METHOD FOR GROWING A SINGLE CRYSTAL, METHOD FOR PRODUCING A SEMICONDUCTOR SUBSTRATE AND SEMICONDUCTOR SUBSTRATE

Abstract

A method for growing a single crystal of a gallium oxide-based semiconductor is provided, comprising a step of growing a single crystal under an oxidizing atmosphere from a melt in which a raw material of the single crystal is melted. The density and average length of the voids in the single crystal are controlled by relative values ​​of the Si and Sn concentrations of the single crystal.

Description

Single crystal growth method, semiconductor substrate manufacturing method, and semiconductor substrate

[0001] The present invention relates to a method for growing a single crystal, a method for manufacturing a semiconductor substrate, and a semiconductor substrate.

[0002] Conventionally, a technique for growing a gallium oxide single crystal by the vertical Bridgman method (VB method) has been known (see, for example, Patent Document 1). Generally, the growth of a gallium oxide-based semiconductor single crystal by the vertical Bridgman method or the vertical gradient freeze (VGF) method is carried out in an oxidizing atmosphere to prevent damage to a crucible made of a Pt-based material.

[0003] Japanese Patent Application Laid-Open No. 2020-164415

[0004] In the melt growth of gallium oxide semiconductors, the melt is Ga ２ O gas and O ２ Gallium oxide is easily decomposed into gases, and if these gases are incorporated into the growing crystal, voids will form. Furthermore, due to the difference in the solubility limits of oxygen between the melt and the crystal, oxygen is expelled to the solid-liquid interface, forming bubbles, which can then be incorporated into the growing crystal, forming voids. When devices are manufactured using grown gallium oxide-based semiconductor crystals, voids can adversely affect device performance.

[0005] For example, when growing crystals of sapphire, which is a high-melting-point oxide like gallium oxide semiconductors, it is known that the density of voids in the crystal can be reduced by using a reducing gas. However, as mentioned above, the growth of gallium oxide semiconductor crystals by the VB method or the like must be carried out in an oxidizing atmosphere, and the density of voids cannot be reduced by using a reducing gas.

[0006] An object of the present invention is to provide a method for growing a single crystal of a gallium oxide-based semiconductor in an oxygen atmosphere, which is capable of controlling the state of voids in the single crystal in order to suppress the influence on the characteristics of a device manufactured using the grown single crystal, a method for manufacturing a semiconductor substrate using a single crystal grown by the growth method, and a semiconductor substrate manufactured by the manufacturing method.

[0007] In order to achieve the above object, one aspect of the present invention provides the following single crystal growth method, semiconductor substrate manufacturing method, and semiconductor substrate.

[0008] [1] A method for growing a single crystal of a gallium oxide-based semiconductor, comprising a step of growing the single crystal from a melt of raw materials of the single crystal in an oxidizing atmosphere, and controlling the density and average length of voids in the single crystal by the relative values ​​of the Si concentration and the Sn concentration of the single crystal. １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ [3] The method for growing a single crystal according to the above [1], wherein the Si concentration is controlled to be within the range of 14 to 85 μm. １８ cm －３ less than -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ , 14 to 85 μm. [4] A method for producing a semiconductor substrate made of a single crystal of a gallium oxide-based semiconductor, comprising the steps of growing the single crystal in an oxidizing atmosphere from a melt of raw materials for the single crystal, and slicing the semiconductor substrate from the single crystal, wherein the density and average length of voids in the single crystal are controlled by the relative values ​​of Si concentration and Sn concentration of the single crystal. [5] A method for producing a semiconductor substrate according to [4] above, wherein the average length of the voids is controlled according to the thickness and plane orientation of the semiconductor substrate in order to prevent the voids from penetrating between both main surfaces of the semiconductor substrate. [6] A method for producing a semiconductor substrate according to [4] above, wherein the value obtained by subtracting the Sn concentration from the Si concentration is -2.8×10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２[7] The method for manufacturing a semiconductor substrate according to the above [4] or [5], wherein the Si concentration is controlled to be within a range of 14 to 85 μm. １８ cm －３ less than -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ [8] A semiconductor substrate made of a single crystal of a gallium oxide-based semiconductor, wherein the Si concentration minus the Sn concentration is -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ The density and average length are in the range of 56 to 57,000 cm －２ [9] The semiconductor substrate according to [8], wherein the voids do not penetrate between the two main surfaces.

[10] The Si concentration is 2×10 １７ cm －３ and the Sn concentration is 2×10 １６ cm －３ The semiconductor substrate according to the above [8] or [9],

[0009] According to the present invention, it is possible to provide a method for growing a single crystal of a gallium oxide-based semiconductor in an oxygen atmosphere, which is capable of controlling the state of voids in the single crystal in order to suppress the influence on the characteristics of a device manufactured using the grown single crystal, a method for manufacturing a semiconductor substrate using a single crystal grown by the growth method, and a semiconductor substrate manufactured by the manufacturing method.

[0010] FIG. 1 is a vertical cross-sectional view schematically showing the configuration of a single crystal growth apparatus used in the VB method. FIG. 2 is an optical microscope image of a cross section of a semiconductor substrate having a (010) plane as a main surface according to this embodiment. FIG. 3 is an optical microscope image of the cross sections of four types of semiconductor substrates according to this embodiment. FIG. 4 is a graph showing the relationship between the concentrations of dopants Si and Sn and the density of voids in a semiconductor substrate. FIG. 5 is a graph showing the relationship between the concentrations of dopants Si and Sn and the average length of voids in a semiconductor substrate. FIG. 6 is a graph showing the relationship between the density and average length of voids in a semiconductor substrate.

[0011] A method for growing a single crystal according to an embodiment of the present invention (hereinafter referred to as the present growth method) is a method for growing a single crystal of a gallium oxide-based semiconductor, which includes a step of growing the single crystal from a melt of single crystal raw materials in an oxidizing atmosphere, and controls the density and average length of voids in the single crystal by the relative values ​​of the Si concentration and the Sn concentration of the single crystal. ２ O ３ β-Ga containing substitutional impurities such as Al and In, or dopants such as Sn and Si ２ O ３ This refers to the following.

[0012] This growth method uses a method for growing a single crystal of a gallium oxide-based semiconductor in an oxygen atmosphere, such as the vertical Bridgman method (VB method) or the vertical gradient freeze method (VGF method).

[0013] In these methods, the melt becomes Ga-rich (has a high Ga ratio) under a reducing atmosphere. Therefore, when a crucible made of a Pt-based material such as PtRh or PtIr is used, the crucible and Ga are alloyed, lowering the melting point of the crucible, which may cause the crucible to break during growth and leak the melt.

[0014] In this growth method, single crystals are grown in an oxygen atmosphere, so it is not possible to reduce the void density using a reducing gas during growth, as is the case with sapphire single crystals. Therefore, the inventors, through extensive research, discovered that the density and average length of voids in a single crystal can be controlled by adjusting the relative values ​​of the Si and Sn concentrations in the single crystal. This growth method utilizes a technique for controlling the density and length of voids in a single crystal to suppress the adverse effects of voids.

[0015] When cutting a semiconductor substrate from a grown single crystal, it is particularly important to avoid voids penetrating between the two main surfaces (front and back) of the semiconductor substrate. A high-quality epitaxial film cannot be formed on the portion where a void exists that penetrates between the two main surfaces, and abnormal regions in the epitaxial film formed locally by the voids become paths for leakage current. On the other hand, the higher the density of voids in a single crystal, the greater the impact on the characteristics of devices manufactured using that single crystal, so a low density of voids in the single crystal is preferable.

[0016] In this growth method, for example, the value obtained by subtracting the Sn concentration from the Si concentration of the single crystal is −2.8×10 １８ ~3.0 x 10 １８ cm －３ By adjusting the void density and average length in the single crystal within the range of 56 to 57,000 cm －２ The Si concentration of the single crystal minus the Sn concentration is −2.8×10 １８ ~3.0 x 10 １８ cm －３ In order to keep the concentration within this range, for example, the concentrations of Si and Sn in the raw materials for the single crystal are adjusted to fall within the ranges of 0 to 0.03 atomic % and 0 to 0.1 atomic % relative to Ga, respectively.

[0017] Here, as the density of voids in a single crystal decreases, the length of the voids increases, and conversely, as the length of voids in a single crystal decreases, the density tends to increase. For this reason, for example, the density and length of voids in a single crystal can be controlled so that the density is as low as possible within a range in which the voids have a length that makes it difficult for them to penetrate between the two main surfaces of a semiconductor substrate cut out from the single crystal.

[0018] Voids that occur in a single crystal of a gallium oxide-based semiconductor are needle-shaped voids that extend in the

[010] direction of the gallium oxide-based semiconductor crystal. Therefore, when a semiconductor substrate having a (010) plane as its main surface, with the thickness direction being the

[010] direction, is cut out from the single crystal, the voids are most likely to penetrate between the two main surfaces. In this case, for example, by controlling the average length of the voids to be shorter than the thickness of the semiconductor substrate, it is possible to prevent the voids from penetrating between the two main surfaces.

[0019] When a semiconductor substrate having a main surface that is inclined largely from the (010) plane is cut out from a single crystal, the inclination of the direction in which the voids extend from the thickness direction of the semiconductor substrate becomes large, and therefore the length of the voids can be set large to prevent the voids from penetrating between the two main surfaces.

[0020] In this way, in the present growth method, in order to prevent voids contained in the semiconductor substrate from penetrating between the two main surfaces of the semiconductor substrate, the relative values ​​of the Si concentration and Sn concentration in the single crystal are adjusted, and the average length of voids in the single crystal can be controlled according to the thickness and plane orientation of the semiconductor substrate.

[0021] As an example, a method for growing a single crystal by the VB method will be described below.

[0022] 1 is a vertical cross-sectional view showing a schematic configuration of a single crystal growth apparatus 1 used in the VB method. The single crystal growth apparatus 1 includes a crucible 10, a susceptor 11 that is movable in the vertical direction and supports the crucible 10 from below, a tubular furnace tube 14 that surrounds the crucible 10, the susceptor 11, and a crucible support shaft 12, a heater 13 installed outside the furnace tube 14, and a housing 15 made of a heat insulating material that houses these components of the single crystal growth apparatus 1.

[0023] The crucible 10 has a seed crystal section 101 that accommodates a seed crystal 20, and a growth crystal section 102 located above the seed crystal section 101 that crystallizes the accommodated raw material melt 21 to grow a single crystal 22 of a gallium oxide-based semiconductor.

[0024] As shown in FIG. 1 , the grown crystal portion 102 typically includes a constant diameter portion having a constant inner diameter larger than the inner diameter of the seed crystal portion 101, and an increasing diameter portion located between the constant diameter portion and the seed crystal portion 101, the inner diameter of which increases from the seed crystal portion 101 side toward the constant diameter portion side.

[0025] The crucible 10 has a shape and size corresponding to the shape and size of the single crystal 22 to be grown. For example, when growing a single crystal 22 whose constant diameter portion is cylindrical and has a diameter of 2 inches, a crucible 10 is used in which the growing crystal portion 102 has a cylindrical constant diameter portion with an inner diameter of 2 inches. When growing a single crystal 22 whose constant diameter portion has a shape other than cylindrical, for example, a square or hexagonal prism, a crucible 10 is used in which the growing crystal portion 102 has a square or hexagonal prism-shaped constant diameter portion. A lid may be used to cover the opening of the crucible 10.

[0026] The crucible 10 is made of a material that has heat resistance sufficient to withstand the temperature of the molten gallium oxide semiconductor, which is the raw material melt 21 (a temperature equal to or higher than the melting point of the gallium oxide semiconductor), and that does not easily react with the molten gallium oxide semiconductor, such as a PtRh alloy.

[0027] The susceptor 11 is a tubular member that surrounds the seed crystal portion 101 of the crucible 10 and supports the crucible 10 from below. The susceptor 11 has heat resistance that allows it to withstand the growth temperature of a gallium oxide-based semiconductor single crystal, and is made of a material that does not react with the crucible 10 at that growth temperature, such as zirconia or alumina.

[0028] A crucible support shaft 12 is connected to the underside of the susceptor 11, and by moving the crucible support shaft 12 up and down by a drive mechanism (not shown), the susceptor 11 and the crucible 10 supported by the susceptor 11 can be moved up and down. The crucible support shaft 12 may be rotatable about a vertical axis by the drive mechanism. In this case, the crucible 10 supported by the susceptor 11 can be rotated inside the furnace tube 14.

[0029] The crucible support shaft 12 is typically a tubular member, similar to the susceptor 11. In this case, a thermocouple for measuring the temperature of the crucible 10 can be passed through the inside of the susceptor 11 and the crucible support shaft 12. The crucible support shaft 12 is made of a heat-resistant material that can withstand the growth temperature of a gallium oxide-based semiconductor single crystal, such as zirconia or alumina.

[0030] The heater 13 is a heater for melting the raw material of a gallium oxide-based semiconductor contained in the grown crystal portion 102 of the crucible 10 to obtain a raw material melt 21. The heater 13 is inserted into the housing 15 through a hole provided in the housing 15, and is connected to an external device (not shown) outside the housing 15 for supplying current to the heater 13. The heater 13 is typically made of MoSi ２ MoSi ２ It is a heater. MoSi ２ The heater has excellent oxidation resistance and heat resistance, and can be used in an oxidizing atmosphere at a high temperature of approximately 1800° C., which is necessary for growing single crystals of gallium oxide-based semiconductors.

[0031] The furnace tube 14 is used to adjust the heat flow around the crucible 10 and to prevent the introduction of impurities such as Si and Mo from the heater 13. The furnace tube 14 is typically cylindrical. As shown in FIG. 1 , a lid 17 may be provided at the upper opening of the furnace tube 14. The use of the lid 17 prevents heat from escaping upward from the periphery of the crucible 10. The furnace tube 14 and the lid 17 are made of a heat-resistant material that can withstand the growth temperature of a gallium oxide-based semiconductor single crystal, such as zirconia or alumina.

[0032] (Single Crystal Growth Process) First, a gallium oxide-based semiconductor seed crystal 20 is placed in the seed crystal portion 101 of the crucible 10, and a raw material for a gallium oxide-based semiconductor single crystal is placed in the growing crystal portion 102. Here, for example, the concentrations of Si and Sn in the raw material for the single crystal are adjusted to within the ranges of 0 to 0.03 atomic % and 0 to 0.1 atomic % relative to Ga, respectively. The raw material for the single crystal may be, for example, SiO as a Si raw material. ２ powder or SiC powder and SnO as Sn raw material ２ The powder was ２ O ３ Ga doped with Si and Sn, mixed with powder and heated ２ O ３ A sintered body of Ga can be used. ２ O ３ sintered body, SiO ２ Or a sintered body of SiC and SnO ２ The sintered body may be used as a raw material for the single crystal.

[0033] Next, the inside of the single crystal growth apparatus 1 (inside the housing 15) is heated by the heater 13, creating a temperature gradient in which the temperature is higher at the top and lower at the bottom, and the single crystal raw material in the crucible 10 is melted to obtain raw material melt 21.

[0034] In a typical method, first, the crucible support shaft 12 is moved up and down to adjust the height of the crucible 10 so that the temperature of the upper region in the growing crystal section 102 is equal to or higher than the melting point of gallium oxide. This melts a portion of the upper portion of the raw material in the growing crystal section 102. Next, the crucible support shaft 12 is moved upward at a predetermined speed, and the crucible 10 is raised at the same speed, melting the raw material all the way down to the bottom, until the entire raw material and a portion of the seed crystal are melted.

[0035] Next, the crucible support shaft 12 is moved downward, and the crucible 10 is lowered at a predetermined speed, while the raw material melt 21 is crystallized from the bottom (the seed crystal 20 side) to grow a single crystal 22. The single crystal growth is performed in an oxidizing atmosphere. After the raw material melt 21 has entirely crystallized, the single crystal 22 is removed from the crucible 10.

[0036] The obtained single crystal 22 is then sliced ​​in the desired direction at the desired intervals using a multi-wire saw or the like, and the surface is polished to obtain a semiconductor substrate of the desired thickness and with the desired plane orientation as the main surface.

[0037] (Evaluation Results) The following are the results of the β-Ga grown by the VB method. ２ O ３ The results of various evaluations performed on semiconductor substrates cut out from single crystals (hereinafter simply referred to as semiconductor substrates) are shown below.

[0038] Table 1 below shows the concentrations of Si and Sn contained in the five types of semiconductor substrates produced for this evaluation, and the charged concentrations of Si and Sn in the single crystal raw material from which the semiconductor substrates were cut. "Si charged concentration" and "Sn charged concentration" in Table 1 are the charged concentrations of Si and Sn in the single crystal raw material, respectively. "Si-Sn concentration" means the Si concentration minus the Sn concentration. Also, "UID: Unintentional Doped" means that no dopant was intentionally added.

[0039]

[0040] In this evaluation, as shown in Table 1, the concentrations of Si and Sn that are not intentionally added are 2×10 as the concentrations of Si and Sn that are inevitably mixed into the semiconductor substrate. １７ cm －３ and 2 x 10 １6 cm －３ It was as follows.

[0041] According to Table 1, the Si concentration is 2×10 １８ cm －３ and a sample with a Si concentration of 3 × 10 １８ cm －３ The Si loading concentrations of the samples are the same, 0.03 at %, because these two samples were cut out from regions of the same single crystal with different Si concentrations.

[0042] 2 is an image of a cross section of a semiconductor substrate having a (010) plane as a main surface according to this embodiment, observed by an optical microscope. The cross section shown in FIG. 2 is a (100) plane, and the vertical direction of the image in FIG. 2 is β-Ga.​２ O ３ This is the

[010] direction of the single crystal. As can be seen from Figure 2, a plurality of needle-shaped voids extending in the

[010] direction are contained in the semiconductor substrate.

[0043] 3 shows optical microscope images of the cross sections of four types of semiconductor substrates according to this embodiment. The upper left image is the same as that shown in FIG. 2, and is an image of the (100) cross section of a semiconductor substrate having a (010) plane as the main surface, to which no dopant has been intentionally added. The upper right image is an image of the (100) cross section of a semiconductor substrate having a concentration of 3×10 １８ cm －３ The lower left image shows a (100) cross section of a semiconductor substrate having a (010) plane as the main surface, which contains Si. １８ cm －３ The image at the bottom right shows a (100) cross section of a semiconductor substrate having a (011) plane as the main surface, which contains Sn. １７ cm －３ of Si and concentration 3 × 10 １８ cm －３ 1 is an observation image of a (100) cross section of a semiconductor substrate having a (011) plane containing Sn as a main surface.

[0044] It can be seen from FIG. 3 that the density and size of voids in a semiconductor substrate differ depending on the type of dopant contained in the semiconductor substrate, ie, Si, Sn, or both Si and Sn.

[0045] Figure 4 is a graph showing the relationship between the concentrations of dopants Si and Sn and the density of voids in a semiconductor substrate. The horizontal axis of Figure 4, "Si-Sn concentration," represents the Si concentration minus the Sn concentration. The density of voids in the semiconductor substrate was calculated by counting the number of voids in a specified region of the (100) cross section. The area of ​​the specified region is shown as "Observed Area" in Table 2 below.

[0046] FIG. 4 shows that at least the Si—Sn concentration is −2.8×10 １８ ~3.0 x 10 １８ cm －３ This shows that, within this range, as the Si concentration relative to the Sn concentration increases, the void density decreases, and as the Sn concentration relative to the Si concentration increases, the void density increases.

[0047] Figure 5 is a graph showing the relationship between the concentration of dopants Si and Sn and the average length of voids in a semiconductor substrate. The horizontal axis of Figure 5, "Si-Sn concentration," represents the Si concentration minus the Sn concentration. The average length of voids in a semiconductor substrate was obtained by measuring the lengths of voids in a specified region of the (100) cross section and averaging them.

[0048] FIG. 5 shows that at least the Si—Sn concentration is −2.8×10 １８ ~3.0 x 10 １８ cm －３ This shows that, within this range, as the Si concentration relative to the Sn concentration increases, the average length of the voids increases, and as the Sn concentration relative to the Si concentration increases, the average length of the voids decreases.

[0049] The following Table 2 shows the "Si-Sn concentration" of the evaluated semiconductor substrate, the corresponding void density and average length, and the observed area of ​​the cross section of the semiconductor substrate used to calculate the void density and average length, and the number of voids observed.

[0050]

[0051] The results shown in Figures 4 and 5 indicate that the density and average length of voids contained in the single crystal and the semiconductor substrate cut out therefrom can be controlled by the magnitude of the value obtained by subtracting the Sn concentration from the Si concentration. On the other hand, the donor concentration of the single crystal and the semiconductor substrate depends on the sum of the Si concentration and the Sn concentration. Therefore, by intentionally adding both Si and Sn, it is possible to control the density and average length of voids while obtaining a desired donor concentration. Note that when Si and Sn are intentionally added, the respective concentrations of Si and Sn are higher than the concentrations of unintentional addition, for example, the Si concentration is 2 x 10 １７ cm －３ , Sn concentration is 2 × 10 １６ cm －３ The donor concentration of the single crystal and the semiconductor substrate is specifically the sum of the Si concentration and the Sn concentration minus the concentration of Fe, which compensates for the donor. This Fe is mixed into the single crystal from the crucible 10, and is present in the single crystal and the semiconductor substrate at a concentration of approximately 1×10​１７ cm －３ It is present in the following concentrations:

[0052] 6 is a graph showing the relationship between the density and average length of voids in a semiconductor substrate. －２ , which shows that within the range of 14 to 85 μm of average void length, the smaller the void density, the larger the average void length, and conversely, the smaller the average void length, the larger the void density.

[0053] According to the above evaluation results, at least the value obtained by subtracting the Sn concentration from the Si concentration is −2.8×10 １８ ~3.0 x 10 １８ cm －３ The density and average length are in the range of 56 to 57,000 cm －２ It can be seen that it is possible to manufacture a semiconductor substrate containing voids in the range of 14 to 85 μm. Furthermore, by controlling the average length of voids in the single crystal depending on the thickness and plane orientation of the semiconductor substrate, it is also possible to obtain a semiconductor substrate in which voids do not penetrate between the two main surfaces.

[0054] The Si concentration is 4.0×10 １８ cm －３ It has been confirmed that when the Si concentration is 4.0×10 or more, huge voids, which are thought to be a collection of multiple voids, tend to occur in the single crystal. １８ cm －３ If the Si concentration is more than 1000 kJ / cm, the relationship between the value obtained by subtracting the Sn concentration from the Si concentration and the void density, and the relationship between the value obtained by subtracting the Sn concentration from the Si concentration and the average length of the voids may no longer hold. １８ cm －３ If the Si concentration is 4.0 × 10 or less, large voids will not occur in the single crystal, and the relationship between the value obtained by subtracting the Sn concentration from the Si concentration and the void density, and the relationship between the value obtained by subtracting the Sn concentration from the Si concentration and the average length of the voids will certainly hold. １８ cm －３ Preferably, it is smaller than 3.0×10 １８ cm －３More preferably, it is:

[0055] The above evaluations were carried out using β-Ga, a typical example of a gallium oxide semiconductor. ２ O ３ However, similar results can be obtained when evaluating semiconductor substrates cut from single crystals of other gallium oxide-based semiconductors. Furthermore, similar results can be obtained when evaluating semiconductor substrates cut from single crystals grown by methods other than the VB method that grow single crystals in an oxygen atmosphere, such as the VGF method.

[0056] Effect of the embodiment According to the above-described embodiment of the present invention, in a method for growing a single crystal in an oxygen atmosphere in which the void density cannot be reduced by a reducing gas, the density and length of voids contained in the grown gallium oxide-based semiconductor single crystal can be controlled, and the influence of the voids on the characteristics of devices manufactured using semiconductor substrates, etc., cut out from the single crystal can be suppressed.

[0057] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible within the scope of the gist of the invention. Furthermore, the components of the above embodiments can be combined as desired within the scope of the gist of the invention. Furthermore, the above-described embodiments do not limit the invention according to the claims. Furthermore, it should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

[0058] The present invention provides a method for growing a single crystal of a gallium oxide-based semiconductor in an oxygen atmosphere, which is capable of controlling the state of voids in the single crystal in order to suppress the influence on the characteristics of a device manufactured using the grown single crystal; a method for manufacturing a semiconductor substrate using the single crystal grown by the growth method; and a semiconductor substrate manufactured by the manufacturing method.

[0059] REFERENCE SIGNS LIST 1...single crystal growth apparatus, 10...crucible, 101...seed crystal section, 102...growth crystal section, 11...susceptor, 13...heater, 20...seed crystal, 21...raw material melt, 22...single crystal

Claims

1. A method for growing a single crystal of a gallium oxide-based semiconductor, comprising the steps of growing the single crystal in an oxidizing atmosphere from a melt of raw materials for the single crystal, and controlling the density and average length of voids in the single crystal by the relative values ​​of the Si concentration and the Sn concentration of the single crystal.

2. The value obtained by subtracting the Sn concentration from the Si concentration is -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ 2. The method for growing a single crystal according to claim 1, wherein the thickness is controlled within a range of 14 to 85 μm.

3. The Si concentration is 4.0 × 10 １８ cm －３ less than -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ 2. The method for growing a single crystal according to claim 1, wherein the thickness is controlled within a range of 14 to 85 μm.

4. A method for manufacturing a semiconductor substrate made of a single crystal of a gallium oxide-based semiconductor, comprising: growing the single crystal in an oxidizing atmosphere from a melt of a raw material of the single crystal; and cutting out the semiconductor substrate from the single crystal; and controlling the density and average length of voids in the single crystal by the relative values ​​of the Si concentration and Sn concentration of the single crystal.

5. The method for manufacturing a semiconductor substrate according to claim 4, wherein the average length of the voids is controlled according to the thickness and surface orientation of the semiconductor substrate in order to prevent the voids from penetrating between both main surfaces of the semiconductor substrate.

6. The value obtained by subtracting the Sn concentration from the Si concentration is -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ 6. The method for manufacturing a semiconductor substrate according to claim 4, wherein the thickness is controlled within a range of 14 to 85 μm.

7. The Si concentration is 4.0 × 10 １８ cm －３ less than -2.8 × 10 １８ ~3.0 x 10 １８ cm －３ By adjusting the density and average length of the voids within the range of 56 to 57,000 cm －２ 6. The method for manufacturing a semiconductor substrate according to claim 4, wherein the thickness is controlled within a range of 14 to 85 μm.

8. A semiconductor substrate made of a single crystal of a gallium oxide semiconductor, in which the value obtained by subtracting the Sn concentration from the Si concentration is -2.8 x 10 １８ ~3.0 x 10 １８ cm －３ The density and average length are in the range of 56 to 57,000 cm －２ , a semiconductor substrate containing voids in the range of 14 to 85 μm.

9. The semiconductor substrate according to claim 8, wherein the voids do not penetrate between the two main surfaces.

10. The Si concentration is 2×10 １７ cm －３ and the Sn concentration is 2×10 １６ cm －３ The semiconductor substrate according to claim 8 or 9, wherein the thickness of the semiconductor substrate is higher than the thickness of the semiconductor substrate.

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