Semiconductor substrate, semiconductor wafer, and method for manufacturing semiconductor wafer

Abstract

Provided is a gallium oxide-based semiconductor substrate, a semiconductor wafer including the semiconductor substrate and an epitaxial film, and a method for manufacturing a semiconductor wafer, which is capable of forming a gallium oxide-based epitaxial film having a small film thickness distribution and donor concentration distribution and a small density of crystal defects by an HVPE method. As one embodiment, provided is a semiconductor substrate (10) which is a semiconductor substrate (10) having at least one main surface as a growth base surface (11) of a crystal, includes a single crystal of a gallium oxide-based semiconductor, the growth base surface (11) is a (001) surface, in a continuous region of 70% or more of the area of the growth base surface (11), an off angle in the [010] direction is in a range of greater than -0.3° and -0.01° or more and less than 0.3°, in the region of the growth base surface (11), an off angle in the [001] direction is in a range of -1° or more and 1° or less, and the diameter of the semiconductor substrate (10) is 2 inches or more.

Description

Technical Field

[0001] This invention relates to semiconductor substrates, semiconductor wafers, and methods for manufacturing semiconductor wafers. Background Technology

[0002] Previously, inventions for epitaxially growing gallium oxide single crystal films on substrates including gallium oxide single crystals using the HVPE (Halide Vapor Phase Epitaxy) method are known (for example, see Patent Document 1). According to the invention described in Patent Document 1, by setting the orientation of the main surface of the substrate to a predetermined orientation, the growth rate of the epitaxial film using the HVPE method can be increased.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-109902 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] Gallium oxide epitaxial wafers with diameters of 2 inches or more fabricated using conventional techniques suffer from the following problems: the epitaxial film thickness distribution is as large as 11%, and the donor concentration distribution is also large (reaching over 40% even without intentionally adding donors). Furthermore, when film deposition is performed under conditions designed to reduce the thickness distribution, the density of crystal defects caused by epitaxial growth, resulting in etching pits, is as high as 5 × 10⁻⁶. 4 cm -3 In conclusion, due to these issues, it is difficult to manufacture gallium oxide power devices with good yield using conventional gallium oxide epitaxial wafers.

[0008] Therefore, the object of the present invention is to provide a gallium oxide-based semiconductor substrate, a semiconductor wafer having the semiconductor substrate and an epitaxial film, and a method for manufacturing the semiconductor wafer, wherein the semiconductor substrate is capable of forming a gallium oxide-based epitaxial film with small film thickness distribution, small donor concentration distribution and small crystal defect density by the HVPE method.

[0009] Solution for solving the problem

[0010] In order to achieve the above objectives, one aspect of the present invention provides a semiconductor substrate as described in [1], a semiconductor wafer as described in [2] to [5], and a method for manufacturing a semiconductor wafer as described in [6].

[0011] [1] A semiconductor substrate having at least one main surface as a growth substrate surface for a crystal, including a single crystal of a gallium oxide semiconductor, wherein the growth substrate surface is a (001) surface, and in a continuous region of more than 70% of the area of ​​the growth substrate surface, the angle of deviation in the

[010] direction is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°, and in the region of the growth substrate surface, the angle of deviation in the

[001] direction is in the range of greater than -1° and less than 1°, wherein the diameter of the semiconductor substrate is 2 inches or more.

[0012] [2] A semiconductor wafer comprising: a semiconductor substrate as described in [1] above; and an epitaxial film on the growth substrate surface of the semiconductor substrate, comprising a single crystal of a gallium oxide semiconductor and containing Cl from a raw material obtained by the HVPE process, wherein the density of crystal defects appearing as etch pits in the epitaxial film is less than 5 × 10⁻⁶. 4 cm -3 .

[0013] [3] According to the semiconductor wafer described in [2] above, wherein the epitaxial film is in a generated state, and the thickness distribution of the film is less than ±10% in a continuous region of more than 70% of the area of ​​the epitaxial film.

[0014] [4] The semiconductor wafer according to [2] or [3] above, wherein the epitaxial film does not contain intentionally added donors and the donor concentration distribution of the epitaxial film is less than ±40%.

[0015] [5] The semiconductor wafer according to any one of [2] to [4] above, wherein, in a continuous region covering 70% or more of the surface area of ​​the epitaxial film, the in-plane density of pits extending from the surface of the epitaxial film to the surface of the semiconductor substrate is 0.1 pits / cm². 2 the following.

[0016] [6] A method for manufacturing a semiconductor wafer includes: a step of preparing a semiconductor substrate, wherein the semiconductor substrate has at least one main surface as a growth substrate surface for a crystal, including a single crystal of a gallium oxide semiconductor, and the diameter of the semiconductor substrate is 2 inches or more; and a step of forming an epitaxial film by epitaxial growth of a single crystal of a gallium oxide semiconductor on the growth substrate surface of the semiconductor substrate using the HVPE method, wherein the growth substrate surface is a (001) surface, and in a continuous region of 70% or more of the area of ​​the growth substrate surface, the angle of deviation in the

[010] direction is in the range of greater than -0.3° and less than -0.01° or in the range of greater than 0.01° and less than 0.3°, and in the region of the growth substrate surface, the angle of deviation in the

[001] direction is in the range of greater than -1° and less than 1°.

[0017] Invention Effects

[0018] According to the present invention, a gallium oxide-based semiconductor substrate, a semiconductor wafer having the semiconductor substrate and an epitaxial film, and a method for manufacturing the semiconductor wafer are provided. The semiconductor substrate is capable of forming a gallium oxide-based epitaxial film with small film thickness distribution, small donor concentration distribution, and small crystal defect density by the HVPE method. Attached Figure Description

[0019] Figure 1 This is a vertical cross-sectional view of a semiconductor wafer according to an embodiment of the present invention.

[0020] Figure 2A This is a photograph taken from the surface side of the epitaxial film of a semiconductor wafer manufactured by setting the offset angle of the

[010] direction of the growth substrate to 0°.

[0021] Figure 2B This is a photograph taken from the surface side of the epitaxial film of a semiconductor wafer manufactured by setting the offset angle of the

[010] direction of the growth substrate to 0°.

[0022] Figure 3 This is a photograph taken from the surface side of the epitaxial film of a semiconductor wafer manufactured by setting the offset angle of the

[010] direction of the growth substrate to 0°.

[0023] Figure 4 This is a photograph taken from the surface side of the epitaxial film of a semiconductor wafer manufactured by setting the deflection angle of the

[010] direction of the growth substrate to 0.1°.

[0024] Figure 5A This is a top view showing the thickness distribution of a Ga2O3 film deposited on a sapphire substrate by the HVPE method.

[0025] Figure 5B This is a top view showing the thickness distribution of the Ga2O3 film on a sapphire substrate, which has been standardized with a thickness of 1.00 at the center.

[0026] Figure 6 This shows the corrected thickness distribution of the Ga2O3 film on a standardized sapphire substrate. Figure 2B A top view showing the thickness distribution of the epitaxial film.

[0027] Figure 7 This is a coordinate graph showing the measured donor concentrations in regions with linear and non-linear morphologies of 25 epitaxial films. Detailed Implementation

[0028] [Implementation Method]

[0029] (Configuration of Semiconductor Wafer)

[0030] Figure 1 is a vertical cross-sectional view of the semiconductor wafer 1 according to the embodiment of the present invention. The semiconductor wafer 1 includes: a semiconductor substrate 10 composed of a single crystal of a gallium oxide-based semiconductor; and an epitaxial film 20 formed by epitaxial growth on the growth base surface 11 of the semiconductor substrate 10, the epitaxial film 20 being composed of a single crystal of a gallium oxide-based semiconductor.

[0031] Here, the gallium oxide-based semiconductor refers to Ga₂O₃, or Ga₂O₃ added with elements such as Al and In. For example, the gallium oxide-based semiconductor has a composition represented by (Ga x Al y In (1 ₁₋ₓ₋ᵧ)₂O₃ (0<x≤1, 0≤y≤1, 0<x+y≤1). When Al is added to Ga₂O₃, the bandgap becomes wider, and when In is added to Ga₂O₃, the bandgap becomes narrower.

[0032] The single crystals of the gallium oxide-based semiconductor constituting the semiconductor substrate 10 and the epitaxial film 20 have a β-type crystal structure. In addition, the semiconductor substrate 10 and the epitaxial film 20 may also contain dopants such as Si and Sn.

[0033] The semiconductor substrate 10 is a substrate used as a base substrate for epitaxial crystal growth by the HVPE method. The semiconductor substrate 10 is formed, for example, by slicing a bulk crystal of a Ga₂O₃-based single crystal grown by a melt growth method such as the FZ (Floating Zone) method or the EFG (Edge Defined Film Fed Growth) method, and polishing the surface.

[0034] The epitaxial film 20 is formed by the HVPE method using a source gas containing Cl. Therefore, the epitaxial film 20 contains Cl derived from the source material of the HVPE method. The concentration of Cl contained in the epitaxial film 20 is 5×10 16 atoms / cm 3 or less. When the epitaxial film of the gallium oxide-based semiconductor is formed by a method other than the HVPE method, since a source material containing Cl is not used, Cl is usually not contained in the epitaxial film, at least not Cl of 1×10 16 cm -3 or more.

[0035] The feed gases for the epitaxial film 20 include Ga chloride gas such as GaCl gas, GaCl2 gas, GaCl3 gas, and (GaCl3)2 gas; O gas such as O2 gas and H2O gas; and dopant gas such as SiCl4 gas, GeCl4 gas, SnCl4 gas, and PbCl2 gas. Additionally, when the epitaxial film 20 contains Al or In, Al chloride gas such as AlCl is used as the Al chloride gas, or InCl gas such as InCl is used as the In chloride gas.

[0036] Furthermore, since the epitaxial film 20 is formed using the HVPE method, which has a high crystal growth rate, it can be formed to a thicker thickness, for example, 1000 nm or more. Additionally, the growth rate of the epitaxial film 20 using the industrial HVPE method is approximately 200 μm / h. In this case, a thickness up to 1000 μm can be formed within a realistic timeframe. That is, for example, an epitaxial film 20 with a thickness of 1000 nm or more but less than 1000 μm can be formed. Moreover, the crystal growth rate of gallium oxide-based semiconductor epitaxial films using the MBE method is approximately 120 nm / h, requiring more than 8 hours to form a thickness of 1000 nm or more, which is impractical in production settings.

[0037] The semiconductor substrate 10 has at least one main surface as the growth substrate surface 11 for crystals. The growth substrate surface 11 of the semiconductor substrate 10 is the (001) surface. In a continuous region of 70% or more of the area of ​​the growth substrate surface 11 (a continuous region having an area of ​​70% or more of the entire growth substrate surface 11), the angle of deviation in the

[010] direction (the tilt angle from the (001) surface) is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°. Preferably, in a continuous region of 80% or more of the area of ​​the growth substrate surface 11, and more preferably in a continuous region of 90% or more of the area of ​​the growth substrate surface 11, the angle of deviation in the

[010] direction (the tilt angle from the (001) surface) is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°. In addition, in regions where the angle of deviation in the

[010] direction (the angle of inclination from the (001) plane) is greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°, the angle of deviation in the

[001] direction is greater than -1° and less than 1°.

[0038] Furthermore, the off-angle of the growth substrate 11 can be measured using an atomic force microscope. Specifically, when the growth substrate 11 is observed with an atomic force microscope, information about the step-and-terrace structure with the (001) surface as the terrace is obtained, and the off-angle can be obtained using trigonometric functions based on the length of the terrace and the height of the step.

[0039] When a region exists where the angle of deviation of the

[001] direction of the growth substrate 11 is greater than -0.01° and less than 0.01°, a linear morphology extends from a portion of the surface 21 of the epitaxial film 20 in that region.

[0040] Figure 2A , Figure 2B , Figure 3 This is a photograph of the semiconductor wafer 1 taken from the surface 21 side of the epitaxial film 20. Figure 2A , Figure 2B The epitaxial film 20 shown is a Ga2O3 film formed under the same conditions that can suppress powder shedding (described later), and has a thickness of 3 μm and 6 μm, respectively. Figure 2A , Figure 2B The surface 21 of the epitaxial film 20 shown has a linear morphology in region A, a black roughened region in region B, and a white roughened region in region C.

[0041] Figure 3 Is Figure 2B The photograph of the semiconductor wafer 1 shown is a graph showing the values ​​of the deflection angles in the

[010] direction at nine points on the growth substrate surface 11 of the semiconductor substrate 10 under the epitaxial film 20. Figure 3 The area enclosed by the dashed circle represents the region near the 0° angle of the growth basal surface 11. Furthermore, Figure 2A , Figure 2B , Figure 3 The semiconductor substrate 10 of the semiconductor wafer 1 shown is a semiconductor substrate manufactured by setting the deflection angle of the growth substrate surface 11 in the

[010] direction to 0° (no deflection angle). The distribution of the deflection angle is caused by the processing error of slicing and grinding or the distortion of gallium oxide single crystal.

[0042] according to Figure 2A , Figure 2B , Figure 3 It can be seen that the linear morphology of the surface 21 of the epitaxial film 20 begins to extend from the portion grown on the growth substrate 11 at an angle of 0°.

[0043] Because the deposition rate of the linear portion of the epitaxial film 20 on surface 21 is low, the thickness distribution of the epitaxial film 20 increases when both linear and non-linear portions coexist on surface 21. Furthermore, the donor concentration is higher in the linear portions of the epitaxial film 20. It is presumed that the increase in donor concentration is due to the accidental introduction of Cl contained in the feedstock of the HVPE process.

[0044] If the deflection angle of the growth substrate surface 11 of the semiconductor substrate 10 in the

[010] direction is less than -0.01° or more than 0.01°, the generation of linear morphology on the surface 21 of the epitaxial film 20 can be suppressed, the in-plane difference in the film formation rate of the epitaxial film 20 will be suppressed, and thus the thickness distribution of the epitaxial film 20 in the as-grown state (the original state after growth without polishing or the like) will be suppressed to less than ±10% (the deviation of the thickness of the thickest part and the thickness of the thinnest part from their center value is less than ±10% of the center value, that is, the absolute value of the difference between the thickness of the thickest part and the thickness of the thinnest part and their center value is less than 10% of the center value). Since the deflection angle of the

[010] direction in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth substrate 11 is -0.01° or less or 0.01° or more, the thickness distribution of the epitaxial film 20 in the generated state is less than ±10% in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more). Furthermore, the thickness of the epitaxial film 20 can be measured using a Fourier transform infrared spectrophotometer (FT-IR).

[0045] Figure 4 This is a photograph taken from the surface 21 side of the epitaxial film 20 of a semiconductor wafer 1 manufactured by setting the deflection angle of the

[010] direction of the growth substrate 11 to 0.1°. Figure 4 In the semiconductor wafer 1 shown, the

[010] direction deflection angle at the nine points shown on the growth substrate surface 11 of the semiconductor substrate 10 is less than -0.01°, and the area that includes these nine points and occupies most of the growth substrate surface 11 is a white, roughened area (a region without a linear shape).

[0046] Furthermore, if the condition is used where Ga oxide powder is generated in the gas phase and adheres to the growth substrate 11 due to the gas-phase reaction of the raw material gas during film formation (hereinafter referred to as powder fallout), the Ga oxide powder will fall and accumulate on the growth substrate 11 in a distributed manner. Therefore, the in-plane deviation of the epitaxial film thickness 20 caused by the off-angle of the growth substrate 11 can be mitigated. However, due to powder fallout, the density of crystal defects appearing as etch pits increases to 5 × 10⁻⁶.4 cm -3 The above-mentioned defects cause a decrease in the withstand voltage of devices manufactured from semiconductor wafers. Therefore, semiconductor wafers manufactured under conditions that result in powder shedding cannot be put into practical use.

[0047] The density of crystal defects appearing as etching pits was obtained by etching the semiconductor wafer 1 with a 10% KOH solution heated to 85°C for 30 minutes and measuring the density of etching pits appearing on the surface of the epitaxial film 20 using a differential interference microscope.

[0048] When the epitaxial film 20 is not formed under conditions that cause powder shedding, but rather the thickness distribution in the defined region of the epitaxial film 20 is suppressed to less than ±10% by setting the deflection angle in the

[010] direction in a defined region of the growth substrate surface 11 of the semiconductor substrate 10 to -0.01° or less or 0.01° or more, the density of crystal defects caused by epitaxial growth that appear as etching pits is less than 5 × 10⁻⁶. 4 cm -3 .

[0049] Furthermore, if the deflection angle of the growth substrate surface 11 of the semiconductor substrate 10 in the

[010] direction is less than -0.01° or more than 0.01°, then almost no linear morphology can be observed on the surface 21 of the epitaxial film 20, and the accidental introduction of Cl is suppressed. Therefore, when donors are intentionally added to the epitaxial film 20, the donor concentration can be controlled more accurately. In addition, when donors are not intentionally added to the epitaxial film 20, the distribution of donor concentration in the epitaxial film 20 is less than ±40% (the deviation of the concentration of the highest concentration part and the concentration of the lowest concentration part from their center value is less than ±40% of the center value, that is, the absolute value of the difference between the concentration of the highest concentration part and the concentration of the lowest concentration part and their center value is less than 40% of the center value). Since the deflection angle of the

[010] direction in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth substrate 11 is -0.01° or less or 0.01° or more, the donor concentration distribution in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the epitaxial film 20 is less than ±40% without intentionally adding donors to the epitaxial film 20. Furthermore, the donor concentration of the epitaxial film 20 can be determined by capacitance measurement (CV measurement).

[0050] When there is a region where the angle of deviation of the growth substrate surface 11 of the semiconductor substrate 10 in the

[010] direction is less than -0.3° or more than 0.3°, deep pits (hereinafter referred to as through pits) from the surface 21 of the epitaxial film 20 to the semiconductor substrate 10 are easily generated in this region.

[0051] If the deflection angle of the growth substrate surface 11 of the semiconductor substrate 10 in the

[010] direction is within the range of greater than -0.3° and less than 0.3°, the in-plane density of the through-holes on the surface 21 of the epitaxial film 20 will be suppressed to 0.1 holes / cm². 2 The following applies. Since the angle of deviation in the

[010] direction in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth substrate 11 is within the range of greater than -0.3° and less than 0.3°, the in-plane density of through-holes in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the surface 21 of the epitaxial film 20 is 0.1 holes / cm². 2 Furthermore, the in-plane density of the through-holes contained in the epitaxial film 20 can be measured using an optical microscope.

[0052] Various effects obtained by satisfying the condition that "the angle of deviation (the tilt angle from the (001) surface) in the

[010] direction of a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth base surface 11 is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°" can be obtained as long as the angle of deviation in the

[001] direction in that region is at least in the range of greater than -1° and less than 1°.

[0053] Furthermore, the larger the diameter of the semiconductor substrate 10, the more difficult it is to satisfy the condition that "the angle of deviation (the tilt angle from the (001) plane) in the

[010] direction of a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth substrate 11 is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°", but this condition is satisfied even if the semiconductor substrate 10 is 2 inches or larger. In addition, it is possible to manufacture semiconductor substrates 10 with diameters up to 8 inches that satisfy this condition.

[0054] (Semiconductor wafer manufacturing methods)

[0055] The method for manufacturing a semiconductor wafer 1 according to an embodiment of the present invention includes: a step of preparing a semiconductor substrate 10, wherein the semiconductor substrate 10 has at least one main surface as a growth substrate surface 11 for a crystal, including a single crystal of gallium oxide semiconductor, and the diameter of the semiconductor substrate 10 is 2 inches or more; and a step of forming an epitaxial film 20 by epitaxial growth of a single crystal of gallium oxide semiconductor on the growth substrate surface 11 of the semiconductor substrate 10 by the HVPE method.

[0056] In the process of forming the epitaxial film 20, the pressure and temperature of the space in the reaction chamber of the HVPE apparatus where the semiconductor substrate 10 is placed are maintained, for example, at 0.5 to 1.5 atm and 900 to 1100°C, respectively. The raw material gas of Ga, the raw material gas of O (and, if the epitaxial film 20 contains Al, the raw material gas of Al is used; if it contains In, the raw material gas of In is used; and if it contains dopants, the raw material gas of the dopant is used) and the inert gas as a carrier gas flow into the space together, and the single crystal epitaxial growth of gallium oxide semiconductor is carried out on the growth substrate surface 11 of the semiconductor substrate 10.

[0057] Here, for example, the partial voltage of GaCl is set to 1.5 × 10⁻⁶. -3 At a speed below atm, the VI / III ratio (the supply ratio of GaCl to O) is set to 10, and the linear velocity of the gas inside the reaction chamber is set to 150 cm / s or higher to form an epitaxial film 20. This suppresses the aforementioned powder shedding and reduces the density of crystal defects caused by epitaxial growth in the epitaxial film 20, which appear as etching pits, to less than 5 × 10⁻⁶. 4 cm -3 .

[0058] Furthermore, Ga chloride gas, preferably GaCl gas, is used as the feed gas for Ga. GaCl gas is the Ga chloride gas that can maintain the growth driving force of Ga2O3 semiconductor single crystals to the highest temperature. In order to obtain high-purity, high-quality Ga2O3 semiconductor single crystals, it is effective to grow them at high growth temperatures; therefore, GaCl gas, which has a high growth driving force at high temperatures, is preferred.

[0059] Furthermore, to suppress the accidental introduction of other impurities, chloride-based gases are preferably used as the feed gas for doping. For example, when Si, Ge, Sn, or Pb, which are group 14 elements, are used as dopants, chloride-based gases such as SiCl4, GeCl4, SnCl4, and PbCl2 are used respectively. In addition, chloride-based gases are not limited to compounds that react only with chlorine; silane-based gases such as SiHCl3 can also be used.

[0060] Furthermore, if hydrogen is present in the atmosphere during the formation of the epitaxial film 20, the flatness of the surface 21 of the epitaxial film 20 and the crystal growth driving force will decrease. Therefore, hydrogen-free O2 gas is preferred as the raw material gas for O.

[0061] (Effects of the implementation method)

[0062] According to the above embodiments, by keeping the deflection angle of the growth substrate surface 11 of the semiconductor substrate 10 within a specified range, an epitaxial film 20 with small film thickness distribution, small donor concentration distribution, and small crystal defect density can be formed by the HVPE method.

[0063] Generally, a manufacturing yield of semiconductor devices within the wafer plane is required to be 60% or higher. To achieve this, the effective area of ​​the wafer (the area usable for manufacturing semiconductor devices) must be greater than 60%, for example, 70% or higher. As described above, in the semiconductor wafer 1, in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the growth substrate 11, the angle of deviation in the

[010] direction (the tilt angle from the (001) plane) is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°. Therefore, in a continuous region of 70% or more (preferably 80% or more, more preferably 90% or more) of the epitaxial film 20, the film thickness distribution, donor concentration distribution, and in-plane density of vias are small. Therefore, when the effective area of ​​the semiconductor wafer 1 is 70%, 80%, or 90% or more, the manufacturing yield of semiconductor devices can be significantly improved.

[0064] Example

[0065] Regarding the phenomena described in the above embodiments, such as "when the angle of deviation of the growth substrate 11 in the

[010] direction is in the range of greater than -0.01° and less than 0.01°, a linear morphology extends from a portion of the surface 21 of the epitaxial film 20 in that region" and "the film formation rate of the portion of the epitaxial film 20 with a linear morphology on the surface 21 is low", experimental results will be provided for explanation.

[0066] The thickness distribution of the epitaxial film 20 is caused by factors beyond the distribution of the

[010] direction offset of the growth substrate surface 11 of the semiconductor substrate 10; it is also due to manufacturing process factors. Therefore, in this embodiment, in order to accurately determine the relationship between the offset of the

[010] direction of the growth substrate surface 11 and the thickness distribution of the epitaxial film 20, the manufacturing process factors using the HVPE apparatus are first eliminated through correction.

[0067] Figure 5A This is a top view showing the thickness distribution of a Ga2O3 film deposited on a sapphire substrate with the C-plane as the main surface using the HVPE method. The in-plane distribution of the sapphire substrate's angle of deviation is within ±0.05 degrees, allowing the angle of deviation of the entire main surface to be considered almost 0°. Furthermore, it is known that the thickness distribution of the Ga2O3 film deposited on a sapphire substrate with the C-plane as the main surface is almost independent of the sapphire substrate's angle of deviation. Therefore, the thickness distribution of the Ga2O3 film on the sapphire substrate is almost entirely due to manufacturing process factors. Specifically, in the reaction chamber of the HVPE apparatus, the feed gas flows from the upper side of the figure onto the substrate, and the film thickness increases downstream of the feed gas flow (lower side of the figure).

[0068] Since the Ga2O3 film on the sapphire substrate and the epitaxial film 20 are formed using the same HVPE apparatus under the same conditions, the thickness distribution of the Ga2O3 film on the sapphire substrate can be used to correct the thickness distribution of the epitaxial film 20, and only the influence of the deflection angle of the growth substrate 11 on the thickness distribution of the epitaxial film 20 is extracted.

[0069] Figure 5B This is a top view showing the thickness distribution of the Ga2O3 film on a sapphire substrate, normalized with a thickness of 1.00 at the center. Figure 5B The normalized film thickness at various points on the Ga2O3 film on the sapphire substrate shown is used as a correction value.

[0070] Figure 6 This shows the corrected thickness distribution of the Ga2O3 film on a standardized sapphire substrate. Figure 2B A top view of the thickness distribution of the epitaxial film 20 shown. Figure 6 The values ​​at each point represent the corrected film thickness (in μm), and the values ​​in parentheses represent the original film thickness. Correction is achieved by dividing the film thickness at each point of the epitaxial film 20 by the correction value. Figure 5B The normalized film thickness of the Ga2O3 film on the sapphire substrate shown is used for this purpose.

[0071] according to Figure 6 It can be confirmed that the thickness of the linear portion of the epitaxial film 20 is smaller than that of other portions.

[0072] Next, experimental results demonstrating the phenomenon described in the above embodiments, namely, "the donor concentration increases in the linear portion of the epitaxial film 20", will be explained.

[0073] Figure 7 This is a coordinate graph showing the measured values ​​of the effective donor concentration (Nd-Na) in the regions with linear morphology (corresponding to region A above) and the regions without linear morphology (corresponding to regions B and C above) of the 25 epitaxial films 20. Figure 7 All 25 epitaxial films involved contained a concentration of 1×10⁻⁶. 16 cm -3 A trace amount of Si on the left and right.

[0074] Figure 7 The donor concentration in regions with linear morphology is shown to be higher and more significantly different from that in regions without linear morphology. This is likely because regions with linear morphology are more prone to introducing impurities that act as donors (presumably Cl contained in the feedstock of the HVPE process).

[0075] The above describes the embodiments and examples of the present invention. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made without departing from the spirit of the invention. Furthermore, the constituent elements of the above embodiments and examples can be arbitrarily combined without departing from the spirit of the invention.

[0076] Furthermore, the embodiments and examples described above do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the embodiments and examples are essential for solving the problems of the invention.

[0077] Industrial availability

[0078] A gallium oxide-based semiconductor substrate, a semiconductor wafer having the semiconductor substrate and an epitaxial film, and a method for manufacturing the semiconductor wafer are provided. The semiconductor substrate is capable of forming a gallium oxide-based epitaxial film with small film thickness distribution, small donor concentration distribution, and small crystal defect density by the HVPE method.

[0079] Explanation of reference numerals in the attached figures

[0080] 1… Semiconductor wafer, 10… Semiconductor substrate, 11… Growth substrate surface, 20… Epitaxial film, 21… Surface.

Claims

1. A semiconductor substrate, wherein at least one main surface is used as the growth substrate surface of a crystal, characterized in that, Including single crystals of gallium oxide semiconductors, The growth substrate surface is the (001) surface. In a continuous region covering more than 70% of the area of ​​the growth substrate, the deflection angle of the [010] direction is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°. In the region of the growth substrate, the deflection angle of the [001] direction is within the range of -1° to 1°. The semiconductor substrate has a diameter of 2 inches or more.

2. A semiconductor wafer, characterized in that, have: The semiconductor substrate of claim 1; and The epitaxial film on the growth substrate surface of the semiconductor substrate includes a single crystal of gallium oxide semiconductor and contains Cl from raw materials obtained by the HVPE process. The density of crystal defects appearing as etching pits in the epitaxial film is less than 5 × 10⁻⁶. 4 cm -3 .

3. The semiconductor wafer according to claim 2, wherein, The epitaxial film is in a generated state. In a continuous region of more than 70% of the area of ​​the epitaxial film, the film thickness distribution is less than ±10%.

4. The semiconductor wafer according to claim 2 or 3, wherein, The epitaxial film does not contain intentionally added donors. The donor concentration distribution of the epitaxial film is less than ±40%.

5. The semiconductor wafer according to claim 2 or 3, wherein, In a continuous region covering more than 70% of the surface area of ​​the epitaxial film, the in-plane density of pits extending from the surface of the epitaxial film to the surface of the semiconductor substrate is 0.1 pits / cm². 2 the following.

6. A method for manufacturing a semiconductor wafer, characterized in that, Include: A process for preparing a semiconductor substrate, wherein at least one main surface of the semiconductor substrate is used as a growth substrate surface for a crystal, including a single crystal of a gallium oxide semiconductor, and the diameter of the semiconductor substrate is 2 inches or more; and The process of forming an epitaxial film by epitaxial growth of a single crystal gallium oxide semiconductor on the growth substrate surface of the semiconductor substrate using the HVPE method. The growth substrate surface is the (001) surface. In a continuous region covering more than 70% of the area of ​​the growth substrate, the deflection angle of the [010] direction is in the range of greater than -0.3° and less than -0.01° or greater than 0.01° and less than 0.3°. In the region of the growth substrate, the deflection angle of the [001] direction is in the range of -1° to 1°.

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