JP3922074B2 - Method and apparatus for producing silicon carbide single crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a silicon carbide single crystal.
[0002]
[Prior art]
Since silicon carbide single crystal has characteristics of high breakdown voltage and high electron mobility, it is expected as a semiconductor substrate for power devices. A single crystal growth method generally called a sublimation method (improved Rayleigh method) is used for the silicon carbide single crystal. In the modified Rayleigh method, a silicon carbide raw material is inserted into a graphite crucible, a seed crystal is disposed so as to face the raw material portion, and the raw material portion is heated to 2200 to 2400 ° C. to generate sublimation gas. A silicon carbide single crystal is grown by recrystallizing into a seed crystal cooled to several tens to several hundreds of degrees C. from the part. In this improved Rayleigh method, the amount of silicon carbide raw material decreases as the silicon carbide single crystal grows, so that the amount that can be grown is limited. Even if the raw material is added during the growth, the sublimation gas concentration in the crucible is increased if the raw material is added during the growth because the Si / C ratio sublimates when SiC sublimates. Fluctuates and becomes an obstacle to the continuous production of crystals of high quality.
[0003]
On the other hand, a technique for epitaxially growing silicon carbide by CVD is disclosed in Japanese Patent Laid-Open No. 11-508531. FIG. 4 is a schematic sectional view of a manufacturing apparatus using this technique. As shown in FIG. 4, a cylindrical susceptor 101 is disposed near the center of the cylindrical case 100. The susceptor 101 is made of high purity graphite or the like. A silicon carbide single crystal substrate 102 serving as a seed crystal is disposed on the upper end surface of susceptor 101. A heating means 103 for heating the gas in the susceptor 101 is disposed at a position corresponding to the outer periphery of the susceptor 101 outside the case 100. The periphery of the susceptor 101 is filled with porous graphite 104 which is a heat insulating material. A funnel-shaped passage 105 is formed by the heat insulating material 104 at the lower end of the susceptor 101. A mixed gas introduction pipe 106 for supplying a mixed gas containing Si and C necessary for the growth of the silicon carbide single crystal is disposed at the lower end of the case 100. Further, a passage 107 through which the mixed gas is exhausted is formed at the upper end surface of the susceptor 101, and a gas passage 108 connected to the outside of the case 100 is formed at the upper portion of the case 100. In the manufacturing apparatus having such a configuration, the mixed gas supplied from the mixed gas introduction pipe 106 moves into the susceptor 101 through the passage 105 formed by the heat insulating material 104, and the mixed gas is heated by the heating means 103. A silicon carbide single crystal is epitaxially grown from seed crystal 102. The remaining mixed gas passes through the passage 107 on the upper end surface of the susceptor 101 and is exhausted through the passage 108 formed in the upper portion of the case 100.
[0004]
However, in the manufacture of the silicon carbide single crystal by this CVD, the mixed gas introduced into the susceptor 101 is heated in the susceptor 101 and a part thereof is consumed by crystal growth, but the gas that has not contributed to the growth is the susceptor 101. It becomes a foreign substance (particles etc.) on the inner wall of the glass, and rises in the susceptor 101 and adheres to the surface of the grown crystal, which significantly deteriorates the quality of the grown crystal. Further, since the mixed gas is cooled at the discharge port, the discharge port is blocked by SiC polycrystal or the above-described foreign matter (particles, etc.), and it becomes difficult to increase the pressure in the susceptor 101 and continue crystal growth.
[0005]
[Problems to be solved by the invention]
The present invention has been made under such a background. The purpose of the present invention is to eliminate defects caused by the introduction of mixed gas and the clogging of the reaction vessel outlet and the high quality silicon carbide single unit. It is to be able to produce crystals.
[0006]
[Means for Solving the Problems]
In the method for producing a silicon carbide single crystal according to claim 1 or 2 , the discharge flow path opposite to the flow of the mixed gas toward the silicon carbide single crystal substrate to be a seed crystal is along the inner wall of the reaction vessel. It is characterized in that it is formed and gas is forcibly exhausted through this discharge channel. Therefore, foreign substances generated in the reaction vessel (particles generated in the reaction vessel, exfoliation of the inner surface of the reaction vessel, etc.) generated in the reaction vessel are not directed to the silicon carbide single crystal substrate through the discharge channel, but by the gas. It is washed away to the outside. Thereby, it is suppressed that a foreign material reaches a silicon carbide single crystal substrate. Further, the gas is forcibly exhausted through the discharge channel, and clogging due to foreign matters is suppressed.
[0007]
As a result, it is possible to manufacture a high-quality silicon carbide single crystal by eliminating the problems caused by the introduction of the mixed gas and the introduction of foreign substances and clogging of the outlet of the reaction vessel.
As a manufacturing apparatus therefor, as described in claims 6 and 7 , a bottom surface of the reaction vessel is provided with a through hole that communicates the inside and outside of the reaction vessel, and an exhaust pipe is connected to the bottom surface of the vacuum vessel. This can be realized by providing the exhaust pipe with an exhaust pump for exhausting the gas in the reaction container to the outside of the vacuum container through the through hole.
[0008]
In particular, according to the first and sixth aspects of the invention, since the seed crystal is attached with the seed crystal facing downward, foreign matter (particles, etc.) can be made less likely to adhere to the crystal surface, and a high-quality silicon carbide single crystal can be obtained. Can be manufactured.
[0009]
Further , according to the inventions of claims 2 and 7 , since the temperature of the gas discharge port is higher than that of the seed crystal, the source gas is not recrystallized. Therefore, clogging at the gas discharge port can be suppressed, and a high-quality silicon carbide single crystal can be manufactured.
[0010]
According to the invention of Claims 3 and 8 , it can suppress that a foreign material (particles etc.) rolls up by flowing an inert gas. That is, once the foreign matter discharged from the reaction vessel can be prevented from moving again toward the silicon carbide single crystal substrate serving as a seed crystal in the reaction vessel. Thereby, a high quality silicon carbide single crystal can be manufactured.
[0011]
According to the inventions described in claims 4 and 9 , foreign substances (particles, etc.) can be swept up and mixed into the reaction container by capturing the foreign substances in the gas from the discharge channel outside the vacuum container. Therefore, a high-quality silicon carbide single crystal can be manufactured.
[0012]
According to the inventions described in claims 5 and 10 , it is possible to prevent exhaust gas from being temporarily stored in the storage chamber and foreign matter from being accumulated in the storage chamber and returning to the reaction vessel. Therefore, foreign substances (particles or the like) are not lifted and mixed in the reaction vessel, and a high quality silicon carbide single crystal can be manufactured.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, the schematic sectional drawing of the manufacturing apparatus of the silicon carbide single crystal in this embodiment is shown.
[0014]
In FIG. 1, the apparatus is provided with a vacuum vessel 1 and a cylindrical vessel body 2 is arranged in an upright state. That is, the opening portions at both ends of the container body 2 are fixed in a state where they are positioned vertically. The container body 2 is made of, for example, quartz. The upper surface opening of the container body 2 is closed by an upper lid member (flange) 3, and the lower surface opening of the container body 2 is closed by a lower lid member (flange) 4.
[0015]
Inside the vacuum vessel 1, a cylindrical heat insulating material 5 is arranged along the inner wall of the vessel body 2. Inside the heat insulating material 5, a cylindrical reaction vessel 6 is arranged along the inner wall of the heat insulating material 5. The upper surface of the reaction vessel 6 is closed and the lower surface is opened. A silicon carbide single crystal substrate 7 serving as a seed crystal is disposed facing downward in the upper part of reaction container 6 (specifically, on the ceiling surface in reaction container 6). With respect to the heat insulating material 5 and the reaction vessel 6, the heat insulating material 5 is arranged at a predetermined interval on the side surface and the upper surface of the reaction vessel 6.
[0016]
As a material of the reaction vessel 6, for example, high-purity graphite that can withstand high temperatures (about 2400 ° C.) can be used. By using such high purity graphite, it is possible to reduce the generation of impurities from the heated reaction vessel 6 and the incorporation of impurities into the crystal during crystal growth.
[0017]
A concave portion 8 is formed in a central portion of the lower lid member (flange) 4 so as to protrude downward. The inner side of the recess 8 is the storage chamber R1, and has a structure having the storage chamber R1 in the lower part in the vacuum vessel 1. A mixed gas introduction pipe 9 is formed on the bottom surface of the recess 8, and the mixed gas introduction pipe 9 extends in the vertical direction. The upper end side of the mixed gas introduction tube 9 extends inside the vacuum vessel 1, and the mixed gas introduction tube 10 extends upward from the upper end of the mixed gas introduction tube 9. The mixed gas introduction pipe 10 extends from the lower surface opening 6 a of the reaction vessel 6 into the reaction vessel 6. The lower lid member (flange) 4, the recessed portion 8, and the mixed gas introduction pipe 9 are integrated, and are made of, for example, a stainless steel plate material (SUS material).
[0018]
In this way, the mixed gas introduction pipes 9 and 10 are extended from below the reaction vessel 6 toward the silicon carbide single crystal substrate 7 in the reaction vessel 6 so that the mixed gas can be supplied to the surface of the seed crystal 7. It has become. Specifically, for example, a mixture of monosilane (a gas containing Si), propane (a gas containing C), and a carrier gas such as argon in a predetermined ratio is used as the mixed gas.
[0019]
An exhaust pipe 11 is connected to the side surface portion of the recess 8 described above. That is, the exhaust pipe 11 communicates with the storage chamber R1. An exhaust pump 13 is connected to the exhaust pipe 11 via a particle collector 12. That is, a particle collector 12 is provided between the vacuum vessel 1 and the exhaust pump 13 as a device for capturing foreign substances such as particles in the gas.
[0020]
In this manner, the bottom surface of the reaction vessel 6 is provided with a through hole 6a that communicates the inside and outside of the reaction vessel 6, the exhaust pipe 11 is connected to the lower portion of the vacuum vessel 1, and the exhaust pipe 11 is further connected to the reaction vessel An exhaust pump 13 is provided for exhausting the gas in 6 to the outside of the vacuum vessel 1 through the through-hole 6a.
[0021]
On the other hand, an inert gas introduction pipe 14 is formed at the center of the above-described upper lid member (flange) 3. The lower end of the inert gas introduction pipe 14 extends to the notch 5 a in the heat insulating material 5 in the vacuum vessel 1. An inert gas (for example, argon gas) is introduced from the inert gas introduction pipe 14 and moves downward from the upper surface of the reaction vessel 6 through the side surface in the vacuum vessel 1. That is, an inert gas flows downward from the vicinity of the center of the upper lid member 3 through the inert gas introduction pipe 14, and flows downward around the reaction vessel 6 through the periphery of the reaction vessel 6. In this manner, an inert gas is introduced into the reaction vessel 6 from above the reaction vessel 6 in the vacuum vessel 1, and an air flow that directs the gas (foreign matter) in the reaction vessel 6 to the outside of the vacuum vessel 1 through the through holes 6 a. Can be made. The upper lid member (flange) 3 and the inert gas introduction pipe 14 are integrated, and are made of, for example, a stainless steel plate material (SUS material).
[0022]
A heating coil (RF coil) 15 as a heating means is wound around the outer peripheral portion of the vacuum vessel 1 in the vessel body 2. The heating coil 15 includes an upper coil 15a and a lower coil 15b. The upper coil 15a can heat the upper portion of the reaction vessel 6, and the lower coil 15b can heat the lower portion of the reaction vessel 6. Moreover, the frequency of the alternating current applied to each coil 15a, 15b is different, and the temperature of the upper part and the lower part of the reaction vessel 6 can be controlled independently. Specifically, heating coil 15 (upper coil 15a, lower coil 15b) heats a portion where through hole 6a is formed in reaction vessel 6 to a higher temperature than silicon carbide single crystal substrate 7 that serves as a seed crystal.
[0023]
The gas introduced into the reaction vessel 6 is heated in the reaction vessel 6, part of the gas is crystallized in the silicon carbide single crystal substrate 7, and the unreacted gas flows to the lower side of the reaction vessel 6.
[0024]
Next, a method for producing a silicon carbide single crystal will be described.
A silicon carbide single crystal substrate 7 to be a seed crystal is placed in the vacuum vessel 1. Then, a mixed gas (a gas containing at least a gas containing Si and a gas containing C) is introduced into the vacuum vessel 1 (reaction vessel 6) from the mixed gas introduction pipes 9 and 10. Thereby, silicon carbide single crystal 20 grows from silicon carbide single crystal substrate 7. That is, the silicon carbide single crystal substrate 7 to be a seed crystal is disposed in the reaction vessel 6, and a mixed gas containing at least Si-containing gas and C-containing gas is introduced into the reaction vessel 6 from below. Thus, silicon carbide single crystal 20 is grown from silicon carbide single crystal substrate 7.
[0025]
Further, the exhaust pump 13 is driven, and the gas in the reaction vessel 6 is discharged from the exhaust pipe 11 through the through hole 6a. In this way, a discharge flow path that is opposite to the flow of the mixed gas toward the silicon carbide single crystal substrate 7 serving as a seed crystal is formed along the inner wall of the reaction vessel 6, and the gas is passed through the discharge flow path. Force exhaust. Therefore, the foreign matter generated in the reaction vessel 6 (particles generated in the reaction vessel 6, peeled material on the inner surface of the reaction vessel 6, etc.) generated in the reaction vessel 6 does not go to the silicon carbide single crystal substrate 7 through the discharge channel. Is pushed away to the outside of the vacuum vessel 1. Thereby, it is suppressed that a foreign material reaches silicon carbide single crystal substrate 7. Further, the gas is forcibly exhausted through the discharge channel, and clogging due to foreign matters is suppressed. As a result, it is possible to produce a high-quality silicon carbide single crystal by eliminating problems caused by the introduction of mixed gas and the introduction of foreign substances and clogging of the outlet of the reaction vessel 6.
[0026]
In addition, by driving the heating coil 15, more specifically, by driving the lower coil 15b (heating operation), the gas discharge port (the portion where the through hole 6a is formed) in the reaction vessel 6 is placed above the reaction vessel 6, that is, a silicon carbide single unit. Heat to a higher temperature than the crystal substrate 7. Therefore, since the temperature of the discharge port is higher than that of the seed crystal 7, the source gas is not recrystallized. Therefore, the high-quality silicon carbide single crystal 20 can be manufactured without clogging the polycrystal at the discharge port. Specifically, clogging due to excessive polycrystalline growth accompanying the once the mixed gas heated to a high temperature in the reaction vessel 6 is cooled in the vicinity of the outlet of the reaction vessel 6 can be prevented. Further, after the gas discharge port of the reaction vessel 6, the gas is cooled to generate particles, but (i) the discharge port 6 a is arranged on the lower side of the reaction vessel 6, and (ii) the flow of gas in the direction of gravity. By providing the exhaust pipe 11 on the lower side of the vacuum vessel 1 so as to be able to prevent particles from being rolled up and mixed into the reaction vessel 6, a high quality silicon carbide single crystal 20 can be grown.
[0027]
In addition, since the seed crystal 7 is mounted face down, foreign substances (particles, etc.) can be made less likely to adhere to the crystal surface, and a high-quality silicon carbide single crystal can be manufactured.
[0028]
Further, an inert gas is allowed to flow downward from above the reaction vessel 6 along the gas discharge flow path in the vacuum vessel 1. This prevents foreign matter discharged from the reaction vessel 6 from returning to the reaction vessel 6 again. Thus, it can suppress that a foreign material (particles etc.) rolls up. That is, once the foreign matter discharged from the reaction vessel 6 can be prevented from going again to the silicon carbide single crystal substrate 7 that becomes the seed crystal in the reaction vessel 6. This also makes it possible to produce a high-quality silicon carbide single crystal.
[0029]
Further, the generated particles flow downstream of the reaction vessel 6, but a storage chamber R1 for temporarily storing gas (foreign matter) from the discharge channel is formed on the outer wall portion on the lower surface of the vacuum vessel 1, from which the vacuum vessel is formed. By discharging the gas to the outside of 1, it is possible to prevent foreign matter from accumulating in the storage chamber R <b> 1 and returning to the reaction vessel 6. Therefore, foreign substances (particles or the like) are not lifted and mixed in the reaction vessel 6, and a high-quality silicon carbide single crystal can be manufactured. Furthermore, by capturing the foreign matter in the gas from the gas discharge channel outside the vacuum vessel 1 by the particle collector 12, the foreign matter (particles or the like) is not swung up into the reaction vessel 6 and mixed. A quality silicon carbide single crystal can be manufactured.
[0030]
In addition, since the particle collector 12 and the storage chamber R1 are provided, the particles in the vacuum vessel 1 are released even after evacuation after the pressure in the vacuum vessel 1 is released to atmospheric pressure by attaching the seed crystal 7 in the reaction vessel 6 or the like. Can be easily recovered. Therefore, a high-quality silicon carbide single crystal can be manufactured without being swirled into the reaction vessel 6 and mixed therein.
[0031]
Hereinafter, application examples will be described.
Although the upper part of the reaction vessel 6 in FIG. 1 is closed, instead of this, as shown in FIG. 2, a through hole 6 b is provided around the site where the seed crystal 7 is fixed on the ceiling surface of the reaction vessel 6. Then, the inert gas introduced from the inert gas introduction pipe 14 is introduced into the reaction vessel 6 from the inert gas introduction port 6b. If it carries out like this, the raw material gas concentration of the mixed gas in the discharge port 6a of the reaction container 6 can be lowered | hung, the clogging of the discharge port 6a can be prevented, and generation | occurrence | production of a particle can be suppressed.
[0032]
Alternatively, as shown in FIG. 3, pedestal 30 to which silicon carbide single crystal substrate 7 is attached is fixed to shaft 31. The shaft 31 can be rotated and moved up and down by a rotation / up and down movement mechanism 32. Further, an inert gas is introduced from the inside of the shaft 31 and is taken out of the shaft 31 through the through hole 31a. A large number of through holes 31 a are formed on the circumference of the shaft 31. Further, the inert gas moves downward along the inner peripheral surface of the reaction vessel 6 through a gap between the outer peripheral surface of the pedestal 30 and the inner peripheral surface of the reaction vessel 6. By doing in this way, an inert gas can be equally introduced with respect to the inside of the reaction vessel 6 in the circumferential direction. In addition, since the crystal can be pulled up and rotated, a longer crystal can be produced with high quality.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a silicon carbide single crystal manufacturing apparatus according to an embodiment.
FIG. 2 is a schematic cross-sectional view of another example of an apparatus for producing a silicon carbide single crystal.
FIG. 3 is a schematic cross-sectional view of another example of a silicon carbide single crystal manufacturing apparatus.
FIG. 4 is a cross-sectional view for explaining the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Container main body, 3 ... Upper cover material (flange), 4 ... Lower cover material (flange), 5 ... Heat insulation material, 5a ... Notch part, 6 ... Reaction container, 6a ... Through-hole, 7 DESCRIPTION OF SYMBOLS Silicon carbide single crystal substrate used as seed crystal, 8 ... Recess, 9 ... Mixed gas introduction pipe, 10 ... Mixed gas introduction pipe, 11 ... Exhaust pipe, 12 ... Particle collector, 13 ... Exhaust pump, 14 ... Inert gas introduction Tube, 15 ... heating coil, 15a ... upper coil, 15b ... lower coil.

Claims (10)

Inside the vacuum vessel (1), a silicon carbide single crystal substrate (7) serving as a seed crystal is placed in the reaction vessel (6), and at least Si-containing gas and C are contained in the reaction vessel (6). In the method for producing a silicon carbide single crystal, the silicon carbide single crystal (20) is grown from the silicon carbide single crystal substrate (7) by introducing a mixed gas containing
The silicon carbide single crystal substrate (7) serving as the seed crystal is disposed facing downward in the upper part of the reaction vessel (6), and is opposite to the flow of the mixed gas toward the silicon carbide single crystal substrate (7). A method for producing a silicon carbide single crystal, wherein a discharge channel in the direction is formed along the inner wall of the reaction vessel (6), and gas is forcibly exhausted through the discharge channel. Inside the vacuum vessel (1), a silicon carbide single crystal substrate (7) serving as a seed crystal is placed in the reaction vessel (6), and at least Si-containing gas and C are contained in the reaction vessel (6). In the method for producing a silicon carbide single crystal, the silicon carbide single crystal (20) is grown from the silicon carbide single crystal substrate (7) by introducing a mixed gas containing
  A discharge channel opposite to the flow of the mixed gas toward the silicon carbide single crystal substrate (7) serving as the seed crystal is formed along the inner wall of the reaction vessel (6), and the reaction vessel (6) The method for producing a silicon carbide single crystal is characterized in that the gas discharge port in is heated to a temperature higher than that of the silicon carbide single crystal substrate (7), and the gas is forcibly exhausted through the discharge channel. An inert gas is allowed to flow along the discharge flow path in the vacuum vessel (1) to prevent foreign matter discharged from the reaction vessel (6) from returning to the reaction vessel (6) again. A method for producing a silicon carbide single crystal according to claim 1 or 2, wherein: The method for producing a silicon carbide single crystal according to any one of claims 1 to 3, wherein foreign substances in the gas from the discharge channel are captured outside the vacuum vessel (1). . A storage chamber (R1) for temporarily storing gas from the discharge flow path is formed in the outer wall of the vacuum vessel (1), and the gas is discharged from the vacuum vessel (1) to the outside, whereby foreign substances are removed. The silicon carbide single crystal according to any one of claims 1 to 4, wherein the silicon carbide single crystal according to any one of claims 1 to 4 is prevented from being deposited in the storage chamber (R1) and returning to the inside of the reaction vessel (6). Production method. Inside the vacuum vessel (1), a silicon carbide single crystal substrate (7) serving as a seed crystal is placed in the reaction vessel (6), and at least Si-containing gas and C are contained in the reaction vessel (6). In a silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal (20) from the silicon carbide single crystal substrate (7) by introducing a mixed gas containing a gas to be generated from below,
  The silicon carbide single crystal substrate (7) serving as the seed crystal is arranged in the upper part in the reaction vessel (6) so that the inside and outside of the reaction vessel (6) are placed on the lower surface of the reaction vessel (6). A communicating through hole (6a) is provided, and the gas in the reaction vessel (6) is passed through the through hole (6a) to the exhaust pipe (11) connected to the lower part of the vacuum vessel (1). An apparatus for producing a silicon carbide single crystal, characterized in that an exhaust pump (13) for discharging to the outside is provided. Inside the vacuum vessel (1), a silicon carbide single crystal substrate (7) serving as a seed crystal is placed in the reaction vessel (6), and at least Si-containing gas and C are contained in the reaction vessel (6). In a silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal (20) from the silicon carbide single crystal substrate (7) by introducing a mixed gas containing a gas to be generated from below,
  A through hole (6a) that communicates the inside and outside of the reaction vessel (6) is provided on the lower surface of the reaction vessel (6), and the formation portion of the through hole (6a) in the reaction vessel (6) is A heating means (15) for heating to a higher temperature than the silicon carbide single crystal substrate (7) serving as a seed crystal is provided, and the reaction vessel (11) is connected to the exhaust pipe (11) connected to the lower portion of the vacuum vessel (1). 6) An exhaust pump (13) for exhausting the gas inside the vacuum vessel (1) through the through hole (6a) is provided. An apparatus for producing a silicon carbide single crystal. In the vacuum vessel (1), an inert gas is introduced into the reaction vessel (6) from above the reaction vessel (6), and the gas in the reaction vessel (6) passes through the through-hole (6a) to form a vacuum vessel ( The apparatus for producing a silicon carbide single crystal according to claim 6 or 7, further comprising an inert gas introduction pipe (14) for generating an air flow directed to the outside of 1). The silicon carbide according to any one of claims 6 to 8, wherein a device (12) for capturing foreign substances in the gas is provided between the vacuum vessel (1) and the exhaust pump (13). Single crystal manufacturing equipment. The storage chamber (R1) is formed in the lower part in the vacuum vessel (1), and the exhaust pipe (11) is connected to communicate with the storage chamber (R1). The manufacturing apparatus of the silicon carbide single crystal of any one of these.

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