Method for producing crystalline film, vapor phase growth apparatus, and [beta]-gallium oxide crystalline film

Abstract

A method for producing a crystalline film, in which a plurality of raw material gases are merged at a merging position to obtain a mixed gas containing trimethyl gallium, oxygen, and a silicon dopant in argon, the obtained mixed gas is heated from the merging position so that the temperature of the merging position is 850-1100 DEG C, the heated mixed gas is guided to the surface of a substrate (2), and the substrate (2) is subjected to heat treatment so that the temperature of the merging position is 850-1100 DEG C. A [beta]-gallium oxide crystal film is grown on the surface of a substrate (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a method for manufacturing a crystalline film, a vapor phase growth apparatus, and a β-gallium oxide crystalline film. This application claims priority from Japanese Patent Application No. 2023-084641 filed on May 23, 2023, and the contents thereof are hereby incorporated by reference. BACKGROUND

[0002] A vapor phase growth method is a method for forming a thin film of a raw material for a thin film in a gaseous state on a substrate and depositing the thin film on the surface of the substrate by a chemical reaction. For example, a gallium nitride-based semiconductor thin film, which is a material for a blue light emitting diode, a green light emitting diode, or a violet laser diode, is manufactured by a MOCVD (Metal Organic Chemical Vapor Deposition) method using an organic metal as a raw material.

[0003] As a vapor phase growth apparatus for forming a semiconductor thin film by a vapor phase growth method, there is, for example, the apparatus disclosed in Patent Literature 1. The vapor phase growth apparatus of Patent Literature 1 heats the vicinity of a substrate, and on the other hand, in order to prevent a raw material gas from being deposited in a flow path before reaching the substrate, a cooling device is used to cool the raw material gas flow path. In addition, by separating the raw material gas flow path and the vicinity of the substrate with an adiabatic plate, the raw material gas flow path is prevented from being heated together with the vicinity of the substrate.

[0004] In recent years, gallium oxide has attracted attention as a new type of semiconductor material. Gallium oxide has different crystal structures recorded as α, β, γ, δ, and ε types. Among them, the thermal stability of the β type is the best.

[0005] β-gallium oxide (β-Ga2O3) has excellent physical properties such as a band gap of about 5 eV and a breakdown electric field of about 8 MV / cm, and is expected to be applied to high-voltage power devices.

[0006] In Non-Patent Literature 1, it is reported that β-gallium oxide crystals are deposited by MOCVD.

[0007] Patent Literature 1: Japanese Patent No. 4542860

[0008] Non-Patent Literature 1: F. Alema, B. Hertog, A. Osinsky, P. Mukhopadhyay, M. Toporkov, and W. V. Schoenfeld, J. Cryst. Growth 475 (2017) 77-82

[0009] In order to realize a high-voltage power device, it is necessary to grow a high-purity β-Ga2O3 crystalline film. However, it is difficult to obtain a high-purity β-Ga2O3 crystalline film by the existing MOCVD method. SUMMARY

[0010] The present application has been achieved in view of the above circumstances, and provides a crystalline film manufacturing method, a vapor phase growth apparatus, and a β-gallium oxide crystalline film capable of manufacturing a high-purity β-Ga2O3 crystalline film.

[0011] In order to achieve the above object, the present application adopts the following configuration.

[0012] [1] A crystalline film manufacturing method of causing a plurality of raw material gases to converge at a convergence position, obtaining a mixed gas containing trimethylgallium, oxygen, and a silicon dopant in argon, and heating the obtained mixed gas from the convergence position, and then guiding the heated mixed gas to a substrate surface, and growing a β-gallium oxide crystalline film on the substrate surface.

[0013] [2] The crystalline film manufacturing method according to [1], wherein heating is performed so that the temperature of the convergence position is 850 to 1100°C.

[0014] [3] The crystalline film manufacturing method according to [1] or [2], wherein the plurality of raw material gases are composed of a first raw material gas containing trimethylgallium and a silicon dopant in argon and a second raw material gas containing oxygen in argon.

[0015] [4] A vapor phase growth apparatus of supplying a mixed gas containing trimethylgallium, oxygen, and a silicon dopant in argon to a substrate disposed in a reaction furnace, and performing film formation of a β-gallium oxide crystalline film by a vapor phase growth method, wherein the vapor phase growth apparatus is provided with, in the reaction furnace, a raw material gas flow path that guides a plurality of raw material gases to a convergence position, respectively, and a mixed gas flow path that guides the mixed gas obtained at the convergence position from the convergence position to a surface of the substrate and then discharges it, and is provided with a heating device that performs heating so that the temperature of the convergence position is 850 to 1100°C.

[0016] [5] The vapor phase growth apparatus according to [4], wherein the heating device is disposed around a portion of the reaction furnace that surrounds the convergence position.

[0017] [6] The vapor phase growth apparatus according to [4] or [5], wherein the raw material gas flow path is composed of a flow path of a first raw material gas containing trimethylgallium and a silicon dopant in argon and a flow path of a second raw material gas containing oxygen in argon.

[0018] [7] A β-gallium oxide crystalline film in which the total content of carbon, hydrogen, and nitrogen is 2 x 1017 cm -3 The following, and doped with silicon.

[0019] [8] The β-gallium oxide crystalline film according to [7], wherein the donor concentration N d and the acceptor concentration N a differ by 10 d cm a or less. 15 cm -3 or more and 10 19 cm -3 or less.

[0020] [9] The β-gallium oxide crystalline film according to [7] or [8], wherein the mobility is 30 cm 2 / Vs or more.

[0021] The manufacturing method of a crystalline film and the vapor phase growth apparatus according to the present application can manufacture a β-Ga2O3crystalline film with high purity. In addition, the β-gallium oxide crystalline film of the present application is a film with high purity, and realization of a high-voltage power device can be expected. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a diagram showing the general configuration of a vapor phase growth apparatus of the first embodiment, viewed from the front.

[0023] Figure 2 is a diagram showing the general configuration of a vapor phase growth apparatus of the first embodiment, viewed from above.

[0024] Figure 3 is a diagram showing the general configuration of a vapor phase growth apparatus of the second embodiment, viewed from the front.

[0025] Figure 4 is a graph showing the results of Experimental Example 1.

[0026] Figure 5 is a graph showing the results of Experimental Example 4.

[0027] Figure 6 is a graph showing the results of Experimental Example 5. DETAILED DESCRIPTION

[0028] <First Embodiment>

[0029] [Vapor phase growth apparatus]

[0030] Figure 1 and Figure 2 is a vapor phase growth apparatus according to the first embodiment of the present application. Figure 1The vapor phase growth apparatus is an apparatus for forming β-gallium oxide crystalline films using the vapor phase growth method. It includes a reaction tube 1 with a substrate 2 disposed inside and a zone heater 10 for heating the reaction tube 1. In this embodiment, the zone heater 10 corresponds to the heating apparatus of the present invention. Furthermore, the reaction tube 1 corresponds to the reaction furnace of the present invention.

[0031] An upstream flow channel 20, an intermediate flow channel 26, and a downstream flow channel 29 are formed within the reaction tube 1. The upstream flow channel 20 corresponds to the feed gas flow path of the present invention, which guides multiple feed gases to the confluence position. Furthermore, the intermediate flow channel 26 and the downstream flow channel 29 are flow paths that guide the mixed gas from the confluence position to the substrate surface and then discharge it, corresponding to the mixed gas flow path of the present invention.

[0032] In the upstream flow channel 20, three flow paths are formed sequentially from top to bottom: a top channel 21, a middle channel 22, and a bottom channel 23. The middle channel 22 serves as the raw material gas flow path for supplying the first raw material gas to the substrate 2, while the top channel 21 and the bottom channel 23 serve as the raw material gas flow paths for supplying the second raw material gas to the substrate 2.

[0033] like Figure 1 and Figure 2 As shown, in this embodiment, the vertical cross-section of the upstream flow channel 20 narrows as it moves from upstream to downstream, while the horizontal cross-section widens as it moves from upstream to downstream. Furthermore, at the downstream end, it has a flattened shape that expands horizontally, with the first raw material gas flowing out from the center in the vertical direction and the second raw material gas flowing out from its upper and lower sides.

[0034] The intermediate flow channel 26 is connected to the downstream side of the upstream flow channel 20. This connection point, i.e. the upstream end of the intermediate flow channel 26, corresponds to the confluence position of the multiple raw material gases of the present invention.

[0035] The first raw material gas flowing out of the middle channel 22 and the second raw material gas flowing out of the top channel 21 and the bottom channel 23 merge at the confluence point, and the resulting mixed gas flows in the middle flow channel 26. Point A, indicated by the black circle in the diagram, is the center of the confluence point.

[0036] An upper opening 27 is formed on the upper wall of the intermediate flow channel 26, and a suspended substrate holder 3 is fitted into the upper opening 27. The lower side of the suspended substrate holder 3 facing into the intermediate flow channel 26 has multiple claws for supporting the substrate 2. Furthermore, by arranging the substrate 2 in the suspended substrate holder 3, the lower surface of the substrate 2 is exposed to the mixed gas within the intermediate flow channel 26.

[0037] By making the lower side surface of substrate 2 a so-called "face-down type" that is exposed to the mixed gas, accidental particle adhesion can be easily avoided.

[0038] The downstream flow channel 29 is connected to the downstream side of the intermediate flow channel 26, and the mixed gas passing through the intermediate flow channel 26 is discharged from the downstream side of the downstream flow channel 29 to the outside of the reaction tube 1.

[0039] A raw material gas supply pipe is connected to the upstream side of the upstream flow channel 20. Specifically, the first raw material gas supply pipe 31 is connected to the intermediate channel 22 and supplies the first raw material gas to the intermediate channel 22. In addition, the second raw material gas supply pipe 32a is connected to the top channel 21 and supplies the second raw material gas to the top channel 21. In addition, the second raw material gas supply pipe 32b is connected to the bottom channel 23 and supplies the second raw material gas to the bottom channel 23.

[0040] The zone heater 10 is arranged in a ring along the outer wall of the reaction tube 1. The zone heater 10 consists of an upstream heating heater 11, an intermediate heating heater 12, and a downstream heating heater 13, and the upstream heating heater 11, the intermediate heating heater 12, and the downstream heating heater 13 can each be individually set to temperature.

[0041] The upstream heating heater 11 is disposed around the portion of the outer wall of the reaction tube 1 surrounding point A, so as to heat the area near point A (the upstream side portion of the intermediate flow channel 26) where the first and second raw material gases merge.

[0042] The intermediate heating heater 12 is disposed around the portion of the outer wall of the reaction tube 1 that surrounds the portion where the upper opening 27 is provided, so as to heat the portion of the intermediate flow channel 26 where the upper opening 27 is provided, i.e., the portion where the substrate 2 is disposed.

[0043] The downstream heating heater 13 is disposed around the downstream side of the portion of the outer wall of the reaction tube 1 that is provided with the upper opening 27, so as to heat the downstream side of the portion of the intermediate flow channel 26 that is provided with the upper opening 27 and the downstream flow channel 29.

[0044] The downstream side of the upstream flow channel 20 (near point A) is covered by an insulating box 5. The insulating box 5 can be constructed, for example, by sealing an alumina insulating material inside a quartz annular box that is hollow inside.

[0045] By incorporating an insulated box 5, it is possible to prevent gallium and other materials from adhering to the upstream flow channel 20 due to thermal decomposition of the raw material gas within the upstream flow channel 20.

[0046] Instead of the insulation box 5, insulation pads or the like can be wound around the downstream side of the upstream flow channel 20.

[0047] If an insulated box 5 is used, it can be moved along the flow direction of the raw material gas while maintaining its overall shape, thus making it easy to adjust the temperature near point A.

[0048] [Method for manufacturing crystalline films]

[0049] In order to manufacture a crystalline film using the vapor phase growth apparatus of the first embodiment, the substrate 2 is suspended by the suspended substrate holder 3, and the mixed gas is brought into contact with the lower side surface of the substrate 2 under specified heating conditions.

[0050] The substrate 2 is not particularly limited as long as it is plate-shaped and can support the crystalline film; it can be any known substrate. It can be an insulating substrate, a conductive substrate, or a semiconductor substrate. In this embodiment, the substrate is preferably a crystalline substrate.

[0051] The crystalline substrate is not particularly limited as long as it contains crystalline material as its main component; it can be any known substrate. It can be an insulating substrate, a conductive substrate, or a semiconductor substrate. It can be a single-crystal substrate or a polycrystalline substrate. Examples of crystalline substrates include those with a corundum structure and containing crystalline material as its main component, those with a β-gallia structure and containing crystalline material as its main component, and those with a hexagonal crystal structure. The term "main component" refers to a substrate containing 50% or more of the crystalline material as a percentage of the substrate's composition, preferably 70% or more, and more preferably 90% or more.

[0052] Examples of substrates having a corundum structure and containing crystalline materials as the main component include sapphire substrates and alpha-type gallium oxide substrates. Examples of substrates having a β-gallia structure and containing crystalline materials as the main component include β-Ga₂O₃ substrates or mixed crystal substrates containing β-Ga₂O₃ and Al₂O₃. Furthermore, examples of substrates having a hexagonal crystal structure include SiC substrates, ZnO substrates, and GaN substrates. Examples of other crystalline substrates include Si substrates.

[0053] In this embodiment, the crystalline substrate is preferably a sapphire substrate. Examples of sapphire substrates include c-plane sapphire substrates, m-plane sapphire substrates, and a-plane sapphire substrates. In this embodiment, the crystalline substrate is preferably a c-plane sapphire substrate. Furthermore, in this embodiment, the crystalline substrate is preferably an m-plane sapphire substrate, and the sapphire substrate may have an offset angle. The offset angle is not particularly limited, but is preferably 0° to 15° along the a-axis or m-axis or in a direction encompassing them. Moreover, the thickness of the crystalline substrate is not particularly limited, but is preferably 50 to 2000 μm, more preferably 200 to 800 μm.

[0054] The mixed gas contains trimethylgallium, oxygen, and silicon-doped gas vaporized in argon.

[0055] Trimethylgallium is the source of gallium atoms, oxygen (oxygen molecules) is the source of oxygen atoms, and argon is the support. Examples of silicon dopants include monosilane, tetramethylsilane, and tetraethylsilane.

[0056] Trimethylgallium and oxygen contained in the gas mixture are preferably supplied separately to the merging point. This avoids the reaction between trimethylgallium and oxygen before merging.

[0057] Trimethylgallium and silicon dopant are preferably supplied to the confluence location in a pre-mixed state. This allows for stable control of the supply ratio of silicon dopant to trimethylgallium.

[0058] In this embodiment, the first raw material gas is set to "a gas containing trimethylgallium and silicon dopants in argon", and can be supplied to the confluence position via the intermediate channel 22. In addition, the second raw material gas is set to "a gas containing oxygen in argon", and can be supplied to the confluence position via the top channel 21 and the bottom channel 23.

[0059] The supply ratio of silicon dopant to trimethylgallium can be adjusted according to the amount of silicon doped in the crystalline film, preferably a silicon to trimethylgallium molar ratio of 10. -9 ~10 -4 .

[0060] According to this embodiment, the situation where silicon is unintentionally included in the mixed gas as an impurity can be suppressed, and the amount of doped silicon can be easily adjusted by the supply ratio of silicon dopant to trimethylgallium.

[0061] The growth temperature, i.e., the temperature of the mixed gas in contact with the surface of the substrate 2, is preferably 575 to 1100°C. By setting the growth temperature to a value above the preferred lower limit, the concentration of impurities introduced into the crystalline film can be reduced.

[0062] The growth temperature is preferably kept approximately constant over the entire range of the upstream and downstream surfaces of the substrate 2.

[0063] The temperature at location A is preferably 850–1100°C, more preferably 870–1080°C, even more preferably 890–1060°C, and particularly preferably 900–1050°C. By keeping the temperature at location A above the preferred lower limit, the concentration of impurities introduced into the crystalline film can be reduced. By keeping the temperature at location A below the preferred upper limit, the appropriate growth temperature can be avoided before contact with the surface of substrate 2.

[0064] The temperature of the mixed gas, including at location A, before contacting the surface of the substrate 2 is preferably below the growth temperature, and more preferably below the growth temperature. This prevents gallium or gallium oxide from adhering to the upstream flow channel 20 or the upstream side of the intermediate flow channel 26 due to thermal decomposition of the mixed gas before reaching the surface of the substrate 2.

[0065] The temperature of the mixed gas preferably increases gradually from point A up to the upstream side of the surface of substrate 2.

[0066] The temperature within the intermediate flow channel 26 at location A can be confirmed by inserting a thermocouple 4 into the flow path.

[0067] When measuring the temperature at location A, insert the tip of thermocouple 4 into the position at location A. When measuring the temperature at location B (the position indicated by the white circle in the diagram), insert the tip of thermocouple 4 into the position at location B. Figure 1 and Figure 2 This indicates that the front end of thermocouple 4 has been moved to a slightly downstream position from point B.

[0068] However, if thermocouple 4 is inserted beforehand during actual film formation, undesirable conditions such as gallium oxide film adhering to thermocouple 4 may occur. Therefore, when using thermocouple 4 for measurement, nitrogen free of trimethylgallium, silicon dopant, and oxygen is used for flow. Furthermore, thermocouple 4 is pulled out of reaction tube 1 before film formation.

[0069] <Second Implementation Method>

[0070] Figure 3 This is the vapor phase growth apparatus according to the second embodiment of the present invention. Regarding... Figure 3 The vapor phase growth apparatus is the same as in the first embodiment, except that the upper surface of the substrate 2 is exposed to the mixed gas, a so-called "face-up" type. Figure 3 In the text, structural elements that are the same as those in the first embodiment are labeled and... Figure 1 The same reference numerals are used in the accompanying drawings, and their detailed descriptions are omitted.

[0071] Since the vapor phase growth apparatus of this embodiment is a so-called upward-facing type, a lower opening 28 is formed on the lower side wall of the intermediate flow channel 26, and an upper-mounted substrate holder 6 is fitted into the lower opening 28.

[0072] A recess for mounting the substrate 2 is formed on the upper surface of the upper substrate holder 6. By placing the substrate 2 in the upper substrate holder 6, the upper surface of the substrate 2 is exposed to the mixed gas in the intermediate flow channel 26.

[0073] The method for manufacturing a crystalline film using the vapor phase growth apparatus of this embodiment is the same as the method for manufacturing a crystalline film using the vapor phase growth apparatus of the first embodiment, except that the substrate 2 is placed in the upper substrate holder 6.

[0074] <Other Implementation Methods>

[0075] In the above embodiments, the upstream flow channel 20 may be configured to have an intermediate channel 22 for supplying the first raw material gas, a top channel 21 for supplying the second raw material gas, and a bottom channel 23. However, it may be further configured to have a fourth channel for supplying the third raw material gas. In this case, the silicon dopant is not contained in the first raw material gas, and the gas containing the silicon dopant in argon gas may be designated as the third raw material gas.

[0076] Alternatively, an apparatus can be used to simultaneously perform film deposition based on both face-down and face-up methods by installing both a suspended substrate holder 3 and an upper-load substrate holder 6 in the intermediate flow channel 26.

[0077] Furthermore, various modifications may be made without departing from the spirit of this invention.

[0078] Mechanism of Action

[0079] According to the above embodiments, β-gallium oxide crystalline films with few impurities can be effectively obtained. The reasons are as follows.

[0080] First, in the above embodiments, trimethylgallium is used as the gallium source.

[0081] When triethylgallium is used instead of trimethylgallium as the gallium source, triethylgallium, with its low decomposition temperature, readily reacts with silicon dioxide contained in materials (such as quartz) in components that come into contact with the raw material gas, such as flow channels. As a result, a large amount of thermally decomposed silicon is introduced into the crystalline film. In addition, due to the low vapor pressure of triethylgallium, it is also difficult to supply a high concentration of gallium to the reactor.

[0082] In the above embodiments, since trimethylgallium, which has a high decomposition temperature and is difficult to decompose spontaneously, is used as the gallium source, the reaction with quartz and the like can be suppressed, thereby reducing the amount of silicon unintentionally introduced into the crystalline film.

[0083] In addition, due to the high vapor pressure of trimethylgallium, a high concentration of gallium can be supplied to the reactor, thereby enabling the rapid growth of the crystalline film.

[0084] In addition, when organometallic materials are used as the metal source, there is a tendency for carbon and hydrogen from hydrocarbon groups to be introduced into the crystalline film.

[0085] In the above embodiments, since the mixed gas is sufficiently heated from the confluence point, the hydrocarbons produced by the decomposition of trimethylgallium can undergo a sufficient combustion reaction with oxygen before reaching the substrate. As a result, the introduction of carbon and hydrogen from hydrocarbon groups into the crystalline film can be suppressed.

[0086] In the above embodiments, argon is used as the carrier. If nitrogen is used as the carrier, nitrogen is introduced into the membrane to form an acceptor. Argon does not form a donor or acceptor in the membrane.

[0087] Thus, in the above embodiments, the amount of impurities unintentionally mixed into the β-gallium oxide crystalline film can be reduced. As a result, by adjusting the supply ratio of silicon dopant to trimethylgallium, the electron concentration in the crystalline film can be stably controlled.

[0088] Conventionally, to prevent the raw material gas from forming a film within the flow path before reaching the substrate, a cooling device is used to cool the raw material gas flow path. In contrast, in the above embodiment, not only is cooling not performed, but the mixed gas is intentionally heated from the confluence point, yet film formation within the flow path is effectively suppressed in practical applications. This is because the hydrocarbon group is more likely to react with oxygen first compared to gallium derived from trimethylgallium.

[0089] The crystalline film obtained in the above embodiments will now be described in detail.

[0090] <Crystal membrane>

[0091] The crystalline film in this embodiment is a β-type gallium oxide crystalline film. The total content of carbon, hydrogen, and nitrogen in the crystalline film of this embodiment is 2 × 10⁻⁶. 17 cm -3 The following is a preferred total content of carbon, hydrogen, and nitrogen: 10. 17 cm -3 The following is more preferably 10 16 cm -3 the following.

[0092] In this specification and claims, the unit for representing the content of each atom contained in the crystalline film is described as "cm". -3This unit represents the number of atoms per cubic centimeter, and can be recorded as "atoms / cm". 3 ". Figure 5 The electron concentration shown is the same.

[0093] The preferred carbon content is 10. 17 cm -3 The following is more preferably 10 16 cm -3 Hereinafter, 10 is further preferred. 15 cm -3 The hydrogen content is preferably 10%. 17 cm -3 The following is more preferably 10 16 cm -3 Hereinafter, 10 is further preferred. 15 cm -3 The nitrogen content is preferably 10%. 17 cm -3 The following is more preferably 10 16 cm -3 Hereinafter, 10 is further preferred. 15 cm -3 the following.

[0094] The silicon content contained in the silicon dopant that is not intended to be used as a dopant is preferably 10%. 16 cm -3 The following is more preferably 10 15 cm -3 the following.

[0095] The contents of carbon, hydrogen, nitrogen and silicon are the average concentrations in the range of 1 to 3 μm from the membrane surface, as determined by secondary ion mass spectrometry (SIMS).

[0096] In this embodiment, the crystalline film is doped with silicon to form an n-type structure. Donor concentration N0 d With receptor concentration N a The difference [N] d -N a ] is 10 15 cm -3 Above and 10 19 cm -3 the following.

[0097] In addition, the difference [N] d -N a The value is the average of the values ​​within a range of 2 to 3 μm from the membrane surface, calculated by measuring the electrostatic capacitance-voltage (CV) using a mercury probe.

[0098] The preferred difference [Nd-Na] is 10. 15 cm-3 And the above 10 19 cm -3 the following.

[0099] In this embodiment, the migration rate of the crystalline film is preferably 30 cm. 2 / Vs or more, preferably 50cm 2 / Vs or higher, further preferably 100cm 2 / Vs or higher. High mobility can suppress power loss during semiconductor device operation.

[0100] The thickness of the crystalline film in this embodiment is preferably 0.5 to 100 μm.

[0101] The crystalline film of this embodiment is particularly suitable for use in semiconductor devices, especially power devices. Examples of semiconductor devices formed using the crystalline film of this embodiment include transistors or TFTs such as MIS or HEMT, Schottky barrier diodes utilizing semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light-emitting elements. The crystalline film of this embodiment can be used in semiconductor devices, etc., while it is formed on a substrate, or it can be applied to semiconductor devices, etc., after using known methods such as peeling off the substrate.

[0102] Semiconductor devices, using known methods, are suitable for use as power modules, inverters, or converters, and thus suitable for use in semiconductor systems, for example, that use power supply devices.

[0103] Example

[0104] <Substrate>

[0105] The following substrates were used in the following experimental examples.

[0106] Substrate A: (010) surface, 0.50 mm thick, Sn-doped Ga2O3 substrate (manufactured by Novel Crystal Technology Co., Ltd.).

[0107] Substrate B: (0001) surface, thickness 0.43mm, m-axis offset angle 0.15°, sapphire substrate (manufactured by Orbray Corporation).

[0108] <Ingredients>

[0109] The following raw materials were used in the following experimental examples.

[0110] TMGa: trimethylgallium (manufactured by Taiyo Nippon Sanso Co., Ltd.).

[0111] O2: Oxygen (manufactured by Taiyo Nippon Sanso Corporation).

[0112] Ar: Argon (manufactured by Taiyo Nippon Sanso Corporation).

[0113] TMSi: Tetramethylsilane (manufactured by Taiyo Nippon Sanso Corporation).

[0114] <Determination Method>

[0115] Regarding the content of carbon, hydrogen, and nitrogen as impurities, a CAMECA-manufactured IMS-6f secondary ion mass spectrometer was used to measure the concentration at 64 points within a range of 1–3 μm from the membrane surface at 0.031 μm intervals. The average value of the 64 measurements was taken as the content. Regarding the silicon content, the same apparatus was used as for the carbon, hydrogen, and nitrogen measurements, and the concentration at 53 points within a range of 1–3 μm from the membrane surface at 0.038 μm intervals was taken. The average value of the 53 measurements was taken as the content.

[0116] Difference [N] d -N a Using a Model 802B (CV) measurement device manufactured by MATERIALS DEVELOPMENT CORPORATION with a mercury probe, the concentration was measured at six points within a range of 2–3 μm from the membrane surface at 0.2 μm intervals. The average value of the six measurement results was set as the difference [N]. d -N a ].

[0117] Electron concentration and mobility were determined using the ResiTest8300 manufactured by Toyo Seiseki Co., Ltd., via AC Hall effect measurement (alternating current electromagnetic field method).

[0118] The flow rates of Ar, O2, and TMGa gases were measured using Fujikin's FCST1030MZDTC-4J1-F5L-AR-R6-D28, FCST1005MZDTC-4J1-F1L-O2-R5-D28, and FCST1005MZDTC-4J1-F1L-AR4-D28 vacuum gauges, respectively. The combined pressure was measured using a diaphragm vacuum gauge. The flow rate of the mixed gas was calculated from the combined temperature, pressure, and flow rate.

[0119] <Experimental Example 1>

[0120] In addition to replacing the insulation box 5, by winding an alumina insulation material of the same volume as the insulation box onto the upstream flow channel 20, and... Figure 1 The same apparatus confirmed the temperature distribution. The distance from point A to point B was 200 mm. Additionally, the height and width of the intermediate flow channel 26 were 10 mm and 80 mm, respectively.

[0121] To confirm the temperature distribution using thermocouple 4, only N2 is introduced into the device. The flow rates of N2 supplied from the first raw material gas supply pipe 31, the second raw material gas supply pipe 32a, and the second raw material gas supply pipe 32b are 3.0 L / min and 9.0 L / min respectively, and the combined pressure is 1.4 kPa.

[0122] As a result, the flow rate of the mixed gas at a temperature of 1000℃ was 63.2 m / s, and the time for the mixed gas to reach the center of the substrate holder from point A was 0.0019 seconds.

[0123] Regarding the set temperature of the zone heater 10, the upstream heating heater 11 is set to 600°C, and the intermediate heating heater 12 and the downstream heating heater 13 are set to 960°C.

[0124] As a result, we obtained Figure 4 The temperature distribution shown. Figure 4 As shown, the temperature at location A is 903°C, and the temperature near the substrate is a constant temperature of approximately 1000°C.

[0125] <Experimental Example 2>

[0126] Using the same apparatus as in Experimental Example 1, a 5 μm thick β-Ga₂O₃ crystalline film was grown on substrate A. Thermocouple 4 was not used.

[0127] The gas supplied from the first raw material gas supply pipe 31 is a gas containing TMGa in Ar, and the gas supplied from the second raw material gas supply pipe 32a and the second raw material gas supply pipe 32b is a gas containing O2 in Ar. TMSi is not used as a dopant.

[0128] The supply rate of TMGa was set to 182 μmol / min, and the supply rate of O2 was set to 178,571 μmol / min (2.0 L / min). The oxygen to trimethylgallium supply ratio, expressed as a molar ratio of oxygen molecules to trimethylgallium, was 981. The growth time was 60 minutes. The set temperature of the zone heater 10 was the same as in Experimental Example 1. The total flow rate of the mixed gas (total flow rate after merging), the pressure after merging, the flow rate of the mixed gas at 1000°C, and the time it took for the mixed gas to reach the center of the substrate holder from point A were 8.4 L / min, 2.4 kPa, 34.4 m / s, and 0.0035 s, respectively.

[0129] When measuring the impurity concentration in the obtained crystalline film, the carbon concentration was 3 × 10⁻⁶. 16 cm -3 The hydrogen concentration is 7×10 16 cm -3 The nitrogen concentration is 9×10 15 cm -3The silicon concentration is 1×10 15 cm -3 All showed very low values, equivalent to the background levels measured by SIMS.

[0130] The combined content of carbon, hydrogen, and nitrogen is 2 × 10⁻⁶. 17 cm -3 the following.

[0131] In addition, the difference [N] obtained by (CV) measurement d -N a ] is 2×10 15 cm -3 Therefore, by setting the temperature at the confluence point to 903°C, it can be confirmed that the impurities are controlled at an extremely low concentration.

[0132] <Experimental Example 3>

[0133] Using the same apparatus as in Experimental Example 1, a 5 μm thick β-Ga₂O₃ crystalline film was grown on the substrate shown in Table 1. Thermocouple 4 was not used.

[0134] The gas supplied from the first raw material gas supply pipe 31 is a gas containing TMGa in Ar, and the gas supplied from the second raw material gas supply pipe 32a and the second raw material gas supply pipe 32b is a gas containing O2 in Ar. TMSi is not used as a dopant.

[0135] The TMGa supply rate was set to 182 μmol / min, and the O2 supply rate was set to 178571 μmol / min (2.0 L / min). The oxygen to trimethylgallium supply ratio, expressed as the molar ratio of oxygen molecules to trimethylgallium, was 981. The growth time was 60 minutes.

[0136] The total flow rate, pressure, flow velocity of the mixed gas at 1000°C, and arrival time of the mixed gas from point A to the center of the substrate holder were varied in each example as shown in Table 1. The set temperature of the zone heater 10 was the same as in Experimental Example 1.

[0137] The carbon concentration in the obtained crystalline film was measured, and the results are shown in Table 1.

[0138] Therefore, by setting the temperature at the confluence point to 903°C, if the flow rate of the mixed gas is reduced and the arrival time from point A to the center of the substrate is extended, it can be confirmed that the concentration of impurities is controlled to be lower.

[0139] [Table 1]

[0140]

[0141] <Experimental Example 4>

[0142] Using the same apparatus as in Experimental Example 1, a 5 μm thick β-Ga₂O₃ crystalline film was grown on the substrate shown in Table 1. Thermocouple 4 was not used.

[0143] The gas supplied from the first raw material gas supply pipe 31 is a gas containing TMGa and TMSi in Ar, and the gas supplied from the second raw material gas supply pipe 32a and the second raw material gas supply pipe 32b is a gas containing O2 in Ar.

[0144] By fixing the TMGa supply rate at 182 μmol / min and varying the TMSi supply rate, the TMSi / TMGa supply ratio (the molar ratio of tetramethylsilane to trimethylgallium) in the first feed gas is changed from 9.97 × 10⁻⁶. -5 Change to 4.98×10 -7 .

[0145] The O2 supply was set at 178,571 μmol / min (2.0 L / min). The oxygen to trimethylgallium supply ratio, expressed as a molar ratio of oxygen molecules to trimethylgallium, was 981. The growth time was 60 minutes.

[0146] The total flow rate, pressure, flow rate of the mixed gas at a temperature of 1000°C, and time for the mixed gas to reach the center of the substrate holder from point A, as well as the set temperature of the zone heater 10, are the same as in Experimental Example 1.

[0147] The results of measuring the electron concentration of the crystalline film are shown below. Figure 5 .like Figure 5 As shown, the electron concentration varies linearly with respect to the TMSi / TMGa supply ratio.

[0148] Therefore, by setting the temperature at the confluence point to 903°C, the influence of impurities can be suppressed and the electron concentration can be stably controlled by changing the TMSi / TMGa supply ratio.

[0149] <Experimental Example 5>

[0150] to and Figure 1 The same device (the position of insulation box 5 is also the same) Figure 1 (Same as above) The temperature distribution was confirmed. The distance from point A to point B is 200 mm. In addition, the height and width of the intermediate flow channel 26 are 10 mm and 80 mm, respectively.

[0151] To confirm the temperature distribution using thermocouple 4, only N2 is introduced into the device. The flow rates of N2 supplied from the first raw material gas supply pipe 31, the second raw material gas supply pipe 32a, and the second raw material gas supply pipe 32b are 3.0 L / min and 9.0 L / min respectively, and the combined pressure is 1.4 kPa.

[0152] As a result, the flow rate of the mixed gas at a temperature of 1000℃ was 63.2 m / s, and the time for the mixed gas to reach the center of the substrate holder from point A was 0.0019 seconds.

[0153] Regarding the set temperature of the zone heater 10, the upstream heater 11 was set to 600°C in Experiment 5-1 and 960°C in Experiment 5-2. The intermediate heater 12 and the downstream heater 13 were both set to 960°C in both Experiment 5-1 and Experiment 5-2. The results showed... Figure 6 The temperature distribution shown. Figure 6 As shown, the temperature at location A was 923°C in Experiment 5-1 and 939°C in Experiment 5-2. The temperature near the substrate could be set to a constant temperature of approximately 1000°C in both Experiment 5-1 and Experiment 5-2.

[0154] <Experimental Example 6>

[0155] Using the same apparatus as in Experimental Example 1, a 5 μm thick β-Ga₂O₃ crystalline film was grown on substrate A. Thermocouple 4 was not used.

[0156] The gas supplied from the first raw material gas supply pipe 31 is a gas containing TMGa in Ar, and the gas supplied from the second raw material gas supply pipe 32a and the second raw material gas supply pipe 32b is a gas containing O2 in Ar. TMSi is not used as a dopant.

[0157] The supply rate of TMGa was set to 182 μmol / min, and the supply rate of O2 was 178571 μmol / min (2.0 L / min). The oxygen to trimethylgallium supply ratio, expressed as a molar ratio of oxygen molecules to trimethylgallium, was 981. The growth time was 60 minutes. The set temperature of the zone heater 10 was the same for Experiment 6-1 and Experiment 5-1, and for Experiment 6-2 and Experiment 5-2, respectively. The total flow rate of the mixed gas (after merging), the pressure after merging, the flow rate of the mixed gas at 1000°C, and the time it took for the mixed gas to reach the center of the substrate holder from point A were 8.4 L / min, 1.4 kPa, 59.0 m / s, and 0.0020 s, respectively.

[0158] The carbon concentration in the obtained crystalline film was measured; in Experiment 6-1, the carbon concentration was 6 × 10⁻⁶. 17 cm-3 The carbon concentration in Experiment 6-2 was 1 × 10⁻⁶. 17 cm -3 .

[0159] Therefore, if the temperature at location A is increased from 923°C to 939°C, it can be confirmed that the carbon concentration is controlled at an even lower level.

[0160] Explanation of reference numerals in the attached figures

[0161] 1 reaction tube

[0162] 2 substrates

[0163] 3 Suspended substrate holder

[0164] 4 thermocouples

[0165] 5 Insulation Box

[0166] 6-type substrate holder

[0167] 10 Zone Heaters

[0168] 11. Heaters for upstream heating

[0169] 12. Intermediate heating heater

[0170] 13. Heaters for downstream heating

[0171] 20 upstream flow channels

[0172] 21 Top Channel

[0173] 22 Middle Channel

[0174] 23 Bottom Channel

[0175] 26 intermediate flow channels

[0176] 27. Opening at the top

[0177] 28. Lower opening

[0178] 29 Downstream Flow Channel

[0179] 31 First raw material gas supply pipe

[0180] 32a Second Raw Material Gas Supply Pipe

[0181] 32b Second Raw Material Gas Supply Pipe

Claims

1. A method for manufacturing a crystalline film, comprising merging multiple raw material gases at a confluence location to obtain a mixed gas containing trimethylgallium, oxygen, and silicon dopants in argon, and heating the obtained mixed gas from the confluence location. The heated mixed gas is then directed to the substrate surface to allow a β-gallium oxide crystal film to grow on the substrate surface.

2. The method for manufacturing a crystalline film according to claim 1, wherein, Heating is performed to bring the temperature at the confluence point to 850–1100°C.

3. The method for manufacturing the crystalline film according to claim 1 or 2, wherein, The plurality of raw material gases consist of a first raw material gas containing trimethylgallium and silicon dopants in argon and a second raw material gas containing oxygen in argon.

4. A vapor phase growth apparatus, wherein a mixed gas containing trimethylgallium, oxygen, and silicon dopant in argon is supplied to a substrate disposed in a reactor, and a β-gallium oxide crystalline film is formed by vapor phase growth, wherein... The vapor phase growth apparatus within the reactor comprises: a raw material gas flow path that guides multiple raw material gases to a confluence position; and a mixed gas flow path that guides the mixed gas obtained at the confluence position to the surface of the substrate and then discharges it. It also has a heating device for heating the confluence location to a temperature of 850–1100°C.

5. The vapor phase growth apparatus according to claim 4, wherein, The heating device is arranged around the portion of the reactor that surrounds the confluence location.

6. The vapor phase growth apparatus according to claim 4 or 5, wherein, The feed gas flow path consists of a first feed gas containing trimethylgallium and silicon dopants in argon and a second feed gas containing oxygen in argon.

7. A β-gallium oxide crystalline film, wherein, The combined content of carbon, hydrogen, and nitrogen is 2 × 10⁻⁶. 17 cm -3 Below that, and it is doped with silicon.

8. The β-gallium oxide crystalline film according to claim 7, wherein, Donor concentration N d With receptor concentration N a The difference [N] d -N a ] is 10 15 cm -3 Above and 10 19 cm -3 the following.

9. The β-gallium oxide crystalline film according to claim 7 or 8, wherein, The migration rate is 30cm 2 / Vs and above.

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