JP6533982B2 - Quantum well structure, laminated structure and semiconductor device - Google Patents

Description

  The present invention relates to a novel quantum well structure, a stacked structure, and a semiconductor device using the quantum well structure or the stacked structure.

A semiconductor device using gallium oxide (Ga ₂ O ₃ ) with a large band gap has attracted attention as a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance, and is used for power semiconductor devices such as inverters. Application is expected. According to Non-Patent Document 1, it is possible to control the band gap of the gallium oxide by mixing indium or aluminum respectively or in combination to form a mixed crystal, and in particular, In _{X 1} Al _{Y 1} Ga _{Z 1} 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 a very 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 ≦ X 2 <1) is formed on an α-Al ₂ O ₃ substrate. Semiconductor devices are described. However, in the semiconductor device described in Patent Document 2, there is a problem also in the quality of the crystal, and there are many limitations when applied to the semiconductor device, and in the MBE method, the α-Ga ₂ O ₃ single crystal film ( In the case of X2 = 0), it is difficult to produce, and since ion implantation and heat treatment at high temperature are required to obtain a p-type semiconductor, it is difficult to realize p-type α-Ga ₂ O ₃ itself. In fact, the semiconductor element itself described in Patent Document 1 was difficult to realize.

  Patent Document 2 describes a corundum-structured oxide crystal containing aluminum and gallium, and describes that the phase transition at high temperature is suppressed. However, mixed crystals having a large band gap still have many problems. For example, even when used as a buffer layer, rotational domains are present in an epitaxially grown crystal, or warping occurs, and it is not always necessary. It was not satisfactory.

JP, 2013-58637, A JP, 2015-017027, A

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

  An object of the present invention is to provide a quantum well structure useful as a buffer layer capable of reducing rotational domain and warpage.

As a result of intensive studies to achieve the above object, the present inventors alternately laminate at least one first layer and at least one second layer containing a material different from the first layer as a main component. A quantum well structure, wherein the main component of the first layer is an oxide having a corundum structure, and the main component of the second layer is an oxide containing aluminum. Successful creation of the well structure, if such a quantum well structure is used as a buffer layer, not only rotational domains but also warpage are reduced in the crystal grown on the buffer layer, and the conventional problem is solved in one shot. I found that it was something that could be solved.
In addition, after obtaining the above-mentioned findings, the present inventors repeated studies to complete the present invention.

That is, the present invention relates to the following inventions.
[1] A quantum well structure in which a first layer and a second layer containing a material different from the first layer as a main component are alternately stacked in at least one layer,
The main component of the first layer is an oxide having a corundum structure,
A quantum well structure characterized in that the main component of the second layer is an oxide containing aluminum.
[2] The quantum well structure according to the above [1], wherein the oxide having a corundum structure is a semiconductor.
[3] The quantum well structure according to the above [1] or [2], wherein the oxide having a corundum structure at least contains one or more metals selected from gallium, indium and aluminum.
[4] The quantum well structure according to any one of the above [1] to [3], wherein the oxide containing aluminum is a semiconductor.
[5] The quantum well structure according to any one of the above [1] to [4], wherein the oxide containing aluminum further contains gallium, iron, indium, vanadium, titanium, chromium, rhodium, nickel or cobalt.
[6] The quantum well structure according to any one of the above [1] to [5], wherein the concentration of aluminum in the metal element of the second layer is 1 atomic% or more.
[7] The quantum well structure according to any one of the above [1] to [6], wherein at least two layers of the first layer and the second layer are stacked.
[8] A laminated structure in which a third layer containing a material having a corundum structure as a main component is laminated on the quantum well structure according to any one of the above [1] to [7] .
[9] The stacked structure according to the above [8], wherein the quantum well structure constitutes a buffer layer.
[10] The layered structure according to the above [8] or [9] , wherein the material having a corundum structure contains an oxide semiconductor containing one or more selected from aluminum, gallium and indium as a main component.
[11] A semiconductor device including the quantum well structure according to any one of [1] to [7] or the laminated structure according to any one of [8] to [10] .

  The quantum well structure of the present invention is useful as a buffer layer that can reduce rotational domain and warpage.

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. 8 shows XRD data of crystalline oxide semiconductor films in Examples. The XRD data in the comparative example 1 are shown. The XRD data in comparative example 2 are shown.

  The crystalline oxide semiconductor film of the present invention has a quantum well structure in which at least one first layer and a second layer containing a material different from the first layer as a main component are alternately stacked. The main component of the first layer is an oxide having a corundum structure, and the main component of the second layer is an oxide containing aluminum.

The first layer is not particularly limited as long as it has an oxide having a corundum structure as a main component, but the oxide is preferably a semiconductor, that is, an oxide semiconductor, and is a single species of aluminum, gallium and indium. It is more preferable to contain at least two or more, and it is most preferable to contain at least gallium. Examples of the oxide semiconductor include α-Ga ₂ O ₃ , α- (Al _x Ga _1-x ) ₂ O ₃ (where 1>X> 0), and α- (In _Y Ga _1-Y ) _2. Examples include 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. Here, "main component", for example, an oxide when the semiconductor is a α-Ga ₂ O _3, gallium atomic ratio α-Ga ₂ O ₃ at a ratio of more than 0.5 in the metal elements of the layer It is fine if it is included. In the present invention, the atomic ratio of gallium in the metal element in the layer is preferably 0.7 or more, more preferably 0.8 or more.

The second layer is not particularly limited as long as it is a material different from the first layer and contains an oxide containing aluminum as a main component, but the oxide is preferably a semiconductor, and gallium, iron, More preferably, it further comprises indium, vanadium, titanium, chromium, rhodium, nickel or cobalt, and most preferably it further comprises gallium. As such an oxide semiconductor, for example, α- (Al _x Ga _{1 -x} ) ₂ O ₃ (where 1>x> 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. Here, when the oxide semiconductor is, for example, α- (Al _x Ga _{1 -x} ) ₂ O ₃ , the “main component” means that the total atomic ratio of aluminum and gallium in the metal element of the layer is 0. What is necessary is that α- (Al _x Ga _{1 -x} ) ₂ O ₃ be contained in a ratio of 5 or more. In the present invention, the total atomic ratio of aluminum and gallium in the metal element in the layer is preferably 0.7 or more, more preferably 0.8 or more. The “material different from the first layer” may be, for example, the same component as the first layer or a composition ratio different from the first layer.

  Further, in the present invention, it is preferable that the concentration of aluminum in the metal element of the second layer is 1 atomic% or more because the rotational domain and the warpage can be further reduced, and the atomic ratio of 2 atomic% or more is more preferable. preferable. The upper limit of the aluminum concentration is not particularly limited, but is usually 99 at% or less, preferably 80 at% or less, more preferably 50 at% or less, and most preferably 30 at% or less .

The means for forming the quantum well structure is not particularly limited as long as the object of the present invention is not impaired, but a means for forming by crystal growth using a mist on a substrate is preferable.
Hereinafter, as means for forming the quantum well structure, means for forming the quantum well structure and the like will be described using mist on a substrate, but the present invention is not limited thereto.

  The mist or droplets generated by atomizing or dropletizing the raw material solution are carried to the substrate with a carrier gas, and then the mist or the droplets are reacted on the substrate to form a buffer layer. In addition, the quantum well structure in which the first layer and the second layer are alternately stacked 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. Can be formed.

(Raw material solution)
The raw material solution is not particularly limited as long as it contains a material capable of atomization or dropletization, and may be an inorganic material or an organic material, but in the present invention, it is a metal or a metal compound. Is preferably selected from one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium, silicon, yttrium, strontium and barium. It is more preferable to include. The raw material solution for the second layer contains at least aluminum.

  In the present invention, as the raw material solution, one in which the metal is dissolved or dispersed in the form of a complex or a salt in an organic solvent or water can be suitably used. Examples of the form of the complex include acetylacetonato complex, carbonyl complex, ammine complex, hydride complex and the like. Examples of the salt form include organic metal salts (eg, metal acetates, metal oxalates, metal citrates, etc.), metal sulfides, metal nitrates, metal phosphates, metal halides (eg metal chlorides) Salts, metal bromide salts, metal iodide salts and the like) and the like.

Further, additives such as hydrohalic acid and an oxidizing agent may be mixed in the raw material solution. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, hydroiodic acid and the like. Among these, 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 ), 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, and the like.

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, and p-type dopants. The concentration of the dopant may generally be about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant may be low, for example, about 1 × 10 ¹⁷ / cm ³ or less. 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 membrane. The material of the substrate is also not particularly limited as long as the object of the present invention is not impaired, and the substrate may be a known substrate, may be an organic compound, or may be an inorganic compound. The shape of the substrate may be any shape, and is effective for any shape, for example, plate-like such as flat plate or disc, fiber-like, rod-like, cylindrical, prismatic, Although cylindrical shape, helical shape, spherical shape, ring shape etc. are mentioned, a substrate is preferable in the present invention. 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-like 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. It is also preferred 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 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 An underlying substrate may, for example, be mentioned. Here, “main component” means that the substrate material having the above-mentioned specific crystal structure is, in atomic ratio, preferably 50% or more, more preferably 70% or more, still more preferably 90% to all components of the substrate material. It means that% or more is included, and it may mean that 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 known. Examples of the substrate material having the corundum structure described above include the same as those exemplified as the material having the corundum structure described above, and in the present invention, α-Al ₂ O ₃ or α-Ga ₂ O is used. ₃ is preferred. And as a base substrate which has substrate material which has corundum structure as a main component, a sapphire substrate (preferably c surface sapphire substrate), alpha type gallium oxide substrate, etc. are mentioned as a suitable example. As a base substrate having a substrate material having a β-gallia structure as a main component, for example, a β-Ga ₂ O ₃ substrate, or containing Ga ₂ O ₃ and Al ₂ O ₃ , Al ₂ O ₃ is more than 0 wt% and A mixed crystal substrate having 60 wt% or less and the like can be mentioned. Moreover, as a base substrate which has a substrate material which has a hexagonal crystal structure as a main component, a SiC substrate, a ZnO substrate, a GaN substrate etc. are mentioned, for example. Note that each layer may be stacked directly or through another layer (for example, a buffer layer) on the base substrate containing a substrate material having a hexagonal crystal structure as a main component.

  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 laminating method is not particularly limited, but preferably, the raw material solution is atomized or dropletized (atomizing / dropletizing step), and the generated mist or droplet is supplied to the substrate by the carrier gas Film formation (film formation process) by reacting the supplied mist or liquid droplets on the substrate (film formation process).

  In the atomization / droplet formation step, the raw material solution is adjusted, and the raw material solution is atomized or formed into droplets to generate mist. Although the compounding ratio of the said metal is not specifically limited, 0.0001 mol / L-20 mol / L are preferable with respect to the whole raw material solution. The means for atomizing or dropletizing is not particularly limited as long as it can atomize or dropletize the raw material solution, and may be a known atomizing means or dropletizing means, but in the present invention Preferably, it is an atomizing means or a dropletizing means using sound waves. It is preferable that the mist or the droplets have an initial velocity of zero and be suspended in the air, for example, a mist that floats in space and can be transported as a gas rather than being sprayed like a spray is more preferable. preferable. The droplet size is not particularly limited, and may be about several mm, but preferably 50 μm or less, more preferably 1 to 10 μm.

  In the mist / droplet supply step, the carrier gas supplies the mist or the droplets to the substrate. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired. For example, oxygen, ozone, inert gas such as nitrogen or argon, or reducing gas such as hydrogen gas or forming gas is preferable. Can be mentioned as In addition, although one kind of carrier gas may be used, it may be two or more kinds, and a dilution gas (for example, 10-fold dilution gas etc.) in which the carrier gas concentration is changed may be used as the second carrier gas. You may use further. Further, the carrier gas may be supplied not only to one place, but also to two or more places. Although the flow rate of the carrier gas is not particularly limited, the linear velocity in the reactor (more specifically, the reactor is at a high temperature and changes depending on the environment, so assuming room temperature 0.1 m / s-100 m / s are preferable in converted linear velocity), and 1 m / s-10 m / s are more preferable.

  In the film forming step, the mist or the droplets are reacted to form a film on part or all of the surface of the substrate. The reaction is not particularly limited as long as 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 any reaction as long as the mist or the droplets react with heat, and the reaction conditions are not particularly limited as long as the object of the present invention is not impaired. In the present step, the thermal reaction is usually carried out at a temperature higher than the evaporation temperature of the solvent, but preferably not higher than the temperature. The thermal reaction may be performed under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere, as long as the object of the present invention is not impaired. Although it may be carried out under any conditions of reduced pressure and reduced pressure, in the present invention, it is preferred to be carried out under atmospheric pressure in that the calculation of the evaporation temperature is simplified. 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 thickness of each of the first layer and the second layer in the quantum well is preferably 200 nm or less, more preferably 100 nm or less, and most preferably 20 nm or less.

  In the present invention, after the formation of the quantum well structure, the obtained quantum well structure can be used as a buffer layer. In the present invention, a crystalline oxide semiconductor mainly comprising an oxide semiconductor having a corundum structure and containing at least one or two or more of aluminum, gallium and indium on the buffer layer. It is preferred to form a membrane.

  Further, in the present invention, the formation of the crystalline oxide semiconductor film may be performed by a known method, and may be similar to the formation of the quantum well structure described above, but in the present invention, by mist CVD, It is preferable to form a crystalline oxide semiconductor film. More specifically, for example, a mist or droplets generated by atomizing or dropletizing a raw material solution is carried by a carrier gas to a substrate, and then the mist or the droplets are reacted on the substrate to crystallize. Forming a crystalline oxide semiconductor film. The raw material solution and the substrate may be the same as the raw material solution and the substrate in the above-mentioned buffer layer formation. The lamination method may be the same as the lamination method in the formation of the buffer layer.

  As described above, in the crystalline oxide semiconductor film obtained through the buffer layer having a quantum well structure, the content of rotational domains in the film is reduced to, for example, 0.02% by volume or less. Furthermore, the warpage is also reduced to, for example, 0.3 μm or less. The “rotational domain content” is measured using an X-ray diffraction apparatus, and more specifically, can be determined from the count number of rotational domains obtained using an X-ray diffraction apparatus . The warpage 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 apex of the concave or convex. In the present invention, for example, when the shortest distance between the shortest straight line passing the end points of 5 mm between the films and the apex of the concave or convex is warpage, the warpage is 0.06 μm / mm or less. Is preferred. Although the content of the rotational domain is usually about 0.02% by volume or less, in the present invention, the content is preferably 0.01% by volume or less, and substantially does not contain the rotational domain. More preferable. For example, it is more preferable that the peak intensity of the rotation domain in the crystalline oxide semiconductor film determined by X-ray diffraction measurement is 10% or less of the intensity of the main peak.

  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 3 μm. It is more preferable that it is more than. The crystal of the crystalline oxide semiconductor film is usually single crystal, but may be polycrystalline.

  The crystalline oxide semiconductor film can be used in 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 off the substrate or the like.

  As a semiconductor device formed using the crystalline oxide semiconductor film or the crystalline laminated structure, for example, a semiconductor laser, a diode, a transistor or the like can be mentioned, and more specifically, for example, MIS, HEMT, etc. A transistor, a TFT, a Schottky barrier diode using a semiconductor-metal junction, a PN or PIN diode combined with another P layer, a light emitting / receiving element, etc. may be mentioned.

1. Film Forming Apparatus First, the film forming apparatus 1 used in the present embodiment will be described using 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 delivered from the carrier gas source 2a, and a carrier gas for supplying a carrier gas (dilution). (Dilution) source 2b, flow control valve 3b for adjusting the flow rate of carrier gas (dilution) delivered from carrier gas (dilution) source 2b, mist generation source 4 in which raw material solution 4a is stored, and water 5a A container 5 to be placed, an ultrasonic transducer 6 attached to the bottom of the container 5, a film forming chamber 7, a quartz supply pipe 9 connecting the mist source 4 to the film forming chamber 7, a film forming chamber And a hot plate 8 installed in the inside of the apparatus. A substrate 10 is placed on the hot plate 8.
FIG. 2 shows the atomization / dropletization unit. The mist generation source 4 which consists of a container in which the raw material solution 4a is accommodated is accommodated in the container 5 in which the water 5a is accommodated using a support body (not shown). At the bottom of the container 5, an ultrasonic transducer 6 is provided, and the ultrasonic transducer 6 and the oscillator 16 are connected. Then, when the oscillator 16 is operated, the ultrasonic transducer 6 vibrates, and the ultrasonic wave propagates into the mist generation source 4 through the water 5a, so that the raw material solution 4a is atomized or drips. ing.
FIG. 3 shows the ultrasonic transducer 6 shown in FIG. The ultrasonic transducer 6 is provided with 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. There is. Then, when an oscillator is connected to the electrode to change the oscillation frequency, an ultrasonic wave having a resonance frequency in the thickness direction of the piezoelectric vibrator and a resonance frequency in the radial direction is generated.

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

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

3. Preparation for film formation The raw material solution 4 a obtained in the above was contained 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 let it warm. 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 in the film forming chamber 7 is sufficiently replaced with the carrier gas. Thereafter, 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. In addition, oxygen was used as carrier gas.

4. Formation of Quantum Well Structure The ultrasonic transducer 6 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 4a through the water 5a to make the raw material solution 4a into fine particles, thereby generating raw material fine particles 4b. The raw material fine particles 4 b 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. . In addition, as said raw material solution 4a, said 2. above. By alternately using the first raw material solution and the second raw material solution obtained in the above, a quantum well structure in which 50 layers of the first layer and the second layer are alternately laminated is formed. did. 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, when identified 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 Layer was composed of α-Ga ₂ O ₃ .

5. Formation of crystalline oxide semiconductor film The quantum well structure obtained by was used as a buffer layer. Further, the third raw material solution is used 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 the water 5a to make the raw material solution 4a into fine particles. The raw material fine particles 4b were produced. The raw material fine particles 4b are introduced into the film forming chamber 7 by the carrier gas, and at atmospheric pressure, at 500 ° C., the mist reacts in the film forming chamber 7 to form a buffer layer (quantum well structure). A thin film was formed. 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%. A TEM image of the obtained crystalline oxide semiconductor film is shown in FIG. 4, and a TEM image of a buffer layer (quantum well structure) is shown in FIG. In addition, XRD data of the crystalline oxide semiconductor film is shown in FIG.

(Comparative example 1)
The above-mentioned 5., except that the film formation temperature is set to 600 ° C. and the film formation time is set to 60 minutes, using the following material solutions for comparative examples as the material solution. A buffer layer was formed by depositing in the same manner as in the above. After the formation of the buffer layer, the above 5. In the same manner as by depositing on the buffer layer to form a α-Ga ₂ O ₃ film. The identification of the phase used the X-ray-diffraction apparatus. The XRD data is shown in FIG.

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

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

6. Evaluation Above 5. The resulting crystalline oxide semiconductor film and α-Ga ₂ O ₃ film obtained in Comparative Examples were evaluated respective properties. The results are shown in Table 1 below. In addition, curvature measured the shortest distance of the shortest straight line which passes through the point of the both ends between 5 mm, and the concave or convex vertex. Further, in Table 1, for “presence or absence of the 1010 heterophase peak”, reciprocal lattice mapping of the 1010 plane was measured, and the presence or absence of peaks other than the substrate and the film was confirmed. In addition, the content of the rotation domain and the like were measured using an X-ray diffractometer (Smartlab, manufactured by Rigaku Corporation). The conditions for measurement are as follows.

(X-ray measurement conditions)
Conducted 104 plane 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
ス キ ャ ン scan 0 to 360 deg
CBO selection slit PB
Incident optical element Ge (220) x 2
Incident parallel slit Soller_slit_open
Longitudinal restriction slit 5.0 mm
Light receiving parallel slit Soller_slit_5.0deg
Light receiving optical element PSA_open
Light receiving parallel slit Soller_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 films of Examples have no rotational 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 the example and the 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 films obtained in the examples also have excellent electrical characteristics.

  The quantum well structure of the present invention is useful as a buffer layer, and furthermore, it can be used in all fields such as semiconductors (eg compound semiconductor electronic devices etc.), electronic parts / electrical equipment parts, optical / electrophotographic related devices, industrial members In particular, it is useful for semiconductor devices.

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 particle 5 container 5a water 6 ultrasonic transducer 6a electrode 6b piezoelectric element 6c electrode 6d elastic body 6e support 7 film forming chamber 8 hot plate 9 supply pipe 10 substrate 16 oscillator

Claims (10)

A quantum well structure in which a first layer and a second layer containing a material different from the first layer as a main component are alternately stacked in at least one layer.
The main component of the first layer is an oxide having a corundum structure, the main component the main component of the second layer, on the oxide der Ru said quantum well structure including aluminum, a material having a corundum structure A laminated structure comprising a third layer comprising: The laminated structure according to claim 1, wherein the oxide having a corundum structure is a semiconductor. The laminated structure according to claim 1 or 2, wherein the oxide having a corundum structure contains at least one or more metals selected from gallium, indium and aluminum. The laminated structure according to any one of claims 1 to 3, wherein the oxide containing aluminum is a semiconductor. The laminated structure according to any one of claims 1 to 4, wherein the oxide containing aluminum further contains gallium, iron, indium, vanadium, titanium, chromium, rhodium, nickel or cobalt. The laminated structure according to any one of claims 1 to 5, wherein the concentration of aluminum in the metal element of the second layer is 1 atomic% or more. The laminated structure according to any one of claims 1 to 6, wherein at least two layers of the first layer and the second layer are laminated. The laminated structure according to any one of claims 1 to 7, wherein the quantum well structure constitutes a buffer layer. The laminated structure according to any one of claims 1 to 8, wherein the material having a corundum structure mainly includes an oxide semiconductor containing one or more selected from aluminum, gallium and indium. A semiconductor device comprising the stacked structure according to any one of claims 1 to 9 .