Semiconductor device

Abstract

To provide a display device including a capacitor whose charge capacity can be increased while having a high aperture ratio, provide a display device including a capacitor whose charge capacity can be increased while having a high transmittance of a pixel portion, and provide a display device which consumes low power.SOLUTION: The display device includes a transistor including a first oxide semiconductor film in a channel formation region, a second oxide semiconductor film formed on the same surface as the first oxide semiconductor film, a pixel electrode electrically connected to the transistor, and a light-transmitting capacitor in which a dielectric film is provided between a pair of electrodes. One of the pair of electrodes is the second oxide semiconductor film, and the other is the pixel electrode. The second oxide semiconductor film has a smaller thickness than 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 widely used. In a display device such as a liquid crystal display, pixels arranged in the row and column directions The switching element includes a transistor and a liquid crystal display electrically connected to the transistor. A liquid crystal element and a capacitance 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. For example, zinc oxide or In-Ga-Zn-based 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] Japanese Patent Application Laid-Open No. 2007-123861 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-96055 [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 wiring is formed of a conductive film having a conductive property.

[0008] In addition, the larger the capacitance value of the capacitance element, the more the liquid crystal element will be deformed 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, the ability to extend this period reduces the number of times image data is rewritten. This allows for a reduction in 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 means for increasing the area where the pair of electrodes overlap. In the 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, by forming the pair of electrodes using a light-transmitting material, The charge capacity can be increased and the aperture ratio of the pixel can be increased. If the transmittance of the material is low, the amount of light from the light source such as the backlight is increased. This increases power consumption, and the capacitance element becomes colored, which is a problem. 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, one aspect of the present invention is to provide a liquid crystal display device having a high aperture ratio and an increased charge capacity. Another object of the present invention is to provide a display device having a capacitor element that can be used for a large-capacitance display. One embodiment of the present invention is a capacitance device that has high transmittance in a pixel portion and can increase charge capacitance. Another object of the present invention is to provide a display device having a display element. One of the goals is to provide a place for

[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. It is possible to extract other issues 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 formed on the same surface as the first oxide semiconductor film; a pixel electrode electrically connected to the pixel electrode, and a light-transmitting dielectric film sandwiched between the pair of electrodes. a capacitor including a pair of electrodes, one of which is 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. This 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 the channel formation region of the transistor. Therefore, the transmittance of the pixel portion is high. It is possible to provide a display device having a capacitance element that can increase 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 formed on the same surface as the first 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. Therefore, the transmittance of the pixel portion is high. It is possible to provide a display device having a capacitor element that can reduce the capacitance and increase the charge capacity.

[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 a second oxide semiconductor film 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 by the above.

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

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

[0020] [Figure 1] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a display device. [Figure 2] FIG. 1 is a top view illustrating one embodiment of a display device. [Figure 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. [Figure 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 INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various modifications may be made to the modes and details thereof. The present invention will be easily understood by reading the following description of the 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 as the same. The same reference numerals are used in common among different drawings, and repeated explanations thereof will be omitted. When referring to a part that has a function, the hatch pattern is the same and no particular symbol is attached. be.

[0023] In each figure described in this specification, the size of each structure, the thickness of a film, or the area is shown for clarity. The figures may be exaggerated for illustrative purposes only 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 replaced with "second" or " can be appropriately replaced with "third" etc. The ordinal numbers used to identify an aspect of the present invention may not match. be.

[0025] In addition, the functions of the "source" and "drain" in one aspect of the present invention are as follows: This may be reversed if the direction of the current changes. 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 includes a pixel portion 100 and a The scanning line driving circuit 104 and the signal line driving circuit 106 are arranged parallel or approximately parallel to each other. and m scanning lines 107 whose potentials are controlled by a scanning line driving circuit 104, n signal lines arranged in a row or substantially in parallel, the potentials of which are controlled by a signal line driving circuit 106. The pixel section 100 has a plurality of pixels arranged in a matrix. 301. In addition, along the scanning line 107, there are capacitors arranged parallel or approximately parallel to each other. 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 rows. In FIG. 1A, the capacitance line 115 is a scanning line. Although the configuration in which the LED is connected to the line driving circuit 104 has been exemplified, 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 is connected 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 of the rows. is m pixels 301 arranged in m rows and n columns, and m pixels 301 arranged in any one of the columns. 1. Both m and n are integers equal to or greater than 1. is n pixels 301 arranged in any row among the pixels 301 arranged in m rows and n columns. 1. Capacitor lines 115 are arranged along the signal line 109 in parallel or When the pixels 301 are arranged in approximately parallel, one of the pixels 301 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. One electrode of the transistor 103 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. The electrode (counter electrode) that is connected to the pixel electrode is connected to the wiring that supplies the counter 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 on which the light is formed controls the transmission or non-transmission of light. Alternatively, the liquid crystal element 108 may be a transistor 103, a pixel electrode, and a 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 controlled by the liquid crystal. The pixel is controlled by the electric field (including the vertical electric field and the diagonal electric field). When an opposing electrode (also called a common electrode) is formed on the substrate on which the electrode is formed, the liquid crystal The electric field applied to the electrode is a horizontal 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 (electroluminescent) element. Electroluminescence) elements (EL elements including organic and inorganic materials, organic EL elements, inorganic EL elements LEDs (white LEDs, red LEDs, green LEDs, blue LEDs, etc.), transistors transistors (transistors that emit light according to the 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., have electromagnetic effects that improve contrast and brightness. Some display media have variable 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 Examples of display devices using liquid crystal elements include transparent Transflective liquid crystal display, transflective liquid crystal display, reflective liquid crystal display, direct view liquid crystal display, Examples of display devices using electronic ink or electrophoretic elements include projection-type liquid crystal display devices. 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. 2(A), a conductive film 304a functioning as a gate, a gate insulating film (FIG. 2(A) ) are not shown in the figure. ) The oxide semiconductor film 308a in which a channel formation region is formed, the source and The transistor 102 is formed by the conductive films 310a and 310b that function as drains. The oxide semiconductor film 308a is provided over the gate insulating film. The conductive film 304b formed at the same time as the conductive films 310a and 310b 310c, and a light-transmitting conductive film 316 that connects the conductive film 304b and the conductive film 310c. The light-transmitting conductive film 316a is formed in the opening 374a. 4b and is connected to the conductive film 310c in the opening 374b.

[0034] In FIG. 2B, the conductive film 304c functioning as the scan line 107 is connected to the signal line 109. The signal lines 109 are provided so as to extend in directions substantially perpendicular to each other (left and right directions in the drawing). The conductive film 310d extends in a direction (vertical direction in the drawing) substantially perpendicular to the scanning line 107. 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 capacitor 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 exemplified, but as shown in FIG. 2(B), The capacitor line 115 may be connected to the signal line driver circuit 106 .

[0035] The transistor 103 is provided in the area 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 the 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. 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 2B, the scanning line functions as a source or drain of the gate electrode 103. 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, and Fluctuations in the electrical characteristics of 3 can be suppressed.

[0036] 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 element 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 formed on the gate insulating film. a conductive film 308c having a light-transmitting property which functions as a pixel electrode; a conductive film 316b having a light-transmitting property which functions as a pixel electrode; and a dielectric film formed 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 light-transmitting properties, the capacitor 105 is large and can be placed in the pixel 301. Therefore, it is possible to increase the aperture ratio. Typically, the charge capacity can be 55% or more, preferably 60% or more. For example, in a liquid crystal display device with high resolution, Therefore, 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 capacitance element is reduced. Since the capacitor 105 shown in the embodiment has a light-transmitting property, by providing the capacitor 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 It can be used for.

[0039] The thickness of the light-transmitting conductive film 308c which is one electrode of the capacitor 105 is The thickness is thinner than 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 that functions as a signal line and a The side parallel to the conductive film 304c functioning as a scanning line is longer than the side, and 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 it is possible to reduce the capacitance, 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] Furthermore, 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 for 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 Figures 2(A) and 2(B) are The plan view is shown in Figure 3(A).

[0043] The display device shown in FIG. 3A includes 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 has a light-transmitting conductive film 316b over the substrate 302 and a conductive film 316c that controls alignment. a liquid crystal layer 320; and a conductive film 350. 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 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 Crystal tal) mode, AFLC(AntiFerroelectric Liquid Cr ystal) mode, MVA(Multi-domain Vertical Align) nment) mode, PVA(Patterned Vertical Alignme) nt) mode, IPS mode, FFS mode, or TBA (Transverse Beam Inversion) Also, a display device having a liquid crystal element may be used. In addition to the above-mentioned driving method, the device can also be driven by an ECB (Electrically Controlled Bias Circuit) ontrolled Birefringence) mode, PDLC (Polymer Dispersed Liquid Crystal mode, PNLC (Polym Network Liquid Crystal mode, guest host mode, etc. However, there are various methods for driving a display device having a liquid crystal element, without being limited to these. 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 following. The liquid crystal that exhibits the blue phase has a response speed of 1 msec or less. Since it is short and optically isotropic, alignment treatment is not required and viewing angle dependency is small.

[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 a liquid crystal element. The 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., arranged in It is also called an LCD module.

[0049] In the driver circuit portion, the conductive film 304a functions as a gate, and the conductive film 304b functions as 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 conductive films 310a and 310b which function as a source and a drain. The oxide semiconductor film 308a is provided on the 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, the conductive film 304c functions as a gate, and the gate insulating film Insulating films 305 and 306, oxide films in which channel formation regions are formed on the gate insulating films 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 the 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 The insulating film 312 and the insulating film 314 are connected to the conductive film 310e through openings formed therein.

[0052] In addition, a light-transmitting conductive film 308c which functions as one electrode of the capacitor 105, The insulating film 314 serving 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 that functions as a light-transmitting 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 formed simultaneously with the conductive films 310a, 310b, 310d, and 310e. The light-transmitting conductive film 310c is formed at the same time as the light-transmitting conductive film 316b. It is connected via 6a.

[0054] The display device described in this embodiment includes an oxide semiconductor film of a transistor and an oxide semiconductor film of a capacitor. A light-transmitting conductive film that functions as a pixel electrode is formed. The other electrode of the element is used. Since a film forming step is not required, the manufacturing steps of the display device can be reduced. The pair of electrodes are formed using a light-transmitting conductive film, and therefore have light-transmitting properties. The area occupied by the capacitor 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) are formed on the surface of the oxide semiconductor film 308. The first portion is formed by improving the interface characteristics with the oxide semiconductor film, such as the insulating film 306 and the insulating film 312. Since the oxide semiconductor film 308a is in contact with the film formed of a material capable of being evaporated, The oxide semiconductor film 308a functions as a semiconductor. The star 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 in 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 and aluminum. It is made of a material that prevents potassium metal, alkaline earth metal, etc. from diffusing into the oxide semiconductor film. Therefore, the hydrogen contained in the insulating film 314 is transferred to the oxide semiconductor film When the light-transmitting conductive film 308c is diffused into the conductive film 308a and 308b, the light-transmitting conductive film 308c is In the conductive film 308c having optical properties, 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 said to be an oxide semiconductor film with high conductivity. do.

[0057] The light-transmitting conductive film 308c is formed by using the oxide film of the transistors 102 and 103. The thickness of the semiconductor film 308 is thinner than that of the semiconductor film 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 can be made thinner than that of the oxide semiconductor films 308a and 308b. It is possible.

[0058] Here, an enlarged 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. is.

[0059] As shown in FIG. 3B, the thickness of the oxide semiconductor film 308b of the transistor 103 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 capacitor 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 degrade 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 with this characteristic is called a depletion type transistor. It is also considered that no drain current flows when the gate voltage is 0V. A transistor that can do this is called a normally-off transistor. The 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 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 the 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 to oxide It can also be caused by hydrogen contained in semiconductors (including hydrogen compounds such as water). The hydrogen contained in the oxide semiconductor reacts with the oxygen that bonds with the metal atoms to form water. The oxygen vacancies (or oxygen vacancies) are formed in the lattice where the oxygen has been removed (or in the part where the 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 the channel formation regions of the transistors 102 and 103 are 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 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 or less, more preferably 1 × 10 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 x 10 16 ato ms / cm3 Alkali metals and alkaline earth metals bond with oxide semiconductors. When the voltage is increased, carriers may be generated, which increases the off-state current of the transistors 102 and 103. This may happen.

[0065] In this way, 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 doing so, 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. Furthermore, 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 proven through various experiments. For example, if 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 In the range of 10V, the off-state current is below the measurement limit of the semiconductor parameter analyzer, that is, Wachi 1×10 -13 In this case, the off-state current is The value divided by the channel width of the transistor is 100 zA / μm or less. The capacitance element and the transistor are connected to each other, and the charge flowing into or out of the capacitance element is applied. 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 element is formed. The off-state current of the transistor is measured from the change in the amount of charge per unit time. When the voltage between the source and drain of the transistor is 3V, the current is even lower, at several tens of yA / μm. Therefore, a transistor using a highly purified oxide semiconductor film can , the off-state current is significantly 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 the oxide semiconductor films 308a and 308b. Compared to the conductive film 3 b, the oxygen deficiency and / or hydrogen concentration are 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 silicate glass, or the like. For mass production, the substrate 302 is made of glass material such as borosilicate glass. Generation (2160mm x 2460mm), 9th generation (2400mm x 2800mm, or 2 450mm x 3050mm), 10th generation (2950mm x 3400mm), etc. It is preferable to use mother glass. If the processing temperature is high and the processing time is long, the glass will deteriorate significantly. 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 metal elements mentioned above. It can be formed using an alloy containing the above-mentioned metal elements or an alloy combining the above-mentioned metal elements. The conductive films 304a, 304b, and 304c may have a single layer structure or a stacked 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 formed on the aluminum film, and then a titanium film is formed on the aluminum film. There are also aluminum alloys with titanium, tantalum, tungsten, molybdenum, etc. A film of elements selected from the group consisting of 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. It 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 nitride oxide film, an aluminum nitride film, an aluminum nitride oxide 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 amount 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 by the oxide semiconductor. This can prevent the material from moving or diffusing into the membranes 308a and 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 the following.

[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 containing 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 rubber film or the like may be used, and the film may be provided as a laminated layer or a single layer.

[0076] The insulating film 306 is made of hafnium silicate (HfSiO x ), nitrogen-containing 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 This reduces the gate leakage of the transistors 102 and 103.

[0077] Silicon nitride film has a higher dielectric constant than silicon oxide film, and is equivalent to silicon oxide film. Since the film thickness required to obtain this capacitance is large, it is necessary to physically thicken the gate insulating film. Therefore, it is possible to suppress the decrease in the dielectric strength voltage of the transistor and further improve the dielectric strength voltage. This makes it possible to suppress electrostatic breakdown of the transistor.

[0078] Over the insulating film 306, oxide semiconductor films 308a and 308b, 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 gate electrode 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. The electrode 8c functions as one of the electrodes 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 % In and less than 50 atomic % 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 ion beam using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XP S) can be compared.

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

[0083] The light-transmitting conductive film 308c is made of In, similar to the oxide semiconductor films 308a and 308b. or an oxide semiconductor film containing Ga and containing impurities. Impurities include hydrogen. Instead of hydrogen, impurities such as boron, phosphorus, and sulfur can also be used. 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. It is an oxide semiconductor film containing In or Ga formed on a silicon insulating film, but the impurity concentration is Specifically, the light-transmitting conductive film 308 is different from the oxide semiconductor films 308a and 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 or less, more preferably 1 × 10 16 atoms / cm 3 Below The hydrogen concentration in the light-transmitting conductive film 308c is 8×10 19 atom s / cm 3 or more, preferably 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 twice as high, preferably 10 times or more as high. Above.

[0085] 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 formed of, for example, a non- The non-single crystal structure may be, for example, a CAAC-OS (C Axis Coupling) structure, which will be described later. Aligned Crystalline Oxide Semiconductor ), polycrystalline structure, microcrystalline structure as 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: 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 stacked 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 conductive films 310a, 310b, 310c, 310d, and 310e, The conductive film 310a is electrically connected to the oxide semiconductor film 308a. and 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 one of a source and a drain. 308b and the light-transmitting conductive film 316b, The gate 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, molyb A metal consisting of aluminum, silver, tantalum, or tungsten, or a metal containing this as its main component The alloy is used as a single layer or a laminated structure. For example, a titanium film is laminated 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 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 or molybdenum nitride film is overlaid with an aluminum film or copper film. A three-layer structure is formed by laminating a layer of molybdenum or molybdenum nitride on top of that. It is also possible to use a transparent conductive material containing indium oxide, tin oxide, or zinc oxide. .

[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 on the insulating film 312. The insulating film 312 is made of an oxide semiconductor, similar to the insulating film 306. It is preferable to use a material that can improve the interface characteristics with the film. , as well as the insulating film 305, external impurities such as water, alkali metals, alkaline earth metals, etc. It is preferable to use a material that can prevent metal or the like from diffusing into the oxide semiconductor films 308a and 308b. Desirable.

[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 can be formed. The insulating film 312 is formed by the insulating film 312. ... For example, thermal desorption spectroscopy (TDS) The temperature is 100°C or higher and 700°C or lower, preferably 100°C or higher, as measured by the method described above. The amount of oxygen molecules released during heat treatment at 500°C or less is 1.0 x 10 18 molecules / cm 3 Below By using the oxide insulating film, oxygen vacancies in the oxide semiconductor films 308a and 308b can be reduced. The loss can be compensated.

[0093] The insulating film 312 has a stacked structure, and the insulating film 312 is provided on the side in contact with the oxide semiconductor films 308a and 308b. The first oxide insulating film is an oxide insulating film having a low interface state with the oxide semiconductor films 308a and 308b. a second oxide insulating film having the above stoichiometric composition formed thereon; 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 Below, preferably 5.0×10 16 spins / cm 3 By using the following oxide insulating film, an oxide semiconductor film It is possible to reduce the interface states with 308a and 308b. The spin density at g=2.001 measured by the measurement is the dangling electrons contained in the first oxide insulating film. corresponds to the abundance of the bonds.

[0095] In addition, light-transmitting conductive films 316a and 316b 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 transparent conductive film 310c is electrically connected to the conductive film 310c in 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, and functions as a 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, and zinc oxide. The conductive film 316a includes 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] Further, below the substrate 342, a film having color (hereinafter referred to as a color film 346) is formed. The colored film 346 functions as a color filter. A light-shielding film 344 adjacent to the substrate 346 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 colored film 346 may not be provided.

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

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

[0100] An insulating film 348 is formed below the colored film 346. The insulating film 348 is The function of the color film 346 is to diffuse impurities that may be contained in the color film 346 to the liquid crystal element side. 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, 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 moisture from entering from the outside. preferable.

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

[0104] <Method for manufacturing a display device> Next, a method for manufacturing an element portion provided over a substrate 302 of a display device shown in FIG. 3(A) will be described. This will be explained with reference to FIGS. 4 to 7.

[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 carried out by forming a mask by first patterning in a desired region, and then covering the mask. It can be formed by etching the uncut area (see Figure 4(A)).

[0107] The conductive films 304a, 304b, and 304c are typically formed by evaporation, CVD, or spatula. The conductive film 30 can be formed by a pulverizing method, a spin coating method, or the like. 4a, 304b, and 304c are formed by sputtering tungsten films with 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 when the insulating film 305 and the insulating film 306 are formed successively in a vacuum, the insulating film This is preferable because it prevents impurities from being mixed into 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 The thin film can be formed by using ablation method or the like.

[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 rare gas and oxygen. In the case of a mixture of rare gas and oxygen, the ratio of the oxygen gas to the rare gas is A higher ratio is preferred.

[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, preferably 100°C or higher. The temperature is set to 450°C or lower, and more preferably 150°C or higher and 350°C or lower, and the oxidation is carried out 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. High vacuum evacuation (5×10) was performed using a suction-type vacuum evacuation pump such as -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 addition, 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 also necessary to highly purify the sputtering gas. The oxygen gas or argon gas used has a dew point of -40°C or less, preferably -80°C or less, more preferably Preferably, a gas purified to a temperature of -100°C or less, more preferably -120°C or less, is used. By doing so, moisture and 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 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 by forming a second pattern in desired regions. A mask is formed by turning, and the area not covered by the mask is etched. The etching method can be dry etching or wet etching. Etching, or a combination of both can be used.

[0120] Next, it is preferable to carry out a first heat treatment. ℃ or less, preferably 300℃ to 500℃, in an inert gas atmosphere, an oxidizing gas atmosphere The first heat treatment may be carried out 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 replace the oxygen that has been removed. The first heat treatment may be performed in an atmosphere containing 10 ppm or more of fluorine. 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 sample was heated in a nitrogen atmosphere at 350°C for 1 hour, and then heated 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 with a thickness of 50 nm, an aluminum film with a thickness of 400 nm, and a 10 Then, a 0 nm titanium film is deposited by sputtering.

[0125] Next, the conductive film 309 is processed into a desired region, thereby forming conductive films 310a, 310b, and 311. 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 mask can be formed by etching the area not covered by the mask (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 to cover the layers 310a, 310b, 310c, 310d, and 310e. (See Figure 5(C)).

[0127] The insulating film 311 is formed by using a material having interface properties with the oxide semiconductor films 308a, 308b, and 308d. It is preferable to use a material that can improve the insulating properties of the insulating film. A typical example is 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 required for 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 maintained 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 at 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 or less, more preferably 0.25 W / cm 2 Over 0 .35W / cm 2 The purpose is to supply the following high frequency power:

[0129] The source gas of the insulating film 311 is a deposition gas containing silicon, and examples thereof include silane, di Examples of oxidizing gases include silane, trisilane, and fluorinated silane. Examples include nitrous oxide and nitrogen dioxide.

[0130] As a condition for forming the insulating film 311, a high frequency voltage having the above power density is applied in a processing chamber under the above pressure. By supplying power, the decomposition efficiency of the source gas in the plasma increases, and oxygen radicals increase. As the oxidation of the source gas progresses, the oxygen content in the insulating film 311 becomes higher than the stoichiometric composition. However, when the substrate temperature is above this level, the bonding strength between silicon and oxygen is As a result, the oxygen content is lower than the stoichiometric composition. It is possible to form an oxide insulating film that contains more oxygen than the silicon dioxide and from which part 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, 308b to lower the interface state. As the insulating film, an oxide insulating film containing more oxygen than the oxygen satisfying the above stoichiometric composition is provided. That's 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 maintained 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 maintain 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 processing 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 this case, 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 dioxide 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 supply. A silicon oxynitride film with a thickness of 50 nm is formed using the D device. Silane at a flow rate of 200 sccm and dinitrogen monoxide at a flow rate of 4000 sccm were used as raw material gases. The pressure in the processing chamber was set to 200 Pa, the substrate temperature to 220°C, and a high frequency power supply of 27.12 MHz was used. A thick film was formed by a PE-CVD device using a parallel plate electrode with 1500W of high frequency power. The PE-CVD device is designed to form a silicon oxynitride film with a thickness of 400 nm. 000cm 2 It is a parallel plate type PE-CVD device, and the supplied power is This corresponds to a power density of 0.26 W / cm 2 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 by forming a mask by the fourth patterning in a desired region. The mask can be formed by 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 a value that the light-transmitting conductive film 308c to be formed later will be a capacitor. The thickness is sufficient as long as it can 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 compared to 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 above embodiment, the opening 372 is formed so as to be covered by the metal. However, the present invention is not limited to this. For example, the opening 37 2, the entire surface of the oxide semiconductor film 308d is exposed, and the oxide semiconductor film 308 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 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 bonds with oxygen, generating electrons as carriers. The oxide semiconductor film 308d has high conductivity and becomes a 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 zero or very little. For example, a silicon nitride film can be used for the insulating film 313. It can be formed by using the VD method.

[0141] The silicon nitride film is preferably formed at a high temperature to enhance blocking properties. For example, the substrate temperature is 100°C or higher and lower than the strain point of the substrate, 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 silane at a flow rate of 5000 sccm. The source gases were nitrogen and ammonia at a flow rate of 100 sccm, and 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 supply was used with a power of 1000W (power The density is 1.6 x 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 This can be achieved by etching the area not covered by the metal (see Figure 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 by, for example, dry etching. However, the method for forming the openings 374a, 374b, and 374c is The etching method is not limited to this, and may be a wet etching method or a dry etching method. A formation method in combination with wet etching 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 is formed (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. An indium tin oxide film containing silicon 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 capacitor 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 the 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 an element such as fluorine or the like. 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 alkali metals, alkaline earth metals, etc. to d, a solution containing the impurities 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. Give an explanation.

[0153] First, a substrate 342 is prepared. The substrate 342 is made of the same material as the substrate 302. Next, a light-shielding film 344 and a colored film 346 are formed on the substrate 342. The colored film 44 and the colored film 346 are made of various materials by printing, inkjet printing, photolithography, etc. They are formed at the desired positions by etching 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 such as an acrylic resin can be used as the insulating film 348. 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 provided. 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 conductive film 350 is formed by the conductive film 31 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 The alignment film 318 and the alignment film 352 are formed on the substrate 10, respectively. The film can be formed by using a rubbing method, a photo-alignment method, etc. Then, the substrate 302 and the substrate The liquid crystal layer 320 is formed between the substrate 342 and the liquid crystal layer 320. or by using capillary action after bonding the substrate 302 and the substrate 342 together. An injection method of 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 the 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 90a, an oxide semiconductor film 388b, and an oxide film 390b. 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 oxide film 390b and the oxide film 390b will be described in detail below.

[0161] Oxide semiconductor films 388a and 388b (hereinafter also referred to as oxide semiconductor films 388 in the specification) ) and oxide films 390a and 390b (hereinafter referred to as oxide film 390 in the specification). It is preferable to use a metal oxide having at least one of the same constituent elements as the metal oxide. Alternatively, the oxide semiconductor film 388 and the oxide film 390 may be made of the same constituent elements, and the combination of the two may be made of the same constituent elements. The composition may be different.

[0162] The oxide semiconductor film 388 is an In-M-Zn oxide (M is Al, Ga, Ge, Y, Zr, S In the case of In, La, Ce or Hf, the spatula used to deposit In-M-Zn oxide The atomic ratio of the metal elements in the target preferably satisfies In≧M, 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 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% variation in eggplant.

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

[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 greater than or equal to 3 nm and less than or equal to 200 nm, preferably greater than or equal to 3 nm and less than or equal 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, or In-MnO. 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 more 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 therefore 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. In addition, the element M has a low bonding strength with oxygen. Since M is a strong metallic element, having a higher atomic ratio than In makes it difficult for oxygen vacancies to occur. It becomes difficult.

[0168] When the oxide film 390 is an In-M-Zn oxide, the In and M oxides are present except for Zn and O. 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 The atomic ratio of M contained in the oxide film 390 is large compared to that of the oxide semiconductor. The amount of the atoms contained in the membrane 388 is 1.5 times or more, preferably 2 times or more, Preferably, the atomic ratio is 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 film 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 greater than y2 / x2. More preferably, y1 / x1 is at least twice as large as y2 / x2, and even more preferably, y1 / x1 is three times or more larger than y2 / x2. When y2 is greater than or equal to x2, a transistor including an oxide semiconductor can have stable electrical characteristics. However, if y2 is three times or more of x2, it is difficult to obtain a 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 the 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 oxide film 390 is The error is the planar ratio of the atomic number of the metal elements contained in the sputtering target. Includes fluctuations of ±20%.

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

[0173] The oxide film 390 is formed by oxidation when forming 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 set to 100 nm or more, preferably 3 nm or more and 50 nm or less.

[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) concentration) is 2 x 10 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0175] In addition, in the oxide semiconductor film 388, alkali metal ions 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 x 10 16 atoms / cm 3 The alkali metals and alkaline earth metals are as follows: When bonded to an oxide semiconductor, carriers may be generated, increasing the off-state current of the transistor. Therefore, the alkali metal or alkali metal in the oxide semiconductor film 388 may be increased. It is preferable to reduce the concentration of alkali earth metals.

[0176] When nitrogen is contained in the oxide semiconductor film 388, electrons serving as carriers are generated, and As a result, the carrier density increases and it becomes easier to make the semiconductor n-type. Therefore, the transistor having the oxide semiconductor film 388 tends to be normally on. In this case, it is preferable that nitrogen is reduced as much as possible. For example, in secondary ion mass spectrometry, The nitrogen concentration obtained by the method is 5 x 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. The structure in which the energy of the bottom of the conduction band changes continuously between the layers is called the "junction." That is, at the interface of each film, a transistor for the oxide semiconductor is formed. The stacking layer is free of impurities that form defect levels such as drop centers and recombination centers. If 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 being exposed to the atmosphere. Each chamber in the sputtering device 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 pumping (5×10 -7 Pa~1×10 -4 It is preferable to Alternatively, a turbomolecular pump and cold trap can be combined to evacuate the chamber from the exhaust system. It is preferable to prevent gases, especially gases containing carbon or hydrogen, from flowing back into the .

[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 included in the transistors 102 and 103. Here, when silicon oxide layers are provided as the insulating films 306 and 312, In addition, EcI1 shown in FIG. 8(B) is the oxide silicon used as the insulating film 306. EcS1 indicates the energy of the bottom of the conduction band of the silicon layer, and EcS2 indicates the energy of the bottom of the conduction band of the oxide semiconductor film 388. EcS2 denotes the energy of the bottom of the conduction band of the oxide film 390, and E cI2 represents 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 the channel formation region It can be seen that the oxide semiconductor film 388 is formed. The oxide semiconductor film 390 has a continuously changing energy at the bottom of the conduction band. It can be said that the oxide film 390 and the oxide film 88 are continuously joined together.

[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 Although a level may be formed, the oxide film 390 is provided, and therefore, the oxide semiconductor film 3 However, the energy between EcS1 and EcS2 can be 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 the trap level, a negative fixed charge As a result, the threshold voltage of the transistor shifts in the positive direction. The energy difference between EcS1 and EcS2 is 0.1 eV or more, preferably 0.15 eV or more. This is preferable because it reduces fluctuations in the threshold voltage of the transistor and provides stable electrical characteristics. It is suitable.

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

[0185] In the cross-sectional view of FIG. 9A, the transistor 103 has an oxide film in the channel formation region. The oxide semiconductor film 388b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (here, the insulating film 306). 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 shown in FIG. 9A, the thickness of the light-transmitting conductive film 388c is The thickness of the conductive film 388c having light-transmitting properties is thinner than that of the 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. an oxide semiconductor film 388b used in the insulating layer and an oxide film 390b over the oxide semiconductor film 388b; Compared to laminated films, 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 capacitance. 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. 9A.

[0189] In the cross-sectional view of FIG. 9B, the transistor 103 has an oxide film in the channel formation region. The oxide semiconductor film 388b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (here, the insulating film 306). 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 compared to the cross-sectional structure shown in FIG. 9(A). The thickness of the conductive film 388c is different. The thickness of the conductive film 388c having optical properties is approximately the same as that of the oxide semiconductor film 388b. As shown in the figure, 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, However, the transmittance of the capacitor element 105 can be improved by the amount corresponding to 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. 9A.

[0192] In the cross-sectional view of FIG. 9C, the transistor 103 has an oxide film in the channel formation region. The oxide semiconductor film 388b is provided over the oxide semiconductor film 388b. The compound semiconductor film 388b is provided on the gate insulating film (here, the insulating film 306). The capacitor 105 includes a light-transmitting conductive film 388c and an oxide film 388d 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). formed on top.

[0193] In the cross-sectional view shown in FIG. 9(C), the thickness of the oxide film 390c is In this way, by forming the oxide film 390c to a small thickness, 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 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 The 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. The pixel 301b of the display device shown in FIG. 10 is the same as that of the display device shown in FIG. 10 is a top view of a modified example of pixel 301. As described above, the pixel shape of the display device is 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 ( The conductive film 310d that functions as a signal line is provided so as to extend in the left-right direction in the drawing. The capacitors are arranged to extend in a direction substantially perpendicular to the scan lines (vertical direction in the drawing). The conductive film 304d extends in a direction parallel to the scanning lines. Compared 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 304a functioning as a scanning line. 4c, and the conductive film 304d that 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 formed by the conductive film 310f (note that in FIG. 10, the conductive film 310f is formed by the conductive film 310f). The conductive film 310f is connected to the conductive film 3 10d and 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 capacitor line through the conductive film 304c. To be continued.

[0202] The pixel 301b shown in FIG. 10 has a side parallel to the conductive film 310d that 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 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 allows the aperture ratio to be increased.

[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 as a gate insulating film will be described.

[0205] <Crystallineness 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 a CAAC-OS (C Axis Aligned Crystal Polycrystalline oxide semiconductor film The oxide semiconductor film includes a film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, and the like.

[0208] First, the CAAC-OS film will be described.

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

[0210] The CAAC-OS film was observed under a transmission electron microscope (TEM). When observed under a tron ​​microscope, clear boundaries between the crystalline parts are 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 observed, it can be confirmed that metal atoms are arranged in layers in the crystalline part. Each layer of the CAAC-OS film is formed on a surface (also called a surface to be formed) or on a concave surface of the upper surface. The shape reflects the convexity and is aligned parallel to the surface on which the CAAC-OS film is formed or the 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 also includes the case where the angle is between -5° and 5°. "Perpendicular" refers to two straight lines that form an angle of 80° or more and 100° or less. Therefore, the angle may be between 85° and 95°.

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

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

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

[0216] On the other hand, the in-p X-rays incident on the CAAC-OS film are perpendicular to the c-axis. In the Lane analysis, a peak may appear around 2θ of 56°. The crystal structure of InGaZnO4 is composed of a single crystal of InGaZnO4. 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 2θ. Even when the φ is fixed at around 56° and scanned, no clear peak appears.

[0217] From the above, it can be concluded that the orientation of the a-axis and b-axis is uniform between different crystal regions in the CAAC-OS film. Although it is irregular, it has a c-axis orientation, and the c-axis is parallel to the normal vector of the surface on which it is formed or the upper surface. Therefore, the layered structure confirmed by the cross-sectional TEM observation mentioned above is consistent with the Each layer of arranged metal atoms is a plane parallel to the ab plane of the crystal.

[0218] The crystalline part is formed when the CAAC-OS film is formed or after a crystallization treatment such as a heat treatment. As described above, the c-axis of the crystal is aligned with the surface on which the CAAC-OS film is to be formed. Therefore, 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 normal vector of the face or top surface.

[0219] Furthermore, the crystallinity of the CAAC-OS film may not be uniform. When the crystalline part of the film is formed by crystal growth from the vicinity of the top surface of the CAAC-OS film, The area near the surface may have a higher crystallinity than the area near the surface to be formed. When impurities are added to the AC-OS film, the crystallinity of the region where the impurities are added changes, and the Regions of differing crystallinity may be formed.

[0220] In addition, the out-of-plane structure of the CAAC-OS film with InGaZnO4 crystals In the analysis by the NMR method, in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ around 36° is due to the presence of c-axis orientation in part of the CAAC-OS film. The CAAC-OS film contains crystals that do not have crystalline structure. It is preferable that the peak is exhibited at 2θ of about 36° and that the peak is not exhibited at 2θ of about 36°.

[0221] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is made of an element other than the main component, such as silicon or a transition metal element. The elements such as ZnO, which have stronger bonding strength with oxygen than the metal elements constituting the oxide semiconductor film, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disturbed, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Because the diameter (or molecular radius) is large, when the molecule is contained inside the oxide semiconductor film, The impurities contained in the oxide semiconductor film are likely to disturb the atomic arrangement of the oxide semiconductor film, which may result in a decrease in crystallinity. The pure material may act as a carrier trap or a carrier generation source.

[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. There is little gender variation.

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

[0225] In the microcrystalline oxide semiconductor film, crystal parts can be clearly seen in the TEM image. The crystal parts contained in the microcrystalline oxide semiconductor film may have a size of 1 nm or more and 100 nm or more. In particular, the size of the particles is between 1 nm and 10 nm. Nanocrystals (nc) are microcrystals with a diameter of 1 nm or less, or 1 nm to 3 nm. The oxide semiconductor film having nc-OS (nanocrystalline O The nc-OS film is called an oxide semiconductor film. In EM observation images, the grain boundaries may not be clearly visible.

[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 analytical method. For example, XRD, which uses X-rays with a diameter larger than that of the crystal part, is used for nc-OS films. When structural analysis is performed using the device, the crystal plane is analyzed using the out-of-plane method. In addition, the peaks indicating the crystal grains with a diameter larger than that of the crystalline part (e.g., When electron beam diffraction (also called selected area electron beam diffraction) is performed using an electron beam of 50 nm or more, On the other hand, the nc-OS film has a large crystalline area. Electron beams with a diameter close to or smaller than the crystal size (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, there are cases where regions with high luminance are observed in a circular (ring-shaped) pattern. Also, When performing nano-beam electron diffraction on the nc-OS film, there are cases where multiple spots are observed within the ring-shaped region.

[0227] The nc-OS film is an oxide semiconductor film with higher regularity than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect energy levels than an amorphous oxide semiconductor film. However, in the nc-OS film, no regularity is observed in the crystal orientation between different crystal parts. Therefore, the nc-OS film has a higher density of defect energy 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 are cleaved from the a-b plane and peeled off as plate-shaped or pellet-shaped sputtering particles having a plane parallel to the a-b plane. In this case, the CAAC-OS film can be formed by the plate-shaped or pellet-shaped sputtering particles reaching the substrate while maintaining their crystal state. The plate-shaped or pellet-shaped sputtering particles are, for example, equivalent to a circle of a plane parallel to the a-b plane.

[0230] Diameter is 3 nm or more and 10 nm or less, and thickness (length 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 surface may be an equilateral triangle or a regular hexagon. Here, the circle-equivalent diameter of a surface is the area of ​​the surface. 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 prevented. Specifically, the substrate temperature is set to 100°C or higher and 740°C or lower, preferably 200°C or higher. 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 sputtering particles adheres to the substrate. By using 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 can be reduced. A deposition gas at 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 can be reduced. The oxygen ratio in the film forming gas is 30% by volume or more, preferably 100% by volume or more. Expressed as volume %.

[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 The film is formed at a concentration of at least 100% by volume, 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 1 minute to 24 hours, preferably 6 minutes to 4 hours. The heat treatment may be carried out 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 carried out at a pressure of 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 sputtering. 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 temperature is set to 0°C or lower, and the oxygen ratio in the film-forming gas is set to 30% by volume or more, preferably 100% by volume. To film.

[0240] Next, heat treatment is performed to form a second oxide semiconductor film from the first CAAC-OS film by solid-phase growth. The second CAAC-OS film was obtained by heating at a temperature of 350 The temperature is set to 740°C or higher, preferably 450°C or higher and 650°C or lower. The heating time is from 1 minute to 24 hours, preferably from 6 minutes to 4 hours. The heat treatment may be carried out in an inert atmosphere or an oxidizing atmosphere. Preferably, the heat treatment is carried out in an inert atmosphere. After that, 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 deficiency can be reduced by heat treatment in a reactive atmosphere. It may be carried out under reduced pressure of 000 Pa or less, 100 Pa or less, 10 Pa or less, or 1 Pa or less. Under reduced pressure, the impurity concentration of 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. You can be there.

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

[0243] When the surface to be formed is at a low temperature, the sputtered particles fall irregularly onto the surface. For example, because there is no migration, there is no area 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 may not only be uniform but also have a disordered crystal orientation. The sputter particles have crystalline portions (nanocrystals) to maintain the crystallinity to some extent.

[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 particles cannot be separated and are fragmented (for example, into individual atoms). The atoms separated from the particles are deposited on the surface, forming an amorphous oxide film. This may be the case.

[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 separated 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 nozzle fly to the surface where the particles are to be formed. 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 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 occur.

[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 FIGS. 11 and 12. 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 and 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 needed to fit the size of the 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 006 to make it an optical touch panel.

[0253] The backlight unit 8007 includes a light source 8008. It may be provided at the end of the light source unit 8007 and may be configured to use a light diffusion plate.

[0254] The frame 8009 has a function of protecting the display panel 8006 and also a function of preventing the movement of the printed circuit board 8010. It also functions as an electromagnetic shield to block electromagnetic waves generated by the operation of the The frame 8009 may also function as a heat sink.

[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 Body 5000, display unit 5001, speaker 5003, LED lamp 5004, 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, a microphone 5009, etc. can.

[0258] FIG. 12(A) shows a mobile computer, which includes, in addition to the above, a switch 5009 , an infrared port 5010, etc. FIG. 12(B) shows a portable terminal equipped with a recording medium. A portable image reproducing device (for example, a DVD reproducing device) is also included. The display unit 5002, the recording medium reading unit 5011, etc. It is a group-type display, and in addition to the above, it has a second display unit 5002, a support unit 5012 , earphones 5013, etc. FIG. 12(D) shows a portable gaming machine. In addition to the above, it may have a recording medium reading unit 5011, etc. It is a digital camera with a TV 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. It is a belt-type gaming 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, has It can have a tuner, an image processor, etc. FIG. 12(H) shows a portable television receiver. In addition to the above, it has a charger 5017 capable of transmitting and receiving signals, etc. can be done.

[0259] The electronic devices shown in FIGS. 12A to 12H can have various functions. For example, functions to display various information (still images, videos, text images, etc.) on the display, Panel function, calendar, date or time display function, various software ( It has a function to control processing by a program, a wireless communication function, and various controls using the wireless communication function. Functions for connecting to computer networks, transmitting various data using wireless communication functions, 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 another display section is used mainly to display text information. or a function to display images that take parallax into account on multiple displays to create a three-dimensional effect. Furthermore, in electronic devices having an image receiving unit, The camera has the functions to take still images, record videos, and automatically or manually correct captured images. function to correct the image, to save the captured image to 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 can be It can have.

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

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

[0262] 100 pixel unit 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 Capacitance 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 Alignment Film 320 Liquid Crystal Layer 342 PCB 344 Light-shielding film 346 Colored film 348 Insulating Film 350 Conductive Film 352 Alignment 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 cabinets 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 first conductive film, a second conductive film, a first oxide semiconductor film, a second oxide semiconductor film, and a third conductive film; the first conductive film and the second conductive film contain copper; a semiconductor device, wherein the third conductive film functions as a gate electrode, In a plan view, the first conductive film has a first portion, a second portion, and a third portion; In a plan view, the first portion and the second portion each have a shape extending along a first direction, In a plan view, the first portion and the second portion are each connected to the third portion; In a plan view, the second conductive film has a fourth portion, a fifth portion, and a sixth portion, In a plan view, the fourth portion and the fifth portion each have a shape extending along the first direction, In a plan view, the fourth portion and the fifth portion are each connected to the sixth portion; In a plan view, the first portion has a region disposed between the fourth portion and the fifth portion, In a plan view, the fifth portion has a region disposed between the first portion and the second portion, In a plan view, the first oxide semiconductor film has a shape extending along a second direction intersecting the first direction, the second oxide semiconductor film is disposed at an interval from the first oxide semiconductor film in the first direction and has a shape extending along the second direction in a plan view; the first portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film; the first portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film; the second portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the second portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film; the fourth portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the fourth portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film, the fifth portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the fifth portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film, In a plan view, the first oxide semiconductor film has a region sandwiched between the fourth portion and the first portion, a region sandwiched between the first portion and the fifth portion, and a region sandwiched between the fifth portion and the second portion; In a plan view, the second oxide semiconductor film has a region sandwiched between the fourth portion and the first portion, a region sandwiched between the first portion and the fifth portion, and a region sandwiched between the fifth portion and the second portion; the third conductive film has, in a plan view, a region overlapping with the entire first oxide semiconductor film and a region overlapping with the entire second oxide semiconductor film.

2. a first conductive film, a second conductive film, a first oxide semiconductor film, a second oxide semiconductor film, and a third conductive film; the first conductive film and the second conductive film contain copper; the first oxide semiconductor film includes a third oxide semiconductor film and a first oxide film having a region located above the third oxide semiconductor film; the second oxide semiconductor film includes a fourth oxide semiconductor film and a second oxide film having a region located above the fourth oxide semiconductor film; a semiconductor device, wherein the third conductive film functions as a gate electrode, In a plan view, the first conductive film has a first portion, a second portion, and a third portion; In a plan view, the first portion and the second portion each have a shape extending along a first direction, In a plan view, the first portion and the second portion are each connected to the third portion; In a plan view, the second conductive film has a fourth portion, a fifth portion, and a sixth portion, In a plan view, the fourth portion and the fifth portion each have a shape extending along the first direction, In a plan view, the fourth portion and the fifth portion are each connected to the sixth portion; In a plan view, the first portion has a region disposed between the fourth portion and the fifth portion, In a plan view, the fifth portion has a region disposed between the first portion and the second portion, In a plan view, the first oxide semiconductor film has a shape extending along a second direction intersecting the first direction, the second oxide semiconductor film is disposed at an interval from the first oxide semiconductor film in the first direction and has a shape extending along the second direction in a plan view; the first portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film; the first portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film; the second portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the second portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film; the fourth portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the fourth portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film, the fifth portion has a region that overlaps with the first oxide semiconductor film and is in contact with the first oxide semiconductor film, the fifth portion has a region that overlaps with the second oxide semiconductor film and is in contact with the second oxide semiconductor film, In a plan view, the first oxide semiconductor film has a region sandwiched between the fourth portion and the first portion, a region sandwiched between the first portion and the fifth portion, and a region sandwiched between the fifth portion and the second portion; In a plan view, the second oxide semiconductor film has a region sandwiched between the fourth portion and the first portion, a region sandwiched between the first portion and the fifth portion, and a region sandwiched between the fifth portion and the second portion; the third conductive film has, in a plan view, a region overlapping with the entire first oxide semiconductor film and a region overlapping with the entire second oxide semiconductor film.

Images