Crystalline oxide film

Abstract

A crystalline oxide film is provided which contains a highly crystalline oxide containing indium as a main component and further contains a corundum structure. [Solution] Using a cold-wall mist CVD device, a raw material solution is atomized or turned into droplets, and the resulting mist or droplets are transported to a substrate installed in a film-forming chamber using a carrier gas.The mist or droplets are then thermally reacted at 500°C or less in the film-forming chamber to obtain a crystalline oxide film on the substrate that is highly crystalline and contains an indium-containing oxide as its main component and also contains a corundum structure.

Description

Technical Field

[0001] The present invention relates to a crystalline oxide film and its uses.

Background Art

[0002] By doping indium oxide film with tin, it exhibits a metallic electrical resistivity of about 1×10 -4 Ωcm and at the same time maintains transparency, so it is suitable as a transparent conductive film and is widely used as a pixel electrode of a liquid crystal display, a carrier collection electrode of a solar cell, etc. When used for such applications, a high surface resistance value causes a decrease in output, so generally a relatively low surface resistance value is desired. Therefore, a highly crystalline indium oxide film is required (Patent Document 1).

[0003] In addition, in the field of oxide electronics, indium oxide is a promising semiconductor based on a large band gap of 3.6 to 3.75 eV. When indium oxide is used as a semiconductor, it is necessary to devise a way to increase the mobility as much as possible. One way to increase the mobility is to increase the crystallinity of indium oxide. Furthermore, when constructing a device, an insulating film is often required in addition to a semiconductor film with high mobility. In such a case, if highly mobile indium oxide and insulating indium oxide can be obtained, by laminating them on each other, for example, an electronic device such as an FET transistor can be realized. When indium oxide is used as an insulating film, contrary to the case of a transparent electrode material, it is necessary to increase the electrical resistivity as much as possible. Therefore, it is necessary to devise a method to remove impurity ions as much as possible and not to create oxygen defects as much as possible (Patent Document 2).

[0004] As an effort to enhance the crystallinity of indium oxide films, as in the invention described in Patent Document 3, the study of creating indium oxide films using the mist CVD method has been underway. Further, for example, in Non-Patent Document 1, using the mist CVD method, an In 2 O 3 thin film having a corundum structure is grown on a sapphire substrate, and success has been achieved in obtaining a highly oriented thin film with a rocking curve full width at half maximum of 182 arcsec by X-ray diffraction method. However, even when using these techniques, it has been difficult to create a film with a lower full width at half maximum, and usually only thin films of about 300 to 1000 arcsec have been obtained. Also, such films have problems such as pits occurring on the surface, and the surface smoothness has not been satisfactory.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a crystalline oxide film containing, as a main component, a highly crystalline indium-containing oxide and further containing a cordierite structure.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that when a film is formed using the mist CVD method under specific conditions, a crystalline oxide film containing, as a main component, a highly crystalline indium-containing oxide and further containing a metastable cordierite structure can be formed. The present inventors have also found that such a crystalline oxide film can solve the above conventional problems at once. In addition, after obtaining the above findings, the present inventors have further repeated studies and completed the present invention.

[0009] That is, the present invention relates to the following inventions. [1] In a semiconductor device including at least a semiconductor layer and an electrode, a crystalline oxide film containing an oxide having a corundum structure and containing indium as a main component is used for the semiconductor layer, and the semiconductor device is characterized by being a transistor. [2] The oxide is α-In 2 O 3 The semiconductor device according to [1] above. [3] The semiconductor device according to [1] or [2] above, wherein the crystalline oxide film is a transparent conductive film. [4] The semiconductor device according to any one of [1] to [3] above, wherein the field-effect mobility is 187 cm 2 / Vs or more. [5] The semiconductor device according to any one of [1] to [4] above, wherein the effective mobility is 240 cm 2 / Vs or more. [6] The semiconductor device according to any one of [1] to [5] above, which is a metal oxide semiconductor field effect transistor (MOSFET).

Effects of the Invention

[0010] According to the present invention, a crystalline oxide film containing, as a main component, a highly crystalline indium-containing oxide and further containing a cordierite structure can be provided.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0012] The crystalline oxide film of the present invention is a crystalline oxide film containing an oxide containing indium as a main component, includes a corundum structure, and is characterized in that the rocking curve half-value width of the X-ray diffraction method is 100 arcsec or less.

[0013] The crystalline oxide film of the present invention may be any of an insulating film, a semiconductor film, or a conductive film, and may also be a conductive film or a transparent conductive film.

[0014] The crystal having a corundum structure contained in the crystalline oxide film may be a single crystal, a polycrystal, or a mixture thereof. In the present invention, it is preferable that the crystal having the corundum structure is composed of an oxide containing indium. Note that the “main component” means a composition ratio (atomic ratio) in the crystalline oxide film that contains 50% or more of the oxide, preferably 70% or more, and more preferably 90% or more.

[0015] The oxide is not particularly limited as long as it contains indium. Examples of the indium-containing oxide include indium oxide, tin-doped indium oxide (ITO), gallium-doped indium oxide, indium-doped zinc oxide, and the like. Preferably, the oxide is indium oxide or tin-doped indium oxide, and more preferably, indium oxide. In the present invention, it is preferable that the oxide has a corundum structure, more preferably indium oxide or tin-doped indium oxide having a corundum structure, and most preferably indium oxide having a corundum structure.

[0016] The film thickness of the crystalline oxide film is not particularly limited, but in the present invention, the film thickness is preferably 1 μm or more, more preferably 1.5 μm or more, and most preferably 1.8 μm or more. The shape and the like of the crystalline oxide film are not particularly limited, and it may be square, circular, or polygonal. The surface area of the crystalline oxide film is not particularly limited, but in the present invention, it is preferably 3 mm square or more, more preferably 5 mm square or more, and most preferably 50 mm in diameter or more.

[0017] The crystalline oxide film may contain a dopant. The dopant is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, or p-type dopants. In the present invention, the dopant is preferably tin. The content of the dopant is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and most preferably 0.00001 atomic% to 10 atomic% in the composition of the crystalline oxide film.

[0018] The "half-value width" refers to the value obtained by measuring the rocking curve half-value width by XRD (X-ray diffraction). The plane orientation is not particularly limited, and examples include

[0006] . In the present invention, the above half-value width is usually 100 arcsec or less, preferably 50 arcsec or less, and more preferably 40 arcsec or less.

[0019] Hereinafter, the preferred manufacturing method of the crystalline oxide film will be described, but the present invention is not limited to these preferred manufacturing methods.

[0020] As a preferred manufacturing method of the crystalline oxide film, for example, using a cold-wall type mist CVD apparatus as shown in FIG. 1, the raw material solution is atomized or dropletized (atomization / dropletization step), and the obtained mist or droplets are transported to a substrate installed in the film formation chamber by a carrier gas (inert gas) (transport step). Then, in the film formation chamber, the mist or droplets are thermally reacted at 500 °C or lower to form a crystalline oxide film on the substrate (film formation step). Examples of such methods include.

[0021] (Atomization / dropletization step) In the atomization / dropletization step, the raw material solution is atomized or dropletized. The atomization means or dropletization means of the raw material solution is not particularly limited as long as it can atomize or dropletize the raw material solution, and it may be a known means. In the present invention, however, an atomization means or dropletization means using ultrasonic waves is preferred. The mist or droplets obtained using ultrasonic waves have an initial velocity of zero and float in the air, which is preferable. For example, instead of spraying like a spray, it is a mist that can float in space and be transported as a gas, so there is no damage due to collision energy, which is very suitable. The droplet size is not particularly limited and may be droplets of about several mm, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm.

[0022] (Raw material solution) The raw material solution can be atomized or dropletized and is not particularly limited as long as it contains indium. In the present invention, as the raw material solution, those in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or a salt can be preferably used. Examples of the form of the complex include acetylacetonate complex, carbonyl complex, ammine complex, hydride complex, and the like. Examples of the form of the salt include organometallic salts (such as metal acetates, metal oxalates, metal citrates, etc.), metal sulfide salts, metal nitrate salts, metal phosphate salts, metal halide salts (such as metal chloride salts, metal bromide salts, metal iodide salts, etc.). In the present invention, it is preferable that the raw material solution is a metal halide salt of indium. By using such a preferable raw material solution, the surface smoothness of the film can be made good, and furthermore, the crystallinity of the film can be made better.

[0023] The raw material solution may contain a dopant. By including a dopant in the raw material solution, doping can be performed well. The dopant is not particularly limited as long as it does not inhibit the object of the present invention. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, or p-type dopants, and the like. The concentration of the dopant is usually about 1×10 16 / cm 3 ~1×10 22 / cm 3 and may be, or the concentration of the dopant may be, for example, about 1×10 17 / cm 3 or lower at a low concentration. Further, according to the present invention, the dopant may be contained at a high concentration of about 1×10 20 / cm 3 or higher.

[0024] The solvent of the raw material solution is not particularly limited and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of an inorganic solvent and an organic solvent. In the present invention, it is preferable that the solvent contains water, more preferably water or a mixed solvent of water and alcohol, and most preferably water. More specifically, examples of the water include pure water, ultrapure water, tap water, well water, mineral water, mineral water, hot spring water, spring water, fresh water, seawater, etc. In the present invention, ultrapure water is preferable.

[0025] (Transportation step) In the transportation step, the mist or the droplets are transported into the film formation chamber with a carrier gas. As the carrier gas, an inert gas such as nitrogen or argon is used. Also, the type of the carrier gas may be one type, but may also be two or more types. A dilution gas with a reduced flow rate (for example, 10-fold dilution gas, etc.) may be further used as the second carrier gas. Also, the supply location of the carrier gas may not be only one location, but may be two or more locations. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of the dilution gas, the flow rate of the dilution gas is preferably 0.001 to 2 L / min, and more preferably 0.1 to 1 L / min.

[0026] (Film formation step) In the film formation process, a crystalline oxide film is formed on a substrate by thermally reacting the mist or droplets in a film formation chamber. The thermal reaction only needs the mist or droplets to react with heat, and the reaction conditions and the like are not particularly limited as long as they do not inhibit the object of the present invention. In this process, the thermal reaction is usually carried out at a temperature of 500 °C or lower, preferably 400 °C or lower, more preferably 350 °C or lower, and most preferably 150 °C to 350 °C. Further, the thermal reaction may be carried out in any atmosphere of under vacuum, in a non-oxygen atmosphere, in a reducing gas atmosphere, and in an oxygen atmosphere as long as it does not inhibit the object of the present invention, but it is preferably carried out in a non-oxygen atmosphere (for example, in an atmosphere of an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas), and more preferably carried out in an inert gas atmosphere. Also, it may be carried out under any conditions of atmospheric pressure, under pressure, and under reduced pressure, but in the present invention, it is preferably carried out under atmospheric pressure. Note that the film thickness can be set by adjusting the film formation time.

[0027] (substrate) The substrate is not particularly limited as long as it can support the crystalline oxide film. The material of the substrate is also not particularly limited as long as it does not inhibit the object of the present invention, and it may be a known substrate, an organic compound, or an inorganic compound. The shape of the substrate may be any shape and is effective for any shape. For example, plate-like shapes such as flat plates and disks, fibrous shapes, rod-like shapes, cylindrical shapes, prismatic shapes, tubular shapes, spiral shapes, spherical shapes, ring-shaped shapes, porous body shapes, etc. can be mentioned. In the present invention, a substrate is preferred. The thickness of the substrate is not particularly limited in the present invention.

[0028] The substrate is plate-shaped and is not particularly limited as long as it serves as a support for the crystalline oxide film. It may be an insulator substrate, a semiconductor substrate, a metal substrate, or a conductive substrate, but it is preferably an insulator substrate and also preferably a substrate having a metal film on its surface. The shape of the substrate is not particularly limited and may be substantially circular (e.g., circular, elliptical, etc.), polygonal (e.g., triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, etc.), and various shapes can be suitably used. In the present invention, by making the shape of the substrate a preferable shape, the shape of the film formed on the substrate can be set. Also, in the present invention, a large-area substrate can be used, and by using such a large-area substrate, the area of the crystalline oxide film can be increased. Examples of the substrate include a base substrate mainly containing a substrate material having a corundum structure, a base substrate mainly containing a substrate material having a β-gallia structure, a base substrate mainly containing a substrate material having a hexagonal crystal structure, and the like. Here, "main component" means that the substrate material having the specific crystal structure is preferably contained at 50% or more, more preferably 70% or more, still more preferably 90% or more, and may be 100% in terms of atomic ratio with respect to all components of the substrate material.

[0029] The substrate material is not particularly limited as long as it does not inhibit the object of the present invention and may be a known one. Examples of the substrate material having a corundum structure include, for example, α-Al 2 O 3 (sapphire substrate) or α-Ga 2 O 3 are preferably mentioned, and a-plane sapphire substrate, m-plane sapphire substrate, r-plane sapphire substrate, c-plane sapphire substrate, α-type gallium oxide substrate (a-plane, m-plane or r-plane), etc. are more preferable examples. Examples of the base substrate mainly containing a substrate material having a β-gallia structure include, for example, β-Ga 2 O 3 substrate, or Ga 2 O 3 and Al 2 O 3including Al 2 O 3 Examples include a polycrystalline substrate in which 2 Al 3 O is more than 0 wt% and 60 wt% or less. Further, examples of the base substrate mainly composed of a substrate material having a hexagonal crystal structure include a SiC substrate, a ZnO substrate, a GaN substrate, and the like.

[0030] In the present invention, it is preferable that the substrate has a corundum structure, more preferably a base substrate mainly composed of a substrate material having a corundum structure, and most preferably a sapphire substrate or an α-gallium oxide substrate. Further, it is preferable that the substrate contains aluminum, more preferably a base substrate mainly composed of an aluminum-containing substrate material having a corundum structure, and most preferably a sapphire substrate (preferably a c-plane sapphire substrate, an a-plane sapphire substrate, an m-plane sapphire substrate, an r-plane sapphire substrate).

[0031] In the present invention, a film may be formed directly on the substrate, but it is preferable to form a film on the substrate via a buffer layer after laminating the buffer layer on the substrate. Examples of the buffer layer include a semiconductor layer, an insulator layer, or a conductor layer containing a corundum structure, and among them, a semiconductor layer containing a corundum structure is preferable. Examples of the semiconductor layer containing a corundum structure include α-Fe 2 O 3 、α-Ga 2 O 3 、α-Al 2 O 3 and the like. The lamination means of the buffer layer is not particularly limited and may be the same as the lamination means of the crystalline oxide film.

[0032] The crystalline oxide film obtained as described above has a rocking curve half-width of 100 arcsec or less by X-ray diffraction method, indicating excellent crystallinity. Such a crystalline oxide film can be suitably used for devices and the like. Examples of the device include a solar cell, a display, lighting, an electronic paper, a transistor, a printable circuit, or a transparent planar heating element. In the present invention, it is preferable that the device is a device including at least one or more films selected from an insulating film, a semiconductor film, and a conductive film and an electrode.

[0033] In the present invention, further, by forming a film by mist CVD method using a buffer layer or a dopant, a crystalline oxide film containing an oxide containing indium as a main component, including a corundum structure, and having a carrier density of 3.1×10 18 cm -3 or less and a mobility of 143 cm 2 / Vs or more can be easily obtained. Since such a crystalline oxide film has excellent semiconductor characteristics, it can be suitably used as the semiconductor layer in a semiconductor device including at least a semiconductor layer and an electrode. The application method and the like are not particularly limited, and known means may be used.

[0034] Examples of the semiconductor device include a diode and a transistor. More specifically, for example, a Schottky barrier diode (SBD), a metal-semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), a metal-oxide-semiconductor field effect transistor (MOSFET), a static induction transistor (SIT), a junction field effect transistor (JFET), an insulated gate bipolar transistor (IGBT), or a light-emitting diode. In the present invention, it is preferable that the semiconductor device is an SBD, a MESFET, a HEMT, a MOSFET, or an SIT, and more preferably a MOSFET.

[0035] The semiconductor device obtained as described above has excellent characteristics of the semiconductor device. Specifically, for example, as a buffer layer, α-(Alx , Ga x-1 ) 2 O 3 When using the 2 O 2 film (0 < x < 1), a semiconductor device with a field-effect mobility of 187 cm

Example

[0036] Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

[0037] (Example 1) 1. Film-forming apparatus Using FIG. 1, the mist CVD apparatus 1 used in this example will be described. The mist CVD apparatus 1 includes a carrier gas source 2a for supplying a carrier gas, a flow rate regulating valve 3a for regulating the flow rate of the carrier gas sent out from the carrier gas source 2a, a carrier gas (dilution) source 2b for supplying a carrier gas (dilution), a flow rate regulating valve 3b for regulating the flow rate of the carrier gas (dilution) sent out from the carrier gas (dilution) source 2b, a mist generation source 4 containing a precursor solution 4a, a container 5 containing water 5a, an ultrasonic vibrator 6 attached to the bottom surface of the container 5, a film-forming chamber 7, a supply pipe 9 connecting the mist generation source 4 to the film-forming chamber 7, a hot plate 8 installed in the film-forming chamber 7, and an exhaust port 11 for discharging the mist, droplets and exhaust gas after the thermal reaction. A substrate 10 is installed on the hot plate 8. 2. Preparation of precursor solution Indium bromide was mixed with ultrapure water, and an aqueous solution was adjusted to contain 0.025 mol of indium bromide.

[0038] 3. Film-forming preparation The precursor solution 4a obtained in 2. above was accommodated in the mist generation source 4. Next, as the substrate 10, α-Fe was used as a buffer layer on the surface 2 O 3A sapphire substrate (2-inch diameter) with a film laminated thereon was placed on a hot plate 8, and the hot plate 8 was operated to raise the temperature in the film deposition chamber 7 to 350 °C. Next, the flow control valves 3a and 3b were opened, and carrier gas was supplied into the film deposition chamber 7 from the carrier gas supply means 2a and 2b, which are carrier gas sources. After sufficiently replacing the atmosphere in the film deposition chamber 7 with the carrier gas, the flow rate of the carrier gas was adjusted to 5.0 L / min, and the flow rate of the carrier gas (diluted) was adjusted to 0.5 L / min. Nitrogen was used as the carrier gas.

[0039] 4. Film Formation Next, the ultrasonic oscillator 6 was vibrated at 2.4 MHz, and the vibration was propagated to the precursor solution 4a through the water 5a, thereby atomizing the precursor solution 4a to generate a mist 4b. This mist 4b was introduced into the film deposition chamber 7 through the supply pipe 9 by the carrier gas. Under atmospheric pressure and at 350 °C, the mist underwent a thermal reaction in the film deposition chamber 7, and an indium oxide film was formed on the substrate 10. The film thickness was 1.8 μm, and the film deposition time was 120 minutes.

[0040] The indium oxide film obtained in the above 4. was a clean crystal without turbidity. When the film was identified using an X-ray diffractometer, the obtained film was an α-In 2 O 3 film. Also, the rocking curve half-value width measured by the X-ray diffraction method was 36 arcsec, indicating a highly crystalline film. Furthermore, when the film surface was observed with an atomic force microscope (AFM), as shown in Figure 3, a film with no pits or the like on the surface and excellent surface smoothness was obtained.

[0041] (Comparative Example 1) Using FIG. 4, the mist CVD apparatus 19 used in Comparative Example 1 will be described. The mist CVD apparatus 19 includes a susceptor 21 on which a substrate 20 is placed, a carrier gas supply means 22a for supplying a carrier gas, a flow rate adjustment valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas supply means 22a, a carrier gas (dilution) supply means 22b for supplying a carrier gas (dilution), a flow rate adjustment valve 23b for adjusting the flow rate of the carrier gas sent out from the carrier gas (dilution) supply means 22b, a mist generation source 24 in which a raw material solution 24a is accommodated, a container 25 into which water 25a is put, an ultrasonic vibrator 26 attached to the bottom surface of the container 25, a supply pipe 27 made of a quartz tube with an inner diameter of 40 mm, and a heater 28 installed in the peripheral portion of the supply pipe 27. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal plane. By making both the supply pipe 27 and the susceptor 21, which form the film formation chamber, of quartz, it is possible to suppress the mixing of impurities derived from the apparatus into the film formed on the substrate 20.

[0042] As a film forming apparatus, film formation was carried out in the same manner as in Example 1 except that the mist CVD apparatus 19 shown in FIG. 4 was used and the film formation time was 40 minutes. When the obtained film was identified using an X-ray diffractometer, it was α-In 2 O 3 . Further, when the full width at half maximum was measured using an X-ray diffractometer, it was 187 arcsec. The film thickness was 250 nm.

[0043] As described above, it can be seen that the crystalline oxide film of the present invention is excellent in crystallinity.

[0044] (Test Example) According to the above example, Fe 2 O 3 buffer layer and Ga 2 O 3 buffer layer (first layer) were each used together with ozone to form α-In 2 O 3A film (second layer) was obtained. Also, in accordance with the above example, magnesium acetylacetonate and zinc acetylacetonate were respectively mixed into the raw materials, and α-In was subjected to Mg doping and Zn doping. 2 O 3 A film was obtained. The obtained α-In 2 O 3 For the film, after confirming the crystal structure with an X-ray diffractometer, annealing treatment was performed and Hall effect measurement was carried out to evaluate the carrier density and mobility. The results are shown in Fig. 4. As is clear from Fig. 4, a carrier density of 3.1×10 18 cm -3 and a mobility of 143 cm / Vs were obtained, and it was found that the doping was good, the relationship between the carrier density and the mobility was also clarified, and by doping, the carrier density was reduced to 3.1×10 18 cm -3 or less, and it was found that the mobility could be made 143 cm 2 / Vs or more.

[0045] (Production Example) The MOSFET shown in Fig. 5 was fabricated. First, in accordance with the above example, magnesium acetylacetonate was mixed into the raw materials, and further, α-(Al 0.1 Ga 0.9 ) 2 O 3 The buffer layer (first layer) 36 was used together with ozone to obtain an α-In 2 O 3 film (second layer) 35 as a semiconductor layer on the substrate 37. The film thickness was set to 60 nm to turn off the MOSFET. On the fabricated α-In 2 O 3 film, a source electrode 32 and a drain electrode 33 were respectively provided. Specifically, after the α-In 2 O 3 film was washed with acetone, a resist was formed, the surface was protected with a photomask, followed by exposure and then development to form a pattern, and a gold (Au) film (70 nm thick) was formed. After the fabrication of the source and drain electrodes was completed, an amorphous a-Al which is an insulating layer 2 O 3The thin film 34 was formed using the mist CVD method. After forming the insulating layer, the gate electrode 31 (Au film, 100 nm thick) was fabricated in the same manner as the source and drain electrodes. The insulating layer on the fabricated source and drain electrodes was removed by etching to fabricate a MOSFET.

[0046] For the fabricated MOSFET, the S value indicating the performance as the switching characteristic was 1.83 V / dec. And a ON / OFF ratio of 10 5 was obtained. From this, it can be seen that the gate characteristics are good. Also, using the evaluation of the gate characteristics, the IV measurement results, and the constants in Table 1, the field-effect mobility μ FE and the effective mobility μ eff were calculated. As a result, the field-effect mobility was 187 cm 2 / Vs, and the effective mobility was 240 cm 2 / Vs. From this result, it can be seen that a MOSFET with a field-effect mobility of 187 cm 2 / Vs or more and an effective mobility of 240 cm 2 / Vs or more, which has excellent mobility, was obtained.

[0047]

Table 1

Industrial Applicability

[0048] The crystalline oxide film of the present invention can be used in various devices, and is particularly useful for solar cells, displays, lighting, electronic paper, transistors, printable circuits, or transparent planar heaters, etc.

Explanation of Reference Numerals

[0049] 1 Mist CVD apparatus 2a Carrier gas source 2b Carrier gas (diluted) source 3a Flow rate regulating valve 3b Flow rate regulating valve 4 Mist generation source 4a Raw material solution 4b Mist 5 Container 5a Water 6 Ultrasonic vibrator 7 Film formation chamber 8 Hot plate 9 Supply pipe 10 Substrate 11 Exhaust port 19 Mist CVD apparatus 20 Substrate 21 Susceptor 22a Carrier gas supply means 22b Carrier gas (diluted) supply means 23a Flow rate regulating valve 23b Flow rate regulating valve 24 Mist generation source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic vibrator 27 Supply pipe 28 Heater 29 Exhaust port 31 Gate electrode 32 Source electrode 33 Drain electrode 34 Gate insulating film 35 Semiconductor layer (second layer) 36 Buffer layer (first layer) 37 Substrate

Claims

1. A semiconductor device comprising at least a semiconductor layer, a gate insulating film, and a gate electrode, wherein the semiconductor layer is a crystalline oxide film having a first layer mainly composed of a first oxide and a second layer mainly composed of a second oxide containing indium, the gate electrode is disposed via the gate insulating film on the second layer side of the semiconductor layer, is a transistor, at least magnesium is doped in the second layer, and the second oxide has a corundum structure. A semiconductor device characterized by this.

2. The semiconductor device according to claim 1, wherein the first oxide contains at least one of iron, gallium, and aluminum and has a corundum structure.

3. The semiconductor device according to claim 1 or 2, wherein the gate insulating film is an amorphous film.

4. The semiconductor device according to any one of claims 1 to 3, which is a lateral device.

5. wherein the second oxide is α-In ２ O ３ The semiconductor device according to any one of claims 1 to 4

6. The semiconductor device according to any one of claims 1 to 5, wherein the crystalline oxide film is transparent.

7. The semiconductor device according to any one of claims 1 to 6, which is a metal-oxide-semiconductor field-effect transistor (MOSFET).

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