JP6433757B2 - Semiconductor devices, display devices, electronic equipment - Google Patents

Description

  The present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, machine, manufacture, or composition (composition of matter). One embodiment of the present invention relates to a semiconductor device, a display device, an electronic device, a manufacturing method thereof, or a driving method thereof. In particular, one embodiment of the present invention relates to a semiconductor device including a transistor and a capacitor, for example.

  Transistors used in many flat panel displays typified by liquid crystal display devices and light-emitting display devices are composed of silicon semiconductors such as amorphous silicon, single crystal silicon, or polycrystalline silicon formed on a glass substrate. . In addition, a transistor including the silicon semiconductor is used for an integrated circuit (IC) or the like.

  In recent years, a technique using a metal oxide exhibiting semiconductor characteristics for a transistor instead of a silicon semiconductor has attracted attention. Note that in this specification, a metal oxide exhibiting semiconductor characteristics is referred to as an oxide semiconductor. For example, a technique is disclosed in which a transistor using zinc oxide or an In—Ga—Zn-based oxide as an oxide semiconductor is manufactured, and the transistor is used for a switching element of a pixel of a display device or the like (Patent Document 1). And Patent Document 2).

  In addition, in order to increase the aperture ratio, a capacitor element in which an oxide semiconductor film provided over the same surface as the oxide semiconductor film of the transistor and a pixel electrode connected to the transistor are provided at a predetermined distance is provided. A display device is disclosed (see Patent Document 3).

JP 2007-123861 A JP 2007-96055 A US Pat. No. 8,102,476

  A capacitor element is provided with a dielectric film between a pair of electrodes, and at least one of the pair of electrodes is formed of a light-shielding conductive film such as a gate electrode, a source, or a drain constituting a transistor. There are many things.

  In order to increase the capacitance value of the capacitor, there is a means of increasing the area occupied by the capacitor, specifically, increasing the area where the pair of electrodes overlap. However, in the display device, when the area of the light-shielding conductive film is increased in order to increase the area where the pair of electrodes overlap, the aperture ratio of the pixel is reduced and the display quality of the image is deteriorated.

  In view of the above problems, an object of one embodiment of the present invention is to provide a semiconductor device including a capacitor that has a high aperture ratio and can increase a capacitance value. Another object is to provide a semiconductor device with low manufacturing cost. Another object is to provide a novel semiconductor device or the like.

  Note that the description of these problems does not disturb the existence of other problems. Note that one embodiment of the present invention does not have to solve all of these problems. Issues other than these will be apparent from the description of the specification, drawings, claims, etc., and other issues can be extracted from the descriptions of the specification, drawings, claims, etc. It is.

  One embodiment of the present invention is a semiconductor device including a transistor including a first oxide semiconductor film and a second oxide semiconductor film, and a capacitor including an insulating film between a pair of electrodes. The transistor includes a first oxide semiconductor film, a gate insulating film provided in contact with the first oxide semiconductor film, a position provided in contact with the gate insulating film, and a position overlapping with the first oxide semiconductor film. And a source electrode and a drain electrode connected to the first oxide semiconductor film, and one of the pair of electrodes of the capacitor element is the second oxide semiconductor film. A semiconductor device is provided over the same surface as a semiconductor film.

  Another embodiment of the present invention is a semiconductor device including a transistor including a first oxide semiconductor film and a second oxide semiconductor film, and a capacitor including an insulating film between a pair of electrodes. The transistor includes a gate electrode including a second oxide semiconductor film, a gate insulating film on the gate electrode, a first oxide semiconductor film in a position overlapping with the gate electrode on the gate insulating film, A semiconductor including a source electrode and a drain electrode over the first oxide semiconductor film, wherein one of the pair of electrodes of the capacitor is provided over the same surface as the second oxide semiconductor film; Device.

  Another embodiment of the present invention is a semiconductor device including a transistor including a first oxide semiconductor film and a second oxide semiconductor film, and a capacitor including an insulating film between a pair of electrodes. The transistor includes a first oxide semiconductor film, a source electrode and a drain electrode on the first oxide semiconductor film, a gate insulating film on the first oxide semiconductor film, and a gate insulating film. A gate electrode including a second oxide semiconductor film at a position overlapping with the first oxide semiconductor film, and one of the pair of electrodes of the capacitor has the same surface as the second oxide semiconductor film A semiconductor device is provided over the semiconductor device.

  In each of the above structures, the other of the pair of electrodes of the capacitor is preferably provided over the same surface as the first oxide semiconductor film. In addition, the capacitor element preferably has a light-transmitting property in visible light.

  In each of the above structures, the first oxide semiconductor film and the second oxide semiconductor film are In-M-Zn oxides (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, Represents Sn or Hf).

  In addition, display devices and electronic devices using the semiconductor devices having the above structures are included in one embodiment of the present invention.

  According to one embodiment of the present invention, a semiconductor device including a capacitor that has a high aperture ratio and can increase a capacitance value can be provided. In addition, a semiconductor device with low manufacturing cost can be provided. Alternatively, a novel semiconductor device or the like can be provided.

  Note that the description of these effects does not disturb the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. It should be noted that the effects other than these are naturally obvious from the description of the specification, drawings, claims, etc., and it is possible to extract the other effects from the descriptions of the specification, drawings, claims, etc. It is.

8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. 8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 9 is a cross-sectional view illustrating one embodiment of a method for manufacturing a semiconductor device. 8A and 8B are a cross-sectional view and a band diagram illustrating one embodiment of a semiconductor device. 10A and 10B are a block diagram and a circuit diagram illustrating a display device. The figure explaining a display module. 10A and 10B each illustrate an electronic device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device. 8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. 8A and 8B are a top view and cross-sectional views illustrating one embodiment of a semiconductor device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 14 is a cross-sectional view illustrating one embodiment of a semiconductor device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, one embodiment of the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the gist and scope of the present invention. The Therefore, one embodiment of the present invention is not construed as being limited to the description of the following embodiment modes. In the embodiments described below, the same portions or portions having similar functions are denoted by the same reference numerals or the same hatch patterns in different drawings, and description thereof is not repeated.

  Note that in each drawing described in this specification, the size, the film thickness, or the region of each component is exaggerated for clarity in some cases. Therefore, it is not necessarily limited to the scale.

  In addition, the first and second ordinal numbers used in this specification and the like are given in order to avoid mixing of constituent elements, and are not limited numerically. Therefore, for example, the description can be made by appropriately replacing “first” with “second” or “third”.

  Note that the functions of the “source” and “drain” of the transistor may be interchanged when a transistor with a different polarity is used or when the direction of current changes during circuit operation. Therefore, in this specification, the terms “source” and “drain” can be used interchangeably.

(Embodiment 1)
In this embodiment, a semiconductor device of one embodiment of the present invention will be described with reference to FIGS.

<Configuration example of semiconductor device>
1A is a top view of the semiconductor device of one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the dashed-dotted line AB in FIG. 1A and between the dashed-dotted line CD. It corresponds to a sectional view of the surface. Note that in FIG. 1A, some components (such as a gate insulating film) of the semiconductor device are not illustrated in order to avoid complexity.

  A semiconductor device illustrated in FIGS. 1A and 1B includes a transistor 150 including a first oxide semiconductor film 110a and a second oxide semiconductor film 104a, and a capacitor including an insulating film between a pair of electrodes. Element 160. Note that in the capacitor 160, one of the pair of electrodes is the second oxide semiconductor film 104b on the same plane as the second oxide semiconductor film 104a, and the other of the pair of electrodes is the first oxide semiconductor film. This is the first oxide semiconductor film 110b on the same plane as 110a.

  The transistor 150 includes a gate electrode including the second oxide semiconductor film 104a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104a, and the insulating film 108. The gate electrode includes the first oxide semiconductor film 110a at a position overlapping with the gate electrode including the second oxide semiconductor film 104a, and the source electrode 112a and the drain electrode 112b on the first oxide semiconductor film 110a. In other words, the transistor 150 is provided in contact with the first oxide semiconductor film 110a, the insulating film 108 serving as a gate insulating film provided in contact with the first oxide semiconductor film 110a, and the insulating film 108. A second oxide semiconductor film 104a provided at a position overlapping with the first oxide semiconductor film 110a, and a source electrode 112a and a drain electrode 112b connected to the first oxide semiconductor film 110a. . Note that the transistor 150 illustrated in FIGS. 1A and 1B has a so-called bottom gate structure.

  Note that the first oxide semiconductor film 110 a functions as a channel region of the transistor 150. The second oxide semiconductor film 104a functions as a gate electrode of the transistor 150. Therefore, the resistivity of the second oxide semiconductor film 104a is lower than that of the first oxide semiconductor film 110a. The first oxide semiconductor film 110a and the second oxide semiconductor film 104a preferably include the same metal element. By using the same metal element for the first oxide semiconductor film 110a and the second oxide semiconductor film 104a, a manufacturing apparatus (eg, a film formation apparatus or a processing apparatus) can be used in common. Therefore, the manufacturing cost can be suppressed.

  Therefore, the transistor 150 includes the first oxide semiconductor film 110a, the insulating film 108 in contact with the first oxide semiconductor film 110a, the insulating film 108, and the position overlapping with the first oxide semiconductor film 110a. A second oxide semiconductor film 104a, and the first oxide semiconductor film 110a and the second oxide semiconductor film 104a have the same metal element, and the first oxide semiconductor film 110a Also, the resistivity of the second oxide semiconductor film 104a is low.

  Alternatively, a wiring or the like formed using a metal film or the like may be connected to the second oxide semiconductor films 104a and 104b. For example, in the case where the semiconductor device illustrated in FIG. 1 is used for a transistor and a capacitor in a pixel portion of a display device, a lead wiring, a gate wiring, or the like is formed using a metal film, and the second oxide semiconductor film 104a, A configuration in which 104b is connected may be used. By forming the lead wiring, the gate wiring, or the like with a metal film, the wiring resistance can be lowered, so that signal delay or the like can be suppressed.

  In addition, insulating films 114, 116, and 118 are formed over the transistor 150, more specifically, over the first oxide semiconductor film 110a, the source electrode 112a, and the drain electrode 112b. The insulating films 114, 116, and 118 function as protective insulating films for the transistor 150.

  The capacitor 160 includes a second oxide semiconductor film 104b that functions as one of a pair of electrodes over the substrate 102, and an insulating film 108 that functions as a dielectric film over the second oxide semiconductor film 104b. And the first oxide semiconductor film 110b functioning as the other of the pair of electrodes in a position overlapping with the second oxide semiconductor film 104b with the insulating film 108 interposed therebetween. In addition, an insulating film 118 having a function as a protective insulating film is formed over the capacitor 160, more specifically, over the first oxide semiconductor film 110b.

  Note that as described above, the insulating film 108 functions as a gate insulating film in the transistor 150 and functions as a dielectric film in the capacitor 160. In this embodiment mode, the insulating film 108 has a stacked structure of the insulating film 106 and the insulating film 107. Note that one embodiment of the present invention is not limited thereto, and the insulating film 108 may have a single-layer structure or a stacked structure including three or more layers.

  Further, the capacitor 160 has a light-transmitting property. That is, the first oxide semiconductor film 110b, the second oxide semiconductor film 104b, and the insulating film 108 included in the capacitor 160 are each formed using a light-transmitting material. In this manner, since the capacitor 160 has a light-transmitting property, it can be formed large (in a large area) in a region other than a portion where a transistor in a pixel is formed. An increased semiconductor device can be obtained. As a result, a semiconductor device having excellent display quality can be obtained. Further, the capacitor 160 can be manufactured by using a manufacturing process of the transistor 150. Therefore, a semiconductor device with a low manufacturing cost can be obtained.

  Note that as the insulating film 106 used for the transistor 150 and the capacitor 160 and the insulating film 118 provided over the transistor 150 and the capacitor 160, an insulating film containing at least hydrogen is used. As the insulating film 107 used for the transistor 150 and the capacitor 160 and the insulating films 114 and 116 provided over the transistor 150 and the capacitor 160, an insulating film containing at least oxygen is used. As described above, the insulating film used for the transistor 150 and the capacitor 160 and the insulating film used for the transistor 150 and the capacitor 160 are formed using the insulating film having the above structure, so that the first transistor 150 and the capacitor 160 have the first structure. The resistivity of the oxide semiconductor film and the second oxide semiconductor film can be controlled.

  Specifically, in the transistor 150, since the first oxide semiconductor film 110a is used as a channel region, the resistivity is higher than that of the first oxide semiconductor film 110b and the second oxide semiconductor films 104a and 104b. high. On the other hand, the first oxide semiconductor film 110b and the second oxide semiconductor films 104a and 104b have functions as electrodes, and thus have a lower resistivity than the first oxide semiconductor film 110a.

  Here, a method for controlling the resistivity of the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b will be described below.

<Method for controlling resistivity of oxide semiconductor>
The oxide semiconductor films that can be used for the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b are oxygen vacancies in the films and / or impurities such as hydrogen and water in the films. It is a semiconductor material whose resistivity can be controlled by concentration. Therefore, treatment for increasing oxygen vacancies and / or impurity concentration or treatment for reducing oxygen vacancies and / or impurity concentration is performed on the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b. By selecting, the resistivity of each oxide semiconductor film formed in the same process can be controlled.

  Specifically, the second oxide semiconductor film 104a that functions as a gate electrode of the transistor 150, the second oxide semiconductor film 104b that functions as an electrode of the capacitor 160, and the first electrode that functions as an electrode of the capacitor 160 The oxide semiconductor film used for the oxide semiconductor film 110b is subjected to plasma treatment to increase oxygen vacancies in the oxide semiconductor film and / or increase impurities such as hydrogen and water in the oxide semiconductor film Thus, an oxide semiconductor film with high carrier density and low resistivity can be obtained. In addition, an oxide semiconductor film with high carrier density and low resistivity is formed by forming an oxide semiconductor film in contact with an insulating film containing hydrogen and diffusing hydrogen from the insulating film containing hydrogen into the oxide semiconductor film. It can be.

  On the other hand, the first oxide semiconductor film 110a functioning as the channel region of the transistor 150 is not in contact with the insulating films 106 and 118 containing hydrogen by providing the insulating films 107, 114, and 116. By supplying an insulating film containing oxygen to at least one of the insulating films 107, 114, and 116, in other words, an insulating film capable of releasing oxygen is supplied to the first oxide semiconductor film 110a. can do. The first oxide semiconductor film 110a to which oxygen is supplied becomes an oxide semiconductor film with high resistivity by filling oxygen vacancies in the film or at the interface. Note that as the insulating film from which oxygen can be released, for example, a silicon oxide film or a silicon oxynitride film can be used.

  In order to obtain an oxide semiconductor film with low resistivity, hydrogen, boron, phosphorus, or nitrogen is implanted into the oxide semiconductor film by an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or the like. May be.

  Further, in order to obtain an oxide semiconductor film with low resistivity, plasma treatment may be performed on the oxide semiconductor film. For example, the plasma treatment typically includes plasma treatment using a gas containing one kind selected from a rare gas (He, Ne, Ar, Kr, Xe), hydrogen, and nitrogen. More specifically, plasma treatment in an Ar atmosphere, plasma treatment in a mixed gas atmosphere of Ar and hydrogen, plasma treatment in an ammonia atmosphere, plasma treatment in a mixed gas atmosphere of Ar and ammonia, or nitrogen For example, plasma treatment in an atmosphere.

  Through the above plasma treatment, the oxide semiconductor film forms oxygen vacancies in a lattice from which oxygen is released (or a portion from which oxygen is released). The oxygen deficiency may be a factor that generates carriers. In addition, when hydrogen is supplied from the vicinity of the oxide semiconductor film, more specifically, from the insulating film in contact with the lower side or the upper side of the oxide semiconductor film, the oxygen vacancies and hydrogen are combined to form electrons serving as carriers. May be generated.

On the other hand, an oxide semiconductor film in which oxygen vacancies are filled and the hydrogen concentration is reduced can be said to be a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film. Here, substantially intrinsic means that the carrier density of the oxide semiconductor film is less than 1 × 10 ¹⁷ pieces / cm ³ , preferably less than 1 × 10 ¹³ pieces / cm ³ , more preferably It means 1 × 10 ⁻⁹ pieces / cm ³ or more and less than 1 × 10 ¹¹ pieces / cm ³ . A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has few carrier generation sources, and thus can have a low carrier density. In addition, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low defect level density; therefore, the trap level density can be reduced.

Further, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has an extremely small off-state current, a channel width of 1 × 10 ⁶ μm, and a channel length L of 10 μm. When the voltage between the drain electrodes (drain voltage) is in the range of 1V to 10V, it is possible to obtain a characteristic that the off-current is less than the measurement limit of the semiconductor parameter analyzer, that is, 1 × 10 ⁻¹³ A or less. Therefore, the transistor 150 in which the first oxide semiconductor film 110a using the above-described high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor film is used for a channel region has little variation in electrical characteristics and high reliability. It becomes a transistor.

As the insulating film 106, for example, an insulating film containing hydrogen, in other words, an insulating film capable of releasing hydrogen, typically a silicon nitride film, is used to form the second oxide semiconductor films 104 a and 104 b. Hydrogen can be supplied. As the insulating film 118, for example, an insulating film containing hydrogen is used as in the insulating film 106, so that hydrogen can be supplied to the first oxide semiconductor film 110b. As the insulating film capable of releasing hydrogen, the concentration of hydrogen contained in the film is preferably 1 × 10 ²² atoms / cm ³ or more. By forming such an insulating film in contact with the second oxide semiconductor films 104a and 104b and the first oxide semiconductor film 110b, the second oxide semiconductor films 104a and 104b and the first oxide semiconductor film are formed. Hydrogen can be effectively contained in the film 110b. In this manner, the resistivity of the oxide semiconductor film can be controlled by changing the structures of the insulating films in contact with the second oxide semiconductor films 104a and 104b and the first oxide semiconductor film 110b.

  Hydrogen contained in the oxide semiconductor film reacts with oxygen bonded to metal atoms to become water, and forms oxygen vacancies in a lattice from which oxygen is released (or a portion from which oxygen is released). When hydrogen enters the oxygen vacancies, electrons serving as carriers may be generated. In some cases, a part of hydrogen is bonded to oxygen bonded to a metal atom, so that an electron serving as a carrier is generated. Therefore, the second oxide semiconductor films 104a and 104b and the first oxide semiconductor film 110b provided in contact with the insulating film containing hydrogen have a carrier density higher than that of the first oxide semiconductor film 110a. A high oxide semiconductor film is obtained.

In the first oxide semiconductor film 110a in which the channel region of the transistor 150 is formed, hydrogen is preferably reduced as much as possible. Specifically, in the first oxide semiconductor film 110a, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is 2 × 10 ²⁰ atoms / cm ³ or less, preferably 5 × 10 ¹⁹ atoms / cm ³ or less, more preferably 1 × 10 ¹⁹ atoms / cm ³ or less, less than 5 × 10 ¹⁸ atoms / cm ³ , preferably 1 × 10 ¹⁸ atoms / cm ³ or less, more preferably 5 × 10 ¹⁷ atoms / cm ³ or less, more preferably 1 × 10 ¹⁶ atoms / cm ³ or less.

  On the other hand, the second oxide semiconductor films 104a and 104b functioning as the gate electrode of the transistor 150 and the electrode of the capacitor 160, and the oxide semiconductor film 110b functioning as the electrode of the capacitor 160 are formed of the first oxide semiconductor film. The oxide semiconductor film has a higher hydrogen concentration and / or oxygen deficiency than 110a and a low resistivity.

  In addition, the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b have the same metal element. It is preferable that the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b have the same metal element because manufacturing costs can be reduced. Note that the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b may have different compositions even if they have the same metal element. For example, a metal element in a film may be detached during a manufacturing process of a transistor and a capacitor to have a different metal composition.

  As described above, in the semiconductor device of one embodiment of the present invention, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor are formed at the same time. In other words, the conductive film functions as the gate electrode of the transistor. The manufacturing cost can be reduced by forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor over the same surface. In addition, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor each include an oxide semiconductor film. By performing an appropriate treatment on the oxide semiconductor film, a conductive film having low resistivity and translucency can be obtained. By using the conductive film, the transistor and / or the capacitor can be provided with a light-transmitting property.

  Here, details of other components of the semiconductor device illustrated in FIGS. 1A and 1B will be described below.

<Board>
There is no particular limitation on the material of the substrate 102, but it is necessary that the substrate 102 have at least heat resistance to withstand heat treatment performed later. For example, a glass substrate, a ceramic substrate, a quartz substrate, a sapphire substrate, or the like may be used as the substrate 102. In addition, a single crystal semiconductor substrate made of silicon or silicon carbide, a polycrystalline semiconductor substrate, a compound semiconductor substrate such as silicon germanium, an SOI substrate, or the like can be applied, and a semiconductor element is provided over these substrates. A substrate may be used as the substrate 102. When a glass substrate is used as the substrate 102, the sixth generation (1500 mm × 1850 mm), the seventh generation (1870 mm × 2200 mm), the eighth generation (2200 mm × 2400 mm), the ninth generation (2400 mm × 2800 mm), the tenth generation. By using a large area substrate such as a generation (2950 mm × 3400 mm), a large display device can be manufactured. Alternatively, a flexible substrate may be used as the substrate 102, and the transistor 150, the capacitor 160, and the like may be formed directly over the flexible substrate.

  In addition to these, a transistor can be formed using various substrates as the substrate 102. The kind of board | substrate is not limited to a specific thing. Examples of the substrate include a plastic substrate, a metal substrate, a stainless steel substrate, a substrate having a stainless steel foil, a tungsten substrate, a substrate having a tungsten foil, a flexible substrate, a bonded film, and a fibrous material. Or a base film. Examples of the glass substrate include barium borosilicate glass, aluminoborosilicate glass, and soda lime glass. As an example of the flexible substrate, there are plastics typified by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES), or a synthetic resin having flexibility such as acrylic. Examples of the laminated film include polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride. Examples of the base film include polyester, polyamide, polyimide, an inorganic vapor deposition film, and papers. In particular, by manufacturing a transistor using a semiconductor substrate, a single crystal substrate, an SOI substrate, or the like, a transistor with small variation in characteristics, size, or shape, high current capability, and small size can be manufactured. . When a circuit is formed using such transistors, the power consumption of the circuit can be reduced or the circuit can be highly integrated.

  Note that a transistor may be formed using a certain substrate, and then the transistor may be transferred to another substrate, and the transistor may be disposed on another substrate. As an example of the substrate on which the transistor is transferred, in addition to the substrate on which the transistor can be formed, a paper substrate, a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (natural fiber (silk, cotton, hemp), There are synthetic fibers (nylon, polyurethane, polyester) or recycled fibers (including acetate, cupra, rayon, recycled polyester), leather substrates, rubber substrates, and the like. By using these substrates, it is possible to form a transistor with good characteristics, a transistor with low power consumption, manufacture a device that is not easily broken, impart heat resistance, reduce weight, or reduce thickness.

<First oxide semiconductor film and second oxide semiconductor film>
The first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b each include at least indium (In), zinc (Zn), and M (Al, Ti, Ga, Y, Zr, La, Ce). In addition, a film represented by an In-M-Zn oxide containing a metal such as Sn or Hf is preferable. Or it is preferable that both In and Zn are included. In addition, in order to reduce variation in electrical characteristics of the transistor including the oxide semiconductor, a stabilizer is preferably included together with the transistor.

  Examples of the stabilizer include gallium (Ga), tin (Sn), hafnium (Hf), aluminum (Al), zirconium (Zr), and the like, including the metals described in M above. Other stabilizers include lanthanoids such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb). ), Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and the like.

  Examples of oxide semiconductors included in the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b include In—Ga—Zn-based oxides, In—Al—Zn-based oxides, In-Sn-Zn-based oxide, In-Hf-Zn-based oxide, In-La-Zn-based oxide, In-Ce-Zn-based oxide, In-Pr-Zn-based oxide, In-Nd-Zn Oxide, In-Sm-Zn oxide, In-Eu-Zn oxide, In-Gd-Zn oxide, In-Tb-Zn oxide, In-Dy-Zn oxide, In -Ho-Zn-based oxide, In-Er-Zn-based oxide, In-Tm-Zn-based oxide, In-Yb-Zn-based oxide, In-Lu-Zn-based oxide, In-Sn-Ga- Zn-based oxide, In-Hf-Ga-Zn-based oxide, In-Al-G -Zn-based oxide, In-Sn-Al-Zn-based oxide, In-Sn-Hf-Zn-based oxide can be used In-Hf-Al-Zn-based oxide.

  Note that here, an In—Ga—Zn-based oxide means an oxide containing In, Ga, and Zn as its main components, and there is no limitation on the ratio of In, Ga, and Zn. Moreover, metal elements other than In, Ga, and Zn may be contained.

  The first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b have the same metal element among the above oxides. By using the same metal element for the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b, manufacturing cost can be reduced. For example, manufacturing costs can be reduced by using metal oxide targets having the same metal composition. In addition, when a metal oxide target having the same metal composition is used, an etching gas or an etching solution for processing the oxide semiconductor film can be used in common.

<Insulating film>
The insulating films 106 and 107 functioning as the gate insulating film of the transistor 150 and the dielectric film of the capacitor 160 are formed using a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a nitride film by plasma CVD, sputtering, or the like. An insulating layer including one or more of silicon film, aluminum oxide film, hafnium oxide film, yttrium oxide film, zirconium oxide film, gallium oxide film, tantalum oxide film, magnesium oxide film, lanthanum oxide film, cerium oxide film, and neodymium oxide film, Each can be used. Note that a single insulating layer selected from the above materials may be used instead of the stacked structure of the insulating films 106 and 107.

  Note that the insulating film 107 in contact with the first oxide semiconductor film 110a functioning as the channel region of the transistor 150 is preferably an oxide insulating film, and includes a region containing oxygen in excess of the stoichiometric composition ( More preferably, it has an oxygen-excess region. In other words, the insulating film 107 is an insulating film capable of releasing oxygen. In order to provide the oxygen-excess region in the insulating film 107, for example, the insulating film 107 may be formed in an oxygen atmosphere. Alternatively, oxygen may be introduced into the insulating film 107 after film formation to form an oxygen excess region. As a method for introducing oxygen, an ion implantation method, an ion doping method, a plasma immersion ion implantation method, a plasma treatment, or the like can be used.

  In addition, when hafnium oxide is used as the insulating films 106 and 107, the following effects are obtained. Hafnium oxide has a higher dielectric constant than silicon oxide or silicon oxynitride. Therefore, since the physical film thickness can be increased with respect to the equivalent oxide film thickness, the leakage current due to the tunnel current can be reduced even when the equivalent oxide film thickness is 10 nm or less or 5 nm or less. That is, a transistor with a small off-state current can be realized. Further, hafnium oxide having a crystal structure has a higher dielectric constant than hafnium oxide having an amorphous structure. Therefore, in order to obtain a transistor with low off-state current, it is preferable to use hafnium oxide having a crystal structure. Examples of the crystal structure include a monoclinic system and a cubic system. Note that one embodiment of the present invention is not limited thereto.

  Note that in this embodiment, a silicon nitride film is formed as the insulating film 106 and a silicon oxide film is formed as the insulating film 107. The silicon nitride film has a higher relative dielectric constant than that of the silicon oxide film and a large film thickness necessary for obtaining the same capacitance as that of the silicon oxide film. Therefore, the gate insulating film of the transistor 150 and the capacitor 160 By including a silicon nitride film as the insulating film 108 functioning as a dielectric film, the insulating film can be physically thickened. Accordingly, a decrease in the withstand voltage of the transistor 150 and the capacitor 160 can be suppressed, and further, the withstand voltage can be improved, so that electrostatic breakdown of the transistor 150 and the capacitor 160 can be suppressed.

<Source electrode and drain electrode>
As a material that can be used for the source electrode 112a and the drain electrode 112b, a single metal made of aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or a main component thereof is used. The alloy to be used can be used as a single layer structure or a laminated structure. For example, a two-layer structure in which a titanium film is laminated on an aluminum film, a two-layer structure in which a titanium film is laminated on a tungsten film, a two-layer structure in which a copper film is laminated on a molybdenum film, or an alloy film containing molybdenum and tungsten Two-layer structure in which a copper film is laminated, two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a titanium film or a titanium nitride film, and an aluminum film or copper layered on the titanium film or titanium nitride film A three-layer structure in which a film is stacked and a titanium film or a titanium nitride film is further formed thereon, a molybdenum film or a molybdenum nitride film, and an aluminum film or a copper film is stacked on the molybdenum film or the molybdenum nitride film, Further, there is a three-layer structure on which a molybdenum film or a molybdenum nitride film is formed. When the source electrode 112a and the drain electrode 112b have a three-layer structure, the first and third layers include titanium, titanium nitride, molybdenum, tungsten, an alloy containing molybdenum and tungsten, an alloy containing molybdenum and zirconium, Alternatively, a film made of molybdenum nitride is preferably formed, and a film made of a low resistance material such as copper, aluminum, gold or silver, or an alloy of copper and manganese is preferably formed as the second layer. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used. A material that can be used for the source electrode 112a and the drain electrode 112b can be formed by a sputtering method, for example.

<Protective insulating film>
As the insulating films 114, 116, and 118 that function as protective insulating films for the transistor 150 and the insulating film 118 that functions as a protective insulating film for the capacitor 160, a silicon oxide film or a silicon oxynitride film is formed by a plasma CVD method, a sputtering method, or the like. Silicon nitride oxide film, silicon nitride film, aluminum oxide film, hafnium oxide film, yttrium oxide film, zirconium oxide film, gallium oxide film, tantalum oxide film, magnesium oxide film, lanthanum oxide film, cerium oxide film and neodymium oxide film One or more insulating layers can be used.

  Note that in the capacitor 160, the insulating film 118 also has a function of reducing the resistivity of the first oxide semiconductor film 110 b that functions as an electrode of the capacitor 160.

  The insulating film 114 in contact with the first oxide semiconductor film 110a functioning as the channel region of the transistor 150 is preferably an oxide insulating film, and an insulating film capable of releasing oxygen is used. In other words, the insulating film capable of releasing oxygen is an insulating film having a region (oxygen-excess region) containing oxygen in excess of the stoichiometric composition. In order to provide the oxygen excess region in the insulating film 114, for example, the insulating film 114 may be formed in an oxygen atmosphere. Alternatively, oxygen may be introduced into the insulating film 114 after film formation to form an oxygen excess region. As a method for introducing oxygen, an ion implantation method, an ion doping method, a plasma immersion ion implantation method, a plasma treatment, or the like can be used.

By using an insulating film capable of releasing oxygen as the insulating film 114, oxygen is transferred to the first oxide semiconductor film 110 a functioning as a channel region of the transistor 150, so that the first oxide semiconductor film 110 a It is possible to reduce the amount of oxygen deficiency. For example, oxygen molecules measured by thermal desorption gas analysis (hereinafter referred to as TDS analysis) performed by heat treatment at a film surface temperature of 100 ° C. to 700 ° C., preferably 100 ° C. to 500 ° C. With the use of the insulating film having a release amount of 1.0 × 10 ¹⁸ molecules / cm ³ or more, the amount of oxygen vacancies contained in the first oxide semiconductor film 110a can be reduced.

  The thickness of the insulating film 114 can be 5 nm to 150 nm, preferably 5 nm to 50 nm, preferably 10 nm to 30 nm. The thickness of the insulating film 116 can be greater than or equal to 30 nm and less than or equal to 500 nm, preferably greater than or equal to 150 nm and less than or equal to 400 nm.

  In addition, since the insulating films 114 and 116 can be formed using the same kind of insulating film, the interface between the insulating film 114 and the insulating film 116 may not be clearly confirmed. Therefore, in this embodiment mode, the interface between the insulating film 114 and the insulating film 116 is indicated by a broken line. Note that in this embodiment, the two-layer structure of the insulating film 114 and the insulating film 116 is described; however, the present invention is not limited to this, and for example, It is good also as a laminated structure of three or more layers.

  Note that the insulating film 122 may be provided between the source electrode 112a and the drain electrode 112b and the first oxide semiconductor film 110a. An example in that case is shown in FIGS. The source electrode 112 a and the drain electrode 112 b are connected to the first oxide semiconductor film 110 a through a contact hole provided in the insulating film 122. The insulating film 122 can employ the same material and film quality as those described for the insulating film 108.

<Method for Manufacturing Display Device>
Next, an example of a method for manufacturing the semiconductor device illustrated in FIGS. 1A and 1B will be described with reference to FIGS.

  First, the gate electrode including the second oxide semiconductor film 104a and the second oxide semiconductor film 104b functioning as one electrode of the pair of electrodes are formed over the substrate 102. After that, the insulating film 108 including the insulating films 106 and 107 is formed over the substrate 102 and the second oxide semiconductor films 104a and 104b (see FIG. 2A).

  Note that the substrate 102, the second oxide semiconductor films 104a and 104b, and the insulating films 106 and 107 can be formed by being selected from the materials listed above. Note that in this embodiment, a glass substrate is used as the substrate 102, and an In—Ga—Zn oxide film (In: Ga: Zn = 1: 1: 1) is used as the second oxide semiconductor films 104a and 104b. 1 is used, and a silicon nitride film capable of releasing hydrogen is used as the insulating film 106, and a silicon oxynitride capable of releasing oxygen is used as the insulating film 107. Use a membrane.

  By providing the second oxide semiconductor films 104a and 104b with a silicon nitride film capable of releasing hydrogen, the resistivity of the second oxide semiconductor films 104a and 104b can be reduced.

  The second oxide semiconductor films 104a and 104b are patterned so that a desired region of the oxide semiconductor film remains after the oxide semiconductor film is formed over the substrate 102, and then unnecessary regions are etched. Is formed.

  Next, the first oxide semiconductor film 110a and the second oxide semiconductor film 104b on the insulating film 108 are overlapped with each other at a position overlapping with the gate electrode including the second oxide semiconductor film 104a over the insulating film 108. A first oxide semiconductor film 110b is formed in each position (see FIG. 2B).

  The first oxide semiconductor films 110a and 110b can be formed by selecting from the materials listed above. Note that in this embodiment, an In—Ga—Zn oxide film (a metal oxide target of In: Ga: Zn = 1: 1: 1 is used as the first oxide semiconductor films 110a and 110b. ) Is used.

  The first oxide semiconductor films 110a and 110b are patterned so that a desired region of the oxide semiconductor film remains after the oxide semiconductor film is formed over the insulating film 108, and then unnecessary regions are etched. It is formed by doing.

  In addition, since the first oxide semiconductor film 110a and the first oxide semiconductor film 110b are formed by processing from the same oxide semiconductor film, at least the same metal element is included. In addition, when the first oxide semiconductor films 110a and 110b are etched, a part of the insulating film 107 (a region exposed from the first oxide semiconductor films 110a and 110b) is etched by over-etching to have a film thickness. May decrease.

  It is preferable to perform heat treatment after the formation of the first oxide semiconductor films 110a and 110b. The heat treatment is performed at a temperature of 250 ° C. or higher and 650 ° C. or lower, preferably 300 ° C. or higher and 500 ° C. or lower, more preferably 350 ° C. or higher and 450 ° C. or lower, an inert gas atmosphere, an atmosphere containing an oxidizing gas of 10 ppm or more, or a reduced pressure atmosphere Just do it. The heat treatment may be performed in an atmosphere containing 10 ppm or more of an oxidizing gas in order to supplement oxygen released from the first oxide semiconductor films 110a and 110b after the heat treatment in an inert gas atmosphere. . By the heat treatment here, impurities such as hydrogen and water can be removed from at least one of the insulating films 106 and 107 and the first oxide semiconductor films 110a and 110b. Note that the heat treatment may be performed before the first oxide semiconductor films 110a and 110b are processed into island shapes.

  Note that in order to impart stable electric characteristics to the transistor 150 including the first oxide semiconductor film 110a as a channel region, impurities in the first oxide semiconductor film 110a are reduced and the first oxide semiconductor film 110a is used. It is effective to make the film 110a intrinsic or substantially intrinsic.

  Next, a conductive film is formed over the insulating film 108 and the first oxide semiconductor films 110a and 110b, patterned so that a desired region of the conductive film remains, and then unnecessary regions are etched. Then, the source electrode 112a and the drain electrode 112b are formed over the insulating film 108 and the first oxide semiconductor film 110a (see FIG. 2C).

  The source electrode 112a and the drain electrode 112b can be formed by selecting from the materials listed above. Note that in this embodiment, a three-layer structure of a titanium film, an aluminum film, and a titanium film is used as the source electrode 112a and the drain electrode 112b.

  Next, insulating films 114 and 116 are formed over the insulating film 108, the first oxide semiconductor films 110a and 110b, the source electrode 112a, and the drain electrode 112b (see FIG. 2D).

  The insulating films 114 and 116 can be formed by selecting from the materials listed above. Note that in this embodiment, as the insulating films 114 and 116, a silicon oxynitride film capable of releasing oxygen is used.

  Next, patterning is performed so that desired regions of the insulating films 114 and 116 remain, and then unnecessary regions are etched to form openings 140 (see FIG. 3A).

  The opening 140 is formed so that the first oxide semiconductor film 110b is exposed. As a method for forming the opening 140, for example, a dry etching method can be used. However, the formation method of the opening 140 is not limited to this, and may be a wet etching method or a formation method in which a dry etching method and a wet etching method are combined. Note that the thickness of the first oxide semiconductor film 110b may be reduced by the etching step for forming the opening 140.

  Thereafter, it is preferable to perform a heat treatment. Through the heat treatment, part of oxygen contained in the insulating film 114 or the insulating film 116 can be moved to the first oxide semiconductor film 110a so that oxygen vacancies in the first oxide semiconductor film 110a can be filled. It is. As a result, the amount of oxygen vacancies contained in the first oxide semiconductor film 110a can be reduced. On the other hand, since the amount of oxygen vacancies in the first oxide semiconductor film 110b that is not in contact with the insulating film 114 is not reduced, the first oxide semiconductor film 110b contains more oxygen vacancies than the first oxide semiconductor film 110a. Will be. The conditions for the heat treatment can be the same as those after the first oxide semiconductor films 110a and 110b are formed.

  Next, the insulating film 118 is formed over the insulating film 116 and the first oxide semiconductor film 110b so as to cover the opening 140 (see FIG. 3B).

  The insulating film 118 can be formed by selecting from the materials listed above. Note that in this embodiment, a silicon nitride film capable of releasing hydrogen is used as the insulating film 118. When hydrogen contained in the insulating film 118 diffuses into the first oxide semiconductor film 110b, the resistivity of the first oxide semiconductor film 110b decreases. Note that as the resistivity of the first oxide semiconductor film 110b is decreased, the hatching of the first oxide semiconductor film 110b illustrated in FIGS. 3A and 3B is changed.

The resistivity of the first oxide semiconductor film 110b is at least lower than that of the first oxide semiconductor film 110a, preferably 1 × 10 ⁻³ Ωcm or more and less than 1 × 10 ⁴ Ωcm, more preferably 1 × 10. It is good that it is ⁻³ Ωcm or more and less than 1 × 10 ⁻¹ Ωcm. Note that the insulating film 118 also has an effect of preventing impurities from the outside, for example, water, alkali metal, alkaline earth metal, and the like from diffusing into the first oxide semiconductor film 110a included in the transistor 150.

  In addition, the silicon nitride film used as the insulating film 118 in this embodiment is preferably formed at a high temperature in order to improve blockability, for example, 100 ° C. or higher and lower than the strain point of the substrate, more preferably 300 ° C. It is preferable to form a film by heating at a temperature of 400 ° C. or lower.

  Further, the capacitor 160 is manufactured with the formation of the first oxide semiconductor film 110b. The capacitor 160 has a structure in which a dielectric layer is sandwiched between a pair of electrodes, one of the pair of electrodes is the second oxide semiconductor film 104b, and the other of the pair of electrodes is the first oxide semiconductor. This is the film 110b. Further, the insulating film 108 functions as a dielectric layer of the capacitor 160.

  Through the above steps, the transistor 150 and the capacitor 160 can be formed over the same substrate.

  As described above, the structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.

(Embodiment 2)
In this embodiment, a modified example of the semiconductor device described in Embodiment 1 will be described with reference to FIGS. Note that portions that are the same as those shown in FIGS. 1 to 3 of Embodiment 1 or have the same functions are denoted by the same reference numerals, and repeated description thereof is omitted.

<Configuration Example of Semiconductor Device (Modification 1)>
4A is a top view of the semiconductor device of one embodiment of the present invention, and FIG. 4B is a cross-sectional view taken along the dashed-dotted line EF and between the dashed-dotted line GH in FIG. It corresponds to a sectional view of the surface. Note that in FIG. 4A, some components (such as a gate insulating film) of the semiconductor device are omitted in order to avoid complexity.

  4A and 4B includes a transistor 151 including a first oxide semiconductor film 110a and a second oxide semiconductor film 104a, and a capacitor including an insulating film between a pair of electrodes. Element 161. Note that in the capacitor 161, one of the pair of electrodes is the first oxide semiconductor film 104b on the same plane as the second oxide semiconductor film 104a, and the other of the pair of electrodes is the conductive film 120.

  The transistor 151 includes a gate electrode including the second oxide semiconductor film 104a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104a, and the insulating film 108. The gate electrode includes the first oxide semiconductor film 110a at a position overlapping with the gate electrode including the second oxide semiconductor film 104a, and the source electrode 112a and the drain electrode 112b on the first oxide semiconductor film 110a. Note that the transistor 151 illustrated in FIGS. 4A and 4B has a so-called bottom gate structure.

  In addition, insulating films 114, 116, and 118 are formed over the transistor 151, more specifically, over the first oxide semiconductor film 110a, the source electrode 112a, and the drain electrode 112b. The insulating films 114, 116, and 118 have a function as a protective insulating film of the transistor 151. In addition, an opening 142 reaching the drain electrode 112 b is formed in the insulating films 114, 116, and 118, and a conductive film 120 is formed on the insulating film 118 so as to cover the opening 142. The conductive film 120 functions as, for example, a pixel electrode.

  The capacitor 161 includes a second oxide semiconductor film 104b that functions as one of a pair of electrodes over the substrate 102, and an insulating film 108 that functions as a dielectric film over the second oxide semiconductor film 104b. , 114, 116, 118, and the conductive film 120 functioning as the other of the pair of electrodes at positions overlapping with the second oxide semiconductor film 104 b with the insulating films 108, 114, 116, 118 interposed therebetween, Have That is, the conductive film 120 has a function as a pixel electrode and a function as an electrode of a capacitor.

  Note that as described above, the insulating film 108 functions as a gate insulating film in the transistor 151, and functions as part of a dielectric film in the capacitor 161. The insulating films 114, 116, and 118 function as protective insulating films in the transistor 151, and function as part of a dielectric film in the capacitor 161. 4A and 4B illustrate the structure in which the insulating films 114, 116, and 118 are provided as part of the dielectric film, the present invention is not limited to this. For example, in the manufacturing process of the transistor 151, the insulating films 114, 116, and 118 of the capacitor 161 may be removed when the opening 142 is formed.

  Further, the capacitor 161 has a light-transmitting property. That is, the second oxide semiconductor film 104b, the insulating films 108, 114, 116, and 118, and the conductive film 120 included in the capacitor 161 are each formed using a light-transmitting material. In this manner, since the capacitor 161 has a light-transmitting property, the capacitor 161 can be formed large (in a large area) in a region other than a portion where the transistor in the pixel is formed. Therefore, the capacitance value can be increased while increasing the aperture ratio. An increased semiconductor device can be obtained. As a result, a semiconductor device having excellent display quality can be obtained. Further, the capacitor 161 can be manufactured by using a manufacturing process of the transistor 151. Therefore, a semiconductor device with a low manufacturing cost can be obtained.

  Note that as the insulating films 106 and 118, an insulating film containing at least hydrogen is used. As the insulating films 107, 114, and 116, an insulating film containing at least oxygen is used. In this manner, the insulating film used for the transistor 151 and the capacitor 161 or the insulating film in contact with the transistor 151 and the capacitor 161 is used as the insulating film having the above structure, whereby the first oxidation of the transistor 151 and the capacitor 161 is performed. The resistivity of the physical semiconductor film and the second oxide semiconductor film can be controlled.

  Note that the resistivity of the first oxide semiconductor film 110a and the second oxide semiconductor films 104a and 104b can be controlled with reference to the description in Embodiment 1.

  A main difference between the semiconductor device described in FIGS. 1A and 1B of Embodiment 1 and the semiconductor device illustrated in FIGS. 4A and 4B is that the other electrode of the capacitor 161 is electrically conductive. This is the point that the film 120 is used. As described above, the other of the pair of electrodes of the capacitor 161 may be the conductive film 120 functioning as a pixel electrode.

  As described above, in the semiconductor device of one embodiment of the present invention, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor are formed at the same time, in other words, functioning as the gate electrode of the transistor. The manufacturing cost can be reduced by forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor over the same surface. In addition, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor each include an oxide semiconductor film. By performing an appropriate treatment on the oxide semiconductor film, a conductive film with high conductivity and translucency can be obtained. By using the conductive film, the transistor and / or the capacitor can be provided with a light-transmitting property.

  Note that the insulating film 122 may be provided between the source electrode 112a and the drain electrode 112b and the first oxide semiconductor film 110a. An example in that case is shown in FIGS.

  Note that the conductive film 120a formed at the same time as the conductive film 120 and etched at the same time may be provided so as to overlap with the channel region of the transistor. Examples of such cases are shown in FIGS. 15A and 19A. For example, the conductive film 120a has the same material because it is formed at the same time as the conductive film 120, etched at the same time, and formed at the same time. Therefore, an increase in process steps can be suppressed. Note that one embodiment of the present invention is not limited to this. The conductive film 120a may be formed in a step different from that of the conductive film 120. The conductive film 120a has a region overlapping with the channel region of the transistor. Therefore, the conductive film 120a functions as the second gate electrode of the transistor. Therefore, the conductive film 120a may be connected to the second oxide semiconductor film 104a. Alternatively, the conductive film 120a may be supplied with a different signal or a different potential from the second oxide semiconductor film 104a without being connected to the second oxide semiconductor film 104a.

  Here, details of other components of the semiconductor device illustrated in FIGS. 4A and 4B will be described below.

<Conductive film>
The conductive film 120 functions as a pixel electrode. For the conductive film 120, for example, a material having a light-transmitting property in visible light may be used. Specifically, a material containing one kind selected from indium (In), zinc (Zn), and tin (Sn) may be used. As the conductive film 120, for example, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium tin oxide (ITO ), A light-transmitting conductive material such as indium zinc oxide or indium tin oxide to which silicon oxide is added can be used. Further, the conductive film 120 can be formed by, for example, a sputtering method.

<Method for Manufacturing Display Device (Modification 1)>
Next, an example of a method for manufacturing the semiconductor device illustrated in FIGS. 4A and 4B will be described with reference to FIGS.

  First, the gate electrode including the second oxide semiconductor film 104a and the second oxide semiconductor film 104b functioning as one electrode of the pair of electrodes are formed over the substrate 102. After that, the insulating film 108 including the insulating films 106 and 107 is formed over the second oxide semiconductor films 104a and 104b (see FIG. 5A).

  Next, the first oxide semiconductor film 110a is formed over the insulating film 108 at a position overlapping with the gate electrode including the second oxide semiconductor film 104a (see FIG. 5B).

  The first oxide semiconductor film 110a is formed by forming an oxide semiconductor film over the insulating film 108, patterning the oxide semiconductor film so that a desired region remains, and then etching unnecessary regions. Is done.

  In addition, when the first oxide semiconductor film 110a is etched, part of the insulating film 107 (a region exposed from the first oxide semiconductor film 110a) is etched by overetching, so that the film thickness is reduced. is there.

  After the first oxide semiconductor film 110a is formed, heat treatment is preferably performed. This heat treatment can be performed in consideration of the heat treatment after the formation of the first oxide semiconductor film 110a in Embodiment 1.

  Next, a conductive film is formed over the insulating film 108 and the first oxide semiconductor film 110a, patterned so that a desired region of the conductive film remains, and then an unnecessary region is etched to first. A source electrode 112a and a drain electrode 112b are formed over the oxide semiconductor film 110a (see FIG. 5C).

  Next, insulating films 114, 116, and 118 are formed over the insulating film 108, the first oxide semiconductor film 110a, the source electrode 112a, and the drain electrode 112b (see FIG. 5D).

  Next, patterning is performed so that a desired region of the insulating films 114, 116, and 118 remains, and then an unnecessary region is etched to form an opening 142 (see FIG. 6A).

  The opening 142 is formed so that the drain electrode 112b is exposed. As a method for forming the opening 142, for example, a dry etching method can be used. However, the formation method of the opening 142 is not limited to this, and may be a wet etching method or a formation method in which a dry etching method and a wet etching method are combined.

  Next, a conductive film is formed over the insulating film 118 so as to cover the opening 142, and patterning and etching are performed so that a desired region of the conductive film remains, so that the conductive film 120 is formed (FIG. 6B). reference).

  Through the above steps, the transistor 151 and the capacitor 161 can be formed over the same substrate.

  Note that the insulating film 118 a may be provided over the insulating film 118. Examples of such cases are shown in FIGS. 15B and 15C and FIGS. 19B and 19C. The insulating film 118a can be formed using an organic resin material, for example. Examples of a material that can be used for the insulating film 118a include acrylic resin, polyimide resin, and polyamide resin.

  Note that as shown in FIGS. 15C and 19C, a conductive film 121 may be provided. The conductive film 121 may be provided so as to overlap with a channel region of the transistor. The conductive film 121 may be formed using a material similar to that described for the conductive film 120. The conductive film 121 has a region overlapping with the channel region of the transistor. Therefore, the conductive film 121 functions as a second gate electrode of the transistor. Therefore, the conductive film 121 may be connected to the second oxide semiconductor film 104a. Alternatively, the conductive film 121 may be supplied with a different signal or a different potential from the second oxide semiconductor film 104a without being connected to the second oxide semiconductor film 104a.

  Note that the capacitor may be formed by forming the conductive film 121 at the same time as the conductive film 121 and simultaneously etching the conductive film 121a so as to overlap with the electrode of the capacitor. Examples of such cases are shown in FIGS. 20 (A), (B), and (C). As a result, the capacitance value of the capacitive element can be increased.

  As described above, the structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.

(Embodiment 3)
In this embodiment, a modified example of the semiconductor device described in Embodiment 1 will be described with reference to FIGS. Note that portions that are the same as those shown in FIGS. 1 to 3 of Embodiment 1 or have the same functions are denoted by the same reference numerals, and repeated description thereof is omitted.

<Configuration Example of Semiconductor Device (Modification 2)>
7A is a top view of the semiconductor device of one embodiment of the present invention, and FIG. 7B is a cross-sectional view taken along the dashed-dotted line I-J and between the dashed-dotted line KL in FIG. It corresponds to a sectional view of the surface. Note that in FIG. 7A, some components (such as a gate insulating film) of the semiconductor device are omitted in order to avoid complexity.

  A semiconductor device illustrated in FIGS. 7A and 7B includes a transistor 152 including a first oxide semiconductor film 110a and a second oxide semiconductor film 104a, and a capacitor including an insulating film between a pair of electrodes. An element 162.

  The transistor 152 includes a gate electrode including the second oxide semiconductor film 104a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104a, and the insulating film 108. The gate electrode includes the first oxide semiconductor film 110a at a position overlapping with the gate electrode including the second oxide semiconductor film 104a, and the source electrode 112a and the drain electrode 112b on the first oxide semiconductor film 110a. Note that the transistor 152 illustrated in FIGS. 7A and 7B has a so-called bottom gate structure.

  In addition, insulating films 114, 116, and 118 are formed over the transistor 152, more specifically, over the first oxide semiconductor film 110a, the source electrode 112a, and the drain electrode 112b. The insulating films 114, 116, and 118 function as protective insulating films for the transistor 152. In addition, an opening 142 reaching the drain electrode 112 b is formed in the insulating films 114, 116, and 118, and a conductive film 120 is formed on the insulating film 118 so as to cover the opening 142. The conductive film 120 functions as, for example, a pixel electrode.

  In the capacitor 162, one of the pair of electrodes is the second oxide semiconductor film 104b, and the other of the pair of electrodes is the conductive film 120. The capacitor 162 further includes an electrode between the pair of electrodes. The electrode is a first oxide semiconductor film 110b formed on the same plane as the first oxide semiconductor film 110a.

  As described above, by further providing an electrode between the pair of electrodes, the capacitance can be increased without increasing the area of the capacitor. For example, the capacitor 162 can be regarded as the following structure. The capacitor 162 includes a first capacitor using the insulating film 108 sandwiched between the second oxide semiconductor film 104b and the first oxide semiconductor film 110a as a dielectric film, and the first oxide semiconductor film 110a. And a second capacitor element in which an insulating film 118 sandwiched between the conductive films 120 is used as a dielectric film.

  Note that as described above, the insulating film 108 functions as a gate insulating film in the transistor 152 and functions as part of a dielectric film in the capacitor 162. The insulating films 114, 116, and 118 function as protective insulating films in the transistor 152. In addition, the insulating film 118 functions as part of the dielectric film in the capacitor 162.

  Further, the capacitor 162 has a light-transmitting property. That is, the first oxide semiconductor film 110b, the second oxide semiconductor film 104b, the insulating films 108 and 118, and the conductive film 120 included in the capacitor 162 are each formed using a light-transmitting material. In this manner, since the capacitor 162 has a light-transmitting property, the capacitor 162 can be formed large (in a large area) in a region other than a portion where a transistor is formed in a pixel, so that the capacitance value can be increased while increasing the aperture ratio. An increased semiconductor device can be obtained. As a result, a semiconductor device having excellent display quality can be obtained. Further, the capacitor 162 can be manufactured by using a manufacturing process of the transistor 152. Therefore, a semiconductor device with a low manufacturing cost can be obtained.

  Note that as the insulating films 106 and 118, an insulating film containing at least hydrogen is used. As the insulating films 107, 114, and 116, an insulating film containing at least oxygen is used. As described above, the insulating film used for the transistor 152 and the capacitor 162 or the insulating film in contact with the transistor 152 and the capacitor 162 is the insulating film having the above structure, whereby the first oxidation of the transistor 152 and the capacitor 162 is performed. The resistivity of the physical semiconductor film and the second oxide semiconductor film can be controlled.

  Note that the resistivity of the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b can be controlled with reference to the description in Embodiment 1.

  A main difference between the semiconductor device illustrated in FIGS. 1A and 1B of Embodiment 1 and the semiconductor device illustrated in FIGS. 7A and 7B is an electrode structure of the capacitor 162.

  In the semiconductor device of one embodiment of the present invention, a conductive film functioning as a gate electrode of a transistor and a conductive film functioning as an electrode of a capacitor are formed at the same time; in other words, a conductive film functioning as a gate electrode of a transistor By forming a conductive film functioning as an electrode of a capacitor over the same surface, manufacturing cost can be reduced. In addition, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor each include an oxide semiconductor film. By performing an appropriate treatment on the oxide semiconductor film, a conductive film with high conductivity and translucency can be obtained. By using the conductive film, the transistor and / or the capacitor can be provided with a light-transmitting property.

  Note that as a method for manufacturing the semiconductor device illustrated in FIGS. 7A and 7B, the semiconductor device illustrated in FIGS. 1A and 1B and the semiconductor device illustrated in FIGS. It can be formed by combining manufacturing methods.

  Note that as in FIG. 15A, the conductive film 120a may be provided so as to overlap with a channel region of the transistor. Examples of such cases are shown in FIGS. 16 (A) and 19 (A).

  Further, as in FIGS. 15B and 15C, the insulating film 118 a may be provided over the insulating film 118. Examples of such cases are shown in FIGS. 16B and 16C, and FIGS. 19B and 19C.

  As described above, the structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.

(Embodiment 4)
In this embodiment, a modified example of the semiconductor device described in Embodiment 1 will be described with reference to FIGS. Note that portions that are the same as those shown in FIGS. 1 to 3 of Embodiment 1 or have the same functions are denoted by the same reference numerals, and repeated description thereof is omitted.

<Configuration Example of Semiconductor Device (Modification 3)>
8A is a top view of the semiconductor device of one embodiment of the present invention, and FIG. 8B is a cross-sectional view taken along the dashed-dotted line MN and between the dashed-dotted line OP in FIG. It corresponds to a sectional view of the surface. Note that in FIG. 8A, some components (such as a gate insulating film) of the semiconductor device are omitted in order to avoid complexity.

  8A and 8B includes a transistor 250 including a first oxide semiconductor film 210 and a second oxide semiconductor film 204a, and a capacitor including an insulating film between a pair of electrodes. And element 260. Note that in the capacitor 260, one of the pair of electrodes is the second oxide semiconductor film 204b on the same plane as the second oxide semiconductor film 204a, and the other of the pair of electrodes is the conductive film 220.

  The transistor 250 includes an insulating film 216 over the substrate 202, a first oxide semiconductor film 210 over the insulating film 216, a source electrode 212 a and a drain electrode 212 b over the first oxide semiconductor film 210, An insulating film 208 functioning as a gate insulating film over the oxide semiconductor film 210; a gate electrode including a second oxide semiconductor film 204a in a position overlapping with the first oxide semiconductor film 210 over the insulating film 208; Have Note that the transistor 250 illustrated in FIGS. 8A and 8B has a so-called top gate structure.

  In addition, insulating films 218 and 217 are formed over the transistor 250, more specifically over the gate electrode, the source electrode 212a, and the drain electrode 212b including the second oxide semiconductor film 204a. The insulating films 218 and 217 have a function as a protective insulating film of the transistor 250. In addition, an opening 240 reaching the drain electrode 212 b is formed in the insulating films 218 and 217, and a conductive film 220 is formed on the insulating film 217 so as to cover the opening 240. The conductive film 220 functions as a pixel electrode, for example.

  The capacitor 260 includes an insulating film 216 over the substrate 202, an insulating film 208 over the insulating film 216, a second oxide semiconductor film 204 b that functions as one of a pair of electrodes over the insulating film 208, The insulating films 218 and 217 functioning as dielectric films over the second oxide semiconductor film 204b and the other of the pair of electrodes at positions overlapping with the second oxide semiconductor film 204b with the insulating films 218 and 217 interposed therebetween And a conductive film 220 having a function. That is, the conductive film 220 has a function as a pixel electrode and a function as an electrode of a capacitor.

  Note that as described above, the insulating film 208 functions as a gate insulating film in the transistor 250, and functions as part of a dielectric film in the capacitor 260. The insulating films 218 and 217 function as protective insulating films in the transistor 250 and function as part of a dielectric film in the capacitor 260. 8A and 8B illustrate the structure in which the insulating films 218 and 217 are provided as part of the dielectric film, the present invention is not limited to this. For example, part of the insulating films 218 and 217 of the capacitor 260 may be removed during the manufacturing process of the transistor 250.

  Further, the capacitor 260 has a light-transmitting property. That is, the insulating films 216, 206, 207, 218, and 217 included in the capacitor 260 are each formed using a light-transmitting material. In this manner, since the capacitor 260 has a light-transmitting property, the capacitor 260 can be formed large (in a large area) in a region other than a portion where the transistor in the pixel is formed, so that the capacitance value can be increased while increasing the aperture ratio. An increased semiconductor device can be obtained. As a result, a semiconductor device having excellent display quality can be obtained. Further, the capacitor 260 can be manufactured by using a manufacturing process of the transistor 250. Therefore, a semiconductor device with a low manufacturing cost can be obtained.

  Note that as the insulating films 207 and 218, an insulating film containing at least hydrogen is used. As the insulating films 216, 206, and 217, an insulating film containing at least oxygen is used. As described above, the insulating film used for the transistor 250 and the capacitor 260 or the insulating film in contact with the transistor 250 and the capacitor 260 is the insulating film having the above structure, whereby the first oxidation of the transistor 250 and the capacitor 260 is performed. The resistivity of the physical semiconductor film and the second oxide semiconductor film can be controlled.

  Specifically, in the transistor 250, since the first oxide semiconductor film 210 is used as a channel formation region, the resistivity is higher than those of the second oxide semiconductor films 204a and 204b. On the other hand, since the second oxide semiconductor films 204a and 204b function as electrodes, the resistivity is low.

  Here, a method for controlling the resistivity of the first oxide semiconductor film 210 and the second oxide semiconductor films 204a and 204b is described below.

<Method 2 for controlling resistivity of oxide semiconductor>
The oxide semiconductor that can be used for the first oxide semiconductor film 210 and the second oxide semiconductor films 204a and 204b has oxygen vacancies in the film and / or concentration of impurities such as hydrogen and water in the film. It is a semiconductor material whose resistivity can be controlled. Therefore, a process for increasing oxygen vacancies and / or impurity concentrations or a process for reducing oxygen vacancies and / or impurity concentrations is selected for the first oxide semiconductor film 210 and the second oxide semiconductor films 204a and 204b. Thus, the resistivity of each oxide semiconductor can be controlled.

  Specifically, plasma treatment is performed on the oxide semiconductor film used for the second oxide semiconductor film 204a functioning as the gate electrode of the transistor 250 and the second oxide semiconductor film 204b functioning as the electrode of the capacitor 260; By increasing oxygen vacancies in the oxide semiconductor film and / or increasing impurities such as hydrogen and water in the oxide semiconductor film, the oxide semiconductor film has a high carrier density and a low resistance. Can do. An oxide semiconductor with high carrier density and low resistivity is formed by forming an oxide semiconductor in contact with an insulating film containing hydrogen and diffusing hydrogen from the insulating film containing hydrogen into the oxide semiconductor. Can do.

  On the other hand, the first oxide semiconductor film 210 functioning as a channel formation region of the transistor 250 is not in contact with the insulating film 218 containing hydrogen by providing the insulating films 216 and 206. Further, at least one of the insulating films 216 and 206 is an insulating film from which oxygen can be released, so that oxygen can be supplied to the first oxide semiconductor film 210. The first oxide semiconductor film 210 to which oxygen is supplied becomes a high-resistance oxide semiconductor by filling oxygen vacancies in the film or at the interface. Note that as the insulating film from which oxygen can be released, for example, a silicon oxide film or a silicon oxynitride film can be used.

  As described above, in the semiconductor device of one embodiment of the present invention, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor are formed at the same time, in other words, functioning as the gate electrode of the transistor. The manufacturing cost can be reduced by forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor over the same surface. In addition, the conductive film functioning as the gate electrode of the transistor and the conductive film functioning as the electrode of the capacitor each include an oxide semiconductor film. By performing an appropriate treatment on the oxide semiconductor film, a conductive film with high conductivity and translucency can be obtained. By using the conductive film, the transistor and / or the capacitor can be provided with a light-transmitting property.

  Here, details of other components of the semiconductor device illustrated in FIGS. 8A and 8B will be described below.

<Insulating film>
The insulating film 216 can be formed using the materials listed for the insulating film 116 in Embodiment 1. The insulating films 206 and 207 can be formed by using the materials listed in the insulating films 106 and 107 of Embodiment 1, respectively.

<First oxide semiconductor film and second oxide semiconductor film>
The first oxide semiconductor film 210 can be formed using the materials listed for the first oxide semiconductor film 110a in Embodiment 1. The second oxide semiconductor films 204a and 204b can be formed using the materials listed in the second oxide semiconductor films 104a and 104b in Embodiment 1.

<Source electrode and drain electrode>
The source electrode 212a and the drain electrode 212b can be formed using the materials listed for the source electrode 112a and the drain electrode 112b in Embodiment 1.

<Conductive film>
The conductive film 220 can be formed using the materials listed for the conductive film 120 in Embodiment 2.

<Method for Manufacturing Display Device (Modification 2)>
Next, an example of a method for manufacturing the semiconductor device illustrated in FIGS. 8A and 8B will be described with reference to FIGS.

  First, the insulating film 216 is formed over the substrate 202, and an oxide semiconductor film is formed over the insulating film 216. After that, patterning is performed so that a desired region of the oxide semiconductor film remains, and then unnecessary regions are etched to form a first oxide semiconductor film 210 (see FIG. 9A).

  Next, a conductive film is formed over the insulating film 216 and the first oxide semiconductor film 210, patterned so that a desired region of the conductive film remains, and then an unnecessary region is etched, whereby the source electrode is etched. 212a and a drain electrode 212b are formed (see FIG. 9B).

  Next, the insulating film 208 including the insulating films 206 and 207 and the second oxide semiconductor film 204 are formed over the insulating film 216, the first oxide semiconductor film 210, the source electrode 212a, and the drain electrode 212b. (See FIG. 9C).

  Next, a resist mask is formed over the second oxide semiconductor film 204, patterned so that a desired region of the second oxide semiconductor film 204 remains, and then unnecessary regions are etched, whereby the second region is etched. The oxide semiconductor films 204a and 204b are formed. At this time, the insulating films 206 and 207 below the second oxide semiconductor films 204a and 204b are also etched at the same time to form insulating films 206 and 207 separated into island shapes (see FIG. 9D).

  Next, insulating films 218 and 217 are formed over the insulating film 216, the source electrode 212a, the drain electrode 212b, and the second oxide semiconductor films 204a and 204b (see FIG. 10A).

  Next, a resist mask is formed over the insulating film 217, patterning is performed so that desired regions of the insulating films 218 and 217 are left, and then unnecessary regions are etched to form openings 240. Note that the opening 240 is formed so as to reach the drain electrode 212b (see FIG. 10B).

  Next, a conductive film is formed over the insulating film 217 so as to cover the opening 240, a resist mask is formed over the conductive film, and patterning is performed so that a desired region of the conductive film remains, and then unnecessary regions are formed. The conductive film 220 is formed by etching (see FIG. 10C).

  Through the above steps, the transistor 250 and the capacitor 260 can be formed over the same substrate.

  As described above, the structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.

(Embodiment 5)
In this embodiment, a modified example of the semiconductor device described in Embodiment 1 will be described with reference to FIGS.

<Configuration Example of Semiconductor Device (Modification 4)>
The semiconductor device illustrated in FIG. 11A has a structure in which the first oxide semiconductor films 110a and 110b of the transistor 150 and the capacitor 160 described in Embodiment 1 are oxide stacked films 410a and 410b. Therefore, other structures are the same as those of the transistor 150 and the capacitor 160, and a detailed description thereof is omitted.

  Details of the oxide stacked films 410a and 410b will be described below.

  The oxide stacked films 410a and 410b include oxide semiconductor films 420a and 420b and oxide films 422a and 422b. Note that in the following description, the oxide semiconductor films 420a and 420b are described as the oxide semiconductor film 420, and the oxide films 422a and 422b are described as the oxide film 422, respectively.

  As the oxide semiconductor film 420 and the oxide film 422, a metal oxide including at least one same constituent element is preferably used. Alternatively, the constituent elements of the oxide semiconductor film 420 and the oxide film 422 may be the same, and the compositions of the elements may be different.

  In the case where the oxide semiconductor film 420 is an In-M-Zn oxide (M represents Al, Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), an In-M-Zn oxide is formed. The atomic ratio of the metal elements of the sputtering target used for forming the film preferably satisfies In ≧ M and Zn ≧ M. As the atomic ratio of the metal elements of such a sputtering target, In: M: Zn = 1: 1: 1, In: M: Zn = 5: 5: 6 (1: 1: 1.2), In: M : Zn = 3: 1: 2 etc. are preferable. Note that the atomic ratio of the oxide semiconductor film 420 to be formed includes a variation of plus or minus 20% of the atomic ratio of the metal element contained in the sputtering target as an error.

  Note that when the oxide semiconductor film 420 is an In-M-Zn oxide and the sum of In and M is 100 atomic%, the atomic ratio of In and M is preferably such that In is 25 atomic% or more and M is It is less than 75 atomic%, more preferably, In is 34 atomic% or more and M is less than 66 atomic%.

  The oxide semiconductor film 420 has an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more. In this manner, off-state current of a transistor can be reduced by using an oxide semiconductor with a wide energy gap.

  The thickness of the oxide semiconductor film 420 is 3 nm to 200 nm, preferably 3 nm to 100 nm, more preferably 3 nm to 50 nm.

  The oxide film 422 is typically an In—Ga oxide, an In—Zn oxide, or an In—M—Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, Sn). Or the energy at the lower end of the conduction band is closer to the vacuum level than the oxide semiconductor film 420. Typically, the energy at the lower end of the conduction band of the oxide film 422 and the oxide semiconductor The difference from the energy at the lower end of the conduction band of the film 420 is 0.05 eV or more, 0.07 eV or more, 0.1 eV or more, or 0.15 eV or more, 2 eV or less, 1 eV or less, 0.5 eV or less, or 0. 4 eV or less. That is, the difference between the electron affinity of the oxide film 422 and the electron affinity of the oxide semiconductor film 420 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. Hereinafter, it is 0.5 eV or less, or 0.4 eV or less.

  The oxide film 422 may have the following effects when the element M has the atomic ratio higher than that of In. (1) The energy gap of the oxide film 422 is increased. (2) The electron affinity of the oxide film 422 is reduced. (3) Shield impurities from the outside. (4) Compared with the oxide semiconductor film 420, the insulating property is increased. In addition, since the element M is a metal element having a strong bonding force with oxygen, oxygen vacancies are less likely to occur by having M at a higher atomic ratio than In.

  In the case where the oxide film 422 is an In-M-Zn oxide and the sum of In and M is 100 atomic%, the atomic ratio of In and M is preferably such that In is less than 50 atomic% and M is 50 atomic% As described above, more preferably, In is less than 25 atomic% and M is 75 atomic% or more.

  In the case where the oxide semiconductor film 420 and the oxide film 422 are In-M-Zn oxide (M represents Al, Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), oxidation is performed. The atomic ratio of M contained in the oxide film 422 is larger than that of the oxide semiconductor film 420, typically 1.5 times or more compared to the above atoms contained in the oxide semiconductor film 420, The atomic ratio is preferably 2 times or more, more preferably 3 times or more.

The oxide film 422 is In: M: Zn = x ₁ : y ₁ : z ₁ [atomic number ratio], and the oxide semiconductor film 420 is In: M: Zn = x ₂ : y ₂ : z ₂ [number of atoms]. Ratio], y ₁ / x ₁ is larger than y ₂ / x ₂ , and preferably y ₁ / x ₁ is 1.5 times or more larger than y ₂ / x ₂ . More preferably, y ₁ / x ₁ is twice or more larger than y ₂ / x ₂ , and more preferably y ₁ / x ₁ is three times or larger than y ₂ / x ₂ . At this time, it is preferable that y ₂ be x ₂ or more in the oxide semiconductor film 420 because stable electrical characteristics can be imparted to a transistor including an oxide semiconductor. However, when y ₂ is 3 times or more of x ₂ , the field-effect mobility of a transistor including an oxide semiconductor is decreased. Therefore, y ₂ is preferably less than 3 times x ₂ .

  In the case where the oxide semiconductor film 420 and the oxide film 422 are In-M-Zn oxide, the atomic ratio of the metal element of the sputtering target used for forming the In-M-Zn oxide is M> In, It is preferable to satisfy Zn ≧ M. As the atomic ratio of the metal elements of such a sputtering target, 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: Zn = 1: 6: 7, In: Ga: Zn = 1: 6: 8, In: Ga: Zn = 1: 6: 9, In: Ga: Zn = 1: 6: 10 is preferred. Note that the atomic ratio of the metal elements contained in the oxide semiconductor film 420 and the oxide film 422 formed using the sputtering target is an error in addition to the atomic ratio of the metal elements contained in the sputtering target. Includes a minus 20% variation.

  Note that the composition is not limited thereto, and a transistor having an appropriate composition may be used depending on required semiconductor characteristics and electrical characteristics (field-effect mobility, threshold voltage, and the like) of the transistor. In addition, in order to obtain necessary semiconductor characteristics of the transistor, the carrier density, impurity concentration, defect density, atomic ratio of metal element to oxygen, interatomic distance, density, and the like of the oxide semiconductor film 420 are appropriate. It is preferable.

  The oxide film 422 also functions as a damage reducing film for the oxide semiconductor film 420 when the insulating film 114 or the insulating film 116 to be formed later is formed. The thickness of the oxide film 422 is 3 nm to 100 nm, preferably 3 nm to 50 nm.

When silicon or carbon which is one of Group 14 elements is included in the oxide semiconductor film 420, oxygen vacancies increase in the oxide semiconductor film 420, and the oxide semiconductor film 420 becomes n-type. Therefore, the concentration of silicon or carbon in the oxide semiconductor film 420 or the concentration of silicon or carbon in the vicinity of the interface between the oxide film 422 and the oxide semiconductor film 420 (concentration obtained by secondary ion mass spectrometry) is determined. 2 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁷ atoms / cm ³ or less.

In the oxide semiconductor film 420, the concentration of alkali metal or alkaline earth metal obtained by secondary ion mass spectrometry is 1 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁶ atoms / cm ³ or less. To. When an alkali metal and an alkaline earth metal are combined with an oxide semiconductor, carriers may be generated, and the off-state current of the transistor may be increased. Therefore, it is preferable to reduce the concentration of alkali metal or alkaline earth metal in the oxide semiconductor film 420.

Further, when nitrogen is contained in the oxide semiconductor film 420, electrons as carriers are generated, the carrier density is increased, and the oxide semiconductor film 420 is likely to be n-type. As a result, a transistor including an oxide semiconductor containing nitrogen is likely to be normally on. Therefore, nitrogen in the oxide semiconductor film 420 is preferably reduced as much as possible. For example, the nitrogen concentration obtained by secondary ion mass spectrometry is preferably 5 × 10 ¹⁸ atoms / cm ³ or less. .

  Note that the oxide semiconductor film 420 and the oxide film 422 are not formed by simply stacking the layers, but a continuous junction (here, a structure in which the energy at the lower end of the conduction band continuously changes between the films) is formed. Prepare as follows. That is, a stacked structure in which an impurity that forms a defect level such as a trap center or a recombination center does not exist in an oxide semiconductor at the interface of each film. If impurities are mixed between the stacked oxide semiconductor film 420 and the oxide film 422, energy band continuity is lost, and carriers are trapped at the interface or recombined to disappear. End up.

In order to form a continuous bond, it is necessary to use a multi-chamber type film forming apparatus (sputtering apparatus) provided with a load lock chamber to continuously laminate each film without exposure to the atmosphere. Each chamber in the sputtering apparatus is evacuated (5 × 10 ⁻⁷ Pa to 1 × 1) using an adsorption-type evacuation pump such as a cryopump in order to remove as much water as possible from the oxide semiconductor film. ^{X10 −4} Pa) is preferable. Alternatively, it is preferable to combine a turbo molecular pump and a cold trap so that a gas, particularly a gas containing carbon or hydrogen, does not flow backward from the exhaust system into the chamber.

  Here, a band structure of the oxide stacked film will be described with reference to FIG.

  FIG. 11B schematically illustrates part of a band structure of an oxide stacked film and an insulating film in contact with the oxide stacked film. Here, the case where a silicon oxide film is provided as the insulating film 107 and the insulating film 114 is described. Note that EcI1 shown in FIG. 11B represents energy at the lower end of the conduction band of the silicon oxide film used as the insulating film 107, EcS1 represents energy at the lower end of the conduction band of the oxide semiconductor film 420, and EcS2 represents the oxide film 422. EcI2 represents the energy at the lower end of the conduction band of the silicon oxide film used as the insulating film 114.

  As shown in FIG. 11B, in the oxide semiconductor film 420 and the oxide film 422, the energy at the lower end of the conduction band changes smoothly without a barrier. In other words, it can be said that it changes continuously. This is because the oxide semiconductor film 420 and the oxide film 422 contain a common element, and oxygen moves between the oxide semiconductor film 420 and the oxide film 422 to form a mixed layer. It can be said that there is.

  FIG. 11B shows that the oxide semiconductor film 420 serves as a well and a channel region is formed in the oxide semiconductor film 420. Note that it can be said that the oxide semiconductor film 420 and the oxide film 422 are continuously joined to each other because the energy at the lower end of the conduction band is continuously changed.

  Note that as shown in FIG. 11B, in the vicinity of the interface between the oxide film 422 and the insulating film 114, trap levels caused by impurities or defects such as silicon or carbon which are constituent elements of the insulating film 114 are formed. However, when the oxide film 422 is provided, the oxide semiconductor film 420 and the trap level can be separated from each other. Note that in the case where the energy difference between EcS1 and EcS2 is small, electrons in the oxide semiconductor film 420 may reach the trap level exceeding the energy difference. When electrons are trapped in the trap level, negative fixed charges are generated at the insulating film interface, and the threshold voltage of the transistor is shifted in the positive direction. Therefore, it is preferable that the energy difference between EcS1 and EcS2 be 0.1 eV or more, preferably 0.15 eV or more, because fluctuations in threshold voltage of the transistor are reduced and stable electric characteristics are obtained.

  As described above, the structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.

(Embodiment 6)
In this embodiment, an example of an oxide semiconductor film that can be used for a transistor and a capacitor of the semiconductor device of one embodiment of the present invention will be described.

<Crystallinity of oxide semiconductor film>
Hereinafter, the structure of the oxide semiconductor film is described.

  An oxide semiconductor film is roughly classified into a non-single-crystal oxide semiconductor film and a single-crystal oxide semiconductor film. The non-single-crystal oxide semiconductor film refers to a CAAC-OS (C Axis Crystalline Oxide Semiconductor) film, a polycrystalline oxide semiconductor film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, or the like.

  First, the CAAC-OS film is described.

  The CAAC-OS film is one of oxide semiconductor films having a plurality of c-axis aligned crystal parts.

  When the CAAC-OS film is observed with a transmission electron microscope (TEM), a clear boundary between crystal parts, that is, a grain boundary (also referred to as a grain boundary) cannot be confirmed. Therefore, it can be said that the CAAC-OS film is unlikely to decrease in electron mobility due to crystal grain boundaries.

  When the CAAC-OS film is observed by TEM (cross-sectional TEM observation) from a direction substantially parallel to the sample surface, it can be confirmed that metal atoms are arranged in layers in the crystal part. Each layer of metal atoms has a shape reflecting unevenness of a surface (also referred to as a formation surface) or an upper surface on which the CAAC-OS film is formed, and is arranged in parallel with the formation surface or the upper surface of the CAAC-OS film. .

  On the other hand, when the CAAC-OS film is observed by TEM (planar TEM observation) from a direction substantially perpendicular to the sample surface, it can be confirmed that metal atoms are arranged in a triangular shape or a hexagonal shape in the crystal part. However, there is no regularity in the arrangement of metal atoms between different crystal parts.

  From the cross-sectional TEM observation and the planar TEM observation, it is found that the crystal part of the CAAC-OS film has orientation.

  In this specification, “parallel” refers to a state in which two straight lines are arranged at an angle of −10 ° to 10 °. Therefore, the case of −5 ° to 5 ° is also included. “Vertical” refers to a state in which two straight lines are arranged at an angle of 80 ° to 100 °. Therefore, the case of 85 ° to 95 ° is also included.

In addition, most crystal parts included in the CAAC-OS film fit in a cube whose one side is less than 100 nm. Therefore, the case where a crystal part included in the CAAC-OS film fits in a cube whose one side is less than 10 nm, less than 5 nm, or less than 3 nm is included. Note that a plurality of crystal parts included in the CAAC-OS film may be connected to form one large crystal region. For example, in a planar TEM image, a crystal region that is 2500 nm ² or more, 5 μm ² or more, or 1000 μm ² or more may be observed.

When structural analysis is performed on a CAAC-OS film using an X-ray diffraction (XRD) apparatus, for example, in the analysis of a CAAC-OS film having an InGaZnO ₄ crystal by an out-of-plane method, A peak may appear when the diffraction angle (2θ) is around 31 °. Since this peak is attributed to the (009) plane of the InGaZnO ₄ crystal, the CAAC-OS film crystal has c-axis orientation, and the c-axis is in a direction substantially perpendicular to the formation surface or the top surface. Can be confirmed.

On the other hand, when the CAAC-OS film is analyzed by an in-plane method in which X-rays are incident from a direction substantially perpendicular to the c-axis, a peak may appear when 2θ is around 56 °. This peak is attributed to the (110) plane of the InGaZnO ₄ crystal. In the case of a single crystal oxide semiconductor film of InGaZnO ₄ , when 2θ is fixed in the vicinity of 56 ° and analysis (φ scan) is performed while rotating the sample with the normal vector of the sample surface as the axis (φ axis), Six peaks attributed to the crystal plane equivalent to the (110) plane are observed. On the other hand, in the case of a CAAC-OS film, a peak is not clearly observed even when φ scan is performed with 2θ fixed at around 56 °.

  From the above, in the CAAC-OS film, the orientation of the a-axis and the b-axis is irregular between different crystal parts, but the c-axis is aligned, and the c-axis is a normal line of the formation surface or the top surface. It can be seen that the direction is parallel to the vector. Therefore, each layer of metal atoms arranged in a layer shape confirmed by the above-mentioned cross-sectional TEM observation is a plane parallel to the ab plane of the crystal.

  Note that the crystal part is formed when a CAAC-OS film is formed or when crystallization treatment such as heat treatment is performed. As described above, the c-axis of the crystal is oriented in a direction parallel to the normal vector of the formation surface or the top surface of the CAAC-OS film. Therefore, for example, when the shape of the CAAC-OS film is changed by etching or the like, the c-axis of the crystal may not be parallel to the normal vector of the formation surface or the top surface of the CAAC-OS film.

  In the CAAC-OS film, the distribution of c-axis aligned crystal parts is not necessarily uniform. For example, in the case where the crystal part of the CAAC-OS film is formed by crystal growth from the vicinity of the upper surface of the CAAC-OS film, the ratio of the crystal part in which the region near the upper surface is c-axis aligned than the region near the formation surface May be higher. In addition, in the case where an impurity is added to the CAAC-OS film, the region to which the impurity is added may be changed, and a region having a different ratio of partially c-axis aligned crystal parts may be formed.

Note that when the CAAC-OS film including an InGaZnO ₄ crystal is analyzed by an out-of-plane method, a peak may also appear when 2θ is around 36 ° in addition to the peak where 2θ is around 31 °. A peak at 2θ of around 36 ° indicates that a crystal having no c-axis alignment is included in part of the CAAC-OS film. The CAAC-OS film preferably has a peak at 2θ of around 31 ° and no peak at 2θ of around 36 °.

  The CAAC-OS film is an oxide semiconductor film with a low impurity concentration. The impurity is an element other than the main component of the oxide semiconductor film, such as hydrogen, carbon, silicon, or a transition metal element. In particular, an element such as silicon, which has a stronger bonding force with oxygen than the metal element included in the oxide semiconductor film, disturbs the atomic arrangement of the oxide semiconductor film by depriving the oxide semiconductor film of oxygen, and has crystallinity. It becomes a factor to reduce. In addition, heavy metals such as iron and nickel, argon, carbon dioxide, and the like have large atomic radii (or molecular radii). Therefore, if they are contained inside an oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disturbed, resulting in crystallinity. It becomes a factor to reduce. Note that the impurity contained in the oxide semiconductor film might serve as a carrier trap or a carrier generation source.

  The CAAC-OS film is an oxide semiconductor film with a low density of defect states. For example, oxygen vacancies in the oxide semiconductor film can serve as carrier traps or can generate carriers by capturing hydrogen.

  A low impurity concentration and a low density of defect states (small number of oxygen vacancies) is called high purity intrinsic or substantially high purity intrinsic. A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has few carrier generation sources, and thus can have a low carrier density. Therefore, a transistor including the oxide semiconductor film rarely has electrical characteristics (also referred to as normally-on) in which the threshold voltage is negative. A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has few carrier traps. Therefore, a transistor including the oxide semiconductor film has a small change in electrical characteristics and has high reliability. Note that the charge trapped in the carrier trap of the oxide semiconductor film takes a long time to be released, and may behave as if it were a fixed charge. Therefore, a transistor including an oxide semiconductor film with a high impurity concentration and a high density of defect states may have unstable electrical characteristics.

  In addition, a transistor including a CAAC-OS film has little variation in electrical characteristics due to irradiation with visible light or ultraviolet light.

  Next, a microcrystalline oxide semiconductor film is described.

  In the microcrystalline oxide semiconductor film, there is a case where a crystal part cannot be clearly confirmed in an observation image using a TEM. In most cases, a crystal part included in the microcrystalline oxide semiconductor film has a size of 1 nm to 100 nm, or 1 nm to 10 nm. In particular, an oxide semiconductor film including a nanocrystal (nc) that is a microcrystal of 1 nm to 10 nm, or 1 nm to 3 nm is referred to as an nc-OS (nanocrystalline Oxide Semiconductor) film. In the nc-OS film, for example, a crystal grain boundary may not be clearly confirmed in an observation image using a TEM.

  The nc-OS film has periodicity in atomic arrangement in a very small region (eg, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In addition, the nc-OS film does not have regularity in crystal orientation between different crystal parts. Therefore, orientation is not seen in the whole film. Therefore, the nc-OS film may not be distinguished from an amorphous oxide semiconductor film depending on an analysis method. For example, when structural analysis is performed on the nc-OS film using an XRD apparatus using X-rays having a diameter larger than that of the crystal part, a peak indicating a crystal plane is not detected in the analysis by the out-of-plane method. Further, when electron beam diffraction (also referred to as limited-field electron diffraction) using an electron beam with a probe diameter (for example, 50 nm or more) larger than that of the crystal part is performed on the nc-OS film, a diffraction pattern such as a halo pattern is obtained. Is observed. On the other hand, when nc-OS film is subjected to electron diffraction (also referred to as nanobeam electron diffraction) using an electron beam with a probe diameter (for example, 1 nm to 30 nm) that is close to the crystal part or smaller than the crystal part. Spots are observed. In addition, when nanobeam electron diffraction is performed on the nc-OS film, a region with high luminance may be observed so as to draw a circle (in a ring shape). Further, when nanobeam electron diffraction is performed on the nc-OS film, a plurality of spots may be observed in the ring-shaped region.

  The nc-OS film is an oxide semiconductor film that has higher regularity than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect states than the amorphous oxide semiconductor film. Note that the nc-OS film does not have regularity in crystal orientation between different crystal parts. Therefore, the nc-OS film has a higher density of defect states than the CAAC-OS film.

  Note that the oxide semiconductor film may be a stacked film including two or more of an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, and a CAAC-OS film, for example.

  As the oxide semiconductor film included in the transistor and the capacitor in the semiconductor device of one embodiment of the present invention, any of the above-described crystalline oxide semiconductor films may be applied. In the case of including an oxide semiconductor film having a stacked structure, the crystal states of the oxide semiconductor films may be different. Note that a CAAC-OS film is preferably used as the oxide semiconductor film functioning as a channel region of the transistor. In addition, since the oxide semiconductor film functioning as an electrode of the capacitor has a higher impurity concentration than the oxide semiconductor film included in the transistor, crystallinity may be reduced.

  As described above, the structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 7)
In this embodiment, a display device using the semiconductor device of one embodiment of the present invention will be described with reference to FIGS. Note that portions similar to those shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  A display device illustrated in FIG. 12A includes a region having a pixel of a display element (hereinafter referred to as a pixel portion 302) and a circuit portion (hereinafter referred to as a pixel portion 302) that is disposed outside the pixel portion 302 and has a circuit for driving the pixel. , A driver circuit portion 304), a circuit having a function of protecting an element (hereinafter referred to as a protection circuit 306), and a terminal portion 307. Note that the protection circuit 306 may not be provided.

  Part or all of the driver circuit portion 304 is preferably formed over the same substrate as the pixel portion 302. Thereby, the number of parts and the number of terminals can be reduced. If part or all of the driver circuit portion 304 is not formed over the same substrate as the pixel portion 302, part or all of the driver circuit portion 304 may be COG (Chip On Glass) or TAB (Tape). (Automated Bonding).

  The pixel portion 302 includes a circuit (hereinafter referred to as a pixel circuit 301) for driving a plurality of display elements arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). The driver circuit unit 304 outputs a signal (scanning signal) for selecting a pixel (hereinafter referred to as a gate driver 304a), and a circuit (data signal) for supplying a signal (data signal) for driving a display element of the pixel. Hereinafter, it has a drive circuit such as a source driver 304b).

  The gate driver 304a includes a shift register and the like. The gate driver 304a receives a signal for driving the shift register via the terminal portion 307 and outputs a signal. For example, the gate driver 304a receives a start pulse signal, a clock signal, and the like and outputs a pulse signal. The gate driver 304a has a function of controlling the potential of a wiring to which a scanning signal is supplied (hereinafter referred to as scanning lines GL_1 to GL_X). Note that a plurality of gate drivers 304a may be provided, and the scanning lines GL_1 to GL_X may be divided and controlled by the plurality of gate drivers 304a. Alternatively, the gate driver 304a has a function of supplying an initialization signal. However, the present invention is not limited to this, and the gate driver 304a can supply another signal.

  The source driver 304b includes a shift register and the like. In addition to a signal for driving the shift register, the source driver 304b receives a signal (image signal) as a source of the data signal through the terminal portion 307. The source driver 304b has a function of generating a data signal to be written in the pixel circuit 301 based on the image signal. The source driver 304b has a function of controlling the output of the data signal in accordance with a pulse signal obtained by inputting a start pulse, a clock signal, and the like. The source driver 304b has a function of controlling the potential of a wiring to which a data signal is supplied (hereinafter referred to as data lines DL_1 to DL_Y). Alternatively, the source driver 304b has a function of supplying an initialization signal. However, the present invention is not limited to this, and the source driver 304b can supply another signal.

  The source driver 304b is configured using, for example, a plurality of analog switches. The source driver 304b can output a signal obtained by time-division of the image signal as a data signal by sequentially turning on the plurality of analog switches. Further, the source driver 304b may be configured using a shift register or the like.

  Each of the plurality of pixel circuits 301 receives a pulse signal through one of the plurality of scanning lines GL to which the scanning signal is applied, and receives the data signal through one of the plurality of data lines DL to which the data signal is applied. Entered. Also. In each of the plurality of pixel circuits 301, writing and holding of data of the data signal is controlled by the gate driver 304a. For example, the pixel circuit 301 in the m-th row and the n-th column receives a pulse signal from the gate driver 304a via the scanning line GL_m (m is a natural number equal to or less than X), and the data line DL_n (n Is a natural number less than or equal to Y), the data signal is input from the source driver 304b.

  The protection circuit 306 illustrated in FIG. 12A is connected to, for example, the scanning line GL which is a wiring between the gate driver 304a and the pixel circuit 301. Alternatively, the protection circuit 306 is connected to a data line DL that is a wiring between the source driver 304 b and the pixel circuit 301. Alternatively, the protection circuit 306 can be connected to a wiring between the gate driver 304 a and the terminal portion 307. Alternatively, the protection circuit 306 can be connected to a wiring between the source driver 304 b and the terminal portion 307. Note that the terminal portion 307 is a portion where a terminal for inputting a power supply, a control signal, and an image signal from an external circuit to the display device is provided.

  The protection circuit 306 is a circuit that brings a wiring into a conductive state when a potential outside a certain range is applied to the wiring to which the protection circuit 306 is connected.

  As shown in FIG. 12A, by providing a protection circuit 306 in each of the pixel portion 302 and the driver circuit portion 304, resistance of the display device to an overcurrent generated by ESD (Electro Static Discharge) or the like is increased. be able to. However, the configuration of the protection circuit 306 is not limited thereto, and for example, a configuration in which the protection circuit 306 is connected to the gate driver 304a or a configuration in which the protection circuit 306 is connected to the source driver 304b may be employed. Alternatively, the protection circuit 306 can be connected to the terminal portion 307.

  12A illustrates an example in which the driver circuit portion 304 is formed using the gate driver 304a and the source driver 304b; however, the present invention is not limited to this structure. For example, only the gate driver 304a may be formed and a substrate on which a separately prepared source driver circuit is formed (for example, a driver circuit substrate formed of a single crystal semiconductor film or a polycrystalline semiconductor film) may be mounted.

  A plurality of pixel circuits 301 illustrated in FIG. 12A can have a structure illustrated in FIG.

  A pixel circuit 301 illustrated in FIG. 12B includes a liquid crystal element 370, a transistor 150, and a capacitor 160. Note that as the transistor 150 and the capacitor 160, the semiconductor device having the structure in FIG. 1 described in Embodiment 1 can be used.

  One potential of the pair of electrodes of the liquid crystal element 370 is appropriately set according to the specification of the pixel circuit 301. The alignment state of the liquid crystal element 370 is set by written data. Note that a common potential may be applied to one of the pair of electrodes of the liquid crystal element 370 included in each of the plurality of pixel circuits 301. Further, a different potential may be applied to one of the pair of electrodes of the liquid crystal element 370 of the pixel circuit 301 in each row.

  For example, as a method for driving a display device including the liquid crystal element 370, a TN mode, an STN mode, a VA mode, an ASM (Axial Symmetrical Aligned Micro-cell) mode, an OCB (Optically Compensated Birefringence) mode, and an FLC (Ferroelectric mode) , AFLC (Anti Ferroelectric Liquid Crystal) mode, MVA mode, PVA (Patterned Vertical Alignment) mode, IPS mode, FFS mode, TBA (Transverse Bend Alignment) mode, etc. may be used. In addition to the above-described driving methods, there are ECB (Electrically Controlled Birefringence) mode, PDLC (Polymer Dispersed Liquid Crystal) mode, PNLC (Polymer Network Liquid Host mode), and other driving methods for the display device. However, the present invention is not limited to this, and various liquid crystal elements and driving methods thereof can be used.

  In addition, a liquid crystal element may be formed using a liquid crystal composition including a liquid crystal exhibiting a blue phase and a chiral agent. A liquid crystal exhibiting a blue phase has a short response speed of 1 msec or less. In addition, a liquid crystal exhibiting a blue phase is optically isotropic, so that alignment treatment is unnecessary and viewing angle dependency is small.

  In the pixel circuit 301 in the m-th row and the n-th column, one of the source electrode and the drain electrode of the transistor 150 is electrically connected to the data line DL_n, and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 370. The Further, the gate electrode of the transistor 150 is electrically connected to the scan line GL_m. The transistor 150 has a function of controlling data writing of the data signal by being turned on or off.

  One of the pair of electrodes of the capacitor 160 is electrically connected to a wiring to which a potential is supplied (hereinafter, potential supply line VL), and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 370. The Note that the value of the potential of the potential supply line VL is appropriately set according to the specifications of the pixel circuit 301. The capacitor 160 has a function as a storage capacitor that holds written data.

  For example, in the display device including the pixel circuit 301 in FIG. 12A, the pixel circuits 301 in each row are sequentially selected by the gate driver 304a, the transistors 150 are turned on, and data signal data is written.

  The pixel circuit 301 in which data is written is brought into a holding state when the transistor 150 is turned off. By sequentially performing this for each row, an image can be displayed.

Note that although the example in which the liquid crystal element 370 is used as the display element is shown, one embodiment of the present invention is not limited to this.

  For example, in this specification and the like, a display element, a display device that is a device including a display element, a light-emitting element, and a light-emitting device that is a device including a light-emitting element have various forms or have various elements. I can do it. As an example of a display element, a display device, a light emitting element, or a light emitting device, an EL (electroluminescence) element (an EL element including an organic substance and an inorganic substance, an organic EL element, an inorganic EL element), an LED (white LED, red LED, green LED) , Blue LED, etc.), transistor (transistor that emits light in response to current), electron-emitting device, liquid crystal device, electronic ink, electrophoretic device, grating light valve (GLV), plasma display (PDP), MEMS (micro electro Mechanical system), digital micromirror device (DMD), DMS (digital micro shutter), IMOD (interference modulation) element, electrowetting element, piezoelectric ceramic display, carbon nanotube, etc. , By an electric magnetic action, those having contrast, brightness, reflectance, a display medium such as transmittance changes. An example of a display device using an EL element is an EL display. As an example of a display device using an electron-emitting device, there is a field emission display (FED), a SED type flat display (SED: Surface-Conduction Electron-Emitter Display), or the like. As an example of a display device using a liquid crystal element, there is a liquid crystal display (a transmissive liquid crystal display, a transflective liquid crystal display, a reflective liquid crystal display, a direct view liquid crystal display, a projection liquid crystal display) and the like. An example of a display device using electronic ink or an electrophoretic element is electronic paper.

  An example in which a liquid crystal element is used as the display element is shown in FIG. A common electrode 124 is provided on the substrate 102a. A liquid crystal layer 123 is provided between the common electrode 124 and the conductive film 120.

  Alternatively, an example in which a light-emitting element is used as a display element is illustrated in FIG. An insulating film 132, a light emitting layer 125, and a common electrode 124 are provided over the conductive film 120.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 8)
In this embodiment, a display module and an electronic device each using the semiconductor device of one embodiment of the present invention will be described with reference to FIGS.

  A display module 8000 shown in FIG. 13 includes a touch panel 8004 connected to the FPC 8003, a display panel 8006 connected to the FPC 8005, a backlight unit 8007, a frame 8009, a printed circuit board 8010, between the upper cover 8001 and the lower cover 8002. A battery 8011 is included.

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

  The shapes and dimensions of the upper cover 8001 and the lower cover 8002 can be changed as appropriate in accordance with the sizes of the touch panel 8004 and the display panel 8006.

  As the touch panel 8004, a resistive touch panel or a capacitive touch panel can be used by being superimposed on the display panel 8006. In addition, the counter substrate (sealing substrate) of the display panel 8006 can have a touch panel function. In addition, an optical sensor can be provided in each pixel of the display panel 8006 to provide an optical touch panel.

  The backlight unit 8007 has a light source 8008. The light source 8008 may be provided at an end portion of the backlight unit 8007 and a light diffusing plate may be used.

  The frame 8009 has a function as an electromagnetic shield for blocking electromagnetic waves generated by the operation of the printed board 8010 in addition to a protective function of the display panel 8006. The frame 8009 may have a function as a heat sink.

  The printed board 8010 includes a power supply circuit, a signal processing circuit for outputting a video signal and a clock signal. As a power supply for supplying power to the power supply circuit, an external commercial power supply may be used, or a power supply using a battery 8011 provided separately may be used. The battery 8011 can be omitted when a commercial power source is used.

  The display module 8000 may be additionally provided with a member such as a polarizing plate, a retardation plate, or a prism sheet.

  FIG. 14A to FIG. 14H illustrate electronic devices. These electronic devices include a housing 5000, a display portion 5001, a speaker 5003, an LED lamp 5004, operation keys 5005 (including a power switch or operation switch), a connection terminal 5006, a sensor 5007 (force, displacement, position, speed, Measure acceleration, angular velocity, number of rotations, distance, light, liquid, magnetism, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, smell or infrared A microphone 5008, and the like.

  FIG. 14A illustrates a mobile computer which can include a switch 5009, an infrared port 5010, and the like in addition to the above components. FIG. 14B illustrates a portable image reproducing device (eg, a DVD reproducing device) including a recording medium, which includes a second display portion 5002, a recording medium reading portion 5011, and the like in addition to the above-described components. it can. FIG. 14C illustrates a goggle type display which can include a second display portion 5002, a support portion 5012, an earphone 5013, and the like in addition to the above components. FIG. 14D illustrates a portable game machine that can include the memory medium reading portion 5011 and the like in addition to the above objects. FIG. 14E illustrates a digital camera with a television receiving function, which can include an antenna 5014, a shutter button 5015, an image receiving portion 5016, and the like in addition to the above objects. FIG. 14F illustrates a portable game machine that can include the second display portion 5002, the recording medium reading portion 5011, and the like in addition to the above objects. FIG. 14G illustrates a television receiver that can include a tuner, an image processing portion, and the like in addition to the above components. FIG. 14H illustrates a portable television receiver that can include a charger 5017 that can transmit and receive signals in addition to the above components.

  The electronic devices illustrated in FIGS. 14A to 14H can have a variety of functions. For example, a function for displaying various information (still images, moving images, text images, etc.) on the display unit, a touch panel function, a function for displaying a calendar, date or time, a function for controlling processing by various software (programs), Wireless communication function, function for connecting to various computer networks using the wireless communication function, function for transmitting or receiving various data using the wireless communication function, and reading and displaying programs or data recorded on the recording medium It can have a function of displaying on the section. Further, in an electronic device having a plurality of display units, one display unit mainly displays image information and another one display unit mainly displays character information, or the plurality of display units consider parallax. It is possible to have a function of displaying a three-dimensional image, etc. by displaying the obtained image. Furthermore, in an electronic device having an image receiving unit, a function for capturing a still image, a function for capturing a moving image, a function for correcting a captured image automatically or manually, and a captured image on a recording medium (externally or incorporated in a camera) A function of saving, a function of displaying a photographed image on a display portion, and the like can be provided. Note that the functions of the electronic devices illustrated in FIGS. 14A to 14H are not limited to these, and can have various functions.

  The electronic device described in this embodiment includes a display portion for displaying some information.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

102 substrate 102a substrate 104a oxide semiconductor film 104b oxide semiconductor film 106 insulating film 107 insulating film 108 insulating film 110a oxide semiconductor film 110b oxide semiconductor film 112a source electrode 112b drain electrode 114 insulating film 116 insulating film 118 insulating film 118a insulating Film 120 conductive film 120a conductive film 121 conductive film 121a conductive film 122 insulating film 132 insulating film 140 opening 142 opening 150 transistor 151 transistor 152 transistor 160 capacitor element 161 capacitor element 162 capacitor element 202 substrate 204 oxide semiconductor film 204a oxide semiconductor film 204b Oxide semiconductor film 206 Insulating film 207 Insulating film 208 Insulating film 210 Oxide semiconductor film 212a Source electrode 212b Drain electrode 216 Insulating film 217 Insulating film 218 Insulating film 220 Conduction Electrode film 240 Opening 250 Transistor 260 Capacitor element 301 Pixel circuit 302 Pixel part 304 Driver circuit part 304a Gate driver 304b Source driver 306 Protection circuit 307 Terminal part 370 Liquid crystal element 410a Oxide laminated film 410b Oxide laminated film 420 Oxide semiconductor film 420a Oxide semiconductor film 420b Oxide semiconductor film 422 Oxide film 422a Oxide film 422b Oxide film 5000 Housing 5001 Display unit 5002 Display unit 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 unit 5013 Earphone 5014 Antenna 5015 Shutter button 5016 Image receiving unit 5017 Battery charger 8000 Display module Le 8001 top cover 8002 bottom 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 (7)

A first oxide semiconductor film;
A second oxide semiconductor film on the same plane as the first oxide semiconductor film;
A first silicon nitride film on the first oxide semiconductor film and on the second oxide semiconductor film;
A first silicon oxide film on the first silicon nitride film;
A third oxide semiconductor film and a fourth oxide semiconductor film on the first silicon oxide film;
A source electrode and a drain electrode electrically connected to the third oxide semiconductor film;
A second silicon oxide film on the third oxide semiconductor film and the fourth oxide semiconductor film;
A second silicon nitride film on the second silicon oxide film,
The first oxide semiconductor film has a region overlapping with the third oxide semiconductor film through the first silicon nitride film and the first silicon oxide film,
The first silicon nitride film has a region in contact with the first oxide semiconductor film;
The first silicon nitride film has a region in contact with the second oxide semiconductor film;
The second silicon oxide film has an opening,
The second silicon nitride film has a region in contact with the fourth oxide semiconductor film in the opening;
The first oxide semiconductor film functions as a gate electrode of a transistor,
The second oxide semiconductor film has a function as a first electrode of a capacitor,
The fourth oxide semiconductor film is a semiconductor device having a function as a second electrode of the capacitor. A first oxide semiconductor film;
A second oxide semiconductor film;
A source electrode and a drain electrode electrically connected to the first oxide semiconductor film;
A first silicon oxide film on the first oxide semiconductor film;
A first silicon nitride film on the first silicon oxide film;
A third oxide semiconductor film on the first silicon nitride film;
A second silicon nitride film on the second oxide semiconductor film and the third oxide semiconductor film;
A second silicon oxide film on the second silicon nitride film;
A conductive film on the second silicon oxide film,
The third oxide semiconductor film has a region overlapping with the first oxide semiconductor film through the first silicon nitride film and the first silicon oxide film,
The first silicon nitride film has a region in contact with the third oxide semiconductor film;
The second silicon nitride film has a region in contact with the third oxide semiconductor film;
The second silicon nitride film has a region in contact with the second oxide semiconductor film;
The third oxide semiconductor film has a function as a gate electrode of a transistor;
The second oxide semiconductor film has a function as a first electrode of a capacitor,
The conductive film is a semiconductor device having a function as a second electrode of the capacitor. In claim 2,
The conductive film is a semiconductor device having a function as a pixel electrode. In any one of Claims 1 to 3,
The capacitive element, the semi-conductor device that having a transmissive in visible light. In any one of Claim 1 thru | or 4 ,
The first oxide semiconductor film to the third oxide semiconductor film,
An In, M, a metal oxide containing Zn (M is Al, Ti, Ga, Y, Zr, La, representing the Ce, Nd, Sn or Hf) der Ru semiconductors devices. A display device using a semiconductor device according to any one of claims 1 to 5. An electronic apparatus using the semiconductor device according to any one of claims 1 to 5 .

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