Metal oxide film

Abstract

To provide a metal oxide film having a novel structure. A metal oxide film with highly stable physical properties is provided. A highly reliable semiconductor device using the metal oxide is provided.SOLUTION: The metal oxide film includes In, Ga, and Zn, a plurality of first layers in which In atoms are periodically arranged and a plurality of second layers in which Ga atoms or Zn atoms are periodically arranged are observed in a cross-sectional observation image, and a first region including n (n is a natural number) second layers between a pair of first layers and a second region including m (m is a natural number other than n) second layers between another pair of first layers are included.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a metal oxide film. Regarding placement.

[0002] In this specification and the like, a semiconductor device is a device that can function by utilizing semiconductor characteristics. Refers to devices in general, including transistors, semiconductor circuits, memory devices, imaging devices, electro-optical devices, and power generation devices. Devices (including thin-film solar cells, organic thin-film solar cells, etc.) and electronic devices can also be called semiconductor devices. do. [Background technology]

[0003] A technology for constructing a transistor using a semiconductor film formed on a substrate with an insulating surface is The transistor is used in integrated circuits (ICs) and image display devices (also known simply as display devices). These are widely used in electronic devices such as semiconductors that can be applied to transistors. Silicon-based semiconductor materials are widely known as the body film, but other materials with semiconductor properties are also available. Metal oxides (oxide semiconductors) that exhibit this property are attracting attention.

[0004] For example, amorphous oxides containing In, Zn, Ga, Sn, etc. are used as oxide semiconductors. Patent Document 1 discloses a technique for fabricating a transistor using this method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-165529 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of one embodiment of the present invention is to provide a metal oxide film having a novel structure. .

[0007] Another object of one embodiment of the present invention is to provide a metal oxide film having highly stable physical properties. It shall be one.

[0008] Another embodiment of the present invention provides a highly reliable semiconductor device to which the above-described metal oxide is applied. One of our goals is to provide

[0009] The description of these problems does not preclude the existence of other problems. It is not necessary for one embodiment to solve all of these problems. The subject matter will be self-evident from the description, drawings, claims, etc. It is possible to extract other issues from the drawings, claims, etc. [Means for solving the problem]

[0010] One aspect of the present invention is a crystal that contains In, Ga, and Zn, and in a cross-sectional observation image, In atoms are periodically arranged. and a second layer in which Ga atoms or Zn atoms are periodically arranged. A first region is observed, having a pair of first layers and n (n is a natural number) second layers between them; a second region having m (m is a natural number other than n) second layers between another pair of first layers; The metal oxide film has the following structure:

[0011] In the metal oxide film, the first region and the second region are parallel to the first layer. and one of the first regions is adjacent to the first region in the vertical direction at the boundary between the first region and the second region. It is preferable that the layers are shared.

[0012] Alternatively, the first region and the second region are adjacent to each other in a direction parallel to a plane parallel to the first layer. However, it is preferable that one first layer is continuous at the boundary between the first region and the second region. stomach.

[0013] In the first region or the second region of the metal oxide film, the first layer is a It is preferably parallel to the forming surface.

[0014] Furthermore, no grain boundary is observed between the first region and the second region in the metal oxide film. It is preferable that

[0015] Another aspect of the present invention is a semiconductor device comprising any one of the metal oxide films described above, a gate electrode, and a metal oxide film. A gate insulating layer is provided between the film and the gate electrode, and a source electrode and a gate electrode are electrically connected to the metal oxide film. and a drain electrode, and a channel is formed in the metal oxide film. .

[0016] In this specification, the fact that the surface A is parallel to the surface B means that the angle between the normal to the surface A and the normal to the surface B is In this specification, the C-plane is defined as a plane that is inclined from -20° to 20°. Perpendicular to surface B means that the angle between the normal to surface C and the normal to surface B is between 70° and 110°. In addition, in this specification, the expression "line C is approximately perpendicular to surface B" refers to the normal of line C and surface B. This refers to a state in which the angle between the lines is between -20° and 20°. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a metal oxide film having a novel structure. Alternatively, a highly reliable metal oxide film can be provided by using the above-mentioned metal oxide. A semiconductor device can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] 1A to 1C illustrate a metal oxide film according to an embodiment; [Figure 2] 1A to 1C illustrate a metal oxide film according to an embodiment; [Figure 3] 1A to 1C are diagrams illustrating a crystal structure of a metal oxide according to an embodiment; [Figure 4] 1A to 1C are diagrams illustrating a crystal structure included in a metal oxide film according to an embodiment; [Figure 5] 1A to 1C illustrate structural examples of transistors according to an embodiment. [Figure 6] 1A to 1C illustrate an example of a method for manufacturing a transistor according to an embodiment. [Figure 7] 1A to 1C illustrate structural examples of transistors according to an embodiment. [Figure 8] 1A to 1C illustrate a structure of a display panel according to an embodiment. [Figure 9] 1A to 1C are block diagrams illustrating electronic devices according to embodiments of the present invention. [Figure 10] 1A to 1C are diagrams illustrating external views of electronic devices according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description. The present invention is not limited to the above embodiments, and various changes and modifications may be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention is based on the following embodiments. The present disclosure should not be construed as being limited to the contents of the preceding paragraph.

[0020] In the configuration of the invention described below, the same parts or parts having similar functions are The same reference numerals are used in common between different drawings, and repeated explanations thereof will be omitted. When referring to a function, the hatch pattern may be the same and no particular symbol may be assigned.

[0021] In each figure described in this specification, the size, layer thickness, or area of ​​each component is The figures may be exaggerated for clarity and are not necessarily limited to that scale. stomach.

[0022] (Embodiment 1) In this embodiment, a metal oxide film of one embodiment of the present invention will be described with reference to drawings. .

[0023] [Crystal structure of metal oxide films] The metal oxide film of one embodiment of the present invention has a metal oxide containing two or more different metal elements. In addition, the metal oxide is an oxide whose crystal structure can have a layered structure, and Alternatively, an oxide that can exhibit different periodic structures due to differences in composition can be used.

[0024] The various periodic structures that appear due to differences in composition are also called homologous phases. When the crystal structure is a layered structure in which layer A containing metal A and layer B containing metal B are arranged in layers, In this case, the number of B layers sandwiched between a pair of A layers changes continuously depending on the composition. As a result, different periodic structures are realized depending on the composition. A structure that can take on different periodic structures depending on the composition is called a homologous structure.

[0025] For example, In-Ga-Zn oxide is InGaO_3(ZnO) m (m is a natural number) The homologous structure shown in Figure 3 is an example of the crystal structure of an In-Ga-Zn oxide. The crystal structure shown in Figure 3(A) is InGaO_3(ZnO) m(m=1) The crystal structure shown in Figure 3(B) is InGaO_3(ZnO) m The crystal structure shown in Figure 3(C) is InGa O_3(ZnO) m This is the crystal structure expressed as (m=3).

[0026] The metal oxide film according to one embodiment of the present invention has regions having different crystal structures (periodic structures) in the film. It is characterized by a mixture of regions.

[0027] For example, when an In-Ga-Zn oxide is used as the metal oxide, A layer made of an oxide of Ga and Zn (Ga, Zn) It has a layered structure in which two layers, α-layer and β-layer, are arranged in layers.

[0028] Furthermore, the number of (Ga, Zn)O layers sandwiched between a pair of InO2 layers can be varied. For example, the structure shown in FIG. 4(A) has a pair of InO2 layers and a layer of (Ga, Zn )O layer. The structure shown in FIG. 4(B) has two (Ga) layers between a pair of InO2 layers. Zn)O layer (also called (Ga,Zn)2O2 layer). The structure is a pair of InO2 layers with three (Ga, Zn)O layers (also known as (Ga, Zn)3O3 layers) between them. (hereinafter referred to as "the Company").

[0029] In this way, when an In-Ga-Zn-based oxide is used as a metal oxide film according to one embodiment of the present invention, In this case, the number of (Ga, Zn)O layers present between a pair of InO2 layers in the metal oxide film is It contains two or more different crystalline regions.

[0030] The crystalline regions contained in the metal oxide can be observed by, for example, a transmission electron microscope (TEM). It can be observed by using techniques such as Electron Microscopy. In addition, the crystalline regions observed by TEM were further analyzed using techniques such as electron diffraction. The crystal structure can also be identified by analyzing it using the method.

[0031] Here, for example, a scanning transmission electron microscope (STEM) is used to observe the cross section of a metal oxide film. canning Transmission Electron Microscopy ), it is difficult to observe oxygen atoms, which are a light element, when performing high-resolution observations. Only the arrangement of metal atoms can be confirmed.

[0032] Next, FIG. 1 shows a cross-sectional observation image of a metal oxide film according to one embodiment of the present invention.

[0033] Here, as an example of a metal oxide film, an In-Ga-Zn oxide film is formed on a quartz glass substrate. The metal oxide film shown in Figure 1 was formed under the following conditions: In Sputtering using an oxide target with Ga:Zn=1:1:1 (atomic ratio) According to the method, under an oxygen atmosphere (flow rate 45sccm), pressure 0.4Pa, direct current (DC) power supply power The power was 0.5 kW and the substrate temperature during film formation was room temperature. The metal oxide film after the heat treatment was subjected to ion milling. The specimen was then thinned by the method described above to prepare a sample for cross-sectional observation.

[0034] Cross-sectional observation was performed using a transmission electron microscope (Hitachi High-Technologies: HD-2700) under accelerating electron microscope. The voltage was 200 kV and the magnification was 12 million times. Annular Dark-Field Scanning Transmissio Electron Microscopy (EMM) images were observed.

[0035] As shown in Figure 1, atoms (specifically electrons) in the metal oxide film are observed to be highly bright. ) and multiple layers of periodically arranged atoms, which are observed to have low brightness. Here, the atoms observed to have high brightness are In atoms, and the atoms observed to have low brightness are In atoms. The atoms are Ga or Zn atoms.

[0036] An enlarged view of the area 1 enclosed by the dashed line in Figure 1(A) is shown in Figure 1(B). Between the layers in which Ga atoms or Zn atoms are periodically arranged, two layers in which Ga atoms or Zn atoms are periodically arranged exist. It can be confirmed that it exists.

[0037] As mentioned above, the O atoms that make up the metal oxide can be directly observed in the cross-sectional observation image. Therefore, it is difficult to know the composition of O atoms and the bonding state between O atoms and metal atoms from cross-sectional observation images. Therefore, in the following, we will focus on the periodically arranged particles obtained from the cross-sectional observation image. The layer of electrons (specifically, electrons) is an InO2 layer or a (Ga, Zn)O layer in the actual crystal structure. This will be written to distinguish it from layers such as

[0038] Specifically, in the cross-sectional observation image, a layer in which pairs of In atoms are periodically arranged is shown below. In the cross-sectional observation image, Ga atoms or Zn atoms are One layer in which atoms are periodically arranged is referred to as the (Ga, Zn) layer or the second layer.

[0039] In addition, when metal oxides other than In-Ga-Zn oxides were used, the cross-sectional observation images showed Among the multiple layers that are periodically arranged and observed, the brightest atom (those with equal brightness) The first layer, the second layer, the third layer, the third layer, the third layer, the third layer, the fourth layer, the fifth ... This will be referred to as the layer.

[0040] Next, an enlarged view of the area 2 enclosed by the dashed line in FIG. 1(A) is shown in FIG. 1(C). It can be seen that three (Ga, Zn) layers exist between the In layers.

[0041] As described above, in the cross-sectional observation image of the metal oxide film according to one embodiment of the present invention, a pair of first A first region having n (n is a natural number) layers of second layers between the layers of the first region and another pair of first layers The second region has m (m is a natural number other than n) layers in the first layer. Let's say.

[0042] The types of crystal structures in the crystalline regions contained in the metal oxide film are limited to two types. Instead, the crystal structure may include three or more crystalline regions having different types of crystal structures.

[0043] In Figure 1(A), regions 1 and 2 are stacked in a direction perpendicular to the direction parallel to the In layer. Furthermore, when we look at the boundary between Region 1 and Region 2, we can see that one In You can see that they share layers.

[0044] In this way, regions with different crystal structures are stacked, and one of them shares an In layer. By providing two regions so that they are parallel to each other, no grain boundaries are formed between these regions, resulting in high structural integrity. Furthermore, defects in the metal oxide film caused by the presence of grain boundaries are reduced. It is possible.

[0045] Furthermore, as shown in Figure 1, the upper layer of region 1 has a layer between a pair of In layers, similar to region 2. There are three (Ga, Zn) layers in the region, and one In layer exists between them. You can see that they share layers.

[0046] In this way, multiple regions with different crystal structures are stacked, each sharing an In layer. As a result, structural stability is obtained over a wide range in the metal oxide film, A metal oxide film with reduced defects can be achieved.

[0047] FIG. 2 is a cross-sectional observation image of another part of the sample.

[0048] In the cross-sectional observation image shown in Figure 2, two (Ga, Zn) layers exist between a pair of In layers. Region 3 is mixed with region 4, where three (Ga, Zn) layers exist between another pair of In layers. Regions 3 and 4 are adjacent to each other in the direction parallel to the plane parallel to the In layer. are.

[0049] Furthermore, in FIG. 2, one In layer constituting region 3 extends to region 4, and the I In other words, one In layer exists continuously between region 3 and region 4. is doing.

[0050] In this way, the In layers exist continuously between adjacent regions with different crystal structures. As a result, no grain boundaries are formed between these regions, realizing high structural stability. Furthermore, defects in the metal oxide film due to the presence of grain boundaries can be reduced.

[0051] A metal oxide film according to one embodiment of the present invention is a metal oxide film that has high structural stability. By applying such a metal oxide film to the semiconductor layer in which the channel of a transistor is formed, As a result, a highly reliable transistor can be realized.

[0052] Furthermore, in the metal oxide film of one embodiment of the present invention, the crystalline regions are continuously present, and the regions Since there are no grain boundaries between the regions, the metal oxide film has reduced defects in the film. By applying a metal oxide film to the semiconductor layer of a transistor, carrier transport due to defects can be prevented. The trapping is suppressed, high field effect mobility is realized, and the fluctuation of electrical properties is suppressed. A transistor can be realized.

[0053] Note that a structural example of a transistor including a metal oxide film of one embodiment of the present invention will be described later. This will be explained in the following embodiment.

[0054] [Method for forming metal oxide film] The method for forming a metal oxide film according to this embodiment will be described below.

[0055] The metal oxide film of this embodiment is formed by sputtering in an oxygen-containing atmosphere. The film can be formed by forming a thin film in an atmosphere containing oxygen. By using the atmosphere, oxygen vacancies in the metal oxide film are reduced, and the crystallization is facilitated by the subsequent heat treatment. It can be a membrane that includes a region.

[0056] In the metal oxide film of this embodiment, by reducing oxygen vacancies, it is possible to obtain a film with stable physical properties. In particular, the metal oxide film of this embodiment is a metal oxide film that exhibits semiconductor properties. When a semiconductor device is manufactured using a nitride film (oxide semiconductor film), The oxygen vacancies caused by the oxidation of the silicon dioxide become a factor in fluctuations in the electrical characteristics of semiconductor devices. By manufacturing a semiconductor device using an oxide semiconductor film, a highly reliable semiconductor device can be obtained. This can be done.

[0057] In the metal oxide film of this embodiment, when the oxygen partial pressure in the film formation atmosphere is increased, oxygen More specifically, the oxygen partial pressure in the film formation atmosphere is preferably It is preferable to set it to 33% or more.

[0058] The target used in the sputtering method is not limited to In-Ga-Zn oxides. Multi-component metal oxides that can have homologous structures can be used. For example, In-M -Zn-based oxides (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf, etc.) It can be used.

[0059] In addition, the composition of the metal oxide contained in the target used in the sputtering method is homologous. There is no particular limitation as long as the composition can have a crystalline structure. For example, in the case of an In-Ga-Zn oxide In this case, if the Ga composition is larger than Zn, it is easier to form a spinel structure rather than a layered structure. Therefore, it is preferable to make the Zn content larger than that of Ga. Zn is also used in sputtering. When the Zn content in the metal oxide film decreases due to sublimation during film formation by this method, Therefore, it is necessary to use a target with a higher Zn content than the composition of the desired metal oxide film. is preferred.

[0060] In addition, when forming a metal oxide film by sputtering, the surface on which the film is to be formed is not heated. The film may be formed at room temperature or may be heated. When heating, for example, it is preferable to heat the film to 150°C or higher, for example, 3 00℃ or higher, or 450℃ or higher, etc.

[0061] After the metal oxide film is formed, it is subjected to a heat treatment. The heat treatment rearranges the atoms in the film. This results in the formation of crystalline regions in the metal oxide film.

[0062] At this time, since the degree of dynamic freedom is relatively high near the membrane surface, the initial stage is A rearrangement of the adjacent atoms occurs, and a layer is formed in the vicinity of the film surface, which is approximately parallel to the film surface. After that, as the crystallization progresses from the film surface toward the depth direction, multiple layers approximately parallel to the film surface are formed. A crystalline region having a multi-layer structure is formed. The first layer and the second layer are aligned in a direction parallel to the membrane surface.

[0063] Here, the metal oxide film before the heat treatment has a distribution in the metal element concentration. During the atomic rearrangement during the heat treatment, a pair of In atoms forms in the region where the concentration of In atoms in the film is relatively high. It is thought that regions with fewer (Ga, Zn) layers between the In layers are formed. In the region where the concentration of In atoms in the film is relatively low, the (Ga, Zn) As a result, regions with a higher number of crystalline layers are formed in the film. This process can be used to form metal oxide films. The same applies to multi-component metal oxides other than the above-mentioned oxides that can have homologous structures.

[0064] For example, the film is formed at room temperature or below without heating the surface to be formed. By doing so, it is possible to form a metal oxide film having regions with different concentrations of metal elements. Cut.

[0065] The heat treatment is carried out at 550°C or higher, preferably 600°C or higher, and more preferably 650°C or higher. For example, heat treatment at 650°C for 1 hour is sufficient. The higher the heat treatment temperature, the better the The longer the time, the greater the proportion of crystalline regions contained in the metal oxide film. .

[0066] The heat treatment can be carried out, for example, in a nitrogen atmosphere or a reduced pressure atmosphere. By performing a heat treatment under an atmosphere, hydrogen in the metal oxide film can be effectively desorbed. In addition, oxygen may be released from the metal oxide film during the heat treatment. Subsequently, it is preferable to further perform a heat treatment in an oxygen atmosphere to reduce oxygen vacancies in the film. stomach.

[0067] In the above manner, the metal oxide film of one embodiment of the present invention can be formed.

[0068] This embodiment may be implemented in appropriate combination with other embodiment modes described in this specification. This can be done.

[0069] (Embodiment 2) In this embodiment, a metal oxide film according to one embodiment of the present invention, which exhibits semiconductor characteristics, is described. A semiconductor device using a nitride semiconductor film (oxide semiconductor film) will be described with reference to the drawings. Here, a configuration example of a transistor will be described as an example of a semiconductor device.

[0070] [Transistor configuration example] FIG. 5A is a schematic cross-sectional view of a transistor 100, which will be described below. The transistor 100 shown is a bottom-gate transistor.

[0071] The transistor 100 includes a gate electrode 102 provided on a substrate 101 and a gate electrode 103 formed on the substrate 101 and a gate electrode 104 formed on the substrate 101. An insulating layer 103 is provided on the gate electrode 102, and the gate electrode 102 is provided on the insulating layer 103. The oxide semiconductor layer 104 is provided so as to overlap with the upper surface of the oxide semiconductor layer 104. The insulating layer 103 and the oxide semiconductor layer 10 4. An insulating layer 106 covering the pair of electrodes 105a and 105b, and an insulating layer 10 on the insulating layer 106. 7 is provided.

[0072] The oxide semiconductor film of one embodiment of the present invention is applied to the oxide semiconductor layer 104 of the transistor 100. It can be used.

[0073] [Substrate 101] There is no particular restriction on the material of the substrate 101, but it should be strong enough to withstand the subsequent heat treatment. For example, a glass substrate, a ceramic substrate, a quartz substrate, a surface treatment substrate, etc. A fiber substrate, a YSZ (yttria stabilized zirconia) substrate, or the like is used as the substrate 101. In addition, a single crystal semiconductor substrate such as silicon or silicon carbide, a polycrystalline semiconductor substrate, a silicon It is also possible to use compound semiconductor substrates such as silicon germanium, SOI substrates, etc. .

[0074] A semiconductor substrate or an SOI substrate on which a semiconductor element is provided is referred to as a substrate 101. In this case, the transistor 100 is formed on the substrate 101 via an interlayer insulating layer. At this time, the gate of the transistor 100 is connected to the connection electrode embedded in the interlayer insulating layer. At least one of the electrode 102, the electrode 105a, and the electrode 105b is electrically connected to the semiconductor element. The transistor 10 may be electrically connected to the semiconductor element via an interlayer insulating layer. By providing 0, the increase in area due to the addition of the transistor 100 is suppressed. It is possible.

[0075] A flexible substrate such as plastic is used as the substrate 101, and a Alternatively, the transistor 100 may be formed by connecting the substrate 101 and the transistor 100. A peeling layer may be provided between the first and second semiconductor layers. The peeling layer is a layer on which a part or all of the transistor is formed. After the formation, it can be separated from the substrate 101 and used for transfer to another substrate. As a result, the transistor 100 can be mounted on a substrate with poor heat resistance or a flexible substrate.

[0076] [Gate electrode 102] The gate electrode 102 may be made of aluminum, chromium, copper, tantalum, titanium, molybdenum, or titanium. or an alloy containing the above metals, or It can be formed by using a combination of alloys, etc. Also, manganese, zirconium, etc. The gate electrode 102 may be made of a single metal. The film may have a layer structure or a laminate structure of two or more layers. For example, an aluminum film containing silicon a single-layer structure, a two-layer structure with a titanium film laminated on an aluminum film, and a titanium nitride film on a titanium Two-layer structure with a tungsten film laminated on a titanium nitride film, two-layer structure with a tungsten film laminated on a titanium nitride film, a two-layer structure in which a tungsten film is laminated on a titanium film or a tungsten nitride film; A three-layer structure in which an aluminum film is layered on top of the titanium film, and a titanium film is then formed on top of that. In addition, titanium, tantalum, tungsten, molybdenum, chromium, etc. are used in aluminum. an alloy film made by combining one or more metals selected from aluminum, neodymium, and scandium; Alternatively, nitride films of these may be used.

[0077] The gate electrode 102 is made of indium tin oxide, indium containing tungsten oxide, or the like. oxide, indium zinc oxide with tungsten oxide, indium oxide with titanium oxide oxide, indium tin oxide containing titanium oxide, indium zinc oxide, silicon oxide A light-transmitting conductive material such as indium tin oxide may also be used. Alternatively, the light-transmitting conductive material and the metal may be laminated together.

[0078] In addition, an In—Ga—Zn-based oxynitride semiconductor is formed between the gate electrode 102 and the insulating layer 103. film, In-Sn-based oxynitride semiconductor film, In-Ga-based oxynitride semiconductor film, In-Zn-based oxynitride nitride semiconductor film, Sn-based oxynitride semiconductor film, In-based oxynitride semiconductor film, metal nitride film (InN These films have a work energy of 5 eV, preferably 5.5 eV or more. The electron affinity of the oxide semiconductor is larger than that of the oxide semiconductor. The threshold voltage of the transistor can be shifted to the positive side, and so-called normally-off characteristics can be achieved. For example, an In-Ga-Zn oxynitride semiconductor film can be used to realize a switching element. In this case, the nitrogen concentration is at least higher than that of the oxide semiconductor layer 104, specifically, 7 atomic % or more. The In-Ga-Zn oxynitride semiconductor film is used.

[0079] [Insulating layer 103] The insulating layer 103 functions as a gate insulating film.

[0080] The insulating layer 103 is made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, or silicon nitride. Silicon, aluminum oxide, hafnium oxide, gallium oxide or Ga-Zn based metal oxide Silicon nitride or the like may be used, and the insulating layer may be formed as a laminated layer or a single layer.

[0081] The insulating layer 103 is made of hafnium silicate (HfSiO x ), nitrogen is added Hafnium silicate (HfSi x O y N z ), nitrogen-doped hafnium aluminate (HfAl x O y N z ), high-k materials such as hafnium oxide and yttrium oxide The use of this material can reduce gate leakage of transistors.

[0082] [Pair of electrodes 105a, 105b] The pair of electrodes 105a and 105b are the source and drain electrodes of the transistor. It functions as such.

[0083] The pair of electrodes 105a and 105b are made of a conductive material such as aluminum, titanium, chromium, Nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tung A single metal consisting of stainless steel or an alloy with this as the main component is used in a single layer structure or a laminated structure. For example, a single layer structure of an aluminum film containing silicon, an aluminum film containing silicon, Two-layer structure with titanium film laminated on tungsten film, two-layer structure with titanium film laminated on tungsten film , a two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a titanium film or A titanium nitride film and an aluminum or copper film overlaid on the titanium film or titanium nitride film. A three-layer structure in which a titanium film or titanium nitride film is formed on top of the molybdenum A film or molybdenum nitride film is laminated on the molybdenum film or molybdenum nitride film. A aluminum or copper film is laminated, and then a molybdenum or molybdenum nitride film is formed on top of that. There are three-layer structures formed. An electrically conductive material may also be used.

[0084] [Insulating layers 106, 107] The insulating layer 106 is an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition. It is preferable to use an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition. When the film is heated, some oxygen is desorbed. The oxide insulating film containing In the ion spectroscopy analysis, the amount of oxygen released in terms of oxygen atoms was 1 .0×10 18 atoms / cm 3 or more, preferably 3.0 × 10 20 atoms / cm 3 The oxide insulating film is as described above.

[0085] For example, the insulating layer 106 can be made of silicon oxide, silicon oxynitride, or the like. Cut.

[0086] The insulating layer 106 is formed to cover the oxide semiconductor layer 1 when the insulating layer 107 is formed later. It also functions as a membrane to mitigate damage to 04.

[0087] In addition, an oxide film that transmits oxygen is provided between the insulating layer 106 and the oxide semiconductor layer 104. Good too.

[0088] As the oxide film that transmits oxygen, silicon oxide, silicon oxynitride, etc. may be used. In this specification, the silicon oxynitride film is a film containing more than nitrogen as a composition. A silicon nitride film is a film that contains more oxygen than silicon dioxide. Also refers to a film with a high nitrogen content.

[0089] The insulating layer 107 may be an insulating film having a blocking effect against oxygen, hydrogen, water, etc. By providing the insulating layer 107 over the insulating layer 106, the oxide semiconductor layer 104 can be easily oxidized. The diffusion of elements to the outside and the intrusion of hydrogen, water, and the like into the oxide semiconductor layer 104 from the outside can be prevented. Examples of insulating films that have a blocking effect against oxygen, hydrogen, water, etc. include silicon nitride, Silicon nitride oxide, aluminum oxide, aluminum oxynitride, gallium oxide, oxynitride Gallium, yttrium oxide, yttrium oxynitride, hafnium oxide, hafnium oxynitride There are Um et al.

[0090] [Example of how to make a transistor] Next, an example of a method for manufacturing the transistor 100 illustrated in FIG. 5A will be described. .

[0091] First, as shown in FIG. 6(A), a gate electrode 102 is formed on a substrate 101. An insulating layer 103 is formed on the electrode 102 .

[0092] Here, a glass substrate is used as the substrate 101.

[0093] [Formation of gate electrode] The gate electrode 102 is formed by the following methods. First, a sputtering method, a CVD method, A conductive film is formed by a vapor deposition method or the like, and a photolithography is performed on the conductive film using a first photomask. A resist mask is formed by a photolithography process. The portion is etched to form the gate electrode 102. Then, the resist mask is removed. .

[0094] The gate electrode 102 may be formed by electrolytic plating, printing, ink, or the like instead of the above-mentioned method. It may also be formed by a jet method or the like.

[0095] [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.

[0096] The insulating layer 103 may be a silicon oxide film, a silicon oxynitride film, or a silicon nitride oxide film. When forming the above, a deposition gas containing silicon and an oxidizing gas are used as the source gas. Representative examples of silicon-containing deposition gases include silane, disilane, trisilane, and thiazolinone. Examples of oxidizing gases include oxygen, ozone, nitrous oxide, and Nitric oxide, etc.

[0097] When forming a silicon nitride film as the insulating layer 103, a two-stage formation method is used. First, a mixture gas of silane, nitrogen, and ammonia is used as a raw material gas. A first silicon nitride film with few defects is formed by the plasma CVD method using the above method. The source gas is changed to a mixture of silane and nitrogen, and the hydrogen concentration is low and hydrogen is not blown. A second silicon nitride film capable of rocking is formed. The insulating layer 103 is made of silicon nitride, which has few defects and hydrogen blocking properties. A film can be formed.

[0098] When a gallium oxide film is formed as the insulating layer 103, MOCVD (Metal Organic Chemical Vapor Deposition (OCVD) method It can be achieved.

[0099] [Formation of Oxide Semiconductor Layer] Next, as shown in FIG. 6B, the oxide semiconductor layer 104 is formed over the insulating layer 103.

[0100] A method for forming the oxide semiconductor layer 104 will be described below. First, the method described in Embodiment 1 will be described. Then, a second photomask is formed on the oxide semiconductor film. A resist mask is formed by a photolithography process using the resist mask. The oxide semiconductor film is partly etched using a mask to form the oxide semiconductor layer 104. The resist mask is then removed.

[0101] Note that the heat treatment described in Embodiment 1 as an example may be performed immediately after the oxide semiconductor film is formed. Alternatively, the etching may be performed after part of the oxide semiconductor film is etched.

[0102] Here, the oxide semiconductor has a large energy gap of 3.0 eV or more. The oxide semiconductor film obtained by processing the substrate under appropriate conditions and sufficiently reducing its carrier density is In the applied transistor, the leakage current between the source and drain in the off state (on The current (flash current) is extremely low compared to conventional silicon-based transistors. can be done.

[0103] When a large amount of hydrogen is contained in the oxide semiconductor film, the hydrogen is bonded to the oxide semiconductor. Some of the elements become donors, generating electrons as carriers. Therefore, the threshold voltage of the oxide semiconductor film is shifted in the negative direction. After that, dehydration treatment (dehydrogenation treatment) is performed to remove hydrogen or moisture from the oxide semiconductor film. It is preferable to remove impurities to achieve high purity so that the impurities are not included as much as possible.

[0104] Note that dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film Oxygen may also decrease at the same time. The oxygen that has been simultaneously reduced by the oxidation treatment is added to the oxide semiconductor, or oxygen is removed. It is preferable to supply oxygen to fill oxygen vacancies in the oxide semiconductor film. Supplying oxygen to a compound semiconductor film may be referred to as oxygen-adding treatment.

[0105] In this way, the oxide semiconductor film is dehydrated by dehydration treatment (dehydrogenation treatment). By removing oxygen and filling the oxygen vacancies through oxygen addition treatment, the i-type (intrinsic) or The oxide semiconductor film can be an oxide semiconductor film that is very close to i-type and is substantially i-type (intrinsic). Note that the term "substantially intrinsic" means that there are very few carriers derived from donors in the oxide semiconductor film. (close to zero), and the carrier density is 1×10 17 / cm 3 Below, 1×10 16 / cm 3 below , 1×10 15 / cm 3 Below, 1×10 14 / cm 3 Below, 1×10 13 / cm 3 Below It says something.

[0106] In addition, a transistor including an i-type or substantially i-type oxide semiconductor film can be For example, a transistor using an oxide semiconductor film can be The drain current per 1 μm of channel width when the transistor is off is 1×10 -18 A or less, preferably 1×10 -21 A or less, more preferably 1×10 -24 A or less, or 1 x 10 at 85°C -15 A or less, preferably 1×10 -18 After A or less, more preferably 1 × 10 -21 A or less. In the case of an n-channel transistor, the off state is when the gate voltage is sufficiently higher than the threshold voltage. Specifically, when the gate voltage is 1V or more, 2V or more than the threshold voltage, Or, if it is 3V or more lower, the transistor is turned off.

[0107] [Formation of a pair of electrodes] Next, as shown in FIG. 6(C), a pair of electrodes 105a and 105b are formed.

[0108] The pair of electrodes 105a and 105b are formed by the following method. First, a sputtering method is used. A conductive film is formed by a CVD method, a vapor deposition method, or the like. Next, a third photomask is used on the conductive film. A resist mask is formed by a photolithography process. The conductive film is partially etched using a fluorine-containing gas to form a pair of electrodes 105a and 105b. After that, the resist mask is removed.

[0109] Note that as shown in FIG. 6C, when the conductive film is etched, the top of the oxide semiconductor layer 104 is Therefore, the oxide semiconductor layer 104 may be partially etched and thinned. It is preferable that the thickness of the oxide semiconductor film be set to be thick in advance during the formation.

[0110] [Formation of insulating layer] Next, as shown in FIG. 6D, the oxide semiconductor layer 104 and the pair of electrodes 105a and 105b are An insulating layer 106 is formed on 5b, and then an insulating layer 107 is formed on the insulating layer 106.

[0111] When a silicon oxide film or a silicon oxynitride film is formed as the insulating layer 106, the raw material gas As the gas, it is preferable to use a deposition gas containing silicon and an oxidizing gas. Representative examples of deposition gases containing silane include silane, disilane, trisilane, and fluorosilane. Oxidizing gases include oxygen, ozone, nitrous oxide, and nitrogen dioxide.

[0112] For example, a substrate placed in a vacuum-evacuated processing chamber of a plasma CVD device is heated to 180°C or higher. The temperature is kept at 260°C or lower, more preferably 200°C or higher and 240°C or lower, and raw material gas is introduced into the treatment chamber. By introducing gas, the pressure in the processing chamber is set to 100 Pa or more and 250 Pa or less, more preferably The pressure is between 100 Pa and 200 Pa, and the electrode installed in the processing chamber is set to 0.17 W / cm 2 Below Upper 0.5W / cm 2 or less, more preferably 0.25 W / cm 2 More than 0.35W / cm 2 Silicon oxide film or silicon oxynitride film is formed under the following conditions of supplying high frequency power. Complete.

[0113] As a film formation condition, high frequency power with the above power density is supplied in a reaction chamber with the above pressure. This increases the decomposition efficiency of the source gas in the plasma, increases the oxygen radicals, and As a result, the oxygen content in the oxide insulating film becomes higher than the stoichiometric ratio. However, when the substrate temperature is above this level, the bonding strength between silicon and oxygen is weak, so heating As a result, the oxygen content is greater than the stoichiometric ratio. In this case, an oxide insulating film from which part of oxygen is released by heating can be formed.

[0114] In addition, when an oxide insulating film is provided between the oxide semiconductor layer 104 and the insulating layer 106, In the process of forming the insulating oxide layer 106, the insulating oxide layer serves as a protective film for the oxide semiconductor layer 104. As a result, damage to the oxide semiconductor layer 104 can be reduced while a high frequency with a high power density can be achieved. Electrical power can be used to form the insulating layer 106 .

[0115] For example, a substrate placed in a vacuum-evacuated processing chamber of a plasma CVD device is heated to 180°C or higher. The temperature is kept at 400°C or lower, more preferably 200°C or higher and 370°C or lower, and raw material gas is introduced into the processing chamber. By introducing gas, the pressure in the processing chamber is set to 20 Pa or more and 250 Pa or less, more preferably 1 The pressure is set to 0.0 Pa or more and 250 Pa or less, and high frequency power is supplied to the electrode installed in the processing chamber. Depending on the conditions, a silicon oxide film or a silicon oxynitride film may be formed as the oxide insulating film. Furthermore, by setting the pressure in the treatment chamber to 100 Pa or more and 250 Pa or less, the oxide Damage to the oxide semiconductor layer 104 can be reduced when an insulating layer is formed. .

[0116] As the source gas for the oxide insulating film, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of silicon-containing deposition gases include silane, disilane, trisilane, and thiazolinone. Examples of oxidizing gases include oxygen, ozone, nitrous oxide, and Nitric oxide, etc.

[0117] The insulating layer 107 can be formed by a sputtering method, a CVD method, or the like.

[0118] When a silicon nitride film or a silicon nitride oxide film is formed as the insulating layer 107, the raw material The gases used may include a deposition gas containing silicon, an oxidizing gas, and a gas containing nitrogen. Representative examples of silicon-containing deposition gases include silane, disilane, trisilane, and the like. Examples of oxidizing gases include oxygen, ozone, nitrous oxide, and dioxygen. Nitrogen dioxide, etc. Nitrogen-containing gases include nitrogen and ammonia.

[0119] After the insulating layers 106 and 107 are formed, heat treatment is preferably performed. The oxygen released from the insulating layer 106 is supplied to the oxide semiconductor layer 104, and the oxide semiconductor layer 1 It is possible to reduce oxygen deficiency in 04.

[0120] Through the above steps, the transistor 100 can be formed.

[0121] [Modifications of Transistor 100] Below, an example of a transistor configuration that is partially different from the transistor 100 will be described. .

[0122] [Variation 1] 5B is a schematic cross-sectional view of a transistor 110, which will be described below as an example. The transistor 110 differs from the transistor 100 in the structure of the oxide semiconductor layer.

[0123] The oxide semiconductor layer 114 included in the transistor 110 is an oxide semiconductor layer 114a and an oxide semiconductor layer 114b. The organic semiconductor layer 114b is laminated on the organic semiconductor layer 114a.

[0124] Note that the boundary between the oxide semiconductor layer 114a and the oxide semiconductor layer 114b may be unclear. Therefore, in the drawings such as FIG. 5(B), these boundaries are shown by dashed lines.

[0125] One or both of the oxide semiconductor layer 114a and the oxide semiconductor layer 114b The oxide semiconductor film of one embodiment of the present invention can be applied to the above-described semiconductor layer.

[0126] For example, the oxide semiconductor layer 114a is typically made of In—Ga oxide or In—Zn oxide. , In-M-Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, or When the oxide semiconductor layer 114a is an In-M-Zn oxide, I The atomic ratio of n to M is preferably such that In is less than 50 atomic % and M is 50 atomic %. ic% or more, more preferably, In is less than 25 atomic % and M is 75 atomic % % or more. For example, the oxide semiconductor layer 114a has an energy gap of 2 eV or more. A material having a surface tension of preferably 2.5 eV or more, more preferably 3 eV or more is used.

[0127] For example, the oxide semiconductor layer 114b contains In or Ga, 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 lower end of the conduction band is lower than that of the oxide semiconductor layer 114a. The energy of the oxide semiconductor layer 114b is close to the vacuum level, and is typically at the bottom of the conduction band of the oxide semiconductor layer 114b. the difference between the energy of the lower end of the conduction band of the oxide semiconductor layer 114a and the energy of the lower end of the conduction band of the oxide semiconductor layer 114a is 0.05 eV or more, 0.07eV or more, 0.1eV or more, or 0.15eV or more and 2eV or more It is preferable that the electron transport potential is set to 1 eV or less, 0.5 eV or less, or 0.4 eV or less.

[0128] For example, when the oxide semiconductor layer 114b is an In-M-Zn oxide, the In and M The atomic ratio is preferably 25 atomic % or more of In and less than 75 atomic % of M. More preferably, In is 34 atomic % or more and M is less than 66 atomic %. do.

[0129] The oxide semiconductor layer 114a may be formed of, for example, In:Ga:Zn=1:1:1 or 3:1: In-Ga-Zn oxide having an atomic ratio of 1:2 can be used. 14b, for example, In:Ga:Zn=1:3:4, 1:3:6, 1:6:8, or An In-Ga-Zn oxide having an atomic ratio of 1:6:10 can be used. The atomic ratios of the semiconductor layer 114a and the oxide semiconductor layer 114b are each calculated by adding the above error. This includes a variation of plus or minus 20% in the atomic ratio.

[0130] The oxide semiconductor layer 114b provided on the upper layer has a higher stability than the oxide semiconductor layer 114a. By using an oxide with a high Ga content that functions as a riser, the oxide semiconductor layer 1 This can suppress release of oxygen from the oxide semiconductor layer 14a and the oxide semiconductor layer 114b.

[0131] However, the semiconductor characteristics and electrical characteristics (field effect) of the required transistors are not limited to these. It is sufficient to use an appropriate composition depending on the characteristics (e.g., the mobility, threshold voltage, and variations). In order to obtain required semiconductor characteristics of the transistor, the oxide semiconductor layer 114a and the oxide The carrier density, impurity concentration, defect density, atomic ratio of metal elements to oxygen in the semiconductor layer 114b, It is preferable to make the interatomic distance, density, etc. appropriate.

[0132] Note that in the above description, the oxide semiconductor layer 114 has a structure in which two oxide semiconductor layers are stacked. However, a structure in which three or more oxide semiconductor layers are stacked may also be used.

[0133] [Variation 2] FIG. 5C is a schematic cross-sectional view of a transistor 120, which will be described below as an example. The transistor 120 is different from the transistor 100 in the structure of the oxide semiconductor layer. It differs from 10.

[0134] The oxide semiconductor layer 124 included in the transistor 120 includes an oxide semiconductor layer 124a and an oxide semiconductor layer 124b. The organic semiconductor layer 124b and the oxide semiconductor layer 124c are stacked in this order.

[0135] The oxide semiconductor layer 124a and the oxide semiconductor layer 124b are stacked on the insulating layer 103. The oxide semiconductor layer 124c is formed on the upper surface of the oxide semiconductor layer 124b and on the pair of The electrodes 105a and 105b are provided in contact with the upper and side surfaces thereof.

[0136] Among the oxide semiconductor layer 124a, the oxide semiconductor layer 124b, and the oxide semiconductor layer 124c, The oxide semiconductor film of one embodiment of the present invention is applied to any one, two, or all of the above. It is possible.

[0137] For example, the oxide semiconductor layer 124b may be the oxide semiconductor layer 11 exemplified in the first modification. For example, the oxide semiconductor layers 124a and 124b may have a similar structure to that of the oxide semiconductor layers 124a and 124b. c may have the same structure as the oxide semiconductor layer 114b exemplified in the first modification. can.

[0138] For example, the oxide semiconductor layer 124a provided below the oxide semiconductor layer 124b and the oxide semiconductor layer 124b provided above the oxide semiconductor layer 124a The oxide semiconductor layer 124c provided in the oxide semiconductor layer 124b has a content of Ga that functions as a stabilizer. By using a large amount of oxide, the oxide semiconductor layer 124a, the oxide semiconductor layer 124b, and In addition, release of oxygen from the oxide semiconductor layer 124c can be suppressed.

[0139] In addition, when a channel is mainly formed in the oxide semiconductor layer 124b, for example, The semiconductor layer 124b is made of an oxide containing a large amount of In. By providing the pair of electrodes 105a and 105b, the on-state current of the transistor 120 is increased. It can be made bigger.

[0140] [Other examples of transistor configurations] Hereinafter, a top-gate transistor to which the oxide semiconductor film of one embodiment of the present invention can be applied will be described. An example of the configuration of the star will be described.

[0141] In the following, components having the same configuration or function as those described above will be referred to as follows: The same symbols are used and duplicate content is omitted.

[0142] [Configuration example] FIG. 7A is a schematic cross-sectional view of a top-gate transistor 150 exemplified below. .

[0143] The transistor 150 includes an oxide semiconductor layer 100 formed on a substrate 101 on which an insulating layer 151 is provided. 4, a pair of electrodes 105a and 105b in contact with the top surface of the oxide semiconductor layer 104, and The insulating layer 103 is provided on the conductor layer 104 and the pair of electrodes 105a and 105b. The gate electrode 102 overlaps with the oxide semiconductor layer 104 on the insulating layer 103. An insulating layer 152 is provided over the gate electrode 102 and the semiconductor layer 103 .

[0144] The oxide semiconductor film described as an example in Embodiment 1 can be used as the oxide semiconductor layer 104.

[0145] The insulating layer 151 has a function of suppressing the diffusion of impurities from the substrate 101 to the oxide semiconductor layer 104. In addition, the oxide semiconductor layer 104 has a function of supplying oxygen to the oxide semiconductor layer 104 by heating. For example, the insulating layer 106 or the insulating layer 107 may have the same structure as the insulating layer 106 or the insulating layer 107, or It may have a laminated structure.

[0146] The insulating layer 152 is an insulating layer from which oxygen is released by heating, and the oxide semiconductor layer 104 is For example, the insulating layer 106 may have the same structure as the insulating layer 106. .

[0147] The insulating layer 153 is an insulating layer that has a blocking effect against oxygen, hydrogen, water, etc. For example, it may have the same structure as the insulating layer 107 described above.

[0148] The insulating layer 152 is an insulating layer having a blocking effect against oxygen, hydrogen, water, etc. In that case, the insulating layer 153 may not be provided.

[0149] [Variation 3] Below, an example of the configuration of a transistor that is partially different from the transistor 150 will be described. do.

[0150] 7B is a schematic cross-sectional view of a transistor 160, which will be described below as an example. The transistor 160 differs from the transistor 150 in the structure of the oxide semiconductor layer.

[0151] The oxide semiconductor layer 164 included in the transistor 160 includes an oxide semiconductor layer 164a and an oxide semiconductor layer 164b. The organic semiconductor layer 164b and the oxide semiconductor layer 164c are stacked in this order.

[0152] Among the oxide semiconductor layers 164a, 164b, and 164c, Any one, any two, or all of the oxide semiconductor films may be any of the oxide semiconductor films described in Embodiment 1. can be applied.

[0153] For example, the oxide semiconductor layer 164b may be the oxide semiconductor layer 11 exemplified in the first modification. For example, the oxide semiconductor layer 164a and the oxide semiconductor layer 4a may be formed in the same manner. The semiconductor layer 164c has the same structure as the oxide semiconductor layer 114b exemplified in the first modification. can be used.

[0154] For example, the oxide semiconductor layer 164a provided under the oxide semiconductor layer 164b and the oxide semiconductor layer 164b provided over the oxide semiconductor layer 164a are The oxide semiconductor layer 164c provided in the oxide semiconductor layer 164b has a content of Ga that functions as a stabilizer. By using an oxide having a large amount of oxide, the oxide semiconductor layer 164a, the oxide semiconductor layer 164b, and the oxide This can suppress the release of oxygen from the oxide semiconductor layer 164c.

[0155] [Variation 4] Hereinafter, transistors that are partially different from the transistors 150 and 160 will be described. A configuration example of the above will be described.

[0156] The transistor 170 illustrated in FIG. 7C includes an oxide semiconductor layer, a gate insulating layer, and the like. The transistor 150 and the transistor 160 differ in this respect.

[0157] The oxide semiconductor layer 164c of the oxide semiconductor layer 164 included in the transistor 170 , and the oxide semiconductor layer 164b and the ends of the electrodes 105a and 105b. It is being done.

[0158] In addition, the oxide semiconductor layer 164c and the insulating layer 103 are connected to the gate electrode 102. The same photomask was used to process the patterns so that they were approximately identical.

[0159] The insulating layer 152 is provided in contact with the side surfaces of the insulating layer 103 and the oxide semiconductor layer 164c. It is being done.

[0160] The transistor exemplified in this embodiment has a semiconductor layer in which a channel is formed. The metal oxide film shown in 1 is applied. Therefore, the carrier trapping due to defects is prevented. High reliability with suppressed fluctuations in electrical characteristics. It is a high performance transistor.

[0161] This embodiment may be implemented in appropriate combination with other embodiment modes described in this specification. This can be done.

[0162] (Embodiment 3) In this embodiment, a structural example of a display panel according to one embodiment of the present invention will be described.

[0163] [Configuration example] FIG. 8A is a top view of a display panel according to one embodiment of the present invention, and FIG. 8B is a top view of a display panel according to one embodiment of the present invention. A pixel circuit that can be used when a liquid crystal element is applied to a pixel of a display panel of one embodiment is described. 8C is a circuit diagram for explaining a pixel of a display panel according to one embodiment of the present invention. FIG. 1 is a circuit diagram illustrating a pixel circuit that can be used when an organic EL element is applied. do.

[0164] The transistor disposed in the pixel portion can be formed according to Embodiment 2. Since the transistor can be easily made into an n-channel type, the n-channel transistor in the driver circuit can be easily made into an n-channel type. A part of the driver circuit can be configured with a transistor of the same type as the transistor of the pixel part. In this way, the transistor described in Embodiment 2 is formed in the pixel portion or the driver circuit. By using this, a highly reliable display device can be provided.

[0165] An example of a block diagram of an active matrix display device is shown in FIG. On a substrate 500, a pixel section 501, a first scanning line driving circuit 502, a second scanning line driving circuit The pixel portion 501 has a signal line driver circuit 503 and a signal line driver circuit 504. A plurality of scanning lines are arranged extending from the first scanning line driving circuit 502, and The scanning line driving circuit 503 is arranged to extend from the scanning line driving circuit 503. In the display area, pixels each having a display element are arranged in a matrix. The substrate 500 is a connection board for FPC (Flexible Printed Circuit) etc. It is connected to a timing control circuit (also called a controller or control IC) via .

[0166] In FIG. 8A, a first scanning line driver circuit 502, a second scanning line driver circuit 503, a signal line The driver circuit 504 is formed on the same substrate 500 as the pixel portion 501. This reduces the number of components, such as the drive circuit, that are required on the substrate 5, thereby reducing costs. 00When an external drive circuit is provided, it becomes necessary to extend the wiring, and the number of connections between the wiring increases. When a driving circuit is provided on the same substrate 500, the number of connections between the wirings can be reduced. Therefore, it is possible to improve reliability or yield.

[0167] [LCD panel] An example of the circuit configuration of a pixel is shown in Figure 8(B). 1 shows a pixel circuit that can be applied to the pixel.

[0168] This pixel circuit can be applied to a configuration in which one pixel has multiple pixel electrode layers. The pixel electrode layer is connected to different transistors, and each transistor is driven by a different gate signal. This allows individual pixels of the multi-domain designed pixel to be moved. The signals applied to the electrode layers can be controlled independently.

[0169] 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 applied. The source electrode layer or drain electrode layer 514 functioning as a transistor 516 is connected to the transistor 516. The transistors 516 and 517 are commonly used. The transistors described in the second embodiment can be used as appropriate. A display panel can be provided.

[0170] A first pixel electrode layer electrically connected to the transistor 516 and a second pixel electrode layer electrically connected to the transistor 517 are The shape of the second pixel electrode layer that is electrically connected to the first pixel electrode layer will be described. The shape of the pixel electrode layer is separated by slits. The first pixel electrode layer spreads in a V-shape. The second pixel electrode layer is formed so as to surround the outside of the first pixel electrode layer.

[0171] The gate electrode of the transistor 516 is connected to the gate wiring 512, and the gate electrode of the transistor 517 is connected to the gate wiring 512. The gate electrode of the gate electrode 512 is connected to the gate wiring 513. 3, different gate signals are applied to transistors 516 and 517. By varying the voltage, the orientation of the liquid crystal can be controlled.

[0172] Also, the capacitor wiring 510, the gate insulating film functioning as a dielectric, and the first pixel electrode layer Alternatively, a storage capacitor may be formed by a capacitor electrode electrically connected to the second pixel electrode layer.

[0173] The multi-domain structure has 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 therebetween. The second liquid crystal element 519 is composed of a second pixel electrode layer, a counter electrode layer, and a liquid crystal layer therebetween. can be.

[0174] Note that the pixel circuit shown in FIG. 8B is not limited to this. For example, Pixels can be equipped with new elements such as switches, resistors, capacitors, transistors, sensors, or logic circuits. may be added.

[0175] [Organic EL panel] Another example of the circuit configuration of a pixel is shown in Figure 8(C). The pixel structure of the panel is shown.

[0176] In an organic EL element, when a voltage is applied to the light-emitting element, electrons are emitted from one of the pair of electrodes. and holes are injected from the other side into the layer containing the light-emitting organic compound, causing a current to flow. The electrons and holes recombine to form an excited state in the light-emitting organic compound, When the excited state returns to the ground state, light is emitted. The optical element is called a current-excited light-emitting element.

[0177] FIG. 8C is a diagram showing an example of an applicable pixel circuit. An example in which two transistors are used in one pixel is shown. The film can be used for the channel formation region of an n-channel transistor. The pixel circuit can be applied with digital time gray scale driving.

[0178] Regarding the configuration of applicable pixel circuits and pixel operation when digital time gray scale driving is applied, and explain.

[0179] The pixel 520 includes a switching transistor 521, a driving transistor 522, and a light emitting element. The switching transistor 521 has a gate element 524 and a capacitor element 523. The source electrode layer is connected to the scanning line 526, and the first electrode (one of the source electrode layer and the drain electrode layer) is connected to the scanning line 526. The first electrode (the other of the source electrode layer and the drain electrode layer) is connected to a signal line 525, and the second electrode (the other of the source electrode layer and the drain electrode layer) is connected to a signal line 525. It is connected to the gate electrode layer of the driving transistor 522. The gate electrode layer is connected to a power supply line 527 via a capacitor element 523, and 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 formed on the same substrate. It is electrically connected to the common potential line formed thereon.

[0180] The switching transistor 521 and the driving transistor 522 are the same as those in the second embodiment. The transistors described below can be used as appropriate. This allows for a highly reliable organic EL display. A display panel can be provided.

[0181] The potential of the second electrode (common electrode 528) of the light emitting element 524 is set to a low power supply potential. The low power supply potential is a potential lower than the high power supply potential set to the power supply line 527, for example, GN The low power supply potential can be set to D, 0V, etc. The high power supply potential and the low power supply potential are set so that the potential difference is equal to or greater than the minimum voltage. By applying a voltage to the light emitting element 524, a current flows through the light emitting element 524, causing it to emit light. The forward voltage of 24 refers to the voltage required to achieve the desired brightness, and is at least Includes threshold voltage.

[0182] The capacitor 523 is substituted for the gate capacitance of the driving transistor 522. The gate capacitance of the driving transistor 522 can be omitted. A capacitance may be formed between the gate electrode layer and the insulating layer.

[0183] Next, a description will be given of the signal input to the driving transistor 522. Voltage input voltage driving In this method, the driving transistor 522 is in two states: fully on or off. A video signal that becomes the same as the video signal is input to the driving transistor 522. In order to operate the motor 522 in the linear region, a voltage higher than the voltage of the power supply line 527 is applied to the drive A signal line 525 is connected to the gate electrode layer of the transistor 522. A voltage equal to or greater than the threshold voltage Vth of the driving transistor 522 is applied.

[0184] When analog gradation driving is performed, the gate electrode layer of the driving transistor 522 is connected to the light emitting element 5 24 plus the threshold voltage Vth of the driving transistor 522. In addition, the video signal is input so that the driving transistor 522 operates in the saturation region. This causes a current to flow through the light emitting element 524. In addition, the driving transistor 522 is operated in a saturation region. In order to achieve this, the potential of the power supply line 527 is set higher than the gate potential of the driving transistor 522. By converting the video signal into an analog signal, a current corresponding to the video signal is passed through the light emitting element 524. Furthermore, analog gradation driving can be performed.

[0185] The configuration of the pixel circuit is not limited to the pixel configuration shown in FIG. C) The pixel circuit shown in You can also add roads etc.

[0186] This embodiment may be implemented in appropriate combination with other embodiment modes described in this specification. This can be done.

[0187] (Fourth embodiment) In this embodiment, a semiconductor device and an electronic device using a metal oxide film according to one embodiment of the present invention will be described. An example of the configuration will be described.

[0188] FIG. 9 is a block diagram of an electronic device including a semiconductor device to which a metal oxide film of one embodiment of the present invention is applied. This is a diagram.

[0189] FIG. 10 illustrates an external view of an electronic device including a semiconductor device to which a metal oxide film of one embodiment of the present invention is applied. Figure.

[0190] The electronic device shown in FIG. 9 includes an RF circuit 901, an analog baseband circuit 902, a digital baseband circuit 903, and a A baseband circuit 903, a battery 904, a power supply circuit 905, an application processor 906, flash memory 910, display controller 911, memory circuit 91 2. Display 913, touch sensor 919, audio circuit 917, keyboard 918, etc. It is composed of:

[0191] The application processor 906 includes a CPU 907, a DSP 908, and an interface (IF) 909. The memory circuit 912 is composed of SRAM or DRAM. It is possible.

[0192] By applying the transistor described in Embodiment 2 to the memory circuit 912, Therefore, it is possible to provide a highly reliable electronic device that can write and read information.

[0193] Furthermore, the transistor described in the second embodiment may be included in the CPU 907 or the DSP 908. By applying this to registers, etc., the reliability of writing and reading information can be improved. It is possible to provide a high-performance electronic device.

[0194] Note that when the off-leak current of the transistor described in Embodiment 2 is extremely small, Long-term memory retention is possible, and power consumption is sufficiently reduced. It is possible to provide a memory circuit 912. In addition, during the power-gated period, The CPU 907 or DSP 90 can store the state before loading in a register or the like. 8 can be provided.

[0195] The display 913 includes a display unit 914, a source driver 915, a gate driver 916, and a It consists of 16.

[0196] The display unit 914 has a plurality of pixels arranged in a matrix. The pixel circuit is electrically connected to a gate driver 916 .

[0197] The transistor described in Embodiment 2 is appropriately provided in the pixel circuit or the gate driver 916. This makes it possible to provide a highly reliable display.

[0198] Examples of electronic devices include television sets (televisions or television receivers) (also called "computer monitors"), cameras such as digital cameras and digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), Examples include large game machines such as small game machines, mobile information terminals, sound reproduction devices, and pachinko machines. can be.

[0199] FIG. 10A shows a portable information terminal, which includes a main body 1001, a housing 1002, a display unit 1003, and a display unit 1004. The display unit 1003a, 1003b, etc. The display unit 1003b is a touch panel. By touching the keyboard button 1004 displayed on the display unit 1003b, Of course, the display unit 1003a can be configured as a touch panel. The transistor described in Embodiment 2 may be used as a switching element in a liquid crystal panel. By fabricating an organic light-emitting panel and applying it to the display units 1003a and 1003b, reliability can be improved. It can be a highly portable information terminal.

[0200] The portable information terminal shown in FIG. 10(A) displays various information (still images, videos, text images, etc.). Functions that display calendars, dates, or times on the display, functions that display Functions for manipulating or editing displayed information, processing by various software (programs) In addition, external connection terminals can be provided on the back and sides of the housing. It may also be configured to include a connector (such as an earphone jack or USB terminal), a recording medium insertion section, etc.

[0201] The portable information terminal shown in FIG. 10(A) is configured to be capable of transmitting and receiving information wirelessly. You can also purchase and download desired book data from an electronic book server wirelessly. It is also possible to configure it so that it is downloaded.

[0202] FIG. 10B shows a portable music player, and the main body 1021 has a display unit 1023 and earphones. a fixing part 1022 for attaching to a speaker, an operation button 1024, an external memory slot, The transistor shown in the second embodiment is used as a switching element. By manufacturing a liquid crystal panel or an organic light-emitting panel as a display unit 1023, This makes the portable music player more reliable.

[0203] Furthermore, the portable music player shown in FIG. 10(B) is equipped with an antenna, a microphone function, and a wireless function. If you carry it and connect it to your mobile phone, you can enjoy wireless hands-free driving while driving a car. Conversations in Lee are also possible.

[0204] FIG. 10C shows a mobile phone, which is composed of two housings, a housing 1030 and a housing 1031. The housing 1031 is provided with a display panel 1032, a speaker 1033, a microphone, and the like. a phone 1034, a pointing device 1036, a camera lens 1037, an external connection terminal The housing 1030 also includes a solar cell for charging the mobile phone. The device is equipped with a cell 1040, an external memory slot 1041, etc. The transistor described in Embodiment 2 is built in the display panel 103. By applying this to 2, a highly reliable mobile phone can be achieved.

[0205] The display panel 1032 is equipped with a touch panel, and the image displayed in FIG. The multiple operation keys 1035 are shown by dotted lines. A boost circuit is also implemented to boost the input voltage to the voltage required for each circuit.

[0206] For example, the power transistor used in a power supply circuit such as a booster circuit is also described in the second embodiment. The thickness of the metal oxide film of the transistor to be described is set to 2 μm or more and 50 μm or less. It is possible.

[0207] The display direction of the display panel 1032 changes appropriately depending on the usage mode. The camera lens 1037 is located on the same surface as the lens 1032, so video calls are possible. The speaker 1033 and the microphone 1034 are not limited to voice calls, but also to video calls. Furthermore, the housing 1030 and the housing 1031 can be slid apart. As shown in Figure 10(C), the device can be folded from the unfolded state to the overlapped state, making it easy to carry. Suitable miniaturization is possible.

[0208] The external connection terminal 1038 can be connected to various cables such as AC adapters and USB cables. It is possible to charge the battery and to communicate data with a personal computer, etc. By inserting a recording medium into the external memory slot 1041, it is possible to store and transfer a larger amount of data. Cut.

[0209] In addition to the above functions, it also has infrared communication functions, TV reception functions, etc. Good too.

[0210] FIG. 10D shows an example of a television device. The television device 1050 is A display unit 1053 is built into the housing 1051. The display unit 1053 displays an image. In addition, the CPU is built into the stand 1055 that supports the housing 1051. The transistor described in the second embodiment is applied to the display unit 1053 and the CPU. By using this, television device 1050 can be made highly reliable.

[0211] The television device 1050 can be operated using an operation switch provided on the housing 1051 or a separate remote control. This can be done by a remote control operation device. A display unit may be provided to display information output from the device.

[0212] The television device 1050 is configured to include a receiver, a modem, and the like. It is possible to receive general television broadcasts, and also to receive wired or wireless signals via a modem. By connecting to a communication network, it can be one-way (sender to receiver) or two-way It is also possible to communicate information in both directions (between a sender and a receiver, or between receivers). .

[0213] The television device 1050 also includes an external connection terminal 1054 and a storage medium playback / recording unit 1055. 052, and an external memory slot. The external connection terminal 1054 is for connecting a USB cable or the like. It can be connected to any type of cable, enabling data communication with a personal computer, etc. In the storage medium playback / recording unit 1052, a disk-shaped recording medium is inserted and It is possible to read the stored data and write it to the recording medium. Images and videos stored in the external memory 1056 inserted in the reslot It is also possible to display it on the display unit 1053.

[0214] Furthermore, when the off-leak current of the transistor described in Embodiment 2 is extremely small, By applying this transistor to external memory 1056 and CPU, power consumption is sufficiently reduced. This results in a highly reliable television device 1050 with reduced noise. [Explanation of symbols]

[0215] 100 transistors 101 Substrate 102 gate electrode 103 Insulating layer 104 Oxide semiconductor layer 105a electrode 105b electrode 106 Insulating layer 107 Insulating layer 110 Transistor 114 Oxide semiconductor layer 114a Oxide semiconductor layer 114b Oxide semiconductor layer 120 transistors 124 Oxide semiconductor layer 124a Oxide semiconductor layer 124b Oxide semiconductor layer 124c Oxide semiconductor layer 150 transistors 151 Insulating layer 152 Insulating layer 153 Insulating Layer 160 transistors 164 Oxide semiconductor layer 164a Oxide semiconductor layer 164b Oxide semiconductor layer 164c Oxide semiconductor layer 170 transistors 500 boards 501 Pixel unit 502 Scanning line driving circuit 503 Scanning line driving circuit 504 Signal line driver circuit 510 Capacitance wiring 512 Gate wiring 513 Gate wiring 514 Drain electrode layer 516 Transistor 517 Transistor 518 Liquid crystal element 519 Liquid crystal element 520 pixels 521 Switching Transistor 522 Drive transistor 523 Capacitor 524 Light-emitting element 525 signal line 526 scan lines 527 Power 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 section 915 Source Driver 916 Gate Driver 917 Voice Circuit 918 keyboard 919 Touch Sensor 1001 Main Unit 1002 Case 1003a Display section 1003b Display section 1004 keyboard buttons 1021 Main Unit 1022 Fixed part 1023 Display section 1024 operation buttons 1025 external memory slots 1030 Case 1031 Case 1032 Display Panel 1033 Speaker 1034 Microphone 1035 Operation Key 1036 Pointing Device 1037 Camera Lenses 1038 External connection terminal 1040 solar cell 1041 External memory slot 1050 Television Equipment 1051 Case 1052 Storage media playback and recording unit 1053 Display section 1054 External connection terminal 1055 Stand 1056 external memory

Claims

[Claim 1] containing In, Ga, and Zn, In the cross-sectional observation image, a plurality of first layers in which In atoms are periodically arranged and a plurality of second layers in which Ga atoms or Zn atoms are periodically arranged are observed, a first region having n (n is a natural number) layers of the second layer between a pair of the first layers; a second region having m (m is a natural number other than n) layers of the second layer between another pair of the first layers, Metal oxide film.

Images