JP6999754B2 - Semiconductor device - Google Patents

Description

One aspect of the present invention relates to a metal oxide film. Further, the present invention relates to a semiconductor device using the metal oxide film.

In the present specification and the like, the semiconductor device refers to all devices that can function by utilizing the semiconductor characteristics, such as a transistor, a semiconductor circuit, a storage device, an image pickup device, an electro-optical device, and a power generation device (thin-film solar cell,). (Including organic thin-film solar cells, etc.) and electronic devices can be said to be semiconductor devices.

Attention is being paid to a technique for constructing a transistor using a semiconductor film formed on a substrate having an insulating surface. The transistor is widely applied to electronic devices such as integrated circuits (ICs) and image display devices (also referred to simply as display devices). Silicon-based semiconductor materials are widely known as semiconductor films applicable to transistors, but metal oxides (oxide semiconductors) exhibiting semiconductor characteristics are attracting attention as other materials.

For example, Patent Document 1 discloses a technique for manufacturing a transistor using an amorphous oxide containing In, Zn, Ga, Sn and the like as an oxide semiconductor.

Japanese Unexamined Patent Publication No. 2006-165529

One aspect of the present invention is to provide a metal oxide film having a novel structure.

Alternatively, one aspect of the present invention is to provide a metal oxide film having high physical stability.

Alternatively, one aspect of the present invention is to provide a highly reliable semiconductor device to which the above-mentioned metal oxide is applied.

The description of these issues does not preclude the existence of other issues. It should be noted that one aspect of the present invention does not need to solve all of these problems. Issues other than these are self-evident from the description of the description, drawings, claims, etc.
It is possible to extract problems other than these from the drawings, claims, and the like.

One aspect of the present invention includes In, Ga, and Zn, and in a cross-sectional observation image, a first layer in which In atoms are periodically arranged and a second layer in which Ga or Zn atoms are periodically arranged. , Are observed in plurality, and between the pair of first layers, a first region having a second layer n (n is a natural number) layer and
It is a metal oxide film having a second region having an m (m is a natural number other than n) layer between the other pair of first layers.

Further, in the metal oxide film, the first region and the second region are adjacent to each other in the direction perpendicular to the plane parallel to the first layer, and the boundary between the first region and the second region. In one of the first
It is preferable to share the layer of.

Alternatively, the first region and the second region are adjacent to each other in a direction parallel to the plane parallel to the first layer, and at the boundary between the first region and the second region, one first region is used. It is preferable that the layers of are continuous.

Further, in the first region or the second region of the metal oxide film, it is preferable that the first layer is parallel to the surface to be formed.

Further, it is preferable that no grain boundary is observed between the first region and the second region of the metal oxide film.

Further, one aspect of the present invention is a source that electrically connects any of the above metal oxide films, a gate electrode, a gate insulating layer between the metal oxide film and the gate electrode, and the metal oxide film. It is a semiconductor device having an electrode and a drain electrode, and a channel is formed in a metal oxide film.

In the present specification and the like, the term "A plane parallel to the B plane" means that the angle formed by the normal line of the A plane and the normal line of the B plane is −20 ° or more and 20 ° or less. Further, in the present specification and the like, the term “C plane perpendicular to B plane” means a state in which the angle formed by the normal line of C plane and the normal line of B plane is 70 ° or more and 110 ° or less. Further, in the present specification and the like, the fact that the C line is substantially perpendicular to the B plane means that the angle formed by the normal lines of the C line and the B plane is −20 ° or more and 20 ° or less.

According to the present invention, it is possible to provide a metal oxide film having a novel structure. Alternatively, it is possible to provide a metal oxide film having high physical stability. Alternatively, it is possible to provide a highly reliable semiconductor device to which the above-mentioned metal oxide is applied.

The figure explaining the metal oxide film which concerns on embodiment. The figure explaining the metal oxide film which concerns on embodiment. The figure explaining the crystal structure of the metal oxide which concerns on embodiment. The figure explaining the crystal structure contained in the metal oxide film which concerns on embodiment. The figure explaining the structural example of the transistor which concerns on embodiment. The figure explaining the example of the manufacturing method of the transistor which concerns on embodiment. The figure explaining the structural example of the transistor which concerns on embodiment. The figure explaining the structure of the display panel which concerns on embodiment. The figure explaining the block diagram of the electronic device which concerns on embodiment. The figure explaining the external view of the electronic device which concerns on embodiment.

The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that the form and details of the present invention can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention is not construed as being limited to the description of the embodiments shown below.

In the configuration of the invention described below, the same reference numerals are commonly used between different drawings for the same parts or parts having similar functions, and the repeated description thereof will be omitted. Further, when referring to the same function, the hatch pattern may be the same and no particular reference numeral may be added.

In addition, in each figure described in this specification, the size of each structure, the thickness of a layer, or a region is referred to as a region.
May be exaggerated for clarity. Therefore, it is not necessarily limited to that scale.

(Embodiment 1)
In the present embodiment, the metal oxide film of one aspect of the present invention will be described with reference to the drawings.

[Crystal structure of metal oxide film]
The metal oxide film of one aspect of the present invention has a metal oxide containing two or more different metal elements. Further, as the metal oxide, an oxide having a crystal structure capable of forming a layered structure and having a different periodic structure due to a difference in composition can be used.

The various periodic structures expressed by different compositions are also called homologous phases. For example, when a certain crystal structure has a layered structure in which an A layer containing a metal A and a B layer containing a metal B are arranged in a layered manner, the number of B layers sandwiched between the pair of A layers depends on the composition. It changes continuously. As a result, different periodic structures are realized depending on the composition. In the present specification and the like, a structure that can have a different periodic structure depending on the composition is referred to as a homologous structure.

For example, the In—Ga—Zn-based oxide may have a homologous structure represented by _{InGaO_3} (ZnO) _m (m is a natural number). FIG. 3 shows an example of the crystal structure of the In—Ga—Zn-based oxide. The crystal structure shown in FIG. 3A is a crystal structure represented by _{InGaO_3} (ZnO) _m (m = 1). The crystal structure shown in FIG. ₃ (B) is InGaO_3 (ZnO) _m .
It is a crystal structure represented by (m = 2). The crystal structure shown in FIG. 3C is InGa.
It is a crystal structure represented by O_3 (ZnO) _m (m = ₃ ).

The metal oxide film of one aspect of the present invention is characterized in that regions having different crystal structures (periodic structures) coexist in the film.

For example, when an In—Ga—Zn-based oxide is used as the metal oxide, a layer composed of InO ₂ (also referred to as InO ₂ layer) and a layer composed of Ga and Zn oxides ((Ga, Zn).
) It has a layered structure in which two layers (also referred to as O layer) are arranged in a layered manner.

Further, the number of (Ga, Zn) O layers sandwiched between the pair of InO _two layers can take various values. For example, the structure shown in FIG. 4 (A) has one layer (Ga, Zn) between _two layers of InO.
) It has an O layer. Further, the structure shown in FIG. 4B has two layers (Ga) between the pair of InO _two layers.
, Zn) O layer (also referred to as (Ga, Zn) ₂ O ₂ layer). Further, the structure shown in FIG. 4C has _three (Ga, Zn) O layers (also referred to as (Ga, Zn) 3O ₃ layers) between the pair of InO _two layers.

As described above, when the In—Ga—Zn-based oxide is used as the metal oxide film of one aspect of the present invention, it exists between the pair of InO ₂ layers in the metal oxide film (Ga, Zn) Includes two or more crystal regions with different numbers of O layers.

The crystal region contained in the metal oxide is, for example, a transmission electron microscope (TEM: Transmi).
It can be observed by ssion Electron Microscope) or the like. Further, the crystal structure of the crystal region observed by the TEM can be specified by further analyzing the crystal region by using a technique such as electron diffraction.

Here, as a cross-sectional observation of the metal oxide film, for example, a scanning transmission electron microscope (STEM: S)
canning Transition Electron Microscopy
), It is difficult to observe oxygen atoms, which are light elements, when high-resolution observations are made, and only the arrangement of metal atoms can be confirmed.

Subsequently, FIG. 1 shows a cross-sectional observation image of the metal oxide film of one aspect of the present invention.

Here, as an example of the metal oxide film, a sample in which an In—Ga—Zn-based oxide film was formed on a quartz glass substrate with a thickness of about 50 nm was used. The film forming conditions for the metal oxide film shown in FIG. 1 are In.
: Ga: Zn = 1: 1: 1 (atomic number ratio) by sputtering method using an oxide target, under an oxygen atmosphere (flow rate 45 sccm), pressure 0.4 Pa, direct current (DC) power supply power 0.5 kW, The substrate temperature at the time of film formation was set to room temperature. Further, the temperature is 650 ° C. under a nitrogen atmosphere, 1
The heat treatment was carried out for hours. Further, the metal oxide film after the heat treatment was sliced by the ion milling method to prepare a sample for cross-sectional observation.

For cross-sectional observation, use a transmission electron microscope (Hitachi High-Technologies Corporation: HD-2700) with an acceleration voltage of 200 kV and a magnification of 12 million times, and HAADF-STEM (High-Angle).
Annular Dark-Field Scanning Transmissio
n Electron Microscope) image was observed.

As shown in FIG. 1, in the metal oxide film, a layer in which atoms (specifically, electrons) observed to have high brightness are periodically arranged and atoms observed to have low brightness are arranged periodically. Multiple layers are observed. Here, the atom observed with high luminance is an In atom, and the atom observed with low luminance is a Ga atom or a Zn atom.

An enlarged view of the area 1 surrounded by the broken line in FIG. 1 (A) is shown in FIG. 1 (B). It can be confirmed that there are two layers in which Ga atoms or Zn atoms are periodically arranged between the layers in which a pair of In atoms are periodically arranged.

Here, since it is difficult to directly observe the O atoms constituting the metal oxide in the cross-sectional observation image as described above, the composition of the O atom and the bonding state between the O atom and the metal atom can be seen from the cross-sectional observation image. It is difficult to know. Therefore, in the following, the layers of periodically arranged atoms (specifically, electrons) obtained in the cross-sectional observation image are distinguished from the layers such as the _InO2 layer and the (Ga, Zn) O layer in the actual crystal structure. It will be written.

Specifically, in the following, in the cross-sectional observation image, one layer in which a pair of In atoms are periodically arranged is referred to as an In layer or a first layer. Also, in the cross-sectional observation image, Ga atom or Zn
One layer in which atoms are periodically arranged is referred to as a (Ga, Zn) layer or a second layer.

Further, when a metal oxide other than the In-Ga-Zn-based oxide is used, the atom having the highest brightness (the brightness is the same) among the plurality of periodically arranged layers observed in the cross-sectional observation image. In some cases, the atom containing the largest atomic number) is included in the first layer, the second layer, and the third layer in order.
It shall be described as a layer of.

Subsequently, an enlarged view of the area 2 surrounded by the broken line in FIG. 1 (A) is shown in FIG. 1 (C). It can be confirmed that three (Ga, Zn) layers exist between the pair of In layers.

As described above, the metal oxide film of one aspect of the present invention is a pair of first in the cross-sectional observation image thereof.
A first region having an n (n is a natural number) layer between the layers of, and an m (m is a natural number other than n) layer having a second layer between the other pair of first layers. It is characterized in that the second region having the same is mixed.

The type of crystal structure in the crystal region contained in the metal oxide film is not limited to two types, and may include three or more crystal regions having different types of crystal structures.

Further, in FIG. 1A, it can be confirmed that the region 1 and the region 2 are laminated in the direction perpendicular to the direction parallel to the In layer. Furthermore, focusing on the boundary between region 1 and region 2, one In
It can be confirmed that the layers are shared.

By stacking regions having different crystal structures in this way and providing two regions so as to share one In layer, grain boundaries do not occur between these regions, and high structural stability is realized. Has been done. Further, defects in the metal oxide film due to the presence of grain boundaries can be reduced.

Further, as shown in FIG. 1, in the upper layer of the region 1, as in the region 2, there is a region in which three (Ga, Zn) layers are present between the pair of In layers, and these are Even between one In
It can be confirmed that the layers are shared.

As described above, a plurality of regions having different crystal structures may be laminated while sharing the In layer. As a result, structural stability is obtained over a wide range in the metal oxide film, and structural stability is obtained.
A metal oxide film with reduced defects can be realized.

FIG. 2 is a cross-sectional observation image of another part of the sample.

In the cross-sectional observation image shown in FIG. 2, the region 3 in which two (Ga, Zn) layers exist between the pair of In layers and the (Ga, Zn) layer 3 between the other pair of In layers. Regions 4 in which layers exist are mixed. Further, the region 3 and the region 4 exist adjacent to each other in the direction parallel to the plane parallel to the In layer.

Further, in FIG. 2, one In layer constituting the region 3 extends to the region 4, and I in the region 4
It constitutes a part of n layers. That is, one In layer exists continuously in the region 3 and the region 4.

As described above, since the In layers have different crystal structures and are continuously present between adjacent regions, grain boundaries do not occur between these regions, and high structural stability is realized. There is.
Further, defects in the metal oxide film due to the presence of grain boundaries can be reduced.

The metal oxide film of one aspect of the present invention is a metal oxide film having high structural stability.
By applying such a metal oxide film to the semiconductor layer on which the channel of the transistor is formed, a highly reliable transistor can be realized.

Further, the metal oxide film according to one aspect of the present invention is a metal oxide film in which defects in the film are reduced because the crystal regions are continuously present and there are no grain boundaries between the regions. .. By applying such a metal oxide film to the semiconductor layer of a transistor, it is possible to realize a transistor in which carrier trapping due to defects is suppressed, high field effect mobility can be realized, and fluctuations in electrical characteristics are suppressed. Can be done.

A configuration example of the transistor to which the metal oxide film of one aspect of the present invention is applied will be described in a later embodiment.

[Method of forming a metal oxide film]
The method for forming the metal oxide film of the present embodiment will be described below.

The metal oxide film of the present embodiment can be formed by forming a film by a sputtering method in an atmosphere containing oxygen and then applying a heat treatment. By setting the film forming atmosphere to an atmosphere containing oxygen, oxygen deficiency in the metal oxide film can be reduced, and a film containing a crystal region can be obtained by a subsequent heat treatment.

By reducing oxygen deficiency in the metal oxide film of the present embodiment, it is possible to obtain a film having stable physical properties. In particular, when a semiconductor device is manufactured by applying a metal oxide film (oxide semiconductor film) exhibiting semiconductor characteristics as the metal oxide film of the present embodiment, oxygen deficiency in the oxide semiconductor film is caused by the semiconductor device. It becomes a factor that changes the electrical characteristics. Therefore, by manufacturing a semiconductor device using an oxide semiconductor film having reduced oxygen deficiency, it is possible to obtain a highly reliable semiconductor device.

In the metal oxide film of the present embodiment, it is preferable to increase the oxygen partial pressure in the film forming atmosphere because oxygen deficiency can be further reduced. More specifically, it is preferable that the oxygen partial pressure in the film forming atmosphere is 33% or more.

The target used in the sputtering method is not limited to the In—Ga—Zn-based oxide, and a multidimensional metal oxide having a homologous structure can be used. For example, In-M
-Zn-based oxides (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, Hf, etc.) can be used.

Further, the composition of the metal oxide contained in the target used in the sputtering method is not particularly limited as long as it can have a homologous structure. For example, in the case of an In—Ga—Zn-based oxide, if the composition of Ga is larger than that of Zn, it becomes easier to form a spinel structure instead of a layered structure. Therefore, it is preferable to increase the Zn content more than Ga. Further, since Zn may be sublimated during film formation by the sputtering method and the composition of Zn in the formed metal oxide film may be lowered, the composition of Zn is higher than the composition of the desired metal oxide film. It is preferable to use a target having a high zinc content.

Further, when the metal oxide film is formed by the sputtering method, the film may be formed at room temperature without heating the surface to be formed, or may be heated. When heating, for example, 150 ° C or higher, 3
The temperature may be 00 ° C. or higher, 450 ° C. or higher, and the like.

After forming the metal oxide film, heat treatment is performed. Atoms in the film are rearranged by heat treatment to form crystal regions in the metal oxide film.

At this time, since the dynamic degree of freedom is relatively high in the vicinity of the film surface, the atoms in the vicinity of the film surface are first rearranged in the initial stage, and the layer substantially parallel to the film surface is formed in the vicinity of the film surface. To. After that, in the process of crystallization proceeding from the film surface toward the depth direction, a crystal region having a laminated structure in which a plurality of layers substantially parallel to the film surface are laminated is formed. That is, the first layer and the second layer included in the crystal region are arranged in a direction parallel to the film surface.

Here, in the metal oxide film before the heat treatment, the metal element concentration is distributed. and,
When the atoms are rearranged during the heat treatment, it is considered that a region having a small number of (Ga, Zn) layers existing between the pair of In layers is formed in the region where the concentration of In atoms in the film is relatively high. Be done. On the other hand, in the region where the concentration of In atoms in the film is relatively low, it exists between a pair of In layers (Ga, Zn).
) A region with a large number of layers is formed. As a result, it is possible to form a metal oxide film having regions having different crystal structures in the film. It should be noted that such a forming process is In-Ga-Zn.
The same applies to a multidimensional metal oxide having a homologous structure other than the system oxide.

For example, a metal oxide film having regions having different concentrations of metal elements can be formed by forming the film at room temperature or at a temperature of room temperature or lower without heating the surface to be formed at the time of film formation.

The heat treatment is carried out at 550 ° C. or higher, preferably 600 ° C. or higher, more preferably 650 ° C. or higher. For example, the heat treatment may be performed at 650 ° C. for 1 hour. The higher the temperature of the heat treatment and the longer the time, the larger the proportion of the crystal region contained in the metal oxide film can be increased.

The heat treatment can be performed, for example, in a nitrogen atmosphere or a reduced pressure atmosphere. By performing the heat treatment in such an atmosphere, hydrogen in the metal oxide film can be effectively desorbed. In addition, oxygen in the metal oxide film may also be desorbed during the above heat treatment.
Subsequently, it is preferable to perform further heat treatment in an oxygen atmosphere to reduce oxygen deficiency in the membrane.

As described above, the metal oxide film of one aspect of the present invention can be formed.

This embodiment can be appropriately combined with other embodiments described in the present specification.

(Embodiment 2)
In the present embodiment, a semiconductor device to which a metal oxide film (oxide semiconductor film) exhibiting semiconductor characteristics, which is a metal oxide film of one aspect of the present invention, is applied will be described with reference to the drawings. Here, an example of a transistor configuration will be described as an example of a semiconductor device.

[Transistor configuration example]
FIG. 5A shows a schematic cross-sectional view of the transistor 100 exemplified below. The transistor 100 exemplified in this configuration example is a bottom gate type transistor.

The transistor 100 includes a gate electrode 102 provided on the substrate 101, an insulating layer 103 provided on the substrate 101 and the gate electrode 102, and a gate electrode 102 on the insulating layer 103.
It has an oxide semiconductor layer 104 provided so as to overlap with the oxide semiconductor layer 104, and a pair of electrodes 105a and 105b in contact with the upper surface of the oxide semiconductor layer 104, and also has an insulating layer 103 and an oxide semiconductor layer 10.
4. An insulating layer 106 that covers the pair of electrodes 105a and 105b, and an insulating layer 10 on the insulating layer 106.
7 is provided.

The oxide semiconductor film of one aspect of the present invention can be applied to the oxide semiconductor layer 104 of the transistor 100.

[Board 101]
There are no major restrictions on the material of the substrate 101, but at least a material having heat resistance sufficient to withstand the subsequent heat treatment is used. For example, a glass substrate, a ceramic substrate, a quartz substrate, a sapphire substrate, a YSZ (yttria-stabilized zirconia) substrate, or the like may be used as the substrate 101. Further, it is also possible to apply a single crystal semiconductor substrate such as silicon or silicon carbide, a polycrystalline semiconductor substrate, a compound semiconductor substrate such as silicon germanium, an SOI substrate, or the like.

Further, a semiconductor substrate or an SOI substrate on which a semiconductor element is provided may be used as the substrate 101. In that case, the transistor 100 is formed on the substrate 101 via the interlayer insulating layer. At this time, at least one of the gate electrode 102, the electrode 105a, and the electrode 105b of the transistor 100 may be electrically connected to the semiconductor element by the connection electrode embedded in the interlayer insulating layer. Transistor 10 on a semiconductor device via an interlayer insulating layer
By providing 0, it is possible to suppress an increase in the area due to the addition of the transistor 100.

Further, a flexible substrate such as plastic may be used as the substrate 101, and the transistor 100 may be formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate 101 and the transistor 100. The release layer can be used for forming a part or all of the transistor on the upper layer, separating the transistor from the substrate 101, and reprinting the transistor on another substrate. As a result, the transistor 100 can be reprinted on a substrate having inferior heat resistance or a flexible substrate.

[Gate electrode 102]
The gate electrode 102 may be formed by using a metal selected from aluminum, chromium, copper, tantalum, titanium, molybdenum, and tungsten, an alloy containing the above-mentioned metal as a component, an alloy obtained by combining the above-mentioned metals, and the like. can. Further, a metal selected from one or more of manganese and zirconium may be used. Further, the gate electrode 102 may have a single-layer structure or a laminated structure having two or more layers. For example, a single-layer structure of an aluminum film containing silicon, 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 titanium nitride film, and a tungsten film on which a tungsten film is laminated. A layered structure, a two-layer structure in which a tungsten film is laminated on a tantalum nitride film or a tungsten nitride film, a titanium film, and
There is a three-layer structure in which an aluminum film is laminated on the titanium film and a titanium film is further formed on the aluminum film. Further, an alloy film in which one or a plurality of metals selected from titanium, tantalum, tungsten, molybdenum, chromium, neodymium, and scandium are combined with aluminum, or a nitrided film thereof may be used.

Further, the gate electrode 102 includes indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, and indium zinc oxide. , A translucent conductive material such as indium tin oxide to which silicon oxide is added can also be applied. Further, it is also possible to form a laminated structure of the conductive material having the translucency and the metal.

Further, between the gate electrode 102 and the insulating layer 103, an In—Ga—Zn-based oxynitride semiconductor film, an In—Sn-based oxynitride semiconductor film, an In—Ga-based oxynitride semiconductor film, and an In—Zn system. Nitride semiconductor film, Sn-based oxynitride semiconductor film, In-based oxynitride semiconductor film, metal nitride film (InN)
, ZnN, etc.) may be provided. Since these films have a work function of 5 eV, preferably 5.5 eV or more, and have a value larger than the electron affinity of the oxide semiconductor, the threshold voltage of the transistor using the oxide semiconductor is positively shifted. It is possible to realize a switching element having so-called normally-off characteristics. For example, when an In-Ga-Zn-based oxynitride semiconductor film is used, an In-Ga-Zn-based oxynitride semiconductor film having a nitrogen concentration higher than that of the oxide semiconductor layer 104, specifically, 7 atomic% or more is used. ..

[Insulation layer 103]
The insulating layer 103 functions as a gate insulating film.

For the insulating layer 103, for example, silicon oxide, silicon nitride nitride, silicon nitride, silicon nitride, aluminum oxide, hafnium oxide, gallium oxide or Ga—Zn-based metal oxide, silicon nitride or the like may be used, and the insulating layer 103 may be laminated or single layered. prepare.

Further, as the insulating layer 103, hafnium silicate (HfSiO _x ), nitrogen-added hafnium silicate ( _{HfSi xOyNz} ), nitrogen-added _{hafniumaluminate ( HfAl xOyNz} ), hafnium oxide, and the like. By using a high-k material such as yttrium oxide, the gate leak of the transistor can be reduced.

[Pair pair of electrodes 105a, 105b]
The pair of electrodes 105a and 105b function as source or drain electrodes of the transistor.

The pair of electrodes 105a and 105b are made of aluminum, titanium, chromium, as conductive materials.
A simple substance composed of nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or an alloy containing the same as a main component can be used as a single layer structure or a laminated structure. For example, a single-layer structure of an aluminum film containing silicon, 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, and a copper film on a copper-magnesium-aluminum alloy film. Two-layer structure to be laminated, a titanium film or a titanium nitride film, and a three-layer structure in which an aluminum film or a copper film is laminated on the titanium film or the titanium nitride film, and a titanium film or a titanium nitride film is formed on the aluminum film or a copper film. , A molybdenum film or a molybdenum nitride film, an aluminum film or a copper film laminated on the molybdenum film or the molybdenum nitride film, and a three-layer structure in which the molybdenum film or the molybdenum nitride film is formed. A transparent conductive material containing indium oxide, tin oxide or zinc oxide may be used.

[Insulating layers 106, 107]
For the insulating layer 106, it is preferable to use an oxide insulating film containing more oxygen than oxygen satisfying the stoichiometric composition. An oxide insulating film containing more oxygen than oxygen satisfying a stoichiometric composition is desorbed from some oxygen by heating. Oxide insulating films containing more oxygen than oxygen satisfying the stoichiometric composition are described by Thermal Desorption Gas Spectroscopy (TDS).
In ion spectroscopy) analysis, the amount of oxygen desorbed in terms of oxygen atoms is 1.
.. 0 × 10 ¹⁸ atoms / cm ³ or more, preferably 3.0 × 10 ²⁰ atoms / cm
It is an oxide insulating film having ³ or more.

For example, as the insulating layer 106, silicon oxide, silicon oxide and the like can be used.

The insulating layer 106 is the oxide semiconductor layer 1 when the insulating layer 107 to be formed later is formed.
It also functions as a damage mitigation film for 04.

Further, an oxide film that allows oxygen to pass through may be provided between the insulating layer 106 and the oxide semiconductor layer 104.

As the oxide film that permeates oxygen, silicon oxide, silicon oxynitride, or the like can be used. In the present specification, the silicon oxide film refers to a film having a higher oxygen content than nitrogen in its composition, and the silicon nitride film has a nitrogen content higher than oxygen in its composition. Refers to a membrane with a lot of oxygen.

As the insulating layer 107, an insulating film having a blocking effect of oxygen, hydrogen, water and the like can be used. By providing the insulating layer 107 on the insulating layer 106, it is possible to prevent the diffusion of oxygen from the oxide semiconductor layer 104 to the outside and the invasion of hydrogen, water, etc. from the outside into the oxide semiconductor layer 104. As an insulating film having a blocking effect of oxygen, hydrogen, water, etc., silicon nitride,
There are silicon nitride, aluminum oxide, aluminum nitride, gallium oxide, gallium nitride, yttrium oxide, yttrium oxide, hafnium oxide, hafnium oxide and the like.

[Example of manufacturing method of transistor]
Subsequently, an example of a method for manufacturing the transistor 100 illustrated in FIG. 5A will be described.

First, as shown in FIG. 6A, the gate electrode 102 is formed on the substrate 101, and the insulating layer 103 is formed on the gate electrode 102.

Here, a glass substrate is used as the substrate 101.

[Formation of gate electrode]
The method of forming the gate electrode 102 is shown below. First, the sputtering method, the CVD method,
A conductive film is formed by a vapor deposition method or the like, and a resist mask is formed on the conductive film by a photolithography step using a first photomask. Next, a part of the conductive film is etched with the resist mask to form the gate electrode 102. After that, the resist mask is removed.

The gate electrode 102 may be formed by an electrolytic plating method, a printing method, an inkjet method, or the like, instead of the above-mentioned forming method.

[Formation of gate insulating layer]
The insulating layer 103 is formed by a sputtering method, a CVD method, a vapor deposition method, or the like.

When a silicon oxide film, a silicon nitride film, or a silicon nitride film is formed as the insulating layer 103, it is preferable to use a depositary gas containing silicon and an oxidizing gas as the raw material gas. Typical examples of the sedimentary gas containing silicon include silane, disilane, trisilane, and fluorinated silane. Examples of the oxidizing gas include oxygen, ozone, nitrous oxide, nitrogen dioxide and the like.

Further, when forming the silicon nitride film as the insulating layer 103, it is preferable to use a two-step forming method. First, a first silicon nitride film having few defects is formed by a plasma CVD method using a mixed gas of silane, nitrogen, and ammonia as a raw material gas. next,
The raw material gas is switched to a mixed gas of silane and nitrogen to form a second silicon nitride film having a low hydrogen concentration and capable of blocking hydrogen. By such a forming method, a silicon nitride film having few defects and having hydrogen blocking property can be formed as the insulating layer 103.

Further, when forming a gallium oxide film as the insulating layer 103, MOCVD (Metal) is used.
It can be formed by using the Organic Chemical Vapor Deposition) method.

[Formation of oxide semiconductor layer]
Next, as shown in FIG. 6B, the oxide semiconductor layer 104 is formed on the insulating layer 103.

The method for forming the oxide semiconductor layer 104 is shown below. First, an oxide semiconductor film is formed by the method exemplified in the first embodiment. Subsequently, a resist mask is formed on the oxide semiconductor film by a photolithography step using a second photomask. Next, a part of the oxide semiconductor film is etched with the resist mask to form the oxide semiconductor layer 104. After that, the resist mask is removed.

The heat treatment exemplified in the first embodiment may be performed immediately after the oxide semiconductor film is formed, or may be performed after etching a part of the oxide semiconductor film.

Here, the oxide semiconductor has a large energy gap of 3.0 eV or more, and a transistor to which an oxide semiconductor film obtained by processing the oxide semiconductor under appropriate conditions and sufficiently reducing the carrier density thereof is applied. In, the leakage current (off current) between the source and the drain in the off state can be made extremely low as compared with the conventional transistor using silicon.

When a large amount of hydrogen is contained in the oxide semiconductor film, a part of hydrogen becomes a donor by binding to the oxide semiconductor, and electrons that are carriers are generated. As a result, the threshold voltage of the transistor shifts in the negative direction. Therefore, after the oxide semiconductor film is formed, dehydration treatment (dehydrogenation treatment) is performed to remove hydrogen or water from the oxide semiconductor film to purify the oxide semiconductor film so that impurities are not contained as much as possible. preferable.

In addition, oxygen may be reduced from the oxide semiconductor film at the same time by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film. Therefore, it is preferable to add oxygen to the oxide semiconductor, which has been reduced at the same time by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, or to supply oxygen to compensate for the oxygen deficiency of the oxide semiconductor film. .. In the present specification and the like, the case of supplying oxygen to the oxide semiconductor film may be referred to as oxygenation treatment.

In this way, the oxide semiconductor film is made i-type (intrinsic) or i-type by removing hydrogen or water by dehydrogenation treatment (dehydrogenation treatment) and compensating for oxygen deficiency by oxygenation treatment. It can be an oxide semiconductor film that is as close as possible to substantially i-type (intrinsic).
In addition, substantially true means that the number of carriers derived from the donor is extremely small (close to zero) in the oxide semiconductor film, and the carrier density is 1 × 10 ¹⁷ / cm ³ or less and 1 × 10 ¹⁶ / cm ³ or less. It means that it is 1 × 10 ¹⁵ / cm ³ or less, 1 × 10 ¹⁴ / cm ³ or less, and 1 × 10 ¹³ / cm ³ or less.

Further, as described above, the transistor provided with the i-type or substantially i-type oxide semiconductor film can realize extremely excellent off-current characteristics. For example, the drain current per 1 μm of channel width when the transistor using the oxide semiconductor film is off is 1 × 10 ^-18 A or less, preferably 1 × 10 ^-21 A or less at room temperature (about 25 ° C.). , More preferably 1x10
It can be ^-24 A or less, or 1 × 10 ^-15 A or less at 85 ° C., preferably 1 × 10 ^-18 A or less, and more preferably 1 × 10 ^-21 A or less. The transistor off state means a state in which the gate voltage is sufficiently smaller than the threshold voltage in the case of an n-channel type transistor. Specifically, if the gate voltage is 1 V or more and 2 V or more or 3 V or more smaller than the threshold voltage, the transistor is turned off.

[Formation of a pair of electrodes]
Next, as shown in FIG. 6C, a pair of electrodes 105a and 105b are formed.

The method of forming the pair of electrodes 105a and 105b is shown below. First, a conductive film is formed by a sputtering method, a CVD method, a vapor deposition method, or the like. Next, a resist mask is formed on the conductive film by a photolithography step using a third photomask. Next, a part of the conductive film is etched with the resist mask to form a pair of electrodes 105a and 105b. After that, the resist mask is removed.

As shown in FIG. 6C, a part of the upper part of the oxide semiconductor layer 104 may be etched to form a thin film when the conductive film is etched. Therefore, when forming the oxide semiconductor layer 104, it is preferable to set the thickness of the oxide semiconductor film to be thick in advance.

[Formation of insulating layer]
Next, as shown in FIG. 6D, the oxide semiconductor layer 104 and the pair of electrodes 105a and 10
The insulating layer 106 is formed on the 5b, and then the insulating layer 107 is formed on the insulating layer 106.

When a silicon oxide film or a silicon oxynitride film is formed as the insulating layer 106, it is preferable to use a depositary gas containing silicon and an oxidizing gas as the raw material gas. Typical examples of the sedimentary gas containing silicon include silane, disilane, trisilane, and fluorinated silane. Examples of the oxidizing gas include oxygen, ozone, nitrous oxide, nitrogen dioxide and the like.

For example, the substrate placed in the vacuum-exhausted processing chamber of the plasma CVD apparatus is kept at 180 ° C. or higher and 260 ° C. or lower, more preferably 200 ° C. or higher and 240 ° C. or lower, and the raw material gas is introduced into the treatment chamber to introduce the raw material gas into the processing chamber. The pressure is 100 Pa or more and 250 Pa or less, more preferably 100 Pa or more and 200 Pa or less, and 0.17 W / cm ² or more and 0.5 W / cm ² or less, more preferably 0.25 W / cm ² or more and 0 for the electrodes provided in the processing chamber. .35W / cm ²
A silicon oxide film or a silicon nitride film is formed under the following conditions for supplying high-frequency power.

By supplying high-frequency power with the above power density in the reaction chamber of the above pressure as the film forming condition, the decomposition efficiency of the raw material gas is increased in the plasma, the oxygen radicals are increased, and the oxidation of the raw material gas is promoted. The oxygen content in the insulating film is higher than the chemical quantity theory ratio. However, when the substrate temperature is the above temperature, the bonding force between silicon and oxygen is weak, so that a part of oxygen is desorbed by heating. As a result, it is possible to form an oxide insulating film containing more oxygen than oxygen satisfying the stoichiometric composition and desorbing a part of oxygen by heating.

When an oxide insulating film is provided between the oxide semiconductor layer 104 and the insulating layer 106, the oxide insulating film serves as a protective film for the oxide semiconductor layer 104 in the step of forming the insulating layer 106. As a result, the insulating layer 106 can be formed by using high frequency power having a high power density while reducing damage to the oxide semiconductor layer 104.

For example, the substrate placed in the vacuum-exhausted processing chamber of the plasma CVD apparatus is kept at 180 ° C. or higher and 400 ° C. or lower, more preferably 200 ° C. or higher and 370 ° C. or lower, and the raw material gas is introduced into the treatment chamber to introduce the raw material gas into the processing chamber. Pressure at 20 Pa or more and 250 Pa or less, more preferably 1
A silicon oxide film or a silicon oxide nitride film can be formed as an oxide insulating film under the condition that the frequency is 00 Pa or more and 250 Pa or less and high frequency power is supplied to the electrodes provided in the processing chamber. Further, by setting the pressure in the processing chamber to 100 Pa or more and 250 Pa or less, it is possible to reduce damage to the oxide semiconductor layer 104 when the oxide insulating layer is formed.

As the raw material gas for the oxide insulating film, it is preferable to use a sedimentary gas containing silicon and an oxidizing gas. Typical examples of the sedimentary gas containing silicon include silane, disilane, trisilane, and fluorinated silane. Examples of the oxidizing gas include oxygen, ozone, nitrous oxide, nitrogen dioxide and the like.

The insulating layer 107 can be formed by a sputtering method, a CVD method, or the like.

When a silicon nitride film or a silicon nitride film is formed as the insulating layer 107, it is preferable to use a depositary gas containing silicon, an oxidizing gas, and a gas containing nitrogen as the raw material gas. Typical examples of the sedimentary gas containing silicon include silane, disilane, trisilane, and fluorinated silane. Examples of the oxidizing gas include oxygen, ozone, nitrous oxide, nitrogen dioxide and the like. Examples of the gas containing nitrogen include nitrogen, ammonia and the like.

It is preferable to perform heat treatment after forming the insulating layer 106 and the insulating layer 107. The oxygen released by the insulating layer 106 by the heat treatment is supplied to the oxide semiconductor layer 104, and the oxide semiconductor layer 1 is supplied.
Oxygen deficiency in 04 can be reduced.

The transistor 100 can be formed by the above steps.

[Modification example of transistor 100]
Hereinafter, a configuration example of a transistor that is partially different from the transistor 100 will be described.

[Modification 1]
FIG. 5B shows a schematic cross-sectional view of the transistor 110 illustrated below. The transistor 110 is different from the transistor 100 in that the structure of the oxide semiconductor layer is different.

The oxide semiconductor layer 114 included in the transistor 110 is configured by laminating the oxide semiconductor layer 114a and the oxide semiconductor layer 114b.

Since the boundary between the oxide semiconductor layer 114a and the oxide semiconductor layer 114b may be unclear, these boundaries are shown by broken lines in the drawings such as FIG. 5B.

The oxide semiconductor film of one aspect of the present invention can be applied to either or both of the oxide semiconductor layer 114a and the oxide semiconductor layer 114b.

For example, the oxide semiconductor layer 114a is typically an In—Ga oxide, an In—Zn oxide, or an In—M—Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd). , Or Hf). Further, when the oxide semiconductor layer 114a is an In—M—Zn oxide, I
The atomic number ratio of n and M is preferably less than 50 atomic% for In and 50 atom for M.
ic% or more, more preferably In is less than 25 atomic%, M is 75 atomic
% Or more. Further, for example, the oxide semiconductor layer 114a uses a material having an energy gap of 2 eV or more, preferably 2.5 eV or more, and more preferably 3 eV or more.

For example, the oxide semiconductor layer 114b contains In or Ga, and is typically In—Ga.
Oxide, In—Zn oxide, In—M—Zn oxide (M is Al, Ti, Ga, Y, Zr,
La, Ce, Nd or Hf), and the energy at the lower end of the conduction band is closer to the vacuum level than the oxide semiconductor layer 114a, typically with the energy at the lower end of the conduction band of the oxide semiconductor layer 114b. , The difference from the energy at the lower end of the conduction band of the oxide semiconductor layer 114a is 0.05.
It is preferably 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.

Further, for example, when the oxide semiconductor layer 114b is an In—M—Zn oxide, the atomic number ratio of In and M is preferably 25 atomic% or more for In, less than 75 atomic% for M, and more preferably In. It is assumed that 34 atomic% or more and M is less than 66 atomic%.

As the oxide semiconductor layer 114a, for example, In: Ga: Zn = 1: 1: 1 or 3: 1: 1.
In—Ga—Zn oxide having an atomic number ratio of 2 can be used. Further, the oxide semiconductor layer 1
As 14b, for example, In—Ga—Zn oxide having an atomic number ratio of In: Ga: Zn = 1: 3: 4, 1: 3: 6, 1: 6: 8, or 1: 6: 10 can be used. can. The atomic number ratios of the oxide semiconductor layer 114a and the oxide semiconductor layer 114b each include a fluctuation of plus or minus 20% of the above atomic number ratio as an error.

By using an oxide having a higher content of Ga, which functions as a stabilizer, as the oxide semiconductor layer 114b provided on the upper layer as compared with the oxide semiconductor layer 114a, the oxide semiconductor layer 1 is used.
It is possible to suppress the release of oxygen from the 14a and the oxide semiconductor layer 114b.

Not limited to these, a transistor having an appropriate composition may be used according to the required semiconductor characteristics and electrical characteristics (field effect mobility, threshold voltage, variation, etc.) of the transistor. Further, in order to obtain the required semiconductor characteristics of the transistor, the carrier density and impurity concentration of the oxide semiconductor layer 114a and the oxide semiconductor layer 114b, the defect density, the atomic number ratio of the metal element and oxygen,
It is preferable that the interatomic distance, density, etc. are appropriate.

In the above description, as the oxide semiconductor layer 114, a configuration in which two oxide semiconductor layers are laminated is exemplified, but a configuration in which three or more oxide semiconductor layers are laminated may be used.

[Modification 2]
FIG. 5C shows a schematic cross-sectional view of the transistor 120 illustrated below. The transistor 120 is different in the configuration of the oxide semiconductor layer from the transistor 100 and the transistor 1.
It is different from 10.

The oxide semiconductor layer 124 included in the transistor 120 is configured by laminating the oxide semiconductor layer 124a, the oxide semiconductor layer 124b, and the oxide semiconductor layer 124c in this order.

The oxide semiconductor layer 124a and the oxide semiconductor layer 124b are provided by being laminated on the insulating layer 103. The oxide semiconductor layer 124c is provided in contact with the upper surface of the oxide semiconductor layer 124b and the upper surfaces and side surfaces of the pair of electrodes 105a and 105b.

Of the oxide semiconductor layer 124a, the oxide semiconductor layer 124b, and the oxide semiconductor layer 124c,
The oxide semiconductor film of one aspect of the present invention can be applied to any one, any two, or all of them.

For example, as the oxide semiconductor layer 124b, the oxide semiconductor layer 11 exemplified in the modification 1 is described above.
The same configuration as 4a can be used. Further, for example, the oxide semiconductor layers 124a and 124
As c, the same configuration as that of the oxide semiconductor layer 114b exemplified in the above modification 1 can be used.

For example, by using an oxide having a high content of Ga that functions as a stabilizer for the oxide semiconductor layer 124a provided in the lower layer of the oxide semiconductor layer 124b and the oxide semiconductor layer 124c provided in the upper layer, the oxide semiconductor is used. It is possible to suppress the release of oxygen from the layer 124a, the oxide semiconductor layer 124b, and the oxide semiconductor layer 124c.

Further, for example, when a channel is mainly formed in the oxide semiconductor layer 124b, an oxide having a high content of In is used in the oxide semiconductor layer 124b, and the pair of electrodes 105a and 105b are in contact with the oxide semiconductor layer 124b. By providing the transistor 120, the on-current of the transistor 120 can be increased.

[Other configuration examples of transistors]
Hereinafter, a configuration example of a top gate type transistor to which the oxide semiconductor film of one aspect of the present invention can be applied will be described.

In the following, the components having the same configuration as the above or the same functions will be referred to.
The same reference numerals are given, and duplicate contents are omitted.

[Configuration example]
FIG. 7A shows a schematic cross-sectional view of the top gate type transistor 150 illustrated below.

The transistor 150 is an oxide semiconductor layer 10 on a substrate 101 provided with an insulating layer 151.
4, a pair of electrodes 105a and 105b in contact with the upper surface of the oxide semiconductor layer 104, an insulating layer 103 provided on the oxide semiconductor layer 104 and a pair of electrodes 105a and 105b, and an insulating layer 1.
A gate electrode 102 that overlaps with the oxide semiconductor layer 104 is provided on the 03. In addition, the insulating layer 10
The insulating layer 152 is provided so as to cover the 3 and the gate electrode 102.

The oxide semiconductor film exemplified in the first embodiment can be applied to the oxide semiconductor layer 104.

The insulating layer 151 has a function of suppressing the diffusion of impurities from the substrate 101 to the oxide semiconductor layer 104. Further, it may have a function of supplying oxygen to the oxide semiconductor layer 104 by heating. For example, it may have the same structure as the insulating layer 106 or the insulating layer 107, or a laminated structure thereof.

The insulating layer 152 is an insulating layer from which oxygen is desorbed by heating, and has a function of supplying oxygen to the oxide semiconductor layer 104. For example, the same configuration as that of the insulating layer 106 can be used.

Further, the insulating layer 153 is an insulating layer having a blocking effect of oxygen, hydrogen, water and the like. For example, the same configuration as that of the insulating layer 107 can be used.

As the insulating layer 152, an insulating layer having a blocking effect of oxygen, hydrogen, water, etc. may be used. In that case, the configuration may be such that the insulating layer 153 is not provided.

[Modification 3]
Hereinafter, a configuration example of a transistor that is partially different from the transistor 150 will be described.

FIG. 7B shows a schematic cross-sectional view of the transistor 160 illustrated below. The transistor 160 is different from the transistor 150 in that the structure of the oxide semiconductor layer is different.

The oxide semiconductor layer 164 included in the transistor 160 is configured by laminating the oxide semiconductor layer 164a, the oxide semiconductor layer 164b, and the oxide semiconductor layer 164c in this order.

Of the oxide semiconductor layer 164a, the oxide semiconductor layer 164b, and the oxide semiconductor layer 164c,
The oxide semiconductor film exemplified in the first embodiment can be applied to any one, any two, or all of them.

For example, as the oxide semiconductor layer 164b, the oxide semiconductor layer 11 exemplified in the modification 1 is described above.
The same configuration as 4a can be used. Further, for example, as the oxide semiconductor layer 164a and the oxide semiconductor layer 164c, the same configuration as that of the oxide semiconductor layer 114b exemplified in the above modification 1 can be used.

For example, by using an oxide having a high content of Ga that functions as a stabilizer in the oxide semiconductor layer 164a provided in the lower layer of the oxide semiconductor layer 164b and the oxide semiconductor layer 164c provided in the upper layer, the oxide semiconductor is used. It is possible to suppress the release of oxygen from the layer 164a, the oxide semiconductor layer 164b, and the oxide semiconductor layer 164c.

[Modification 4]
Hereinafter, a configuration example of a transistor that is partially different from the transistor 150 and the transistor 160 will be described.

The transistor 170 shown in FIG. 7C is different from the transistor 150 and the transistor 160 in that the configurations of the oxide semiconductor layer, the gate insulating layer, and the like are different.

Of the oxide semiconductor layer 164 included in the transistor 170, the oxide semiconductor layer 164c is provided so as to cover the oxide semiconductor layer 164b and the ends of the electrodes 105a and 105b.

Further, the ends of the oxide semiconductor layer 164c and the insulating layer 103 are processed by using the same photomask so as to substantially coincide with the ends of the gate electrode 102.

Further, the insulating layer 152 is provided in contact with the side surfaces of the insulating layer 103 and the oxide semiconductor layer 164c.

In the transistor exemplified in the present embodiment, the metal oxide film exemplified in the first embodiment is applied to the semiconductor layer on which the channel is formed. Therefore, it is a highly reliable transistor in which carrier trapping due to defects is suppressed, high field effect mobility can be realized, and fluctuations in electrical characteristics are suppressed.

This embodiment can be appropriately combined with other embodiments described in the present specification.

(Embodiment 3)
In the present embodiment, a configuration example of the display panel according to one aspect of the present invention will be described.

[Configuration example]
FIG. 8A is a top view of the display panel of one aspect of the present invention, and FIG. 8B can be used when a liquid crystal element is applied to the pixels of the display panel of one aspect of the present invention. It is a circuit diagram for demonstrating a pixel circuit. Further, FIG. 8C is a circuit diagram for explaining a pixel circuit that can be used when an organic EL element is applied to the pixels of the display panel of one aspect of the present invention.

The transistor arranged in the pixel portion can be formed according to the second embodiment. Further, since the transistor can be easily made into an n-channel type, a part of the drive circuit that can be configured by the n-channel type transistor is formed on the same substrate as the transistor of the pixel portion. As described above, by using the transistor shown in the second embodiment for the pixel portion and the drive circuit, it is possible to provide a highly reliable display device.

FIG. 8A shows an example of a block diagram of the active matrix type display device. On the substrate 500 of the display device, a pixel unit 501, a first scanning line driving circuit 502, a second scanning line driving circuit 503, and a signal line driving circuit 504 are provided. A plurality of signal lines are extended from the signal line drive circuit 504 and arranged in the pixel unit 501, and a plurality of scan lines are extended from the first scan line drive circuit 502 and the second scan line drive circuit 503. Have been placed. In the intersection region between the scanning line and the signal line, pixels having a display element are provided in a matrix. Further, the substrate 500 of the display device is connected to a timing control circuit (also referred to as a controller or a control IC) via a connection portion such as an FPC (Flexible Printed Circuit).

In FIG. 8A, the first scanning line driving circuit 502, the second scanning line driving circuit 503, and the signal line driving circuit 504 are formed on the same substrate 500 as the pixel unit 501. Therefore, the number of parts such as a drive circuit provided externally is reduced, so that the cost can be reduced. In addition, the substrate 5
When a drive circuit is provided outside 00, it becomes necessary to extend the wiring, and the number of connections between the wiring increases. When the drive circuit is provided on the same substrate 500, the number of connections between the wirings can be reduced, and the reliability or the yield can be improved.

[LCD panel]
Further, an example of the pixel circuit configuration is shown in FIG. 8 (B). Here, a pixel circuit that can be applied to the pixels of a VA type liquid crystal display panel is shown.

This pixel circuit can be applied to a configuration having a plurality of pixel electrode layers in one pixel. Each pixel electrode layer is connected to a different transistor, and each transistor is configured to be driven by a different gate signal. As a result, the signal applied to each pixel electrode layer of the multi-domain designed pixel can be independently controlled.

The gate wiring 512 of the transistor 516 and the gate wiring 513 of the transistor 517 are separated so that different gate signals can be given. On the other hand, the source electrode layer or the drain electrode layer 514 that functions as a data line is commonly used in the transistor 516 and the transistor 517. As the transistor 516 and the transistor 517, the transistor described in the second embodiment can be appropriately used. This makes it possible to provide a highly reliable liquid crystal display panel.

The shapes of the first pixel electrode layer electrically connected to the transistor 516 and the second pixel electrode layer electrically connected to the transistor 517 will be described. The shapes of the first pixel electrode layer and the second pixel electrode layer are separated by a slit. The first pixel electrode layer has a V-shaped spreading shape, and the second pixel electrode layer is formed so as to surround the outside of the first pixel electrode layer.

The gate electrode of the transistor 516 is connected to the gate wiring 512, and the transistor 517 is connected.
The gate electrode of is connected to the gate wiring 513. Gate wiring 512 and gate wiring 51
It is possible to control the orientation of the liquid crystal display by giving different gate signals to 3 to make the operation timings of the transistor 516 and the transistor 517 different.

Further, the holding capacitance may be formed by the capacitive wiring 510, the gate insulating film that functions as a dielectric, and the capacitive electrode that is electrically connected to the first pixel electrode layer or the second pixel electrode layer.

The multi-domain structure includes a first liquid crystal element 518 and a second liquid crystal element 519 in one pixel. The first liquid crystal element 518 is composed of a first pixel electrode layer, a counter electrode layer, and a liquid crystal layer in between, and the second liquid crystal element 519 includes a second pixel electrode layer, a counter electrode layer, and a liquid crystal layer in between. Consists of.

The pixel circuit shown in FIG. 8B is not limited to this. For example, a switch, a resistance element, a capacitive element, a transistor, a sensor, a logic circuit, or the like may be newly added to the pixel shown in FIG. 8 (B).

[Organic EL panel]
Another example of the pixel circuit configuration is shown in FIG. 8 (C). Here, the pixel structure of the display panel using the organic EL element is shown.

In the organic EL element, by applying a voltage to the light emitting element, electrons are injected from one of the pair of electrodes and holes are injected from the other into the layer containing the luminescent organic compound, and a current flows. Then, by recombination of electrons and holes, the luminescent organic compound forms an excited state, and the luminescent organic compound forms an excited state.
It emits light when its excited state returns to the ground state. Due to such a mechanism, such a light emitting device is called a current excitation type light emitting device.

FIG. 8C is a diagram showing an example of an applicable pixel circuit. Here, an example in which two n-channel type transistors are used for one pixel is shown. The metal oxide film of one aspect of the present invention can be used in the channel forming region of an n-channel transistor. Further, the pixel circuit can be driven by digital time gradation.

The configuration of the applicable pixel circuit and the operation of the pixel when the digital time gradation drive is applied will be described.

The pixel 520 has a switching transistor 521, a driving transistor 522, a light emitting element 524, and a capacitive element 523. In the switching transistor 521, the gate electrode layer is connected to the scanning line 526, the first electrode (one of the source electrode layer and the drain electrode layer) is connected to the signal line 525, and the second electrode (source electrode layer and drain electrode layer) is connected. The other) is connected to the gate electrode layer of the driving transistor 522. Drive transistor 522
The gate electrode layer is connected to the power supply line 527 via the capacitive element 523, the first electrode is connected to the power supply line 527, and the second electrode is connected to the first electrode (pixel electrode) of the light emitting element 524. .. The second electrode of the light emitting element 524 corresponds to the common electrode 528. The common electrode 528 is electrically connected to a common potential line formed on the same substrate.

As the switching transistor 521 and the driving transistor 522, the transistor described in the second embodiment can be appropriately used. This makes it possible to provide a highly reliable organic EL display panel.

The potential of the second electrode (common electrode 528) of the light emitting element 524 is set to a low power supply potential. note that,
The low power potential is a potential lower than the high power potential set in the power line 527, for example, GN.
D, 0V and the like can be set as the low power supply potential. A high power supply potential and a low power supply potential are set so as to be equal to or higher than the forward threshold voltage of the light emitting element 524, and the potential difference is set to the light emitting element 52.
By applying it to 4, a current is passed through the light emitting element 524 to cause light emission. The light emitting element 5
The forward voltage of 24 refers to a voltage when the desired brightness is obtained, and includes at least a forward threshold voltage.

The capacitive element 523 can be omitted by substituting the gate capacitance of the driving transistor 522. Regarding the gate capacitance of the drive transistor 522, a capacitance may be formed between the channel forming region and the gate electrode layer.

Next, the signal input to the drive transistor 522 will be described. Voltage input In the case of the voltage drive method, a video signal is input to the drive transistor 522 so that the drive transistor 522 is sufficiently turned on or off. In order to operate the drive transistor 522 in the linear region, a voltage higher than the voltage of the power supply line 527 is applied to the gate electrode layer of the drive transistor 522. Further, a voltage equal to or higher than the value obtained by adding the threshold voltage Vth of the driving transistor 522 to the power line voltage is applied to the signal line 525.

When analog gradation driving is performed, the light emitting element 5 is formed on the gate electrode layer of the driving transistor 522.
A voltage equal to or higher than the value obtained by adding the threshold voltage Vth of the driving transistor 522 to the forward voltage of 24 is applied. A video signal is input so that the driving transistor 522 operates in the saturation region, and a current is passed through the light emitting element 524. Further, in order to operate the drive transistor 522 in the saturation region, the potential of the power supply line 527 is set higher than the gate potential of the drive transistor 522. By making the video signal analog, an analog gradation drive can be performed by passing a current corresponding to the video signal through the light emitting element 524.

The configuration of the pixel circuit is not limited to the pixel configuration shown in FIG. 8C. For example, FIG.
A switch, a resistance element, a capacitive element, a sensor, a transistor, a logic circuit, or the like may be added to the pixel circuit shown in C).

This embodiment can be appropriately combined with other embodiments described in the present specification.

(Embodiment 4)
In this embodiment, a configuration example of a semiconductor device and an electronic device using the metal oxide film of one aspect of the present invention will be described.

FIG. 9 is a block diagram of an electronic device including a semiconductor device to which the metal oxide film of one aspect of the present invention is applied.

FIG. 10 is an external view of an electronic device including a semiconductor device to which the metal oxide film of one aspect of the present invention is applied.

The electronic devices shown in FIG. 9 include RF circuit 901, analog baseband circuit 902, digital baseband circuit 903, battery 904, power supply circuit 905, application processor 906, flash memory 910, display controller 911, and memory circuit 91.
2. It is composed of a display 913, a touch sensor 919, a voice circuit 917, a keyboard 918, and the like.

The application processor 906 has a CPU 907, a DSP 908, and an interface (IF) 909. Further, the memory circuit 912 can be configured by SRAM or DRAM.

By applying the transistor described in the second embodiment to the memory circuit 912, it is possible to provide a highly reliable electronic device capable of writing and reading information.

Further, by applying the transistor described in the second embodiment to a register included in the CPU 907 or the DSP 908, it is possible to provide a highly reliable electronic device capable of writing and reading information.

When the off-leakage current of the transistor described in the second embodiment is extremely small,
It is possible to provide a memory circuit 912 capable of holding a memory for a long period of time, capable of holding a memory for a long period of time, and having sufficiently reduced power consumption. Further, during the period of power gating, the CPU 907 or DSP 90 that can store the state before power gating in a register or the like.
8 can be provided.

The display 913 has a display unit 914, a source driver 915, and a gate driver 9.
It is composed of 16.

The display unit 914 has a plurality of pixels arranged in a matrix. The pixels include a pixel circuit, which is electrically connected to the gate driver 916.

The transistor described in the second embodiment can be appropriately used in the pixel circuit or the gate driver 916. This makes it possible to provide a highly reliable display.

Examples of electronic devices include television devices (also referred to as televisions or television receivers), monitors for computers, digital cameras, cameras such as digital video cameras, digital photo frames, and mobile phones (mobile phones, mobile phones). (Also referred to as a device), a portable game machine, a mobile information terminal, a sound reproduction device, a large game machine such as a pachinko machine, and the like.

FIG. 10A is a portable information terminal, which includes a main body 1001, a housing 1002, and a display unit 10.
It is composed of 03a, 1003b and the like. The display unit 1003b is a touch panel, and screen operations and character input can be performed by touching the keyboard button 1004 displayed on the display unit 1003b. Of course, the display unit 1003a may be configured as a touch panel. By manufacturing a liquid crystal panel or an organic light emitting panel using the transistor shown in the second embodiment as a switching element and applying it to the display units 1003a and 1003b, a highly reliable portable information terminal can be obtained.

The portable information terminal shown in FIG. 10A has a function of displaying various information (still images, moving images, text images, etc.), a function of displaying a calendar, a date, a time, etc. on the display unit, and a function of displaying the information on the display unit. It can have a function of manipulating or editing the information, a function of controlling processing by various software (programs), and the like. Further, the back surface or the side surface of the housing may be provided with an external connection terminal (earphone terminal, USB terminal, etc.), a recording medium insertion portion, or the like.

Further, the portable information terminal shown in FIG. 10A may be configured to be able to transmit and receive information wirelessly. It is also possible to purchase and download desired book data or the like from an electronic book server wirelessly.

FIG. 10B is a portable music player, and the main body 1021 is provided with a display unit 1023, a fixed unit 1022 to be attached to an ear, a speaker, an operation button 1024, an external memory slot 1025, and the like. By manufacturing a liquid crystal panel or an organic light emitting panel using the transistor shown in the second embodiment as a switching element and applying it to the display unit 1023.
It can be a more reliable portable music player.

Further, if the portable music player shown in FIG. 10B is provided with an antenna, a microphone function, and a wireless function and is linked with a mobile phone, wireless hands-free conversation is possible while driving a passenger car or the like.

FIG. 10C shows a mobile phone, which is composed of two housings, a housing 1030 and a housing 1031. The housing 1031 includes a display panel 1032, a speaker 1033, a microphone 1034, a pointing device 1036, a camera lens 1037, an external connection terminal 1038, and the like. Further, the housing 1030 is provided with a solar cell 1040 for charging a mobile phone, an external memory slot 1041 and the like. The antenna is the housing 1
It is built in 031. Display panel 103 for the transistor described in the second embodiment
By applying to 2, a highly reliable mobile phone can be obtained.

Further, the display panel 1032 is provided with a touch panel, and in FIG. 10C, a plurality of operation keys 1035 displayed as images are shown by dotted lines. A booster circuit for boosting the voltage output by the solar cell 1040 to the voltage required for each circuit is also mounted.

For example, a power transistor used in a power supply circuit such as a booster circuit can also be formed by setting the thickness of the metal oxide film of the transistor described in the second embodiment to 2 μm or more and 50 μm or less.

The display direction of the display panel 1032 changes as appropriate depending on the usage pattern. Further, since the camera lens 1037 is provided on the same surface as the display panel 1032, a videophone can be made. The speaker 1033 and the microphone 1034 are not limited to voice calls, but can be used for videophones, recording, playback, and the like. Further, the housing 1030 and the housing 1031 slide, and the housing 1030 and the housing 1031 slide.
As shown in FIG. 10C, it is possible to change from the expanded state to the overlapping state, and it is possible to reduce the size suitable for carrying.

The external connection terminal 1038 can be connected to various cables such as an AC adapter and a USB cable, and can be charged and data communication with a personal computer or the like is possible. Further, a recording medium can be inserted into the external memory slot 1041 to support storage and movement of a larger amount of data.

Further, in addition to the above functions, an infrared communication function, a television reception function, and the like may be provided.

FIG. 10D shows an example of a television device. In the television device 1050, the display unit 1053 is incorporated in the housing 1051. The display unit 1053 can display an image. Further, the CPU is built in the stand 1055 that supports the housing 1051. By applying the transistor described in the second embodiment to the display unit 1053 and the CPU, a highly reliable television device 1050 can be obtained.

The operation of the television device 1050 can be performed by an operation switch included in the housing 1051 or a separate remote control operating device. Further, the remote controller operating device may be provided with a display unit for displaying information output from the remote controller operating device.

The television device 1050 is configured to include a receiver, a modem, and the like. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via a modem, one-way (sender to receiver) or two-way (sender and receiver). It is also possible to perform information communication between (or between receivers, etc.).

Further, the television device 1050 has an external connection terminal 1054 and a storage medium reproduction / recording unit 1.
052, equipped with an external memory slot. The external connection terminal 1054 can be connected to various cables such as a USB cable, and can perform data communication with a personal computer or the like. The storage medium reproduction recording unit 1052 can insert a disc-shaped recording medium, read data stored in the recording medium, and write data to the recording medium. Further, it is also possible to display an image, a video, or the like stored in the external memory 1056 inserted in the external memory slot on the display unit 1053.

Further, when the off-leakage current of the transistor described in the second embodiment is extremely small,
By applying the transistor to the external memory 1056 or the CPU, it is possible to obtain a highly reliable television device 1050 with sufficiently reduced power consumption.

100 Transistor 101 Substrate 102 Gate electrode 103 Insulation layer 104 Oxide semiconductor layer 105a Electrode 105b Electron 106 Insulation layer 107 Insulation layer 110 Transistor 114 Oxide semiconductor layer 114a Oxide semiconductor layer 114b Oxide semiconductor layer 120 Transistor 124 Oxide semiconductor layer 124a Oxide semiconductor layer 124b Oxide semiconductor layer 124c Oxide semiconductor layer 150 Transistor 151 Insulation layer 152 Insulation layer 153 Insulation layer 160 Transistor 164 Oxide semiconductor layer 164a Oxide semiconductor layer 164b Oxide semiconductor layer 164c Oxide semiconductor layer 170 Transistor 500 Substrate 501 Pixel part 502 Scan line drive circuit 503 Scan line drive circuit 504 Signal line drive circuit 510 Capacitive wiring 512 Gate wiring 513 Gate wiring 514 Drain electrode layer 516 Transistor 517 Transistor 518 Liquid crystal element 319 Liquid crystal element 520 Pixel 521 Switching transistor 522 Drive Transistor 523 Capacitive element 524 Light emitting element 525 Signal line 526 Scan line 527 Power supply line 528 Common electrode 901 RF circuit 902 Analog baseband circuit 903 Digital baseband circuit 904 Battery 905 Power supply circuit 906 Application processor 907 CPU
908 DSP
910 Flash memory 911 Display controller 912 Memory circuit 913 Display 914 Display unit 915 Source driver 916 Gate driver 917 Voice circuit 918 Keyboard 919 Touch sensor 1001 Main unit 1002 Housing 1003a Display unit 1003b Display unit 1004 Keyboard button 1021 Main unit 1022 Fixed unit 1023 Display unit 1024 Operation button 1025 External memory slot 1030 Housing 1031 Housing 1032 Display panel 1033 Speaker 1034 Microphone 1035 Operation key 1036 Pointing device 1037 Camera lens 1038 External connection terminal 1040 Solar cell 1041 External memory slot 1050 Television device 1051 Housing 1052 Storage medium playback Recording unit 1053 Display unit 1054 External connection terminal 1055 Stand 1056 External memory

Claims (1)

A semiconductor device having a metal oxide film having In, Ga, and Zn, and a gate electrode having a region overlapping with the metal oxide film.
In the HAADF-STEM image of the metal oxide film,
The metal oxide film has a first crystal region and a second crystal region.
The first crystal region includes a first layer which is an InO ₂ layer, a second layer which is a (Ga, Zn) O layer on the first layer, and InO ₂ on the second layer. It has a third layer, which is a layer , and no other layer is interposed between the first layer to each of the third layers.
The second crystal region includes a fourth layer which is an InO ₂ layer, a fifth layer which is a (Ga, Zn) O layer on the fourth layer, and the fifth layer on the fifth layer. It has one layer, with no other layers intervening between the fourth layer and the fifth layer, and between the fifth layer and the first layer.
The second layer has an array of atoms in the n (n is a natural number of 2 or more) layer.
The fifth layer has an array of atoms in the m (m is a natural number of 2 or more and is a natural number other than n) layer.
The brightness of the atoms of the first layer and the third layer is higher than the brightness of the atoms of the second layer.
The brightness of the atoms of the fourth layer and the first layer is higher than the brightness of the atoms of the fifth layer.
The first layer is shared between the first crystal region and the second crystal region .
A semiconductor device characterized in that the first crystal region and the second crystal region are laminated in a direction perpendicular to a direction parallel to the first layer .

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