JP2014034509A - Apparatus and method for manufacturing silicon carbide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing SiC single crystals that can curb an influence on growth of SIC single crystals by controlling radiant heat generated by heating of a lower coil.SOLUTION: The outer diameter of a coil for induction heating that constitutes a first heater 12 is made smaller than the outer diameter of an upper crucible 8c. This reduces a volume of a raw-material decomposition space where a raw material gas 3a is subjected to thermolysis, that is, a volume that the first heater 12 is responsible for heating. Therefore, the thermolysis of the raw material gas 3a is efficiently performed with a small power supplied to the first heater 12, which reduces radiant heat from a lower crucible 8a. Heating the growth surface of SiC single crystals 20 by radiant heat from the lower crucible 8a is thus suppressed to curb an influence on growth of the SiC single crystals 20, leading to good growth of the SiC single crystals 20.

Description

  The present invention relates to a SiC single crystal manufacturing apparatus and manufacturing method for manufacturing a SiC single crystal by supplying a raw material gas to a seed crystal composed of a silicon carbide (hereinafter referred to as SiC) single crystal. .

  Conventionally, as a SiC single crystal manufacturing apparatus, for example, a manufacturing apparatus having a structure shown in Patent Document 1 has been proposed. In this conventional SiC single crystal manufacturing apparatus, a heating coil is arranged so as to surround a cylindrical vacuum vessel, a source gas heating vessel and a crystal growth vessel are arranged inside the vacuum vessel, and the crystal growth vessel is moved up and down. It can be pulled up by a moving mechanism. The heating coil includes a lower coil that heats the lower part of the heating container and an upper coil that heats the periphery of the SiC single crystal, and can be driven independently. Then, the raw material gas introduced into the heating vessel is thermally decomposed by the lower coil, and the surface of the SiC single crystal can be controlled to a temperature suitable for crystal growth by the upper coil.

  In such a configuration, the raw material gas is heated and decomposed by heating the raw material gas heating vessel by induction heating of the heater with a heating coil so that a SiC single crystal can be grown on the surface of the seed crystal attached to the crystal growth vessel. The temperature distribution is controlled according to the state in the apparatus. Further, the SiC single crystal can be grown long by pulling up the crystal growth vessel by the vertical movement mechanism. And the SiC single crystal surface temperature in the long direction (growth direction) of a SiC single crystal is controlled by adjusting the power of a heating coil with the long growth of a SiC single crystal. Thereby, the temperature and supersaturation degree of the surface of the SiC single crystal can be controlled, and it is possible to obtain the same growth rate as in the initial stage of growth even during long growth.

JP 2008-169098 A

  However, in the SiC single crystal manufacturing apparatus described in Patent Document 1 described above, a large amount of power must be applied to the lower coil in order to thermally decompose the source gas by heating with the lower coil. Therefore, the growth surface of the SiC single crystal is also heated by the heat radiation of the heater heated by induction in the lower coil, which hinders the growth of the SiC single crystal. In particular, if the SiC single crystal has a certain length, the surface temperature of the SiC single crystal becomes higher than the growth possible temperature without applying power to the upper coil, and the SiC single crystal can be grown. It will disappear.

  In view of the above points, an object of the present invention is to provide a SiC single crystal manufacturing apparatus capable of suppressing radiant heat generated based on heating by a lower coil and suppressing an influence on the growth of a SiC single crystal.

  In order to achieve the above object, according to the invention described in claims 1 to 5, the crucible (8) is formed in a stepped cylindrical shape whose outer diameter changes, and the raw material gas (introduced into the hollow portion by the crucible ( 3a) a raw material decomposition region for thermally decomposing and a growth region for growing a silicon carbide single crystal (20), and a lower crucible (8a) below the crucible is heated by a heating device (12) By supplying the source gas to the surface of the seed crystal while thermally decomposing the gas, a silicon carbide single crystal is formed on the surface of the seed crystal (5) using the inside of the upper crucible (8c), which is the upper part of the crucible, as a growth region. An apparatus for producing a silicon carbide single crystal for crystal growth, wherein the heating device is disposed so as to surround the lower crucible, and the outer diameter of the heating device is smaller than the outer diameter of the upper crucible. It is a feature.

  Thus, the outer diameter of the heating device is made smaller than the outer diameter of the upper crucible. For this reason, the volume of the raw material decomposition | disassembly area | region which performs thermal decomposition of raw material gas, ie, the volume which must be heated with a heating apparatus, can be made small. Therefore, it is possible to efficiently decompose the raw material gas by applying a small amount of power to the heating device, and to reduce the heat radiation from the lower crucible. Therefore, heating of the growth surface of the SiC single crystal due to thermal radiation of the lower crucible can be suppressed, and the influence on the growth of the SiC single crystal can be suppressed, and the SiC single crystal can be grown well.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is sectional drawing of the SiC single crystal manufacturing apparatus 1 concerning 1st Embodiment of this invention. It is sectional drawing of the SiC single crystal manufacturing apparatus 1 concerning 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
As shown in FIG. 1, the SiC single crystal manufacturing apparatus 1 supplies a source gas 3a from a source gas supply source 3 through an inlet 2 provided at the bottom and out of the source gas 3a through an outlet 4 at the top. Unreacted gas is discharged. Then, the SiC single crystal manufacturing apparatus 1 forms an ingot of the SiC single crystal 20 by growing the SiC single crystal 20 on the seed crystal 5 made of the SiC single crystal substrate disposed in the apparatus.

  The SiC single crystal manufacturing apparatus 1 includes a source gas supply source 3, a vacuum vessel 6, a heat insulating material 7, a crucible 8, a crucible inner cylinder 9, a pedestal 10, a rotary pulling mechanism 11, and first and second heating devices 12 and 13. , A purge gas supply source 14 is provided.

  The source gas supply source 3 supplies an SiC source gas 3 a containing Si and C together with a carrier gas (for example, a mixed gas of a silane-based gas such as silane and a hydrocarbon-based gas such as propane) from the inlet 2.

  The vacuum vessel 6 is made of quartz glass or the like, has a hollow shape, can introduce and lead the carrier gas and the source gas 3a, and accommodates other components of the SiC single crystal manufacturing apparatus 1, The structure is such that the internal space accommodated therein can be depressurized by evacuation. The inlet 2 of the source gas 3a is provided at the bottom of the vacuum vessel 6, and the outlet 4 of the source gas 3a is provided at the upper part (specifically, the position above the side wall). Further, in the present embodiment, the vacuum vessel 6 has a stepped cylindrical shape in which the inner diameter and the outer diameter are changed in the middle of the flow direction of the raw material gas 3a, and the inner diameter is larger in the flow direction upstream than in the flow direction downstream. And the outer diameter is made small. Hereinafter, the upstream side in the flow direction of the raw material gas 3a whose inner diameter and outer diameter are reduced in the vacuum vessel 6, that is, the lower part is referred to as the container lower portion 6a, and the flow of the raw material gas 3a whose inner diameter and outer diameter are increased. A portion located downstream in the direction, that is, above is referred to as a container upper portion 6b.

  The first heating device 12 is disposed on the outer periphery of the lower portion 6a of the container. The inner diameter of the first heating device 12 is preferably smaller than the outer diameter of the SiC single crystal 20. The outer diameter of the lower part 6 a is made smaller than the diameter of the SiC single crystal 20.

  The heat insulating material 7 has an intermediate heat insulating material 7a and a cylindrical heat insulating material 7b. For example, graphite or graphite whose surface is covered with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide). By being configured, thermal etching can be suppressed.

  The intermediate heat insulating material 7a has a disk shape with an opening formed in the center, and has an outer diameter slightly smaller than the inner diameter of the container upper part 6b, and is constituted by a container lower part 6a and a container upper part 6b in the vacuum container 6. It is arranged on the stepped part. The opening formed in the center of the intermediate heat insulating material 7a has a circular shape, and the inner diameter is larger than the inner diameter of the container lower part 6a. For this reason, the hollow part of the container lower part 6a is in the state accommodated inside the opening part of the intermediate heat insulating material 7a.

  The cylindrical heat insulating material 7b is a cylindrical member whose outer diameter is slightly smaller than the inner diameter of the container upper part 6b, and is disposed coaxially with the vacuum container 6 so as to cover the inner wall surface of the vacuum container 6. Yes. The cylindrical heat insulating material 7b is installed on the outer edge of the intermediate heat insulating material 7a. As a result, the intermediate heat insulating material 7a is arranged at one of the open ends of the cylindrical heat insulating material 7b, the heat insulating material 7 becomes a bottomed cylindrical shape, and the portion other than the container lower part 6a in the vacuum vessel 6 is covered. It is supposed to be.

  The crucible 8 is formed in a stepped cylindrical shape having a hollow portion in which the inner diameter and the outer diameter change in the middle of the flow direction of the raw material gas 3a, constitutes a raw material decomposition region, and the surface of the seed crystal 5 A growth region for growing the SiC single crystal 20 is formed. The crucible 8 is also made of, for example, graphite or graphite whose surface is covered with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide), so that thermal etching can be suppressed. In the present embodiment, the crucible 8 is configured to have a lower crucible 8a, an intermediate crucible 8b, and an upper crucible 8c.

  The lower crucible 8a is configured by a cylindrical member having a hollow portion disposed in the container lower portion 6a. In the case of the present embodiment, the lower crucible 8a becomes a heating container (heater) that is induction-heated by the first heating device 12, and the raw material that flows into the lower crucible 8a with the internal space of the lower crucible 8a as the raw material decomposition region. The gas 3a is thermally decomposed.

  The intermediate crucible 8b is disposed so as to cover the inner wall surface of the opening from the upper surface of the intermediate heat insulating material 7a. That is, the intermediate crucible 8b is composed of a disk-shaped member having a hollow central portion, and a protruding portion that protrudes toward the lower crucible 8a is formed at the central portion, and this protruding portion is within the opening of the intermediate heat insulating material 7a. It is fitted and covers the inner wall surface of the opening. And it connects with the lower crucible 7a in the front-end | tip position of a projection part. Moreover, the inner wall surface of the hollow part located in the center of the protrusion part of the intermediate crucible 8b is made into the taper surface where the internal diameter was gradually expanded as it went to the flow direction downstream of the raw material gas 3a.

  The upper crucible 8c is a cylindrical member whose outer diameter is slightly smaller than the inner diameter of the cylindrical heat insulating material 7b, and is arranged coaxially with respect to the vacuum vessel 6 and the cylindrical heat insulating material 7b. It covers the wall. The upper crucible 8c is arranged from the upstream side in the flow direction of the source gas 3a to the downstream side with respect to the pedestal 10 so as to surround the pedestal 10. Moreover, the upper crucible 8c is installed on the outer edge of the intermediate crucible 8b. As a result, the intermediate crucible 8b is connected at one of the open ends of the upper crucible 8c, and the lower crucible 8a, the intermediate crucible 8b, and the upper crucible 8c are connected and arranged, whereby the inner wall surface of the heat insulating material 7 is obtained. Is supposed to be covered.

  The crucible inner cylindrical portion 9 is disposed further inside the lower crucible 8a. The source gas 3a is supplied to the seed crystal 5 side through the inside of the crucible inner cylindrical portion 9. The crucible inner cylindrical portion 9 has an outer diameter smaller than the inner diameter of the lower crucible 8a and is disposed coaxially with the lower crucible 8a. For this reason, a gap is formed between the lower crucible 8a and the crucible inner cylindrical portion 9, and the purge gas 14a containing an inert gas or an etching gas can be introduced by using the gap as a purge gas introduction hole. The crucible inner cylindrical portion 9 is also made of, for example, graphite or graphite whose surface is covered with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide) so that thermal etching can be suppressed. It is.

  The pedestal 10 is composed of a plate-like member that is arranged coaxially with the central axis of the crucible 8. For example, the pedestal 10 is made of graphite or graphite whose surface is coated with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide), so that thermal etching can be suppressed. The seed crystal 5 is affixed to the pedestal 10, and an SiC single crystal 20 is grown on the surface of the seed crystal 5. The pedestal 10 is formed in a shape corresponding to the shape of the seed crystal 5 to be grown, for example, a disk shape, and the outer diameter when the pedestal 10 is formed in a disk shape is larger than the outer diameter of the first heating device 12. ing. And the base 10 is connected with the pipe-shaped support shaft 11a with which the rotation pulling mechanism 11 was equipped in the surface on the opposite side to the surface where the seed crystal 5 is arrange | positioned.

  The rotary pulling mechanism 11 rotates and pulls up the pedestal 10 via a pipe-like support shaft 11a. One end of the support shaft 11 a is connected to the surface of the pedestal 10 on the side opposite to the attaching surface of the seed crystal 5, and the other end is connected to the main body of the rotary pulling mechanism 11. The support shaft 11a is also made of, for example, graphite or graphite whose surface is covered with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide), so that thermal etching can be suppressed. . With such a configuration, the pedestal 10, the seed crystal 5 and the SiC single crystal 20 can be rotated and pulled together with the support shaft 11a, and the growth surface of the SiC single crystal 20 has a desired temperature distribution. The growth surface temperature can always be adjusted to a temperature suitable for growth.

  The first and second heating devices 12 and 13 are constituted by induction heating coils, and are arranged so as to surround the vacuum vessel 6 and the crucible 8. The 1st heating apparatus 12 is arrange | positioned so that the circumference | surroundings of the container lower part 6a and the lower crucible 8a may be enclosed, and the 2nd heating apparatus 13 is arrange | positioned in the position corresponding to the container upper part 6b and the crucible upper part 8c. Specifically, the induction heating coil constituting the first heating device 12 is wound along the outer peripheral surface of the container lower portion 6a, and the outer diameter thereof is made at least smaller than the outer diameter of the upper crucible 8c. Yes. Preferably, the inner diameter of the induction heating coil constituting the first heating device 12 is preferably smaller than the outer diameter of the pedestal 10, that is, the outer diameter of the SiC single crystal 20. The induction heating coil constituting the second heating device 13 is wound along the outer peripheral surface of the container upper portion 6 b, and the outer diameter thereof is larger than the outer diameter of the first heating device 12. These 1st, 2nd heating apparatuses 12 and 13 are comprised so that temperature control can be carried out independently, respectively. By using the first and second heating devices 12 and 13 configured as described above, the temperature of the lower portion of the crucible 8 can be controlled by the first heating device 12, and the pedestal 10 and the second heating device 13 can be controlled. The temperature around the seed crystal 5 and the SiC single crystal 20 can be controlled.

  With this structure, the SiC single crystal manufacturing apparatus 1 according to the present embodiment is configured. Then, the manufacturing method of the SiC single crystal 20 using the SiC single crystal manufacturing apparatus 1 concerning this embodiment is demonstrated.

  First, the seed crystal 5 is attached to the pedestal 10 and installed in the crucible 8. Then, by controlling the first and second heating devices 12 and 13 and induction heating the lower crucible 8a and the upper crucible 8c, a desired temperature distribution is provided in the device. That is, the source gas 3a is recrystallized on the surface of the seed crystal 5 so that the SiC single crystal 20 grows and the sublimation rate is higher in the crucible 8 than the recrystallization rate. To do.

Further, the raw material gas 3a is introduced through the inlet 2 while introducing a carrier gas using an inert gas such as Ar or He, or an etching gas such as H ₂ or HCl, as necessary, while keeping the vacuum vessel 6 at a desired pressure. Thereby, source gas 3a flows as indicated by an arrow in FIG. 1, and is supplied to seed crystal 5 to grow SiC single crystal 20. At the same time, by introducing purge gas 14a as necessary, SiC single crystal 20 can be grown on the surface of seed crystal 5 while preventing polycrystals from adhering to the inner wall surface of crucible 8 or the like. Then, the base 10, the seed crystal 5, and the SiC single crystal 20 are rotated by the rotary pulling mechanism 11 through the support shaft 11 a while being pulled up according to the growth rate of the SiC single crystal 20. Thereby, the height of the growth surface of the SiC single crystal 20 is kept substantially constant, and the temperature distribution of the growth surface temperature can be controlled with good controllability, so that the SiC single crystal 20 is grown with good crystallinity. Is possible.

  At this time, the outer diameter of the induction heating coil constituting the first heating device 12 is made smaller than the outer diameter of the upper crucible 8c. For this reason, the volume of the raw material decomposition | disassembly area | region which performs the thermal decomposition of the raw material gas 3a, ie, the volume which must be heated by the 1st heating apparatus 12, can be made small. Therefore, it is possible to efficiently decompose the raw material gas 3a by applying a small amount of power to the first heating device 12, and to reduce the heat radiation from the lower crucible 8a. Therefore, heating of the growth surface of the SiC single crystal 20 due to thermal radiation of the lower crucible 8a can be suppressed, and the influence on the growth of the SiC single crystal 20 can be suppressed, and the SiC single crystal 20 can be favorably grown. .

  In particular, if the outer diameter of the first heating device 12 is made smaller than the outer diameter of the SiC single crystal 20, the radiant heat can be applied only to the vicinity of the central portion of the SiC single crystal 20. The influence of heat radiation can be more limited. For this reason, it becomes possible to suppress the influence on the growth of SiC single crystal 20 more effectively.

  In the case of the present embodiment, the intermediate heat insulating material 7a is arranged between the lower crucible 8a and the upper crucible 8c. For this reason, a temperature difference can be easily formed between the raw material decomposition region and the growth region. Thereby, the growth of the SiC single crystal 20 can be further promoted.

  Further, in the case of the present embodiment, the crucible 8 is provided with an intermediate crucible 8b, and the inner wall surface of the opening of the intermediate crucible 8b is gradually tapered toward the downstream side in the flow direction of the source gas 3a. It is trying to become. Since the source gas 3a is preferentially flowed in the straight direction, the inner wall surface of the intermediate crucible 8b can be separated from the flow of the source gas 3a. For this reason, it is possible to reduce the contact between the source gas 3a and the inner wall surface of the intermediate crucible 8b, and it is possible to make it difficult for SiC polycrystal to adhere to the inner wall surface of the intermediate crucible 8b.

  In particular, when the purge gas 14a is introduced from between the crucible inner cylindrical portion 9 and the lower crucible 8a, the contact of the source gas 3a with the inner wall surface of the intermediate crucible 8b by the wall of the purge gas 14a can be further suppressed. Therefore, it is possible to make it difficult for the SiC polycrystal to adhere to the inner wall surface of the intermediate crucible 8b.

(Second Embodiment)
A second embodiment of the present invention will be described. In the present embodiment, the heating mode of the first heating device 12 is changed with respect to the first embodiment, and the other aspects are the same as those in the first embodiment. To do.

  As shown in FIG. 2, the first heating device 12 is disposed on the outer periphery of the lower crucible 8a. In this embodiment, the first heating device 12 is configured by a resistance heating device including a resistance heating coil. ing. The lower crucible 8a is directly heated by the heating of the first heating device 12 itself.

  In addition, since the first heating device 12 itself is heated, a cylindrical intermediate heat insulating material 7a is installed so as to surround the first heating device 12, and the outer periphery of the intermediate heat insulating material 7a is surrounded. It is set as the structure provided with the vacuum vessel 6. For this reason, the vacuum container 6 of the present embodiment is not a stepped shape having different outer diameters in the container lower part 6a and the container upper part 6a as in the first embodiment, but is a cylindrical shape.

  Thus, even when the first heating device 12 is configured by a resistance heating device, the first embodiment is achieved by reducing the outer diameter of the first heating device 12 to be smaller than the outer diameter of the upper crucible 8c. The same effect can be obtained.

(Other embodiments)
In the first embodiment, the crucible inner cylindrical portion 9 is arranged in the lower crucible 8a, and the purge gas 14a is introduced through the gap between them, but the same structure as that of the second embodiment is used. You may make it prepare. Moreover, in the said 1st Embodiment, although the inner wall surface of the opening part of the intermediate crucible 8b became a taper surface, it can be set as the same structure also with respect to 2nd Embodiment.

  Further, in the first embodiment, the example in which the purge gas 14a is introduced has been described. However, even if the purge gas 14a is not introduced, the inner wall surface of the opening of the intermediate crucible 8b can be simply formed as a tapered surface. Adhesion suppression effect is obtained. That is, since it becomes possible to reduce the contact between the source gas 3a preferentially flowing in the straight direction and the inner wall surface of the intermediate crucible 8b, it is difficult for SiC polycrystal to adhere to the inner wall surface of the intermediate crucible 8b. You can

DESCRIPTION OF SYMBOLS 1 SiC single crystal manufacturing apparatus 3a Source gas 5 Seed crystal 6 Vacuum vessel 7 Heat insulating material 8 Crucible 8a Lower crucible 8b Intermediate crucible 8c Upper crucible 10 Base 12, 13 1st, 2nd heating apparatus 20 SiC single crystal

Claims (6)

Growth having a hollow portion and a stepped cylindrical shape having a changing outer diameter, and a raw material decomposition region for thermally decomposing the raw material gas (3a) introduced into the hollow portion and a silicon carbide single crystal (20) A crucible (8) constituting the region;
A pedestal (10) disposed in the growth region in the crucible;
A heating device (12) for heating the crucible,
A seed crystal (5) made of a silicon carbide single crystal substrate is placed on the pedestal, and the lower crucible (8a) below the crucible is heated by the heating device to thermally decompose the source gas. While supplying the source gas to the surface of the seed crystal, the silicon carbide single crystal is grown on the surface of the seed crystal using the upper crucible (8c) above the crucible as the growth region. An apparatus for producing a silicon carbide single crystal,
The said heating apparatus is arrange | positioned surrounding the said lower crucible, The outer diameter of this heating apparatus is made smaller than the outer diameter of the said upper crucible, The manufacturing apparatus of the silicon carbide single crystal characterized by the above-mentioned.   The said heating apparatus is a manufacturing apparatus of the silicon carbide single crystal of Claim 1 by which the internal diameter of this heating apparatus is made smaller than the outer diameter of the said base.   The apparatus for producing a silicon carbide single crystal according to claim 1, wherein a heat insulating material (7a) is disposed between the lower crucible and the upper crucible. The heat insulating material has an opening formed at a position corresponding to the hollow portion into which the source gas is introduced in the lower crucible,
The crucible is provided with an intermediate crucible (8b) connected to the lower crucible and the upper crucible and covering an inner wall surface of the opening portion of the heat insulating material, and is located in the opening portion of the heat insulating material in the intermediate crucible. The inner wall surface of the hollow portion to be formed is a tapered surface having an inner diameter gradually enlarged toward the downstream side in the flow direction of the source gas. An apparatus for producing a silicon carbide single crystal. Inside the lower crucible, provided with a crucible inner cylindrical portion (9) having a hollow portion arranged coaxially with respect to the lower crucible,
The raw material gas is introduced through a hollow portion of the crucible inner cylindrical portion, and a purge gas containing an inert gas or an etching gas is introduced from a gap between the crucible inner cylindrical portion and the lower crucible. The apparatus for producing a silicon carbide single crystal according to any one of claims 1 to 4, wherein:   Using the silicon carbide single crystal manufacturing apparatus according to any one of claims 1 to 5, the raw material gas is thermally decomposed by the heating device and supplied to the seed crystal attached to the pedestal. The silicon carbide single crystal is grown on the surface of the seed crystal in the growth region.

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