Display device

Abstract

To provide a display having a capacitive element that has a high opening ratio and can increase a charge capacity; to provide a display having a capacitive element that has high transmittance in a pixel part and can increase a charge capacity; to provide a display with low power consumption.SOLUTION: A display has: a transistor that has a first oxide semiconductor film in a channel formation area; a second oxide semiconductor film that is formed on the same surface as the first oxide semiconductor film; a pixel electrode that is electrically connected with the transistor; and a capacitive element that has a dielectric film sandwiched between a pair of electrodes and has light transparency. One of the pair of electrodes is the second oxide semiconductor film, and the other of the pair of electrodes is the pixel electrode. The film thickness of the second oxide semiconductor film is smaller than the film thickness of the first oxide semiconductor film.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The invention disclosed in this specification and elsewhere relates to a display device and an electronic device using the display device. [Background technology]

[0002] In recent years, flat panel displays such as liquid crystal displays (LCDs) have become widespread. In a display device such as a liquid crystal display, pixels arranged in the row and column directions The semiconductor device includes a transistor as a switching element and a liquid crystal display electrically connected to the transistor. A liquid crystal element and a capacitive element connected in parallel to the liquid crystal element are provided.

[0003] The semiconductor material constituting the semiconductor film of the above transistor is amorphous (non-crystalline) Silicon semiconductors such as silicon or polysilicon (polycrystalline) are widely used.

[0004] Metal oxides that exhibit semiconductor properties (hereinafter, referred to as oxide semiconductors) are used in transistors. It is a semiconductor material that can be applied to the semiconductor film of the following: zinc oxide or In-Ga-Zn system oxide Techniques for fabricating transistors using nitride semiconductors have been disclosed (Patent Document 1 and Patent Document 2). See patent document 2. ).

[0005] In order to increase the aperture ratio, a metal oxide film is provided on the same surface as the oxide semiconductor film of the transistor. The oxide semiconductor film and the pixel electrode connected to the transistor are provided at a predetermined distance from each other. A display device having such a capacitive element has been disclosed (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-123861 A [Patent Document 2] JP 2007-96055 A [Patent Document 3] U.S. Patent No. 8,102,476 Summary of the Invention [Problem to be solved by the invention]

[0007] The capacitance element has a pair of electrodes and a dielectric film between them. The other electrode is a light-shielding electrode such as a gate electrode, source or drain that constitutes a transistor. In many cases, the insulating film is made of a conductive film having a thickness of 100 .mu.m.

[0008] In addition, the larger the capacitance of the capacitance element, the more the liquid crystal element will dissipate when an electric field is applied. The period during which the orientation of the crystal molecules can be kept constant can be extended. In a display device in which the period can be extended, the number of times that image data is rewritten can be reduced. This makes it possible to reduce power consumption.

[0009] In order to increase the charge capacity of the capacitance element, the area occupied by the capacitance element is increased. Specifically, there is a method for increasing the area where a pair of electrodes overlap. In the above display device, a light-shielding layer is provided to increase the area where the pair of electrodes overlap. If the area of ​​the conductive film to be covered is increased, the aperture ratio of the pixel is reduced, and the display quality of the image is degraded.

[0010] For example, the pair of electrodes is formed of a light-transmitting material. The charge capacity can be increased and the aperture ratio of the pixel can be increased. When the transmittance of the material is low, the amount of light from the light source such as the backlight is increased. This can lead to problems such as increased power consumption, and coloring of the capacitance element, This causes a problem that light of a certain wavelength is attenuated, resulting in a deterioration in the display quality of the image.

[0011] In view of the above problems, one aspect of the present invention provides a liquid crystal display device having a high aperture ratio and an increased charge capacity. It is an object of the present invention to provide a display device having a capacitor element capable of reducing the capacitance. One embodiment of the present invention is a capacitance device that has a high transmittance in a pixel portion and can increase a charge capacity. Another object of the present invention is to provide a display device having a display element. One of the objectives of the project is to provide a place where

[0012] The description of these problems does not preclude the existence of other problems. It is not necessary for one embodiment to solve all of these problems. The subject matter will be self-evident from the description, drawings, claims, etc. Other issues can be extracted from the drawings, claims, etc. [Means for solving the problem]

[0013] One embodiment of the present invention is a transistor including a first oxide semiconductor film in a channel formation region. A second oxide semiconductor film is formed on the same surface as the first oxide semiconductor film, and A pixel electrode electrically connected to the pixel electrode and a dielectric film sandwiched between the pair of electrodes. a capacitor having a pair of electrodes including a second oxide semiconductor film, The other is a pixel electrode, and the thickness of the second oxide semiconductor film is greater than the thickness of the first oxide semiconductor film. The display device is characterized by being thinner than the conventional display device.

[0014] The thickness of the second oxide semiconductor film which is one of a pair of electrodes of the light-transmitting capacitor is The thickness of the first oxide semiconductor film is formed thinner than that of the first oxide semiconductor film used for a channel formation region of a transistor. This makes it possible to improve the transmittance of the capacitance element. It is possible to provide a display device having a capacitance element capable of increasing the charge capacity. In addition, the thickness of the first oxide semiconductor film used for the channel formation region of the transistor is optimized. Therefore, a highly reliable display device can be obtained.

[0015] Another embodiment of the present invention is a transistor having a first oxide semiconductor film in a channel formation region. a first oxide film formed on the first oxide semiconductor film; A second oxide semiconductor film is formed on the same surface as the first oxide semiconductor film, and a second oxide semiconductor film is formed on the second oxide semiconductor film. a pixel electrode electrically connected to the transistor; and a second oxide film electrically connected to the pixel electrode. a light-transmitting capacitor element having a dielectric film sandwiched between the first and second electrodes; the other of the pair of electrodes is a pixel electrode; The display device is characterized in that the oxide film has a thickness smaller than that of the first oxide film.

[0016] The thickness of the second oxide film, which is a part of one of a pair of electrodes of the light-transmitting capacitor element, is The thickness of the first oxide film is formed thinner than that of the first oxide film used in a part of the channel forming region of the transistor. This makes it possible to improve the transmittance of the capacitance element. It is possible to provide a display device having a capacitive element capable of increasing the charge capacity and reducing the capacitance.

[0017] Another embodiment of the present invention is a transistor having a first oxide semiconductor film in a channel formation region. a first oxide film formed on the first oxide semiconductor film; a second oxide semiconductor film formed on the same surface as the first oxide semiconductor film and electrically connected to the transistor; and a light-transmitting capacitor element having a pair of electrodes and a dielectric film sandwiched between the pair of electrodes. One of the pair of electrodes is a second oxide semiconductor film, and the other of the pair of electrodes is a pixel electrode. The display device is characterized in that

[0018] One of a pair of electrodes of the light-transmitting capacitor is a second oxide semiconductor film. A first oxide semiconductor film to be used for a channel formation region of a transistor and a The first oxide film is formed as a single layer structure compared to the laminated film. Display device having a capacitive element with high transmittance of element portion and increased charge capacity In addition, the transistor can be provided in which a first oxide film is formed over a first oxide semiconductor film. Therefore, a highly reliable display device can be obtained. Effect of the Invention

[0019] According to one embodiment of the present invention, a capacitance element having a high aperture ratio and capable of increasing a charge capacity is provided. In addition, a display device having a high transmittance and a charge capacity can be provided. It is possible to provide a display device having a capacitor capable of increasing the capacitance. A display device with low power consumption can be provided. [Brief description of the drawings]

[0020] [Figure 1] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a display device. [Diagram 2] FIG. 1 is a top view illustrating one embodiment of a display device. [Diagram 3] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 4] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device. [Diagram 5] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device. [Figure 6] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device. [Figure 7] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device. [Figure 8] 1A and 1B are a cross-sectional view and a band diagram illustrating one embodiment of a display device. [Figure 9] FIG. 1 is a cross-sectional view illustrating one embodiment of a display device. [Figure 10] FIG. 1 is a top view illustrating one embodiment of a display device. [Figure 11] FIG. 2 is a diagram illustrating a display module. [Figure 12] FIG. 1 is a diagram illustrating an electronic device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various changes can be made in form and detail. The present invention is not limited to the description of the following embodiments. It is not something that is done.

[0022] In the configuration of the present invention described below, the same parts or parts having similar functions are designated by the same reference numerals. The same reference numerals are used in different drawings, and the repeated explanations are omitted. When referring to a part having a function, the hatch pattern is the same and no symbol is attached. be.

[0023] In each figure described in this specification, the size of each structure, the thickness of the film, or the area is not shown for the sake of clarity. The figures may be exaggerated for illustrative purposes and are not necessarily limited to that scale.

[0024] In this specification and elsewhere, ordinal numbers such as 1st, 2nd, etc. are used for convenience. Therefore, for example, "first" may be changed to "second" or " " can be appropriately replaced with "the third" etc. The ordinal numbers used to identify an aspect of the present invention may not match those used in the present invention. be.

[0025] In addition, the functions of the "source" and "drain" in one embodiment of the present invention are as follows: In some cases, such as when the direction of the current changes due to a change in the In this regard, the terms "source" and "drain" may be used interchangeably. .

[0026] (Embodiment 1) In this embodiment, a display device which is one embodiment of the present invention will be described with reference to drawings. Note that in this embodiment, a display device which is one embodiment of the present invention will be described using a liquid crystal display device as an example. do.

[0027] <Display device configuration> FIG. 1A shows an example of a display device. The display device shown in FIG. 1A has a pixel portion 100 and The scanning line driving circuit 104 and the signal line driving circuit 106 are arranged in parallel or approximately in parallel to each other. The potential of each of the m scanning lines 107 is controlled by a scanning line driving circuit 104. The n signal lines are arranged in a row or substantially in parallel, and the potentials of which are controlled by a signal line driver circuit 106. The pixel section 100 further includes a plurality of pixels arranged in a matrix. 301. In addition, the capacitances are arranged parallel or approximately parallel to each other along the scanning line 107. The capacitance lines 115 are arranged parallel or approximately parallel to the signal line 109. The scanning line driver circuit 104 and the signal line driver circuit 106 may be arranged in a row. In FIG. 1A, the capacitance line 115 is a scanning Although the configuration in which the line driver circuit 104 is connected has been illustrated, the present invention is not limited to this. For example, The capacitance line 115 may not be connected to the scanning line driver circuit 104 .

[0028] Each scanning line 107 corresponds to one of the pixels 301 arranged in m rows and n columns in the pixel section 100. The signal lines 109 are electrically connected to the n pixels 301 arranged in any one row. is m pixels 301 arranged in m rows and n columns, and m pixels 301 arranged in any one of the columns. 1. m and n are both integers of 1 or more. is n pixels 301 arranged in any one of the rows among the pixels 301 arranged in m rows and n columns. 1. Capacitive lines 115 are arranged parallel to or in parallel with the signal line 109. In the case where the pixels 301 are arranged in m rows and n columns, It is electrically connected to m pixels 301 arranged in a column.

[0029] FIG. 1B is an example of a circuit diagram of a pixel 301 included in the display device shown in FIG. The pixel 301 shown in FIG. 1B is a transistor electrically connected to the scanning line 107 and the signal line 109. A transistor 103, one electrode of which is electrically connected to the drain of the transistor 103, The other electrode of the capacitor 105 is electrically connected to a capacitor line 115 that supplies a constant potential. The pixel electrode is electrically connected to the drain of the transistor 103 and one electrode of the capacitor 105. An electrode (opposite electrode) that is connected to the pixel electrode is connected to a wiring that supplies an opposite potential. and a liquid crystal element 108 electrically connected thereto.

[0030] The liquid crystal element 108 is formed by a substrate on which the transistor 103 and the pixel electrode are formed and a counter electrode. The optical modulation effect of the liquid crystal sandwiched between the substrates controls the transmission or non-transmission of light. Alternatively, the liquid crystal element 108 includes the transistor 103, the pixel electrode, and the counter electrode. The optical modulation effect of the liquid crystal sandwiched between the substrate on which the counter electrode is formed and the sealing substrate The optical modulation effect of liquid crystal is The pixel is controlled by an electric field (including a vertical electric field or a diagonal electric field). When a counter electrode (also called a common electrode) is formed on the substrate on which the electrodes are formed, the liquid crystal The electric field applied to is a lateral electric field.

[0031] The liquid crystal element 108 is not limited to a liquid crystal element, but may be any other suitable element such as a display element or a light emitting element. For example, an example of a display element or a light-emitting element is an EL (electroluminescence) element. Electroluminescence (EL) elements (including organic and inorganic EL elements, organic EL elements, inorganic EL elements, etc.) LEDs (white LEDs, red LEDs, green LEDs, blue LEDs, etc.), transistors (transistors that emit light according to electric current), electron-emitting devices, liquid crystal devices, electronic ink, Electrophoretic element, Grating light valve (GLV), Plasma display (PDP) , MEMS (Micro-Electro-Mechanical Systems), Digital Micromirror Device (DMD), DMS (Digital Micro Shutter), MIRASOL (registered trademark), IMOD (Interference Modulation) element, Piezoelectric ceramic Displays, carbon nanotubes, etc., are subject to electromagnetic effects, resulting in contrast, brightness, etc. Some display media have a changeable brightness, reflectance, transmittance, etc. An example of such a device is an EL display. Examples include field emission displays (FED) or SED flat panel displays. Spray (SED: Surface-conduction Electron-emissive An example of a display device using liquid crystal elements is a transparent Transflective liquid crystal display device, transflective liquid crystal display device, reflective liquid crystal display device, direct view liquid crystal display device, Projection type liquid crystal display devices are examples of display devices using electronic ink or electrophoretic elements. Examples include electronic paper.

[0032] Next, a specific example of a pixel 301 of a liquid crystal display device will be described. A top view of a part of the driver circuit 104 is shown in FIG. 2(A), and a top view of a part of the pixel 301 is shown in FIG. 2(A) and 2(B), the counter electrode and the liquid crystal element are omitted. is doing.

[0033] In FIG. 2A, a conductive film 304a functioning as a gate, a gate insulating film (FIG. 2A ) are not shown in FIG. 3. The transistor 102 is formed by the conductive films 310a and 310b which function as drains. The oxide semiconductor film 308a is provided over the gate insulating film. A conductive film 304b formed at the same time as the conductive films 310a and 310b. 310c, and a light-transmitting conductive film 316 which connects the conductive film 304b and the conductive film 310c. The light-transmitting conductive film 316a is provided in the opening 374a. 4b, and then connects to the conductive film 310c in the opening 374b.

[0034] In FIG. 2B, the conductive film 304c functioning as the scan line 107 is The signal lines 109 are arranged to extend in a direction substantially perpendicular to each other (the left and right direction in the drawing). The conductive film 310d extends in a direction substantially perpendicular to the scanning line 107 (the vertical direction in the figure). The conductive film 310f that functions as the capacitance line 115 extends in a direction parallel to the signal line 109. The conductive film 304c functioning as the scan line 107 is It is electrically connected to the operating circuit 104 (see FIG. 1(A)) and functions as a signal line 109. The conductive film 310d functioning as the capacitance line 115 and the conductive film 310f functioning as the signal line driving circuit In FIG. 1A, the capacitance line 115 is electrically connected to the line 106. The configuration connected to the scan line driver circuit 104 has been illustrated, but as shown in FIG. The capacitance line 115 may be connected to the signal line driver circuit 106 .

[0035] The transistor 103 is provided in a region where the scanning line 107 and the signal line 109 intersect. The transistor 103 includes a conductive film 304c functioning as a gate, a gate insulating film (FIG. 2 (not shown in FIG. 1B), which is formed on the gate insulating film and in which a channel forming region is formed. The oxide semiconductor film 308b and the conductive films 310d and 310e functioning as a source and a drain The conductive film 304c also functions as a scan line and is formed of the oxide semiconductor film 3 The region overlapping with the conductive film 31 functions as the gate of the transistor 103. 0d also functions as a signal line, and a region overlapping with the oxide semiconductor film 308b is a transistor 103. In FIG. 2B, the scanning line In the top view, the end portion is located outside the end portion of the oxide semiconductor film 308b. The scanning lines function as a light shielding film that blocks light from a light source such as a backlight. The oxide semiconductor film 308b included in the transistor 103 is not irradiated with light. Fluctuations in the electrical characteristics of 3 can be suppressed.

[0036] In addition, the conductive film 310e has a light-transmitting property that functions as a pixel electrode in the opening 374c. The conductive film 316b is electrically connected to the conductive film 316b.

[0037] The capacitor 105 is formed by a conductive film 310f which functions as a capacitor line 115 in the opening 372. The capacitor 105 is connected to a light-transmitting insulating film. a conductive film 308c which functions as a pixel electrode; a conductive film 316b which has a light-transmitting property; The dielectric film is made of a nitride insulating film provided on the resistor 103. That is, the capacitor 105 has a light-transmitting property.

[0038] In this way, since the capacitor 105 has a light-transmitting property, the capacitor 105 is large in the pixel 301. Therefore, it is possible to increase the aperture ratio. Typically, the charge capacity can be 55% or more, and preferably 60% or more. For example, in a liquid crystal display device with high resolution, In this case, the area of ​​the pixel is small, and the area of ​​the capacitance element is also small. In the display device, the charge capacity stored in the capacitive element is reduced. Since the capacitor 105 shown in the embodiment has a light-transmitting property, the capacitor is provided in the pixel. It is possible to increase the aperture ratio while obtaining a sufficient charge capacity in each pixel. Suitable for high-resolution display devices with pixel density of 200 ppi or more, and even 300 ppi or more can be used.

[0039] The thickness of the light-transmitting conductive film 308c which is one electrode of the capacitor 105 is The thickness of the oxide semiconductor film 308a and the thickness of the oxide semiconductor film 308b are smaller than those of the oxide semiconductor films 308a and 308b of the transistors 102 and 103. Therefore, the transmittance of the capacitor 105 can be improved.

[0040] In addition, the pixel 301 shown in FIG. 2B has a conductive film 310d functioning as a signal line and a The side parallel to the conductive film 304c functioning as the scanning line is longer than the side The conductive film 310f functioning as a capacitance line is parallel to the conductive film 310d functioning as a signal line. As a result, the area of ​​the conductive film 310f in the pixel 301 is Since the number of the conductors can be reduced, the aperture ratio can be increased. The conductive film 310f having a light-transmitting property is in direct contact with the conductive film 308c having a light-transmitting property without using a connection electrode. Therefore, the aperture ratio can be further increased.

[0041] In addition, according to one embodiment of the present invention, the aperture ratio can be increased even in a high-resolution display device. In addition, the high transmittance of the pixels allows efficient use of light from light sources such as backlights. This makes it possible to reduce the power consumption of the display device.

[0042] Next, the cuts between the dashed lines AB and CD shown in FIG. 2(A) and (B) are The surface view is shown in FIG.

[0043] The display device shown in FIG. 3A is a display device including a pair of substrates (a substrate 302 and a substrate 34). 2) A liquid crystal element 108 is sandwiched between them.

[0044] The liquid crystal element 108 is connected to a light-transmitting conductive film 316b above the substrate 302 to control the alignment. A liquid crystal layer 320 and a conductive film 350 are arranged in a liquid crystal display device. Note that the light-transmitting conductive film 316b is used as one electrode of the liquid crystal element 108. The conductive film 350 functions as the other electrode of the liquid crystal element 108 .

[0045] There are three types of driving methods for display devices having liquid crystal elements: TN mode, STN mode, and VA mode. ASM (Axially Symmetric Aligned Micro-ce) ll) mode, OCB (Optically Compensated Birefringence ngence) mode, FLC (Ferroelectric Liquid Crys tal) mode, AFLC(AntiFerroelectric Liquid Cr ystal) mode, MVA(Multi-domain Vertical Alig) nment) mode, PVA(Patterned Vertical Alignme) nt) mode, IPS mode, FFS mode, or TBA (Transverse Beam Inversion) mode In addition, a display device having a liquid crystal element may be used. In addition to the above-mentioned driving method, the device can be driven by ECB (Electrically Controlled Bias Circuit). ontrolled Birefringence) mode, PDLC (Polymer Dispersed Liquid Crystal mode, PNLC (Polym er Network Liquid Crystal) mode, guest host mode, etc. However, the present invention is not limited to these, and various driving methods for display devices having liquid crystal elements can be used. can be used.

[0046] 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 liquid crystal that exhibits the blue phase. Since it is short and optically isotropic, alignment treatment is not required and viewing angle dependency is small.

[0047] In this embodiment, a vertical electric field type liquid crystal display device will be described.

[0048] Thus, a liquid crystal display device is a device that has liquid crystal elements. The liquid crystal display device includes a driving circuit for driving a plurality of pixels. A control circuit, a power supply circuit, a signal generating circuit, a backlight module, etc., are arranged in It is also called a liquid crystal module.

[0049] In the driver circuit portion, a conductive film 304a functions as a gate, and a gate insulating film the insulating films 305 and 306, the oxide semiconductor film 308a in which a channel formation region is to be formed, The transistor 102 is formed by the conductive films 310a and 310b which function as a source and a drain. The oxide semiconductor film 308a is provided on a gate insulating film. An insulating film 312 and an insulating film 314 are provided on the conductive film 308a and the conductive films 310a and 310b. It is provided as a protective film.

[0050] In the pixel portion, a conductive film 304c functions as a gate, and a gate insulating film Insulating films 305 and 306, an oxide film in which a channel forming region is formed on the gate insulating film The semiconductor film 308b and the conductive films 310d and 310e functioning as a source and a drain are The oxide semiconductor film 308b is provided over a gate insulating film. In addition, an insulating film 3 is formed over the oxide semiconductor film 308b and the conductive films 310d and 310e. 12. An insulating film 314 is provided as a protective film.

[0051] In the pixel portion, the conductive film 316b having a light-transmitting property and functioning as a pixel electrode is In an opening provided in the insulating film 312 and the insulating film 314, the conductive film 310e is connected to the conductive film 310e.

[0052] In addition, a light-transmitting conductive film 308c which functions as one electrode of the capacitor 105; The insulating film 314 which functions as a dielectric film of the capacitor 105 and the other electrode of the capacitor 105 The capacitor 105 is formed by the light-transmitting conductive film 316b which functions as a light-transmitting conductive film. The light-transmitting conductive film 308c is provided over the gate insulating film. The conductive film 316b has a function as a pixel electrode and a function as the other electrode of the capacitor 105. do.

[0053] In the driving circuit section, the conductive film 304a and the conductive film 304c are formed at the same time. 4b and the conductive film 31 The light-transmitting conductive film 310c is formed at the same time as the light-transmitting conductive film 316b. Connected via 6a.

[0054] In the display device described in this embodiment, a semiconductor film for a capacitor is formed simultaneously with an oxide semiconductor film for a transistor. A light-transmitting conductive film that functions as a pixel electrode is formed. The other electrode of the element is used. Since a process for forming a film is not required, the manufacturing process of a display device can be reduced. Since the pair of electrodes are formed using a conductive film having a light-transmitting property, the electrode has a light-transmitting property. The area occupied by the capacitive element can be increased while increasing the aperture ratio of the pixel.

[0055] The light-transmitting conductive film 308c is formed simultaneously with the oxide semiconductor films 308a and 308b. The oxide semiconductor films 308a and 308b (oxide semiconductor films The first portion is formed by forming the insulating film 306 and the insulating film 312, etc., so as to improve interface characteristics with the oxide semiconductor film. Since the oxide semiconductor film 308a is in contact with the film formed of a material capable of being heated, The oxide semiconductor film 308a and the oxide semiconductor film 308b function as a semiconductor. The sintered material has excellent electrical properties.

[0056] On the other hand, the light-transmitting conductive film 308c (the second portion of the oxide semiconductor film) is formed through the opening 372. The insulating film 314 is in contact with the insulating film 314. The insulating film 314 is resistant to impurities from the outside, such as water, aluminum, etc. It is made of a material that prevents potassium metal, alkaline earth metal, etc. from diffusing into the oxide semiconductor film. Therefore, hydrogen contained in the insulating film 314 is converted into hydrogen by the oxide semiconductor film. When the light-transmitting conductive film 308c is formed at the same time as the light-transmitting conductive film 308a and the light-transmitting conductive film 308b, the light-transmitting conductive film 308c is diffused. In the conductive film 308c having a light-emitting property, hydrogen is bonded to oxygen, and electrons serving as carriers are generated. As a result, the light-transmitting conductive film 308c has high conductivity and functions as a conductor. In other words, the light-transmitting conductive film 308c can be regarded as a highly conductive oxide semiconductor film. do.

[0057] The light-transmitting conductive film 308c is formed of an oxide film included in the transistors 102 and 103. The thickness of the semiconductor film 308 is smaller than that of the semiconductor films 308a and 308b. The light-transmitting conductive film 308c can be formed in the formation of the opening 372. By processing the oxide semiconductor films 308a and 308b simultaneously, the thickness of the oxide semiconductor films 308a and 308b is made thinner than that of the oxide semiconductor films 308a and 308b. It is possible.

[0058] Here, an enlarged view of the cross-sectional view of the display device shown in FIG. 3(A) is shown in FIG. 3(B). 3A is an enlarged cross-sectional view of a part of the transistor 103 and the capacitor 105 shown in FIG. It is.

[0059] As shown in FIG. 3B, the thickness of the oxide semiconductor film 308b in the transistor 103 is The thickness of the light-transmitting conductive film 308c of the capacitor 105 is thinner than that of the light-transmitting conductive film 308c of the capacitor 105. The thickness of the conductive film 308c is set to a value that allows the film to function as an electrode of the capacitor element 105. It is preferable that the thickness of the conductive film is thick enough to improve the transmittance of the capacitance element. The thickness of the oxide semiconductor film 308c is, for example, 2 / 3 or less of the thickness of the oxide semiconductor film 308b. More preferably, it is 1 / 2 or less.

[0060] Next, the characteristics of a transistor using an oxide semiconductor will be described. The transistor used is an n-channel transistor. The electron vacancies may generate carriers, which degrades the electrical characteristics and reliability of the transistor. For example, in the case of an n-channel transistor, the threshold voltage of the transistor When the gate voltage fluctuates in the negative direction, drain current flows when the gate voltage is 0V. In this way, the fact that drain current flows when the gate voltage is 0V is called a no-no. This is called a marion characteristic, and a transistor that has this characteristic is called a depletion type transistor. When the gate voltage is 0V, it is considered that no drain current flows. A transistor that can achieve this is called a normally-off transistor. Such a transistor is called an enhancement type transistor.

[0061] An oxide semiconductor film 308a in which channel formation regions of the transistors 102 and 103 are formed. In the case of 308b, it is preferable that defects, typically oxygen vacancies, are reduced as much as possible. It is desirable to reduce defects, typically oxygen vacancies, contained in an oxide semiconductor film as much as possible. , it is possible to prevent the transistors 102 and 103 from becoming normally-on. The electrical characteristics and reliability of the display device can be improved. can be reduced.

[0062] The negative shift in the threshold voltage of a transistor is not only due to oxygen vacancies, but also due to oxide It can also be caused by hydrogen contained in semiconductors (including hydrogen compounds such as water). Hydrogen contained in oxide semiconductors reacts with oxygen that is bonded to metal atoms to form water. A defect (which can also be called an oxygen defect) is formed in the lattice from which oxygen has been removed (or in the part from which oxygen has been removed). In addition, some of the hydrogen reacts with oxygen to generate electrons, which act as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen has a normally-on characteristic. It is easy to become sexually

[0063] Therefore, an oxide semiconductor film in which a channel formation region of the transistors 102 and 103 is formed is It is preferable that hydrogen is reduced as much as possible in 308a and 308b. In the oxide semiconductor films 308a and 308b, The hydrogen concentration is 5×10 19 atoms / cm 3 Less than 5 x 10 18 atom s / cm 3 Less than 1 x 10 18 atoms / cm 3 Less than or equal to 5x, more preferably 10 17 atoms / cm 3 Less than 1×10, more preferably 16 atoms / cm 3 Below Below.

[0064] In addition, the oxide semiconductor film 3 in which the channel formation regions of the transistors 102 and 103 are formed 08a, 308b are alkali metal or alkaline earth metals obtained by secondary ion mass spectrometry. The concentration of metals is 1×10 18 atoms / cm 3 Less than or equal to 2×10 16 ato ms / cm3 Alkali metals and alkaline earth metals bond to oxide semiconductors. When the transistors 102 and 103 are turned on, carriers may be generated, which increases the off-state current of the transistors 102 and 103. This may happen.

[0065] In this manner, impurities (hydrogen, nitrogen, alkali metals, etc.) in the oxide semiconductor films 308a and 308b and a highly purified oxide semiconductor film in which the amount of metals (such as metals or alkaline earth metals) is reduced as much as possible. By this, the transistors 102 and 103 become enhancement type, and the transistor 1 This prevents the transistors 102 and 103 from becoming normally-on. Therefore, the off-state current of the display device can be significantly reduced. In addition, a display device with improved reliability can be manufactured.

[0066] The reason why the off-state current of a transistor using a highly purified oxide semiconductor film is low is that This can be proved by various experiments. For example, when the channel width W is 1×10 6 Channel length in μm Even with an element with L of 10 μm, the voltage between the source and drain (drain voltage) is 1 V to In the range of 10 V, the off-state current is below the measurement limit of the semiconductor parameter analyzer, that is, Wachi 1×10 -13 In this case, the off-current is The value divided by the channel width of the transistor is less than 100 zA / μm. A capacitance element and a transistor are connected to each other to store the charge flowing into or out of the capacitance element. The off-state current is measured using a circuit controlled by the transistor. A highly purified oxide semiconductor film is used in a channel formation region of a transistor, and a unit of a capacitor is formed. The off-state current of the transistor is measured based on the change in the charge amount per unit time. When the voltage between the source and drain of the transistor is 3 V, the current is reduced to several tens of yA / μm. Therefore, a transistor using a highly purified oxide semiconductor film can have a low off-state current. , the off-current is remarkably small.

[0067] On the other hand, the oxide semiconductor films 308a and 308b of the transistors 102 and 103 The light-transmitting conductive film 308c formed in one step is formed by removing the oxide semiconductor films 308a and 308b. b, the oxygen deficiency and / or hydrogen concentration is high. The conductivity of 08c can be increased.

[0068] Here, other components of the display device shown in FIG. 3(A) will be described below.

[0069] Conductive films 304a, 304b, and 304c are formed on the substrate 302. 04a is formed in the scanning line driving circuit 104 and serves as the gate of a transistor in the driving circuit section. The conductive film 304c is formed in the pixel portion 100 and functions as a transistor in the pixel portion. The conductive film 304b functions as a gate of the scan line driver circuit 104. The conductive film 316a is connected to the conductive film 310c through a light-transmitting conductive film 316a.

[0070] The substrate 302 may be made of aluminosilicate glass, aluminoborosilicate glass, barium oxide glass, or the like. A glass material such as borosilicate glass is used. For mass production, the substrate 302 is made of 8th generation glass. 2nd generation (2160mm x 2460mm), 9th generation (2400mm x 2800mm, or 450mm x 3050mm), 10th generation (2950mm x 3400mm) etc. Mother glass is preferably used. High processing temperatures and long processing times can cause significant damage to the mother glass. Therefore, when using mother glass for mass production, heat treatment in the manufacturing process is not preferred. Preferably, the temperature is 600°C or lower, more preferably, 450°C or lower, and even more preferably, 350°C or lower. It is desirable to do so.

[0071] The conductive films 304a, 304b, and 304c may be made of aluminum, chromium, copper, or tantalum. , titanium, molybdenum, tungsten, or the above-mentioned metal elements The alloy may be formed using an alloy containing the above-mentioned metal elements or a combination of the above-mentioned metal elements. The conductive films 304a, 304b, and 304c may have a single-layer structure or a laminated structure of two or more layers. For example, a two-layer structure in which a titanium film is laminated on an aluminum film, a titanium nitride film Two-layer structure with a titanium film laminated on top, and two-layer structure with a tungsten film laminated on a titanium nitride film , a two-layer structure in which a tungsten film is laminated on a tantalum nitride film or a tungsten nitride film, A titanium film is laminated on the titanium film, an aluminum film is laminated on the aluminum film, and a titanium film is formed on the aluminum film. There are also three-layer structures, such as aluminum, titanium, tantalum, tungsten, and molybdenum. A film of elements selected from the group consisting of arsenic, chromium, neodymium, and scandium, or a combination of multiple elements. An alloy film or a nitride film may also be used.

[0072] Insulating films 305 and 306 are formed on the substrate 302 and the conductive films 304a, 304b, and 304c. The insulating films 305 and 306 are formed on the transistor 10 of the scanning line driving circuit 104. 2 and functions as a gate insulating film of the transistor 103 in the pixel portion 100. has.

[0073] The insulating film 305 is resistant to external impurities such as water, alkali metals, alkaline earth metals, etc. However, it is preferable to use a material that prevents diffusion of the oxide semiconductor film into the oxide semiconductor film. The insulating film 305 is typically a nitride insulating film. For example, a silicon nitride film, a silicon oxynitride film, an aluminum nitride film, an aluminum oxynitride film, The insulating film 305 may be formed as a laminated layer or a single layer. In this case, the first silicon nitride film is a silicon nitride film with few defects. A silicon nitride film with a low hydrogen release rate is formed on the silicon nitride film as a second silicon nitride film. As a result, hydrogen and nitrogen contained in the insulating film 305 are absorbed in the oxide semiconductor This can inhibit the migration or diffusion to the membranes 308a, 308b.

[0074] Silicon oxynitride is an insulating material that contains more oxygen than nitrogen. Silicon nitride oxide is an insulating material in which the nitrogen content is greater than the oxygen content. This refers to...

[0075] The insulating film 306 can improve interface characteristics with the oxide semiconductor films 308a and 308b. It is preferable to use a material that can be used, and typically, an inorganic insulating material that contains oxygen is used. The insulating film 306 is typically an oxide insulating film. For example, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, an aluminum oxynitride film, A film or the like may be used, and the film may be provided as a laminate or a single layer.

[0076] The insulating film 306 is made of hafnium silicate (HfSiO x ), nitrogen-containing halide HfSix O y N z ), hafnium aluminate with nitrogen (H fAl x O y N z ), hafnium oxide, yttrium oxide, and other high-k materials are used. This can reduce the gate leakage of the transistors 102 and 103.

[0077] Silicon nitride film has a higher relative dielectric constant than silicon oxide film, and is equivalent to silicon oxide film. Since a large film thickness is required to obtain the capacitance of 1000 Ω, it is necessary to physically thicken the gate insulating film. This makes it possible to suppress the decrease in the dielectric strength of the transistor and further improve the dielectric strength. As a result, electrostatic damage to the transistor can be suppressed.

[0078] Over the insulating film 306, oxide semiconductor films 308a and 308b and a light-transmitting conductive film The oxide semiconductor film 308a is formed so as to overlap with the conductive film 304a. The transistor 102 in the driver circuit portion is formed in the same position as the first insulating film 101 and functions as a channel formation region of the transistor 102 in the driver circuit portion. In addition, the oxide semiconductor film 308b is formed in a position overlapping with the conductive film 304c. The light-transmitting conductive film 30 functions as a channel formation region of the transistor 103 in FIG. The electrode 8 c functions as one electrode of the capacitor 105 .

[0079] The oxide semiconductor films 308a and 308b are oxide semiconductor films containing In or Ga. Representative examples include In-Ga oxide, In-Zn oxide, and In-M-Zn oxide (M is Al). , Ti, Ga, Y, Zr, La, Ce, Nd, or Hf).

[0080] When the oxide semiconductor films 308a and 308b are made of In-M-Zn oxide, In and The atomic ratio of M is preferably less than 50 atomic % for In and less than 50 atomic % for M. % or more, more preferably, In is less than 25 atomic % and M is 75 atomic % or more. The above.

[0081] The content of the material contained in the oxide semiconductor films 308a and 308b (for example, In, Ga, etc.) ) is a method for analyzing the structure of a sample by using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XP S) can be used for comparison.

[0082] The oxide semiconductor films 308a and 308b have an energy gap of 2 eV or more. Since the potential is 2.5 eV or more, and more preferably 3 eV or more, the potential of the transistor to be formed later is increased. The off-current can be reduced.

[0083] The light-transmitting conductive film 308c is made of In, like the oxide semiconductor films 308a and 308b. or an oxide semiconductor film containing Ga and containing impurities. The impurities include hydrogen. Instead of hydrogen, boron, phosphorus, and sulfur can also be used as impurities. It may contain zinc, antimony, rare gas elements, alkali metals, alkaline earth metals, etc. .

[0084] The oxide semiconductor films 308a and 308b and the light-transmitting conductive film 308c are all gate electrodes. The oxide semiconductor film is formed on the insulating film and contains In or Ga. The impurity concentration is Specifically, the oxide semiconductor film 308a and the oxide semiconductor film 308b are different from the light-transmitting conductive film 308a and the oxide semiconductor film 308b. For example, the oxide semiconductor films 308a and 308b have a high impurity concentration. The hydrogen concentration is 5×10 19 atoms / cm 3 Less than 5 x 1018 atom s / cm 3 Less than 1 x 10 18 atoms / cm 3 Less than or equal to 5x, more preferably 10 17 atoms / cm 3 Less than 1×10, more preferably 16 atoms / cm 3 Below The hydrogen concentration in the light-transmitting conductive film 308c is 8×10 19 atom s / cm 3 More than 1×10 20 atoms / cm 3 More preferably, 5x 10 20 atoms / cm 3 In addition, compared with the oxide semiconductor films 308a and 308b, In comparison, the hydrogen concentration in the light-transmitting conductive film 308c is two times, preferably ten times or more. Above.

[0085] In addition, the light-transmitting conductive film 308c has a lower resistance than the oxide semiconductor films 308a and 308b. The resistivity of the light-transmitting conductive film 308c is low compared to that of the oxide semiconductor films 308a and 308b. b resistivity 1×10 -8 more than 1x10 -1 It is preferable that the ratio is less than 1 / 2. 1×10 -3 Ωcm or more 1×10 4 Ωcm, and more preferably a resistivity of 1×10 - 3 Ωcm or more 1×10 -1 It is preferable that the resistivity is less than Ωcm.

[0086] The oxide semiconductor films 308a and 308b and the light-transmitting conductive film 308c are, for example, The non-single crystal structure may be, for example, a CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor ), polycrystalline structure, microcrystalline structure (described below), or amorphous structure.

[0087] Note that the oxide semiconductor films 308a and 308b and the light-transmitting conductive film 308c are C The mixed film had two or more structural regions, namely, AAC-OS, microcrystalline structure, and amorphous structure. The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, and a CAAC-O The mixed film has, for example, an amorphous structure region and a microcrystalline structure region. The CAAC-OS region may have a laminated structure.

[0088] Note that the oxide semiconductor film may be, for example, single crystal.

[0089] The insulating film 306, the oxide semiconductor films 308a and 308b, and the light-transmitting conductive film 308 On the other hand, conductive films (hereinafter referred to as conductive films 310a, 310b, 310c, 310d, and 310e) are formed on the conductive films 310a, 310b, 310c, 310d, and 310e. The conductive film 310a is electrically connected to the oxide semiconductor film 308a. 1, which is connected to one of the source and drain of the transistor 102 in the driver circuit portion. The conductive film 310b is electrically connected to the oxide semiconductor film 308a. The other of the source and drain of the transistor 102 in the driver circuit portion The conductive film 310c is formed through openings provided in the insulating films 312 and 314. The conductive film 310d is electrically connected to the light-transmitting conductive film 316a. The source of the transistor 103 in the pixel portion is electrically connected to the oxide semiconductor film 308b. The conductive film 310e functions as either a source or a drain. 308b and the light-transmitting conductive film 316b are electrically connected to the transistor in the pixel portion. The second electrode 103 functions as the other of the source and drain.

[0090] The conductive films 310a, 310b, 310c, 310d, and 310e are made of a conductive material. , aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum A metal consisting of tantalum, silver, tantalum, or tungsten, or a metal that has this as its main component. The alloy is used as a single layer or a multilayer structure. For example, a titanium film is stacked on an aluminum film. Two-layer structure with a titanium film on a tungsten film, two-layer structure with a copper-magnesium- A two-layer structure in which a copper film is laminated on an aluminum alloy film, a titanium film or a titanium nitride film, and An aluminum film or a copper film is laminated on the titanium film or the titanium nitride film, and then the aluminum film or the copper film is laminated on the titanium film or the titanium nitride film. A three-layer structure in which a titanium film or titanium nitride film is formed on top, a molybdenum film or molybdenum nitride film A molybdenum film and an aluminum film or a copper film are laminated on the molybdenum film or the molybdenum nitride film. A three-layer structure is formed by laminating a layer of a molybdenum film or a molybdenum nitride film on top of the layer of a silicon nitride film. A transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used. .

[0091] An insulating film 306, oxide semiconductor films 308a and 308b, a light-transmitting conductive film 308c, An insulating film 312 is formed on the conductive films 310a, 310b, 310c, 310d, and 310e. An insulating film 314 is formed. The insulating film 312 is made of an oxide semiconductor, similar to the insulating film 306. It is preferable to use a material capable of improving the interface characteristics with the film. As with the insulating film 305, impurities from the outside, such as water, alkali metals, alkaline earth metals, etc. It is preferable to use a material that can prevent a metal or the like from diffusing into the oxide semiconductor films 308a and 308b. I wish.

[0092] The insulating film 312 is an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition. In this way, the oxide semiconductor films 308a and 308b may be formed as a In addition to preventing oxygen from being released, oxygen contained in the insulating film 312 is moved to the oxide semiconductor film. For example, thermal desorption spectroscopy (TDS) can be used to compensate for oxygen deficiencies. The temperature is 100°C or higher and 700°C or lower, preferably 100°C or higher. The amount of oxygen molecules released during heat treatment at 500°C or less is 1.0×10 18 molecule / cm 3 Below By using the oxide insulating film described above, oxygen vacancies in the oxide semiconductor films 308a and 308b can be prevented. The loss can be compensated for.

[0093] The insulating film 312 has a stacked structure. The first oxide insulating film is an oxide semiconductor film having a low interface state with the oxide semiconductor films 308a and 308b. A second oxide insulating film having the above stoichiometric composition is formed on the first oxide insulating film. An oxide insulating film containing as much oxygen as possible may be provided.

[0094] For example, the first oxide insulating film has a g value of 2.001 (E´ -center) spin density is 3.0×10 17 spins / cm 3 Hereinafter, preferably 5.0×10 16 spins / cm 3 The following oxide insulating film can be used to form an oxide semiconductor film. It is possible to reduce the interface states with 308a and 308b. The spin density at g value = 2.001 determined by the measurement is the dangling valence corresponds to the abundance of

[0095] In addition, conductive films 316a and 316b having light-transmitting properties are formed over the insulating film 314. The light-transmitting conductive film 316a is electrically connected to the conductive film 304b in the opening 374a. The conductive film 310c is electrically connected to the conductive film 310c through the opening 374b. The conductive film 316a having optical properties serves as a connection electrode that connects the conductive film 304b and the conductive film 310c. The light-transmitting conductive film 316b functions as a conductive film in the opening 374c. The film 310e is electrically connected to the pixel electrode of the pixel. The conductive film 316b can function as the other of the pair of electrodes of the capacitor 105. do.

[0096] The light-transmitting conductive films 316a and 316b are formed of indium oxide, tin oxide, or zinc oxide. The conductive film 316a has a light-transmitting property and contains at least one oxide selected from the group consisting of lead and lead. Examples of 316b include indium oxide containing tungsten oxide, tungsten oxide, Indium zinc oxide containing titanium oxide, Indium oxide containing titanium oxide Indium Tin Oxide, ITO, Indium Zinc Oxide, Indium Doped Silicon Oxide A light-transmitting conductive material such as tin oxide can be used.

[0097] In addition, a film having color (hereinafter, referred to as a color film 346) is formed below the substrate 342. The color film 346 functions as a color filter. A light-shielding film 344 adjacent to the substrate 46 is formed below the substrate 342. The light-shielding film 344 is a black The colored film 346 does not necessarily have to be provided. For example, if the display device is black and white, the color film 346 may not be provided.

[0098] The colored film 346 may be any colored film that transmits light in a specific wavelength range. For example, A red (R) color filter that transmits light in the red wavelength range, and a green (G) color filter that transmits light in the green wavelength range. A green (G) color filter transmits light in the blue wavelength range, and a blue (B) color filter transmits light in the blue wavelength range. A filter or the like can be used.

[0099] The light-shielding film 344 may be made of a metal or other material as long as it has a function of blocking light in a specific wavelength range. Alternatively, an organic insulating film containing a black pigment or the like can be used.

[0100] In addition, an insulating film 348 is formed below the colored film 346. The insulating film 348 has a flat The function of the color film 346 is to diffuse impurities that may be contained in the color film 346 toward the liquid crystal element. It has the function of suppressing

[0101] In addition, a conductive film 350 is formed on the insulating film 348. The conductive film 350 is The electrode functions as one of a pair of electrodes of the liquid crystal element 108. The alignment films 318 and 352 are formed in contact with the conductive films 316a and 316b and the conductive film 350. It has been done.

[0102] In addition, between the conductive film 316b having light-transmitting properties and the conductive film 350, more specifically, between the alignment film 3 A liquid crystal layer 320 is formed between the liquid crystal layer 18 and the alignment film 352. A sealing material (not shown) is used to seal between the substrate 302 and the substrate 342. The sealing material is configured to come into contact with inorganic materials in order to prevent the intrusion of moisture from the outside. preferable.

[0103] In addition, a liquid crystal layer 320 is provided between the conductive films 316a and 316b having light-transmitting properties and the conductive film 350. A spacer may be provided to maintain the thickness (also called the cell gap) of the pixel.

[0104] <Manufacturing method of display device> Next, a method for manufacturing an element portion provided on a substrate 302 of a display device shown in FIG. This will be described with reference to FIG. 4 to FIG.

[0105] First, prepare a substrate 302. Here, a glass substrate is used as the substrate 302.

[0106] Next, a conductive film is formed on the substrate 302 and processed into a desired shape. The conductive films 304a, 304b, and 304c are formed. The formation of c is performed by forming a mask by a first patterning in a desired region, and then covering the mask. It can be formed by etching the uncut areas (see FIG. 4(A)).

[0107] The conductive films 304a, 304b, and 304c are typically formed by deposition, CVD, or spatula. The conductive film 30 can be formed by using a dipping method, a spin coating method, or the like. 4a, 304b, and 304c are formed by sputtering tungsten films having a thickness of 100 nm. It is formed by:

[0108] Next, an insulating film 305 is formed on the substrate 302 and the conductive films 304a, 304b, and 304c. Then, an insulating film 306 is formed over the insulating film 305 (see FIG. 4A).

[0109] The insulating film 305 and the insulating film 306 are formed by a sputtering method, a CVD method, or the like. It should be noted that the insulating film 305 and the insulating film 306 can be formed in succession in a vacuum. This is preferable because it suppresses the inclusion of impurities at the interface between the insulating film 305 and the insulating film 306. 05, a silicon nitride film having a thickness of 400 nm is formed by the PE-CVD method. As the insulating film 306, a silicon oxynitride film having a thickness of 50 nm is formed by the PE-CVD method. do.

[0110] Next, an oxide semiconductor film 307 is formed over the insulating film 306 (see FIG. 4B).

[0111] The oxide semiconductor film 307 can be formed by a sputtering method, a coating method, a pulsed laser deposition method, a laser deposition method, or the like. The thin film can be formed by using a method such as ablation.

[0112] When the oxide semiconductor film 307 is formed by a sputtering method, plasma is generated. The power supply may be an RF power supply, an AC power supply, a DC power supply, or the like. .

[0113] The sputtering gas is a rare gas (typically argon), oxygen, or a mixture of a rare gas and oxygen. In the case of a mixture of rare gas and oxygen, the amount of oxygen gas is appropriately adjusted relative to the amount of rare gas. A higher ratio is preferred.

[0114] Note that when the oxide semiconductor film 307 is formed by a sputtering method, for example, The substrate temperature is set to room temperature (for example, 20° C.) or higher and lower than 500° C., and preferably to 100° C. or higher. The temperature is set to 450°C or less, and more preferably 150°C to 350°C, and the oxidation is performed while heating. A compound semiconductor film 307 may be formed.

[0115] When the oxide semiconductor film 307 is formed by a sputtering method, In order to reduce the hydrogen concentration in 307, each chamber in the sputtering equipment was oxidized. A cryopump that can remove as much hydrogen and other impurities as possible from semiconductor films. A high vacuum pump (5×10 -7 Pa~1×10 - 4 It is preferable to use a turbo molecular pump and a cold trap. In combination, this prevents gases, especially those containing carbon or hydrogen, from flowing back into the chamber from the exhaust system. It is preferable to keep this in mind.

[0116] In order to reduce the hydrogen concentration in the oxide semiconductor film 307, the inside of the chamber was evacuated to a high vacuum. In addition, it is necessary to increase the purity of the sputtering gas. The oxygen gas or argon gas used has a dew point of -40°C or less, preferably -80°C or less, and more preferably A gas that has been highly purified to a temperature of preferably -100°C or lower, more preferably -120°C or lower, is used. By providing the insulating film, moisture or the like can be prevented from being taken into the oxide semiconductor film as much as possible.

[0117] Here, the oxide semiconductor film 307 is an In-Ga-Zn oxide film having a thickness of 35 to 100 nm. A thin film (In:Ga:Zn=1:1:1) is formed by sputtering.

[0118] Next, the oxide semiconductor film 307 is processed into a desired shape to form an island-shaped oxide semiconductor film 3 308a, 308b, and 308d are formed (see FIG. 4(C)).

[0119] Note that the oxide semiconductor films 308a, 308b, and 308d are formed in desired regions. A mask is formed by turning, and the areas not covered by the mask are etched. The etching can be performed by dry etching or wet etching. Alternatively, etching, annealing, or a combination of both may be used.

[0120] Next, a first heat treatment is preferably performed. The first heat treatment is performed at a temperature of 250° C. or higher and 650° C. or higher. ℃ or less, preferably 300 ℃ to 500 ℃, in an inert gas atmosphere, an oxidizing gas atmosphere The first heat treatment may be performed in an atmosphere containing 10 ppm or more of fluorine or under reduced pressure. The atmosphere is an inert gas atmosphere, and then an oxidizing gas is introduced to replenish the oxygen that has been removed. The first heat treatment may be performed in an atmosphere containing 10 ppm or more of oxide semiconductor film 3. The crystallinity of the oxide semiconductors used for the insulating films 308a, 308b, and 308d is improved, and the insulating film 306 and removing impurities such as hydrogen and water from the oxide semiconductor films 308a, 308b, and 308d. Note that a first heating step may be performed before etching the oxide semiconductor. stomach.

[0121] Here, the specimen is heat-treated in a nitrogen atmosphere at 350°C for 1 hour, and then cooled in an oxygen atmosphere at 350°C for 1 hour. Heat treatment for 1 hour.

[0122] Next, a conductive film 3 is formed over the insulating film 306 and the oxide semiconductor films 308a, 308b, and 308d. 09 (see Figure 5(A)).

[0123] The conductive film 309 can be formed by, for example, a sputtering method.

[0124] Here, a titanium film having a thickness of 50 nm, an aluminum film having a thickness of 400 nm, and a Then, a 100 nm thick titanium film is laminated on the SiO2 film by sputtering.

[0125] Next, the conductive film 309 is processed into a desired region to form conductive films 310a, 310b, and 311. In addition, the conductive films 310a, 310b, 310c, 310d, and 310e are formed. The formation of 10d and 310e involves forming a mask by third patterning in a desired area. The regions not covered by the mask can be etched away to form the etched region (FIG. 5( See B).

[0126] Next, the insulating film 306, the oxide semiconductor films 308a, 308b, and 308d, and the conductive film 31 An insulating film 311 is formed so as to cover the layers 310a, 310b, 310c, 310d, and 310e. (See FIG. 5(C)).

[0127] The insulating film 311 is made of a material having good interface characteristics with the oxide semiconductor films 308a, 308b, and 308d. It is preferable to use a material capable of improving the insulating property, typically an inorganic insulating material containing oxygen. It is preferable to use a material such as an oxide insulating film. The film 11 can be formed by using, for example, a PE-CVD method, a sputtering method, or the like. Cut.

[0128] The insulating film 311 is made of an oxide film containing more oxygen than the oxygen that satisfies the stoichiometric composition. When the insulating film 311 is formed, the insulating film 311 can be formed under the following conditions. In the case where a silicon oxide film or a silicon oxynitride film is formed as the insulating film 311, The formation conditions are as follows: The substrate is kept at 180° C. or higher and 260° C. or lower, more preferably 180° C. or higher and 230° C. or lower. A raw material gas is introduced into the processing chamber to set the pressure in the processing chamber to 100 Pa or more and 250 Pa or less. More preferably, the pressure should be between 100 Pa and 200 Pa, and the pressure should be 0. 17W / cm 2 More than 0.5W / cm 2 Less than or equal to 0.25 W / cm 2 More than 0 .35W / cm 2 The object is to supply high frequency power as follows:

[0129] The source gas for the insulating film 311 is a deposition gas containing silicon, typically silane, diphenyl ether, etc. Examples of oxidizing gases include oxygen, ozone, and fluorinated silane. These include nitrous oxide and nitrogen dioxide.

[0130] The conditions for forming the insulating film 311 are as follows: high frequency power of the above power density in a processing chamber at the above pressure. By supplying power, the efficiency of decomposition of the source gas in the plasma increases, and the number of oxygen radicals increases. As the oxidation of the source gas progresses, the oxygen content in the insulating film 311 becomes lower than the stoichiometric composition. However, when the substrate temperature is set to the above temperature, the bonding strength between silicon and oxygen becomes As a result, the oxygen in the stoichiometric composition is less than that of the oxygen in the stoichiometric composition. It is possible to form an oxide insulating film that contains more oxygen than the silicon oxide film and from which some of the oxygen is released by heating. Cut.

[0131] The insulating film 311 has a stacked structure, and the first oxide insulating film is made of at least an oxide semiconductor. An oxide insulating film is formed on the insulating film 308a and 308b so that the interface state between the insulating film 308a and 308b is low. A second oxide film is formed on the insulating film 308a and 308b. As the insulating film, an oxide insulating film containing more oxygen than the oxygen satisfying the above stoichiometric composition is provided. This is also fine.

[0132] The oxide insulating film having a low interface state with at least the oxide semiconductor films 308a and 308b is The oxide insulating film can be formed under the following conditions. The formation conditions are as follows: The substrate placed in the evacuated processing chamber of the CVD device is heated to 180°C or higher and 400°C or lower. Furthermore, the temperature is preferably kept at 200° C. or higher and 370° C. or lower, and the silicon-containing raw material gas is introduced into the processing chamber. Deposition gas and oxidizing gas are introduced to keep the pressure in the processing chamber at 20 Pa or more and 250 Pa or less. The pressure is preferably 40 Pa or more and 200 Pa or less, and a high pressure is applied to the electrodes provided in the treatment chamber. These are the conditions for supplying high frequency power.

[0133] The source gas for the first oxide insulating film contains more oxygen than the oxygen required for the stoichiometric composition. The source gas can be applicable to the oxide insulating film. In the step of forming the oxide insulating film, at least the oxide semiconductor films 308a and 308b are protected. As a result, the second oxide insulating film is formed using high-frequency power with high power density. In addition, damage to the oxide semiconductor films 308a and 308b can be suppressed.

[0134] Here, the insulating film 311 has a stacked structure of a first oxide insulating film and a second oxide insulating film. The oxide insulating film of No. 1 was prepared by using silane at a flow rate of 30 sccm and dioxygen at a flow rate of 4000 sccm. Nitrogen was used as the source gas, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 220°C. PE-CV in which 150 W of RF power was supplied to parallel plate electrodes using a MHz RF power source. A silicon oxynitride film with a thickness of 50 nm is formed using the D device. The raw material gases were silane at a flow rate of 200 sccm and dinitrogen monoxide at a flow rate of 4000 sccm. The pressure in the processing chamber was 200 Pa, the substrate temperature was 220° C., and a high-frequency power source of 27.12 MHz was used. A PE-CVD apparatus was used to supply 1500W of high frequency power to parallel plate electrodes. The PE-CVD device is a silicon oxynitride film with a thickness of 400 nm. 000cm 2 This is a parallel plate type PE-CVD device, and the power supplied is This corresponds to a power density of 0.26 W / cm 2 It is.

[0135] Next, the insulating film 311 is processed into a desired shape to form an insulating film 312 and an opening 372. The opening 372 is formed in a desired region by a mask formed by a fourth patterning. The mask may be formed by forming a mask and then etching the area not covered by the mask. (See Figure 6(A)).

[0136] Note that the opening 372 is formed so as to expose the oxide semiconductor film 308d. By forming the opening 372, the oxide semiconductor film 308d (the second portion of the oxide semiconductor film 307) ) is thicker than the oxide semiconductor films 308a and 308b (the first portion of the oxide semiconductor film 307). Specifically, the thickness of the oxide semiconductor film 308d is thinner than that of the oxide semiconductor film 308a. The thickness of the oxide semiconductor layer 308b is preferably 2 / 3 or less, more preferably 1 / 2 or less. The lower limit of the thickness of the film 308d is set to be a thickness at which the light-transmitting conductive film 308c to be formed later is formed as a capacitor element. The thickness is preferably within a range that allows the film to function as one of the electrodes, for example, 5 nm to 50 nm. When the thickness of the oxide semiconductor film 308d is in the above range, The transmittance of the oxide semiconductor film 308d can be improved as compared with that of the oxide semiconductor films 308a and 308b. In this embodiment, the oxide semiconductor film 307 is formed to a thickness of 35 to 100 nm. Therefore, the thickness of the oxide semiconductor film 308d is set to, for example, 15 nm to 50 nm. It is possible.

[0137] The opening 372 can be formed by, for example, dry etching. However, the method for forming the opening 372 is not limited to this, and may be a wet etching method. Alternatively, a combination of dry etching and wet etching may be used. stomach.

[0138] In this embodiment, the periphery of the oxide semiconductor film 308d is covered with the insulating film 312. In the embodiment, the opening 372 is formed so as to be covered by the metal plate 36, but the present invention is not limited to this. In the formation of the oxide semiconductor film 308, the entire surface of the oxide semiconductor film 308d is exposed. The film thickness of the entire surface of d may be thinned.

[0139] Next, the insulating film 313 is formed over the insulating film 312 and the oxide semiconductor film 308d. By forming the film 313, the oxide semiconductor film 308d is turned into the light-transmitting conductive film 3 The result is 08c (see Figure 6(B)).

[0140] The insulating film 313 is resistant to external impurities such as water, alkali metals, alkaline earth metals, etc. The film is formed of a material that prevents diffusion of hydrogen into the oxide semiconductor film and further contains hydrogen. Therefore, when hydrogen in the insulating film 313 diffuses into the oxide semiconductor film 308d, the oxide semiconductor In the film 308d, hydrogen combines with oxygen to generate electrons, which are carriers. The oxide semiconductor film 308d has high conductivity and becomes the light-transmitting conductive film 308c. On the other hand, the oxide semiconductor films 308a and 308b have an insulating film 312 between them. Therefore, the diffusion of hydrogen contained in the insulating film 313 is not observed or is very small. For example, a silicon nitride film can be used for the insulating film 313. It can be formed by using a VD method.

[0141] The silicon nitride film is preferably formed at a high temperature in order to enhance blocking properties. For example, the substrate temperature is 100° C. or higher and lower than the distortion point of the substrate, and more preferably 300° C. or higher and 400° C. or lower. It is preferable to form the film by heating at the following temperature. Oxygen is released from the oxide semiconductor used as the dielectric films 308a and 308b, and the carrier concentration increases. Therefore, the temperature should be set at a level at which such a phenomenon does not occur.

[0142] Here, the insulating film 313 is made of silane at a flow rate of 50 sccm and SiO2 at a flow rate of 5000 sccm. The raw gases were nitrogen at a flow rate of 100 sccm and ammonia at a flow rate of 100 sccm. The pressure in the processing chamber was set to 200 P. a) The substrate temperature was set to 220°C, and a 27.12MHz high-frequency power source was used to generate 1000W (power The density is 1.6×10 -1 W / cm 2 ) high frequency power was supplied to the parallel plate electrodes. A silicon nitride film having a thickness of 50 nm is formed by the CVD method.

[0143] Next, the insulating film 313 is processed into a desired shape to form an insulating film 314 and an opening 374. The insulating film 314 and the openings 374a, 374b, and 374c are formed. b, 374c form a mask by fifth patterning in a desired area, and the mask This can be achieved by etching the areas not covered by the metal (see FIG. 6(C)). .

[0144] The opening 374a is formed so as to expose the conductive film 304a. The opening 374b is formed so as to expose the conductive film 310c. It is formed so that 310e is exposed.

[0145] The openings 374a, 374b, and 374c can be formed, for example, by dry etching. However, the method for forming the openings 374a, 374b, and 374c may be The etching method is not limited to this, and may be a wet etching method or a dry etching method. A formation method in which wet etching is combined may also be used.

[0146] Next, a conductive film 31 is formed on the insulating film 314 so as to cover the openings 374a, 374b, and 374c. 5 (see FIG. 7(A)).

[0147] The conductive film 315 can be formed by, for example, a sputtering method.

[0148] Here, the conductive film 315 is a silicon oxide film having a thickness of 100 nm formed by a sputtering method. A film of indium tin oxide containing potassium is formed.

[0149] Next, the conductive film 315 is processed into a desired shape to form a light-transmitting conductive film 316a, The light-transmitting conductive films 316a and 316b are formed. A mask is formed on the region by a sixth patterning, and the region not covered by the mask is It can be formed by etching (see FIG. 7(B)).

[0150] Through the above steps, a pixel portion having a transistor and a driver circuit portion are formed on the substrate 302. In the manufacturing process shown in this embodiment, the first to sixth patterned That is, the transistors 102, 103, and the capacitance element 105 are simultaneously formed using six masks. It can be formed into.

[0151] Note that in this embodiment, hydrogen contained in the insulating film 314 is diffused into the oxide semiconductor film 308d. The oxide semiconductor film 308d was then dispersed with an oxide semiconductor to increase its conductivity. The films 308a and 308b are covered with a mask, and impurities, typically, Hydrogen, boron, phosphorus, tin, antimony, rare gas elements, alkali metals, alkaline earth metals The conductivity of the oxide semiconductor film 308d may be increased by adding, for example, The method of adding hydrogen, boron, phosphorus, tin, antimony, rare gas elements, etc. to d is as follows: On the other hand, the oxide semiconductor film 308 As a method for adding an alkali metal, an alkaline earth metal, etc. to d, a solution containing the impurity is There is a method of exposing the oxide semiconductor film 308d to light.

[0152] Next, the structure formed on the substrate 342 provided opposite the substrate 302 will be described below. Provide an explanation.

[0153] First, a substrate 342 is prepared. The substrate 342 is made of the same material as that of the substrate 302. Next, a light-shielding film 344 and a colored film 346 are formed on the substrate 342. The color film 346 and the colored film 44 are formed by using various materials, by printing, inkjet printing, photolithography, etc. They are formed at the desired positions by an etching method using a graphic technique.

[0154] Next, an insulating film 348 is formed on the light-shielding film 344 and the colored film 346. For example, an organic insulating film made of an acrylic resin or the like can be used. By forming the colored film 346, for example, impurities contained in the colored film 346 are transported to the liquid crystal layer 320 side. However, the insulating film 348 is not necessarily required. Alternatively, a structure in which the insulating film 348 is not formed may be used.

[0155] Next, a conductive film 350 is formed over the insulating film 348. The materials shown in 5 can be used.

[0156] Through the above steps, the structure formed on the substrate 342 can be formed.

[0157] Next, the insulating film 31 formed on the substrate 302 and the substrate 342, more specifically, on the substrate 302, 4. The conductive films 316a and 316b having light transmitting properties and the conductive film 35 formed on the substrate 342 0, an alignment film 318 and an alignment film 352 are formed. The film can be formed by using a rubbing method, a photo-alignment method, or the like. A liquid crystal layer 320 is formed between the substrate 342 and the liquid crystal layer 320. or by bonding the substrate 302 and the substrate 342 together and then using the capillary phenomenon. An injection method for injecting liquid crystal can be used.

[0158] Through the above steps, the display device shown in FIG. 3A can be manufactured.

[0159] <Variation 1> The display device shown in FIG. 8A includes a transistor 102 included in the display device described above. The oxide semiconductor films 308a and 308b of the oxide semiconductor film 388a and the oxide film 3 9A, an oxide semiconductor film 388b, and an oxide film 390b are stacked in a stacked structure. Therefore, the other configurations are the same as those of the transistors 102 and 103, and the above description is This can be taken into consideration.

[0160] Here, the oxide semiconductor film 388a, the oxide film 390a, and the oxide semiconductor film 388 The details of the oxide film 390b will be described below.

[0161] Oxide semiconductor films 388a and 388b (hereinafter referred to as oxide semiconductor films 388 in the specification) ) and oxide films 390a and 390b (hereinafter, also referred to as oxide film 390 in the specification). It is preferable to use a metal oxide having at least one identical constituent element as the above-mentioned. Alternatively, the oxide semiconductor film 388 and the oxide film 390 may be formed using the same elements. The composition may be different.

[0162] The oxide semiconductor film 388 is an In-M-Zn oxide (wherein M is Al, Ga, Ge, Y, Zr, or S In the case of In, La, Ce or Hf, the spatula used to deposit the In-M-Zn oxide film The atomic ratio of the metal elements in the ion implantation target preferably satisfies In≧M and Zn≧M. The atomic ratio of the metal elements in such a sputtering target is In:M:Z. n=1:1:1, In:M:Zn=5:5:6(1:1:1.2), In:M:Zn=3 Note that the atomic ratio of the oxide semiconductor film 388 to be formed is preferably, for example, The error is the plus or minus of the atomic ratio of the metal elements contained in the sputtering target. Includes a 20% fluctuation in eggplant.

[0163] When the oxide semiconductor film 388 is an In-M-Zn oxide, the The atomic ratio of In and M is preferably 25 atomic % or more of In and 75 atomic % or more of M. mic%, more preferably In is 34 atomic % or more and M is 66 atomic % or more. % or less.

[0164] The oxide semiconductor film 388 has an energy gap of 2 eV or more, preferably 2.5 eV or more. In this way, the oxide semiconductor having a wide energy gap is By using a conductor, the off-state current of a transistor can be reduced.

[0165] The thickness of the oxide semiconductor film 388 is 3 nm to 200 nm, preferably 3 nm to 100 nm. 00 nm or less, and more preferably 3 nm or more and 50 nm or less.

[0166] The oxide film 390 is typically made of In-Ga oxide, In-Zn oxide, In-MnO2, or In-ZnO. n-oxide (M is Al, Ga, Ge, Y, Zr, Sn, La, Ce or Hf) and The energy of the bottom of the conduction band is closer to the vacuum level than that of the oxide semiconductor film 388. , the energy of the bottom of the conduction band of the oxide film 390 and the energy of the bottom of the conduction band of the oxide semiconductor film 388 The difference in energy between the 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 That is, the electron affinity of the oxide film 390 and the electron affinity of the oxide semiconductor film 388 are The difference is 0.05 eV or more, 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.

[0167] The oxide film 390 has the above-mentioned element M in a higher atomic ratio than In, and thus has the following effects: (1) The energy gap of the oxide film 390 is increased. (2) (3) To reduce the electron affinity of the oxide film 390. (4) To block impurities from the outside. The insulating property is higher than that of the oxide semiconductor film 388. Since M is a strong metallic element, by having a higher atomic ratio than In, oxygen vacancies are less likely to occur. It becomes hard.

[0168] When the oxide film 390 is an In-M-Zn oxide, the In and M oxides except for Zn and O are The atomic ratio is preferably less than 50 atomic % for In and 50 atomic % or more for M. More preferably, In is less than 25 atomic % and M is 75 atomic % or more. do.

[0169] The oxide semiconductor film 388 and the oxide film 390 are made of In-M-Zn oxide (M is Al , Ga, Ge, Y, Zr, Sn, La, Ce or Hf), the oxide semiconductor film 388 In comparison, the atomic ratio of M contained in the oxide film 390 is large, and typically, The amount of the atoms contained in the membrane 388 is at least 1.5 times, preferably at least 2 times, The atomic ratio is preferably three times or more higher.

[0170] The oxide film 390 is In:M:Zn=x1:y1:z1 [atomic ratio], and the oxide semiconductor If the atomic ratio of the membrane 388 is In:M:Zn=x2:y2:z2, then y1 / x1 is y 2 / x2, and preferably, y1 / x1 is 1.5 times or more larger than y2 / x2. More preferably, y1 / x1 is at least twice as large as y2 / x2, and even more preferably, The ratio y1 / x1 is three times larger than the ratio y2 / x2. When y2 is equal to or larger than x2, a transistor including an oxide semiconductor can have stable electrical characteristics. However, if y2 is three times or more larger than x2, it is necessary to use an oxide semiconductor. Therefore, y2 should be less than three times x2. preferable.

[0171] When the oxide semiconductor film 388 and the oxide film 390 are In-M-Zn oxide, The atomic ratio of metal elements in the sputtering target used to form a Zn oxide film is: It is preferable that M>In and Zn≧M are satisfied. The atomic ratio of the group elements is In:Ga:Zn=1:3:2, In:Ga:Zn=1:3: 3, In:Ga:Zn=1:3:4, In:Ga:Zn=1:3:5, In:Ga:Zn =1:3:6, In:Ga:Zn=1:3:7, In:Ga:Zn=1:3:8, In: Ga:Zn=1:3:9, In:Ga:Zn=1:3:10, In:Ga:Zn=1:6 :4, In:Ga:Zn=1:6:5, In:Ga:Zn=1:6:6, In:Ga:Z n=1:6:7, In:Ga:Zn=1:6:8, In:Ga:Zn=1:6:9, In The preferred ratio is Ga:Zn=1:6:10. The atomic ratio of metal elements contained in the formed oxide semiconductor film 388 and the formed oxide film 390 is The atomic ratio of the metal elements contained in the sputtering target is included as an error. Includes fluctuations of ±20%.

[0172] In addition, the semiconductor characteristics and electrical characteristics (field effect) of the required transistors are not limited to these. It is sufficient to use a material with an appropriate composition according to the required properties (e.g., the resultant mobility, threshold voltage, etc.). In order to obtain semiconductor characteristics of a transistor, the carrier density and impurity of the oxide semiconductor film 388 are The concentration of metals, defect density, atomic ratio of metal elements to oxygen, interatomic distance, density, etc. are appropriately adjusted. It is preferred.

[0173] The oxide film 390 is formed by oxidizing the insulating film 312 or the insulating film 314 to be formed later. The oxide film 390 also functions as a film for mitigating damage to the oxide semiconductor film 388. The thickness is from 3 nm to 100 nm, preferably from 3 nm to 50 nm.

[0174] The oxide semiconductor film 388 contains silicon or carbon, which is one of Group 14 elements. As a result, oxygen vacancies increase in the oxide semiconductor film 388, causing the oxide semiconductor film 388 to become n-type. The concentration of silicon or carbon in the oxide semiconductor film 388, or the concentration of the oxide film 390 and the oxide semiconductor The concentration of silicon and carbon near the interface with the conductive film 388 (obtained by secondary ion mass spectrometry) The concentration of 18 atoms / cm 3 Less than or equal to 2×10 17 atoms / cm 3 The following applies.

[0175] In addition, in the oxide semiconductor film 388, an alkali metal ion was obtained by secondary ion mass spectrometry. The concentration of metal or alkaline earth metal is 1×10 18 atoms / cm 3 The following is preferably is 2 × 10 16 atoms / cm 3 The following are the alkali metals and alkaline earth metals: When a compound is bonded to an oxide semiconductor, carriers may be generated, increasing the off-state current of a transistor. For this reason, the alkali metal or alkali metal in the oxide semiconductor film 388 may be It is preferable to reduce the concentration of alkaline earth metals.

[0176] When the oxide semiconductor film 388 contains nitrogen, electrons that serve as carriers are generated, and The carrier density increases and it becomes easier to make the material n-type. Therefore, the transistor having the oxide semiconductor film 388 tends to be normally on. In the present invention, it is preferable that the nitrogen content is reduced as much as possible. For example, in the case of secondary ion mass spectrometry, The nitrogen concentration obtained by the method is 5×10 18 atoms / cm 3 It is preferable to do the following: stomach.

[0177] Note that the oxide semiconductor film 388 and the oxide film 390 are not simply stacked but are formed continuously. A continuous junction (here, a structure in which the energy at the bottom of the conduction band changes continuously between each film) That is, the oxide semiconductor is formed at the interface of each film. The stacking layer is free of impurities that may form defect levels such as trip centers or recombination centers. Assume that impurities are present between the stacked oxide semiconductor film 388 and the oxide film 390. When they are mixed, the continuity of the energy bands is lost, carriers are trapped at the interface, Or they recombine and disappear.

[0178] 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 exposing it to the air. Each chamber in the sputtering apparatus is required for the oxide semiconductor film. In order to remove impurities such as water as much as possible, an adsorption type vacuum pump such as a cryopump is used. High vacuum pump (5×10 -7 Pa~1×10 -4 It is preferable to use a temperature of up to about 1 Pa. Alternatively, a turbo molecular pump and cold trap can be combined to evacuate the chamber from the exhaust system. It is preferable to prevent gas, especially gas containing carbon or hydrogen, from flowing back into the .

[0179] Here, the band structure of the stacked structure included in the transistors 102 and 103 is shown in FIG. This will be explained using (B).

[0180] FIG. 8B is a schematic diagram showing a part of the band structure of the transistors 102 and 103. Here, a silicon oxide layer is provided as the insulating film 306 and the insulating film 312. In addition, EcI1 shown in FIG. 8B is the oxide silicon used as the insulating film 306. The energy of the conduction band edge of the silicon layer is shown, and EcS1 is the conduction band edge of the oxide semiconductor film 388. EcS2 denotes the energy of the conduction band minimum of the oxide film 390, and E cI2 indicates the energy of the bottom of the conduction band of the silicon oxide layer used as the insulating film 312.

[0181] As shown in FIG. 8B, the oxide semiconductor film 388 and the oxide film 390 have a conduction band The energy at the bottom changes smoothly without any barrier. In other words, it changes continuously. This can be said to be because the oxide semiconductor film 388 and the oxide film 390 contain a common element. Oxygen is transferred between the oxide semiconductor film 388 and the oxide film 390, forming a mixed layer. This can be said to be because

[0182] As shown in FIG. 8B, the oxide semiconductor film 388 serves as a well, and a channel formation region It can be seen that the oxide semiconductor film 388 is formed. Since the energy of the conduction band minimum of the oxide semiconductor film 390 changes continuously, It can also be said that 88 and the oxide film 390 are in continuous contact.

[0183] As shown in FIG. 8B, in the vicinity of the interface between the oxide film 390 and the insulating film 312, Traps due to impurities or defects such as silicon or carbon, which are constituent elements of the insulating film 312 However, since the oxide film 390 is provided, the oxide semiconductor film 3 However, the energy between EcS1 and EcS2 can be increased by 1 / 2. When the energy difference is small, electrons in the oxide semiconductor film 388 pass through the oxide film 390 and are trapped. When an electron is captured in a trap level, it becomes a fixed negative charge. As a result, the threshold voltage of the transistor shifts in the positive direction. The energy difference between cS1 and EcS2 is 0.1 eV or more, preferably 0.15 eV or more. This reduces the fluctuation in the threshold voltage of the transistor and results in stable electrical characteristics, which is preferable. It is appropriate.

[0184] Next, an enlarged cross-sectional structure of the transistor 103 and the capacitor 105 shown in FIG. Shown in Figure 9(A).

[0185] In the cross-sectional view shown in FIG. 9A, the transistor 103 has an oxide The oxide film 390b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (the insulating film 306 in this example). The capacitor 105 includes a light-transmitting conductive film 388c as one of a pair of electrodes and a pair of electrodes The other of the conductive films 316a and 316b has a light-transmitting property. The oxide semiconductor film 388c is formed on the same surface (the insulating film 306) as the oxide semiconductor film 388b. That is, the light-transmitting conductive film 388c has the same composition as the oxide semiconductor film 388b. .

[0186] In the cross-sectional view of FIG. 9A, the thickness of the light-transmitting conductive film 388c is In this manner, the thickness of the light-transmitting conductive film 388c is smaller than that of the light-transmitting conductive film 388b. By forming the film to be thin, the transmittance of the capacitor 105 can be improved.

[0187] In the structure shown in FIG. 9A, a pair of electrodes of the light-transmitting capacitor 105 One of the two is a light-transmitting conductive film 388c, which is a channel formation region of the transistor 103. The oxide semiconductor film 388b used in the insulating region and the oxide film 390b over the oxide semiconductor film 388b Compared to a laminated film, it is formed in a single layer structure. Therefore, the transmittance of the pixel part is high and the It is possible to provide a display device having a capacitive element capable of increasing the load capacity. In the transistor 103, the oxide film 390b is formed over the oxide semiconductor film 388b. A highly reliable display device can be obtained.

[0188] Next, FIG. 9B shows a modification of the cross-sectional structure of the display device shown in FIG.

[0189] In the cross-sectional view shown in FIG. 9B, the transistor 103 has an oxide The oxide film 390b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (the insulating film 306 in this example). The capacitor 105 includes a light-transmitting conductive film 388c as one of a pair of electrodes and a pair of electrodes The other of the conductive films 316a and 316b has a light-transmitting property. The oxide semiconductor film 388c is formed on the same surface (the insulating film 306) as the oxide semiconductor film 388b. That is, the light-transmitting conductive film 388c has the same composition as the oxide semiconductor film 388b. .

[0190] The cross-sectional structure shown in FIG. 9(B) has a light-transmitting property in comparison with the cross-sectional structure shown in FIG. 9(A). The conductive film 388c has a different thickness. The thickness of the optically conductive film 388c and the thickness of the oxide semiconductor film 388b are approximately the same. As shown in FIG. 13, only the oxide film 390c on the light-transmitting conductive film 388c may be removed. Compared with the oxide semiconductor film 388b and the oxide film 390b included in the transistor 103, In addition, the transmittance of the capacitor element 105 is improved by the absence of the oxide film 390c. can be done.

[0191] Next, FIG. 9C shows a modification of the cross-sectional structure of the display device shown in FIG.

[0192] In the cross-sectional view shown in FIG. 9C, the transistor 103 has an oxide The oxide film 390b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (the insulating film 306 in this example). The capacitance element 105 includes a light-transmitting conductive film 388c and an oxide film 388b as one of a pair of electrodes. 90c and a light-transmitting conductive film 316b as the other of the pair of electrodes. The light-transmitting conductive film 388c is on the same surface as the oxide semiconductor film 388b (the insulating film 306). is formed on top.

[0193] In the cross-sectional view shown in FIG. 9C, the thickness of the oxide film 390c is In this way, the oxide film 390c is formed to be thin, which is thinner than the oxide film 390b. Therefore, the transmittance of the capacitor 105 can be improved.

[0194] Note that the method for forming one electrode of the capacitor 105 shown in FIGS. It can be formed by the following method.

[0195] The oxide semiconductor film 388b and the oxide film 390b of the transistor 103 are formed in the same process. Then, a light-transmitting conductive film 388c and an oxide film 390c are formed. In forming the second insulating film 72, the oxide film 390c on the light-transmitting conductive film 388c is removed. As a result, the structures shown in Figures 9(A) and 9(B) are obtained. Note that Figure 9(C) shows, for example, This can be achieved by setting the etching time shorter than that in FIG. 9(A).

[0196] In the structure shown in FIG. 9C, one electrode of the capacitor 105 has a light-transmitting property. The conductive film 388c and the oxide film 390c are in contact with each other. The diffusion of hydrogen from the conductive film 388c and the oxide film 390c having light-transmitting properties The electrical conductivity of the layer is improved, and the layer becomes a light-transmitting conductive film.

[0197] <Variation 2> Here, a modification of the pixel 301 of the display device shown in FIG. 2B will be described with reference to FIG. Note that the pixel 301b of the display device shown in FIG. FIG. 3 is a top view of a modified example of pixel 301. The user can select the most suitable shape as appropriate.

[0198] In FIG. 10, the conductive film 304c functioning as the scanning line is oriented in a direction substantially perpendicular to the signal line ( The conductive film 310d that functions as a signal line is provided so as to extend in a direction perpendicular to the plane of the drawing. The capacitor line extends in a direction substantially perpendicular to the scan line (vertical direction in the figure). The conductive film 304d extends in a direction parallel to the scanning lines. In comparison with the pixel 301, the pixel 301b shown in FIG. 10 has a conductive film 310 which functions as a signal line. The side parallel to the conductive film 304c functioning as a scanning line is shorter than the side parallel to d. The conductive film 304d functioning as a capacitance line is different from the conductive film 304 functioning as a scanning line. The conductive film 304d is provided so as to extend in a direction parallel to the conductive film 304c and functions as a capacitance line. However, the difference is that the conductive film 304c that functions as a scan line is formed at the same time.

[0199] The light-transmitting conductive film 308c is a conductive film 310f (note that in FIG. 10, The conductive film 310f is connected to the conductive film 3 10d, 310e are formed at the same time.

[0200] In addition, an opening 374d formed in the same manner as the opening 374c is formed on the conductive film 304d. In addition, an opening 374c is formed on the conductive film 310f. 4e is formed.

[0201] In the opening 374d, the conductive film 304d and the light-transmitting conductive film 316c are connected to each other. In addition, in the opening 374e, the conductive film 310f and the light-transmitting conductive film 316 That is, the conductive film 304d and the conductive film 310f are light-transmitting conductive films. Therefore, the conductive film 310f and the light-transmitting conductive film 316 The light-transmitting conductive film 308c is connected to the conductive film 304d functioning as a capacitance line through the conductive film 304c. To be continued.

[0202] In the pixel 301b shown in FIG. 10, the side parallel to the conductive film 310d functioning as a signal line is The side parallel to the conductive film 304c functioning as the scanning line is shorter than the side parallel to the conductive film 304c. The conductive film 304d that functions as a scanning line extends in a direction parallel to the conductive film 304c that functions as a scanning line. As a result, the area of ​​the conductive film 304d in the pixel can be reduced. This makes it possible to increase the aperture ratio.

[0203] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0204] (Embodiment 2) In this embodiment, the transistor and the capacitor of the display device described in Embodiment 1 can be applied to An example of an oxide semiconductor film that can be used in the present invention will be described.

[0205] <Crystallization of oxide semiconductor film>

[0206] The structure of the oxide semiconductor film will be described below.

[0207] Oxide semiconductor films are roughly classified into non-single-crystal oxide semiconductor films and single-crystal oxide semiconductor films. The non-single-crystal oxide semiconductor film is called CAAC-OS (C Axis Aligned Crystal-Oxide Semiconductor Film). (stalline oxide semiconductor) film, polycrystalline oxide semiconductor The oxide semiconductor film includes a film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, and the like.

[0208] First, we will explain the CAAC-OS film.

[0209] The CAAC-OS film is one of the oxide semiconductor films that has multiple crystal parts. The crystal part is small enough to fit inside a cube with one side less than 100 nm. The crystal parts contained in the OS film are cubes with one side less than 10 nm, 5 nm, or 3 nm. This also includes cases where the size fits within the

[0210] The CAAC-OS film was observed under a transmission electron microscope (TEM). When observed using a quartz crystal microscope, clear boundaries between the crystals were observed. It is not possible to confirm the grain boundary. It can be said that the AAC-OS film is less susceptible to the decrease in electron mobility caused by grain boundaries.

[0211] The CAAC-OS film was observed by TEM from a direction roughly parallel to the sample surface (cross-sectional TEM observation). When the metal atoms are observed, it can be confirmed that they are arranged in layers in the crystal part. Each layer of the CAAC-OS film is formed on a surface on which the film is to be formed (also called a surface on which the film is to be formed) or on a concave surface on the upper surface. The shape reflects a convexity, and is aligned parallel to the surface on which the CAAC-OS film is formed or the upper surface.

[0212] In this specification, "parallel" means that two straight lines are at an angle of -10° or more and 10° or less. Therefore, it includes the case where the angle is between -5° and 5°. "Perpendicular" refers to two straight lines that form an angle between 80° and 100°. Therefore, cases between 85° and 95° are also included.

[0213] On the other hand, the CAAC-OS film was observed by TEM from a direction roughly perpendicular to the sample surface (plane T EM observation reveals that metal atoms are arranged in triangular or hexagonal shapes in the crystals. However, no regularity was observed in the arrangement of metal atoms between different crystal regions. do not have.

[0214] Cross-sectional and planar TEM observations revealed that the crystals in the CAAC-OS film had an orientation. It can be seen that...

[0215] X-ray diffraction (XRD) of CAAC-OS film When the structure was analyzed using the device, for example, CAAC-OS with InGaZnO4 crystals was In the out-of-plane analysis of the film, the diffraction angle (2θ) peaked at around 31°. This peak is attributed to the (009) plane of the InGaZnO4 crystal. Therefore, the crystals of the CAAC-OS film have a c-axis orientation, and the c-axis faces the surface on which the film is formed or the upper surface. It can be seen that it is oriented in a roughly vertical direction.

[0216] On the other hand, in-p X-rays are incident on the CAAC-OS film from a direction approximately perpendicular to the c-axis. In the lane method, a peak may appear at 2θ around 56°. is attributed to the (110) plane of the InGaZnO4 crystal. In the case of a nitride semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is the axis (φ axis). When the sample is rotated and analyzed (φ scan), a crystal plane equivalent to the (110) plane is detected. In contrast, in the case of the CAAC-OS film, six peaks are observed, which are assigned to Even when φ is fixed at around 56° and scanned, no clear peak appears.

[0217] From the above, it is considered 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 in a plane parallel to the ab plane of the crystal.

[0218] The crystalline part is formed when the CAAC-OS film is formed or after a crystallization process such as a heat treatment. As described above, the c-axis of the crystal is aligned to the surface on which the CAAC-OS film is to be formed. For example, in the CAAC-OS film, When the shape is changed by etching, the c-axis of the crystal is aligned with the CAAC-OS film. It may not be parallel to the face or top surface normal vector.

[0219] In addition, the crystallinity in the CAAC-OS film does not have to 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 on which it is formed. When impurities are added to the AC-OS film, the crystallinity of the region to which the impurities are added changes, resulting in a partial In some cases, regions of differing crystallinity may be formed.

[0220] In addition, the out-of-plane crystal structure of the CAAC-OS film with InGaZnO4 crystals In the analysis by the method, in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ of around 36° may be due to the c-axis orientation in some parts of the CAAC-OS film. The CAAC-OS film contains crystals that do not have the 2θ value of about 31°. It is preferable that the spectrum shows a peak at 2θ of about 36° and does not show a peak at 2θ of about 36°.

[0221] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is preferably made of silicon or a transition metal element other than the main component of the oxide semiconductor film. The elements that bond to oxygen stronger than the metal elements that form the oxide semiconductor film, such as Zn, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disturbed, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Since the diameter (or molecular radius) of the ions is large, when the ions are contained inside the oxide semiconductor film, the oxide semiconductor film The impurities contained in the oxide semiconductor film are disturbed, which causes a decrease in crystallinity. Pure materials may act as carrier traps or carrier generation sources.

[0222] The CAAC-OS film is an oxide semiconductor film with a low density of defect states.

[0223] In addition, the electrical characteristics of transistors using CAAC-OS films are improved by irradiation with visible light or ultraviolet light. Gender variation is small.

[0224] Next, a microcrystalline oxide semiconductor film will be described.

[0225] In the TEM image of the microcrystalline oxide semiconductor film, crystal parts can be clearly seen. 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 to 3 nm or less. The oxide semiconductor film having nc-OS (nanocrystalline O The nc-OS film is called a T In EM images, grain boundaries may not be clearly visible.

[0226] The nc-OS film is a microscopic region (e.g., a region of 1 nm to 10 nm, especially a region of 1 nm or less). The nc-OS film has a periodic atomic arrangement in the region of 3 nm or less. There is no regularity in the crystal orientation between the crystal parts, and therefore no orientation is observed throughout the film. Therefore, the nc-OS film cannot be distinguished from an amorphous oxide semiconductor film depending on the analysis method. For example, 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 out-of-plane method, the crystal planes are In addition, the nc-OS film had 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 with a diameter of 50 nm or more, On the other hand, the nc-OS film has a large crystalline area. Electron beams with a diameter close to the size of the crystal or smaller than the crystal part (for example, 1 nm to 30 nm) are used. When performing sub-beam diffraction (also referred to as nano-beam electron diffraction), spots are observed. Also, When performing nano-beam electron diffraction on the nc-OS film, regions with high luminance may be observed in a circular (ring-shaped) pattern. Also, when performing nano-beam electron diffraction on the nc-OS film, multiple spots may be observed within the ring-shaped region.

[0227] The nc-OS film is an oxide semiconductor film with higher regularity than the amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect levels than the amorphous oxide semiconductor film. However, in the nc-OS film, no regularity in crystal orientation is observed between different crystal parts. Therefore, the nc-OS film has a higher density of defect levels than the CAAC-OS film.

[0228] Note that the oxide semiconductor film may be, for example, a laminated film having two or more of an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, and a CAAC-OS film.

[0229] <Method for forming a CAAC-OS film> The CAAC-OS film is formed, for example, by a sputtering method using a target for oxide semiconductor sputtering that is polycrystalline. When ions collide with the sputtering target, the crystal regions contained in the sputtering target split from the a-b plane and are peeled off as flat plate-shaped or pellet-shaped sputtering particles having a plane parallel to the a-b plane. In this case, the flat plate-shaped or pellet-shaped sputtering particles reach the substrate while maintaining their crystal state, and thus a CAAC-OS film can be formed.

[0230] The flat plate-shaped or pellet-shaped sputtering particles are, for example, equivalent to a circle of a plane parallel to the a-b plane. The diameter is 3 nm or more and 10 nm or less, and the thickness (length in the direction perpendicular to the ab plane) is 0.7 nm or more. The sputtered particles in the form of plates or pellets are parallel to the ab plane. The face may be an equilateral triangle or a regular hexagon. Here, the circle equivalent diameter of the face is calculated by multiplying the area of ​​the face by The diameter of an equal circle.

[0231] In addition, the following conditions are preferably applied to form the CAAC-OS film.

[0232] By increasing the substrate temperature during film formation, migration of sputtered particles after reaching the substrate is suppressed. Specifically, the substrate temperature is set to 100° C. or higher and 740° C. or lower, preferably 200° C. or lower. The film is formed at a temperature of 500°C or less. By increasing the substrate temperature during film formation, flat or pellet-shaped films can be formed. When sputtered particles reach the substrate, migration occurs on the substrate, The flat surface of the sputtered particles adheres to the substrate. At this time, the sputtered particles are positively charged. By applying an electric current, the sputtering particles repel each other while adhering to the substrate. The CAAC-OS film is formed with uniform thickness without unevenly overlapping the coating particles. It is possible.

[0233] By reducing the amount of impurities mixed in during film formation, it is possible to prevent the crystal state from being destroyed by impurities. For example, the concentration of impurities (hydrogen, water, carbon dioxide, nitrogen, etc.) present in the film formation chamber can be In addition, the impurity concentration in the deposition gas may be reduced. A deposition gas having a temperature of -80°C or lower, preferably -100°C or lower, is used.

[0234] In addition, by increasing the oxygen ratio in the deposition gas and optimizing the power, plasma damage during deposition is reduced. The oxygen ratio in the deposition gas is preferably 30% by volume or more, and more preferably 100% by volume or more. Expressed as volume percent.

[0235] Alternatively, the CAAC-OS film is formed by the following method.

[0236] First, a first oxide semiconductor film is formed to a thickness of 1 nm or more and less than 10 nm. The semiconductor film is formed by sputtering. Specifically, the substrate temperature is set to 100°C or higher. The temperature is set to 500° C. or less, preferably 150° C. to 450° C., and the oxygen ratio in the deposition gas is set to 30 % by volume or more, preferably 100% by volume.

[0237] Next, heat treatment is performed to convert the first oxide semiconductor film into a first CAAC-OS film having high crystallinity. The temperature of the heat treatment is 350°C or higher and 740°C or lower, preferably 450°C or higher and 650°C or lower. The heat treatment time is from 1 minute to 24 hours, preferably from 6 minutes to 4 hours. The heat treatment may be performed in an inert atmosphere or an oxidizing atmosphere. Alternatively, heat treatment is performed in an inert atmosphere, and then heat treatment is performed in an oxidizing atmosphere. By the heat treatment in the atmosphere, the impurity concentration of the first oxide semiconductor film can be reduced in a short time. On the other hand, oxygen vacancies are generated in the first oxide semiconductor film by heat treatment in an inert atmosphere. In this case, the oxygen deficiency can be reduced by heat treatment in an oxidizing atmosphere. Heat treatment can be performed at 1000 Pa or less, 100 Pa or less, 10 Pa or less, or The step of removing the oxide semiconductor film from the first oxide semiconductor film may be performed under a reduced pressure of 1 Pa or less. can be reduced in an even shorter time.

[0238] The first oxide semiconductor film has a thickness of 1 nm or more and less than 10 nm. Compared with a thickness of 0 nm or more, it can be easily crystallized by heat treatment.

[0239] Next, a second oxide semiconductor film having the same composition as the first oxide semiconductor film is formed to a thickness of 10 nm or more. The second oxide semiconductor film is formed to a thickness of 0 nm or less by a sputtering method. Specifically, the substrate temperature is set to 100° C. or higher and 500° C. or lower, preferably 150° C. or higher and 450° C. or lower. The oxygen ratio in the deposition gas is set to 30% by volume or more, preferably 100% by volume. To film.

[0240] Next, heat treatment is performed to grow a second oxide semiconductor film from the first CAAC-OS film through solid phase epitaxial growth. The second CAAC-OS film is formed with high crystallinity by the heat treatment at a temperature of 350 The temperature is from 450°C to 650°C, preferably from 450°C to 650°C. The heating time is from 1 minute to 24 hours, preferably from 6 minutes to 4 hours. The heat treatment may be performed in an inert atmosphere or an oxidizing atmosphere. Preferably, the heat treatment is performed in an inert atmosphere. After that, a heat treatment is performed in an oxidizing atmosphere. The impurity concentration of the nitride semiconductor film can be reduced in a short time. Oxygen vacancies may be generated in the second oxide semiconductor film by the heat treatment. The oxygen vacancies can be reduced by heat treatment in a reactive atmosphere. The pressure may be reduced to 000 Pa or less, 100 Pa or less, 10 Pa or less, or 1 Pa or less. Under reduced pressure, the impurity concentration in the second oxide semiconductor film can be reduced in a shorter time. Cut.

[0241] In this manner, a CAAC-OS film having a total thickness of 10 nm or more is formed. The CAAC-OS film can be suitably used as an oxide semiconductor film in an oxide stack. There can be.

[0242] Next, for example, the substrate is not heated, and the surface to be formed is kept at a low temperature (for example, less than 130° C.). , oxide film at temperatures below 100℃, below 70℃, or room temperature (20℃ to 25℃) A method for forming the above will be described.

[0243] When the surface to be formed is at a low temperature, the sputtered particles rain down irregularly on the surface to be formed. For example, because there is no migration, there are no areas where other sputtered particles have already accumulated. That is, the oxide film obtained by deposition has a uniform thickness, for example. The oxide film obtained in this way is not only a simple structure, but also has a disordered crystal orientation. In order to maintain the crystallinity of the putter particles to a certain extent, the putter particles have crystalline portions (nanocrystals).

[0244] In addition, for example, when the pressure during film formation is high, the flying sputtered particles may be mixed with other gases such as argon. The frequency of collisions with other particles (atoms, molecules, ions, radicals, etc.) increases. However, the crystal structure may be destroyed by collisions with other particles during flight (resputtering). For example, sputtered particles maintain their flat shape by colliding with other particles. In some cases, the particle cannot be separated into individual atoms and is fragmented (e.g., split into individual atoms). As the atoms separated from the nanoparticles are deposited on the surface, an amorphous oxide film is formed. There may be cases where this occurs.

[0245] Also, instead of a sputtering method using a target having a polycrystalline oxide as a starting point, In the case of a method of forming a film using a liquid, or by gasifying a solid such as a target, a film is formed. In the case of the method, the atoms fly in a split state and deposit on the surface to be formed, so amorphous oxide In addition, for example, in the laser ablation method, the target Atoms, molecules, ions, radicals, clusters, etc. emitted from the target fly and form a layer on the target surface. Due to the deposition, an amorphous oxide film may be formed.

[0246] The oxide semiconductor film included in the transistor and the capacitor of the display device of one embodiment of the present invention is The oxide semiconductor film may have any of the above crystal states. When a conductive film is included, the crystal state of each oxide semiconductor film may be different. A CAAC-OS film is used as the oxide semiconductor film that functions as a channel formation region of the transistor. In addition, it is preferable that the oxide semiconductor film (light-transmitting conductive film) included in the capacitor be The impurity concentration of the oxide semiconductor film in the transistor is higher than that of the oxide semiconductor film in the transistor, and therefore the crystallinity is reduced. This may be the case.

[0247] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0248] (Embodiment 3) In this embodiment, a display module and a display device in which the display device of one embodiment of the present invention can be used will be described. The electronic device will be described with reference to FIG. 11 and FIG.

[0249] The display module 8000 shown in FIG. 11 includes an upper cover 8001 and a lower cover 8002. Between them, touch panel 8004 connected to FPC8003, A display panel 8006, a backlight unit 8007, a frame 8009, a printed circuit board It has a board 8010 and a battery 8011 .

[0250] The display device of one embodiment of the present invention can be used for the display panel 8006, for example.

[0251] 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 appropriate to match the size of 8006.

[0252] The touch panel 8004 is a resistive or capacitive touch panel. The display panel 8006 can be used by overlapping it with the opposing substrate (sealing substrate). It is also possible to provide the display panel 8 with a touch panel function. It is also possible to provide an optical sensor in each pixel of the display panel 006 to make it into an optical touch panel.

[0253] The backlight unit 8007 includes a light source 8008. Alternatively, the light diffusing plate may be provided at the end of the light receiving unit 8007.

[0254] The frame 8009 protects the display panel 8006 and also supports 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 frame. The frame 8009 may also function as a heat sink.

[0255] 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.

[0256] The display module 8000 also includes components such as a polarizing plate, a retardation plate, and a prism sheet. Additional ones may be provided.

[0257] 12(A) to 12(H) are diagrams showing electronic devices. These electronic devices are A body 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, and an operation key 50 05 (including a power switch or an operation switch), a connection terminal 5006, a sensor 5007 ( Force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances , sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, 5008, etc.) can.

[0258] FIG. 12A shows a mobile computer, which includes, in addition to the above, a switch 5009 , an infrared port 5010, etc. FIG. 12(B) shows a mobile phone equipped with a recording medium. A portable image reproducing device (e.g., a DVD reproducing device) and, in addition to the above, the following devices are also included: The display unit 5002, the recording medium reading unit 5011, etc. In addition to the above, the display includes a second display unit 5002 and a support unit 5012. , earphones 5013, etc. FIG. 12(D) shows a portable game machine. In addition to the above, the recording medium reading unit 5011 and the like can be included. FIG. 12(E) shows This is a digital camera with a television receiving function, and in addition to the above, it also has an antenna 5014, The mobile phone may have a shutter button 5015, an image receiving unit 5016, etc. This is a slot machine, and in addition to the above, it has a second display unit 5002, a recording medium reading unit 5011, , etc. FIG. 12(G) shows a television receiver, which, in addition to the above, The portable television receiver may include a tuner, an image processor, etc. In addition to the above, the device includes a charger 5017 capable of transmitting and receiving signals. can be done.

[0259] The electronic devices illustrated in FIGS. 12A to 12H can have various functions. For example, the function to display various information (still images, videos, text images, etc.) on the display, Panel function, calendar, date or time display function, various software (platform A function to control processing by a program, a wireless communication function, and a function to control various Functions for connecting to computer networks, wireless communication functions for transmitting various data, The function of receiving, reading out the program or data recorded on the recording medium and displaying it on the display Furthermore, in an electronic device having multiple display units, In this case, one display section is used mainly to display image information, and the other display section is used mainly to display text information. A function to display images with parallax taken into account on multiple displays to create a stereoscopic effect. Furthermore, in electronic devices having an image receiving unit, These include functions for taking still images, taking videos, and automatically or manually correcting the images. The camera has a function to correct the captured image, a function to save the captured image on a recording medium (external or built-in to the camera), The image displayed on the display unit can have a function of displaying the image. The functions that the electronic device shown in 2(H) can have are not limited to these, and various functions may be possible. It is possible to have.

[0260] The electronic device described in this embodiment has a display unit for displaying some information. It is characterized by the above.

[0261] The structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. can be done. [Explanation of symbols]

[0262] 100 pixels 102 Transistor 103 Transistor 104 Scanning line driving circuit 105 Capacitive element 106 Signal line driver circuit 107 Scan Lines 108 Liquid crystal element 109 Signal Line 115 Capacitive Line 301 pixels 301b pixels 302 Substrate 304a Conductive film 304b Conductive film 304c conductive film 304d conductive film 305 Insulating film 306 Insulating film 307 Oxide Semiconductor Film 308a Oxide semiconductor film 308b Oxide semiconductor film 308c conductive film 308d Oxide semiconductor film 309 Conductive Film 310a Conductive film 310b Conductive film 310c conductive film 310d conductive film 310e conductive film 310f conductive film 311 Insulating film 312 Insulating film 313 Insulating film 314 Insulating film 315 Conductive Film 316a Conductive film 316b Conductive film 316c Conductive film 318 Orientation Film 320 Liquid crystal layer 342 Substrate 344 Light-shielding film 346 Colored film 348 Insulating Film 350 Conductive Film 352 Orientation Film 372 Opening 374a opening 374b opening 374c opening 374d opening 374e opening 388 Oxide Semiconductor Film 388a Oxide semiconductor film 388b Oxide semiconductor film 388c conductive film 390 Oxide Film 390a oxide film 390b Oxide film 390c oxide film 5000 cabinet 5001 Display section 5002 Display section 5003 Speaker 5004 LED Lamp 5005 Operation key 5006 Connection terminal 5007 Sensor 5008 Microphone 5009 Switch 5010 Infrared port 5011 Recording medium reading unit 5012 Support part 5013 Earphones 5014 Antenna 5015 Shutter button 5016 Image receiving unit 5017 charger 8000 Display Module 8001 Top cover 8002 Lower cover 8003 FPC 8004 Touch Panel 8005 FPC 8006 Display Panel 8007 Backlight unit 8008 light source 8009 Frame 8010 Printed Circuit Board 8011 Battery

Claims

1. A display device having a scanning line driving circuit, The scanning line driving circuit includes: a first conductive film having a first region, a second region, and a third region arranged branching from a trunk region in a plan view; a second conductive film having a fourth region and a fifth region arranged branching from a trunk region in a plan view; a first oxide semiconductor film; a second oxide semiconductor film; and having In a plan view, the first region, the second region, and the third region are each arranged to extend along a first direction, In a plan view, the fourth region and the fifth region are arranged to extend along a second direction opposite to the first direction, the fourth region is disposed between the first region and the second region and spaced apart from the first region and the second region in a plan view; the fifth region is disposed between the second region and the third region and spaced apart from the second region and the third region in a plan view; In a plan view, the first oxide semiconductor film is disposed to extend along a third direction intersecting each of the first direction and the second direction, the second oxide semiconductor film is disposed at an interval from the first oxide semiconductor film in a plan view and extends along the third direction; one of a source and a drain of a first transistor is disposed in the first region; the other of the source and the drain of the first transistor is disposed in the fourth region; one of a source and a drain of a second transistor is disposed in the second region; the other of the source and the drain of the second transistor is disposed in the fourth region; one of a source and a drain of a third transistor is disposed in the second region; the other of the source and the drain of the third transistor is disposed in the fifth region; one of a source and a drain of a fourth transistor is disposed in the third region; the other of the source and the drain of the fourth transistor is disposed in the fifth region; one of a source and a drain of a fifth transistor is disposed in the first region; the other of the source and the drain of the fifth transistor is disposed in the fourth region; one of a source and a drain of a sixth transistor is disposed in the second region; the other of the source and the drain of the sixth transistor is disposed in the fourth region; one of a source and a drain of a seventh transistor is disposed in the second region; the other of the source and the drain of the seventh transistor is disposed in the fifth region; one of a source and a drain of an eighth transistor is disposed in the third region; the other of the source and the drain of the eighth transistor is disposed in the fifth region; channel formation regions of the first to fourth transistors are disposed in the first oxide semiconductor film, a second oxide semiconductor film formed on the first oxide semiconductor layer and a second oxide semiconductor film formed on the second oxide semiconductor layer;

2. A display device having a scanning line driving circuit, The scanning line driving circuit includes: a first conductive film having a first region, a second region, and a third region arranged branching from a trunk region in a plan view; a second conductive film having a fourth region and a fifth region arranged branching from a trunk region in a plan view; a first oxide semiconductor film; a second oxide semiconductor film; and having In a plan view, the first region, the second region, and the third region are each arranged to extend along a first direction, In a plan view, the fourth region and the fifth region are arranged to extend along a second direction opposite to the first direction, the fourth region is disposed between the first region and the second region and spaced apart from the first region and the second region in a plan view; the fifth region is disposed between the second region and the third region and spaced apart from the second region and the third region in a plan view; In a plan view, the first oxide semiconductor film is disposed to extend along a third direction intersecting each of the first direction and the second direction, the second oxide semiconductor film is disposed at an interval from the first oxide semiconductor film in a plan view and extends along the third direction; one of a source and a drain of a first transistor is disposed in the first region; the other of the source and the drain of the first transistor is disposed in the fourth region; a sixth region of the first oxide semiconductor film is disposed between a source and a drain of the first transistor; one of a source and a drain of a second transistor is disposed in the second region; the other of the source and the drain of the second transistor is disposed in the fourth region; a seventh region of the first oxide semiconductor film is disposed between a source and a drain of the second transistor; one of a source and a drain of a third transistor is disposed in the second region; the other of the source and the drain of the third transistor is disposed in the fifth region; an eighth region of the first oxide semiconductor film is disposed between a source and a drain of the third transistor; one of a source and a drain of a fourth transistor is disposed in the third region; the other of the source and the drain of the fourth transistor is disposed in the fifth region; a ninth region of the first oxide semiconductor film is disposed between a source and a drain of the fourth transistor; one of a source and a drain of a fifth transistor is disposed in the first region; the other of the source and the drain of the fifth transistor is disposed in the fourth region; a tenth region of the second oxide semiconductor film is disposed between a source and a drain of the fifth transistor; one of a source and a drain of a sixth transistor is disposed in the second region; the other of the source and the drain of the sixth transistor is disposed in the fourth region; an eleventh region of the second oxide semiconductor film is disposed between a source and a drain of the sixth transistor; one of a source and a drain of a seventh transistor is disposed in the second region; the other of the source and the drain of the seventh transistor is disposed in the fifth region; a twelfth region of the second oxide semiconductor film is disposed between a source and a drain of the seventh transistor; one of a source and a drain of an eighth transistor is disposed in the third region; the other of the source and the drain of the eighth transistor is disposed in the fifth region; a thirteenth region of the second oxide semiconductor film is disposed between a source and a drain of the eighth transistor.

3. In claim 1 or claim 2, A third conductive film is provided, the gates of the first to eighth transistors are disposed on the third conductive film.

4. In any one of claims 1 to 3, the first oxide semiconductor film and the second oxide semiconductor film each contain In, Zn, and M (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf).

Images