JP2019050405A - Semiconductor device - Google Patents

Abstract

To provide a semiconductor device that has a high aperture ratio and a capacitive element whose capacitance value can be increased, and provides a low manufacturing cost.SOLUTION: A semiconductor device includes: a transistor 150 including a first oxide semiconductor film 110a and a second oxide semiconductor film 104a; and a capacitive element 160 including an insulation film 108 between a pair of electrodes. The transistor 150 includes: the first oxide semiconductor film 110a; the insulation film 108 provided so as to be in contact with the first oxide semiconductor film 110a, the insulation film functioning as a gate insulation film; the second oxide semiconductor film 104a provided so as to be in contact with the insulation film 108, the second oxide semiconductor film being provided at a position overlapping with the first oxide semiconductor film 110a; and a source electrode 112a and a drain electrode 112b that are connected to the first oxide semiconductor film 110a. One of the pair of electrodes of the capacitive element 160 is the second oxide semiconductor film 104a on the same plane as that of the second oxide semiconductor film 104a.SELECTED DRAWING: Figure 1

Description

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

A transistor used in many flat panel displays represented by a liquid crystal display device and a light emitting display device is formed of a silicon semiconductor such as amorphous silicon, single crystal silicon or polycrystalline silicon formed on a glass substrate. . In addition, transistors using the silicon semiconductor are also used in integrated circuits (ICs) and the like.

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

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

Unexamined-Japanese-Patent No. 2007-123861 JP 2007-96055 A U.S. Pat. No. 8,102,476

In the capacitor element, a dielectric film is provided between a pair of electrodes, and at least one of the pair of electrodes is formed of a conductive film having a light shielding property such as a gate electrode constituting a transistor, a source, or a drain. Often

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

Therefore, in view of the above problems, an object of one embodiment of the present invention is to provide a semiconductor device including a capacitor having a high aperture ratio and capable of increasing a capacitance value. Also,
It is an object to provide a semiconductor device whose manufacturing cost is low. Alternatively, one of the problems is to provide a novel semiconductor device or the like.

Note that the descriptions of these objects do not disturb the existence of other objects. Note that in one embodiment of the present invention, it is not necessary to solve all of these problems. In addition, problems other than these are naturally apparent from the description in the specification, drawings, claims, etc., and the specification,
Other problems can be extracted from the description of the drawings, claims, and the like.

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 is provided in contact with the first oxide semiconductor film, the gate insulating film provided in contact with the first oxide semiconductor film, and the gate insulating film, and overlaps 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 is a second oxide. A semiconductor device is provided on 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 over the gate electrode, and a first oxide semiconductor film at a position overlapping with the gate electrode over the gate insulating film. First
And a source electrode and a drain electrode over the oxide semiconductor film, and one of the pair of electrodes of the capacitor is provided over the same surface as the second oxide semiconductor film. is there.

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 over the first oxide semiconductor film, a gate insulating film over the first oxide semiconductor film, and a gate insulating film. And 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 element has the same surface as the second oxide semiconductor film. It is a semiconductor device characterized by being provided on top.

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, it is preferable that the capacitor have translucency in visible light.

In each of the above structures, the first oxide semiconductor film and the second oxide semiconductor film are In
-M-Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, Sn or H
It is preferable that it represents f).

Further, a display device and an electronic device which use the semiconductor device having each of the above structures are also included in one embodiment of the present invention.

According to one embodiment of the present invention, it is possible to provide a semiconductor device including a capacitor element that has a high aperture ratio and can increase a capacitance value. 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. Note that effects other than these are naturally apparent from the description of the specification, drawings, claims and the like, and other effects can be extracted from the descriptions of the specification, drawings, claims and the like. It is.

7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. 7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A to 7D are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. 7A and 7B are a cross-sectional view and a band diagram illustrating one embodiment of a semiconductor device. 7A and 7B are a block diagram and a circuit diagram illustrating a display device. FIG. 6 illustrates a display module. 5A to 5C illustrate electronic devices. FIG. 7 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 7 is a cross-sectional view illustrating one embodiment of a semiconductor device. 7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. 7A and 7B are a top view and a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 7 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 7 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 7 is a cross-sectional view illustrating one embodiment of a semiconductor device. FIG. 7 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, it is easily understood by those skilled in the art that one aspect of the present invention is not limited to the following description, and that various changes can be made in the form and details without departing from the spirit of the present invention and the scope thereof. Ru. Therefore, one embodiment of the present invention is not construed as being limited to the description of the embodiment modes described below.
In the embodiments described below, the same reference numerals or the same hatch patterns are used in common between different drawings for the same portions or portions having similar functions, and the repetitive description thereof will be omitted.

It should be noted that in the figures described herein, the size of each component, the thickness of the film, or the area may be exaggerated for clarity. Therefore, it is not necessarily limited to the scale.

Also, the first and second ordinal numbers used in the present specification and the like are added to avoid mixing of the constituent elements, and are not limited numerically. Therefore, for example, "first" can be appropriately replaced with "second" or "third" and the like.

Note that the functions of the “source” and “drain” of the transistor may be interchanged when adopting transistors of different polarities or when the direction of current changes in circuit operation. Therefore, in the present 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>
FIG. 1A is a top view of a semiconductor device of one embodiment of the present invention, and FIG. 1B is a top view of FIG.
) Corresponds to a cross-sectional view of a cross section between the dashed dotted line A-B and the dashed dotted line CD. Note that in FIG. 1A, some components of the semiconductor device (such as a gate insulating film) are omitted for simplicity.

The semiconductor device illustrated in FIGS. 1A and 1B includes a transistor 150 including a first oxide semiconductor film 110 a and a second oxide semiconductor film 104 a, and a capacitor including an insulating film between a pair of electrodes. And an 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. The first oxide semiconductor film 110 b is on the same plane as the surface 110 a.

The transistor 150 includes a gate electrode including the second oxide semiconductor film 104 a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104 a, and the insulating film 108. The first oxide semiconductor film 110a and the source electrode 112a and the drain electrode 112b over the first oxide semiconductor film 110a are provided so as to overlap with the gate electrode including the upper second oxide semiconductor film 104a. In other words, transistor 150
A first oxide semiconductor film 110 a, an insulating film 108 serving as a gate insulating film provided in contact with the first oxide semiconductor film 110 a, and the first oxide semiconductor film 110 a are provided in contact with the insulating film 108. A second oxide semiconductor film 104a provided at a position overlapping with the oxide semiconductor film 110a;
The source electrode 112 a and the drain electrode 112 connected to the first oxide semiconductor film 110 a
and b. 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 104 a functions as a gate electrode of the transistor 150. Thus, the second oxide semiconductor film 104 is more than the first oxide semiconductor film 110a.
The resistivity of a is low. In addition, the first oxide semiconductor film 110 a and the second oxide semiconductor film 104
It is preferable that a have the same metal element. When the first oxide semiconductor film 110 a and the second oxide semiconductor film 104 a have the same metal element, a manufacturing device (e.g., a film formation device, a processing device, or the like) can be used in common. Therefore, the manufacturing cost can be suppressed.

Thus, the transistor 150 is in a position where the first oxide semiconductor film 110a, the insulating film 108 in contact with the first oxide semiconductor film 110a, and the insulating film 108 are in contact with each other and overlap with the first oxide semiconductor film 110a. And the first oxide semiconductor film 110 a and the second oxide semiconductor film 104 a have the same metal element, and the first oxide semiconductor film 110 a The resistivity of the second oxide semiconductor film 104a is low.

Further, a wiring or the like formed separately using a metal film or the like may be connected to the second oxide semiconductor films 104 a and 104 b. 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 a second oxide semiconductor film 104a is formed over the metal film. You may use the structure which connects 104b. By forming the lead wiring, the gate wiring, or the like with a metal film, the wiring resistance can be reduced, so that signal delay and 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 have a function as protective insulating films of the transistor 150.

The capacitive element 160 has a second function as one electrode of a pair of electrodes on the substrate 102.
Of the first oxide semiconductor film 104 b, the insulating film 108 which functions as a dielectric film over the second oxide semiconductor film 104 b, and a pair of layers overlapping with the second oxide semiconductor film 104 b with the insulating film 108 interposed therebetween. And a first oxide semiconductor film 110 b having a function of the other electrode of the electrode. Further, over the capacitor 160, more specifically, over the first oxide semiconductor film 110b, an insulating film 118 having a function as a protective insulating film is formed.

Note that the insulating film 108 functions as a gate insulating film in the transistor 150 and functions as a dielectric film in the capacitor 160 as described above. Further, in this embodiment, 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-layer structure of three or more layers.

In addition, the capacitor 160 has a light transmitting property. That is, the first capacitive element 160 has
The oxide semiconductor film 110b, the second oxide semiconductor film 104b, and the insulating film 108 are each formed of a light transmitting material. As described above, since the capacitor 160 has translucency, it can be formed large (in a large area) in a region other than the portion where the transistor in the pixel is formed. Therefore, the capacitance value is increased while the aperture ratio is increased. An increased number of semiconductor devices can be obtained. As a result, a semiconductor device with excellent display quality can be obtained. Also, the capacitive element 16
As 0, the transistor can be manufactured by using a manufacturing process of the transistor 150. Therefore,
A semiconductor device with 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. In addition, the insulating film 10 used for the transistor 150 and the capacitor 160
7 and the insulating films 114 and 116 provided over the transistor 150 and the capacitor 160.
As the insulating film, 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 over the transistor 150 and the capacitor 160 are the insulating films having the above-described structure, whereby the first transistor of the transistor 150 and the capacitor 160 is provided. The resistivity of the oxide semiconductor film and the second oxide semiconductor film can be controlled.

Specifically, since the first oxide semiconductor film 110 a is used as a channel region in the transistor 150, the first oxide semiconductor film 110 b and the second oxide semiconductor film 104 are used.
Resistivity is high compared with a and 104b. On the other hand, the first oxide semiconductor film 110 b and the second oxide semiconductor film 110
The oxide semiconductor films 104 a and 104 b have a function as electrodes, and thus have lower resistivity than the first oxide semiconductor film 110 a.

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

<Method of controlling resistivity of oxide semiconductor>
First oxide semiconductor films 110 a and 110 b and second oxide semiconductor films 104 a and 10
The oxide semiconductor film that can be used for 4 b is a semiconductor material whose resistivity can be controlled by the oxygen vacancy in the film and / or the concentration of impurities such as hydrogen and water in the film. for that reason,
First oxide semiconductor films 110 a and 110 b and second oxide semiconductor films 104 a and 104
The resistivity of each of the oxide semiconductor films formed in the same step is controlled by selecting a treatment in which the oxygen vacancy and / or impurity concentration is increased to b or a treatment in which the oxygen vacancy and / or impurity concentration is decreased. be able to.

Specifically, the second oxide semiconductor film 1 which functions as a gate electrode of the transistor 150
04a, plasma treatment is performed on the oxide semiconductor film used for the second oxide semiconductor film 104b which functions as an electrode of the capacitor 160, and the first oxide semiconductor film 110b which functions as an electrode of the capacitor 160; An oxide semiconductor film having a high carrier density and a low resistivity by increasing oxygen vacancies in a film of a compound semiconductor and / or increasing impurities such as hydrogen and water in a film of an oxide semiconductor Can. Further, an oxide semiconductor film is formed in contact with an insulating film containing hydrogen, and hydrogen is diffused from the insulating film containing hydrogen to the oxide semiconductor film, whereby the oxide semiconductor film has a high carrier density and a low resistivity. It can be done.

On the other hand, the first oxide semiconductor film 110 which functions as a channel region of the transistor 150
a is an insulating film 106 containing hydrogen by providing the insulating films 107, 114, 116;
It does not contact with 118. Oxygen is supplied to the first oxide semiconductor film 110 a by applying 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. can do. The first oxide semiconductor film 110a to which oxygen is supplied becomes an oxide semiconductor film with high resistivity because an oxygen vacancy in the film or at the interface is compensated. Note that as an insulating film capable of releasing oxygen, for example, a silicon oxide film,
Alternatively, a silicon oxynitride film can be used.

Further, in order to obtain an oxide semiconductor film having 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

In order to obtain an oxide semiconductor film having low resistivity, plasma treatment may be performed on the oxide semiconductor film. For example, as the plasma treatment, typically, a rare gas (He, Ne, A
and plasma treatment using a gas containing one selected from r, Kr, Xe), hydrogen, and nitrogen. More specifically, plasma treatment in 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 Plasma treatment under an atmosphere or the like can be mentioned.

By the 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 for generating carriers. In addition, when hydrogen is supplied from an insulating film in the vicinity of the oxide semiconductor film, more specifically, in contact with the lower side or the upper side of the oxide semiconductor film, an electron which is a carrier is formed when the oxygen vacancy and the hydrogen are bonded. May generate

On the other hand, an oxide semiconductor film in which oxygen vacancies have been compensated for and whose hydrogen concentration has been reduced is highly pure.
Alternatively, it can be said that the oxide semiconductor film is substantially purified to be intrinsic. Here, substantially true is
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 1 × 10 ⁻⁹ pieces / cm ³ or more It means that it is less than 1 × 10 ¹¹ pieces / cm ³ . A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film can reduce carrier density because there are few carriers. In addition, since the oxide semiconductor film which has high purity intrinsic or substantially high purity intrinsic has a low density of defect states, the trap state density can be reduced.

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

For example, an insulating film containing hydrogen, in other words, an insulating film capable of releasing hydrogen, typically a silicon nitride film, is used as the insulating film 106, whereby the second oxide semiconductor film 104a is formed.
, 104b can be supplied with hydrogen. In addition, as the insulating film 118, hydrogen can be supplied to the first oxide semiconductor film 110b by using an insulating film containing hydrogen as in the case of the insulating film 106, for example. As an insulating film which can release hydrogen, the hydrogen concentration 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 can be formed. Membrane 110
b can effectively contain hydrogen. Thus, the second oxide semiconductor film 104
The resistivity of the oxide semiconductor film can be controlled by changing the structure of the insulating film in contact with the first and the second oxide semiconductor films 110a and 104b.

Hydrogen contained in the oxide semiconductor film reacts with oxygen bonded to a metal atom to form water, and also 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 which are carriers may be generated. In addition, when a part of hydrogen bonds to oxygen which is bonded to a metal atom, an electron which is a carrier may be generated.
Therefore, the second oxide semiconductor film 104 is provided in contact with the insulating film containing hydrogen.
The a and 104 b and the first oxide semiconductor film 110 b are oxide semiconductor films with higher carrier density than the first oxide semiconductor film 110 a.

In the first oxide semiconductor film 110 a in which the channel region of the transistor 150 is formed, hydrogen is preferably reduced as much as possible. Specifically, the first oxide semiconductor film 11
At 0a, secondary ion mass spectrometry (SIMS: Secondary Ion Mas
Hydrogen concentration obtained by s Spectrometry) 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 × 1
0 ¹⁸ atoms / cm ³ or less, more preferably 5 × 10 ¹⁷ atoms / cm ³ or less,
More preferably, it is 1 × 10 ¹⁶ atoms / cm ³ or less.

Meanwhile, the second electrode functions as the gate electrode of the transistor 150 and the electrode of the capacitor 160.
The oxide semiconductor films 104 a and 104 b and the oxide semiconductor film 110 b functioning as an electrode of the capacitor 160 have a hydrogen concentration and / or an oxygen deficiency larger than that of the first oxide semiconductor film 110 a and a low resistivity. It is an oxide semiconductor film.

In addition, the first oxide semiconductor films 110a and 110b and the second oxide semiconductor film 104a,
104 b have the same metal element. The structure in which the first oxide semiconductor films 110a and 110b and the second oxide semiconductor films 104a and 104b have the same metal element is preferable because manufacturing cost can be reduced. However, the first oxide semiconductor films 110a and 110b
Even if the second oxide semiconductor films 104a and 104b have the same metal element, the compositions may be different. For example, the metal element in the film may be released during the manufacturing process of the transistor and the capacitor to have different metal compositions.

Thus, 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 simultaneously formed. In other words, they function as the gate electrode of the transistor. By forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor on the same surface, the manufacturing cost can be reduced. Also,
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 appropriate treatment on the oxide semiconductor film,
The conductive film can have low resistivity and light transmittance. By using the conductive film, light transmission can be provided to the transistor and / or the capacitor.

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

<Board>
The material of the substrate 102 and the like are not particularly limited, but at least the heat resistance needs to be able to withstand the heat treatment to be 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. Further, 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 semiconductor elements are provided on these substrates. The 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 × 220)
0mm), 8th generation (2200mm x 2400mm), 9th generation (2400mm x 280)
By using a large area substrate such as 0 mm) and 10th generation (2950 mm × 3400 mm)
A large display device can be manufactured. In addition, a flexible substrate is used as the substrate 102,
The transistor 150, the capacitor 160, and the like may be formed directly over a flexible substrate.

In addition to these, various substrates can be used as the substrate 102 to form a transistor. The type of substrate is not limited to a specific one. Examples of the substrate include a plastic substrate, a metal substrate, a stainless steel still substrate, a substrate having a stainless steel still foil, a tungsten substrate, a substrate having a tungsten foil, a flexible substrate,
There is a laminated film, a paper containing a fibrous material, or a base film. Examples of the glass substrate include barium borosilicate glass, aluminoborosilicate glass, or soda lime glass. An example of a flexible substrate is polyethylene terephthalate (PE
T) Plastics typified by polyethylene naphthalate (PEN) and polyether sulfone (PES), and flexible synthetic resins such as acrylic. Examples of the laminated film include polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride and the like. Examples of the base film include polyester, polyamide, polyimide, inorganic vapor-deposited 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 ability, and small size can be manufactured. . When a circuit is formed using such a transistor, power consumption of the circuit can be reduced or integration of the circuit can be increased.

Note that one substrate may be used to form a transistor, and then the transistor may be transposed to another substrate and the transistor may be disposed on another substrate. As an example of a substrate on which a transistor is transposed, a paper substrate, a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (natural fiber (silk, cotton, hemp), Synthetic fiber (nylon, polyurethane, polyester) or regenerated fiber (acetate, cupra, rayon,
(Including recycled polyester), leather substrates, rubber substrates, and the like. By using these substrates, formation of a transistor with good characteristics, formation of a transistor with low power consumption, manufacture of a device that is not easily broken, provision of heat resistance, weight reduction, or thickness reduction can be achieved.

<First Oxide Semiconductor Film and Second Oxide Semiconductor Film>
First oxide semiconductor films 110 a and 110 b and second oxide semiconductor films 104 a and 10
4b is at least indium (In), zinc (Zn) and M (Al, Ti, Ga, Y,
It is preferable to include a film represented by an In-M-Zn oxide containing a metal such as Zr, La, Ce, Sn, or Hf. Alternatively, it is preferable to contain both In and Zn. In addition, in order to reduce variation in electrical characteristics of a transistor including the oxide semiconductor, a stabilizer is preferably included.

Examples of the stabilizer include the metals described in the above M, such as gallium (Ga), tin (Sn), hafnium (Hf), aluminum (Al), or zirconium (Zr)
Etc. Another stabilizer is lanthanide, 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.

First oxide semiconductor films 110 a and 110 b and second oxide semiconductor films 104 a and 10
As an oxide semiconductor forming 4b, for example, In—Ga—Zn-based oxide, In—Al—
Zn-based oxide, In-Sn-Zn-based oxide, In-Hf-Zn-based oxide, In-La-Z
n-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 oxide, In-Er-Zn oxide, In-Tm-Zn oxide, In-Yb-Zn oxide, In-Lu-Zn oxide, In-Sn-Ga- Zn-based oxide, In-Hf-Ga-
Zn-based oxide, In-Al-Ga-Zn-based oxide, In-Sn-Al-Zn-based oxide, I
An n-Sn-Hf-Zn-based oxide or an In-Hf-Al-Zn-based oxide can be used.

Here, an In—Ga—Zn-based oxide means an oxide having In, Ga, and Zn as main components, and there is no limitation on the ratio of In, Ga, and Zn. Also, In, Ga and Z
Metal elements other than n may be contained.

In addition, the first oxide semiconductor films 110a and 110b and the second oxide semiconductor film 104a,
104 b has the same metal element among the above oxides. First oxide semiconductor film 110
The manufacturing cost can be reduced by using the a and 110 b and the second oxide semiconductor films 104 a and 104 b as the same metal element. For example, manufacturing costs can be reduced by using metal oxide targets of the same metal composition. Further, by using a metal oxide target having the same metal composition, an etching gas or an etching solution can be commonly used in processing the oxide semiconductor film.

<Insulating film>
As the insulating films 106 and 107 functioning as the gate insulating film of the transistor 150 and the dielectric film of the capacitor 160, a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, nitrided by a plasma CVD method, a sputtering method, or the like. An insulating layer containing one or more of a silicon film, an aluminum oxide film, a hafnium oxide film, a yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, and a neodymium oxide film Each can be used. Insulating films 106 and 10
Instead of the laminated structure of 7, a single-layer insulating layer selected from the above-mentioned materials may be used.

Note that the first oxide semiconductor film 110 which functions as a channel region of the transistor 150
The insulating film 107 in contact with a is preferably an oxide insulating film, and more preferably has a region containing excess oxygen (oxygen excess region) in excess of the stoichiometric composition. In other words
The insulating film 107 is an insulating film capable of releasing oxygen. Note that 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, 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 can be obtained. Hafnium oxide has a higher dielectric constant than silicon oxide or silicon oxynitride. Therefore, the physical film thickness can be increased relative to the equivalent oxide film thickness.
Even in the case of m or less or 5 nm or less, the leak current due to the tunnel current can be reduced. That is, a transistor with small off current can be realized. Furthermore, hafnium oxide having a crystal structure has a high dielectric constant as compared to hafnium oxide having an amorphous structure. Therefore, in order to obtain a transistor with low off current, it is preferable to use hafnium oxide having a crystal structure. Examples of the crystal structure include monoclinic system and cubic system. However, one embodiment of the present invention is not limited to these.

Note that in this embodiment, a silicon nitride film is formed as the insulating film 106, and the insulating film 107 is formed.
As a silicon oxide film is formed. The silicon nitride film has a high relative dielectric constant as compared to the silicon oxide film, and a film thickness necessary to obtain capacitance equivalent to that of the silicon oxide film is large. Insulating film 108 that functions as a dielectric film
By including a silicon nitride film, the insulating film can be physically thickened. Accordingly, a reduction in the withstand voltage of the transistor 150 and the capacitor 160 can be suppressed, and further, the withstand voltage can be improved and electrostatic breakdown of the transistor 150 and the capacitor 160 can be suppressed.

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

<Protective insulating film>
As the insulating films 114, 116, and 118 functioning as a protective insulating film of the transistor 150 and the insulating film 118 functioning as a protective insulating film of the capacitor 160, a silicon oxide film or a silicon oxynitride film is formed by plasma CVD, sputtering, or the like. , Silicon nitride oxide film,
An insulating layer containing one or more of a silicon nitride film, an aluminum oxide film, a hafnium oxide film, a yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film and a neodymium oxide film , Can be used respectively.

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

In addition, the first oxide semiconductor film 110 which functions as a channel region of the transistor 150
The insulating film 114 in contact with a is preferably an oxide insulating film, and an insulating film capable of releasing oxygen is used. In other words, an insulating film capable of releasing oxygen is an insulating film having a region (oxygen excess region) containing oxygen in excess of the stoichiometric composition. Note that 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, 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 110a which functions as a channel region of the transistor 150, and the first oxide semiconductor film 110a is formed. Oxygen deficiency can be reduced. For example, oxygen molecules measured by thermal desorption analysis (hereinafter referred to as TDS analysis) which is performed by heat treatment at a surface temperature of the film of 100 ° C. to 700 ° C., preferably 100 ° C. to 500 ° C. By using an insulating film having a released amount of 1.0 × 10 ¹⁸ molecules / cm ³ or more, the amount of oxygen vacancies contained in the first oxide semiconductor film 110 a can be reduced.

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

In addition, since the insulating films 114 and 116 can use insulating films of the same material, the interface between the insulating film 114 and the insulating film 116 may not be clearly confirmed. Therefore, in the present embodiment, the interface between the insulating film 114 and the insulating film 116 is illustrated by a broken line. Note that although the two-layer structure of the insulating film 114 and the insulating film 116 is described in this embodiment, the present invention is not limited to this. For example, a single layer structure of the insulating film 114, a single layer structure of the insulating film 116, or 3
A layered structure of layers or more may be used.

Note that the source electrode 112 a and the drain electrode 112 b, and the first oxide semiconductor film 110.
An insulating film 122 may be provided between a and a. The example in that case is shown to FIG. 17 (A) and (B). 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. Insulating film 122
The same material and film quality as the contents described for the insulating film 108 can be adopted.

<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.
This will be described using

First, a gate electrode including the second oxide semiconductor film 104 a and a second oxide semiconductor film 104 b functioning as one of a pair of electrodes are formed over the substrate 102. After that, substrate 1
The insulating film 108 including the insulating films 106 and 107 is formed over the second oxide semiconductor film 104 a and the second oxide semiconductor film 104 b (see FIG. 2A).

Note that the substrate 102, the second oxide semiconductor films 104a and 104b, and the insulating films 106 and 1
07 can be formed by selecting from among the materials listed above. Note that in this embodiment, a glass substrate is used as the substrate 102, and the second oxide semiconductor film 104a is used.
As the insulating film 106, hydrogen can be released using an In-Ga-Zn oxide film (using a metal oxide target of In: Ga: Zn = 1: 1: 1) as the insulating film 106b. A silicon nitride film is used as the insulating film 107, and a silicon oxynitride film capable of releasing oxygen is used.

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

In addition, after the oxide semiconductor film is formed over the substrate 102, the second oxide semiconductor films 104a and 104b are patterned such that a desired region of the oxide semiconductor film remains, and then unnecessary regions are etched. It is formed by

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

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

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

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

After the first oxide semiconductor films 110 a and 110 b are formed, heat treatment is preferably performed. The heat treatment is performed at a temperature of 250 ° C. to 650 ° C., preferably 300 ° C. to 500 ° C., more preferably 350 ° C. to 450 ° C., an inert gas atmosphere, an atmosphere containing 10 ppm or more of an oxidizing gas, or a reduced pressure atmosphere. You can do it in The heat treatment may be performed in an atmosphere containing 10 ppm or more of an oxidizing gas in order to compensate for oxygen released from the first oxide semiconductor films 110 a and 110 b after the heat treatment is performed 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 110 a and 110 b. Note that the heat treatment may be performed before the first oxide semiconductor films 110a and 110b are processed into an island shape.

Note that in order to provide stable electrical characteristics to the transistor 150 in which the first oxide semiconductor film 110 a is a channel region, impurities in the first oxide semiconductor film 110 a are reduced.
It is effective to make the first oxide semiconductor 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, and patterning is performed so that a desired region of the conductive film is left, and then unnecessary regions are etched. A source electrode 112a on the insulating film 108 and the first oxide semiconductor film 110a;
And the drain electrode 112b (see FIG. 2C).

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

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

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

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

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

After this, heat treatment is preferably performed. By 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 110 a and oxygen deficiency in the first oxide semiconductor film 110 a can be compensated. 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 110 b not in contact with the insulating film 114 is not reduced, the first oxide semiconductor film 110 b contains more oxygen vacancies than the first oxide semiconductor film 110 a. It will be done. The heat treatment can be performed under the same conditions as the heat treatment after the first oxide semiconductor films 110 a and 110 b are formed.

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

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

The resistivity of the first oxide semiconductor film 110b is at least the first oxide semiconductor film 110a.
Lower than, ^{preferably, 1 × 10 -3 1 × 10} 4 less [Omega] cm or more [Omega] cm, more preferably, it is less than 1 × ^{10 -3} Ωcm or more 1 × ^{10 -1} Ωcm. Insulating film 11
8 also has an effect of preventing external impurities such as water, an alkali metal, an alkaline earth metal and the like from diffusing into the first oxide semiconductor film 110 a included in the transistor 150.

The silicon nitride film used as the insulating film 118 in this embodiment is preferably formed at a high temperature, for example, 100 ° C. or higher, more preferably 300 ° C. or lower, in order to enhance the block property. It is preferable to form a film by heating at a temperature of 400 ° C. or less.

In addition, the capacitor element 160 is manufactured along with the formation of the first oxide semiconductor film 110 b. 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 104 b, and the other of the pair of electrodes is the first oxide semiconductor Membrane 110
b. In addition, 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.

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.

Second Embodiment
In this embodiment, as a semiconductor device of one embodiment of the present invention, a modification of the semiconductor device described in Embodiment 1 is described with reference to FIGS. The same reference numerals are used for portions similar to the reference numerals shown in FIGS. 1 to 3 of the first embodiment or portions having similar functions, and the repetitive description thereof will be omitted.

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

The semiconductor device illustrated in FIGS. 4A and 4B includes a transistor 151 including the first oxide semiconductor film 110 a and the second oxide semiconductor film 104 a, and a capacitor including an insulating film between a pair of electrodes. And the 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 104 a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104 a, and the insulating film 108. The first oxide semiconductor film 110a and the source electrode 112a and the drain electrode 112b over the first oxide semiconductor film 110a are provided so as to overlap with the gate electrode including the upper second oxide semiconductor film 104a. 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 protective insulating films of the transistor 151. Further, 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 has, for example, a function as a pixel electrode.

The capacitive element 161 has a second function as one of the pair of electrodes on the substrate 102.
A second oxide semiconductor film 104b, insulating films 108, 114, 116, and 118 functioning as a dielectric film over the second oxide semiconductor film 104b, and second insulating films 108, 114, 116, and 118. And a conductive film 120 functioning as the other of the pair of electrodes in a position overlapping with the oxide semiconductor film 104 b. That is, the conductive film 120 has a function as a pixel electrode and a function as an electrode of a capacitor.

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

In addition, the capacitor element 161 has translucency. That is, the second capacitor element 161 has a second
Oxide semiconductor film 104 b, the insulating films 108, 114, 116, and 118, and the conductive film 120.
Each is made of a material having translucency. As described above, when the capacitor element 161 has translucency, it can be formed large (in a large area) in a region other than the portion where the transistor in the pixel is formed. Therefore, the capacitance value is increased while the aperture ratio is increased. An increased number of semiconductor devices can be obtained. As a result, a semiconductor device with excellent display quality can be obtained. In addition, the capacitor 161 can be manufactured by using a manufacturing process of the transistor 151. Therefore, a semiconductor device with low manufacturing cost can be obtained.

Note that as the insulating films 106 and 118, an insulating film containing at least hydrogen is used. Also,
As the insulating films 107, 114, and 116, an insulating film containing at least oxygen is used. Thus, the insulating film or the transistor 151 used for the transistor 151 and the capacitor 161
And controlling the resistivity of the first oxide semiconductor film and the second oxide semiconductor film included in the transistor 151 and the capacitor 161 by using the insulating film in contact with the capacitor 161 with the above-described structure. be able to.

Note that the first oxide semiconductor film 110 a and the second oxide semiconductor films 104 a and 104 b
The resistivity of V can be controlled by referring to the description of Embodiment 1.

The main difference between the semiconductor device shown in FIGS. 1A and 1B of the first embodiment and the semiconductor device shown in FIGS. 4A and 4B is that the other electrode of the capacitor element 161 is electrically conductive. The point is 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 which functions as a pixel electrode.

Thus, 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 simultaneously formed. In other words, they function as the gate electrode of the transistor. By forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor on the same surface, the manufacturing cost can be reduced. Also,
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 appropriate treatment on the oxide semiconductor film,
A conductive film having high conductivity and light transmittance can be provided. By using the conductive film, light transmission can be provided to the transistor and / or the capacitor.

Note that the source electrode 112 a and the drain electrode 112 b, and the first oxide semiconductor film 110.
An insulating film 122 may be provided between a and a. Examples in that case are shown in FIGS. 18 (A) and 18 (B).

Note that the conductive film 1 is formed simultaneously with the conductive film 120 and is simultaneously etched and formed.
20a may be provided to overlap with the channel region of the transistor. An example in that case is shown in FIG. 15 (A) and FIG. 19 (A). As an example, the conductive film 120 a is formed at the same time as the conductive film 120 and etched and formed at the same time, so that the conductive film 120 a includes the same material. Therefore, the increase in the number of process steps can be suppressed. However, one aspect of the embodiment of the present invention is not limited to this. The conductive film 120 a may be formed in a process different from that of the conductive film 120. The conductive film 120 a has a region overlapping with the channel region of the transistor. Thus, the conductive film 120 a functions as a 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 120 a may be supplied with a different signal or a different potential from the second oxide semiconductor film 104 a without being connected to the second oxide semiconductor film 104 a.

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 has a function as a pixel electrode. For the conductive film 120, for example, a material having translucency in visible light may be used. Specifically, indium (In),
It is preferable to use a material containing one selected from zinc (Zn) and tin (Sn). For 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, indium tin oxide to which silicon oxide is added, or the like can be used. The conductive film 120 can be formed by, for example, a sputtering method.

<Method of Manufacturing Display Device (Modified Example 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.
This will be described using

First, a gate electrode including the second oxide semiconductor film 104 a and a second oxide semiconductor film 104 b functioning as one of a 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 on the insulating film 108 so as to overlap with the gate electrode including the second oxide semiconductor film 104a (see FIG. 5B).

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

In addition, a portion of the insulating film 107 (a region exposed from the first oxide semiconductor film 110 a) is etched by over etching during etching of the first oxide semiconductor film 110 a to reduce the film thickness. is there.

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

Next, a conductive film is formed over the insulating film 108 and the first oxide semiconductor film 110 a, and patterning is performed so that a desired region of the conductive film is left, and then unnecessary regions are etched. The source electrode 112 a and the drain electrode 112 b are formed over the oxide semiconductor film 110 a (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 desired regions of the insulating films 114, 116, and 118 remain, and then unnecessary regions are etched to form the openings 142 (see FIG. 6A).

The opening 142 is formed so as to expose the drain electrode 112 b. As a method of forming the opening 142, for example, a dry etching method can be used. However, the opening 1
The formation method of 42 is not limited to this, and a wet etching method or a combination of a dry etching method and a wet etching method may be used.

Next, a conductive film is formed over the insulating film 118 so as to cover the opening 142, and patterning and etching are performed to leave a desired region of the conductive film, whereby a conductive film 120 is formed (FIG.
)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. An example in that case is shown in FIG.
(B), (C), and FIG. 19 (B), (C) show. As the insulating film 118a, for example,
It can be formed using an organic resin material. As a material applicable to the insulating film 118a, for example, an acrylic resin, a polyimide resin, a polyamide resin, and the like can be given.

Note that as shown in FIGS. 15C and 19C, the conductive film 121 may be provided. The conductive film 121 may be provided so as to overlap with the 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. Thus, the conductive film 121 functions as a second gate electrode of the transistor. Therefore, the conductive film 121 is
It may be connected to the second oxide semiconductor film 104a. Alternatively, the conductive film 121 is
A signal or a different potential may be supplied to the second oxide semiconductor film 104 a without being connected to the second oxide semiconductor film 104 a.

Note that the conductive film 1 is formed simultaneously with the conductive film 121 and is simultaneously etched and formed.
The capacitor 21 may be provided so as to overlap with the electrode of the capacitor. The example in that case is shown to FIG. 20 (A), (B), (C). As a result, the capacitance value of the capacitive element can be increased.

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.

Third Embodiment
In this embodiment, as a semiconductor device of one embodiment of the present invention, a modified example of the semiconductor device described in Embodiment 1 will be described with reference to FIG. The same reference numerals are used for portions similar to the reference numerals shown in FIGS. 1 to 3 of the first embodiment or portions having similar functions, and the repetitive description thereof will be omitted.

<Configuration Example of Semiconductor Device (Modified Example 2)>
FIG. 7A is a top view of a semiconductor device of one embodiment of the present invention, and FIG. 7B is a top view of FIG.
) Corresponds to a cross-sectional view of a cross section taken along a dashed dotted line I-J and a dashed dotted line K-L. Note that in FIG. 7A, some components (such as a gate insulating film) of components of the semiconductor device are not illustrated in order to avoid complication.

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

The transistor 152 includes a gate electrode including the second oxide semiconductor film 104 a over the substrate 102, an insulating film 108 functioning as a gate insulating film over the gate electrode including the second oxide semiconductor film 104 a, and the insulating film 108. The first oxide semiconductor film 110a and the source electrode 112a and the drain electrode 112b over the first oxide semiconductor film 110a are provided so as to overlap with the gate electrode including the upper second oxide semiconductor film 104a. 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 of the transistor 152. Further, 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 has, for example, a function as a pixel electrode.

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

By thus providing an electrode between the pair of electrodes, the capacitance can be increased without increasing the area of the capacitor. The capacitive element 162 can be regarded as, for example, the following structure. A capacitor element 162 is a first capacitor element in which the insulating film 108 sandwiched between the second oxide semiconductor film 104 b and the first oxide semiconductor film 110 a is a dielectric film;
A second capacitor element in which the insulating film 118 sandwiched between the first oxide semiconductor film 110 a and the conductive film 120 is a dielectric film is stacked is provided.

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. In addition, insulating film 11
4, 116, and 118 function as protective insulating films in the transistor 152. In addition, the insulating film 118 functions as part of a dielectric film in the capacitor 162.

In addition, the capacitor 162 has a light transmitting property. That is, the capacitor 162 has the first
The oxide semiconductor film 110b, the second oxide semiconductor film 104b, the insulating films 108 and 118, and the conductive film 120 are each formed of a light-transmitting material. As described above, when the capacitor element 162 has translucency, it can be formed large (in a large area) in a region other than the portion where the transistor in the pixel is formed. Therefore, the capacitance value is increased while the aperture ratio is increased. An increased number of semiconductor devices can be obtained. As a result, a semiconductor device with 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 low manufacturing cost can be obtained.

Note that as the insulating films 106 and 118, an insulating film containing at least hydrogen is used. Also,
As the insulating films 107, 114, and 116, an insulating film containing at least oxygen is used. Thus, the insulating film or the transistor 152 used for the transistor 152 and the capacitor 162
And controlling the resistivity of the first oxide semiconductor film and the second oxide semiconductor film included in the transistor 152 and the capacitor 162 by forming the insulating film in contact with the capacitor 162 with the above-described insulating film. be able to.

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

The main difference between the semiconductor device shown in FIGS. 1A and 1B of the first embodiment and the semiconductor device shown in FIGS. 7A and 7B is the electrode structure of the capacitor 162.

In the semiconductor device of one embodiment of the present invention, a conductive film which functions as a gate electrode of a transistor and a conductive film which functions as an electrode of a capacitor are simultaneously formed. In other words, a conductive film which functions as a gate electrode of the transistor By forming a conductive film functioning as an electrode of a capacitor on the same surface, manufacturing cost can be reduced. 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 appropriate treatment on the oxide semiconductor film, the conductive film can have high conductivity and light transmittance. By using the conductive film, light transmission can be provided to the transistor and / or the capacitor.

As a method for manufacturing the semiconductor device shown in FIGS. 7A and 7B, FIGS.
These semiconductor devices can be formed by combining the semiconductor device shown in and the method for manufacturing the semiconductor devices shown in FIGS. 4A and 4B.

Note that as in FIG. 15A, the conductive film 120a may be provided so as to overlap with the channel region of the transistor. An example in that case is shown in FIG. 16 (A) and FIG. 19 (A).

Further, as in FIGS. 15B and 15C, the insulating film 118a may be provided over the insulating film 118. Examples in that case are shown in FIGS. 16 (B) and (C) and FIGS. 19 (B) and (C).

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, as a semiconductor device of one embodiment of the present invention, a variation of the semiconductor device described in Embodiment 1 will be described with reference to FIGS. The same reference numerals are used for portions similar to the reference numerals shown in FIGS. 1 to 3 of the first embodiment or portions having similar functions, and the repetitive description thereof will be omitted.

<Configuration Example of Semiconductor Device (Modified Example 3)>
FIG. 8A is a top view of a semiconductor device of one embodiment of the present invention, and FIG. 8B is a top view of FIG.
) Corresponds to a cross-sectional view of a cross section between the dashed dotted line M-N and the dashed dotted line OP. Note that in FIG. 8A, some components (such as a gate insulating film) of components of the semiconductor device are not illustrated in order to avoid complication.

The semiconductor device illustrated in FIGS. 8A and 8B includes a transistor 250 including a first oxide semiconductor film 210 and a second oxide semiconductor film 204 a, and a capacitor including an insulating film between a pair of electrodes. And an 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 212a and a drain electrode 212b over the first oxide semiconductor film 210, and a first An insulating film 2 which functions as a gate insulating film over the oxide semiconductor film 210
And a gate electrode including the second oxide semiconductor film 204 a which overlaps with the first oxide semiconductor film 210 over the insulating film 208. 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 including the second oxide semiconductor film 204a, the source electrode 212a, and the drain electrode 212b. The insulating films 218 and 217 have a function as a protective insulating film of the transistor 250. Further, an opening 240 reaching the drain electrode 212 b is formed on the insulating films 218 and 217.
The conductive film 220 is formed on the insulating film 217 so as to cover the opening 240. The conductive film 220 has a function as, for example, a pixel electrode.

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

Note that 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 as described above. The insulating films 218 and 217 function as a protective insulating film in the transistor 250 and function as part of a dielectric film in the capacitor 260. Although FIGS. 8A and 8B illustrate the configuration 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 in the capacitor 260 may be removed in the process of manufacturing the transistor 250.

In addition, 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 of a light-transmitting material. As described above, since the capacitor 260 has translucency, it can be formed large (in a large area) in a region other than the portion where the transistor in the pixel is formed, so that the capacitance value can be increased while the aperture ratio is increased. An increased number of semiconductor devices can be obtained. As a result, a semiconductor device with excellent display quality can be obtained. The capacitor 260 can be manufactured by using a manufacturing process of the transistor 250. Therefore, a semiconductor device with low manufacturing cost can be obtained.

Note that as the insulating films 207 and 218, an insulating film containing at least hydrogen is used. Also,
As the insulating films 216, 206, and 217, an insulating film containing at least oxygen is used. Thus, the insulating film or the transistor 250 used for the transistor 250 and the capacitor 260
And controlling the resistivity of the first oxide semiconductor film and the second oxide semiconductor film included in the transistor 250 and the capacitor 260 by forming the insulating film in contact with the capacitor 260 with the above-described insulating film. be able to.

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

Here, the first oxide semiconductor film 210 and the second oxide semiconductor films 204 a and 204 b
The control method of the resistivity of will be described below.

<Method 2 of controlling resistivity of oxide semiconductor>
Oxide semiconductors that can be used for the first oxide semiconductor film 210 and the second oxide semiconductor films 204 a and 204 b are determined depending on oxygen vacancies in the film and / or impurities such as hydrogen and water in the film. It is a semiconductor material whose resistivity can be controlled. Therefore, the treatment for increasing the concentration of oxygen vacancies and / or impurities or the treatment for reducing the concentration of oxygen vacancies and / or impurities 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, the second oxide semiconductor film 2 which functions as a gate electrode of the transistor 250
04a, plasma treatment is performed on the oxide semiconductor film used for the second oxide semiconductor film 204b which functions as an electrode of the capacitor 260 to increase oxygen vacancies in the oxide semiconductor film, and / or the oxide semiconductor By increasing impurities such as hydrogen and water in the film, the carrier density can be high and the oxide semiconductor can have low resistance. In addition, by forming an insulating film containing hydrogen in contact with an oxide semiconductor and diffusing hydrogen from the insulating film containing hydrogen into the oxide semiconductor, the oxide semiconductor has high carrier density and low resistivity. Can.

On the other hand, the first oxide semiconductor film 2 which functions as a channel formation region of the transistor 250
In the structure 10, the insulating films 216 and 206 are provided so as not to be in contact with the insulating film 218 containing hydrogen. In addition, when at least one of the insulating films 216 and 206 is an insulating film capable of releasing oxygen, oxygen can be supplied to the first oxide semiconductor film 210. The first oxide semiconductor film 210 supplied with oxygen compensates for oxygen vacancies in the film or at the interface, and becomes a high-resistance oxide semiconductor. Note that as the insulating film capable of releasing oxygen, for example, a silicon oxide film or a silicon oxynitride film can be used.

Thus, 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 simultaneously formed. In other words, they function as the gate electrode of the transistor. By forming the conductive film to be formed and the conductive film functioning as an electrode of the capacitor on the same surface, the manufacturing cost can be reduced. Also,
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 appropriate treatment on the oxide semiconductor film,
A conductive film having high conductivity and light transmittance can be provided. By using the conductive film, light transmission can be provided to the transistor and / or the capacitor.

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

<First Oxide Semiconductor Film and Second Oxide Semiconductor Film>
As the first oxide semiconductor film 210, the first oxide semiconductor film 110a of Embodiment 1 can be used.
It can be formed by incorporating the materials listed above. In addition, the second oxide semiconductor film 2
The materials 04a and 204b can be formed by using the materials listed in the second oxide semiconductor films 104a and 104b in Embodiment 1.

<Source electrode and drain electrode>
As the source electrode 212a and the drain electrode 212b, the source electrode 1 of the first embodiment is used.
It can form by using the material enumerated to 12a and the drain electrode 112b.

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

<Method of 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.
This will be described using 0.

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 an unnecessary region is 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, and patterned so that a desired region of the conductive film is left, and then an unnecessary region is etched to form a source electrode. 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. (Refer FIG.9 (C).).

Next, a resist mask is formed over the second oxide semiconductor film 204, and patterning is performed so that a desired region of the second oxide semiconductor film 204 is left, and then unnecessary regions are etched to form a second Oxide semiconductor films 204a and 204b are formed. At this time, the insulating films 206 and 207 under the second oxide semiconductor films 204a and 204b are also etched simultaneously to form island-shaped insulating films 206 and 207 (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 remain, and then an unnecessary region is etched to form the opening 240. The opening 240 is formed to reach the drain electrode 212 b (see FIG.
See FIG. 10 (B)).

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 such that a desired region of the conductive film remains; 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.

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.

Fifth Embodiment
In this embodiment, as a semiconductor device of one embodiment of the present invention, a modification of the semiconductor device described in Embodiment 1 will be described with reference to FIG.

<Configuration Example of Semiconductor Device (Modified Example 4)>
The semiconductor device illustrated in FIG. 11A includes the first oxide semiconductor films 110 a and 110 b of the transistor 150 and the capacitor 160 described in Embodiment 1 and the oxide stacked films 410 a and 410 b.
The configuration is b. Therefore, the other configurations are the transistor 150 and the capacitive element 1
It is the same as 60, and the detailed explanation is omitted.

  The details of the oxide laminated 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 film 420
In the description, a 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, metal oxides having at least one of the same constituent elements are preferably used. Alternatively, the oxide semiconductor film 420 and the oxide film 42
The constituent elements of 2 may be the same, and the compositions of the two may be different.

The oxide semiconductor film 420 is an In-M-Zn oxide (M is Al, Ti, Ga, Y, Zr, L
In the case of “a”, “Ce”, “Nd”, “Sn” or “Hf”, the atomic ratio of the metal elements of the sputtering target used to form the In—M—Zn oxide satisfies In ≧ M and Zn ≧ M. Is preferred. As an atomic ratio of 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 above sputtering target as an error.

Note that when the sum of In and M is 100 atomic% when the oxide semiconductor film 420 is an In-M-Zn oxide, the atomic number ratio of In to M is preferably 25 at.
greater than or equal to M, less than 75 atomic% in M, and more preferably 34 at
c% or more, 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. As described above, with the use of the oxide semiconductor with a wide energy gap, the off-state current of the transistor can be reduced.

The thickness of the oxide semiconductor film 420 is 3 nm to 200 nm, preferably 3 nm to 1 nm.
The thickness is set to 00 nm or less, more preferably 3 nm to 50 nm.

The oxide film 422 is typically an In-Ga oxide, an In-Zn oxide, or In-M-Z.
n oxide (M represents Al, Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), and the energy at the lower end of the conduction band is lower than that of the oxide semiconductor film 420 at a vacuum level. In the vicinity, typically, the difference between the energy of the lower end of the conduction band of the oxide film 422 and the energy of the lower end of the conduction band of the oxide semiconductor film 420 is 0.05 eV or more, 0.07 eV or more, 0.1 eV
More than, or 0.15 eV or more and 2 eV or less, 1 eV or less, 0.5 eV or less, or 0.4 eV or less. 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 or less, 0.5 eV or less, or 0.4 eV or less.

The oxide film 422 may have the following effects by having the above-described element M at a higher atomic ratio than 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)
The insulating property is higher than that of the oxide semiconductor film 420. Further, since the element M is a metal element having a strong bonding force with oxygen, oxygen deficiency becomes difficult to occur by having M at an atomic ratio higher than that of In.

When the oxide film 422 is an In-M-Zn oxide, the sum of In and M is 100 ato
The atom number ratio of In to M is preferably 50 atomic% of In, assuming that it is mic%
Less than, M is 50 atomic% or more, more preferably, In is less than 25 atomic%, and M is 75 atomic% or more.

In addition, the oxide semiconductor film 420 and the oxide film 422 are formed using In-M-Zn oxide (M is Al
, Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), the ratio of the number of M contained in the oxide film 422 is larger than that of the oxide semiconductor film 420, and Specifically, the atomic ratio is 1.5 times or more, preferably 2 times or more, more preferably 3 times or more higher than the atoms included in the oxide semiconductor film 420.

Further, the oxide film 422 is represented by In: M: Zn = x ₁ : y ₁ : z ₁ [atomic number ratio], and the oxide semiconductor film 420 is represented by In: M: Zn = x ₂ : y ₂ : z ₂ [the number of atoms] Ratio], y ₁ / x ₁ is y
₂ / _{x 2} greater than, and _preferably, y 1 / _{x 1} is 1.5 times more than _y 2 / _{x 2.} More preferably, y ₁ / x ₁ is at least twice as large as y ₂ / x ₂ , more preferably
in _which y ₁ / _{x 1} is three or more times greater 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 given to the transistor including an oxide semiconductor. However, when y ₂ is three or more times as large as x ₂ , the field-effect mobility of the transistor including an oxide semiconductor is reduced, so y ₂ is preferably less than three times as large as x ₂ .

When the oxide semiconductor film 420 and the oxide film 422 are In-M-Zn oxides, In-M-
The atomic ratio of the metal elements of the sputtering target used to deposit Zn oxide is
It is preferable to satisfy M> In and Zn ≧ M. In: Ga: Zn = 1: 3: 2, In: Ga: Zn = 1: 3 as an atomic ratio of metal elements of such a sputtering target.
3 In: Ga: Zn = 1: 3: 4, In: Ga: Zn = 1: 3: 5, In: Ga: Zn
= 1: 3: 6, In: Ga: Zn = 1: 3: 7, In: Ga: Zn = 1: 3: 8, In:
Ga: Zn = 1: 3: 9, In: Ga: Zn = 1: 3: 10, In: Ga: Zn = 1: 6
: 4, In: Ga: Zn = 1: 6: 5, In: Ga: Zn = 1: 6: 6, In: Ga: Z
n = 1: 6: 7, In: Ga: Zn = 1: 6: 8, In: Ga: Zn = 1: 6: 9, In
: Ga: Zn = 1: 6: 10 is preferable. Note that the atomic ratio of the metal elements contained in the oxide semiconductor film 420 and the oxide film 422 formed using the above sputtering target is, as an error, the positive of the atomic ratio of the metal elements contained in the above sputtering target. Includes a negative 20% change.

Note that the composition is not limited to those described above, and a composition having an appropriate composition may be used according to the semiconductor characteristics and electrical characteristics (field effect mobility, threshold voltage, and the like) of the required transistor. In addition, in order to obtain semiconductor characteristics of a required transistor, 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 made appropriate. Is preferred.

The oxide film 422 also functions as a film which relieves damage to 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
The thickness is from 100 nm to 100 nm, preferably from 3 nm to 50 nm.

When silicon or carbon which is one of the group 14 elements is contained 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 (the concentration obtained by secondary ion mass spectrometry) is , 2 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁷ atoms
/ Cm ³ or less.

Further, in the oxide semiconductor film 420, the concentration of an alkali metal or an 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 Make it Alkali metals and alkaline earth metals are
When it is combined with an oxide semiconductor, carriers may be generated, which may increase the off-state current of the transistor. Therefore, it is preferable to reduce the concentration of alkali metal or alkaline earth metal in the oxide semiconductor film 420.

In addition, when nitrogen is contained in the oxide semiconductor film 420, electrons which are carriers are generated, carrier density is increased, and n-type is easily formed. As a result, a transistor including an oxide semiconductor which contains nitrogen is likely to be normally on. Therefore, in the oxide semiconductor film 420, nitrogen 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 simply stacked layers, but a continuous junction (here, in particular, a structure in which the energy at the lower end of the conduction band continuously changes between the respective films) is formed. To make the That is, a stacked-layer structure in which no impurity that forms a defect level such as a trap center or a recombination center exists in the oxide semiconductor at the interface between the films is provided. If an impurity is mixed between the stacked oxide semiconductor film 420 and the oxide film 422, continuity of energy bands is lost, and carriers are trapped at the interface.
Or they recombine and disappear.

In order to form a continuous junction, it is necessary to use the multi-chamber type film forming apparatus (sputtering apparatus) provided with a load lock chamber to continuously stack the respective films without exposure to the atmosphere. Each chamber in the sputtering apparatus is evacuated at a high vacuum (5 × 10 ⁻⁷ Pa to 1 × 10 ⁻⁷ Pa by using an adsorption-type evacuation pump such as a cryopump in order to remove water and the like that become impurities to the oxide semiconductor film as much as possible. It is preferable to set it to about ^10-4 Pa). Alternatively, it is preferable that a turbo molecular pump and a cold trap be combined to prevent backflow of a gas, particularly a gas containing carbon or hydrogen, from the exhaust system into the chamber.

  Here, the band structure of the oxide stack film is described with reference to FIG.

FIG. 11B schematically illustrates an oxide stack film and part of a band structure of an insulating film in contact with the oxide stack film. Here, the case where a silicon oxide film is provided as the insulating film 107 and the insulating film 114 will be described. Note that EcI1 shown in FIG. 11B indicates the energy at the lower end of the conduction band of the silicon oxide film used as the insulating film 107, and EcS1 is the oxide semiconductor film 42.
The energy of the lower end of the conduction band of 0 is shown, EcS2 is the energy of the lower end of the conduction band of the oxide film 422, and EcI2 is the energy of 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 gradually without any 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 is mutually transferred between the oxide semiconductor film 420 and the oxide film 422 to form a mixed layer. It can be said that there is.

From FIG. 11B, it can be seen that the oxide semiconductor film 420 serves as a well and a channel region is formed in the oxide semiconductor film 420. Note that in the oxide semiconductor film 420 and the oxide film 422, the energy at the lower end of the conduction band changes continuously.
It can be said that 0 and the oxide film 422 are continuously bonded.

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. Although the oxide film 422 can be formed, the oxide semiconductor film 420 and the trap state can be separated. However, 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 beyond the energy difference. By trapping electrons in the trap level, negative fixed charge is generated at the insulating film interface, and the threshold voltage of the transistor is shifted in the positive direction.
Therefore, the energy difference between EcS1 and EcS2 is 0.1 eV or more, preferably 0.1.
The threshold voltage of 15 eV or more is preferable because variations in threshold voltage of the transistor are reduced and stable electrical characteristics can be obtained.

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.

Sixth Embodiment
In this embodiment, an example of an oxide semiconductor film which can be applied to the transistor and the capacitor in the semiconductor device of one embodiment of the present invention will be described.

<Crystallinity of Oxide Semiconductor Film>
The structure of the oxide semiconductor film is described below.

Oxide semiconductor films are roughly classified into non-single-crystal oxide semiconductor films and single-crystal oxide semiconductor films.
A non-single crystal oxide semiconductor film is a CAAC-OS (C Axis Aligned Cry).
stalline Oxide Semiconductor film, a polycrystalline oxide semiconductor film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, or the like.

  First, a CAAC-OS film is described.

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

CAAC-OS film as a transmission electron microscope (TEM: Transmission Elec)
When observed with a tron microscope, it is not possible to confirm clear boundaries between crystal parts, that is, grain boundaries (also referred to as grain boundaries). Therefore, C
It can be said that in the AAC-OS film, the decrease in electron mobility due to crystal grain boundaries does not easily occur.

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

On the other hand, the CAAC-OS film is observed by TEM from a direction substantially perpendicular to the sample surface (Plane T
EM observation) can confirm that the 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 the present specification, “parallel” refers to a state in which two straight lines are arranged at an angle of −10 ° or more and 10 ° or less. Therefore, the case of -5 degrees or more and 5 degrees or less is also included. Also,"
The term “perpendicular” refers to a state in which two straight lines are disposed at an angle of 80 ° or more and 100 ° or less.
Therefore, the case of 85 degrees or more and 95 degrees or less is also included.

Further, most of the crystal parts included in the CAAC-OS film each fit inside a cube whose one side is less than 100 nm. Therefore, the crystal part included in the CAAC-OS film has 10 sides
Also included is the case of a size that fits within a cube of less than nm, less than 5 nm, or less than 3 nm. However, 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, 2500 nm ² or more, 5 μm
There are cases where crystal region becomes ² or more, or 1000 .mu.m ^more is observed.

X-ray diffraction (XRD: X-Ray Diffraction) for CAAC-OS film
When structural analysis is performed using a device, for example, a CAAC-OS having a crystal of InGaZnO ₄
In the analysis by the out-of-plane method of a film, a peak may appear near a diffraction angle (2θ) of 31 °. Since this peak is attributed to the (009) plane of the InGaZnO ₄ crystal, the crystal of the CAAC-OS film has c-axis orientation, and the c-axis points in a direction substantially perpendicular to the formation surface or the top surface. It can be confirmed that

On the other hand, in-p, in which X-rays are made incident on the CAAC-OS film in a direction substantially perpendicular to the c-axis
In the analysis by the lane method, 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 , 2θ is fixed near 56 °, and the normal vector of the sample surface is the axis (φ axis)
When analysis (φ scan) is performed while rotating the sample, six peaks attributed to crystal planes equivalent to the (110) plane are observed. On the other hand, in the case of the CAAC-OS film, a clear peak does not appear 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 has c-axis orientation and the c-axis is a normal to the formation surface or the top surface It turns out that it is pointing in the direction parallel to the vector. Therefore, each layer of the metal atoms arranged in the layer form 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, distribution of c-axis aligned crystal parts is not necessarily uniform. For example, in the case where a crystal part of a CAAC-OS film is formed by crystal growth from the vicinity of the top surface of the CAAC-OS film, the ratio of c-axis aligned regions in the region near the top surface is higher than the region near the formation surface Can be high. In the case where an impurity is added to the CAAC-OS film, a region to which the impurity is added may be altered to form a region in which the proportions of crystal parts which are partially c-axis aligned are different.

Note that the out-of-plane of a CAAC-OS film having a crystal of InGaZnO ₄
In the analysis by the method, in addition to the peak at 2θ of around 31 °, a peak may also appear at around 2θ of 36 °. The peak at 2θ of around 36 ° indicates that a part of the CAAC-OS film contains a crystal having no c-axis alignment. It is preferable that the CAAC-OS film 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 low impurity concentration. The impurity is an element other than the main components of the oxide semiconductor film such as hydrogen, carbon, silicon, or a transition metal element. In particular, an element such as silicon having a stronger bonding force with oxygen than a metal element constituting the oxide semiconductor film disturbs the atomic arrangement of the oxide semiconductor film by depriving the oxide semiconductor film of oxygen, thereby causing crystallinity Cause a decrease in In addition, heavy metals such as iron and nickel, argon, carbon dioxide, and the like have large atomic radius (or molecular radius), and therefore, if contained within the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disturbed and crystallinity Cause a decrease in Note that an impurity contained in the oxide semiconductor film may be a carrier trap or a carrier generation source.

The CAAC-OS film is an oxide semiconductor film with low density of defect states. For example, oxygen vacancies in the oxide semiconductor film may be carrier traps or may be a carrier generation source by capturing hydrogen.

A low impurity concentration and a low density of defect levels (less oxygen vacancies) are referred to as high purity intrinsic or substantially high purity intrinsic. A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film can reduce carrier density because there are few carriers. Thus, a transistor including the oxide semiconductor film rarely has negative threshold voltage (also referred to as normally on). In addition, the highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has few carrier traps. Thus, the transistor including the oxide semiconductor film has small variation in electrical characteristics and is highly reliable. Note that the charge trapped in the carrier trap in the oxide semiconductor film may take a long time to be released and behave as if it were fixed charge. Therefore, in the transistor including the oxide semiconductor film, which has a high impurity concentration and a high density of defect states, electrical characteristics may be unstable.

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

  Next, a microcrystalline oxide semiconductor film is described.

In a microcrystalline oxide semiconductor film, in some cases, a crystal part can not be clearly confirmed in an observation image by TEM. The crystal part included in the microcrystalline oxide semiconductor film often has a size of 1 nm to 100 nm, or 1 nm to 10 nm. In particular, 1 nm to 10 n
nanocrystals which are microcrystals of m or less or 1 nm or more and 3 nm or less (nc: nanocrys
nc), the oxide semiconductor film having the
Called xide Semiconductor) membrane. Also, the nc-OS film is, for example, T
In the observation image by EM, grain boundaries may not be clearly identified.

The nc-OS film has periodicity in atomic arrangement in a minute region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In addition, in the nc-OS film, regularity is not observed in crystal orientation between different crystal parts. Therefore, no orientation can be seen in the entire film.
Therefore, the nc-OS film may not be distinguished from the amorphous oxide semiconductor film depending on the analysis method. For example, XRD using an X-ray having a diameter larger than that of a crystal part for an nc-OS film
When structural analysis is performed using an apparatus, in the analysis by the out-of-plane method, a peak indicating a crystal plane is not detected. In addition, electron 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 with respect to the nc-OS film.
When it is done, a diffraction pattern like a halo pattern is observed. On the other hand, when performing electron beam diffraction (also referred to as nanobeam electron beam diffraction) using an electron beam with a probe diameter (for example, 1 nm or more and 30 nm or less) close to or smaller than the size of the crystal part on the nc-OS film. Spots are observed. In addition, when nanobeam electron diffraction is performed on the nc-OS film, a region with high luminance may be observed in a ring shape (in a ring shape). In addition, 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 an amorphous oxide semiconductor film. However, the nc-OS film does not have regularity in crystal orientation between different crystal parts. Therefore, nc-
The OS film has a higher density of defect states than the CAAC-OS film.

Note that the oxide semiconductor film is, for example, an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, or C
Among the AAC-OS films, a stacked film having two or more types may be used.

The oxide semiconductor film in any of the above crystal states may be applied to the oxide semiconductor film included in the transistor and the capacitor of the semiconductor device of one embodiment of the present invention. In the case where an oxide semiconductor film having a stacked structure is included, the crystal states of the oxide semiconductor films may be different. Note that the CAAC-OS film is preferably used for the oxide semiconductor film which functions as a channel region of the transistor. In addition, the oxide semiconductor film functioning as an electrode of the capacitor may have lower crystallinity because the impurity concentration is higher than that of the oxide semiconductor film included in the transistor.

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

Seventh Embodiment
In this embodiment, a display device using the semiconductor device of one embodiment of the present invention will be described with reference to FIGS. The same portions as the functions shown in the first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted.

The display device illustrated in FIG. 12A includes a region including a pixel of a display element (hereinafter referred to as a pixel portion 302) and a circuit portion provided outside the pixel portion 302 and having a circuit for driving the pixel (see FIG.
Hereinafter, drive circuit portion 304) and a circuit having a protection function of an element (hereinafter, protection circuit 30)
6) and a terminal portion 307. Note that the protective circuit 306 may not be provided.

It is preferable that part or all of the driver circuit portion 304 be formed over the same substrate as the pixel portion 302. Thereby, the number of parts and the number of terminals can be reduced. Drive circuit unit 304
When 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 can be formed using COG (Chip On Glass) or TAB (T
It can be implemented by "ape Automated Bonding".

The pixel portion 302 has 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 portion 304 outputs a signal (scanning signal) for selecting a pixel (hereinafter referred to as a gate driver 304a) and a circuit for supplying a signal (data signal) for driving a display element of the pixel (data signal). Hereinafter, driver circuits such as the source driver 304 b) are included.

The gate driver 304a has a shift register and the like. The gate driver 304a is
A signal for driving the shift register is input through the terminal portion 307, and the signal is output. 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 potentials of wirings (hereinafter, referred to as scan lines GL_1 to GL_X) to which scan signals are supplied. Note that a plurality of gate drivers 304 a may be provided, and the scan lines GL_1 to GL_X may be divided and controlled by the plurality of gate drivers 304 a. Alternatively, the gate driver 304a has a function capable of supplying an initialization signal. However, the present invention is not limited to this.
4a can also supply another signal.

The source driver 304 b has a shift register and the like. The source driver 304 b is
In addition to the signal for driving the shift register, the signal (image signal) which is the source of the data signal is input through the terminal portion 307. The source driver 304 b has a function of generating a data signal to be written to the pixel circuit 301 based on an image signal. In addition, the source driver 304 b has a function of controlling output of a data signal in accordance with a pulse signal obtained by inputting a start pulse, a clock signal, and the like. In addition, the source driver 304 b has a function of controlling the potentials of wirings (hereinafter, referred to as data lines DL_1 to DL_Y) to which data signals are supplied. Alternatively, the source driver 304 b has a function capable of supplying an initialization signal. However, without being limited to this, the source driver 304 b can also supply another signal.

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

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

The protective circuit 306 illustrated in FIG. 12A includes, for example, the gate driver 304 a and the pixel circuit 3.
It is connected to the scanning line GL which is a wiring between 01. Alternatively, the protection circuit 306 is connected to a data line DL which is a wiring between the source driver 304 b and the pixel circuit 301. Alternatively, the protective circuit 306 can be connected to a wiring between the gate driver 304 a and the terminal portion 307. Alternatively, the protective 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 refers to a portion provided with a terminal for inputting a power supply, a control signal, and an image signal from an external circuit to the display device.

The protective circuit 306 is a circuit which brings a wiring and another wiring into conduction when the wiring connected to the protection circuit 306 is supplied with a potential outside the predetermined range.

As shown in FIG. 12A, the pixel portion 302 and the driver circuit portion 304 each have a protective circuit 30.
By providing 6, the ESD (Electro Static Discharge:
It is possible to increase the resistance of the display device to an overcurrent generated by electrostatic discharge or the like.
However, the configuration of the protection circuit 306 is not limited to this. For example, the protection circuit 306 may be connected to the gate driver 304 a or the protection circuit 306 may be connected to the source driver 304 b. Alternatively, the protective circuit 306 can be connected to the terminal portion 307.

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

In addition, the plurality of pixel circuits 301 illustrated in FIG. 12A can have a configuration illustrated in FIG. 12B, for example.

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

The potential of one of the pair of electrodes of the liquid crystal element 370 is appropriately set in accordance with the specification of the pixel circuit 301. The alignment state of the liquid crystal element 370 is set by the data to be written. Note that a common potential (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. Alternatively, different potentials may be applied to one of the pair of electrodes of the liquid crystal element 370 in the pixel circuit 301 in each row.

For example, as a method of driving a display provided with the liquid crystal element 370, a TN mode, an STN mode, a VA mode, an ASM (Axially Symmetric Aligned M) can be used.
icro-cell mode, OCB (Optically Compensated)
Birefringence) mode, FLC (Ferroelectric Liqu)
id Crystal) mode, AFLC (AntiFerroelectric Li
quid crystal mode, MVA mode, PVA (patterned Ve
rtical alignment) mode, IPS mode, FFS mode, or TBA
(Transverse Bend Alignment) mode or the like may be used.
Further, as a method of driving the display device, ECB (Electric
ally Controlled Birefringence mode, PDLC (P
olymer dispersed liquid crystal) mode, PNLC
(Polymer Network Liquid Crystal) mode, guest host mode, etc. However, the present invention is not limited to this, and various liquid crystal elements and driving methods thereof can be used.

Alternatively, the liquid crystal element may be formed of a liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent. The liquid crystal exhibiting a blue phase has a short response speed of 1 msec or less. In addition, since liquid crystals exhibiting a blue phase are optically isotropic, alignment processing is unnecessary.
And the viewing angle dependency is small.

In the m-th row and n-th pixel circuit 301, 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. Ru. Further, the gate electrode of the transistor 150 is connected to the scanning line G.
It is electrically connected to L_m. The transistor 150 has a function of controlling writing of data of a data signal by being turned on or off.

One of the pair of electrodes of capacitive element 160 is a wiring to which a potential is supplied (hereinafter referred to as potential supply line VL).
And the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 370. Note that the value of the potential of the potential supply line VL is appropriately set in accordance with the specification of the pixel circuit 301. The capacitive element 160 has a function as a storage capacitor for storing the written data.

For example, in a display device including the pixel circuit 301 in FIG.
The pixel circuits 301 in each row are sequentially selected by a, and the transistor 150 is turned on to write data signal data.

The pixel circuit 301 to which data is written is brought into the holding state when the transistor 150 is turned off. Images can be displayed by sequentially performing this on a row-by-row basis.

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

For example, in this specification and the like, a display element, a display device which is a device having a display element, a light emitting element, and a light emitting device which is a device having a light emitting element use various modes or have various elements. Can do. As an example of a display element, a display device, a light emitting element or a light emitting device, an EL (electroluminescent) element (an EL element containing an organic substance and an inorganic substance, an organic E
L element, inorganic EL element), LED (white LED, red LED, green LED, blue LED etc.), transistor (transistor emitting light according to current), electron emitting element, liquid crystal element,
Electronic ink, electrophoretic element, grating light valve (GLV), plasma display (PDP), MEMS (micro-electro-mechanical system), digital micro mirror device (DMD), DMS (digital micro shutter), IM
OD (interference modulation) elements, electrowetting elements, piezoelectric ceramic displays, carbon nanotubes, etc.
Some have display media in which the contrast, brightness, reflectance, transmittance, etc. change. EL
An example of a display device using an element is an EL display. A field emission display (FED) or SE is an example of a display device using an electron emission element.
D method flat display (SED: Surface-conduction Elec)
tron-emitter Display) and the like. Examples of a display device using a liquid crystal element include a liquid crystal display (transmissive liquid crystal display, semi-transmissive liquid crystal display, reflective liquid crystal display, direct view liquid crystal display, projection liquid crystal display) and the like. Examples of a display device using an electronic ink or an electrophoretic element include electronic paper.

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

Alternatively, an example of using a light emitting element 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.

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

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

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

The shapes and sizes 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.

The touch panel 8004 can be used by overlapping a resistive touch panel or a capacitive touch panel with the display panel 8006. In addition, the opposite substrate (the sealing substrate) of the display panel 8006 can have a touch panel function. In addition, display panel 8
It is also possible to provide an optical sensor in each pixel of 006 to make an optical touch panel.

The backlight unit 8007 has a light source 8008. The light source 8008 may be provided at an end of the backlight unit 8007 and may be configured to use a light diffusion plate.

The frame 8009 has a function as an electromagnetic shield for blocking an electromagnetic wave generated by the operation of the printed substrate 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 circuit board 8010 has a power supply circuit and 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. Battery 801
1 is omissible when using a commercial power supply.

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

14A to 14H illustrate an electronic device. These electronic devices include a housing 5000, a display portion 5001, a speaker 5003, an LED lamp 5004, and an operation key 50.
05 (including a power switch or operation switch), connection terminal 5006, sensor 5007 (
Force, displacement, position, velocity, acceleration, angular velocity, number of rotations, distance, light, liquid, magnetism, temperature, chemical substance, voice, time, hardness, electric field, current, voltage, electric power, radiation, flow, humidity, inclination, And the like), a microphone 5008, and the like.

FIG. 14A shows a mobile computer, which has a switch 5009 in addition to those described above.
, Infrared port 5010, and the like. FIG. 14B shows a portable image reproducing apparatus (for example, a DVD reproducing apparatus) provided with a recording medium, which may have a second display portion 5002, a recording medium reading portion 5011, and the like in addition to those described above. it can. FIG. 14C shows a goggle type display, which has a second display portion 5002 and a support portion 5012 in addition to those described above.
, An earphone 5013, and the like. FIG. 14D illustrates a portable game machine, which can include the memory medium reading portion 5011 and the like in addition to the above components. FIG. 14E illustrates a digital camera having 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 components. FIG. 14F illustrates a portable game machine, which includes a second display portion 5002 and a recording medium reading portion 5011 in addition to the above components.
, And so on. FIG. 14 (G) shows a television receiver, in addition to the ones described above,
A tuner, an image processing unit, and the like can be included. FIG. 14H illustrates a portable television receiver, which can include a charger 5017 that can transmit and receive signals and the like in addition to the above components.

The electronic devices illustrated in FIGS. 14A to 14H can have various functions.
For example, a function of displaying various information (still image, moving image, text image, etc.) on the display unit, a touch panel function, a calendar, a function of displaying date or time, etc., a function of controlling processing by various software (programs), A wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, reading out and displaying a program or data recorded in a recording medium It can have a function of displaying on a unit, and the like. Furthermore, in an electronic device having a plurality of display units, the function of displaying image information mainly on one display unit and displaying character information mainly on another display unit or considering parallax in a plurality of display units It is possible to have a function of displaying a three-dimensional image and the like by displaying the captured image. Furthermore, in an electronic device having an image receiving unit, the function of capturing a still image, the function of capturing a moving image, the function of automatically or manually correcting the captured image, the captured image in a recording medium (externally or built in a camera) A function to save, a function to display a captured image on a display portion, and the like can be provided. 14A to 1.
The functions that the electronic device illustrated in 4 (H) can have are not limited to these, and can have various functions.

The electronic device described in this embodiment is characterized by having a display portion for displaying some kind of 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 insulation film 107 insulation film 108 insulation film 110a oxide semiconductor film 110b oxide semiconductor film 112a source electrode 112b drain electrode 114 insulation film 116 insulation film 118 insulation film 118 insulation The film 120 conductive film 120 a conductive film 121 conductive film 121 a conductive film 122 insulating film 132 insulating film 140 opening 142 opening 150 transistor 151 transistor 152 transistor 160 capacitive element 161 capacitive element 162 capacitive element 202 substrate 204 oxide semiconductor film 204 a oxide semiconductor film 204 b oxide semiconductor film 206 insulation film 207 insulation film 208 insulation film 210 oxide semiconductor film 212 a source electrode 212 b drain electrode 216 insulation film 217 insulation film 218 insulation film 220 conduction Electrolytic film 240 Opening 250 Transistor 260 Capacitive element 301 Pixel circuit 302 Pixel portion 304 Drive circuit portion 304a Gate driver 304b Source driver 306 Protection circuit 307 Terminal portion 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 Case 5001 Display portion 5002 Display portion 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 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 (4)

A first conductive film,
A second conductive film,
A first insulating film above the first conductive film and above the second conductive film;
A first oxide semiconductor film above the first insulating film;
A second oxide semiconductor film above the first insulating film;
A third conductive film electrically connected to the first oxide semiconductor film;
A fourth conductive film electrically connected to the first oxide semiconductor film;
And a fifth conductive film above the first oxide semiconductor film;
The first oxide semiconductor film has a channel formation region of a transistor,
The first conductive film has a region overlapping with the channel formation region via the first insulating film,
The second conductive film has a function as a first electrode of a capacitive element,
The first conductive film is electrically connected to the fifth conductive film,
The fifth conductive film has a region overlapping with the channel formation region via a second insulating film,
The second oxide semiconductor film functions as a second electrode of the capacitor;
The semiconductor device having a region in which the second oxide semiconductor film has a resistivity lower than that of the channel formation region. A first conductive film,
A second conductive film,
A first insulating film above the first conductive film and above the second conductive film;
A first oxide semiconductor film above the first insulating film;
A second oxide semiconductor film above the first insulating film;
A third conductive film electrically connected to the first oxide semiconductor film;
A fourth conductive film electrically connected to the first oxide semiconductor film;
And a fifth conductive film above the first oxide semiconductor film;
The first oxide semiconductor film has a channel formation region of a transistor,
The first conductive film has a region overlapping with the channel formation region via the first insulating film,
The second conductive film has a function as a first electrode of a capacitive element,
The first conductive film is electrically connected to the fifth conductive film,
The fifth conductive film has a region overlapping with the channel formation region via a second insulating film,
The second oxide semiconductor film functions as a second electrode of the capacitor;
The second oxide semiconductor film has a region having a resistivity lower than that of the channel formation region,
The semiconductor device in which the first oxide semiconductor film and the second oxide semiconductor film contain In, Ga, and Zn as main components. A first conductive film,
A second conductive film,
A first insulating film above the first conductive film and above the second conductive film;
A first oxide semiconductor film above the first insulating film;
A second oxide semiconductor film above the first insulating film;
A third conductive film electrically connected to the first oxide semiconductor film;
A fourth conductive film electrically connected to the first oxide semiconductor film;
A fifth conductive film above the first oxide semiconductor film;
And a pixel electrode above the fourth conductive film,
The first oxide semiconductor film has a channel formation region of a transistor,
The first conductive film has a region overlapping with the channel formation region via the first insulating film,
The second conductive film has a function as a first electrode of a capacitive element,
The first conductive film is electrically connected to the fifth conductive film,
The fifth conductive film has a region overlapping with the channel formation region via a second insulating film,
The second oxide semiconductor film functions as a second electrode of the capacitor;
The second oxide semiconductor film has a region having a resistivity lower than that of the channel formation region,
The pixel electrode is electrically connected to the fourth conductive film,
The semiconductor device in which the second oxide semiconductor film has a region overlapping with the pixel electrode. A first conductive film,
A second conductive film,
A first insulating film above the first conductive film and above the second conductive film;
A first oxide semiconductor film above the first insulating film;
A second oxide semiconductor film above the first insulating film;
A third conductive film electrically connected to the first oxide semiconductor film;
A fourth conductive film electrically connected to the first oxide semiconductor film;
A fifth conductive film above the first oxide semiconductor film;
And a pixel electrode above the fourth conductive film,
The first oxide semiconductor film has a channel formation region of a transistor,
The first conductive film has a region overlapping with the channel formation region via the first insulating film,
The second conductive film has a function as a first electrode of a capacitive element,
The first conductive film is electrically connected to the fifth conductive film,
The fifth conductive film has a region overlapping with the channel formation region via a second insulating film,
The second oxide semiconductor film functions as a second electrode of the capacitor;
The second oxide semiconductor film has a region having a resistivity lower than that of the channel formation region,
The pixel electrode is electrically connected to the fourth conductive film,
The second oxide semiconductor film has a region overlapping with the pixel electrode,
The semiconductor device in which the first oxide semiconductor film and the second oxide semiconductor film contain In, Ga, and Zn as main components.

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