JP2009018957A - Method and apparatus for producing silicon carbide monocrystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method, in an embedded growth process, capable of preventing the loss of the uniformity of the temperature in the growth space region by thermal radiation, to thereby prevent a crack of silicon carbide monocrystal. <P>SOLUTION: In a cylinder covering member 23c arranged in the hollow section of a cylinder 23b, the shape of inner wall surfaces 23e vertical to the central axis of a crucible is polygonal. Thereby, the thermal energy emitted from the inner wall surfaces 23e of the cylinder covering member 23c in the diameter direction of the crucible is reflected at the angle of reflection according to the angle of incidence entering each side of the polygonal, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for producing silicon carbide (hereinafter referred to as SiC) single crystal that can be used as a material for a power MOSFET or the like.

  Conventionally, a method of growing a SiC single crystal in a crucible by heating the crucible with a resistance heater arranged on the outer periphery of the crucible has been proposed (for example, see Patent Document 1). Specifically, in patent document 1, while joining a seed crystal in a graphite crucible and heating the SiC powder raw material arranged at the bottom of the crucible to 2300 ° C., for example, the SiC powder raw material is sublimated and sublimated. There has been proposed a method of crystallizing a gas on a seed crystal set at a temperature lower than the raw material temperature.

  FIG. 3 is a diagram showing a schematic cross-sectional structure of a SiC single crystal manufacturing apparatus used for the sublimation reprecipitation method. As shown in this figure, a cylindrical projection J3 is provided on the inner wall of a lid member J2 of a graphite crucible J1, and a seed crystal J4 is attached to the end face of the projection J3. Further, a shielding plate J6 is provided which has a surface facing the growth surface of the seed crystal J4 and forms a growth space region J5 with the seed crystal J4.

  In addition, a skirt-like cylindrical portion J7 formed of graphite is provided on the cover material J2 so as to surround the seed crystal J4, and the radial temperature distribution on the seed crystal J4 side of the crucible J1 is provided by the cylindrical portion J7 and the shielding plate J6. Is made smaller. In this way, the SiC single crystal J8 is grown on the seed crystal J4 so as to keep the soaking in the growth space region J5. In this case, buried growth accompanied by polycrystal also occurs around the SiC single crystal J8.

  However, in such an apparatus, there is a problem that when the crucible J1 is heated, graphite fine particles jump out from the cylindrical portion J7 into the growth space region J5 and are mixed as impurities into the SiC single crystal J8.

  Therefore, in order to prevent the inclusion of graphite fine particles into the SiC single crystal J8, there has been proposed one provided with a cylindrical TaC member J9 so as to cover the inner wall of the cylindrical portion J7 (see, for example, Patent Document 2). . FIG. 4 is a view of the lid member J2 shown in FIG. 3 as viewed from the shielding plate J6 side. As shown in this figure, since the inner wall of the cylindrical portion J7 is covered by the TaC member J9, even if graphite fine particles jump out of the inner wall of the cylindrical portion J7 toward the SiC single crystal J8, the TaC member J9 Of fine particles. In this way, graphite fine particles are prevented from being mixed into the growing SiC single crystal J8.

The shielding plate J6 is also made of graphite. In this case, a TaC coating film (not shown) is formed on the shielding plate J6 so that graphite fine particles do not protrude from the shielding plate J6 to the growth space region J5.
JP 2001-114598 A JP 2005-225710 A

  However, in the above conventional technique, as shown in FIG. 4, in the TaC member J9, the cross-sectional shape of the inner wall surface J10 perpendicular to the central axis of the crucible J1 is a perfect circle. For this reason, when the heat of the heated crucible J1 is given to the TaC member J9, the thermal radiation generated from the inner wall of the TaC member J9 acts on the TaC member J9 to the maximum.

  Specifically, when the TaC member J9 is heated by heating the crucible J1, thermal energy is emitted from the inner wall surface J10 of the TaC member J9. As described above, since the shape of the inner wall surface J10 perpendicular to the central axis of the crucible J1 in the TaC member J9 is a perfect circle, the heat energy is emitted from the inner wall surface J10 in the radial direction of the crucible J1, and the center of the perfect circle That is, it reaches the opposite inner wall surface J10 via the central axis of the crucible J1, and contributes to heating of the inner wall surface J10. In this case, the thermal energy emitted from all the inner wall surfaces J10 of the TaC member J9 reaches all the symmetric inner wall surfaces J10 around the central axis of the crucible J1, contributes to the heating of each place, and is reflected and reflected again. I will return to the place. For this reason, the entire inner wall surface J10 of the TaC member J9 is repeatedly heated by thermal radiation, and the soaking of the growth space region J5 that is the hollow portion of the TaC member J9 cannot be maintained, resulting in a high temperature.

  Thus, in the growth space region J5, if the temperature of the inner wall surface J10 of the TaC member J9 becomes higher than the temperature in the vicinity of the central axis of the crucible J1, the crystal growth in the vicinity of the central axis of the crucible J1 having a low temperature is accelerated. By doing so, the diameter expansion and the convex growth of the SiC single crystal J8 proceed rapidly. In particular, in the c-plane off-growth of the SiC single crystal J8, the problem is that a flat surface of (0001) called facet formed on the growth surface easily moves to the central axis of the crucible J1, and the SiC single crystal J8 has a big problem. There arises a problem that distortion occurs and the SiC single crystal J8 breaks.

  In addition, since the cross-sectional shape of the inner wall surface J10 perpendicular to the central axis of the crucible J1 in the cylindrical portion J7 is a perfect circle, even when TaC is coated on the inner wall surface J10 of the cylindrical portion J7, the same as described above due to thermal radiation. Problems arise.

  In view of the above points, the present invention provides a manufacturing apparatus and a manufacturing method capable of preventing the soaking of the growth space region from being maintained due to thermal radiation in embedded growth, and thus preventing the silicon carbide single crystal from cracking. The purpose is to provide.

  In order to achieve the above object, according to the present invention, the lid (20) is plate-shaped, and the surface of the plate is arranged perpendicular to the central axis of the crucible (1). The cylinder is formed in a cylindrical shape and protrudes from the support plate (23a) to the silicon carbide raw material (50) side by integrating one of the open ends of the cylinder with one surface of the support plate (23a). A cylindrical portion covering a portion (23b) and a cylindrical portion disposed in a hollow portion of the cylindrical portion (23b), wherein the hollow portion of the tube is used as a growth space region (60) and sublimation gas is supplied The cylindrical portion covering member (23c) is configured to have a surface with a different distance from the central axis in the radial direction of the crucible (1) with the central axis of the crucible (1) as a center. And an inner wall surface (23e).

  According to this, out of the thermal energy spreading in the radial direction of the crucible (1) around the central axis of the crucible (1), it is reflected by the inner wall surface (23e) within a certain range and returns to the central axis of the crucible (1) again. Even if there is one place of the incoming inner wall surface (23e), reflection is performed at a reflection angle according to the incident angle with respect to the inner wall surface (23e) at the other place of the inner wall surface (23e) within a certain range. For this reason, it is possible to disperse the thermal energy that travels from the central axis of the crucible (1) in the radial direction of the crucible (1), reducing the influence of the thermal radiation received on the inner wall surface (23e) of the cylindrical portion covering member (23c). can do. Therefore, the temperature gradient in the hollow part of cylindrical part (23b) can be made small, and the growth space area | region (60) in which a silicon carbide single crystal (70) grows can be maintained at soaking | uniform_heating. By the above, the diameter expansion and convex growth of the silicon carbide single crystal (70) can be prevented, and cracking of the silicon carbide single crystal (70) can be prevented.

  In this case, in the cylindrical portion covering member (23c), the shape of the inner wall surface (23e) in the direction perpendicular to the central axis of the crucible (1) is a polygon.

  Thereby, the thermal energy emitted from the inner wall surface (23e) of the cylindrical portion covering member (23c) in the radial direction of the crucible (1) is reflected at a reflection angle according to the incident angle incident on each side of the polygon. And heat energy can be dispersed.

  Further, the cylindrical portion covering member (23c) can be configured by combining a plurality of plate materials into a cylindrical shape. Thereby, the cylindrical part covering member (23c) in which the cross-sectional shape of the inner wall surface (23e) in the direction perpendicular to the central axis of the crucible (1) is a polygon can be easily configured.

  In the above description, the silicon carbide single crystal manufacturing apparatus has been described, but the same can be said for the silicon carbide single crystal manufacturing method. That is, as the cylindrical portion covering member (23c), an inner wall surface (23e) having a surface with a different distance from the central axis in the radial direction of the crucible (1) around the central axis of the crucible (1). The thing provided with can be used. Thereby, since heat energy can be reflected and dispersed at a reflection angle according to the incident angle with respect to each point of the inner wall surface (23e), the heat radiation of the inner wall surface (23e) of the cylindrical portion covering member (23c) is reduced. The influence can be reduced.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional configuration of the SiC single crystal manufacturing apparatus according to the first embodiment of the present invention. As shown in this figure, the SiC single crystal manufacturing apparatus includes a graphite crucible 1 including a bottomed cylindrical container body 10 and a circular lid body 20.

  A pedestal 11 is disposed on the bottom of the container body 10 in the crucible 1, and a shaft 12 is erected on the pedestal 11. A shield plate 13 having a surface facing the growth surface of the seed crystal 40 is attached to the tip of the shaft 12.

  Furthermore, a SiC powder raw material 50 serving as a sublimation gas supply source is disposed in the container body 10. The sublimation gas from the powder raw material 50 is recrystallized on the surface of the seed crystal 40 using the space between the seed crystal 40 and the shielding plate 13 in the space in the crucible 1 as a growth space region 60. The SiC single crystal 70 is grown on the surface.

  The lid 20 includes a cylindrical side wall portion 21, a disk-shaped lid member 22 that closes one of the openings of the side wall portion 21, and a shielding portion 23 that is accommodated in the side wall portion 21. . The lid member 22 is provided with a cylindrical protrusion 22a, and, for example, a circular SiC seed crystal 40 is attached to the opening end of the protrusion 22a so as to close the opening end. The shielding plate 13 is coated with a TaC material (not shown) so that powder generated from the shielding plate 13 by heating the crucible 1 does not contribute to the growth of the SiC single crystal 70 as an impurity.

  The shielding part 23 includes a support plate 23a, a cylindrical part 23b, and a cylindrical part covering member 23c. The support plate 23a is provided with a window portion 23d through which the plate penetrates, and the side surface is fixed to the inner wall of the side wall portion 21 in a state where the projection portion 22a of the lid member 22 is inserted into the window portion 23d. . The cylindrical portion 23b has a skirt shape, that is, a cylindrical shape, and one end side of the cylindrical portion is integrated with one surface of the support plate 23a. The cylindrical portion 23b serves to reduce the radial temperature distribution around the seed crystal 40, that is, to soak the growth space region 60. In addition, the growth surface of the seed crystal 40 becomes lower in temperature than other portions by the cylindrical portion 23b.

  The cylindrical portion covering member 23c plays a role of preventing graphite fine particles from jumping out of the cylindrical portion 23b into the growth space region 60 and being mixed into the SiC single crystal 70 as impurities when the crucible 1 is heated. is there. The cylindrical portion covering member 23c has a cylindrical shape, and one end side is integrated with one surface of the support plate 23a. In this case, the other end side of the cylindrical portion covering member 23c protrudes closer to the powder raw material 50 than the other end side of the cylindrical portion 23b. Thereby, all the inner walls of the cylindrical portion 23 b are covered with the cylindrical portion covering member 23 c, and the movement of the graphite fine particles to the SiC single crystal 70 can be prevented.

  FIG. 2 is a view of the lid 20 shown in FIG. 1 as viewed from the shielding plate 13 side. In FIG. 2, the SiC single crystal 70 and the like are omitted. In the present embodiment, the cylindrical portion covering member 23 c includes an inner wall surface 23 e having a surface with a different distance from the central axis in the radial direction of the crucible 1 around the central axis of the crucible 1. Specifically, as shown in FIG. 2, in the cylindrical portion covering member 23 c, the cross-sectional shape of the inner wall surface 23 e perpendicular to the central axis of the crucible 1 is not a perfect circle but a polygon. Thereby, the incident angle which faces the central axis of the crucible 1 differs depending on the location of the inner wall surface 23e.

  A TaC material is employed as the cylindrical portion covering member 23c. As the material of the cylindrical portion covering member 23c, any material containing Ta may be used. For example, a carbide of Ta or a Ta material can be employed. The Ta material is heated during the growth of the SiC single crystal 70 to become TaC.

  The hollow portion of the cylindrical portion covering member 23c is used as a buried growth space, that is, a growth space region 60, and sublimation gas is supplied.

  And the resistance heater which is not illustrated is arrange | positioned so that the outer periphery of the crucible 1 may be enclosed. The above is the configuration of the SiC single crystal manufacturing apparatus according to the present embodiment.

  Next, a method for manufacturing a SiC single crystal using the SiC single crystal manufacturing apparatus will be described with reference to the drawings. First, as shown in FIG. 1, the seed crystal 40 is attached to the opening end of the protrusion 22 a of the lid member 22, and the lid member 22 is attached to the side wall portion 21 to which the shielding portion 23 is attached. On the other hand, the pedestal 11 is disposed on the container body 10, the shielding plate 13 is attached via the shaft 12, and the powder material 50 is disposed on the container body 10.

  The shielding plate 13 is coated with TaC so that powder is not generated from the shielding plate 13 and mixed into the SiC single crystal 70.

  Subsequently, the crucible 1 is placed in a heating chamber (not shown), and gas is discharged using an exhaust mechanism (not shown), whereby the inside of the external chamber including the inside of the crucible 1 is evacuated and the resistance heater is energized. Is heated, and the crucible 1 is heated by the radiant heat to bring the inside of the crucible 1 to a predetermined temperature. At this time, a temperature difference is generated by the heater by changing the power of energization to each heater.

  For example, an inert gas (Ar gas or the like), hydrogen, or a mixed gas such as nitrogen serving as a dopant to the crystal flows into the heating chamber. This inert gas is discharged via the exhaust pipe. Until the temperature of the growth surface of the seed crystal 40 and the temperature of the SiC powder raw material 50 are raised to the target temperature, the atmosphere in the heating chamber is set to an atmospheric pressure close to atmospheric pressure to suppress sublimation from the powder raw material 50 and reach the target temperature. The pressure is reduced to a predetermined atmospheric pressure. For example, when the growth crystal is 4H—SiC, the temperature of the powder raw material 50 is 2100 to 2300 ° C., the temperature of the growth crystal surface is lower by about 10 to 200 ° C., and the atmospheric pressure is 0.1 to 20 Torr. And

  Thus, the powder raw material 50 is sublimated by heating the powder raw material 50, and sublimation gas is generated from the powder raw material 50. The sublimation gas passes through the growth space region 60 and is supplied to the seed crystal 40, and the SiC single crystal 70 grows. In this case, buried growth involving the polycrystal 45 also occurs around the SiC single crystal 70.

  When growing the SiC single crystal 70 as described above, when the crucible 1 is heated, the cylindrical portion covering member 23c is also heated, so that heat radiation is generated from the inner wall surface 23e of the cylindrical portion covering member 23c. Arise. When the thermal energy reaches the inner wall surface 23e on the opposite side via the central axis of the crucible 1, it contributes to the heating of the inner wall surface 23e.

  However, in the cylindrical portion covering member 23c, the inner wall surface 23e perpendicular to the central axis of the crucible 1 has a polygonal shape, so that radiation that spreads in the radial direction of the crucible 1 around the central axis of the crucible 1, that is, heat Of the energy, there is only one point on one side that is reflected by one side of the polygon and returns to the central axis of the crucible 1 again. That is, in a place excluding one point on each side of the polygon, the thermal energy is reflected at a reflection angle according to the incident angle with respect to each side, so that the thermal energy traveling in the radial direction of the crucible 1 from the central axis of the crucible 1 is Distributed on each side of the polygon. Thus, the thermal energy does not return to the place where the thermal energy is emitted, and the effect of thermal radiation on each side is weakened. That is, the influence of heat radiation on the inner wall surface 23e of the cylindrical portion covering member 23c is reduced, and the temperature rise of the inner wall surface 23e of the cylindrical portion covering member 23c due to heat radiation can be prevented.

  Of course, the thermal energy emitted from one side of the polygon proceeds in the radial direction of the crucible 1 via the central axis of the crucible 1 and is reflected by the inner wall surface 23e of the cylindrical portion covering member 23c to be reflected on the central axis of the crucible 1 again. Although there are paths returning, the number of the paths is small, and the temperature rise of the inner wall surface 23e of the cylindrical portion covering member 23c can be suppressed.

  As described above, in the cylindrical portion covering member 23c, the influence of thermal radiation on the inner wall surface 23e of the cylindrical portion covering member 23c is reduced by making the inner wall surface 23e perpendicular to the central axis of the crucible 1 into a polygonal shape. Therefore, the growth space region 60 surrounded by the cylindrical portion covering member 23c is kept soaked. Thereby, the expansion of the diameter of SiC single crystal 70 and the progress of convex growth are suppressed, SiC single crystal 70 is not distorted, and cracking of SiC single crystal 70 can be prevented. In this case, in the c-plane off-growth of the SiC single crystal 70, the facet can be suppressed from moving to the central axis of the crucible 1.

  As described above, in the present embodiment, in the cylindrical portion covering member 23c disposed in the hollow portion of the cylindrical portion 23b, the cross-sectional shape of the inner wall surface 23e perpendicular to the central axis of the crucible 1 is a polygonal shape. Is a feature.

  Thereby, the thermal energy emitted in the radial direction of the crucible 1 from the inner wall surface 23e of the cylindrical portion covering member 23c can be reflected at a reflection angle according to the incident angle incident on each side of the polygon. Thereby, thermal energy can be dispersed on each surface constituting the inner wall surface 23e of the cylindrical portion covering member 23c, and the entire inner wall surface 23e can be prevented from being affected repeatedly by heat radiation. In this way, the effect of heat radiation can be reduced. That is, in the growth space region 60, the expansion of the temperature gradient in the radial direction of the crucible 1 can be suppressed, and the growth space region 60 can be maintained soaking.

  As a result, since the SiC single crystal 70 grows in a state where the temperature difference is reduced in the radial direction of the crucible 1, the stress in the SiC single crystal 70 can be reduced, and the convex growth of the SiC single crystal 70 can be suppressed. . Therefore, distortion of SiC single crystal 70 can be suppressed, and as a result, cracking of SiC single crystal 70 can be prevented.

(Other embodiments)
In the above embodiment, the cylindrical portion covering member 23c is made of TaC material. However, the cylindrical portion covering member 23c can be made of a plate material coated with TaC. Further, the cylindrical portion covering member 23c may be configured by combining a plurality of plates made of TaC material. Further, as the cylindrical portion covering member 23c, a TaC coating may be used by combining a plurality of plates having high heat resistance.

  In the above embodiment, the effect of heat radiation is reduced by making the shape of the inner wall surface 23e perpendicular to the central axis of the crucible 1 in the cylindrical portion covering member 23c into a polygon, but the inner wall surface 23e is rough. It may be a surface. In this case, since heat energy is irregularly reflected by the rough surface, the effect of heat radiation can be reduced, and the high temperature of the inner wall of the cylindrical portion covering member 23c can be suppressed.

It is a section lineblock diagram of a SiC single crystal manufacturing device concerning a 1st embodiment of the present invention. It is the figure which looked at the cover body shown by FIG. 1 from the shielding board side. It is a typical cross-section figure of the conventional SiC single crystal manufacturing apparatus. It is the figure which looked at the cover material shown by FIG. 3 from the shielding board side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Crucible, 10 ... Container main body, 20 ... Cover body, 23 ... Shielding part, 23a ... Supporting plate, 23b ... Cylindrical part, 23c ... Cylindrical part covering member, 23e ... Inner wall surface, 40 ... Seed crystal, 50 ... Powder raw material 60 ... Growth space region, 70 ... SiC single crystal.

Claims (6)

A hollow cylindrical crucible (1) having a bottomed cylindrical container body (10) and a lid (20) for closing the container body (10); By disposing a seed crystal (40) made of a silicon carbide substrate in (20) and disposing a silicon carbide raw material (50) in the container body (10) and supplying a sublimation gas of the silicon carbide raw material (50). In the silicon carbide single crystal manufacturing apparatus for growing the silicon carbide single crystal (70) on the seed crystal (40),
The lid (20)
A support plate (23a) which is plate-shaped and whose surface is disposed perpendicular to the central axis of the crucible (1);
It has a cylindrical shape, and one side of the opening end of the cylinder is integrated with one surface of the support plate (23a), thereby protruding from the support plate (23a) to the silicon carbide raw material (50) side. A cylindrical portion (23b),
Cylindrical portion covering member (23c) which is disposed in a hollow portion of the cylindrical portion (23b), and in which the hollow portion of the tube is used as a growth space region (60) and the sublimation gas is supplied. And
The cylindrical portion covering member (23c) has an inner wall surface (23e) having a surface with a different distance from the central axis in the radial direction of the crucible (1) around the central axis of the crucible (1). And a silicon carbide single crystal manufacturing apparatus. The inner wall surface (23e) of the cylindrical portion covering member (23c) has a polygonal cross-sectional shape perpendicular to the central axis of the crucible (1). Silicon carbide single crystal production equipment. The said cylindrical part coating | coated member (23c) is a manufacturing apparatus of the silicon carbide single crystal of Claim 1 or 2 comprised by combining several board | plate materials in the cylinder shape. A hollow cylindrical crucible (1) having a bottomed cylindrical container body (10) and a lid (20) for closing the container body (10); By disposing a seed crystal (40) made of a silicon carbide substrate in (20) and disposing a silicon carbide raw material (50) in the container body (10) and supplying a sublimation gas of the silicon carbide raw material (50). In the method for producing a silicon carbide single crystal, the silicon carbide single crystal (70) is grown on the seed crystal (40).
As the lid (20),
A support plate (23a) which is plate-shaped and whose surface is disposed perpendicular to the central axis of the crucible (1);
It has a cylindrical shape, and one side of the opening end of the cylinder is integrated with one surface of the support plate (23a), thereby protruding from the support plate (23a) to the silicon carbide raw material (50) side. A cylindrical portion (23b),
Cylindrical portion covering member (23c) which is disposed in a hollow portion of the cylindrical portion (23b), and in which the hollow portion of the tube is used as a growth space region (60) and the sublimation gas is supplied. And
The cylindrical portion covering member (23c) has an inner wall surface (23e) having a surface with a different distance from the central axis in the radial direction of the crucible (1) around the central axis of the crucible (1). )
After the silicon carbide raw material (50) is arranged in the container body (10) and the container body (10) is closed with the lid body (20) to form the crucible (1), the crucible ( 1) is heated to generate the sublimation gas from the silicon carbide raw material (50), and the sublimation gas is supplied to the growth space region (60), whereby the silicon carbide single crystal is added to the seed crystal (40). A method for producing a silicon carbide single crystal, comprising growing a crystal (70). As the cylindrical portion covering member (23c), the inner wall surface (23e) of the cylindrical portion covering member (23c) has a polygonal cross-sectional shape perpendicular to the central axis of the crucible (1). The method for producing a silicon carbide single crystal according to claim 4. The method for producing a silicon carbide single crystal according to claim 4 or 5, wherein the cylindrical portion covering member (23c) is configured by combining a plurality of plate members into a cylindrical shape.

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