JP7016489B2 - Crystalline oxide semiconductor film, semiconductor device - Google Patents

Description

The present invention relates to a novel crystalline oxide semiconductor film and a semiconductor device using the crystalline oxide semiconductor film.

As a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance, semiconductor devices using gallium oxide (Ga ₂ O ₃ ) with a large bandgap are attracting attention, and are used for power semiconductor devices such as inverters. Expected to be applied. According to Non-Patent Document 1, the gallium oxide can control the bandgap by forming a mixed crystal of indium or aluminum, respectively, or in combination with each other. Among them, In _X1 Al _Y1 Ga _Z1 O ₃ The InAlGaO-based semiconductor represented by (0 ≦ X1 ≦ 2, 0 ≦ Y1 ≦ 2, 0 ≦ Z1 ≦ 2, X1 + Y1 + Z1 = 1.5 to 2.5) is an extremely attractive material.

In Patent Document 1, a Ga ₂ O ₃ system in which a p-type α- (Al _X2 Ga _1-X2 ) ₂ O ₃ single crystal film (0 ≦ X2 <1) is formed on an α-Al ₂ O ₃ substrate. Semiconductor devices are described. However, the semiconductor device described in Patent Document 2 has many restrictions in being applied to the semiconductor device due to problems in crystal quality, and in the MBE method, the α-Ga ₂ O 3 single crystal film (α-Ga 2 O ₃ single crystal film ( (When X2 = 0) is difficult to manufacture, and since ion injection and heat treatment at a high temperature are required to obtain a p-type semiconductor, it is difficult to realize the p-type α-Ga ₂ O ₃ itself. Actually, the semiconductor device itself described in Patent Document 1 is difficult to realize.

Patent Document 2 describes corundum-structured oxide crystals containing aluminum and gallium, and describes that the phase transition at high temperature is suppressed. However, a mixed crystal having a large bandgap still has many problems. For example, even if it is used as a buffer layer, a rotating domain may be present in the epitaxially grown crystal or warpage may occur, so that the mixed crystal does not always have many problems. I wasn't satisfied.

Japanese Unexamined Patent Publication No. 2013-58637 JP-A-2015-017027

Kentaro Kaneko, "Growth and Physical Properties of Corundum Structure Gallium Oxide Mixed Crystal Thin Film", Doctoral Dissertation, Kyoto University, March 2013

An object of the present invention is to provide a crystalline oxide semiconductor film having a reduced rotation domain and warpage.

As a result of diligent studies to achieve the above object, the present inventors have obtained a crystalline oxide semiconductor film containing α-Ga ₂ O ₃ as a main component, and the content of the rotational domain in the film is 0.02. We have succeeded in creating a crystalline oxide semiconductor film with a volume of% or less, and according to such a crystalline oxide semiconductor film, not only the rotation domain but also the warp is reduced, and the conventional problems are solved at once. I found out what I could do.
In addition, after obtaining the above findings, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following invention.
[1] A crystalline oxide semiconductor film containing α-Ga ₂ O ₃ as a main component, characterized in that the content of rotational domains in the film is 0.02% by volume or less. Semiconductor film.
[2] The crystalline oxide semiconductor film according to the above [1], wherein the content of the rotational domain in the film is 0.01% by volume or less .
[3] The crystalline oxide semiconductor film according to the above [1] or [2], wherein the warp is 0.3 μm or less.
[4] The crystalline oxide semiconductor film according to any one of the above [1] to [3], which has a film thickness of 1 μm or more .
[5] The crystalline oxide semiconductor film according to the above [1], wherein the atomic ratio of gallium in the crystalline oxide semiconductor film is 0.7 or more .
[6] The crystalline oxide semiconductor film according to the above [1], wherein the atomic ratio of gallium in the crystalline oxide semiconductor film is 0.8 or more .
[7] A laminated structure in which a substrate and a crystalline oxide semiconductor film are laminated on the substrate via a buffer layer, and the buffer layer is different from the first layer and the first layer. The second layer containing the material as a main component has a quantum well structure in which at least one layer is alternately laminated, and the crystalline oxide semiconductor film is the above-mentioned [1] to [6]. A laminated structure characterized by being the crystalline oxide semiconductor film according to any one.
[8] The laminated structure according to the above [7], wherein the main component of the first layer of the quantum well structure is an oxide having a corundum structure, and the main component of the second layer is an oxide containing aluminum. ..
[9] The laminated structure according to the above [8] , wherein the aluminum concentration in the metal element of the second layer is 1 atomic% or more.
[10] A semiconductor device including the crystalline oxide semiconductor film according to any one of [1] to [6] or the laminated structure according to any one of [7] to [9] .
[11] The semiconductor device according to the above [10], which is a semiconductor laser, a diode, or a transistor.

The crystalline oxide semiconductor film of the present invention has reduced rotational domains and warpage, and is useful for semiconductor devices.

It is a schematic block diagram of the film forming apparatus (mist CVD) used in an Example. It is a figure explaining the atomization / droplet atomization part used in an Example. It is a figure explaining the ultrasonic oscillator in FIG. The TEM image in the Example is shown. The TEM image of the buffer layer in an Example is shown. The XRD data of the crystalline oxide semiconductor film in an Example is shown. The XRD data in Comparative Example 1 is shown. The XRD data in Comparative Example 2 is shown.

The crystalline oxide semiconductor film of the present invention is a crystalline oxide semiconductor film containing α-Ga ₂ O ₃ as a main component, and the content of the rotational domain in the film is 0.02% by volume or less. It is characterized by.

The "content of the rotating domain" is measured by using an X-ray diffractometer, and more specifically, it can be obtained from the count number of the rotating domains obtained by using the X-ray diffractometer. The content of the rotation domain is usually about 0.02% by volume or less, but in the present invention, it is preferably 0.01% by volume or less, and it is substantially free of rotation domains. More preferred. For example, it is more preferable that the count number of the rotational domains in the crystalline oxide semiconductor film determined by X-ray diffraction measurement is 0 count with respect to 100,000 count.

The "main component" includes, for example, when the oxide semiconductor is α-Ga ₂ O ₃ , α-Ga ₂ O ₃ is contained at a ratio of gallium in the metal element of the film having an atomic ratio of 0.5 or more. If so, that's fine. In the present invention, the atomic ratio of gallium in the metal element in the thin film is preferably 0.7 or more, more preferably 0.8 or more. The thickness of the crystalline oxide semiconductor thin film is not particularly limited and may be 1 μm or less or 1 μm or more, but in the present invention, it is preferably 1 μm or more, and is preferably 3 μm. The above is more preferable. The oxide semiconductor is usually a single crystal, but may be a polycrystal.

The oxide semiconductor is not particularly limited as long as it has a corundum structure and contains at least one or more of aluminum, gallium and indium. Examples of the oxide semiconductor include α-Ga ₂ O ₃ , α- (Al _x Ga _1-x ) ₂ O ₃ (however, 1>X> 0), α- (In _Y Ga _1-Y ) ₂ . Examples thereof include O ₃ (however, 1>Y> 0), α- (Al _Z1 Ga _Z2 In _Z3 ) ₂ O ₃ (however, 1> Z1, Z2, Z3> 0 and Z1 + Z2 + Z3 = 1). In the present invention, it is preferable that the oxide semiconductor contains at least gallium.

Further, in the present invention, the warp of the crystalline oxide semiconductor film is preferably 0.3 μm or less, and more preferably 0.25 μm or less. The "warp" refers to the shortest distance between the shortest straight line passing through the points at both ends of the film (for example, both ends between 5 mm) and the concave or convex apex. In the present invention, for example, when the shortest straight line passing through the points at both ends between 5 mm of the film and the shortest distance between the concave or convex vertices is the warp, the warp is 0.06 μm / mm or less. Is preferable.

The means for forming the crystalline oxide semiconductor film is not particularly limited as long as the object of the present invention is not impaired, but a means for producing the crystal by growing crystals on the substrate using mist is preferable, and a buffer layer is formed on the substrate. The means for growing crystals through the process is more preferable. The buffer layer is not particularly limited as long as it does not impair the object of the present invention, but is preferably an oxide semiconductor having a corundum structure, and the first layer and a material different from the first layer are the main components. It is more preferable to have a quantum well structure in which at least one layer is alternately laminated with the second layer. Regarding the quantum well structure, the main component of the first layer is preferably an oxide having a corundum structure, and the main component of the second layer is preferably an oxide containing aluminum, preferably the first layer. It is more preferable that the main component of the second layer is a gallium-containing oxide semiconductor and the main component of the second layer is an aluminum-containing oxide semiconductor. The "main component" is the same as above. Further, in the present invention, when the second layer contains at least aluminum, the concentration of aluminum in the metal element of the second layer is preferably 1 atomic% or more, preferably 2 atomic% or more. Is more preferable. The upper limit of the aluminum concentration is not particularly limited, but is usually 99 atomic% or less, preferably 80 atomic% or less, more preferably 50 atomic% or less, and most preferably 30 atomic% or less. ..

Hereinafter, as a preferred method for producing the crystalline oxide semiconductor film, a means for growing crystals through the buffer layer having the quantum well structure by using mist on a substrate will be described, and the present invention describes these. Not limited to.

As a suitable means for crystal growth using mist, a mist or droplet produced by atomizing or dropletizing a raw material solution is conveyed to a substrate by a carrier gas, and then the mist or the liquid is carried on the substrate. The droplets are reacted to form a buffer layer. By alternately using the raw material solution as the raw material solution of the first layer and the raw material solution of the second layer, the first layer and the second layer are alternately laminated as the buffer layer. It is possible to form a quantum well structure. After forming the buffer layer, the crystalline oxide semiconductor film is formed on the buffer layer in the same manner as described above.

(Raw material solution)
The raw material solution contains a material capable of atomization or droplet formation, and is not particularly limited as long as it contains at least one or more of aluminum, gallium and indium, and may be an inorganic material. Although it may be an organic material, in the present invention, it is preferably a metal or a metal compound, and gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium and calcium. , Silicon, indium, strontium and gallium are more preferably contained.

In the present invention, as the raw material solution, a solution 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 an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. The form of the salt is, for example, an organic metal salt (for example, metal acetate, metal oxalate, metal citrate, etc.), a metal sulfide salt, a nitrified metal salt, a phosphor oxide metal salt, a halogenated metal salt (for example, metal chloride). Salts, metal bromide salts, metal iodide salts, etc.) and the like.

Further, an additive such as a hydrohalic acid or an oxidizing agent may be mixed with the raw material solution. Examples of the hydrohalogen acid include hydrogen bromide, hydrochloric acid, and hydroiodide, and among them, hydrobromic acid or hydroiodide is preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), benzoyl peroxide (C ₆ H ₅ CO) ₂ O ₂ and the like. Peroxides, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, organic peroxides such as peracetic acid and nitrobenzene can be mentioned.

The raw material solution may contain a dopant. The dopant is not particularly limited as long as it does not interfere with the object of the present invention. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. The concentration of the dopant may be usually about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant may be as low as about 1 × 10 ¹⁷ / cm ³ or less, for example. You may. Further, according to the present invention, the dopant may be contained in a high concentration of about 1 × 10 ²⁰ / cm ³ or more.

(Hypokeimenon)
The substrate is not particularly limited as long as it can support the film. The material of the substrate is not particularly limited as long as it does not impair the object of the present invention, and 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, fibrous, rod-like, columnar, prismatic, such as a flat plate or a disk. Cylindrical, spiral, spherical, ring-shaped and the like can be mentioned, but in the present invention, a substrate is preferable. The thickness of the substrate is not particularly limited in the present invention.

The substrate is not particularly limited as long as it has a plate shape and serves as a support for the crystal film. It may be an insulator substrate, a semiconductor substrate, or a conductive substrate, but the substrate is preferably an insulator substrate and has a metal film on the surface. It is also preferable that it is a substrate. The substrate includes, for example, a base substrate containing a substrate material having a corundum structure as a main component, a substrate substrate containing a substrate material having a β-galia structure as a main component, and a substrate material having a hexagonal structure as a main component. Examples include a base substrate. Here, the "main component" means that the substrate material having the specific crystal structure has an atomic ratio of preferably 50% or more, more preferably 70% or more, still more preferably 90% with respect to all the components of the substrate material. It means that it is contained in% or more, and may be 100%.

The substrate material is not particularly limited and may be known as long as it does not interfere with the object of the present invention. Examples of the substrate material having the corundum structure include the same materials as those exemplified as the material having the corundum structure, but in the present invention, α-Al ₂ O ₃ or α-Ga ₂ O. ₃ is preferable. Preferable examples of the base substrate containing a substrate material having a corundum structure as a main component include a sapphire substrate (preferably a c-plane sapphire substrate) and an α-type gallium oxide substrate. As the base substrate containing the substrate material having a β-Galia structure as a main component, for example, β-Ga ₂ O ₃ substrate or Ga ₂ O ₃ and Al ₂ O ₃ are included, and Al ₂ O ₃ is more than 0 wt%. Examples thereof include a mixed crystal substrate having a content of 60 wt% or less. Examples of the base substrate containing a substrate material having a hexagonal structure as a main component include a SiC substrate, a ZnO substrate, and a GaN substrate. It should be noted that each layer may be laminated directly or via another layer (eg, a buffer layer) on the base substrate whose main component is a substrate material having a hexagonal structure.

In the present invention, the substrate is preferably a base substrate containing a substrate material having a corundum structure as a main component, more preferably a sapphire substrate or an α-type gallium oxide substrate, and is a c-plane sapphire substrate. Is the most preferable.

(Laminating method)
The buffer layers are preferably laminated by the mist CVD method. In the mist CVD, the raw material solution is atomized or dropleted (atomization / droplet atomization step), and the generated mist or droplet is supplied to the substrate by a carrier gas (mist / droplet supply step). The supplied mist or droplet is reacted to form a film on the substrate (deposition step).

In the atomization / droplet atomization step, the raw material solution is prepared, and the raw material solution is atomized or dropletized to generate mist. The mixing ratio of the metal is not particularly limited, but is preferably 0.0001 mol / L to 20 mol / L with respect to the entire raw material solution. The atomizing or droplet-forming means is not particularly limited as long as it can atomize or dropletize the raw material solution, and may be a known atomizing means or droplet-forming means, but in the present invention, it is super It is preferably an atomizing means or a droplet forming means using sound waves. The mist or the droplet is preferably one that has an initial velocity of zero and floats in the air, and is more preferably a mist that floats in space and can be conveyed as a gas instead of being sprayed like a spray. preferable. The droplet size is not particularly limited and may be a droplet of about several mm, but is preferably 50 μm or less, and more preferably 1 to 10 μm.

In the mist / droplet supply step, the mist or the droplet is supplied to the substrate by the carrier gas. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired, and for example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is a suitable example. Is mentioned as. Further, the type of the carrier gas may be one type, but may be two or more types, and a diluted gas having a changed carrier gas concentration (for example, a 10-fold diluted gas or the like) may be used as the second carrier gas. Further may be used. Further, the carrier gas may be supplied not only at one place but also at two or more places. The flow rate of the carrier gas is not particularly limited, but the linear velocity in the reactor (more specifically, the reactor is hot and changes depending on the environment, so room temperature is assumed. The converted linear velocity) is preferably 0.1 m / s to 100 m / s, more preferably 1 m / s to 10 m / s.

In the film forming step, the mist or the droplets are reacted to form a film on a part or all of the surface of the substrate. The reaction is not particularly limited as long as it is a reaction in which a film is formed from the mist or the droplets, but in the present invention, a thermal reaction is preferable. The thermal reaction may be such that the mist or the droplets react with heat, and the reaction conditions and the like are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually carried out at a temperature equal to or higher than the evaporation temperature of the solvent, but is preferably not too high or lower. Further, the thermal reaction may be carried out under any of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, and the thermal reaction may be carried out under atmospheric pressure or pressure. It may be carried out under either reduced pressure or reduced pressure, but in the present invention, it is preferable to carry out under atmospheric pressure because the calculation of the evaporation temperature becomes easy. In the case of vacuum, the evaporation temperature can be lowered. Further, the film thickness can be set by adjusting the film formation time. In the present invention, the thicknesses of the first layer and the second layer in the quantum well are not particularly limited, but are preferably 200 nm or less, more preferably 100 nm or less, and 20 nm or less, respectively. Is the most preferable.

After forming the buffer layer, a crystalline oxide semiconductor film containing α-Ga ₂ O ₃ as a main component is formed on the buffer layer.

In the present invention, the formation of the crystalline oxide semiconductor film may be carried out by a known means and may be the same as the formation of the buffer layer, but in the present invention, the crystallinity is obtained by the mist CVD method. It is preferable to form an oxide semiconductor film. More specifically, for example, a mist or droplet generated by atomizing or dropletizing a raw material solution is conveyed to a substrate with a carrier gas, and then the mist or droplet is reacted on the substrate to form crystals. Form a sex oxide semiconductor film. The raw material solution and the substrate may be the same as the raw material solution and the substrate in the buffer layer formation described above. Further, the laminating method may be the same as the laminating method in the buffer layer formation described above.

As described above, the crystalline oxide semiconductor film obtained via the buffer layer having a quantum well structure has a rotation domain content of 0.02% by volume or less in the film, and further warps. It has been reduced.

The crystalline oxide semiconductor film can be used in a semiconductor device or the like as a laminated structure together with the substrate and the buffer layer. Further, in the present invention, the crystalline oxide semiconductor film may be used in a semiconductor device or the like after using a known means such as peeling from the substrate or the like.

Examples of the semiconductor device formed by using the crystalline oxide semiconductor film or the crystalline laminated structure include a semiconductor laser, a diode, a transistor, and the like, and more specifically, for example, MIS, HEMT, and the like. Examples thereof include transistors and TFTs, shotkey barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, light receiving and receiving elements, and the like.

1. 1. Film forming apparatus First, the film forming apparatus 1 used in this embodiment will be described with reference to the drawings. The film forming apparatus 1 includes a carrier gas source 2a for supplying a carrier gas, a flow control valve 3a for adjusting the flow rate of the carrier gas sent out from the carrier gas source 2a, and a carrier gas (diluted) for supplying the carrier gas (diluted). Diluted) source 2b, flow control valve 3b for adjusting the flow rate of carrier gas (diluted) sent out from the carrier gas (diluted) source 2b, mist generation source 4 containing the raw material solution 4a, and water 5a. A container 5 to be put in, an ultrasonic transducer 6 attached to the bottom surface of the container 5, a film forming chamber 7, a gas supply pipe 9 connecting the mist generation source 4 to the film forming chamber 7, and a film forming chamber. It is provided with a hot plate 8 installed in 7. A substrate 10 is installed on the hot plate 8.
FIG. 2 shows an atomized / droplet atomized portion. The mist generation source 4 composed of a container containing the raw material solution 4a is stored in the container 5 containing the water 5a by using a support (not shown). An ultrasonic oscillator 6 is provided at the bottom of the container 5, and the ultrasonic oscillator 6 and the oscillator 16 are connected to each other. Then, when the oscillator 16 is operated, the ultrasonic oscillator 6 vibrates, the ultrasonic waves propagate into the mist generation source 4 via the water 5a, and the raw material solution 4a is configured to be atomized or dropleted. ing.
FIG. 3 shows the ultrasonic transducer 6 shown in FIG. The ultrasonic transducer 6 is provided with a disk-shaped piezoelectric element 6b in a cylindrical elastic body 6d on the support 6e, and electrodes 6a and 6c are provided on both sides of the piezoelectric element 6b. There is. Then, when an oscillator is connected to the electrodes and the oscillation frequency is changed, ultrasonic waves having a resonance frequency in the thickness direction and a resonance frequency in the radial direction of the piezoelectric vibrator are configured to be generated.

2. 2. Preparation of raw material solution (raw material solution of the first layer)
The aqueous solution was adjusted so that the ratio of gallium acetylacetonate was 3 mol / L to 9 mol / L of aluminum acetylacetonate, and at this time, hydrochloric acid was further contained so as to be 2% by volume, and this was first. Was used as the raw material solution.
(Raw material solution of the second layer)
An aqueous solution of gallium bromide 0.1 mol / L to which germanium oxide was added was prepared so that the atomic ratio of germanium to gallium was 1: 0.01, and at this time, a 48% hydrobromic acid solution was further added by volume ratio. It was contained so as to be 10%, and this was used as a second raw material solution.

(Raw material solution for crystalline oxide semiconductor film)
An aqueous solution of gallium bromide 0.1 mol / L to which germanium oxide was added was prepared so that the atomic ratio of germanium to gallium was 1: 0.01, and at this time, a 48% hydrobromic acid solution was further added by volume ratio. It was contained so as to be 10%, and this was used as a third raw material solution.

3. 3. Preparation for film formation 2. The raw material solution 4a obtained in 1) was housed in the mist generation source 4. Next, using a 4-inch c-plane sapphire substrate as the substrate 10, the c-plane sapphire substrate is placed on the hot plate 8 and the hot plate 8 is operated to raise the temperature in the film forming chamber 7 to 500 ° C. I warmed it up. Next, the flow control valve 3 (3a, 3b) is opened to supply the carrier gas from the carrier gas source 2 (2a, 2b) into the film forming chamber 7, and the atmosphere of the film forming chamber 7 is sufficiently replaced with the carrier gas. After that, the flow rate of the carrier gas was adjusted to 5 L / min, and the flow rate of the carrier gas (diluted) was adjusted to 0.5 L / min. Oxygen was used as the carrier gas.

4. Formation of buffer layer The ultrasonic transducer 6 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 4a through water 5a to atomize the raw material solution 4a to generate raw material fine particles 4b. The raw material fine particles 4b were introduced into the film forming chamber 7 by the carrier gas, and the mist reacted in the film forming chamber 7 at 600 ° C. under atmospheric pressure to form a thin film on the substrate 10. .. As the raw material solution 4a, the above 2. By alternately using the first raw material solution and the second raw material solution obtained in the above, the quantum well structure has a quantum well structure in which the first layer and the second layer are alternately laminated by 50 layers each. A buffer layer was formed. The film forming time using the first raw material solution was 3 minutes / layer, and the film forming time using the second raw material solution was 30 seconds / layer. Further, as a result of identification using an X-ray diffractometer, the first layer is composed of α- (Al _0.02 Ga _0.98 ) ₂ O ₃ having an aluminum concentration of 2 atomic%, and the second layer. The layer was composed of α-Ga ₂ O ₃ .

5. Formation of Crystallized Oxide Semiconductor Film Using the third raw material solution as the raw material solution 4a, the ultrasonic transducer 6 is vibrated at 2.4 MHz, and the vibration is propagated to the raw material solution 4a through water 5a. The raw material solution 4a was atomized to produce raw material fine particles 4b. The raw material fine particles 4b were introduced into the film forming chamber 7 by the carrier gas, and the mist reacted in the film forming chamber 7 at 500 ° C. under atmospheric pressure to form a thin film on the buffer layer. .. The film formation time was 180 minutes and the film thickness was 8 μm. When the obtained thin film was measured using an X-ray diffractometer (Smartlab manufactured by Rigaku Co., Ltd.), it was α-Ga ₂ O ₃ , and the content of the rotating domain was 0%. The TEM image of the obtained crystalline oxide semiconductor film is shown in FIG. 4, and the TEM image of the buffer layer is shown in FIG. Further, the XRD data is shown in FIG.

(Comparative Example 1)
The above 5. The above 5. The buffer layer was formed by forming a film in the same manner as in the above. After forming the buffer layer, the above 5. In the same manner as above, an α-Ga ₂ O ₃ film was formed by forming a film on the buffer layer. An X-ray diffractometer was used to identify the phase. The XRD data is shown in FIG.

(Raw material solution for Comparative Example 1)
The aqueous solution was adjusted so that the ratio of gallium acetylacetonate was 2 mol / L to 14 mol / L of aluminum acetylacetonate, and at this time, hydrochloric acid was further contained so as to be 2% by volume, and this was used as a comparative example. It was used as a raw material solution.

(Comparative Example 2)
The α-Ga ₂ O ₃ film was formed in the same manner as in the above embodiment except that the buffer layer was not formed. The XRD data is shown in FIG.

6. Evaluation Above 5. The physical characteristics of the crystalline oxide semiconductor film obtained in 1 and the α-Ga ₂ O ₃ film obtained in Comparative Example were evaluated. The results are shown in Table 1 below. For the warp, the shortest distance between the shortest straight line passing through the points at both ends between 5 mm and the concave or convex apex was measured. In addition, in Table 1, “presence / absence of 1010 heterogeneous peaks” was measured by measuring the reciprocal lattice mapping of 1010 planes, and the presence / absence of peaks other than the substrate and the membrane was confirmed. In addition, the content of the rotating domain and the like were measured using an X-ray diffractometer (Smartlab manufactured by Rigaku Co., Ltd.). The measurement conditions are as follows.

(X-ray measurement conditions)
Performed 104-sided Φ scan
XG_CURRENT 200mA
XG_VOLTAGE 45kV
X-ray source CuKα1
Detector Monochromator SC-70
SCAN_SPEED 200 deg / min
SCAN_STEP 0.200 deg
Φ scan 0-360deg
CBO selection slit PB
Incident optical element Ge (220) x2
Incident parallel slit Slider_slit_open
Longitudinal limiting slit 5.0 mm
Light receiving parallel slit Slider_slit_5.0deg
Light receiving optical element PSA_open
Light receiving parallel slit Slider_slit_5.0deg
HV 660V
PHA 561.25mV

From the results in Table 1, it can be seen that the α-Ga ₂ O ₃ film of the example has no rotation domain, is excellent in film formation quality such as crystallinity, and has reduced warpage.

In addition, Hall effect measurements were performed on the α _- Ga ₂ O3 films of Examples and Comparative Examples 2. The results are shown in Table 2 below. From the results in Table 2, it can be seen that the crystalline oxide semiconductor film of the present invention is also excellent in electrical characteristics.

The crystalline oxide semiconductor film of the present invention can be used in all fields such as semiconductors (for example, compound semiconductor electronic devices, etc.), electronic parts / electrical equipment parts, optical / electrophotographic-related equipment, industrial parts, etc., but in particular, semiconductors. Useful for equipment.

1 Formation device 2a Carrier gas source 2b Carrier gas (diluted) source 3a Flow control valve 3b Flow control valve 4 Mist generation source 4a Raw material solution 4b Raw material fine particles 5 Container 5a Water 6 Ultrasonic oscillator 6a Electrode 6b Piezoelectric element 6c Electrode 6d Elastic body 6e Support 7 Formation chamber 8 Hot plate 9 Supply pipe 10 Substrate 16 Oscillator

Claims (10)

A crystalline oxide semiconductor film containing α-Ga ₂ O ₃ as a main component, further containing a dopant, having a rotation domain content of 0.02% by volume or less in the film, and a film thickness of 1 μm or more. A crystalline oxide semiconductor film characterized by being present. The crystalline oxide semiconductor film according to claim 1, wherein the content of the rotational domain in the film is 0.01% by volume or less. The crystalline oxide semiconductor film according to claim 1 or 2, wherein the warp is 0.3 μm or less. The crystalline oxide semiconductor film according to claim 1, wherein the atomic ratio of gallium in the metal element in the crystalline oxide semiconductor film is 0.7 or more. The crystalline oxide semiconductor film according to claim 1, wherein the atomic ratio of gallium in the metal element in the crystalline oxide semiconductor film is 0.8 or more. A laminated structure in which a substrate and a crystalline oxide semiconductor film are laminated on the substrate via a buffer layer, wherein the buffer layer is mainly made of a material different from the first layer and the first layer. The crystal according to any one of claims 1 to 5 , wherein the second layer as a component has a quantum well structure in which at least one layer is alternately laminated. A laminated structure characterized by being a sex oxide semiconductor film. The laminated structure according to claim 6 , wherein the main component of the first layer of the quantum well structure is an oxide having a corundum structure, and the main component of the second layer is an oxide containing aluminum. The laminated structure according to claim 7 , wherein the aluminum concentration in the metal element of the second layer is 1 atomic% or more. A semiconductor device comprising the crystalline oxide semiconductor film according to any one of claims 1 to 5 or the laminated structure according to any one of claims 6 to 8 . The semiconductor device according to claim 9 , which is a semiconductor laser, a diode, or a transistor.

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