch pattern may be the same and no particular reference numeral may be assigned.

[0117] FIG. 4A is a top view of a transistor 150 which is a semiconductor device of one embodiment of the present invention. 4(B) corresponds to a cross-sectional view of the cut surface taken along the dashed line X1-X2 shown in FIG. 4(A). 4(C) is a cross-sectional view taken along the dashed line Y1-Y2 in FIG. 4(A). Correct.

[0118] The transistor 150 includes a conductive film 104 over a substrate 102, which functions as a first gate electrode. an insulating film 106 on the substrate 102 and the conductive film 104; and an insulating film 107 on the insulating film 106. , the oxide semiconductor film 108 on the insulating film 107, and the insulating film 114 on the oxide semiconductor film 108. , an insulating film 116 on the insulating film 114, and openings provided in the insulating film 114 and the insulating film 116. The electrode 141a functions as a source electrode electrically connected to the oxide semiconductor film 108. Through the conductive film 112a and the opening 141b provided in the insulating film 114 and the insulating film 116, A conductive film 112b functioning as a drain electrode electrically connected to the oxide semiconductor film 108 In addition, the conductive films 112a and 112b are formed on the transistor 150, more specifically, on the conductive films 112a and 112b. An insulating film 118 is provided on the insulating film 114 and the insulating film 116. The insulating film 118 functions as a protective insulating film for the oxide semiconductor film 108. It functions as a protective insulating film for the sta 150.

[0119] The transistor 150 also includes an indium layer near the interface between the insulating film 116 and the insulating film 118. It has.

[0120] The transistor 100 shown above has a channel-etched structure, whereas The transistor 150 shown in FIGS. 4A, 4B, and 4C has a channel-protective structure. As described above, the semiconductor device of one embodiment of the present invention can be used in both of the channel etch type and the channel protection type. The present invention can be applied to the following transistor structures.

[0121] The transistor 150 is a transistor including an oxide semiconductor film, similar to the transistor 100 described above. Since the insulating films 114 and 116 are provided on the insulating film 108, The oxygen contained in the oxide semiconductor film 108 can fill oxygen vacancies in the oxide semiconductor film 108.

[0122] <Configuration Example 3 of Semiconductor Device> Next, examples of a configuration different from that of the transistor 150 shown in FIGS. 5(A)(B)(C) will be used. Note that the functions described above are the same as those described above. In some cases, the hatch pattern may be the same and no particular reference numeral may be assigned.

[0123] FIG. 5A is a top view of a transistor 160 which is a semiconductor device of one embodiment of the present invention. 5(B) corresponds to a cross-sectional view of the cut surface taken along the dashed line X1-X2 shown in FIG. 5(A). 5(C) is a cross-sectional view taken along the dashed line Y1-Y2 in FIG. 5(A). Correct.

[0124] The transistor 160 includes a conductive film 104 over a substrate 102, which functions as a first gate electrode. an insulating film 106 on the substrate 102 and the conductive film 104; and an insulating film 107 on the insulating film 106. , the oxide semiconductor film 108 on the insulating film 107, and the insulating film 114 on the oxide semiconductor film 108. , an insulating film 116 on the insulating film 114, and a source electrode electrically connected to the oxide semiconductor film 108. The conductive film 112a serving as an electrode and the drain electrically connected to the oxide semiconductor film 108 are The transistor 160 also has a conductive film 112b which functions as a gate electrode. More specifically, an insulating film 118 is provided over the conductive films 112a and 112b and the insulating film 116. The insulating films 114 and 116 function as protective insulating films for the oxide semiconductor film 108. The insulating film 118 functions as a protective insulating film for the transistor 160.

[0125] The transistor 160 also includes an indium layer near the interface between the insulating film 116 and the insulating film 118. It has.

[0126] The transistor 160 is a transistor 150 and an insulating film 1 shown in FIGS. Specifically, the shapes of the insulating films 114 and 116 of the transistor 160 are different. The oxide semiconductor film 108 is provided in an island shape on the channel region of the oxide semiconductor film 108. It is similar to the transistor 150 and has the same effect.

[0127] <Configuration Example 4 of Semiconductor Device> Next, examples of structures different from those of the transistor 100 shown in FIGS. 6(A)(B)(C) will be used for the explanation. Note that the functions described above are the same as those described above. In some cases, the hatch pattern may be the same and no particular reference numeral may be assigned.

[0128] FIG. 6A is a top view of a transistor 170 which is a semiconductor device of one embodiment of the present invention. 6(B) corresponds to a cross-sectional view of the cut surface taken along the dashed line X1-X2 shown in FIG. 6(A). 6(C) is a cross-sectional view taken along the dashed line Y1-Y2 in FIG. 6(A). Correct.

[0129] The transistor 170 includes a conductive film 104 over a substrate 102, which functions as a first gate electrode. an insulating film 106 on the substrate 102 and the conductive film 104; and an insulating film 107 on the insulating film 106. , the oxide semiconductor film 108 on the insulating film 107, and the insulating film 114 on the oxide semiconductor film 108. , an insulating film 116 on the insulating film 114, and a source electrode electrically connected to the oxide semiconductor film 108. The conductive film 112a serving as an electrode and the drain electrically connected to the oxide semiconductor film 108 are The conductive film 112b functions as an inner electrode, and the conductive films 112a and 112b and the insulating film 116 The insulating film 118 is formed on the substrate 110, and conductive films 120a and 120b are formed on the insulating film 118.

[0130] The transistor 170 also includes an indium layer near the interface between the insulating film 116 and the insulating film 118. It has.

[0131] In addition, in the transistor 170, the insulating films 114, 116, and 118 are The second insulating film of the transistor 170 functions as a second gate insulating film. The conductive film 120a functions as, for example, a pixel electrode used in a display device. The conductive film 120a is formed through the openings 142c formed in the insulating films 114, 116, and 118. , and the conductive film 112b. In the transistor 170, the conductive film 120b , which functions as a second gate electrode (also called a back gate electrode).

[0132] As shown in FIG. 6C, the conductive film 120b is formed by insulating films 106, 107, 114, and 1 In the openings 142a and 142b formed in the gate electrodes 16 and 118, Therefore, the conductive film 120b and the conductive film 104 are connected to the conductive film 104. A potential is applied.

[0133] In this embodiment, openings 142a and 142b are provided, and the conductive film 120b and Although the configuration in which the conductive film 104 is connected has been exemplified, the present invention is not limited to this. Only one of the openings 142a and 142b is formed. The conductive film 104 is connected, or the openings 142a and 142b are not provided, and the conductive film 104 is not connected. The conductive film 120b and the conductive film 104 may not be connected to each other. In the case where the conductive film 104 is not connected, the conductive film 120b and the conductive film 104 are respectively connected to different A potential can be applied.

[0134] As shown in FIG. 6B, the oxide semiconductor film 108 functions as a first gate electrode. and a conductive film 120b that functions as a second gate electrode. The second gate electrode is sandwiched between two conductive films that function as gate electrodes. The length in the channel length direction and the length in the channel width direction of the conductive film 120b that functions as a gate electrode The length is larger than the length of the oxide semiconductor film 108 in the channel length direction and the length of the oxide semiconductor film 108 in the channel width direction. The entire oxide semiconductor film 108 is conductive via insulating films 114, 116, and 118. The conductive film 120b functions as a second gate electrode. The conductive film 104 functioning as the first gate electrode is made of insulating films 106, 107, 114, and 1 16, 118 are connected at openings 142a, 142b. The side surfaces of the conductive film 108 in the channel width direction are connected to the second insulating film 114, 116, and 118 via the insulating films 114, 116, and 118. It faces the conductive film 120b that functions as the gate electrode.

[0135] In other words, in the channel width direction of the transistor 170, The conductive film 104 functioning as the first gate electrode and the conductive film 120b functioning as the second gate electrode are The insulating films 106 and 107 function as gate insulating films, and the insulating film 108 function as a second gate insulating film. The insulating films 114, 116, and 118 are connected to each other through openings, and the first gate The insulating films 106 and 107 function as first gate insulating films, and the insulating film 108 functions as a second gate insulating film. The oxide semiconductor film 108 is surrounded by insulating films 114, 116, and 118.

[0136] With such a structure, the oxide semiconductor film 108 included in the transistor 170 The conductive film 104 functions as a first gate electrode and the conductive film 105 functions as a second gate electrode. The transistor 170 can be electrically surrounded by the electric field of the conductive film 120b. The electric field of the first gate electrode and the second gate electrode causes the oxide film to form a channel region. The device structure of the transistor that electrically surrounds the oxide semiconductor film is called the surrounded ch This can be called an s-channel structure.

[0137] Since the transistor 170 has an s-channel structure, it has a first gate electrode The conductive film 104 functions as a gate electrode, and the electric field for inducing the channel is effectively applied to the oxide semiconductor. This allows the voltage to be applied to the body membrane 108, improving the current driving capability of the transistor 170. It is possible to obtain high on-current characteristics. It is also possible to increase the on-current. Therefore, it is possible to miniaturize the transistor 170. The conductive film 104 functions as a first gate electrode and the conductive film 105 functions as a second gate electrode. Since the transistor 170 has a structure surrounded by the conductive film 120b, the mechanical strength of the transistor 170 is increased. It can be done.

[0138] <Configuration Example 5 of Semiconductor Device> Next, examples of structures different from those of the transistor 100 shown in FIGS. 7(A)(B)(C)(D) will be used. Note that the same functions as those explained above will be used. If they have the same hatch pattern, they may not be given special symbols.

[0139] 7A and 7B are cross-sectional views of modified examples of the transistor 100 shown in FIGS. 1B and 1C. 7C and 7D show modified examples of the transistor 100 shown in FIGS. FIG.

[0140] The transistor 100A shown in FIGS. 7A and 7B is a transistor having a structure similar to that shown in FIGS. The oxide semiconductor film 108 included in the capacitor 100 has a three-layer structure. The oxide semiconductor film 108 included in the transistor 100A includes an oxide semiconductor film 108a and an oxide semiconductor film 108b. The semiconductor layer 108 includes a nitride semiconductor film 108b and an oxide semiconductor film 108c.

[0141] The transistor 100B shown in FIGS. 7(C) and 7(D) is a transistor having a structure similar to that shown in FIGS. The oxide semiconductor film 108 included in the capacitor 100 has a two-layer structure. The oxide semiconductor film 108 included in the transistor 100B includes an oxide semiconductor film 108a and an oxide semiconductor film 108b. and a nitride semiconductor film 108b.

[0142] Here, the oxide semiconductor films 108a, 108b, and 108c and the oxide semiconductor film 108b The band structure of the insulating film in contact with the insulating film 108c will be described with reference to FIG.

[0143] FIG. 8A shows the insulating film 107, the oxide semiconductor films 108a, 108b, and 108c, and the insulating film 108b. 8(B) is an example of a band structure in the thickness direction of a laminated structure having an insulating film 114. a stacked structure including the insulating film 107, the oxide semiconductor films 108b and 108c, and the insulating film 114; This is an example of the band structure in the film thickness direction of a structure. The conduction band of the insulating film 107, the oxide semiconductor films 108a, 108b, and 108c, and the insulating film 114 The lowest energy level (Ec) is shown.

[0144] 8A, silicon oxide films are used as the insulating films 107 and 114, and oxide semiconductor The metal oxide film 108a is made of metal oxide with an atomic ratio of In:Ga:Zn=1:3:2. The oxide semiconductor film 108b is formed using a metal target. The atomic ratio of the elements was In:Ga:Zn=1:1:1. The oxide semiconductor film 108c is formed by using an oxide semiconductor film having an atomic ratio of metal elements of In: An oxide semiconductor film formed using a metal oxide target with a Ga:Zn=1:3:2 was used. FIG. 1 is a band diagram of the configuration.

[0145] 8B, silicon oxide films are used as the insulating films 107 and 114, and oxide semiconductor The metal oxide film 108b has an atomic ratio of In:Ga:Zn=1:1:1. The oxide semiconductor film 108c is formed using a metal target. The atomic ratio of the elements was In:Ga:Zn=1:3:2. FIG. 10 is a band diagram of a structure using an oxide semiconductor film.

[0146] As shown in FIGS. 8A and 8B, in the oxide semiconductor films 108a, 108b, and 108c, In other words, the energy level at the bottom of the conduction band changes smoothly. In order to have such a band structure, the oxide The interface between the semiconductor film 108a and the oxide semiconductor film 108b or the interface between the oxide semiconductor film 108b and the oxide semiconductor film 108a At the interface with the oxide semiconductor film 108c, defect states such as trap centers and recombination centers are formed. Assume that there are no impurities that would form

[0147] In order to form a continuous junction in the oxide semiconductor films 108a, 108b, and 108c, Each film is deposited using a multi-chamber deposition system (sputtering system) equipped with a lock chamber. It is necessary to continuously stack the layers without exposing them to the air.

[0148] With the structure shown in FIGS. 8A and 8B, the oxide semiconductor film 108b serves as a well. In the transistor using the above stacked structure, the channel region is formed of the oxide semiconductor film 10 It can be seen that it is formed in 8b.

[0149] Note that impurities or defects may be present at or near the interface between the oxide semiconductor film and the insulating film. By providing the oxide semiconductor films 108a and 108c, trap states can be formed. In this case, the trap states are located farther away from the oxide semiconductor film 108b where the channel region is formed. This can be done.

[0150] In addition, the energy level of the trap states is lower than the energy level of the bottom of the conduction band of the oxide semiconductor film 108b. If the electron trap level is lower than the energy level (Ec), electrons tend to accumulate in the trap level. When electrons accumulate in the trap level, they become a negative fixed charge, and the transistor The threshold voltage of the trap level is shifted in the positive direction. The energy level is higher than the energy level (Ec) of the conduction band minimum of the oxide semiconductor film 108b. By doing so, electrons are less likely to accumulate in the trap level. This makes it possible to increase the on-current of the transistor and also to improve field-effect mobility. The degree can be increased.

[0151] In addition, in FIGS. 8A and 8B, the oxide semiconductor films 108a and 108c are oxide semiconductor films. The energy level of the bottom of the conduction band is closer to the vacuum level than the oxide film 108b. The energy level of the conduction band minimum of the semiconductor film 108b and the energy level of the oxide semiconductor films 108a and 108c The difference between the energy level of the conduction band minimum and the energy level of the That is, the oxide semiconductor films 108a and 108c have a valence of 2 eV or less, or 1 eV or less. the difference between the electron affinity of the oxide semiconductor film 108a and the electron affinity of the oxide semiconductor film 108b is 0.15 eV or more, or or 0.5 eV or more and 2 eV or less, or 1 eV or less.

[0152] With such a structure, the oxide semiconductor film 108b serves as a main path for current, and The oxide semiconductor films 108a and 108c function as a channel region. The oxide semiconductor film 108b is formed by using an oxide semiconductor material containing one or more metal elements. Since the oxide semiconductor film 108a is an oxide semiconductor film, the interface between the oxide semiconductor film 108a and the oxide semiconductor film 108b, Alternatively, interface scattering occurs at the interface between the oxide semiconductor film 180b and the oxide semiconductor film 108c. Therefore, the movement of carriers is not hindered at the interface, and the transistor The field effect mobility of the silicon dioxide increases.

[0153] In addition, the oxide semiconductor films 108a and 108c function as part of a channel region. In order to prevent this, a material having sufficiently low electrical conductivity is used. 108a and 108c are the electron affinities (the difference between the vacuum level and the energy level at the bottom of the conduction band). is smaller than that of the oxide semiconductor film 108b, and the energy level of the conduction band minimum is Use a material that has a difference (band offset) with the conduction band bottom energy level of 108b In addition, the difference in threshold voltage depending on the magnitude of the drain voltage is suppressed. In order to suppress this, the energy level of the conduction band minimum of the oxide semiconductor films 108a and 108c must be The energy level of the oxide semiconductor film 108b is lower than the vacuum level by 0.2 eV or more. It is preferable to use a material close to the vacuum level, preferably a material close to the vacuum level by 0.5 eV or more.

[0154] In addition, the oxide semiconductor films 108a and 108c do not contain a spinel crystal structure. It is preferable that the oxide semiconductor films 108a and 108c have a spinel crystal structure. When the spinel type crystal structure is contained, the conductive film 112a, 11 The constituent elements of 2b may diffuse into the oxide semiconductor film 108b. When the conductive films 108a and 108c are made of CAAC-OS, which will be described later, the conductive films 112a and 11 This is preferable because it increases the blocking ability of the constituent elements of 2b, for example, copper element.

[0155] The thicknesses of the oxide semiconductor films 108a and 108c are determined by the amount of the constituent elements of the conductive films 112a and 112b. The insulating film has a thickness that is greater than or equal to a thickness that can prevent the insulating film from diffusing into the oxide semiconductor film 108b. The thickness of the oxide semiconductor film 108b is set to be less than the thickness that prevents oxygen from being supplied from the film 114 to the oxide semiconductor film 108b. When the thickness of the oxide semiconductor films 108a and 108c is 10 nm or more, the conductive films 112a and This can prevent the constituent elements of the oxide semiconductor film 112b from diffusing into the oxide semiconductor film 108b. In addition, when the thickness of the oxide semiconductor films 108a and 108c is 100 nm or less, the insulating film 114 , oxygen can be effectively supplied from 116 to the oxide semiconductor film 108b.

[0156] When the oxide semiconductor films 108a and 108c are In-M-Zn oxides, M is Ti. , Ga, Sn, Y, Zr, La, Ce, Nd, or Hf in a higher atomic ratio than In By doing so, the energy gap of the oxide semiconductor films 108a and 108c can be increased, and the electron affinity can be increased. Therefore, the difference in electron affinity between the oxide semiconductor film 108b and the oxide semiconductor film 108c can be reduced by adjusting the composition of the element M. In addition, it may be possible to control the amount of Ti, Ga, Sn, Y, Zr, L Since a, Ce, Nd, and Hf are metal elements with strong bonding strength with oxygen, these elements By having a higher atomic ratio of In than In, oxygen vacancies are less likely to occur.

[0157] When the oxide semiconductor films 108a and 108c are made of In-M-Zn oxide, Zn and The atomic ratio of In and M excluding O is preferably 50 atomic % In. less than 50 atomic %, M is higher than 50 atomic %, and more preferably In is 25 atomic % The oxide semiconductor films 108a and 108c are made to have a conductivity of less than 100 Å and a conductivity of more than 75 atomic %. A gallium oxide film may be used as the insulating film.

[0158] In addition, when the oxide semiconductor films 108a, 108b, and 108c are made of In-M-Zn oxide, , compared with the oxide semiconductor film 108b, M contained in the oxide semiconductor films 108a and 108c The atomic ratio of the above atoms is typically larger than that of the above atoms contained in the oxide semiconductor film 108b. The atomic ratio is 1.5 times or more, preferably 2 times or more, and more preferably 3 times or more. .

[0159] In addition, when the oxide semiconductor films 108a, 108b, and 108c are made of In-M-Zn oxide, The oxide semiconductor film 108b is formed by mixing In:M:Zn=x1:y1:z1 [atomic ratio] and the oxide semiconductor When the conductor films 108a and 108c have an atomic ratio of In:M:Zn=x2:y2:z2, y2 / x2 is greater than y1 / x1, and preferably y2 / x2 is greater than y1 / x1 by 1. More preferably, y2 / x2 is at least two times larger than y1 / x1, and Preferably, y2 / x2 is three or four times larger than y1 / x1. In the oxide semiconductor film 108b, when y1 is equal to or larger than x1, the oxide semiconductor film 108b It is preferable because it can give stable electrical characteristics to a transistor using y1. When the value is three times or more of 1, the field-effect mobility of the transistor including the oxide semiconductor film 108b is Therefore, it is preferable that y1 is less than three times x1.

[0160] When the oxide semiconductor film 108b is an In-M-Zn oxide, the oxide semiconductor film 108b is formed by In the target used for forming the film, the atomic ratio of the metal elements is In:M:Zn=x1: If y1:z1 、 x1 / y1 is between 1 / 3 and 6, and further between 1 and 6. , z1 / y1 is preferably 1 / 3 or more and 6 or less, and more preferably 1 or more and 6 or less. When z1 / y1 is set to 1 or more and 6 or less, the oxide semiconductor film 108b can be obtained by the CAA method described later. The atomic ratio of the target metal elements is typically I. n:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=3:1 :There are 2nd class.

[0161] When the oxide semiconductor films 108a and 108c are made of an In-M-Zn oxide, the oxide semiconductor In the target used to form the solid films 108a and 108c, the number of atoms of the metal element is If the ratio is In:M:Zn=x2:y2:z2 、 x2 / y2 <x1 / y1であって、z 2 / y2 is preferably 1 / 3 or more and 6 or less, and more preferably 1 or more and 6 or less. By increasing the atomic ratio of M to indium, the oxide semiconductor films 108a and 108b can be formed. Since it is possible to increase the energy gap of c and reduce the electron affinity, y2 It is preferable that / x2 is 3 or more, or 4 or more. Representative examples are In:M:Zn=1:3:2, In:M:Zn=1:3:4, In: M:Zn=1:3:5, In:M:Zn=1:3:6, In:M:Zn=1:4:2, I n:M:Zn=1:4:4, In:M:Zn=1:4:5, In:M:Zn=1:5:5 etc.

[0162] When the oxide semiconductor films 108a and 108c are made of an In-M oxide, M is divalent gold. By not including metal atoms (e.g., zinc), it has a spinel-type crystal structure. In addition, the oxide semiconductor films 108a and 108c can be formed without any oxide semiconductor. The films 108a and 108c may be, for example, In-Ga oxide films. For example, an In-Ga oxide film can be formed by using an In-Ga metal oxide target (In:Ga= 7:93) can be formed by sputtering. In order to form the solid films 108a and 108c by a sputtering method using DC discharge, When n:M=x:y [atomic number ratio], y / (x+y) is 0.96 or less, preferably It is recommended to set it to 0.95 or less, for example 0.93.

[0163] Note that the atomic ratios of the oxide semiconductor films 108a, 108b, and 108c are each calculated using an error. The atomic ratios listed above may vary by ±40%.

[0164] In addition, the transistor according to this embodiment can be freely combined with each of the above structures. It is possible to do this.

[0165] <Method 1 for manufacturing semiconductor device> Next, a method for manufacturing the transistor 100 illustrated in FIGS. 1A and 1B, which is a semiconductor device of one embodiment of the present invention, will be described. This will be described in detail below with reference to FIGS.

[0166] Note that the films (insulating film, oxide semiconductor film, conductive film, etc.) constituting the transistor 100 are Sputtering, Chemical Vapor Deposition (CVD), Vacuum Evaporation, Pulsed Laser Deposition (PLD) Alternatively, it can be formed by a coating method or a printing method. The typical film formation methods are sputtering and plasma enhanced chemical vapor deposition (PECVD). However, thermal CVD may also be used. An example of a thermal CVD method is MOCVD (metal organic chemical vapor deposition). The multiplication method may also be used.

[0167] In the thermal CVD method, the pressure in the chamber is atmospheric or reduced, and the source gas and oxidant are simultaneously mixed. The reaction is carried out in the chamber near or on the substrate, where it is deposited on the substrate to form a film. As described above, the thermal CVD method is a film formation method that does not generate plasma. This has the advantage that defects are not generated due to damage.

[0168] In addition, in the ALD method, the pressure inside the chamber is atmospheric or reduced, and the source gas for the reaction is The gases are introduced into the chamber in sequence, and the film is formed by repeating this gas introduction sequence. By switching each switching valve (also called high-speed valve), two or more types of raw materials can be The source gases are supplied to the chamber in order, and the first source gas is supplied to the chamber in order to prevent the mixture of the source gases. Simultaneously with or after the second gas, an inert gas (argon, nitrogen, etc.) is introduced. Introduce the source gas. If an inert gas is introduced at the same time, the inert gas is used as a carrier gas. In addition, an inert gas may be introduced at the same time as the second source gas is introduced. Alternatively, instead of introducing an inert gas, the first source gas is discharged by vacuum evacuation, and then the second source gas is introduced. The first source gas may be adsorbed on the surface of the substrate to form a first monoatomic layer. The second monoatomic layer is formed by reacting with the second source gas introduced later. Layer upon layer is laminated to form a thin film.

[0169] This gas introduction sequence is repeated multiple times while controlling it until the desired thickness is achieved. The thickness of the thin film increases depending on the number of times the gas introduction sequence is repeated. Therefore, precise film thickness control is possible, and fine transistors can be fabricated. It is suitable for manufacturing.

[0170] First, a conductive film is formed on the substrate 102, and the conductive film is then subjected to a lithography process and an etching process. Then, a conductive film 104 is formed, which functions as a first gate electrode. On the conductive film 104, insulating films 106 and 107 are formed to function as a first gate insulating film (see FIG. 9(A)).

[0171] The conductive film 104 functioning as the first gate electrode is formed by a method such as sputtering, chemical vapor deposition ( It can be formed using the CVD method, vacuum evaporation method, pulsed laser deposition (PLD) method, etc. Alternatively, it can be formed by a coating method or a printing method. The most common methods are the plasma-enhanced chemical vapor deposition (PECVD) method, but the organic metal Thermal CVD methods such as MOCVD or atomic layer deposition (ALD) can also be used. good.

[0172] In this embodiment, a glass substrate is used as the substrate 102, and a gate electrode is formed on the substrate 102. A tungsten film having a thickness of 100 nm is formed as the conductive film 104 by sputtering. .

[0173] The insulating films 106 and 107, which function as the first gate insulating film, are formed by sputtering, PE It can be formed by using a CVD method, a thermal CVD method, a vacuum deposition method, a PLD method, etc. In this embodiment, a silicon nitride film having a thickness of 400 nm is formed as the insulating film 106 by the PECVD method. Then, a silicon oxynitride film having a thickness of 50 nm is formed as the insulating film 107.

[0174] The insulating film 106 may have a stacked structure of silicon nitride films. The insulating film 106 is made of a first silicon nitride film, a second silicon nitride film, and a third silicon nitride film. A three-layer laminated structure with a silicon film can be formed. An example of the three-layer laminated structure is as follows: It can be formed as follows.

[0175] The first silicon nitride film is formed by, for example, silane at a flow rate of 200 sccm, PE-CV was performed using nitrogen at a flow rate of 100 sccm and ammonia gas at a flow rate of 100 sccm as source gases. The pressure in the reaction chamber was controlled to 100 Pa, and a 27.12 MHz high frequency was generated. If a power of 2000 W is supplied using a frequency power supply and the thickness is formed to be 50 nm, good.

[0176] For the second silicon nitride film, silane at a flow rate of 200 sccm and 2000 sccm The PECVD equipment was operated using nitrogen at a flow rate of 2000 sccm and ammonia gas at a flow rate of 2000 sccm as raw material gases. The pressure in the reaction chamber was controlled to 100 Pa, and a 27.12 MHz high frequency power supply A power of 2000 W may be supplied using a heater to form the film to a thickness of 300 nm.

[0177] The third silicon nitride film was formed using silane at a flow rate of 200 sccm and silane at a flow rate of 5000 sccm. The pressure in the reaction chamber was adjusted to 100 The thickness was measured by controlling the temperature to 50 Pa and supplying 2000 W of power using a 27.12 MHz high frequency power supply. It is sufficient to form it so that the thickness is 50 nm.

[0178] The first silicon nitride film, the second silicon nitride film, and the third silicon nitride film The substrate temperature during the formation can be set to 350°C.

[0179] By forming the insulating film 106 as a three-layered structure of silicon nitride films, for example, the conductive film 10 When a conductive film containing copper (Cu) is used for 4, the following effects are achieved.

[0180] The first silicon nitride film can suppress the diffusion of copper (Cu) elements from the conductive film 104. The second silicon nitride film has the function of releasing hydrogen and functions as a gate insulating film. The third silicon nitride film has low hydrogen release and can improve the breakdown voltage of the insulating film. Furthermore, the diffusion of hydrogen released from the second silicon nitride film can be suppressed.

[0181] The insulating film 107 is formed by using a material having a thickness of 100 nm to improve interface characteristics with an oxide semiconductor film 108 to be formed later. Therefore, it is preferable that the insulating film be formed of an insulating film containing oxygen.

[0182] Next, the oxide semiconductor film 108 is formed over the insulating film 107 (see FIG. 9B).

[0183] In this embodiment, an In-Ga-Zn metal oxide target (In:Ga:Zn=1: 1:1.2 (atomic ratio)) to form an oxide semiconductor film by sputtering, A mask is formed on the oxide semiconductor film by a lithography process, and the oxide semiconductor film is By processing the oxide semiconductor film 108 into this shape, an island-shaped oxide semiconductor film 108 is formed.

[0184] After the oxide semiconductor film 108 is formed, the substrate is heated at 150° C. or higher and lower than the distortion point of the substrate, preferably at 200° C. A heat treatment may be carried out at a temperature of from 300°C to 450°C, more preferably from 300°C to 450°C. The heat treatment here is one of treatments for purifying the oxide semiconductor film. It is possible to reduce the amount of hydrogen, water, etc. contained in 108. The heat treatment may be performed before the oxide semiconductor film 108 is processed into an island shape.

[0185] The heat treatment on the oxide semiconductor film 108 can be performed using an electric furnace, an RTA apparatus, or the like. By using an RTA device, it is possible to perform heat treatment at a temperature above the distortion point of the substrate for a short period of time. This makes it possible to shorten the heating time.

[0186] Note that the heat treatment on the oxide semiconductor film 108 is performed using nitrogen, oxygen, or ultra-dry air (which contains air at 20 ppm or less, preferably 1 ppm or less, preferably 10 ppb or less, or The process may be carried out under an atmosphere of a rare gas (argon, helium, etc.). It is preferable that the dry air or rare gas does not contain hydrogen, water, etc. After the heat treatment in the gas atmosphere, the material may be heated in an oxygen or ultra-dry air atmosphere. Hydrogen, water, and the like contained in the oxide semiconductor film are released, and oxygen is introduced into the oxide semiconductor film. As a result, the amount of oxygen vacancies in the oxide semiconductor film can be reduced. This can be done.

[0187] When the oxide semiconductor film 108 is formed by a sputtering method, a sputtering gas In this case, a rare gas (typically argon), oxygen, or a mixed gas of a rare gas and oxygen is appropriately used. In the case of a mixed gas, it is preferable to increase the ratio of oxygen to rare gas. It is also necessary to increase the purity of the sputtering gas. For example, the oxygen used as the sputtering gas The dew point of the gas or argon gas is -40°C or less, preferably -80°C or less, more preferably By using gas that has been highly purified to temperatures below -100°C, and more preferably below -120°C, This can prevent moisture and the like from being taken into the oxide semiconductor film 108 as much as possible.

[0188] In addition, when the oxide semiconductor film 108 is formed by a sputtering method, a sputtering apparatus The chamber is designed to remove water and other impurities that may be present in the oxide semiconductor film 108 as much as possible. To remove the gas, a high vacuum (5×10) was created using an adsorption type vacuum pump such as a cryopump. -7 Pa to 1 x 10 -4 It is preferable to evacuate the gas to a temperature of about 100 Pa. A combination of a pump and a cold trap is used to extract gases, especially carbon or water, from the exhaust system into the chamber. It is preferable to prevent backflow of oxygen-containing gas.

[0189] Next, a source electrode and a drain electrode are formed over the insulating film 107 and the oxide semiconductor film 108. Functional conductive films 112a and 112b are formed (see FIG. 9C).

[0190] In this embodiment, the conductive films 112a and 112b are made of tungsten films having a thickness of 50 nm. A laminated film of the aluminum film having a thickness of 400 nm was formed by sputtering. A mask is formed on the layer film by a lithography process, and the layer film is processed into a desired shape. In this embodiment, the conductive films 112a and 112b are formed. However, the present invention is not limited to this. For example, the conductive film 112 a, 112b are tungsten films with a thickness of 50 nm and aluminum films with a thickness of 400 nm. Alternatively, a three-layer structure may be formed by stacking a 100 nm thick titanium film and a 100 nm thick titanium film.

[0191] After the conductive films 112a and 112b are formed, the surface of the oxide semiconductor film 108 (back The cleaning method may be, for example, cleaning with a chemical solution such as phosphoric acid. By performing cleaning using a chemical solution such as phosphoric acid, the surface of the oxide semiconductor film 108 can be cleaned. Remove impurities (such as elements contained in the conductive films 112a and 112b) adhering to the surface. It is possible.

[0192] In addition, when the conductive films 112a and 112b are formed and / or in the above cleaning process, oxidation A recess may be formed in part of the compound semiconductor film 108.

[0193] Through the above steps, the transistor 100 is formed.

[0194] Next, the transistor 100, specifically, the oxide semiconductor film 108 of the transistor 100, and an insulating film serving as a protective insulating film for the transistor 100 is formed on the conductive films 112a and 112b. The velum 114 and 116 are formed (see FIG. 9(D)).

[0195] After the insulating film 114 is formed, the insulating film 116 is successively formed without exposure to the air. After the insulating film 114 is formed, it is preferable to control the flow rate, pressure, and temperature of the source gas without exposing the insulating film 114 to the atmosphere. By adjusting one or more of the frequency power and the substrate temperature, the insulating film 116 is continuously formed. The concentration of impurities derived from atmospheric components can be reduced at the interface between the insulating film 114 and the insulating film 116. At the same time, oxygen contained in the insulating films 114 and 116 is transferred to the oxide semiconductor film 108. As a result, the amount of oxygen vacancies in the oxide semiconductor film 108 can be reduced.

[0196] For example, a silicon oxynitride film is formed as the insulating film 114 by using a PECVD method. In this case, the source gas may be a deposition gas containing silicon and an oxidizing gas. It is preferable to use the following gases. Typical examples of deposition gases containing silicon include silane, disilane, and the like. Examples of oxidizing gases include nitrous oxide, nitrous dioxide, etc. In addition, the oxidizing gas is more than 20 times but less than 100 times the deposition gas. The pressure in the treatment chamber is set to less than 100 Pa, preferably 40 times or more and 80 times or less. By using the PECVD method at a pressure of 50 Pa or less, the insulating film 114 contains nitrogen and The insulating film has a small number of defects.

[0197] In this embodiment, the insulating film 114 is formed by heating the substrate 102 at a temperature of 220°C. Silane at a flow rate of 50 sccm and dinitrogen monoxide at a flow rate of 2000 sccm were used as source gases. The pressure in the processing chamber was set to 20 Pa, and the high frequency power supplied to the parallel plate electrodes was set to 13.56 M. Hz, 100W (power density is 1.6 x 10 -2 W / cm 2 ) PECVD method A silicon oxynitride film is formed using the silicon oxynitride film.

[0198] The insulating film 116 is formed by depositing a substrate placed in a vacuum-evacuated processing chamber of a PECVD device. The temperature is maintained at 180°C or higher and 280°C or lower, more preferably 200°C or higher and 240°C or lower. The raw material gas is introduced into the chamber to set the pressure in the processing chamber to 100 Pa or more and 250 Pa or less, and Preferably, the pressure is 100 Pa or more and 200 Pa or less, and 0.17 W is applied to the electrodes provided in the processing chamber. / cm 2 More than 0.5W / cm 2 or less, more preferably 0.25 W / cm 2 Over 0.35 W / cm 2 Under the following conditions for supplying high frequency power, silicon oxide film or silicon oxynitride film is formed. Form a con film.

[0199] The conditions for forming the insulating film 116 are as follows: a high frequency voltage of the above power density in a reaction chamber of the above pressure; By supplying power, the decomposition efficiency of the source gas in the plasma increases, and oxygen radicals increase. As the oxidation of the source gas progresses, the oxygen content in the insulating film 116 becomes higher than the stoichiometric composition. On the other hand, in the film formed at the above substrate temperature, the bonding strength between silicon and oxygen is As a result, the stoichiometric amount of oxygen in the film is reduced by the heat treatment in the subsequent process. Oxides that contain more oxygen than the stoichiometric composition and lose some of the oxygen when heated An insulating film can be formed.

[0200] In the step of forming the insulating film 116, the insulating film 114 serves as a protection film for the oxide semiconductor film 108. Therefore, the power density can be reduced while reducing damage to the oxide semiconductor film 108. The insulating film 116 can be formed using high radio frequency power.

[0201] In the film formation conditions for the insulating film 116, a deposition gas containing silicon is mixed with an oxidizing gas. By increasing the flow rate of the gas, it is possible to reduce the number of defects in the insulating film 116. In the ESR measurement, the g value of 2.001, which is due to the dangling bond of silicon, The spin density of the signal is 6×10 17 spins / cm 3 Less than 3 x 10 17 spins / cm 3 Less than or equal to 1.5 × 10 17 spins / cm 3 The following is a missing An oxide insulating layer with fewer defects can be formed, resulting in improved reliability of the transistor. It can be done.

[0202] After the insulating films 114 and 116 are formed, heat treatment may be performed. The nitrogen oxides contained in the insulating films 114 and 116 can be reduced. As a result, part of the oxygen contained in the insulating films 114 and 116 is transferred to the oxide semiconductor film 108. This can reduce the amount of oxygen vacancies in the oxide semiconductor film 108.

[0203] The temperature for the heat treatment of the insulating films 114 and 116 is typically 150° C. or higher and 400° C. or lower. The temperature is preferably 300°C or higher and 400°C or lower, more preferably 320°C or higher and 370°C or lower. Heat treatment is carried out in nitrogen, oxygen, or ultra-dry air (water content of 20 ppm or less, preferably 1 ppm). m or less, preferably 10 ppb or less of air), or rare gases (argon, helium, etc.) The reaction may be carried out under an atmosphere of nitrogen, oxygen, ultra-dry air, or a rare gas, hydrogen, water, etc. For the heat treatment, an electric furnace, an RTA device, etc. may be used. do.

[0204] In this embodiment mode, heat treatment is performed in a nitrogen and oxygen atmosphere at 350° C. for 1 hour.

[0205] Next, a film 130 having a function of suppressing oxygen release is formed on the insulating film 116 (see FIG. 10(A)).

[0206] The film 130 having the function of suppressing oxygen release may be a conductive film containing indium, or A semiconductor film containing indium can be used.

[0207] In this embodiment, the film 130 having the function of suppressing the release of oxygen is a spa A 5 nm thick ITSO film is formed using a quenching device. When the thickness is 1 nm or more and 20 nm or less, or 2 nm or more and 10 nm or less, oxygen can be suitably transmitted. This is also preferable because it can suppress the release of oxygen.

[0208] Next, oxygen 139 is added to the insulating films 114 and 116 and the oxide semiconductor film 108 through the film 130. is added (see FIG. 10(B)).

[0209] Oxygen 139 is added to the insulating films 114 and 116 and the oxide semiconductor film 108 through the film 130. The method includes ion doping, ion implantation, plasma treatment, and the like.

[0210] In addition, when adding oxygen 139, applying a bias voltage to the substrate side effectively increases the oxygen The element 139 can be added to the insulating films 114 and 116 and the oxide semiconductor film 108. The bias voltage is, for example, a voltage applied to the substrate side of an ashing device. The power density of the applied bias voltage is 1 W / cm 2 More than 5W / cm 2 The following is sufficient. The substrate temperature when adding oxygen 139 is from room temperature to 300°C, preferably By setting the temperature to 100° C. or more and 250° C. or less, oxygen can be efficiently added to the insulating films 114 and 116. It is possible.

[0211] By providing the film 130 on the insulating film 116 and adding oxygen, the film 130 is Therefore, the insulating films 114 and 11 function as a protective film that suppresses oxygen from being released from the insulating film 114. A large amount of oxygen can be added to the oxide semiconductor film 6 and the oxide semiconductor film 108.

[0212] In addition, when oxygen is introduced in plasma treatment, the oxygen is excited by microwaves to form high-density oxygen. By generating oxygen plasma, the amount of oxygen introduced into the insulating film 116 can be increased. .

[0213] Next, the film 130 having the function of suppressing the release of oxygen is removed using an etchant 142. Remove (see Figure 10(C)).

[0214] The etchant 142 is an etchant capable of removing the film 130 having a function of suppressing the release of oxygen. In this embodiment, a chemical solution or an etching gas may be used. As the etchant 142, a 5% oxalic acid aqueous solution is used. As for 2, after using the above 5% oxalic acid aqueous solution, a 0.5% fluoride aqueous solution was further added. Hydrofluoric acid can also be used. By using 0.5% hydrofluoric acid, oxygen release can be suppressed. This allows for the preferable removal of films that have the function of removing the film.

[0215] Next, an insulating film 118 is formed over the insulating film 116, thereby forming the transistor 10 shown in FIG. 0 is formed (see FIG. 10(D)).

[0216] When the insulating film 118 is formed by the PECVD method, the substrate temperature is set to 300° C. or more and 400° C. or less. Preferably, the temperature is 320° C. or higher and 370° C. or lower, since a dense film can be formed. stomach.

[0217] For example, when a silicon nitride film is formed as the insulating film 118 by the PECVD method, the silicon It is preferable to use a deposition gas containing carbon, nitrogen, and ammonia as the source gas. By using a small amount of ammonia compared to nitrogen, ammonia dissociates in the plasma and becomes active. The activated species react with silicon and hydrogen contained in the silicon-containing deposition gas. This breaks the silicon-nitrogen triple bond, promoting the bonding of silicon and nitrogen. To form a dense silicon nitride film with few bonds between silicon and hydrogen and few defects. On the other hand, if the amount of ammonia relative to nitrogen is large, the deposition gas containing silicon and Nitrogen decomposition does not progress, silicon and hydrogen bonds remain, defects increase, and roughness occurs. For these reasons, the source gas should be ammonia-free. The flow rate ratio of nitrogen to oxygen is preferably 5 or more and 50 or less, and more preferably 10 or more and 50 or less.

[0218] In this embodiment, the insulating film 118 is formed by depositing silane, nitrogen, and the like using a PECVD apparatus. A silicon nitride film with a thickness of 50 nm is formed from the source gases of hydrogen and ammonia. , silane 50sccm, nitrogen 5000sccm, ammonia 100sccm The pressure in the processing chamber was 100 Pa, the substrate temperature was 350°C, and a high frequency of 27.12 MHz was used. A high-frequency power of 1000 W is supplied to the parallel plate electrodes using a high-frequency power supply. The polar area is 6000 cm 2 It is a parallel plate type PECVD device, and the supplied power is measured as This translates to 1.7 x 10 power per area (power density). -1 W / cm 2 is.

[0219] Note that heat treatment is performed before or after the insulating film 118 is formed to form an insulating film. Excess oxygen contained in the films 114 and 116 is diffused into the oxide semiconductor film 108, and the oxide semiconductor Alternatively, the insulating film 118 can be formed by heating and filling the oxygen vacancies in the insulating film 108. By this, excess oxygen contained in the insulating films 114 and 116 is diffused into the oxide semiconductor film 108. By this, oxygen vacancies in the oxide semiconductor film 108 can be filled. The temperature of the heat treatment, which can be performed before or after the formation of the insulating film 118, is typically: 150°C or higher and 400°C or lower, preferably 300°C or higher and 400°C or lower, preferably 320°C The temperature must be above 370°C.

[0220] Through the above steps, the transistor 100 shown in FIG. 1 can be manufactured.

[0221] <Method 2 for manufacturing semiconductor device> Next, a method for manufacturing the transistor 150 illustrated in FIGS. 4A and 4B, which is a semiconductor device of one embodiment of the present invention, will be described. This will be described in detail below with reference to FIGS.

[0222] First, the steps up to the step shown in FIG. 9B are performed, and then the insulating film 107 and the oxide semiconductor film 1 On the substrate 08, insulating films 114 and 116 and a film 130 having a function of suppressing oxygen release are formed. (See FIG. 11(A)).

[0223] Next, the insulating films 114, 116, and Further, oxygen 139 is added to the oxide semiconductor film 108 (see FIG. 11B).

[0224] Next, the film 130 having the function of suppressing the release of oxygen is removed using an etchant 142. Remove (see Figure 11(C)).

[0225] Next, a mask is formed on the insulating film 116 by a lithography process, and the insulating film 114 and the insulating film 116 are Openings 141a and 141b are formed in desired areas of the velum 116. , 141b reach the oxide semiconductor film 108 (see FIG. 11D).

[0226] Next, the oxide semiconductor film 108 and the insulating film 11 are formed so as to cover the openings 141a and 141b. A conductive film is formed on the conductive film 6, a mask is formed on the conductive film by a lithography process, and the conductive film The conductive film 112a and the conductive film 112b are formed by processing the conductive film 112a into a desired shape (see FIG. 12(A)). see).

[0227] Next, an insulating film 118 is formed on the insulating film 116 and the conductive films 112a and 112b (FIG. 12(B)).

[0228] Through the above steps, the transistor 150 shown in FIG. 4 can be manufactured.

[0229] The transistor 160 shown in FIGS. 5A, 5B, and 5C has an opening 141a, When forming the insulating films 114 and 111b, the insulating films 114 and 111b are formed on the channel region of the oxide semiconductor film 108. It can be fabricated by leaving 6.

[0230] <Method 3 for manufacturing semiconductor device> Next, a method for manufacturing a transistor 170, which is a semiconductor device of one embodiment of the present invention, illustrated in FIGS. This will be described in detail below with reference to FIGS.

[0231] 13(A)(C) and 14(A)(C) show the transistors in the manufacturing process. 13(B)(D) and 14(B)(D) show cross-sectional views of the capacitor 170 in the channel length direction. 1A and 1B are cross-sectional views of a transistor 170 in the channel width direction during a manufacturing process.

[0232] First, the steps up to the step shown in FIG. 10(D) are carried out (see FIGS. 13(A) and (B)).

[0233] Next, a mask is formed on the insulating film 118 by a lithography process, and the insulating films 114 and 11 An opening 142c is formed in a desired region of the insulating film 118. A mask is formed by a film process, and the desired insulating films 106, 107, 114, 116, and 118 are formed. The openings 142a and 142b are formed in the conductive film 112. The openings 142a and 142b are formed so as to reach the conductive film 10 4 (see Figures 13(C) and (D)).

[0234] The openings 142a, 142b and the opening 142c may be formed at the same time or in different locations. The openings 142a, 142b and the opening 142c may be formed at the same time. In this case, for example, a gray-tone mask or a half-tone mask can be used. Cut.

[0235] Next, a conductive film 12 is formed on the insulating film 118 so as to cover the openings 142a, 142b, and 142c. 0 (see Figures 14(A) and (B)).

[0236] The conductive film 120 may be made of, for example, indium (In), zinc (Zn), or tin (Sn). In particular, the conductive film 120 may be made of a material containing one selected from the group consisting of: Indium oxide containing tungsten oxide, Indium zinc oxide containing tungsten oxide , indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium Translucent materials such as indium tin oxide, indium zinc oxide, and indium tin oxide containing silicon oxide In addition, the conductive film 120 can be made of a conductive material that can suppress the release of oxygen. By using the same material as the film 130 having the function of being able to perform the function, the manufacturing cost can be reduced, which is preferable. It is suitable.

[0237] The conductive film 120 can be formed by, for example, a sputtering method. In this embodiment, an ITSO film having a thickness of 110 nm is formed by sputtering. do.

[0238] Next, a mask is formed on the conductive film 120 by a lithography process, and the conductive film 120 is The conductive film 120a and the conductive film 120b are formed (see FIGS. 14(C) and 14(D)).

[0239] Through the above steps, the transistor 170 shown in FIG. 6 can be manufactured.

[0240] As described above, the structures and methods described in this embodiment mode may be appropriately combined with the structures and methods described in other embodiments. They can be used in combination.

[0241] (Embodiment 2) In this embodiment, a structure of an oxide semiconductor film included in a semiconductor device of one embodiment of the present invention will be described. This will be explained in detail below.

[0242] Oxide semiconductor films are roughly classified into non-single-crystal oxide semiconductor films and single-crystal oxide semiconductor films. The non-single-crystal oxide semiconductor film is a CAAC-OS (C Axis Aligned Crystal Polycrystalline oxide semiconductor film The oxide semiconductor film includes a film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, and the like.

[0243] First, the CAAC-OS film will be described.

[0244] The CAAC-OS film is one of the oxide semiconductor films that has multiple crystal parts aligned along the c-axis. .

[0245] Transmission Electron Microscope (TEM) A combined analysis image of the bright-field image and diffraction pattern of the CAAC-OS film was obtained using a microscope. (also called high-resolution TEM images) On the other hand, high-resolution TEM images also clearly show the boundaries between crystals, i.e., grain boundaries. Therefore, the CAAC-OS film is It can be said that the decrease in electron mobility caused by the grain boundaries is unlikely to occur.

[0246] When a high-resolution TEM image of the cross section of the CAAC-OS film was observed from a direction approximately parallel to the sample surface, It can be seen that the metal atoms are arranged in layers in the crystal part. The CAAC-OS film is formed on a surface (also called a surface on which the film is formed) or on the upper surface. The CAAC-OS film has a shape similar to that of the crystalline silicon film, and is arranged parallel to the surface on which the CAAC-OS film is formed or the upper surface thereof.

[0247] On the other hand, a high-resolution TEM image of the plane of the CAAC-OS film was observed from a direction almost perpendicular to the sample surface. They then confirmed that the metal atoms in the crystals were arranged in triangular or hexagonal shapes. However, there is no regularity in the arrangement of metal atoms between different crystal parts.

[0248] X-ray diffraction (XRD) of the CAAC-OS film When structural analysis is performed using this device, for example, CAAC-OS with InGaZnO4 crystals can be seen. In the out-of-plane analysis of the film, the diffraction angle (2θ) peaks around 31°. This peak is attributed to the (009) plane of the InGaZnO4 crystal. Therefore, the crystals of the CAAC-OS film have a c-axis orientation, and the c-axis faces the surface on which the film is formed or the upper surface. It can be seen that it is oriented in a substantially vertical direction.

[0249] In addition, the out-of-plane structure of the CAAC-OS film with InGaZnO4 crystals In the analysis by the NMR method, in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ around 36° is due to the presence of c-axis orientation in part of the CAAC-OS film. The CAAC-OS film contains crystals that do not have crystalline structure. It is preferable that the peak is exhibited at 2θ of about 36° and that the peak is not exhibited at 2θ of about 36°.

[0250] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is made of an element other than the main component, such as silicon or a transition metal element. The elements such as ZnO, which have stronger bonding strength with oxygen than the metal elements constituting the oxide semiconductor film, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disrupted, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Because the diameter (or molecular radius) is large, when the molecule is contained inside the oxide semiconductor film, The impurities contained in the oxide semiconductor film are likely to disturb the atomic arrangement of the oxide semiconductor film, which may result in a decrease in crystallinity. The pure material may act as a carrier trap or a carrier generation source.

[0251] The CAAC-OS film is an oxide semiconductor film with a low density of defect states. Oxygen vacancies in semiconductor films can act as carrier traps and trap hydrogen. This can become a carrier generation source.

[0252] The low impurity concentration and low defect level density (low oxygen vacancies) are called high-purity intrinsic or The term "high-purity intrinsic" refers to a substantially high-purity intrinsic oxide semiconductor. The film has a small number of carrier generation sources, so the carrier density can be reduced. The transistor including the oxide semiconductor film has electrical characteristics in which the threshold voltage is negative. (also called normally-on) is rare. An oxide semiconductor film with intrinsic purity has few carrier traps. Transistors using conductor films have little fluctuation in electrical characteristics and are highly reliable. Note that it takes time for the charges trapped in the carrier traps in the oxide semiconductor film to be released. The time it takes for the impurity concentration to reach the target is long, and it may behave as if it were a fixed charge. A transistor using an oxide semiconductor film with a high density of defect states has unstable electrical characteristics. This may be the case.

[0253] In addition, the electrical characteristics of transistors using CAAC-OS films are improved by irradiation with visible light or ultraviolet light. There is little gender variation.

[0254] Next, a microcrystalline oxide semiconductor film will be described.

[0255] The microcrystalline oxide semiconductor film has crystalline parts that can be confirmed in high-resolution TEM images. The microcrystalline oxide semiconductor has a region where a crystal part is not clearly observed and a region where a crystal part is not clearly observed. The crystal parts contained in the film are large, with sizes of 1 nm to 100 nm or 1 nm to 10 nm. In particular, the size is between 1 nm and 10 nm, or between 1 nm and 3 nm. An oxide semiconductor film having nanocrystals (nc) which are microcrystals is called n c-OS(nanocrystalline oxide semiconductor ) film. In addition, the nc-OS film clearly shows the grain boundaries in high-resolution TEM images, for example. It may not be possible to confirm.

[0256] The nc-OS film is a microscopic region (e.g., a region of 1 nm to 10 nm, especially a region of 1 nm or less). The nc-OS film has a periodic atomic arrangement in the region of 3 nm or less. There is no regularity in the crystal orientation between the crystal parts, and therefore no orientation is observed throughout the film. Therefore, the nc-OS film cannot be distinguished from an amorphous oxide semiconductor film depending on the analysis method. For example, in the case of nc-OS films, X-rays with a diameter larger than that of the crystals are used. When structural analysis is performed using an RD device, the crystal In addition, the peaks indicating the crystal planes were not detected in the nc-OS film. Electron diffraction (also called selected area electron diffraction) using an electron beam with a diameter of 50 nm or more. When the diffraction pattern is changed to nc-OS film, a halo-like diffraction pattern is observed. Nano-beam electrons are used, which use an electron beam with a probe diameter close to or smaller than the size of the crystal. When nanobeam electron diffraction is performed on the nc-OS film, spots are observed. When you do this, you may see a circular (ring-shaped) area of ​​high brightness. Nanobeam electron diffraction of the nc-OS film revealed multiple spots within the ring-shaped region. may be observed.

[0257] The nc-OS film is an oxide semiconductor film with higher order than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect states than the amorphous oxide semiconductor film. In the nc-OS film, there is no regularity in the crystal orientation between different crystal parts. The OS film has a higher density of defect states than the CAAC-OS film.

[0258] Next, the amorphous oxide semiconductor film will be described.

[0259] The amorphous oxide semiconductor film has an irregular atomic arrangement in the film and does not have a crystalline portion. An example is an oxide semiconductor film that has an amorphous state like quartz.

[0260] In amorphous oxide semiconductor films, no crystalline parts can be identified in high-resolution TEM images. .

[0261] When the structure of the amorphous oxide semiconductor film is analyzed using an XRD device, out-of- In the analysis by the plane method, no peaks indicating crystal planes are detected. When electron diffraction is performed on a semiconductor film, a halo pattern is observed. When nanobeam electron diffraction is performed on a semiconductor film, no spots are observed, and a halo pattern is observed. is observed.

[0262] Note that the oxide semiconductor film has a structure that exhibits physical properties intermediate between the nc-OS film and the amorphous oxide semiconductor film. An oxide semiconductor film having such a structure may be formed, particularly, by using an amorphous oxide. amorphous-like oxide semiconductors (a-like OS) This is called an iconductor membrane.

[0263] In the a-like OS film, voids are observed in high-resolution TEM images. In addition, crystals may not be clearly visible in high-resolution TEM images. The a-like OS film has regions where crystals are visible and regions where no crystals are visible. Crystallization occurs when a small amount of electrons is irradiated, similar to the amount observed with a TEM, and the growth of the crystals can be seen. On the other hand, if the nc-OS film is of good quality, the amount of precipitation is so small that it can be observed by TEM. Almost no crystallization due to electron irradiation is observed.

[0264] The size of the crystalline parts of the a-like OS film and the nc-OS film was measured using a high-resolution This can be done using TEM images. For example, InGaZnO4 crystals have a layered structure. There are two Ga-Zn-O layers between the In-O layers. The device has three In-O layers and six Ga-Zn-O layers, for a total of nine layers aligned along the c-axis. It has a layered structure. Therefore, the distance between adjacent layers is (009) The lattice spacing (also called the d value) is approximately the same as that of the Therefore, focusing on the lattice fringes in the high-resolution TEM image, In the area where the spacing is 0.28 nm or more and 0.30 nm or less, each lattice fringe is In It corresponds to the ab plane of the GaZnO4 crystal.

[0265] In addition, the density of an oxide semiconductor film may differ depending on the structure. If the composition of the conductive film is known, the density can be determined by comparing it with the density of a single crystal with the same composition. For example, the structure of the oxide semiconductor film can be estimated by using the following formula: The density of the -like OS film is 78.6% or more and less than 92.3%. The density of the nc-OS film and the CAAC-OS film is 92.3% or more of the density of the crystal. Note that an oxide semiconductor film having a density of less than 78% of the density of a single crystal is However, it is difficult to form the film.

[0266] The above will be explained using a specific example. For example, In:Ga:Zn=1:1:1 [atom In the oxide semiconductor film that satisfies the [atomic ratio], single-crystal InGaZnO with a rhombohedral crystal structure The density of 4 is 6.357 g / cm 3 Therefore, for example, In:Ga:Zn=1:1: In an oxide semiconductor film that satisfies the atomic ratio of 1, the density of the a-like OS film is 5.0 g / cm 3 More than 5.9g / cm 3 For example, In:Ga:Zn=1:1 In the oxide semiconductor film satisfying the atomic ratio of 0.1 to 1, the density and CAAC of the nc-OS film were The density of the -OS film is 5.9 g / cm 3 More than 6.3g / cm 3 It will be less than.

[0267] In some cases, single crystals with the same composition do not exist. In such cases, crystals with different compositions may be used in any proportion. By combining single crystals with the desired composition, the density corresponding to the single crystal of the desired composition can be calculated. The density of a single crystal of a desired composition varies depending on the ratio of the single crystals of different compositions combined. However, the density should be calculated using as few types of single crystals as possible. It is preferable to calculate it by combining the above.

[0268] The oxide semiconductor film may be, for example, an amorphous oxide semiconductor film, an a-like OS film, or a microcrystalline silicon film. The film may be a stacked film including two or more of a crystalline oxide semiconductor film and a CAAC-OS film. .

[0269] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0270] (Embodiment 3) In this embodiment, a display device including the transistor described in the previous embodiment will be described. An example will be described below with reference to FIGS.

[0271] 15 is a top view showing an example of a display device. The display device 700 shown in FIG. A pixel portion 702 is provided on the first substrate 701, and a source driver 703 is provided on the second substrate 701. The pixel section 702, the source driver circuit section 704, the gate driver circuit section 706, a sealant 712 disposed to surround the path portion 704 and the gate driver circuit portion 706; and a second substrate 705 provided so as to face the first substrate 701. The first substrate 701 and the second substrate 705 are sealed with a sealant 712. That is, the pixel section 702, the source driver circuit section 704, and the gate driver circuit section 706 are The first substrate 701, the sealant 712, and the second substrate 705 seal the entire structure. Although not shown in FIG. 15, a display element is provided between the first substrate 701 and the second substrate 705. It can be done.

[0272] The display device 700 is surrounded by a sealant 712 on the first substrate 701. The pixel section 702, the source driver circuit section 704, and the gate driver circuit section 706 are arranged in a region different from the region. and an FPC terminal portion 708 (FPC: Flexible Printed Circuit) electrically connected to the flexible printed circuit portion 706. In addition, the FPC terminal portion 708 is provided with The FPC 716 is connected to the pixel section 702 and the source driver circuit Various signals are supplied to the pixel section 704 and the gate driver circuit section 706. 02, a source driver circuit section 704, a gate driver circuit section 706, and an FPC terminal section 7 08 are connected to signal lines 710. Various signals are supplied by the FPC 716. 7. The pixel section 702, the source driver circuit section 704, the gate driver circuit section 706, and the like are connected to each other via a signal line 710. The power supply is provided to a driver circuit portion 706 and an FPC terminal portion 708.

[0273] Furthermore, the display device 700 may be provided with a plurality of gate driver circuits 706. The device 700 includes a source driver circuit section 704 and a gate driver circuit section 706. Although an example in which the pixel portion 702 is formed on the same first substrate 701 is shown, the present invention is not limited to this configuration. For example, only the gate driver circuit section 706 may be formed on the first substrate 701. Alternatively, only the source driver circuit portion 704 may be formed on the first substrate 701. In this case, the substrate on which the source driver circuit or the gate driver circuit etc. is formed (for example, A driving circuit board formed of a monocrystalline semiconductor film or a polycrystalline semiconductor film is mounted on a first substrate 701. The method of connecting the separately formed drive circuit board is not particularly limited. Instead of COG (Chip On Glass) method, wire bonding method, etc. can be used.

[0274] The display device 700 also includes a pixel section 702, a source driver circuit section 704, and a gate The driver circuit portion 706 includes a plurality of transistors. A transistor having a specific position can be applied.

[0275] The display device 700 can also include various elements, such as: Liquid crystal elements, EL (electroluminescence) elements (EL elements including organic and inorganic materials, Organic EL elements, inorganic EL elements), LEDs (white LEDs, red LEDs, green LEDs, blue LEDs) ED, etc.), transistors (transistors that emit light according to the current), electron-emitting elements, electron Ink, electrophoretic element, grating light valve (GLV), plasma display (PDP), display element using MEMS (microelectromechanical systems) Digital Micromirror Device (DMD), DMS (Digital MicroShutter) MIRASOL (registered trademark), IMOD (Interference Modulation shutter-type MEMS display elements, optical interference-type MEMS display elements, Using electrowetting elements, piezoelectric ceramic displays, and carbon nanotubes In addition to these, it has at least one electrical or magnetic function. Even if the display medium has a variable contrast, brightness, reflectance, transmittance, etc. depending on the use, An example of a display device using an EL element is an EL display. An example of a display device using an emission element is a field emission display (FED) ) or SED type flat panel display (SED: Surface-conduction Electron-emitter Displays (ELDs) are also available. An example of a display device is a liquid crystal display (transmissive liquid crystal display, semi-transmissive liquid crystal display, etc.). LCD, reflective LCD, direct-view LCD, projection LCD An example of a display device using electronic ink or electrophoretic elements is an electronic pen. In addition, there are also other LCDs that can be used to realize semi-transmissive LCDs and reflective LCDs. In this case, a part or all of the pixel electrodes should function as a reflective electrode. For example, a part or the whole of the pixel electrode may contain aluminum, silver, etc. Furthermore, in this case, a memory circuit such as an SRAM may be provided under the reflective electrode. This makes it possible to further reduce power consumption.

[0276] The display method of the display device 700 may be a progressive method or an interlace method. In addition, the color elements controlled by pixels when displaying colors include R It is not limited to the three colors GB (R stands for red, G stands for green, B stands for blue). For example, It may be composed of four pixels: a pixel, a B pixel, and a W (white) pixel. Like the column, two colors of RGB make up one color element, and two different colors are created by the color element. Alternatively, you can select one or more colors such as yellow, cyan, magenta, etc. for RGB. The size of the display area may be different for each dot of the color element. However, the disclosed invention is not limited to color display devices, but also to monochrome display devices. The present invention can also be applied to display devices such as those shown in the accompanying drawings.

[0277] In addition, the backlight (organic EL element, inorganic EL element, LED, fluorescent lamp, etc.) uses white light ( In order to display full color on the display device, a colored layer (also called a color filter) is used. The colored layer may be, for example, red (R), green (G), blue (B) Yellow (Y) and other colors can be used in combination as appropriate. The color reproducibility can be improved compared to when no color layer is used. By arranging a region having a colored layer and a region not having a colored layer, the region not having a colored layer can be The white light in the region may be directly used for display. This reduces the decrease in brightness caused by the colored layer during bright display, reducing power consumption by 20%. However, it may be possible to reduce the light emission by about 30%. When using a device to display full color, R, G, B, Y, and white (W) are It is also possible to emit light from an element having a luminescent color. In some cases, power consumption can be reduced even further than when the

[0278] In this embodiment, a liquid crystal element and an EL element are used as display elements. 16 and 17. Note that FIG. 16 shows the area indicated by the dashed line QR in FIG. 17 is a cross-sectional view of the liquid crystal display device, which uses a liquid crystal element as a display element. 15 is a cross-sectional view taken along the dashed line QR shown in FIG. 15, and shows a configuration in which an EL element is used as a display element. is.

[0279] First, the common parts shown in Fig. 16 and Fig. 17 will be explained, and then the different parts will be explained. This will be explained below.

[0280] <Explanation of common parts of display devices> The display device 700 shown in FIGS. 16 and 17 includes a wiring portion 711, a pixel portion 702, and a , a source driver circuit section 704, and an FPC terminal section 708. The line portion 711 includes a signal line 710. The pixel portion 702 includes a transistor 750 and The source driver circuit portion 704 includes a transistor 752. Has.

[0281] The transistors 750 and 752 may be the transistors shown above. can.

[0282] The transistor used in this embodiment is made of a highly purified oxide in which the formation of oxygen vacancies is suppressed. The transistor has a semiconductor film. The transistor has a low current value in an off state (off-state current value). Therefore, the retention time of the electric signals such as the image signals can be extended, and the power supply When it is on, the write interval can be set longer. Therefore, the frequency of refresh operations can be reduced. This has the effect of reducing power consumption.

[0283] In addition, the transistor used in this embodiment has a relatively high field-effect mobility. For example, a transistor capable of such high speed driving can be used in a liquid crystal display. By using this in a display device, the switching transistor in the pixel section and the driver circuit section can be In other words, the driver transistor can be formed on the same substrate as a separate driver circuit. Therefore, it is not necessary to use a semiconductor device formed from a silicon wafer or the like. The number of components can be reduced. By using a register, high quality images can be provided.

[0284] The capacitor 790 has a structure in which a dielectric is provided between a pair of electrodes. One electrode of the transistor 790 is a conductive film that functions as a gate electrode of the transistor 750. The other electrode of the capacitor 790 is formed using a conductive film formed in the same process as that of the transistor. A conductive film is used to function as a source electrode and a drain electrode of the transistor 750. The dielectric sandwiched between the electrodes functions as the gate insulating film of the transistor 750. An insulating film is used.

[0285] 16 and 17, the transistor 750, the transistor 752, and the capacitor The insulating films 764, 766, and 768, the oxide semiconductor film 767, and the planarization film 768 are formed over the capacitor 790. An insulating film 770 is provided.

[0286] The insulating films 764, 766, and 768 are the same as the insulating film 114 shown in the previous embodiment. , 116, 118 can be formed using the same materials and manufacturing methods. The oxide semiconductor film 767 may be formed using the same material as the oxide semiconductor film 117 described in the above embodiment. The planarization insulating film 770 can be formed by the same method as above. resin, acrylic resin, polyimide amide resin, benzocyclobutene resin, polyamide resin Heat-resistant organic materials such as grease and epoxy resin can be used. The planarization insulating film 770 may be formed by stacking a plurality of insulating films formed from the same material. The planarization insulating film 770 may not be provided.

[0287] The signal line 710 is connected to the source and drain electrodes of the transistors 750 and 752. The signal line 710 is formed in the same process as the conductive film that functions as the transistor 75. 0, 752 source electrode and drain electrode, a conductive film formed in a different process, such as a gate The signal line 710 may be formed of a conductive film containing, for example, copper. When this material is used, there is little signal delay caused by wiring resistance, making it possible to display on a large screen. do.

[0288] The FPC terminal portion 708 includes a connection electrode 760, an anisotropic conductive film 780, and an FPC 71. 6. The connection electrode 760 is connected to the source and drain electrodes of the transistors 750 and 752. The connection electrode 760 is formed in the same process as the conductive film that functions as the drain electrode. The terminal of the PC 716 is electrically connected via an anisotropic conductive film 780 .

[0289] The first substrate 701 and the second substrate 705 may be made of, for example, glass. In addition, the first substrate 701 and the second substrate 705 may be flexible substrates. The flexible substrate may be, for example, a plastic substrate. do.

[0290] In addition, a structure 778 is provided between the first substrate 701 and the second substrate 705. The structure 778 is a columnar spacer obtained by selectively etching an insulating film. The distance (cell gap) between the first substrate 701 and the second substrate 705 is controlled. It should be noted that a spherical spacer may be used as the structure 778. In this embodiment, the structure 778 is provided on the first substrate 701 side. For example, a structure 778 may be provided on the second substrate 705 side, or Alternatively, the structure 778 may be provided on both the first substrate 701 and the second substrate 705. .

[0291] On the second substrate 705 side, there is a light-shielding film 738 that functions as a black matrix, A colored film 736 that functions as a color filter, a light-shielding film 738, and a film that contacts the colored film 736 An insulating film 734 is provided.

[0292] <Configuration example of a display device using a liquid crystal element as a display element> The display device 700 shown in FIG. 16 includes a liquid crystal element 775. The liquid crystal element 775 includes a conductive film The conductive film 774 is formed on the second substrate 705. The display device 700 shown in FIG. The alignment state of the liquid crystal layer 776 changes depending on the voltage applied to the conductive film 772 and the conductive film 774. This controls whether light is transmitted or not, allowing images to be displayed.

[0293] The conductive film 772 serves as a source electrode and a drain electrode of the transistor 750. The conductive film 772 is connected to a conductive film that functions as a pixel electrode. The conductive film 772 functions as a reflective electrode, that is, one of the electrodes of the display element. The display device 700 shown in FIG. 16 uses external light and emits light through a conductive film 772. and displays the reflected light through the colored film 736, which is a so-called reflective color liquid crystal display device.

[0294] The conductive film 772 may be a conductive film that transmits visible light or a conductive film that reflects visible light. A conductive film having a light-transmitting property in visible light can be used. For example, a material containing one of the elements selected from indium (In), zinc (Zn), and tin (Sn) As a conductive film that is reflective in visible light, for example, aluminum In this embodiment, the conductive film 772 may be formed using a material containing silver or silver. A conductive film that is reflective in visible light is used.

[0295] In addition, when a conductive film that is reflective to visible light is used as the conductive film 772, the conductive film The film may have a laminated structure. For example, an aluminum film having a thickness of 100 nm is formed as a lower layer, A 30 nm thick silver alloy film (e.g., an alloy film containing silver, palladium, and copper) is formed on the upper layer. The above-described structure provides the following excellent effects.

[0296] (1) The adhesiveness between the base film and the conductive film 772 can be improved. (2) The chemical solution This allows the aluminum film and the silver alloy film to be etched at the same time. The cross-sectional shape of the conductive film 772 can be made into a good shape (for example, a tapered shape). The reason for this is that the etching rate of aluminum films with chemicals is slower than that of silver alloy films. Or, after etching the upper silver alloy film, when the lower aluminum film is exposed, the silver alloy The electrons are taken from aluminum, which is a metal less noble than gold, in other words, a metal with a high tendency to ionize. The etching of the silver alloy film is suppressed by pulling out the film, and the etching of the underlying aluminum film is suppressed. This is because the progression is faster.

[0297] In the display device 700 shown in FIG. 16, the planarization insulating film 770 of the pixel section 702 The unevenness is formed in a part of the insulating film 770 by, for example, forming the planarization insulating film 770 with an organic resin film or the like. The reflection current can be formed by forming a film on the surface of the organic resin film and providing irregularities on the surface of the organic resin film. The conductive film 772 that functions as an electrode is formed along the above-mentioned unevenness. When light is incident on the conductive film 772, it is possible for the light to be diffused and reflected on the surface of the conductive film 772. This makes it possible to improve visibility.

[0298] The display device 700 shown in FIG. 16 is a reflective color liquid crystal display device. However, the conductive film 772 is not limited to this. For example, a conductive film that transmits visible light may be used. By using an electrically conductive film, a transmissive color liquid crystal display device may be formed. In the case of the device, the unevenness provided on the planarization insulating film 770 may not be provided. stomach.

[0299] Although not shown in FIG. 16, the conductive films 772 and 774 are in contact with the liquid crystal layer 776. Although not shown in FIG. Optical members (optical substrates) such as optical members, phase difference members, and anti-reflection members may be provided as appropriate. For example, circularly polarized light produced by a polarizing substrate and a retardation substrate may be used. Critters, sidelights, etc. may also be used.

[0300] When liquid crystal elements are used as display elements, thermotropic liquid crystals, low molecular weight liquid crystals, polymer liquid crystals, The liquid crystals that can be used include polymer dispersed liquid crystals, ferroelectric liquid crystals, and antiferroelectric liquid crystals. Depending on the conditions, the liquid crystal material can be in a cholesteric phase, a smectic phase, a cubic phase, or a chiral phase. It shows nematic phase, isotropic phase, etc.

[0301] In addition, when the in-plane switching method is adopted, a liquid crystal that exhibits a blue phase without using an alignment film may be used. The blue phase is one of the liquid crystal phases, and when the temperature of cholesteric liquid crystal is increased, the cholesteric The blue phase appears just before the transition from the black phase to the isotropic phase. Therefore, in order to improve the temperature range, a liquid crystal composition containing a chiral agent of several weight percent or more is used. The liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent is used in a liquid crystal layer. It has a short response time and is optically isotropic. It also contains a liquid crystal that exhibits a blue phase and a chiral agent. The liquid crystal composition does not require alignment treatment and has little viewing angle dependency. Since the rubbing process is unnecessary, electrostatic breakdown caused by the rubbing process can be prevented. Therefore, defects and damage to the liquid crystal display device during the manufacturing process can be reduced. do.

[0302] When a liquid crystal element is used as a display element, a TN (Twisted Nematic) ) mode, IPS (In-Plane-Switching) mode, FFS (Frin ge Field Switching) mode, ASM (Axially Symme tric aligned Micro-cell) mode, OCB(Optical Compensated Birefringence mode, FLC (Ferrero) lectric Liquid Crystal) mode, AFLC (AntiFerr It can be used in dielectric liquid crystal mode. .

[0303] Furthermore, normally black type liquid crystal display devices, such as those employing vertical alignment (VA) mode, The vertical alignment mode may be a transmission type liquid crystal display device. For example, MVA (Multi-Domain Vertical Alignment) ) mode, PVA (Patterned Vertical Alignment) mode Mode, ASV mode, etc. can be used.

[0304] <Display device using light-emitting elements as display elements> The display device 700 shown in FIG. 17 includes a light-emitting element 782. The light-emitting element 782 is made of a conductive film 17 includes a light-emitting layer 784, an EL layer 786, and a conductive film 788. The EL layer 786 of the light element 782 emits light, thereby displaying an image. do.

[0305] The conductive film 784 serves as a source electrode and a drain electrode of the transistor 750. The conductive film 784 is connected to a conductive film that functions as a pixel electrode. The conductive film 784 functions as an electrode, that is, one electrode of the display element. In this case, a conductive film that is light-transmitting or a conductive film that is reflective to visible light can be used. Examples of conductive films that are transparent to visible light include indium (In) and zinc (Zn). It is recommended to use a material containing one of the following elements: (Zn) and tin (Sn). As the reflective conductive film, for example, a material containing aluminum or silver is preferably used. stomach.

[0306] 17, the display device 700 has an insulating film over the planarization insulating film 770 and the conductive film 784. An insulating film 730 is provided. The insulating film 730 covers part of the conductive film 784. 782 has a top emission structure. Therefore, the conductive film 788 has a light transmitting property, and It transmits light emitted by the L layer 786. In this embodiment, the top emission The structure is exemplified, but is not limited to, for example, a bottom emission structure in which light is emitted to both the conductive film 784 and the conductive film 788; It can also be applied to al-emission structures.

[0307] A colored film 736 is provided at a position overlapping the light-emitting element 782, and a colored film 736 is provided at a position overlapping the insulating film 730. A light-shielding film 738 is provided in the position where the light-shielding film 738 is to be drawn, the wiring portion 711, and the source driver circuit portion 704. The colored film 736 and the light-shielding film 738 are covered with an insulating film 734. In addition, the space between the light emitting element 782 and the insulating film 734 is filled with a sealing film 732. In the display device 700 shown in FIG. 1, a configuration in which a colored film 736 is provided is exemplified. For example, when the EL layer 786 is formed by coloring, The film 736 may not be provided.

[0308] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0309] (Fourth embodiment) In this embodiment, a display device including a semiconductor device of one embodiment of the present invention will be described with reference to FIG. This will be used to explain.

[0310] The display device shown in FIG. 18A has a region having pixels of a display element (hereinafter referred to as a pixel portion 502). ) and a circuit section ( hereinafter referred to as a drive circuit section 504), and a circuit having a function of protecting the element (hereinafter referred to as a protection circuit 50 6) and a terminal portion 507. Note that the protection circuit 506 is not provided in the configuration. That's fine.

[0311] A part or the whole of the driver circuit portion 504 is formed on the same substrate as the pixel portion 502. This makes it possible to reduce the number of parts and terminals. When a part or all of the pixel portion 502 is not formed on the same substrate, the driving circuit A part or the whole of the path portion 504 is COG or TAB (Tape Automated Bearing). It can be implemented by

[0312] The pixel section 502 is arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). The display device has a circuit for driving a plurality of display elements (hereinafter referred to as pixel circuit 501), The path section 504 is a circuit (hereinafter referred to as a gate driver) that outputs a signal (scanning signal) for selecting a pixel. 504a), for supplying signals (data signals) for driving the display elements of the pixels. The source driver 504b includes a driving circuit such as the circuit (hereinafter referred to as a source driver 504b).

[0313] The gate driver 504a includes a shift register and the like. A signal for driving the shift register is inputted through the terminal section 507, and a signal for outputting the shift register is outputted. For example, the gate driver 504a receives a start pulse signal, a clock signal, etc. The gate driver 504a receives a scanning signal and outputs a pulse signal. The gate has a function of controlling the potential of the scanning lines GL_1 to GL_X. A plurality of drivers 504a are provided, and the plurality of gate drivers 504a drive the scanning lines GL_1 to Alternatively, the gate driver 504a may control the GL_X by dividing it into the initialization signal However, the gate driver 50 has a function of supplying 4a may also provide other signals.

[0314] The source driver 504b includes a shift register and the like. Through the terminal section 507, signals for driving the shift register as well as the source of the data signal are transmitted. The source driver 504b receives a signal (image signal) that is to be output from the pixel circuit The source driver 504b has a function of generating a data signal to be written to the source driver 501. A data signal is generated in accordance with a pulse signal obtained by inputting a start pulse, a clock signal, etc. The source driver 504b has a function of controlling the output of a data signal. The data lines DL_1 to DL_Y are connected to the data lines DL_2 through DL_Y. Alternatively, the source driver 504b may have a function of supplying an initialization signal. However, the present invention is not limited to this, and the source driver 504b may also supply other signals. It is possible.

[0315] The source driver 504b is configured using, for example, a plurality of analog switches. The source driver 504b sequentially turns on a plurality of analog switches, A signal obtained by time-sharing an image signal can be output as a data signal.

[0316] Each of the plurality of pixel circuits 501 is connected to one of the plurality of scanning lines GL to which a scanning signal is applied. A pulse signal is input via the data line DL, and a data signal is given via one of the data lines DL. Each of the pixel circuits 501 is connected to a gate driver 504a controls writing and holding of data of the data signal. The second pixel circuit 501 is connected to a gate driver GL_m (where m is a natural number equal to or less than X) via a scanning line GL_m. A pulse signal is input from 504a, and the data line DL_n ( A data signal is input from the source driver 504b via the input terminal 504a (n is a natural number equal to or less than Y).

[0317] The protection circuit 506 shown in FIG. 18(A) is, for example, a gate driver 504a and a pixel circuit 5 01. Alternatively, the protection circuit 506 is connected to the scanning line GL, which is the wiring between the source driver The data line DL is connected between the driver 504b and the pixel circuit 501. The protection circuit 506 can be connected to the wiring between the gate driver 504a and the terminal section 507. Alternatively, the protection circuit 506 may be formed by wiring between the source driver 504b and the terminal section 507. The terminal section 507 can be connected to a power supply and a line from an external circuit to the display device. This refers to the part where terminals for inputting control signals and image signals are provided.

[0318] When a potential outside a certain range is applied to the wiring to which the protection circuit 506 is connected, the protection circuit 506 This is a circuit that brings one wire into electrical continuity with another wire.

[0319] As shown in FIG. 18A, a pixel section 502 and a driver circuit section 504 are provided with a protection circuit 50. 6, ESD (Electro Static Discharge: This can improve the resistance of the display device to overcurrents caused by electrostatic discharges and the like. However, the configuration of the protection circuit 506 is not limited to this. For example, A configuration in which a protection circuit 506 is connected, or a configuration in which the protection circuit 506 is connected to the source driver 504b Alternatively, a configuration in which a protection circuit 506 is connected to the terminal portion 507 may be used. It can also be done as follows.

[0320] In FIG. 18A, the gate driver 504a and the source driver 504b Therefore, although an example in which the driver circuit portion 504 is formed is shown, the present invention is not limited to this configuration. For example, only the gate driver 504a is formed, and a separately prepared source driver circuit is formed. A substrate (for example, a drive circuit substrate formed of a single crystal semiconductor film or a polycrystalline semiconductor film) is implemented. It may also be configured to be equipped with

[0321] Furthermore, the plurality of pixel circuits 501 shown in FIG. 18(A) may be, for example, a configuration shown in FIG. 18(B). It can be said that:

[0322] The pixel circuit 501 shown in FIG. 18B includes a liquid crystal element 570, a transistor 550, and a capacitor. The transistor 550 may be any of the transistors described in the previous embodiments. can be applied.

[0323] The potential of one of the pair of electrodes of the liquid crystal element 570 is set appropriately according to the specifications of the pixel circuit 501. The orientation state of the liquid crystal element 570 is set by the written data. A common potential is applied to one of a pair of electrodes of the liquid crystal element 570 included in each of the pixel circuits 501. A common potential may be applied to the pair of liquid crystal elements 570 of the pixel circuits 501 in each row. One of the electrodes may be given a different potential.

[0324] For example, the display device including the liquid crystal element 570 can be driven in a TN mode, an STN mode, or the like. Mode, VA mode, ASM (Axially Symmetric Aligned Mode) Micro-cell mode, OCB (Optically Compensated Birefringence mode, FLC (Ferroelectric Liquid Crystal id Crystal) mode, AFLC (AntiFerroelectric Li Quid Crystal) mode, MVA mode, PVA (Patterned Ve Vertical Alignment mode, IPS mode, FFS mode, or TBA (Transverse Bend Alignment) mode may also be used. In addition to the above-mentioned driving method, the display device can also be driven by an ECB (Electric Carrier Board) or the like. Ally Controlled Birefringence mode, PDLC (P Polymer Dispersed Liquid Crystal (PNLC) mode (Polymer Network Liquid Crystal) mode, guest However, there are various types of liquid crystal elements and their driving methods, and they are not limited to these. A variety of materials can be used.

[0325] In the pixel circuit 501 in the mth row and the nth column, the source electrode or the drain electrode of the transistor 550 One of the electrodes is electrically connected to the data line DL_n, and the other is connected to a pair of electrodes of the liquid crystal element 570. The gate electrode of the transistor 550 is electrically connected to the other of the electrodes of the scan line G. L_m. The transistor 550 can be turned on or off. This provides a function of controlling the writing of data signals.

[0326] One of the pair of electrodes of the capacitor 560 is connected to a wiring to which a potential is supplied (hereinafter, a potential supply line VL ) and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 570. The value of the potential of the potential supply line VL is set appropriately according to the specifications of the pixel circuit 501. The capacitor 560 functions as a storage capacitor for storing written data.

[0327] For example, in a display device having the pixel circuit 501 of FIG. 18(B), The pixel circuits 501 in each row are sequentially selected by the gate driver 504a shown in FIG. 550 is turned on to write data of the data signal.

[0328] The pixel circuit 501 in which data has been written is turned off by turning off the transistor 550. By repeating this process for each row, an image can be displayed.

[0329] Furthermore, the plurality of pixel circuits 501 shown in FIG. 18(A) may be, for example, a configuration shown in FIG. 18(C). It can be said that:

[0330] The pixel circuit 501 shown in FIG. 18C includes transistors 552 and 554 and a capacitor. The transistor 552 and the transistor 554 The transistor described in the above embodiment can be used for either one or both of the above. .

[0331] One of the source and drain electrodes of the transistor 552 is supplied with a data signal. The transistor 5 is electrically connected to a wiring (hereinafter referred to as a data line DL_n). The gate electrode 52 is connected to a wiring (hereinafter referred to as a scanning line GL_m) to which a gate signal is applied. electrically connected.

[0332] Transistor 552 is turned on or off to transfer the data of the data signal. It has the function of controlling the writing of data.

[0333] One of the pair of electrodes of the capacitor 562 is connected to a wiring to which a potential is applied (hereinafter, a potential supply line VL _a), and the other is electrically connected to the source electrode and drain electrode of the transistor 552. The second electrode is electrically connected to the other of the first and second electrodes.

[0334] The capacitor 562 functions as a storage capacitor for holding written data.

[0335] One of the source electrode and the drain electrode of the transistor 554 is connected to the potential supply line VL_a. Furthermore, the gate electrode of transistor 554 is electrically connected to the It is electrically connected to the other of the source electrode and the drain electrode.

[0336] One of the anode and cathode of the light emitting element 572 is electrically connected to the potential supply line VL_b. The other is electrically connected to the other of the source electrode and drain electrode of the transistor 554. will be done.

[0337] The light emitting element 572 may be, for example, an organic electroluminescence element (also known as an organic EL element). However, the light emitting element 572 is not limited to this. Alternatively, an inorganic EL element made of an inorganic material may be used.

[0338] A high power supply potential VDD is applied to one of the potential supply lines VL_a and VL_b. and the other is supplied with a low power supply potential VSS.

[0339] In a display device having the pixel circuit 501 of FIG. 18(C), for example, The pixel circuits 501 in each row are sequentially selected by the gate driver 504a, and the transistors 552 are turned on. The data signal is written by turning it on.

[0340] The pixel circuit 501 to which the data has been written is turned off by turning off the transistor 552. Furthermore, the potential of the transistor 554 changes depending on the potential of the written data signal. The amount of current flowing between the source electrode and the drain electrode is controlled, and the light emitting element 572 The light is emitted at a brightness that corresponds to the flow rate. By repeating this process row by row, an image can be displayed.

[0341] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0342] (Embodiment 5) In this embodiment, a display module and an electronic device including a semiconductor device according to one embodiment of the present invention will be described. This will be explained with reference to FIGS. 19 and 20.

[0343] The display module 8000 shown in FIG. 19 includes an upper cover 8001 and a lower cover 8002. Between them, touch panel 8004 connected to FPC8003 and Display panel 8006, backlight 8007, frame 8009, printed circuit board 801 0, has battery 8011.

[0344] The semiconductor device of one embodiment of the present invention can be used for the display panel 8006, for example.

[0345] The upper cover 8001 and the lower cover 8002 are connected to the touch panel 8004 and the display panel The shape and dimensions can be changed as needed to fit the size of the 8006.

[0346] The touch panel 8004 is a resistive or capacitive touch panel. The display panel 8006 can be used by overlapping it with the opposing substrate (sealing substrate). It is also possible to provide the display panel 8 with a touch panel function. It is also possible to provide an optical sensor in each pixel of 006 to make it an optical touch panel.

[0347] The backlight 8007 has a light source 8008. In FIG. Although the configuration in which the light source 8008 is disposed on the base 8007 has been illustrated, the present invention is not limited to this. For example, a light source 8008 is arranged at the end of a backlight 8007, and a light diffusion plate is further used. In addition, when a self-luminous light emitting element such as an organic EL element is used, or when a reflective In the case of a flat panel or the like, the backlight 8007 may not be provided.

[0348] The frame 8009 has a function of protecting the display panel 8006 and also a function of preventing the movement of the printed circuit board 8010. It also functions as an electromagnetic shield to block electromagnetic waves generated by the operation of the The frame 8009 may also function as a heat sink.

[0349] The printed circuit board 8010 includes a power supply circuit, a signal circuit for outputting a video signal and a clock signal. The power supply circuit is provided with a signal processing circuit. Alternatively, the power source may be a battery 8011 provided separately. This can be omitted if a commercial power source is used.

[0350] In addition, the display module 8000 includes components such as a polarizing plate, a retardation plate, and a prism sheet. It may also be provided in addition.

[0351] 20(A) to 20(G) are diagrams showing electronic devices. These electronic devices are housed in a housing. A body 9000, a display unit 9001, a speaker 9003, operation keys 9005 (power switch, includes an operation switch), a connection terminal 9006, a sensor 9007 (force, displacement, position, speed, Acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electricity Measures field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared It may have a microphone 9008, etc.

[0352] The electronic devices shown in FIGS. 20A to 20G can have various functions. For example, functions to display various information (still images, videos, text images, etc.) on the display, Touch panel function, calendar, date or time display function, various software ( It has the function of controlling processing by using a program, wireless communication function, and various functions using wireless communication function. Functions for connecting to computer networks, transmitting various data using wireless communication functions, or receiving the program or data recorded on the recording medium, and It is to be noted that the functions shown in FIGS. 20(A) to 20(G) can be implemented. The functions that the electronic device shown in the figure can have are not limited to these, and it may have various functions. Although not shown in FIGS. 20(A) to 20(G), the electronic device may include: The electronic device may have a plurality of display units. The function to take pictures, take videos, and save the images to a recording medium (external or built-in to the camera) ) and a function to display the captured image on the display unit.

[0353] The electronic devices shown in FIGS. 20A to 20G will be described in detail below.

[0354] FIG. 20A is a perspective view showing a mobile information terminal 9100. The display portion 9001 is flexible. The display unit 9001 can be incorporated along the screen. It is equipped with a touch panel, and can be operated by touching the screen with a finger or a stylus. By touching the icon displayed on the display 9001, the application can be started. can.

[0355] 20(B) is a perspective view showing a portable information terminal 9101. For example, the device has one or more functions selected from a telephone, a notebook, an information viewing device, etc. Specifically, it can be used as a smartphone. Although the speaker 9003, the connection terminal 9006, the sensor 9007, etc. are omitted in the illustration, 20(A) can be provided in the same position as the mobile information terminal 9100 shown in FIG. The information terminal 9101 can display text and image information on multiple surfaces. For example, Three operation buttons 9050 (also called operation icons or simply icons) are displayed on the display unit 900. 9051 shown in a dashed rectangle can be displayed on one side of the display unit 90. 01. An example of the information 9051 is an e-mail A display that notifies you of incoming calls, SNS (social networking services), etc. , subject of email or SNS, sender name of email or SNS, date and time, time, The remaining battery level, antenna reception strength, etc. Or, information 9051 is displayed. In place of the information 9051, an operation button 9050 or the like may be displayed.

[0356] 20C is a perspective view showing a portable information terminal 9102. , and has the function of displaying information on three or more surfaces of the display unit 9001. An example is shown in which information 9053 and information 9054 are displayed on different sides. The user of the portable information terminal 9102 stores the portable information terminal 9102 in the breast pocket of the clothes. In this state, the display (information 9053 in this case) can be confirmed. The telephone number or name of the caller is displayed in a position that can be observed from above the mobile information terminal 9102. The user can view the display without taking the mobile information terminal 9102 out of his pocket. You can check the call and decide whether to accept it or not.

[0357] 20(D) is a perspective view showing a wristwatch-type portable information terminal 9200. The 9200 is suitable for mobile phone calls, e-mail, document browsing and writing, music playback, and internet communications. It is possible to run various applications such as computer games. The display surface of the display unit 9001 is curved, and the display is performed along the curved display surface. In addition, the portable information terminal 9200 can perform short-distance wireless communication according to a communication standard. For example, by communicating with a wireless headset, handset The mobile information terminal 9200 also has a connection terminal 9006. It has a connector and can directly exchange data with other information terminals. Charging can also be performed via the connection terminal 9006. It may also be possible to supply power wirelessly without going through 6.

[0358] 20(E), (F), and (G) are perspective views showing a foldable portable information terminal 9201. FIG. 20(E) is a perspective view of the portable information terminal 9201 in an unfolded state, and FIG. (F) shows the mobile information terminal 9201 being changed from one of the unfolded state and the folded state to the other. 20(G) is a perspective view of the portable information terminal 9201 in a folded state. The portable information terminal 9201 is highly portable when folded, and is easily portable when unfolded. When the display is turned on, the seamless, wide display area provides excellent visibility of the display. The display unit 9001 of the display device 01 is made up of three housings 9000 connected by hinges 9055. The two housings 9000 are supported by the hinge 9055. This allows the portable information terminal 9201 to be reversibly transformed from an unfolded state to a folded state. For example, the portable information terminal 9201 can be bent with a radius of curvature of 1 mm or more and 150 mm or less. It can be done.

[0359] The electronic device described in this embodiment has a display unit for displaying some information. However, the semiconductor device of one embodiment of the present invention is an electronic device that does not have a display portion. The present invention can also be applied to the display unit of the electronic device described in this embodiment. In the case of a display device, it is possible to use a flexible display device that can display information along a curved display surface, or a folding display device. Although a foldable display unit configuration has been exemplified, the present invention is not limited to this. A display may be provided on the surface.

[0360] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done. [Example]

[0361] In this example, the analytical sample 600 shown in FIG. 21(A) and the analytical sample 600 shown in FIG. 21(B) A transistor 650 shown in FIG. 1 was fabricated, and a sample for analysis 600 was analyzed by SIMS and The electrical characteristics of Transistor 650 were measured.

[0362] 21B and 21C are top views of the transistor 650 shown in FIG. 21B is a top view of the transistor 170. 21(C) is a cross-sectional view of the transistor 650 in the channel length direction. 1 is a cross-sectional view in the channel width direction.

[0363] In this example, the analytical sample 600 was prepared using the following sample B1 and sample B2. Sample B2 was fabricated. As the transistor 650, Samples C1 and C2 shown below were fabricated. Sample B1 and Sample C1 are semiconductor devices of one embodiment of the present invention, and Sample Samples B2 and C2 are comparative semiconductor devices.

[0364] First, the method for producing the analytical sample 600 produced in this example will be described below. .

[0365] (Sample B1 and Sample B2) First, a conductive film was formed on the substrate 602, and then the conductive film was removed. A glass substrate was used for the conductive film. The conductive film was formed by using a sputtering apparatus. An etching device was used.

[0366] Next, insulating films 606 and 607 were formed on the substrate 602. The insulating film 606 had a thickness of A 400 nm silicon nitride film was formed using a PECVD apparatus. As the film thickness, a silicon oxynitride film having a thickness of 50 nm was formed using a PECVD apparatus.

[0367] Next, an oxide semiconductor film 608a was formed over the insulating film 607. The formation conditions of the oxide semiconductor film 608a are different from those in Example 2.

[0368] The oxide semiconductor film 608a of the sample B1 was an IGZO film having a thickness of 35 nm, which was formed by sputtering. The oxide semiconductor film 608a of Sample B1 was formed using a ring apparatus. The substrate temperature was set to 170°C, and argon gas with a flow rate of 100 sccm and cm of oxygen gas was introduced into the chamber, and the pressure was set to 0.6 Pa. 2500W to a polycrystalline target (In:Ga:Zn=1:1:1.2 [atomic ratio]) The film was formed by applying an AC power of 1000 W.

[0369] The oxide semiconductor film 608a of sample B2 was an IGZO film having a thickness of 35 nm, which was formed by sputtering. The oxide semiconductor film 608a of Sample B2 was formed using a ring apparatus. The substrate temperature was set to 170°C, and argon gas with a flow rate of 100 sccm and cm of oxygen gas was introduced into the chamber, and the pressure was set to 0.6 Pa. A 2500W A laser was applied to a polycrystalline target (In:Ga:Zn=1:1:1 [atomic ratio]). C power was applied to form the film.

[0370] Next, a first heat treatment was carried out at 450° C. in a nitrogen atmosphere. Heat treatment for 1 hour at 450°C in a nitrogen and oxygen mixed gas atmosphere. It was decided.

[0371] Next, a conductive film is formed over the insulating film 607 and the oxide semiconductor film 608a. The conductive film was a 50 nm thick tungsten film and a 400 nm thick tungsten film. A 100 nm thick aluminum film and a 100 nm thick titanium film were deposited in a vacuum using a sputtering device. The conductive film was continuously formed in a dry etching apparatus. Ta.

[0372] Next, a chemical solution is applied from above the oxide semiconductor film 608a, and the surface of the oxide semiconductor film 608a is The washing method was as follows: 100 times the amount of 85% phosphoric acid solution was used. The diluted solution was applied to the oxide semiconductor film 608a and washed for 15 seconds.

[0373] Next, an insulating film 614 and an insulating film 616 were formed over the oxide semiconductor film 608a. As the substrate 614, a silicon oxynitride film having a thickness of 50 nm is formed using a PECVD apparatus. The insulating film 616 was a silicon oxynitride film having a thickness of 400 nm, which was deposited by PECVD. The insulating film 614 and the insulating film 616 were formed using a PECVD apparatus. The layers were formed continuously in a vacuum.

[0374] The conditions for forming the insulating film 614 were a substrate temperature of 220° C. and a silica flow rate of 50 sccm. Nitrogen gas and nitrous oxide gas at a flow rate of 2000 sccm were introduced into the chamber, and the pressure was increased to 2 The pressure was set to 0 Pa, and 100 W of RF power was applied between the parallel plate electrodes installed in the PECVD device. The insulating film 616 was formed under the conditions of a substrate temperature of 220° C. and a flow rate of 1000 kJ / cm. Silane gas at a flow rate of 160 sccm and nitrous oxide gas at a flow rate of 4000 sccm were introduced into the chamber. The pressure was set to 200 Pa, and the gas was introduced into the chamber between the parallel plate electrodes installed in the PECVD device. The film was formed by supplying RF power of 1500 W to the substrate.

[0375] Next, a second heat treatment was carried out in a mixed gas atmosphere of nitrogen and oxygen. The mixture was heated at 350°C for 1 hour.

[0376] Next, after the second heat treatment, the following three steps were carried out only on sample B1.

[0377] <1, ITSO film formation process> An ITSO film having a thickness of 5 nm was formed on the insulating film 616 using a sputtering device. The target composition used for the ITSO film was In2O3:SnO2:SiO 2 = 85:10:5 [wt %].

[0378] <2. Oxygen addition treatment process> Next, oxygen addition treatment was performed on the ITSO film. Using this device, oxygen gas was introduced into the chamber at a flow rate of 250 sccm, and the pressure was set to 15 Pa. Parallel plate electrodes installed in the ashing device so that a bias is applied to the substrate side. An RF power of 4500 W was supplied between the electrodes.

[0379] <3, ITSO film removal process> Next, the ITSO film was removed to expose the insulating film 616. For this purpose, a wet etching device is used to apply a 5% oxalic acid solution onto the insulating film 616. After etching for 300 seconds, 0.5% hydrofluoric acid was applied to the insulating film 61 6 and etched for 15 seconds.

[0380] Next, in both Sample B1 and Sample B2, an insulating film 618 was formed on the insulating film 616. As the film 618, a silicon nitride film having a thickness of 100 nm is formed using a PECVD apparatus. The conditions for forming the insulating film 618 were a substrate temperature of 350° C. and a flow rate of 50 sccm. Run gas, nitrogen gas with a flow rate of 5000 sccm, and ammonia gas with a flow rate of 100 sccm The pressure was set to 100 Pa, and the parallel flat plate installed in the PECVD device was The film was formed by supplying 1000 W of RF power between the electrodes of the plate.

[0381] Next, a third heat treatment was carried out. The third heat treatment was carried out at 250° C. in a nitrogen atmosphere. It was time.

[0382] Through the above steps, samples B1 and B2 of this example were fabricated.

[0383] Next, the oxide semiconductor film 608a and the insulating films 614 and 616 of the samples B1 and B2 fabricated as described above were SIMS analysis was performed to measure the indium concentration in the 16,618 film. The analytical results of sample B1 are shown in FIG. 22(A), and the analytical results of sample B2 are shown in FIG. 22(B). In Figures 22(A) and 22(B), the horizontal axis represents the depth (nm) and the vertical axis represents the indium concentration (a toms / cm 3 ) respectively.

[0384] From the results shown in FIGS. 22(A) and 22(B), it is clear that the sample B1 has a high thermal conductivity at the interface between the insulating film 616 and the insulating film 618. Indium is 5×10 16 atoms / cm 3 It was confirmed at concentrations above 100. In the sample B2, the indium concentration was 5×10 16 atoms / cm 3 In the above SIMS analysis, the indium content was The lower limit is 1 x 10 15 atoms / cm 3 The following is the result.

[0385] Furthermore, when comparing sample B1 and sample B2, the insulating film 616 and the insulating film 618 of sample B1 The amount of indium detected near the interface between the insulating film 616 and the insulating film 618 of sample B2 was This is greater than the amount of indium detected nearby.

[0386] From the results shown in FIGS. 22(A) and 22(B), it is clear that sample B1 has a function of suppressing oxygen release. The indium in the ITSO film used as a functional film was converted into the insulating film 61 during the oxygen addition treatment. 6, indium was detected near the interface between the insulating film 616 and the insulating film 618. On the other hand, in the sample B2, the ITSO film formation process and the oxygen addition process were performed on the insulating film 616. Since the treatment process and the ITSO film removal process are not performed, the surface of the insulating film 616, in other words, As a result, no indium was detected near the interface between the insulating film 616 and the insulating film 618.

[0387] Since the insulating film 616 contains oxygen, if the insulating film 616 contains excess oxygen, Even in this case, oxygen, one of the main components, may not be accurately measured by SIMS analysis. For example, even if the insulating film 616 contains oxygen exceeding the stoichiometric composition, In SIMS analysis, it can be difficult to measure oxygen beyond the stoichiometric composition. However, as shown in the semiconductor device of one embodiment of the present invention, oxygen is released onto the insulating film 616. An ITSO film is formed as a film having the function of suppressing the outflow, and an insulating film is formed through the ITSO film. When oxygen is added to the insulating film 616, as shown in FIG. 22(A), In other words, indium is detected near the interface between the insulating film 616 and the insulating film 618. Therefore, in order to confirm whether the step of adding oxygen to the insulating film 616 has been performed, This can be confirmed by measuring the impurity concentration near the surface of the film 616, in this case the indium concentration. There are cases where this happens.

[0388] As described above, the oxygen in the insulating film 616 cannot be accurately measured by SIMS analysis. In this case, the physical properties of the film in contact with the insulating film 616, It is important to analyze the indium concentration near the interface with 8.

[0389] Next, a method for manufacturing the transistor 650 manufactured in this example will be described below.

[0390] (Sample C1 and Sample C2) Samples C1 and C2 have a channel length L of 3 μm and a channel width W of 50 μm in the substrate. Five μm-sized transistors were fabricated.

[0391] First, a conductive film is formed on a substrate 602, and then the conductive film is processed to form a conductive film 604. As the conductive film 604, a tungsten film having a thickness of 100 nm was deposited by a sputtering apparatus. It was formed using

[0392] Next, insulating films 606 and 607 were formed on the substrate 602 and the conductive film 604 .

[0393] Next, an oxide semiconductor film 608a is formed over the insulating film 607. The oxide semiconductor film 608 was formed by processing the oxide semiconductor film into an island shape. The conditions for forming the oxide semiconductor film 608 are different.

[0394] The oxide semiconductor film 608 of Sample C1 was the oxide semiconductor film 608 of Sample B1 shown above. After forming under the same conditions as in a, it was processed into an island shape.

[0395] The oxide semiconductor film 608 of Sample C2 was the oxide semiconductor film of Sample B2 shown above. After being formed under the same conditions as 608a, it was processed into an island shape.

[0396] Next, a first heat treatment was carried out.

[0397] Next, a conductive film is formed over the insulating film 607 and the oxide semiconductor film 608 and processed. The conductive films 612a and 612b were formed by the above process. A tungsten film with a thickness of 50 nm, an aluminum film with a thickness of 400 nm, and a 100 nm The titanium film was formed in succession in a vacuum using a sputtering device.

[0398] Next, an insulating film 614 and an insulating film 616 are formed over the oxide semiconductor film 608 and the conductive films 612a and 612b. A velum 616 was formed.

[0399] Next, a second heat treatment was carried out.

[0400] Next, sample C1 was subjected to the ITSO film formation process and oxygen addition process in the same manner as sample B1. In addition, the sample C2 was treated with the ITO film removal process, similar to the sample B2 described above. The TSO film formation step, oxygen addition treatment step, and ITSO film removal step were not performed.

[0401] Next, an insulating film 618 was formed on the insulating film 616 .

[0402] Next, an opening 642c reaching the conductive film 612b and an opening 642b reaching the conductive film 604 are formed. The openings 642a, 642b, and 642c were formed by dry etching. The film was formed using a chipping apparatus.

[0403] Next, a conductive film is formed on the insulating film 618 so as to cover the openings 642a, 642b, and 642c. The conductive film was processed to form conductive films 620a and 620b. , 620b, a 100 nm thick ITSO film is formed using a sputtering device. The composition of the target used for the ITSO film was the same as that used in the ITSO film formation process described above. The composition was the same as that of the previous one.

[0404] Next, a third heat treatment was performed.

[0405] Samples C1 and C2 were fabricated through the above steps.

[0406] Next, the electrical characteristics of the transistors of Samples C1 and C2 fabricated as described above were measured. The electrical characteristics of 1 and C2 are shown in Figures 23(A) and 23(B).

[0407] FIG. 23(A) shows the electrical characteristics of sample C1, and FIG. 23(B) shows the electrical characteristics of sample C2. The electrical characteristics are shown in Fig. 23(A) and (B). The horizontal axis represents the gate voltage (Vg). The vertical axis represents the drain current (Id), and the data for five transistors are overlaid. The voltage between the source electrode and the drain electrode (Vd) is set to 1 V and 10 V. , Vg was applied from −15 V to 20 V in 0.5 V intervals.

[0408] From the results shown in FIGS. 23(A) and 23(B), it can be seen that in sample C1 according to one embodiment of the present invention, multiple traces It can be seen that there is little variation in the transistor. On the other hand, in the comparative sample C2, It is confirmed that there is a large variation among multiple transistors. It was confirmed that the transistor characteristics were normally on.

[0409] The difference in transistor characteristics between the samples C1 and C2 is that the insulating films 614 and 616 are made of oxygen-added material. This suggests that this is due to the presence or absence of a heat treatment process. An ITSO film is formed on the insulating film 614, 616, and oxygen is added to the insulating film 614, 616 through the ITSO film. This suggests that excess oxygen can be suitably added to the insulating films 614 and 616. Furthermore, the excess oxygen compensates for oxygen vacancies in the oxide semiconductor film 608, This suggests that a transistor with little variation and good rising characteristics was formed. can be.

[0410] From the above, the transistor of sample C1 of this example has little variation and high reliability. It was shown to be a high-performance transistor.

[0411] As described above, the configuration shown in this embodiment can be used in appropriate combination with other embodiments. . [Explanation of symbols]

[0412] 100 transistors 100A transistor 100B transistor 102 Circuit Board 104 Conductive film 106 insulating film 107 Insulating film 108 Oxide semiconductor film 108a Oxide semiconductor film 108b Oxide semiconductor film 108c Oxide semiconductor film 112a Conductive film 112b Conductive film 114 insulating film 116 Insulating film 117 Oxide semiconductor film 118 insulating film 120 Conductive film 120a Conductive film 120b Conductive film 130 membrane 139 Oxygen 141a opening 141b opening 142 Etchant 142a opening 142b opening 142c opening 150 transistors 160 transistors 170 transistors 180b Oxide semiconductor film 200 Semiconductor device 202 Substrate 204 insulating film 206 Insulating film 230 membrane 239 Oxygen 242 Etchant 501 pixel circuit 502 pixel section 504 Drive circuit section 504a Gate Driver 504b source driver 506 Protection circuit 507 Terminal section 550 transistors 552 transistor 554 Transistor 560 Capacitor 562 Capacitor 570 Liquid Crystal Devices 572 Light-emitting element 600 analytical samples 602 Substrate 604 Conductive film 606 Insulating film 607 Insulating film 608 Oxide semiconductor film 608a Oxide semiconductor film 612a Conductive film 612b Conductive film 614 Insulating film 616 Insulating film 618 Insulating film 620a Conductive film 620b Conductive film 642a opening 642b opening 642c opening 650 transistors 700 Display device 701 PCB 702 pixel section 704 Source driver circuit section 705 PCB 706 Gate driver circuit section 708 FPC terminal section 710 Signal Line 711 Wiring section 712 Sealing material 716 FPC 730 insulating film 732 Sealing film 734 Insulating Film 736 Colored film 738 Light-shielding film 750 transistors 752 transistors 760 connecting electrode 764 insulating film 766 Insulating Film 767 Oxide semiconductor film 768 insulating film 770 Planarization insulating film 772 Conductive film 774 Conductive film 775 Liquid Crystal Elements 776 Liquid Crystal Layer 778 Structure 780 Anisotropic Conductive Film 782 Light-emitting element 784 Conductive Film 786 EL layer 788 Conductive Film 790 Capacitor 8000 Display Module 8001 Top cover 8002 Lower cover 8003 FPC 8004 Touch Panel 8005 FPC 8006 Display Panel 8007 Backlight 8008 light source 8009 Frame 8010 Printed Circuit Board 8011 Battery 9000 chassis 9001 Display section 9003 Speaker 9005 Operation key 9006 Connection terminal 9007 Sensor 9008 Microphone 9050 Operation button 9051 Information 9052 Information 9053 Information 9054 Information 9055 Hinge 9100 Mobile Information Terminal 9101 Mobile Information Terminal 9102 Mobile Information Terminal 9200 Mobile Information Terminal 9201 Mobile Information Terminal

Claims

[Claim 1] an oxide semiconductor film; a first insulating film having a region located above the oxide semiconductor film; a second insulating film having a region located above the first insulating film, the first insulating film has a first region and a second region located above the first region; the second insulating film has a third region and a fourth region located above the third region, The semiconductor device, wherein the indium concentration in the third region is lower than the indium concentration in the fourth region.

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