METHOD OF PRODUCING SiC SINGLE CRYSTAL

Abstract

In the present invention, in producing a SiC single crystal in accordance with a solution method, a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less is used as the crucible to be used as a container for a SiC solution. In another embodiment, a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less is placed in the crucible to be used as a container for a SiC solution. SiC, which is the main component of these, serves as a source for Si and C and allows Si and C to elute into the SiC solution by heating. Since the oxygen content of SiC is 100 ppm or less, generation of gas in the SiC solution is suppressed.

Claims

1: A method of producing a SiC single crystal, which is a method of growing a silicon carbide crystal in accordance with a solution method, comprising using a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less as a container for a SiC solution, heating the crucible to allow Si and C derived from a SiC source, which is a main component of the crucible, to elute from a high temperature region of a crucible surface in contact with the SiC solution, into the SiC solution, and bringing a SiC seed crystal from the top of the crucible into contact with the SiC solution to allow a SiC single crystal to grow on the SiC seed crystal.

2: A method of producing a SiC single crystal, which is a method of growing a silicon carbide crystal in accordance with a solution method, comprising placing a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less in a crucible serving as a container for a SiC solution, heating the crucible to allow Si and C derived from a SiC source, which is a main component of the sintered body, to elute from a surface of the sintered body in contact with the SiC solution, into the SiC solution, and bringing a SiC seed crystal from the top of the crucible into contact with the SiC solution to allow a SiC single crystal to grow on the SiC seed crystal.

3: The method of producing a SiC single crystal according to claim 1, wherein a metal element M having an effect of enhancing solubility of C to the SiC solution is added to the SiC solution in advance.

4: The method of producing a SiC single crystal according to claim 3, wherein the metal M is at least one of a first metal element M1, which is at least one metal element selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Lu, and a second metal element M2, which is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni and Cu.

5: The method of growing a silicon carbide crystal according to claim 4, wherein the metal M consists of both the first metal element M1 and the second metal element M2, and the total content of the metal M in the SiC solution is specified as 1 at % to 80 at %.

6: The method of growing a silicon carbide crystal according to claim 5, wherein the content of the first metal element M1 in the SiC solution is specified as 10 at % or more; and the second metal element M2 in the SiC solution is specified as 1 at % or more.

7: The method of producing a SiC single crystal according to claim 3, wherein the metal M is at least one metal element selected from the group consisting of Al, Ga, Ge, Sn, Pb and Zn.

8: The method of growing a silicon carbide crystal according to claim 1, wherein the temperature of the SiC solution is controlled by the heating to fall in the range of 1300 C. to 2300 C.

9: The method of producing a SiC single crystal according to claim 1, wherein the heating is carried out in a state where the crucible is housed in a second crucible made of a heat-resistant carbon material.

10: The method of producing a SiC single crystal according to claim 2, wherein a metal element M having an effect of enhancing solubility of C to the SiC solution is added to the SiC solution in advance.

11: The method of producing a SiC single crystal according to claim 10, wherein the metal M is at least one of a first metal element M1, which is at least one metal element selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Lu, and a second metal element M2, which is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni and Cu.

12: The method of growing a silicon carbide crystal according to claim 11, wherein the metal M consists of both the first metal element M1 and the second metal element M2, and the total content of the metal M in the SiC solution is specified as 1 at % to 80 at %.

13: The method of growing a silicon carbide crystal according to claim 12, wherein the content of the first metal element M1 in the SiC solution is specified as 10 at % or more; and the second metal element M2 in the SiC solution is specified as 1 at % or more.

14: The method of producing a SiC single crystal according to claim 10, wherein the metal M is at least one metal element selected from the group consisting of Al, Ga, Ge, Sn, Pb and Zn.

15: The method of growing a silicon carbide crystal according to claim 2, wherein the temperature of the SiC solution is controlled by the heating to fall in the range of 1300 C. to 2300 C.

16: The method of producing a SiC single crystal according to claim 2, wherein the heating is carried out in a state where the crucible is housed in a second crucible made of a heat-resistant carbon material.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] FIG. 1 is a view showing a first configuration example of a main part of an apparatus for growing a silicon carbide crystal in accordance with the method of the present invention.

[0033] FIG. 2 is a view showing a second configuration example of a main part of an apparatus for growing a silicon carbide crystal in accordance with the method of the present invention.

[0034] FIG. 3 is a conceptual view for describing how to elute Si and C into a SiC solution from the wall surface of a SiC crucible during growth of silicon carbide crystal according to the method of the present invention.

[0035] FIG. 4 The figure shows an optical photograph (FIG. 4 (A)) of a cross-section of the crystal obtained in a preliminary experiment; an optical photograph (FIG. 4 (B)) of a surface thereof; and a spectrum (FIG. 4 (C)) obtained by XPS analysis of a void wall.

[0036] FIG. 5 shows an optical photograph (FIG. 5 (A)) of a cross-section of the crystal obtained in Example 1 and an optical photograph (FIG. 5 (B)) of a surface thereof.

[0037] FIG. 6 shows an optical photograph (FIG. 6 (A)) of a cross-section of the crystal obtained in Example 2 and an optical photograph (FIG. 6 (B)) of a surface thereof.

[0038] FIG. 7 shows an optical photograph (FIG. 7 (A)) of a cross-section of the crystal obtained in Comparative Example 2 and an optical photograph (FIG. 7 (B)) of a surface thereof.

[0039] FIG. 8 shows optical photographs of cross-sections of the crystals obtained in Example 3 (FIG. 8 (A)), Example 4 (FIG. 8 (B)), Comparative Example 3 (FIG. 8 (C)) and Comparative Example 4 (FIG. 8 (D)).

[0040] FIG. 9 is a graph showing the relationship between the concentration of oxygen contained in a SiC crucible and the density of voids in a crystal.

DESCRIPTION OF EMBODIMENTS

[0041] Now, referring to the drawings, the method of producing a SiC single crystal according to the present invention will be descried. Note that, in the following description, an embodiment where a crucible is heated at a high frequency, will be described; however, the heating method is not limited to using high frequency. Another heating method such as resistance heating may be employed depending upon e.g., the temperature of a SiC solution to be controlled.

[0042] In consideration of the aforementioned problems with conventional solution methods, the present inventors studied on a technique for obtaining a high-quality single crystal silicon carbide with few defects by not only reducing a composition variation of the SiC solution but also suppressing precipitation of a polycrystal on the inner wall of a crucible.

[0043] According to the studies by the present inventors, it was found that a high-quality single crystal silicon carbide with few defects compared to conventional ones can be obtained by using a crucible (SiC crucible) containing SiC as a main component as a container for a SiC solution, or placing a sintered body (SiC sintered body) containing SiC as a main component in a crucible to be used as a container for a SiC solution; eluting Si and C derived from a main component, SiC of the crucible or sintered body from the surface of the SiC crucible or the SiC sintered body in contact with the SiC solution into the SiC solution; and bringing a SiC seed crystal from the top of the crucible into contact with the SiC solution to allow a SiC single crystal to grow on the SiC seed crystal. The SiC single crystal thus obtained is suitable for use in a SiC semiconductor device such as a power device. In other words, the SiC crucible and sintered body used in the present invention are suitable for use in producing a single crystal applicable to a SiC semiconductor device.

[0044] The reason why a high-quality SiC single crystal can be stably obtained for a long time by the above method can be summarized as follows.

[0045] A conventional solution method includes using a crucible formed of a heat-resistant carbon material represented by a graphite crucible, putting a solution in the crucible and allowing C to elute from the crucible to supply C in the solution. However, as growth of a SiC crystal proceeds, a decrease of the composition ratio of a Si component in the solution inevitably occurs.

[0046] In contrast, in the above method, Si and C are supplied into the solution from a source, SiC, which is a main component of the SiC crucible and SiC sintered body. In this case, even if a SiC crystal is grown on a seed crystal, Si and C in the solution consumed by growth of the crystal are supplied from the SiC crucible or SiC sintered body. As a result, composition variation of the solution is suppressed, and a SiC single crystal can be grown stability for a long time.

[0047] Such a crystal growth method is analogous to the FZ method or can be said a kind of FZ method. In the FZ method, melting of a polycrystal part and growth of a single crystal part proceed via a Si melting part. Also in the above crystal growth method, a crucible or a sintered body corresponding to the polycrystal part is melted by heating and a SiC single crystal is grown on a seed crystal via a solution containing Si and C corresponding to the melting part above.

[0048] However, when the SiC single crystal thus obtained was more closely checked, many voids were observed in the crystal. The present inventors further investigated a cause to produce such voids and reached the conclusion that oxygen incorporated in a crucible or a sintered body containing SiC as a main component is the cause. Although specific mechanism is unknown, the present inventors are considering two possible mechanisms described below.

[0049] One of the mechanisms is: oxygen contained in a SiC crucible or a SiC sintered body forms an oxide (SiO). Since the boiling point of the SiO is in the vicinity of 1880 C., if the temperature of a SiC solution is the boiling point or more, SiO eluted with elution of SiC is gasified in the SiC solution, reaches the interface (solid-liquid interface) between the SiC solution and a growing SiC single crystal and is incorporated in the surface of a growing crystal to form voids.

[0050] The other mechanism is: oxygen contained in a SiC crucible or a SiC sintered body elutes into a SiC solution with elution of SiC. If the temperature of the SiC solution is equal to or less than the boiling point of SiO, oxygen reacts with Si in the SiC solution to form SiO. SiO reaches the interface (solid-liquid interface) of the SiC solution and a growing SiC single crystal and is incorporated in the surface of a growing crystal to form voids.

[0051] Based on the finding, in the present invention, occurrence of voids is remarkably suppressed by controlling the oxygen content of a SiC crucible or a SiC sintered body to be 100 ppm or less.

[0052] More specifically, in the present invention, a SiC single crystal is allowed to grow on a SiC seed crystal by using a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less, as a container for a SiC solution in producing the SiC single crystal in accordance with a solution method; heating the crucible to allow Si and C (derived from a source, i.e., SiC, which is a main component of the crucible) to elute from a high temperature region of the crucible surface in contact with the SiC solution, into the SiC solution; and bringing the SiC seed crystal from the top of the crucible into contact with the SiC solution.

[0053] In another embodiment, a SiC single crystal is allowed to grow on the SiC seed crystal by placing a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less in a crucible to be used as a container for a SiC solution in producing the SiC single crystal in accordance with a solution method; heating the crucible to allow Si and C (derived from a source, i.e., SiC, which is a main component of the sintered body) to elute from the surface of the sintered body in contact with the SiC solution; and bringing the SiC seed crystal from the top of the crucible into contact with the SiC solution.

[0054] FIG. 1 is a view showing a first configuration example of a main part of an apparatus for growing a silicon carbide crystal in accordance with the method of the present invention.

[0055] In the figure, reference numeral 1 represents a crucible containing SiC as a main component, having an oxygen content of 100 ppm or less and serving as a container for a SiC solution; reference numeral 2 represents a second crucible made of a heat-resistant carbon material and housing the SiC crucible 1; reference numeral 3 represents a SiC single crystal serving as a seed crystal; reference numeral 4 represents a SiC solution put in the SiC crucible 1; reference numeral 5 represents a shaft for rotating the crucible 1 (and crucible 2) during crystal growth of SiC; reference numeral 6 represents a shaft for holding and rotating the seed crystal 3 during crystal growth of SiC; reference numeral 7 represents a susceptor formed of e.g., a graphite material; reference numeral 8 represents an insulating material formed also of e.g., a graphite material; reference numeral 9 represents a top cover for suppressing evaporation of the SiC solution; and reference numeral 10 represents a high frequency coil for heating the SiC crucible 1 and providing a preferable temperature distribution within the SiC solution 4.

[0056] Note that, although not shown in the figure, an exhaust port and an exhaust valve for evacuating the air in the furnace; and a gas inlet and a gas inlet valve for introducing a gas are provided. To the SiC crucible 1 before heating is filled with Si and may be filled with Si together with a source for C.

[0057] Note that, in the embodiment shown in FIG. 1, a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less is used as the crucible 1. However, a crucible made of e.g., graphite may be used in place of this as a container for a SiC solution and a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less, may be placed in the crucible.

[0058] FIG. 2 is a view showing a second configuration example of a main part of an apparatus for growing a silicon carbide crystal in accordance with the method of the present invention. In the figure, reference numeral 11 represents a sintered body (SiC sintered body) containing SiC as a main component and having an oxygen content of 100 ppm or less. In this embodiment, the crucible 1 may be the crucible containing SiC as a main component and having an oxygen content of 100 ppm or less, as is the case with the embodiment of FIG. 1, and may be a crucible of e.g., graphite.

[0059] Note that, in the above configuration example, the second crucible 2 made of a heat-resistant carbon material is used for housing the crucible 1; however, the second crucible 2 is not necessarily required in the present invention. However, if use of the second crucible 2 is advantageous because the temperature distribution within the SiC solution can be easily and preferably controlled.

[0060] In the present invention, owing to induction heating of the crucible 1 by the high frequency coil 10, a preferable temperature distribution of the SiC solution 4 for crystal growth is provided; at the same time, Si and C derived from SiC as a main component are allowed to elute from the surface of the crucible 1 or the surface of the SiC sintered body 11 in contact with the SiC solution 4, into the SiC solution 4; and then, the SiC seed crystal 3 is brought from the top of the crucible 1 into contact with the SiC solution 4 to allow a SiC single crystal to grow on the SiC seed crystal 3. The temperature of the SiC solution during crystal growth is usually controlled to fall within the temperature range of 1300 C. to 2300 C.

[0061] Accordingly, at least the temperature of the inner wall of the crucible in contact with the SiC solution, if a SiC crucible is used; and the surface temperature of the SiC sintered body in contact with the SiC solution if the SiC sintered body is used, are each controlled be a sufficiently high temperature to allow constituent elements Si and C of SiC (main component of the crucible and sintered body) to elute in the SiC solution 4. The temperature in the vicinity of the solid-liquid interface between the SiC seed crystal 3 and the SiC solution 4 is controlled to be a sufficient temperature for a SiC single crystal to grow on the SiC seed crystal 3.

[0062] FIG. 3 is a conceptual view for describing how to elute Si and C into a SiC solution from the wall surface of a SiC crucible during the growth of a silicon carbide crystal according to the method of the present invention.

[0063] If the temperature distribution as mentioned above is provided, Si and C derived from SiC (a main component of the SiC crucible 1) elute into the SiC solution 4 from the surface (high temperature region) of the SiC crucible 1 in contact with the SiC solution 4. Naturally, the Si and C thus eluted newly serve as Si component and C component in the SiC solution 4 and as sources for a single crystal to be grown on the SiC seed crystal 3. Note that, reference symbol M in the figure represents a metal element having an effect of enhancing the solubility of C to the SiC solution 4. The metal element to be added is not limited to a singly type. A plurality of types of metal elements may be added.

[0064] In the environment where Si and C are eluted into the SiC solution 4 from the SiC crucible 1, a problem of precipitation of a SiC polycrystal on the surface of the crucible in contact with the SiC solution, does not occur. This is because, in the environment where SiC (a main component of the crucible 1) is eluted as Si and C into the SiC solution 4, there is no possibility that Si and C are precipitated as SiC. In other words, precipitation of a SiC polycrystal on the surface of the crucible in contact with the SiC solution is suppressed by using a crucible containing SiC as a main component as the container for a SiC solution.

[0065] In addition, use of the SiC crucible is effective since formation of a metal carbide, which is formed by binding an additive metal element M and carbon C, is suppressed. In the case of using a graphite crucible, if the ratio of a Si composition in the SiC solution decreases or if the Si/C (composition) ratio is lowered by excessive dissolution of C into the solution, a metal element M, which is added in order to facilitate dissolution of C, is easily combined to carbon C, with the result that a metal carbide tends to be formed. Such a metal carbide has a high melting point, moves through the SiC solution while floating, reaches the portion in the vicinity of the surface of a seed crystal and serves as a factor of inhibiting crystallization of a SiC single crystal. In contrast, in the case of using a SiC crucible, carbon C is not excessively dissolved in the SiC solution, with the result that the formation of a metal carbide is suppressed and the SiC single crystal to be grown can be easily crystallized.

[0066] As described above, in the method of growing a silicon carbide crystal according to the present invention, use of a crucible containing SiC as a main component as a container for a SiC solution is advantageous since precipitation of a SiC polycrystal on the surface of the crucible in contact with the SiC solution is suppressed. If a SiC sintered body housed in a graphite crucible is used as a source for crystal growth in place of a SiC crucible, the above effect is low; however, since the SiC sintered body is housed in the graphite crucible, the contact area between the graphite crucible and the SiC solution decreases, with the result that this case has an effect of suppressing precipitation of a SiC polycrystal, compared to conventional methods.

[0067] Si and C are continuously eluted from the crucible; however, since a single crystal is grown usually by rotating the crucible and a seed crystal, the SiC solution gets a stirring effect and the composition thereof can be homogenized. As a result, the state of the solution as shown in FIG. 3 can be realized.

[0068] Note that the conditions of the induction heating by the high frequency coil 10 are appropriately controlled during a process for growing a SiC single crystal to obtain a suitable temperature distribution. Furthermore, if the position of the crucible 1 is moved up and down and/or the crucible 1 and the seed crystal 3 are rotated, the growth rate of a SiC single crystal and the elution rate of Si and C into the SiC solution 4 can be properly controlled. Moreover, if Si and C, which are consumed from the SiC solution 4 as the growth of the SiC single crystal proceeds, are solely supplied from the crucible 1, the composition variation of the SiC solution 4 can be suppressed. The same can apply to the case where a SiC sintered body is used in place of SiC crucible.

[0069] As mentioned above, the metal element represented by M in FIG. 3 and having an effect of enhancing the solubility of C to the SiC solution 4 is not limited to a single type. A plurality of types of metal elements may be added.

[0070] As such a metal element, at least one metal element selected from the group consisting of, for example, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Lu, can be mentioned.

[0071] At least one type of metal element selected from the group consisting of, for example, Ti, V, Cr, Mn, Fe, Co, Ni and Cu, can be mentioned.

[0072] Further, at least one type of metal element selected from the group consisting of, for example, Al, Ga, Ge, Sn, Pb and Zn, can be mentioned.

[0073] Note that, the above metal elements may be used in combination. For example, at least one metal element M1 selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Lu may be used in combination with at least one metal element M2 selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni and Cu.

[0074] The total addition amount of such metal elements in the SiC solution usually falls within the range of 1 at % to 80 at %.

[0075] For example, the content of the first metal element M1 in the SiC solution is specified as 10 at % or more; whereas the content of the second metal element M2 in the SiC solution is specified as 1 at % or more.

EXAMPLES

[0076] Now, the method for growing a crystal of the present invention will be more specifically described below by way of Examples.

[Preliminary Experiment] (Comparative Example 1)

[0077] A crystal was grown by using a SiC sintered crucible (90/80H90/80 mm, theoretical density: 96%) manufactured by Nippon Fine Ceramics Co., Ltd. in an apparatus having the structure shown in FIG. 1. La (20 at %) and Cr (20 at %) with Si as the balance were initially supplied to a crucible. The initial supply amounts were determined based on various density calculations and the depth of a SiC solution was controlled to be 27 mm. As a seed crystal, a single crystal (polytype:4H) having a size of 2 inchest0.4 mm and bonded to a seed shaft (47 mm) made of graphite arranged such that a crystal was grown on the C surface, was used.

[0078] A crystal was grown in an argon atmosphere at 2000 C. for 20 hrs. at a pulling rate of 0.1 mm/hr. while rotating the crucible at 20 rpm and the seed shaft at 20 rpm in the opposite direction.

[0079] When the resultant crystal was evaluated, the resultant crystal was plane without dust; however, many voids were observed in the surface of the crystal grown and a cross section.

[0080] FIG. 4 shows an optical photograph (FIG. 4 (A)) of a cross-section of the crystal; an optical photograph (FIG. 4 (B)) of a surface thereof; and a spectrum (FIG. 4 (C)) obtained by XPS analysis of a void wall. According to the XPS analysis, SiO as large as 23% was detected on the wall surface of voids.

[0081] Then, to find a cause for void occurrence, the following investigation was carried out. As mentioned above, the present inventors postulated that a cause for void occurrence may be a gas originated within the crucible and presumed what is a source of the gas.

[0082] The impurities of a SiC crucible used for growing a crystal were analyzed by glow discharge mass spectrometry (GMDM). As a result, it was found that 160 ppm of oxygen is contained. There is a high possibility that the oxygen formed a compound with Si. This reacts with Si in the SiC solution to produce SiO. Since the boiling point of SiO is 1880 C., there is a high possibility that SiO is gasified in the SiC solution and acts as a cause to form voids. This is presumably a source for SiO as large as 23% detected by XPS analysis on the wall surface of voids.

[0083] Provided that 50 g of the SiC crucible is eluted as a SiC solution, theoretically, 4 ml of SiO gas is to be generated. The amount of SiO gas is presumably sufficient for forming voids. In other words, Occurrence of voids is conceivably suppressed by reducing the amount of oxygen contained in the SiC crucible. The same can apply to the case where a SiC sintered body was used.

Example 1

[0084] A crystal was grown in the same conditions as in the preliminary experiment (Comparative Example 1) except that a SiC crucible having an oxygen amount reduced up to 15 ppm was used.

[0085] FIG. 5 is an optical photograph (FIG. 5 (A)) of a cross-section of the crystal obtained in Example 1, and an optical photograph (FIG. 5 (B)) of a surface thereof. No void occurrence was observed in FIG. 5 (A) and FIG. 5 (B) shows that the crystal growth surface is smooth.

Example 2 and Comparative Example 2

[0086] In order to confirm that oxygen in SiC is a cause of void occurrence based on the above results, SiC plates different in oxygen amount were prepared into a SiC sintered body as mentioned above and crystal growth was carried out. The growth conditions were as follows. A SiC plate (49 mmt5 mm) having an oxygen amount of 90 ppm (Example 2) and a SiC plate (49 mmt5 mm) having an oxygen amount of 170 ppm (Comparative Example 2) were each disposed on the bottom of a carbon crucible having an inner diameter of 50 mm and a crystal was grown in an apparatus having the structure shown in FIG. 2. La (20 at %) and Cr (20 at %) and Si as the balance were initially supplied to a crucible. The initial supply amounts were determined based on various density calculations and the depth of a SiC solution was controlled to be 27 mm. As a seed crystal, a single crystal (polytype:4H) having a size of 2 inchest0.4 mm and bonded to a seed shaft (47 mm) made of graphite arranged such that a crystal was grown on the C surface, was used.

[0087] A crystal was grown in an argon atmosphere, at 2000 C. for 10 hrs. at a pulling rate of 0.1 mm/hr while rotating the crucible at 20 rpm and the seed shaft at 20 rpm in the opposite direction.

[0088] When the resultant crystal was evaluated, no voids were formed in the crystal of the case where a SiC plate having an oxygen amount of 90 ppm was disposed (Example 2); however, voids were observed in a crystal of the case where a SiC plate having an oxygen amount of 170 ppm was disposed in a carbon crucible (Comparative Example 2).

[0089] FIG. 6 (A) and FIG. 6 (B) are optical photographs of a cross-section of the crystal obtained in Example 2 and the surface thereof. FIG. 7 (A) and FIG. 7 (B) are optical photographs of a cross-section of the crystal obtained in Comparative Example 2 and the surface thereof.

Examples 3, 4 and Comparative Examples 3, 4

[0090] In order to clarify the relationship between the oxygen amount in a SiC crucible and void occurrence, SiC crucibles having an oxygen content of 14 to 360 ppm were prepared and a crystal growth test was carried out in the same conditions as in Comparative Example 1. Cross-sections of the resultant crystals were observed with respect to the presence or absence of voids and the number of voids were counted.

[0091] FIGS. 8 (A) to (D) show optical photographs of cross-sections of the crystals obtained in Example 3 (FIG. 8 (A)), Example 4 (FIG. 8 (B)), Comparative Example 3 (FIG. 8 (C)), and Comparative Example 4 (FIG. 8 (D)).

[0092] FIG. 9 is a graph showing the relationship between the concentration of oxygen contained in a SiC crucible and the density of voids in a crystal summarizing the above results.

[0093] Table 1 summarizes the relationship between the oxygen amount in a SiC crucible of each of Examples and Comparative Examples and the void density thereof.

TABLE-US-00001 TABLE 1 Sample Oxygen content (ppm) Void density (cm.sup.2) Comparative 160 75 Example 1 Comparative 110 70 Example 3 Comparative 360 245 Example 4 Example 3 100 0 Example 4 14 0

[0094] According to these results, it was found that voids are formed in the case of a SiC crucible in which the concentration of oxygen in the SiC crucible exceeds 100 ppm. In particular, many voids were observed over the entire section of a crystal in the case where the concentration of oxygen was 360 ppm.

[0095] In contrast, in the case where the concentration of oxygen was 100 ppm or less, void occurrence was not observed.

[0096] From these results, it was found that void occurrence can be suppressed by reducing the amount of oxygen in a SiC crucible to 100 ppm or less. The conclusion derived from the results applies to the case where a SiC sintered body is used.

[0097] As mentioned above, according to the method of growing a silicon carbide crystal of the present invention, a high-quality single crystal silicon carbide with few defects can be obtained compared to a conventional method using a graphite crucible.

INDUSTRIAL APPLICABILITY

[0098] The present invention provides a high-quality single crystal silicon carbide with few defects. Such a SiC single crystal is suitable for a SiC semiconductor device such as a power derive. In short, the SiC crucible to be used in the present invention is suitable for producing a single crystal to be used in SiC semiconductor devices

REFERENCE SIGNS LIST

[0099] 1 Crucible containing SiC as a main component [0100] 2 Second crucible formed of a heat-resistant carbon material [0101] 3 Seed crystal [0102] 4 SiC solution [0103] 5 Crucible rotation shaft [0104] 6 Seed crystal rotation shaft [0105] 7 Susceptor [0106] 8 Insulation material [0107] 9 Top cover [0108] 10 High frequency coil [0109] 11 SiC sintered body