Display device

Abstract

To provide a manufacturing method capable of reducing cost in a semiconductor device which has high opening ratio and has a capacitive element capable of increasing charge capacity; or provide a manufacturing method capable of reducing cost in the semiconductor device capable of reducing power consumption.SOLUTION: A mask formed by a process of using a multi-gradation photo mask is used to form a metal oxide film having a channel region, the metal oxide film functioning as a pixel electrode, and a source electrode and a drain electrode. An oxide insulation film is further formed on the metal oxide film having the channel region, and a nitride insulation film is formed on the oxide insulation film and the metal oxide film functioning as the pixel electrode; as a result, conductivity of the metal oxide film functioning as the pixel electrode can be improved.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an article, a method, or a manufacturing method. The invention relates to the manufacture or composition of matter. One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, or any of these devices. In particular, the present invention relates to a method for driving a transistor, for example, or a manufacturing method thereof. The present invention relates to a method for manufacturing a semiconductor device having a capacitor. [Background technology]

[0002] It is used in many flat panel displays, such as liquid crystal displays and light-emitting displays. The transistors used are made of amorphous silicon and single-crystal silicon formed on a glass substrate. It is made of silicon semiconductor such as silicon or polycrystalline silicon. Transistors using semiconductors are also used in integrated circuits (ICs).

[0003] In recent years, metal oxides that exhibit semiconductor properties have been used in transistors instead of silicon semiconductors. In this specification, metal oxides that exhibit semiconductor properties are referred to as oxides. We will call it a semiconductor.

[0004] For example, a transistor using zinc oxide or an In-Ga-Zn oxide as an oxide semiconductor may be used. A transistor is fabricated and used as a switching element for a pixel of a display device. A technique for this has been disclosed (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-123861 Summary of the Invention [Problem to be solved by the invention]

[0006] Display devices on the market tend to be larger, with screen sizes of 40 inches or more diagonally. Furthermore, development is underway with a view to screen sizes of 120 inches or more diagonally. For this reason, glass substrates used in display devices are becoming larger in area than the 8th generation. It's progressing.

[0007] As the area of ​​glass substrates increases, the exposure equipment used in the manufacturing process of display devices is becoming increasingly large. The photomasks used are becoming larger, and the cost of the photomasks is becoming an issue. Since 10th generation photomasks are expensive, costing over 100 million yen each, we are trying to reduce the number of photomasks. There is a need to develop a manufacturing process that reduces this.

[0008] On the other hand, in a liquid crystal display device, which is an example of a display device, the charge capacitance value of a capacitive element is increased. The more the electric field is applied, the more the liquid crystal molecules in the liquid crystal element can be kept aligned. In a display device that displays a still image, the period can be extended. This reduces the number of times image data needs to be rewritten, which reduces power consumption. Hopefully.

[0009] Therefore, in order to increase the charge capacity of the capacitance element, the area occupied by the capacitance element is increased. Specifically, there is a means to increase the area where the pair of electrodes overlap. Therefore, in the above display device, in order to increase the area where the pair of electrodes overlap, If the area of ​​the conductive film is increased, the aperture ratio of the pixel is reduced, and the display quality of the image is deteriorated. .

[0010] In view of the above, one embodiment of the present invention provides a capacitor that has a high aperture ratio and can increase the charge capacity. To provide a manufacturing method capable of reducing costs in a semiconductor device having a quantum element Another object of one embodiment of the present invention is to provide a semiconductor device capable of reducing power consumption. It is an object of the present invention to provide a manufacturing method that can reduce costs in the device. Another object of one embodiment of the present invention is to provide a novel semiconductor device. An object of one embodiment of the present invention is to provide a novel display device. The description of the problem does not preclude the existence of other problems. However, it is not necessary to solve all of these problems. Problems other than these may be solved by the specification, drawings, etc. It is clear from the description of the specification, drawings, claims, etc. From the above description, it is possible to extract other issues. [Means for solving the problem]

[0011] One embodiment of the present invention is to provide a method for manufacturing a photosensitive drum using a mask formed by a process using a multi-tone photomask. a metal oxide film having a channel region, a metal oxide film functioning as a pixel electrode, and a source electrode. The feature is that a source electrode and a drain electrode are formed using a multi-tone photomask. As a result, a mask having a first shape and a second thickness greater than the first thickness is formed. The metal oxide film and the conductive film on the substrate are etched using the mask of the first shape. The metal oxide film having the channel region and the metal oxide film functioning as the pixel electrode are formed by the above-mentioned method. Next, the mask of the first shape is processed to remove the mask in the region of the first thickness. , leaving the second thickness region as a mask of the second shape. Next, The conductive film formed on the metal oxide film is etched using a In this step, a capacitance line may be formed. An oxide insulating film is formed on the metal oxide film having a pixel region, and the oxide insulating film and the pixel electrode are By forming a nitride insulating film on the metal oxide film that functions as a pixel electrode, The conductivity of the metal oxide film can be increased.

[0012] One embodiment of the present invention is to form a gate electrode and a gate insulating film on an insulating surface, a first metal oxide film and a first conductive film are formed on the first conductive film; a first mask having an area having a thickness greater than the first thickness and an area having a second thickness greater than the first thickness; forming a second mask having the same thickness as the first mask; and The first conductive film and the first metal oxide film are etched using the etching solution, and the second conductive film is Then, the second and third conductive films, the second metal oxide film, and the third metal oxide film are formed. After processing the first mask to form a third mask and removing the second mask, The second conductive film is etched using a third mask to form a soaked layer on the second metal oxide film. A fourth conductive film and a fifth conductive film are formed to function as a source electrode and a drain electrode, respectively. Then, the third conductive film is removed. Next, the second metal oxide film, the fourth conductive film, and the fifth conductive film are removed. a first insulating film is formed on the film; and a second insulating film is formed on the first insulating film and the third metal oxide film. After forming the first insulating film and the second insulating film, a part of the first insulating film and the second insulating film are etched. An opening is formed in the second insulating film. Next, a portion of the insulating film that functions as a pixel electrode is formed in contact with the fifth conductive film. a sixth conductive film that contacts the third metal oxide film and functions as a capacitance line; and a seventh conductive film that contacts the third metal oxide film and functions as a capacitance line. This is a method for manufacturing a semiconductor device in which a film is formed.

[0013] The first insulating film has an opening on the third metal oxide film.

[0014] The second metal oxide film and the third metal oxide film have different hydrogen concentrations. The third metal oxide film has a higher hydrogen concentration than the second metal oxide film.

[0015] The third metal oxide film has electrical conductivity, and the third metal oxide film, the second insulating film, and The capacitor element is formed of a conductive film having a light-transmitting property.

[0016] The first metal oxide film, the second metal oxide film, and the third metal oxide film are light-transmitting. The first metal oxide film, the second metal oxide film, and the third metal oxide film have The first metal oxide film and the second metal oxide film have at least one of In, Ga, and Zn. It is preferable that the first metal oxide film and the third metal oxide film are composed of the same metal element. .

[0017] The first insulating film is formed using an oxide insulating film. The second insulating film preferably includes an oxide insulating film from which part of oxygen is released by the The insulating film is formed using a nitride insulating film. [Effects of the Invention]

[0018] According to one embodiment of the present invention, a capacitor element having a high aperture ratio and capable of increasing charge capacity can be provided. In the method for manufacturing a semiconductor device having a semiconductor device, the cost can be reduced. In a method for manufacturing a semiconductor device that can reduce the number of semiconductor devices, costs can be reduced. According to one embodiment of the present invention, a novel semiconductor device can be provided. According to one embodiment, a novel display device can be provided. It is to be noted that one embodiment of the present invention does not necessarily have these effects. It is not necessary for the invention to have all of the above effects. Effects other than these may be included in the specification, drawings, claims, etc. This is self-evident from the description, drawings, claims, etc. It is possible to extract effects other than these. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a semiconductor device. [Figure 2] FIG. 1 is a top view illustrating one mode of a pixel. [Figure 3] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 4] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 5] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 6] FIG. 1 is a top view illustrating one mode of a pixel. [Figure 7] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 8] FIG. 1 is a top view illustrating one mode of a pixel. [Figure 9] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 10] 1A to 1C are cross-sectional views illustrating one mode of a manufacturing method of an element substrate. [Figure 11] FIG. 1 is a cross-sectional view illustrating one embodiment of a transistor. [Figure 12] FIG. 1 is a diagram illustrating an electronic device. [Figure 13] FIG. 1 is a cross-sectional view illustrating one embodiment of an element substrate. [Figure 14] FIG. 1 is a top view illustrating one mode of a pixel. [Figure 15] FIG. 1 is a cross-sectional view illustrating one embodiment of a transistor. [Figure 16] FIG. 2 is a diagram illustrating a display module. [Figure 17] FIG. 10 is a diagram illustrating the temperature dependence of resistivity. [Figure 18] 1A and 1B are a top view and a cross-sectional view illustrating the structure of a sample. [Figure 19] FIG. 10 is a diagram illustrating the resistance value of a metal oxide film. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and the embodiments and methods thereof may be modified without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the design and details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments and examples. In the embodiments and examples described below, the same parts or parts having similar functions In the case of parts, the same symbols or the same hatch patterns are used in common among different drawings, and the repetition The explanation of repetition will be omitted.

[0021] In each figure described in this specification, the size of each component, the thickness of the film, or the area is The figures may be exaggerated for clarity and are not necessarily limited to that scale. stomach.

[0022] In addition, terms such as first, second, and third used in this specification are used interchangeably to avoid confusion of components. It is not intended to limit the number of items. The terms "second" or "third" can be used interchangeably to explain the present invention.

[0023] The functions of the "source" and "drain" are also different when the direction of the current changes during circuit operation. For this reason, in this specification, the terms "sauce" and "dressing" are used interchangeably. The terms "in" and "in" may be used interchangeably.

[0024] Voltage refers to the potential difference between two points, and potential refers to the electrostatic field at a certain point. This refers to the electrostatic energy (electrical potential energy) of a unit charge in a particle. However, in general, the potential difference between the potential at a certain point and a reference potential (for example, ground potential) This is simply called potential or voltage, and potential and voltage are often used synonymously. Therefore, in this specification, unless otherwise specified, the term "potential" may be read as "voltage." , voltage may be read as potential.

[0025] In this specification, when an etching step is performed after a photolithography step, The mask formed in the photolithography process is removed.

[0026] (Embodiment 1) In this embodiment, a capacitor element having a high aperture ratio and capable of increasing the charge capacity is provided. The object is to provide a manufacturing method capable of reducing costs in a semiconductor device having Another embodiment of the present invention is a semiconductor device capable of reducing power consumption. Therefore, one object is to provide a manufacturing method that can reduce costs.

[0027] In addition, in the metal oxide, an oxide semiconductor, which is a metal oxide having semiconductor properties, is used. In the case of a transistor, oxygen is an example of a defect that can lead to poor electrical characteristics of the transistor. For example, a transistor using an oxide semiconductor film containing oxygen vacancies The threshold voltage of the transistor tends to fluctuate in the negative direction, and the transistor tends to have normally-on characteristics. This is because oxygen vacancies in the oxide semiconductor film generate charges, which lower the resistance. If a transistor has normally-on characteristics, malfunctions are likely to occur during operation. This can cause various problems, such as the power consumption during non-operation being high. The electrical characteristics of transistors, typically the amount of change in threshold voltage, are measured by the application of thermal and stress tests. There is a growing problem.

[0028] In addition to oxygen deficiency, impurities such as silicon and carbon, which are constituent elements of the insulating film, also affect the Therefore, the impurities are mixed into the oxide semiconductor film, which causes poor electrical characteristics of the transistor. As a result, the resistance of the oxide semiconductor film is reduced, and the oxide semiconductor film is susceptible to deterioration over time and stress testing. This leads to a problem of an increase in the amount of fluctuation in the electrical characteristics of the transistor, typically the threshold voltage. There is.

[0029] In this embodiment, in addition to the problem to be solved by the present invention, In a semiconductor device including a transistor, An object is to reduce oxygen vacancies and the impurity concentration in the oxide semiconductor film.

[0030] In this embodiment mode, as a method for solving one of the above problems, a manufacturing method of a semiconductor device will be described. In this embodiment, a process using a multi-tone photomask is performed. forming a metal oxide film having a channel region, a source electrode, and a drain electrode; It is characterized by:

[0031] 1A shows an example of a semiconductor device. The semiconductor device shown in FIG. 1A includes a pixel portion 11 , a scanning line driving circuit 14, and a signal line driving circuit 16 are arranged parallel or approximately parallel to each other. The scanning lines 17 are parallel to each other and the potential of each of the scanning lines 17 is controlled by the scanning line driving circuit 14. n signal lines arranged in parallel or substantially parallel to each other, and the potentials of which are controlled by a signal line driving circuit 16. 19. Furthermore, the pixel section 11 has a plurality of pixels 13 arranged in a matrix. In addition, the capacitor lines 15 are arranged parallel or approximately parallel to each other along the signal lines 19. The capacitance lines 15 are arranged parallel or approximately parallel to each other along the scanning lines 17. The scanning line driving circuit 14 and the signal line driving circuit 16 may be collectively referred to as a driving circuit section. This is sometimes said.

[0032] Each scanning line 17 corresponds to one of the pixels 13 arranged in m rows and n columns in the pixel section 11. Each signal line 19 is electrically connected to n pixels 13 arranged in m rows and n Among the pixels 13 arranged in a column, m pixels 13 arranged in any one column are electrically connected. Both m and n are integers equal to or greater than 1. The capacitance lines 15 are arranged in m rows and n columns. Among the pixels 13 arranged in one row, the n-number of pixels 13 are electrically connected to the n-number of pixels 13 arranged in one row. The capacitance lines 15 are arranged parallel or approximately parallel to the signal lines 19. In this case, m pixels 13 arranged in any one of the columns of the pixels 13 arranged in m rows and n columns are 13 is electrically connected to

[0033] 1B and 1C show circuitry that can be used for the pixel 13 of the display device shown in FIG. 1A. 1 shows an example of a road configuration.

[0034] The pixel 13 shown in FIG. 1B includes a liquid crystal element 21, a transistor 22, and a capacitor 25. , has.

[0035] The potential of one of the pair of electrodes of the liquid crystal element 21 is set appropriately according to the specifications of the pixel 13 . The alignment state of the liquid crystal element 21 is set by the written data. A common potential is applied to one of the pair of electrodes of the liquid crystal element 21 of each of the liquid crystal display devices 3. Alternatively, different potentials may be applied to one of the pair of electrodes of the liquid crystal element 21 for each pixel 13 in each row. May be given.

[0036] The liquid crystal element 21 controls the transmission or non-transmission of light by the optical modulation action of the liquid crystal. The optical modulation effect of the liquid crystal is achieved by the electric field applied to the liquid crystal (horizontal electric field, vertical electric field). The liquid crystal element 21 is controlled by a vertical electric field (including a diagonal electric field or an oblique electric field). , nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, thermotropic liquid crystal, Examples include iotropic liquid crystal, ferroelectric liquid crystal, and antiferroelectric liquid crystal.

[0037] The display device having the liquid crystal element 21 can be driven in, for example, TN mode, VA mode, or the like. , ASM(Axially Symmetric Aligned Micro-cel l) mode, OCB (Optically Compensated Birefringence Gence mode, MVA mode, PVA (Patterned Vertical Alignment) mode, IPS mode, FFS mode, or TBA (Trans You can also use the (Verse Bend Alignment) mode. The present invention is not limited to the above, and various liquid crystal elements and driving methods thereof can be used.

[0038] Also, a liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent The liquid crystal element may be configured by the following. The liquid crystal that exhibits the blue phase has a response speed of 1 msec or less. Since it is short and optically isotropic, alignment treatment is not required and viewing angle dependency is small.

[0039] In the configuration of the pixel 13 shown in FIG. 1B, the source electrode and the drain electrode of the transistor 22 One of the electrodes is electrically connected to the signal line 19, and the other is the other of the pair of electrodes of the liquid crystal element 21. The gate electrode of the transistor 22 is electrically connected to the scanning line 17. The transistor 22 is turned on or off to The transistor 22 has a function of controlling the writing of signal data. The transistor described in any of Embodiments 1 to 7 can be used.

[0040] In the configuration of the pixel 13 shown in FIG. 1B, one of the pair of electrodes of the capacitor 25 is connected to a potential The other end is electrically connected to the other of the pair of electrodes of the liquid crystal element 21. The potential value of the capacitance line 15 is set appropriately according to the specifications of the pixel 13. The capacitor element 25 functions as a storage capacitor for storing written data. do.

[0041] For example, in a display device having the pixel 13 shown in FIG. 1B, the scanning line driving circuit 14 drives each row The pixels 13 are selected in sequence, the transistors 22 are turned on, and the data of the data signal is written. Enter.

[0042] The pixel 13 into which the data has been written is in a holding state when the transistor 22 is turned off. By performing this process row by row, an image can be displayed.

[0043] The pixel 13 shown in FIG. 1C includes a transistor 33 that switches the display element. a transistor 22 for controlling driving of the pixel, a transistor 35, a capacitor element 25, and a light-emitting element 31.

[0044] An example of the light-emitting element 31 is a light-emitting element including an anode, a cathode, and an EL layer sandwiched between the anode and the cathode. An example of an EL layer is a device in which light emission (fluorescence) from singlet excitons occurs. a layer having a material capable of emitting light from triplet excitons (phosphorescence); Materials capable of emitting light from single excitons (fluorescence) and materials capable of emitting light from triplet excitons (phosphorescence) The layer may include a layer having a material.

[0045] One of the source electrode and the drain electrode of the transistor 33 is connected to a signal line to which a data signal is applied. The gate electrode of transistor 33 is electrically connected to line 19. is electrically connected to a scan line 17 to which a signal is applied.

[0046] The transistor 33 is turned on or off to transmit the data of the data signal. It has the function of controlling the writing of

[0047] One of the source and drain electrodes of the transistor 22 functions as an anode line. The other of the source electrode and the drain electrode of the transistor 22 is electrically connected to the wiring 37. , is electrically connected to one electrode of the light emitting element 31. Furthermore, the gate of the transistor 22 The electrode is the other of the source electrode and the drain electrode of the transistor 33 and one of the capacitor elements 25. The electrode is electrically connected to the other electrode.

[0048] The transistor 22 is turned on or off to allow current to flow to the light emitting element 31. It has the function of controlling the current flowing through it.

[0049] One of the source and drain electrodes of the transistor 35 is given a data reference potential. The other of the source electrode and the drain electrode of the transistor 35 is connected to a wiring 39 that is connected to a light-emitting element. It is electrically connected to one electrode of the element 31 and the other electrode of the capacitive element 25. The gate electrode of the transistor 35 is electrically connected to the scanning line 17 to which a gate signal is applied. can be.

[0050] The transistor 35 has a function of adjusting the current flowing through the light-emitting element 31. When the internal resistance of the light emitting element 31 increases due to deterioration of the light emitting element 31, the transistor 35 The current flowing through the wiring 39 to which one of the source electrode and the drain electrode of the By doing so, it is possible to correct the current flowing through the light emitting element 31. The potential can be set to 0V, for example.

[0051] One of the pair of electrodes of the capacitor 25 is connected to the source electrode and the drain electrode of the transistor 33. and the gate electrode of the transistor 22, and a pair of capacitors 25 The other electrode is connected to the other of the source electrode and drain electrode of the transistor 35 and the light emitting element 3 1 is electrically connected to one electrode of the

[0052] In the configuration of the pixel 13 shown in FIG. 1C, the capacitor element 25 stores the written data. It functions as a storage capacitor.

[0053] One of the pair of electrodes of the light emitting element 31 is the source electrode and the drain electrode of the transistor 35. the other end of the capacitor 25, and the other end of the source electrode and drain electrode of the transistor 22. The other of the pair of electrodes of the light emitting element 31 functions as a cathode. The wiring 41 is electrically connected to the wiring 41.

[0054] The light-emitting element 31 may be, for example, an organic electroluminescence element (also called an organic EL element). However, the light emitting element 31 is not limited to this, and An inorganic EL element made of organic materials may also be used.

[0055] A high power supply potential VDD is applied to one of the wiring 37 and the wiring 41, and a low power supply potential VDD is applied to the other. In the configuration shown in FIG. 1C, a high power supply potential VSS is applied to the wiring 37. VDD is applied to the wiring 41, and a low power supply potential VSS is applied to the wiring 42.

[0056] In the display device having the pixel 13 of FIG. 1C, the pixel 1 of each row is driven by the scanning line driving circuit 14. 3 are selected in sequence, and the transistor 22 is turned on to write the data of the data signal.

[0057] The pixel 13 into which the data has been written is in a holding state when the transistor 22 is turned off. Furthermore, since the transistor 22 is connected to the capacitance element 25, the written The data can be retained for a long time. The amount of current flowing between the drain electrode and the gate electrode is controlled, and the light emitting element 31 emits a light according to the amount of current flowing. By repeating this process row by row, an image can be displayed.

[0058] In this specification and the like, the term "display element," "display device having a display element," "light emitting element," "light emitting device," "light emitting element ... A light-emitting device, which is a device having a light-emitting element and a light-emitting element, can be used in various forms or in various Examples of a display element, a display device, a light-emitting element, or a light-emitting device include EL (electroluminescence) elements (EL elements containing organic and inorganic materials, organic EL elements, inorganic EL elements), transistors (transistors that emit light according to current), electrons Emission element, liquid crystal element, electronic ink, electrophoretic element, digital micromirror device (D MD), DMS (Digital Micro Shutter), etc., are made by electromagnetic action. Some have display media that change contrast, brightness, reflectance, transmittance, etc. An example of a display device using electron-emitting devices is an EL display. An example of such a display device is a field emission display (FED) or SE D-type flat panel display (SED: Surface-conduction Electro Display devices using liquid crystal elements include An example is a liquid crystal display (transmissive liquid crystal display, semi-transmissive liquid crystal display). , reflective LCD displays, direct-view LCD displays, projection LCD displays, etc. An example of a display device using electronic ink or electrophoretic elements is electronic paper. There is.

[0059] Next, a specific example of an element substrate of a liquid crystal display device using a liquid crystal element for the pixel 13 will be described. Here, a top view of the pixel 13 shown in FIG. 1(B) is shown in FIG.

[0060] In FIG. 2, the conductive film 103 functioning as a scanning line is oriented in a direction substantially perpendicular to the signal line ( The conductive film 114 that functions as a signal line is provided so as to extend in the horizontal direction. The conductive lines function as capacitance lines. The conductive film 116 is provided so as to extend in a direction parallel to the signal lines. Therefore, when the conductive film 124 is connected to the conductive film 116 of an adjacent pixel, By this, the conductive films 116 of the adjacent pixels are electrically connected. The functioning conductive film 103 is electrically connected to the scanning line driving circuit 14 (see FIG. 1(A)). The conductive film 114 functions as a signal line, the conductive film 116 functions as a capacitance line, and The conductive film 124 is electrically connected to the signal line driving circuit 16 (see FIG. 1(A)). do.

[0061] The transistor 22 is provided in the area where the scanning line and the signal line intersect. The gate electrode 22 includes a conductive film 103 that functions as a gate electrode, a gate insulating film (not shown in FIG. 2), a metal oxide film 109a in which a channel region is formed on the gate insulating film; The conductive films 114 and 115 function as a drain electrode and a drain electrode. The conductive film 103 also functions as a scanning line, and the area overlapping with the metal oxide film 109a forms a transistor. The conductive film 114 also functions as a signal line. The region overlapping with the metal oxide film 109a is the source electrode or the drain electrode of the transistor 22. It functions as a pole.

[0062] In this embodiment, in a plan view, metal is formed on the outside of the ends of the conductive films 114 and 115. The end of the oxide film 109a is located on the conductive layer 109b. The edge of the metal oxide film 109c is located outside the edge of the film 116.

[0063] Since the metal oxide film 109a is formed using a metal oxide having semiconductor properties, A channel region is formed in the metal oxide film 109a between the conductive film 114 and the conductive film 115. It is done.

[0064] The conductive film 115 is electrically connected to the light-transmitting conductive film 123 which functions as a pixel electrode. is connected to.

[0065] The metal oxide film 109c is a film formed simultaneously with the metal oxide film 109a. This film has oxygen vacancies due to plasma damage, etc., and has high conductivity. The metal oxide film 109c is a film formed simultaneously with the metal oxide film 109a, and does not contain impurities. The metal oxide film 109c is a film whose conductivity is increased by containing metal. This film is formed at the same time as the oxide film 109a, contains impurities, and is not susceptible to plasma damage. The film has oxygen vacancies due to the formation of a gallium arsenide (GA) and has increased conductivity.

[0066] The capacitance element 25 is made up of a metal oxide film 109c formed on the gate insulating film and a pixel electrode. and a light-transmitting conductive film 123 that functions as a gate insulating film and a nitride insulating film provided over the transistor 22. The metal oxide film 109c is a transparent film. Therefore, the capacitor 25 has a light-transmitting property. The metal oxide film 109c is connected to a conductive film 116 that functions as a capacitance line.

[0067] In this way, since the capacitance element 25 is transparent, the capacitance element 25 can be made large ( Therefore, it is possible to form the aperture ratio to be 50% or more, preferably 50% or more, while increasing the aperture ratio. It is possible to increase the charge capacity to 55% or more, preferably 60% or more. For example, a semiconductor device with high resolution, such as a liquid crystal display device, can be obtained. In this case, the area of ​​the pixel is small, and the area of ​​the capacitance element is also small. In a semiconductor device with a high capacitance, the charge capacity stored in the capacitance element is small. Therefore, since the capacitor 25 shown in this embodiment mode has a light-transmitting property, the capacitor is provided in the pixel. By doing so, it is possible to obtain a sufficient charge capacity in each pixel while increasing the aperture ratio. In terms of pixel density, it is 200ppi or more, or even 300ppi or more, or even 500ppi. The present invention can be suitably used for high-resolution semiconductor devices having a resolution of i or higher.

[0068] 2, the pixel 13 has a side parallel to the conductive film 103 that functions as a scanning line. The side parallel to the conductive film 114 functioning as a signal line is shorter than the side parallel to the conductive film 114 functioning as a capacitance line. The conductive film 116 functions as a conductive film 116, and the conductive film 116 formed in the adjacent pixel is electrically connected. The conductive film 124 is provided to extend in a direction parallel to the conductive film 114 that functions as a signal line. As a result, the area of ​​the conductive films 114 and 116 in the pixel 13 can be reduced. This allows for an increased aperture ratio.

[0069] Furthermore, according to one embodiment of the present invention, the aperture ratio can be increased even in a high-resolution display device. This allows for efficient use of light from light sources such as backlights, and reduces the power consumption of the display device. The force can be reduced.

[0070] Next, using the cross-sectional views of the dashed and dotted lines AB and CD shown in Figure 2, A method for manufacturing the element substrate of the device will be described.

[0071] As shown in FIG. 3(A), a conductive film 102 is formed on a substrate 101. Next, a first photo A mask 131 is formed on the conductive film 102 by a photolithography process using a mask. do.

[0072] There is no particular restriction on the material of the substrate 101, but it should be strong enough to withstand the subsequent heat treatment. For example, glass substrates, ceramic substrates, quartz substrates, and A fire substrate or the like may be used as the substrate 101. Also, silicon, silicon carbide, etc. A single crystal semiconductor substrate, a polycrystalline semiconductor substrate, a silicon germanium or the like formed using It is also possible to apply a compound semiconductor substrate, an SOI substrate, etc., and a semiconductor element is formed on these substrates. A substrate provided with a substrate may be used as the substrate 101. When using a substrate, the 6th generation (1500mm x 1850mm) and 7th generation (1870mm) m x 2200mm), 8th generation (2200mm x 2400mm), 9th generation (2400m 10th generation (2950mm x 3400mm) and large area substrates By doing so, a large display device can be manufactured.

[0073] In addition, a flexible substrate is used as the substrate 101, and a conductive film 102 is formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate 101 and the conductive film 102, and a transfer film may be formed on the release layer. After forming an element portion having a transistor, the element portion is peeled off from the substrate 101 at the peeling layer, As a result, the device can be mounted on a substrate with low heat resistance or a flexible substrate. A department may be established.

[0074] The conductive film 102 will later become a conductive film 103 that functions as a gate electrode. The conductive film 102 is made of a conductive material that can be used as a gate electrode. 2 is selected from aluminum, chromium, copper, tantalum, titanium, molybdenum, and tungsten. The metal elements mentioned above, or alloys containing the above metal elements, or combinations of the above metal elements It can be formed by using an alloy of manganese and zirconium. Alternatively, the conductive film 102 may have a single layer structure. For example, a single layer of aluminum film containing silicon may be used. a layer structure, a two-layer structure with an aluminum film laminated on a titanium film, and a titanium film laminated on a titanium nitride film. Two-layer structure with tungsten film laminated on titanium nitride film, two-layer structure with tantalum nitride film laminated on titanium nitride film Two-layer structure: tungsten film on tungsten nitride film, copper film on titanium film A two-layer structure in which a titanium film is laminated, and an aluminum film is laminated on top of the titanium film. There are also three-layer structures, such as a titanium film formed on aluminum. One of the elements selected from the group consisting of tungsten, molybdenum, chromium, neodymium, and scandium Alternatively, an alloy film or a nitride film made by combining a plurality of layers may be used.

[0075] The conductive film 102 may be formed of an indium tin oxide film or an indium oxide film containing tungsten oxide. oxide film, indium zinc oxide film containing tungsten oxide, indium zinc oxide film containing titanium oxide oxide film, indium tin oxide film containing titanium oxide, indium zinc oxide film, silicon oxide A film formed of a light-transmitting conductive material such as an indium tin oxide film doped with indium is suitably used. In addition, a film formed of the above-mentioned light-transmitting conductive material and the above-mentioned metal It may also have a laminated structure of films formed from elements.

[0076] Here, a tungsten film having a thickness of 100 nm is deposited by sputtering as the conductive film 102. Next, a mask is formed by a photolithography process.

[0077] Next, a part of the conductive film 102 is etched using a mask 131 to form a gate electrode. A functional conductive film 103 is formed by dry etching or / and wet etching. The conductive film 102 can be etched by using a method. After that, the mask 131 is removed. (See Figure 3(B)).

[0078] Here, a tungsten film formed as the conductive film 102 is dry-etched using a mask. Then, a conductive film 103 that functions as a gate electrode is formed.

[0079] Next, as shown in FIG. 3(C), the insulating film 105, the insulating film 106, the metal oxide film 108, The conductive film 110 is then formed in this order. Next, a photolithography process is performed using a second photomask. In this step, masks 133 and 134 are formed on the conductive film 110. The mask is characterized by using a multi-tone mask.

[0080] A multi-level photomask is a mask that can perform exposure with multiple levels of light intensity. Specifically, there are gray-tone masks and half-tone masks. A light-shielding portion and a diffraction grating are formed on a substrate having optical properties. The diffraction grating has slits, dots, and The intervals between the light transmitting regions such as meshes are equal to or less than the resolution limit of the light used for exposure. This configuration controls the light transmittance. The semi-transmitting portion controls the transmittance of light used for exposure. .

[0081] By using a multi-tone mask, three levels of light intensity can be achieved: exposed area, semi-exposed area, and unexposed area. As a result, by using a multi-tone photomask, it is possible to perform exposure in one exposure. and a development process to form resist masks with multiple (typically two) thicknesses. This allows for a reduction in the number of photomasks required. In the process of forming the oxide film and the conductive films 114, 115, and 116, a multi-tone photomask is used. This reduces the number of photomasks required by one.

[0082] The insulating film 105 and the insulating film 106 will later become a gate insulating film. The conductive film 103 functions as a gate electrode and the metal oxide film 108 is To prevent the diffusion of impurities, it is preferable to form the insulating film using a nitride insulating film. The insulating film 106 contacts the metal oxide film 108. In order to reduce the surface state density, the insulating film 106 is preferably formed using an oxide insulating film.

[0083] The insulating film 105 is made of silicon nitride, silicon nitride oxide, aluminum nitride, or aluminum nitride oxide. The insulating film 10 may be formed using aluminum or the like, and may be provided as a laminated layer or a single layer.

[0084] The insulating film 106 is made of silicon oxide, silicon oxynitride, aluminum oxide, hafnium oxide, or the like. The insulating layer may be formed using aluminum, gallium oxide, Ga-Zn-based metal oxide, or the like. is provided in a single layer.

[0085] The insulating film 106 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 By forming the gate electrode using this material, it is possible to reduce gate leakage of the transistor.

[0086] The total thickness of the insulating film 105 and the insulating film 106 is preferably 5 nm or more and 400 nm or less. Preferably, the thickness is 10 nm or more and 300 nm or less, and more preferably, 50 nm or more and 250 nm or less. It is good.

[0087] The insulating film 105 and the insulating film 106 are formed by a CVD method, a sputtering method, a vapor deposition method, a coating method, or the like. It can be used as appropriate.

[0088] By providing the insulating film 105 made of a nitride insulating film as a part of the gate insulating film, Impurities from the conductive film 103 functioning as a gate electrode, typically hydrogen, nitrogen, alkali, It is possible to prevent metals, alkaline earth metals, etc. from migrating to the metal oxide film 109a. can.

[0089] In addition, as a gate insulating film, an insulating film formed of an oxide insulating film on the metal oxide film 109a side is used. By providing the film 106, the defect level at the interface between the gate insulating film and the metal oxide film 109a is As a result, a transistor with little deterioration in electrical characteristics can be obtained. This can be done.

[0090] The metal oxide film 108 is typically an In-Ga oxide film, an In-Zn oxide film, or an In -M-Zn oxide film (M is Al, Ga, Ti, Y, Zr, La, Ce, or Nd), etc. Since the metal oxide film has semiconductor properties, it is possible to use the metal oxide film as an oxide semiconductor. It is also possible to say this.

[0091] When the metal oxide film 108 is an In-M-Zn oxide film, the sum of In and M is When the atomic percentage is 100 atomic %, the atomic ratio of In and M is preferably 100 atomic %. The molecular ratio is preferably such that In is greater than 25 atomic % and M is less than 75 atomic %. More preferably, In is greater than 34 atomic % and M is less than 66 atomic %. It is full.

[0092] The energy gap of the metal oxide film 108 is 2 eV or more, preferably 2.5 eV or more. , and more preferably 3 eV or more. By forming the transistor using the above, the off-state current of a transistor to be formed later can be reduced. .

[0093] The metal oxide film 108 is a metal oxide film with a low carrier density. The metal oxide film 108 has a carrier density of 1×10 17 pieces / cm 3 Less than 1 × 10 15 pieces / cm 3 or less, more preferably 1 × 10 13 pieces / cm 3 Below, more preferably 1 x10 11 pieces / cm 3 The following metal oxide films are used:

[0094] The thickness of the metal oxide film 108 is 3 nm or more and 200 nm or less, preferably 3 nm or more and 10 0 nm or less, and more preferably 3 nm or more and 50 nm or less.

[0095] The metal oxide film 108 can be formed by a sputtering method, a coating method, a pulsed laser deposition method, a laser It can be formed by using an ablation method or the like.

[0096] When the metal oxide film 108 is formed by sputtering, a plasma generating method is required. The power supply may be an RF power supply, an AC power supply, a DC power supply, or the like.

[0097] The sputtering gas may be a rare gas (typically argon) atmosphere, an oxygen atmosphere, a rare gas and In the case of a mixed gas of rare gas and oxygen, the rare gas It is preferable to increase the gas ratio of oxygen.

[0098] The metal oxide film 108 is an In-M-Zn oxide film (M is Al, Ti, Ga, Y, Zr, In the case of La, Ce, Nd or Hf, it is used to deposit In-M-Zn oxide films. The atomic ratio of the metal elements in the sputtering target is In:M:Z. If n=x1:y1:z1 、 x1 / y1 is between 1 / 3 and 6, and between 1 and 6. and z1 / y1 is preferably 1 / 3 or more and 6 or less, and more preferably 1 or more and 6 or less. By setting z1 / y1 to 1 or more and 6 or less, the metal oxide film 108 can be formed as described later. CAAC-OS(C Axis Aligned Crystalline Oxid e) Semiconductor film is easily formed. Typical examples of the molecular ratio are In:M:Zn=1:1:1, In:M:Zn=3:1:2, The atomic ratio of the metal oxide film 108 to be formed is, for example, In:M:Zn=5:5:6. are the plus or minus of the atomic ratio of the metal elements contained in the target as errors. Includes a 40% variation.

[0099] In order to obtain a highly pure metal oxide film 108, the chamber must be evacuated to a high vacuum. In addition, it is also necessary to increase the purity of the sputtering gas. Gongas has a dew point of -40°C or less, preferably -80°C or less, more preferably -100°C or less. Preferably, the gas is highly purified to -120°C or less. This can prevent moisture and other substances from being absorbed into the film as much as possible.

[0100] The conductive film 110 is made up of conductive films 114 and 115 which will later function as a pair of electrodes, and a capacitor line. Therefore, the conductive film 110 can be used as an electrode. The conductive film 110 is made of aluminum, titanium, chromium, nickel, from copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten The metal or an alloy containing the metal as a main component is used as a single layer structure or a laminated structure. For example, a single layer structure of aluminum film containing silicon, or a laminated aluminum film on a titanium film Two-layer structure with aluminum film on tungsten film, two-layer structure with copper-magnesium film Two-layer structure with copper film laminated on aluminum alloy film, two-layer structure with copper film laminated on titanium film a two-layer structure in which a copper film is laminated on a tungsten film; a titanium film or titanium nitride film; An aluminum film or a copper film is laminated on the titanium film or titanium nitride film, and then A three-layer structure in which a titanium film or titanium nitride film is formed on top of a molybdenum film or molybdenum nitride film A molybdenum film and an aluminum film or copper film are superimposed on the molybdenum film or molybdenum nitride film. Three-layer structure in which a film is laminated and then a molybdenum film or molybdenum nitride film is formed on top of that It should be noted that the transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used. You may do so.

[0101] The conductive film 110 is formed by sputtering, CVD, vapor deposition, or the like.

[0102] Here, a silicon nitride film having a thickness of 400 nm is formed as the insulating film 105 by the CVD method. Also, as the insulating film 106, a silicon oxynitride film having a thickness of 50 nm is formed by the CVD method. In addition, as the metal oxide film 108, an In-Ga-Zn oxide target A 35-nm thick I film was formed by sputtering using (In:Ga:Zn=1:1:1). An n-Ga-Zn oxide film is formed. A tungsten film having a thickness of 50 nm and a copper film having a thickness of 300 nm are formed.

[0103] Next, a part of the conductive film 110 is etched using the masks 133 and 134. 111 and 113 are formed by dry etching or / and wet etching. Then, the conductive film 110 can be etched using the masks 133 and 134. Then, a part of the metal oxide film 108 is etched to form metal oxide films 109a and 109b. The metal oxide film is formed by dry etching and / or wet etching. 108 can be etched.

[0104] Here, the conductive film 110 and the metal oxide film 108 are each formed by dry etching. A portion of the substrate is etched.

[0105] Next, the masks 133 and 134 are processed. Here, the size of the mask 133 is reduced. At the same time, the mask 134 is removed. The masks 133 and 134 are exposed to the generated plasma by plasma treatment. 34. The oxygen-containing atmosphere includes oxygen, ozone, nitrous oxide, and nitrogen dioxide. The atmosphere contains an oxidizing gas such as oxygen. The masks 133 and 134 may be exposed to the plasma generated by the plasma treatment. An example of such an apparatus is an ashing apparatus.

[0106] As a result, as shown in FIG. 3(D), the mask 133 is retracted to form masks 135 and 136. In addition, the mask 134 can be recessed to form a mask 137. In FIG. 3(D), the dashed lines represent the mask 133 shown in FIG. 3(C), Equivalent to 134.

[0107] Next, using masks 135, 136, and 137, portions of the conductive films 111 and 113 are removed. is etched to form conductive films 114, 115, and 116, and the metal oxide film 10 9a and 109b are exposed by dry etching or / and wet etching. The conductive films 111, 112, and 113 can be etched by etching. The conductive films 111 and 113 are etched, and the metal oxide films 109a and 109b are etched. The metal oxide films 109a and 109b are not etched, or are etched more slowly than the conductive films 111 and 113. It is preferable to use conditions where the aging rate is small.

[0108] Here, the conductive films 111 and 113 are partially etched by dry etching. .

[0109] As a result, as shown in FIG. 3E, a conductive film functioning as a pair of electrodes of a transistor is formed. 114 and 115, and a conductive film 116 that functions as a capacitor line can be formed. A portion of each of the metal oxide films 109a and 109b is exposed.

[0110] Through the above process, a metal oxide film including the channel region of a transistor can be formed using a single photomask. a conductive film 114 and a conductive film 115 which function as a pair of electrodes of a transistor; The metal oxide film 109b will later become one electrode of the capacitor element, and the conductive film 109b will later function as a capacitor line. A film 116 can be formed.

[0111] In order to form the conductive films 114 and 115 which function as a pair of electrodes of the transistor, In the etching process, the areas of the metal oxide films 109a and 109b exposed to the plasma As a result, the metal oxide film 109a and the metal oxide film 109b are damaged and oxygen vacancies are formed. The conductivity of the exposed region of the oxide film 109b is increased.

[0112] Next, it is preferable to carry out a heat treatment. The temperature of the heat treatment is typically 150° C. or higher. Lower than the strain point of the upper substrate, preferably 300°C or higher and 500°C or lower, preferably 320°C or higher and 47°C or lower Keep below 0℃.

[0113] 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 distortion point of the substrate for a short period of time. The processing time can be reduced.

[0114] The heat treatment is carried out in a nitrogen, oxygen, or ultra-dry air (water content of 20 ppm or less, preferably 1 ppm). pm or less, preferably 10 ppb or less air), or rare gases (argon, helium, etc.) The above-mentioned nitrogen, oxygen, ultra-dry air, or rare gas may be mixed with hydrogen, water, or the like. It is preferable that the above is not included.

[0115] Here, after heat treatment at 450°C for 1 hour in a nitrogen atmosphere, The mixture is heated in a gas atmosphere at 450°C for 1 hour.

[0116] In addition, the conductive films 114, 115, and 116 are in contact with the metal oxide films 109a and 109b. Tungsten, titanium, aluminum, copper, molybdenum, chromium, or titanium are used in the area where the By using conductive materials that easily bond with oxygen, such as tantalum or alloys, a metal oxide film The oxygen in 109a and 109b is drawn to the conductive material that easily bonds with oxygen. The oxide films 109a and 109b are coated with tungsten, titanium, aluminum, copper, molybdenum, Chromium or tantalum itself or some of the constituent elements of the alloy may be mixed in. As a result, the conductive films 114, 115, and 116 in the metal oxide films 109a and 109b A low resistance region is formed near the area in contact with the metal. It is possible to reduce the contact resistance between the oxide film 109a and the conductive films 114 and 115, It is possible to increase the on-state current of the transistor. Therefore, the contact resistance with the conductive film 116 can be reduced, and the resistance of the signal line and the capacitance line can be reduced. It can be reduced.

[0117] Next, as shown in FIG. 4A, an insulating film 118 is formed. Next, a third photomask A mask 138 is formed on the insulating film 118 by a photolithography process using a mask.

[0118] The insulating film 118 is formed by oxidation in order to reduce the interface state at the interface with the metal oxide film 108. The insulating film 118 is preferably formed using a silicon oxide insulating film. , silicon oxynitride, aluminum oxide, hafnium oxide, gallium oxide or Ga-Z The insulating film 11 may be formed using an n-based metal oxide or the like, and may be provided as a stacked layer or a single layer.

[0119] In addition, the insulating film 118 may contain more oxygen than the stoichiometric composition as a part or the whole of the insulating film 118. It is preferable to form the insulating film using an oxide insulating film containing oxygen having a stoichiometric composition. When an oxide insulating film contains more oxygen than the element, some of the oxygen is released by heating. The oxide insulating film containing more oxygen than the oxygen that satisfies the theoretical composition is analyzed by TDS. The amount of oxygen released is 1.0 × 10 18 atoms / cm 3 Above, preferably 3. 0×10 20 atoms / cm 3 The oxide insulating film is as described above.

[0120] Furthermore, it is preferable that the insulating film 118 has a small number of defects. The spin density of the signal at g=2.001 originating from the silicon dangling bond is 1.5 x 10 18 spins / cm 3 Less than or even 1×10 18 spins / cm 3 Below Bottom, 1×10 17 spins / cm 3 or less, and more preferably below the lower limit of detection. .

[0121] The thickness of the insulating film 118 is 30 nm or more and 500 nm or less, preferably 50 nm or more and 400 nm or less. nm or less.

[0122] The insulating film 118 is an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition. By forming the insulating film 118 using a metal oxide film, oxygen released from the insulating film 118 by heat treatment can be absorbed by the metal oxide film. As a result, the metal oxide film 109a can be moved to the metal oxide film 109a. Oxygen deficiency can be reduced.

[0123] The insulating film 118 can be formed by a sputtering method, a CVD method, or the like.

[0124] When the insulating film 118 is formed by the CVD method, the source gas is a silicon-containing deposit. It is preferable to use an oxidizing gas and an insulating gas. Representative examples of the silicon-containing deposition gas are: Examples of oxidizing gases include silane, disilane, trisilane, and fluorinated silane. Examples include oxygen, ozone, nitrous oxide, and nitrogen dioxide.

[0125] An oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition of the insulating film 118 When forming the film using the above method, a substrate is placed in a processing chamber of a plasma CVD apparatus that has been evacuated. The plate is maintained at a temperature of 180°C or higher and 280°C or lower, more preferably 200°C or higher and 240°C or lower, A raw material gas is introduced into the processing chamber to set the pressure in the processing chamber to 20 Pa or more and 250 Pa or less; 0.17W / cm to the electrode installed in the processing chamber 2 More than 0.5W / cm 2 Below are some more preferred Or 0.25W / cm 2 More than 0.35W / cm 2 Under the following conditions for supplying high frequency power: In this way, a silicon oxide film or a silicon oxynitride film can be formed.

[0126] The conditions for forming the insulating film 118 are as follows: a high frequency voltage of the above power density in a reaction chamber of the above pressure; By supplying power, the decomposition efficiency of the source gas in the plasma increases, and oxygen radicals increase. As the oxidation of the source gas progresses, the oxygen content in the insulating film 118 becomes higher than the stoichiometric composition. On the other hand, in the film formed at the above substrate temperature, the bonding strength between silicon and oxygen is As a result, the stoichiometric amount of oxygen in the film is reduced by the heat treatment in the subsequent process. An insulating film that contains more oxygen than satisfies the stoichiometric composition and loses some of the oxygen when heated 118 can be formed.

[0127] The insulating film 118 has a multilayer structure of a first insulating film and a second insulating film. The second insulating film is formed using an oxide insulating film that can transmit oxygen. An acid that contains more oxygen than the stoichiometric composition and loses some of the oxygen when heated. By forming the layered structure, the second insulating film can be formed. As a result, the first insulating film acts as a protective film for the metal oxide film. The second insulating film can be formed using high frequency power with high power density while reducing the do.

[0128] Alternatively, an insulating film is formed by a sputtering method, a CVD method, or the like, and then oxygen is added to the insulating film. By adding oxygen, the insulating film 118 can be formed. The method of adding the ion is ion doping, ion implantation, etc. Oxygen is added to the insulating film by exposing the insulating film to plasma containing oxygen generated in the atmosphere. It is possible.

[0129] Here, the insulating film 118 is formed by using silane at a flow rate of 200 sccm and silane at a flow rate of 4000 sccm. The reaction chamber pressure was 200 Pa and the substrate temperature was 220°C. A 27.12MHz high-frequency power supply was used to supply 1500W of high-frequency power to the parallel plate electrodes. A silicon oxynitride film having a thickness of 400 nm is formed by the plasma CVD method. The plasma CVD device has an electrode area of ​​6000 cm 2 A parallel plate type plasma CVD apparatus The supplied power is converted to power per unit area (power density) of 0.25W / c m 2 Furthermore, masks 133 and 135 are formed using half-tone masks.

[0130] Next, a part of the insulating film 118 is etched using the mask 138 to form the insulating film 118 shown in FIG. In this way, an insulating film 119 having an opening 151 is formed. In the opening 151, a metal A part of the oxide film 109b is exposed. The insulating film 118 can be etched using a etching method. Next, the mask 138 is removed. do.

[0131] In the etching process for forming the insulating film 119, the metal oxide film 109b The area exposed to the plasma is damaged and oxygen vacancies are formed. In the metal oxide film 109b, the conductivity of the region not covered with the insulating film 119 is increased.

[0132] Here, a part of the insulating film 118 is etched by dry etching.

[0133] Next, as shown in FIG. 4(C), an insulating film is formed on the metal oxide film 109b and the insulating film 119. Next, a photolithography process using a fourth photomask is performed to form A mask 139 is formed on the insulating film 120 .

[0134] A nitride insulating film is provided as the insulating film 120. Examples of nitride insulating films include silicon nitride, Silicon nitride oxide, aluminum nitride, aluminum nitride oxide, etc. In this way, a nitride insulating film containing hydrogen may be formed.

[0135] The thickness of the insulating film 120 is 10 nm or more and 400 nm or less, and more preferably 50 nm or more and 300 nm or less. 00nm or less.

[0136] The insulating film 120 can be formed by using a sputtering method, a CVD method, or the like. After forming an insulating film by using a sputtering method, a CVD method, or the like, hydrogen is added to the insulating film. The method of adding hydrogen to the insulating film may include ion doping, ion Alternatively, the insulating film can be exposed to plasma generated in a gas atmosphere containing hydrogen. In this way, hydrogen can be added to the insulating film.

[0137] Here, the insulating film 120 is formed by a plasma process using silane, ammonia, and nitrogen as raw material gases. A silicon nitride film with a thickness of 100 nm is formed by the Zuma CVD method.

[0138] Plasma damage occurs when forming the insulating film 120 on the insulating film 119, causing metal oxide Therefore, oxygen vacancies are formed in the metal oxide film 109b. The conductivity of the area not covered with the insulating film 119 is increased. By using a nitride insulating film containing hydrogen, hydrogen is transferred from the insulating film 120 to the metal oxide film 109b. When hydrogen moves to the oxygen vacancy, electrons are generated as carriers. As a result, the metal oxide film 109b becomes highly conductive, and the conductive metal oxide film 109c The metal oxide film 109c functions as one electrode of the capacitor 25.

[0139] The nitride insulating film also functions as a blocking film for water, hydrogen, etc. By providing a nitride insulating film as 20, hydrogen and water from the outside are prevented from entering the metal oxide film 109a. It is possible to prevent intrusions such as

[0140] The metal oxide film 109a and the metal oxide film 109c are both formed on the insulating film 106. However, the impurity concentration is different. The impurity concentration of the film 109c is high. For example, the hydrogen concentration contained in the metal oxide film 109a is 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 less than , preferably 1 x 10 18 atoms / cm 3 Less than or equal to 5 × 10 17 ato ms / cm 3 or less, more preferably 1 × 10 16 atoms / cm 3 is less than or equal to metal The hydrogen concentration in the oxide film 109c is 8×10 19 or more, preferably 1 × 10 20 a toms / cm 3 More preferably, 5 × 10 20 The above is the case. The hydrogen concentration in the metal oxide film 109c is twice as high, preferably 10 times as high as that in the metal oxide film 109a. That's all.

[0141] The metal oxide film 109c has a lower resistivity than the metal oxide film 109a. The resistivity of the film 109c is 1×10 -8 1×10 times more - 1 It is preferably less than 1×10 -3 Ωcm or more 1×10 4 Ωcm not yet More preferably, the resistivity is less than 1×10 -3 Ωcm or more 1×10 -1 Less than Ωcm It is good.

[0142] Next, a heat treatment may be performed. The temperature of the heat treatment is typically 150° C. or higher and 40° C. or lower. 0°C or lower, preferably 300°C or higher and 400°C or lower, preferably 320°C or higher and 370°C or lower Let's say.

[0143] The nitride insulating film has a small diffusion coefficient for hydrogen, water, and oxygen, and is a blocking material for hydrogen, water, and oxygen. In addition, the insulating film 119 contains more oxygen than the oxygen required for the stoichiometric composition. By forming the insulating film using an oxide insulating film containing oxygen, it is possible to The oxygen contained in the film 109a can be prevented from diffusing to the outside. The diffusion of oxygen contained in 109a to the outside can be suppressed. Furthermore, the amount of oxygen vacancies in the metal oxide film 109a can be reduced. Therefore, the diffusion of hydrogen, water, etc. into the metal oxide film 109a can be suppressed. As a result, highly reliable transistors can be manufactured. It is possible.

[0144] Here, heat treatment is performed in a nitrogen and oxygen atmosphere at 350° C. for 1 hour.

[0145] Next, a mask 139 is used to etch a part of the insulating films 119 and 120, and the insulating films 119 and 120 are removed as shown in FIG. As shown in Fig. 1D, an opening 152 is formed and the insulating film 120 is etched. Openings 153 and 154 are formed. Also, the insulating film 120 is etched to form an insulating film. 121. In the opening 152, a part of the conductive film 115 is exposed. 3, 154, a part of the conductive film 116 is exposed. The insulating film 120 can be etched using a wet etching method. , and remove the mask 139.

[0146] Here, a part of the insulating film 120 is etched by dry etching.

[0147] Next, as shown in FIG. 5A, a light-transmitting film is formed on the insulating film 121 and the conductive films 115 and 116. Next, a conductive film 122 having a thickness of 100 nm is formed by photolithography using a fifth photomask. Masks 140 and 141 are formed on the conductive film 122 through a process.

[0148] The conductive film 122 will later become a conductive film 123 that functions as a pixel electrode. The conductive film 122 is made of a conductive material that can be used as a pixel electrode. , indium tin oxide film, indium oxide film containing tungsten oxide, tungsten oxide Indium zinc oxide film containing titanium oxide, indium oxide film containing titanium oxide Indium tin oxide film containing indium, indium zinc oxide film containing indium, silicon oxide added film containing indium A film formed of a light-transmitting conductive material such as a tin oxide film can be used.

[0149] The conductive film 122 is formed by a sputtering method, an evaporation method, a coating method, or the like.

[0150] Here, a 100 nm thick ITO film is formed as the conductive film 122 by sputtering. Form.

[0151] Next, a part of the conductive film 122 is etched using masks 140 and 141 to form the conductive film 1 The conductive film 123 functions as a pixel electrode. The conductive film 124 is formed on the adjacent The conductive film 116 has a function of electrically connecting the conductive film 116 formed in the corresponding pixel. The conductive film 24 functions as a capacitance line in the same manner as the conductive film 116 .

[0152] The conductive film 123 is in contact with the conductive film 115 which functions as a pair of electrodes and is also The metal oxide film 109c is formed by a dry etching method. The conductive film 122 can be etched by using a wet etching method. After this, the masks 140 and 141 are removed (see FIG. 5(B)).

[0153] Here, part of the conductive film 122 is etched by wet etching.

[0154] Through the above steps, the conductive film 103 functioning as a gate electrode and the gate insulating film The insulating films 105 and 106, the metal oxide film 109a, and the metal oxide film 109a are in contact with each other. The transistor 22 has conductive films 114 and 115 that function as a source electrode and a drain electrode. In addition, the pixel A conductive film 123 functioning as an electrode can be formed on the insulating film 106. The capacitor element 25 includes the metal oxide film 109c, the insulating film 121, and the conductive film 123. That is, the transistor 22 and the conductive film 123 functioning as a pixel electrode can be manufactured. , and the element substrate having the capacitor element 25 can be manufactured using five photomasks. In this embodiment, a metal oxide film and a conductive film functioning as a source electrode and a drain electrode are used. Since the photomask is used to form the element substrate, the number of photomasks required to fabricate the element substrate is This can reduce the risk.

[0155] In addition, the semiconductor device described in this embodiment has a metal oxide film including a channel region of a transistor. At the same time as forming the metal oxide film, a metal oxide film that will become one of the electrodes of the capacitance element is formed. A metal oxide film including a channel region of a capacitor and a metal oxide film that will be one of the electrodes of a capacitor element. The conductive film that functions as a pixel electrode is made of the same metal element as the capacitor element. For this reason, a new conductive film is formed to form a capacitor element. Since the step of forming a capacitor is not required, the manufacturing steps of the display device can be reduced. Since both the metal oxide film 109c and the conductive film 123, which are electrodes, have light-transmitting properties, As a result, the area occupied by the capacitor element can be increased while increasing the aperture ratio of the pixel. Furthermore, a display device with reduced power consumption can be manufactured.

[0156] In FIG. 4B, an opening 151 is provided, but in one aspect of the embodiment of the present invention, As shown in FIG. 13(A), depending on the situation, It is also possible to not provide the opening 151.

[0157] In FIG. 4B, the conductive film 124 is connected to the conductive film 116 of the adjacent pixel. However, one aspect of the embodiment of the present invention is not limited to this. In this way, the conductive film 116 may be extended and connected depending on the situation. is also possible.

[0158] <Variation 1, Regarding the Undercoat Insulating Film> In the transistor described in this embodiment, the substrate 101 and the gate electrode may be formed as needed. A base insulating film can be provided between the conductive film 103 and the insulating film 104. are silicon oxide, silicon oxynitride, silicon nitride, silicon nitride oxide, gallium oxide , hafnium oxide, yttrium oxide, aluminum oxide, aluminum oxide nitride, etc. The base insulating film can be formed by using silicon nitride, gallium oxide, or oxide. By forming the substrate 1 using hafnium oxide, yttrium oxide, aluminum oxide, etc. Impurities, typically alkali metals, water, hydrogen, etc., diffuse from O1 into the metal oxide film 109a. can be suppressed.

[0159] The base insulating film can be formed by a sputtering method, a CVD method, or the like.

[0160] <Modification 2: Gate insulating film> The insulating film 105 formed of a nitride insulating film is replaced with a first nitride insulating film having fewer defects and a water The gate insulating film can be formed as a laminated structure of a second nitride insulating film having high electron blocking properties. By providing a nitride insulating film with few defects as the film, the dielectric strength of the gate insulating film is improved. In addition, a nitride insulating film with high hydrogen blocking properties can be used as a gate insulating film. By providing the insulating film 105, hydrogen from the conductive film 103 which functions as a gate electrode and the insulating film 105 can be It is possible to prevent the metal from migrating to the metal oxide film 109a.

[0161] Alternatively, the insulating film 105 may be formed of a nitride insulating film having high impurity blocking properties. The first nitride insulating film has a low defect content, the second nitride insulating film has a low defect content, and the second nitride insulating film has a high hydrogen blocking property. A second nitride insulating film is laminated in this order from the conductive film 103 side that functions as the gate electrode. The gate insulating film can have a laminated structure. By providing the nitride insulating film, impurities from the conductive film 103 functioning as a gate electrode, Typically, hydrogen, nitrogen, an alkali metal, an alkaline earth metal, or the like is added to the metal oxide film 10. This will prevent you from moving to 9a.

[0162] <Modification 3: Metal Oxide Film> <About metal oxide films> When hydrogen is added to an oxide semiconductor with oxygen vacancies, hydrogen enters the oxygen vacancy sites. A donor level is formed near the conduction band. As a result, the oxide semiconductor has high conductivity. The oxide semiconductor that has become a conductor can be called an oxide conductor. Oxide semiconductors have a large energy gap and therefore transmit visible light. On the other hand, an oxide conductor is an oxide semiconductor that has a donor level near the conduction band. Therefore, the influence of absorption due to the donor level is small, and the transparency to visible light is the same as that of an oxide semiconductor. It has photosensitivity.

[0163] Here, a film formed of an oxide semiconductor such as that used for the metal oxide film 109a (hereinafter referred to as The metal oxide film 109c is an oxide semiconductor film (hereinafter referred to as an oxide semiconductor film (OS)). Resistance in a film formed of an oxide conductor (hereinafter referred to as an oxide conductor film (OC)) The temperature dependency of the efficiency will be explained using FIG. 17. In FIG. 17, the horizontal axis represents the measurement temperature. The vertical axis shows the resistivity, and the vertical axis shows the measurement results for the oxide semiconductor film (OS). The measurement results for the oxide conductor film (OC) are shown by square marks.

[0164] The sample including the oxide semiconductor film (OS) was formed on a glass substrate with an atomic ratio of In:Ga Zn=1:1:1.2 sputtering target. An In-Ga-Zn oxide film with a thickness of 35 nm was formed, and the atomic ratio was In:Ga:Zn=1:4. :5 sputtering target was used to deposit a 20 nm thick In- A Ga-Zn oxide film was formed, and after heat treatment in a nitrogen atmosphere at 450°C, and heat treatment in a mixed gas atmosphere of silicon and oxygen, and then a silicon oxynitride film is formed by plasma CVD. was formed and produced.

[0165] The sample containing the oxide conductor (OC) film was formed on a glass substrate with an atomic ratio of In:Ga. Zn=1:1:1 sputtering target was used to deposit a 10 ... After forming a 00 nm In-Ga-Zn oxide film and heat-treating it in a nitrogen atmosphere at 450°C, The silicon nitride film was then heated at 450°C in a mixed gas atmosphere of nitrogen and oxygen, and then deposited by plasma CVD. It was prepared by forming a com film.

[0166] As can be seen from FIG. 13, the temperature dependence of resistivity in the oxide conductor film (OC) is The temperature dependence of resistivity is smaller than that of oxide semiconductor films (OS). Typically, it is 80K or higher. The resistivity change rate of the oxide conductor film (OC) at 290K or less is less than ±20% Alternatively, the rate of change in resistivity between 150K and 250K is less than ±10%. That is, an oxide conductor is a degenerate semiconductor, and the conduction band edge and the Fermi level are coincident or approximately coincident. Therefore, it is considered that the oxide conductor film is used for the resistance element, wiring, and capacitance element. It can be used for electrodes, pixel electrodes, common electrodes, etc.

[0167] <Oxide Semiconductor Films and Metal Oxide Films> Next, one embodiment applicable to a metal oxide film and an oxide semiconductor film having semiconductor properties will be described. Here, an oxide semiconductor film will be used as a typical example. The structure of the semiconductor film can be applied to the metal oxide film.

[0168] The oxide semiconductor film is preferably a CAAC-OS film. The S film has a c-axis orientation and clear crystal grain boundaries (also called grain boundaries) can be confirmed. As a result, in a channel-etched transistor, As a result, the amount of over-etching of the oxide semiconductor film when forming the oxide semiconductor film is small. By using a CAAC-OS film as the main film, a channel-etched transistor is fabricated. In addition, a channel-etched transistor can be formed by dividing the gap between a pair of electrodes, i.e., the channel The channel length is set to 0.5 μm or more and 6.5 μm or less, preferably 1 μm or more and 6.5 μm or less. It is possible to make it smaller than μm.

[0169] The oxide semiconductor film is formed by using an oxide semiconductor having a single crystal structure (hereinafter referred to as a single crystal oxide semiconductor). ), a polycrystalline oxide semiconductor (hereinafter referred to as a polycrystalline oxide semiconductor), and a microcrystalline oxide semiconductor. The oxide semiconductor layer may be made of one or more of the following oxide semiconductors (hereinafter referred to as microcrystalline oxide semiconductors): Below, we will discuss CAAC-OS, single-crystalline oxide semiconductors, polycrystalline oxide semiconductors, and microcrystalline oxide semiconductors. The conductor will now be described.

[0170] <caac-os> The CAAC-OS film is one of oxide semiconductor films having multiple crystal parts. The crystals contained in the AC-OS film have a c-axis orientation. The area of ​​the crystal part contained in the C-OS film is 2500 nm 2 More preferably, 5 μm or more 2 Below More preferably 1000 μm or more 2 In addition, in the cross-sectional TEM image, the crystal By having 50% or more, preferably 80% or more, and more preferably 95% or more of the above-mentioned portion, The resulting thin film has properties close to those of a crystal.

[0171] The CAAC-OS film was observed under a transmission electron microscope (TEM). When observed under a tron ​​microscope, clear boundaries between the crystals are clearly visible. In other words, it is not possible to confirm the grain boundary. Therefore, it can be said that the CAAC-OS film is less susceptible to the decrease in electron mobility caused by the grain boundaries. .

[0172] The CAAC-OS film was observed by TEM from a direction roughly parallel to the sample surface (cross-sectional TEM observation). When observed, it can be confirmed that metal atoms are arranged in layers in the crystalline part. Each layer of the CAAC-OS film is formed on a surface (also called a surface to be formed) or on a concave surface of the upper surface. The shape reflects the convexity and is aligned parallel to the surface on which the CAAC-OS film is formed or the top surface. In this specification, "parallel" means that two straight lines are arranged at an angle of -10° or more and 10° or less. Therefore, it includes the case where the angle is between -5° and 5°. " refers to a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This includes angles between 85° and 95°.

[0173] On the other hand, the CAAC-OS film was observed by TEM from a direction approximately perpendicular to the sample surface (plane T EM observation reveals that metal atoms are arranged in triangular or hexagonal shapes in the crystalline region. However, no regularity was observed in the arrangement of metal atoms between different crystal regions. do not have.

[0174] When electron diffraction is performed on the CAAC-OS film, spots (bright spots) indicating orientation are observed. is observed.

[0175] Cross-sectional and planar TEM observations revealed that the crystals in the CAAC-OS film had an orientation. It can be seen that this is the case.

[0176] X-ray diffraction (XRD) of the CAAC-OS film The structure of the CAAC-OS film was analyzed using the out-of-plane method. In the analysis, a peak may appear at a diffraction angle (2θ) of around 31°. This peak is due to the Since it is attributed to the (00x) plane (x is an integer) of the nGaZn oxide crystal, The crystals of the OS film have a c-axis orientation, and the c-axis is oriented in a direction approximately perpendicular to the surface on which the film is formed or the upper surface. It can be confirmed that there is.

[0177] On the other hand, the in-p X-rays incident on the CAAC-OS film are perpendicular to the c-axis. In the Lane analysis, a peak may appear around 2θ of 56°. The crystal structure of InGaZn oxide is composed of (110) plane. In the case of a crystalline oxide semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is aligned with the axis (φ When the analysis (φ scan) is performed while rotating the sample around the (110) axis, the bonds equivalent to the (110) plane are observed. In contrast, in the case of the CAAC-OS film, 2 peaks are observed. Even when θ is fixed at around 56° and φ is scanned, no clear peak appears.

[0178] From the above, it can be concluded that the orientation of the a-axis and b-axis is uniform between different crystal regions in the CAAC-OS film. Although it is irregular, it has a c-axis orientation, and the c-axis is parallel to the normal vector of the surface on which it is formed or the upper surface. Therefore, the layered structure confirmed by the cross-sectional TEM observation mentioned above is consistent with the Each layer of arranged metal atoms is a plane parallel to the ab plane of the crystal.

[0179] The crystalline part is formed when the CAAC-OS film is formed or after a crystallization treatment such as a heat treatment. As described above, the c-axis of the crystalline part is aligned with the surface on which the CAAC-OS film is formed. Or, the orientation is parallel to the normal vector of the upper surface. When the shape of the CAAC-OS film is changed by etching, the c-axis of the crystal part is aligned with the surface of the CAAC-OS film. It may not be parallel to the normal vector of the forming surface or top surface.

[0180] Furthermore, the crystallinity of the CAAC-OS film may not be uniform. When the crystalline part of the film is formed by crystal growth from the vicinity of the top surface of the CAAC-OS film, The area near the surface may have a higher crystallinity than the area near the surface to be formed. When impurities are added to the AC-OS film, the crystallinity of the region where the impurities are added changes, and the Regions of differing crystallinity may be formed.

[0181] In addition, in the out-of-plane analysis of the CAAC-OS film, 2θ was 31° In addition to the peaks around 2θ around 36°, a peak may also appear. The peaks around the center of the CAAC-OS film indicate that the CAAC-OS film contains crystalline parts that do not have the c-axis orientation. The CAAC-OS film exhibits a peak at 2θ of around 31° and a peak at 2θ of around 36°. It is preferable that no peaks are present nearby.

[0182] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is made of an element other than the main component, such as silicon or a transition metal element. The elements such as ZnO, which have stronger bonding strength with oxygen than the metal elements constituting the oxide semiconductor film, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disrupted, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Because the diameter (or molecular radius) is large, when the molecule is contained inside the oxide semiconductor film, The impurities contained in the oxide semiconductor film are likely to disturb the atomic arrangement of the oxide semiconductor film, which may result in a decrease in crystallinity. The pure material may act as a carrier trap or a carrier generation source.

[0183] The CAAC-OS film is an oxide semiconductor film with a low density of defect states. Oxygen vacancies in semiconductor films can act as carrier traps and trap hydrogen. This can become a carrier generation source.

[0184] The low impurity concentration and low defect level density (low oxygen vacancies) are called high-purity intrinsic or The term "high-purity intrinsic" refers to a substantially high-purity intrinsic oxide semiconductor. Since the film has a small number of carrier generation sources, the carrier density can be reduced. The transistor using the oxide semiconductor film has electrical characteristics (noise) such that the threshold voltage is negative. It is also called "marine.") It is rare for it to become pure or substantially pure. An intrinsic oxide semiconductor film has few carrier traps. Transistors using this film have little fluctuation in electrical characteristics and are highly reliable. Note that it takes time for the charges trapped in the carrier traps in the oxide semiconductor film to be released. The time is long and the charge may behave as if it is fixed. Therefore, a transistor using an oxide semiconductor film with a high density of defect states has unstable electrical characteristics. This may be the case.

[0185] In addition, the electrical characteristics of transistors using CAAC-OS films are improved by irradiation with visible light or ultraviolet light. There is little gender variation.

[0186] <Single-crystal oxide semiconductor> The single-crystal oxide semiconductor film has a low impurity concentration and a low density of defect states (few oxygen vacancies). Therefore, the carrier density can be reduced. A transistor using a crystalline oxide semiconductor film rarely has normally-on electrical characteristics. Furthermore, since the single-crystal oxide semiconductor film has a low impurity concentration and a low density of defect states, Therefore, in the case of a transistor using a single-crystal oxide semiconductor film, the number of carrier traps may be reduced. The transistor has small fluctuations in electrical characteristics and is highly reliable.

[0187] Note that the oxide semiconductor film has a high density when it has few defects. High crystallinity increases density. In addition, the oxide semiconductor film has a low concentration of impurities such as hydrogen. The density of a single-crystal oxide semiconductor film is higher than that of a CAAC-OS film. The CAAC-OS film has a higher density than the microcrystalline oxide semiconductor film. The conductor film has a higher density than the microcrystalline oxide semiconductor film. The density is higher than that of an crystalline oxide semiconductor film.

[0188] <Polycrystalline oxide semiconductor> In the polycrystalline oxide semiconductor film, crystal grains can be confirmed by high-resolution TEM observation. The crystal grains contained in the polycrystalline oxide semiconductor film can be observed, for example, by high-resolution TEM. In the observation image, 2nm to 300nm, 3nm to 100nm, or 5nm to 50nm In addition, polycrystalline oxide semiconductor films are often characterized by grain sizes of 100 μm or less using high-resolution TEM. In some cases, grain boundaries can be identified in the observed image.

[0189] The polycrystalline oxide semiconductor film has a plurality of crystal grains, and the crystal orientation between the plurality of crystal grains is In addition, when an XRD device is used for a polycrystalline oxide semiconductor film, When structural analysis is performed, for example, the out of polycrystalline oxide semiconductor film having InGaZnO4 crystals In the t-of-plane analysis, there is a peak at 2θ around 31° and a peak at 2θ around 36°. peak or other peaks may appear.

[0190] A polycrystalline oxide semiconductor film has high crystallinity and therefore may have high electron mobility. Therefore, a transistor using a polycrystalline oxide semiconductor film has high field-effect mobility. However, in a polycrystalline oxide semiconductor film, impurities may segregate at the grain boundaries. The grain boundaries of the polycrystalline oxide semiconductor film become defect states. Since the oxide semiconductor film may become a carrier trap or a carrier generation source, The transistors using the CAAC-OS film showed a small change in electrical characteristics compared to the transistors using the CAAC-OS film. may result in a transistor with low reliability.

[0191] <Microcrystalline oxide semiconductor> In the microcrystalline oxide semiconductor film, crystal parts can be clearly seen in the TEM image. The crystal parts contained in the microcrystalline oxide semiconductor film may have a size of 1 nm or more and 100 nm or more. In particular, the size of the particles is between 1 nm and 10 nm. Nanocrystals (nc) are microcrystals with a diameter of 1 nm or less, or 1 nm to 3 nm. The oxide semiconductor film having nc-OS (nanocrystalline O The nc-OS film is called an oxide semiconductor film. In EM observation images, the grain boundaries may not be clearly visible.

[0192] The nc-OS film is a microscopic region (e.g., a region of 1 nm to 10 nm, especially a region of 1 nm or less). The nc-OS film has a periodic atomic arrangement in the region of 3 nm or less. There is no regularity in the crystal orientation between the crystal parts, and therefore no orientation is observed throughout the film. Therefore, the nc-OS film cannot be distinguished from an amorphous oxide semiconductor film depending on the analytical method. For example, XRD, which uses X-rays with a diameter larger than that of the crystal part, is used for nc-OS films. When structural analysis is performed using the device, the crystal plane is analyzed using the out-of-plane method. In addition, the peaks indicating the crystal grains with a diameter larger than that of the crystalline part (e.g., When electron beam diffraction (also called selected area electron beam diffraction) is performed using an electron beam of 50 nm or more, On the other hand, for the nc-OS film, the crystalline The probe diameter is close to the size of the crystal part or smaller than the crystal part (for example, 1 nm to 30 nm). When electron beam diffraction using a sagittal beam (also called nanobeam electron diffraction) is performed, spots are observed. Furthermore, when nanobeam electron diffraction is performed on nc-OS, a circular pattern (phosphorus) is observed. In addition, when nanobeam electrons are applied to the nc-OS, areas with high brightness (like a circle) may be observed. When sagittal diffraction is performed, multiple spots may be observed within the ring-shaped region.

[0193] The nc-OS film is an oxide semiconductor film with higher order than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect states than the amorphous oxide semiconductor film. In the nc-OS film, there is no regularity in the crystal orientation between different crystal parts. The OS film has a higher density of defect states than the CAAC-OS film.

[0194] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0195] (Embodiment 2) In this embodiment mode, a method for manufacturing an element substrate of a display device, which is different from that in Embodiment Mode 1, will be described. In this embodiment, as in the first embodiment, a metal oxide semiconductor having a channel region is used. The metal oxide film and the conductive film that functions as the source electrode and the drain electrode are formed on one photomask. On the other hand, in this embodiment, the structure of the conductive film functioning as the capacitance line is Different from form 1.

[0196] A specific example of an element substrate of a liquid crystal display device using liquid crystal elements for the pixels 13 will be described. Here, a top view of the pixel 13 shown in FIG. 1(B) is shown in FIG.

[0197] In the pixel 13 shown in FIG. 6, a part of the metal oxide film 109c functions as a capacitance line. The metal oxide films 109c provided in adjacent pixels are connected by a conductive film 173.

[0198] In the pixel 13 shown in FIG. 6, an opening provided in the insulating film 119 (see FIG. 7(A)) 171 and 172, a metal oxide film 109c and a conductive film 12 functioning as a pixel electrode The conductive film 173 formed at the same time as the metal oxide film 109c is connected to the opening 151. (See FIG. 4(B)). As a result, the metal oxide film 109c functions as a capacitance line and also functions as a capacitance line. It functions as one electrode of the quantum element.

[0199] The capacitance element 25 is made up of a conductive metal oxide film 109c, an insulating film 121 (see FIG. 7(B)), and a The conductive film 123 functions as a pixel electrode. The film 109c is connected to the conductive film 173, and thus one electrode ( Here, the conductive metal oxide film 109c) can be set to the same potential.

[0200] In the pixel 13 shown in this embodiment, the conductive films 114 and 115 are formed as capacitor lines at the same time. The conductive films 114 and 115 have a light-shielding property, and therefore the aperture ratio of the pixel is increased. It can be increased.

[0201] Next, using the cross-sectional views of the dashed and dotted lines AB and CD shown in Figure 6, A method for manufacturing the element substrate of the device will be described.

[0202] Through the same steps as in the first embodiment, the first to third photomasks are used. By this process, a conductive film functioning as a gate electrode is formed on the substrate 101 as shown in FIG. film 103, insulating films 105, 106, metal oxide films 109a, 109c, conductive films 114, 1 15, an insulating film 119, and an insulating film 120 are formed. The metal oxide film 109a is not formed by the second photomask. , 109c and conductive films 114 and 115 can be formed. This reduces the number of photomasks required.

[0203] Next, a photolithography process using a fourth photomask is performed on the insulating film 120. After forming the mask, the insulating films 119 and 120 are etched using the mask to form conductive layers. An opening 152 exposing the film 115 is formed, and the insulating film 120 is etched. Openings 171 and 172 are formed to expose the conductive metal oxide film (see FIG. 7(B)). (See FIG. 1). Also, the insulating film 121 can be formed by this etching.

[0204] Next, the conductive metal oxide film 109c, the exposed portion of the conductive film 115, and the insulating film A light-transmitting conductive film is formed on the substrate 121. Next, a photoresist is formed on the substrate 121 using a fifth photomask. A mask is formed on the light-transmitting conductive film by a lithography process. The conductive film having light-transmitting properties is etched to form a conductive film 123 that functions as a pixel electrode. The conductive film 173 is formed in the adjacent pixels. The metal oxide film 109c has a function of electrically connecting the metal oxide film 109c formed on the surface of the insulating film 109. After that, the mask is removed (see FIG. 7(C)).

[0205] Through the above steps, the transistor 22 and the capacitor 25 can be manufactured. By the above steps, an element substrate having pixels with a higher aperture ratio can be manufactured. .

[0206] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0207] (Embodiment 3) In this embodiment, a FFS (Fringe Field Switch) is used as an example of a horizontal electric field method. The pixel structure of a liquid crystal display device in a switching mode will be used for explanation.

[0208] In the FFS mode liquid crystal display device shown in this embodiment, the common electrodes are striped. The liquid crystal orientation is controlled by applying an electric field generated by the pixel electrode and the common electrode between the two electrodes to the liquid crystal. FFS mode LCD devices have a high aperture ratio and can provide a wide viewing angle. Cut.

[0209] Here, a top view of the pixel 13 shown in FIG. 1(B) is shown in FIG.

[0210] The pixel 13 shown in FIG. 8 has one metal oxide film 183 in each pixel. Conductive films 181 and 182 functioning as a source electrode and a drain electrode are provided on the semiconductor substrate 83. The conductive film 181 also functions as a signal line. In addition, the conductive film 181 electrically connects the conductive films 181 provided in the adjacent pixels. The conductive film 187 is provided on the conductive film 181 via an insulating film (not shown). The conductive film 181 is connected to the openings 184 and 185. A conductive film 186 is provided to function as a striped common electrode. 86 are formed simultaneously.

[0211] In the display device described in this embodiment, the conductive film 186 functioning as a common electrode is Since the conductive films 181, 187 and As a result, the area overlapping with the conductive film 103 functioning as the scanning line is reduced. 3 and the conductive film 186, and between the conductive films 181, 187 and the conductive film 186. The parasitic capacitance can be reduced.

[0212] Next, using the cross-sectional views of the dashed and dotted lines AB and EF shown in FIG. A method for manufacturing the element substrate of the device will be described.

[0213] After the same steps as in the first embodiment, a first photomask is used to form the semiconductor device shown in FIG. 9(A As shown in FIG. 1, a conductive film 103 that functions as a gate electrode is formed on a substrate 101. In the same manner as in the first embodiment, insulating films 105 and 106 are formed on the substrate 101 and the conductive film 103. A metal oxide film 108 and a conductive film 110 are formed.

[0214] Next, by the process using the second photomask shown in Embodiment 1, In this way, the metal oxide film 183 and the conductive films 181 and 182 are formed. As with the conductive film 114 in Embodiment 1, one of the source and drain electrodes of the transistor The conductive film 182 functions as a signal line and also as a gate electrode. Similarly to the conductive film 115, the conductive film 115 functions as the other of the source electrode and the drain electrode of the transistor. Here, the metal oxide film 183, the conductive film 181, and the first photomask are removed by the second photomask. 82 can be formed, reducing the number of photomasks used in the element substrate manufacturing process. can.

[0215] Next, an opening 151 is formed by a process using the third photomask shown in the first embodiment. After forming the insulating film 119, the insulating film 120 is formed on the metal oxide film 183 and the insulating film 119. (See FIG. 9(C)).

[0216] In the metal oxide film 183, a region 191 in contact with the insulating film 120 is As a result, the insulating film 11 functions as a pixel electrode. 9 is formed using an oxide insulating film. The region in contact with the insulating film 119 has a low interface state density with the insulating film 119. , which is formed using an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition. Then, oxygen contained in the insulating film 119 moves to the metal oxide film 183, and As a result, the oxygen vacancy content in the metal oxide film 183 can be reduced. Therefore, the region 192 in contact with the insulating film 119 functions as a channel region. In the conductive film 183, the regions in contact with the conductive films 181 and 182 become low resistance regions.

[0217] When forming the insulating film 119 having the opening 151, the edge of the opening 151 and the scanning The distance between the conductive film functioning as a signal line and the edge of the opening 151 is The distance to the film 181 is set to be greater than 1.5 μm and greater than 2 μm. In the metal oxide film 183, the region in contact with the insulating film 120 has oxygen vacancies. Or, the conductivity is increased by including impurities, but the conductivity is also increased in the region adjacent to the region. This is because the impurities diffuse laterally, and the conductivity of the metal oxide film 183 increases. Therefore, impurities are contained in the region not in contact with the insulating film 121, and the resistance is reduced. Therefore, the distance between the edge of the opening 151 and the conductive film functioning as the scanning line is set to 1.5 By making the thickness larger than 2 μm, the channel of the transistor 22 It is possible to prevent the resistance of the region from decreasing, and to create a transistor with normally-off characteristics. In addition, the edge of the opening 151 and the conductive film 181 that functions as a signal line can be formed. By making the distance larger than 1.5 μm, or even larger than 2 μm, The conductive film 181 functions as a pixel electrode, and the metal oxide film 183 functions as a pixel electrode. The voltages of 1 and 2 do not affect each other, preventing display defects.

[0218] Next, a photolithography process using a fourth photomask is performed on the insulating film 121. After forming the mask, the insulating films 119 and 120 are etched using the mask to form conductive layers. Openings 184 and 185 are formed to expose the film 181, and an insulating film 121 is formed. (See Figure 10(A)).

[0219] Next, a light-transmitting conductive film is formed over the exposed portion of the conductive film 181 and the insulating film 121. Next, a photolithography process using a fifth photomask is performed to form a light-transmitting film. A mask is formed over the conductive film, and the light-transmitting conductive film is etched using the mask. The conductive film 186 that functions as a common electrode is formed, and the conductive film 186 that functions as a signal line is formed. A conductive film 187 is formed. The conductive film 187 electrically connects the conductive films 181 provided in the adjacent pixels. After this, the mask is removed (see FIG. 10(B)).

[0220] Through the above steps, the transistor 22 and the capacitor 25 can be manufactured. By the above steps, an element substrate having pixels with a higher aperture ratio can be manufactured. Furthermore, it is possible to fabricate an FFS mode liquid crystal display device.

[0221] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0222] (Fourth embodiment) In this embodiment, the defect amount of the metal oxide film is smaller than that of the first to third embodiments. A semiconductor device having a transistor capable of further reducing the The transistor described in this embodiment has a structure similar to that of the transistors in Embodiments 1 and 2. In comparison, a multilayer film having a plurality of metal oxide films is provided instead of the metal oxide film. The points are different.

[0223] 11 shows a transistor of the semiconductor device, which is shown by a point on the dashed lines AB and CD in FIG. FIG. 1 is a cross-sectional view taken along dashed lines AB and CD.

[0224] The transistor 22b shown in FIG. 11A has multilayer films 250a and 250b on the insulating film 106. The multilayer film 250a includes a first metal oxide film 251a in contact with the insulating film 106, a second metal oxide film 251b in contact with the insulating film 106, and a third metal oxide film 251c in contact with the insulating film 106. and a second metal oxide film 252a in contact with the first metal oxide film 251a and the insulating film 119. It has.

[0225] The multilayer film 250b provided on the insulating film 106 shown in FIG. 11(A) functions as a capacitance electrode. The multilayer film 250b includes a first metal oxide film 251b in contact with the insulating film 107b, and The second metal oxide film 252b is in contact with the first metal oxide film 251b and the insulating film 119. do.

[0226] The second metal oxide films 252a and 252b are formed on the first metal oxide films 251a and 251b. It is a metal oxide film composed of one or more constituent elements. At the interfaces between the metal oxide films 251a and 251b and the second metal oxide films 252a and 252b, Therefore, the movement of carriers is not hindered at the interface, The field effect mobility of the transistor is increased.

[0227] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 252b are Representative examples include In-Ga oxide, In-Zn oxide, and In-M-Zn oxide (M is Al). , Ga, Ti, Y, Zr, La, Ce, or Nd).

[0228] The second metal oxide films 252a and 252b are formed on the first metal oxide films 251a and 251b. The energy of the bottom of the conduction band is closer to the vacuum level than 1b, and is typically a second metal oxide. The energy of the lower end of the conduction band of the first metal oxide film 251a, 252b is The difference in energy between the lower end of the conduction band of 51b and the lower end of the conduction band of 51b is 0.05 eV or more, 0.07 eV or more, or 0 0.1eV or more, or 0.15eV or more and 2eV or less, 1eV or less, 0.5eV or less , or 0.4 eV or less. That is, the electron affinity of the second metal oxide films 252a and 252b is The difference between the electron affinity of the first metal oxide film 251a and the electron affinity of the first metal oxide film 251b is 0.05 eV or less. above, 0.07 eV or more, 0.1 eV or more, or 0.15 eV or more and 2 eV or less, 1 eV or less, 0.5 eV or less, or 0.4 eV or less.

[0229] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 252b are The inclusion of In is preferable because it increases carrier mobility (electron mobility).

[0230] The second metal oxide films 252a and 252b may be made of Al, Ga, Ti, Y, Zr, La, Having Ce or Nd in a higher atomic ratio than In may have the following effects: (1) The energy gap of the second metal oxide films 252a and 252b is increased. (2) The electron affinity of the second metal oxide films 252a and 252b is reduced. (3) From the outside (4) Compared to the first metal oxide films 251a and 251b, the diffusion of impurities from the first metal oxide films 251a and 251b is suppressed. (5) Ga, Y, Zr, La, Ce, or Nd bonds with oxygen. Because it is a strong metallic element, oxygen deficiency is less likely to occur.

[0231] When the first metal oxide films 251a and 251b are In-M-Zn oxides, In and When the sum of In and M is 100 atomic %, the atomic ratio of In to M is preferably I The atomic ratio of n to M is preferably such that In is greater than 25 atomic % and M is greater than 75 atomic %. % or less, more preferably In is greater than 34 atomic % and M is 66 atomic % or less. It must be less than mic%.

[0232] When the second metal oxide films 252a and 252b are In-M-Zn oxides, In and When the sum of In and M is 100 atomic %, the atomic ratio of In to M is preferably I n is less than 50 atomic % and M is greater than 50 atomic %, more preferably Assume that In is less than 25 atomic % and M is greater than 75 atomic %.

[0233] In addition, the first metal oxide films 251a and 251b and the second metal oxide films 252a and 25 2b is In-M-Zn oxide M (M is Al, Ga, Ti, Y, Zr, La, Ce, or In the case of Nd, the second metal oxide film is thicker than the first metal oxide film 251a, 251b. M (Al, Ga, Ti, Y, Zr, La, Ce, or The atomic ratio of Nd) is large, and typically, the first metal oxide films 251a and 251b contain It is 1.5 times or more, preferably 2 times or more, and more preferably 3 times as large as the atoms contained in the above-mentioned This is a high atomic ratio.

[0234] In addition, the first metal oxide films 251a and 251b and the second metal oxide films 252a and 25 2b is In-M-Zn oxide (M is Al, Ga, Ti, Y, Zr, La, Ce, or In the case where the second metal oxide films 252a and 252b are made of In:M:Zn=x1:y1 :z1 [atomic ratio], and the first metal oxide films 251a and 251b are In:M:Zn=x2: When y2:z2 is the atomic ratio, y1 / x1 is greater than y2 / x2, and preferably, y1 / x1 is 1.5 times or more than y2 / x2. More preferably, y1 / x1 is y More than twice as large as 2 / x2, more preferably, y1 / x1 is more than three times larger than y2 / x2. Greater than.

[0235] When the first metal oxide films 251a and 251b are In-M-Zn oxides (M is Al, Ga, Ti, Y, Zr, La, Ce, or Nd), in the target used to form the first metal oxide films 251a and 25 1b, if the atomic ratio of metal elements is In:M:Zn =x1:y1:z1, then 、 x1 / y1 is 1 / 3 or more and 6 or less, further 1 or more and 6 or less and z1 / y1 is preferably 1 / 3 or more and 6 or less, further 1 or more and 6 or less. By setting z1 / y1 to 1 or more and 6 or less, it becomes easier to form a CAAC-OS film as the first metal oxide films 251a and 25 1b. Representative examples of the atomic ratio of metal elements of the target include In:M:Zn = 1:1: 1, In:M:Zn = 1:1:1.2, In :M:Zn = 3:1:2, etc.

[0236] When the second metal oxide films 252a and 252b are In-M-Zn oxides (M is Ga, Y, Z r, La, Ce, or Nd), in the target used to form the second metal oxide films 252a and 252b, if the atomic ratio of metal elements is In: M:Zn = x2:y2 :z2, then 、 x2 / y2 < x1 / y1 and z2 / y2 is preferably from 1 / 3 to 6, more preferably from 1 to 6. By setting z2 / y2 to 1 or more and 6 or less, it becomes easier to form a CAAC-OS film as the second metal oxide films 252a and 252b. Representative examples of the atomic ratio of metal elements of the target include In:M:Zn = 1:3:2 ​, In:M:Zn=1:3:4, In:M:Zn=1:3:6, In:M:Zn=1:3 :8 etc.

[0237] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 25 The atomic ratio of 2b is subject to a margin of error of plus or minus 40% from the atomic ratio above. include.

[0238] The second metal oxide films 252a and 252b are formed as the first metal oxide films when forming the film that will become the insulating film 119. It also functions as a film for reducing damage to the metal oxide film 251a of No. 1.

[0239] The thickness of the first metal oxide films 251a and 251b is preferably 3 nm or more and 200 nm or less. The thickness is preferably 3 nm or more and 100 nm or less, and more preferably 3 nm or more and 50 nm or less. The thickness of the metal oxide films 252a and 252b is 3 nm or more and 100 nm or less, preferably 3 nm or more and 50 nm.

[0240] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 252b are For example, the non-single crystal structure may be a CAAC-OS (C Axis Aligned-Crystalline Oxide Semiconductor uctor), polycrystalline structure, microcrystalline structure (described below), or amorphous structure.

[0241] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 25 In 2b, there are amorphous structure regions, microcrystalline structure regions, polycrystalline structure regions, and CAAC-O A mixed film having two or more of the S region and the single crystal structure region may be formed. For example, amorphous structure regions, microcrystalline structure regions, polycrystalline structure regions, CAAC-OS regions In some cases, the crystal structure may be a single layer structure having two or more regions of either a single crystal structure or a mixed structure. The composite film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CAAC- It may have a layered structure of two or more regions, either an OS region or a single crystal structure region. .

[0242] Here, the second metal oxide film 251a is formed between the first metal oxide film 251a and the insulating film 119. Therefore, the second metal oxide film 252a and the insulating film 119 are In this case, even if carrier traps are formed by impurities and defects, the carrier traps There is a gap between the region where the gap is to be formed and the first metal oxide film 251a. Electrons flowing through the first metal oxide film 251a are less likely to be captured by carrier traps, and the It is possible to increase the on-current of the transistor 22b and also to enhance the field effect mobility. Furthermore, when an electron is captured in a carrier trap, the electron becomes a negative fixed charge. As a result, the threshold voltage of the transistor varies. There is a gap between the first metal oxide film 251a and the region where carrier traps are formed. Therefore, it is possible to suppress the capture of electrons in the carrier traps, and the threshold voltage Pressure fluctuations can be reduced.

[0243] In addition, the second metal oxide film 252a can block impurities from the outside. Therefore, it is possible to reduce the amount of impurities that move from the outside to the first metal oxide film 251a. In addition, oxygen vacancies are less likely to form in the second metal oxide film 252a. It is possible to reduce the impurity concentration and oxygen vacancy in the first metal oxide film 251a. be.

[0244] The first metal oxide films 251a and 251b and the second metal oxide films 252a and 25 2b is a continuous junction (in particular, the energy at the bottom of the conduction band) rather than simply stacking each film. The structure is such that the thickness of each film changes continuously. At the interface, the first metal oxide films 251a and 251b have trap centers and recombination centers. Impurities that form barriers that hinder the flow of carriers, or defect levels like nuclei The laminated structure is such that the first metal oxide film 251a and the second metal oxide film 251b are not present. If impurities are present between the second metal oxide films 251a and 251b and the second metal oxide films 252a and 252b, the energy The continuity of the energy band is lost, and carriers are trapped or recombined at the interface, It will disappear.

[0245] To form continuous junctions, a multi-chamber deposition system equipped with a load lock chamber is required. Each film is laminated in succession using a sputtering device without being exposed to the atmosphere. Each chamber in the sputtering equipment is indispensable for the metal oxide film. An adsorption type vacuum pump such as a cryopump is used to remove as much water as possible. High vacuum pumping (5×10 -7 Pa~1×10 -4 It is preferable to Alternatively, a turbomolecular pump and cold trap can be combined to evacuate the chamber from the exhaust system. It is preferable to prevent gases, especially gases containing carbon or hydrogen, from flowing back into the .

[0246] As shown in FIG. 11B, the transistor 22c has a multilayer film 255a. Alternatively, the multilayer film 255b may be provided as a capacitance electrode.

[0247] The multilayer film 255a includes a third metal oxide film 253a, a first metal oxide film 251a, and A second metal oxide film 252a is laminated in this order. A third metal oxide film 253a is laminated in this order. The first metal oxide film 252a is in contact with the insulating film 106, the second metal oxide film 252b is in contact with the insulating film 119, and the first metal oxide film 252c is in contact with the insulating film 119. The oxide film 251a functions as a channel region.

[0248] The multilayer film 255b includes a third metal oxide film 253b, a first metal oxide film 251b, and The second metal oxide film 252b is laminated in this order. The third metal oxide film 253b is laminated in this order. The second metal oxide film 252b is in contact with the insulating film 106, and the second metal oxide film 252b is in contact with the insulating film 119.

[0249] The third metal oxide films 253a and 253b are formed in a layer similar to the second metal oxide films 252a and 252b. Similar materials and forming methods can be used as appropriate.

[0250] The third metal oxide films 253a and 153b are thicker than the first metal oxide films 251a and 251b. It is preferable that the thickness of the third metal oxide films 253a and 153b is 1 nm or more. By making the thickness 5 nm or less, preferably 1 nm or more and 3 nm or less, the threshold voltage of the transistor can be reduced. It is possible to reduce the amount of pressure fluctuation.

[0251] The transistor described in this embodiment has the insulating film 106 and the first metal oxide film 251a. The third metal oxide film 253a is provided between the first metal oxide film 251 and the second metal oxide film 252. A second metal oxide film 252a is provided between the insulating film 119 and the insulating film 119. Therefore, the insulating film 106 and the first metal oxide film 251a are separated from each other by the insulating film 106 and the first metal oxide film 251b. Carrier traps are formed between the insulating film 119 and the insulating layer 111 due to impurities and defects. However, there is a gap between the region where the carrier traps are formed and the first metal oxide film 251a. As a result, electrons flowing through the first metal oxide film 251a are trapped in the carrier traps. This makes it possible to increase the on-current of the transistor 22c. In addition, when electrons are captured in the carrier traps, As a result, the threshold voltage of the transistor However, the first metal oxide film 251a and the carrier traps are formed. The gap between the region where the carrier trap is formed reduces the capture of electrons in the carrier trap. This can reduce the fluctuation in the threshold voltage of the transistor 22c. .

[0252] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0253] (Embodiment 5) In this embodiment, the on-state current is large, the field effect mobility is high, and the variation in electrical characteristics is small. A method for manufacturing a small number of transistors and capacitors by reducing the number of photomasks is described. 14 and 15. In this embodiment, the transistor shown in the second embodiment is used. Although the present embodiment will be described using a transistor and a manufacturing method thereof, the present embodiment will be applied to other embodiments as appropriate. Furthermore, the description of the configuration that overlaps with the second embodiment will be omitted.

[0254] 14 is a top view of the pixel 13, and FIG. 15(A) shows the pixel 13 along the dashed lines AB and CD in FIG. 15(A) is a cross-sectional view taken along the dashed line EF in FIG. 14, and FIG. 15(B) is a cross-sectional view taken along the dashed line EF in FIG.

[0255] The transistor 22d is provided in the area where the scanning line and the signal line intersect. The gate electrode 22d is made up of a conductive film 103 which functions as a gate electrode, a gate insulating film (not shown in FIG. 15), and a gate insulating film 106. ), a metal oxide film 109a in which a channel region is formed on the gate insulating film, Conductive films 114 and 115 functioning as source and drain electrodes, and a metal oxide film 109 a, an insulating film (not shown in FIG. 15) covering the conductive films 114 and 115, and a gate electrode The transistor 22d is formed by the conductive film 243 that functions as a gate electrode. The conductive film 103 and the conductive film 243 functioning as gate electrodes are connected to each other. do.

[0256] Next, the cross-sectional structure of the transistor 22d will be described with reference to FIG. 15(B) is a cross-sectional view of the transistor 22d in the channel length direction, and FIG. 15(C) is a cross-sectional view of the transistor 22d in the channel length direction. 22d in the channel direction.

[0257] The transistor 22d shown in FIGS. 15A and 15B is a channel-etched transistor. A conductive film 103 that functions as a gate electrode is provided on a substrate 101. An insulating film 105 in contact with the plate 101 and the conductive film 103, and an insulating film 106 in contact with the insulating film 105. and a metal oxide film 109a overlapping the conductive film 103 via insulating films 105 and 106. The insulating film 105 and the conductive films 114 and 115 are in contact with the metal oxide film 109a. The insulating film 119 contacting the insulating film 106, the metal oxide film 109a, and the conductive films 114 and 115. an insulating film 121 in contact with the insulating film 119 and a gate electrode in contact with the insulating film 121; The insulating film 105 and the insulating film 106 function as gate insulating films. The insulating films 119 and 121 function as gate insulating films.

[0258] As shown in FIG. 15B, the conductive film 103 and the conductive film 243 are formed by the insulating film 105 and the insulating film 106, the insulating film 119, and the insulating film 121 are connected in an opening 241. In addition, in the channel width direction of the transistor, the end of the conductive film 243 is formed on the metal oxide film The insulating film 119 and the insulating film 121 are disposed on the outer side of the end of the metal oxide film 109a. The side surface of the oxide film 109a faces the conductive film 243. The conductive film 243 is formed in the opening 241. , it faces the side surface of the metal oxide film 109a.

[0259] The conductive film 243 is formed using a material and a manufacturing method similar to those of the conductive films 123 and 124. The opening 241 can be formed at the same time as the opening 152 is formed. As a result, five photomasks can be used without increasing the number of photomasks. This can be used to fabricate transistor 22d.

[0260] In FIG. 15B, the metal oxide film 109 The side surface of the conductive film 103 a faces the conductive film 243 that functions as a gate electrode. The electric field of the conductive film 243 affects not only the plane of the metal oxide film 109a but also the side surface. As a result, the region in which carriers flow in the metal oxide film 109a is separated by the insulating film 106 and the metal The metal oxide film 109a and the insulating film 119 are the only interfaces between the metal oxide film 109a and the insulating film 119. The area is wide, including the inside of the metal oxide film 109a, and therefore the capacitance of the transistor is As a result, the on-current of the transistor increases and the electric field The field-effect mobility is high, typically 10 cm 2 / V·s or more, and even 20cm 2 / V·s or more. The L length of the transistor is set to 0.5 μm or more and 6.5 μm or more. By setting the thickness to be preferably greater than 1 μm and less than 6 μm, the increase in field effect mobility becomes noticeable. Author.

[0261] In addition, at the end of the metal oxide film 109a processed by etching or the like, The damage caused by this leads to the formation of defects, and the wafer is contaminated by the adhesion of impurities. One of the conductive film 103 and the conductive film 243 which functions as a gate electrode of a transistor When only the metal oxide film 109a is formed, even if the metal oxide film 109a is intrinsic or substantially intrinsic, the electric field By applying such stress, the edge of the metal oxide film 109a is activated, and n In addition, the n-type region is likely to become a low-resistance region. If the n-type region is placed linearly between the n-type and n-type regions, the n-type region will become a carrier path, resulting in a parasitic channel. As a result, the drain current rises gradually with the threshold voltage. In addition, the threshold voltage of the transistor is shifted negatively. As shown in FIG. 15(B), the conductive film 103 and the conductive film 243 are at the same potential, and the channel In the width direction, the conductive film 243 faces the side surface of the metal oxide film 109a, thereby forming a conductive The electric field of the film 243 also affects the side surface of the metal oxide film 109a. The occurrence of parasitic channels at the side surface of the O9a or at the edge including the side surface and its vicinity is suppressed. As a result, the drain current rises sharply at the threshold voltage, resulting in excellent electrical characteristics. This results in a transistor that is

[0262] In addition, the conductive film 103 and the conductive film 243 are provided to shield the electric field from the outside. In order to have a shielding function, a conductive film 243 is provided between the substrate 101 and the conductive film 243 and on the conductive film 243. As a result, the fixed charges generated by the metal oxide film 109a do not affect the metal oxide film 109a. Apply a negative potential to the gate electrode - Gate Bias-Temperature Transistor (GBT) The degradation of the drain voltage during the stress test is suppressed, and the on-state current at different drain voltages is also improved. Fluctuations in the rising voltage of the current can be suppressed.

[0263] The BT stress test is a type of accelerated test that detects the transitions that occur during long-term use. It is possible to evaluate the characteristic changes (i.e., aging) of the transistor in a short time. The amount of change in the threshold voltage of a transistor before and after stress testing is used to examine reliability. This is an important indicator. The smaller the amount of change in threshold voltage before and after the BT stress test, the better. Therefore, it can be said that this is a highly reliable transistor.

[0264] In addition, in FIG. 15B, one side of the metal oxide film 109a in the channel width direction An opening is provided on the side of the conductive film 103 and the conductive film 243 in the opening. An opening is also provided on the other side surface, and the conductive film 103 and the conductive As a result, an increase in the resistance value of the conductive film 243 can be prevented. At the same time, the electric field of the conductive film 243 is applied to both sides of the metal oxide film 109a. It is possible to affect the dielectric film 109a, thereby increasing the on-current of the transistor. In addition, the field effect mobility can be increased.

[0265] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0266] (Sixth embodiment) A driver circuit can be formed using the transistors and capacitors described in any of Embodiments 1 to 5. It can be made.

[0267] The transistor 22d described in Embodiment 4 has a large on-state current and high mobility. Therefore, circuits that are made up of transistors that need to pass a large current, such as buffers, By using the transistor 22d, the channel length and the channel width can be reduced. This allows the area of ​​the transistor to be reduced. In a semiconductor device having a driving circuit in the peripheral portion, typically a display device, By reducing the area of ​​the operating circuit, the area of ​​the pixel portion in the display device can be increased. That is, it is possible to narrow the frame of the display device.

[0268] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0269] (Embodiment 7) In this embodiment, a display module to which the semiconductor device of one embodiment of the present invention is applied will be described. The explanation will be given with reference to FIG.

[0270] The display module 8000 shown in FIG. 16 includes an upper cover 8001 and a lower cover 8002. Between them, touch panel 8004 connected to FPC8003 and A display panel 8006, a backlight unit 8007, a frame 8009, a printed circuit board The backlight unit 8007, the battery 8011, and the The telly 8011, the touch panel 8004, etc. may not be provided.

[0271] The semiconductor device of one embodiment of the present invention can be used for the display panel 8006, for example.

[0272] The upper cover 8001 and the lower cover 8002 are connected to the touch panel 8004 and the display panel The shape and dimensions can be changed as needed to fit the size of the 8006.

[0273] The touch panel 8004 is a resistive or capacitive touch panel. The display panel 8006 can be used by overlapping it with the opposing substrate (sealing substrate). It is also possible to provide a touch panel function to the display panel. It is also possible to provide an optical sensor in each pixel of the 8006 to create an optical touch panel. Alternatively, a touch sensor electrode is provided in each pixel of the display panel 8006, and a capacitive touch sensor is used. It is also possible to use it as a touch panel.

[0274] The backlight unit 8007 includes a light source 8008. It may be provided at the end of the light source unit 8007 and may be configured to use a light diffusion plate.

[0275] The frame 8009 has a function of protecting the display panel 8006 and also a function of preventing the movement of the printed circuit board 8010. It also functions as an electromagnetic shield to block electromagnetic waves generated by the operation of the The frame 8009 may also function as a heat sink.

[0276] The printed circuit board 8010 includes a power supply circuit, a signal circuit for outputting a video signal and a clock signal. The power supply circuit is provided with a signal processing circuit. Alternatively, the power source may be a battery 8011 provided separately. 1 can be omitted if commercial power is used.

[0277] The display module 8000 also includes components such as a polarizing plate, a retardation plate, and a prism sheet. Additional ones may be provided.

[0278] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. can be done.

[0279] (Embodiment 8) In this embodiment, the semiconductor device described in the above embodiment is used as an example of a semiconductor device. The electronic devices that can be installed will be described.

[0280] Examples of electronic devices include television sets (also known as televisions or television receivers). (hereinafter referred to as "computer monitors"), digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, Examples include portable information terminals, audio playback devices, and large game machines such as pachinko machines. A specific example of such an electronic device is shown in FIG.

[0281] FIG. 12(A) shows an example of a television device. The television device 7100 is A display unit 7103 is incorporated in the housing 7101. The display unit 7103 displays an image. The display device described in the above embodiment modes can be used for the display portion 7103. In this example, the housing 7101 is supported by a stand 7105. It shows.

[0282] The television device 7100 can be operated using an operation switch provided on the housing 7101 or a separate remote control. This can be done by the remote controller 7110. The operation keys 7109 can be used to operate the channel and volume. The image displayed on the remote controller 7110 can be controlled. A display unit 7107 for displaying information output from the remote controller is provided. You may do so.

[0283] The television device 7100 includes a receiver, a modem, and the like. It is possible to receive general television broadcasts, and also to receive wired or wireless signals via a modem. By connecting to a communication network, it can be one-way (sender to receiver) or two-way It is also possible to communicate information in both directions (between a sender and a receiver, or between receivers). .

[0284] FIG. 12B shows a computer, which includes a main body 7201, a housing 7202, a display unit 7203, It includes a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. Note that the computer uses the display device described in the above embodiment mode as the display portion 7203. It is possible.

[0285] FIG. 12C shows a portable gaming machine, which is composed of two housings, a housing 7301 and a housing 7302. The housing 7301 is connected to the connector 7303 so as to be openable and closable. A display portion 7305 is incorporated in the housing 7302. The portable gaming machine shown in FIG. 12(C) also includes a speaker unit 7306, a recording medium insertion unit 73 07, LED lamp 7308, input means (operation key 7309, connection terminal 7310, sensor 7311 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature , chemicals, voice, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, (including functions for measuring vibration, odor, or infrared rays), microphone 7312) Of course, the configuration of the portable gaming machine is not limited to the above. The display device described in the above embodiment mode may be used for both or either of the display portion 7304 and the display portion 7305. The equipment used may be any suitable equipment, and other auxiliary equipment may be provided as needed. The portable gaming machine shown in 2(C) reads the program or data recorded on the recording medium. It also has the function of displaying information on the display screen and communicating wirelessly with other portable gaming machines. The functions of the portable gaming machine shown in FIG. 12(C) are not limited to these. , can have a variety of functions.

[0286] FIG. 12D shows an example of a mobile phone. The mobile phone 7400 includes a housing 740 1, in addition to a display unit 7402, operation buttons 7403, an external connection port 7404, The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, and the like. The display device described in the above embodiment mode is used for the display portion 7402 .

[0287] In a mobile phone 7400 shown in FIG. 12D, when the display portion 7402 is touched with a finger or the like, You can input information, make calls, write emails, etc. This can be done by touching the display portion 7402 with a finger or the like.

[0288] The screen of the display unit 7402 has three main modes. The first is a mode that mainly displays images. The first mode is a display mode, and the second mode is an input mode that mainly inputs information such as characters. This is a display + input mode that combines the display mode and the input mode.

[0289] For example, when making a call or creating an email, the display portion 7402 is used for inputting characters. In this case, you can input characters displayed on the screen. In this case, a keyboard or number buttons can be displayed on most of the screen of the display unit 7402. preferable.

[0290] In addition, the mobile phone 7400 includes a sensor for detecting tilt, such as a gyro or an acceleration sensor. By providing a detection device having the above, the orientation of the mobile phone 7400 (portrait or landscape) can be determined, The screen display on the display portion 7402 can be automatically switched.

[0291] The screen mode can be switched by touching the display portion 7402 or the housing 7401. This is done by operating the operation button 7403. Also, the type of image displayed on the display unit 7402 can be changed. For example, the image signal to be displayed on the display unit may be switched depending on the type. If it is image data, the mode is switched to display mode, and if it is text data, the mode is switched to input mode.

[0292] In the input mode, a signal detected by the optical sensor of the display unit 7402 is detected and displayed. If there is no input by touch operation on the display unit 7402 for a certain period of time, the screen mode is changed to the input mode. Alternatively, the display mode may be switched from the normal mode to the display mode.

[0293] The display portion 7402 can also function as an image sensor. By touching 402 with the palm or fingers and capturing an image of the palm print, fingerprint, etc., personal authentication can be performed. In addition, a backlight that emits near-infrared light in the display unit or a sensing device that emits near-infrared light By using a light source, it is also possible to capture images of finger veins, palm veins, etc.

[0294] FIG. 12(E) shows an example of a folding computer. The computer 7450 is made up of a housing 7451L and a housing 7451R connected by a hinge 7454. In addition, the operation button 7453, the left speaker 7455L and the right speaker 7455L are provided. In addition to the 455R, the computer 7450 also has an external connection port 745 (not shown) on the side of the computer 7450. 6. The display unit 7452L is provided on the housing 7451L, and the display unit 7452R is provided on the housing 7451R. When the hinge 7454 is folded so that the display portions 7452R face each other, the display The part can be protected by a housing.

[0295] The display unit 7452L and the display unit 7452R not only display images but also display information when touched with a finger or the like. For example, you can touch and select an icon representing an installed program. You can also start a program by changing the distance between your fingers touching two points on the image. You can zoom in or out on the image by touching a point on the image or by moving your finger. You can also display an image of a keyboard and use your fingers to move the displayed letters and symbols. You can also select and enter information.

[0296] In addition, the computer 7450 is equipped with a gyro, an acceleration sensor, and a GPS (Global Positioning System). It is equipped with a GPS receiver, a fingerprint sensor, and a video camera. For example, a detection device having a sensor for detecting tilt such as a gyro or an acceleration sensor may be used. By setting up a position, the orientation of the computer 7450 (portrait or landscape) can be determined and the screen to be displayed can be adjusted. You can set it to automatically switch orientation.

[0297] The computer 7450 can also be connected to a network. In addition to being able to display information on the Internet, it can also remotely control other electronic devices connected to the network. It can be used as a terminal to operate from.

[0298] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination. [Example]

[0299] In this example, the lateral diffusion length of a conductive region in a metal oxide film was investigated. Ta.

[0300] First, the structure of the sample will be explained.

[0301] FIG. 18(A) shows a top view of the sample, and FIG. 18(B) shows a cross-sectional view corresponding to AB in FIG. 8(B).

[0302] The sample is composed of a substrate 301, an insulating film 303 on the substrate 301, and a metal oxide film on the insulating film 303. a pair of conductive films 307 and 308 in contact with a part of the metal oxide film 305; an insulating film 309 in contact with a part of each of the oxide film 305 and the pair of conductive films 307 and 308; The insulating film 303, the metal oxide film 305, the pair of conductive films 307 and 308, and the insulating film 309 The insulating film 309 has openings 310a and 310b. The insulating film 311 is in contact with the metal oxide film 305 in the openings 310a and 310b. To contact.

[0303] Here, a glass substrate was used as the substrate 301 .

[0304] The insulating film 303 is made of a first silicon nitride film having a thickness of 50 nm and a second silicon nitride film having a thickness of 300 nm. a second silicon nitride film having a thickness of 50 nm, a third silicon nitride film having a thickness of 50 nm, and an oxide film having a thickness of 50 nm. A laminated film in which silicon nitride films are laminated in order was used.

[0305] As the metal oxide film 305, an In-Ga-Zn oxide film having a thickness of 35 nm was used. The In-Ga-Zn oxide film is an In-Ga-Zn film with a composition of In:Ga:Zn=1:1:1. It was formed by sputtering using an n-oxide target.

[0306] A pair of conductive films 307 and 308 are made of a first titanium film having a thickness of 50 nm and a second titanium film having a thickness of 4 A laminated film consisting of a 100 nm thick aluminum film and a second 100 nm thick titanium film stacked in sequence. was used.

[0307] As the insulating film 309, a silicon oxynitride film having a thickness of 450 nm was used.

[0308] As the insulating film 311, a silicon nitride film having a thickness of 100 nm was used.

[0309] The metal oxide film 305 is formed by absorbing the insulating film 309 at the openings 310a and 310b. Therefore, the metal oxide film 305 has a region 305a in contact with the insulating film 309 and a region 305b in contact with the insulating film 309. The insulating film 311 has regions 305b and 305c that are in contact with the insulating film 311. Since the regions 305b and 305c are made of a silicon dioxide film, they are and has high conductivity.

[0310] The hydrogen contained in the insulating film 311 diffuses laterally in the metal oxide film 305. The region where the ions are diffused becomes highly conductive. , 310b, the conductivity also becomes high in the region 305a, Even if it is in contact with the insulating film 309, it will not function as a channel region of the transistor.

[0311] Therefore, the width of the insulating film 309, that is, the distance d between the openings 310a and 310b, was varied. Next, the potential difference between the pair of conductive films 307 and 308 was set to 0.99 V. A voltage was applied and the resistance value of the entire metal oxide film 305 was measured.

[0312] Table 1 and FIG. 19 show the relationship between the distance d between the openings 310a and 310b and the resistance of the metal oxide film 305. As comparative examples, two samples were prepared. Comparative example 1 was prepared by opening the insulating film 309. The sample without the openings 310a and 310b, that is, the sample in which the metal oxide film 305 is entirely made of silicon oxynitride, The comparative example 2 is a sample that is in contact with the insulating film 309 formed of a silicon film. The sample without the metal oxide film 305, that is, the sample without the metal oxide film 305 and the insulating film 311 formed entirely of silicon nitride film. It is a sample that comes into contact with the surface.

[0313] [Table 1]

[0314] From Table 1 and FIG. 19, when the distance d between the openings 310a and 310b exceeds 3 μm, metal oxidation Since the resistance value of the metal oxide film 305 increases, the highly conductive region in the metal oxide film 305 The diffusion length in the lateral direction of the regions 305b and 305c is estimated to be about 1.5 to 2 um per side. can be.

[0315] Therefore, the channel region of the transistor and the electrode of the capacitor are formed in one metal oxide film. When forming a capacitor, the distance between the channel region of the transistor and the electrode of the capacitor is set to 1.5 μm or less. By making it larger than 2μm, or even 3μm or more, excellent switching performance can be achieved. A transistor with switching characteristics and an electrode of a highly conductive capacitor element are connected to one metal oxide It can be formed of a film.

Claims

1. A pixel device comprising: a first pixel and a second pixel adjacent to each other; a first conductive layer; and a second conductive layer; Each of the first pixel and the second pixel is a semiconductor layer having a channel formation region of a transistor; a third conductive layer electrically connected to the semiconductor layer; a pixel electrode electrically connected to the semiconductor layer via the third conductive layer; a metal oxide film having an area overlapping the pixel electrode; the metal oxide film in the first pixel is electrically connected to the metal oxide film in the second pixel via the first conductive layer and the second conductive layer; the first conductive layer has the same material as the third conductive layer; the second conductive layer has the same material as the pixel electrode; the second conductive layer has a region overlapping with the metal oxide film of the first pixel and a region overlapping with the metal oxide film of the second pixel; a capacitance element formed in a region where the pixel electrode and the metal oxide film overlap in each of the first pixel and the second pixel;

2. A pixel device comprising a first pixel and a second pixel adjacent to each other, and first to third conductive layers, Each of the first pixel and the second pixel is a semiconductor layer having a channel formation region of a transistor; a fourth conductive layer electrically connected to the semiconductor layer; a pixel electrode electrically connected to the semiconductor layer via the fourth conductive layer; a metal oxide film having an area overlapping the pixel electrode; the metal oxide film in the first pixel is electrically connected to the metal oxide film in the second pixel via the first to third conductive layers; each of the first conductive layer and the third conductive layer has the same material as the fourth conductive layer; the second conductive layer has the same material as the pixel electrode; the second conductive layer has a region overlapping with the metal oxide film of the first pixel and a region overlapping with the metal oxide film of the second pixel; a capacitance element formed in a region where the pixel electrode and the metal oxide film overlap in each of the first pixel and the second pixel;

3. A pixel device comprising: a first pixel and a second pixel adjacent to each other; a first conductive layer; and a second conductive layer; Each of the first pixel and the second pixel is a semiconductor layer having a channel formation region of a transistor; a third conductive layer electrically connected to the semiconductor layer; a pixel electrode electrically connected to the semiconductor layer via the third conductive layer; a metal oxide film having an area overlapping the pixel electrode; the metal oxide film in the first pixel is electrically connected to the metal oxide film in the second pixel via the first conductive layer and the second conductive layer; the first conductive layer has the same material as the third conductive layer; the second conductive layer has the same material as the pixel electrode; the second conductive layer has a region overlapping with the metal oxide film of the first pixel and a region overlapping with the metal oxide film of the second pixel; each of the first conductive layer and the second conductive layer does not have an area overlapping with a pixel electrode of the first pixel and does not have an area overlapping with a pixel electrode of the second pixel; a capacitance element formed in a region where the pixel electrode and the metal oxide film overlap in each of the first pixel and the second pixel;

4. A pixel device comprising a first pixel and a second pixel adjacent to each other, and first to third conductive layers, Each of the first pixel and the second pixel is a semiconductor layer having a channel formation region of a transistor; a fourth conductive layer electrically connected to the semiconductor layer; a pixel electrode electrically connected to the semiconductor layer via the fourth conductive layer; a metal oxide film having an area overlapping the pixel electrode; the metal oxide film in the first pixel is electrically connected to the metal oxide film in the second pixel via the first to third conductive layers; each of the first conductive layer and the third conductive layer has the same material as the fourth conductive layer; the second conductive layer has the same material as the pixel electrode; the second conductive layer has a region overlapping with the metal oxide film of the first pixel and a region overlapping with the metal oxide film of the second pixel; each of the first conductive layer and the second conductive layer does not have an area overlapping with a pixel electrode of the first pixel and does not have an area overlapping with a pixel electrode of the second pixel; a capacitance element formed in a region where the pixel electrode and the metal oxide film overlap in each of the first pixel and the second pixel;

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