Method for growing single crystal, method for manufacturing semiconductor substrate, and semiconductor substrate
Patent Information
- Application Number
- JP2022156772
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-09-29
- Publication Date
- 2025-03-07
- Estimated Expiration
- 2042-09-29
AI Technical Summary
The growth of gallium oxide semiconductor crystals using the VB method or VGF method in an oxidizing atmosphere leads to void formation due to the decomposition of Ga2O3 and O2 gases, which affects device characteristics.
A method for growing gallium oxide semiconductor single crystals in an oxidizing atmosphere by controlling the density and average length of voids through the relative concentrations of Si and Sn, adjusting the Si concentration to be less than -2.8×10^18 cm^-3 and the Sn concentration to be within 0 to 0.1 atomic % relative to Ga, to prevent voids from penetrating between the main surfaces of the semiconductor substrate.
This method effectively reduces the impact of voids on device characteristics by controlling void density and length, ensuring high-quality epitaxial film formation and preventing leakage current paths.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a method for growing a single crystal, a method for producing a semiconductor substrate, and a semiconductor substrate. [Background technology]
[0002] Conventionally, a technique for growing a gallium oxide single crystal by the vertical Bridgman method (VB method) is known (see, for example, Patent Document 1). In general, the growth of a single crystal of a gallium oxide-based semiconductor 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. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] JP 2020-164415 A Summary of the Invention [Problem to be solved by the invention]
[0004] In the melt growth of gallium oxide semiconductors, the melt is easily decomposed into Ga2O gas and O2 gas, and when these gases are incorporated into the crystal being grown, voids are formed. In addition, oxygen is expelled to the solid-liquid interface due to the difference in the solid solubility limit of oxygen between the melt and the crystal, forming bubbles, which may be incorporated into the growing crystal and become voids. When devices are manufactured using the grown gallium oxide semiconductor crystals, the voids may affect the device characteristics.
[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 crystals 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 effect 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 said growth method, and a semiconductor substrate manufactured by said manufacturing method. [Means for solving the problem]
[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 the steps of growing the single crystal in an oxidizing atmosphere from a melt of a raw material of the single crystal, and controlling the density and average length of voids in the single crystal by the relative values of Si concentration and Sn concentration of the single crystal. [2] The value obtained by subtracting the Sn concentration from the Si concentration is -2.8×10 18 ~3.0×10 18 cm -3 By adjusting the density and average length of the voids within the range of 56 to 57,000 cm -2 The method for growing a single crystal according to the above [1], wherein the diameter of the crystal 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 ~3.0×10 18 cm -3 By adjusting the density and average length of the voids within the range of 56 to 57,000 cm -2 The method for growing a single crystal according to the above-mentioned [1], wherein the diameter of the crystal 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 the steps of: 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, 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 manufacturing a semiconductor substrate according to the above [4], further comprising controlling an average length of the voids according to a thickness and a 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 ~3.0×10 18 cm -3 By adjusting the density and average length of the voids within the range of 56 to 57,000 cm -2 The method for producing a semiconductor substrate according to the above [4] or [5], wherein the thickness is controlled within a range of 14 to 85 μm. [7] The silicon concentration is 4.0×10 18 cm -3 less than -2.8×10 18 ~3.0×10 18 cm -3 By adjusting the density and average length of the voids within the range of 56 to 57,000 cm -2 The method for producing a semiconductor substrate according to the above [4] or [5], 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 Si concentration minus the Sn concentration is -2.8 × 10 18 ~3.0×10 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 [8] above, wherein the void does not penetrate between both main surfaces.
[10] The Si concentration is 2×10 17 cm -3 The Sn concentration is higher than 2×1016 cm -3 The semiconductor substrate according to the above [8] or [9], Effect of the Invention
[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 effect 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. [Brief description of the drawings]
[0010] [Figure 1] FIG. 1 is a vertical sectional view showing a schematic configuration of a single crystal growth apparatus used in the VB method. [Diagram 2] FIG. 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 with an optical microscope. [Diagram 3] FIG. 3 shows images of cross sections of four types of semiconductor substrates according to this embodiment observed with an optical microscope. [Figure 4] FIG. 4 is a graph showing the relationship between the concentration of dopants Si and Sn and the density of voids in a semiconductor substrate. [Diagram 5] FIG. 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. [Figure 6] FIG. 6 is a graph showing the relationship between the density and average length of voids in a semiconductor substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[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. Here, the gallium oxide-based semiconductor refers to β-Ga2O3 or β-Ga2O3 containing substitutional impurities such as Al, In, or dopants such as Sn, Si.
[0012] This growth method uses a method for growing single crystals of gallium oxide-based semiconductors 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 form an alloy, 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, the single crystal is grown in an oxygen atmosphere, so it is not possible to reduce the density of voids by using a reducing gas during growth, as is the case with sapphire single crystals. As a result of intensive research, the inventors have found that the density and average length of voids in a single crystal can be controlled by the relative values of the Si concentration and Sn concentration of the single crystal. In this growth method, the technology for controlling the density and length of voids in the single crystal is used to suppress the adverse effects of voids.
[0015] When cutting out a semiconductor substrate from a grown single crystal, it is particularly important to avoid voids penetrating between both main surfaces (between the front and back surfaces) of the semiconductor substrate. A quality epitaxial film cannot be formed on the portion where a void that penetrates between both main surfaces exists, 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 a device manufactured using that single crystal, so it is preferable for the density of voids in the single crystal to be low.
[0016] In this growth method, for example, the Si concentration of a single crystal minus the Sn concentration is −2.8×10 18 ~3.0×10 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 ~3.0×10 18 cm -3 In order to fall within this range, 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.
[0017] Here, when the density of voids in the single crystal is low, the length of the voids tends to be large, and conversely, when the length of the voids in the single crystal is small, the density tends to be high. For this reason, for example, the density and length of the voids in the 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 both 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
[0010] direction of the gallium oxide-based semiconductor crystal. For this reason, when a semiconductor substrate having a main surface as a (010) plane, in which the thickness direction is the
[0010] direction, is cut out from the single crystal, the voids are most likely to penetrate between both main surfaces. In this case, for example, by controlling the average length of the voids to be smaller than the thickness of the semiconductor substrate, it is possible to prevent the voids from penetrating between both main surfaces.
[0019] When a semiconductor substrate having a main surface that is largely inclined from the (010) plane is cut out from a single crystal, the inclination of the extension direction of the void from the thickness direction of the semiconductor substrate becomes large, so the length of the void can be set large to prevent the void 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 the Sn concentration in the single crystal are adjusted, making it possible to control the average length of the voids in the single crystal in accordance with 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] (Single crystal growth equipment) 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 thermal 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 comprises 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 and having an inner diameter that increases from the seed crystal portion 101 side toward the constant diameter portion side.
[0025] The crucible 10 has a shape and size according to the shape and size of the single crystal 22 to be grown. For example, when growing a single crystal 22 having a cylindrical constant diameter portion with a diameter of 2 inches, a crucible 10 is used in which the grown crystal portion 102 has a cylindrical constant diameter portion with an inner diameter of 2 inches. When growing a single crystal 22 having a constant diameter portion with a shape other than cylindrical, for example, a square or hexagonal columnar shape, a crucible 10 is used in which the grown crystal portion 102 has a square or hexagonal columnar constant diameter portion. A lid for covering the opening of the crucible 10 may be used.
[0026] The crucible 10 is made of a material that has heat resistance sufficient to withstand the temperature of the gallium oxide based semiconductor melt, which is the raw material melt 21 (a temperature equal to or higher than the melting point of the gallium oxide based semiconductor) and does not easily react with the gallium oxide based semiconductor melt, 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 is made of a material that has heat resistance capable of withstanding the growth temperature of a single crystal of a gallium oxide-based semiconductor and does not react with the crucible 10 at the growth temperature, such as zirconia or alumina.
[0028] A crucible support shaft 12 is connected to the underside of the susceptor 11, and the susceptor 11 and the crucible 10 supported by the susceptor 11 can be moved up and down by moving the crucible support shaft 12 up and down by a drive mechanism (not shown). The crucible support shaft 12 may be capable of rotating about an axis in the vertical direction 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 material having heat resistance capable of withstanding the growth temperature of a single crystal of a gallium oxide-based semiconductor, such as zirconia or alumina.
[0030] The heater 13 is a heater for melting the raw material of the gallium oxide-based semiconductor contained in the grown crystal portion 102 of the crucible 10 to obtain the 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 a current to the heater 13. The heater 13 is typically a MoSi2 heater, which is a resistance heating element made of MoSi2. The MoSi2 heater has excellent oxidation resistance and heat resistance, and can be used in a high-temperature oxidizing atmosphere of about 1800°C, which is necessary for growing a single crystal of a gallium oxide-based semiconductor.
[0031] The furnace tube 14 is used to adjust the flow of heat around the crucible 10 and to suppress the intrusion 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 can suppress the heat around the crucible 10 from escaping upward. The furnace tube 14 and the lid 17 are made of a heat-resistant material capable of withstanding the growth temperature of a single crystal of a gallium oxide-based semiconductor, such as zirconia or alumina.
[0032] (Single crystal growth process) First, the seed crystal 20 of the gallium oxide semiconductor is accommodated in the seed crystal portion 101 of the crucible 10, and the raw material of the single crystal of the gallium oxide semiconductor is accommodated in the grown crystal portion 102. Here, for example, the charged concentrations of Si and Sn in the raw material of the single crystal are adjusted within the ranges of 0 to 0.03 atomic % and 0 to 0.1 atomic % with respect to Ga, respectively. As the raw material of the single crystal, for example, a sintered body of Ga2O3 to which Si or Sn is added can be used, which is obtained by mixing SiO2 powder or SiC powder as a Si raw material or SnO2 powder as a Sn raw material with Ga2O3 powder and heating it. In addition, a sintered body of Ga2O3, a sintered body of SiO2 or SiC, and a sintered body of SnO2 may be used as the raw material of the single crystal.
[0033] Next, the inside of the single crystal growth apparatus 1 (the inside of the housing 15) is heated by the heater 13 to form 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 grown crystal section 102 is equal to or higher than the melting point of gallium oxide. This melts an upper part of the raw material in the grown crystal section 102. Next, the crucible support shaft 12 is moved upward at a predetermined speed to raise the crucible 10 at a predetermined speed while melting the raw material down to the bottom, and finally melting the entire raw material and part of the seed crystal.
[0035] Next, the crucible support shaft 12 is moved downward to lower the crucible 10 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 above single crystal growth is performed in an oxidizing atmosphere. After the raw material melt 21 is entirely crystallized, the single crystal 22 is taken out of the crucible 10.
[0036] The obtained single crystal 22 is then sliced in a desired direction at desired intervals using a multi-wire saw or the like, and the surface is polished to obtain a semiconductor substrate of a desired thickness and having a principal surface with a desired plane orientation.
[0037] (Evaluation Results) The following are the results of various evaluations performed on the semiconductor substrate (hereinafter simply referred to as the semiconductor substrate) cut out from the β-Ga2O3 single crystal obtained by this growth method using the VB method.
[0038] Table 1 below shows the concentrations of Si and Sn contained in the five types of semiconductor substrates manufactured for this evaluation, and the Si and Sn feed concentrations in the single crystal raw material from which the semiconductor substrates were cut. "Si feed concentration" and "Sn feed concentration" in Table 1 are the Si feed concentration and Sn feed concentration in the single crystal raw material, respectively. "Si-Sn concentration" refers to the Si concentration minus the Sn concentration. Additionally, "UID: Unintentional Doped" means that the dopant was not intentionally added.
[0039] JPEG2024050122000002.jpg60170
[0040] In this evaluation, as shown in Table 1, the concentrations of Si and Sn that are not intentionally added are 2×10 17 cm -3 and 2×10 16 cm -3 The results were 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 the two samples were cut from regions of the same single crystal with different Si concentrations.
[0042] Fig. 2 is an image of a cross section of a semiconductor substrate having a (010) plane as a main surface according to the present embodiment, observed by an optical microscope. The cross section shown in Fig. 2 is a (100) plane, and the up-down direction of the image in Fig. 2 is the
[0010] direction of the β-Ga2O3 single crystal. Fig. 2 shows that a plurality of needle-like voids extending in the
[0010] direction are included in the semiconductor substrate.
[0043] Fig. 3 shows images of the cross sections of four types of semiconductor substrates according to this embodiment observed by an optical microscope. The image on the upper left 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 image on the upper right shows the cross section of a semiconductor substrate having a concentration of 3 × 10 18 cm -3 The bottom left image shows a (100) cross section of a semiconductor substrate with a (010) surface containing Si. 18 cm -3 The bottom right image shows a (100) cross section of a semiconductor substrate with a (011) surface containing Sn. 17 cm -3 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] From FIG. 3, it can be seen that the density and size of voids in the semiconductor substrate vary 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," refers to 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] Figure 4 shows that the Si-Sn concentration is at least -2.8×10 18 ~3.0×10 18 cm -3 This shows that within this range, as the Si concentration increases relative to the Sn concentration, the void density decreases, and as the Sn concentration increases relative to the Si concentration, 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," means the Si concentration minus the Sn concentration. The average length of voids in a semiconductor substrate was obtained by measuring the length of voids in a specified area of the (100) cross section and taking the average value.
[0048] Figure 5 shows that the Si-Sn concentration is at least -2.8×10 18 ~3.0×10 18 cm -3 This shows that within this range, as the Si concentration increases relative to the Sn concentration, the average void length increases, and as the Sn concentration increases relative to the Si concentration, the average void length decreases.
[0049] Table 2 below shows the "Si-Sn concentration" of the evaluated semiconductor substrate, the corresponding void density and average length, as well as 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] JPEG2024050122000003.jpg122170
[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 from it 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 mixing, for example, the Si concentration is 2 × 10 17 cm -3 , Sn concentration is 2×10 16 cm -3The 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 that compensates for the donor. This Fe is mixed into the single crystal from the crucible 10, and is 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, as the void density decreases, the average void length increases, and conversely, as the average void length decreases, the void density increases.
[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 ~3.0×10 18 cm -3 The density and average length are in the range of 56 to 57,000 cm -2 It can be seen that a semiconductor substrate containing voids in the range of 14 to 85 μm can be manufactured. In addition, by controlling the average length of the voids in the single crystal according to the thickness and plane orientation of the semiconductor substrate, a semiconductor substrate in which no voids penetrate between both main surfaces can be obtained.
[0054] In addition, the Si concentration is 4.0×10 18 cm -3 It has been confirmed that when the Si concentration is more than 4.0×10, huge voids, which are thought to be multiple voids packed together, tend to occur in the single crystal. 18 cm -3 If the Si concentration is more than 3.0×10, the relationship between the Si concentration minus the Sn concentration and the void density, and the relationship between the Si concentration minus the Sn concentration and the average void length may no longer hold. 18 cm -3If the Si concentration is less than 4.0×10, giant 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, as well as the relationship between the value obtained by subtracting the Sn concentration from the Si concentration and the average length of the voids, are certainly established. Therefore, the Si concentration is 4.0×10 18 cm -3 Preferably smaller than 3.0×10 18 cm -3 It is more preferable that:
[0055] Although the above evaluations were performed on semiconductor substrates cut from single crystals of β-Ga2O3, a typical example of gallium oxide semiconductors, similar results can be obtained when evaluating semiconductor substrates cut from single crystals of other gallium oxide semiconductors. Also, similar results can be obtained when evaluating semiconductor substrates cut from single crystals grown by a method of growing single crystals in an oxygen atmosphere other than the VB method, such as the VGF method.
[0056] (Effects 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 effect 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 embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. Furthermore, the components of the above embodiment can be combined as desired without departing from the spirit of the invention. Furthermore, the above-described embodiment does not limit the invention according to the claims. Furthermore, it should be noted that not all of the combinations of features described in the embodiment are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]
[0058] 1...single crystal growth apparatus, 10...crucible, 101...seed crystal section, 102...grown 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 from a melt of the raw material of the single crystal under an oxidizing atmosphere; The density and average length of voids in the single crystal are controlled by the relative values of the Si concentration and the Sn concentration of the single crystal. How to grow single crystals.
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 , controlled within the range of 14 to 85 μm; The method for growing a single crystal according to claim 1.
3. The Si concentration is 4.0×10 １８ cm －３ less than the Si concentration minus the Sn concentration of −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 , controlled within the range of 14 to 85 μm; The method for growing a single crystal according to claim 1.
4. A method for manufacturing a semiconductor substrate made of a single crystal of a gallium oxide based semiconductor, comprising the steps of: growing the single crystal from a melt of the raw material of the single crystal under an oxidizing atmosphere; cutting the semiconductor substrate from the single crystal; Including, The density and average length of voids in the single crystal are controlled by the relative values of the Si concentration and the Sn concentration of the single crystal. A method for manufacturing a semiconductor substrate.
5. controlling an average length of the voids according to a thickness and a surface orientation of the semiconductor substrate in order to prevent the voids from penetrating between both main surfaces of the semiconductor substrate; The method for manufacturing a semiconductor substrate according to claim 4 .
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 , controlled within the range of 14 to 85 μm; The method for manufacturing a semiconductor substrate according to claim 4 or 5.
7. The Si concentration is 4.0×10 １８ cm －３ less than the Si concentration minus the Sn concentration of −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 , controlled within the range of 14 to 85 μm; The method for manufacturing a semiconductor substrate according to claim 4 or 5.
8. A semiconductor substrate made of a single crystal of a gallium oxide based semiconductor, Density and average length are 56-57,000 cm －２ , including voids in the range of 14 to 85 μm; Semiconductor substrate.
9. The value obtained by subtracting the Sn concentration from the Si concentration is within the range of -2.8 x 10 18 to 3.0 x 10 18 cm -3 . The semiconductor substrate according to claim 8 .
10. The Si concentration is less than 4.0×10 18 cm −3 , the ratio of the Si concentration to the Sn concentration is within the range of 2×10 17 / 3×10 18 to 3×10 18 / 2×10 16 ; The semiconductor substrate according to claim 8 .
11. The void does not penetrate between the two main surfaces. The semiconductor substrate according to any one of claims 8 to 10.
12. The Si concentration is 2×10 １７ cm －３ The Sn concentration is higher than 2×10 １６ cm －３ Higher, The semiconductor substrate according to any one of claims 8 to 10.