JP2016157878A - Crystal oxide semiconductor film, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal oxide semiconductor film of which the rotation domains and warp are reduced.SOLUTION: A crystal oxide semiconductor film is formed by mist on a base through a buffer layer having a quantum well structure arranged by alternately laminating at least one first layer and at least one second layer including, as a primary component, a material different from that of the first layer. The crystal oxide semiconductor film has a corundum structure, and comprises, as a primary component, an oxide semiconductor including at least one or more kinds of a group consisting of aluminum, gallium and indium. In the film, rotation domains account for 0.02 vol.% or less.SELECTED DRAWING: None

Description

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

A semiconductor device using gallium oxide (Ga ₂ O ₃ ) having a large band gap has been attracting attention as a next-generation switching element that can achieve high breakdown voltage, low loss, and high heat resistance. Application is expected. According to Non-Patent Document 1, the gallium oxide can control the band gap by using a mixed crystal of indium and aluminum, respectively, or a combination thereof. Among them, In _X1 Al _Y1 Ga _Z1 O ₃ An 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.

Patent Document 1 discloses a Ga ₂ O ₃ system in which a p-type α- (Al _{X 2} Ga ₁ -X 2) ₂ O ₃ single crystal film (0 ≦ X2 <1) is formed on an α-Al ₂ O ₃ substrate. A semiconductor device is described. However, the semiconductor element described in Patent Document 2 has a problem in the quality of crystals, and there are many restrictions on application to a semiconductor element. In the MBE method, an α-Ga ₂ O ₃ single crystal film ( In the case of X2 = 0, it is difficult to manufacture, and in addition, p-type α-Ga ₂ O ₃ itself is difficult to realize because ion implantation and high-temperature heat treatment are necessary to obtain a p-type semiconductor. Actually, the semiconductor element itself described in Patent Document 1 is difficult to realize.

  Patent Document 2 describes a corundum structure oxide crystal containing aluminum and gallium, and describes that phase transition at high temperatures is suppressed. However, a mixed crystal having a large band gap still has many problems.For example, even when it is used as a buffer layer, there is a rotation domain in the crystal grown epitaxially or warpage occurs. It was not satisfactory.

JP2013-58637A Japanese Patent Application Laid-Open No. 2015-017027

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

  An object of the present invention is to provide a crystalline oxide semiconductor film with reduced rotational domains and warpage.

As a result of intensive studies to achieve the above object, the inventors of the present invention have, as a main component, an oxide semiconductor having a corundum structure and containing at least one or more of aluminum, gallium, and indium. A crystalline oxide semiconductor film having a rotational domain content of 0.02% by volume or less was successfully created. According to such a crystalline oxide semiconductor film, It has been found that not only the rotation domain but also the warpage is reduced, and the conventional problems can be solved all at once.
In addition, after obtaining the above knowledge, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following inventions.
[1] A crystalline oxide semiconductor film having a corundum structure and containing as a main component an oxide semiconductor containing at least one or more of aluminum, gallium and indium,
A crystalline oxide semiconductor film characterized in that the content of rotational domains in the film is 0.02% by volume or less.
[2] The crystalline oxide semiconductor film according to the above [1], which does not substantially contain a rotation domain in the film.
[3] The crystalline oxide semiconductor film according to [1] or [2], wherein the warp is 0.3 μm or less.
[4] The crystalline oxide semiconductor film according to any one of [1] to [3], wherein the crystal is grown on a substrate using mist.
[5] The crystalline oxide semiconductor film according to any one of [1] to [4], wherein the crystal is grown on a substrate via a buffer layer.
[6] The buffer layer has a quantum well structure in which a first layer and a second layer mainly composed of a material different from the first layer are alternately stacked at least one layer. [5] The crystalline oxide semiconductor film according to [5].
[7] The crystalline oxidation according to [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. Semiconductor film.
[8] The crystalline oxide according to [6] or [7], wherein the main component of the first layer is a gallium-containing oxide semiconductor, and the main component of the second layer is an aluminum-containing oxide semiconductor. Semiconductor film.
[9] The crystalline oxide semiconductor film according to [7] or [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 [9].
[11] The semiconductor device according to [10], which is a semiconductor laser, a diode, or a transistor.

  The crystalline oxide semiconductor film of the present invention has reduced rotation domains and warpage, and is useful for a semiconductor device.

It is a schematic block diagram of the film-forming apparatus (mist CVD) used in the Example. It is a figure explaining the atomization / droplet formation part used in the Example. It is a figure explaining the ultrasonic transducer | vibrator in FIG. The TEM image in an Example is shown. The TEM image of the buffer layer in an Example is shown. 3 shows XRD data of a crystalline oxide semiconductor film in Examples. The XRD data in the comparative example 1 are shown. The XRD data in the comparative example 2 are shown.

  The crystalline oxide semiconductor film of the present invention is a crystalline oxide semiconductor film having a corundum structure and containing an oxide semiconductor containing at least one or more of aluminum, gallium, and indium as a main component. And the content rate of the rotation domain in a film | membrane is 0.02 volume% or less, It is characterized by the above-mentioned.

  The “rotational domain content” is measured using an X-ray diffractometer, and more specifically, can be determined from the rotational domain count obtained using the X-ray diffractometer. The content of the rotational 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 does not substantially contain the rotational domain. More preferred. For example, the rotational domain count in the crystalline oxide semiconductor film obtained by X-ray diffraction measurement is more preferably 0 count with respect to 100,000 count.

The "main component", for example, when an oxide semiconductor is α-Ga ₂ O _3, the atomic ratio of gallium in a metal element of said membrane contains α-Ga ₂ O ₃ at a ratio of more than 0.5 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, and 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. In the present invention, it is preferably 1 μm or more, and 3 μm. More preferably. Note that the oxide semiconductor is usually single crystal, but may be polycrystalline.

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 (where 1>X> 0), α- (In _Y Ga _1-Y ) _2. O ₃ (where 1>Y> 0), α- (Al _Z1 Ga _Z2 In _Z3 ) ₂ O ₃ (where 1> Z1, Z2, Z3> 0 and Z1 + Z2 + Z3 = 1) and the like. In the present invention, the oxide semiconductor preferably contains at least gallium.

  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 vertex. In the present invention, for example, when the shortest distance between the shortest straight line passing through the points on both ends of 5 mm of the film and the concave or convex vertex is warped, the warp is 0.06 μm / mm or less. Is preferred.

  The means for forming the crystalline oxide semiconductor film is not particularly limited as long as it does not hinder the object of the present invention, but a means for manufacturing by crystal growth using a mist on a substrate is preferable. More preferably, the crystal growth means is used. The buffer layer is not particularly limited as long as the object of the present invention is not impaired. However, the buffer layer is preferably an oxide semiconductor having a corundum structure, and the first layer and the first layer are mainly composed of different materials. It is more preferable that the second layer has a quantum well structure in which at least one layer is alternately stacked. For 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. More preferably, the main component 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 described above. In the present invention, when the second layer contains at least aluminum, the aluminum concentration in the metal element of the second layer is preferably 1 atomic% or more, and preferably 2 atomic% or more. Is more preferable. The upper limit of the aluminum concentration is not particularly limited, but is usually 99 atomic percent or less, preferably 80 atomic percent or less, more preferably 50 atomic percent or less, and most preferably 30 atomic percent or less. .

  Hereinafter, as a preferable method for producing the crystalline oxide semiconductor film, means for growing a crystal through the buffer layer having the quantum well structure using mist on a substrate will be described. It is not limited to.

  As a suitable means for crystal growth using mist, the mist or droplet generated by atomizing or dropletizing the raw material solution is transported to the substrate with a carrier gas, and then the mist or the liquid on the substrate. The drops are reacted to form a buffer layer. By using the raw material solution alternately as the first layer raw material solution and the second layer raw material solution, the first layer and the second layer are alternately stacked as the buffer layer. A quantum well structure can be formed. After the buffer layer is formed, the crystalline oxide semiconductor film is formed over the buffer layer in the same manner as described above.

(Raw material solution)
The raw material solution includes a material that can be atomized or formed into droplets, and is not particularly limited as long as it contains at least one or more of aluminum, gallium, and indium. In the present invention, it is preferably a metal or a metal compound. Gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium More preferably, it contains one or more metals selected from silicon, yttrium, strontium and barium.

  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 suitably used. Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, hydride complexes, and the like. Examples of the salt form include organic metal salts (for example, metal acetates, metal oxalates, metal citrates, etc.), sulfide metal salts, nitrate metal salts, phosphorylated metal salts, metal halide salts (for example, metal chlorides). Salt, metal bromide salt, metal iodide salt, etc.).

Moreover, you may mix additives, such as a hydrohalic acid and an oxidizing agent, with the said raw material solution. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, hydroiodic acid, etc. Among them, hydrobromic acid or hydroiodic acid is preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), and benzoyl peroxide (C ₆ H ₅ CO) ₂ O _2. Peroxides, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, organic peroxides such as peracetic acid and nitrobenzene.

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

(Substrate)
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 the object of the present invention is not impaired, 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 all shapes, for example, a plate shape such as a flat plate or a disk, a fiber shape, a rod shape, a columnar shape, a prismatic shape, A cylindrical shape, a spiral shape, a spherical shape, a ring shape and the like can be mentioned. 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 is plate-shaped and serves as a support for the crystal film. The substrate 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. A substrate is also preferred. Examples of the substrate include a base substrate containing a substrate material having a corundum structure as a main component, a base substrate containing a substrate material having a β-gallia structure as a main component, and a substrate material having a hexagonal crystal structure as a main component. Examples thereof include a base substrate. Here, the “main component” means that the substrate material having the specific crystal structure is preferably 50% or more, more preferably 70% or more, and still more preferably 90% by atomic ratio with respect to all components of the substrate material. % Or more, and it may be 100%.

The substrate material is not particularly limited as long as the object of the present invention is not impaired, and may be a known material. Examples of the substrate material having the corundum structure include the same materials as those exemplified as the material having the corundum structure. In the present invention, α-Al ₂ O ₃ or α-Ga ₂ O is used. ₃ is preferred. As a base substrate mainly composed of a substrate material having a corundum structure, a sapphire substrate (preferably a c-plane sapphire substrate), an α-type gallium oxide substrate, or the like is given as a suitable example. As a base substrate mainly composed of a substrate material having a β-gallia structure, for example, a β-Ga ₂ O ₃ substrate, or a Ga ₂ O ₃ and Al ₂ O ₃ containing Al ₂ O ₃ content of more than 0 wt% Examples thereof include a mixed crystal substrate of 60 wt% or less. In addition, examples of the base substrate whose main component is a substrate material having a hexagonal crystal structure include a SiC substrate, a ZnO substrate, and a GaN substrate. Note that each layer may be stacked directly or via another layer (for example, a buffer layer) on a base substrate whose main component is a substrate material having a hexagonal crystal structure.

  In the present invention, the base is preferably a base substrate mainly composed of a substrate material having a corundum structure, more preferably a sapphire substrate or an α-type gallium oxide substrate, and a c-plane sapphire substrate. Is most preferred.

(Lamination method)
The buffer layer is preferably stacked by a mist CVD method. In the mist CVD, the raw material solution is atomized or dropletized (atomization / droplet forming step), and the generated mist or droplet is supplied to the substrate by a carrier gas (mist / droplet supplying step). The supplied mist or droplets are reacted to form a film on the substrate (film formation process).

  In the atomization / droplet forming step, a raw material solution is prepared, and the raw material solution is atomized or formed into droplets to generate mist. The blending 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 atomization or droplet formation means is not particularly limited as long as the raw material solution can be atomized or dropletized, and may be a known atomization means or droplet formation means. An atomizing means or a droplet forming means using sound waves is preferable. The mist or the droplet preferably has a zero initial velocity and floats in the air.For example, the mist or the droplet is more preferably a mist that floats in a space and can be transported as a gas instead of spraying 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 supplying step, the mist or the droplet is supplied to the substrate by the carrier gas. The type of the carrier gas is not particularly limited as long as the object of the present invention is not impaired. For example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is preferable. As mentioned. Further, the type of carrier gas may be one type, but may be two or more types, and a diluent gas (for example, a 10-fold diluted gas) whose carrier gas concentration is changed is used as the second carrier gas. Further, it may be used. Further, the supply location of the carrier gas is not limited to one location but may be two or more locations. The flow rate of the carrier gas is not particularly limited, but the linear velocity in the reactor (more specifically, the reactor is at a high temperature and changes depending on the environment. 0.1 m / s to 100 m / s is preferable, and 1 m / s to 10 m / s is more preferable.

  In the film forming step, the mist or the droplet is reacted to form a film on a part or all of the substrate surface. The reaction is not particularly limited as long as it is a reaction in which a film is formed from the mist or the droplet, but in the present invention, a thermal reaction is preferable. The thermal reaction may be performed as long as the mist or the droplet reacts with heat, and the reaction conditions are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually performed at a temperature not lower than the evaporation temperature of the solvent, but is preferably not higher than the temperature. Further, the thermal reaction may be performed in any atmosphere of a vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, and an oxygen atmosphere as long as the object of the present invention is not impaired. Although the reaction may be performed under reduced pressure or reduced pressure, in the present invention, the reaction is preferably performed under atmospheric pressure from the viewpoint of simplifying the calculation of the evaporation temperature. In the case of a vacuum, the evaporation temperature can be lowered. 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 more preferably 20 nm or less. Is most preferred.

  After the buffer layer is formed, a crystalline oxide semiconductor film including, as a main component, an oxide semiconductor having a corundum structure and containing at least one or more of aluminum, gallium, and indium on the buffer layer Form.

  In the present invention, the crystalline oxide semiconductor film may be formed by a known means, which may be the same as the formation of the buffer layer, but in the present invention, the crystalline oxide semiconductor film is formed by mist CVD. An oxide semiconductor film is preferably formed. More specifically, for example, a mist or droplet generated by atomizing or dropletizing a raw material solution is transported to a substrate with a carrier gas, and then the mist or the droplet is reacted on the substrate to form a crystal. A conductive oxide semiconductor film is formed. 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. Also, the lamination method may be the same as the lamination method in the buffer layer formation.

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

  The crystalline oxide semiconductor film can be used for a semiconductor device or the like as a stacked structure together with the base and the buffer layer. In the present invention, the crystalline oxide semiconductor film may be used for 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 using the crystalline oxide semiconductor film or the crystalline stacked structure include a semiconductor laser, a diode, and a transistor, and more specifically, for example, MIS and HEMT. Examples include transistors, TFTs, Schottky barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light emitting / receiving elements.

1. Film Forming Apparatus First, the film forming apparatus 1 used in this example 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 rate adjusting valve 3a for adjusting the flow rate of the carrier gas sent out from the carrier gas source 2a, and a carrier gas for supplying a carrier gas (dilution). A dilution source 2b, a flow rate adjusting valve 3b for adjusting the flow rate of the carrier gas (dilution) sent from the carrier gas (dilution) source 2b, a mist generating source 4 in which the raw material solution 4a is accommodated, and water 5a. A container 5 to be placed, an ultrasonic vibrator 6 attached to the bottom surface of the container 5, a film forming chamber 7, a quartz supply pipe 9 connecting the mist generating source 4 to the film forming chamber 7, and a film forming chamber 7 and a hot plate 8 installed inside. A substrate 10 is installed on the hot plate 8.
FIG. 2 shows an atomizing / droplet forming unit. A mist generating source 4 composed of a container in which the raw material solution 4a is accommodated is accommodated in a container 5 in which water 5a is accommodated using a support (not shown). An ultrasonic transducer 6 is provided at the bottom of the container 5, and the ultrasonic transducer 6 and the oscillator 16 are connected to each other. Then, when the oscillator 16 is operated, the ultrasonic vibrator 6 vibrates, the ultrasonic wave propagates into the mist generation source 4 through the water 5a, and the raw material solution 4a is atomized or droplets configured. ing.
FIG. 3 shows the ultrasonic transducer 6 shown in FIG. The ultrasonic transducer 6 includes a disk-like piezoelectric element 6b in a cylindrical elastic body 6d on a support 6e, and electrodes 6a and 6c are provided on both sides of the piezoelectric element 6b. Yes. When the oscillator is connected to the electrode and the oscillation frequency is changed, an ultrasonic wave having a resonance frequency in the thickness direction and a resonance frequency in the radial direction of the piezoelectric vibrator is generated.

2. Preparation of raw material solution (first layer raw material solution)
The aqueous solution was adjusted to a ratio of 3 mol / L of gallium acetylacetonate to 9 mol / L of aluminum acetylacetonate. At this time, hydrochloric acid was further contained at a volume ratio of 2%. A raw material solution was prepared.
(Secondary layer raw material solution)
A 0.1 mol / L aqueous solution of gallium bromide to which germanium oxide was added was prepared so that the atomic ratio of germanium to gallium was 1: 0.01. At this time, a 48% hydrobromic acid solution was further added at a volume ratio. It was made to contain so that it might become 10%, and let this be the 2nd raw material solution.

(Raw material solution for crystalline oxide semiconductor film)
A 0.1 mol / L aqueous solution of gallium bromide to which germanium oxide was added was prepared so that the atomic ratio of germanium to gallium was 1: 0.01. At this time, a 48% hydrobromic acid solution was further added at a volume ratio. It was contained so that it might become 10%, and this was made into the 3rd raw material solution.

3. Preparation of film formation The raw material solution 4a obtained in the above was accommodated in the mist generating 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. Allowed to warm. Next, the flow rate adjusting 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 in 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 (dilution) was adjusted to 0.5 L / min. Note that oxygen was used as a carrier gas.

4). Formation of Buffer Layer The ultrasonic vibrator 6 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 4a through the water 5a, whereby the raw material solution 4a was made fine 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 600 ° C. under atmospheric pressure to form a thin film on the substrate 10. . As the raw material solution 4a, 2. By using alternately the first raw material solution and the second raw material solution obtained in step 1, the first layer and the second layer have a quantum well structure in which 50 layers are stacked alternately. A buffer layer was formed. The film formation time using the first raw material solution was 3 minutes / layer, and the film formation time using the second raw material solution was 30 seconds / layer. Moreover, were identified using X-ray diffraction apparatus, the first layer, the aluminum concentration is 2 atomic% α- _{(Al 0.02 Ga 0.98)} is constituted by ₂ O _3, a second The layer was composed of α-Ga ₂ O ₃ .

5. Formation of Crystalline Oxide Semiconductor Film Using the third raw material solution as the raw material solution 4a, the ultrasonic vibrator 6 is vibrated at 2.4 MHz, and the vibration is propagated to the raw material solution 4a through the water 5a. The raw material solution 4a was atomized 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 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. The resulting thin film, X-rays diffractometer (manufactured by Rigaku Corporation, SmartLab) was measured using a a _α-Ga 2 _{O 3,} the content of rotational domain was 0%. Note that a TEM image of the obtained crystalline oxide semiconductor film is shown in FIG. 4, and a TEM image of the buffer layer is shown in FIG. XRD data is shown in FIG.

(Comparative Example 1)
The above 5. except that the following raw material solution for comparative example was used as the raw material solution, the film forming temperature was 600 ° C., and the film forming time was 60 minutes. A buffer layer was formed by forming a film in the same manner as described above. After the formation of the buffer layer, the above 5. In the same manner as described above, an α-Ga ₂ O ₃ film was formed by forming a film on the buffer layer. An X-ray diffractometer was used for phase identification. XRD data is shown in FIG.

(Raw material solution for Comparative Example 1)
An aqueous solution was prepared so as to have a ratio of 2 mol / L of gallium acetylacetonate with respect to 14 mol / L of aluminum acetylacetonate. At this time, hydrochloric acid was further added to a volume ratio of 2%. A raw material solution was obtained.

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

6). Evaluation 5. The physical properties of the crystalline oxide semiconductor film obtained in 1 and the α-Ga ₂ O ₃ film obtained in the comparative example were evaluated. The results are shown in Table 1 below. In addition, curvature measured the shortest distance of the shortest straight line which passed the point of both ends between 5 mm, and a concave or convex vertex. In Table 1, “1010 different phase peak presence / absence” was measured by reciprocal lattice mapping on 10 10 planes to confirm the presence / absence of peaks other than the substrate and film. Moreover, the content rate etc. of the rotation domain were measured using the X-ray-diffraction apparatus (the Rigaku company make, Smartlab). The measurement conditions are as follows.

(X-ray measurement conditions)
104 surface 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 Soller_slit_open
Longitudinal restriction slit 5.0mm
Light receiving parallel slit Soller_slit_5.0 deg
Receiving optical element PSA_open
Light receiving parallel slit Soller_slit_5.0 deg
HV 660V
PHA 561.25mV

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

In addition, Hall effect measurement was performed on the α-Ga ₂ O ₃ films of Examples and Comparative Example 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 has excellent electrical characteristics.

  The crystalline oxide semiconductor film of the present invention can be used in various fields such as semiconductors (for example, compound semiconductor electronic devices), electronic parts / electric equipment parts, optical / electrophotographic related apparatuses, industrial members, etc. Useful for equipment.

DESCRIPTION OF SYMBOLS 1 Film-forming apparatus 2a Carrier gas source 2b Carrier gas (dilution) source 3a Flow control valve 3b Flow control valve 4 Mist generation source 4a Raw material solution 4b Raw material fine particle 5 Container 5a Water 6 Ultrasonic vibrator 6a Electrode 6b Piezoelectric element 6c Electrode 6d Elastic body 6e Support body 7 Deposition chamber 8 Hot plate 9 Supply pipe 10 Substrate 16 Oscillator

Claims (11)

A crystalline oxide semiconductor film having a corundum structure and an oxide semiconductor containing at least one or more of aluminum, gallium and indium as a main component,
A crystalline oxide semiconductor film characterized in that the content of rotational domains in the film is 0.02% by volume or less.   2. The crystalline oxide semiconductor film according to claim 1, which contains substantially no rotation domain in the film.   The crystalline oxide semiconductor film according to claim 1, wherein the warp is 0.3 μm or less.   The crystalline oxide semiconductor film according to claim 1, wherein the crystalline oxide semiconductor film is grown on a substrate using mist.   The crystalline oxide semiconductor film according to claim 1, wherein the crystalline oxide semiconductor film is grown on a substrate via a buffer layer.   The buffer layer has a quantum well structure in which the first layer and the second layer mainly composed of a material different from the first layer are alternately stacked at least one layer. Crystalline oxide semiconductor film.   The crystalline oxide semiconductor film according to claim 6, wherein a main component of the first layer of the quantum well structure is an oxide having a corundum structure, and a main component of the second layer is an oxide containing aluminum.   The crystalline oxide semiconductor film according to claim 6 or 7, wherein a main component of the first layer is a gallium-containing oxide semiconductor, and a main component of the second layer is an aluminum-containing oxide semiconductor.   The crystalline oxide semiconductor film according to claim 7 or 8, 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 claim 1. The semiconductor device according to claim 10, which is a semiconductor laser, a diode, or a transistor.