Production method of silicon carbide single crystal

Abstract

To provide a production method of a silicon carbide single crystal capable of growing a high quality silicon carbide single crystal at high speed.SOLUTION: A production method of a silicon carbide single crystal includes a step for preparing a silicon carbide solution 20 containing at least one kind of rare-earth element selected from the group consisting of Y, La, Ce, Pr, and Nd, as well as Si and C, and a step for bringing the silicon carbide solution 20 into contact with a crystal growth surface 30a of a silicon carbide seed crystal 30 having a 4H crystal structure to grow a silicon carbide single crystal on the crystal growth surface 30a. The silicon carbide solution 20 preferably contains the rare-earth element at a rate of 25 atm% or more and less than 45 atm% relative to the total of the rare-earth element and Si. The crystal growth surface 30a preferably has an off-angle inclined from the (0001) plane. The silicon carbide solution 20 is preferably kept at a temperature of 1,800-2,000°C in the step of growing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application relates to a method for producing a silicon carbide single crystal. [Background technology]

[0002] Silicon carbide (SiC) semiconductors have a higher dielectric breakdown field strength, electron saturation drift velocity, and thermal conductivity than silicon semiconductors. For this reason, silicon carbide semiconductors can realize power devices that can operate at higher temperatures, higher speeds, and higher currents than conventional silicon devices, and are attracting attention as semiconductors for realizing switching elements that drive motors used in electric vehicles, hybrid cars, etc. with high efficiency.

[0003] However, compared to silicon semiconductors and GaAs semiconductors, it is generally difficult to obtain large, high-quality silicon carbide single crystals. In particular, it is difficult to achieve both high quality and high-speed growth in the growth of silicon carbide single crystals. Silicon carbide single crystals currently on the market are manufactured by the sublimation method from the viewpoint of productivity. As mentioned above, if high-speed growth is prioritized, it is difficult to obtain high quality, so higher crystal quality is required for silicon carbide single crystals manufactured by the sublimation method.

[0004] On the other hand, a solution growth method is known as a crystal growth method that can achieve high quality. For example, Non-Patent Document 1 discloses a method for growing silicon carbide single crystals using a Si-Cr solution. [Prior art documents] [Patent documents]

[0005] [Non-Patent Document 1] M. Kado, et al.: Mat. Sci. Forum, 740-742 (2013) 73-76. Summary of the Invention [Problem to be solved by the invention]

[0006] The solution growth method is more advantageous than the sublimation method in terms of crystal quality, but there is a demand for increasing the growth rate. The present application provides a method for producing a silicon carbide single crystal that is capable of growing a high-quality silicon carbide single crystal at a high rate. [Means for solving the problem]

[0007] A method for producing a silicon carbide single crystal according to one embodiment of the present disclosure includes the steps of preparing a silicon carbide solution containing a rare earth element including at least one selected from the group consisting of Y, La, Ce, Pr, and Nd, Si, and C, and contacting the silicon carbide solution with a crystal growth surface of a silicon carbide seed crystal having a 4H crystal structure to grow a silicon carbide single crystal on the crystal growth surface.

[0008] The silicon carbide solution may contain the rare earth element in a ratio of 25 atomic % or more and less than 45 atomic % with respect to the total of the rare earth element and the Si.

[0009] The silicon carbide solution may contain the rare earth element in a ratio of 35 atomic % or more and less than 40 atomic % with respect to the total of the rare earth element and the Si.

[0010] The crystal growth plane may have an off-angle inclined from the (0001) plane.

[0011] The off angle may be 0.5° or more and 8° or less.

[0012] In the growing step, the silicon carbide solution may be held at a temperature of 1800° C. or more and 2000° C. or less.

[0013] In the step of preparing the silicon carbide solution, the silicon carbide solution may be held in a crucible made of graphite or silicon carbide.

[0014] The preparing step may include placing the rare earth element and the Si in the crucible, heating the crucible to dissolve the rare earth element and the Si, and dissolving the graphite from the crucible or C from the silicon carbide into the solution of the rare earth element and the Si to obtain the silicon carbide solution. Effect of the Invention

[0015] According to an embodiment of the present disclosure, there is provided a method for producing a silicon carbide single crystal that is capable of growing a high-quality silicon carbide single crystal at a high rate. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a production apparatus used in the method for producing a silicon carbide single crystal of the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the crystal orientation of a silicon carbide seed crystal used in the method for producing a silicon carbide single crystal of the present embodiment. [Diagram 3] FIG. 3 shows an example of a diffraction pattern obtained by measuring the sample of the experimental example by the XRD method. [Figure 4] FIG. 4 shows an example of a diffraction pattern obtained by measuring the sample of the experimental example by the XRD method. [Diagram 5] FIG. 5 shows an example of a diffraction pattern obtained by measuring the sample of the experimental example by the XRD method. [Figure 6] FIG. 6 shows an example of a diffraction pattern obtained by measuring the sample of the experimental example by the XRD method. [Figure 7] FIG. 7 is a graph showing the relationship between the addition ratio of a solution containing Si and a rare earth element or Cr and the surface tension. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In the solution growth method, a seed crystal is immersed in a silicon carbide solution containing silicon and carbon, a temperature gradient is applied in the solution, and the vicinity of the growth interface is made into a carbon supersaturated state, thereby growing the crystal. According to this method, the temperature difference at the growth interface is small and close to thermal equilibrium, so the grown crystal has a small dislocation density and is known to have better crystal quality than the sublimation method. However, there is an issue that the crystal growth rate is slower than the sublimation method.

[0018] Non-Patent Document 1 reports that carbon solubility affects the crystal growth rate, and that the carbon concentration in the silicon carbide solution can be increased by adding Cr to the silicon carbide solution, thereby increasing the growth rate. However, according to the study by the present inventors, it was found that the quality of the grown silicon carbide single crystal is reduced by adding Cr.

[0019] There are various polytypes of silicon carbide single crystals with different atomic arrangements. For example, there are polytypes of silicon carbide single crystals such as 2H, 3C, 4H, and 6H, and 4H silicon carbide single crystals are suitable for power semiconductor devices. The difference in polytypes is the difference in atomic arrangement, and a crystal growth method suitable for manufacturing one polytype is not necessarily suitable for manufacturing silicon carbide single crystals of other polytypes.

[0020] In view of these problems, the inventors of the present application have conceived of a novel method for producing silicon carbide single crystals and a silicon carbide solution for producing silicon carbide single crystals that can satisfy both high quality and high growth rates compared to the conventional methods. The method for producing silicon carbide single crystals and the silicon carbide solution for producing silicon carbide single crystals of the present invention will be described in detail below.

[0021] 1 is a schematic cross-sectional view of a manufacturing apparatus 101 used in the method for manufacturing a silicon carbide single crystal of this embodiment. The method for manufacturing a silicon carbide single crystal of this embodiment includes the steps of (1) preparing a silicon carbide solution containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, and Nd, Si, and C, and (2) contacting the silicon carbide solution with a crystal growth surface of a silicon carbide seed crystal having a 4H crystal structure to grow a silicon carbide single crystal on the crystal growth surface.

[0022] (1) Preparing a silicon carbide solution First, a silicon carbide solution to be used for solution growth is prepared. The silicon carbide solution 20 contains rare earth elements including at least one selected from the group consisting of Y, La, Ce, Pr, and Nd, Si, and C.

[0023] The inventors of the present application have studied in detail the additive elements to the silicon carbide solution, and found that the additive elements can affect not only the carbon solubility but also the crystal quality of the growing silicon carbide single crystal. In particular, it has been found that the surface tension of the silicon carbide solution changes depending on the type of additive element, and affects the crystal disorder on the crystal growth surface. In other words, it is preferable that the additive element added to the silicon carbide solution increases the carbon solubility and reduces the surface tension of the silicon carbide solution. In addition, the growth temperature of the silicon carbide single crystal is 1800°C or higher. For this reason, it is preferable that the vapor pressure is low at temperatures of 1800°C or higher. If the vapor pressure is high at high temperatures, the additive element evaporates from the silicon carbide solution, and the concentration of the additive element decreases during crystal growth, making it difficult to obtain the effect of the additive element.

[0024] The inventors of the present application found that rare earth elements are suitable as additive elements having such characteristics. Specifically, the rare earth elements are one or more selected from the group consisting of Y, La, Ce, Pr, and Nd. The silicon carbide solution 20 preferably contains rare earth elements at a ratio of 25 atomic % or more and less than 45 atomic % with respect to the total of the rare earth elements and Si. More preferably, the addition ratio of the rare earth elements is 30 atomic % or more and less than 40 atomic % with respect to the total of the rare earth elements and Si. When the silicon carbide solution 20 contains two or more rare earth elements, it is preferable that the total addition ratio of the two or more rare earth elements is within the above-mentioned range. When the addition ratio of the rare earth elements is less than 25 atomic %, the effect of improving the carbon solubility is not sufficient. On the other hand, when the addition ratio of the rare earth elements is 45 atomic % or more, the rare earth carbides are precipitated, which increases the possibility that the crucible 10 is damaged or the carbon solubility is reduced.

[0025] Among the rare earth elements mentioned above, Y can increase the solubility of carbon even when added in a smaller amount than La, Ce, Pr, and Nd. On the other hand, when the amount of Y added is large, carbon compounds such as YC2 are easily formed. Therefore, when Y is added alone or Y and one or more selected from the group consisting of La, Ce, Pr, and Nd to a silicon carbide solution, the addition ratio of Y is preferably 25 atomic % or more and less than 35 atomic %.

[0026] Y, La, Ce, Pr and Nd are rare earth elements in the fifth and sixth periods, and have a larger atomic radius than elements in the fourth period. Therefore, they are difficult to incorporate into the grown single crystal during crystal growth, and the concentration of these transition metals in the resulting silicon carbide single crystal is low. Therefore, they are preferable as additive elements for silicon carbide solutions in terms of the purity of the silicon carbide.

[0027] The silicon carbide solution 20 contains Si and C in addition to rare earth elements. The silicon carbide solution 20 preferably does not substantially contain elements other than rare earth elements, Si, and C, and is preferably composed of rare earth elements, Si, and C. Here, "substantially does not contain elements other than rare earth elements, Si, and C" means that the silicon carbide solution 20 may contain other elements contained as impurities in the raw materials used as the rare earth element source, Si source, and C source, or other elements inevitably contained from the manufacturing equipment during the production of silicon carbide seed crystals. Examples of other elements inevitably contained include N, B, Al, Fe, etc.

[0028] According to detailed studies by the inventors of the present application, it is preferable that Cr is not included as an additive element in the silicon carbide solution. Although Cr increases carbon solubility, it also increases the surface tension of the silicon carbide solution, which disturbs the morphology on the crystal growth surface, making it easier for crystal defects to be included in the growing silicon carbide single crystal. It is considered that Al reduces the surface tension of the silicon carbide solution. However, at temperatures of 1800°C or higher, which is the growth temperature of silicon carbide single crystals, the saturated vapor pressure of Al is high. For this reason, Al may evaporate during crystal growth, resulting in a deterioration in the quality of the crystal. Since the atomic radius of transition metals in the fourth period, such as Fe, Ti, Mn, and Cr, is smaller than that of rare earth elements, they are easily incorporated into the grown single crystal during crystal growth. From these viewpoints, it is preferable that the silicon carbide solution does not contain Cr, Al, Fe, Ti, and Mn.

[0029] However, the silicon carbide solution may contain Cr, Al, Fe, Ti, or Mn, provided that the physical properties of the silicon carbide solution are not changed in terms of the above-mentioned surface tension, fluctuation in saturated vapor pressure, or inclusion in the grown single crystal. For example, the silicon carbide solution may contain at least one element selected from the group consisting of Cr, Al, Fe, Ti, and Mn, within a range of about several atomic % relative to the entire solution.

[0030] The composition ratio of the constituent elements of the silicon carbide solution is determined according to the addition ratio of the rare earth element described above. As will be described in the following experimental example, the addition ratio of the rare earth element is 25 atomic % or more and less than 45 atomic % with respect to the entire silicon carbide solution, and at this time, the content ratio of soluble C is 2.7 atomic % or more and less than 20 atomic %, and the remainder is occupied by Si. In other words, the content ratio of Si is 35 atomic % or more and 72.3 atomic % or less. The higher the content ratio of the rare earth element in the silicon carbide solution, the higher the content ratio of carbon, and the faster the growth rate of silicon carbide single crystal can be.

[0031] As shown in FIG. 1, the silicon carbide solution 20 is prepared, for example, in a manufacturing apparatus 101. The manufacturing apparatus 101 includes a furnace 11, a crucible 10 disposed in the furnace 11, and an induction coil 12 disposed outside the furnace 11. The silicon carbide solution 20 is held in the crucible 10. The crucible 10 is made of graphite (C) or silicon carbide. For example, the silicon carbide solution 20 is prepared by weighing out one or more rare earth element raw materials selected from the group consisting of Y, La, Ce, Pr, and Nd, a Si raw material, and a C raw material in the above-mentioned composition ratio and putting them into the crucible 10. Thereafter, power is applied to the induction coil 12, and the raw materials are melted at a crystal growth temperature by, for example, induction heating, to obtain the silicon carbide solution 20. The C raw material may not be added. In this case, the rare earth element raw material and the Si raw material are placed in the crucible 10, and the rare earth element and Si are melted by induction heating. When a solution of the rare earth element and Si is obtained, the C constituting the crucible 10 dissolves into the solution from the crucible 10, and a silicon carbide solution 20 containing C can be obtained.

[0032] (2) Growing silicon carbide single crystals A crystal growth surface 30a of a silicon carbide seed crystal 30 having a 4H crystal structure is brought into contact with the silicon carbide solution 20, and a silicon carbide crystal is grown on the crystal growth surface 30a. As shown in FIG. 1, the silicon carbide seed crystal 30 is attached to the rotating shaft 14 and positioned so that the crystal growth surface 30a is in contact with the silicon carbide solution 20.

[0033] FIG. 2 is a schematic diagram of a cross section of a silicon carbide seed crystal 30. The silicon carbide seed crystal 30 is a 4H silicon carbide single crystal, and is preferably an off-substrate having an off-angle θ. Specifically, the crystal growth surface 30a (or the normal 30n of the crystal growth surface 30a) is aligned with the c-plane ( <0001> It is preferable that the off angle θ is inclined from the <11-20> direction to the <11-20> direction. The off angle θ is preferably 0.5° or more and 8° or less, and more preferably 0.5° or more and 5° or less.

[0034] In order to improve the crystal quality of silicon carbide single crystals, it is necessary to reduce the dislocation density. Threading dislocations such as threading edge dislocations parallel to the c-axis present in silicon carbide seed crystals propagate and remain in the grown silicon carbide single crystal. For this reason, it is generally not easy to improve the crystal quality beyond that of silicon carbide seed crystals. As a method for solving such problems, it is known to bend the direction of threading dislocations parallel to the c-axis by step-flow growth, that is, to convert them to dislocations parallel to the a-axis and remove the dislocations from the crystal growth direction, thereby reducing the dislocation density. For this purpose, it is effective to use an off-substrate as a silicon carbide seed crystal to increase the microsteps of the crystal growth surface. However, in a solution growth method in which carbon solubility is increased using an additive element, if such an off-substrate is used as a silicon carbide seed crystal, the morphology at the growth interface is easily disturbed because the growth rate is increased by increasing the carbon solubility. In other words, it is considered that it is not appropriate to use an off-substrate silicon carbide seed crystal in a solution growth method in which carbon solubility is increased using an additive element. The inventors of the present application have focused on the surface tension of silicon carbide solution in order to suppress disturbance of morphology, and have found that if the surface tension of silicon carbide solution can be suppressed to a low level by adding an element, it is possible to achieve both high crystal quality and high growth rate, which are in a trade-off relationship in the solution growth method. For this reason, silicon carbide seed crystal 30 having an off-angle can be suitably combined with a silicon carbide solution containing a rare earth element.

[0035] The temperature during growth of the silicon carbide single crystal is preferably 1800° C. or higher and 2000° C. or lower. In particular, it is more preferable to grow the crystal at a temperature of about 1900° C. Conditions such as the temperature gradient near the crystal growth surface 30a, the atmosphere in the furnace 11 during growth, and the pressure can be set to the same conditions as those used in conventional solution growth methods.

[0036] During growth of the silicon carbide single crystal, the silicon carbide seed crystal 30 may be rotated by a rotating shaft 14. Similarly, the crucible 10 may be rotated by a rotating shaft 13.

[0037] By the above steps (1) and (2), a high-quality silicon carbide single crystal can be produced at a high growth rate. The silicon carbide single crystal produced as described above contains almost no rare earth elements in the silicon carbide solution. However, it is difficult to completely eliminate the rare earth elements in the silicon carbide solution, and rare earth elements may be contained in the silicon carbide solution as long as they do not affect the characteristics of the semiconductor device to be produced. For example, as described above, when conventional solution growth conditions are used in the production method of this embodiment, for example, 10 15 / cm 3 The rare earth elements of the silicon carbide solution may be present in concentrations of about 1000000000000.

[0038] According to this embodiment, the silicon carbide solution used in the solution growth method contains a rare earth element. The rare earth element increases the carbon solubility in the silicon carbide solution and reduces the surface tension of the silicon carbide solution. In addition, the rare earth element has a lower vapor pressure at temperatures of 1800°C or higher than Cr, Al, etc., and is therefore less likely to evaporate from the silicon carbide solution, so that the effect of adding the rare earth element can be sustained for a long time.

[0039] Furthermore, by reducing the surface tension of the silicon carbide solution, it is possible to use a 4H silicon carbide off-substrate as a seed crystal, reduce crystal defects in the crystal, and suppress morphological disturbances at the growth interface, thereby growing high-quality silicon carbide single crystals.

[0040] According to the manufacturing method of this embodiment, it is possible to manufacture silicon carbide single crystals at a rate equal to or higher than the crystal growth rate in the solution growth method with the addition of Cr. Moreover, the obtained silicon carbide single crystals can have higher quality than silicon carbide single crystals manufactured by the solution growth method with the addition of Cr.

[0041] (Experimental Example) The results of preparing silicon carbide solutions containing rare earth elements and measuring the carbon solubility are shown below. One of Y, La, Ce, Pr, and Nd and Si were weighed out so that the ratio of the rare earth element to the total of the rare earth element and Si was 20, 25, 30, 35, 40, 45, and 50 atomic %. The weighed rare earth element and Si were placed in a graphite crucible and held at 1800 ° C or 1900 ° C for 1 hour by induction heating. The rare earth element and Si were dissolved by heating, and carbon was dissolved from the crucible into the resulting solution to obtain a silicon carbide solution. For comparison, a silicon carbide solution was prepared in the same manner using Cr and Si.

[0042] The resulting silicon carbide solution was cooled, and the carbon content was measured by elemental analysis of the solidified silicon carbide solution in the crucible. The analysis was performed using a combustion-infrared absorption method. Some of the solidified silicon carbide solution was analyzed by the XRD method to identify the elements and compounds contained in the solidified material.

[0043] Table 1 shows the carbon solubility at 1900°C, and Table 2 shows the carbon solubility at 1800°C. In Tables 1 and 2, blank spaces indicate samples for which no preparation or carbon solubility was measured. Also, notations such as ">10 at%" indicate that an accurate value could not be obtained due to analytical precision, but the value was greater than the indicated number, for example, 10 atomic %.

[0044] In Tables 1 and 2, the ratios (20, 25, 30, 35, 40, 45, 50 atomic %) shown as the ratio of rare earth elements are the ratios of rare earth elements to the sum of rare earth elements and Si, as described above. In contrast, the carbon solubility value indicates the ratio of C to the entire silicon carbide solution. The addition ratio of rare earth elements to the entire silicon carbide solution after C has dissolved is obtained by multiplying the ratio shown as the ratio of rare earth elements by the ratio of elements other than C to the entire silicon carbide solution. For example, in Table 1, in a silicon carbide solution to which La has been added at a ratio of 30 atomic %, C is dissolved at a ratio of 3.7 atomic % to the entire solution, and it can be seen that the ratio of La to the entire silicon carbide solution at this time is 30×(1−0.037)=28.89 (atomic %).

[0045] [Table 1]

[0046] [Table 2]

[0047] As shown in Table 1, in the experiment at 1900°C, the carbon solubility of the silicon carbide solution with the addition ratio of Y, Pr, and Nd of 20 atomic % is smaller than that of the silicon carbide solution with the addition of Cr of 20 atomic %. However, the carbon solubility of the silicon carbide solution with the addition ratio of Y of 25 atomic % is larger than that of the silicon carbide solution with the addition of Cr of 20 atomic %. In the experiment at 1800°C, except for the silicon carbide solution with Pr added, in both the experiments at 1800°C and 1900°C, the silicon carbide solutions with the addition of 30 atomic % or more of rare earth elements have a higher carbon solubility than the silicon carbide solutions with the same ratio of Cr added.

[0048] These results show that by containing one of the rare earth elements Y, La, Ce, Pr, or Nd in a ratio of 25 atomic % or more relative to the total of the rare earth elements and Si, it is possible to increase the carbon solubility in the silicon carbide solution more than when Cr is added.

[0049] In addition, from a comparison between Tables 1 and 2, when the rare earth element addition ratio is 30 atomic % and 40 atomic %, the carbon solubility at 1900°C is about 1.3 to 2.2 times the value of the carbon solubility at 1800°C. For example, when the La addition ratio is 30 atomic %, the carbon solubility at 1900°C is about 1.3 times the value of the carbon solubility at 1800°C, and when the La addition ratio is 40 atomic %, the carbon solubility at 1900°C is about 2.2 times the value of the carbon solubility at 1800°C. In contrast, when the Cr addition ratio is 30 atomic %, the carbon solubility at 1900°C is about 1.5 times the value of the carbon solubility at 1800°C, and when the Cr addition ratio is 40 atomic %, the carbon solubility at 1900°C is about 1.7 times the value of the carbon solubility at 1800°C. In other words, it is clear that the temperature change in carbon solubility is as large as or greater than that of Cr in the temperature range from about 1800°C to 1900°C. Also, in a silicon carbide solution that does not contain Cr but contains only Si and C, the carbon solubility is about 1 atomic % even at 1900°C.

[0050] The growth rate of silicon carbide single crystals by the solution growth method is related to the degree of carbon supersaturation in the silicon carbide solution, and generally, the higher the degree of supersaturation, the higher the growth rate of silicon carbide single crystals. The degree of supersaturation depends on the carbon solubility in the silicon carbide solution and the temperature change of carbon solubility. As described above, according to the method for producing silicon carbide single crystals of this embodiment, the silicon carbide solution contains a rare earth element, so that the carbon solubility and the temperature change of carbon solubility are equal to or greater than those of a silicon carbide solution containing Cr. Therefore, according to the method for producing silicon carbide single crystals of this embodiment, it is considered that it is possible to realize a state of carbon supersaturation equal to or greater than that of a silicon carbide solution containing Cr, and to grow silicon carbide single crystals at a high speed.

[0051] Figures 3, 4 and 5 show examples of diffraction patterns measured by XRD for solidified silicon carbide solutions obtained by adding Nd at 40, 45 and 50 atomic %. Figure 6 shows an example of a diffraction pattern measured by XRD for solidified silicon carbide solutions obtained by adding Y at 40 atomic %. Table 3 shows elements and compounds detected by XRD when Nd and Y are added. Figures 3, 4 and 5 show that NdC2, a rare earth element carbide, was not detected in the solidified product with an Nd addition ratio of 40 atomic %, but NdC2 was found to be contained in the solidified products with an Nd addition ratio of 45 and 50 atomic %. Also, as shown in Figure 6, YC2 was detected in the solidified product with an Y addition ratio of 40 atomic %.

[0052] [Table 3]

[0053] These results indicate that the higher the ratio of rare earth elements added, the more likely the rare earth elements' carbides are formed. Specifically, it is preferable for the ratio of Nd to be less than 45 atomic %, and for Y to be less than 40 atomic %.

[0054] Figure 7 is a graph showing the results of calculations of the relationship between the surface tension and the addition ratio of rare earth elements Y, La, Ce, Pr, or Nd and Si in a solution at 1900°C. For comparison, the relationship between the addition ratio of Cr in a solution containing Si and Cr is also shown. As can be seen from Figure 7, in the cases of Y, La, Ce, Pr, and Nd, even if these rare earth elements are not included (0 atomic %), and even if the addition ratio of the rare earth element increases, the surface tension value remains almost the same. In contrast, in the case of Cr, the surface tension of the solution increases as the addition ratio increases.

[0055] From these results, it is believed that adding Y, La, Ce, Pr, or Nd to a silicon carbide solution has almost no effect on the surface tension, and that the surface tension is maintained at the same level as when these rare earth elements are not included. Therefore, even if the silicon carbide solution contains these rare earth elements, it is believed that high-quality silicon carbide single crystals can be grown, just as in the case of growing crystals from a silicon carbide solution containing only Si and C. [Industrial Applicability]

[0056] The method for producing a silicon carbide single crystal according to the present disclosure is suitably used for producing high-quality silicon carbide single crystals that can be used for a variety of applications, and is particularly suitable for producing silicon carbide single crystals that are suitable for power devices. [Explanation of symbols]

[0057] 10 Crucible 11 Furnace 12 Induction coil 13, 14 Rotation axis 20 Silicon carbide solution 30 Silicon carbide seed crystal 30a Crystal growth surface 101 Manufacturing equipment

Claims

1. In a silicon carbide solution composed of Si, C, and at least one additive element selected from rare earth elements, in which C is dissolved by heating at 1900° C. or higher, The solubility of carbon in the silicon carbide solution is 1 atomic % or more and 20 atomic % or less, The surface tension of the silicon carbide solution was maintained below 0.85 N / m. Silicon carbide solution.

2. The surface tension of the silicon carbide solution was maintained in the range of 0.60 N / m to 0.80 N / m.

2. The silicon carbide solution of claim 1.

3. The surface tension of the silicon carbide solution was maintained in the range of 0.65 N / m to 0.75 N / m. The silicon carbide solution according to claim 1 or 2.

4. The additive element is Y, The ratio of the additive element to the silicon carbide solution is less than 40 atomic %; 2. The silicon carbide solution of claim 1.

5. The additive element is at least one element selected from La, Ce, and Pr.

2. The silicon carbide solution of claim 1.

6. The additive element is Nd, The ratio of the additive element to the silicon carbide solution is less than 45 atomic %; The silicon carbide solution according to claim 1 or 2.

7. preparing a silicon carbide solution containing Si, C, and at least one additive element selected from rare earth elements, and in which C is dissolved by heating at 1900° C. or higher; contacting a crystal growth surface of a silicon carbide seed crystal having a 4H crystal structure with the silicon carbide solution and growing a silicon carbide single crystal on the crystal growth surface; The solubility of carbon in the silicon carbide solution is 1 atomic % or more and 20 atomic % or less, The surface tension of the silicon carbide solution is maintained at 0.85 N / m or less; The crystal growth surface has an off-angle inclined from the (0001) plane. A method for producing silicon carbide single crystals.

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