Semiconductor device

Abstract

To provide a semiconductor device having a transistor using an oxide semiconductor, which has large on-state current.SOLUTION: In a semiconductor device having a first transistor provided in a drive circuit part and a second transistor provided in a pixel part, the first transistor and the second transistor have structures different from each other. The first transistor and the second transistor are top gate transistors and a gate electrode does not overlap a conductive film functioning as a source electrode and a drain electrode. The semiconductor device has an impurity element in an oxide semiconductor film in a region where the gate electrode does not overlap the source electrode and the drain electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] In this specification and the like, a semiconductor device is a device that can function by utilizing semiconductor characteristics. Refers to devices in general, including semiconductor elements such as transistors, semiconductor circuits, arithmetic units, and memory The device is one aspect of a semiconductor device. Optical devices, power generation devices (including thin-film solar cells, organic thin-film solar cells, etc.), and electronic devices The device may include a semiconductor device. [Background technology]

[0004] A transistor (thin film transistor) is made using a semiconductor thin film formed on a substrate with an insulating surface. The technology of constructing thin-film transistors (also called thin-film transistors (TFTs)) is attracting attention. It is widely used in electronic devices such as integrated circuits (ICs) and image display devices (display devices). Semiconductor materials, such as silicon, are widely known as semiconductor thin films that can be used in transistors. However, oxide semiconductors are attracting attention as another material.

[0005] For example, amorphous oxides containing In, Zn, Ga, Sn, etc. are used as oxide semiconductors. Patent Document 1 discloses a technique for fabricating a transistor using this method. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-165529 Summary of the Invention [Problem to be solved by the invention]

[0007] As a transistor using an oxide semiconductor film, for example, an inverted staggered type (bottom gate structure) The oxide semiconductor is a planar type (also called a top gate structure) or a planar type (also called a top gate structure). When a transistor using a conductor film is applied to a display device, it is more However, the manufacturing process of the inverted staggered transistor is relatively simple and the manufacturing cost can be reduced. However, as the screen size of display devices increases, High definition image quality of devices (for example, 4k x 2k (horizontal pixel count = 3840 pixels, vertical pixel count = 1000 pixels) Prime number = 2048 pixels) or 8k x 4k (horizontal pixel count = 7680 pixels, vertical pixel count = 7680 pixels) As high-resolution display devices (represented by a 4320 pixel display) advance, inverted staggered transistors In the case of a transistor, there is a parasitic capacitance between the gate electrode and the source electrode and between the gate electrode and the drain electrode. The capacitance increases signal delays and the like, which causes problems such as deterioration of the image quality of the display device. In addition, in the case of an inverted staggered transistor, the transistor Therefore, a planar transistor using an oxide semiconductor film is proposed. For Renner-type transistors, the structure has stable semiconductor characteristics and high reliability. Furthermore, there is a demand for the development of a transistor that can be formed through a simple manufacturing process.

[0008] In view of the above problems, one embodiment of the present invention provides a novel semiconductor device including an oxide semiconductor. In particular, a planar semiconductor device using an oxide semiconductor is provided. To provide a semiconductor device using a conductor with a large on-state current, or to provide an off-state semiconductor using an oxide semiconductor To provide a semiconductor device with a small current, or to provide a semiconductor device with a small area using an oxide semiconductor To provide a semiconductor device using an oxide semiconductor and having stable electrical characteristics. or to provide a highly reliable semiconductor device using an oxide semiconductor, or to provide a novel semiconductor One of the objects is to provide a semiconductor device or a novel display device.

[0009] The above description of the problem does not preclude the existence of other problems. The embodiment does not necessarily have to solve all of these problems. Problems other than those mentioned above can be solved by the specification. It is clear from the description of the specification, etc. that the problems other than those mentioned above cannot be extracted from the description of the specification, etc. It is possible to issue it. [Means for solving the problem]

[0010] One embodiment of the present invention is a semiconductor device including a first transistor provided in a driver circuit portion and a second transistor provided in a pixel portion. a semiconductor device having a first transistor and a second transistor, The first and second transistors have different structures. A transistor with a gate structure, which functions as a gate electrode, a source electrode, and a drain electrode. In addition, the gate electrode and the source electrode are not overlapped with each other in the oxide semiconductor film. The impurity element is contained in a region that does not overlap with the drain electrode.

[0011] Impurity elements include hydrogen, boron, carbon, nitrogen, fluorine, aluminum, silicon, and lithium. These include fluorine, chlorine, or rare gas elements.

[0012] The oxide semiconductor film has increased conductivity when it contains at least one impurity element. Therefore, in the oxide semiconductor film, a region containing the impurity element is formed between the gate electrode and the source electrode. By providing the gate electrode in a region that does not overlap with the gate and drain electrodes, the parasitic resistance of the transistor is reduced. This allows the transistor to have a high on-state current.

[0013] Note that the first transistor provided in the driver circuit portion overlaps with the first transistor provided with an oxide semiconductor film interposed therebetween. It may have two gate electrodes.

[0014] The first transistor provided in the driver circuit section has a first film and a second film stacked thereon. a second transistor provided in a pixel portion and a first film; The second transistor may have an oxide semiconductor film having a different atomic ratio of elements. The included oxide semiconductor film is a second film included in the oxide semiconductor film of the first transistor. The atomic ratio of the metal elements may be the same. [Effects of the Invention]

[0015] According to one embodiment of the present invention, a novel semiconductor device including an oxide semiconductor can be provided. In particular, a planar semiconductor device using an oxide semiconductor can be provided. Alternatively, a semiconductor device including an oxide semiconductor and having a large on-state current can be provided. A semiconductor device using an oxide semiconductor and having a small off-state current can be provided. A semiconductor device using an oxide semiconductor and occupying a small area can be provided. A semiconductor device using an oxide semiconductor and having stable electrical characteristics can be provided. In this way, a highly reliable semiconductor device using an oxide semiconductor can be provided. A novel semiconductor device can be provided. Alternatively, a novel display device can be provided. .

[0016] The description of these effects does not preclude the existence of other effects. An embodiment does not necessarily have to have all of these effects. The above will be made clear from the description, drawings, claims, etc. It is possible to extract other effects from the descriptions in the aspects and claims. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 2] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 3] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 4] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 5] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 6] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 7] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 8] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 9]1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 10] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 11] FIG. 1 is a diagram showing an example of a band structure. [Figure 12] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 13] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 14] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 15] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 16] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 17] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 18] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 19] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 20] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 21] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 22] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 23] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 24] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 25] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 26] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 27] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 28] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 29] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 30] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 31]1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 32] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 33] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 34] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 35] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 36] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 37] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 38] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 39] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 40] FIG. 1 is a top view illustrating one embodiment of a display device. [Figure 41] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 42] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 43] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 44] 1A and 1B are a block diagram and a circuit diagram illustrating a display device. [Figure 45] FIG. 2 is a diagram illustrating a display module. [Figure 46] 1A to 1C illustrate electronic devices. [Figure 47] Cs-corrected high-resolution TEM image of a cross section of CAAC-OS, and a schematic cross-sectional diagram of CAAC-OS. [Figure 48] Cs-corrected high-resolution TEM image of the CAAC-OS in the plane. [Figure 49] 10A and 10B illustrate structural analyses of a CAAC-OS and a single-crystal oxide semiconductor by XRD. [Figure 50] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 51] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 52] 1A to 1C are cross-sectional views illustrating one embodiment of a manufacturing process of a semiconductor device. [Figure 53] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 54] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 55] Electron diffraction pattern of CAAC-OS. [Figure 56] FIG. 1 shows the change in the crystalline part of an In-Ga-Zn oxide due to electron irradiation. [Figure 57] Schematic diagram illustrating the film formation model of CAAC-OS and nc-OS. [Figure 58] A diagram explaining InGaZnO4 crystals and pellets. [Figure 59] Schematic diagram illustrating a film formation model of CAAC-OS. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the invention disclosed in this specification will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and any deviation from the spirit and scope of the present invention is not permitted. It will be readily understood by those skilled in the art that various modifications can be made to the form and details of the present invention. Therefore, the present invention should not be construed as being limited to the following description of the embodiments. .

[0019] In addition, the position, size, range, etc. of each component shown in the drawings etc. are not necessarily shown in order to facilitate understanding. It may not represent the actual position, size, range, etc. Therefore, the disclosed invention The position, size, range, etc. are not necessarily limited to those disclosed in the drawings, etc.

[0020] In this specification, ordinal numbers such as "first," "second," and "third" refer to the order of components. It should be noted that this is added to avoid confusion and is not intended to limit the number.

[0021] In this specification, the terms "above" and "below" are used to indicate whether the positional relationship of a component is "directly above" or "below." For example, the term "gate electrode on the gate insulating film" does not necessarily mean "directly under" the gate insulating film. If the expression "electrode" is used, it excludes those that include other components between the gate insulating film and the gate electrode. do not.

[0022] In addition, the terms "electrode" and "wiring" used in this specification and the like refer to these components functionally. This is not a limitation. For example, an "electrode" may be used as part of a "wiring." , and vice versa. Furthermore, the terms "electrode" and "wiring" may be used interchangeably with "electrodes" and "wiring." This also includes cases where the wiring is formed integrally.

[0023] Also, the functions of "source" and "drain" can be changed by using transistors with different polarities. Or, when the direction of the current changes during circuit operation, the positions may be swapped. Therefore, in this specification and the like, the terms "source" and "drain" are used interchangeably. It is assumed that this is possible.

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

[0025] (Embodiment 1) In this embodiment mode, one mode of a semiconductor device and a manufacturing method of the semiconductor device will be described with reference to FIGS. This will be explained using:

[0026] <Configuration 1 of semiconductor device> 1 and 6 show a top-gate structure transistor as an example of a transistor included in a semiconductor device. Here, a display device will be described as an example of a semiconductor device. In addition, the structure of a transistor provided in each of a driver circuit and a pixel portion of a display device will be described. do.

[0027] In FIG. 6, the transistor 154 provided in the driver circuit portion and the transistor 155 provided in the pixel portion are 1 shows a top view of transistor 150, and FIG. 1 shows a cross-sectional view of transistor 154 and transistor 150. 6A is a top view of the transistor 154, and FIG. 1A is a cross-sectional view taken along the dashed line X1-X2 in FIG. 6A, and 6(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 6B is a cross-sectional view taken along the line Y1-Y2, and a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 6, for clarity, the substrate 102, the insulating film 104, the insulating film 108, the insulating film 116, and the insulating film 118 are shown. The insulating film 118 and the like are omitted. Also, FIG. 1A shows the transistor 150 and the transistor 1B is a cross-sectional view of the transistor 150 in the channel length direction. 10 is a cross-sectional view of a transistor 154 in the channel width direction.

[0028] In the top view of the transistor, the transistor 150 and As with the transistor 154, some of the components may be omitted in the illustration. The dashed-dotted lines X1-X2 and X3-X4 indicate the channel length direction, and the dashed-dotted lines Y1- The Y2 direction and the dashed dotted line Y3-Y4 direction may be referred to as the channel width direction.

[0029] The transistor 150 shown in FIG. 1 is an oxide film on an insulating film 104 formed on a substrate 102. A semiconductor film 106, an insulating film 108 in contact with the oxide semiconductor film 106, and an opening in the insulating film 108 The conductive film 110 in contact with the oxide semiconductor film 106 in part of the portion 140a and the insulating film 108 The conductive film 112 is in contact with the oxide semiconductor film 106 in part of the opening 140b. The conductive film 114 overlaps with the oxide semiconductor film 106 with the transistor 108 interposed therebetween. An insulating film 116 and an insulating film 118 may be provided on the star 150 .

[0030] The transistor 154 includes a conductive film 201 formed over the substrate 102 and a conductive film 202 formed over the conductive film 201. The insulating film 104, the oxide semiconductor film 206 on the insulating film 104, and a film in contact with the oxide semiconductor film 206 The insulating film 108 is formed by the oxide semiconductor film 20 in a part of the opening 220a of the insulating film 108. 6, and the oxide semiconductor in a part of the opening 220b of the insulating film 108. The conductive film 212 in contact with the oxide semiconductor film 206 overlaps with the insulating film 108 interposed therebetween. The conductive film 214 is also included.

[0031] The transistor 154 includes a conductive film 204 overlapping with the oxide semiconductor film 206 with the insulating film 104 interposed therebetween. 01. That is, the conductive film 201 functions as a gate electrode. The transistor 154 is a transistor with a dual gate structure.

[0032] The conductive film 214 and the conductive film 201 are not connected to each other, and different potentials are applied to them. , the threshold voltage of the transistor 154 can be controlled. In this way, the conductive film 214 and the conductive film 201 are connected and the same potential is applied, so that the initial Reduction of characteristic variations, -GBT (-Gate Bias-Temperature) Suppression of degradation in the non-resistance test and variation of the on-current rise voltage at different drain voltages In addition, the region where carriers flow in the oxide semiconductor film 206 is a film. As the capacitance becomes larger in the thickness direction, the amount of carrier movement increases. As the on-current of the transistor 154 increases, the field effect mobility also increases. By setting the channel length to less than 2.5 μm or 1.45 μm to 2.2 μm, the on-state As the current further increases, the field effect mobility can be increased.

[0033] The conductive film 201 may have a structure in which it does not overlap with the conductive film 210 or the conductive film 212. 54A shows an example of the case where the conductive film 201 is a conductive film 210 or a conductive film 21 2 and the entire oxide semiconductor film 106. An example of this case is shown in FIG. 4(B).

[0034] In the display device described in this embodiment, the driver circuit portion and the pixel portion include a transistor. The transistors included in the drive circuit section have a dual gate structure. The driver circuit portion includes a transistor having a higher field-effect mobility than the pixel portion.

[0035] In addition, in the display device, the channel lengths of the transistors included in the driver circuit portion and the pixel portion are It may be different.

[0036] Typically, the channel length of the transistor 154 included in the driving circuit section is set to less than 2.5 μm. On the other hand, the thickness of the pixel portion can be set to 1.45 μm or more and 2.2 μm or less. The channel length of the transistor 150 is set to 2.5 μm or more, or 2.5 μm or more and 20 μm or less. It is possible.

[0037] The channel length of the transistor 154 included in the driving circuit section is set to less than 2.5 μm, preferably By making the thickness of the transistor 150 included in the pixel portion 150 equal to or larger than 1.45 μm and equal to or smaller than 2.2 μm, Compared to the above, it is possible to increase the field effect mobility and the on-current. As a result, a driver circuit section capable of high-speed operation can be manufactured.

[0038] The high field-effect mobility of the transistor allows the signal line driver circuit, which is an example of a driver circuit section, to be The demultiplexer circuit can be formed by Since this is a circuit that distributes an input signal to one of multiple outputs, the number of input terminals for the input signal is For example, if one pixel has a red sub-pixel, a green sub-pixel, and By providing a demultiplexer circuit in each pixel, The input signal can be divided by the demultiplexer circuit, so It is possible to reduce the number of children by one-third.

[0039] The transistor provided in the pixel portion has a gate electrode, a source electrode, and a drain electrode. Furthermore, the gate electrode and the source electrode and drain electrode do not overlap, so the parasitic capacitance is small. In a region where the oxide semiconductor film does not overlap with the dopant electrode, the oxide semiconductor film has a region containing an impurity element. Therefore, the parasitic resistance is small. For these reasons, transistors with large on-current are installed in the pixel area. As a result, signal delay can be reduced in large display devices and high-resolution display devices. , it is possible to suppress display unevenness.

[0040] In the oxide semiconductor film 106, the conductive films 110, 112, and 114 overlap with each other. The oxide semiconductor film 206 contains an element that forms oxygen vacancies. In addition, oxygen vacancies are formed in regions that do not overlap with the conductive films 210, 212, and 214. Hereinafter, the elements that form oxygen vacancies will be described as impurity elements. Representative examples of pure elements include hydrogen, boron, carbon, nitrogen, fluorine, aluminum, and silicon. Typical examples of rare gas elements include helium and neon. , argon, krypton, and xenon.

[0041] When an impurity element is added to an oxide semiconductor film, the metal element and oxygen in the oxide semiconductor film are The bond is broken, and oxygen vacancies are formed. Alternatively, an impurity element is added to the oxide semiconductor film. When this occurs, oxygen that has been bonded to a metal element in the oxide semiconductor film is bonded to an impurity element, and the metal element As a result, oxygen is released from the oxide semiconductor film, and oxygen vacancies are formed. The carrier density increases and the conductivity increases.

[0042] Here, an enlarged view of the oxide semiconductor film 106 and its vicinity is shown in FIG. The following description will be given with reference to an enlarged view of the oxide semiconductor film 106 and its vicinity included in the transistor 150. As shown in the figure, the oxide semiconductor film 106 is in contact with the conductive film 110 and the conductive film 112. 6a, a region 106b in contact with the insulating film 116, a region 106c overlapping with the insulating film 108, and and region 106d.

[0043] The region 106a functions as a source region and a drain region. The film 112 is made of tungsten, titanium, aluminum, copper, molybdenum, chromium, or tantalum. When the material is a conductive material that easily bonds with oxygen, such as a simple substance or an alloy, the oxide semiconductor The oxygen contained in the conductive film is bonded to the conductive material contained in the conductive film 110 and the conductive film 112, Oxygen vacancies are formed in the oxide semiconductor film. In addition, some of the constituent elements of the conductive material that forms the conductive film 112 may be mixed in. As a result, the conductivity of the region 106a in contact with the conductive film 110 and the conductive film 112 increases, and the source The gate electrode functions as a gate region and a drain region.

[0044] The region 106b and the region 106c function as low resistance regions. The region 106c contains impurity elements. Note that the region 106b contains more impurities than the region 106c. In addition, when the side surface of the conductive film 114 has a tapered shape, the element concentration in the region 106c is high. A part of the conductive film 114 may overlap with the conductive film 114 .

[0045] The impurity element is a rare gas element, and the oxide semiconductor film 106 is formed by a sputtering method. When the region 106a to the region 106d are formed, each of the regions 106a to 106d contains a rare gas element, and the region 106 The concentration of rare gas elements in regions 106b and 106c is higher than that in regions 106a and 106d. This is because when the oxide semiconductor film 106 is formed by a sputtering method, Since a rare gas is used as a ring gas, the rare gas is contained in the oxide semiconductor film 106; In addition, in the regions 106b and 106c, oxygen vacancies are intentionally formed. This is because the gas is added. The region 106a and the region 106d may be doped with a different rare gas element.

[0046] The impurity element is boron, carbon, nitrogen, fluorine, aluminum, silicon, phosphorus, or In the case of chlorine, the impurity element is contained only in the region 106b and the region 106c. Compared with 106a and 106d, regions 106b and 106c have more impurity elements. In the region 106b and the region 106c, the concentration of SIMS (Secondary Ion Mass Spectrometry) The resulting impurity element concentration is 1×10 18 atoms / cm 3 More than 1×10 22 ato ms / cm 3 or less, or 1 x 10 19 atoms / cm 3 More than 1×10 21 atoms / cm 3 or less, or 5 x 10 19 atoms / cm 3 5x10 or more 20 atoms / cm 3 It can be as follows:

[0047] When the impurity element is hydrogen, the region 106b is smaller than the region 106a and the region 106d. The concentration of the impurity element is higher in the regions 106b and 106c. The hydrogen concentration obtained by secondary ion mass spectrometry is 8×10 19 atoms / cm 3 or more, or 1 x 1020 atoms / cm 3 or more, or 5 x 10 20 atoms / cm 3 It can be more than that.

[0048] Since the regions 106b and 106c contain impurity elements, oxygen vacancies increase, and the carrier As a result, the regions 106b and 106c become more conductive and have a lower It acts as a resistance area.

[0049] The impurity elements are hydrogen, boron, carbon, nitrogen, fluorine, aluminum, silicon, It may be the case that one or more of phosphorus or chlorine and one or more of the rare gases are used. In this case, the region 10 6b and region 106c, oxygen vacancies formed by rare gases and added to the regions of hydrogen, boron, carbon, nitrogen, fluorine, aluminum, silicon, phosphorus, or chlorine Regions 106b and 106c may become more conductive due to interactions with one or more of the There is a match.

[0050] The region 106d functions as a channel.

[0051] a region of the insulating film 108 that overlaps with the oxide semiconductor film 106 and the conductive film 114; A region overlapping with the oxide semiconductor film 206 and the conductive film 214 functions as a gate insulating film. In addition, in the insulating film 108, the oxide semiconductor film 106, the conductive film 110, and the conductive film 112 are The overlapping region and the region where the oxide semiconductor film 206 overlaps with the conductive film 210 and the conductive film 212 The region functions as an interlayer insulating film.

[0052] The conductive films 110 and 112 and the conductive films 210 and 212 are used as the source electrode and The conductive film 114 and the conductive film 214 function as a gate electrode and a drain electrode. It functions as such.

[0053] The transistor 150 and the transistor 154 described in this embodiment function as channels. A low resistance region is provided between the region functioning as a source region and a region functioning as a drain region. The resistance between the channel and the source and drain regions is reduced. The transistors 150 and 154 have a large on-state current. It has high field-effect mobility.

[0054] In addition, in the manufacturing process of the transistor 150 and the transistor 154, the conductive film 114 and the conductive film 214 functioning as a source electrode and a drain electrode; The conductive films 110 and 112 and the conductive films 210 and 212 are simultaneously formed. Therefore, in the transistor 150, the conductive film 114, the conductive film 110, and the conductive film The conductive film 114 does not overlap with the conductive film 112, and the parasitic In addition, in the transistor 154, the conductive film 214 and The conductive film 210 and the conductive film 212 do not overlap each other, and the conductive film 214 and the conductive film 210 and the conductive film 212 are not overlapped with each other. As a result, the parasitic capacitance between the substrate 102 and the film 212 can be reduced. When a surface-area substrate is used, the conductive film 110, the conductive film 112, the conductive film 114, and the conductive film 2 10. It is possible to reduce signal delay in the conductive film 212 and the conductive film 214.

[0055] In the transistor 150, the conductive films 110, 112, and 114 are An impurity element is added to the oxide semiconductor film 106 using the mask. In 54, the conductive film 210, the conductive film 212, and the conductive film 214 are used as a mask to form an impurity source. The element is added to the oxide semiconductor film 206. That is, a low resistance region is formed by self-alignment. It is possible.

[0056] The configuration shown in FIG. 1 will be described in detail below.

[0057] The substrate 102 can be made of various substrates and is not limited to a specific one. Examples of the substrate include a semiconductor substrate (for example, a single crystal substrate or a silicon substrate), an SOI Substrates, glass substrates, quartz substrates, plastic substrates, metal substrates, stainless steel substrates, Stainless steel foil substrate, tungsten substrate, tungsten foil a substrate having a fibrous material, a flexible substrate, a laminated film, a paper containing a fibrous material, or a base film Examples of glass substrates include barium borosilicate glass and aluminoborose glass. Examples include fluorine-based glass and soda-lime glass. Flexible substrates, lamination films, substrates Examples of material films include the following: Polyethylene naphthalate (PET), polyethylene naphthalate (PEN), polyethersulfone ( Plastics such as PES are also available. For example, synthetic resins such as acrylic are also available. Examples include polypropylene, polyester, polyvinyl fluoride, Or polyvinyl chloride, etc. Or, for example, polyamide, polyimide, aramide, etc. Examples include adhesives, epoxy, inorganic vapor deposition films, and paper. In particular, semiconductor substrates and single crystal substrates By manufacturing transistors using a silicon-on-insulator (SOI) substrate, the characteristics, size, is used to manufacture small-sized transistors with little variation in shape, high current capacity, etc. When a circuit is constructed using such transistors, the circuit consumes less power. This allows for a higher integration of the circuit.

[0058] In addition, a flexible substrate is used as the substrate 102, and a transistor is formed directly on the flexible substrate. Alternatively, a separation layer may be provided between the substrate 102 and the transistor. After a semiconductor device is partially or entirely completed thereon, it is separated from the substrate 102 and then attached to another substrate. In this case, the transistors can be mounted on substrates with poor heat resistance or flexible substrates. The above-mentioned release layer may be formed, for example, by a tungsten film and a silicon oxide film. The laminated structure of inorganic film with acrylic film, or organic resin film such as polyimide formed on the substrate The configuration etc. can be used.

[0059] An example of a substrate on which a transistor is transferred is a substrate on which the above-mentioned transistor is formed. In addition to the substrates that can be used, paper substrates, cellophane substrates, aramid film substrates, polyimide film substrates, Lum substrate, stone substrate, wood substrate, fabric substrate (natural fibers (silk, cotton, linen), synthetic fibers (nylon) , polyurethane, polyester) or regenerated fiber (acetate, cupra, rayon, These substrates include recycled polyester, leather substrates, and rubber substrates. By using this, it is possible to form transistors with good characteristics and low power consumption. This allows for the manufacture of devices that are less likely to break, heat resistant, lightweight, or thin.

[0060] The insulating film 104 can be formed as a single layer or a stacked layer of an oxide insulating film or a nitride insulating film. Note that the interfacial characteristics between the oxide semiconductor film 106 and the oxide semiconductor film 206 can be improved. Therefore, in the insulating film 104, at least the oxide semiconductor film 106 and the oxide semiconductor film 206 The region in contact with the insulating film 104 is preferably formed of an oxide insulating film. By using an oxide insulating film that releases oxygen by heat treatment, The oxygen can be transferred to the oxide semiconductor film 106 and the oxide semiconductor film 206. be.

[0061] The thickness of the insulating film 104 is 50 nm or more, or 100 nm or more and 3000 nm or less, or 2 By making the insulating film 104 thick, the insulating film 104 can be formed to have a thickness of 1000 nm or more and 1000 nm or less. The amount of oxygen released from the insulating film 104 can be increased, and the insulating film 104 and the oxide semiconductor The interface states at the interfaces between the oxide semiconductor film 106 and the oxide semiconductor film 206 and the oxide semiconductor film 1 Oxygen vacancies in the oxide semiconductor film 206 and the oxide semiconductor film 208 can be reduced.

[0062] The insulating film 104 may be, for example, a silicon oxide film, a silicon oxynitride film, or a silicon nitride oxide film. film, silicon nitride film, aluminum oxide film, hafnium oxide film, gallium oxide film or Ga A Zn oxide film or the like may be used, and may be provided as a single layer or a multilayer.

[0063] The oxide semiconductor film 106 and the oxide semiconductor film 206 are typically In—Ga oxide films. , In-Zn oxide film, In-M-Zn oxide film (M is Mg, Al, Ti, Ga, Y, It is formed of a metal oxide film such as Zr, La, Ce, Nd, or Hf. The oxide semiconductor film 106 and the oxide semiconductor film 206 have light-transmitting properties.

[0064] When the oxide semiconductor film 106 and the oxide semiconductor film 206 are an In-M-Zn oxide, The atomic ratio of In to M is 2 when the sum of In and M is 100 atomic %. More than 5 atomic % and M is less than 75 atomic % or In is 34 atomic % % and M is less than 66 atomic %.

[0065] The oxide semiconductor film 106 and the oxide semiconductor film 206 have an energy gap of 2 eV or more. , 2.5 eV or more, or 3 eV or more.

[0066] The oxide semiconductor film 106 and the oxide semiconductor film 206 each have a thickness of 3 nm to 200 nm. , or 3 nm or more and 100 nm or less, or 3 nm or more and 50 nm or less.

[0067] The oxide semiconductor film 106 and the oxide semiconductor film 206 are In-M-Zn oxide films (M is M In-MZ The atomic ratio of the metal elements in the sputtering target used to form the n-oxide film is It is preferable that In≧M and Zn≧M are satisfied. The atomic ratio of group elements is In:M:Zn=1:1:1, In:M:Zn=1:1:1. 2, In:M:Zn=2:1:1.5, In:M:Zn=2:1:2.3, In:M:Z Preferably, n=2:1:3, In:M:Zn=3:1:2, etc. The atomic ratios of the conductor film 106 and the oxide semiconductor film 206 are each calculated by adding the above-mentioned sputtering error. The atomic ratio of metal elements contained in the target varies by ±40%. .

[0068] In addition, in the oxide semiconductor film 106 and the oxide semiconductor film 206, one of the Group 14 elements When silicon or carbon is contained, the oxide semiconductor film 106 and the oxide semiconductor film 206 In this case, oxygen vacancies increase, and the oxide semiconductor film 106 and the oxide semiconductor film 108 become n-type. The concentration of silicon and carbon in the nitride semiconductor film 206, especially in the region 106d, is high (secondary The concentration obtained by ion mass spectrometry was 2 × 10 18 atoms / cm 3 The following, or 2×10 17 atoms / cm 3 As a result, the transistor can be It has electrical characteristics in which the threshold voltage is positive (also called normally-off characteristics).

[0069] In addition, in the oxide semiconductor film 106 and the oxide semiconductor film 206, particularly in the region 106d, In the above, the concentration of alkali metals or alkaline earth metals obtained by secondary ion mass spectrometry , 1 x 10 18 atoms / cm 3 or less, or 2 x 10 16 atoms / cm 3 and Alkali metals and alkaline earth metals can form catalytic groups when bonded to oxide semiconductors. This may generate carriers, which may increase the off-state current of the transistor. Therefore, it is preferable to reduce the concentration of alkali metal or alkaline earth metal in the region 106d. As a result, the transistor has electrical characteristics in which the threshold voltage is positive (normally-on). It also has the characteristic of

[0070] In addition, in the oxide semiconductor film 106 and the oxide semiconductor film 206, particularly in the region 106d, When nitrogen is included, electrons that act as carriers are generated, the carrier density increases, and the material becomes n-type. As a result, a transistor using an oxide semiconductor film containing nitrogen may Therefore, the oxide semiconductor film, particularly the region 106 In the secondary ion mass spectrometer, it is preferable that nitrogen is reduced as much as possible. The nitrogen concentration obtained by the analytical method is 5 x 10 18 atoms / cm 3 You can do the following: Cut.

[0071] In the oxide semiconductor film 106 and the oxide semiconductor film 206, particularly in the region 106d, By reducing the impurity elements, the carrier density of the oxide semiconductor film can be reduced. Therefore, the oxide semiconductor film 106 and the oxide semiconductor film 206, particularly the region 106 In d, the carrier density is 1×10 17 pieces / cm 3 or less, or 1 x 10 15 pieces / cm 3 or less, or 1 x 10 13 pieces / cm 3 or less, or 1 x 10 11 pieces / cm 3 The following shall be done: can be done.

[0072] The oxide semiconductor film 106 and the oxide semiconductor film 206 have low impurity concentrations and defect states. A transistor with better electrical characteristics by using a low-density oxide semiconductor film Here, the impurity concentration is low and the defect level density is low (oxygen deficiency). High purity genuine or substantially high purity genuine is called high purity genuine or substantially high purity genuine. A transistor using an intrinsic oxide semiconductor has few carrier generation sources, Therefore, the carrier density can be reduced in the oxide semiconductor film. The transistor in which the region is formed has electrical characteristics in which the threshold voltage is positive (normally-on). Also, high purity intrinsic or substantially high purity intrinsic oxide tends to have a tendency to become unstable. Since the defect level density of the compound semiconductor film is low, the trap level density may also be low. A transistor using a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film is The drain current is extremely small, and the voltage between the source and drain electrodes (drain voltage) is In the range of 10V, the off-state current is below the measurement limit of the semiconductor parameter analyzer, that is, Wachi 1×10 -13 Therefore, the oxide semiconductor film The transistor in which the channel region is formed has small fluctuations in electrical characteristics and is a highly reliable transistor. It may be a transistor.

[0073] The oxide semiconductor film 106 and the oxide semiconductor film 206 may have a non-single-crystal structure, for example. The non-single crystal structure is, for example, a C-Axis Aligned Array (CAAC-OS) structure, which will be described later. Crystalline Oxide Semiconductor), polycrystalline structure, This includes the microcrystalline structure or amorphous structure described below. Among non-single crystal structures, the amorphous structure is the most The defect density is high in CAAC-OS, and the defect density is lowest in CAAC-OS.

[0074] Note that the oxide semiconductor film 106 and the oxide semiconductor film 206 have an amorphous structure and a microcrystalline structure. Two or more of the structure region, polycrystalline structure region, CAAC-OS region, and single crystal structure region are The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, and , a polycrystalline structure region, a CAAC-OS region, and a single-crystalline structure region. The mixed film may have a single layer structure with an amorphous structure, a microcrystalline structure, or the like. The structure region, the polycrystalline structure region, the CAAC-OS region, and the single-crystal structure region are either two or more of the following: There are cases where the structure is made up of more than one species stacked on top of each other.

[0075] Note that in the oxide semiconductor film 106 and the oxide semiconductor film 206, the region 106b and the region The crystallinity of the oxide semiconductor film 106 and the oxide semiconductor region 106d may be different. In the solid film 206, the crystallinity of the region 106c may differ from that of the region 106d. This is because when an impurity element is added to the region 106b or the region 106c, This is because the region 106c is damaged, resulting in a decrease in crystallinity.

[0076] The insulating film 108 can be formed as a single layer or a stacked layer of an oxide insulating film or a nitride insulating film. Note that the interfacial characteristics between the oxide semiconductor film 106 and the oxide semiconductor film 206 can be improved. Therefore, in the insulating film 108, at least the oxide semiconductor film 106 and the oxide semiconductor film 206 The region in contact with the insulating film 108 is preferably formed using an oxide insulating film. For example, a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, an oxide Aluminum film, hafnium oxide film, gallium oxide film, Ga-Zn oxide film, etc. It may be provided as a single layer or a multilayer.

[0077] In addition, an insulating film having a blocking effect against oxygen, hydrogen, water, etc. is set as the insulating film 108. By this, oxygen from the oxide semiconductor film 106 and the oxide semiconductor film 206 can be diffused to the outside. This prevents hydrogen, water, and the like from entering the oxide semiconductor film 106 and the oxide semiconductor film 206 from the outside. As an insulating film having a blocking effect against oxygen, hydrogen, water, etc., an oxide film is used. aluminum film, aluminum oxide nitride film, gallium oxide film, gallium oxide nitride film, yttrium film, yttrium oxynitride film, hafnium oxide film, hafnium oxynitride film, etc. be.

[0078] The insulating film 108 is made of hafnium silicate (HfSiO x ), nitrogen is added Hafnium silicate (HfSi x O y N z ), nitrogen-doped hafnium aluminate (HfAl x O y N z ), high-k materials such as hafnium oxide and yttrium oxide The use of this material can reduce gate leakage of transistors.

[0079] In addition, by using an oxide insulating film that releases oxygen by heating as the insulating film 108, By the heat treatment, oxygen contained in the insulating film 108 is removed from the oxide semiconductor film 106 and the oxide semiconductor film 108. It can be transferred to the membrane 206 .

[0080] As the insulating film 108, a silicon oxynitride film with few defects can be used. Silicon oxynitride films with few defects are measured at ESR below 100K after heat treatment. The first signal in the spectrum obtained by , the second signal with a g value of 2.001 to 2.003, and the second signal with a g value of 1.964 to 1. A third signal of 0.966 or less is observed. Note that the first and second signals The split width of the first signal and the split width of the third signal are The ESR measurement of this material shows that the g value is approximately 5 mT. 1 signal, a second signal with a g value between 2.001 and 2.003, and a g value between 1. The sum of the spin densities of the third signals, which are greater than or equal to 964 and less than or equal to 1.966, is 1×10 18 spins / cm 3 less than 1 × 10 17 spins / cm 3 1x1 or more 0 18 spins / cm 3 is less than.

[0081] In addition, the g value is between 2.037 and 2.039 in the ESR spectrum below 100K. The first signal has a g value of 2.001 or more and 2.003 or less, and the second signal has a g value of 1 The third signal, between 0.964 and 1.966, is nitrogen oxide (NO x , x is between 0 and 2 Representative examples of nitrogen oxides include monooxygenated nitrogen (NOx) and monooxygenated nitrogen (NOx). Nitrogen dioxide, nitrogen dioxide, etc. In other words, the first signal with a g value of 2.037 or more and 2.039 or less null, a second signal with a g value between 2.001 and 2.003, and a g value between 1.964 and 1.964. The lower the sum of the spin densities of the third signals, which are above 1.966, the more the oxynitride spins are formed. It can be said that the content of nitrogen oxides contained in the silicon film is low.

[0082] In addition, the silicon oxynitride film with few defects has a nitrogen concentration measured by secondary ion mass spectrometry. Degrees are 6 x 10 20 atoms / cm 3 The insulating film 108 is an oxide film with few defects. By using a silicon nitride film, nitrogen oxides are less likely to be generated, and the oxide semiconductor film 1 106, and the oxide semiconductor film 206 and the insulating film 108. In addition, the threshold voltage of a transistor included in a semiconductor device can be reduced. Therefore, it is possible to reduce the fluctuation of the electrical characteristics of the transistor. .

[0083] The thickness of the insulating film 108 is 5 nm or more and 400 nm or less, or 5 nm or more and 300 nm or less. Alternatively, it can be 10 nm or more and 250 nm or less.

[0084] The conductive film 110, the conductive film 112, and the conductive film 114, as well as the conductive film 210, the conductive film 212, and the conductive film 214 Since the conductive film 214 and the conductive film 215 are formed at the same time, they are made of the same material (for example, metal elements) and have the same laminated structure. The conductive film 110, the conductive film 112, the conductive film 114, the conductive film 210, the conductive film The conductive film 212 and the conductive film 214 are made of aluminum, chromium, copper, tantalum, titanium, or molybdenum. , nickel, iron, cobalt, tungsten, or the above-mentioned metal elements It can be formed using an alloy containing the above metal elements or an alloy combining the above metal elements. In addition, the present invention uses a metal element selected from one or more of manganese and zirconium. In addition, the conductive film 110, the conductive film 112, the conductive film 114, and the conductive film 210 may be The conductive film 212 and the conductive film 214 may have a single-layer structure or a stacked structure of two or more layers. For example, a single layer structure of aluminum film containing silicon, a single layer structure of copper film containing manganese, Two-layer structure with titanium film stacked on aluminum film, two-layer structure with titanium film stacked on titanium nitride film Layer structure, two-layer structure in which a tungsten film is laminated on a titanium nitride film, tantalum nitride film or nitride film Two-layer structure with tungsten film stacked on top of tungsten film, copper film stacked on top of copper film containing manganese A two-layer structure, a titanium film and an aluminum film laminated on top of the titanium film, A three-layer structure in which a titanium film is formed on top, a copper film is layered on top of a copper film containing manganese, and There are also three-layer structures in which a copper film containing manganese is formed on the aluminum. Elements selected from tantalum, tungsten, molybdenum, chromium, neodymium, and scandium Alternatively, an alloy film or a nitride film made by combining one or more of the above may be used.

[0085] In addition, the conductive film 110, the conductive film 112, and the conductive film 114, as well as the conductive film 210 and the conductive film 2 12 and the conductive film 214 are made of indium tin oxide, indium oxide containing tungsten oxide. Indium zinc oxide containing tungsten oxide, Indium oxide containing titanium oxide Indium tin oxide containing titanium oxide, indium zinc oxide, indium oxide containing silicon oxide The insulating film 11 can also be formed using a light-transmitting conductive material such as indium tin oxide. Alternatively, the light-transmitting conductive material and the metal element may be laminated together.

[0086] The conductive film 110, the conductive film 112, and the conductive film 114, as well as the conductive film 210, the conductive film 212, and the conductive film 214 The thickness of the conductive film 214 is 30 nm or more and 500 nm or less, or 100 nm or more and 400 nm or less. It can be as follows:

[0087] The insulating film 116 can be formed as a single layer or a stacked layer of an oxide insulating film or a nitride insulating film. Note that the interfacial characteristics between the oxide semiconductor film 106 and the oxide semiconductor film 206 can be improved. Therefore, in the insulating film 116, at least the oxide semiconductor film 106 and the oxide semiconductor film 206 The region in contact with the insulating film 116 is preferably formed of an oxide insulating film. By using an oxide insulating film that releases oxygen by heat treatment, The oxygen can be transferred to the oxide semiconductor film 106 and the oxide semiconductor film 206. be.

[0088] The insulating film 116 may be, for example, a silicon oxide film, a silicon oxynitride film, or a silicon nitride oxide film. film, silicon nitride film, aluminum oxide film, hafnium oxide film, gallium oxide film or Ga A Zn oxide film or the like may be used, and may be provided as a single layer or a multilayer.

[0089] The insulating film 118 is preferably a film that functions as a barrier film against hydrogen, water, and the like from the outside. The insulating film 118 may be, for example, a silicon nitride film, a silicon nitride oxide film, or an aluminum oxide film. A film or the like may be used, and it may be provided as a single layer or a multilayer.

[0090] The thickness of the insulating film 116 and the insulating film 118 is 30 nm or more and 500 nm or less, or It can be 100 nm or more and 400 nm or less.

[0091] <Configuration 2 of semiconductor device> Next, another configuration of the semiconductor device will be described with reference to FIG. The following description will be given using transistor 151 as a modified example of the transistor 150. The transistor 154 in the operating circuit section has the insulating film 104 of the transistor 151 or the conductive film The structures of the conductive film 110, the conductive film 112, and the conductive film 114 can be applied as appropriate.

[0092] 3A to 3C are top views and cross-sectional views of a transistor 151 included in a semiconductor device. 3A is a top view of the transistor 151, and FIG. 3B is a top view of the transistor 151. 3(A) and FIG. 3(C) is a cross-sectional view taken along the dashed line X3-Y4 in FIG. Cross-sectional view of section X4.

[0093] The transistor 151 illustrated in FIG. 3 includes the conductive films 110, 112, and 114. Each of them has a three-layer structure. The other components are a stacked-layer structure of a transistor insulating film 104a and an oxide insulating film 104b. It is similar to Transistor 150 and has the same effect.

[0094] First, the conductive films 110, 112, and 114 will be described.

[0095] The conductive film 110 is formed by laminating a conductive film 110a, a conductive film 110b, and a conductive film 110c in this order. The conductive film 110a and the conductive film 110c cover the surface of the conductive film 110b. That is, the conductive film 110a and the conductive film 110c function as a protective film for the conductive film 110b. do.

[0096] Similar to the conductive film 110, the conductive film 112 includes a conductive film 112a, a conductive film 112b, and a conductive film 112c. The conductive film 112a and the conductive film 112c are laminated in this order, and the conductive film 112a and the conductive film 112c are laminated in this order. It covers the surface of 2b.

[0097] Similar to the conductive film 110, the conductive film 114 includes a conductive film 114a, a conductive film 114b, and a conductive film 114c. The conductive film 114a and the conductive film 114c are laminated in this order, and the conductive film 114a and the conductive film 114c are laminated in this order. It covers the surface of 4b.

[0098] The conductive film 110a, the conductive film 112a, and the conductive film 114a are 2b, a material for preventing a metal element contained in the conductive film 114b from diffusing into the oxide semiconductor film 106; The conductive films 110a, 112a, and 114a are formed using titanium. Titanium, tantalum, molybdenum, tungsten, or titanium nitride or its alloys The conductive film can be formed using tantalum, molybdenum nitride, tantalum nitride, or the like. The conductive film 110a, the conductive film 112a, and the conductive film 114a are made of a Cu-X alloy (X is Mn, Ni, C The layer can be formed using, for example, r, Fe, Co, Mo, Ta, or Ti.

[0099] In addition, Cu-X alloy (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) In the case of the insulating film, a coating film is formed in a region in contact with the oxide semiconductor film or the insulating film by heat treatment. The coating film may be formed from a compound containing X. An example of a compound containing X is Examples include X oxide, In-X oxide, Ga-X oxide, In-Ga-X oxide, and In- The conductive film 110a, the conductive film 112a, and the conductive film 114a include Ga-Zn-X oxides. The coating film formed on the surface acts as a blocking film, preventing the formation of a metal in the Cu-X alloy film. It is possible to prevent Cu from entering the oxide semiconductor film.

[0100] Note that the copper concentration in the region of the oxide semiconductor film 106 that functions as a channel is set to 1×1 0 18 atoms / cm 3 By setting the following, the insulating film 108 functioning as a gate insulating film can be formed. Therefore, the density of electron trap states at the interface between the oxide semiconductor film 106 and the silicon dioxide film 108 can be reduced. As a result, it is possible to fabricate transistors with excellent subthreshold swing values ​​(S values). It is possible.

[0101] The conductive films 110b, 112b, and 114b are formed using a low-resistance material. The conductive films 110b, 112b, and 114b are made of copper, aluminum, gold, It can be formed using a simple substance such as silver, an alloy, or a compound containing silver as the main component. do.

[0102] The conductive film 110c, the conductive film 112c, and the conductive film 114c are 2b, by forming the conductive film 114b using a film in which the metal element contained in the conductive film 114b is passivated, The metal elements contained in the conductive films 110b, 112b, and 114b are In this case, the conductive film 1 can be prevented from moving to the oxide semiconductor film 106 during the formation process. 10c, the conductive film 112c, and the conductive film 114c are made of a metal silicide, a metal silicide nitride, or the like. It can be formed using, typically, CuSi x (x>0), CuSi x N y (x>0, y>0), etc.

[0103] Here, a method for forming the conductive film 110c, the conductive film 112c, and the conductive film 114c will be described. The conductive films 110b, 112b, and 114b are formed using copper. The conductive film 110c, the conductive film 112c, and the conductive film 114c are made of CuSi x N y ( x>0, y>0).

[0104] The conductive films 110b, 112b, and 114b are treated with hydrogen, ammonia, carbon monoxide, The conductive film 110b, the conductive film 112b, and the conductive film 112c are exposed to plasma generated in a reducing atmosphere such as nitrogen. The oxide on the surface of the conductive film 114b is reduced.

[0105] Next, the conductive film 110b, the conductive film 112b, and the conductive film 112c are heated at a temperature of 200° C. or more and 400° C. or less. As a result, the conductive film 110b, the conductive film 112b, and the conductive film 114b are exposed to silane. The copper contained in the film 114b acts as a catalyst, and silane is decomposed into Si and H2. , CuSi on the surfaces of the conductive film 110b, the conductive film 112b, and the conductive film 114b. x (x>0) is formed.

[0106] Next, the conductive films 110b, 112b, and 114b are treated with ammonia, nitrogen, or the like. By exposing the conductive film 110b and the conductive film 112 to plasma generated in an atmosphere containing nitrogen, b and CuSi formed on the surface of the conductive film 114b x (x>0) is the nitrogen contained in the plasma The conductive film 110c, the conductive film 112c, and the conductive film 114c are formed by reacting with CuSi x N y (x>0, y>0) is formed.

[0107] In the above process, the conductive film 110b, the conductive film 112b, and the conductive film 114b are uncoated. After exposure to plasma generated in an atmosphere containing nitrogen, such as ammonium nitrate or nitrogen, the The conductive film 110b, the conductive film 112b, and the conductive film 114b are silicided while being heated at 00° C. or less. By exposing the conductive film 110c, the conductive film 112c, and the conductive film 114c to the ion beam, CuSi x N y (x>0, y>0) may be formed.

[0108] Next, the insulating film 104 in which the nitride insulating film 104a and the oxide insulating film 104b are stacked is and explain.

[0109] For example, the nitride insulating film 104a may be a silicon nitride film, a silicon nitride oxide film, an aluminum nitride film, or the like. The insulating layer can be formed using aluminium film, aluminum oxide nitride film, etc. The insulating film 104b may be a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or the like. By providing the nitride insulating film 104a on the substrate 102 side, This can prevent hydrogen, water, and the like from diffusing into the oxide semiconductor film 106.

[0110] <Configuration 3 of semiconductor device> Next, another configuration of the semiconductor device will be described with reference to FIGS. 4, 5 and 11. As a modification of the transistor 150 provided in the pixel portion, a transistor 152 and a transistor The transistor 153 will be used for the description, but the transistor 154 in the driving circuit section will be The structure of the oxide semiconductor film 106 included in the transistor 152 or the oxide semiconductor film 106 included in the transistor 153 The structure of the compound semiconductor film 106 can be appropriately applied.

[0111] 4A to 4C are top views and cross-sectional views of a transistor 152 included in a semiconductor device. 4A is a top view of the transistor 152, and FIG. 4B is a side view of the transistor 152. 4(A) and FIG. 4(C) is a cross-sectional view taken along the dashed line X3-Y4 in FIG. Cross-sectional view of section X4.

[0112] The transistor 152 shown in FIG. 4 is characterized in that the oxide semiconductor film 106 has a multilayer structure. Specifically, the oxide semiconductor film 106 is formed by arranging the oxide semiconductor film 106 in contact with the insulating film 104. 107a, an oxide semiconductor film 107b in contact with the oxide semiconductor film 107a, and an oxide semiconductor film 107b, an oxide film in contact with the conductive film 110, the conductive film 112, the insulating film 108, and the insulating film 116 The other components are the same as those of the transistor 150. This has the effect of:

[0113] The oxide semiconductor films 107a, 107b, and 107c are Generally, there are In-Ga oxide films, In-Zn oxide films, and In-M-Zn oxide films (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf) is formed.

[0114] The oxide semiconductor films 107a and 107c are typically made of In-G a oxide film, In-Zn oxide film, In-Mg oxide film, Zn-Mg oxide film, In-M -Zn oxide film (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or H f) and the energy of the conduction band minimum is closer to the vacuum level than that of the oxide semiconductor film 107b. Typically, the energy at the bottom of the conduction band of the oxide semiconductor film 107a and the oxide semiconductor film 107c is the difference between the energy of the oxide semiconductor film 107b and the energy of the bottom of the conduction band of the oxide semiconductor film 107b is 0.05 eV or more, 0.07 eV or more, 0.1 eV or more, or 0.2 eV or more and 2 eV or less, 1 e V or less, 0.5 eV or less, or 0.4 eV or less. The energy difference is also called electron affinity.

[0115] The oxide semiconductor film 107b is an In-M-Zn oxide film (M is Mg, Al, Ti, Ga, In the case of the oxide semiconductor film 107b, the oxide semiconductor film 107b is formed by adding a metal oxide such as Y, Zr, La, Ce, Nd, or Hf. In the target used for this purpose, the atomic ratio of the metal elements is In:M:Zn=x1:y1:z If we set it to 1, 、x1 / y1 is 1 / 3 or more and 6 or less, and further 1 or more and 6 or less, and z1 / It is preferable that y1 is 1 / 3 or more and 6 or less, and more preferably 1 or more and 6 or less. When y1 is 1 or more and 6 or less, a CAAC-OS film is formed as the oxide semiconductor film 107b. A typical example of the atomic ratio of the target metal elements is In:M:Zn. =1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=2:1:1.5, I n:M:Zn=2:1:2.3, In:M:Zn=2:1:3, In:M:Zn=3:1 :There are 2nd class.

[0116] The oxide semiconductor film 107a and the oxide semiconductor film 107c are In-M-Zn oxide films (M is , Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf), oxide semi-conductor In the target used for depositing the conductive film 107a and the oxide semiconductor film 107c, If the atomic ratio of metal elements is In:M:Zn=x2:y2:z2, 、 x2 / y2 <x1 / y1, and z2 / y2 is 1 / 3 or more and 6 or less, and further 1 or more and 6 or less. Note that when z2 / y2 is greater than or equal to 1 and less than or equal to 6, the oxide semiconductor films 107a and 107b can be formed. A CAAC-OS film is easily formed as the oxide semiconductor film 107c. Typical examples of atomic ratios of group elements are In:M:Zn=1:3:2, In:M:Zn=1 :3:4, In:M:Zn=1:3:6, In:M:Zn=1:3:8, In:M:Zn =1:4:3, In:M:Zn=1:4:4, In:M:Zn=1:4:5, In:M: Zn=1:4:6, In:M:Zn=1:6:3, In:M:Zn=1:6:4, In: M:Zn=1:6:5, In:M:Zn=1:6:6, In:M:Zn=1:6:7, I Examples include n:M:Zn=1:6:8 and In:M:Zn=1:6:9.

[0117] When the oxide semiconductor film 107a and the oxide semiconductor film 107c are In—Ga oxide films, In this case, for example, an In-Ga metal oxide target (In:Ga=7:93) is used. The oxide semiconductor film 107a and the oxide semiconductor film 107b can be formed by a quenching method. As the conductive film 107c, an In-Ga oxide film is formed by sputtering using DC discharge. In order to achieve this, when the atomic ratio is In:Ga=x:y, y / (x+y) must be 0.9. It is preferably 6 or less, more preferably 0.95 or less, for example 0.93.

[0118] Note that the oxide semiconductor films 107a, 107b, and 107c The atomic ratios of each element include a margin of error of plus or minus 40%. .

[0119] The atomic ratio is not limited to these, and an appropriate atomic ratio may be selected depending on the required semiconductor characteristics. Just use something.

[0120] The oxide semiconductor film 107a and the oxide semiconductor film 107c may have the same composition. For example, the oxide semiconductor film 107a and the oxide semiconductor film 107c may be formed of In:Ga:Zn=1: Atomic ratio of 3:2, 1:3:4, 1:4:5, 1:4:6, 1:4:7, or 1:4:8 Alternatively, an In-Ga-Zn oxide may be used.

[0121] Alternatively, the oxide semiconductor film 107a and the oxide semiconductor film 107c may have different compositions. For example, the oxide semiconductor film 107a may be made of In, Ga, Zn, or Zn having an atomic ratio of In:Ga:Zn=1:3:2. The oxide semiconductor film 107c is made of In:Ga:Zn=1:3. An In-Ga-Zn oxide having an atomic ratio of 4 or 1:4:5 may also be used.

[0122] The oxide semiconductor film 107a and the oxide semiconductor film 107c have a thickness of 3 nm to 100 nm. The thickness of the oxide semiconductor film 107b is 3 nm or more, or 3 nm or more and 50 nm or less. 200nm or less, or 3nm to 100nm or 3nm to 50nm Note that the oxide semiconductor films 107a and 107c are oxide semiconductor films. By making the thickness thinner than 107b, the amount of fluctuation in the threshold voltage of the transistor can be reduced. It is possible to do this.

[0123] The oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107c The interface is observed by STEM (Scanning Transmission Electron Microscopy). It may be possible to observe the lesion using a microscope.

[0124] The oxide semiconductor films 107a, 107b, and 107c are The crystal structure of the oxide semiconductor film 106 described in Embodiment 1 can be used as appropriate.

[0125] The oxide semiconductor films 107a and 107b are less likely to have oxygen vacancies than the oxide semiconductor films 107a and 107b. The oxide semiconductor film 107c is provided in contact with the upper and lower surfaces of the oxide semiconductor film 107b. By this, oxygen vacancies in the oxide semiconductor film 107b can be reduced. The oxide semiconductor film 107b contains one or more metal elements constituting the oxide semiconductor film 107b. The oxide semiconductor film 107a and the oxide semiconductor film 107c are in contact with each other. the interface between the oxide semiconductor film 107a and the oxide semiconductor film 107b; The interface state density at the interface with the oxide semiconductor film 107b is extremely low. It is possible to reduce the oxygen vacancies contained therein.

[0126] In addition, the oxide semiconductor film 107b may be an insulating film having a different constituent element (for example, a silicon oxide film When the semiconductor comes into contact with an insulating film containing the silicon dioxide, an interface state is formed, and the interface state forms a channel. In such cases, transistors with different threshold voltages appear, and However, the apparent threshold voltage of the oxide semiconductor film 107 may vary. The oxide semiconductor film 107a containing one or more metal elements constituting the oxide semiconductor film 107b Since the oxide semiconductor film 107a is in contact with the oxide semiconductor film 107b, an interface state is formed at the interface between the oxide semiconductor film 107a and the oxide semiconductor film 107b. Therefore, by providing the oxide semiconductor film 107a, the transistor This can reduce variations in electrical characteristics such as threshold voltage.

[0127] When a channel is formed at the interface between the insulating film 108 and the oxide semiconductor film 107b, Interface scattering occurs at the interface, reducing the field-effect mobility of the transistor. The oxide semiconductor film 107c containing one or more metal elements included in the oxide semiconductor film 107b is an oxide semiconductor film. Since the oxide semiconductor film 107b is provided in contact with the oxide semiconductor film 107b, the oxide semiconductor film 107b and the oxide semiconductor At the interface with the film 107c, scattering of carriers is unlikely to occur, and the field effect mobility of the transistor is can be increased.

[0128] The oxide semiconductor films 107a and 107c are formed between the insulating film 104 and the insulating film 106. The constituent elements of the film 108 or the constituent elements of the conductive film 110 and the conductive film 112 are oxide semiconductor films. 107b, and the formation of impurity levels in the oxide semiconductor film 107 is suppressed. It also functions as a barrier film to prevent

[0129] For example, the insulating film 104 and the insulating film 108 may be an insulating film containing silicon or a film containing carbon. In the case of an insulating film, silicon in the insulating film 104 and the insulating film 108, or the insulating film 104 and the insulating film The carbon mixed in the film 108 is mixed in the oxide semiconductor film 107a and the oxide semiconductor film 107c. Impurities such as silicon and carbon can get into the oxide semiconductor up to a depth of a few nanometers from the interface. When the impurity enters the film 107b, it forms an impurity level, which acts as a donor and generates electrons. This can sometimes result in n-type.

[0130] However, the thickness of the oxide semiconductor film 107a and the oxide semiconductor film 107c is several nm. If the thickness is larger than 100 μm, impurities such as silicon and carbon may reach the oxide semiconductor film 107 b. Therefore, the influence of the impurity level is reduced.

[0131] From the above, the transistor described in this embodiment has electrical characteristics such as threshold voltage. This is a transistor with reduced variation.

[0132] FIG. 5 shows a transistor with a different structure from that shown in FIG.

[0133] 5A to 5C are top views and cross-sectional views of a transistor 153 included in a semiconductor device. 5A is a top view of the transistor 153, and FIG. 5B is a top view of the transistor 153. 5(A) and FIG. 5(C) is a cross-sectional view taken along the dashed line X3-Y4 in FIG. Cross-sectional view of section X4.

[0134] As in the transistor 153 illustrated in FIG. 5, the oxide semiconductor film 106 is in contact with the insulating film 104. the oxide semiconductor film 107b in contact with the oxide semiconductor film 107b and the insulating film 108; The other configuration may be a stacked structure of the transistor 150 and the semiconductor film 107c. It is similar and has the same effect.

[0135] <Band structure> Here, the band structures of the transistors shown in FIGS. 4 and 5 will be described. 1(A) is the band structure of the transistor 153 shown in FIG. , insulating film 104, oxide semiconductor film 107a, oxide semiconductor film 107b, oxide semiconductor film 1 11B shows the energy (Ec) of the conduction band minimum of the insulating film 108. is the band structure of the transistor 154 shown in FIG. 5. For ease of understanding, 104, the oxide semiconductor film 107b, the oxide semiconductor film 107c, and the insulating film 108 The edge energy (Ec) is shown.

[0136] As shown in FIG. 11A, the oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107b are In the compound semiconductor film 107c, the energy of the bottom of the conduction band changes continuously. The oxide semiconductor films 107a, 107b, and 107c are formed by This can be understood from the fact that oxygen easily diffuses between the two elements. The oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107c are a composite. Although it is a laminate of films with different compositions, it can also be said to be continuous in terms of physical properties.

[0137] The oxide semiconductor film, which is stacked with a common main component, is not simply stacked, but is continuously Junction (here, specifically, a U-shaped well where the energy of the bottom of the conduction band changes continuously between layers) The structure is fabricated so that a U-Shape Well structure is formed. In the oxide semiconductor, defect levels such as trap centers and recombination centers, or carrier The laminated structure is formed so that there are no impurities that hinder the flow of oxygen. When impurities are mixed between layers of a semiconductor film, the continuity of the energy band is lost, and the boundary At this surface, carriers disappear due to trapping or recombination.

[0138] Note that in FIG. 11A, the Ec values ​​of the oxide semiconductor films 107a and 107c are Although the cases where they are similar are shown, they may be different.

[0139] 11A, the oxide semiconductor film 107b serves as a well, and the oxide semiconductor film 107b is In 52, it can be seen that a channel is formed in the oxide semiconductor film 107b. The oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107c are Since the energy at the edge changes continuously, a U-shaped well structure channel is used as a buried channel. It can also be called "ru."

[0140] 11B, the oxide semiconductor film 107b and the oxide semiconductor film 107 In c, the energy of the conduction band minimum may change continuously.

[0141] As shown in FIG. 11B, the oxide semiconductor film 107b serves as a well, and the oxide semiconductor film 107b is In 53, it can be seen that a channel is formed in the oxide semiconductor film 107b.

[0142] The transistor 152 illustrated in FIG. 4 includes an oxide semiconductor film 107b containing one kind of metal element. Since the oxide semiconductor films 107a and 107c contain the above-mentioned oxide semiconductor films, The interface between the oxide semiconductor film 107a and the oxide semiconductor film 107b and the oxide semiconductor film 107 Therefore, an interface state is less likely to be formed at the interface between the oxide semiconductor film 107c and the oxide semiconductor film 107b. By providing the conductive film 107a and the oxide semiconductor film 107c, the threshold voltage of the transistor is This can reduce variations and fluctuations in electrical characteristics such as voltage.

[0143] The transistor 153 illustrated in FIG. 5 includes an oxide semiconductor film 107b containing one kind of metal element. Since the oxide semiconductor film 107c contains the above-mentioned oxide semiconductor film, the oxide semiconductor film 107c and the oxide semiconductor film Therefore, the interface state is less likely to be formed at the interface with the oxide semiconductor film 107b. By providing 107c, variations in electrical characteristics such as the threshold voltage of the transistor and Fluctuations can be reduced.

[0144] <Method 1 for manufacturing semiconductor device> Next, a method for manufacturing the transistor 150 and the transistor 154 shown in FIG. 7 to 9 will be used to explain this.

[0145] Films constituting the transistor 150 and the transistor 154 (insulating film, oxide semiconductor film, Conductive films, etc.) are deposited by sputtering, chemical vapor deposition (CVD), vacuum deposition, pulse laser, It can be formed using the laser deposition (PLD) method. Alternatively, it can be formed by coating or printing methods. The film formation method can be sputtering, plasma chemical vapor deposition (PE The most common method is MOCVD, but thermal CVD is also acceptable. (Metal Organic Chemical Vapor Deposition) or ALD (Atomic Layer Deposition) may also be used.

[0146] In the thermal CVD method, the pressure in the chamber is atmospheric or reduced, and the source gas and oxidant are simultaneously mixed in the chamber. The reaction is carried out near or on the substrate, and the film is deposited on the substrate. As described above, the thermal CVD method is a film formation method that does not generate plasma. This has the advantage that no defects are created by the image.

[0147] In the ALD method, the pressure inside the chamber is atmospheric or reduced, and the source gases for the reaction are sequentially introduced. Next, the gas is introduced into the chamber, and the film is formed by repeating this gas introduction sequence. By switching each switching valve (also called high-speed valve), two or more types of raw materials can be The gases are supplied to the chamber in order, and the first source gas is supplied to the chamber in order to prevent the mixture of the source gases. Simultaneously with or after this, an inert gas (argon, nitrogen, etc.) is introduced, and the second raw material If an inert gas is introduced at the same time, the inert gas is introduced as a carrier gas. In addition, an inert gas may be introduced at the same time as the second source gas is introduced. Instead of introducing an inert gas, the first source gas is discharged by evacuation, and then the second source gas is introduced. A source gas may be introduced. The first source gas is adsorbed on the surface of the substrate to form a first layer, The second layer is deposited on the first layer by reacting with the second source gas introduced later, forming a thin film. is formed.

[0148] This gas introduction sequence is repeated multiple times while controlling it until the desired thickness is achieved. The thickness of the thin film increases depending on the number of times the gas introduction sequence is repeated. Therefore, precise film thickness control is possible, and fine transistors can be fabricated. It is suitable for manufacturing.

[0149] As shown in FIG. 7C, a conductive film 201 is formed on the substrate 102. An insulating film 104 is formed on the substrate.

[0150] The conductive film 201 can be formed by a sputtering method, a vacuum deposition method, a pulsed laser deposition (PLD) method, A conductive film is formed using a thermal CVD method or the like, and a mask is formed on the conductive film by a lithography process. After forming the insulating film, etching is performed to form the insulating film.

[0151] In addition, a tungsten film is formed as the conductive film 201 using a film forming apparatus that uses ALD. In this case, WF6 gas and B2H6 gas are introduced repeatedly in sequence to form the initial Then, WF6 gas and H2 gas are introduced simultaneously to form a tungsten film. It should be noted that SiH4 gas may be used instead of B2H6 gas.

[0152] The conductive film 201 may be formed by electrolytic plating, printing, inkjet printing, or the like instead of the above-mentioned method. It may be formed by a tubing method or the like.

[0153] The insulating film 104 can be formed by a method such as sputtering, CVD, evaporation, or pulsed laser deposition (PLD). The insulating film 102 can be formed by using a suitable method such as a lithography method, a printing method, or a coating method. After forming the film, oxygen can be added to the insulating film to form the insulating film 104. The oxygen added to the insulating film can be oxygen radicals, oxygen atoms, oxygen atomic ions, or oxygen molecular ions. The doping method includes ion doping, ion implantation, plasma treatment, etc. Furthermore, after forming a film that suppresses oxygen desorption on the insulating film, the insulating film is Oxygen may be added to the membrane.

[0154] In addition, the substrate placed in the evacuated processing chamber of the plasma CVD device is heated to 180°C or higher. The temperature is kept at 280°C or below, or 200°C to 240°C, and the raw material gas is introduced into the processing chamber. The pressure in the treatment room should be between 100 Pa and 250 Pa, or between 100 Pa and 200 Pa. The electrode in the processing chamber is set to 0.17 W / cm 2 More than 0.5W / cm 2 Below, again is 0.25W / cm 2 More than 0.35W / cm 2 Under the following conditions for supplying high frequency power: A silicon oxide film or a silicon oxynitride film capable of releasing oxygen by heat treatment is used as an insulating film. It can be formed as a veneer 104.

[0155] Here, a film for suppressing oxygen desorption is formed on the insulating film, and then oxygen is introduced into the insulating film through the film. The method of adding the element will be explained with reference to FIGS. 7(A) and 7(B).

[0156] As shown in FIG. 7A, an insulating film 103 is formed over a substrate 102 and a conductive film 201 .

[0157] Next, as shown in FIG. 7(B), a film 119 for suppressing oxygen desorption is formed on the insulating film 103. Next, oxygen 121 is added to the insulating film 103 through the film 119.

[0158] The film 119 for suppressing oxygen desorption may be made of aluminum, chromium, tantalum, titanium, molybdenum, or the like. a metal element selected from iridium, nickel, iron, cobalt, and tungsten; Alloys containing the above elements, alloys combining the above metal elements, alloys containing the above metal elements metal nitrides containing the above-mentioned metal elements, metal oxides containing the above-mentioned metal elements, metal nitrides containing the above-mentioned metal elements, The insulating film is formed using a conductive material such as an oxide.

[0159] The thickness of the film 119 for suppressing oxygen desorption is 1 nm or more and 20 nm or less, or 2 nm or more and 10 nm or less. It can be 0 nm or less.

[0160] The oxygen 121 can be added to the insulating film 103 through the film 119 by ion doping. The film 119 is provided on the insulating film 103, and oxygen is introduced into the film 119. By adding the above, the film 119 functions as a protective film that suppresses oxygen desorption from the insulating film 103. Therefore, more oxygen can be added to the insulating film 103.

[0161] In addition, when oxygen is introduced in plasma treatment, the oxygen is excited by microwaves to form high-density oxygen. By generating oxygen plasma, the amount of oxygen introduced into the insulating film 103 can be increased. .

[0162] After that, the film 119 is removed, and oxygen is left on the substrate 102 as shown in FIG. 7(C). The insulating film 104 to which oxygen is added can be formed. In the case where the insulating film 104 can be formed, the oxygen addition shown in FIGS. It is not necessary to perform this process.

[0163] Next, as shown in FIG. 7D, an oxide semiconductor film 106 and an oxide semiconductor film 107 are formed on the insulating film 104. The conductive film 206 is formed. Next, the insulating film 104, the oxide semiconductor film 106, and the oxide semiconductor An insulating film 108 is formed on the film 206 .

[0164] Methods for forming the oxide semiconductor film 106 and the oxide semiconductor film 206 will be described below. On the insulating film 104, a sputtering method, a coating method, a pulse laser deposition method, a laser ablation method, An oxide semiconductor film is formed by a deposition method, thermal CVD method, etc. Next, a heat treatment is performed to form an insulating film. Oxygen contained in the film 104 is transferred to the oxide semiconductor film. After forming a mask by a lithography process, part of the oxide semiconductor film is etched using the mask. As a result of this, the oxide semiconductor film 106 and the oxide semiconductor film 107 are After that, the mask is removed. After the oxide semiconductor film 106 is formed by etching the portion, heat treatment may be performed.

[0165] In addition, the oxide semiconductor film 106 and the oxide semiconductor film 206 are formed by a printing method. The oxide semiconductor film 106 and the oxide semiconductor film 206 that are isolated from each other can be directly formed. Cut.

[0166] When an oxide semiconductor film is formed by a sputtering method, a power source for generating plasma is used. The device may be an RF power supply device, an AC power supply device, a DC power supply device, or the like. The CAAC-OS film can be formed by using an AC power supply or a DC power supply. In addition, the oxide semiconductor film is formed by a sputtering method using an RF power supply. In addition, oxide semiconductor films are formed by sputtering using AC or DC power supplies. This is preferable because it results in a uniform distribution of the film thickness, the film composition, or the crystallinity.

[0167] The sputtering gas is a rare gas (typically argon), oxygen, or a mixture of rare gas and oxygen. In the case of a mixture of rare gas and oxygen, the ratio of the oxygen gas to the rare gas is A higher ratio is preferred.

[0168] The target may be appropriately selected depending on the composition of the oxide semiconductor film to be formed. .

[0169] Note that when the oxide semiconductor film is formed by, for example, a sputtering method, The temperature is set to 150°C or higher and 750°C or lower, or 150°C or higher and 450°C or lower, or 200°C or higher and 3 The oxide semiconductor film is formed at a temperature of 50° C. or less to form a CAAC-OS film. Furthermore, by setting the substrate temperature to 25° C. or higher and lower than 150° C., a microcrystalline oxide semiconductor A film can be formed.

[0170] In addition, in order to form a CAAC-OS film described later, the following conditions are preferably applied: It's nice.

[0171] By suppressing the inclusion of impurities 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 film formation chamber can be In addition, the impurity concentration in the deposition gas can be reduced. A deposition gas having a temperature of -80°C or lower or -100°C or lower is used.

[0172] In addition, by increasing the oxygen ratio in the deposition gas and optimizing the power, plasma damage during deposition can be reduced. The oxygen ratio in the film forming gas is preferably 30% by volume or more, or 100% by volume. Let's say.

[0173] After the oxide semiconductor film is formed, heat treatment is performed to dehydrogenate or The temperature of the heat treatment is typically 150°C or higher and lower than the substrate distortion point, or The temperature is 250°C or higher and 450°C or lower, or 300°C or higher and 450°C or lower.

[0174] Heat treatment is carried out using rare gases such as helium, neon, argon, xenon, krypton, or nitrogen. It is carried out in an inert gas atmosphere containing oxygen, or after heating in an inert gas atmosphere, it is heated in an oxygen atmosphere. It is to be noted that the inert atmosphere and oxygen atmosphere must not contain hydrogen, water, etc. The treatment time is preferably from 3 minutes to 24 hours.

[0175] The heat treatment can be carried out using an electric furnace, an RTA device, or the like. Therefore, heat treatment can be performed at a temperature above the strain point of the substrate for a short period of time. The processing time can be reduced.

[0176] The oxide semiconductor film is formed while being heated, and after the oxide semiconductor film is formed, By performing heat treatment, the oxide semiconductor film is The hydrogen concentration is 5×10 19 atoms / cm 3 or less, or 1 x 10 19 atoms / cm 3 Below, 5 x 10 18 atoms / cm 3 or less, or 1 x 10 18 atoms / cm 3 Below Below, or 5x10 17 atoms / cm 3 or less, or 1 x 10 16 atoms / cm 3 Below It can be below.

[0177] The film formation equipment using ALD is used to form oxide semiconductor films, such as In-Ga-Zn-O films. When depositing an In-O layer, In(CH3)3 gas and O3 gas are introduced repeatedly in sequence. Then, Ga(CH3)3 gas and O3 gas are introduced simultaneously to form a Ga-O layer. Then, Zn(CH3)2 and O3 gases are introduced simultaneously to form a Zn-O layer. The order of these layers is not limited to this example. In addition, by mixing these gases, an In-Ga-O layer Alternatively, a mixed compound layer such as an In-Zn-O layer or a Ga-Zn-O layer may be formed. Instead of the gas 3, H2O gas bubbled with an inert gas such as Ar may be used. It is preferable to use O3 gas that does not contain In(CH3)3. Alternatively, Ga(CH)3 gas may be used instead of Ga(CH). 5)3 gas may be used. Zn(CH3)2 gas may also be used.

[0178] Here, an oxide semiconductor film having a thickness of 35 nm is formed by a sputtering method. Heat treatment is performed to move oxygen contained in the insulating film 104 to the oxide semiconductor film. A mask is formed over the oxide semiconductor film, and part of the oxide semiconductor film is selectively etched. In this way, the oxide semiconductor film 106 and the oxide semiconductor film 206 are formed.

[0179] The heat treatment should be performed at a temperature between 350°C and 650°C, or between 450°C and 600°C. By doing so, the CAAC conversion rate will be 60% or more but less than 100%, or 80% or more but less than 100%, Alternatively, an oxide semiconductor film having a conductivity of 90% or more and less than 100%, or 95% or more and 98% or less can be obtained. The CAAC ratio is determined by measuring the transmission electron diffraction pattern using a transmission electron diffraction measurement device. The diffraction pattern of the CAAC-OS film is observed in a certain range by the measurement of the diffraction pattern. It is also possible to obtain an oxide semiconductor film with reduced contents of hydrogen, water, and the like. That is, it is possible to form an oxide semiconductor film with a low impurity concentration and a low density of defect states. It is possible.

[0180] The insulating film 108 can be formed by using the method for forming the insulating film 104 as appropriate.

[0181] When a low-resistance material is used for the conductive film 109, for example, the low-resistance material is mixed into the oxide semiconductor film. If the conductive film 1 is introduced, the electrical characteristics of the transistor may be deteriorated. By forming the insulating film 108 before forming the oxide semiconductor film 109, the oxide semiconductor film 106 and the oxide semiconductor film 109 can be prevented from being damaged. Since the channel of the conductive film 206 does not contact the conductive film 109, the electrical characteristics of the transistor, In effect, the amount of fluctuation in the threshold voltage can be suppressed.

[0182] The insulating film 108 is formed by using a silicon oxide film or a silicon oxynitride film by using a CVD method. In this case, the source gas may be a deposition gas containing silicon and an oxidizing gas. Representative examples of deposition gases containing silicon include silane, disilane, and the like. Examples of oxidizing gases include silane, trisilane, and fluorinated silane. Examples of oxidizing gases include oxygen, ozone, and monoxide. Examples include dinitrogen and nitrogen dioxide.

[0183] In addition, the insulating film 108 is formed by mixing an oxidizing gas with a deposition gas that is 20 times or more and 100 times or more. The pressure in the processing chamber should be less than 100 Pa or 50 Pa or less. By using the CVD method described below, it is possible to form a silicon oxynitride film with a small amount of defects. can.

[0184] The insulating film 108 is placed in a vacuum-evacuated processing chamber of a plasma CVD apparatus. The substrate is maintained at a temperature of 280°C or higher and 400°C or lower, and raw material gas is introduced into the processing chamber. The pressure in the air is set to 20 Pa or more and 250 Pa or less, more preferably 100 Pa or more and 250 Pa or less. Under the conditions under which high frequency power is supplied to an electrode provided in the processing chamber, the insulating film 108 and As a result, a dense silicon oxide film or silicon oxynitride film can be formed.

[0185] The insulating film 108 may be formed by a plasma CVD method using microwaves. Microwaves refer to the frequency range from 300MHz to 300GHz. In this case, the electron temperature is low and the electron energy is small. A smaller proportion of the electrons are used to accelerate the molecules, and more are used to dissociate and ionize the molecules. It is possible to excite a high density plasma (high density plasma). The insulating film 108 is formed with less defects due to less plasma damage to the surface to be deposited and the deposits. It is possible.

[0186] The insulating film 108 can be formed by a CVD method using organic silane gas. The organic silane gases include ethyl silicate (TEOS: chemical formula Si(OC2H5)4), Tetramethylsilane (TMS: chemical formula Si(CH3)4), tetramethylcyclotetrasilane Octamethylcyclotetrasiloxane (TMCTS), Octamethylcyclotetrasiloxane (OMCTS), Hexa Methyldisilazane (HMDS), triethoxysilane (SiH(OC2H5)3), tri Silicon-containing compounds such as dimethylaminosilane (SiH(N(CH3)2)3) are used. By using the CVD method with organic silane gas, it is possible to obtain insulating films with high coating properties. A membrane 108 can be formed.

[0187] When a gallium oxide film is formed as the insulating film 108, MOCVD (Metal Organic Chemical Vapor Deposition (OCVD) method It can be achieved.

[0188] The insulating film 108 is formed by oxidizing a film using a thermal CVD method such as an MOCVD method or an ALD method. When forming a hafnium film, a liquid containing a solvent and a hafnium precursor compound (hafnium Alkoxide solution, typically tetrakisdimethylamidohafnium (TDMAH) Two types of gases are used: the source gas vaporized from and ozone (O3) as an oxidizing agent. The chemical formula for tetrakisdimethylamidohafnium is Hf[N(CH3)2]4. Other liquid materials include tetrakis(ethylmethylamido)hafnium.

[0189] The insulating film 108 is formed by oxidizing a film using a thermal CVD method such as an MOCVD method or an ALD method. When forming an aluminum film, a liquid containing a solvent and an aluminum precursor compound (trimethylsilylsilane) is used. Two types of gas are used: vaporized methylaluminum (TMA, etc.) and H2O as an oxidizer. The chemical formula of trimethylaluminum is Al(CH3)3. Other liquid materials include tris(dimethylamido)aluminum and triisobutylaluminum. Aluminum, aluminum tris(2,2,6,6-tetramethyl-3,5-heptanedioate) In addition, by forming it using the ALD method, it is possible to obtain an insulating film with high coverage and thin film thickness. A membrane 108 can be formed.

[0190] The insulating film 108 is formed by oxidizing a film using a thermal CVD method such as an MOCVD method or an ALD method. When forming a silicon film, hexachlorodisilane is adsorbed onto the surface to be formed, and the adsorbed material Removes chlorine and provides radicals of oxidizing gases (O2, nitrous oxide) to absorb and react with it.

[0191] Here, a silicon oxynitride film is formed as the insulating film 108 by plasma CVD. do.

[0192] Next, as shown in FIG. 8(A), a mask is formed on the insulating film 108 by a lithography process. After the formation of the insulating film 108, part of the insulating film 108 is etched to expose part of the oxide semiconductor film 106. The openings 140a and 140b expose the oxide semiconductor film 206. A mouth portion 220a and an opening portion 220b are formed.

[0193] The insulating film 108 is etched by wet etching or / and dry etching. A coating method can be used as appropriate.

[0194] Next, as shown in FIG. 8B, the oxide semiconductor film 106, the oxide semiconductor film 206, and the insulating film A conductive film 109 is formed on the insulating film 108 .

[0195] The conductive film 109 can be formed by using the method for forming the conductive film 201 as appropriate.

[0196] Next, as shown in FIG. 8(C), a mask 1 is formed on the conductive film 109 by a lithography process. After forming the conductive film 109, the conductive film 109 is exposed to an etching solution and / or etching gas 123. The conductive film 110, the conductive film 112, and the conductive film 114, as well as the conductive film 210 and the conductive film 21 2 and a conductive film 214 are formed.

[0197] The conductive film 109 is etched by wet etching or / and dry etching. After the conductive film 109 is etched, the insulating film 10 A cleaning step may be performed to remove residues on the side surfaces of the gate electrode 8. The conductive film 114 and the oxide semiconductor film 106 functioning as a gate electrode are connected to each other. Therefore, leakage current between the conductive film 214 and the oxide semiconductor film 206 can be reduced.

[0198] The conductive film 110, the conductive film 112, and the conductive film 114, as well as the conductive film 210 and the conductive film 2 The conductive film 12 and the conductive film 214 may be formed by electrolytic plating, printing, inkjet printing, etc. instead of the above-mentioned methods. It may be formed by a tubing method or the like.

[0199] Next, as shown in FIG. 9A, the oxide semiconductor film 106 and the The impurity element 117 is added to the oxide semiconductor film 206. The impurity element is doped into the region not covered by the mask 111. By adding 17, oxygen vacancies are formed in the oxide semiconductor film 106 and the oxide semiconductor film 206. will be done.

[0200] The impurity element 117 can be added by ion doping, ion implantation, plasma In the case of plasma treatment, the plasma is heated in a gas atmosphere containing the impurity element to be added. By generating a plasma and performing a plasma treatment, impurity elements can be added. The plasma generating device may be a dry etching device or a plasma CVD device. A high-density plasma CVD apparatus or the like can be used.

[0201] The source gases for the impurity element 117 are B2H6, PH3, CH4, N2, and NH3 , AlH3, AlCl3, SiH4, Si2H6, F2, HF, H2 and one or more of the rare gases Alternatively, B2H6, PH3, N2, NH3, A diluted with rare gases can be used. One or more of IH3, AlCl3, F2, HF, and H2 can be used. Dilution with a noble gas of B2H6, PH3, N2, NH3, AlH3, AlCl3, F2, HF and H2 The impurity element 117 is added to the oxide semiconductor film 106 and the oxide semiconductor film 206 using one or more impurity elements. By adding rare gases, hydrogen, boron, carbon, nitrogen, fluorine, aluminum, and silicon At least one of phosphorus and chlorine is added to the oxide semiconductor film 106 and the oxide semiconductor film 206 at the same time. can be added.

[0202] Alternatively, after adding a rare gas to the oxide semiconductor film 106 and the oxide semiconductor film 206, B2H 6, PH3, CH4, N2, NH3, AlH3, AlCl3, SiH4, Si2H6, F 2. Adding one or more of HF and H2 to the oxide semiconductor film 106 and the oxide semiconductor film 206 Good too.

[0203] or B2H6, PH3, CH4, N2, NH3, AlH3, AlCl3, SiH4, One or more of Si2H6, F2, HF, and H2 is mixed with the oxide semiconductor film 106 and the oxide semiconductor film 2 After the rare gas was added to the oxide semiconductor film 106 and the oxide semiconductor film 206, Good too.

[0204] The addition of the impurity element 117 is controlled by appropriately setting implantation conditions such as acceleration voltage and dose amount. For example, when adding argon by ion implantation, the acceleration voltage is 10 kV, The amount of deviation is 1×10 13 ions / cm 2 More than 1×10 16 ions / cm 2 If we do the following, For example, 1×10 14 ions / cm 2 In addition, phosphorus can be implanted by ion implantation. When adding ions, the acceleration voltage is 30 kV and the dose is 1 × 10 13 ions / cm 2 Below Top 5×10 16 ions / cm 2 For example, 1×10 15 ions / c m 2 This can be done as follows.

[0205] Here, when the impurity element 117 is added to the oxide semiconductor film 106, A conceptual diagram of the region where the impurity element is added is shown in Figure 10. As a representative example, The following description will be given with reference to an enlarged view of the oxide semiconductor film 106 and its vicinity included in the transistor 150.

[0206] As shown in FIG. 10(A), the region where the impurity element 117 is added is covered with the insulating film 104, the oxide semiconductor, and the like. It may be formed on the conductive film 106 and the insulating film 108. In the depth direction of the exposed region, the end 135 of the doped region is located in the insulating film 104. The depth direction is parallel to the thickness direction of the oxide semiconductor film 106 and is parallel to the thickness direction of the insulating film 1 The direction is from 08 to the insulating film 104.

[0207] Alternatively, as shown in FIG. 10B, the region to which the impurity element 117 is added is In some cases, the insulating film 106 and the insulating film 108 are formed on the oxide semiconductor film 106. In the depth direction of the region, the end 136 of the doped region is adjacent to the insulating film 104 and the oxide semiconductor film 1 Located at the interface of 06.

[0208] Alternatively, as shown in FIG. 10C, the region to which the impurity element 117 is added is In some cases, the insulating film 106 and the insulating film 108 are formed on the oxide semiconductor film 106. In the depth direction of the region, an end portion 137 of the doped region is located in the oxide semiconductor film 106. .

[0209] As a result, low-resistance regions are formed in the oxide semiconductor film 106 and the oxide semiconductor film 206. Specifically, the region 106b and the region 106c shown in FIG. Note that the region 106c is formed by insulating film 108 between the oxide semiconductor film 106 and the oxide semiconductor film 106. Since the impurity element is added to the conductive film 206, the concentration of the impurity element is lower than that of the region 106b. After that, the mask 111 is removed as shown in FIG.

[0210] Note that the oxide semiconductor film 106 and the oxide semiconductor film 2 are formed using the mask 111. The impurity element 117 was added to the conductive film 110 after the mask 111 was removed. The conductive film 112 and the conductive film 114, as well as the conductive film 210, the conductive film 212 and the conductive film 214 are mass-produced. The impurity element 117 is added to the oxide semiconductor film 106 and the oxide semiconductor film 206 as a gate insulating film. Good too.

[0211] After that, a heat treatment is performed to further increase the conductivity of the region where the impurity element 117 is added. The temperature of the heat treatment is typically 150°C or higher and lower than the substrate strain point, or 250°C or higher. or higher and lower than 450°C, or higher and lower than 300°C and lower than 450°C.

[0212] Next, as shown in FIG. 9C, the oxide semiconductor film 106, the insulating film 108, and the conductive film 110 are , the conductive film 112, the conductive film 114, the oxide semiconductor film 206, the conductive film 210, the conductive film 212, and The insulating film 116 is formed on the conductive film 214, and the insulating film 118 is formed on the insulating film 116. good.

[0213] The insulating films 116 and 118 are formed by appropriately using the method for forming the insulating films 104 and 108. It can be formed by

[0214] In addition, the substrate placed in the evacuated processing chamber of the plasma CVD device is heated to 180°C or higher. The temperature is kept at 280°C or below, or 200°C to 240°C, and the raw material gas is introduced into the processing chamber. The pressure in the treatment room should be between 100 Pa and 250 Pa, or between 100 Pa and 200 Pa. The electrode in the processing chamber is set to 0.17 W / cm 2 More than 0.5W / cm 2 Below, again is 0.25W / cm 2 More than 0.35W / cm 2 Under the following conditions for supplying high frequency power: A silicon oxide film or a silicon oxynitride film capable of releasing oxygen by heat treatment is used as an insulating film. It can be formed as a veneer 116 .

[0215] Alternatively, the oxide semiconductor film 106, the conductive film 110, the conductive film 112, and the conductive film 114, and The oxide semiconductor film 206, the conductive film 210, the conductive film 212, and the conductive film 214 are covered with aluminum. After forming the aluminum oxide film, a heat treatment is performed to form the region 106 shown in FIG. In FIG. 1B, oxygen contained in the oxide semiconductor film 106 and the oxide semiconductor film 206 is converted to aluminum. The aluminum film or aluminum oxide film reacts with the silicon dioxide film, and the aluminum oxide film is formed as the insulating film 116. At the same time, oxygen vacancies are formed in the region 106b in FIG. Furthermore, the conductivity of the region 106b can be increased.

[0216] After that, a heat treatment is performed to further increase the conductivity of the region where the impurity element 117 is added. The temperature of the heat treatment is typically 150°C or higher and lower than the substrate strain point, or 250°C or higher. or higher and lower than 450°C, or higher and lower than 300°C and lower than 450°C.

[0217] Through the above steps, the transistor 150 and the transistor 154 can be manufactured. do.

[0218] <Method 2 for manufacturing semiconductor device> A method for manufacturing the transistor 151 shown in FIG. 3 will be described. The conductive film 110c included in the conductive film 110, the conductive film 112, and the conductive film 114 of 151, the formation of the film 112c and the conductive film 114c, and the formation of the oxide semiconductor film 106 containing the impurity element 117 The step of adding the above will be described.

[0219] 7 and 8(A) to 8(C), an insulating film 104 and an oxide film 105 are formed on the substrate 102. The semiconductor film 106, the insulating film 108, the conductive film 110, the conductive film 112, the conductive film 114, and the mass Forming the 111.

[0220] Next, as shown in FIG. 8C, an impurity element 117 is added to the oxide semiconductor film 106. .

[0221] Next, the mask 111 is removed.

[0222] Next, the conductive film 110 included in each of the conductive film 110, the conductive film 112, and the conductive film 114 b) The conductive film 112b and the conductive film 114b are exposed to plasma generated in a reducing atmosphere, and the conductive film 112b and the conductive film 114b are The oxides on the surfaces of the conductive film 110b, the conductive film 112b, and the conductive film 114b are reduced. The conductive film 110b, the conductive film 112b, and the conductive film 111 are heated at a temperature of 0° C. or more and 400° C. or less. Next, the conductive film 110b, the conductive film 112b, and the conductive film 114b are exposed to silane. By exposing the conductive film 11 to plasma generated in an atmosphere containing nitrogen such as ammonia or nitrogen, CuSi as the conductive film 0c, the conductive film 112c and the conductive film 114c x N y (x>0, y>0) It can be formed.

[0223] In addition, when exposed to plasma generated in an atmosphere containing nitrogen such as ammonia or nitrogen, The oxide semiconductor film 106 is formed by plating in an atmosphere containing nitrogen such as ammonia or nitrogen. Because the oxide semiconductor film 106 is exposed to the magnetic field, nitrogen and / or hydrogen can be added to the oxide semiconductor film 106. is.

[0224] Note that the mask 111 is removed before the impurity element 117 is added to the oxide semiconductor film 106. The conductive film 110c and the conductive film 110c included in the conductive film 110, the conductive film 112, and the conductive film 114 are 12c and a conductive film 114c may be formed.

[0225] After that, the transistor 151 can be manufactured through the process of FIG.

[0226] The transistor described in this embodiment has a conductive film which functions as a source electrode and a drain electrode. Since the film does not overlap with the conductive film that functions as the gate electrode, the parasitic capacitance can be reduced. Furthermore, the transistor described in this embodiment has a stable low Since it is possible to form a resistive region, the on-current is improved compared to conventional devices, and the transistor Variation in electrical characteristics is reduced.

[0227] The configurations and methods described in this embodiment may be different from the configurations and methods described in other embodiments. can be used in appropriate combination.

[0228] (Embodiment 2) In this embodiment mode, one mode of a semiconductor device and a manufacturing method of the semiconductor device will be described with reference to FIGS. 2 will be used for the description. In this embodiment, the low resistance region is formed in a simple manner as compared with the first embodiment. The manufacturing method is different.

[0229] <Configuration 1 of semiconductor device> 12 and 17 show a top gate transistor as an example of a transistor included in a semiconductor device. 1 shows a transistor of this structure.

[0230] In FIG. 17, a transistor 194 provided in a driver circuit and a transistor provided in a pixel portion are 12 shows a cross-sectional view of transistor 194 and transistor 190. 17A is a top view of the transistor 194, and FIG. 12A is a cross-sectional view of the rotor 190 taken along the dashed line X1-X2 in FIG. 12(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 12(B) and FIG. 17(B). 17(A) is a cross-sectional view taken along the dashed line Y1-Y2, and FIG. 17(B) is a cross-sectional view taken along the dashed line Y3-Y4. 12A is a cross-sectional view of the transistor 190 in the channel length direction. 12B is a cross-sectional view of the transistor 190 in the channel width direction.

[0231] The transistor 190 shown in FIG. 12 is an oxide film on an insulating film 164 formed on a substrate 162. an oxide semiconductor film 166; an insulating film 168 in contact with the oxide semiconductor film 166; The conductive film 170 is in contact with the oxide semiconductor film 166 in a part of the opening 180a, and the insulating film 16 The conductive film 172 is in contact with the oxide semiconductor film 166 in part of the opening 180b of FIG. The conductive film 174 overlaps with the oxide semiconductor film 166 with the film 168 interposed therebetween. An insulating film 176 is provided on the resistor 190. An insulating film 178 is also provided on the insulating film 176. may be provided.

[0232] The transistor 194 shown in FIG. 12 includes a conductive film 221 formed over a substrate 162 and a conductive The insulating film 164 on the film 221, the oxide semiconductor film 226 on the insulating film 164, and the oxide semiconductor The insulating film 168 in contact with the film 226 and the oxide film in a part of the opening 240a of the insulating film 168 In the conductive film 230 in contact with the semiconductor film 226 and in a part of the opening 240b of the insulating film 168 The conductive film 232 in contact with the oxide semiconductor film 226 and the oxide semiconductor film 227 are formed with the insulating film 168 interposed therebetween. 26 and a conductive film 234 overlapping the conductive film 234.

[0233] The transistor 194 includes a conductive film 224 overlapping with the oxide semiconductor film 226 with the insulating film 164 interposed therebetween. That is, the conductive film 221 functions as a gate electrode. The transistor 194 is a transistor with a dual gate structure.

[0234] The conductive film 234 and the conductive film 221 are not connected to each other and different potentials are applied to them. The threshold voltage of the transistor 194 can be controlled. In this way, the conductive film 234 and the conductive film 221 are connected through the opening 183, and the same potential is applied. By adding this, it is possible to reduce the initial characteristic variations, suppress deterioration in the -GBT stress test, and It is possible to suppress fluctuations in the on-current rise voltage at a drain voltage of In the oxide semiconductor film 226, the region through which carriers flow increases in the film thickness direction. As a result, the on-current of the transistor 194 increases. Both of these increase the field-effect mobility. By setting the thickness to 45 μm or more and 2.2 μm or less, the on-current is further increased and the electric field The effect of this is to increase mobility.

[0235] In the display device described in this embodiment, the driver circuit portion and the pixel portion include a transistor. The transistors included in the drive circuit section have a dual gate structure. The driver circuit portion includes a transistor having a higher field-effect mobility than the pixel portion.

[0236] In addition, in the display device, the channel lengths of the transistors included in the driver circuit portion and the pixel portion are It may be different.

[0237] Typically, the channel length of the transistor 194 included in the driving circuit section is set to less than 2.5 μm. On the other hand, the thickness of the pixel portion can be set to 1.45 μm or more and 2.2 μm or less. The channel length of the transistor 190 is set to 2.5 μm or more, or 2.5 μm or more and 20 μm or less. It is possible.

[0238] The channel length of the transistor 194 included in the driving circuit section is set to less than 2.5 μm, preferably By making the thickness of the transistor 190 included in the pixel portion 190 equal to or larger than 1.45 μm and equal to or smaller than 2.2 μm, Compared with the above, it is possible to increase the field effect mobility and increase the on-current. As a result, a driver circuit section capable of high-speed operation can be manufactured.

[0239] The high field-effect mobility of the transistors included in the driver circuit reduces the number of input terminals In addition, it is possible to increase the on-state current of the transistor included in the pixel portion. Therefore, uneven display of the pixel portion can be suppressed.

[0240] In the oxide semiconductor film 166, the conductive films 170, 172, and 174 overlap with each other. The oxide semiconductor film 226 contains an element that forms oxygen vacancies. In addition, oxygen vacancies are formed in regions that do not overlap with the conductive films 230, 232, and 234. Hereinafter, the elements that form oxygen vacancies will be described as impurity elements. Typical examples of pure elements include hydrogen and rare gas elements. Typical examples of rare gas elements include: There are helium, neon, argon, krypton and xenon. In addition, impurity elements In addition, boron, carbon, nitrogen, fluorine, aluminum, silicon, phosphorus, and chlorine are contained in oxide semiconductors. The oxide semiconductor film 166 and the oxide semiconductor film 226 may be included.

[0241] The insulating film 176 is a film containing hydrogen, and is typically a nitride insulating film. The insulating film 176 is in contact with the oxide semiconductor film 166 and the oxide semiconductor film 226. The contained hydrogen diffuses into the oxide semiconductor film 166 and the oxide semiconductor film 226. As a result, The oxide semiconductor film 166 and the oxide semiconductor film 226 are formed in a region in contact with the insulating film 176. It contains a lot of hydrogen.

[0242] When a rare gas element is added to an oxide semiconductor film as an impurity element, The bond between the metal element and oxygen is broken, and oxygen vacancies are formed. The interaction between oxygen vacancies and hydrogen increases the electrical conductivity of the oxide semiconductor film. When hydrogen enters the oxygen vacancies in the oxide semiconductor film, electrons are generated as carriers. This results in a high conductivity.

[0243] Here, an enlarged view of the vicinity of the oxide semiconductor film 166 is shown in FIG. The following description will be given with reference to an enlarged view of the oxide semiconductor film 166 and its vicinity included in the transistor 190. 3, the oxide semiconductor film 166 is in contact with the conductive film 170 or the conductive film 172. 166a, a region 166b in contact with the insulating film 176, and a region 166c overlapping with the insulating film 168. and region 166d.

[0244] The region 166a functions as a source region and a drain region. The region 166a in contact with the film 172 is electrically conductive, similar to the region 106a shown in the first embodiment. The raised portions function as source and drain regions.

[0245] The region 166b and the region 166c function as low resistance regions. The region 166c contains at least a rare gas and hydrogen as impurity elements. The region 166b has a higher impurity element concentration than the region 166c. In this case, part of the region 166c may overlap with the conductive film 174.

[0246] In the case where the oxide semiconductor film 166 is formed by a sputtering method, the regions 166a to 166c are 66d each contain a rare gas element, and compared to region 166a and region 166d, regions The regions 166b and 166c have higher concentrations of rare gas elements. When 66 is formed by sputtering, a rare gas is used as the sputtering gas. Therefore, a rare gas is contained in the oxide semiconductor film 166, and the regions 166b and 166c are In c, rare gases are intentionally added to form oxygen vacancies. In addition, the regions 166b and 166c are different from the regions 166a and 166d. A rare gas element may be added.

[0247] In addition, since the region 166b is in contact with the insulating film 176, it is In comparison, the concentration of hydrogen is higher in the region 166b. When hydrogen diffuses, the region 166c has a higher hydrogen concentration than the region 166a and the region 166d. However, the hydrogen concentration is higher in the region 166b than in the region 166c.

[0248] In the region 166b and the region 166c, hydrogen concentration obtained by secondary ion mass spectrometry is The concentration is 8 x 10 19 atoms / cm 3 or more, or 1 x 10 20 atoms / cm 3 Below Above, or 5x10 20 atoms / cm 3 The above can be done. and the hydrogen concentration obtained by secondary ion mass spectrometry in region 166d is 5×10 19 at oms / cm 3 or less, or 1 x 10 19 atoms / cm3 or less, or 5 x 10 18 at oms / cm 3 or less, or 1 x 10 18 atoms / cm 3 or less, or 5 x 10 17 at oms / cm 3 or less, or 1 x 10 16 atoms / cm 3 It can be as follows:

[0249] In addition, impurity elements such as boron, carbon, nitrogen, fluorine, aluminum, silicon, and lithium are used. When chlorine or chlorine is added to the oxide semiconductor film 166, the regions 166b and 166c Therefore, compared with the region 166a and the region 166d, the region The concentration of the impurity element is higher in the region 166b and the region 166c. In 166c, the concentration of impurity elements obtained by secondary ion mass spectrometry is 5 × 10 18 atoms / cm 3 More than 1×10 22 atoms / cm 3 Below, 1×10 19 ato ms / cm 3 More than 1×10 21 atoms / cm 3 or less, or 5 x 10 19 atoms / cm 3 5x10 or more 20 atoms / cm 3 It can be as follows:

[0250] Compared to the region 166d, the regions 166b and 166c have a high hydrogen concentration and are rare. The amount of oxygen deficiency caused by the addition of gas elements is large. This results in high conductivity and a low resistance region. Typically, the resistivity of the region 166b and the region 166c is 1×10 -3 Ωcm or more 1×10 4 Less than Ωcm or 1×10 -3 Ωcm or more 1×10 -1 Less than Ωcm It can be said that:

[0251] In the regions 166b and 166c, the amount of hydrogen is equal to or less than the amount of oxygen vacancies. If there is no oxygen vacancy, hydrogen is easily captured by the oxygen vacancy and is difficult to diffuse into the region 166d which is the channel. As a result, a transistor with normally-off characteristics can be manufactured.

[0252] In addition, in the regions 166b and 166c, the amount of oxygen vacancies is greater than the amount of hydrogen. In this case, the carrier density in the regions 166b and 166c can be controlled by controlling the amount of hydrogen. Alternatively, the amount of oxygen vacancy in the region 166b and the region 166c can be controlled. When the amount of hydrogen is relatively large, the amount of oxygen vacancies can be controlled to reduce the area between the region 166b and the region 16 The carrier density of the region 166b and the region 166c can be controlled. Carrier density 5×10 18 pieces / cm 3 or more, or 1 x 10 19 pieces / cm 3 or more, or 1x 10 20 pieces / cm 3 By doing so, the distance between the channel and the source and drain regions is It is possible to manufacture a transistor with low resistance and large on-state current.

[0253] Region 166d functions as a channel.

[0254] a region of the insulating film 168 that overlaps with the oxide semiconductor film 166 and the conductive film 174; A region overlapping with the oxide semiconductor film 226 and the conductive film 234 functions as a gate insulating film. In addition, in the insulating film 168, the oxide semiconductor film 166, the conductive film 170, and the conductive film 172 and a region where the oxide semiconductor film 226 overlaps with the conductive film 230 and the conductive film 232. The region functions as an interlayer insulating film.

[0255] The conductive films 170 and 172 and the conductive films 230 and 232 are the source electrodes and The conductive film 174 and the conductive film 234 function as a gate electrode and a drain electrode. It functions as such.

[0256] The transistor 190 and the transistor 194 described in this embodiment function as channels. Between the region 166d functioning as a source region and a drain region, and the region 166a functioning as a source region and a drain region, The channel and source have regions 166b and 166c which function as low resistance regions. The resistance between the source and drain regions of the transistor 190 can be reduced. The transistor 194 has a large on-state current and a high field-effect mobility.

[0257] In addition, in the manufacturing process of the transistor 190 and the transistor 194, The conductive film 174 and the conductive film 234 function as a source electrode and a drain electrode. The conductive film 170 and the conductive film 172 are formed at the same time. In the example shown in FIG. 1, the conductive film 174 does not overlap with the conductive film 170 and the conductive film 172. It is possible to reduce the parasitic capacitance between the conductive film 170 and the conductive film 172. In addition, in the transistor 194, the conductive film 234 overlaps with the conductive film 230 and the conductive film 232. Furthermore, the parasitic capacitance between the conductive film 234 and the conductive film 230 and the conductive film 232 can be reduced. As a result, when a large-area substrate is used as the substrate 162, the conductive film 170, The conductive films 172 and 174, as well as the conductive films 230, 232 and 234 It is possible to reduce the signal delay in the

[0258] In the transistor 190, the conductive films 170, 172, and 174 are A rare gas element is added to the oxide semiconductor film 166 as a mask, and the oxide semiconductor film 166 has oxygen vacancies. In the transistor 194, the conductive film 230, the conductive film 232, and The impurity element is added to the oxide semiconductor film 226 using the conductive film 234 as a mask. A region having oxygen vacancies is formed. Furthermore, the region having oxygen vacancies is formed by the insulating layer containing hydrogen. Since the insulating film 176 is in contact with the insulating film 176, hydrogen contained in the insulating film 176 diffuses into the region having oxygen vacancies. In other words, a low resistance region is formed by self-alignment. This can be done.

[0259] The transistor 190 and the transistor 194 described in this embodiment are formed in the region 166 By adding a rare gas to the region 166b and the region 166c, oxygen vacancies are formed and hydrogen is This makes it possible to increase the conductivity in the regions 166b and 166c. It is possible to obtain a uniform conductivity between the region 166b and the region 166c for each transistor. That is, the rare gas and the ion-exchange gas are introduced into the region 166b and the region 166c. By adding hydrogen, the conductivity of the region 166b and the region 166c can be controlled.

[0260] The configuration shown in FIG. 12 will be described in detail below.

[0261] As the substrate 162, the substrate 102 described in Embodiment 1 can be used as appropriate.

[0262] The insulating film 164 can be formed using any of the materials used for the insulating film 104 in Embodiment 1 as appropriate. can be done.

[0263] The oxide semiconductor film 166 and the oxide semiconductor film 226 can be formed by the oxide semiconductor film described in Embodiment 1. The materials and structures shown for the semiconductor film 106 can be used as appropriate.

[0264] The insulating film 168 can be formed using any of the materials used for the insulating film 108 in Embodiment 1. can be done.

[0265] The conductive film 170, the conductive film 172, and the conductive film 174, as well as the conductive film 230, the conductive film 232, and the conductive film 233 The conductive film 110, the conductive film 112, and the conductive film 114 shown in Embodiment 1 can be used as the conductive film 234. The materials shown in 14 can be used appropriately.

[0266] The insulating film 176 is a film containing hydrogen, and is typically a nitride insulating film. The insulating film 10 can be formed using silicon nitride, aluminum nitride, or the like.

[0267] The insulating film 178 can be formed using any of the materials for the insulating film 118 described in Embodiment 1 as appropriate. can be done.

[0268] <Configuration 2 of semiconductor device> Next, another structure of the semiconductor device will be described with reference to FIG. The transistor 191 will be used as a modification of the transistor 190. The transistor 194 in the driving circuit section is provided with the insulating film 164 of the transistor 191 or the conductive film. The structures of the conductive films 170, 172, and 174 can be applied as appropriate.

[0269] 14A to 14C are top views and diagrams of a transistor 191 included in a semiconductor device. 14A is a top view of the transistor 191, and FIG. 14B is a cross-sectional view of the transistor 191. 14(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 14(A), and FIG. 14(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. FIG. 10 is a cross-sectional view taken along the dashed dotted line X3-X4.

[0270] The transistor 191 illustrated in FIG. 14 includes the conductive films 170, 172, and 174. , each of which has a three-layer structure. The insulating film 164a and the oxide insulating film 164b are stacked in layers. It is similar to the transistor 190 and has the same effect.

[0271] First, the conductive films 170, 172, and 174 will be described.

[0272] The conductive film 170 is formed by laminating a conductive film 170a, a conductive film 170b, and a conductive film 170c in this order. The conductive film 170a and the conductive film 170c cover the surface of the conductive film 170b. That is, the conductive film 170a and the conductive film 170c function as a protective film for the conductive film 170b. do.

[0273] Similar to the conductive film 170, the conductive film 172 includes a conductive film 172a, a conductive film 172b, and a conductive film 172c. The conductive film 172a and the conductive film 172c are laminated in this order, and the conductive film 172a and the conductive film 172c are laminated in this order. It covers the surface of 2b.

[0274] Similar to the conductive film 170, the conductive film 174 includes a conductive film 174a, a conductive film 174b, and a conductive film 174c. The conductive film 174a and the conductive film 174c are laminated in this order, and the conductive film 174a and the conductive film 174c are laminated in this order. It covers the surface of 4b.

[0275] The conductive films 170a, 172a, and 174a may be the conductive films shown in Embodiment 1. Similarly to the conductive film 110a, the conductive film 112a, and the conductive film 114a, the conductive film 170b, the conductive film 1 72b, and the conductive film 174b are formed by the insulating layer 172a. Any suitable material can be used.

[0276] The conductive films 170b, 172b, and 174b may be the conductive films shown in Embodiment 1. Similarly to the conductive film 110b, the conductive film 112b, and the conductive film 114b, a low-resistance material is appropriately used. This can be done.

[0277] The conductive films 170c, 172c, and 174c may be the conductive films shown in Embodiment 1. Similarly to the conductive film 110c, the conductive film 112c, and the conductive film 114c, the conductive film 170b, the conductive film 1 The metal elements contained in the conductive film 172b and the conductive film 174b are formed using a film in which the metal elements are passivated. As a result, the conductive film 170b, the conductive film 172b, and the conductive film 174b The metal element is moved to the oxide semiconductor film 166 in the process of forming the insulating film 176. It can be prevented.

[0278] Next, the insulating film 164 in which the nitride insulating film 164a and the oxide insulating film 164b are stacked is and explain.

[0279] The nitride insulating film 164a and the oxide insulating film 164b can be formed by the same method as those described in Embodiment 1. The materials shown in the nitride insulating film 104a and the oxide insulating film 104b can be used as appropriate. .

[0280] <Configuration 3 of semiconductor device> Next, another configuration of the semiconductor device will be described with reference to FIGS. 15 and 16. As a modification of the transistor 190 provided in the pixel portion, a transistor 192 and a transistor The transistor 193 will be used for the explanation, but the transistor 194 in the driving circuit section 2 or the oxide semiconductor film 166 included in the transistor 193. The configuration of the conductive film 166 can be appropriately applied.

[0281] 15A to 15C are top views and diagrams of a transistor 192 included in a semiconductor device. 15A is a top view of the transistor 192, and FIG. 15B is a cross-sectional view of the transistor 192. 15(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 15(A), and FIG. 15(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. FIG. 10 is a cross-sectional view taken along the dashed dotted line X3-X4.

[0282] The transistor 192 illustrated in FIG. 15 is characterized in that the oxide semiconductor film 166 has a multilayer structure. Specifically, the oxide semiconductor film 166 is formed by 167a, an oxide semiconductor film 167b in contact with the oxide semiconductor film 167a, and an oxide semiconductor The oxide film 167b, the conductive film 170, the conductive film 172, the insulating film 168, and the insulating film 176 are in contact with each other. The other configurations are the same as those of the transistor 190. It has the same effect.

[0283] The oxide semiconductor films 167a, 167b, and 167c are The oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107c described in Embodiment 1 are The material and crystal structure shown in the semiconductor film 107c can be used as appropriate.

[0284] The oxide semiconductor films 167a and 167b are less likely to have oxygen vacancies than the oxide semiconductor films 167a and 167b. The oxide semiconductor film 167c is provided in contact with the upper and lower surfaces of the oxide semiconductor film 167b. By doing so, oxygen vacancies in the oxide semiconductor film 167b can be reduced. The oxide semiconductor film 167b contains one or more metal elements constituting the oxide semiconductor film 167b. The oxide semiconductor film 167a and the oxide semiconductor film 167c are in contact with each other. 7a and the oxide semiconductor film 167b, and the interface between the oxide semiconductor film 167b and the oxide semiconductor film 16 The interface state density at the interface with the oxide semiconductor film 167b is extremely low. It is possible to reduce the oxygen vacancies contained therein.

[0285] Furthermore, by providing the oxide semiconductor film 167a, the threshold voltage of the transistor and the like can be reduced. Therefore, the variation in the electrical characteristics can be reduced.

[0286] In addition, the oxide semiconductor film 167b contains one or more metal elements. Since the oxide semiconductor film 7c is provided in contact with the oxide semiconductor film 167b, the oxide semiconductor film 167b and the oxide semiconductor film 7c are At the interface with the compound semiconductor film 167c, scattering of carriers is unlikely to occur, and the field effect of the transistor is The resultant mobility can be increased.

[0287] The oxide semiconductor films 167a and 167c are formed between the insulating film 164 and the insulating film 165. The constituent elements of the film 168 or the conductive films 170 and 172 are the oxide semiconductor film 1 As a barrier film to prevent impurities from mixing into 67b and forming levels also works.

[0288] From the above, the transistor described in this embodiment has electrical characteristics such as threshold voltage. This is a transistor with reduced variation.

[0289] FIG. 16 shows a transistor having a different structure from that shown in FIG.

[0290] 16A to 16C are top views and diagrams of a transistor 193 included in a semiconductor device. 16A is a top view of the transistor 193, and FIG. 16B is a cross-sectional view of the transistor 193. 16(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 16(A), and FIG. 16(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. FIG. 10 is a cross-sectional view taken along the dashed dotted line X3-X4.

[0291] In a transistor 193 illustrated in FIG. 16, an oxide semiconductor film 166 is formed between the insulating film 164 and the The oxide semiconductor film 167b in contact with the insulating film 168 and the oxide semiconductor film 167b in contact with the insulating film 168 are The other configuration may be the same as that of the transistor 19. It is the same as 0 and has the same effect.

[0292] <Method 1 for manufacturing semiconductor device> Next, a method for manufacturing the transistor 190 and the transistor 194 shown in FIGS. This will be explained with reference to FIGS.

[0293] As shown in FIG. 18A, a conductive film 221 is formed on a substrate 162. An insulating film 164 is formed thereon.

[0294] The conductive film 221 can be formed by appropriately using the formation method of the conductive film 201 described in Embodiment 1. This can be done.

[0295] The insulating film 164 can be formed by the formation method of the insulating film 104 described in Embodiment 1 as appropriate. do.

[0296] Next, as shown in FIG. 18B, an oxide semiconductor film 166 and an oxide Next, the insulating film 164, the oxide semiconductor film 166, and the oxide semiconductor film 226 are formed. The insulating film 168 is formed on the oxide semiconductor film 226. The oxide semiconductor film 26 and the insulating film 168 are the oxide semiconductor film 106 and the insulating film 168 described in Embodiment 1, respectively. The film 108 can be formed by using an appropriate method.

[0297] Next, as shown in FIG. 19(A), a mask is formed on the insulating film 168 by a lithography process. After the formation, part of the insulating film 168 is etched to expose part of the oxide semiconductor film 166. The openings 180a and 180b expose the oxide semiconductor film 226. An opening 240a and an opening 240b are formed.

[0298] Next, as shown in FIG. 19B, the oxide semiconductor film 166, the oxide semiconductor film 226, and A conductive film 169 is formed over the insulating film 168 .

[0299] The conductive film 169 can be formed by appropriately using the formation method of the conductive film 201 described in Embodiment 1. This can be done.

[0300] Next, as shown in FIG. 19(C), a mask is formed on the conductive film 169 by a lithography process. After forming 111, the conductive film 169 is immersed in an etching solution and / or etching gas 167. By exposing the conductive film 170, the conductive film 172, and the conductive film 174, as well as the conductive film 230 and the conductive film 2 32 and a conductive film 234 are formed.

[0301] The conductive film 169 is etched by wet etching or / and dry etching. A coating method can be used as appropriate.

[0302] The conductive film 170, the conductive film 172, the conductive film 174, the conductive film 230, the conductive film 2 The conductive film 32 and the conductive film 234 may be formed by electrolytic plating, printing, inkjet printing, etc. instead of the above-mentioned forming method. It may be formed by a tubing method or the like.

[0303] Next, as shown in FIG. 20A, the oxide semiconductor film 166 A rare gas is added to the oxide semiconductor film 226 as the impurity element 177. The impurity element is added to the region of the compound semiconductor film that is not covered by the mask 111. By adding the impurity element 177, oxygen vacancies are formed in the oxide semiconductor film.

[0304] The impurity element 177 can be added by the same method as that of adding the impurity element 117 described in Embodiment 1. The method can be used as appropriate.

[0305] Here, when the impurity element 177 is added to the oxide semiconductor film 166, A conceptual diagram of the region where the impurity element is added is shown in Figure 21. As a representative example, An enlarged view of the oxide semiconductor film 166 and its vicinity included in the transistor 190 will be used for description.

[0306] As shown in FIG. 21(A), the region where the impurity element 177 is added is covered with the insulating film 164, the oxide semiconductor, and the like. In some cases, the oxide semiconductor film 166 is formed on the conductive film 166 and the insulating film 168. In the depth direction of the exposed region, the end 195 of the doped region is located in the insulating film 164. .

[0307] Alternatively, as shown in FIG. 21B, the region to which the impurity element 177 is added is 66 and the insulating film 168. In the depth direction of the region, the end 196 of the doped region is adjacent to the insulating film 164 and the oxide semiconductor film 1 Located at the interface of 66.

[0308] Alternatively, as shown in FIG. 21C, the region to which the impurity element 177 is added is 66 and the insulating film 168. In the depth direction of the region, an end portion 197 of the doped region is located in the oxide semiconductor film 166. .

[0309] After that, the mask 111 is removed as shown in FIG. 20(B).

[0310] Note that the oxide semiconductor film 166 and the oxide semiconductor film 2 are formed using the mask 111. The impurity element 177 was added to the conductive film 170 after the mask 111 was removed. The conductive film 172 and the conductive film 174, as well as the conductive film 230, the conductive film 232 and the conductive film 234 are mass-produced. The impurity element 177 is added to the oxide semiconductor film 166 and the oxide semiconductor film 226 as a gate insulating film. Good too.

[0311] In addition, the step of forming the conductive film 169, the step of etching the conductive film 169, or the subsequent step of forming the insulating film 1 In the formation process of 76, the oxide semiconductor film 166 and the oxide semiconductor film 226 are damaged. If oxygen vacancies are formed, the impurity element 177 does not need to be added.

[0312] Next, as shown in FIG. 20C, the oxide semiconductor film 166, the insulating film 168, and the conductive film 17 0, conductive film 172, conductive film 174, oxide semiconductor film 226, conductive film 230, conductive film 232 An insulating film 176 is formed on the conductive film 234, and an insulating film 178 is formed on the insulating film 176. That's fine.

[0313] The insulating film 176 can be formed by a sputtering method, a CVD method, a vacuum deposition method, a pulse deposition method, or the like. Laser deposition (PLD) method, etc. Silane and ammonia, or silane and nitrogen A silicon nitride film containing hydrogen is formed by the plasma CVD method using the above as a raw material gas. In addition, by using the plasma CVD method, the oxide semiconductor film 166 is not damaged. As a result, oxygen vacancies can be formed in the oxide semiconductor film 166.

[0314] Since the insulating film 176 contains hydrogen, the oxide semiconductor film 166 and the oxide semiconductor film In 226, the region to which the impurity element is added and the insulating film 176 come into contact with each other, forming an insulating film. The hydrogen contained in 176 is transferred to a region of the oxide semiconductor film to which an impurity element is added. Since the region to which the impurity element is added contains oxygen vacancies, the oxide semiconductor film 16 6 and the oxide semiconductor film 226. The region 166b and the region 166c shown in FIG. The oxide semiconductor film 166 and the oxide semiconductor film 226 are doped with the insulating film 168. , the concentration of impurity elements is lower than that of region 166b.

[0315] Note that by forming the insulating film 176 under heating, hydrogen contained in the oxide semiconductor film is However, when hydrogen migrates to the oxygen vacancy, the hydrogen becomes energetically stable. This makes it difficult for hydrogen to be released from the oxygen vacancies. In addition, due to the interaction between oxygen vacancies and hydrogen, Electrons, which are carriers, are generated. For this reason, the insulating film 176 is formed while heating. This makes it possible to form a low resistance region with little fluctuation in conductivity.

[0316] After that, heat treatment is performed to further increase the conductivity of the region where the impurity element 177 is added. The temperature of the heat treatment is typically 150°C or higher and lower than the substrate strain point, or 250°C or higher. or 300°C or more and 450°C or less. It is possible to improve the conductivity and reduce the fluctuation of the conductivity in the low resistance region. .

[0317] The insulating film 178 is formed by appropriately using the method for forming the insulating film 164 and the insulating film 168. can be done.

[0318] In addition, the substrate placed in the evacuated processing chamber of the plasma CVD device is heated to 180°C or higher. The temperature is kept at 280°C or below, or 200°C to 240°C, and the raw material gas is introduced into the processing chamber. The pressure in the treatment room should be between 100 Pa and 250 Pa, or between 100 Pa and 200 Pa. The electrode in the processing chamber is set to 0.17 W / cm 2 More than 0.5W / cm 2 Below, again is 0.25W / cm 2 More than 0.35W / cm 2 Under the following conditions for supplying high frequency power: A silicon oxide film or a silicon oxynitride film capable of releasing oxygen by heat treatment is used as an insulating film. It can be formed as a veneer 178.

[0319] Through the above steps, a transistor can be manufactured.

[0320] <Method 2 for manufacturing semiconductor device> A method for manufacturing the transistor 191 shown in FIG. 14 will be described. The conductive film 170c included in the conductive film 170, the conductive film 172, and the conductive film 174 of the capacitor 191 the formation of the conductive film 172c and the conductive film 174c, and the formation of the oxide semiconductor film 166 containing the impurity element 17 The step of adding 7 will be described.

[0321] 18 and 19(A) to 19(C), an insulating film 164 is formed on a substrate 162. , the oxide semiconductor film 166, the insulating film 168, the conductive film 170, the conductive film 172, the conductive film 174, and Then, a mask 111 is formed.

[0322] Next, as shown in FIG. 20A, an impurity element 177 is added to the oxide semiconductor film 166. do.

[0323] Next, the mask 111 is removed.

[0324] Next, the conductive film 170 included in each of the conductive film 170, the conductive film 172, and the conductive film 174 b, the conductive film 172b and the conductive film 174b are exposed to plasma generated in a reducing atmosphere, and the conductive film 172b and the conductive film 174b are The oxides on the surfaces of the conductive film 170b, the conductive film 172b, and the conductive film 174b are reduced. The conductive film 170b, the conductive film 172b, and the conductive film 17 Next, the conductive film 170b, the conductive film 172b, and the conductive film 174b are exposed to silane. By exposing the conductive film 17 to plasma generated in an atmosphere containing nitrogen such as ammonia or nitrogen, CuSi as the conductive film 172c and the conductive film 174c x N y (x>0, y>0) It can be formed.

[0325] In addition, when exposed to plasma generated in an atmosphere containing nitrogen such as ammonia or nitrogen, The oxide semiconductor film 166 is formed by plating in an atmosphere containing nitrogen such as ammonia or nitrogen. Because the oxide semiconductor film 166 is exposed to the magnetic field, nitrogen and / or hydrogen can be added to the oxide semiconductor film 166. is.

[0326] Note that the mask 111 is removed before the impurity element 177 is added to the oxide semiconductor film 166. The conductive film 170c and the conductive film 170b included in the conductive film 170, the conductive film 172, and the conductive film 174 are 72c and a conductive film 174c may be formed.

[0327] After that, the transistor 191 can be manufactured through the process of FIG.

[0328] <Method 3 for manufacturing semiconductor device> Another method for manufacturing the transistor 190 shown in FIG. 12 will be described. The step of adding elements and the step of forming the insulating film 176 will be described with reference to FIG.

[0329] 18 and 19(A) to 19(C), an insulating film 164 is formed on a substrate 162. , the oxide semiconductor film 166, the insulating film 168, the conductive film 170, the conductive film 172, the conductive film 174, and Then, a mask 111 is formed. After that, as shown in FIG. 22(A), the mask 111 is removed. do.

[0330] Next, as shown in FIG. 22(B), the oxide semiconductor film 166, the insulating film 168, and the conductive film 17 0, an insulating film 176 is formed on the conductive film 172 and the conductive film 174, and then the conductive film 170 and the conductive film 174 are The oxide semiconductor film 16 is then formed on the conductive film 172 and the conductive film 174 as a mask with the insulating film 176 interposed therebetween. 6 is doped with an impurity element 177.

[0331] Next, as shown in FIG. 22(C), an insulating film 178 may be formed. , transistor 190 can be fabricated.

[0332] The transistor described in this embodiment has a conductive film which functions as a source electrode and a drain electrode. Since the film does not overlap with the conductive film that functions as the gate electrode, the parasitic capacitance can be reduced. Furthermore, the transistor described in this embodiment has a stable low Since it is possible to form a resistive region, the on-current increases compared to conventional transistors. Variation in electrical characteristics is reduced.

[0333] The configurations and methods described in this embodiment may be different from the configurations and methods described in other embodiments. can be used in appropriate combination.

[0334] (Embodiment 3) In this embodiment mode, one mode of a semiconductor device and a manufacturing method thereof will be described with reference to FIGS. 5 will be used for the description. In this embodiment, as compared with the first embodiment, a conductive film functioning as a source electrode and a conductive film functioning as a drain electrode; The method of forming the conductive film is different from that of forming the low-resistance region included in the transistor. Therefore, the method shown in the second embodiment is used.

[0335] <Configuration 1 of semiconductor device> FIG. 23 shows a top-gate transistor as an example of a transistor included in a semiconductor device. This indicates a transistor.

[0336] In FIG. 28, a transistor 394 provided in the driver circuit and a transistor provided in the pixel portion are 23 shows a cross-sectional view of transistor 394 and transistor 390. 28A is a top view of transistor 394, and FIG. 23(A) is a cross-sectional view taken along the dashed line X1-X2 in FIG. 23(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 23(B) and FIG. 28(B). 28(A) is a cross-sectional view taken along the dashed line Y1-Y2, and FIG. 28(B) is a cross-sectional view taken along the dashed line Y3-Y4. 23A is a cross-sectional view of the transistor 390 in the channel length direction. 23B is a cross-sectional view of the transistor 390 in the channel width direction.

[0337] The transistor 390 shown in FIG. 23 is an oxide film on an insulating film 364 formed on a substrate 362. The oxide semiconductor film 366, the conductive film 368 and the conductive film 370 in contact with the oxide semiconductor film 366, and the insulating film and a conductive film 374 overlapping with the oxide semiconductor film 366 with the insulating film 372 interposed therebetween. Note that an insulating film 376 is provided over the transistor 390.

[0338] The transistor 394 shown in FIG. 23 is an oxide film on an insulating film 364 formed on a substrate 362. The oxide semiconductor film 266, the conductive film 268 and the conductive film 270 in contact with the oxide semiconductor film 266, and the insulating film The insulating film 272 is a conductive film 274 that overlaps with the oxide semiconductor film 266 with the insulating film 272 interposed therebetween. do.

[0339] The transistor 394 includes a conductive film 2 overlapping with the oxide semiconductor film 266 with the insulating film 364 interposed therebetween. That is, the conductive film 261 functions as a gate electrode. The transistor 394 is a transistor with a dual gate structure. The configuration is the same as that of the transistor 390, and the same effect is achieved.

[0340] The conductive film 274 and the conductive film 261 are not connected to each other, and different potentials are applied to each of them. In this case, the threshold voltage of the transistor 394 can be controlled. As shown in FIG. 1, the conductive film 274 and the conductive film 261 are connected to each other and the same potential is applied to them. Reduction of variations in characteristics, suppression of deterioration in GBT stress tests, and performance at different drain voltages In addition, the oxide semiconductor film 26 can suppress fluctuations in the on-state current rise voltage. In 6, the area in which carriers flow is larger in the film thickness direction, and therefore the carrier migration As a result, the on-current of the transistor 394 increases and the field effect High mobility. Transistor channel length is less than 2.5 μm or more than 1.45 μm. By setting the thickness to 2.2 μm or less, the on-current is further increased and the field effect mobility is improved. It can be done.

[0341] In the display device described in this embodiment, the driver circuit portion and the pixel portion include a transistor. The transistors included in the drive circuit section have a dual gate structure. The driver circuit portion includes a transistor having a higher field-effect mobility than the pixel portion.

[0342] In addition, in the display device, the channel lengths of the transistors included in the driver circuit portion and the pixel portion are It may be different.

[0343] Typically, the channel length of the transistor 394 included in the driving circuit section is set to less than 2.5 μm. On the other hand, the thickness of the pixel portion can be set to 1.45 μm or more and 2.2 μm or less. The channel length of the transistor 390 is set to 2.5 μm or more, or 2.5 μm or more and 20 μm or less. It is possible.

[0344] The channel length of the transistor 394 included in the driving circuit section is set to less than 2.5 μm, preferably By making the thickness of the transistor 390 included in the pixel portion 1.45 μm or more and 2.2 μm or less, Compared with the above, it is possible to increase the field effect mobility and increase the on-current. As a result, a driver circuit section capable of high-speed operation can be manufactured. Since it is possible to increase the on-current of the included transistor, it is possible to reduce display irregularities in the pixel area. can be suppressed.

[0345] The high field-effect mobility of the transistors included in the driver circuit reduces the number of input terminals It is possible.

[0346] In the oxide semiconductor film 366, the conductive films 368, 370, and 374 overlap with each other. The oxide semiconductor film 266 contains an element that forms oxygen vacancies. In addition, oxygen vacancies are formed in regions that do not overlap with the conductive films 268, 270, and 274. Hereinafter, the elements that form oxygen vacancies will be referred to as impurity elements. Typical examples of pure elements include hydrogen and rare gas elements. Typical examples of rare gas elements include: There are helium, neon, argon, krypton and xenon. In addition, impurity elements In addition, boron, carbon, nitrogen, fluorine, aluminum, silicon, phosphorus, chlorine, etc. form oxide semiconductors. The oxide semiconductor film 366 and the oxide semiconductor film 266 may be included.

[0347] The insulating film 376 is a film containing hydrogen, and is typically a nitride insulating film. The insulating film 376 is in contact with the oxide semiconductor film 366 and the oxide semiconductor film 266. The contained hydrogen diffuses into the oxide semiconductor film 366 and the oxide semiconductor film 266. The oxide semiconductor film 366 and the oxide semiconductor film 266 are formed in a region in contact with the insulating film 376. It contains a lot of hydrogen.

[0348] When a rare gas element is added to an oxide semiconductor film as an impurity element, The bond between the metal element and oxygen is broken, and oxygen vacancies are formed. The interaction between oxygen vacancies and hydrogen increases the electrical conductivity of the oxide semiconductor film. When hydrogen enters the oxygen vacancies in the oxide semiconductor film, electrons are generated as carriers. This results in a high conductivity.

[0349] Here, an enlarged view of the vicinity of the oxide semiconductor film 366 is shown in FIG. The following description will be given with reference to an enlarged view of the oxide semiconductor film 366 and its vicinity included in the transistor 390. 4, the oxide semiconductor film 366 is in contact with the conductive film 368 or the conductive film 370. 366a, a region 366b in contact with the insulating film 376, and a region 366d in contact with the insulating film 372. When the side surface of the conductive film 374 has a tapered shape, It may have an area 366c that overlaps with the pad portion.

[0350] The region 366a functions as a source region and a drain region. The region 366a in contact with the film 370 is electrically conductive, similar to the region 106a shown in the first embodiment. The raised portions function as source and drain regions.

[0351] The region 366b functions as a low resistance region. At least a rare gas and hydrogen are included. The impurity element passes through the tapered portion of the conductive film 374 and is added to the region 366c. The region 366c has a lower concentration of rare gas elements, which are an example of impurity elements, compared to the region 366b. , impurity elements are included. By having the region 366c, the source-drain This can increase the breakdown voltage.

[0352] When the oxide semiconductor film 366 is formed by a sputtering method, the regions 366a to 366c are 66d each contain a rare gas element, and compared to region 366a and region 366d, regions The region 366b and the region 366c have higher concentrations of the rare gas element. When 66 is formed by sputtering, a rare gas is used as the sputtering gas. Therefore, the oxide semiconductor film 366 contains a rare gas, and the regions 366b and 366c In c, rare gases are intentionally added to form oxygen vacancies. In addition, the areas 366b and 366c are different from the areas 366a and 366d. A rare gas element may be added.

[0353] In addition, since the region 366b is in contact with the insulating film 376, it is In comparison, the concentration of hydrogen is higher in the region 366b. When hydrogen diffuses, the region 366c has a higher hydrogen concentration than the region 366a and the region 366d. However, the hydrogen concentration is higher in the region 366b than in the region 366c.

[0354] In the region 366b and the region 366c, hydrogen concentration obtained by secondary ion mass spectrometry is The concentration is 8 x 10 19 atoms / cm 3 That's it, 1×10 20 atoms / cm3 That's all, or 5 x 10 20 atoms / cm 3 The above can be done. The hydrogen concentration obtained by secondary ion mass spectrometry in region 366d is 5 × 10 19 atom s / cm 3 Below, 1×10 19 atoms / cm 3 Below, 5 x 10 18 atoms / cm 3 Below, 1×10 18 atoms / cm 3 Below, 5 x 10 17 atoms / cm 3 below, or 1 x 10 16 atoms / cm 3 It can be as follows:

[0355] In addition, impurity elements such as boron, carbon, nitrogen, fluorine, aluminum, silicon, and lithium are used. When chlorine or chlorine is added to the oxide semiconductor film 366, the regions 366b and 366c Therefore, compared with the region 366a and the region 366d, the region The concentration of the impurity element is higher in the region 366b and the region 366c. In 366c, the concentration of impurity elements obtained by secondary ion mass spectrometry is 1 × 10 18 atoms / cm 3 More than 1×10 22 atoms / cm 3 or less, or 1 x 10 19 a toms / cm 3 More than 1×10 21 atoms / cm 3 or less, or 5 x 10 19 atom s / cm 3 5x10 or more 20 atoms / cm 3It can be as follows:

[0356] Compared to the region 366d, the regions 366b and 366c have a high hydrogen concentration and are rare. The amount of oxygen deficiency caused by the addition of gas elements is large. This results in high conductivity and a low resistance region. Typically, the resistivity of the region 366b and the region 366c is 1×10 -3 Ωcm or more 1×10 4 Less than Ωcm or 1×10 -3 Ωcm or more 1×10 -1 Less than Ωcm It can be said that:

[0357] In the regions 366b and 366c, the amount of hydrogen is equal to or less than the amount of oxygen vacancies. If there is no oxygen vacancy, hydrogen is easily captured by the oxygen vacancy and is difficult to diffuse into the region 366d which is the channel. As a result, a transistor with normally-off characteristics can be manufactured.

[0358] Region 366d functions as a channel.

[0359] In addition, the oxide semiconductor film 3 After the impurity element is added to the conductive film 66, the conductive film 368, the conductive film 370, and the conductive film 374 are formed. This may reduce the area of ​​the top surface shape of the conductive film 368, the conductive film 370, and the conductive film 371. In the process of forming the conductive film 374, the conductive film 368, the conductive film 370, and the mass on the conductive film 374 are The mask is then slimmed to create a mask with a finer structure. 24(B) by etching the conductive film 368, the conductive film 370, and the conductive film 374. ) can form a conductive film 368d, a conductive film 370d, and a conductive film 374d. The trimming process may be, for example, an ashing process using oxygen radicals. This can be done.

[0360] As a result, in the oxide semiconductor film 366, the region 366c and the region 3 An offset region 366e is formed between the first and second electrodes 366d. The length of the offset region 366e is set to be less than 0.1 μm, thereby reducing the on-current of the transistor. It is possible to suppress the decrease in

[0361] The insulating film 372 and the insulating film 272 function as gate insulating films.

[0362] The conductive film 368 and the conductive film 370, as well as the conductive film 268 and the conductive film 270, form a source electrode. and functions as a drain electrode.

[0363] The conductive film 374 and the conductive film 274 function as gate electrodes.

[0364] The transistor 390 and the transistor 394 in this embodiment function as channels. Between the region 366d functioning as a source region and a drain region, and the region 366a functioning as a source region and a drain region, The channel has a region 366b and / or a region 366c that function as a low resistance region. and the resistance between the source region and the drain region of the transistor. The transistor 390 and the transistor 394 have a large on-state current and a high field-effect mobility.

[0365] In the transistor 390, the conductive film 374, the conductive film 368, and the conductive film 370 The conductive film 374 does not overlap with the conductive film 368 and the conductive film 370, thereby reducing the parasitic capacitance between the conductive film 374 and the conductive film 368 and the conductive film 370. In addition, in the transistor 394, the conductive film 274 and the conductive film 26 8 and the conductive film 270 do not overlap, and the conductive film 274, the conductive film 268, and the conductive film 270 As a result, a large-area substrate can be used as the substrate 362. In this case, the conductive film 368, the conductive film 370, and the conductive film 374, as well as the conductive film 268 and the conductive film Signal delay in the film 270 and the conductive film 274 can be reduced.

[0366] In the transistor 390, the conductive films 368, 370, and 374 are A rare gas element is added to the oxide semiconductor film 366 as a mask, and the oxide semiconductor film 366 has oxygen vacancies. In the transistor 394, the conductive film 268, the conductive film 270, and The impurity element is added to the oxide semiconductor film 266 using the conductive film 274 as a mask. A region having oxygen vacancies is formed. Furthermore, the region having oxygen vacancies is formed by the insulating layer containing hydrogen. Since the insulating film 376 is in contact with the insulating film 376, hydrogen contained in the insulating film 376 diffuses into the region having oxygen vacancies. In other words, a low resistance region is formed by self-alignment. This can be done.

[0367] The transistors 390 and 394 shown in this embodiment are formed in the region 366 By adding a rare gas to b, oxygen vacancies are formed and hydrogen is added. Therefore, it is possible to increase the conductivity in the region 366b and It is possible to reduce the variation in conductivity of the region 366b for each region. By adding rare gas and hydrogen to 66b, the conductivity of region 366b can be controlled.

[0368] The configuration shown in FIG. 23 will be described in detail below.

[0369] As the substrate 362, the substrate 102 described in Embodiment 1 can be used as appropriate.

[0370] The insulating film 364 can be formed using any of the materials used for the insulating film 104 in Embodiment 1. can be done.

[0371] The oxide semiconductor film 366 and the oxide semiconductor film 266 can be formed by the oxide semiconductor film described in Embodiment 1. The materials and structures shown for the semiconductor film 106 can be used as appropriate.

[0372] The insulating film 372 and the insulating film 272 can be made of the material shown in the insulating film 108 in Embodiment 1. can be used appropriately.

[0373] The conductive film 368, the conductive film 370, and the conductive film 374, as well as the conductive film 261, the conductive film 268, The conductive film 270 and the conductive film 274 can be formed by the same method as the conductive film 110 and the conductive film 11 shown in Embodiment 1. The materials shown in 2 and the conductive film 114 can be used as appropriate.

[0374] The insulating film 376 is a film containing hydrogen, and a representative example is a nitride insulating film. The insulating film can be formed using silicon nitride, aluminum nitride, or the like.

[0375] <Configuration 2 of semiconductor device> Next, another structure of the semiconductor device will be described with reference to FIG. The transistor 391 will be used as a modification of the transistor 390. The insulating film 364 of the transistor 391 is connected to the transistor 394 in the driver circuit portion. The structures of the film 368, the conductive film 370, and the conductive film 374 can be applied as appropriate.

[0376] 25A to 25C are top views and diagrams of a transistor 391 included in a semiconductor device. 25A is a top view of the transistor 391, and FIG. 25B is a cross-sectional view of the transistor 391. 25(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 25(A), and FIG. 25(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. FIG. 10 is a cross-sectional view taken along the dashed dotted line X3-X4.

[0377] The transistor 391 illustrated in FIG. 25 includes the conductive films 368, 370, and 374. The insulating film 364 is characterized by having a three-layer structure. The other components are the transistor. It is similar to the heater 390 and has the same effect.

[0378] First, the conductive films 368, 370, and 374 will be described.

[0379] The conductive film 368 is formed by laminating a conductive film 368a, a conductive film 368b, and a conductive film 368c in this order. The conductive film 368a and the conductive film 368c cover the surface of the conductive film 368b. That is, the conductive film 368a and the conductive film 368c function as protective films for the conductive film 368b. do.

[0380] Similar to the conductive film 368, the conductive film 370 includes a conductive film 370a, a conductive film 370b, and a conductive film 370c. The conductive film 370a and the conductive film 370c are stacked in this order, and the conductive film 370a and the conductive film 370c are stacked in this order. It covers the surface of 0b.

[0381] The conductive film 374 is formed by stacking a conductive film 374a and a conductive film 374b in this order.

[0382] The conductive films 368a, 370a, and 374a may be formed by the conductive films shown in Embodiment 1. Similarly to the conductive film 110a, the conductive film 112a, and the conductive film 114a, the conductive film 368b, the conductive film 3 70b, a metal element contained in the conductive film 374b is prevented from diffusing into the oxide semiconductor film 366. Any suitable material can be used.

[0383] The conductive films 368b, 370b, and 374b may be the conductive films shown in Embodiment 1. Similarly to the conductive film 110b, the conductive film 112b, and the conductive film 114b, a low-resistance material is appropriately used. This can be done.

[0384] The conductive film 368c and the conductive film 370c can be formed by the conductive film 110c and the conductive film 110c shown in Embodiment 1. The conductive films 112c and 114c are similar to those included in the conductive films 368b and 370b. As a result, the conductive film 3 can be formed using a film in which the metal elements are passivated. The metal elements contained in the insulating film 376 and the conductive film 370b are oxidized in the process of forming the insulating film 376. Therefore, the migration of the ions into the compound semiconductor film 366 can be prevented.

[0385] Next, the insulating film 364 in which the nitride insulating film 364a and the oxide insulating film 364b are stacked is and explain.

[0386] The nitride insulating film 364a and the oxide insulating film 364b can be formed by the same method as those described in Embodiment 1. The materials shown in the nitride insulating film 104a and the oxide insulating film 104b can be used as appropriate. .

[0387] <Configuration 3 of semiconductor device> Next, another configuration of the semiconductor device will be described with reference to FIGS. 26 and 27. As a modification of the transistor 390 provided in the pixel portion, a transistor 392 and a transistor The transistor 393 in the driving circuit section will be used for the explanation. 2 or the oxide semiconductor film 366 included in the transistor 393. The configuration of the conductive film 366 can be appropriately applied.

[0388] 26A to 26C are top views and diagrams of a transistor 392 included in a semiconductor device. 26A is a top view of the transistor 392, and FIG. 26B is a cross-sectional view of the transistor 392. 26(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 26(A), and FIG. 26(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. FIG. 10 is a cross-sectional view taken along the dashed dotted line X3-X4.

[0389] The transistor 392 illustrated in FIG. 26 is characterized in that the oxide semiconductor film 366 has a multilayer structure. Specifically, the oxide semiconductor film 366 is formed by 367a, an oxide semiconductor film 367b in contact with the oxide semiconductor film 367a, and an oxide semiconductor The oxide film 367b, the conductive film 368, the conductive film 370, the insulating film 372, and the insulating film 376 are in contact with each other. The other configurations are the same as those of the transistor 390. It has the same effect.

[0390] The oxide semiconductor film 367a, the oxide semiconductor film 367b, and the oxide semiconductor film 367c are The oxide semiconductor film 107a, the oxide semiconductor film 107b, and the oxide semiconductor film 107c described in Embodiment 1 are The material and crystal structure shown in the semiconductor film 107c can be used as appropriate.

[0391] The oxide semiconductor films 367a and 367b are less likely to have oxygen vacancies than the oxide semiconductor films 367a and 367b. The oxide semiconductor film 367c is provided in contact with the upper and lower surfaces of the oxide semiconductor film 367b. By doing so, oxygen vacancies in the oxide semiconductor film 367b can be reduced. The oxide semiconductor film 367b contains one or more metal elements constituting the oxide semiconductor film 367b. The oxide semiconductor film 367a and the oxide semiconductor film 367c are in contact with each other. 7a and the oxide semiconductor film 367b, and the interface between the oxide semiconductor film 367b and the oxide semiconductor film 36 The interface state density at the interface with the oxide semiconductor film 367b is extremely low. It is possible to reduce the oxygen vacancies contained therein.

[0392] Furthermore, by providing the oxide semiconductor film 367a, the threshold voltage of the transistor can be reduced. Therefore, the variation in the electrical characteristics can be reduced.

[0393] In addition, the oxide semiconductor film 367b contains one or more metal elements. Since the oxide semiconductor film 7c is provided in contact with the oxide semiconductor film 367b, the oxide semiconductor film 367b and the oxide semiconductor film 7c are At the interface with the semiconductor film 367c, scattering of carriers is unlikely to occur, and the field effect of the transistor is The resultant mobility can be increased.

[0394] The oxide semiconductor films 367a and 367c are formed between the insulating film 364 and the insulating film 365. The constituent elements of the film 372 are mixed into the oxide semiconductor film 367b, and an impurity level is formed. It also functions as a barrier film to prevent the

[0395] From the above, the transistor described in this embodiment has electrical characteristics such as threshold voltage. This is a transistor with reduced variation.

[0396] FIG. 27 shows a transistor having a different structure from that shown in FIG.

[0397] 27A to 27C are top views and diagrams of a transistor 393 included in a semiconductor device. 27A is a top view of the transistor 393, and FIG. 27B is a cross-sectional view of the transistor 393. 27(A) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 27(A), and FIG. 27(C) is a cross-sectional view taken along the dashed line Y3-Y4 in FIG. 27A is a cross-sectional view taken along the dashed line X3-X4. For clarity, in FIG. 27A, the substrate 3 62, insulating film 364, insulating film 372, insulating film 376, etc. are omitted. FIG. 27B is a cross-sectional view of the transistor 393 in the channel width direction. FIG. 3 is a cross-sectional view of a transistor 393 in the channel length direction.

[0398] 27, the oxide semiconductor film 366 is The oxide semiconductor film 367b in contact with the insulating film 372 and the oxide semiconductor film 367b The semiconductor layer 367 may have a laminated structure of a compound semiconductor film 367c.

[0399] <Configuration 4 of semiconductor device> Next, another configuration of the semiconductor device will be described with reference to FIG. A transistor in which a low resistance region is formed using the method shown in 1 will be described.

[0400] The transistor 350 shown in FIG. 36 is an oxide film on an insulating film 364 formed on a substrate 362. The oxide semiconductor film 306, the conductive film 368 and the conductive film 370 in contact with the oxide semiconductor film 306, and the insulating film and a conductive film 374 overlapping with the oxide semiconductor film 306 with the insulating film 312 interposed therebetween. Note that an insulating film 376 is provided over the transistor 350.

[0401] The transistor 354 shown in FIG. 36 includes a conductive film 261 formed over a substrate 362 and a conductive The insulating film 364 on the film 261, the oxide semiconductor film 206 on the insulating film 364, and the oxide semiconductor The conductive film 268, the conductive film 270, and the insulating film 312 in contact with the film 206, and the insulating film 312 The conductive film 274 overlaps with the oxide semiconductor film 206 .

[0402] The transistor 354 includes a conductive film 204 overlapping with the oxide semiconductor film 206 with the insulating film 364 interposed therebetween. That is, the conductive film 261 functions as a gate electrode. The transistor 354 is a transistor with a dual gate structure. The structure is similar to that of the transistor 350, and the same effect is achieved.

[0403] In the transistors 350 and 354, the insulating film 312 serves as a gate insulating film. In addition, the oxide semiconductor film 306, the oxide semiconductor film 206, and the oxide semiconductor film contained therein function as a gate insulating film. The low-resistance regions included in the oxide semiconductor film 306 and the low-resistance regions included in the oxide semiconductor film 308 are the oxide semiconductor film 306 and the oxide semiconductor film 308 described in Embodiment 1, respectively. The membranes 206 and the low resistance regions contained therein can be formed similarly.

[0404] <Configuration 5 of Semiconductor Device> Next, another configuration of the semiconductor device will be described with reference to FIG.

[0405] FIG. 53A is a cross-sectional view of a transistor 390a included in a semiconductor device. 53(B) shows the thickness of the oxide semiconductor film 366 when an impurity element is added thereto. 53A shows a conceptual diagram of a transistor 390a. The cross-sectional views in the direction are the top view shown in FIG. 28(B) and the cross-sectional views in the direction are the top view shown in FIG. 23(A). Since it is the same as the cross-sectional view, the explanation will be omitted here.

[0406] The transistor 390a shown in FIG. 53A is the same as the transistor 390 shown in FIG. This is a modified example of the transistor 390, and is different from the structure of the conductive film 374 of the transistor 390. The transistor 390a shown in FIG. 53(A) has an insulating film 372 and The cross-sectional shape of the insulating film 376 is different from that of the transistor 390a shown in FIG. In other words, the conductive film 374 has a two-layer structure, and the insulating film 372 and the insulating film 376 are The other configurations are the same as those of the transistor 390. It has the same effect.

[0407] The conductive film 374 has a stacked structure of a conductive film 374d and a conductive film 374e. Examples of nitrides include tantalum nitride, titanium nitride, molybdenum nitride, and tungsten nitride. A metal oxide film can be used.

[0408] The conductive film 374e can be formed using the above-described low-resistance metal material. The low resistance metal material may be, for example, aluminum, copper, silver, or tungsten. do.

[0409] In the conductive film 374, the side end of the conductive film 374d is located further outward than the conductive film 374e. In this way, the conductive film 374 has a two-layer laminated structure, and the lower conductive film By forming the conductive film in a protruding shape, it is possible to form a conductive film having a shape similar to that of a hat. By using a silicon shape, the lower conductive film prevents impurities from passing through when adding impurity elements. It may be possible.

[0410] The conductive film 374 can be processed by, for example, dry etching. When the conductive film 374 is processed by the dry etching method, the side edge of the insulating film 372 is A part of the insulating film 37 may be cut off, and the shape of the side edge may have a curvature. When the shape of the side end of the insulating film 372 is curved, the insulating film 372 is formed on the insulating film 372. The shape of the film 376 may also have a curvature at part of the side edge due to the influence of the insulating film 372 .

[0411] Next, using FIG. 53(B), the oxide semiconductor of the transistor 390a shown in FIG. 53(A) The conceptual diagram of the film thickness direction when an impurity element is added to the film 366 is explained below. Reveal.

[0412] In FIG. 53B, the oxide semiconductor film 366 includes a region 366x and a region 366y. When the oxide semiconductor film 366 is, for example, a crystalline oxide semiconductor film, the region 366y is The crystallinity is higher than that of region 366x. The difference in crystallinity is due to the addition of impurity elements. This is because the 366x is damaged and its crystallinity is reduced.

[0413] <Method 1 for manufacturing semiconductor device> Next, a method for manufacturing the transistor 390 and the transistor 394 shown in FIG. 23 will be described. This will be explained using Figures 29 to 31.

[0414] As shown in FIG. 29(A), a conductive film 261 is formed on a substrate 362. An insulating film 364 is formed thereon.

[0415] The conductive film 261 can be formed by appropriately using the formation method of the conductive film 201 described in Embodiment 1. This can be done.

[0416] The insulating film 364 can be formed by appropriately using the method for forming the insulating film 104 described in Embodiment 1. This can be done.

[0417] Next, as shown in FIG. 29B, an oxide semiconductor film 366 and an oxide The oxide semiconductor film 366 and the oxide semiconductor film 266 are formed by The oxide semiconductor film 106 can be formed by the formation method of the oxide semiconductor film 106 described in Mode 1 as appropriate.

[0418] Next, as shown in FIG. 30A, the insulating film 364, the oxide semiconductor film 366, and the oxide semiconductor film 367 are A conductive film 367 is formed on the conductive film 266 .

[0419] The conductive film 367 can be formed by appropriately using the formation method of the conductive film 201 described in Embodiment 1. This can be done.

[0420] Next, as shown in FIG. 30(B), a mask is formed on the conductive film 367 by a lithography process. After forming the conductive film 367, the conductive film 367 is exposed to an etching solution and / or etching gas. The film 368 and the conductive film 370, and the conductive film 268 and the conductive film 270 are formed.

[0421] The conductive film 367 is etched by wet etching or / and dry etching. A coating method can be used as appropriate.

[0422] The conductive films 368 and 370, and the conductive films 268 and 270 have the above-described shapes. Instead of the deposition method, electrolytic plating, printing, ink jet printing, etc. may be used.

[0423] Next, as shown in FIG. 30(C), the insulating film 364, the oxide semiconductor film 366, and the conductive film 36 8, the insulating film 3 is formed on the conductive film 370, the oxide semiconductor film 266, the conductive film 268, and the conductive film 270. The insulating film 372 is formed by the formation method of the insulating film 108 described in Embodiment 1 as appropriate. It can be formed by

[0424] Next, as shown in FIG. 30(D), a conductive film 373 is formed on the insulating film 372.

[0425] The conductive film 373 can be formed by appropriately using the formation method of the conductive film 201 described in Embodiment 1. This can be done.

[0426] Next, as shown in FIG. 31(A), a mask is formed on the conductive film 373 by a lithography process. After forming the insulating film 373, the conductive film 373 is exposed to an etching solution and / or etching gas. The film 372 and the conductive film 374, and the insulating film 272 and the conductive film 274 are formed.

[0427] The conductive film 373 is etched by wet etching or / and dry etching. A coating method can be used as appropriate.

[0428] The conductive film 374 and the conductive film 274 may be formed by electrolytic plating or printing instead of the above-mentioned method. It may also be formed by a printing method, an ink jet method, or the like.

[0429] Next, as shown in FIG. 31B, the mask is removed, and then the oxide semiconductor film 366 and the acid A rare gas is added to the oxide semiconductor film 266 as an impurity element 377. In the conductive film 366, an insufficient area is formed in an area that does not overlap with the conductive film 368, the conductive film 370, and the conductive film 374. The conductive film 268 and the conductive film 27 are added to the oxide semiconductor film 266. The impurity element is added to the region that does not overlap with the conductive film 274. By adding 7, oxygen vacancies are formed in the oxide semiconductor film 366 and the oxide semiconductor film 266. can be.

[0430] The impurity element 377 can be added by the same method as that of adding the impurity element 117 described in Embodiment 1. The method can be used as appropriate.

[0431] Here, when the impurity element 377 is added to the oxide semiconductor film 366, A conceptual diagram of the region where the impurity element is added is shown in Figure 32. As a representative example, An enlarged view of the oxide semiconductor film 366 and its vicinity included in the transistor 390 will be used for description.

[0432] As shown in FIG. 32(A), the region where the impurity element 377 is added is covered with the insulating film 364, the oxide semiconductor, and the like. In some cases, the oxide semiconductor film 366 is formed on the conductive film 366 and the insulating film 372. In the depth direction of the exposed region, the end 385 of the doped region is located in the insulating film 364. .

[0433] Alternatively, as shown in FIG. 32B, the region to which the impurity element 377 is added is the oxide semiconductor film 3 66 and the insulating film 372. In the depth direction of the region, the end 386 of the doped region is separated from the insulating film 364 and the oxide semiconductor film 3 Located at the interface of 66.

[0434] Alternatively, as shown in FIG. 32C, the region to which the impurity element 377 is added is the oxide semiconductor film 3 66 and the insulating film 372. In the depth direction of the region, an end portion 387 of the doped region is located in the oxide semiconductor film 366. .

[0435] Here, the conductive film 368, the conductive film 370, and the conductive film 374 are used as masks to form an oxide film. The impurity element 377 is added to the semiconductor film 366. Before removing the mask for forming the film 374, the oxide semiconductor film 366 was 77 may be added.

[0436] Next, as shown in FIG. 31(C), the oxide semiconductor film 366, the insulating film 372, and the conductive film 36 8, the conductive film 370, the conductive film 374, the oxide semiconductor film 266, the insulating film 272, the conductive An insulating film 376 is formed over the film 268, the conductive film 270, and the conductive film 274.

[0437] The insulating film 376 may be formed by the method for forming the insulating film 176 described in Embodiment 2 as appropriate. It can be formed using

[0438] Since the insulating film 376 contains hydrogen, the oxide semiconductor film 366 and the oxide semiconductor film In the insulating film 266, the region to which the impurity element is added is in contact with the insulating film 376. The hydrogen contained in 376 is transferred to a region of the oxide semiconductor film to which an impurity element is added. Since the region to which the impurity element is added contains oxygen vacancies, the oxide semiconductor film 36 6 and the oxide semiconductor film 266. The region 366b and the region 366c shown in FIG. When the surface has a tapered shape, the impurity element passes through the tapered portion of the conductive film 374 and reaches the region 36 6c, the region 366c is an example of an impurity element compared to the region 366b. The concentration of rare gas elements is low.

[0439] After that, heat treatment is performed to further increase the conductivity of the region where the impurity element 377 is added. The temperature of the heat treatment is typically 150°C or higher and lower than the substrate strain point, or 250°C or higher. or 300°C or more and 450°C or less. The hydrogen contained in the region 366b diffuses into the region 366c. Sexuality increases.

[0440] Through the above steps, a transistor can be manufactured.

[0441] <Method 2 for manufacturing semiconductor device> A method for manufacturing the transistor 391 shown in FIG. 25 will be described. The conductive film 368c and the conductive film 370c included in the conductive film 368 and the conductive film 370 of the capacitor 391 and a step of adding an impurity element 377 to the oxide semiconductor film 366 will be described. do.

[0442] 29 and 30(A) to 30(B), an insulating film 364 is formed on a substrate 362. Then, an oxide semiconductor film 366, a conductive film 368, and a conductive film 370 are formed.

[0443] Next, the conductive films 368b and 370b included in the conductive films 368 and 370 are The conductive film 368b and the conductive film 370b are exposed to plasma generated in a reducing atmosphere. Next, the conductive film 368b and the oxide are reduced while being heated at a temperature of 200°C or more and 400°C or less. The conductive film 368b and the conductive film 370b are then exposed to silane. By exposing the conductive film 368c to plasma generated in an atmosphere containing nitrogen, such as nitrogen or the like, and CuSi as the conductive film 370c. x N y (x>0, y>0) can be formed .

[0444] After this, the transistor 391 is fabricated through the steps of FIG. 30(C), FIG. 30(D) and FIG. It can be made.

[0445] <Method 3 for manufacturing semiconductor device> Another method for manufacturing the transistor 390 shown in FIG. The step of adding the element and the step of forming the insulating film 376 will be described with reference to FIG.

[0446] 29, 30 and 31(A), an insulating film 364 and an oxide film 365 are formed on a substrate 362. A semiconductor film 366, a conductive film 368, a conductive film 370, an insulating film 372, and a conductive film 374 are formed. do.

[0447] Next, as shown in FIG. 33A, the oxide semiconductor film 366, the conductive film 368, and the conductive film 37 33(B) after forming an insulating film 376 on the insulating film 372 and the conductive film 374. As shown in FIG. 1, the oxide semiconductor An impurity element 377 is added to the film 366 .

[0448] Through the above steps, the transistor 390 can be manufactured.

[0449] <Method 4 for manufacturing semiconductor device> A manufacturing method of a transistor having a sidewall insulating film will be described with reference to FIGS. 34 and 35. do.

[0450] 29, 30 and 31(A), an insulating film 364 and an oxide film 365 are formed on a substrate 362. A semiconductor film 366, a conductive film 368, a conductive film 370, an insulating film 372, and a conductive film 374 are formed. In this case, the insulating film 372 is not etched but is formed on the entire surface.

[0451] Next, as shown in FIG. 34(B), the conductive film 368, the conductive film 370, and the conductive film 374 are As a mask, an impurity element 377 is added to the oxide semiconductor film 366 .

[0452] Next, as shown in FIG. 34(C), an insulating film 375 is formed on the insulating film 372 and the conductive film 374. Form.

[0453] The insulating film 375 is a film that will later become a sidewall insulating film. The material and forming method of the insulating film 104 can be appropriately used.

[0454] Next, the insulating film 375 is removed by RIE (Reactive ion etching). By processing it by anisotropic etching such as ion etching, the result shown in Figure 34(D) can be obtained. As shown in FIG. 10, the sidewall insulating film 331a and the sidewall insulating film 331b in contact with the side surfaces of the conductive film 374 are formed by self-etching. It can be formed in a self-aligning manner.

[0455] Next, as shown in FIG. 35(A), a sidewall insulating film 331a and a sidewall insulating film 331b are formed on a mask. Then, the insulating film 372 is etched to expose part of the oxide semiconductor film 366.

[0456] Next, as shown in FIG. 35B, the oxide semiconductor film 366, the conductive film 368, and the conductive film 37 An insulating film 376 is formed over the conductive film 374. The insulating film 376 is a film containing hydrogen. Therefore, hydrogen moves to a region of the oxide semiconductor film 366 which is in contact with the insulating film 376 .

[0457] FIG. 35C is an enlarged view of the oxide semiconductor film 366 and its vicinity in FIG. The compound semiconductor film 366 has a region 366a in contact with the conductive film 368 or the conductive film 370 and an insulating film 366b. 376 and a region 366d that contacts the insulating film 372. It has a region 366c that overlaps with the sidewall insulating films 331a and 331b via the insulating film 372. In addition, when the side surface of the conductive film 374 has a tapered shape, a part of the region 366c is It may overlap with.

[0458] The regions 366b and 366c function as low resistance regions. The impurity elements include at least a rare gas and hydrogen. Furthermore, when hydrogen is diffused from the region 366b, In this case, hydrogen is contained in the region 366c, but the region 366c has more impurity elements than the region 366b. Therefore, the presence of the region 366c increases the source-drain breakdown voltage. can be done.

[0459] The transistor described in this embodiment has a conductive film which functions as a source electrode and a drain electrode. Since the film does not overlap with the conductive film that functions as the gate electrode, the parasitic capacitance can be reduced. Furthermore, the transistor described in this embodiment has a stable low Since it is possible to form a resistive region, the on-current increases compared to conventional transistors. Variation in electrical characteristics is reduced.

[0460] The configurations and methods described in this embodiment may be different from the configurations and methods described in other embodiments. can be used in appropriate combination.

[0461] (Fourth embodiment) In this embodiment mode, one mode of a semiconductor device and a manufacturing method thereof will be described with reference to FIGS. 2 will be used for the explanation. In this embodiment, the transistor of the drive circuit section is The structure of the oxide semiconductor film included in the transistor is different. The method shown in the third embodiment is used to form the resistance region.

[0462] <Configuration of semiconductor device> FIG. 50 shows a top-gate transistor as an example of a transistor included in a semiconductor device. This indicates a transistor.

[0463] FIG. 50A shows a cross-sectional view of the transistor 390 and the transistor 395a. FIG. 50B is a cross-sectional view of the transistor 390 and the transistor 395b. 50 to 52, X1-X2 are cross-sectional views of transistors provided in the driver circuit section. X3-X4 is a cross-sectional view of a transistor provided in a pixel portion.

[0464] FIG. 50 shows a transistor provided in a driver circuit section and a transistor provided in a pixel section. The structure of the oxide semiconductor film is different.

[0465] The transistor 390 in FIG. 50A has the same structure as the transistor 390 in Embodiment 3. Similarly, a single-layer oxide semiconductor film 366 is provided.

[0466] On the other hand, a transistor 395a illustrated in FIG. 50A includes an oxide semiconductor film 267a and an oxide semiconductor film 267b. The semiconductor device is characterized by having an oxide semiconductor film 266 on which an oxide semiconductor film 267b is stacked. In the top view, the oxide semiconductor film 267b is formed on the outer side of the edge of the oxide semiconductor film 267a. That is, the oxide semiconductor film 267b is located on the upper surface of the oxide semiconductor film 267a. The oxide semiconductor film 267a is in contact with the insulating film 364 and covers the side surfaces of the oxide semiconductor film 267a. The insulating film 267b is in contact with the oxide semiconductor film 267a and the insulating film 272.

[0467] 50B. The transistor 395b in FIG. 50B includes an oxide semiconductor film 267a, an oxide The oxide semiconductor film 266 includes a stack of the oxide semiconductor film 267b and the oxide semiconductor film 267c. Note that the oxide semiconductor film 267a and the oxide semiconductor film 267b are The end of the oxide semiconductor film 267b is located outside the end of the oxide semiconductor film 267c. The oxide semiconductor film 267b is formed on the upper surface and side surface of the oxide semiconductor film 267a and the oxide semiconductor film 267b. The oxide semiconductor film 267c covers the side surfaces of the insulating film 364. The conductive film 267b is in contact with the insulating film 272. The oxide semiconductor film 267a is an oxide semiconductor. The oxide semiconductor film 267b is in contact with the oxide semiconductor film 267c.

[0468] In the transistors 395a and 395b and the transistor 390, The compound semiconductor film 267a and the oxide semiconductor film 267b have different compositions. The oxide semiconductor film 267b and the oxide semiconductor film 366 have the same composition. The oxide semiconductor film 67a, the oxide semiconductor film 267b, and the oxide semiconductor film 366 are formed in different steps. In addition, the oxide semiconductor film 267b and the oxide semiconductor film 366 are formed in the same step.

[0469] The transistors 395a and 395b are channel-connected to the oxide semiconductor film 267a. Therefore, the oxide semiconductor film 267a is thicker than the oxide semiconductor film 267b. A large thickness is preferred.

[0470] The thickness of the oxide semiconductor film 267a is 3 nm to 200 nm, or 10 nm to 50 nm. The oxide semiconductor film 267b and the oxide semiconductor film 267c are 0 nm or less, or 20 nm or more and 35 nm or less. The thickness of the compound semiconductor film 366 is 3 nm or more and 200 nm or less, or 3 nm or more and 100 nm or less. or less, or 10 nm or more and 100 nm or less, or 30 nm or more and 50 nm or less.

[0471] The oxide semiconductor film 267a, the oxide semiconductor film 267b, and the oxide semiconductor film 366 are It is formed of a metal oxide film containing at least In, and typically includes an In-Ga oxide film, an In- M-Zn oxide film (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or It is formed from Hf, etc.

[0472] The oxide semiconductor film 267a is made of M (M is Mg, Al, Ti, Ga, Y, Zr, La, C The ratio of the number of atoms of In to the number of atoms of In (e, Nd, or Hf) is large. -M-Zn oxide (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or In the case of Hf), the target used for depositing the oxide semiconductor film 367a is a gold target. If the atomic ratio of group elements is In:M:Zn=x3:y3:z3, 、 x3 / y3 is greater than 1 It is preferable that the atomic ratio is at most 6 or less. A typical example of the atomic ratio of the metal elements in the target is , In:M:Zn=2:1:1.5, In:M:Zn=2:1:2.3, In:M:Zn =2:1:3, In:M:Zn=3:1:2, In:M:Zn=3:1:3, In:M: Zn=3:1:4, etc.

[0473] The oxide semiconductor film 267b and the oxide semiconductor film 366 are made of M (M is Mg, Al, Ti, The atomic ratio of In to Ga, Y, Zr, La, Ce, Nd, or Hf is the same or smaller The oxide semiconductor film 267b and the oxide semiconductor film 366 are In-M-Zn oxide films (M In the case of Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf, oxide In the target used for depositing the semiconductor film 267b and the oxide semiconductor film 366, If the atomic ratio of metal elements is In:M:Zn=x4:y4:z4, 、x4 / y4 is 1 It is preferable that z4 / y4 is 1 / 3 or more and 6 or less. is preferably 1 or more and 6 or less. By setting z4 / y4 to 1 or more and 6 or less, CAAC-OS films are likely to be formed as the oxide semiconductor films 267b and 366. A typical example of the atomic ratio of the metal elements in the target is In:M:Zn=1:1. :1, In:M:Zn=1:1:1.2, In:M:Zn=1:3:2, In:M:Zn =1:3:4, In:M:Zn=1:3:6, In:M:Zn=1:3:8, In:M: Zn=1:4:4, In:M:Zn=1:4:5, In:M:Zn=1:4:6, In: M:Zn=1:4:7, In:M:Zn=1:4:8, In:M:Zn=1:5:5, I n:M:Zn=1:5:6, In:M:Zn=1:5:7, In:M:Zn=1:5:8 , In:M:Zn=1:6:8, etc.

[0474] The transistor 395a and the transistor 395b are made of M (M is Mg, Al, Ti, G oxide semiconductors with a large atomic ratio of In to Since a channel is formed in the conductive film 267a, the field effect mobility is high. Effective mobility is 10cm 2 / Vs is larger than 60cm 2 / Vs less than 15cm 2 / Vs or more 50cm 2 However, when light is irradiated, Therefore, providing a light-shielding film in the drive circuit section This results in a transistor with high field effect mobility and low current in the off state. As a result, a driver circuit portion capable of high-speed operation can be manufactured.

[0475] 51(A) and the transistor 397a shown in FIG. 51(B) As shown in 397b, a conductive film 261 that functions as a light-shielding film may be provided. 261 and the conductive film 274 are connected to each other, and thus the transistor 397a and the transistor This increases the on-state current of the transistor 397b and also increases the field effect mobility.

[0476] On the other hand, transistor 390 is made of M (M is Mg, Al, Ti, Ga, Y, Zr, La, The atomic ratio of In to Ce, Nd, or Hf is the same or smaller than that of In. Since a channel is formed, even when the oxide semiconductor film is irradiated with light, an increase in off-state current is small. For this reason, M (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, The oxide semiconductor film has an oxide semiconductor film having the same or a smaller atomic ratio of In to Nd or Hf. By providing a transistor, deterioration due to light irradiation is reduced, and a pixel section with excellent display quality is manufactured. It is possible.

[0477] The oxide semiconductor film 267c is made of M (M is Mg, Al, Ti, Ga, Y, Zr, La, C The oxide semiconductor film 267c has a low atomic ratio of In to In (e, Nd, or Hf). -M-Zn oxide film (M is Mg, Al, Ti, Ga, Y, Zr, La, Ce, Nd, or In the case where Hf is used as the oxide semiconductor film 267c, the target used for depositing the oxide semiconductor film 267c is If the atomic ratio of metal elements is In:M:Zn=x5:y5:z5, 、 x5 / y5 is 1 / It is preferable that z5 / y5 is 6 or more and less than 1. In addition, z5 / y5 is 1 / 3 or more and 6 or less, and further It is preferable that z5 / y5 is 1 or more and 6 or less. The target metal is easily formed as a CAAC-OS film as the compound semiconductor film 267c. Typical examples of atomic ratios of elements are In:M:Zn=1:3:2, In:M:Zn=1: 3:4, In:M:Zn=1:3:6, In:M:Zn=1:3:8, In:M:Zn= 1:4:4, In:M:Zn=1:4:5, In:M:Zn=1:4:6, In:M:Z n=1:4:7, In:M:Zn=1:4:8, In:M:Zn=1:5:5, In:M :Zn=1:5:6, In:M:Zn=1:5:7, In:M:Zn=1:5:8, In :M:Zn=1:6:8 etc.

[0478] In addition, when the oxide semiconductor film 267c is an In—Ga oxide film, for example, an In—Ga metal Formed by sputtering using an oxide target (In:Ga=7:93) The oxide semiconductor film 267c can be formed by a sputtering method using DC discharge. To form an In-Ga oxide film, the atomic ratio is In:Ga=x:y. y / (x+y) is set to 0.96 or less, preferably 0.95 or less, for example, 0.93. stomach.

[0479] The transistor 395b in FIG. 50B and the transistor 397b in FIG. 51B are provided with The thickness of the oxide semiconductor film 267c is smaller than that of the oxide semiconductor film 267a. 2 nm or more and 100 nm or less, preferably 2 nm or more and 50 nm or less, and more preferably 3 nm or more and 100 nm or less. The insulating film 364 that functions as a gate insulating film and the oxide semiconductor By providing the oxide semiconductor film 267c between the oxide semiconductor films 267a, the threshold voltage of the transistor can be reduced. Pressure fluctuations can be reduced.

[0480] <Method for manufacturing semiconductor device> Next, a method for manufacturing the transistor 390 and the transistor 397a shown in FIG. This will be explained using FIG.

[0481] As shown in FIG. 52(A), a conductive film 261 is formed on a substrate 362. Next, An insulating film 364 is formed over the insulating film 364 and the conductive film 261. A film 265a is formed.

[0482] Next, as shown in FIG. 52(B), a photolithography process is performed on the oxide semiconductor film 265a. After forming a mask by the process, the oxide semiconductor film 265a is etched to form a mask for the driver circuit section. An oxide semiconductor film 267a is formed.

[0483] Next, as shown in FIG. 52C, an oxide semiconductor film 267a is formed on the insulating film 364. The compound semiconductor film 265b is formed.

[0484] Next, as shown in FIG. 52(D), a photolithography process is performed on the oxide semiconductor film 265b. After forming a mask by the process, the oxide semiconductor film 265b is etched to form a mask on the driver circuit portion. An oxide semiconductor film 267b is formed to cover the oxide semiconductor film 267a, and the oxide semiconductor A film 366 is formed.

[0485] In this step, the oxide semiconductor film 267a is formed on the oxide substrate 267b so as to cover the top surface and the side surface of the oxide semiconductor film 267a. By forming the semiconductor film 267b, a conductive film which will later function as a source electrode and a drain electrode is formed. In the step of forming the oxide semiconductor film 267a, the oxide semiconductor film 267a is not etched. In order to reduce the variation in the length of the oxide semiconductor film 267a in the channel width direction of the transistor, This is preferable.

[0486] After that, through the steps of FIG. 30 and FIG. 31, the transistors 390 and 39 7a can be produced.

[0487] The configurations and methods described in this embodiment may be different from the configurations and methods described in other embodiments. can be used in appropriate combination.

[0488] (Embodiment 5) In this embodiment mode, one mode of a semiconductor device will be described with reference to FIGS. Here, a display device will be described as an example of a semiconductor device. Here, a transistor provided in one pixel and the transistor The structure of the capacitive element connected to the

[0489] <Configuration 1 of semiconductor device> FIG. 37 shows a transistor 150 included in a pixel and a capacitor connected to the transistor 150. 1 shows the structure of the quantum element 159.

[0490] 37A and 37B are top views of the transistor 150 and the capacitor 159. 37A is a top view of the transistor 150 and the capacitor 159. 37(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 37(A), and FIG. 37(B) is a cross-sectional view taken along the dashed line X5- Cross-sectional view of section X6.

[0491] The transistor 150 shown in FIG. 37 is the same as the transistor 150 shown in the first embodiment. It has a structure.

[0492] The capacitor 159 includes an oxide semiconductor film 156 over the insulating film 104 and an oxide semiconductor film The insulating film 118 is in contact with the insulating film 156 , and the conductive film 124 is on the insulating film 118 .

[0493] An insulating film 122 is formed on the insulating film 118. The insulating film 116, the insulating film 118, and the insulating film 122 are In the opening 142a of the insulating film 122, the conductive film 124 contacts the conductive film 112. 8, the insulating film 116, and the opening 142b of the insulating film 122, the conductive film 124 is Contact with 118.

[0494] The insulating film 122 is made of an organic resin such as polyimide, acrylic, polyamide, or epoxy. The insulating film 122 has a thickness of 500 nm or more and 10 μm or less. It is preferable that:

[0495] The conductive film 124 may be made of indium tin oxide, indium oxide containing tungsten oxide, or oxide. Indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, Indium tin oxide containing titanium, indium zinc oxide, indium with silicon oxide The insulating film 11 can be formed using a light-transmitting conductive material such as aluminum tin oxide.

[0496] The conductive film 124 may be made of silver, aluminum, chromium, copper, tantalum, titanium, or molybdenum. It can be formed by using a metal element that reflects light, such as tungsten or tungsten. a film formed using a metal element that reflects light and a film formed using the above-mentioned light-transmitting conductive material; Alternatively, the film may be formed by laminating films formed by the above methods.

[0497] The oxide semiconductor film 156 has a light-transmitting property because it is formed at the same time as the oxide semiconductor film 106. In addition, the impurity element is added to the region 106b in the oxide semiconductor film 106. Therefore, the oxide semiconductor film 156 has conductivity.

[0498] When the conductive film 124 is formed using a light-transmitting conductive material, the capacitor 15 Therefore, by providing the capacitor element 159 in the pixel of the display device, It is possible to increase the aperture ratio in the

[0499] <Configuration 2 of semiconductor device> FIG. 38 shows a transistor 190 included in a pixel and a capacitor connected to the transistor 190. 1 shows the structure of the quantum element 199.

[0500] 38A and 38B are top views of the transistor 190 and the capacitor 199. 38A is a top view of the transistor 190 and the capacitor 199. 38(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 38(A), and FIG. 38(B) is a cross-sectional view taken along the dashed line X5- Cross-sectional view of section X6.

[0501] The transistor 190 shown in FIG. 38 is the same as the transistor 190 described in the second embodiment. It has a structure.

[0502] The capacitor 199 includes an oxide semiconductor film 198 over the insulating film 164 and an oxide semiconductor film The insulating film 176 is in contact with the insulating film 198 , and the conductive film 184 is on the insulating film 176 .

[0503] An insulating film 182 is formed on the insulating film 178. The insulating film 176, the insulating film 178, and the insulating film 182 are In the opening 182a of the insulating film 182, the conductive film 184 is in contact with the conductive film 172. 8, in the opening 182b of the insulating film 178 and the insulating film 182, the conductive film 184 is It borders on 76.

[0504] The insulating film 182 can be formed using the same material as the insulating film 122 shown in FIG.

[0505] The conductive film 184 can be formed using the material of the conductive film 124 shown in FIG.

[0506] The oxide semiconductor film 198 has a light-transmitting property because it is formed simultaneously with the oxide semiconductor film 166. In addition, the impurity element is added to the region 166b in the oxide semiconductor film 166. Therefore, the oxide semiconductor film 198 has conductivity.

[0507] When the conductive film 184 is formed using a light-transmitting conductive material, the capacitor 19 Therefore, by providing the capacitor element 199 in the pixel of the display device, It is possible to increase the aperture ratio in the

[0508] In addition, a semiconductor film is formed on the oxide semiconductor film included in the transistor, and the semiconductor film is also formed on the oxide semiconductor film included in the transistor. Therefore, the number of masks does not increase and a conductive oxide semiconductor film can be formed. Therefore, the transistor and the capacitor can be formed at the same time.

[0509] <Configuration 3 of semiconductor device> FIG. 39 shows a transistor 390 included in a pixel and a capacitor connected to the transistor 390. 3 shows the structure of the quantum element 399.

[0510] 39A and 39B are top views of a transistor 390 and a capacitor 399. 39A is a top view of a transistor 390 and a capacitor 399. 39(B) is a cross-sectional view taken along the dashed line X3-X4 in FIG. 39(A), and FIG. 39(B) is a cross-sectional view taken along the dashed line X5- Cross-sectional view of section X6.

[0511] The transistor 390 shown in FIG. 39 is the same as the transistor 390 described in the third embodiment. It has a structure.

[0512] The capacitor 399 includes an oxide semiconductor film 396 over the insulating film 364 and an oxide semiconductor film The insulating film 376 is in contact with the insulating film 396 , and the conductive film 384 is on the insulating film 376 .

[0513] An insulating film 382 is formed on the insulating film 376. Openings in the insulating film 376 and the insulating film 382 In the portion 388a, the conductive film 384 contacts the conductive film 370. In 8b, the conductive film 384 is in contact with the insulating film 376.

[0514] The insulating film 382 can be formed using the same material as the insulating film 122 shown in FIG.

[0515] The conductive film 384 can be formed using the same material as the conductive film 124 shown in FIG.

[0516] The oxide semiconductor film 396 has a light-transmitting property because it is formed at the same time as the oxide semiconductor film 366. In addition, the impurity element is added to the oxide semiconductor film 366 in the same manner as the region 366b included in the oxide semiconductor film 366. Therefore, the oxide semiconductor film 396 has conductivity.

[0517] When the conductive film 384 is formed using a light-transmitting conductive material, the capacitor 39 Therefore, by providing a capacitor element 399 in a pixel of a display device, It is possible to increase the aperture ratio in the

[0518] In addition, a semiconductor film is formed on the oxide semiconductor film included in the transistor, and the semiconductor film is also formed on the oxide semiconductor film included in the transistor. Therefore, the number of masks does not increase and a conductive oxide semiconductor film can be formed. Therefore, the transistor and the capacitor can be formed at the same time.

[0519] The configurations and methods described in this embodiment may be different from the configurations and methods described in other embodiments. can be used in appropriate combination.

[0520] (Embodiment 6) In this embodiment, a structure of an oxide semiconductor film included in a semiconductor device of one embodiment of the present invention will be described. This will be explained in detail below.

[0521] <Structure of oxide semiconductors> The structure of an oxide semiconductor will be described below.

[0522] Oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. As a non-single-crystal oxide semiconductor, CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor, polycrystalline oxide Examples of the oxide semiconductor include a semiconductor, a microcrystalline oxide semiconductor, and an amorphous oxide semiconductor.

[0523] From another point of view, oxide semiconductors are classified into amorphous oxide semiconductors and other crystalline oxides. Crystalline oxide semiconductors are divided into single-crystal oxide semiconductors, CAAC- Examples of such oxide semiconductors include OS, polycrystalline oxide semiconductors, and microcrystalline oxide semiconductors.

[0524] <caac-os> First, let me explain about CAAC-OS. Axis-Aligned Nanocrystals It can also be done as follows.

[0525] CAAC-OS is an oxide having multiple crystal parts (also called pellets) aligned along the c-axis. It is a type of semiconductor.

[0526] Transmission Electron Microscope (TEM) A combined analysis image (high resolution) of the bright-field image and diffraction pattern of CAAC-OS was obtained by using a microscope. When observing a high-resolution TEM image, multiple pellets can be confirmed. On the other hand, high-resolution TEM images reveal the boundaries between pellets, i.e., grain boundaries. Therefore, the CAAC-OS is not clearly characterized by the grain boundaries. It can be said that the resulting decrease in electron mobility is unlikely to occur.

[0527] Below, we will explain the CAAC-OS observed by TEM. 1 shows a high-resolution TEM image of a cross section of CAAC-OS observed from a direction approximately parallel to the sample surface. For high-resolution TEM imaging, spherical aberration correction is required. The spherical aberration correction function was used to obtain high-resolution TEM images. , specifically referred to as a Cs-corrected high-resolution TEM image. Cs-corrected high-resolution TEM images can be obtained, for example, This is performed using an atomic resolution analytical electron microscope such as the JEM-ARM200F manufactured by JEOL Ltd. It is possible.

[0528] An enlarged Cs-corrected high-resolution TEM image of area (1) in Figure 47(A) is shown in Figure 47(B). From Figure 47(B), it can be seen that the metal atoms are arranged in layers in the pellet. The arrangement of each metal atom layer is determined by the surface on which the CAAC-OS film is to be formed (also referred to as the surface on which the film is to be formed). Or it reflects the unevenness of the top surface and is parallel to the surface on which the CAAC-OS is formed or the top surface.

[0529] As shown in Figure 47(B), CAAC-OS has a characteristic atomic arrangement. ) shows the characteristic atomic arrangement with auxiliary lines. ) the size of each pellet is about 1 nm to 3 nm, and the size of each pellet is about 1 nm to 3 nm. It can be seen that the size of the gap caused by the tilt is about 0.8 nm. The pellets may also be referred to as nanocrystals (nc).

[0530] Here, based on the Cs-corrected high-resolution TEM image, the pellets of CAAC-OS on the substrate 5120 were The layout of the 5100 is shown diagrammatically as a stack of bricks or blocks. (See FIG. 47(D)). Between the pellets observed in FIG. 47(C), The portion where the tilt occurs corresponds to the area 5161 shown in FIG.

[0531] FIG. 48(A) shows the C of the plane of the CAAC-OS observed from a direction approximately perpendicular to the sample surface. The s-corrected high-resolution TEM images are shown. Regions (1), (2), and (3) in Figure 48(A). ) are enlarged Cs-corrected high-resolution TEM images shown in Figure 48(B), Figure 48(C), and As shown in Figure 48(D), Figure 48(B), Figure 48(C) and Figure 48(D) show that the pellet It can be seen that the metal atoms are arranged in a triangular, quadrangular or hexagonal shape. However, no regularity is observed in the arrangement of metal atoms among different pellets.

[0532] Next, C analyzed by X-ray diffraction (XRD) For example, CAAC-O with InGaZnO4 crystals When S is subjected to structural analysis using the out-of-plane method, the result is as shown in Figure 49(A). As shown in the figure, a peak may appear at a diffraction angle (2θ) of around 31°. Since this is attributed to the (009) plane of the ZnO4 crystal, it is believed that the CAAC-OS crystal is c-axis oriented. It can be seen that the c-axis is oriented in a direction substantially perpendicular to the surface on which the film is formed or the upper surface.

[0533] In addition, in the structural analysis of CAAC-OS using the out-of-plane method, 2θ is 31 In addition to the peak around 2θ of 36°, a peak may also appear around 2θ of 36°. The peaks in the vicinity indicate that some of the CAAC-OS crystals do not have a c-axis orientation. The more preferable CAAC-OS is a structure produced by the out-of-plane method. The analysis shows a peak at 2θ around 31°, but no peak at 2θ around 36°.

[0534] On the other hand, in-pla, X-rays are incident on the CAAC-OS from a direction almost perpendicular to the c-axis. When structural analysis is performed using the NE method, a peak appears at 2θ around 56°. This peak is due to I It is attributed to the (110) plane of the nGaZnO4 crystal. In the case of CAAC-OS, 2θ is set to 5 The sample is fixed at approximately 6° and analyzed while rotating around the normal vector of the sample surface (φ axis). Even if a (φ scan) is performed, no clear peak appears, as shown in Figure 49(B). On the other hand, in the case of a single crystal oxide semiconductor such as InGaZnO4, 2θ is fixed at around 56° and φ When scanned, it is assigned to a crystal plane equivalent to the (110) plane as shown in Figure 49(C). Six peaks are observed. Therefore, from the structural analysis using XRD, CAAC-OS It can be seen that the orientation of the a-axis and b-axis is irregular.

[0535] Next, we will explain the CAAC-OS analyzed by electron diffraction. For CAAC-OS with ZnO4 crystals, the probe diameter is 300 nm parallel to the sample surface. When an electron beam is incident on the sample, a diffraction pattern (selected area transmission electron diffraction) as shown in Figure 55(A) is generated. This diffraction pattern may appear due to the presence of InGaZnO4 This includes spots due to the (009) plane of the crystal. The pellets contained in the CAAC-OS have a c-axis orientation, and the c-axis faces the surface to be formed or the upper surface. On the other hand, when the probe was applied to the same sample perpendicular to the sample surface, The diffraction pattern when an electron beam with a diameter of 300 nm was incident is shown in Figure 55(B). 5(B), a ring-shaped diffraction pattern is confirmed. Therefore, electron diffraction It can be seen that the a-axis and b-axis of the pellets contained in CAAC-OS do not have any orientation. The first ring in FIG. 55(B) is the (010) plane of the InGaZnO4 crystal. This is thought to be due to the (100) plane and the like. This is thought to be due to the (110) surface.

[0536] In addition, the CAAC-OS is an oxide semiconductor with a low density of defect states. Defects include, for example, defects caused by impurities and oxygen vacancies. AC-OS can also be considered an oxide semiconductor with a low impurity concentration. S can also be said to be an oxide semiconductor with few oxygen vacancies.

[0537] Impurities contained in oxide semiconductors can act as carrier traps or as carrier generation sources. In addition, oxygen vacancies in an oxide semiconductor may become carrier traps or By capturing hydrogen, it may become a carrier generation source.

[0538] The impurities are elements other than the main components of the oxide semiconductor, such as hydrogen, carbon, silicon, and transition metals. For example, metal elements such as silicon are more oxidative than metal elements that constitute oxide semiconductors. Elements with strong bonding strength with the oxide semiconductor remove oxygen from the oxide semiconductor, which changes the atomic arrangement of the oxide semiconductor. In addition, heavy metals such as iron and nickel, argon, Carbon dioxide and other molecules have a large atomic radius (or molecular radius), so the atomic arrangement of oxide semiconductors This disrupts the structure and reduces the crystallinity.

[0539] In addition, oxide semiconductors with low defect state density (few oxygen vacancies) have low carrier density. Such an oxide semiconductor can be a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor. CAAC-OS has a low impurity concentration and a low density of defect states. Therefore, the oxide semiconductor is likely to be a highly pure intrinsic or substantially highly pure intrinsic oxide semiconductor. A transistor using AC-OS has electrical characteristics in which the threshold voltage is negative (normal It is also called "on." It is rare for it to become a high-purity intrinsic or substantially high-purity intrinsic Oxide semiconductors have few carrier traps. The charge that is trapped takes a long time to be released and behaves like a fixed charge. Therefore, transistors using oxide semiconductors with high impurity concentrations and high defect state densities are being developed. On the other hand, transistors using CAAC-OS can have unstable electrical characteristics. The resulting transistor has little fluctuation in electrical characteristics and is highly reliable.

[0540] In addition, CAAC-OS has a low defect level density, so it is possible to generate Therefore, the carriers are less likely to be captured by the defect level. The electrical characteristics of a transistor are less susceptible to change when irradiated with visible light or ultraviolet light.

[0541] <Microcrystalline oxide semiconductor> Next, a microcrystalline oxide semiconductor will be described.

[0542] Microcrystalline oxide semiconductors have regions where crystals can be confirmed in high-resolution TEM images. The microcrystalline oxide semiconductor has a crystal structure including a region where a crystal part is clearly visible and a region where a crystal part is not clearly visible. The crystal part contained is between 1 nm and 100 nm, or between 1 nm and 10 nm in size. In particular, fine crystals of 1 nm to 10 nm or 1 nm to 3 nm are often The oxide semiconductor with nanocrystalline structure is called nc-OS (nanocrystalline silicon). nc-OS is called NC-Oxide Semiconductor. In some cases, the grain boundaries cannot be clearly identified in the TEM images. It is possible that the origin of the pellets in C-OS is the same as that of the pellets in C-OS. The crystalline part of the OS is sometimes called a pellet.

[0543] nc-OS is a material that can be used in microscopic areas (e.g., areas between 1 nm and 10 nm, especially areas between 1 nm and 10 nm). The atomic arrangement is periodic in the region of 3 nm or less. There is no regularity in the crystal orientation between the layers. Therefore, no orientation is observed throughout the film. Therefore, depending on the analysis method, nc-OS may be indistinguishable from amorphous oxide semiconductors. For example, an XRD apparatus using X-rays with a diameter larger than that of the pellet is used for nc-OS. When structural analysis is performed using the out-of-plane method, the crystal plane is shown. In addition, the probe diameter ( For example, electron diffraction (also called selected area electron diffraction) is performed using an electron beam of 50 nm or more. On the other hand, for nc-OS, a halo-like diffraction pattern is observed. Nanobeam electron circuits use electron beams with a probe diameter close to the pellet size or smaller than the pellet. When the nc-OS is subjected to nanobeam electron diffraction, spots are observed. When the light is too bright, a circular (ring-shaped) area of ​​high brightness may be observed. Multiple spots may be observed within a ring-like region.

[0544] In this way, the crystal orientation between the pellets (nanocrystals) is not regular, so nc -OS with RANC (Random Aligned nanocrystals) oxide semiconductors, or NANCs (Non-Aligned Nanocrystals) The semiconductor may also be referred to as an oxide semiconductor having a structure (s).

[0545] The nc-OS is an oxide semiconductor with higher order than an amorphous oxide semiconductor. However, the density of defect states in nc-OS is lower than that in amorphous oxide semiconductors. There is no regularity in the crystal orientation between different pellets in S. Therefore, nc-OS is The defect density is higher than that of AAC-OS.

[0546] <Amorphous oxide semiconductor> Next, the amorphous oxide semiconductor will be described.

[0547] Amorphous oxide semiconductors are oxides in which the atomic arrangement within the film is irregular and does not have crystalline parts. An example is an oxide semiconductor that has an amorphous state, such as quartz.

[0548] In amorphous oxide semiconductors, no crystalline parts can be observed in high-resolution TEM images.

[0549] When structural analysis is performed on amorphous oxide semiconductors using an XRD device, out-of-p In the analysis by the Lane method, no peaks indicating crystal planes were detected. When electron diffraction is performed on a conductor, a halo pattern is observed. When nanobeam electron diffraction is performed on the sample, no spots are observed, and only a halo pattern is observed. Observed.

[0550] There are various views on amorphous structures. For example, A structure that does not have this property is called a completely amorphous structure. The distance between the nearest neighboring atoms or the second nearest neighboring atoms is also called the structure. A structure that has order at the interface but does not have long-range order is sometimes called an amorphous structure. Therefore, according to the strictest definition, an oxide semiconductor that has even a slight degree of order in its atomic arrangement is called a non-metallic oxide semiconductor. Furthermore, it cannot be called an crystalline oxide semiconductor. Therefore, since the semiconductor has crystalline parts, it cannot be called an amorphous oxide semiconductor. For example, CAAC-OS and nc-OS are used as amorphous oxide semiconductors or completely amorphous It cannot be called an oxide semiconductor.

[0551] <Amorphous-like oxide semiconductor> Note that an oxide semiconductor may have a structure between an nc-OS and an amorphous oxide semiconductor. An oxide semiconductor having such a structure is particularly called an amorphous-like oxide semiconductor (aluminum oxide). ike OS:amorphous-like Oxide Semiconducto It is called r).

[0552] In a-like OS, voids (also called voids) are observed in high-resolution TEM images. In addition, crystals can be clearly seen in high-resolution TEM images. and regions where no crystalline portions can be identified.

[0553] Because of the porosity, the a-like OS has an unstable structure. e OS has an unstable structure compared with CAAC-OS and nc-OS. This shows the structural changes caused by electron irradiation.

[0554] The samples to be irradiated with electrons were a-like OS (referred to as sample A), nc-OS (hereinafter referred to as Sample B) and CAAC-OS (hereinafter referred to as Sample C) are prepared. Both samples are In-Ga-Zn oxides.

[0555] First, high-resolution cross-sectional TEM images of each sample are acquired. It can be seen that all the materials have crystalline parts.

[0556] The determination of which part is to be regarded as one crystal part can be made as follows. For example, The unit cell of the InGaZnO4 crystal has three In-O layers and one Ga-Zn-O layer. It is known that the structure has a total of nine layers, six of which are stacked in layers in the c-axis direction. The spacing between these adjacent layers is approximately the same as the lattice spacing (also called the d value) of the (009) plane. The value is calculated to be 0.29 nm from crystal structure analysis. The areas where the spacing is 0.28 nm or more and 0.30 nm or less are considered to be InGaZnO4 crystal parts. The lattice fringes correspond to the ab plane of the InGaZnO4 crystal.

[0557] Figure 56 shows an example of investigating the average size of the crystal parts (22 to 45 locations) of each sample. However, the length of the lattice fringes mentioned above is the size of the crystal part. It can be seen that the crystalline part of ke OS grows in size according to the cumulative amount of electron irradiation. Specifically, as shown in Figure 56 (1), the initial TEM observation showed a size of about 1.2 nm. The crystal part (also called the initial nucleus) was 4.2 × 10 8 e - / n m 2 On the other hand, in the nc-O For S and CAAC-OS, the cumulative electron irradiation dose from the start of electron irradiation was 4.2 × 10 8 e - / nm 2 It can be seen that there is no change in the size of the crystal part within the range of As shown in (2) and (3) in Figure 56, regardless of the cumulative electron dose, the nc-OS and The sizes of the crystal parts of the CAAC-OS and CAAC-OS are approximately 1.4 nm and 2.1 nm, respectively. It can be seen that...

[0558] In this way, the growth of crystalline parts can be observed in a-like OS due to electron irradiation. On the other hand, in nc-OS and CAAC-OS, the growth of the crystals by electron irradiation is almost nonexistent. In other words, a-like OS is not as good as nc-OS and CAAC- It is clear that it has an unstable structure compared to the OS.

[0559] In addition, due to its porosity, a-like OS is more flexible than nc-OS and CAAC-OS. Specifically, the density of a-like OS is lower than that of a single crystal of the same composition. The density of the nc-OS is 78.6% or more and less than 92.3% of that of the normal crystal. The density of C-OS is 92.3% or more but less than 100% of the density of a single crystal of the same composition. It is difficult to form a film of an oxide semiconductor having a crystal density of less than 78%.

[0560] For example, in an oxide semiconductor having an atomic ratio of In:Ga:Zn=1:1:1, The density of single-crystal InGaZnO4 with a rhombohedral crystal structure is 6.357 g / cm 3 It becomes. For example, in an oxide semiconductor that satisfies the atomic ratio of In:Ga:Zn=1:1:1, The density of a-like OS is 5.0 g / cm 3 More than 5.9g / cm 3 It will be less than For example, in an oxide semiconductor having an atomic ratio of In:Ga:Zn=1:1:1, , the density of nc-OS and the density of CAAC-OS are 5.9 g / cm 3 More than 6.3g / cm 3 It will be less than.

[0561] In some cases, single crystals with the same composition do not exist. In such cases, crystals with different compositions may be used in any proportion. By combining single crystals with the desired composition, the density equivalent to that of a single crystal can be estimated. The density corresponding to a single crystal of a desired composition can be obtained by combining single crystals of different compositions. The density should be as low as possible. It is preferable to estimate by combining different types of single crystals.

[0562] As described above, oxide semiconductors have various structures, each of which has various characteristics. The oxide semiconductor may be, for example, an amorphous oxide semiconductor, an a-like OS, or a microcrystalline oxide semiconductor. The layer may be a laminated film containing two or more of a compound semiconductor and a CAAC-OS.

[0563] <Film formation model> An example of a film formation model for CAAC-OS and nc-OS will be described below.

[0564] FIG. 57(A) shows a process of forming a CAAC-OS film by sputtering. Schematic diagram of the inside of the membrane chamber.

[0565] The target 5130 is glued to a backing plate. A plurality of magnets are arranged at positions facing the target 5130 through the magnets. The magnetic field is generated by a number of magnets. The sputtering method used is called magnetron sputtering.

[0566] The substrate 5120 is disposed so as to face the target 5130, and the distance therebetween is d( The target-substrate distance (also called the TS distance) is preferably 0.01 m or more and 1 m or less. The thickness of the film deposition chamber is 0.02m or more and 0.5m or less. oxygen, argon, or a gas mixture containing 5% or more by volume of oxygen) and The pressure is controlled to 1 Pa or more and 100 Pa or less, preferably 0.1 Pa or more and 10 Pa or less. By applying a voltage above a certain level to the target 5130, a discharge begins and plasma is generated. It is confirmed that a high density plasma region is generated near the target 5130 by the magnetic field. In the high density plasma region, the deposition gas is ionized, and ions 5101 The ions 5101 are, for example, positive ions of oxygen (O + ) and argon cations ( Ar + ) etc.

[0567] Here, the target 5130 has a polycrystalline structure having a plurality of crystal grains, and The crystal grains include cleavage planes. The crystal structure of InGaZnO4 is shown in Figure 58(A). This is the structure of InGaZnO4 crystals observed from the outside. In the two Ga-Zn-O layers, the oxygen atoms in each layer are arranged in close proximity. The negative charge of the oxygen atom makes it possible to separate two adjacent atoms. Repulsion occurs between the Ga-Zn-O layers. As a result, the InGaZnO4 crystals are The cleavage plane is located between the two Ga-Zn-O layers.

[0568] Ions 5101 generated in the high-density plasma region are attracted to the target 5130 by the electric field. The particles are accelerated and eventually collide with the target 5130. At this time, flat or planar particles are formed from the cleavage plane. pellets 5100a and 5100b, which are pellet-shaped sputtered particles, are peeled off, The pellets 5100a and 5100b are ejected by the ions 5101. The impact of a collision can cause distortion of the structure.

[0569] The pellet 5100a is a flat plate or pellet having a triangular, for example, equilateral triangular, plane. The pellet 5100b is a sputtered particle having a hexagonal shape, for example, a regular hexagonal plane. The pellets 5100a and 5100b are sputtered particles in the form of plates or pellets. Sputter particles in the form of flat or pellets, such as pellets 5100b, are collectively called pellets. The planar shape of the pellet 5100 is not limited to a triangle or a hexagon, for example. For example, there are cases where the shape is made up of multiple triangles. In some cases, two squares (or polygons) may join together to form a quadrilateral (for example, a rhombus).

[0570] The thickness of the pellet 5100 is determined depending on the type of deposition gas, etc. The reason for this will be explained later. It is preferable that the thickness of the pellet 5100 is uniform. Thin pellets are preferable to thick cubes. The thickness of the PET 5100 is 0.4 nm or more and 1 nm or less, preferably 0.6 nm or more and 0.8 nm or less. For example, the pellet 5100 has a width of 1 nm or more and 3 nm or less, preferably The pellet 5100 is the same as that shown in FIG. ) corresponds to the initial nucleus described in (1). For example, the target 5 having In-Ga-Zn oxide When ions 5101 are bombarded onto the Ga-Zn-O layer 130, as shown in FIG. 58(B), A pellet 5100 having three layers, an In-O layer, and a Ga-Zn-O layer, is exfoliated. Figure 8(C) shows the structure of the exfoliated pellet 5100 observed from a direction parallel to the c-axis. The RET 5100 is a nano-sized wafer with two Ga-Zn-O layers and an In-O layer. It can also be called a sandwich structure.

[0571] As the pellet 5100 passes through the plasma, the sides may become negatively or positively charged. The pellet 5100 may have negatively charged oxygen atoms located on its sides, for example. The sides have charges of the same polarity, which causes repulsion between the charges, resulting in a flat or penetrating shape. It is possible to maintain the shape of the In-Ga-Z In the case of n-oxide, the oxygen atom bonded to the indium atom may be negatively charged. Or, an oxygen atom bonded to an indium atom, a gallium atom, or a zinc atom is negatively charged. In addition, when the pellet 5100 passes through the plasma, it may The area where it grows by bonding with indium atoms, gallium atoms, zinc atoms, oxygen atoms, etc. The difference in size between (2) and (1) in Figure 56 above is due to the growth in the plasma. Here, when the substrate 5120 is at room temperature, the pellets on the substrate 5120 The growth of 5100 is difficult to occur, resulting in nc-OS (see Figure 57(B)). Since the film can be formed at a low temperature, nc-OS can be formed even on a large substrate (5120). In order to grow the pellet 5100 in plasma, the sputtering method is used. Increasing the film formation power in the pellet 5 is effective. 100 structures can be stabilized.

[0572] As shown in Figures 57(A) and 57(B), for example, a pellet 5100 is It flies like a kite through the air and flutters up to the top of the board 5120. Since the pellet 100 is electrically charged, it will be attracted to an area where other pellets 5100 are already deposited. Here, on the upper surface of the substrate 5120, a repulsive force is generated in a direction parallel to the upper surface of the substrate 5120. A horizontal magnetic field (also called a horizontal magnetic field) is generated between the substrate 5120 and the target 5120. Since a potential difference is applied between the substrate 5120 and the target 5130, Therefore, the pellet 5100 is disposed on the upper surface of the substrate 5120 in the following direction: The magnetic field and the electric current act on the object, creating a force (Lorentz force). This can be understood by the left-hand rule.

[0573] The pellet 5100 has a larger mass than an atom. In order to move the surface, it is important to apply some kind of force from the outside. One of these forces is It is possible that the force is generated by the action of a magnetic field and an electric current. To provide sufficient force to move the top surface of 5120, the top surface of substrate 5120 must: The magnetic field parallel to the upper surface of the substrate 5120 is 10 G or more, preferably 20 G or more, and more preferably It is preferable to provide a region where the resistance is 30 G or more, and more preferably 50 G or more. On the upper surface of the plate 5120, a magnetic field parallel to the upper surface of the substrate 5120 The magnetic field is 1.5 times or more, preferably 2 times or more, and more preferably 3 times or more than the magnetic field perpendicular to the upper surface. It is preferable to provide an area where the thickness is 5 times or more, more preferably 5 times or more.

[0574] At this time, the magnet and the substrate 5120 move or rotate relative to each other. The direction of the horizontal magnetic field on the upper surface of the substrate 5120 continues to change. On the upper surface of the plate 5120, the pellet 5100 is subjected to forces from various directions. You can move to.

[0575] Also, when the substrate 5120 is heated as shown in FIG. 57(A), the pellet 510 0 and the substrate 5120, the resistance due to friction etc. is small. The pellet 5100 glides over the top surface of the substrate 5120. The transfer occurs with the flat surface facing the substrate 5120. When the particles reach the side of the pellet 5100, the sides are joined together. The oxygen atom on the side of 00 is released. The released oxygen atom causes the Since oxygen vacancies may be filled, a CAAC-OS with a low density of defect states is obtained. The temperature of the upper surface of the plate 5120 is, for example, 100°C or higher and lower than 500°C, or 150°C or higher and 450°C. or 170° C. or higher and lower than 400° C. Even in such a case, it is possible to form a CAAC-OS film.

[0576] In addition, the pellet 5100 is heated on the substrate 5120, whereby the atoms are rearranged. The distortion of the structure caused by the collision of the ions 5101 is relaxed. 100 is almost a single crystal. Pellet 5100 is almost a single crystal. Even if the pellets 5100 are heated after being bonded together, the pellets 5100 themselves do not expand. Therefore, the gaps between the pellets 5100 widen, and the crystallization Defects such as grain boundaries do not form, and crevasses do not form.

[0577] In addition, the CAAC-OS is not made of a single-crystal oxide semiconductor. The aggregates of pellets 5100 (nanocrystals) resemble bricks or blocks stacked on top of each other. In addition, there are no grain boundaries between the pellets 5100. Heating during film formation, heating after film formation, or bending can cause deformation such as shrinkage in CAAC-OS. Even in such a case, it is possible to relieve local stress or release strain. This structure is suitable for use in flexible semiconductor devices. The resulting arrangement is like a disorderly stack of Red 5100 (nanocrystals).

[0578] When the target 5130 is sputtered by the ions 5101, not only the pellet 5100 but also Zinc oxide is lighter than pellet 5100. Therefore, it reaches the upper surface of the substrate 5120 first. A zinc oxide layer 5102 having a thickness of 2 nm or more and 5 nm or less, or 0.5 nm or more and 2 nm or less, is formed. Figure 59 shows a schematic cross-sectional view.

[0579] As shown in FIG. 59(A), a pellet 5105a and a pellet Here, the pellets 5105a and 5105b are deposited. The pellets 5105c are arranged so that their sides are in contact with each other. After being deposited on pellet 5105b, the pellet 510 slides on pellet 5105b. In another aspect of FIG. 5a, a plurality of particles 510 detached from the target along with zinc oxide. 3 is crystallized by heating from the substrate 5120 to form a region 5105a1. The number of particles 5103 may include oxygen, zinc, indium, and gallium, among others.

[0580] As shown in FIG. 59(B), the region 5105a1 is integral with the pellet 5105a. The pellet 5105c is formed by the side surface of the pellet 5105a. Place it so that it is in contact with another side of 5105b.

[0581] Next, as shown in FIG. 59(C), a pellet 5105d is further added to the pellet 5105a2. After being deposited on pellet 5105a2 and pellet 5105b, It slides on the other side of the pellet 5105c. The pellet 5105e slides on the zinc oxide layer 5102.

[0582] As shown in FIG. 59(D), the pellet 5105d has a side surface similar to that of the pellet 51. The pellet 5105e is placed so that its side faces the pellet 5105a2. Also, the other side of the pellet 5105d is placed in contact with the other side of the pellet 5105c. On the surface, a plurality of particles 5103 peeled off from the target 5130 together with zinc oxide are formed. Heat from plate 5120 causes crystallization, forming region 5105d1.

[0583] As described above, the piled pellets are arranged so that they come into contact with each other, and the side surfaces of the pellets are The growth occurs to form a CAAC-OS on the substrate 5120. The individual pellets of AC-OS are larger than those of nc-OS. The difference in size between (3) and (2) corresponds to the growth after deposition.

[0584] In addition, the gaps between the pellets become extremely small, forming one large pellet. One large pellet may have a single crystal structure. The size is 10 nm or more and 200 nm or less, 15 nm or more and 100 nm or less when viewed from the top surface, or In this case, the size of the transistors used can be between 20 nm and 50 nm. In an oxide semiconductor, a channel formation region may be contained in one large pellet. That is, a region having a single crystal structure can be used as a channel forming region. As the size of the lattice increases, the region with a single crystal structure becomes the channel formation region of the transistor. , may be used as source and drain regions.

[0585] In this way, the channel formation region of the transistor and the like are formed in a region having a single crystal structure. By doing so, it may be possible to improve the frequency characteristics of the transistor.

[0586] Based on the above model, it is assumed that the pellet 5100 is deposited on the substrate 5120. CAAC-OS can be deposited even when the surface does not have a crystalline structure. This indicates that the growth mechanism is different from epitaxial growth. AC-OS does not require laser crystallization and can be grown uniformly even on large glass substrates. For example, if the structure of the upper surface (surface to be formed) of the substrate 5120 is an amorphous structure (e.g., It is possible to form a CAAC-OS film even on amorphous silicon oxide.

[0587] In addition, even if the upper surface of the substrate 5120 on which the formation is performed is uneven, the CAAC-OS It can be seen that the pellets 5100 are arranged along the shape of the substrate 5120. If the surface is atomically flat, the pellet 5100 will have a flat surface that is parallel to the ab plane. If the thickness of the pellet 5100 is uniform, it is flat and has a uniform thickness. A layer with high crystallinity is formed. Then, the layer is stacked in n layers (n is a natural number). By doing so, CAAC-OS can be obtained.

[0588] On the other hand, even if the upper surface of the substrate 5120 has irregularities, the CAAC-OS can be easily formed by the pellet 51 The structure is made up of n layers (n is a natural number) of layers in which 00 are arranged along the unevenness. Because the surface of the CAAC-OS is uneven, gaps tend to form between the pellets. However, even in this case, intermolecular forces act between the pellets 5100, and unevenness may occur. Even if the pellets are uneven, they are arranged so that the gaps between them are as small as possible. Furthermore, a CAAC-OS having high crystallinity can be obtained.

[0589] Since the CAAC-OS film is formed using this model, the sputtered particles are distributed evenly across the film thickness. It is preferable that the sputtered particles are in the form of thick dices. In this case, the surface facing the substrate 5120 is not uniform, and the thickness and crystal orientation cannot be made uniform. There is.

[0590] The film formation model shown above allows for highly crystalline films to be formed even on a surface with an amorphous structure. Therefore, a CAAC-OS having the desired properties can be obtained.

[0591] As described above, the structures and methods described in this embodiment mode may be appropriately combined with the structures and methods described in other embodiments. They can be used in combination.

[0592] (Embodiment 7) In this embodiment, a display device having a display function using the above-described transistor is An example of the device will be described below with reference to FIGS. 40 to 42.

[0593] 40(A) is a top view showing an example of a display device. 0 is a pixel portion 702 provided on the first substrate 701 and a A source driver circuit portion 704 and a gate driver circuit portion 706 are driver circuits, and a pixel 702, the source driver circuit section 704, and the gate driver circuit section 706. The sealing material 712 and the second substrate 701 are disposed opposite to each other. The first substrate 701 and the second substrate 705 are bonded to each other by a sealant 712. That is, the pixel section 702, the source driver circuit section 704, and the gate electrode 706 are sealed. The gate driver circuit section 706 is formed by the first substrate 701, the sealing material 712, and the second substrate 705. Although not shown in FIG. 40(A), the first substrate 701 and the second substrate 702 are sealed. A display element is provided between the substrates 705 .

[0594] The display device 700 is surrounded by a sealant 712 on the first substrate 701. The pixel section 702, the source driver circuit section 704, and the gate driver circuit section 706 are arranged in a region different from the region. The flexible printed circuit (FPC) terminal 708 is electrically connected to the flexible printed circuit (FPC) circuit 706. In addition, the FPC terminal section 708 is provided with an FP The pixel section 702 and the source driver circuit section 704 are connected by the FPC 716. Various signals are supplied to the pixel portion 702, the gate driver circuit portion 706, and the like. The base driver circuit section 704, the gate driver circuit section 706, and the FPC terminal section 708 are , and signal lines 710a are connected to the FPC 716. The pixel section 702, the source driver circuit section 704, and the gate driver 706 are connected via a signal line 710a. It is provided to a circuit portion 706 and an FPC terminal portion 708 .

[0595] 40(B) is a top view showing an example of a display device. 40(A) in place of the pixel portion 702 of the display device 700. 2, and signal line 710b is used instead of signal line 710a.

[0596] Furthermore, the display devices 700 and 800 may be provided with a plurality of gate driver circuit units 706. In addition, the display devices 700 and 800 include a source driver circuit section 704 and a gate driver circuit section 705. 7 shows an example in which the buffer circuit section 706 is formed on the same first substrate 701 as the pixel sections 702 and 802. However, the present invention is not limited to this configuration. For example, the gate driver circuit section 706 alone may be connected to the first The source driver circuit section 704 may be formed on the first substrate 701, or only the source driver circuit section 704 may be formed on the first substrate 701. In this case, a source driver circuit or a gate driver A substrate on which a circuit or the like is formed (for example, a driving circuit formed of a single crystal semiconductor film or a polycrystalline semiconductor film) The first substrate 701 may be mounted on the second substrate 702.

[0597] The method of connecting the separately formed drive circuit board is not particularly limited, and may be any of the following: (Chip On Glass) method, wire bonding method, etc. can be used. In this specification, the term "display device" refers to an image display device or a light source (illumination device). Also refers to connectors such as FPC and TCP (Tape Carrier) The module has a printed wiring board at the end of the TCP. The module or display element is connected to a drive circuit board or IC ( The display device also includes all modules on which a display device (integrated circuit) is directly mounted.

[0598] The display devices 700 and 800 include pixel sections 702 and 802, source driver circuit sections The gate driver circuit section 704 and the gate driver circuit section 706 have a plurality of transistors. A transistor which is one embodiment of the semiconductor device can be used.

[0599] The display device 700 is configured to use a liquid crystal element as a display element, and the display device 80 No. 0 is a configuration in which a light-emitting element is used as a display element.

[0600] Note that a display element, a display device which is a device having a display element, a light-emitting element, and a light-emitting element A light-emitting device, which is a device for emitting light, can take various forms or have various elements. An example of a display element, a display device, a light-emitting element, or a light-emitting device is an EL (electroluminescence) Luminescence) elements (EL elements containing organic and inorganic materials, organic EL elements, inorganic EL elements) , LED (white LED, red LED, green LED, blue LED, etc.), transistor (electric current-dependent light-emitting transistors), electron-emitting devices, liquid crystal devices, electronic ink, electrophoretic devices Child, Grating Light Valve (GLV), Plasma Display (PDP), MEM Display elements using microelectromechanical systems (S), digital microphones Digital Micro Shutter (DMD), Digital Micro Shutter (DMS), MIRAS OL (registered trademark), IMOD (Interference Modulation) element, shutter MEMS display element using the optical interference method, MEMS display element using the electrowetting method Magnetic devices, piezoelectric ceramic displays, carbon nanotubes, etc. Some display media have display characteristics such as contrast, brightness, reflectance, and transmittance that change depending on the display. An example of a display device using an EL element is an EL display. An example of a display device using electrons is a field emission display (FED) or is a SED (Surface-conduction E) flat panel display. LCD displays include liquid crystal displays. An example of the device is a liquid crystal display (transmissive liquid crystal display, semi-transmissive liquid crystal display). LCD, reflective LCD, direct view LCD, projection LCD) An example of a display device using electronic ink or electrophoretic elements is electronic paper. In addition, when realizing a semi-transmissive liquid crystal display or a reflective liquid crystal display, In this case, a part or all of the pixel electrodes may function as a reflective electrode. For example, a part or the whole of the pixel electrode may be made of aluminum, silver, etc. Furthermore, in this case, a memory circuit such as an SRAM can be provided under the reflective electrode. This makes it possible to further reduce power consumption.

[0601] First, the common parts of the display device 700 and the display device 800 will be explained, and then the differences will be explained. Regarding the display device 700 and the display device 800, the details thereof will be explained with reference to FIGS. 41 to 43. I will explain.

[0602] <Explanation of common parts of display devices> FIG. 41 is a cross-sectional view corresponding to the cut surface taken along the dashed line QR shown in FIG. 40(A). FIG. 42 is a cross-sectional view corresponding to the cut surface taken along the dashed line VW shown in FIG. 40(B). .

[0603] The display devices 700 and 800 shown in FIGS. 41 and 42 include a wiring section 711 and a pixel section 702 and 802 , a source driver circuit section 704 , and an FPC terminal section 708 . The lead wiring section 711 includes a signal line 710a or a signal line 710b.

[0604] The signal line 710a of the wiring portion 711 is connected to the transistors 750 and 752. The conductive film is formed in the same process as the conductive film that functions as the source electrode and the drain electrode. The signal line 710b of the routing wiring section 711 is connected to the gate electrodes of the transistors 750 and 752. The signal line 710a is formed in a process different from that of the source electrode and the drain electrode. 710b is a conductive film formed by the same process as the conductive film that functions as the gate electrodes of the transistors 750 and 752. A conductive film formed by a process different from that of the gate electrode, source electrode, or drain electrode. Alternatively, a conductive film formed by

[0605] The FPC terminal portion 708 includes a connection electrode 760, an anisotropic conductive film 780, and an FPC 71. The connection electrode 760 is connected to the source electrode layer and the drain electrode layer of the transistor 750. The connection electrode 760 is formed in the same process as the conductive film that functions as the electrode layer. The terminal of the electrode 716 is electrically connected to the electrode 716 via an anisotropic conductive film 780 .

[0606] In the display devices 700 and 800 shown in FIGS. 41 and 42, the pixel sections 702 and 8 02 includes a transistor 750, and the source driver circuit portion 704 includes a transistor 752. The transistor 750 has the same structure as that of the transistor 750 shown in Embodiment 3. The transistor 752 has the same structure as the transistor 390. The transistors 750 and 752 have the same configuration as the transistor 394. The configuration is limited to the configuration of transistor 390 and transistor 394, respectively. However, other transistor configurations may be used as appropriate.

[0607] The transistor used in this embodiment is made of a highly purified oxide in which the formation of oxygen vacancies is suppressed. The semiconductor film can reduce the current value in the off state (off current value). This allows the retention time of electrical signals such as image signals to be extended, and writing is not possible when the power is on. Therefore, the frequency of refresh operations can be reduced. This has the effect of reducing power consumption.

[0608] In addition, the transistor used in this embodiment is highly purified and the formation of oxygen vacancies is suppressed. The oxide semiconductor film provides relatively high field-effect mobility, enabling high-speed operation. For example, by using such a transistor capable of high-speed driving in a liquid crystal display device, The switching transistor in the pixel section and the driver transistor used in the drive circuit section are the same. In other words, it can be formed on a single substrate, such as a silicon wafer, as a separate driving circuit. Therefore, it is not necessary to use a semiconductor device formed by a semiconductor device, and the number of parts of the semiconductor device can be reduced. In addition, by using a transistor that can be driven at high speed in the pixel portion, High quality images can be provided.

[0609] In addition, a signal connected to a transistor in a pixel portion and a transistor used in a driver circuit portion A wiring containing copper can be used as the wiring. The device has little signal delay caused by wiring resistance, making it possible to display on a large screen.

[0610] In this embodiment, the transistor 750 included in the pixel portion 702 and 802 The transistor 752 included in the source driver circuit section 704 has the same size. However, the present invention is not limited to this. The size (L / W) or the number of transistors used can be changed as needed. 41 and 42, the gate driver circuit section 706 can Although not shown, by changing the connection destination or the connection method, the source driver circuit section It can have the same configuration as 704.

[0611] 41 and 42, the transistors 750 and 752 have A planarization insulating film 770 is provided on the insulating films 764 and 766 .

[0612] The insulating film 766 can be formed using the same materials and the same insulating film 376 described in the above embodiment. It can be formed by a manufacturing method.

[0613] The planarization insulating film 770 may be made of polyimide resin, acrylic resin, or polyimide ammonia. Resin with heat resistance such as benzocyclobutene resin, polyamide resin, epoxy resin, etc. In addition, a plurality of insulating films made of these materials can be stacked. In this way, the planarization insulating film 770 may be formed. It may also be composed.

[0614] In addition, a conductive film serving as a source electrode and a drain electrode of the transistor 750 The conductive film 772 or the conductive film 844 is connected to one of the electrodes. A pixel electrode, which is formed on the planarization insulating film 770 and functions as one electrode of the display element, is formed on the planarization insulating film 770. The conductive film 772 is preferably a conductive film that transmits visible light. The conductive film may be made of a material selected from the group consisting of indium (In), zinc (Zn), and tin (Sn). In addition, the conductive film 844 may be a reflective conductive film. It is preferable to use

[0615] <Configuration Example 1 of a Display Device Using Liquid Crystal Elements as Display Elements> The display device 700 shown in FIG. 41 includes a liquid crystal element 775. The liquid crystal element 775 includes a conductive film The conductive film 774 is formed on the second substrate 705. The display device 700 shown in FIG. The alignment state of the liquid crystal layer 776 changes depending on the voltage applied to the conductive film 772 and the conductive film 774. This controls whether light is transmitted or not, allowing images to be displayed.

[0616] Although not shown in FIG. 41, the conductive films 772 and 774 are in contact with the liquid crystal layer 776. An alignment film may be provided on each of the liquid crystal layers.

[0617] The display device 700 also includes a light-shielding film 738, an insulating film 734, and an adhesive film 736 on the second substrate 705 side. The colored film 736 is provided at a position overlapping with the liquid crystal element 775, and the wiring A light-shielding film 738 is provided on the wiring portion 711 and the source driver circuit portion 704. The color film 736 and the light-shielding film 738 are covered with an insulating film 734. The transistor 752 and the transistor 750 in the pixel portion overlap with the light-shielding film 738. It is possible to prevent external light from being irradiated. Note that a colored film may be provided instead of the light-shielding film 738.

[0618] Although not shown in FIG. 41, optical components such as a polarizing member, a phase difference member, and an anti-reflection member may be used. For example, a circular polarization substrate and a retardation substrate may be used. Alternatively, a backlight, a sidelight, or the like may be used as the light source.

[0619] The first substrate 701 and the second substrate 705 may be, for example, a glass substrate. In addition, flexible substrates are used as the first substrate 701 and the second substrate 705. The flexible substrate may be, for example, a plastic substrate.

[0620] In addition, a spacer 778 is provided between the first substrate 701 and the second substrate 705 . The spacers 778 are columnar spacers obtained by selectively etching the insulating film. The spacers are provided to control the film thickness (cell gap) of the liquid crystal layer 776. A spherical spacer may be used as 778.

[0621] When liquid crystal elements are used as display elements, thermotropic liquid crystals, low molecular weight liquid crystals, polymer liquid crystals, The liquid crystals that can be used include polymer dispersed liquid crystals, ferroelectric liquid crystals, and antiferroelectric liquid crystals. Depending on the conditions, the liquid crystal material can be in a cholesteric phase, a smectic phase, a cubic phase, or a chiral phase. It shows nematic phase, isotropic phase, etc.

[0622] In addition, when the in-plane switching method is adopted, a liquid crystal that exhibits a blue phase without using an alignment film may be used. The blue phase is one of the liquid crystal phases, and when the temperature of cholesteric liquid crystal is increased, the cholesteric The blue phase appears just before the transition from the black phase to the isotropic phase. Therefore, in order to improve the temperature range, a liquid crystal composition containing a chiral agent of several weight percent or more is used. The liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent is used in a liquid crystal layer. It has a short response time and is optically isotropic. It also contains a liquid crystal that exhibits a blue phase and a chiral agent. The liquid crystal composition does not require alignment treatment and has little viewing angle dependency. Since no rubbing treatment is required, static electricity caused by rubbing treatment can be reduced. This can prevent electrical breakdown and reduce defects and damage to the liquid crystal display device during the manufacturing process. can.

[0623] When a liquid crystal element is used as a display element, a TN (Twisted Nematic) ) mode, IPS (In-Plane-Switching) mode, FFS (Frin ge Field Switching) mode, ASM (Axially Symme tric aligned Micro-cell) mode, OCB(Optical Compensated Birefringence mode, FLC (Ferrero) lectric Liquid Crystal) mode, AFLC (AntiFerr It can be used in dielectric liquid crystal mode. .

[0624] In addition, normally black type liquid crystal display devices, for example, those employing vertical alignment (VA) mode The liquid crystal display device may be a transmission type. For example, MVA (Multi-Domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode , ASV mode, etc. can be used.

[0625] The display method in the pixel section 702 may be a progressive method, an interlace method, or the like. In addition, RG can be used as a color element controlled by pixels when displaying colors. For example, the R pixel and the G pixel are not limited to the three colors R, G, and B (R represents red, G represents green, and B represents blue). It may be composed of four pixels: a blue pixel, a blue pixel, and a white pixel. As shown above, two colors of RGB compose one color element, and two different colors are created by the color element. Alternatively, you can add one or more colors such as yellow, cyan, magenta, etc. to RGB. The size of the display area may be different for each dot of the color element. However, the disclosed invention is not limited to color display devices, but also includes monochrome display devices. The present invention can also be applied to display devices such as:

[0626] <Display device using light-emitting elements as display elements> The display device 800 shown in FIG. 42 includes a light-emitting element 880. The light-emitting element 880 includes a conductive film The display device 800 includes a light-emitting element 880. The EL layer 846 of the display panel emits light, thereby displaying an image.

[0627] 42, the display device 800 includes a planarization insulating film 770 and a conductive film 844. An insulating film 830 is provided. The insulating film 830 covers part of the conductive film 844. The element 880 has a top-emission structure. Therefore, the conductive film 848 has a light-transmitting property. It transmits light emitted by the EL layer 846. In this embodiment, For example, a light emitting structure for emitting light to the conductive film 844 side is shown, but the present invention is not limited to this. a bottom emission structure in which light is emitted to both the conductive film 844 and the conductive film 848; It can also be applied to dual emission structures.

[0628] A colored film 836 is provided at a position overlapping the light emitting element 880, and a colored film 836 is provided at a position overlapping the insulating film 830. A light-shielding film 838 is provided in the position where the light-shielding film 838 is to be drawn, the wiring portion 711, and the source driver circuit portion 704. The colored film 836 and the light-shielding film 838 are covered with an insulating film 834. Light-emitting element The space between the insulating film 834 and the insulating film 834 is filled with a sealing film 832. Although the configuration in which the colored film 836 is provided has been exemplified, the present invention is not limited to this. For example, When the EL layer 846 is formed by coloring, the colored film 836 is not provided. You may do so.

[0629] Next, regarding a display device 700a which is a modification of the display device 700 shown in FIG. 41, This will be explained using:

[0630] <Configuration Example 2 of a Display Device Using Liquid Crystal Elements as Display Elements> The display device 700a shown in FIG. 43 includes a liquid crystal element 775. The liquid crystal element 775 is a conductive The conductive film 773 is formed on the first substrate 70. 43. The planarization insulating film 770 on the substrate 1 functions as a reflective electrode. The display device 700a utilizes external light, reflects the light at the conductive film 773, and displays the light through the colored film 836. This is a so-called reflective color liquid crystal display device.

[0631] In the display device 700a shown in FIG. 43, the planarization insulating film 770 of the pixel section 702 The unevenness is formed by, for example, forming the planarization insulating film 770 with an organic resin film or the like. The reflecting layer can be formed by forming a surface of the organic resin film with irregularities. The conductive film 773 functioning as an electrode is formed along the unevenness. When light is incident on the conductive film 773, it can be diffused and reflected by the surface of the conductive film 773. This makes it possible to improve visibility.

[0632] The display device 700a also includes a light-shielding film 838, an insulating film 834, and a The display device 700a includes a colored film 836. The conductive film 773 of the display device 700a includes a transistor The conductive film 750 is electrically connected to the source electrode or the drain electrode. The conductive film 773 can be formed by using the materials and the method described in the conductive film 844. Cut.

[0633] The display device 700a also includes a capacitor 790. The capacitor 790 has a pair of electrodes More specifically, the capacitor 790 has an insulating film between the source and drain of the transistor 750. A conductive film formed in the same process as a conductive film that functions as an electrode or a drain electrode is used as one of the electrodes. The conductive film is used as an electrode and is formed in the same process as the conductive film that functions as the gate electrode of the transistor 750. The conductive film 792 is used as the other electrode, and the transistor 750 is provided between the conductive films. The insulating film is formed in the same process as the insulating film that functions as the gate insulating film.

[0634] As described above, the transistor which is a semiconductor device of one embodiment of the present invention can be used in various display devices. It is possible to apply

[0635] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0636] (Embodiment 8) In this embodiment, a display device in which a semiconductor device of one embodiment of the present invention can be used will be described. This will be explained using FIG.

[0637] The display device shown in FIG. 44(A) has a region having pixels of a display element (hereinafter referred to as a pixel portion 502). ) and a circuit section ( hereinafter referred to as a drive circuit section 504), and a circuit having a function of protecting the element (hereinafter referred to as a protection circuit 50 6) and a terminal portion 507. Note that the protection circuit 506 is not provided. That's fine.

[0638] A part or the whole of the driver circuit portion 504 is formed on the same substrate as the pixel portion 502. This makes it possible to reduce the number of parts and terminals. When a part or all of the pixel portion 502 is not formed on the same substrate, the driving circuit A part or the whole of the path portion 504 is COG or TAB (Tape Automated Bearing). It can be implemented by

[0639] The pixel section 502 is arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). The display device has a circuit for driving a plurality of display elements (hereinafter referred to as pixel circuit 501), The path section 504 is a circuit (hereinafter referred to as a gate driver) that outputs a signal (scanning signal) for selecting a pixel. 504a), for supplying signals (data signals) for driving the display elements of the pixels. The source driver 504b includes a driving circuit such as the circuit (hereinafter referred to as a source driver 504b).

[0640] The gate driver 504a includes a shift register and the like. A signal for driving the shift register is inputted through the terminal section 507, and a signal for outputting the shift register is outputted. For example, the gate driver 504a receives a start pulse signal, a clock signal, etc. The gate driver 504a receives a scanning signal and outputs a pulse signal. The gate has a function of controlling the potential of the scanning lines GL_1 to GL_X. A plurality of drivers 504a are provided, and the plurality of gate drivers 504a drive the scanning lines GL_1 to Alternatively, the gate driver 504a may control the GL_X by dividing it into the initialization signal However, the gate driver 50 has a function of supplying 4a may also provide other signals.

[0641] The source driver 504b includes a shift register and the like. Through the terminal section 507, signals for driving the shift register as well as the source of the data signal are transmitted. The source driver 504b receives a signal (image signal) that is to be output from the pixel circuit The source driver 504b has a function of generating a data signal to be written to the source driver 501. A data signal is generated in accordance with a pulse signal obtained by inputting a start pulse, a clock signal, etc. The source driver 504b has a function of controlling the output of a data signal. The signal lines DL_1 to DL_Y are connected to the power supply 101. Alternatively, the source driver 504b may have a function to supply an initialization signal. However, the present invention is not limited to this, and the source driver 504b may supply other signals. It is Noh.

[0642] The source driver 504b is configured using, for example, a plurality of analog switches. The source driver 504b sequentially turns on a plurality of analog switches, The image signal can be time-divided and output as a data signal. The source driver 504b may be configured using the same.

[0643] Each of the plurality of pixel circuits 501 is connected to one of the plurality of scanning lines GL to which a scanning signal is applied. A pulse signal is input via the signal line DL, and a data signal is given via one of the signal lines DL. A data signal is input to each of the pixel circuits 501. 04a controls the writing and holding of data of the data signal. For example, The pixel circuit 501 is connected to a gate driver 506 via a scanning line GL_m (m is a natural number equal to or less than X). A pulse signal is input from O4a, and the signal line DL_n (n is A data signal is input from the source driver 504b via a line (Y) (a natural number equal to or less than Y).

[0644] The protection circuit 506 shown in FIG. 44(A) is, for example, a gate driver 504a and a pixel circuit 5 01. Alternatively, the protection circuit 506 is connected to the scanning line GL, which is the wiring between the source driver The signal line DL is connected between the driver 504b and the pixel circuit 501. The circuit 506 can be connected to a wiring between the gate driver 504a and the terminal section 507. Alternatively, the protection circuit 506 may be provided on the wiring between the source driver 504b and the terminal section 507. The terminal section 507 can be connected to the display device via an external circuit. This refers to the part where terminals for inputting control signals and image signals are provided.

[0645] When a potential outside a certain range is applied to the wiring to which the protection circuit 506 is connected, the protection circuit 506 This is a circuit that brings one wire into electrical continuity with another wire.

[0646] As shown in FIG. 44A, a pixel section 502 and a driver circuit section 504 are provided with a protection circuit 50. 6, ESD (Electro Static Discharge: This can improve the resistance of the display device to overcurrents caused by electrostatic discharges and the like. However, the configuration of the protection circuit 506 is not limited to this. For example, A configuration in which a protection circuit 506 is connected, or a configuration in which the protection circuit 506 is connected to the source driver 504b Alternatively, a configuration in which a protection circuit 506 is connected to the terminal portion 507 may be used. It can also be done as follows.

[0647] In FIG. 44(A), the gate driver 504a and the source driver 504b Therefore, although an example in which the driver circuit portion 504 is formed is shown, the present invention is not limited to this configuration. For example, only the gate driver 504a is formed, and a separately prepared source driver circuit is formed. A substrate (for example, a drive circuit substrate formed of a single crystal semiconductor film or a polycrystalline semiconductor film) is implemented. It may also be configured to be equipped with

[0648] Furthermore, the plurality of pixel circuits 501 shown in FIG. 44(A) may be, for example, a configuration shown in FIG. 44(B). It can be said that:

[0649] The pixel circuit 501 shown in FIG. 44B includes a liquid crystal element 570, a transistor 550, and a capacitor. and a capacitance element 560.

[0650] The transistor described in the above embodiment can be used as the transistor 550 as appropriate. can.

[0651] The potential of one of the pair of electrodes of the liquid crystal element 570 is set appropriately according to the specifications of the pixel circuit 501. The orientation state of the liquid crystal element 570 is set by the written data. A common potential is applied to one of a pair of electrodes of the liquid crystal element 570 included in each of the pixel circuits 501. In addition, a pair of liquid crystal elements 570 of the pixel circuits 501 in each row may be applied with a common potential. One of the electrodes may be given a different potential.

[0652] For example, the display device including the liquid crystal element 570 can be driven in a TN mode, an STN mode, or the like. Mode, VA mode, ASM (Axially Symmetric Aligned Mode) Micro-cell mode, OCB (Optically Compensated Birefringence mode, FLC (Ferroelectric Liquid Crystal id Crystal) mode, AFLC (AntiFerroelectric Li Quid Crystal) mode, MVA mode, PVA (Patterned Ve Vertical Alignment mode, IPS mode, FFS mode, or TBA (Transverse Bend Alignment) mode may also be used. In addition to the above-mentioned driving method, the display device can also be driven by an ECB (Electric Carrier Board) or the like. Ally Controlled Birefringence mode, PDLC (P Polymer Dispersed Liquid Crystal (PNLC) mode (Polymer Network Liquid Crystal) mode, guest However, there are various types of liquid crystal elements and their driving methods, and they are not limited to these. A variety of materials can be used.

[0653] In the pixel circuit 501 in the mth row and the nth column, the source electrode or the drain electrode of the transistor 550 One of the electrodes is electrically connected to the signal line DL_n, and the other is a pair of electrodes of the liquid crystal element 570. The gate electrode of the transistor 550 is electrically connected to the other of the scan lines GL _m. The transistor 550 can be turned on or off. This has the function of controlling the writing of data of the data signal.

[0654] One of the pair of electrodes of the capacitor 560 is connected to a wiring to which a potential is supplied (hereinafter, a potential supply line VL ) and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 570. The value of the potential of the potential supply line VL is set appropriately according to the specifications of the pixel circuit 501. The capacitor 560 functions as a storage capacitor for storing written data.

[0655] For example, in a display device having the pixel circuit 501 of FIG. 44(B), for example, The pixel circuits 501 in each row are sequentially selected by the gate driver 504a shown in FIG. 550 is turned on to write data of the data signal.

[0656] The pixel circuit 501 in which data has been written is turned off by turning off the transistor 550. By repeating this process for each row, an image can be displayed.

[0657] Furthermore, the plurality of pixel circuits 501 shown in FIG. 44(A) may be, for example, a configuration shown in FIG. 44(C). It can be said that:

[0658] The pixel circuit 501 shown in FIG. 44C includes transistors 552 and 554 and a capacitor. The transistor 552 and the light-emitting element 572 are connected to each other. The transistors described in the above embodiments are applied as appropriate to either one or both of the transistors 554. It is possible.

[0659] One of the source and drain electrodes of the transistor 552 is supplied with a data signal. The gate voltage of the transistor 552 is electrically connected to the wiring (signal line DL_n). The electrodes are electrically connected to wiring (scanning lines GL_m) to which gate signals are applied.

[0660] Transistor 552 is turned on or off to transfer the data of the data signal. It has the function of controlling the writing of data.

[0661] One of the pair of electrodes of the capacitor 562 is connected to a wiring to which a potential is applied (hereinafter, a potential supply line VL _a), and the other is electrically connected to the source electrode and drain electrode of the transistor 552. The second electrode is electrically connected to the other of the first and second electrodes.

[0662] The capacitor 562 functions as a storage capacitor for holding written data.

[0663] One of the source electrode and the drain electrode of the transistor 554 is connected to the potential supply line VL_a. Furthermore, the gate electrode of transistor 554 is electrically connected to the It is electrically connected to the other of the source electrode and the drain electrode.

[0664] One of the anode and cathode of the light emitting element 572 is electrically connected to the potential supply line VL_b. The other is electrically connected to the other of the source electrode and drain electrode of the transistor 554. will be done.

[0665] The light emitting element 572 may be, for example, an organic electroluminescence element (also known as an organic EL element). However, the light emitting element 572 is not limited to this. Alternatively, an inorganic EL element made of an inorganic material may be used.

[0666] A high power supply potential VDD is applied to one of the potential supply lines VL_a and VL_b. and the other is supplied with a low power supply potential VSS.

[0667] In a display device having the pixel circuit 501 of FIG. 44(C), for example, The pixel circuits 501 in each row are sequentially selected by the gate driver 504a, and the transistors 552 are turned on. The data signal is written by turning it on.

[0668] The pixel circuit 501 to which the data has been written is turned off by turning off the transistor 552. Furthermore, the transistor 554 is held in a holding state in response to the potential of the written data signal. The amount of current flowing between the source electrode and the drain electrode is controlled, and the light emitting element 572 The light is emitted at a brightness that corresponds to the flow rate. By repeating this process row by row, an image can be displayed.

[0669] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0670] (Embodiment 9) In this embodiment, a display module in which the semiconductor device of one embodiment of the present invention can be used is describe...

Claims

[Claim 1] a first transistor and a second transistor on an insulating surface; the first transistor includes a first gate electrode, a first insulating film, a first oxide semiconductor film, a pair of first conductive films, a second insulating film, and a second gate electrode; the first insulating film is provided between the first gate electrode and the first oxide semiconductor film; the first gate electrode is connected to the second gate electrode through an opening provided in the first insulating film and the second insulating film in a channel width direction of the first transistor; the pair of first conductive films are in contact with the first oxide semiconductor film; the second insulating film is provided between the first oxide semiconductor film and the second gate electrode; the first oxide semiconductor film contains an impurity element in a region that does not overlap with the second gate electrode and the pair of first conductive films; the second transistor includes a second oxide semiconductor film, a pair of second conductive films, the second insulating film, and a third gate electrode; the pair of second conductive films are in contact with the second oxide semiconductor film; the second insulating film is provided between the second oxide semiconductor film and the third gate electrode; the second oxide semiconductor film contains the impurity element in a region that does not overlap with the third gate electrode and the pair of second conductive films.

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