JP5541269B2 - Silicon carbide single crystal manufacturing equipment - Google Patents

Description

  The present invention relates to an apparatus for producing a silicon carbide (hereinafter referred to as SiC) single crystal that can be used for a material such as a semiconductor or a light emitting diode.

  Conventionally, a sublimation recrystallization method has been widely used as a method for growing a SiC single crystal (for example, see Patent Document 1). This sublimation recrystallization method involves joining a seed crystal to a graphite pedestal placed in a graphite crucible, heating and sublimating the SiC raw material arranged at the bottom of the crucible, and supplying the sublimation gas to the seed crystal. To grow a SiC single crystal.

  In a SiC single crystal manufacturing apparatus using such a sublimation recrystallization method, for example, a graphite crucible is used as a container constituting the growth space of the SiC single crystal. Specifically, a conventional graphite crucible includes a bottomed cylindrical crucible body having an open top surface and a lid member that closes the opening of the crucible body. Then, with the portion protruding at the center of the lid as a pedestal, an SiC single crystal substrate serving as a seed crystal is bonded onto the pedestal via an adhesive or the like, and SiC raw material powder is disposed on the bottom surface of the crucible body. .

  Using the graphite crucible having such a configuration, the raw material powder is heated and sublimated by a heating device arranged on the outer periphery of the graphite crucible and supplied to the surface of the SiC single crystal substrate. A single crystal is grown.

Patent 3792699 JP 2004-338971 A

  However, as shown in Patent Document 1, a conventional SiC single crystal manufacturing apparatus has a structure in which a pedestal is integrally formed with a lid, and therefore, an SiC single crystal grows on the surface of an SiC single crystal substrate. At the same time, SiC polycrystal grows in other parts of the lid material except where the SiC single crystal substrate is installed, and the thermal expansion coefficient of the SiC polycrystal and the lid material during the cooling process after the crystal growth is completed. However, because SiC polycrystal adheres only to the lower side of the lid, the lid material is deformed, cracked, and affected by the stress, which deteriorates the quality of the grown SiC single crystal. There is a problem of making it. In Patent Document 2, the pedestal portion (buffer member) to which the SiC single crystal substrate is bonded is thinned so that no stress is applied to the SiC single crystal substrate and the SiC single crystal. While this method was effective as long as the growth length of the SiC single crystal was small, the longer the SiC single crystal was grown, the thinner the pedestal portion was due to the weight of the SiC single crystal. There is a problem in that the amount of deformation becomes excessive, and the SiC single crystal substrate is also deformed by the influence, thereby degrading the quality of the grown SiC single crystal.

  An object of this invention is to suppress that the quality of a SiC single crystal deteriorates by the deformation | transformation of a cover material in view of the said point.

  In order to achieve the above object, in the present invention, the SiC raw material (2) and the SiC single crystal substrate (3) serving as a seed crystal are disposed in the container (1), and the SiC raw material (2) is heated and sublimated to produce SiC. In a SiC single crystal manufacturing apparatus for growing a SiC single crystal (4) on a single crystal substrate (3), the container (1) has a hollow shape in which one side is open and the SiC raw material (2) is disposed inside. A main body (1a), a lid (1b) disposed on one surface side of the main body (1a), and a base (5) on which the SiC single crystal substrate (3) is disposed, The material (1b) and the pedestal (5) are configured as separate members, and the pedestal (5) is bonded to the lid material (1b) via the joining members (6, 8, 9). Yes.

  Thus, the pedestal (5) is formed of a separate member from the lid (1b). For this reason, the SiC single crystal (4) grows on the surface of the SiC single crystal substrate (3), and at the same time, other parts of the lid (1b) other than the SiC single crystal substrate (3) are installed. The SiC polycrystal (11) grows in the SiC, the SiC polycrystal (11) and the lid material (1b) have different coefficients of thermal expansion, and the SiC polycrystal (11) only under the lid (1b). In the cooling process after the crystal growth of the SiC single crystal (4), even if the lid member (1b) is deformed or cracked, the lid is interposed via the joining member (6). The influence is hardly transmitted to the base (5) bonded to the material (1b). The SiC polycrystal (11) also grows around the pedestal (5), but the pedestal (5) is almost uniformly compressed or pulled by the SiC polycrystal (11). Is not reached. Therefore, the SiC single crystal (4) grown on the SiC single crystal substrate (3) can be grown long with high quality.

  Further, by disposing a thin plate-shaped cushioning material (7) between the lid member (1b) and the pedestal (5), and disposing the joining members (8, 9) on both surfaces of the cushioning material (7), The base (5) is bonded to the lid (1b) via the cushioning material (7) and the joining members (8, 9).

  Thus, the pedestal (5) can also be bonded to the lid material (1b) via the cushioning material (7), and the cushioning material (7) is more influenced by the deformation of the lid material (1b) after crystal growth. It can be made difficult to reach the pedestal (5). Therefore, the SiC single crystal (4) grown on the SiC single crystal substrate (3) can be grown longer with higher quality.

  Also in this case, the recess (1c) can be formed in the lid member (1b), and the cushioning material (7) and the joining members (8, 9) can be arranged in the recess (1c). Further, in this case, if the thickness of the cushioning material (7) and the joining members (8, 9) is made thicker than the depth of the recess (1c), the lid material (1b) and the base (5) are formed. Since it can be made not to contact, it becomes possible to suppress the influence by the deformation | transformation of the cover material (1b) after crystal growth more.

  In addition, the buffer material (7) is disposed on the outer periphery of the base (5) via the joining member (10), thereby further affecting the influence of the SiC polycrystal (11) grown on the lower side of the lid material (1b). It becomes possible to suppress.

  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.

It is a figure which shows the cross-sectional structure of the graphite crucible with which the manufacturing apparatus of the SiC single crystal concerning the reference form of this invention is equipped. It is a figure which shows the cross-sectional structure of the graphite crucible with which the manufacturing apparatus of the SiC single crystal concerning 1st Embodiment of this invention is equipped. It is a figure which shows the cross-sectional structure of the graphite crucible with which the manufacturing apparatus of the SiC single crystal concerning 2nd Embodiment of this invention is equipped.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(Reference form)
A reference embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a state in which a SiC single crystal is grown using the SiC single crystal manufacturing apparatus according to the present embodiment.

  As shown in FIG. 1, a cylindrical graphite crucible 1 is used as a container of a SiC single crystal production apparatus. The graphite crucible 1 sublimates the SiC raw material powder (SiC raw material) 2 provided at the bottom of the graphite crucible 1 by heating to make a 1 mm thick SiC single crystal substrate 3 which is a relatively low temperature seed crystal. The SiC single crystal 4 is grown on the crystal.

  The graphite crucible 1 includes a bottomed cylindrical crucible body 1a having an open top surface and a lid 1b that closes the opening of the crucible body 1a. A concave portion 1c that is recessed in a circular shape is formed in the central portion of the lid 1b that constitutes the graphite crucible 1, and a cylindrical shape is formed in the concave portion 1c via a joining member 6 that is made of a carbon adhesive or the like. A pedestal 5 is attached. The diameter of the pedestal 5 is slightly smaller than the diameter of the recess 1c, and the pedestal 5 is configured to be fitted into the recess 1c by a predetermined amount.

  The pedestal 5 is made of a material having a thermal expansion coefficient substantially equal to that of SiC, and is made of, for example, an isotropic graphite material. By using such a material for the pedestal 5, it is possible to suppress the generation of stress due to the difference in thermal expansion coefficient between the pedestal 5 and the SiC single crystal substrate 3 serving as a seed crystal during crystal growth. Moreover, the shape of the base 5 is a cylindrical shape, and thickness is 30 mm. By making the pedestal 5 have such a strong shape, it is possible to suppress deformation of the pedestal 5 due to weight during crystal growth of the SiC single crystal 4. The pedestal 5 is a rigid body, and the weight of the SiC single crystal 4 during crystal growth can further suppress deformation of the pedestal 5.

  As described above, since the lid member 1b and the pedestal 5 are configured as different members and the joining member 6 is interposed therebetween, it is difficult for the influence of the deformation of the lid member 1b to be transmitted to the pedestal 5 in the cooling process after crystal growth. it can. Note that the pedestal 5 and the graphite lid 1b may be the same material or different materials, and in any case, the graphite lid 1b is deformed by the growth of SiC polycrystal in the cooling process after crystal growth. Therefore, although stress can be generated, the stress can be reduced by the joining member 6. That is, the joining member 6 is made of a carbon adhesive or the like, but is slightly softer than the graphite (tensile strength: 25 to 40 MPa) constituting the lid 1b (tensile strength: 5 to 20 MPa. Liquid carbon adhesion). The agent is cured by heat treatment at several hundreds of degrees Celsius and functions as an adhesive, but during the heat treatment, the organic solvent evaporates, and the path formed in the process of evaporating the organic solvent becomes a void. Therefore, since the solidified adhesive has a weaker bond between atoms than ordinary graphite), even if the lid 1b after crystal growth is greatly warped, the influence of the warp can be mitigated by the buffering of the joining member 6. . The thickness of the joining member 6 is arbitrary.

  On the other hand, a heating device (not shown) such as an induction coil is provided outside the graphite crucible 1 so as to surround the outer periphery of the graphite crucible 1, and the graphite crucible 1 is controlled by controlling the power of the heating device. It is configured so that the temperature inside can be controlled. For example, when the SiC single crystal 4 is grown, the temperature of the SiC single crystal substrate 3 as a seed crystal is kept at a temperature about 100 ° C. lower than the temperature of the SiC raw material powder 2 by adjusting the power of the heating device. Can be drunk. Although not shown, the graphite crucible 1 is housed in a vacuum vessel into which argon gas can be introduced, and can be heated in this vacuum vessel.

  An SiC single crystal manufacturing process using the SiC single crystal manufacturing apparatus configured as described above will be described.

  First, the SiC raw material powder 2 is disposed on the bottom surface side of the main body 1a of the graphite crucible 1, and the SiC single crystal substrate 3 as a seed crystal is attached to the base 1c attached to the lid 1b via the joining member 6. wear. Then, the lid 1b is attached to the main body 1a, the graphite crucible 1 is accommodated in a vacuum container (not shown), and the inside of the vacuum container is made an argon gas atmosphere. Then, the temperature of SiC raw material powder 2 is heated to 2000-2500 degreeC with the heating apparatus which is not illustrated, and the temperature of SiC single crystal substrate 3 becomes lower than the temperature of SiC raw material powder 2 by adjustment of a heating apparatus, etc. In addition, a temperature gradient is provided in the graphite crucible 1.

  Next, the pressure in the graphite crucible 1 is adjusted to 13.3 Pa to 26.7 kPa by adjusting the degree of vacuum of the vacuum vessel, and when the sublimation growth starts, the SiC raw material powder 2 sublimates to become a sublimation gas, and SiC The SiC single crystal 4 grows on the surface of the SiC single crystal substrate 3 that reaches the single crystal 4 and is at a relatively lower temperature than the SiC raw material powder 2 side. Thereafter, the SiC single crystal 4 is grown while making the amount of reduction of the SiC raw material powder 2 constant. For example, the temperature distribution in the graphite crucible 1 can be adjusted by adjusting the power of the heating device. By doing in this way, the silicon / carbon ratio in the crucible 1 can be stabilized.

  Even if the lid 1b is deformed during the cooling process after the crystal growth during the growth of the SiC single crystal 4, the lid 1b and the pedestal 5 are formed as separate members. The influence is not transmitted to the pedestal 5 bonded to the lid 1b. Further, the pedestal 5 is also thermally expanded by heating, but since the material of the pedestal 5 is selected so that the thermal expansion coefficient of the pedestal 5 is substantially the same as the thermal expansion coefficient of SiC, the SiC single crystal substrate 3 Is hardly affected by the thermal expansion coefficient of the base 5. Therefore, the SiC single crystal 4 grown on the SiC single crystal substrate 3 can be grown to a length of 30 mm with high quality.

  As described above, in this embodiment, the pedestal 5 is formed of a member separate from the lid member 1b, so that the SiC single crystal 4 grown on the SiC single crystal substrate 3 can be grown long with high quality. . Further, by selecting a material having a thermal expansion coefficient substantially the same as the thermal expansion coefficient of SiC as the material of the pedestal 5, it becomes possible to grow the SiC single crystal 4 with a higher quality and longer.

(First embodiment)
A first embodiment of the present invention will be described. In the present embodiment, the configuration of the SiC single crystal manufacturing apparatus is changed with respect to the reference embodiment, and the other aspects are the same as those in the reference embodiment, and therefore only different portions will be described.

  FIG. 2 is a cross-sectional view showing a state in which the SiC single crystal is grown using the SiC single crystal manufacturing apparatus according to the present embodiment.

  The cushioning material 7 is disposed in a circular recess 1c formed in the center of the lid 1b. A pedestal 5 is bonded to the cushioning material 7. The buffer material 2 is composed of, for example, a carbon sheet (tensile strength: about 5 MPa), and fulfills the function of mitigating the influence of thermal expansion of the graphite lid material 1b being transmitted to the pedestal 5.

  The buffer material 7 has a circular thin plate shape corresponding to the shape of the recess 1c, and the joining members 8 and 9 made of carbon adhesive or the like are arranged on both sides thereof, so that the joining members 8 and 9 are interposed. In addition to being bonded to the lid member 1 b, it is bonded to the pedestal 5 via the joining members 8 and 9. The diameter of the cushioning material 7 is slightly smaller than the diameter of the recess 1 c and is almost the same as the diameter of the base 5. Thus, the base 5 is fixed to the lid 1b via the cushioning material 2 and the joints 4 and 5, and the base 5 protrudes from the lid 1b.

  The thickness of the cushioning material 7 is not particularly limited, but if the thickness is increased, the amount of elastic deformation can be increased, so that the influence of the deformation of the lid material 1b can be more difficult to be transmitted to the base 5. When the thickness of the cushioning material 7 and the joining members 8 and 9 is larger than the depth of the recess 1c, the base 5 is bonded to the lid material 1b via the cushioning material 7 and the joining members 8 and 9 The lid member 1b and the pedestal 5 preferably have a thickness that does not contact the lid member 1b. Since the lid member 1b and the pedestal 5 are configured as different members, it is difficult for the influence of the thermal expansion of the lid member 1b to be transmitted to the pedestal 5, but the lid member 1b and the pedestal 5 do not come into contact in this way. If it is, it becomes possible to suppress the influence more.

  In this way, the pedestal 5 can be bonded to the lid 1b via the cushioning material 7, and the cushioning material 7 can make it difficult for the influence of the thermal expansion of the lid 1b to be transmitted to the pedestal 5. Therefore, the SiC single crystal 4 grown on the SiC single crystal substrate 3 can be grown to a length of 30 mm with higher quality.

(Second Embodiment)
A second embodiment of the present invention will be described. In this embodiment, the configuration of the SiC single crystal manufacturing apparatus is changed with respect to the first embodiment, and the other parts are the same as those in the reference embodiment, and therefore only different portions will be described.

  FIG. 3 is a cross-sectional view showing a state in which a SiC single crystal is grown using the SiC single crystal manufacturing apparatus according to the present embodiment. As shown in FIG. 3, the cushioning material 7 is further disposed on the outer peripheral side surface of the pedestal 5 via a joining member 10 made of carbon adhesive or the like. By doing so, the SiC single crystal 4 grows, and the SiC polycrystal 11 grown on the lower side of the lid portion 1b grows on the outer periphery of the buffer material 7, so that the deformation of the lid material 1b further increases. It is possible to make it difficult for the influence to be transmitted to the base 5. Therefore, the SiC single crystal 4 grown on the SiC single crystal substrate 3 can be grown to a length of 30 mm with higher quality.

(Other embodiments)
In the first to second embodiments, the cylindrical graphite crucible 1 is taken as an example of the container of the SiC single crystal production apparatus. However, this is merely an example, and the shape of the graphite crucible 1 is not necessarily limited. It does not have to be cylindrical, and not all may be made of graphite. For example, the outer shape of the container may be a regular polygonal column shape, or the inner wall surface may be coated with Ta (tantalum) or the like.

  Moreover, although the example which formed the recessed part 1c in the cover material 1b was shown in 1st-2nd embodiment, the structure in which the recessed part 1c is not formed may be sufficient.

  In the first and second embodiments, the pedestal 5 is a rigid body, and the shape thereof is a cylindrical shape with a thickness of 30 mm. However, even if it is not a rigid body, the above-described shape is sufficiently effective. Further, if the SiC single crystal substrate 3 is a polygon, it may be a polygonal column shape corresponding to the polygon. The thickness may be any thickness as long as it is 5 times or more the thickness of the SiC single crystal substrate 3 and 0.5 times or more that of the SiC single crystal.

  DESCRIPTION OF SYMBOLS 1 ... Graphite crucible, 1a ... Main body, 1b ... Cover material, 2 ... SiC raw material powder, 3 ... Single crystal substrate, 4 ... SiC single crystal, 5 ... Base, 6, 8, 9 ... Joining member, 7 ... Buffer material DESCRIPTION OF SYMBOLS 10 ... Joining member, 11 ... SiC polycrystal

Claims (2)

In a container (1), a silicon carbide raw material (2) and a silicon carbide single crystal substrate (3) to be a seed crystal are arranged, and the silicon carbide raw material (2) is heated and sublimated to form the silicon carbide single crystal substrate (3). In a silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal (4) on
The container (1)
A hollow main body (1a) in which one surface is open and the silicon carbide raw material (2) is disposed inside;
A lid (1b) disposed on the one surface side of the main body (1a) to be opened;
A pedestal (5) on which the silicon carbide single crystal substrate (3) is disposed,
The lid material (1b) and the pedestal (5) are configured as separate members, and the pedestal (5) is bonded to the lid material (1b) via bonding members (6, 8, 9); And
Further, a thin plate-like cushioning material (7) is disposed between the lid material (1b) and the pedestal (5), and the joining members (8, 9) are disposed on both sides of the cushioning material (7). By being arranged, the base (5) is bonded to the lid member (1b) via the cushioning material (7) and the joining member (8, 9) ,
A concave portion (1c) is formed in the lid member (1b), and the cushioning material (7) and the joining member (8, 9) are disposed in the concave portion (1c), and the concave portion (1c) An apparatus for producing a silicon carbide single crystal, wherein the thickness of the cushioning material (7) and the joining member (8, 9) is larger than the depth . The silicon carbide single crystal according to claim 1 , wherein the buffer material (7) and the joining members (8, 9) are thicker than the depth of the recess (1c). apparatus.

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