JP5842725B2 - Silicon carbide single crystal manufacturing equipment - Google Patents

Description

  The present invention relates to a SiC single crystal manufacturing apparatus that manufactures a SiC single crystal by supplying a source gas to a seed crystal composed of a silicon carbide (hereinafter referred to as SiC) single crystal.

  Conventionally, Patent Document 1 discloses a SiC single crystal manufacturing apparatus for growing a SiC single crystal by supplying a raw material gas from below to a seed crystal attached to a pedestal. In this SiC single crystal manufacturing apparatus, the source gas is heated to 1900 ° C. or higher, preferably 2000 to 2500 ° C., so that the source gas is thermally decomposed and supplied to the seed crystal. Then, an SiC single crystal is grown on the surface of the seed crystal while exhaust gas such as unreacted gas is exhausted from the exhaust pipe disposed on the back surface side of the base through the outer periphery of the seed crystal and the base.

  By heating the source gas at such a temperature, etching with hydrogen or other etching gas can be promoted at a high temperature, and a low-quality polycrystalline region is etched more rapidly than a high-quality single-crystal region. You can make it. Thereby, the quality of the grown SiC single crystal can be made higher.

Japanese Patent No. 4121555

  However, since the raw material gas is thermally decomposed at a high temperature, the temperature of the reaction chamber in which the decomposition is performed and the gas temperature become high, and this radiant heat increases the temperature of the crystal surface. In particular, exhaust gas is exhausted to the back side of the pedestal through the outer periphery of the seed crystal and the pedestal, so that heat dissipation proceeds on the outer peripheral surface side of the SiC single crystal, but heat dissipation does not proceed at the center of the crystal, so the center of the crystal As a result, the growth rate at the center of the SiC single crystal decreases. This tendency becomes more prominent because the heat radiation in the pedestal direction of the SiC single crystal is reduced by the thermal resistance of the SiC single crystal itself as the amount of growth of the SiC single crystal increases. For this reason, as the growth amount of the SiC single crystal increases, the growth rate of the central portion of the SiC single crystal decreases, and the growth surface becomes a concave surface that is recessed at the central portion. Crystal growth stops when the temperature of the growth surface cannot be set low.

  In view of the above points, the present invention suppresses the growth rate of the SiC single crystal from being depressed at the central portion by suppressing the growth rate from decreasing at the central portion of the SiC single crystal, thereby improving the quality. An object of the present invention is to provide a SiC single crystal manufacturing apparatus capable of growing a SiC single crystal longer.

In order to achieve the above object, in the invention described in claim 1, a seed crystal (5) made of a silicon carbide single crystal substrate is installed on the pedestal (9), and the pedestal is formed by a heating device (12, 13). The silicon carbide single crystal (20) is grown on the surface of the seed crystal by supplying the silicon carbide source gas (3a) to the surface of the seed crystal while heating the surroundings, and the pedestal is moved by the pulling mechanism (11). A silicon carbide single crystal manufacturing apparatus that elongates a silicon carbide single crystal by pulling up, and a counterbore (9a) is provided on the back surface of the pedestal to make the central portion of the pedestal thinner than the outer edge portion. The counterbore has a cylindrical shape, the thickness of the pedestal is the same at the center, is thicker than the center outside the center, and the depth of the counterbore is the expected silicon carbide unit. Let the amount of crystal growth be the crystal length,
(Equation 1)
(1 / SiC thermal conductivity) x crystal length <(1 / base thermal conductivity) x counterbore depth
It is characterized by being set to a depth that satisfies .

Thus, the counterbore having a recessed base on the back surface of the base is provided to change the thickness of the base in the radial direction so that the outer edge is thicker than the center. For this reason, by providing counterbore, the thermal resistance in the central part is smaller than the outer edge part of the pedestal, the amount of heat radiation is increased, and the central part side is cooler than the outer peripheral surface side of the SiC single crystal. become. Thereby, it becomes possible to suppress the growth surface of the SiC single crystal from becoming concave, and the growth surface of the SiC single crystal is flat, preferably a convex shape in which the center of the growth surface protrudes from the outer peripheral surface side. Can be. Therefore, higher quality crystals can be continuously grown in a long length. In addition, since the depth of the counterbore is set as described above, even if the thermal resistance between the central portion and the outer peripheral surface changes with the growth of the SiC single crystal, until the end of the growth of the SiC single crystal, The central portion of the pedestal can have a lower thermal resistance than the outer peripheral surface side. For this reason, the amount of heat radiation at the center portion of the SiC single crystal is larger than that at the outer peripheral surface side, and the temperature at the center portion side is lower than that at the outer peripheral surface side of the SiC single crystal.

  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. FIG. 3 is a cross-sectional view of SiC single crystal manufacturing apparatus 1 showing a state of growth of SiC single crystal 20. It is the figure which showed the temperature distribution of the SiC single crystal manufacturing apparatus 1 during the growth of the SiC single crystal. It is the figure which showed temperature distribution at the time of making the base 9 with which the SiC single crystal manufacturing apparatus 1 was equipped with the conventional structure. It is sectional drawing of the SiC single crystal manufacturing apparatus 1 concerning 2nd Embodiment of this invention. It is sectional drawing of the SiC single crystal manufacturing apparatus 1 concerning 3rd Embodiment of this invention. It is sectional drawing of the SiC single crystal manufacturing apparatus 1 demonstrated by other embodiment.

  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)
The SiC single crystal manufacturing apparatus 1 shown in FIG. 1 is used to manufacture an ingot of an SiC single crystal 20 by growing the SiC single crystal 20 in a long length. Specifically, the SiC single crystal manufacturing apparatus 1 supplies the raw material gas 3a from the raw material gas supply source 3 through the inlet 2 provided at the bottom, and discharges the unreacted gas through the upper outlet 4. Then, the SiC single crystal 20 is grown on the seed crystal 5 made of the SiC single crystal substrate.

  The SiC single crystal manufacturing apparatus 1 includes a source gas supply source 3, a vacuum container 6, a first heat insulating material 7, a heating container 8, a pedestal 9, a second heat insulating material 10, a rotary pulling mechanism 11, and first and second heating materials. Devices 12 and 13 are 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 cylindrical 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 in which it is housed can be depressurized by evacuating it. An inlet 2 for the source gas 3a is provided at the bottom of the vacuum vessel 6, and an outlet 4 for an exhaust gas such as unreacted gas in the source gas 3a is provided at the top (specifically, above the side wall). ing.

  The first heat insulating material 7 has a cylindrical shape, is disposed coaxially with respect to the vacuum vessel 6, and constitutes a raw material gas introduction pipe 7 a with a hollow portion. The first heat insulating material 7 is made of, for example, 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. Yes.

  Heating vessel 8 is formed in a hollow shape, and constitutes a reaction chamber in which SiC single crystal 20 is grown on the surface of seed crystal 5. Specifically, the heating container 8 has a structure having a hollow cylindrical member, and in the case of the present embodiment, the heating container 8 is configured by a bottomed cylindrical member having an opening at the center of the bottom. The heating container 8 is made of, for example, 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 heating container 8 is disposed so as to surround the pedestal 9, and exhausts unreacted gas or the like in the source gas 3 a through between the inner peripheral surface of the heating container 8 and the outer peripheral surfaces of the seed crystal 5 and the pedestal 9. Gas is guided to the outlet 4 side. By this heating vessel 8, the raw material gas 3 a is decomposed until the raw material gas 3 a supplied from the inlet 2 is led to the seed crystal 5.

  The pedestal 9 is composed of a cylindrical member arranged coaxially with the central axis of the heating container 8. For example, the pedestal 9 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. A seed crystal 5 is attached to the pedestal 9, and an SiC single crystal 20 is grown on the surface of the seed crystal 5. The surface of the pedestal 9 on which the seed crystal 5 is affixed has a shape corresponding to the shape of the seed crystal 5 to be grown, for example, a circular shape, and is rotated on the surface opposite to the surface on which the seed crystal 5 is disposed. It is connected to the upper mechanism 11.

  The thickness of the pedestal 9 is varied in the radial direction so that the outer edge portion is thicker than the central portion. In the present embodiment, the thickness of the base 9 is changed by providing a counterbore 9 a in which the base 9 is recessed on the back surface of the base 9. Specifically, the counterbore 9a has a conical shape, and the depth of the counterbore 9a gradually decreases from the center of the base 9. By adopting such a structure, the thickness of the pedestal 9 is gradually increased toward the radially outer side with the central axis of the pedestal 9 as the center.

  The 2nd heat insulating material 10 comprises the outer periphery heat insulating material which insulates the heating container 8 and its radial direction outer side, enclosing the outer periphery of the heating container 8 or the base 9. In the present embodiment, the second heat insulating material 10 is formed in a cylindrical shape, for example, graphite or graphite whose surface is coated with a refractory metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide). As a result, thermal etching can be suppressed. The inner diameter of the second heat insulating material 10 is larger than the outer diameters of the first heat insulating material 7 and the heating container 8.

  The rotary pulling mechanism 11 rotates and pulls up the pedestal 9 via a support shaft 11a made of a pipe material or the like. One end of the support shaft 11 a is connected to the surface of the pedestal 9 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 coated with a refractory metal carbide such as TaC (tantalum carbide), so that thermal etching can be suppressed. With such a configuration, the pedestal 9, 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, for example, a heating coil (induction heating coil or direct heating coil), and are arranged so as to surround the vacuum vessel 6. In the case of this embodiment, the 1st, 2nd heating apparatuses 12 and 13 are comprised by the coil for induction heating. These 1st, 2nd heating apparatuses 12 and 13 are constituted so that temperature control can be carried out independently, respectively, and the 1st heating apparatus 12 is arranged in the position corresponding to the lower part of heating container 8, The second heating device 13 is disposed at a position corresponding to the base 9. Therefore, the temperature of the lower part of the heating container 8 can be controlled by the first heating device 12, and the temperature around the pedestal 9, the seed crystal 5 and the SiC single crystal 20 can be controlled by the second heating device 13. .

  Thus, the SiC single crystal manufacturing apparatus 1 concerning this embodiment is comprised. Then, the manufacturing method of the SiC single crystal 20 using the SiC single crystal manufacturing apparatus 1 concerning this embodiment is demonstrated with reference to FIGS.

  First, the seed crystal 5 is attached to the pedestal 9 and installed in the heating container 8. And the 1st, 2nd heating apparatuses 12 and 13 are controlled and desired temperature distribution is attached. That is, the source gas 3 a is recrystallized on the surface of the seed crystal 5, so that the SiC single crystal 20 grows and the sublimation rate is higher than the recrystallization rate in the heating vessel 8. To. By doing in this way, the surface side of the seed crystal 5 which should grow the SiC single crystal 20 is heated. Moreover, since the arrangement position of the 2nd heating apparatus 13 is a position corresponding to the base 9, the back surface side of the base 9 can be prevented from being heated so much. For example, the temperature of the bottom of the heating container 8 can be set to 2400 ° C., the temperature of the surface of the seed crystal 5 can be set to 2200 ° C., and the temperature of the back side of the pedestal 9 can be set to about 2100 ° C.

In addition, the source gas 3a is introduced through the source gas introduction pipe 7a while introducing a carrier gas using an inert gas such as Ar or He or an etching gas such as H ₂ or HCl while bringing the vacuum vessel 6 to a desired pressure. To do. Thereby, the source gas 3a flows and is supplied to the seed crystal 5 as shown by the arrow in FIG. 2A, and based on this source gas supply, the seed crystal 5 as shown in FIG. 2B. SiC single crystal 20 is grown on the surface of the substrate. Then, the pedestal 9, 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 SiC single crystal 20 is kept substantially constant, and the temperature distribution of the growth surface temperature can be controlled with good controllability. In addition, since the SiC single crystal 20 is grown by putting it in the high-temperature heating vessel 8, it is possible to prevent adhesion of crystals other than the surface of the seed crystal 5, and to prevent clogging of the outlet 4; It is possible to continuously grow the SiC single crystal 20.

  At this time, as shown by the arrows in FIGS. 2A and 2B, the unreacted gas, the etching gas, etc. in the source gas 3a are exposed to the outer peripheral surface of the base 9, the seed crystal 5 and the SiC single crystal 20 and 2 It is made to flow as a path between the inner wall surfaces of the heat insulating material 10. For this reason, heat dissipation on the outer peripheral surface side of the SiC single crystal 20 proceeds.

  However, in the case of this embodiment, the counterbore 9a is provided on the back surface of the pedestal 9. Therefore, by providing the counterbore 9a, the thermal resistance is smaller in the center portion than the outer edge portion of the pedestal 9, and the amount of heat radiation is further increased. Can be increased. For this reason, the temperature on the center side is lower than that on the outer peripheral surface side of SiC single crystal 20. In other words, as shown in FIG. 3, the temperature distribution is such that the isotherm is located below the outer peripheral surface side at the center portion side of the SiC single crystal 20.

  With such a temperature distribution, the supersaturation at the center of SiC single crystal 20 is increased, and the growth rate at the growth surface of SiC single crystal 20 is faster at the center than at the outer peripheral surface. it can. For this reason, it becomes possible to suppress the growth surface of the SiC single crystal 20 from becoming concave, and the growth surface of the SiC single crystal 20 is flat, preferably a convex surface in which the central portion of the growth surface protrudes from the outer peripheral surface side. It can be shaped. Thereby, the supply of the source gas 3a can be a step supply from the central portion of the SiC single crystal 20, and a higher quality crystal can be continuously grown in a long length.

  In this embodiment, since the depth of the counterbore 9a gradually decreases from the center of the pedestal 9, it is possible to prevent the central portion of the SiC single crystal 20 from being heated at a high temperature without a rapid temperature gradient. Can do. For this reason, it is possible to continuously grow higher quality crystals in a long length.

  For reference, the temperature distribution during the growth of the SiC single crystal 20 was also examined in the case where the counterbore 9a was not provided for the base 9 as in the conventional SiC single crystal manufacturing apparatus 1. As a result, as shown in FIG. 4, the temperature distribution is such that the temperature gradually increases from the central axis of SiC single crystal 20 toward the radially outer side. That is, the temperature of the center portion of the growth surface of SiC single crystal 20 is higher than that of the outer peripheral surface side. For this reason, the growth surface of the SiC single crystal 20 becomes a concave growth that is recessed at the center, and finally the crystal growth stops when the temperature of the growth surface of the SiC single crystal 20 cannot be set lower than the source gas temperature. This causes a malfunction.

  As described above, in the SiC single crystal manufacturing apparatus 1 of the present embodiment, the thickness of the base 9 is changed in the radial direction by providing the counterbore 9a in which the base 9 is recessed on the back surface of the base 9, and the outer edge portion Is thicker than the center. For this reason, by providing the counterbore 9a, the thermal resistance is smaller in the central part than the outer edge part of the pedestal 9, the heat radiation amount is increased, and the central part side is more than the outer peripheral surface side of the SiC single crystal 20. Becomes cooler. This makes it possible to suppress the growth surface of the SiC single crystal 20 from becoming concave, and the growth surface of the SiC single crystal 20 is flat, preferably a convex surface in which the center of the growth surface protrudes from the outer peripheral surface side. It can be shaped. Therefore, higher quality crystals can be continuously grown in a long length.

  Further, in the present embodiment, the counterbore 9a has a conical shape, and the depth of the counterbore 9a gradually decreases from the center of the pedestal 9. Therefore, since it is possible to prevent the central portion of the SiC single crystal 20 from being heated at a high temperature without an abrupt temperature gradient, it is possible to continuously grow higher quality crystals in a long length.

(Second Embodiment)
A second embodiment of the present invention will be described. In this embodiment, the shape of the counterbore 9a is changed with respect to the first embodiment, and the other parts are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIG. 5, in the SiC single crystal manufacturing apparatus 1 of the present embodiment, the counterbore 9a formed on the pedestal 9 is not a conical shape but a cylindrical shape. That is, with respect to the thickness of the pedestal 9, the central portion has the same thickness, and the outer edge portion on the outer side is thicker than the central portion. The depth of the counterbore 9a is arbitrary, but when the SiC single crystal 20 is grown, the expected growth amount of the SiC single crystal 20 (crystal long length) so that the growth surface of the SiC single crystal 20 does not become a concave shape. Amount) and the thermal conductivity of SiC and pedestal 9, the depth is set to the following equation.

(Equation 1)
(1 / SiC thermal conductivity) x crystal length <(1 / pedestal thermal conductivity) x counterbore depth If the depth of the counterbore 9a is set so that this formula holds, the growth of the SiC single crystal 20 will occur. Accordingly, even if the thermal resistance between the central portion and the outer peripheral surface changes, the central portion of the pedestal 9 can have a lower thermal resistance than the outer peripheral surface until the growth of the SiC single crystal 20 ends. Therefore, the heat radiation amount is greater in the central portion of SiC single crystal 20 than in the outer peripheral surface side, and the temperature in the central portion side is lower than that in the outer peripheral surface side of SiC single crystal 20. Thereby, the effect similar to 1st Embodiment can be acquired.

(Third embodiment)
A third embodiment of the present invention will be described. In this embodiment, the configuration of the rotary pull-up mechanism 11 is changed with respect to the first embodiment, and the other parts are the same as those in the first embodiment. Therefore, only different portions from the first embodiment will be described. .

  As shown in FIG. 6, in the SiC single crystal manufacturing apparatus 1 of the present embodiment, the support shaft 11 a is connected to the outer edge portion on the back surface of the base 9, and the support shaft 11 a is not connected to the center portion of the base 9. It has a structure. When the support shaft 11a is connected to the central portion of the back surface of the base 9, the thermal resistance increases correspondingly and the heat radiation amount can be reduced. For this reason, it becomes possible to lower the thermal resistance of the center part of the base 9 more by connecting the support shaft 11a to the outer edge part in the back surface of the base 9 like this embodiment. As a result, the amount of heat released from the center portion of the SiC single crystal 20 is larger than that from the outer peripheral surface side, and the temperature at the center portion side is lower than that from the outer peripheral surface side of the SiC single crystal 20. Thereby, the same effect as 1st Embodiment can further be acquired.

(Other embodiments)
In the third embodiment, the support shaft 11a of the rotary pull-up mechanism 11 is connected only to the outer edge portion of the base 9 with respect to the base 9 having the structure of the first embodiment. The present invention can also be applied to the structure base 9.

  Moreover, in each said embodiment, it can also be set as the structure where the thermal resistance of the outer edge part of the base 9 becomes still higher than a center part. Specifically, as shown in FIG. 7, on the outer peripheral surface of the pedestal 9, a slit 9 b that divides the pedestal 9 into a front surface side (seed crystal 5 side) and a back surface side in the thickness direction is formed. The slit 9b prevents heat conduction from the front surface side to the back surface side at the outer edge portion of the pedestal 9, so that the thermal resistance of the outer edge portion of the pedestal 9 can be further increased.

  In addition, the rotary pulling mechanism 11 capable of both rotating and pulling up the pedestal 9 has been described as an example. However, any pulling mechanism capable of at least pulling up may be used.

  In each of the embodiments described above, as the SiC single crystal manufacturing apparatus 1, the source gas 3 a is supplied to the growth surface of the SiC single crystal 20, and then passes through the outer peripheral surface of the SiC single crystal 20 and the side of the pedestal 9 and is further discharged upward. The method that can be used (upflow method) has been described as an example. However, the present invention is not limited to this, and a method (return flow method) in which the source gas 3a is supplied to the growth surface of the SiC single crystal 20 and then returned again in the same direction as the supply direction, or the source gas 3a is the SiC single crystal 20 It can also be applied to a method (side flow method) in which the gas is supplied to the growth surface and then discharged in the outer peripheral direction of the heating container 8.

  The present invention can also be applied to a growth method different from the gas supply method growth for supplying the source gas 3a. That is, SiC raw material powder is placed in advance in a crucible placed in a vacuum vessel, a raw material gas obtained by sublimating the SiC raw material from the SiC raw material powder is generated by heating with a heating device, and an SiC single crystal is formed on the seed crystal surface. The present invention can also be applied to sublimation growth for growth.

DESCRIPTION OF SYMBOLS 1 Single crystal manufacturing apparatus 3a Source gas 5 Seed crystal 8 Heating container 9 Base 9a Counterbore 11 Rotating pulling mechanism 11a Support shaft 12, 13 1st, 2nd heating apparatus 20 SiC single crystal

Claims (3)

A hollow heating vessel (8) constituting the reaction chamber;
A pedestal (9) disposed in the heating vessel;
A heating device (12, 13) disposed on an outer periphery of the heating container and heating the heating container;
A support shaft (11a) connected to the pedestal, and a pulling mechanism (11) that pulls the pedestal upward through the support shaft;
A seed crystal (5) made of a silicon carbide single crystal substrate is installed on the pedestal, and a silicon carbide source gas (3a) is supplied to the surface of the seed crystal while heating the periphery of the pedestal with the heating device. Thus, a silicon carbide single crystal (20) is crystal-grown on the surface of the seed crystal, and the silicon carbide single crystal manufacturing apparatus for elongating the silicon carbide single crystal by pulling up the pedestal by the pulling mechanism Because
The back surface of the pedestal is provided with a counterbore (9a) that makes the central part of the pedestal thinner than the outer edge part ,
The counterbore has a cylindrical shape, and the thickness of the pedestal is the same at the center, thicker than the center at the outside of the center,
As for the depth of the counterbore, the growth amount of the silicon carbide single crystal that is planned is a crystal long amount,
(Equation 1)
(1 / SiC thermal conductivity) x crystal length <(1 / base thermal conductivity) x counterbore depth
An apparatus for producing a silicon carbide single crystal characterized by being set to a depth satisfying The support shaft is silicon carbide single crystal manufacturing apparatus according to claim 1, characterized in that it is connected only to the outer edge of the back surface of the pedestal. The silicon carbide single crystal manufacturing apparatus according to claim 1 or 2 , wherein a slit (9b) for dividing the pedestal into a front side and a back side is formed on an outer peripheral surface of the pedestal.

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