JPWO2009060561A1 - Single crystal growth equipment - Google Patents

Abstract

A cylindrical guide member (6) whose internal passage becomes narrower from the raw material (3) side toward the seed crystal (5) side is disposed, and the guide member (6) is replaced with the first cylindrical member ( 7), the second cylindrical member (8) is disposed through the heat insulating layer (23) inside, and the inner wall temperature Tg2 of the second cylindrical member (8) during crystal growth is carbonized. By keeping the surface temperature Tc higher than the surface temperature Tc of the silicon single crystal (9), a high-quality silicon carbide single crystal can be grown even if crystal growth is performed for a long time.

Description

  The present invention relates to a single crystal growth apparatus for growing a crystal using a sublimation method.

  Silicon carbide (SiC) has a large thermal conductivity, a low dielectric constant, a wide band gap, and has thermally and mechanically stable characteristics. Therefore, a semiconductor element using silicon carbide has higher performance than a semiconductor element using conventional silicon (Si). The range of use is expected to be environment-resistant device materials, radiation-resistant device materials, power device materials for power control, high-frequency device materials, etc. used in high-temperature environments.

  As a method for producing this silicon carbide single crystal, a sublimation method (also referred to as “improved Rayleigh method”) is mainly employed.

  FIG. 5 is a cross-sectional view of a single crystal growth apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 1-305898) using this sublimation method.

  It is composed of a crucible 1 containing silicon carbide powder as a raw material 3 and a crucible lid portion 2 provided with a seed crystal support portion 4 so that the seed crystal 5 faces the raw material 3 on the seed crystal support portion 4. Is arranged. As seed crystal 5, a silicon carbide single crystal is used. In this state, the raw material 3 side is heated to a high temperature and the seed crystal 5 side is heated to a low temperature, and the sublimation gas of the raw material 3 is recrystallized on the low temperature seed crystal 5, whereby the silicon carbide single crystal 9 is formed. grow up.

  In this single crystal growth apparatus, since the seed crystal 5 is fixed to the seed crystal support portion 4 protruding from the crucible lid portion 2, the silicon carbide single crystal 9 grown from the seed crystal 5 and the seed crystal support portion 4 It is possible to delay contact of silicon carbide polycrystal 19 deposited around.

  However, as the growth proceeds, as shown in FIG. 6, finally, silicon carbide polycrystal 19 precipitated from the periphery of seed crystal support portion 4 comes into contact with silicon carbide single crystal 9. It is known that when the silicon carbide polycrystal 19 comes into contact with the silicon carbide single crystal 9, defects such as cracks, micropipes, and dislocations are generated in the silicon carbide single crystal 9 and the crystal quality is significantly deteriorated. It is considered that these defects occur because stress is generated in silicon carbide single crystal 9 due to a difference in thermal expansion coefficient between silicon carbide polycrystal 19 and silicon carbide single crystal 9 during cooling after the completion of crystal growth. It is done.

  In order to solve this problem, Patent Document 2 (Japanese Patent Laid-Open No. 2005-225710) describes the structure of FIGS.

  In the single crystal growth apparatus of FIG. 7, a cylindrical guide member 6 whose inner diameter gradually decreases from the raw material 3 toward the seed crystal 5 between the raw material 3 and the seed crystal 5, thereby sublimating gas from the seed crystal 5. There is known a method of efficiently growing the silicon carbide single crystal 9 by guiding to the above.

  Further, the guide member 6 is provided with a gap between the side end of the seed crystal 5 and the seed crystal support portion 4, and a part of the sublimation gas is caused to flow toward the crucible lid portion 2 so that the silicon carbide single crystal 9. Is devised to grow without contacting the guide member 6.

However, there is a case where the silicon carbide polycrystal 19 is deposited on the inner wall of the gas guide portion 9 and the silicon carbide polycrystal 19 and the silicon carbide single crystal 9 come into contact with each other. As described above, since a crystal defect occurs in the silicon carbide single crystal and a high-quality silicon carbide single crystal cannot be obtained as described above, in Patent Document 2, as shown in FIG. By installing the heat insulating material 11, heat radiation from the outer wall of the guide member 6 is suppressed, and the inner wall of the guide member 6 is heated to a higher temperature than the surface of the silicon carbide single crystal 9. The polycrystal 19 is configured not to precipitate.
JP-A-1-305898 JP 2005-225710 A

  However, in the conventional configuration, since there is a large temperature difference between the outer wall of the guide member 6 on which the heat insulating material 11 is installed and the side surface of the crucible 1 on the outer side, the heat insulating material 11 is sublimated (deteriorated). It is easy and the heat insulation effect becomes smaller as the growth time elapses.

  Therefore, if the crystal growth is performed for a long time, the inner wall temperature of the guide member 6 cannot be kept higher than the surface temperature of the growing silicon carbide single crystal 9. As a result, as shown in FIG. 9, silicon carbide polycrystal 19 is deposited on the inner wall of guide member 6, and this silicon carbide polycrystal 19 comes into contact with growing silicon carbide single crystal 9. There is a problem that a single crystal cannot be obtained.

  An object of the present invention is to provide a single crystal growth apparatus capable of growing a high-quality silicon carbide single crystal in which generation of crystal defects is suppressed even when crystal growth is performed for a long time.

  In the single crystal growth apparatus of the present invention, a raw material for growing a single crystal is placed in a crystal growth vessel, a seed crystal is placed on top of the raw material, and the crystal growth vessel is heated to sublimate. In a single crystal growth apparatus for growing a single crystal by supplying a gas of the raw material onto the seed crystal, the gas from the raw material side is directed toward the seed crystal so that a gas sublimated from the raw material reaches the seed crystal. In addition, a cylindrical guide member whose internal passage is narrowed is disposed, and the second cylindrical member is disposed inside the first cylindrical member via a heat insulating layer. .

  In addition, the single crystal growth apparatus of the present invention arranges a raw material for growing a single crystal in a crystal growth vessel, arranges a seed crystal above the raw material, and heats the crystal growth vessel. In a single crystal growth apparatus for growing a single crystal by supplying a gas of the raw material to be sublimated onto the seed crystal, the seed crystal side from the raw material side so that the gas sublimated from the raw material reaches the seed crystal A cylindrical guide member whose inner passage becomes narrower toward the inside is disposed, and the guide member is disposed inside the first cylindrical member with a second cylindrical member spaced from each other. To do.

  The guide member partially sandwiches a spacer 10 between the inside of the first tubular member and the outside of the second tubular member, and the first tubular member and the The second cylindrical member is combined.

  The spacer member is made of a graphite sheet material, and the thermal conductivity thereof is 10 W / m · K or less in the thickness direction of the spacer member.

  The second cylindrical member has a melting point equal to or higher than a temperature for growing the single crystal.

  The material of the first tubular member is graphite, and the material of the second tubular member is any one of niobium (Nb), molybdenum (Mo), tantalum (Ta), and tungsten (W). It is characterized by that.

  The material of the first cylindrical member is graphite, and the material of the second cylindrical member is tantalum carbide (TaC).

  According to the single crystal growth apparatus of the present invention, since the second cylindrical member of the guide member during crystal growth can be set to a temperature higher than the surface of the silicon carbide single crystal for a long time, defects in the growing crystal can be obtained. Generation of high quality silicon carbide single crystal can be produced.

Sectional drawing of the single-crystal growth apparatus of Embodiment 1 of this invention Whole sectional view using the single crystal growth apparatus of the embodiment Enlarged view of single crystal growth apparatus during single crystal growth in FIG. 2A The top view and A-AA sectional view of the guide member of the embodiment Production process diagram of second cylindrical member made of TaC used for single crystal growth apparatus of embodiment 2 of the present invention Sectional view of conventional single crystal growth equipment FIG. 5 is a cross-sectional view of the single crystal growth apparatus of FIG. Sectional view of another conventional single crystal growth apparatus Sectional view of yet another conventional single crystal growth apparatus FIG. 8 is a cross-sectional view of the single crystal growth apparatus in FIG.

  Hereinafter, embodiments of a single crystal growth apparatus using the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1 to 3 show a single crystal growth apparatus according to a first embodiment of the present invention.

  FIG. 1 shows a state before crystal growth. This single crystal growth apparatus is composed of a crucible 1 as a crystal growth vessel and a crucible lid 2 detachably attached to an upper opening of the crucible 1. Both the crucible 1 and the crucible lid 2 were made of graphite.

  The silicon carbide powder as the raw material 3 was put on the bottom surface inside the crucible 1, and the seed crystal 5 was fixed at a position facing the raw material 3 on the seed crystal support portion 4 formed in a convex shape on the crucible lid portion 2. The seed crystal 5 was a 4H type silicon carbide single crystal, and its crystal growth plane was a (000-1) plane. The seed crystal affixing surface of the seed crystal support portion 4 has a circular shape with a diameter of 50 mm, and the seed crystal 5 has a circular shape with the same diameter of 50 mm.

  Between the raw material 3 and the seed crystal 5, a cylindrical guide whose internal passage narrows from the raw material 3 side toward the seed crystal 5 in order to efficiently guide the gas sublimated from the raw material 3 to the seed crystal 5. Member 6 was placed. The guide member 6 has a structure in which the second cylindrical member 8 is disposed inside the first cylindrical member 7 via the heat insulating layer 23.

  As the second tubular member 8, it is important to use a high melting point material. In a single crystal growth apparatus that grows a silicon carbide single crystal by a sublimation method, the growth temperature is 2000 ° C. or higher. Therefore, the second cylindrical member 8 must be a high melting point material that can maintain a solid even at this temperature. I must. Here, graphite was used for the first cylindrical member 7, and tantalum (Ta) having a melting point of 3017 ° C. was used for the second cylindrical member 8.

  Under such a high temperature, carbon particles are scattered from the surfaces of the graphite crucible 1 and the first cylindrical member 7. If the carbon particles adhere to the surface of the seed crystal 5 or the surface of the growing silicon carbide single crystal 9, it causes crystal defects such as micropipes. For this purpose, the second cylindrical member 8 prevents the carbon particles from adhering to the surface of the silicon carbide single crystal 9 by arranging the second cylindrical member 8 inside the first cylindrical member 7. be able to.

  After the seed crystal and the raw material are arranged in the single crystal growth apparatus as shown in FIG. 1, crystal growth is performed. FIG. 2 shows a state when crystal growth is performed.

  2A is an overall cross-sectional view for explaining the length of a formed crystal using the single crystal growth apparatus of FIG. 1, and FIG. 2B is an enlarged view of a region A surrounded by a dotted line in FIG. 2A.

  As shown in FIG. 2A, the crucible 1 and the crucible lid 2 constituting the single crystal growth apparatus were covered with a heat insulating material 11. As described above, when the sublimation method is used, a high temperature of 2000 ° C. or higher is required to sublimate the silicon carbide raw material 3, but at a high temperature of 2000 ° C. or higher, the temperature is proportional to the fourth power of the temperature. This is to prevent radiant heat from being lost. The crucible 1 and the crucible lid portion 2 covered with the heat insulating material 11 were arranged inside the reaction tube 12 made of quartz. The reaction tube 12 has a double tube structure, and is cooled by flowing cooling water 13 during crystal growth. A gas inlet 14 is provided at the upper part of the reaction tube 12 and a gas outlet 15 is provided at the lower part.

  Next, the inside of the reaction tube 12 was replaced with an inert gas. As the inert gas, argon (Ar) is suitable in terms of cost, purity, and the like. In this inert gas replacement, the inside of the reaction tube 12 was first evacuated to a high vacuum from the gas exhaust port 15 and then filled with an inert gas from the gas introduction port 14 to normal pressure. Thereafter, the crucible 1 and the crucible lid 2 were heated by induction heating by passing a high-frequency current through a coil 16 spirally wound around the reaction tube 12.

  At the time of heating, the crucible is heated by the radiation thermometer 18 through the quartz temperature measuring window 17 provided at the upper and lower portions of the reaction tube 12 and the temperature measuring hole 11 a provided at the upper and lower portions of the heat insulating material 11. The temperature of 1 lower part and the upper part of the crucible lid part 2 is measured.

  The lower temperature of the crucible 1 and the upper temperature of the crucible lid 2 during heating are determined by the relative positions of the crucible 1 and the crucible lid 2 and the coil 16. In the case of the sublimation method, the temperature of the raw material 3 needs to be higher than that of the seed crystal 5 in order to recrystallize the sublimation gas from the raw material 3 on the seed crystal 5 as described above. In the present embodiment, the relative positions of the crucible 1 and the crucible lid 2 and the coil 16 were adjusted so that the lower temperature of the crucible 1 was 2300 ° C. and the upper temperature of the crucible lid 2 was 2200 ° C.

  By heating in this way, at the time of crystal growth, the surface temperature Ts of the raw material 3 in the crucible 1 is the surface of the silicon carbide single crystal 9 grown from the seed crystal 5 disposed on the seed crystal support 4 of the crucible lid 2. A temperature distribution that is higher than the temperature Tc is formed. Further, due to this temperature distribution, the surface temperature Ts of the raw material 3 becomes higher than the temperature of the guide member 6 disposed between the raw material 3 and the seed crystal 5.

  Here, as shown in FIGS. 1 and 2B, the guide member 6 has a structure in which the second tubular member 8 is disposed inside the first tubular member 7 with a heat insulating layer 23 interposed therebetween. Specifically, a spacer 10 is partially sandwiched between the inside of the first tubular member 7 and the second tubular member 8, and the first tubular member 7 and the second tubular member are interposed via the spacer 10. Since the heat insulating layer 23 is formed between the inner side of the first cylindrical member 7 and the second cylindrical member 8 by joining the cylindrical members 8 to each other, the following effects are obtained.

  During crystal growth, the inner wall of the second cylindrical member 8 inside the first cylindrical member 7 is warmed by the radiant heat of the raw material 3, but the first cylindrical member 7 and the second cylindrical member 8 are heated. Are coupled with the spacer 10 interposed therebetween so that the heat conduction from the second tubular member 8 to the first tubular member 7 is suppressed by the heat insulating layer 23. For this reason, the inner wall temperature Tg2 of the second cylindrical member 8 is maintained at a high temperature.

  On the other hand, the surface of silicon carbide single crystal 9 grown from seed crystal 5 is also warmed by the radiant heat of raw material 3 during crystal growth, but is dissipated from the upper part of crucible lid portion 2 through seed crystal support portion 4. 9 surface temperature Tc decreases. Therefore, the inner wall temperature Tg2 of the second cylindrical member 8 of the guide member 6 can be kept higher than the surface temperature Tc of the adjacent silicon carbide single crystal 9, and the relationship of Ts> Tg2> Tc during crystal growth. Is always kept.

  Accordingly, the sublimation gas sublimated from the raw material 3 adheres to the surface of the low temperature silicon carbide single crystal 9 instead of the inner wall of the high temperature second cylindrical member 8 of the guide member 6, and only the silicon carbide single crystal 9 grows. There is an effect of doing.

  If the first cylindrical member 7 and the second cylindrical member 8 are in direct contact with each other, the second cylindrical member 8 heated by the radiant heat from the raw material 3 is the first cylindrical member 7. The heat is dissipated from the outer wall of the crucible 1 through Tg2 and Tc, and the temperatures become substantially equal. Therefore, the sublimation gas sublimated from the raw material 3 has substantially the same degree of supersaturation on the surface of the silicon carbide single crystal 9 and the inner wall surface of the second cylindrical member 8 and is recrystallized on both surfaces. The silicon carbide recrystallized on the inner wall of the second cylindrical member 8 is polycrystalline (silicon carbide polycrystal 19). As the crystal growth proceeds, the silicon carbide polycrystal 19 and the silicon carbide single crystal 9 Touch. When both come into contact, defects such as cracks, micropipes, and dislocations are generated in the silicon carbide single crystal 9 and the crystal quality is significantly deteriorated. It is considered that these defects occur because stress is generated in silicon carbide single crystal 9 due to a difference in thermal expansion coefficient between silicon carbide polycrystal 19 and silicon carbide single crystal 9 during cooling after the completion of crystal growth. It is done.

  A spacer 10 is partially sandwiched between the surface temperature Tc of the silicon carbide single crystal 9 and the inside of the first cylindrical member 7 and the second cylindrical member 8, and the first cylinder is interposed via the spacer 10. As a result of simulating a preferable temperature difference with the inner wall temperature Tg2 of the second cylindrical member 8 at the time of crystal growth of the guide member 6 in which the cylindrical member 7 and the second cylindrical member 8 are coupled, Tg2 is more than Tc. Good results were obtained in which only the silicon carbide single crystal 9 grew only by raising the temperature to at least about 4 ° C.

  However, in order to suppress the heat conduction from the second tubular member 8 to the first tubular member 7 and obtain the above effect, it is necessary to use a material having a low thermal conductivity as the spacer 10. Specifically, if a graphite sheet having a thermal conductivity of 1 to 10 W / m · K in the thickness direction is used, the second cylindrical member 8 can be kept at a high temperature as described above. If the thermal conductivity is greater than 10 W / m · K in the thickness direction, the heat conduction from the second cylindrical member 8 to the first cylindrical member 7 increases, so the inner wall temperature of the second cylindrical member 8 is increased. Tg2 cannot be kept higher than the surface temperature Tc of the adjacent silicon carbide single crystal 9.

  FIG. 3A is a plan view of the guide member 6 viewed from the seed crystal 5 side, and FIG. 3B is a cross-sectional view taken along the line A-AA in FIG. In this embodiment, a graphite sheet “PERMA-FOIL” manufactured by TOYO TANSO CO., LTD. Having a thermal conductivity of 5 W / m · K in the thickness direction is used as the spacer 10. The thickness was 1.0 mm and 2 mm square. As shown in FIG. 3 (a), the spacers 10 were provided at three locations approximately every 120 ° in plan view, and at two locations in the top and bottom as shown in FIG. 3 (b).

  After the guide member 6 as described above was installed in the single crystal growth apparatus and the temperature was raised to a desired temperature, the pressure was gradually lowered to sublimate the raw material 3 to start crystal growth. The pressure inside the reaction tube 12 was reduced to 0.665 kPa over 1 hour to sublimate the raw material 3 and maintained for 50 hours to perform crystal growth.

  At the end of the crystal growth, contrary to the start of the growth, the pressure inside the reaction tube 12 was increased to 80 kPa over 1 hour to stop sublimation of the raw material 3 and then slowly cooled to room temperature.

As a result of the growth, the silicon carbide polycrystal 19 is not attached to the inner wall of the second cylindrical member 8 of the guide member 6, and the silicon carbide single crystal 9 grown from the seed crystal 5 is The guide member 6 grew while expanding its diameter substantially along the inner wall of the second cylindrical member 8. The growth amount was 12 mm and the maximum diameter was 56 mm. The obtained silicon carbide single crystal 9 was sliced perpendicular to the growth direction and then polished to produce a wafer. The wafer was etched with a potassium hydroxide (KOH) solution heated to 500 ° C. and then observed with an optical microscope. As a result, the micropipe density was 8 cm ⁻² and the etch pit density was 2.6 × 10 ⁴ cm ⁻² . Single crystal.

  As described above, by using the guide member 6 in which the second cylindrical member 8 is disposed inside the first cylindrical member 7 via the heat insulating layer 23, the second cylindrical member 8 that is growing is used. Since the inner wall temperature can always be higher than the surface temperature of the silicon carbide single crystal 9 that grows, it is possible to suppress the silicon carbide polycrystal 19 from adhering to the inner wall of the second cylindrical member 8, and as a result, Generation | occurrence | production can be suppressed and the high quality silicon carbide single crystal 9 can be obtained.

  In the present embodiment, Ta is used as the material of the second cylindrical member 8, but the same effect can be obtained by using other refractory metals such as niobium (Nb), molybdenum (Mo), and tungsten (W). is there.

(Embodiment 2)
FIG. 4 shows a manufacturing process of the second cylindrical member 8 used for the guide member 6 in the second embodiment. The difference from the first embodiment is that tantalum carbide (TaC), which is a compound of tantalum, is used for the material of the second cylindrical member 8 of the guide member 6. Since TaC has higher thermal stability than Ta, crystal growth can be performed for a longer time in order to obtain a long silicon carbide single crystal 9.

  With reference to FIG. 4, a process for producing the second cylindrical member 8 made of TaC will be described.

  First, as shown in FIG. 4A, when the side B-BB and the side C-CC are rounded so as to overlap, a 50 μm thick Ta foil 20 is cut out so as to have the shape of the second cylindrical member 8. It was.

  Thereafter, as shown in FIG. 4B, the Ta foil 20 was fitted into the inner wall of the first graphite member 21 whose inner wall shape was the shape of the second cylindrical member 8. Thereafter, as shown in FIG. 4C, the Ta foil 20 was sandwiched between the second graphite members 22 whose outer wall shape was the shape of the second cylindrical member 8. In this state, heat treatment was performed for 5 hours at 2200 ° C. and 100 Torr in an Ar atmosphere to carbonize the Ta foil 20 to obtain a second cylindrical member 8 made of TaC.

Crystal growth was performed for 100 hours under the same conditions as in Embodiment 1 except that TaC was used as the material of the second cylindrical member 8. As a result, the silicon carbide polycrystal 19 is not attached to the inner wall of the second cylindrical member 8 of the guide member, and the grown silicon carbide single crystal 9 is not removed from the inner wall of the second cylindrical member 8 of the guide member 6. As shown in FIG. 2, the length of the sample was increased while the diameter of the tube was enlarged. The growth amount was 30 mm, and the maximum diameter was 72 mm. The obtained silicon carbide single crystal 9 was sliced perpendicular to the growth direction and then polished to produce a wafer. This wafer was etched with a KOH solution heated to 500 ° C. and then observed with an optical microscope. As a result, it was a high-quality single crystal having a micropipe density of 5 cm ⁻² and an etch pit density of 2.2 × 10 ⁴ cm ^−2. It was.

  As described above, by using TaC as the material of the second cylindrical member 8, a long and high-quality silicon carbide single crystal 9 can be obtained.

  In the first and second embodiments, silicon carbide is described as an example of a single crystal. However, in the case of a single crystal grown using a sublimation method, cadmium sulfide (CdS), cadmium selenide (CdSe), It can also be applied to zinc sulfide (ZnS), aluminum nitride (AlN), boron nitride (BN), and the like.

  INDUSTRIAL APPLICABILITY The present invention can contribute to improvement of various qualities such as environmental resistant device materials, radiation resistant device materials, power control power device materials, and high frequency device materials used in high temperature environments.

  The present invention relates to a single crystal growth apparatus for growing a crystal using a sublimation method.

  Silicon carbide (SiC) has a large thermal conductivity, a low dielectric constant, a wide band gap, and has thermally and mechanically stable characteristics. Therefore, a semiconductor element using silicon carbide has higher performance than a semiconductor element using conventional silicon (Si). The range of use is expected to be environment-resistant device materials, radiation-resistant device materials, power device materials for power control, high-frequency device materials, etc. used in high-temperature environments.

  As a method for producing this silicon carbide single crystal, a sublimation method (also referred to as “improved Rayleigh method”) is mainly employed.

  FIG. 5 is a cross-sectional view of a single crystal growth apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 1-305898) using this sublimation method.

  It is composed of a crucible 1 containing silicon carbide powder as a raw material 3 and a crucible lid portion 2 provided with a seed crystal support portion 4 so that the seed crystal 5 faces the raw material 3 on the seed crystal support portion 4. Is arranged. As seed crystal 5, a silicon carbide single crystal is used. In this state, the raw material 3 side is heated to a high temperature and the seed crystal 5 side is heated to a low temperature, and the sublimation gas of the raw material 3 is recrystallized on the low temperature seed crystal 5, whereby the silicon carbide single crystal 9 is formed. grow up.

  In this single crystal growth apparatus, since the seed crystal 5 is fixed to the seed crystal support portion 4 protruding from the crucible lid portion 2, the silicon carbide single crystal 9 grown from the seed crystal 5 and the seed crystal support portion 4 It is possible to delay contact of silicon carbide polycrystal 19 deposited around.

  However, as the growth proceeds, as shown in FIG. 6, finally, silicon carbide polycrystal 19 precipitated from the periphery of seed crystal support portion 4 comes into contact with silicon carbide single crystal 9. It is known that when the silicon carbide polycrystal 19 comes into contact with the silicon carbide single crystal 9, defects such as cracks, micropipes, and dislocations are generated in the silicon carbide single crystal 9 and the crystal quality is significantly deteriorated. It is considered that these defects occur because stress is generated in silicon carbide single crystal 9 due to a difference in thermal expansion coefficient between silicon carbide polycrystal 19 and silicon carbide single crystal 9 during cooling after the completion of crystal growth. It is done.

  In order to solve this problem, Patent Document 2 (Japanese Patent Laid-Open No. 2005-225710) describes the structure of FIGS.

  In the single crystal growth apparatus of FIG. 7, a cylindrical guide member 6 whose inner diameter gradually decreases from the raw material 3 toward the seed crystal 5 between the raw material 3 and the seed crystal 5, thereby sublimating gas from the seed crystal 5. There is known a method of efficiently growing the silicon carbide single crystal 9 by guiding to the above.

  Further, the guide member 6 is provided with a gap between the side end of the seed crystal 5 and the seed crystal support portion 4, and a part of the sublimation gas is caused to flow toward the crucible lid portion 2 so that the silicon carbide single crystal 9. Is devised to grow without contacting the guide member 6.

  However, there are cases where silicon carbide polycrystal 19 is deposited on the inner wall of gas guide portion 9 and silicon carbide polycrystal 19 and silicon carbide single crystal 9 come into contact with each other. As described above, since a crystal defect occurs in the silicon carbide single crystal and a high-quality silicon carbide single crystal cannot be obtained as described above, in Patent Document 2, the outer wall of the guide member 6 is formed as shown in FIG. By installing the heat insulating material 11, heat radiation from the outer wall of the guide member 6 is suppressed, and the inner wall of the guide member 6 is heated to a higher temperature than the surface of the silicon carbide single crystal 9. The polycrystal 19 is configured not to precipitate.

JP-A-1-305898 JP 2005-225710 A

  However, in the conventional configuration, since there is a large temperature difference between the outer wall of the guide member 6 on which the heat insulating material 11 is installed and the side surface of the crucible 1 on the outer side, the heat insulating material 11 is sublimated (deteriorated). It is easy and the heat insulation effect becomes smaller as the growth time passes.

  Therefore, if the crystal growth is performed for a long time, the inner wall temperature of the guide member 6 cannot be kept higher than the surface temperature of the growing silicon carbide single crystal 9. As a result, as shown in FIG. 9, silicon carbide polycrystal 19 is deposited on the inner wall of guide member 6, and this silicon carbide polycrystal 19 comes into contact with growing silicon carbide single crystal 9. There is a problem that a single crystal cannot be obtained.

  An object of the present invention is to provide a single crystal growth apparatus capable of growing a high-quality silicon carbide single crystal in which generation of crystal defects is suppressed even when crystal growth is performed for a long time.

  In the single crystal growth apparatus of the present invention, a raw material for growing a single crystal is placed in a crystal growth vessel, a seed crystal is placed on top of the raw material, and the crystal growth vessel is heated to sublimate. In a single crystal growth apparatus for growing a single crystal by supplying a gas of the raw material onto the seed crystal, the gas from the raw material side is directed toward the seed crystal so that a gas sublimated from the raw material reaches the seed crystal. In addition, a cylindrical guide member whose internal passage is narrowed is disposed, and the second cylindrical member is disposed inside the first cylindrical member via a heat insulating layer. .

  In addition, the single crystal growth apparatus of the present invention arranges a raw material for growing a single crystal in a crystal growth vessel, arranges a seed crystal above the raw material, and heats the crystal growth vessel. In a single crystal growth apparatus for growing a single crystal by supplying a gas of the raw material to be sublimated onto the seed crystal, the seed crystal side from the raw material side so that the gas sublimated from the raw material reaches the seed crystal A cylindrical guide member whose inner passage becomes narrower toward the inside is disposed, and the guide member is disposed inside the first cylindrical member with a second cylindrical member spaced from each other. To do.

  The guide member partially sandwiches a spacer between the inside of the first tubular member and the outside of the second tubular member, and the first tubular member and the first through the spacer. Two cylindrical members are connected to each other.

  The spacer member is made of a graphite sheet material, and the thermal conductivity thereof is 10 W / m · K or less in the thickness direction of the spacer member.

  The second cylindrical member has a melting point equal to or higher than a temperature for growing the single crystal.

  The material of the first tubular member is graphite, and the material of the second tubular member is any one of niobium (Nb), molybdenum (Mo), tantalum (Ta), and tungsten (W). It is characterized by that.

  The material of the first cylindrical member is graphite, and the material of the second cylindrical member is tantalum carbide (TaC).

  According to the single crystal growth apparatus of the present invention, since the second cylindrical member of the guide member during crystal growth can be set to a temperature higher than the surface of the silicon carbide single crystal for a long time, defects in the growing crystal can be obtained. Generation of high quality silicon carbide single crystal can be produced.

Sectional drawing of the single-crystal growth apparatus of Embodiment 1 of this invention Whole sectional view using the single crystal growth apparatus of the embodiment Enlarged view of single crystal growth apparatus during single crystal growth in FIG. 2A The top view and A-AA sectional view of the guide member of the embodiment Production process diagram of second cylindrical member made of TaC used for single crystal growth apparatus of embodiment 2 of the present invention Sectional view of conventional single crystal growth equipment FIG. 5 is a cross-sectional view of the single crystal growth apparatus of FIG. Sectional view of another conventional single crystal growth apparatus Sectional view of yet another conventional single crystal growth apparatus FIG. 8 is a cross-sectional view of the single crystal growth apparatus in FIG.

  Hereinafter, embodiments of a single crystal growth apparatus using the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1 to 3 show a single crystal growth apparatus according to a first embodiment of the present invention.

  FIG. 1 shows a state before crystal growth. This single crystal growth apparatus is composed of a crucible 1 as a crystal growth vessel and a crucible lid 2 detachably attached to an upper opening of the crucible 1. Both the crucible 1 and the crucible lid 2 were made of graphite.

  The silicon carbide powder as the raw material 3 was put on the bottom surface inside the crucible 1, and the seed crystal 5 was fixed at a position facing the raw material 3 on the seed crystal support portion 4 formed in a convex shape on the crucible lid portion 2. The seed crystal 5 was a 4H type silicon carbide single crystal, and its crystal growth plane was a (000-1) plane. The seed crystal affixing surface of the seed crystal support portion 4 has a circular shape with a diameter of 50 mm, and the seed crystal 5 has a circular shape with the same diameter of 50 mm.

  Between the raw material 3 and the seed crystal 5, a cylindrical guide whose internal passage narrows from the raw material 3 side toward the seed crystal 5 in order to efficiently guide the gas sublimated from the raw material 3 to the seed crystal 5. Member 6 was placed. The guide member 6 has a structure in which the second cylindrical member 8 is disposed inside the first cylindrical member 7 via the heat insulating layer 23.

  As the second tubular member 8, it is important to use a high melting point material. In a single crystal growth apparatus that grows a silicon carbide single crystal by a sublimation method, the growth temperature is 2000 ° C. or higher. Therefore, the second cylindrical member 8 must be a high melting point material that can maintain a solid even at this temperature. I must. Here, graphite was used for the first cylindrical member 7, and tantalum (Ta) having a melting point of 3017 ° C. was used for the second cylindrical member 8.

  Under such a high temperature, carbon particles are scattered from the surfaces of the graphite crucible 1 and the first cylindrical member 7. If the carbon particles adhere to the surface of the seed crystal 5 or the surface of the growing silicon carbide single crystal 9, it causes crystal defects such as micropipes. For this purpose, the second cylindrical member 8 prevents the carbon particles from adhering to the surface of the silicon carbide single crystal 9 by arranging the second cylindrical member 8 inside the first cylindrical member 7. be able to.

  After the seed crystal and the raw material are arranged in the single crystal growth apparatus as shown in FIG. 1, crystal growth is performed. FIG. 2 shows a state when crystal growth is performed.

  2A is an overall cross-sectional view for explaining the length of a formed crystal using the single crystal growth apparatus of FIG. 1, and FIG. 2B is an enlarged view of a region A surrounded by a dotted line in FIG. 2A.

  As shown in FIG. 2A, the crucible 1 and the crucible lid 2 constituting the single crystal growth apparatus were covered with a heat insulating material 11. As described above, when the sublimation method is used, a high temperature of 2000 ° C. or higher is required to sublimate the silicon carbide raw material 3, but at a high temperature of 2000 ° C. or higher, the temperature is proportional to the fourth power of the temperature. This is to prevent radiant heat from being lost. The crucible 1 and the crucible lid portion 2 covered with the heat insulating material 11 were arranged inside the reaction tube 12 made of quartz. The reaction tube 12 has a double tube structure, and is cooled by flowing cooling water 13 during crystal growth. A gas inlet 14 is provided at the upper part of the reaction tube 12 and a gas outlet 15 is provided at the lower part.

  Next, the inside of the reaction tube 12 was replaced with an inert gas. As the inert gas, argon (Ar) is suitable in terms of cost, purity, and the like. In this inert gas replacement, the inside of the reaction tube 12 was first evacuated to a high vacuum from the gas exhaust port 15 and then filled with an inert gas from the gas introduction port 14 to normal pressure. Thereafter, the crucible 1 and the crucible lid 2 were heated by induction heating by passing a high-frequency current through a coil 16 spirally wound around the reaction tube 12.

  At the time of heating, the crucible is heated by the radiation thermometer 18 through the quartz temperature measuring window 17 provided at the upper and lower portions of the reaction tube 12 and the temperature measuring hole 11 a provided at the upper and lower portions of the heat insulating material 11. The temperature of 1 lower part and the upper part of the crucible lid part 2 is measured.

  The lower temperature of the crucible 1 and the upper temperature of the crucible lid 2 during heating are determined by the relative positions of the crucible 1 and the crucible lid 2 and the coil 16. In the case of the sublimation method, the temperature of the raw material 3 needs to be higher than that of the seed crystal 5 in order to recrystallize the sublimation gas from the raw material 3 on the seed crystal 5 as described above. In the present embodiment, the relative positions of the crucible 1 and the crucible lid 2 and the coil 16 were adjusted so that the lower temperature of the crucible 1 was 2300 ° C. and the upper temperature of the crucible lid 2 was 2200 ° C.

  By heating in this way, at the time of crystal growth, the surface temperature Ts of the raw material 3 in the crucible 1 is the surface of the silicon carbide single crystal 9 grown from the seed crystal 5 disposed on the seed crystal support 4 of the crucible lid 2. A temperature distribution that is higher than the temperature Tc is formed. Further, due to this temperature distribution, the surface temperature Ts of the raw material 3 becomes higher than the temperature of the guide member 6 disposed between the raw material 3 and the seed crystal 5.

  Here, as shown in FIGS. 1 and 2B, the guide member 6 has a structure in which the second tubular member 8 is disposed inside the first tubular member 7 with a heat insulating layer 23 interposed therebetween. Specifically, a spacer 10 is partially sandwiched between the inside of the first tubular member 7 and the second tubular member 8, and the first tubular member 7 and the second tubular member are interposed via the spacer 10. Since the heat insulating layer 23 is formed between the inner side of the first cylindrical member 7 and the second cylindrical member 8 by joining the cylindrical members 8 to each other, the following effects are obtained.

  During crystal growth, the inner wall of the second cylindrical member 8 inside the first cylindrical member 7 is warmed by the radiant heat of the raw material 3, but the first cylindrical member 7 and the second cylindrical member 8 are heated. Are coupled with the spacer 10 interposed therebetween so that the heat conduction from the second tubular member 8 to the first tubular member 7 is suppressed by the heat insulating layer 23. For this reason, the inner wall temperature Tg2 of the second cylindrical member 8 is maintained at a high temperature.

  On the other hand, the surface of silicon carbide single crystal 9 grown from seed crystal 5 is also warmed by the radiant heat of raw material 3 during crystal growth, but is dissipated from the upper part of crucible lid portion 2 through seed crystal support portion 4. 9 surface temperature Tc decreases. Therefore, the inner wall temperature Tg2 of the second cylindrical member 8 of the guide member 6 can be kept higher than the surface temperature Tc of the adjacent silicon carbide single crystal 9, and the relationship of Ts> Tg2> Tc during crystal growth. Is always kept.

  Accordingly, the sublimation gas sublimated from the raw material 3 adheres to the surface of the low temperature silicon carbide single crystal 9 instead of the inner wall of the high temperature second cylindrical member 8 of the guide member 6, and only the silicon carbide single crystal 9 grows. There is an effect of doing.

  If the first cylindrical member 7 and the second cylindrical member 8 are in direct contact with each other, the second cylindrical member 8 heated by the radiant heat from the raw material 3 is the first cylindrical member 7. The heat is dissipated from the outer wall of the crucible 1 through Tg2 and Tc, and the temperatures become substantially equal. Therefore, the sublimation gas sublimated from the raw material 3 has substantially the same degree of supersaturation on the surface of the silicon carbide single crystal 9 and the inner wall surface of the second cylindrical member 8 and is recrystallized on both surfaces. The silicon carbide recrystallized on the inner wall of the second cylindrical member 8 is polycrystalline (silicon carbide polycrystal 19). As the crystal growth proceeds, the silicon carbide polycrystal 19 and the silicon carbide single crystal 9 Touch. When both come into contact, defects such as cracks, micropipes, and dislocations are generated in the silicon carbide single crystal 9 and the crystal quality is significantly deteriorated. It is considered that these defects occur because stress is generated in silicon carbide single crystal 9 due to a difference in thermal expansion coefficient between silicon carbide polycrystal 19 and silicon carbide single crystal 9 during cooling after the completion of crystal growth. It is done.

  A spacer 10 is partially sandwiched between the surface temperature Tc of the silicon carbide single crystal 9 and the inside of the first cylindrical member 7 and the second cylindrical member 8, and the first cylinder is interposed via the spacer 10. As a result of simulating a preferable temperature difference with the inner wall temperature Tg2 of the second cylindrical member 8 at the time of crystal growth of the guide member 6 in which the cylindrical member 7 and the second cylindrical member 8 are coupled, Tg2 is more than Tc. Good results were obtained in which only the silicon carbide single crystal 9 grew only by raising the temperature to at least about 4 ° C.

  However, in order to suppress the heat conduction from the second tubular member 8 to the first tubular member 7 and obtain the above effect, it is necessary to use a material having a low thermal conductivity as the spacer 10. Specifically, if a graphite sheet having a thermal conductivity of 1 to 10 W / m · K in the thickness direction is used, the second cylindrical member 8 can be kept at a high temperature as described above. If the thermal conductivity is greater than 10 W / m · K in the thickness direction, the heat conduction from the second cylindrical member 8 to the first cylindrical member 7 increases, so the inner wall temperature of the second cylindrical member 8 is increased. Tg2 cannot be kept higher than the surface temperature Tc of the adjacent silicon carbide single crystal 9.

  FIG. 3A is a plan view of the guide member 6 viewed from the seed crystal 5 side, and FIG. 3B is a cross-sectional view taken along the line A-AA in FIG. In this embodiment, a graphite sheet “PERMA-FOIL” manufactured by TOYO TANSO CO., LTD. Having a thermal conductivity of 5 W / m · K in the thickness direction is used as the spacer 10. The thickness was 1.0 mm and 2 mm square. As shown in FIG. 3 (a), the spacers 10 were provided at three positions approximately every 120 degrees in plan view, and at two positions in the upper and lower positions as shown in FIG. 3 (b).

  After the guide member 6 as described above was installed in the single crystal growth apparatus and the temperature was raised to a desired temperature, the pressure was gradually lowered to sublimate the raw material 3 to start crystal growth. The pressure inside the reaction tube 12 was reduced to 0.665 kPa over 1 hour to sublimate the raw material 3 and maintained for 50 hours to perform crystal growth.

  At the end of the crystal growth, contrary to the start of the growth, the pressure inside the reaction tube 12 was increased to 80 kPa over 1 hour to stop sublimation of the raw material 3 and then slowly cooled to room temperature.

As a result of the growth, the silicon carbide polycrystal 19 is not attached to the inner wall of the second cylindrical member 8 of the guide member 6, and the silicon carbide single crystal 9 grown from the seed crystal 5 is The guide member 6 grew while expanding its diameter substantially along the inner wall of the second cylindrical member 8. The growth amount was 12 mm and the maximum diameter was 56 mm. The obtained silicon carbide single crystal 9 was sliced perpendicular to the growth direction and then polished to produce a wafer. The wafer was etched with a potassium hydroxide (KOH) solution heated to 500 ° C. and then observed with an optical microscope. As a result, the micropipe density was 8 cm ⁻² and the etch pit density was 2.6 × 10 ⁴ cm ⁻² . Single crystal.

  As described above, by using the guide member 6 in which the second cylindrical member 8 is disposed inside the first cylindrical member 7 via the heat insulating layer 23, the second cylindrical member 8 that is growing is used. Since the inner wall temperature can always be higher than the surface temperature of the silicon carbide single crystal 9 that grows, it is possible to suppress the silicon carbide polycrystal 19 from adhering to the inner wall of the second cylindrical member 8, and as a result, Generation | occurrence | production can be suppressed and the high quality silicon carbide single crystal 9 can be obtained.

  In the present embodiment, Ta is used as the material of the second cylindrical member 8, but the same effect can be obtained by using other refractory metals such as niobium (Nb), molybdenum (Mo), and tungsten (W). is there.

(Embodiment 2)
FIG. 4 shows a manufacturing process of the second cylindrical member 8 used for the guide member 6 in the second embodiment. The difference from the first embodiment is that tantalum carbide (TaC), which is a compound of tantalum, is used for the material of the second cylindrical member 8 of the guide member 6. Since TaC has higher thermal stability than Ta, crystal growth can be performed for a longer time in order to obtain a long silicon carbide single crystal 9.

  With reference to FIG. 4, a process for producing the second cylindrical member 8 made of TaC will be described.

  First, as shown in FIG. 4A, when the side B-BB and the side C-CC are rounded so as to overlap, a 50 μm thick Ta foil 20 is cut out so as to have the shape of the second cylindrical member 8. It was.

  Thereafter, as shown in FIG. 4B, the Ta foil 20 was fitted into the inner wall of the first graphite member 21 whose inner wall shape was the shape of the second cylindrical member 8. Thereafter, as shown in FIG. 4C, the Ta foil 20 was sandwiched between the second graphite members 22 whose outer wall shape was the shape of the second cylindrical member 8. In this state, heat treatment was performed for 5 hours at 2200 ° C. and 100 Torr in an Ar atmosphere to carbonize the Ta foil 20 to obtain a second cylindrical member 8 made of TaC.

Crystal growth was performed for 100 hours under the same conditions as in Embodiment 1 except that TaC was used as the material of the second cylindrical member 8. As a result, the silicon carbide polycrystal 19 is not attached to the inner wall of the second cylindrical member 8 of the guide member, and the grown silicon carbide single crystal 9 is not removed from the inner wall of the second cylindrical member 8 of the guide member 6. As shown in FIG. 2, the length of the sample was increased while the diameter of the tube was enlarged. The growth amount was 30 mm, and the maximum diameter was 72 mm. The obtained silicon carbide single crystal 9 was sliced perpendicular to the growth direction and then polished to produce a wafer. This wafer was etched with a KOH solution heated to 500 ° C. and then observed with an optical microscope. As a result, it was a high-quality single crystal having a micropipe density of 5 cm ⁻² and an etch pit density of 2.2 × 10 ⁴ cm ^−2. It was.

  As described above, by using TaC as the material of the second cylindrical member 8, a long and high-quality silicon carbide single crystal 9 can be obtained.

  In the first and second embodiments, silicon carbide is described as an example of a single crystal. However, in the case of a single crystal grown using a sublimation method, cadmium sulfide (CdS), cadmium selenide (CdSe), It can also be applied to zinc sulfide (ZnS), aluminum nitride (AlN), boron nitride (BN), and the like.

  INDUSTRIAL APPLICABILITY The present invention can contribute to improvement of various qualities such as environmental resistant device materials, radiation resistant device materials, power control power device materials, and high frequency device materials used in high temperature environments.

Claims (7)

A raw material for growing a single crystal is arranged in a crystal growth vessel, a seed crystal is arranged on the upper portion of the raw material, and the gas of the raw material sublimated by heating the crystal growth vessel is placed on the seed crystal. In a single crystal growth apparatus for supplying single crystal to grow a single crystal,
While arranging a cylindrical guide member whose internal passage narrows from the raw material side toward the seed crystal so that the gas sublimated from the raw material reaches the seed crystal,
The single crystal growth apparatus which has arrange | positioned the said 2nd cylindrical member through the heat insulation layer inside the 1st cylindrical member. A raw material for growing a single crystal is arranged in a crystal growth vessel, a seed crystal is arranged on the upper portion of the raw material, and the gas of the raw material sublimated by heating the crystal growth vessel is placed on the seed crystal. In a single crystal growth apparatus for supplying single crystal to grow a single crystal,
A cylindrical guide member whose inner passage narrows from the raw material side toward the seed crystal side so that gas sublimated from the raw material reaches the seed crystal,
A single crystal growth apparatus in which the guide member is arranged such that a second cylindrical member is arranged at an interval inside the first cylindrical member. The guide member partially sandwiches a spacer 10 between the inside of the first tubular member and the outside of the second tubular member, and the first tubular member and the The single crystal growth apparatus according to claim 2, wherein the single crystal growth apparatus is coupled to the second cylindrical member. The guide member partially sandwiches a spacer 10 between the inside of the first tubular member and the outside of the second tubular member, and the first tubular member and the The second cylindrical member is coupled, and the spacer member is made of a graphite sheet material, and the thermal conductivity thereof is 10 W / m · K or less in the thickness direction of the spacer member. A single crystal growth apparatus as described in 1. above. The single crystal growth apparatus according to claim 2, wherein the second cylindrical member has a melting point equal to or higher than a temperature for growing the single crystal. The material of the first tubular member is graphite, and the material of the second tubular member is any one of niobium (Nb), molybdenum (Mo), tantalum (Ta), and tungsten (W). The single crystal growth apparatus according to claim 2. The material of the first cylindrical member is graphite,
The single crystal growth apparatus according to claim 2, wherein a material of the second cylindrical member is tantalum carbide (TaC).

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