Semiconductor device

Abstract

To provide a highly reliable semiconductor device.SOLUTION: A semiconductor device includes a gate electrode, a gate insulating film over the gate electrode, a semiconductor film provided at a position overlapping with the gate electrode with a gate insulating film interposed therebetween, a source electrode and a drain electrode in contact with the semiconductor film, and an oxide film over the semiconductor film and the source electrode and the drain electrode, wherein an end portion of the semiconductor film and an end portion of the source electrode or the drain electrode in a region overlapping with the semiconductor film have a gap in a channel width direction, and the semiconductor film and the oxide film include a metal oxide including In, Ga, and Zn, and an atomic ratio of In in the oxide film is lower than that in the semiconductor film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device that utilizes semiconductor characteristics. [Background technology]

[0002] The high mobility obtained by crystalline silicon and the low mobility obtained by amorphous silicon A new semiconductor material called oxide semiconductor has been developed that has the uniform device characteristics. Metal oxides that exhibit conductive properties are attracting attention. Metal oxides are used for a variety of purposes. For example, indium oxide, a well-known metal oxide, is used in liquid crystal displays and light-emitting devices. It is used as a transparent pixel electrode in devices. Examples of oxides include tungsten oxide, tin oxide, indium oxide, and zinc oxide. Transistors using metal oxides that exhibit such semiconducting properties in the channel formation region are already known. (Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-123861 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-96055 Summary of the Invention [Problem to be solved by the invention]

[0004] By the way, transistors used in semiconductor devices tend to deteriorate over time in electrical characteristics such as threshold voltage. It is desirable that the change due to the change in the voltage be small. In this case, the potential output from the circuit is easily affected by the threshold voltage of the transistor. Therefore, in the case of a circuit composed of unipolar transistors, the threshold voltage allowed for the transistors is The voltage range tends to be narrower than that of CMOS circuits. For semiconductor devices with circuits made up of transistors, the electrical characteristics deteriorate over time. It is important to use transistors with small changes in properties in order to ensure reliability.

[0005] In addition, the electrical characteristics required for semiconductor elements vary depending on the circuit design of the semiconductor device. However, when the gate voltage is 0V or less, it is in a non-conducting state, that is, it is normally off. For n-channel transistors, the threshold voltage must be greater than 0V. Therefore, it is desirable that the threshold voltage of a transistor not only changes little with age, but also It is required to have an initial value that satisfies the requirement of normally off.

[0006] Based on the above-mentioned technical background, the present invention provides a semiconductor device having a normally-off transistor. Another object of the present invention is to provide a semiconductor device having high reliability. Provision of such information is one of the challenges. [Means for solving the problem]

[0007] The initial value of the threshold voltage of the transistor and the amount of change in the threshold voltage due to deterioration over time are The relationship between the layout and the layout of the conductive film that functions as the source electrode or the drain electrode. In one aspect of the present invention, the above relationship is utilized to The problem can be solved.

[0008] Specifically, a semiconductor device according to one aspect of the present invention includes a gate electrode, a gate insulating film, and a gate A semiconductor film provided at a position overlapping with the gate electrode with an insulating film sandwiched therebetween, and a semiconductor film contacting the semiconductor film The semiconductor film has a source electrode and a drain electrode. The end of the source electrode or the drain electrode in the region is the area between the source electrode and the drain electrode in the channel width direction. It shall have a gap.

[0009] The edge of the semiconductor film containing an oxide semiconductor is formed by plasma etching for forming the edge. When exposed to the etching gas, chlorine radicals, fluorine radicals, etc. generated from the etching gas react with the oxides. Therefore, at the edge of the semiconductor film, the metal element is easily bonded to the metal element. It is thought that oxygen vacancies are easily formed because the oxygen bonded to the element is easily released. However, in one embodiment of the present invention, the source electrode and the drain electrode are indicates the end of the semiconductor film where the source electrode and the drain electrode are not overlapped, i.e., The end portion of the semiconductor film in the region different from the source voltage can be secured long. The end of the semiconductor film that does not overlap with the source and drain electrodes, i.e., the end of the semiconductor film that does not overlap with the source and drain electrodes, At the end of the semiconductor film in a region different from the region where the electrode is formed, The density of the electric field lines from the edge toward the source electrode is reduced, and the electric field applied to the edge is reduced. Therefore, even if oxygen vacancies are formed at the edge of the semiconductor film, When it is desired to make the transistor non-conductive, a wire is inserted between the source electrode and the drain electrode via the end. Therefore, the leakage current can be kept small. , the threshold voltage of the transistor can be controlled.

[0010] In one embodiment of the present invention, the electric field applied to the edge of the semiconductor film is reduced, thereby Therefore, it is possible to prevent electrons, which are carriers, from being trapped in the gate insulating film. As a result, the change in threshold voltage can be suppressed, and the reliability of the semiconductor device can be improved. [Effects of the Invention]

[0011] In one embodiment of the present invention, a semiconductor device having a normally-off transistor with the above structure In addition, in one aspect of the present invention, the above-described configuration can provide a reliable body device. Therefore, a high-quality semiconductor device can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B are a top view and a cross-sectional view of a transistor. [Figure 2] FIG. [Figure 3] 1A and 1B are a top view and a cross-sectional view of a transistor. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] 1A and 1B are a top view and a cross-sectional view of a transistor. [Figure 7] FIG. [Figure 8] The actual measured values ​​of the change in threshold voltage and the change in shift value. [Figure 9] FIG. 1 is a cross-sectional view of a transistor. [Figure 10] 1A to 1C illustrate a method for manufacturing a semiconductor device. [Figure 11] 1A to 1C illustrate a method for manufacturing a semiconductor device. [Figure 12] FIG. 1 is a diagram showing the configuration of a shift register and a sequential circuit. [Figure 13] FIG. 1 is a diagram showing a configuration of a semiconductor display device. [Figure 14] Electronic equipment illustration. [Figure 15] 1A and 1B are diagrams illustrating band structures of oxide stacks according to one embodiment of the present invention. [Figure 16] 1 is a graph showing the relationship between the gate voltage and the drain current of a transistor. [Figure 17] 1 is a graph showing the relationship between the gate voltage and the drain current of a transistor. [Figure 18] FIG. 1 is a cross-sectional view of a transistor. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and the embodiments and aspects thereof may be modified 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. However, the present invention should not be construed as being limited to the description of the following embodiments.

[0014] The present invention can be applied to any device using transistors, such as integrated circuits, RF tags, and semiconductor display devices. The category includes all semiconductor devices. logic circuit, DSP (Digital Signal Processor), microcomputer LSI (Large Scale Integrated Circuit) including the t), FPGA (Field Programmable Gate Array) and C Programmable logic circuits (PLD: Programmable Logic Devices) such as PLD (Complex PLD) The category includes semiconductor devices. The display device includes a liquid crystal display device and an emissive display device having a light emitting element, such as an organic light emitting element, in each pixel. Device, electronic paper, DMD (Digital Micromirror Device) ), PDP (Plasma Display Panel), FED (Field Em Semiconductor displays that have transistors in the drive circuit, such as a 3D display Devices fall into this category.

[0015] <Transistor type 1> FIG. 1 illustrates one mode of a transistor included in a semiconductor device according to one embodiment of the present invention. FIG. 1(A) is a top view of a transistor 10. FIG. 1(B) is a top view of the transistor shown in FIG. 1(A). FIG. 1(C) corresponds to a diagram showing the cross-sectional structure of the sintered body 10 taken along the dashed line A1-A2. 1(A) shows the cross-sectional structure of the transistor 10 taken along the dashed line A3-A4. Note that in FIG. 1A, the gate is not shown in order to clarify the layout of the transistor 10. Various insulating films such as a gate insulating film are omitted.

[0016] As shown in FIG. 1, a transistor 10 includes a gate electrode and a gate insulating film on a substrate 11 having an insulating surface. a conductive film 12 having a function as a gate insulating film 13 on the conductive film 12; The semiconductor film 14 is provided at a position overlapping the conductive film 12 with the insulating film 3 sandwiched therebetween, and the conductive film 12 is connected to the semiconductor film 14. The conductive film 15 and the conductive film 16 functioning as a source electrode and a drain electrode are formed on the conductive film 15 and the conductive film 16. Has.

[0017] In FIG. 1, an oxide film 17 is provided over the semiconductor film 14, the conductive film 15, and the conductive film 16. In one embodiment of the present invention, the oxide film 17 may be included in the components of the transistor 10. good.

[0018] In addition, in FIG. 1A, the carriers move in the shortest distance between the conductive film 15 and the conductive film 16. The direction of the channel length is indicated by an arrow D1. The direction perpendicular to the channel length direction is the channel width direction, and the channel width direction is indicated by arrow D2. vinegar.

[0019] In one embodiment of the present invention, the edge of the semiconductor film 14 and the region overlapping with the semiconductor film 14 are The ends of the conductive film 15 or the conductive film 16 are spaced apart in the channel width direction. From another perspective, the transistor 10 is formed by dividing the semiconductor film 14 in the channel width direction. The width Wi is the channel width of the region 18 where the conductive film 15 or the conductive film 16 overlaps with the semiconductor film 14. It can be said that this is larger than the width Wsd of the conductive film 15 or the conductive film 16 in the width direction.

[0020] In one embodiment of the present invention, the semiconductor film 14 is separated from the region 1 in the channel width direction by a distance of 100 nm. 8, the conductive film 15 and the conductive film 16 have a gap between their ends. In FIG. 1A, both ends of the semiconductor film 14 and the conductive film 15 and the conductive film 16 in the region 18 are As an example, the film 16 has two ends spaced apart by a distance Wd1 and a distance Wd2. It shows.

[0021] In one embodiment of the present invention, the above structure allows the transistor 10 to be normally off and the threshold voltage The reason for this will be explained in detail below.

[0022] In FIG. 2A, a top view of the transistor 10 shows a broken line between the conductive film 15 and the conductive film 16. In FIG. 2(A), the electric field lines are added. In the case of a panel type, the conductive film 15 is a drain electrode and the conductive film 16 is a source electrode, 1 illustrates lines of force.

[0023] In the transistor 10 shown in FIG. 2A, the electric field flows from the conductive film 15, which is the drain electrode, to the , toward the conductive film 16 which is the source electrode. The conductive films 15 and 16 of the film 14 are arranged in the channel length direction indicated by the arrow D1. In the transistor 10, the electric field lines exist in the region 19a including the path connecting the two electrodes. The electrons flow not only into the region 19a but also into the region 19b of the semiconductor film 14 that is outside the path. Electric field lines exist as shown below.

[0024] Next, as a comparative example, a transistor having a structure different from that of the transistor 10 is shown in FIG. 1 shows a top view of the resistor 20 and the lines of electric force shown as dashed arrows.

[0025] The transistor 20 has a conductive film 22 on an insulating surface, which functions as a gate electrode, and a conductive film 23 on an insulating surface. A gate insulating film (not shown) on the conductive film 22 and a gate insulating film sandwiched between the conductive film 22 and a semiconductor film 24 provided at a position overlapping the semiconductor film 24 and a source electrode or a drain electrode. The conductive film 25 and the conductive film 26 function as inner electrodes.

[0026] The transistor 20 has an end portion of the conductive film 25 or the conductive film 26 and a The end of the semiconductor film 24 in the region where it overlaps with the conductive film 26 has a channel width indicated by an arrow D2. In other words, the transistor 20 has a structure with a gap in the direction. The width Wi of the semiconductor film 24 in the channel width direction is It can be said that this is smaller than the width Wsd of the conductive film 26.

[0027] In FIG. 2B, in the channel width direction, both ends of the conductive film 25 or the conductive film 26 and the conductive film 27 are The semiconductor film 24 is formed so that the gap between the both ends of the semiconductor film 24 and the conductive film 25 or 26 is smaller than the gap Wd3 and interval Wd4.

[0028] In FIG. 2B, the transistor 20 is an n-channel type, and the conductive film 25 is a drain electrode. The diagram illustrates electric field lines when the conductive film 26 is the source electrode.

[0029] In the transistor 20 shown in FIG. 2B, the electric field lines flow from the conductive film 25, which is the drain electrode, The source electrode of the transistor 20 is the conductive film 26. The conductive film 25 and the conductive film 26 of the conductive film 24 are arranged in the channel length direction indicated by the arrow D1. Only electric field lines exist along the path connecting the two.

[0030] Therefore, the edge of the semiconductor film 14 of the transistor 10 shown in FIG. 2A and the edge of the semiconductor film 14 of the transistor 10 shown in FIG. When compared with the edge of the semiconductor film 24 of the transistor 20, the The end of the semiconductor film 14 that does not overlap with the conductive film 15 and the conductive film 16, i.e., the conductive film 15 and The end of the semiconductor film 14 in a region other than the region where the conductive film 16 is formed is a transistor. In the photodiode 20, the end of the semiconductor film 24 that does not overlap with the conductive film 25 and the conductive film 26, i.e., That is, the semiconductor film 24 in a region different from the region where the conductive film 25 and the conductive film 26 are formed is It will be longer than the end.

[0031] 2A and 2B. 20, the transistor 10 overlaps with the conductive film 15 and the conductive film 16. The density of the electric field lines at the end of the semiconductor film 14 that is not and the density of the electric field lines at the end of the semiconductor film 24 that does not overlap with the conductive film 26 is smaller than that at the end of the semiconductor film 24 that does not overlap with the conductive film 26. In other words, the area where the conductive film 15 and the conductive film 16 are formed can be reduced. In the region, the electric field applied to the end of the semiconductor film 14 is induced by the conductive film 25 and the conductive film 26. In a region other than the region where the semiconductor film 24 is formed, the electric field applied to the end of the semiconductor film 24 is made smaller than that applied to the end of the semiconductor film 24. It can be said that this is possible.

[0032] When the semiconductor film 14 and the semiconductor film 24 contain an oxide semiconductor, the semiconductor film 14 and the semiconductor film 24 When the end of the film 24 is exposed to plasma during etching to form the end, Chlorine radicals, fluorine radicals, etc. generated from the etching gas form oxide semiconductors. Therefore, at the end portions of the semiconductor film 14 and the semiconductor film 24, the metal It is thought that oxygen vacancies are easily formed because the oxygen that was bonded to the element is easily released. can be obtained.

[0033] However, in the transistor 10, as described above, the conductive film 15 and the conductive film 16 do not overlap. In addition, in the transistor 10, the end portion of the semiconductor film 14 can be kept long. In a region different from the region where the conductive film 15 and the conductive film 16 are formed, the end portion of the semiconductor film 14 is Therefore, oxygen vacancies at the edge of the semiconductor film 14 can be reduced. Even if the end is formed, when it is desired to put the transistor 10 into a non-conducting state, As a result, the leakage current flowing between the conductive film 15 and the conductive film 16 can be reduced. Therefore, the threshold voltage of the transistor 10 can be controlled so that the transistor 10 is normally off. do.

[0034] In addition, in the transistor 10, the electric field applied to the edge of the semiconductor film 14 is reduced. This can prevent electrons, which are carriers, from being trapped in the gate insulating film 13 from the edge. This suppresses the change in threshold voltage of the transistor 10, The reliability of the semiconductor device using the stator 10 can be improved.

[0035] In one embodiment of the present invention, the oxide film 17 may be formed using a metal oxide.

[0036] By using the oxide film 17 having the above-described structure, a film containing silicon is formed on the oxide film 17. Even if the semiconductor film 14 is provided, the semiconductor film 14 and the silicon-containing film can be separated from each other. In the case where the semiconductor film 14 contains indium, the bond energy with oxygen is A semiconductor film in which silicon, which is larger than indium, does not overlap with the conductive film 15 and the conductive film 16. At the edge of 14, the bond between indium and oxygen is broken to prevent the formation of oxygen vacancies. As a result, in one embodiment of the present invention, the reliability of the transistor can be further improved. This can be done.

[0037] In order to prevent the channel region of the semiconductor film 14 from becoming n-type due to oxygen deficiency, The concentration of silicon in 4 is 2 x 10 18 atoms / cm 3 Below, and even 2×10 17 a toms / cm 3 It is desirable that the following:

[0038] The metal oxide is a metal oxide used as an oxide semiconductor in the semiconductor film 14. In order to realize the above-mentioned configuration, for example, a metal oxide When an In-Ga-Zn oxide is used for the oxide film 17, the metal oxide is In. The atomic ratio of the metal oxides may be lower than that of the metal oxides used in the semiconductor film 14. The oxide film 17 is formed by sputtering in such a manner that the atomic ratio of metals is 1:6:4, or It can be formed using an In-Ga-Zn oxide target with a ratio of 1:3:2. do.

[0039] 1A and 2A, the conductive layer 18 is formed on both ends of the semiconductor film 14. The film 15 and the conductive film 16 have a distance Wd1 and a distance Wd2 between their ends, respectively. In one embodiment of the present invention, either the interval Wd1 or the interval Wd2 does not exist. Even in this case, the above-described effect of one aspect of the present invention can be obtained. The configuration examples of Figures 1(A) and 2(A), in which both d2 and d3 exist, enhance the above effect. This is more desirable because it allows

[0040] When an oxide semiconductor is used for the semiconductor film 14, the conductive films 15 and 16 Depending on the conductive material used, the metal in the conductive film 15 and the conductive film 16 may be an oxide semiconductor or In this case, oxygen may be extracted from the conductive film 15 and the conductive film 1 in the semiconductor film 14. The region in contact with the transistor 6 is made n-type by the formation of oxygen vacancies. A partial region 65 of the semiconductor film 14 is shown enlarged in FIG. The region 14n in contact with the conductive film 15 and the conductive film 16 is made n-type.

[0041] The n-type region 14n functions as a source region or a drain region, and therefore is a semiconductor. The contact resistance between the film 14 and the conductive film 15 and between the film 14 and the conductive film 16 can be reduced. Therefore, the formation of the n-type region 14n improves the mobility and The on-state current can be increased, thereby improving the speed of a semiconductor device using the transistor 10. The operation can be realized.

[0042] The extraction of oxygen by the metal in the conductive film 15 and the conductive film 16 is This can occur when the conductive film 15 and the conductive film 16 are formed by a sputtering method or the like. This can also occur due to a heat treatment carried out after forming 16.

[0043] In addition, the region 14n to be made n-type is made of a conductive material that easily bonds with oxygen. The conductive material can be, for example, Al, C, or the like. Examples include r, Cu, Ta, Ti, Mo, and W.

[0044] <Change in threshold voltage> Next, the transistor 10 shown in FIG. 2A and the transistor 20 shown in FIG. 2B A test was conducted in which a high voltage was applied to the drain electrode to examine the amount of change in the threshold voltage. The results will be explained.

[0045] First, the transistors A and B used in the test have the same structure as the transistor 10. The distance Wd1 and the distance Wd2 are both 3 μm, and the width Ws of the conductive film 15 and the conductive film 16 The distance d between the conductive films 15 and 16 (channel length) was set to 20 μm. The transistors C and D used in the experiment have the same structure as the transistor 20. The distance Wd3 and the distance Wd4 are both 3 μm, the width Wi of the semiconductor film 24 is 20 μm, and the conductive film 2 The distance (channel length) between the conductive film 5 and the conductive film 26 was set to 3 μm.

[0046] In addition, the transistors A and B have a conductive film 12 of 200 nm thickness. A 400 nm thick silicon nitride film and a 500 nm thick silicon nitride film were used as gate insulating films. The insulating film used was a 0 nm silicon oxynitride film stacked in this order from the conductive film 12 side. The film 15 and the conductive film 16 are made of a tungsten film having a thickness of 50 nm and an aluminum film having a thickness of 400 nm. A conductive film is formed by stacking a 100 nm thick titanium film in this order from the semiconductor film 14 side. A membrane was used.

[0047] In addition, the materials used for the gate insulating film and conductive film of transistors C and D are The thickness of the film was the same as that of the transistors A and B. Transistors C and D use a tungsten film with a thickness of 200 nm as the conductive film 22. In addition, a silicon nitride film with a thickness of 400 nm and a nitriding oxide film with a thickness of 50 nm were used as gate insulating films. The insulating film used was a silicon nitride film stacked in this order from the conductive film 22 side. The film 26 is a tungsten film having a thickness of 50 nm, an aluminum film having a thickness of 400 nm, and A conductive film was used in which a titanium film having a thickness of 100 nm was laminated in this order from the semiconductor film 24 side.

[0048] In this specification, the oxynitride used as the silicon oxynitride film or the like has the following composition: , a substance that contains more oxygen than nitrogen, and nitride oxide has the following composition: It refers to a substance that contains more nitrogen than oxygen.

[0049] The semiconductor film 14 of the transistor A and the semiconductor film 24 of the transistor C are A single-layer oxide semiconductor film was used as the oxide semiconductor film. (In), gallium (Ga), and zinc (Zn) in a 1:1:1 ratio. A 35 nm thick In-Ga-Zn oxide semiconductor film (IGZO) was formed using a (111)).

[0050] Also, as the semiconductor film 14 of the transistor B and as the semiconductor film 24 of the transistor D, Two layers of oxide semiconductor films were used. The oxide semiconductor film closest to the gate insulating film The film has a composition of indium (In), gallium (Ga), and zinc (Zn) of 1:1:1. A 35 nm thick In-Ga-Zn oxide semiconductor was formed using a certain oxide target. The oxide semiconductor film on the far side of the gate insulating film is , indium (In), gallium (Ga), and zinc (Zn) in a composition of 1:3:2 A 20 nm thick In-Ga-Zn oxide semiconductor formed using an oxide target The film was IGZO(132).

[0051] In the test, the gate electrode and source electrode were set to the same potential, and the voltage The voltage of the drain electrode (called the drain voltage) when the reference potential is 30V. In the test, the substrate on which the transistors A to D were formed was The temperature is set to 125°C, and the sample is placed in a dark room without light exposure for 1 hour. This applied stress to transistors A to D.

[0052] 16 and 17 show the results of measurements of transistors A to B before and after stress application. The relationship between the gate voltage Vg (V) and the drain current Id (A) of transistor D is shown in Figure 16. In FIG. 17, the relationship between the gate voltage Vg and the drain current Id before applying stress is shown by the dashed line. The solid line shows the relationship between the gate voltage Vg and the drain current Id after applying stress. 16(A) corresponds to the data of transistor A, and FIG. 16(B) corresponds to the data of transistor B. 17(A) corresponds to the data of transistor C, and FIG. 17(B) corresponds to the data of transistor D. This corresponds to the data of transistor D.

[0053] The drain currents of the transistors A to D were measured by setting the gate voltage Vg to - The measurement was carried out by changing the drain voltage Vd from 15V to +30V. The measurements were carried out at 0.1V and 10V. The measurements were carried out in an environment of 40°C. .

[0054] The relationship between the gate voltage Vg (V) and the drain current Id (A) shown in FIGS. 16 and 17 The change in threshold voltage that occurred before and after applying stress, calculated using The change in the shift value (ΔShift) and the change in the voltage (ΔVth) are shown in the graph of FIG. The mobility of each transistor is based on a dielectric constant of 4 and a gate insulating film thickness of 280 nm. The following table 1 shows the thresholds that occurred before and after applying stress. The values ​​of the voltage change amount (ΔVth) and the shift value change amount (ΔShift) are shown.

[0055] [Table 1]

[0056] The shift value is defined as the value of the gate voltage when the drain current rises. Specifically, in the graph showing the relationship between the gate voltage and the drain current, The point where the tangent line where the slope changes most sharply intersects with the scale line corresponding to the minimum drain current is The shift value can be defined as the voltage at the point where the drain voltage is 10V. The values ​​at the time were used.

[0057] As can be seen from FIG. 8, transistor C and transistor Transistor A and transistor B have the structure of transistor 10 compared to transistor D. However, the change in threshold voltage (ΔVth) and the change in shift value (ΔShift) are both small. Therefore, from the above test results, it was found that the transistor 10 It has been found that the threshold voltage of the transistor 20 is less likely to shift to the positive side than that of the transistor 20, and that the reliability is higher. It was.

[0058] <Transistor type 2> Next, FIG. 3 shows another example of a transistor included in a semiconductor device according to one embodiment of the present invention. FIG. 3A is a top view of the transistor 30. FIG. 3B is a top view of the transistor 30 shown in FIG. This corresponds to a diagram showing the cross-sectional structure of the transistor 30 taken along the dashed line B1-B2. FIG. 3C) shows a cross-sectional structure of the transistor 30 shown in FIG. 3A taken along the dashed line B3-B4. FIG. 3(D) corresponds to the diagram of the transistor 30 shown in FIG. 3(A) along the dashed line B5- It should be noted that FIG. 3A corresponds to a diagram showing the cross-sectional structure of the transistor 30. In order to clarify the layout, various insulating films such as gate insulating films are omitted.

[0059] The transistor 30 shown in FIG. 3 is formed of a substrate 31 having an insulating surface, similar to the transistor 10. A conductive film 32 having a function as a gate electrode and a gate insulating film 33 on the conductive film 32 are formed on the substrate. a semiconductor film 34 provided at a position overlapping the conductive film 32 with a gate insulating film 33 interposed therebetween; A conductive film 35 is in contact with the semiconductor film 34 and functions as a source electrode or a drain electrode. and a conductive film 36.

[0060] In addition, in FIG. 3, an oxide film 37 is provided over the semiconductor film 34, the conductive film 35, and the conductive film 36. In one embodiment of the present invention, the oxide film 37 may be included in the components of the transistor 30. good.

[0061] The transistor 30 has a conductive film 35 and a conductive film 36 each having a comb-like shape. The structure is different from that of the transistor 10 shown in FIG. The conductive film 35 and the conductive film 3 6 includes a plurality of protrusions 60 and a connecting portion 61 that connects the plurality of protrusions 60 together. Has.

[0062] In one embodiment of the present invention, in the transistor 30, an edge of the semiconductor film 34 and a semiconductor The end of the conductive film 35 or the conductive film 36 in the area where it overlaps with the body film 34 is indicated by an arrow D2. The transistor 30 has a gap in the channel width direction. The width Wi of the semiconductor film 34 in the channel width direction is equal to or smaller than the width of the conductive film 35 or the conductive film 36. The conductive film 35 or the conductive film 36 in the channel width direction in the region 38 where the conductive film 34 overlaps It can be said that it is larger than the width Wsd of the

[0063] Furthermore, in one embodiment of the present invention, the connecting portion 61 of the conductive film 35 or the conductive film 36 and the semiconductor In other words, the conductive film 35 or the conductive film 36 has a gap between the end of the conductive film 35 and the end of the conductive film 34. 60 partially overlaps with the semiconductor film 34. The end of the conductive film 35 or the conductive film 36 in the region has a plurality of protrusions 60 spaced apart from each other. The connecting portion 61 of the conductive film 35 and the connecting portion 61 of the conductive film 36 are In order to separate both of them from the end of the semiconductor film 34, In this case, the distance Lsd2 between the ends of the connecting portions of the conductive film 35 and the conductive film 36 is , it is necessary that the width be larger than the width Li of the semiconductor film 34.

[0064] In one embodiment of the present invention, the connection portion 61 of the conductive film 35 or the conductive film 36 and the semiconductor film 34 The structure in which the ends of the transistors are spaced apart makes the transistor 30 normally off, and the threshold voltage The reason for this will be explained in detail below.

[0065] FIG. 4 shows a top view of a part of the transistor 30, and also shows the conductive film 35 and the conductive film 36. In FIG. 4, the lines of electric force are shown as dashed arrows. In the case of a channel type, the conductive film 35 is a drain electrode and the conductive film 36 is a source electrode, It illustrates the energy lines.

[0066] In the transistor 30, the edge of the semiconductor film 34 and the conductive region in the region overlapping with the semiconductor film 34 are Since the end of the conductive film 35 or the end of the conductive film 36 are spaced apart in the channel width direction, The end portion of the semiconductor film 34 that does not overlap with the conductive film 35 and the conductive film 36 can be secured long. In addition, in the transistor 30, a region different from the region where the conductive film 35 and the conductive film 36 are formed is At the end of the semiconductor film 34, which can be a current path connecting the conductive film 35 and the conductive film 36, This electric field can be reduced, and oxygen vacancies at the edge of the semiconductor film 34 can be reduced. Even if the terminals are formed, when it is desired to make the transistor 30 non-conductive, As a result, the leakage current flowing between the conductive film 35 and the conductive film 36 can be reduced. Therefore, the threshold voltage of the transistor 30 can be controlled so that the transistor 30 is normally off. do.

[0067] In addition, in the transistor 30, the electric field applied to the end portion of the semiconductor film 34 is reduced. This can prevent electrons, which are carriers, from being trapped in the gate insulating film 33 from the end portion. This suppresses the change in the threshold voltage of the transistor 30, The reliability of the semiconductor device using the starter 30 can be improved.

[0068] In the transistor 30 shown in FIG. 4, the electric field lines are directed from the conductive film 35, which is the drain electrode, to the The source electrode of the transistor 30 is the conductive film 36. The conductive film 35 and the conductive film 36 of the conductive film 34 are arranged in the channel length direction indicated by the arrow D1. In the transistor 30, electric field lines exist in the region 39a including the path connecting the The electrons flow not only into the region 39a but also into a region 39b of the semiconductor film 34 that is outside the path. Electric field lines exist like this.

[0069] Therefore, in the case of the transistor 30, the connecting portion 61 of the conductive film 35 or the conductive film 36 and the semiconductor Compared to a transistor having a configuration in which the conductive film 35 overlaps the conductive film 34, Therefore, in the transistor 30, the density of the electric field lines can be reduced. This can prevent the electric field from concentrating not only at the end of the membrane 34 but also inside the membrane. Therefore, the transistor 30 can suppress the amount of change in threshold voltage to a small value, and the semiconductor device This can improve the reliability of the system.

[0070] Furthermore, in one embodiment of the present invention, the convex portion 60 of the conductive film 35 and the convex portion of the conductive film 36 60 are spaced apart by an interval Lsd1 in the channel length direction indicated by an arrow D1, and the protrusions of the conductive film 35 The protrusions 60 of the conductive film 36 and the protrusions 60 of the conductive film 36 are not intertwined with each other. Thus, the transistor 30 includes a conductive film 32 that functions as a gate electrode and a conductive film 35 Alternatively, the area of ​​the region overlapping with the conductive film 36 can be kept small, and the area formed in that region can be reduced. The capacitance of the transistor 30 can be reduced. This makes it possible to reduce the S value (subthreshold swing value).

[0071] In addition, in the case of a transistor with a large S value, if the threshold voltage is lowered, the gate voltage will be 0V. When the transistor is turned on, the off-state current is large and the transistor is normally on. In a circuit composed of transistors, it becomes difficult to operate normally. This allows for a lower S value, so the normal Therefore, by using the transistor 30, it is possible to use a unipolar transistor. This makes it possible to more reliably ensure the normal operation of the resulting circuit.

[0072] Also, when a negative gate voltage is applied, transistor 30 operates in the same manner as the transistor shown in FIG. 10, the back channel side, that is, the portion of the semiconductor film 34 facing the gate electrode, The electron depletion layer tends to extend to the center of the channel width in the area near the surface opposite to the surface where the electrons are Therefore, the transistor 30 has a higher effective current than the transistor 10 shown in FIG. The channel width can be reduced, and therefore the region through which the off-current flows is narrowed. The current can be reduced.

[0073] In one embodiment of the present invention, the oxide film 37 may be formed using a metal oxide. .

[0074] By using the oxide film 37 having the above-described structure, a film containing silicon is formed on the oxide film 37. Even if the semiconductor film 34 is provided, the semiconductor film 34 and the silicon-containing film can be separated from each other. When the semiconductor film 34 contains indium, the bond energy with oxygen is A semiconductor film in which silicon, which is larger than indium, does not overlap with the conductive film 35 and the conductive film 36. At the end of 34, the bond between indium and oxygen is broken to prevent the formation of oxygen vacancies. As a result, in one embodiment of the present invention, the reliability of the transistor can be further improved. This can be done.

[0075] The metal oxide is a metal oxide used as an oxide semiconductor in the semiconductor film 34. In order to realize the above-mentioned configuration, for example, a metal oxide When an In-Ga-Zn oxide is used for the oxide film 37, the metal oxide is In. The atomic ratio of the metal oxides may be lower than that of the metal oxides used in the semiconductor film 34. The oxide film 37 is formed by sputtering in such a manner that the atomic ratio of metals is 1:6:4, or It can be formed using an In-Ga-Zn oxide target with a ratio of 1:3:2. do.

[0076] As in the case of the transistor 10, the conductive film 35 and the conductive film 3 The region in contact with the transistor 30 may be made n-type. To achieve high speed operation of a semiconductor device using the transistor 30 by increasing the on-state current and the on-state current. can be done.

[0077] <Transistor type 3> In the transistor 30 shown in FIG. 3, the conductive film 35 has a protrusion 60 and the conductive film 36 has a The protrusion 60 has a structure in which it completely overlaps with the protrusion 60 in the channel length direction. In one embodiment of the present invention, the protrusions 60 are configured to partially overlap each other in the channel length direction. It may have.

[0078] FIG. 5(A) shows a structure in which the protrusions 60 partially overlap each other in the channel length direction. 5A is a top view of one embodiment of the transistor 30. The convex portions 60 of the conductive film 35 and the convex portions 60 of the conductive film 36 are aligned in a direction indicated by an arrow D1. They have a partially overlapping structure in the channel length direction.

[0079] In addition, in the transistor 30 shown in FIG. 3, both the conductive film 35 and the conductive film 36 have a plurality of protrusions. 60 is illustrated, the transistor 30 has the conductive film 35 and the conductive film 36. Either one may have a structure having a plurality of protrusions 60 .

[0080] In FIG. 5B, the conductive film 35 has a plurality of protrusions 60, and the conductive film 36 does not have a plurality of protrusions. 5B is a top view of a transistor 30 having a structure in which the semiconductor film 34 overlaps the transistor 30. The end of the conductive film 36 in the region overlapping with the semiconductor film 34 is the same as the end of the conductive film 35 in the region overlapping with the semiconductor film 34. Unlike the end, it is continuous.

[0081] The transistor 30 illustrated in FIGS. 5A and 5B may be the same as the transistor illustrated in FIG. As with the resistor 30, the effect of one aspect of the present invention can be obtained.

[0082] <Transistor type 4> 1 to 5, a bottom gate transistor in which a semiconductor film exists on a gate electrode is shown. The transistors shown in FIGS. 1 to 5 each have a gate It may also be a top gate type in which a semiconductor film exists under the electrode.

[0083] FIG. 6 shows a top-gate transistor included in a semiconductor device according to one embodiment of the present invention. 6A is a top view of the transistor 40. FIG. 6B is a top view of the transistor 40 shown in FIG. This corresponds to a diagram showing the cross-sectional structure of the transistor 40 taken along dashed line C1-C2. 6(C) is a cross-sectional view of the transistor 40 shown in FIG. 6(A) taken along the dashed line C3-C4. FIG. 6(D) corresponds to the diagram showing the transistor 40 shown in FIG. 6(A) along the dashed line C 5-C6. In FIG. 6(A), the transistor In order to clarify the layout of 40, various insulating films such as gate insulating films are omitted.

[0084] The transistor 40 shown in FIG. 6 includes a semiconductor film 44 and a source electrode 45 formed on a substrate 41 having an insulating surface. A conductive film 45 having a function as a source electrode or a drain electrode is provided on the semiconductor film 44. and a conductive film 46, a gate insulating film 43 on the semiconductor film 44, the conductive film 45, and the conductive film 46, The gate electrode is formed at a position overlapping the semiconductor film 44 with the gate insulating film 43 interposed therebetween. and a conductive film 42 provided in the position.

[0085] In FIG. 6, an oxide film 47 is provided on the gate insulating film 43 and the conductive film 42. In one embodiment of the present invention, the oxide film 47 may be included as a component of the transistor 40.

[0086] The transistor 40 has a structure in which the conductive films 45 and 46 have a comb-like shape. 3. The conductive film 45 having a comb-tooth shape and the The conductive film 46 includes a plurality of protrusions 50 and connecting portions 51 that connect the plurality of protrusions 50 to each other. Each has.

[0087] The transistor 40 has an edge portion of the semiconductor film 44 and an area overlapping the semiconductor film 44. The end of the conductive film 45 or the conductive film 46 is spaced apart in the channel width direction indicated by the arrow D2. In this respect, the structure is the same as that of the transistor 30 shown in FIG. In the transistor 40, the width Wi of the semiconductor film 44 in the channel width direction is Alternatively, the conductive film 46 and the semiconductor film 44 overlap each other in the region 48 in the channel width direction. It can be said that the width Wsd of the conductive film 45 or the conductive film 46 is larger than that.

[0088] Furthermore, the transistor 40 has a connecting portion 51 of the conductive film 45 or the conductive film 46 and a semiconductor The structure is the same as that of the transistor 30 shown in FIG. 3 in that there is a gap between the end of the semiconductor film 44 and the semiconductor film 44. Therefore, the conductive film 45 or the conductive film 46 in the region overlapping with the semiconductor film 44 is The ends of the plurality of protrusions 50 are spaced apart from one another. The connecting portion 51 and the connecting portion 51 of the conductive film 46 are both spaced apart from the end of the semiconductor film 44. In order to achieve this, the conductive film 45 and the conductive film 46 are The distance Lsd2 between the ends of the connecting portions is greater than the width Li of the semiconductor film 44. It is necessary to do so.

[0089] As in the case of the transistor 10, the conductive film 45 and the conductive film 4 The region in contact with the transistor 40 may be made n-type. and increasing the on-state current and realizing high-speed operation of a semiconductor device using the transistor 40. can be done.

[0090] <Layout of multiple transistors> 3. Also, as an example, a top view of two transistors 30 shown in FIG. 3 connected in parallel is shown. This is shown in FIG. 7(A).

[0091] In this specification, the state in which transistors are connected in series means, for example, Only one of the source and drain electrodes of the first transistor is connected to the source of the second transistor. This means that the transistor is connected to only one of the source and drain electrodes. The state in which the transistors are connected in parallel is when the source electrode or the drain electrode of the first transistor is one of the source and drain electrodes of the second transistor is connected to one of the source and drain electrodes of the second transistor; The other of the source electrode or the drain electrode of the first transistor is connected to the source electrode of the second transistor. This means that the source electrode or drain electrode is connected to the other of the two electrodes.

[0092] In FIG. 7A, there are two transistors 30 shown in FIG. 3, a transistor 30a and a transistor The conductive film 35 of the transistor 30a and the conductive film 36 of the transistor 30b are shown. The conductive film 35 of the transistor 30b shares a connecting portion 61. The semiconductor film 34 of the transistor 30a and the semiconductor film 34 of the transistor 30b are connected by an arrow D1. The channel length direction indicated by arrow D1 and the channel width direction indicated by arrow D2 are arranged so as to almost coincide with each other. It has been done.

[0093] 7B, the transistor 40 shown in FIG. 6 is replaced by two transistors 40a and 40b. The conductive film 45 of the transistor 40a is shown as the transistor 40b. The conductive film 45 of the transistor 40b shares a connecting portion 51. The semiconductor film 44 of the transistor 40a and the semiconductor film 44 of the transistor 40b are connected as shown by the arrows. The channel length direction indicated by the arrow D1 and the channel width direction indicated by the arrow D2 are aligned so as to almost coincide with each other. are located at.

[0094] Although FIG. 7 shows an example in which two transistors are connected in parallel, three or more transistors can be connected in parallel. The transistors can also be connected in parallel in the same way.

[0095] As shown in FIG. 7, by arranging a plurality of transistors 30 or 40, In the layout of the mask used for the number of transistors 30 or 40, When the periodicity of the mask is low, the photolithography using the mask can be performed. During the photolithography process, interference of light emitted from the exposure device can cause photolithography problems. Conductive films, insulating films, semiconductor films, etc. formed by lithography may be partially narrowed. However, in FIG. 7, a plurality of transistors 30 or The periodicity of the mask layout used for register 40 can be increased, As a result, defects occur in the shape of the conductive film, insulating film, and semiconductor film after the photolithography process. This can prevent this.

[0096] <About semiconductor films> In a semiconductor device according to one embodiment of the present invention, a semiconductor film of a transistor may be formed of an amorphous or microcrystalline Alternatively, a polycrystalline or single-crystalline semiconductor film containing silicon or germanium may be used. It has a wider band gap than silicon and a lower intrinsic carrier density than silicon. A semiconductor film containing a semiconductor such as an oxide semiconductor may also be used.

[0097] Silicon is produced by vapor deposition methods such as plasma CVD or sputtering. The amorphous silicon is then crystallized by laser annealing or other processes. Polycrystalline silicon and single crystal silicon wafers are made by injecting hydrogen ions into the wafer and peeling off the surface layer. Crystalline silicon or the like can be used.

[0098] Impurities such as water or hydrogen, which act as electron donors, are reduced, and oxygen deficiency is eliminated. The oxide semiconductor is highly purified by reducing the amount of Semiconductors are i-type (intrinsic semiconductors) or very close to i-type. Therefore, a transistor having a channel formation region in a highly purified oxide semiconductor film has an off-state current The current is extremely small and highly reliable.

[0099] Specifically, the present invention relates to an oxide semiconductor film having a highly purified oxide semiconductor film as a channel formation region. The small fringe current can be proven by various experiments. For example, 0 6 Even in a device with a channel length of 10 μm, the voltage between the source and drain electrodes In the drain voltage range of 1V to 10V, the off-state current was measured by the semiconductor parameter analyzer. Below the riser measurement limit, i.e., 1×10 -13 It can achieve a characteristic of A or below. In this case, the off-state current normalized by the transistor channel width is 100 zA / μm or less. In addition, by connecting the capacitor and the transistor, Off-state current is measured using a circuit that controls the charge flowing out of the capacitor with the transistor. In the measurement, a highly purified oxide semiconductor film was used as a channel of the transistor. The on / off state of the transistor is determined based on the change in the amount of charge per unit time of the capacitor element. The current was measured. As a result, the voltage between the source and drain electrodes of the transistor was 3V. In this case, it was found that an even smaller off-state current of several tens of yA / μm could be obtained. Therefore, a transistor using a highly purified oxide semiconductor film for a channel formation region has an off-state current The current is significantly smaller than that of a transistor using crystalline silicon.

[0100] Unless otherwise specified, the off-state current in this specification refers to the off-state current in an n-channel transistor. In this case, the drain is at a higher potential than the source and gate, and the source potential is When the gate potential is below 0V, the current that flows between the source and drain is Alternatively, in this specification, the off-state current refers to the off-state current in a p-channel transistor. In this case, the drain is set to a lower potential than the source and gate, and the source potential is set to When the gate potential is 0V or higher, current flows between the source and drain. It means electric current.

[0101] In the case where an oxide semiconductor film is used as the semiconductor film, the oxide semiconductor includes at least It is preferable that the oxide semiconductor contains indium (In) or zinc (Zn). As a stabilizer to reduce the variation in the electrical characteristics of transistors using In addition to these, it is preferable to have gallium (Ga). It is preferable to use hafnium (Hf) as a stabilizer. It is preferable that the stabilizer contains aluminum (Al). It is also preferable that zirconium (Zr) is contained as a stabilizer.

[0102] Among oxide semiconductors, In-Ga-Zn oxides and In-Sn-Zn oxides are carbon-based. Unlike silicon nitride, gallium nitride, or gallium oxide, This makes it possible to produce transistors with excellent electrical characteristics, and is suitable for mass production. Also, unlike silicon carbide, gallium nitride, or gallium oxide, The In-Ga-Zn oxide is used to form a transistor with excellent electrical properties on a glass substrate. It is also possible to manufacture larger substrates.

[0103] Other stabilizers include lanthanides such as lanthanum (La) and cerium ( Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), hol Mium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Ru It may contain one or more of tetraethion (Tetrium) (Lu).

[0104] For example, oxide semiconductors include indium oxide, gallium oxide, tin oxide, zinc oxide, and I n-Zn oxides, Sn-Zn oxides, Al-Zn oxides, Zn-Mg oxides, S n-Mg oxide, In-Mg oxide, In-Ga oxide, In-Ga-Zn oxide (also written as IGZO), In-Al-Zn oxide, In-Sn-Zn oxide, Sn-Ga-Zn oxide, Al-Ga-Zn oxide, Sn-Al-Zn oxide, I n-Hf-Zn oxide, In-La-Zn oxide, In-Pr-Zn oxide, In -Nd-Zn oxide, In-Sm-Zn oxide, In-Eu-Zn oxide, In- Gd-Zn oxide, In-Tb-Zn oxide, In-Dy-Zn oxide, In-H Oxide based on Zn, In-Er-Zn, In-Tm-Zn, In-Yb -Zn-based oxides, In-Lu-Zn-based oxides, In-Sn-Ga-Zn-based oxides, In- Hf-Ga-Zn oxide, In-Al-Ga-Zn oxide, In-Sn-Al-Zn In-Sn-Hf-Zn oxide, In-Hf-Al-Zn oxide It is possible.

[0105] For example, an In-Ga-Zn oxide means an oxide containing In, Ga, and Zn. The ratio of In, Ga, and Zn is not important. In-Ga-Zn oxides have a sufficiently high resistance in the absence of an electric field, and The flow can be made sufficiently small and the mobility is high.

[0106] For example, In:Ga:Zn=1:1:1 (=1 / 3:1 / 3:1 / 3) or In:G In-Ga-Zn oxide with an atomic ratio of a:Zn=2:2:1 (=2 / 5:2 / 5:1 / 5) Alternatively, In:Sn:Zn=1: 1:1(=1 / 3:1 / 3:1 / 3), In:Sn:Zn=2:1:3(=1 / 3:1 / 6:1 / 2) or In:Sn:Zn=2:1:5(=1 / 4:1 / 8:5 / 8) It is preferable to use an In-Sn-Zn oxide with a molecular ratio or an oxide with a composition close to that.

[0107] For example, high mobility can be obtained relatively easily with In-Sn-Zn oxides. Therefore, even in In-Ga-Zn oxides, the mobility can be increased by reducing the defect density in the bulk. It can be done.

[0108] Oxide semiconductor films are roughly classified into single-crystal oxide semiconductor films and non-single-crystal oxide semiconductor films. The single-crystal oxide semiconductor film includes an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, a polycrystalline oxide semiconductor film, and a polycrystalline oxide semiconductor film. Physical semiconductor film, CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor films, etc.

[0109] The amorphous oxide semiconductor film has an irregular atomic arrangement in the film and is an oxide film that does not contain a crystalline component. The film is a compound semiconductor film. It does not have any crystalline parts even in the microscopic areas, and the entire film has a completely amorphous structure. A typical example is an oxide semiconductor film.

[0110] The microcrystalline oxide semiconductor film is made up of, for example, microcrystals (nanocrystals) having a size of 1 nm or more and less than 10 nm. Therefore, the microcrystalline oxide semiconductor film has a lower atomic number than the amorphous oxide semiconductor film. Therefore, the microcrystalline oxide semiconductor film has a higher order of molecular arrangement than the amorphous oxide semiconductor film. The defect level density is also low.

[0111] The CAAC-OS film is one of the oxide semiconductor films that has multiple crystal parts. The crystal part is so large that it fits inside a cube with a side length of less than 100 nm. The crystals contained in the S film are cubic with sides of less than 10 nm, 5 nm, or 3 nm. The CAAC-OS film has a smaller defect density than the microcrystalline oxide semiconductor film. The CAAC-OS film has a low density of recessed states. .

[0112] The CAAC-OS film was observed under a transmission electron microscope (TEM). When observed under a crystalline microscope, clear boundaries between the crystals, i.e., crystal boundaries, are clearly visible. It is not possible to confirm the grain boundary. It can be said that the AC-OS film is less susceptible to the decrease in electron mobility caused by grain boundaries.

[0113] The CAAC-OS film was observed by TEM from a direction roughly parallel to the sample surface (cross-sectional TEM observation). ) It can be confirmed that the metal atoms are arranged in layers in the crystalline part. Each layer has a surface on which the CAAC-OS film is formed (also referred to as a surface on which the CAAC-OS film is formed) or an uneven surface on which the CAAC-OS film is formed. The shape reflects this and is aligned parallel to the surface on which the CAAC-OS film is formed or the top surface.

[0114] In this specification, "parallel" means that two straight lines are arranged at an angle of -10° or more and 10° or less. Therefore, it includes the case where the angle is between -5° and 5°. refers to the state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This includes cases where the angle is between 85° and 95°.

[0115] On the other hand, the CAAC-OS film was observed by TEM from a direction approximately perpendicular to the sample surface (planar TEM). When observed, it was found that the metal atoms were arranged in triangular or hexagonal shapes in the crystals. However, there is no regularity in the arrangement of metal atoms between different crystal parts. stomach.

[0116] Cross-sectional and planar TEM observations revealed that the crystals in the CAAC-OS film had an orientation. It turns out that there are.

[0117] X-ray diffraction (XRD) was performed on the CAAC-OS film. For example, a CAAC-OS film with InGaZnO4 crystals was found by structural analysis using the device. In the out-of-plane analysis, a peak was observed at a diffraction angle (2θ) of approximately 31°. This peak is attributed to the (009) plane of the InGaZnO4 crystal. This indicates that the crystals of the CAAC-OS film have a c-axis orientation, and the c-axis is approximately aligned on the surface on which the film is formed or on the upper surface. It can be seen that it is oriented in a substantially vertical direction.

[0118] On the other hand, in-pl X-rays are incident on the CAAC-OS film from a direction approximately perpendicular to the c-axis. In the analysis by the ane method, a peak may appear at 2θ around 56°. This is attributed to the (110) plane of the InGaZnO4 crystal. In the case of a semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is set as the axis (φ axis). When the sample is rotated and analyzed (φ scan), the crystal plane equivalent to the (110) plane is In contrast, in the case of the CAAC-OS film, 2θ is set to 5 Even when the φ is fixed at around 6° and scanned, no clear peak appears.

[0119] From the above, it is concluded that the a-axis and b-axis orientations are inconsistent between different crystal regions in the CAAC-OS film. Although it is regular, it has a c-axis orientation, and the c-axis is parallel to the normal vector of the surface to be formed or the upper surface. Therefore, the layered arrangement confirmed by the cross-sectional TEM observation mentioned above is consistent with the above. Each layer of aligned metal atoms is a plane parallel to the ab plane of the crystal.

[0120] The crystalline part is formed when the CAAC-OS film is formed or when a crystallization process such as a heat treatment is performed. As described above, the c-axis of the crystal is aligned with the surface on which the CAAC-OS film is formed or the surface on which the CAAC-OS film is formed. The orientation of the CAAC-OS film is parallel to the normal vector of the top surface. When the shape is changed by etching, the c-axis of the crystal is aligned with the surface on which the CAAC-OS film is formed. Or it may not be parallel to the normal vector of the upper surface.

[0121] The crystallinity of the CAAC-OS film may not be uniform. When the crystal part of the CAAC-OS film is formed by crystal growth from the vicinity of the top surface, The area near the surface may have a higher degree of crystallinity than the area near the surface to be formed. When impurities are added to a C-OS film, the crystallinity of the region where the impurities are added changes, resulting in partial In some cases, regions of different crystallinity may be formed.

[0122] In addition, the out-of-plane method of CAAC-OS film with InGaZnO4 crystals In the analysis by , in addition to the peak at 2θ around 31°, a peak also appeared at 2θ around 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 a 2θ of around 31°. It is preferable that the peak is exhibited at 2θ of around 36° and that the peak is not exhibited at 2θ of around 36°.

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

[0124] The oxide semiconductor film may be, for example, an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, or a CA The AC-OS film may be a laminated film having two or more kinds of films.

[0125] The CAAC-OS film is formed by sputtering, for example, using a polycrystalline metal oxide target. When ions collide with the target, the particles contained in the target are The crystal region is cleaved from the ab plane, and the crystal is formed into a flat or pellet-shaped strip with a plane parallel to the ab plane. In this case, the plate-shaped sputtering particles may peel off. The molecules reach the substrate while maintaining their crystalline state, forming a CAAC-OS film. can be done.

[0126] In addition, the following conditions are preferably applied to form the CAAC-OS film.

[0127] By reducing the amount of impurities mixed in during film formation, it is possible to prevent the crystal state from being destroyed by impurities. For example, the concentration of impurities (hydrogen, water, carbon dioxide, nitrogen, etc.) present in the processing chamber can be In addition, the impurity concentration in the deposition gas can be reduced. A deposition gas at a temperature of -80°C or lower, preferably -100°C or lower, is used.

[0128] In addition, by increasing the substrate heating temperature during film formation, the migration of sputtered particles after they reach the substrate is reduced. Specifically, the substrate heating temperature is set to 100°C or higher and 740°C or lower, preferably The film is formed at a temperature between 200°C and 500°C. When a plate-shaped sputtering particle reaches the substrate, migration occurs on the substrate, The flat surface of the sputtered particle adheres to the substrate.

[0129] In addition, increasing the oxygen ratio in the deposition gas and optimizing the power reduces plasma damage during deposition. The oxygen ratio in the deposition gas is preferably 30% by volume or more, and more preferably 100% by volume or more. The product is %.

[0130] As an example of the target, an In-Ga-Zn oxide target will be described below.

[0131] InO X powder, GaO Y Powder and ZnO Z The powders are mixed in a specified molar ratio and pressurized. After that, it is heat-treated at a temperature between 1000℃ and 1500℃ to form polycrystalline In-G The target is a-Zn oxide, where X, Y, and Z are any positive numbers. , the predetermined molar ratio is, for example, InO X powder, GaO Y Powder and ZnO Z Powder, 2 :2:1, 8:4:3, 3:1:1, 1:1:1, 4:2:3 or 3:1:2. The type of powder and the molar ratio of the powder to be mixed are determined appropriately depending on the target to be produced. Just change it.

[0132] The semiconductor film is not limited to being composed of a single oxide semiconductor film, but may be composed of a plurality of stacked oxide semiconductor films. The semiconductor film may be composed of three oxide semiconductor films. An example of the configuration of the transistor 100 in this case is shown in FIG.

[0133] The transistor 100 shown in FIG. 9 is provided on a substrate 111 having an insulating surface. a conductive film 112 having the above function, a gate insulating film 113 on the conductive film 112, and a gate insulating film A semiconductor film 114 is provided in a position overlapping with the conductive film 112 with the semiconductor film 113 sandwiched therebetween. A conductive film 115 and a conductive film 116 are in contact with the conductive film 114 and function as a source electrode or a drain electrode. and a conductive film 116.

[0134] 9, an oxide film 117 is formed over the semiconductor film 114, the conductive film 115, and the conductive film 116. In one embodiment of the present invention, the oxide film 117 is provided as a component of the transistor 100. It may be included in the base.

[0135] In the transistor 100, the oxide semiconductor films 114a to 114c are stacked in this order from the conductive film 112 side that functions as a gate electrode.

[0136] The oxide semiconductor film 114a and the oxide semiconductor film 114c are b) contains at least one of the metal elements constituting b in its constituent elements, and the energy of the conduction band minimum is is greater than that of the oxide semiconductor film 114b by 0.05 eV or more, 0.07 eV or more, or 0.1 eV or more. or above 0.15 eV and below 2 eV, 1 eV, 0.5 eV, or 0.4 The oxide semiconductor film 114b is an oxide film having a conductivity of at least 1000 volts or less, which is close to a vacuum level. In either case, indium is preferably contained because it increases carrier mobility.

[0137] When the transistor 100 has the above structure, the conductive film 1 When a voltage is applied to the semiconductor film 114, an electric field is applied to the semiconductor film 114. A channel region is formed in the oxide semiconductor film 114b having a low energy level at the bottom of the conduction band. That is, the oxide semiconductor film 114c is formed between the oxide semiconductor film 114b and the gate insulating film 113. By providing the gate insulating film 113, the oxide semiconductor film 11 A channel region can be formed in 4b.

[0138] In addition, the oxide semiconductor film 114c contains at least one metal element contained in the oxide semiconductor film 114b. Since both the oxide semiconductor film 114b and the oxide semiconductor film 114c contain one of the elements, Therefore, the movement of carriers is not hindered at the interface. As a result, the field effect mobility of the transistor 100 is increased.

[0139] Furthermore, an interface state is formed at the interface between the oxide semiconductor film 114b and the oxide semiconductor film 114a. Since a channel region is formed in the region near the interface, the threshold voltage of the transistor 100 increases. However, the oxide semiconductor film 114a is formed by the oxide semiconductor film 114b. Since the oxide semiconductor film 114b contains at least one of the metal elements forming the oxide semiconductor film 114b, An interface state is unlikely to be formed at the interface of the oxide semiconductor film 114a. This can reduce variations in the electrical characteristics of the transistor 100, such as the threshold voltage. .

[0140] In addition, the presence of impurities between the oxide semiconductor films prevents the flow of carriers at the interface between the films. To prevent the formation of interface states that hinder the formation of oxide semiconductor films, a plurality of oxide semiconductor films are stacked. When impurities exist between the stacked oxide semiconductor films, the oxide semiconductor The continuity of the energy at the bottom of the conduction band between the layers is lost, and the carriers This is because the electrons are trapped or disappear due to recombination. By reducing the impurities, a plurality of oxide semiconductors each having at least one metal as a main component can be obtained. Rather than simply stacking conductive films, we use continuous junctions (where the energy of the conduction band minimum is The formation of a U-shaped well structure (a state in which the structure changes continuously between the layers) is likely to occur.

[0141] To form continuous junctions, a multi-chamber deposition system equipped with a load lock chamber is required. (sputtering equipment) to continuously stack each film without exposing it to the air. Each chamber in the sputtering equipment must contain impurities for oxide semiconductors. In order to remove as much water as possible, an adsorption type vacuum pump such as a cryopump is used. High vacuum pumping (1×10 -4 Pa~5×10 -7 It is preferable to Alternatively, a turbomolecular pump and cold trap can be combined to evacuate the gas from the exhaust system to the chamber. It is preferable to prevent gas from flowing backward.

[0142] To obtain a high-purity intrinsic oxide semiconductor, it is not enough to evacuate each chamber to a high vacuum. It is also important to increase the purity of the gas used in sputtering. The dew point of the gas or argon gas is -40°C or less, preferably -80°C or less, more preferably - By keeping the temperature at 100°C or less and using highly purified gas, moisture and other substances are prevented from being absorbed into the oxide semiconductor film. This can prevent as many users as possible from being caught in the system.

[0143] For example, the oxide semiconductor film 114a or the oxide semiconductor film 114c may be formed of aluminum, silicon, or the like. Copper, titanium, gallium, germanium, yttrium, zirconium, tin, lanthanum , cerium, or hafnium in an atomic ratio higher than that of the oxide semiconductor film 114b. Specifically, the oxide semiconductor film 114a or the oxide semiconductor film 114c may be The amount of the above elements is 1.5 times or more, preferably 2 times or more, than that of the oxide semiconductor film 114b. More preferably, an oxide film containing the elements at an atomic ratio three times or more higher is used. Since it strongly bonds with oxygen, it has the function of suppressing the occurrence of oxygen vacancies in the oxide film. In this structure, the oxide semiconductor film 114a or the oxide semiconductor film 114c is formed by an oxide An oxide film in which oxygen vacancies are less likely to occur than in the semiconductor film 114b can be used.

[0144] Specifically, the oxide semiconductor film 114b and the oxide semiconductor film 114a or the oxide semiconductor film 114b are When both the oxide semiconductor film 114a and the oxide semiconductor film 114c are In-M-Zn-based oxides, The atomic ratio of the oxide semiconductor film 114c is In:M:Zn=x1:y1:z1. If the atomic ratio of 114b is In:M:Zn=x2:y2:z2, then y1 / x1 is y2 / The atomic ratio should be set so that it is larger than x2. are metal elements that have a strong bond with oxygen, such as Al, Ti, Ga, Y, Zr, Sn, and L. y1 / x1 is preferably greater than y2 / x2. The atomic ratio should be set so that the ratio is 1.5 times or more. The atomic ratio should be set so that 1 / x1 is more than twice as large as y2 / x2. More preferably, the atoms are arranged such that y1 / x1 is three times larger than y2 / x2. Furthermore, in the oxide semiconductor film 114b, y1 is equal to or greater than x1. This is preferable because it can provide stable electrical characteristics to the transistor 100. When x1 is three times or more than x1, the field effect mobility of the transistor 100 decreases. Therefore, it is preferable that y1 is less than three times x1.

[0145] In FIG. 15A, a portion in contact with the stacked oxide semiconductor films 114a to 114c is FIG. 15(A) shows a schematic diagram of a part of the band structure when a silicon oxide film is provided. ), the vertical axis represents the electron energy (eV) and the horizontal axis represents the distance. cI1 and EcI2 are the energies of the bottom of the conduction band of the silicon oxide film, and EcS1 is the The energy of the bottom of the conduction band of the oxide semiconductor film 114a is EcS2. The energy of the bottom of the conduction band of the oxide semiconductor film 114c is indicated by EcS3.

[0146] As shown in FIG. 15A, an oxide semiconductor film 114a, an oxide semiconductor film 114b, and an oxide semiconductor film 114c are formed. In the semiconductor film 114c, the energy of the conduction band minimum changes continuously. The oxide semiconductor film 114a, the oxide semiconductor film 114b, and the oxide semiconductor film 114c have similar compositions. This can also be understood from the fact that oxygen easily diffuses between the materials.

[0147] Note that in FIG. 15A, the oxide semiconductor film 114a and the oxide semiconductor film 114c are similar to each other. The cases where the two have different energy gaps are shown. For example, if EcS1 has a higher energy than EcS3, A part of the band structure is shown in FIG. 15(B). Although not shown in FIG. 15, Ec It is acceptable for EcS3 to have higher energy than S1.

[0148] As shown in FIG. 15, the oxide semiconductor film 114a and the oxide semiconductor film 114c are Trap levels due to impurities and defects are formed near the interface with insulating films such as silicon dioxide films. The oxide semiconductor films 114a and 114c can be used to form an oxide semiconductor film. However, the EcS1 Alternatively, when the energy difference between EcS3 and EcS2 is small, the oxide semiconductor film 114b Electrons can exceed this energy difference and reach the trap level. When trapped, a negative fixed charge is generated at the insulating film interface, and the threshold voltage of the transistor It shifts in the positive direction.

[0149] Therefore, the energy difference between EcS1 and EcS3 and EcS2 is 0.1e V or more, preferably 0.15 eV or more, the fluctuation of the threshold voltage of the transistor is reduced. This reduces the electrical resistance and provides stable electrical characteristics.

[0150] Note that the thickness of the oxide semiconductor film 114a and the oxide semiconductor film 114c is greater than or equal to 3 nm and less than or equal to 100 nm. The thickness of the oxide semiconductor film 114b is set to be equal to or less than 3 nm, preferably equal to or greater than 50 nm. The thickness is 3 nm or more and 200 nm or less, preferably 3 nm or more and 100 nm or less, and The thickness is preferably 3 nm or more and 50 nm or less.

[0151] In the three-layer semiconductor film, the oxide semiconductor films 114a to 114c are It can be either amorphous or crystalline. However, the oxide on which the channel region is formed The semiconductor film 114b is crystalline, which provides the transistor 100 with stable electrical characteristics. Therefore, the oxide semiconductor film 114b is preferably crystalline.

[0152] Note that the channel formation region is a region of the semiconductor film of a transistor that overlaps with the gate electrode and The channel region refers to the region sandwiched between the source electrode and the drain electrode. This refers to the region in the core formation region where current mainly flows.

[0153] For example, the oxide semiconductor films 114a and 114c are formed by a sputtering method. When an In—Ga—Zn-based oxide film formed by The oxide semiconductor film 114c was formed using an In-Ga-Zn oxide (In:Ga:Zn=1 A target having an atomic ratio of 0.1:0.3:2 can be used. The film formation conditions are, for example, The deposition gas was argon gas at 30 sccm and oxygen gas at 15 sccm, and the pressure was 0.4 The substrate temperature is set to 200° C. and the DC power is set to 0.5 kW.

[0154] When the oxide semiconductor film 114b is a CAAC-OS film, The film is made of In-Ga-Zn oxide (In:Ga:Zn=1:1:1 [atomic ratio]) It is preferable to use a target containing a polycrystalline In—Ga—Zn-based oxide. The film formation conditions are, for example, argon gas at 30 sccm and oxygen gas at 15 sccm. cm, pressure 0.4 Pa, substrate temperature 300°C, DC power 0.5 kW. It is possible.

[0155] Note that the transistor 100 shown in FIG. 9 has a structure in which the end portion of the semiconductor film 114 is inclined. Alternatively, the semiconductor film 114 may have a rounded edge.

[0156] Note that FIG. 9 illustrates the semiconductor film 114 in which three oxide semiconductor films are stacked. However, the semiconductor film 114 may have a structure in which a plurality of oxide semiconductor films other than the oxide semiconductor film 3 are stacked. good.

[0157] Note that when the semiconductor film 114 has a structure in which a plurality of oxide semiconductor films are stacked, The metal oxide used in the oxide film 117 has a higher conductivity than the entire semiconductor film 114. For example, an In-Ga-Zn oxide is used as the metal oxide to form the oxide film 11. When used in the semiconductor film 114, the metal oxide has a lower atomic ratio of In than that of the semiconductor film 114. Let's say.

[0158] As in the case of the transistor 10, the conductive film 115 and the conductive film 116 of the semiconductor film 114 are The region in contact with the film 116 may be made n-type. 0 mobility and on-state current, thereby realizing high-speed operation of a semiconductor device using the transistor 100. Furthermore, in the case of the transistor 100, the region to be made n-type is The fact that the oxide semiconductor film 114b, which is the gate region of the transistor 100, is reached This is preferable in terms of increasing the mobility and on-current and realizing even higher speed operation of the semiconductor device.

[0159] <Method for manufacturing semiconductor device> Hereinafter, an example of a method for manufacturing a semiconductor device according to one embodiment of the present invention will be described.

[0160] As shown in FIG. 10(A), a conductive film 201 is formed on a substrate 200 .

[0161] The substrate 200 is preferably a substrate having heat resistance sufficient to withstand the subsequent manufacturing steps. For example, a glass substrate, a ceramic substrate, a quartz substrate, a sapphire substrate, etc. may be used.

[0162] The conductive film 201 may be made of aluminum, titanium, chromium, cobalt, nickel, copper, or yttrium. Thorium, zirconium, molybdenum, ruthenium, silver, tantalum and tungsten It is preferable to form one or more layers of a film made of a conductive material containing at least one of the above-mentioned elements. 01, a conductive film in which a copper film is stacked on a tungsten nitride film, or a single layer of tungsten film It can be used.

[0163] Next, the gate electrode of the transistor and the Specifically, a conductive film 202 having the function of forming a conductive film 202 is formed using a first photomask. Then, a mask made of resist (hereinafter referred to as a resist mask) is formed on the conductive film 201. After that, the conductive film 201 is etched to form a conductive film 202, and then a resist mask is formed. Remove the stub (see FIG. 10(B)).

[0164] Next, a gate insulating film 203 is formed to cover the conductive film 202. A semiconductor film 204 is formed thereon (see FIG. 10(C)).

[0165] The gate insulating film 203 may be made of aluminum oxide, magnesium oxide, silicon oxide, or oxynitride. Silicon oxide, silicon nitride, silicon nitride, gallium oxide, germanium oxide, yttrium oxide , zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide and tantalum oxide An insulating film containing one or more kinds of insulating films may be used as a single layer or a stacked layer.

[0166] For example, when the gate insulating film 203 has a two-layer structure, the first layer is a silicon nitride film and the second layer is a silicon nitride film. The second silicon oxide film can be a silicon oxynitride film. Moreover, the first silicon nitride film can be a silicon nitride oxide film.

[0167] It is preferable to use a silicon oxide film with a small defect density. The g value in ESR (Electron Spin Resonance) is 2.0 The spin density of the spins originating from the O1 signal is 3×10 17 spins / cm 3 Below, I prefer Or 5 x 10 16 spins / cm 3 The silicon oxide film used is as follows: It is preferable to use a silicon oxide film containing excess oxygen. A silicon nitride film is preferable because it can absorb hydrogen and ammonia. The amount of hydrogen and ammonia released is measured by TDS (Therma Desorption Spectroscopy (thermal desorption spectroscopy) analysis Just measure it.

[0168] Next, the semiconductor film 204 is formed into a desired shape by a photolithography process and an etching process. The semiconductor film 205 is formed by processing the second photoresist. A resist mask is formed on the semiconductor film 204 using a mask, and the semiconductor film 204 is etched. This is followed by etching to form a semiconductor film 205. Then, the resist mask is removed.

[0169] The semiconductor film 205 can be formed using any of the above-described oxide semiconductors.

[0170] When a large amount of hydrogen is contained in the oxide semiconductor film used as the semiconductor film 205, By bonding, some of the hydrogen atoms become donors, generating electrons that act as carriers. This causes the threshold voltage of the transistor to shift in the negative direction. After the oxide semiconductor film is formed, dehydration treatment (dehydrogenation treatment) is performed to remove hydrogen from the oxide semiconductor film. Therefore, it is preferable to remove hydrogen or moisture to minimize the amount of impurities contained.

[0171] Note that dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film removes oxygen from the oxide semiconductor film. Therefore, the amount of carbon dioxide that was increased by the dehydration treatment (dehydrogenation treatment) may decrease. In order to fill oxygen vacancies, treatment for adding oxygen to the oxide semiconductor film is preferably performed.

[0172] In this way, hydrogen or moisture is removed from the oxide semiconductor film by dehydration treatment (dehydrogenation treatment). By adding oxygen to the silicon dioxide, the oxygen vacancies are compensated for, resulting in i-type (intrinsic) or A substantially i-type (intrinsic) oxide semiconductor film can be formed.

[0173] Next, a conductive film 206 is formed over the semiconductor film 205 and the gate insulating film 203. The conductive film 06 can be formed using the same conductive material as the conductive film 201 (see FIG. 11A).

[0174] Next, a resist is formed on the conductive film 206 and the gate insulating film 203 using a third photomask. Using this resist mask, the conductive film 206 is etched to form a semiconductor A conductive film 207 and a conductive film 208 are formed in contact with the conductive film 205 (see FIG. 11(B)).

[0175] Next, an insulating film is formed to cover the entire substrate 200. In FIG. 11(C), an oxide film 209 Then, an insulating film 210 and an insulating film 211 are formed.

[0176] It is desirable to use a metal oxide for the oxide film 209. By using the insulating film 210 containing silicon, the insulating film 210 and the semiconductor film 205 are separated. Therefore, when a metal oxide containing indium is used for the semiconductor film 205, When the semiconductor film 2 is in a state where the bonding energy between the silicon and oxygen is larger than that between the silicon and oxygen, the bonding energy between the silicon and oxygen is larger than that between the silicon and oxygen. At the edge of the O5, the bond between indium and oxygen is broken, preventing the formation of oxygen vacancies. As a result, in one embodiment of the present invention, the reliability of the transistor can be further improved. This can be done.

[0177] Specifically, the oxide film 209 is formed by sputtering with a metal atomic ratio of 1:6:4, Alternatively, the film may be formed using an In-Ga-Zn oxide target having a ratio of 1:3:2. This can be done.

[0178] The insulating film 211 is formed continuously after the insulating film 210 is formed without being exposed to the atmosphere. After the insulating film 210 is formed, the flow rate, pressure, and high frequency of the source gas are adjusted without exposing to the atmosphere. By adjusting one or more of the power and the substrate temperature, the insulating film 211 is continuously formed. 210 and the insulating film 211, the impurity concentration at the interface can be reduced. The oxygen contained in the insulating film 211 can be transferred to the semiconductor film 205. The amount of oxygen vacancy in 05 can be reduced.

[0179] The substrate placed in the evacuated processing chamber of the plasma CVD device is heated to 180°C or higher, up to 400°C. The temperature is preferably maintained at 200°C or higher and 370°C or lower, and the raw material gas is introduced into the processing chamber. The pressure in the processing chamber is set to 30 Pa or more and 250 Pa or less, more preferably 40 Pa or more. The pressure is set to 200 Pa or less, and high-frequency power is supplied to the electrodes installed in the processing chamber, The insulating film 210 is formed of a silicon oxide film or a silicon oxynitride film.

[0180] As the source gas of the insulating film 210, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of silicon-containing deposition gases include silane, disilane, trisilane, and the like. Examples of oxidizing gases include oxygen, ozone, nitrous oxide, and dioxygen. Examples include nitrogen dioxide.

[0181] By using the above conditions, an oxide insulating film that transmits oxygen can be formed as the insulating film 210. Furthermore, by providing the insulating film 210, the insulating film 211 can be formed later. In this case, damage to the oxide film 209 can be reduced.

[0182] In addition, by increasing the amount of oxidizing gas to 100 times or more the amount of deposition gas containing silicon, It is possible to reduce the hydrogen content in the insulating film 210 and to The oxygen that moves from the insulating film 211 can be reduced. Since the dangling bonds contained in the insulating film 210 may capture the stoichiometric amount of The oxygen contained in the insulating film 211, which has more oxygen than the theoretical composition, is efficiently transferred to the semiconductor film 20. 5, and oxygen vacancies in the semiconductor film 205 can be compensated for. As a result, the amount of hydrogen mixed into the semiconductor film 205 can be reduced, and the amount of oxygen contained in the semiconductor film 205 can be reduced. It is possible to reduce defects, thereby suppressing the negative shift of the transistor threshold voltage. This can suppress leakage current at the source and drain of the transistor. This allows for a reduction in the amount of charge and improves the electrical characteristics of the transistor.

[0183] In one embodiment of the present invention, the insulating film 210 is formed by using silane at a flow rate of 20 sccm and silane at a flow rate of 3000 sccm. The source gas was dinitrogen monoxide at a flow rate of 40 sccm, the pressure in the processing chamber was 40 Pa, and the substrate temperature was 220°C. A 27.12 MHz high-frequency power source was used to supply 100 W of high-frequency power to the parallel plate electrodes. A silicon oxynitride film with a thickness of 50 nm is formed by the plasma CVD method using the plasma. The Zuma CVD device has an electrode area of ​​6000 cm 2 It is a parallel plate type plasma CVD device. The power supplied can be converted to power per unit area (power density) of 1.6 x 10 -2 W / cm 2 Under these conditions, a silicon oxynitride film that is permeable to oxygen can be formed. do.

[0184] The insulating film 211 is formed by insulating a substrate placed in a processing chamber of a plasma CVD apparatus that has been evacuated. The temperature is maintained at 0°C or higher and 260°C or lower, more preferably 180°C or higher and 230°C or lower, and the temperature is maintained in the processing chamber. The pressure in the processing chamber is adjusted to 100 Pa or more and 250 Pa or less by introducing the raw material gas. or 100 Pa or more and 200 Pa or less, and 0.17 W / c m2 More than 0.5W / cm 2 or less, more preferably 0.25 W / cm 2 More than 0.35W / cm 2 Silicon oxide film or silicon oxynitride film is formed under the following conditions of supplying high frequency power. do.

[0185] The conditions for forming the insulating film 211 are as follows: high frequency power of the above power density in a processing chamber under the above pressure; By supplying the source gas, the decomposition efficiency in the plasma increases, oxygen radicals increase, As the oxidation of the source gas progresses, the oxygen content in the insulating film 211 becomes higher than the stoichiometric composition. However, when the substrate temperature is above this level, the bonding strength between silicon and oxygen becomes weak. As a result, the amount of oxygen in the stoichiometric composition is less than that of the oxygen in the stoichiometric composition. It is possible to form an oxide insulating film that contains a large amount of oxygen and from which part of the oxygen is released by heating. In addition, an insulating film 210 is provided on the oxide film 209. In the formation process, the insulating film 210 serves as a protective film for the oxide film 209. While reducing damage to the film 209, the insulating film 211 is formed by using high-frequency power with high power density. can be formed.

[0186] In one embodiment of the present invention, the insulating film 211 is formed by using silane at a flow rate of 160 sccm and silane at a flow rate of 400 The source gas was nitrous oxide at 0 sccm, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 22 The temperature was set at 0°C, and a 27.12MHz high-frequency power supply was used to apply 1500W of high-frequency power to the parallel plate electrodes. A silicon oxynitride film with a thickness of 400 nm is formed by plasma CVD using a material supplied to the electrode. The plasma CVD device has an electrode area of ​​6000 cm 2 Parallel plate type plasma CVD The power supplied is converted to power per unit area (power density) of 2.5 x 1 0 -1 W / cm 2 is.

[0187] Next, at least the insulating film 211 is formed, and then a heat treatment is performed to form the insulating film 210 or the insulating film 211. The oxygen contained in the insulating film 211 is transferred to the oxide film 209 and the semiconductor film 205, and the oxide film 2 It is preferable to compensate for oxygen vacancies in the semiconductor film 209 and the semiconductor film 205. This may be performed as heat treatment for dehydrogenating or dehydrating the conductive film 205 .

[0188] <Circuit Configuration Example of Semiconductor Device According to One Embodiment of the Present Invention> Next, structural examples of various circuits included in a semiconductor device according to one embodiment of the present invention will be described. 12A to 12C show a sequential circuit 80 and a shift register including the sequential circuit 80. 3 shows an example of the configuration of the controller 300.

[0189] The shift register 300 shown in FIG. 12A includes a first sequential circuit 80 _1 or the Nth time in order ro 80 _N and a plurality of sequential circuits 80 shown by a symbol 81 and a circuit having a function of transmitting a clock signal CLK. The wiring 81 is supplied with a clock signal CLK1, and the wiring 82 is supplied with a clock signal CLK2. A clock signal CLK2 is applied to the wiring 82, and a clock signal CLK3 is applied to the wiring 83. A clock signal CLK4 is applied to the wiring 84.

[0190] The clock signal alternates between high-level potential (H) and low-level potential (L) at regular intervals. In FIG. 12A, the clock signals CLK1 to CLKC are repeated. LK4 is a signal delayed by 1 / 4 period. In the circuit, the sequential circuit 80 is controlled using the clock signal. A plurality of clock signals may be input to the clock signal generator 10.

[0191] First sequential circuit 80 _1 to N-th sequential circuit 80 _N are terminals 91 and 92, respectively. , terminals 93, 94, 95, 96, and 97 (see FIG. 12(B)). ).

[0192] The terminal 91, the terminal 92, and the terminal 93 are connected to any of the wirings 81 to 84. For example, the first sequential circuit 80 _1 In this case, the terminal 91 is connected to the wiring 81, and the terminal 92 is The second sequential circuit 80 has a terminal 93 connected to a wiring 82 and a terminal 94 connected to a wiring 83. _2 In this case, terminal 91 is connected to wiring 82, terminal 92 is connected to wiring 83, and terminal 9 3 is connected to the wiring 84. In FIG. 12(A), the Nth sequential circuit 80 _N Connect with The connected wiring is shown as wiring 82, wiring 83, and wiring 84. Circuit 80 _N The wiring connected to this will differ depending on the value of N.

[0193] In addition, the kth sequential circuit (k is 3 or more and N or less) of the shift register 300 according to one embodiment of the present invention In the (k-1)th sequential circuit, terminal 94 is connected to terminal 96 of the (k-1)th sequential circuit, and terminal 9 5 is connected to terminal 96 of the (k+2)th sequential circuit, and terminal 96 is connected to terminal 96 of the (k+1)th sequential circuit. and a terminal 95 of the (k-2)-th sequential circuit, and a terminal 97 of the OUT_ Output a signal to k.

[0194] In addition, the first sequential circuit 80 _1 Now, connect the start pulse (SP1 ) is input. In addition, the (N-1)th sequential circuit 80 _(N-1) Now, the start pulse (SP2) is input to the terminal 95. In addition, the Nth sequential circuit 80 _N So, Start Pal The start pulse (SP3) is input to the terminal 95. The pulse (SP3) may be an externally input signal or a signal generated within the circuit. It may also be possible to use the following.

[0195] Next, the first sequential circuit 80 _1 to N-th sequential circuit 80 _N Explain the specific configuration of do.

[0196] First sequential circuit 80 _1 to N-th sequential circuit 80 _N Each of the following is shown in FIG. In the following description, the transistors 301 to 311 are The gate of the transistor is connected to the gate terminal, one of the source and drain is connected to the first terminal, and the source and drain are connected to the second terminal. The other end of the drain is called the second terminal.

[0197] In this specification, connection means electrical connection, and the current, voltage, or potential Therefore, the connected state corresponds to the state in which the signal is directly connected. It does not necessarily refer to the state of being connected, but rather to the state in which a current, voltage, or potential is available or is transmitted through circuit elements such as wires, resistors, diodes, and transistors. This also includes the state in which components are indirectly connected through other means. Even when elements are connected to each other, in reality, for example, part of the wiring functions as an electrode. In some cases, a single conductive film may have the functions of multiple components. In the specification, connection means that one conductive film has the functions of multiple components. If so, include it in that category.

[0198] The source of a transistor refers to a source region that is a part of a semiconductor film, or the semiconductor Similarly, the drain of a transistor refers to the source electrode connected to the semiconductor film. The drain region is a part of the semiconductor film, or the drain electrode is connected to the semiconductor film. Also, the term "gate" refers to a gate electrode.

[0199] The source and drain of a transistor are given to the polarity and each terminal of the transistor. The name changes depending on the potential. Generally, in n-channel transistors, The terminal to which a low potential is applied is called the source, and the terminal to which a high potential is applied is called the drain. In addition, in a p-channel transistor, the terminal to which a low potential is applied is called the drain. The terminal to which the high potential is applied is called the source. Explain the connection relationship of a transistor, assuming that the source and drain are fixed. In some cases, the names of source and drain are interchangeable depending on the above potential relationship. .

[0200] The configuration of the sequential circuit shown in FIG. 12(C) will be described.

[0201] The transistor 301 has a first terminal connected to the terminal 91 and a second terminal connected to the terminal 96. The gate terminal of the transistor 307 is connected to the second terminal of the transistor 308. 02 has a first terminal connected to the terminal 96, a second terminal connected to the wiring 71, and a gate terminal The first terminal of the transistor 303 is connected to the second terminal of the transistor 308. The first terminal is connected to the terminal 91, the second terminal is connected to the terminal 97, and the gate terminal is connected to the transistor The first terminal of transistor 304 is connected to terminal 97. , a second terminal is connected to the wiring 71, and a gate terminal is connected to the second The first terminal of the transistor 305 is connected to the wiring 72, and the second terminal of the transistor 305 is connected to the wiring 72. The second terminal is connected to the first terminal of the transistor 306 and the first terminal of the transistor 307. The first terminal of the transistor 306 is connected to the transistor 304, and the gate terminal of the transistor 306 is connected to the terminal 94. A second terminal of the transistor 305 and a first terminal of the transistor 307 are connected to each other. The terminal is connected to the wiring 71, and the gate terminal is connected to the second terminal of the transistor 308. The transistor 307 has a first terminal connected to the second terminal of the transistor 305 and a second terminal of the transistor 306. The first terminal of the transistor 306 is connected to the gate terminal of the transistor 301, and the second terminal of the transistor 306 is connected to the gate terminal of the transistor 301. and the gate terminal of the transistor 303, which is connected to the wiring 72. The first terminal of the transistor 308 is connected to the second terminal of the transistor 310. The second terminal is the gate terminal of the transistor 302, the gate terminal of the transistor 304, and It is connected to the gate terminal of transistor 306 , the gate terminal of which is connected to terminal 92 . The first terminal of the transistor 309 is connected to the second terminal of the transistor 308. The terminal of transistor 3 is connected to wiring 71, and the gate terminal is connected to terminal 94. 10 has a first terminal connected to the wiring 72 and a second terminal connected to the first terminal of the transistor 308. The first terminal of the transistor 311 is connected to the first terminal of the transistor 312, and the gate terminal of the transistor 311 is connected to the terminal 93. a terminal connected to the wiring 72, a second terminal connected to the second terminal of the transistor 308, The gate terminal is connected to terminal 95 .

[0202] The above-described configurations of the sequential circuits are merely examples, and one embodiment of the present invention is not limited to these. do not have.

[0203] The sequential circuit 80 in FIG. 12(C) is the first sequential circuit 80 shown in FIG. 12(A). _1 is In this case, the clock signal CLK1 is applied to the terminal 91, and the clock signal CLK 2 is given to terminal 93, clock signal CLK3 is given to terminal 94, and start signal CLK5 is given to terminal 95. A pulse SP1 is applied to the terminal 95 of the third sequential circuit 80. _3 The output signal (SROUT 3) is input from the terminal 96 to the first sequential circuit 80. _1 The output signal (S ROUT_1) is a second sequential circuit 80 _2 The output is from terminal 94 and the output is from terminal 97. A force signal OUT_1 is output.

[0204] The wiring 71 is supplied with a second potential VSS, and the wiring 72 is supplied with a first potential VDD. do.

[0205] The shift register 300 using the sequential circuit 80 in FIG. 12C has a first potential VDD and and the second potential VSS, the clock signals CLK1 to CLK4, the start pulse SP, and the output The desired pulses are sequentially output as an output signal O according to the input signals SROUT_1 to SROUT_N. These can be obtained as UT_1 to OUT_N.

[0206] In the case of a circuit made up of unipolar transistors, such as the sequential circuit 80 shown in FIG. In this case, the potential of various nodes and terminals of the circuit drops by the threshold voltage of the transistor. In the case of FIG. 12(C), when the transistor 303 is in a conducting state, a voltage is applied to the terminal 91. The potential of the clock signal is dropped from the high level (H) by the threshold voltage of the transistor 303. The potential is applied to terminal 97. Therefore, a circuit consisting of unipolar transistors In this case, the threshold voltage of the transistor must be set to a value that ensures that the transistor is normally off. It is important to keep it low.

[0207] In one embodiment of the present invention, the transistor 10, the transistor 30, and the transistor 40, and the transistor 100 has a threshold voltage that satisfies the normally-off condition. It is possible to have an initial value and to suppress the amount of change in the threshold voltage to the positive side. The transistors 301 to 311 are connected to the transistors 10 and 3. 0, transistor 40, or transistor 100, the reliability of the sequential circuit 80 is improved. It can improve sexuality.

[0208] In particular, when the transistors 301 to 311 are n-channel transistors, the terminal 97 a transistor 303 that provides a high level output signal to terminal 96; The gate terminal of the transistor 301, the transistor 303, and the transistor 301 The transistor 305 that applies a high-level potential to the As a result, the sequential circuit 80 does not operate normally, or even if it does, the terminals 96 and 97 This can easily cause problems such as the high-level potential being output lower than the desired value. Therefore, at least the transistor 303, the transistor 301, and the transistor 305 The transistor 10, the transistor 30, the transistor 40, or the transistor 1 The use of 00 is effective in ensuring the reliability of the sequential circuit 80.

[0209] Note that in one embodiment of the present invention, in the sequential circuit configuration shown in FIG. 12C, all the transistors A back gate may be provided in the resistor. The back gate may be in a floating state. In the latter case, the normal gate (flow The same potential may be applied to the front gate and the back gate. A fixed potential such as a ground potential may be applied only to the gate. By controlling the back gate, the threshold voltage of the transistor can be controlled. By providing a gate, the channel formation region increases, and the drain current can be increased. In addition, the back gate makes it easier for a depletion layer to form in the semiconductor film, which reduces the S value. Improvements can be made.

[0210] <Configuration Example of Semiconductor Display Device> In one embodiment of the present invention, a semiconductor display device corresponding to one of the semiconductor devices of the present invention includes: We will explain about this.

[0211] The panel 460 shown in FIG. 13A includes a pixel section 461, a plurality of pixels 462, and a pixel 463. 2 for each row, the scanning lines GL1 to GLm (m is a natural number) are used. and signal lines SL1 to SL2 for supplying image signals to selected pixels 462. The signal lines SL are indicated by lines SLn (n is a natural number). The input of the signal is controlled by the scanning line driving circuit 463. The output is controlled by a signal line driving circuit 464. The plurality of pixels 462 are connected to the scanning line GL. At least one of the signal lines SL is connected to the output terminal 11 and at least one of the signal lines SL is connected to the output terminal 11.

[0212] The type and number of wirings provided in the pixel portion 461 depend on the configuration, number and wiring of the pixel 462. Specifically, in the case of the pixel portion 461 shown in FIG. 13(A), n Pixels 462 are arranged in a matrix of m columns and m rows, and signal lines SL1 to SLn 1, the scanning lines GL1 to GLm are arranged in the pixel portion 461. do.

[0213] The sequential circuit 80 and the shift register 300 shown in FIG. It can be used in the signal line driver circuit 464. A sequential circuit 80 and a sequential circuit 81 using a transistor 30, a transistor 40, or a transistor 100 The soft register 300 is applied to the scanning line driver circuit 463 or the signal line driver circuit 464. This makes it possible to improve the reliability of the semiconductor display device.

[0214] 13B shows an example of the configuration of a pixel 462. Each pixel 462 has a liquid crystal element 465, a transistor 466 for controlling the supply of an image signal to the liquid crystal element 465, and a liquid crystal The pixel electrode of the crystal element 465 and the common electrode have a capacitance element 467 for maintaining the voltage between them. The liquid crystal element 465 has a pixel electrode, a common electrode, and a voltage applied between the pixel electrode and the common electrode. and a liquid crystal layer containing a liquid crystal material.

[0215] The transistor 466 determines whether or not the potential of the signal line SL is applied to the pixel electrode of the liquid crystal element 465. A predetermined potential is applied to the common electrode of the liquid crystal element 465.

[0216] A specific connection relationship between the transistor 466 and the liquid crystal element 465 will be described below. In 3(B), the gate electrode of the transistor 466 is connected to one of the scanning lines GL1 to GLm. One of the source and drain electrodes of the transistor 466 is connected to one of the signal lines SL1 to SLn, and the solenoid of the transistor 466 The other of the source electrode and the drain electrode is connected to a pixel electrode of the liquid crystal element 465 .

[0217] In FIG. 13B, a pixel 462 has a switch that controls input of an image signal to the pixel 462. 4 shows an example in which one transistor 466 is used as a switch. The pixel 462 may include a plurality of transistors that function as a transistor.

[0218] In one embodiment of the present invention, the transistor 466 may be a transistor 10, a transistor By using the transistor 30, the transistor 40, or the transistor 100, a semiconductor The reliability of the display device can be improved. Since the off-state current of the transistor is extremely small, the transistor is used as the transistor 466. This can prevent charge from leaking through the transistor 466. The potential of the image signal applied to the crystal element 465 and the capacitance element 467 can be more reliably maintained. Therefore, the transmittance of the liquid crystal element 465 is This prevents the image from changing, thereby improving the quality of the displayed image. When the off-state current of the transistor 466 is small, charge leaks through the transistor 466. This can prevent the capacitance element 467 from being overloaded, thereby reducing the area of ​​the capacitance element 467. This increases the transmittance of the panel 460, thereby increasing the light transmittance of the backlight, frontlight, etc. The loss of the light supplied from the supply unit within the panel 460 is reduced, and the liquid crystal display device Alternatively, the power consumption can be reduced by driving the scanning lines during the period when a still image is displayed. The supply of power supply potential or signals to the driving circuit 463 and the signal line driving circuit 464 may be stopped. With the above configuration, the number of times that an image signal is written to the pixel portion 461 is reduced, and the semiconductor display device This can reduce the power consumption of the device.

[0219] 13B shows another example of the pixel 462. The pixel 462 is A transistor 470 for controlling the input of an image signal, a light emitting element 473, and a A transistor 471 for controlling a current value supplied to a light emitting element 473 and a transistor for holding a potential of an image signal and a capacitor 472 for maintaining the capacitance.

[0220] Either the anode or the cathode of the light emitting element 473 is connected to the pixel 462. The potential of either the anode or the cathode of the light emitting element 473 is controlled in accordance with the signal. A predetermined potential is applied to the anode and the cathode. In each of the plurality of pixels 462 included in the pixel portion, The luminance of the element 473 is adjusted in accordance with an image signal having image information, thereby forming a pixel portion 461 The image is displayed.

[0221] Next, a transistor 470, a transistor 471, a capacitor 47 2. The connection configuration of the light emitting element 473 will be explained.

[0222] The transistor 470 has one of a source electrode and a drain electrode connected to a signal line SL. The other of the source electrode and the drain electrode is connected to the gate electrode of the transistor 471. The gate electrode of the transistor 470 is connected to the scanning line GL. 71 has one of its source electrode and drain electrode connected to the power supply line VL, The other drain electrode of the transistor 47 is connected to the light emitting element 473. The other of the source electrode or drain electrode of the light emitting element 473 is connected to either the anode or the cathode of the light emitting element 473. The other of the anode and cathode of the light emitting element 473 is connected to , a predetermined potential is applied.

[0223] Note that although FIG. 13C illustrates an example in which the pixel 462 includes a capacitor 472, For example, the gate capacitance formed between the gate electrode of the transistor 470 and the semiconductor film, When the parasitic capacitance of the output electrode is large enough, the potential of the image signal can be sufficiently maintained by other capacitances. In this case, the capacitor 472 does not necessarily need to be provided in the pixel 462.

[0224] The light emitting element 473 is an LED (Light Emitting Diode) or an OLED ( Organic Light Emitting Diode), etc. For example, an OLED includes an EL layer and a The EL layer is disposed between the anode and the cathode. It is composed of a single layer or multiple layers, and these layers contain luminescent materials. The light-emitting layer includes at least a light-emitting layer containing the light-emitting layer.

[0225] The EL layer is turned on when the potential difference between the cathode and the anode becomes equal to or greater than the threshold voltage of the light emitting element 473. When the current is supplied, electroluminescence is obtained. Luminescence consists of two types of emission: fluorescence when returning from the singlet excited state to the ground state and fluorescence when returning from the triplet excited state. This includes light emission (phosphorescence) when the element returns from the normal state to the ground state.

[0226] <Configuration example of electronic device using semiconductor device> A semiconductor device according to one aspect of the present invention includes a display device, a personal computer, and a recording medium. Image playback devices (typically DVD: Digital Versatile Disc) (Devices having a display that can play back recording media such as DVDs and display the images) In addition, electronic devices in which the semiconductor device according to one embodiment of the present invention can be used are Mobile phones, portable game consoles, personal digital assistants, e-books, video cameras, digital cameras, Cameras such as digital still cameras, goggle-type displays (head-mounted displays) ), navigation systems, sound reproduction devices (car audio, digital audio players) Years, etc.), copiers, fax machines, printers, printer-combined machines, automated teller machines Examples of such electronic devices include ATMs and vending machines. vinegar.

[0227] FIG. 14A shows a portable game machine, which includes a housing 5001, a housing 5002, a display unit 5003, Display unit 5004, microphone 5005, speaker 5006, operation keys 5007, The display unit 5003 or the display unit 5004 or other circuits A semiconductor device according to one embodiment of the present invention can be used for the circuit. The portable game machine has two display units 5003 and 5004. The number of display units that the game machine has is not limited to this.

[0228] FIG. 14B shows a display device, which includes a housing 5201, a display portion 5202, a support base 5203, and the like. The semiconductor device of one embodiment of the present invention is used in the display portion 5202 or other circuits. Display devices include those for personal computers, those for receiving TV broadcasts, This includes all display devices for displaying information, such as advertising displays.

[0229] FIG. 14C shows a notebook personal computer, which includes a housing 5401 and a display portion 5402. The display unit 5402 includes a keyboard 5403, a pointing device 5404, and the like. The semiconductor device according to one embodiment of the present invention can be used in the above-described circuits or other circuits.

[0230] FIG. 14D shows a portable information terminal, which includes a first housing 5601, a second housing 5602, a first display unit, and a 5603, a second display unit 5604, a connection unit 5605, operation keys 5606, etc. Table 1 The display unit 5603 is provided in the first housing 5601, and the second display unit 5604 is provided in the second housing 5602. The first housing 5601 and the second housing 5602 are connected by a connection portion 56 5605, and the angle between the first housing 5601 and the second housing 5602 is The image on the first display unit 5603 can be changed by the connection unit 5605. 605, the first housing 5601 and the second housing 5602 are switched according to the angle between them. The first display portion 5603 or the second display portion 5604, or other circuits The semiconductor device according to one embodiment of the present invention can be used for the first display portion 5603. and a semiconductor device in which a function as a position input device is added to at least one of the first and second display units 5604. The function of the position input device may be realized by a semiconductor device. This can be added by providing a touch panel. Or, it can function as a position input device. The addition can also be achieved by providing a photoelectric conversion element, also called a photosensor, in the pixel portion of the semiconductor device. can be added.

[0231] FIG. 14E shows a video camera, which includes a first housing 5801, a second housing 5802, and a display unit 58 03, operation keys 5804, a lens 5805, a connection part 5806, etc. The lens 5805 is provided in the first housing 5801, and the display unit 5803 is provided in the second housing. The first housing 5801 and the second housing 5802 are connected by a connection part. The first housing 5801 and the second housing 5802 are connected by a The video on the display unit 5803 can be changed by the video input unit 5806. , according to the angle between the first housing 5801 and the second housing 5802 at the connection portion 5806. The semiconductor device according to one embodiment of the present invention may be provided in the display portion 5803 or other circuits. A conductor device may be used.

[0232] FIG. 14F shows a mobile phone, which includes a housing 5901, a display portion 5902, a microphone 5907, a speaker 5908, and a microphone 5909. Speaker 5904, camera 5903, external connection part 5906, and operation button 5905 are installed. The semiconductor device according to one embodiment of the present invention is used in a circuit included in a mobile phone. Furthermore, a liquid crystal display device, which is one of the semiconductor devices according to one embodiment of the present invention, can be made flexible. When the display device is formed on a substrate having a curved surface, it corresponds to a display portion 5902 having a curved surface as shown in FIG. The liquid crystal display device can be applied. [Explanation of symbols]

[0233] 10 transistors 11 Circuit Board 12 Conductive film 13 Gate insulating film 14 Semiconductor film 14n area 15 Conductive film 16 Conductive film 17 Oxide film 18 areas 19a area 19b area 20 transistors 22 Conductive film 24 Semiconductor film 25 Conductive film 26 Conductive film 30 transistors 30a transistor 30b transistor 31 PCB 32 Conductive film 33 Gate insulating film 34 Semiconductor film 35 Conductive film 36 Conductive film 37 Oxide film 38 areas 39a area 39b area 40 transistors 40a transistor 40b transistor 41 PCB 42 Conductive film 43 Gate insulating film 44 Semiconductor Film 45 Conductive film 46 Conductive Film 47 Oxide Film 48 areas 50 convex part 51 Connecting part 60 Convex part 61 Connecting part 65 areas 71 Wiring 72 Wiring 80 sequential circuits 81 Wiring 82 Wiring 83 Wiring 84 Wiring 85 Wiring 91 terminals 92 terminals 93 terminals 94 terminals 95 terminals 96 terminals 97 terminals 100 transistors 111 Substrate 112 Conductive film 113 Gate insulating film 114 Semiconductor film 114a Oxide semiconductor film 114b Oxide semiconductor film 114c Oxide semiconductor film 115 Conductive film 116 Conductive film 117 Oxide film 200 boards 201 Conductive film 202 Conductive film 203 Gate insulating film 204 Semiconductor Film 205 Semiconductor Film 206 Conductive Film 207 Conductive Film 208 Conductive Film 209 Oxide Film 210 insulating film 211 Insulating film 300 Shift Registers 301 Transistor 302 Transistor 303 Transistor 304 Transistor 305 Transistor 306 Transistor 307 Transistor 308 Transistor 309 Transistor 310 Transistor 311 Transistor 460 Panel 461 Pixel section 462 pixels 463 Scanning line driver circuit 464 Signal Line Driver Circuit 465 Liquid Crystal Devices 466 Transistor 467 Capacitor 470 transistors 471 Transistors 472 Capacitor 473 Light-emitting element 5001 Case 5002 Case 5003 Display section 5004 Display section 5005 Microphone 5006 Speaker 5007 Operation key 5008 Stylus 5201 Case 5202 Display section 5203 Support stand 5401 Housing 5402 Display section 5403 Keyboard 5404 Pointing Device 5601 Housing 5602 Housing 5603 Display section 5604 Display section 5605 Connection 5606 Operation Key 5801 Housing 5802 Housing 5803 Display section 5804 Operation key 5805 Lens 5806 Connection 5901 Housing 5902 Display section 5903 Camera 5904 Speaker 5905 Button 5906 External connection part 5907 Mike

Claims

1. a first transistor and a second transistor; a semiconductor device in which one of a source electrode or a drain electrode of the first transistor is electrically connected to one of a source electrode or a drain electrode of the second transistor, a first conductive film that functions as a gate electrode of the first transistor; a semiconductor film having a region disposed above the first conductive film; a second conductive film having a region disposed above the semiconductor film, the second conductive film functioning as one of a source electrode or a drain electrode of the first transistor, and the second conductive film functioning as one of a source electrode or a drain electrode of the second transistor; a third conductive film having a region disposed above the semiconductor film and functioning as the other of the source electrode and the drain electrode of the first transistor; the second conductive film has a first connecting portion, a plurality of first protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a first direction, and a plurality of second protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a direction opposite to the first direction, the third conductive film has a second connecting portion and a plurality of third protrusions connected by the second connecting portion and arranged to extend from the second connecting portion in a direction opposite to the first direction; the first connecting portion does not overlap with the first conductive film, each of the plurality of first protrusions overlaps with a periphery of the first conductive film via the semiconductor film; a region of each of the plurality of first projections overlapping with the semiconductor film, the region overlapping with the first conductive film having a lower surface entirely in contact with the semiconductor film; a region of each of the plurality of first projections that overlaps with the semiconductor film and does not overlap with the first conductive film has a lower surface that is entirely in contact with the semiconductor film; In a plan view, there is a region where the semiconductor film is not disposed between the plurality of first protrusions, In a plan view, at least one third protrusion among the plurality of third protrusions has a region disposed between the region where the semiconductor film is not disposed and the second connecting portion. Semiconductor device.

2. a first transistor and a second transistor; one of a source electrode or a drain electrode of the first transistor is electrically connected to one of a source electrode or a drain electrode of the second transistor; the other of the source electrode and the drain electrode of the first transistor is electrically connected to the other of the source electrode and the drain electrode of the second transistor, a first conductive film that functions as a gate electrode of the first transistor; a semiconductor film having a region disposed above the first conductive film; a second conductive film having a region disposed above the semiconductor film, the second conductive film functioning as one of a source electrode or a drain electrode of the first transistor, and the second conductive film functioning as one of a source electrode or a drain electrode of the second transistor; a third conductive film having a region disposed above the semiconductor film, the third conductive film having a function as the other of the source electrode and the drain electrode of the first transistor, and the third conductive film having a function as the other of the source electrode and the drain electrode of the second transistor; the second conductive film has a first connecting portion, a plurality of first protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a first direction, and a plurality of second protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a direction opposite to the first direction, the third conductive film has a second connecting portion and a plurality of third protrusions connected by the second connecting portion and arranged to extend from the second connecting portion in a direction opposite to the first direction; the first connecting portion does not overlap with the first conductive film, each of the plurality of first protrusions overlaps with a periphery of the first conductive film via the semiconductor film; a region of each of the plurality of first projections overlapping with the semiconductor film, the region overlapping with the first conductive film having a lower surface entirely in contact with the semiconductor film; a region of each of the plurality of first projections that overlaps with the semiconductor film and does not overlap with the first conductive film has a lower surface that is entirely in contact with the semiconductor film; In a plan view, there is a region where the semiconductor film is not disposed between the plurality of first protrusions, In a plan view, at least one third protrusion among the plurality of third protrusions has a region disposed between the region where the semiconductor film is not disposed and the second connecting portion. Semiconductor device.

3. a first transistor and a second transistor; a semiconductor device in which one of a source electrode or a drain electrode of the first transistor is electrically connected to one of a source electrode or a drain electrode of the second transistor, a first conductive film that functions as a gate electrode of the first transistor; a semiconductor film having a region disposed above the first conductive film; a second conductive film having a region disposed above the semiconductor film, the second conductive film functioning as one of a source electrode or a drain electrode of the first transistor, and the second conductive film functioning as one of a source electrode or a drain electrode of the second transistor; a third conductive film having a region disposed above the semiconductor film and functioning as the other of the source electrode and the drain electrode of the first transistor; an insulating film having a region disposed above the second conductive film and a region disposed above the third conductive film, each of the second conductive film and the third conductive film has a region in contact with the insulating film; the second conductive film has a first connecting portion, a plurality of first protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a first direction, and a plurality of second protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a direction opposite to the first direction, the third conductive film has a second connecting portion and a plurality of third protrusions connected by the second connecting portion and arranged to extend from the second connecting portion in a direction opposite to the first direction; the first connecting portion does not overlap with the first conductive film, each of the plurality of first protrusions overlaps with a periphery of the first conductive film via the semiconductor film; a region of each of the plurality of first projections overlapping with the semiconductor film, the region overlapping with the first conductive film having a lower surface entirely in contact with the semiconductor film; a region of each of the plurality of first projections that overlaps with the semiconductor film and does not overlap with the first conductive film has a lower surface that is entirely in contact with the semiconductor film; In a plan view, there is a region where the semiconductor film is not disposed between the plurality of first protrusions, In a plan view, at least one third protrusion among the plurality of third protrusions has a region disposed between the region where the semiconductor film is not disposed and the second connecting portion. Semiconductor device.

4. a first transistor and a second transistor; one of a source electrode or a drain electrode of the first transistor is electrically connected to one of a source electrode or a drain electrode of the second transistor; the other of the source electrode and the drain electrode of the first transistor is electrically connected to the other of the source electrode and the drain electrode of the second transistor, a first conductive film that functions as a gate electrode of the first transistor; a semiconductor film having a region disposed above the first conductive film; a second conductive film having a region disposed above the semiconductor film, the second conductive film functioning as one of a source electrode or a drain electrode of the first transistor, and the second conductive film functioning as one of a source electrode or a drain electrode of the second transistor; a third conductive film having a region disposed above the semiconductor film, the third conductive film functioning as the other of the source electrode and the drain electrode of the first transistor, and the third conductive film functioning as the other of the source electrode and the drain electrode of the second transistor; an insulating film having a region disposed above the second conductive film and a region disposed above the third conductive film, each of the second conductive film and the third conductive film has a region in contact with the insulating film; the second conductive film has a first connecting portion, a plurality of first protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a first direction, and a plurality of second protrusions connected by the first connecting portion and arranged to extend from the first connecting portion in a direction opposite to the first direction, the third conductive film has a second connecting portion and a plurality of third protrusions connected by the second connecting portion and arranged to extend from the second connecting portion in a direction opposite to the first direction; the first connecting portion does not overlap with the first conductive film, each of the plurality of first protrusions overlaps with a periphery of the first conductive film via the semiconductor film; a region of each of the plurality of first projections overlapping with the semiconductor film, the region overlapping with the first conductive film having a lower surface entirely in contact with the semiconductor film; a region of each of the plurality of first projections that overlaps with the semiconductor film and does not overlap with the first conductive film has a lower surface that is entirely in contact with the semiconductor film; In a plan view, there is a region where the semiconductor film is not disposed between the plurality of first protrusions, In a plan view, at least one third protrusion among the plurality of third protrusions has a region disposed between the region where the semiconductor film is not disposed and the second connecting portion. Semiconductor device.

Images