JP2007204309A - Single crystal growth device and single crystal growth method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining a high-quality silicon carbide single crystal at a high growth rate without depositing a polycrystal on a gas guide part. <P>SOLUTION: A raw material to grow a single crystal is housed in a crucible, heated and sublimated by use of a high frequency coil disposed outside a heat insulation material around the crucible to be supplied onto a seed crystal consisting of a single crystal and to grow a single crystal on the seed crystal. In the method, a conical gas guide part 9 is disposed that has an opening apart at a predetermined distance from the seed crystal 2 and having a larger diameter in the raw material side than the diameter in the seed crystal 3 side. The high frequency coil 7 for heating the crucible 2 is placed at a position that gives an approximately right angle between an isothermal line in the crucible during heating and the conical inner wall of the gas guide part 9. The heat insulation material 8 disposed above the crucible cap 1 is placed at a predetermined distance from the crucible cap 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for producing a single crystal such as silicon carbide and a method for growing a single crystal, and a high-quality single crystal having a high growth rate can be obtained.

  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 recrystallization method (also called “improved Rayleigh method”) is mainly employed.

  FIG. 9 is a schematic view of an apparatus used for this sublimation recrystallization method, which is composed of a crucible 2 containing silicon carbide powder as a silicon carbide raw material 4 and a crucible lid portion 1 provided with a seed crystal support portion. The silicon carbide seed crystal 3 is arranged on the seed crystal support portion so as to face the silicon carbide raw material 4. In this state, the silicon carbide raw material 4 side is heated to a high temperature and the silicon carbide seed crystal 3 side is heated to a low temperature, and the sublimation gas of the silicon carbide raw material 4 is recrystallized on the low temperature silicon carbide seed crystal 3 to carbonize. A silicon single crystal 5 grows.

  As a heating method for the heating, high-frequency induction heating is generally used in which a high-frequency current is passed through a coil 7 spirally wound around the reaction tube to generate a current in the crucible and generate heat. At this time, the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 greatly contributes to the growth rate of the single crystal, and the growth rate of the single crystal increases as the temperature gradient increases. In consideration of industrial practicality, it is considered that the growth rate of the single crystal is required to be several hundred μm / hour or more. Therefore, the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 must also be increased to such a degree that this growth rate is possible. Conventionally, the temperature and temperature gradient (temperature difference) of the silicon carbide raw material 4 and the silicon carbide seed crystal 3 are controlled by changing the relative positions of the coil 7 and the crucible 2 (Non-patent Document 1).

  In addition, when silicon carbide is grown by the sublimation recrystallization method, it is necessary to heat to 2000 ° C. or higher necessary for sublimation of silicon carbide, but at a high temperature of 2000 ° C. or higher, radiant heat is proportional to the fourth power of the temperature. Since it is lost, it is necessary to cover the crucible 2 and the crucible upper lid 1 with a heat insulating material 8.

On the other hand, as shown in FIG. 10, by arranging a cylindrical (cone-shaped) gas guide portion 9 between the raw material 4 and the seed crystal 3, the sublimation gas is guided to the seed crystal 3 to efficiently grow the single crystal 5. And the technique of obtaining the high quality single crystal 5 is disclosed (patent document 1). What is important in this technique is the shape of the isotherm 10 in the crucible, particularly in the gas guide part 9 (Non-patent Document 2). Since the sublimation gas moves to the low temperature side in a direction orthogonal to the isotherm 10, if the angle θ formed by the isotherm 10 and the gas guide portion 9 is larger than 90 °, as shown in FIG. There is no sublimation gas toward the part 9, and it is efficiently transported to the seed crystal, and only the single crystal 5 grows. However, as shown in FIG. 10B, when the angle θ formed by the isotherm 10 and the gas guide portion 9 is smaller than 90 °, a part of the sublimation gas is transported to the gas guide portion 9 and is transferred to the gas guide portion 9. Polycrystalline 6 adheres. When the polycrystal 6 comes into contact with the single crystal 5, the growth of the single crystal 5 is inhibited and the single crystal 5 is distorted, and crystal defects are generated in the single crystal 5, and the crystal quality is remarkably deteriorated. Thus, it is indispensable for obtaining a high-quality single crystal that the angle θ formed by the isotherm 10 and the gas guide portion 9 is optimized (greater than 90 °).
JP 2002-60297 A Edited by Hiroyuki Matsunami, “Semiconductor SiC Technology and Applications”, first edition, Nikkan Kogyo Shimbun, March 31, 2003, p. 17 Shin-ichi Nishizawa et. al. , Numerical Simulation of Heat and Mass Transfer in SiC Publication Growth, Materials Science Forum, Switzerland, Trans Technology Publications, 2002, Vols. 389-393, p. 43-46

  However, as a result of investigations by the inventors, there is the following problem with respect to Patent Document 1. As described above, when heating, the silicon carbide raw material 4 side must be heated to a high temperature and the silicon carbide seed crystal 3 side to a low temperature, and the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 is increased. Greatly contributes to the growth rate of the single crystal. Conventionally, the temperature and temperature gradient of the silicon carbide raw material 4 and the silicon carbide seed crystal 3 are controlled by changing the relative positions of the coil 7 and the crucible 2, and the silicon carbide raw material 4 side is at a high temperature and the silicon carbide seed crystal 3 side is at a high temperature. In order to increase the temperature gradient at low temperatures, the position of the coil 7 must be lowered with respect to the crucible 2.

  However, in the experiments by the inventors, when the position of the coil 7 is lowered with respect to the crucible 2, the polycrystal 6 easily adheres to the gas guide portion 9. As a result of the polycrystal 6 adhering to the gas guide portion 9, the grown single crystal 5 comes into contact with the polycrystal 6 adhering to the gas guide portion 9, and the polycrystal 6 distorts the single crystal 5 to cause cracks and dislocations. Such a crystal defect occurred in the single crystal 5. As a result of examining the temperature distribution in the crucible 2 by simulation, as shown in FIGS. 7 and 8, the cause of the polycrystal 6 adhesion to the gas guide portion 9 is that the position of the coil 7 is lowered with respect to the crucible 2. Thus, it was found that the angle θ formed by the isotherm 10 and the gas guide portion 9 was smaller than 90 °, and a part of the raw material gas was transported to the gas guide portion 9.

  In other words, if the temperature of the coil 7 is lowered with respect to the crucible 2 and the temperature gradient between the silicon carbide seed crystal 3 and the silicon carbide raw material 4 is increased in order to increase the crystal growth rate of the single crystal 5, the gas guide 9 is polycrystallized. There is a problem that 6 adheres and the crystal quality of the single crystal 5 is remarkably deteriorated.

  The present invention has been made in order to solve the above-mentioned problems. A single crystal having a high quality and a high growth rate is obtained by increasing the temperature gradient between the raw material and the seed crystal without attaching polycrystals to the gas guide portion. Provide a way to get.

In order to solve the above problems, the single crystal growth apparatus of the present invention stores a raw material for growing a single crystal in a crucible, heats and sublimates the raw material of the single crystal, and supplies the raw material onto a seed crystal made of a single crystal. In the single crystal growth apparatus for growing a single crystal on the seed crystal, a cylindrical seed crystal support portion for supporting the seed crystal on the crucible lid portion at a position facing the raw material of the crucible, and the seed crystal A conical gas guide portion having an opening at a predetermined distance and a raw material side having a larger diameter than the seed crystal side, and
A heat insulating material having a predetermined thickness covering the entire crucible body, and a high-frequency coil disposed outside the heat insulating material disposed around the entire crucible body to heat the seed crystal and the raw material. ,
The heat insulating material disposed on the crucible lid portion is disposed with a predetermined distance from the crucible lid portion.

  Further, the single crystal growth apparatus of the present invention accommodates a raw material for growing a single crystal in a crucible, heats and sublimates the raw material of the single crystal, and supplies the single crystal on a seed crystal. In a single crystal growth apparatus for growing a single crystal, a cylindrical seed crystal support portion that supports the seed crystal on the crucible lid portion at a position facing the raw material of the crucible, and a distance from the seed crystal. In order to heat the seed crystal and the silicon carbide raw material having an opening and a conical gas guide portion whose raw material side is larger in diameter than the seed crystal side, a heat insulating material having a predetermined thickness covering the entire crucible body A high-frequency coil disposed outside the heat insulating material disposed in the crucible around the entire crucible body, the heat insulating material disposed so as to cover the crucible is disposed in contact with the crucible, and 2000 Thermal conductivity at 0 ° C is 0.5 to 1.5 W / m The thickness of the heat insulating material at the upper part of the crucible lid portion is set to be thinner than the thickness of the heat insulating material covering the other crucible portions.

The single crystal growth method of the present invention also includes a seed made of a single crystal by containing a raw material for growing a single crystal in a crucible and heating and sublimating the raw material using a high-frequency coil outside a heat insulating material around the crucible. In a single crystal growth method of supplying on a crystal and growing a single crystal on the seed crystal,
A cone-shaped gas guide portion having an opening having a predetermined distance from the seed crystal and having a larger diameter on the raw material side than the seed crystal side is disposed, and the high-frequency coil position for heating the crucible body is a crucible at the time of heating. An isotherm is disposed at a position where the angle formed by the conical inner wall of the gas guide portion is substantially perpendicular, and the heat insulating material disposed on the crucible lid portion has a predetermined distance from the crucible lid portion. It is characterized by being arranged.

The single crystal growth method of the present invention also includes a seed made of a single crystal by containing a raw material for growing a single crystal in a crucible and heating and sublimating the raw material using a high-frequency coil outside a heat insulating material around the crucible. In a single crystal growth method of supplying on a crystal and growing a single crystal on the seed crystal,
A cone-shaped gas guide portion having an opening having a predetermined distance from the seed crystal and having a larger diameter on the raw material side than the seed crystal side is disposed, and the high-frequency coil position for heating the crucible body is a crucible at the time of heating. A heat insulating material that is disposed at a position where the angle formed between the inner isotherm and the conical inner wall of the gas guide portion is substantially perpendicular, and covers the other crucible portion with the thickness of the heat insulating material at the upper portion of the crucible lid portion It is characterized in that it is set to be thinner than the thickness.

  Embodiments of a single crystal growth apparatus and growth method using the present invention will be described below in detail with reference to the drawings. In addition, although silicon carbide is used as the single crystal, it is naturally applicable to the growth of other single crystals.

FIG. 1 is a schematic view of a growth apparatus used in Example 1. Silicon carbide raw material 4 (silicon carbide powder) was housed in crucible 2, and silicon carbide seed crystal 3 fixed to the seed crystal support portion of crucible lid portion 1 was arranged to face silicon carbide raw material 4. As the silicon carbide seed crystal 3, a 4H type silicon carbide single crystal having a micropipe density of about 30 pieces / cm ² and an etch pit density of about 3 × 10 ⁴ pieces / cm ² is used. -1) A surface. Moreover, the seed crystal sticking surface of the seed crystal support part was a circle having a diameter of 20 mm, and the silicon carbide seed crystal 3 was also a circle having a diameter of 20 mm.

  Between the silicon carbide raw material 4 and the silicon carbide seed crystal 3, in order to efficiently introduce the gas sublimated from the silicon carbide raw material 4 to the seed crystal 3, the silicon carbide raw material 4 side has a larger diameter cone than the silicon carbide seed crystal 3 side. A gas guide portion 9 is arranged. At this time, a distance is provided between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide portion 9. If this distance is less than 0.5 mm, the silicon carbide single crystal 5 growing from the outer peripheral portion of the silicon carbide seed crystal 3 or the silicon carbide polycrystal 6 growing from the side wall surface of the seed crystal support portion of the crucible lid 1 will cause this gap. May be blocked.

  If the distance is larger than 2 mm, the ratio of the sublimation gas toward the lower surface of the crucible lid 1 in the sublimation gas of the silicon carbide raw material 4 increases, and the ratio of the sublimation gas that contributes to the growth of the silicon carbide single crystal 5. Less. Therefore, the growth rate of silicon carbide single crystal 5 is slow. Furthermore, since the growth rate of the silicon carbide polycrystal 6 from the lower surface of the crucible lid 1 is increased, the silicon carbide polycrystal 6 extending from the lower surface of the crucible lid 1 is converted into the crucible lid body when the crystal growth is performed for several tens of hours. It becomes higher than the height of the seed crystal support portion of 1 and comes into contact with the silicon carbide single crystal 5 grown from the seed crystal 3 to give strain to the silicon carbide single crystal 5 to deteriorate the crystal quality. Therefore, the distance between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide part is desirably 0.5 mm or more and 2 mm or less. In this example, specifically, the distance between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide portion was set to 1.0 mm.

  In silicon carbide single crystal growth using the sublimation recrystallization method, a high temperature of 2000 ° C. or higher is required to sublimate the silicon carbide raw material 4. At a high temperature of 2000 ° C. or higher, the radiant heat is lost in proportion to the fourth power of the temperature. Therefore, it is necessary to cover the crucible 2 and the crucible lid 1 with the heat insulating material 8. At this time, a distance was provided between the crucible lid 1 and the heat insulating material 8.

  As shown in FIG. 2, by providing this distance, the temperature gradient between the silicon carbide seed crystal 3 and the silicon carbide raw material 4 can be increased while maintaining the isotherm 10 in the crucible in an optimum shape. That is, the angle θ formed between the isotherm 10 in the crucible and the conical inner wall of the gas guide portion 9 is substantially perpendicular, and the temperature gradient between the silicon carbide seed crystal 3 and the silicon carbide raw material 4 can be increased. .

  The heat conductivity of the heat insulating material 8 at 2000 ° C. is 0.5 to 1.5 W / m · K, and the thickness of the heat insulating material 8 on the crucible lid portion 1 is larger than 10 mm and not larger than 50 mm. If the distance between the lid portion 1 and the heat insulating material 8 is 5 mm or more and 40 mm or less, the isotherm 10 in the crucible is formed by the conical inner wall of the gas guide portion 9 as shown in FIG. The angle θ is substantially a right angle, and the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 can be appropriately set to 10 ° C./cm to 30 ° C./cm. When the distance between the crucible lid portion 1 and the heat insulating material 8 is smaller than 5 mm, as shown in FIG. 3B, the angle θ formed between the isothermal line 10 in the crucible and the conical inner wall of the gas guide portion 9. Is substantially perpendicular, but the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 is too small. When the distance between the crucible lid 1 and the heat insulating material 8 is greater than 40 mm, the isotherm 10 in the crucible is formed by the conical inner wall of the gas guide 9 as shown in FIG. Although the angle θ is substantially a right angle, the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 is too large.

  Furthermore, the growth rate is adjusted by setting the temperature of the silicon carbide raw material 4 to 2200 ° C. to 2300 ° C., the temperature of the silicon carbide silicon carbide seed crystal 3 to 2100 ° C. to 2200 ° C., and the pressure during growth to 0.665 kPa to 3.99 kPa. Also, the preferable range is 200 μm / hour to 600 μm / hour. If the crystal growth rate is smaller than 200 μm / hour, the cost becomes high when a wafer is produced from the grown crystal, and this is not industrially practical. On the other hand, if the growth rate is higher than 600 μm / hour, strain and crystal defects are generated in the grown crystal, or different polytypes are mixed, resulting in poor crystal quality. If the crystal growth rate is in the range of 200 μm / hour to 600 μm / hour, a silicon carbide single crystal can be grown without occurrence of distortion, crystal defects, and mixing of different polytypes.

  In this embodiment, specifically, FGL-203SH manufactured by Nippon Carbon Co., Ltd. as the heat insulating material 8 on the crucible lid 1 side (thermal conductivity at 2000 ° C. in vacuum is about 0.55 W / m · K). The thickness was 25 mm, and the gap with the crucible lid 1 was 10 mm.

  The crucible 2 and the crucible lid portion 1 covered with the heat insulating material 8 were placed in a reaction tube 11 made of quartz. The reaction tube 11 has a double tube structure, and is cooled by flowing cooling water 12 during crystal growth. A gas inlet 13 is provided at the top of the reaction tube 11 and a gas outlet 14 is provided at the bottom.

  Thereafter, the inside of the reaction tube 11 is replaced with an inert gas, and argon (Ar) is suitable as the inert gas in terms of cost, purity, and the like. In this inert gas replacement, first, the inside of the reaction tube 11 was evacuated to a high vacuum from the gas exhaust port 14 and then filled with an inert gas from the gas inlet 13 to normal pressure.

  Thereafter, the crucible 2 and the crucible lid portion 1 were heated at a high frequency by flowing a high-frequency current through the coil 7 spirally wound around the reaction tube 11 to raise the temperature.

  Usually, the relative position of this coil 7 and the aforementioned crucible 2 determines the temperature gradient between the silicon carbide seed crystal 3 and the silicon carbide raw material 4. In the case of the sublimation method, the temperature of the silicon carbide raw material 4 is changed to silicon carbide. It is necessary to make it higher than the seed crystal 3. Furthermore, this temperature gradient greatly affects the crystal growth rate of the single crystal, and the crystal growth rate increases as the temperature gradient increases. Therefore, it is necessary to increase the temperature gradient by lowering the position of the coil 7 with respect to the crucible 2. However, as already described, when the position of the coil 7 is lowered with respect to the crucible 2, the polycrystal tends to adhere to the gas guide portion 9, and the growing single crystal and the polycrystal come into contact with each other. This significantly deteriorates the crystal quality. However, in this embodiment, as described above, a predetermined distance is provided between the crucible lid 1 and the heat insulating material 8 to determine the temperature gradient of the silicon carbide raw material 4 and the silicon carbide seed crystal 3. Accordingly, since it is not necessary to completely control the temperature gradient between the silicon carbide seed crystal 3 and the silicon carbide raw material 4 at the relative position between the crucible 2 and the coil 7, the relative position between the crucible 2 and the coil 7 is the isotherm in the crucible. 10 and the conical inner wall of the gas guide portion 9 are substantially perpendicular, and are determined by simulation of temperature distribution in the crucible and preliminary experiments so that polycrystals do not adhere to the gas guide portion 9.

  At the time of heating, the radiation thermometer 16 and the lower part of the crucible 2 are passed through the quartz temperature measurement windows 15 provided at the upper and lower parts of the reaction tube 11 and the temperature measurement holes provided at the upper and lower parts of the heat insulating material 8. , And the temperature of the upper part of the crucible lid 1 is measured. In the present embodiment, the temperature control is performed by feeding back the temperature of the upper part of the crucible lid 1 to a high frequency power source (not shown) and controlling the high frequency current flowing through the coil 7. The lower temperature of the crucible 2 at that time is determined by the distance between the crucible lid 1 and the heat insulating material 8 described above. In this example, the crucible 2 lower temperature (silicon carbide raw material 4 temperature) was 2250 ° C., and the crucible lid 1 upper temperature (silicon carbide silicon carbide seed crystal 3 temperature) was 2150 ° C.

  When raising the temperature, the inside of the reaction tube 11 needs to be kept at a pressure of about several tens of kPa. This is to prevent sublimation of the silicon carbide raw material 4 at low temperatures (below the desired crystal growth temperature) and prevent crystal growth from starting.

  Thus, after raising the temperature to a desired temperature, the pressure is gradually reduced to start crystal growth. In this example, the pressure inside the reaction tube 11 was 1.33 kPa, and the crystal growth was carried out by holding for 40 hours.

  At the end of crystal growth, contrary to the start of growth, the pressure inside the reaction tube 11 was increased to 80 kPa over 1 hour to stop the sublimation of the silicon carbide raw material 4, and then slowly cooled to room temperature.

  As a result of the growth as described above, no polycrystal was attached to the gas guide part, and only a single crystal was grown substantially along the conical shape of the gas guide part 9. The crystal growth rate of the single crystal was a high crystal growth rate of about 400 μm / hour. The obtained single crystal was sliced perpendicular to the growth direction, both front and back surfaces were mirror-polished, and then observed with a transmission polarization microscope. As a result, no single crystal grew independently without any polycrystals adhering to the gas guide portion 9, and no strain was observed in the single crystal. Further, it was immersed in molten KOH at 500 ° C. for 5 minutes, and then the micropipe density and the etch pit density were measured with a microscope. As a result, on the seed crystal, both values were almost the same as those of the seed crystal, but there were no micropipes in the enlarged diameter portion, and only a few etch pits were observed.

  As described above, the growth apparatus for controlling the temperature gradient between the silicon carbide raw material and the silicon carbide seed crystal by providing a predetermined distance between the crucible lid and the heat insulating material disposed on the crucible lid, It is effective to grow a single crystal at a high crystal growth rate and suppress polycrystal adhesion to the gas guide, and as a result, it is confirmed that a high-quality silicon carbide single crystal can be obtained at a high crystal growth rate. did it.

FIG. 4 is a schematic view of a growth apparatus used in Example 2. Silicon carbide raw material 4 was housed in crucible 2, and silicon carbide seed crystal 3 fixed to the seed crystal support portion of crucible lid portion 1 was arranged to face silicon carbide raw material 4. As the silicon carbide seed crystal 3, a 4H type silicon carbide single crystal having a micropipe density of about 30 pieces / cm ² and an etch pit density of about 3 × 10 ⁴ pieces / cm ² is used. -1) A surface. Moreover, the seed crystal sticking surface of the seed crystal support part was a circle having a diameter of 20 mm, and the silicon carbide seed crystal 3 was also a circle having a diameter of 20 mm.

  Between the silicon carbide raw material 4 and the silicon carbide seed crystal 3, in order to efficiently introduce the gas sublimated from the silicon carbide raw material 4 to the seed crystal 3, the silicon carbide raw material 4 side has a larger diameter cone than the silicon carbide seed crystal 3 side. A gas guide portion 9 is arranged. At this time, a distance is provided between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide portion 9. If this distance is less than 0.5 mm, the silicon carbide single crystal 5 growing from the outer peripheral portion of the silicon carbide seed crystal 3 or the silicon carbide polycrystal 6 growing from the side wall surface of the seed crystal support portion of the crucible lid 1 will cause this gap. May be blocked.

  If the distance is larger than 2 mm, the ratio of the sublimation gas toward the lower surface of the crucible lid 1 in the sublimation gas of the silicon carbide raw material 4 increases, and the ratio of the sublimation gas that contributes to the growth of the silicon carbide single crystal 5. Less. Therefore, the growth rate of silicon carbide single crystal 5 is slow. Furthermore, since the growth rate of the silicon carbide polycrystal 6 from the lower surface of the crucible lid 1 is increased, the silicon carbide polycrystal 6 extending from the lower surface of the crucible lid 1 is converted into the crucible lid body when the crystal growth is performed for several tens of hours. It becomes higher than the height of the seed crystal support portion of 1 and comes into contact with the silicon carbide single crystal 5 grown from the seed crystal 3 to give strain to the silicon carbide single crystal 5 to deteriorate the crystal quality. Therefore, the distance between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide part is desirably 0.5 mm or more and 2 mm or less. In this example, specifically, the distance between the silicon carbide seed crystal 3 and the silicon carbide seed 3 crystal side end of the gas guide portion was set to 1.0 mm.

  In silicon carbide single crystal growth using the sublimation recrystallization method, a high temperature of 2000 ° C. or higher is necessary to sublimate the silicon carbide raw material. At a high temperature of 2000 ° C. or higher, the radiant heat is lost in proportion to the fourth power of the temperature. Therefore, it is necessary to cover the crucible 2 and the crucible lid 1 with the heat insulating material 8. At this time, as shown in FIGS. 5 and 6, the thermal conductivity of the heat insulating material 8 at 2000 ° C. is 0.5 to 1.5 W / m · K, and the thickness of the heat insulating material 8 on the upper portion of the crucible lid 1. Is in the range of 5 mm or more and 10 mm or less, the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 becomes an appropriate temperature gradient while maintaining the isotherm 10 in the crucible in an optimum shape. That is, as shown in FIGS. 5 and 6, the silicon carbide seed crystal 3 and the silicon carbide are maintained while the angle θ formed between the isothermal line 10 in the crucible and the conical inner wall of the gas guide portion 9 is maintained at a substantially right angle. The temperature gradient between the raw materials 4 can be appropriately set at 10 ° C./cm to 30 ° C./cm. When the thickness of the heat insulating material 8 on the upper part of the crucible lid 1 is smaller than 5 mm, the angle formed by the isothermal line 10 in the crucible and the conical inner wall of the gas guide part 9 as shown in FIG. θ is substantially a right angle, but the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 is too large.

  When the thickness of the heat insulating material 8 at the upper part of the crucible lid 1 is larger than 10 mm, the isotherm 10 in the crucible is connected to the conical inner wall of the gas guide 9 as shown in FIG. The formed angle θ is substantially a right angle, but the temperature gradient between the silicon carbide raw material 4 and the silicon carbide seed crystal 3 is too small.

  Furthermore, the growth rate is adjusted by setting the temperature of the silicon carbide raw material 4 to 2200 ° C. to 2300 ° C., the temperature of the silicon carbide silicon carbide seed crystal 3 to 2100 ° C. to 2200 ° C., and the pressure during growth to 0.665 kPa to 3.99 kPa. Also, the preferable range is 200 μm / hour to 600 μm / hour. If the crystal growth rate is smaller than 200 μm / hour, the cost becomes high when a wafer is produced from the grown crystal, and this is not industrially practical. On the other hand, if the growth rate is higher than 600 μm / hour, strain and crystal defects are generated in the grown crystal, or different polytypes are mixed, resulting in poor crystal quality. If the crystal growth rate is in the range of 200 μm / hour to 600 μm / hour, a silicon carbide single crystal can be grown without occurrence of distortion, crystal defects, and mixing of different polytypes.

  In this embodiment, specifically, FGL-203SH manufactured by Nippon Carbon Co., Ltd. as the heat insulating material 8 on the crucible lid 1 side (thermal conductivity at 2000 ° C. in vacuum is about 0.55 W / m · K). The thickness was 10 mm.

  The crucible 2 and the crucible lid portion 1 covered with the heat insulating material 8 were placed in a reaction tube 11 made of quartz. The reaction tube 11 has a double tube structure, and is cooled by flowing cooling water 12 during crystal growth. A gas inlet 13 is provided at the top of the reaction tube 11 and a gas outlet 14 is provided at the bottom.

  Thereafter, the inside of the reaction tube 11 is replaced with an inert gas, and argon (Ar) is suitable as the inert gas in terms of cost, purity, and the like. In this inert gas replacement, first, the inside of the reaction tube 11 was evacuated to a high vacuum from the gas exhaust port 14 and then filled with an inert gas from the gas inlet 13 to normal pressure.

  Thereafter, the crucible 2 and the crucible lid portion 1 were heated at a high frequency by flowing a high-frequency current through the coil 7 spirally wound around the reaction tube 11 to raise the temperature. As in the first embodiment, the relative position of the coil 7 and the crucible 2 is such that the angle θ formed by the isotherm 10 in the crucible and the conical inner wall of the gas guide portion 9 is substantially perpendicular, and the polycrystalline structure is formed in the gas guide portion 9. In order to prevent adhesion, the temperature distribution in the crucible is determined by simulation and preliminary experiments.

  At the time of heating, the radiation thermometer 16 and the lower part of the crucible 2 are passed through the quartz temperature measurement windows 15 provided at the upper and lower parts of the reaction tube 11 and the temperature measurement holes provided at the upper and lower parts of the heat insulating material 8. , And the temperature of the upper part of the crucible lid 1 is measured. In this embodiment, the temperature of the crucible lid portion 1 is fed back to a high frequency power source (not shown) and the high frequency current flowing through the coil 7 is controlled to control the temperature. The lower temperature of the crucible 2 at that time is determined by the thickness of the heat insulating material on the aforementioned crucible lid 1 side. In this example, the crucible 2 lower temperature (silicon carbide raw material 4 temperature) was 2250 ° C., and the crucible lid 1 upper temperature (silicon carbide silicon carbide seed crystal 3 temperature) was 2150 ° C.

  Thereafter, crystal growth was performed in the same manner as in Example 1.

  As a result of the growth as described above, no polycrystal was adhered to the gas guide portion 9, and only a single crystal was grown substantially along a tapered shape. The crystal growth rate of the single crystal was as fast as about 400 μm / hour as in Example 1. The obtained single crystal was sliced perpendicular to the growth direction, both front and back surfaces were mirror-polished, and then observed with a transmission polarization microscope. As a result, no single crystal was grown independently without any polycrystals adhering to the gas guide portion, so no strain was observed in the single crystal. Further, it was immersed in molten KOH at 500 ° C. for 5 minutes, and then the micropipe density and the etch pit density were measured with a microscope. As a result, on the seed crystal, both values were almost the same as those of the seed crystal, but there were no micropipes in the enlarged diameter portion, and only a few etch pits were observed.

  As described above, the growth apparatus that controls the temperature gradient between the silicon carbide raw material and the silicon carbide seed crystal according to the thickness of the heat insulating material on the crucible lid portion grows a single crystal at a high crystal growth rate, and gas It was effective in suppressing polycrystal adhesion to the guide part, and as a result, it was confirmed that a high-quality silicon carbide single crystal could be obtained at a high crystal growth rate.

  The apparatus and method for growing a single crystal according to the present invention has a high growth rate and can obtain a high-quality single crystal. Therefore, cadmium sulfide (CdS) and cadmium selenide, which are single crystals that can be grown by a sublimation method. It can also be applied to (CdSe), zinc sulfide (ZnS), aluminum nitride (AlN), boron nitride (BN), and the like.

Schematic sectional view of a single crystal growth apparatus in Example 1 of the present invention Explaining the relationship between the temperature gradient between the raw material (silicon carbide powder) and the seed crystal according to the distance between the crucible lid portion and the heat insulating material of the single crystal growth apparatus in Example 1 of the present invention, and the angle θ formed between the gas guide portion and the isotherm. Figure to The figure which shows the isotherm shape in the crucible of the single-crystal growth apparatus in Example 1 of this invention. Schematic cross-sectional view of a single crystal growth apparatus in Example 2 of the present invention Relationship between temperature gradient between raw material (silicon carbide powder) and seed crystal due to thickness of heat insulating material on crucible lid portion of single crystal growth apparatus in embodiment 2 of present invention, and angle θ formed by gas guide portion and isotherm Figure explaining The figure which shows the isotherm shape in the crucible of the single-crystal growth apparatus in Example 2 of this invention. The figure explaining the relationship between the temperature (theta) between the raw material (silicon carbide powder) and seed crystal by the coil position with respect to the crucible of a single crystal growth apparatus, and the angle (theta) which an isothermal line forms with a gas guide part. The figure which shows the isothermal shape in a crucible by the coil position with respect to the crucible of a single crystal growth apparatus Schematic cross section of conventional single crystal growth equipment The figure for demonstrating the mode of the crystal growth by angle (theta) which the gas guide part and the isothermal line in the conventional single crystal growth apparatus form

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crucible lid part 2 Crucible 3 Silicon carbide seed crystal 4 Silicon carbide raw material 5 Silicon carbide single crystal 6 Silicon carbide polycrystal 7 Coil 8 Heat insulating material 9 Gas guide part 10 Isotherm 11 Reaction tube 12 Cooling water 13 Gas inlet 14 Gas exhaust Mouth 15 Temperature measurement window 16 Radiation thermometer

Claims (7)

In a single crystal growth apparatus in which a raw material for growing a single crystal is contained in a crucible, the raw material of the single crystal is heated and sublimated, supplied onto a seed crystal made of a single crystal, and a single crystal is grown on the seed crystal.
A columnar seed crystal support that supports the seed crystal on the crucible lid at a position facing the raw material of the crucible;
A conical gas guide portion having a predetermined distance from the seed crystal and having an opening having a larger diameter on the raw material side than the seed crystal side;
A heat insulating material having a predetermined thickness covering the entire crucible body;
A high-frequency coil disposed outside a heat insulating material disposed around the entire crucible body to heat the seed crystal and the raw material;
With
The single crystal growth apparatus, wherein the heat insulating material disposed on the crucible lid portion is disposed at a predetermined distance from the crucible lid portion. The heat insulating material has a thermal conductivity at 2000 ° C. of 0.5 to 1.5 W / m · K, and the thickness of the heat insulating material on the crucible lid portion side is larger than 10 mm and not larger than 50 mm. And the distance between the said crucible cover part and the said heat insulating material is 5 mm or more and 40 mm or less, The single crystal growth apparatus of Claim 1 characterized by the above-mentioned. In a single crystal growth apparatus in which a raw material for growing a single crystal is contained in a crucible, the raw material of the single crystal is heated and sublimated, supplied onto a seed crystal made of a single crystal, and a single crystal is grown on the seed crystal.
A columnar seed crystal support that supports the seed crystal on the crucible lid at a position facing the raw material of the crucible;
A conical gas guide portion having an opening apart from the seed crystal and having a larger diameter on the raw material side than the seed crystal side;
A heat insulating material having a predetermined thickness covering the entire crucible body;
A high-frequency coil disposed outside a heat insulating material disposed in the crucible around the entire crucible body to heat the seed crystal and the silicon carbide raw material;
With
The heat insulating material disposed so as to cover the crucible is placed in contact with the crucible, has a thermal conductivity of 0.5 to 1.5 W / m · K at 2000 ° C., and is provided at the upper part of the crucible lid. A single crystal growth apparatus characterized in that a thickness of a heat insulating material is set to be thinner than a thickness of a heat insulating material covering another crucible portion. The temperature of the seed crystal side is set high in the range of the temperature of the raw material of the single crystal from 2200 ° C. to 2300 ° C., the temperature of the seed crystal from 2100 ° C. to 2200 ° C., and the temperature gradient between the raw material and the seed crystal is set. 4. The single crystal growth apparatus according to claim 2, wherein the growth pressure is set to 0.665 kPa to 3.99 kPa in a range of 10 ° C./cm to 30 ° C./cm. 5. A raw material for growing a single crystal is housed in a crucible, and the raw material is heated and sublimated using a high-frequency coil outside a heat insulating material around the crucible and supplied onto a seed crystal made of a single crystal. In a single crystal growth method for growing a single crystal,
Disposed a predetermined distance away from the seed crystal, and provided a conical gas guide portion having a larger diameter than the seed crystal side on the raw material side,
The high-frequency coil position for heating the crucible body is disposed at a position where the angle formed by the isotherm in the crucible during heating and the conical inner wall of the gas guide portion is substantially perpendicular,
The single crystal growth method, wherein the heat insulating material disposed on the crucible lid portion is disposed at a predetermined distance from the crucible lid portion. A raw material for growing a single crystal is housed in a crucible, and the raw material is heated and sublimated using a high-frequency coil outside a heat insulating material around the crucible and supplied onto a seed crystal made of a single crystal. In a single crystal growth method for growing a single crystal,
Disposed a predetermined distance away from the seed crystal, and provided a conical gas guide portion having a larger diameter than the seed crystal side on the raw material side,
The high-frequency coil position for heating the crucible body is disposed at a position where the angle formed by the isotherm in the crucible during heating and the conical inner wall of the gas guide portion is substantially perpendicular,
And the thickness of the heat insulating material of the said crucible lid part upper part is set thinner than the thickness of the heat insulating material which covers another crucible part, The single crystal growth method characterized by the above-mentioned. The single crystal growth method according to claim 5 or 6, wherein the predetermined distance between the seed crystal and the conical gas guide portion is 0.5 mm or more and 2 mm or less.

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