JP2016183107A - Crystal laminate structure, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal laminate structure having a β-GaOsingle crystal film grown by a growth method of β-GaOand capable of growing a β- GaOsingle crystal film with a high quality and a large diameter efficiently, and a production method therefor.SOLUTION: According to one embodiment, provided are a crystal laminate structure manufactured by a growing method of a β-GaOsingle crystal film by the HVPE method comprising the step of exposing a GaOsubstrate 10 to a gallium chloride gas and an oxygen containing gas to grow a β-GaOsingle crystal film 12 on the principal face 11 of the β-GaOsingle crystal film at a growing temperature of 900°C or higher on the GaOsubstrate 10, and a manufacturing method therefor.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a crystal multilayer structure and a method for manufacturing the same.

Conventionally, MBE (Molecular Beam Epitaxy) method and PLD (Pulsed Laser Deposition) method are known as methods for growing a β-Ga ₂ O ₃ single crystal film (see, for example, Patent Documents 1 and 2). In addition, a growth method by a sol-gel method, a MOCVD (Metal Organic Chemical Vapor Deposition) method, or a mist CVD method is also known.

JP 2013-56803 A Japanese Patent No. 4565062

However, since the MBE method performs crystal growth in a high vacuum chamber, it is difficult to increase the diameter of the β-Ga ₂ O ₃ single crystal film. In general, when the growth temperature is raised, a high-quality film can be obtained. However, since the re-evaporation of the source gas increases, a sufficient film formation rate cannot be obtained, which is not suitable for mass production.

  In addition, regarding the PLD method, the source (raw material supply source to the substrate) is a point source, and the growth rate is different between the source and other locations, so the in-plane distribution of film thickness tends to be non-uniform, Not suitable for growth of large area films. In addition, since the film formation rate is low and it takes a long time to grow a thick film, it is not suitable for mass production.

As for the sol-gel method, MOCVD method, and mist CVD method, it is relatively easy to increase the diameter, but impurities contained in the used raw material are taken into the β-Ga ₂ O ₃ single crystal film during the epitaxial growth. It is difficult to obtain a high-purity single crystal film.

Therefore, one of the objects of the present invention is to provide a β-Ga ₂ O ₃ single crystal film growth method capable of efficiently growing a high-quality and large-diameter β-Ga ₂ O ₃ single crystal film. An object of the present invention is to provide a crystal laminated structure having a grown β-Ga ₂ O ₃ -based single crystal film and a method for producing the same.

  In order to achieve the above object, one embodiment of the present invention provides a crystal multilayer structure according to [1] and [2] below.

[1] A Ga ₂ O ₃ based substrate and a β-Ga ₂ O ₃ based single crystal film containing Cl provided on the main surface of the Ga ₂ O ₃ based substrate, and the β-Ga ₂ O ₃ The system single crystal film is a crystal multilayer structure having a portion containing the Cl in the thickness direction of 1 × 10 ^{16 to} 5 × 10 ¹⁶ (atoms / cm ³ ).

[2] The crystal according to [1], wherein the β-Ga ₂ O ₃ single crystal film is capable of controlling a carrier concentration by a group IV element in a range of 1 × 10 ¹³ to 1 × 10 ²⁰ / cm ^3. Laminated structure.

  In order to achieve the above object, another aspect of the present invention provides a method for producing a crystal laminated structure according to the following [3] and [4].

[3] A manufacturing method for manufacturing the crystal multilayer structure according to [1] by an HVPE method, the step of disposing the Ga ₂ O ₃ based substrate in a crystal growth region in a reaction chamber; Supplying a gas and an oxygen-containing gas to a crystal growth region in the reaction chamber to grow the β-Ga ₂ O ₃ single crystal film on the Ga ₂ O ₃ substrate at 900 ° C. or higher. Manufacturing method of crystal laminated structure.

[4] A chloride-based gas for adding a dopant of a group IV element in addition to the gallium chloride-based gas and the oxygen-containing gas is supplied to the crystal growth region in the reaction chamber, and the β-Ga ₂ O ₃ The method for producing a crystal multilayer structure according to [3], further including a step of setting the carrier concentration of the system single crystal film to a range of 1 × 10 ¹³ to 1 × 10 ²⁰ / cm ³ .

According to the present invention, a β-Ga ₂ O ₃ single crystal film growth method capable of efficiently growing a high-quality and large-diameter β-Ga ₂ O ₃ single crystal film, and a growth method thereof A grown crystal multilayer structure and a method for manufacturing the same can be provided.

FIG. 1 is a vertical sectional view of a crystal multilayer structure according to an embodiment. FIG. 2 is a vertical sectional view of the vapor phase growth apparatus according to the embodiment. FIG. 3 shows the relationship between the growth driving force and the growth temperature of the Ga ₂ O ₃ crystal in each of the cases where the gallium chloride-based gas is composed only of GaCl gas and the case where it is composed only of GaCl ₃ gas. It is a graph showing a relationship. FIG. 4 shows the relationship between the equilibrium partial pressure of GaCl gas, GaCl ₂ gas, GaCl ₃ gas, and (GaCl ₃ ) ₂ gas obtained from the reaction of Ga and Cl ₂ and the ambient temperature obtained by thermal equilibrium calculation. It is a graph. FIG. 5 is a graph showing the relationship between the equilibrium partial pressure of GaCl and the O ₂ / GaCl supply partial pressure ratio when the ambient temperature of Ga ₂ O ₃ crystal growth is 1000 ° C., obtained by thermal equilibrium calculation. FIG. 6 was obtained by a 2θ-ω scan of a crystal laminated structure in which a Ga ₂ O ₃ single crystal film was epitaxially grown on the main surface of a Ga ₂ O ₃ substrate having a (010) plane orientation of the main surface. It is a graph showing an X-ray diffraction spectrum. FIG. 7 shows a 2θ-ω scan of a crystal laminated structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown at 1000 ° C. on a main surface of a Ga ₂ O ₃ substrate having a main surface orientation of (−201). It is a graph showing the X-ray-diffraction spectrum obtained by this. FIG. 8 is obtained by 2θ-ω scanning of a crystal stacked structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown on the main surface of a β-Ga ₂ O ₃ substrate having a (001) main surface orientation. It is a graph showing the acquired X-ray-diffraction spectrum. FIG. 9 is obtained by a 2θ-ω scan of a crystal laminated structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown on the main surface of a β-Ga ₂ O ₃ substrate whose main surface has a plane orientation of (101). It is a graph showing the acquired X-ray-diffraction spectrum. FIGS. 10A and 10B are graphs showing the impurity concentration in the crystal multilayer structure measured by secondary ion mass spectrometry (SIMS). FIG. 11A shows a carrier in the depth direction in a crystal stacked structure in which a β-Ga ₂ O ₃ crystal film is epitaxially grown on a β-Ga ₂ O ₃ substrate whose main surface has a plane orientation of (001). It is a graph showing the profile of a density | concentration. FIG. 11B is a graph showing the withstand voltage characteristics of the laminated structure. FIG. 12 shows a profile of carrier concentration in the depth direction in a crystal stacked structure in which a β-Ga ₂ O ₃ crystal film is epitaxially grown on a β-Ga ₂ O ₃ substrate having a (010) principal plane orientation. It is a graph showing.

Embodiment
(Configuration of crystal laminated structure)
FIG. 1 is a vertical sectional view of a crystal multilayer structure 1 according to an embodiment. The crystal laminated structure 1 has a Ga ₂ O ₃ -based substrate 10 and a β-Ga ₂ O ₃ -based single crystal film 12 formed by epitaxial crystal growth on the main surface 11 of the Ga ₂ O ₃ -based substrate 10.

The Ga ₂ O ₃ based substrate 10 is a substrate made of a Ga ₂ O ₃ based single crystal having a β-type crystal structure. Here, the Ga ₂ O ₃ single crystal refers to a Ga ₂ O ₃ single crystal or a Ga ₂ O ₃ single crystal to which an element such as Al or In is added. For example, a Ga ₂ O ₃ single crystal to which Al and In are added (Ga _x Al _y In _(1-xy) ) ₂ O ₃ (0 <x ≦ 1, 0 ≦ y ≦ 1, 0 <x + y ≦ 1) A single crystal may be used. When Al is added, the band gap is widened, and when In is added, the band gap is narrowed. Further, the Ga ₂ O ₃ based substrate 10 may contain a conductive impurity such as Si.

The plane orientation of the main surface 11 of the Ga ₂ O ₃ based substrate 10 is, for example, (010), (−201), (001), or (101).

The Ga ₂ O ₃ based substrate 10 is obtained by slicing a bulk crystal of a Ga ₂ O ₃ based single crystal grown by a melt growth method such as an FZ (Floating Zone) method or an EFG (Edge Defined Film Fed Growth) method. It is formed by polishing the surface.

The β-Ga ₂ O ₃ single crystal film 12 is made of a Ga ₂ O ₃ single crystal having a β-type crystal structure, like the Ga ₂ O ₃ base substrate 10. Further, the β-Ga ₂ O ₃ based single crystal film 12 may contain a conductivity type impurity such as Si.

(Structure of vapor phase growth equipment)
Below, an example of the structure of the vapor phase growth apparatus used for the growth of the β-Ga ₂ O ₃ based single crystal film 12 according to the present embodiment will be described.

  FIG. 2 is a vertical sectional view of the vapor phase growth apparatus 2 according to the embodiment. The vapor phase growth apparatus 2 is a vapor phase growth apparatus for HVPE (Halide Vapor Phase Epitaxy) method, and includes a first gas introduction port 21, a second gas introduction port 22, a third gas introduction port 23, and an exhaust gas. A reaction chamber 20 having a port 24, and a first heating unit 26 and a second heating unit 27 which are installed around the reaction chamber 20 and heat a predetermined region in the reaction chamber 20.

  The HVPE method has a higher film formation rate than the PLD method or the like. In addition, the uniformity of the in-plane distribution of film thickness is high, and a large-diameter film can be grown. For this reason, it is suitable for mass production of crystals.

The reaction chamber 20 is provided with a reaction vessel 25 containing Ga raw material, a raw material reaction region R1 in which a gallium raw material gas is generated, a Ga ₂ O ₃ based substrate 10 and a β-Ga ₂ O ₃ based. A crystal growth region R2 in which the single crystal film 12 is grown is provided. The reaction chamber 20 is made of, for example, quartz glass.

  Here, the reaction vessel 25 is, for example, quartz glass, and the Ga raw material accommodated in the reaction vessel 25 is metallic gallium.

  The first heating unit 26 and the second heating unit 27 can heat the raw material reaction region R1 and the crystal growth region R2 of the reaction chamber 20, respectively. The first heating unit 26 and the second heating unit 27 are, for example, resistance heating type or radiation heating type heating devices.

The first gas introduction port 21 uses a carrier gas (N ₂ gas, Ar gas, or He gas), which is an inert gas, as a Cl-containing gas, which is Cl ₂ gas or HCl gas, as a raw material reaction region R 1 of the reaction chamber 20. It is a port to introduce in. The second gas introduction port 22 is used to add a dopant such as Si to the oxygen-containing gas such as O ₂ gas or H ₂ O gas which is an oxygen source gas and the β-Ga ₂ O ₃ single crystal film 12. This is a port for introducing a chloride-based gas (for example, silicon tetrachloride) into the crystal growth region R2 of the reaction chamber 20 using a carrier gas (N ₂ gas, Ar gas, or He gas) that is an inert gas. . The third gas introduction port 23 is a port for introducing a carrier gas (N ₂ gas, Ar gas, or He gas) that is an inert gas into the crystal growth region R 2 of the reaction chamber 20.

(Growth of β-Ga ₂ O ₃ single crystal film)
Hereinafter, an example of the growth process of the β-Ga ₂ O ₃ single crystal film 12 according to the present embodiment will be described.

  First, the raw material reaction region R1 of the reaction chamber 20 is heated using the first heating means 26, and the atmospheric temperature of the raw material reaction region R1 is maintained at a predetermined temperature.

  Next, a Cl-containing gas is introduced from the first gas introduction port 21 using a carrier gas, and in the raw material reaction region R1, the metal gallium in the reaction vessel 25 and the Cl-containing gas are reacted at the above atmospheric temperature, Generates gallium chloride gas.

At this time, the atmospheric temperature in the raw material reaction region R1 is such that the partial pressure of the GaCl gas is the highest among the gallium chloride-based gases generated by the reaction between the metal gallium in the reaction vessel 25 and the Cl-containing gas. Temperature is preferred. Here, the gallium chloride-based gas includes GaCl gas, GaCl ₂ gas, GaCl ₃ gas, (GaCl ₃ ) ₂ gas, and the like.

GaCl gas is a gas that can maintain the growth driving force of Ga ₂ O ₃ crystals up to the highest temperature among the gases contained in the gallium chloride-based gas. In order to obtain a high-purity and high-quality Ga ₂ O ₃ crystal, growth at a high growth temperature is effective. Therefore, a gallium chloride-based gas having a high partial pressure of GaCl gas having a high growth driving force is generated at a high temperature. Is preferable for the growth of the β-Ga ₂ O ₃ -based single crystal film 12.

FIG. 3 shows the relationship between the growth driving force and the growth temperature of the Ga ₂ O ₃ crystal in each of the cases where the gallium chloride-based gas is composed only of GaCl gas and the case where it is composed only of GaCl ₃ gas. It is a graph showing a relationship. As calculation conditions, for example, an inert gas such as N ₂ is used as a carrier gas, the furnace pressure is 1 atm, the supply partial pressure of GaCl gas and GaCl ₃ gas is 1 × 10 ⁻³ atm, and the O ₂ / GaCl partial pressure ratio is 10 It was.

The horizontal axis in FIG. 3 represents the growth temperature (° C.) of the Ga ₂ O ₃ crystal, and the vertical axis represents the crystal growth driving force (atm). The larger the value of the crystal growth driving force, the more efficiently the Ga ₂ O ₃ crystal grows.

FIG. 3 shows that the upper limit of the temperature at which the growth driving force can be maintained is higher when GaCl gas is used as the Ga source gas than when GaCl ₃ gas is used.

Incidentally, β-Ga ₂ when O ₃ system contains a hydrogen atmosphere for growing the single crystal film 12, β-Ga ₂ O ₃ system flatness and crystal growth driving force of the surface of the single crystal film 12 In order to decrease, it is preferable to use a Cl ₂ gas containing no hydrogen as the Cl-containing gas.

FIG. 4 shows the equilibrium partial pressure of GaCl gas, GaCl ₂ gas, GaCl ₃ gas, and (GaCl ₃ ) ₂ gas obtained from the reaction of Ga and Cl ₂ and the ambient temperature at the time of reaction obtained by thermal equilibrium calculation. It is a graph showing a relationship. Other calculation conditions were such that an inert gas such as N ₂ was used as the carrier gas, the furnace pressure was 1 atm, and the supply partial pressure of Cl ₂ gas was 3 × 10 ⁻³ atm.

  The horizontal axis in FIG. 4 represents the ambient temperature (° C.), and the vertical axis represents the equilibrium partial pressure (atm). The higher the equilibrium partial pressure, the more gas is generated.

FIG. 4 shows that the reaction partial pressure of GaCl gas, which can particularly enhance the growth driving force of Ga ₂ O ₃ crystal, is increased by reacting metal gallium with a Cl-containing gas at an atmospheric temperature of about 300 ° C. or higher. That is, the partial pressure ratio of GaCl gas in the gallium chloride-based gas is increased. From this, it can be said that it is preferable to react the metal gallium in the reaction vessel 25 and the Cl-containing gas in a state where the atmosphere temperature of the raw material reaction region R1 is maintained at 300 ° C. or higher by the first heating means 26.

Further, for example, under an atmospheric temperature of 850 ° C., the GaCl gas partial pressure ratio is overwhelmingly high (the equilibrium partial pressure of GaCl gas is 4 orders of magnitude higher than GaCl ₂ gas and 8 orders of magnitude higher than GaCl ₃ gas). A gas other than the gas hardly contributes to the growth of the Ga ₂ O ₃ crystal.

  In consideration of the lifetime of the first heating means 26 and the heat resistance of the reaction chamber 20 made of quartz glass or the like, the metal in the reaction vessel 25 is maintained in a state where the atmosphere temperature of the raw material reaction region R1 is kept at 1000 ° C. or lower. It is preferable to react gallium with a Cl-containing gas.

Next, in the crystal growth region R2, the gallium chloride-based gas generated in the raw material reaction region R1 and the oxygen-containing gas introduced from the second gas introduction port 22 are mixed, and Ga ₂ O ₃ is added to the mixed gas. The system substrate 10 is exposed, and the β-Ga ₂ O ₃ system single crystal film 12 is epitaxially grown on the Ga ₂ O ₃ system substrate 10. At this time, the pressure in the crystal growth region R2 in the furnace containing the reaction chamber 20 is maintained at, for example, 1 atm.

Here, when the β-Ga ₂ O ₃ single crystal film 12 containing an additive element such as Si or Al is formed, a source gas of the additive element (for example, silicon tetrachloride (SiCl ₄ ) is supplied from the gas introduction port 22. ) And the like are also introduced into the crystal growth region R2 together with the gallium chloride gas and the oxygen-containing gas.

Incidentally, β-Ga ₂ when O ₃ system contains a hydrogen atmosphere for growing the single crystal film 12, β-Ga ₂ O ₃ system flatness and crystal growth driving force of the surface of the single crystal film 12 to lower, it is preferable to use O ₂ gas not containing hydrogen as the oxygen-containing gas.

FIG. 5 is a graph showing the relationship between the equilibrium partial pressure of GaCl and the O ₂ / GaCl supply partial pressure ratio when the ambient temperature of Ga ₂ O ₃ crystal growth is 1000 ° C., obtained by thermal equilibrium calculation. Here, the ratio of the O ₂ gas supply partial pressure to the GaCl gas supply partial pressure is referred to as an O ₂ / GaCl supply partial pressure ratio. In this calculation, the supply partial pressure value of the GaCl gas is fixed to 1 × 10 ⁻³ atm, the in-furnace pressure is set to 1 atm using an inert gas such as N ₂ as the carrier gas, and the O ₂ gas is supplied. The value of partial pressure was changed.

The horizontal axis in FIG. 5 represents the O ₂ / GaCl supply partial pressure ratio, and the vertical axis represents the equilibrium partial pressure (atm) of GaCl gas. The smaller the supply partial pressure of GaCl gas, the more GaCl gas is consumed for the growth of Ga ₂ O ₃ crystal, that is, the Ga ₂ O ₃ crystal is efficiently grown.

FIG. 5 shows that the equilibrium partial pressure of GaCl gas rapidly decreases when the O ₂ / GaCl supply partial pressure ratio is 0.5 or more.

For this reason, in order to efficiently grow the β-Ga ₂ O ₃ -based single crystal film 12, the ratio of the O ₂ gas supply partial pressure to the GaCl gas supply partial pressure in the crystal growth region R2 is 0.5 or more. In this state, it is preferable to grow the β-Ga ₂ O ₃ -based single crystal film 12.

FIG. 6 is obtained by a 2θ-ω scan of a crystal stacked structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown on a main surface of a β-Ga ₂ O ₃ substrate having a (010) plane orientation of the main surface. It is a graph showing the acquired X-ray-diffraction spectrum. The growth conditions were such that the furnace pressure was 1 atm, the carrier gas was N ₂ gas, the GaCl supply partial pressure was 5 × 10 ⁻⁴ atm, and the O ₂ / GaCl supply partial pressure ratio was 5.

  The horizontal axis of FIG. 6 represents the angle 2θ (degree) formed by the X-ray incident azimuth and reflection azimuth, and the vertical axis represents the X-ray diffraction intensity (arbitrary unit).

6, _β-Ga 2 _{O 3} spectrum of the substrate _(β-Ga 2 _{O 3} No crystal film), and 800 ℃, 850 ℃, 900 ℃ , 950 ℃, 1000 ℃, and respectively at 1050 ℃ β-Ga ₂ 2 shows a spectrum of a crystal laminated structure obtained by epitaxially growing an O ₃ crystal film. The thickness of the β-Ga ₂ O ₃ crystal film of these crystal stacked structures is approximately 300 to 1000 nm.

According to FIG. 6, the (−313) plane due to the presence of non-oriented grains, as seen in the spectrum of the crystal stack structure in which the β-Ga ₂ O ₃ crystal film is grown at growth temperatures of 800 and 850 ° C. The (−204) plane and the (−712) plane or (512) plane diffraction peaks disappear in the spectrum of the crystal stack structure in which the β-Ga ₂ O ₃ crystal film is grown at a growth temperature of 900 ° C. or higher. . This indicates that a β-Ga ₂ O ₃ single crystal film can be obtained by growing a Ga ₂ O ₃ single crystal film at a growth temperature of 900 ° C. or higher.

Even when the plane orientation of the main surface of the β-Ga ₂ O ₃ substrate is (−201), (001), or (101), the β-Ga ₂ O ₃ crystal film is grown at a growth temperature of 900 ° C. or higher. Is grown, a β-Ga ₂ O ₃ single crystal film is obtained. Further, even in the case of using the other _Ga 2 _{O 3} system board in place of _Ga 2 _{O 3} substrate, in the case of forming the other _Ga 2 _{O 3} based crystal film in place of _Ga 2 _{O 3} crystal film Even if it exists, the evaluation result similar to said evaluation result is obtained. That is, when the plane orientation of the main surface of the Ga ₂ O ₃ based substrate 10 is (010), (−201), (001), or (101), β-Ga ₂ O ₃ at a growth temperature of 900 ° C. or higher. The β-Ga ₂ O ₃ single crystal film 12 is obtained by growing the single crystal film 12.

FIG. 7 shows a 2θ-ω of a crystal stacked structure in which a β-Ga ₂ O ₃ single crystal film is epitaxially grown on the main surface of a β-Ga ₂ O ₃ substrate having a main surface orientation of (−201). It is a graph showing the X-ray-diffraction spectrum obtained by the scan. The growth conditions of this β-Ga ₂ O ₃ single crystal film are as follows: the furnace pressure is 1 atm, the carrier gas is N ₂ gas, the GaCl supply partial pressure is 5 × 10 ⁻⁴ atm, and the O ₂ / GaCl supply partial pressure ratio is 5. The growth temperature was 1000 ° C.

FIG. 7 shows a spectrum of a β-Ga ₂ O ₃ substrate (without a β-Ga ₂ O ₃ crystal film) whose plane orientation of the main surface is (−201), and 1000 ° C. on the β-Ga ₂ O ₃ substrate. ₂ shows a spectrum of a crystal stacked structure obtained by epitaxially growing a β-Ga ₂ O ₃ crystal film. The thickness of the β-Ga ₂ O ₃ crystal film of this crystal laminated structure is approximately 300 nm.

FIG. 8 is obtained by 2θ-ω scanning of a crystal stacked structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown on the main surface of a β-Ga ₂ O ₃ substrate having a (001) main surface orientation. It is a graph showing the acquired X-ray-diffraction spectrum. The growth conditions of this β-Ga ₂ O ₃ single crystal film are as follows: the furnace pressure is 1 atm, the carrier gas is N ₂ gas, the GaCl supply partial pressure is 5 × 10 ⁻⁴ atm, and the O ₂ / GaCl supply partial pressure ratio is 5. The growth temperature was 1000 ° C.

FIG. 8 shows a spectrum of a β-Ga ₂ O ₃ substrate (no β-Ga ₂ O ₃ crystal film) whose surface orientation is (001) and 1000 ° C. on the β-Ga ₂ O ₃ substrate. ₂ shows a spectrum of a crystal stacked structure obtained by epitaxially growing a β-Ga ₂ O ₃ crystal film. The thickness of the β-Ga ₂ O ₃ crystal film of this crystal laminated structure is approximately 6 μm.

FIG. 9 is obtained by a 2θ-ω scan of a crystal laminated structure in which a Ga ₂ O ₃ single crystal film is epitaxially grown on the main surface of a β-Ga ₂ O ₃ substrate whose main surface has a plane orientation of (101). It is a graph showing the acquired X-ray-diffraction spectrum. The growth conditions of this β-Ga ₂ O ₃ single crystal film are as follows: the furnace pressure is 1 atm, the carrier gas is N ₂ gas, the GaCl supply partial pressure is 5 × 10 ⁻⁴ atm, and the O ₂ / GaCl supply partial pressure ratio is 5. The growth temperature was 1000 ° C.

FIG. 9 shows a spectrum of a β-Ga ₂ O ₃ substrate (without a β-Ga ₂ O ₃ crystal film) whose plane orientation is (101), and 1000 ° C. on the β-Ga ₂ O ₃ substrate. ₂ shows a spectrum of a crystal stacked structure obtained by epitaxially growing a β-Ga ₂ O ₃ crystal film. The thickness of the β-Ga ₂ O ₃ crystal film of this crystal laminated structure is approximately 4 μm.

  7, 8, and 9, the horizontal axis represents the angle 2θ (degree) formed by the X-ray incident azimuth and the reflection azimuth, and the vertical axis represents the X-ray diffraction intensity (arbitrary unit).

According to FIGS. 7, 8, and 9, the diffraction peak of the spectrum of the crystal stacked structure obtained by growing the β-Ga ₂ O ₃ crystal film at the growth temperature of 1000 ° C. is the diffraction of the spectrum of the β-Ga ₂ O ₃ substrate. It is consistent with the peak. This result shows that a β-Ga ₂ O ₃ crystal is grown at a growth temperature of 1000 ° C. on the main surface of a β-Ga ₂ O ₃ substrate having a plane orientation of (−201), (001), or (101). It shows that a β-Ga ₂ O ₃ single crystal film can be obtained by growing the film.

  FIGS. 10A and 10B are graphs showing the impurity concentration in the crystal multilayer structure measured by secondary ion mass spectrometry (SIMS).

10A and 10B, the horizontal axis represents the depth (μm) from the main surface 13 of the β-Ga ₂ O ₃ single crystal film of the crystal laminated structure, and the vertical axis represents the concentration of each impurity (atoms). / Cm ³ ). Here, the depth of the interface between the β-Ga ₂ O ₃ substrate and the β-Ga ₂ O ₃ single crystal film of the crystal laminated structure is about 0.3 μm. In addition, the horizontal arrows on the right side of FIGS. 10A and 10B represent the lower limit of measurable concentration of each impurity element.

The β-Ga ₂ O ₃ single crystal film of the crystal laminated structure used in this measurement has a growth temperature of 1000 ° C. on the main surface of the β-Ga ₂ O ₃ substrate whose main surface has a (010) plane orientation. It is a grown film.

FIG. 10A shows the concentration of C, Sn, and Si in the crystal stacked structure, and FIG. 10B shows the concentration of H and Cl in the crystal stacked structure. According to FIGS. 10A and 10B, both impurity elements are close to the measurable lower limit of the concentration in the β-Ga ₂ O ₃ single crystal film, and almost the same as the concentration in the Ga ₂ O ₃ substrate. does not change. This indicates that the β-Ga ₂ O ₃ single crystal film is a highly pure film.

Similar evaluation results are obtained when the plane orientation of the main surface of the β-Ga ₂ O ₃ substrate is (−201), (101), or (001). Further, even in the case of using the other _Ga 2 _{O 3} system board in place of the _β-Ga 2 _{O 3} substrate, _β-Ga 2 _{O 3} other _Ga 2 _{O 3} system single crystal in place of the single crystal film Even when a film is formed, an evaluation result similar to the above evaluation result is obtained.

According to FIG. 10B, the β-Ga ₂ O ₃ single crystal film contains approximately 5 × 10 ¹⁶ (atoms / cm ³ ) or less of Cl. This is because the Ga ₂ O ₃ single crystal film is formed by the HVPE method using a Cl-containing gas. Normally, when a Ga ₂ O ₃ single crystal film is formed by a method other than the HVPE method, since a Cl-containing gas is not used, Cl is not contained in the Ga ₂ O ₃ single crystal film. ^{× 10 16 (atoms / cm 3} ) does not contain more Cl.

FIG. 11A shows a carrier in the depth direction in a crystal stacked structure in which a β-Ga ₂ O ₃ crystal film is epitaxially grown on a β-Ga ₂ O ₃ substrate whose main surface has a plane orientation of (001). It is a graph showing the profile of a density | concentration.

In FIG. 11A, the horizontal axis represents the depth (μm) from the surface of the β-Ga ₂ O ₃ crystal film, and the vertical axis represents the carrier concentration, that is, the donor concentration N _d and the acceptor concentration N which are net donor concentrations. It represents the difference _a ^{(cm -3).} Also, drawn curve in terms of in the figure, when the built-in potential when the relative dielectric constant of the _β-Ga 2 _{O 3} 10, contacting the Pt to _β-Ga 2 _{O 3} and 1.5V It is a theoretical curve showing the relationship between donor concentration and depletion layer thickness.

The procedure used to measure the data shown in FIG. 11 (a) is shown below. First, an undoped β-Ga ₂ O ₃ crystal film having a thickness of about 15 μm is formed on an n-type β-Ga ₂ O ₃ substrate doped with Sn and having a plane orientation of (001) by HVPE. Then, it was epitaxially grown. Here, undoped means that the intended doping is not performed, and does not deny the entry of unintended impurities.

The β-Ga ₂ O ₃ substrate was a 10 mm square substrate having a thickness of 600 μm, and the carrier concentration was approximately 6 × 10 ¹⁸ cm ⁻³ . The growth conditions of the β-Ga ₂ O ₃ single crystal film are as follows: furnace pressure is 1 atm, carrier gas is N ₂ gas, GaCl supply partial pressure is 5 × 10 ⁻⁴ atm, O ₂ / GaCl supply partial pressure ratio is 5, The growth temperature was 1000 ° C.

Next, the surface of the undoped β-Ga ₂ O ₃ crystal film was polished by 3 μm by CMP for planarizing the surface.

Next, a Schottky electrode is formed on the β-Ga ₂ O ₃ crystal film and an ohmic electrode is formed on the β-Ga ₂ O ₃ substrate, and the CV measurement is performed by changing the bias voltage in the range of +0 to −10V. went. And the profile of the carrier concentration of the depth direction was computed from the result of CV measurement.

  Here, the Schottky electrode is a circular electrode having a diameter of 800 μm and having a laminated structure in which a Pt film having a thickness of 15 nm, a Ti film having a thickness of 5 nm, and an Au film having a thickness of 250 nm are laminated in this order. The ohmic electrode is a square electrode with a side of 10 mm having a laminated structure in which a Ti film having a thickness of 50 nm and an Au film having a thickness of 300 nm are laminated in this order.

In FIG. 11A, no measurement point exists in a region having a depth shallower than 12 μm, which is equal to the thickness of the β-Ga ₂ O ₃ crystal film, and the horizontal coordinate of all measurement points is 12 μm. ing. This indicates that the entire region of the β-Ga ₂ O ₃ crystal film is depleted when the bias voltage is in the range of +0 to −10V.

For this reason, of course, even when the bias voltage is 0, the entire region of the β-Ga ₂ O ₃ crystal film is depleted. According to the theoretical curve, since the donor concentration when the depletion layer thickness is 12 μm is approximately 1 × 10 ¹³ cm ⁻³ , the residual carrier concentration of the β-Ga ₂ O ₃ crystal film is 1 × 10 ¹³ cm ^−3. It is estimated that this is a very low value as follows.

Since the residual carrier concentration of the β-Ga ₂ O ₃ crystal film is 1 × 10 ¹³ cm ⁻³ or less, for example, by doping a group IV element, the carrier concentration of the β-Ga ₂ O ₃ crystal film is 1 × It can control in the range of 10 < ¹³ > ^-1 * 10 < ²⁰ > cm < ^-3 >.

  FIG. 11B is a graph showing the withstand voltage characteristics of the crystal multilayer structure.

In FIG. 11B, the horizontal axis represents applied voltage (V), and the vertical axis represents current density (A / cm ² ).
Moreover, the straight line drawn by the point in a figure represents a measurement lower limit.

The procedure used to measure the data shown in FIG. 11 (b) is shown below. First, a crystal laminated structure composed of the β-Ga ₂ O ₃ substrate and a β-Ga ₂ O ₃ crystal film was prepared.

Next, a Schottky electrode was formed on the β-Ga ₂ O ₃ crystal film and an ohmic electrode was formed on the β-Ga ₂ O ₃ substrate, and a voltage of 1000 V was applied to measure the current density.

  Here, the Schottky electrode is a circular electrode having a diameter of 200 μm having a laminated structure in which a Pt film having a thickness of 15 nm, a Ti film having a thickness of 5 nm, and an Au film having a thickness of 250 nm are laminated in this order. The ohmic electrode is a square electrode with a side of 10 mm having a laminated structure in which a Ti film having a thickness of 50 nm and an Au film having a thickness of 300 nm are laminated in this order.

FIG. 11B shows that even when a voltage of 1000 V is applied, the leakage current in the crystal laminated structure is as small as about 1 × 10 ⁻⁵ A / cm ² and no dielectric breakdown occurs. Yes. This result is considered to be because the β-Ga ₂ O ₃ crystal film is a high-quality crystal film with few crystal defects and the donor concentration is low.

FIG. 12 shows a profile of carrier concentration in the depth direction in a crystal stacked structure in which a β-Ga ₂ O ₃ crystal film is epitaxially grown on a β-Ga ₂ O ₃ substrate having a (010) principal plane orientation. It is a graph showing.

The horizontal axis of FIG. 12 represents the depth ([mu] m) from the surface of the β-Ga ₂ O ₃ crystal film, and the vertical axis the carrier concentration, i.e., the difference between the donor concentration N _d and the acceptor concentration N _a is the donor concentration of the net (Cm ^<-3> ) is represented. Also, drawn curve in terms of in the figure, when the built-in potential when the relative dielectric constant of the _β-Ga 2 _{O 3} 10, contacting the Pt to _β-Ga 2 _{O 3} and 1.5V It is a theoretical curve showing the relationship between donor concentration and depletion layer thickness.

The procedure used to measure the data shown in FIG. 12 is shown below. First, the surface orientation of the main surface is (010), and an undoped β-Ga ₂ O ₃ crystal film is formed on the Sn-doped n-type β-Ga ₂ O ₃ substrate by an HVPE method to approximately 0.9 μm. Epitaxially grown to a thickness of.

The β-Ga ₂ O ₃ substrate was a square substrate having a thickness of 600 μm and a side of 10 mm, and the carrier concentration was approximately 6 × 10 ¹⁸ cm ⁻³ . The growth conditions of the β-Ga ₂ O ₃ single crystal film are as follows: furnace pressure is 1 atm, carrier gas is N ₂ gas, GaCl supply partial pressure is 5 × 10 ⁻⁴ atm, O ₂ / GaCl supply partial pressure ratio is 5, The growth temperature was 1000 ° C.

Next, a Schottky electrode is formed on the undoped β-Ga ₂ O ₃ crystal film, an ohmic electrode is formed on the β-Ga ₂ O ₃ substrate, and the bias voltage is changed in the range of +0 to −10 V to obtain CV Measurements were made. And the profile of the carrier concentration of the depth direction was computed from the result of CV measurement.

  Here, the Schottky electrode is a circular electrode having a diameter of 400 μm having a stacked structure in which a Pt film having a thickness of 15 nm, a Ti film having a thickness of 5 nm, and an Au film having a thickness of 250 nm are stacked in this order. The ohmic electrode is a square electrode with a side of 10 mm having a laminated structure in which a Ti film having a thickness of 50 nm and an Au film having a thickness of 300 nm are laminated in this order.

In FIG. 12, the horizontal coordinate of the measurement point when the bias voltage is 0 is 0.85 μm (the measurement point in the region deeper than 0.85 μm is the measurement point when the bias voltage is close to −10 V). According to the theoretical curve, since the donor concentration when the depletion layer thickness is 0.85 μm is approximately 2.3 × 10 ¹⁵ cm ⁻³ , the residual carrier concentration of the β-Ga ₂ O ₃ crystal film is 3 × 10 6. It is estimated that it is a very low value of ¹⁵ cm ⁻³ or less.

(Effect of embodiment)
According to the embodiment, by using the HVPE method, the production condition of the gallium source gas and the growth condition of the β-Ga ₂ O ₃ based single crystal film are controlled, so that a high-quality and large-diameter β- A Ga ₂ O ₃ based single crystal film can be efficiently grown. In addition, since the β-Ga ₂ O ₃ single crystal film is excellent in crystal quality, a high-quality crystal film can be grown on the β-Ga ₂ O ₃ single crystal film. For this reason, the crystal laminated structure including the β-Ga ₂ O ₃ -based single crystal film according to this embodiment can be used for manufacturing a high-quality semiconductor device.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

  The embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

1 ... crystal laminated structure, 10 ... _Ga 2 _{O 3} based substrate, 11 ... main _{surface, 12 ... β-Ga 2 O} 3 single crystal film

Claims (4)

A Ga ₂ O ₃ based substrate;
A β-Ga ₂ O ₃ based single crystal film containing Cl provided on the main surface of the Ga ₂ O ₃ based substrate;
Including
The β-Ga ₂ O ₃ based single crystal film is a crystal laminated structure having a portion containing 1 × 10 ^{16 to} 5 × 10 ¹⁶ (atoms / cm ³ ) of Cl in the thickness direction. _2. The crystal multilayer structure according to claim 1, wherein the β-Ga ₂ O ₃ single crystal film is capable of controlling a carrier concentration of a group IV element in a range of 1 × 10 ¹³ to 1 × 10 ²⁰ / cm ³ . A manufacturing method for manufacturing the crystal multilayer structure according to claim 1 by an HVPE method,
Disposing the Ga ₂ O ₃ based substrate in a crystal growth region in a reaction chamber;
Supplying a gallium chloride-based gas and an oxygen-containing gas to a crystal growth region in the reaction chamber to grow the β-Ga ₂ O ₃ -based single crystal film on the Ga ₂ O ₃ -based substrate at 900 ° C. or higher; ,
The manufacturing method of the crystal laminated structure containing this. Supplying a chloride gas for adding a dopant of a group IV element in addition to the gallium chloride gas and oxygen-containing gas to a crystal growth region in the reaction chamber, the β-Ga ₂ O ₃ single crystal The step of bringing the carrier concentration of the film into the range of 1 × 10 ¹³ to 1 × 10 ²⁰ / cm ³ ;
The manufacturing method of the crystal laminated structure of Claim 3 which further contains these.

Images