JP2011168431A - Device for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for producing a single crystal, for example, for producing a SiC single crystal by a sublimation method, the device capable of suppressing degradation of a heat insulating material during growing a single crystal, increasing reproducibility of the temperature distribution in a crucible and suppressing increase in the production cost. <P>SOLUTION: The device for producing a single crystal includes a conductive crucible 10 and a conductive core pipe 11 disposed close to the outer circumference of the crucible 10 and covering a side and an upper part of the crucible 10. When the crucible 10 is heated by using an induction heating method, the core pipe 11 is disposed in such a manner that the lower end of the pipe is positioned lower than the bottom of the crucible 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing a single crystal such as silicon carbide (SiC).

  A silicon carbide (SiC) semiconductor is known as a semiconductor material having excellent thermal and chemical characteristics, and having a forbidden band width larger than that of a silicon (Si) semiconductor, and also excellent in electrical characteristics. Yes. In particular, 4H-type SiC has a high electron mobility and saturated electron velocity, so that practical application as a semiconductor material for power devices is desired.

  As a method for obtaining a single crystal as a semiconductor, an improved Rayleigh method (sublimation method) is widely used. Currently, SiC substrates with a diameter of up to 100 mm are commercially available, but since the crystal defect density is high, it is necessary to further reduce the crystal defect density for use as a semiconductor application. Also, considering the mass productivity of semiconductor devices, it is essential to increase the diameter and length of SiC single crystals.

  The production of SiC single crystal by the sublimation method involves placing a seed crystal (seed substrate), which is an SiC single crystal, and an SiC raw material facing each other in a crucible, and evacuating (evacuating) the inside of the crucible so After air substitution with the active gas, the crucible is heated to a high temperature (about 2400 ° C.), and the SiC raw material is sublimated. At this time, by holding the seed crystal at a temperature lower than that of the raw material, the gas (raw material gas) sublimated from the raw material diffuses according to the temperature gradient, reaches the surface of the seed crystal, and an SiC single crystal ingot grows.

  As a method for heating the crucible at this time, an induction heating method using a high frequency is generally used. The induction heating method utilizes the fact that a conductor generates heat due to an induction current generated in the conductor by a high frequency. For this reason, the material of the crucible is required to have conductivity and be able to withstand at high temperatures. Therefore, graphite is generally used as the crucible material.

  As the shape of the crucible, a cylindrical one is used in order to eliminate temperature non-uniformity due to the skin effect due to high frequency induction heating and to facilitate processing. Furthermore, in order to efficiently heat the crucible while suppressing thermal radiation from the crucible, the periphery of the crucible is covered with a heat insulating material (for example, Patent Document 1). This heat insulating material is required to be non-conductive and to withstand a high temperature of about 2400 ° C., and generally a heat insulating material made of graphite is used.

  The quality of the obtained single crystal greatly depends on the temperature difference between the raw material and the seed crystal during growth and the temperature gradient in the radial direction of the crucible, in addition to the quality of the seed crystal. Therefore, in order to obtain a high quality single crystal, it is necessary to precisely control the temperature distribution of the crucible during crystal growth. In addition, in order to obtain a high quality single crystal repeatedly and stably, it is necessary to increase the reproducibility of the temperature distribution. In the growth of a SiC single crystal, a temperature distribution at a high temperature around 2500 ° C. must be reproduced, and a very advanced technique is required.

  In order to increase the reproducibility of the temperature distribution, it is important to keep the heat shielded state by the heat insulating material around the crucible constant. Currently available graphite insulation materials include felt-like insulation materials and molded insulation materials obtained by molding felt-like insulation materials.

  In addition, in order to obtain a high-quality single crystal by suppressing distortion of the single crystal, it is necessary to independently grow the single crystal grown from the surface of the seed crystal in the crucible without contacting the polycrystal. For this purpose, it is necessary to control the temperature gradient in the radial direction in the crucible with high accuracy. Further, as a technique for easily achieving this, a technique using a tapered cone guide that guides a source gas to a seed crystal is known (for example, Patent Document 2).

JP 2008-110907 A JP 2007-204309 A

  For example, in patent document 1, the felt-like heat insulating material is stuck to the whole surface of the crucible. In the sublimation method, the bottom of the crucible becomes the highest temperature, and the heat insulating material in that portion tends to deteriorate most quickly. For example, if the heat insulating material deteriorates during one growth, the temperature distribution in the crucible changes during the growth of the single crystal, and a single crystal with uniform quality cannot be obtained. In particular, when a single crystal is increased in diameter and lengthened, it takes a long time to grow, and this problem becomes remarkable. Therefore, preventing deterioration of the heat insulating material is an important issue in the future.

  On the other hand, as a method for improving the reproducibility of the temperature distribution in the crucible, a method of replacing the heat insulating material every time the single crystal is grown several times can be considered. From the viewpoint of stability of shape and dimensions, it is advantageous to use molded insulation, but molded insulation is more expensive than felt-like insulation, so if you replace it frequently, the manufacturing cost will increase. . Even if felt-like insulation is used, if the temperature of the felt-like insulation rises extremely, the insulation will deteriorate during the growth and the temperature cannot be kept constant, or it cannot be reused for the next growth. There was a problem.

  The present invention has been made in order to solve the above-described problems. In the production of a single crystal, the first object is to suppress the deterioration of the heat insulating material during the growth of the single crystal. A second object is to improve the reproducibility of the temperature distribution, and a third object is to suppress an increase in manufacturing cost.

  An apparatus for producing a single crystal according to the present embodiment includes a conductive crucible, a heating unit that heats the crucible by induction heating, and a conductive material that is disposed in the vicinity of the outer periphery of the crucible and covers the outer periphery of the crucible. When the crucible is heated by the heating means, the lower end of the furnace core tube is positioned lower than the bottom of the crucible.

  According to the single crystal manufacturing apparatus of the present invention, current concentration at the outer edge portion of the bottom of the crucible is suppressed, so that the temperature of the portion is prevented from excessively rising. As a result, the heat insulating material provided around the crucible is prevented from deteriorating during the growth of the single crystal, and by improving the reproducibility of the temperature distribution in the crucible, a high-quality single crystal can be stably obtained. .

1 is a diagram showing a configuration of a single crystal manufacturing apparatus according to Embodiment 1. FIG. 3 is a cross-sectional view of a crucible in a single crystal manufacturing apparatus according to Embodiment 1. FIG. 3 is a diagram showing a modification of the single crystal manufacturing apparatus according to Embodiment 1. FIG. 6 is a diagram showing a configuration of a single crystal manufacturing apparatus according to Embodiment 3. FIG. 6 is a configuration diagram of a mounting table in a single crystal manufacturing apparatus according to Embodiment 4. FIG. 6 is a top view of a graphite plate used for a mounting table in a fourth embodiment. FIG.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a single crystal manufacturing apparatus according to Embodiment 1. Here, a SiC single crystal manufacturing apparatus is shown as a representative example. As shown in FIG. 1, the manufacturing apparatus includes a crucible 10 and a furnace core tube 11 that covers the crucible 10. The crucible 10 and the furnace core tube 11 are placed on a heat-insulating placing table 20, but a non-conductive felt-like heat insulating material 22 and a graphite sheet 21 are placed between the bottom of the crucible 10 and the placing table 20. (Adhesion prevention sheet) is interposed. The side surface and the upper surface of the furnace core tube 11 are covered with non-conductive felt-like heat insulating materials 23 and 24. Although illustration is omitted, the manufacturing apparatus includes a heating means for heating the crucible 10 by induction heating.

  Hereinafter, the felt-like heat insulating material 22 provided on the bottom surface of the crucible 10 is referred to as “bottom heat insulating material”, the felt-like heat insulating material 23 provided on the side surface of the furnace core tube 11 is referred to as “side heat insulating material”, The felt-like heat insulating material 24 provided on the upper surface is referred to as “upper heat insulating material”. Each of the bottom heat insulating material 22, the side heat insulating material 23, and the top heat insulating material 24 has a laminated structure in which a plurality of graphite felt heat insulating materials overlap each other.

  The crucible 10 needs to have conductivity so that it can be heated by induction heating. In the present embodiment, the crucible 10 is made of graphite. FIG. 2 is a cross-sectional view showing an example of the structure of the crucible 10. The crucible 10 includes a raw material storage container 101 for storing a SiC raw material 102 and a lid 103 having a pedestal 103a to which a seed crystal 104 is attached. On the inner surface of the raw material storage container 101, a tapered guide 105 for guiding the gas sublimated from the raw material 102 to the pedestal 103a is provided.

  The furnace core tube 11 also has conductivity, and in this embodiment, a graphite tube is used. The furnace core tube 11 is close to the side surface of the crucible 10 and has a shape that covers the side and upper side of the crucible 10. On the upper surface of the furnace core tube 11, a heat radiation opening 11 a is provided at the center. As shown in FIG. 1, in the present embodiment, the lower end of the furnace core tube 11 extends to a position lower than the bottom of the crucible 10. When the periphery of the crucible 10 is covered with the furnace core tube 11, the heat insulation effect is improved by the radiation of the furnace core tube 11, so that the crucible 10 can be efficiently heated. The crucible 10 and the furnace core tube 11 may be in contact with each other. However, for convenience of handling, a difference in dimensions (for example, about 0.4 mm) may be provided between the outer diameter of the crucible 10 and the inner diameter of the furnace core tube 11. .

  Here, in the growth of a single crystal by the sublimation method, since it is necessary to heat the bottom of the crucible to a temperature higher than the top, it is necessary to generate a large induced current at the bottom of the crucible. The present inventor has confirmed by simulation that when only the crucible is induction-heated without using the furnace core tube, current concentration occurs in the outer edge of the bottom of the crucible, and local temperature rise occurs in that portion. In addition, when the single crystal was actually grown, the graphite at the outer edge of the crucible sublimated, and the corners of that part dropped and rounded, so it was inferred that the temperature was too high at that part. .

  The inventor covers the crucible 10 with the furnace core tube 11 as shown in FIG. 1 and extends the lower end of the furnace core tube 11 to a position lower than the bottom of the crucible 10, so that the outer edge of the bottom of the crucible 10 It was found that the electric field concentration can be suppressed. Thereby, it can prevent that the temperature of the outer edge part of the bottom of the crucible 10 rises too much. Thereby, deterioration of the bottom heat insulating material 22 in contact with the bottom of the crucible 10 can be suppressed. The inventor also investigated the case where the lower end of the furnace core tube 11 was the same height as the bottom of the crucible 10, but in this case, this effect was hardly obtained.

  The thickness of the furnace core tube 11 is smaller than the penetration depth of the induction current in the induction heating, and is preferably 1/3 or less. The specific resistance of the furnace core tube 11 should be higher than the specific resistance of the crucible 10, and more preferably in the range of 1200 μΩcm to 1300 μΩcm. Thus, if the furnace core tube 11 is made thin and the specific resistance is increased, the magnitude of the induced current generated in the furnace core tube 11 is suppressed, so that the temperature of the furnace core tube 11 is prevented from excessively rising. Therefore, the effect which can prevent deterioration of the side heat insulating material 23 on the side surface of the furnace core tube 11, the upper heat insulating material 24 on the furnace core tube 11, and the mounting table 20 on which the furnace core tube 11 is mounted is obtained. In addition, since the magnitude | size and penetration depth of an induced current depend on the frequency of the oscillator of a heating means, it is good to adjust the thickness and specific resistance of the furnace core tube 11 suitably according to the frequency.

  In the present embodiment, a non-conductive graphite molded heat insulating material is used as the mounting table 20. The mounting table 20 is located at the top and has a first step 201 having the same diameter as the crucible 10, a second step 202 having a diameter larger than that of the first step 201, and a position below the first step 201. The third step portion 203 has a third step portion 203 having a diameter larger than that of the second step portion 202. Further, the mounting table 20 is provided with a through hole 20 a used for measuring the temperature of the crucible 10. When performing induction heating of the crucible 10, as shown in FIG. 1, the crucible 10 is placed on the upper surface of the first step portion 201, and the furnace core tube 11 is placed on the upper surface of the second step portion 202. Thereby, induction heating is possible in a state where the lower end of the furnace core tube 11 is positioned lower than the bottom of the crucible 10.

  If induction heating is performed with the lower end of the furnace core tube 11 positioned lower than the bottom of the crucible 10, the temperature rise at the outer edge of the bottom of the crucible 10 can be suppressed. However, in the sublimation method, the bottom of the crucible 10 is still at the highest temperature. Therefore, the deterioration of the bottom heat insulating material 22 in contact with the bottom of the crucible 10 is faster than the side heat insulating material 23 and the upper heat insulating material 24. Therefore, it is necessary to replace the upper heat insulating material 24 with a relatively high frequency. Therefore, in this embodiment, an inexpensive felt heat insulating material is employed as the bottom heat insulating material 22 to suppress an increase in cost.

  As described above, the shape and size of the felt heat insulating material are unstable. However, the temperature distribution can be reproducible by placing the mounting table 20 of the molded heat insulating material having a stable shape and size below the bottom heat insulating material 22. It suppresses the decline.

  In the present embodiment, a graphite sheet 21 (adhesion prevention sheet) is interposed between the bottom heat insulating material 22 and the mounting table 20. When the crucible 10 is heated, if the bottom heat insulating material 22 of the felt heat insulating material and the mounting table 20 of the molded heat insulating material are in contact with each other, the bottom heat insulating material 22 adheres to the mounting table 20 due to the influence of the heat. Although the coating of the surface of the mounting table 20 is peeled off when the material 22 is replaced, deterioration of the mounting table 20 occurs, but this can be prevented by interposing the graphite sheet 21 therebetween. Although a graphite sheet is used in the present embodiment, other materials can be used as long as they are resistant to heat during heating of the crucible 10 and can prevent adhesion between the mounting table 20 and the bottom heat insulating material 22. Good.

  Note that the graphite sheet 21 and the bottom heat insulating material 22 are provided with openings at positions corresponding to the temperature measurement through holes 20 a of the mounting table 20.

  On the other hand, the side heat insulating material 23 (felt-like heat insulating material) is wound not only on the side surface of the crucible 10 but also on the side of the first step portion 20 and the second step portion 202 of the mounting table 20. That is, the position of the lower end of the side heat insulating material 23 (near the upper surface of the third step portion 203) is further lower than the position of the lower end of the furnace core tube 11 (the upper surface of the second step portion 202). With this structure, the side heat insulating material 23 can prevent heat from leaking from between the lower end of the furnace core tube 11 and the upper surface of the second step portion 202.

  However, the side surface of the third step portion 203 of the mounting table 20 is exposed without winding the side heat insulating material 23. Since the side part of the mounting table 20 (molded heat insulating material) having a stable shape is exposed, the transporter holds the crucible 10 when the crucible 10 is mounted and the mounting table 20 wound with the side heat insulating material 23 is transported. It becomes easy to do.

  In FIG. 1, since the diameter of the second step portion 202 of the mounting table 20 is larger than the diameter of the furnace core tube 11, among the felt-like heat insulating materials of the side heat insulating materials 23, the inner several pieces are the second step. The lower end of the portion 202 is aligned with the lower end of the furnace core tube 11 without being wound around the side surface of the portion 202. However, as shown in FIG. 3, the diameter of the second step portion 202 is made substantially equal to the diameter of the furnace core tube 11, and all of the felt-like heat insulating material constituting the side heat insulating material 23 is placed on the side surface of the second step portion 202. It is good also as a structure also wound. In the configuration of FIG. 3, the work of winding the side heat insulating material 23 around the furnace core tube 11 and the mounting table 20 becomes easy, but the diameter of the second step portion 202 of the mounting table 20 is higher than that of the configuration of FIG. 1. It should be noted that it is necessary to process with accuracy.

  The upper heat insulating material 24 provided on the upper surface of the furnace core tube 11 has a laminated structure in which a plurality of felt heat insulating materials are stacked, and a position corresponding to the heat radiation opening 11 a of the furnace core tube 11 is opened. The temperature gradient in the longitudinal direction and the radial direction of the crucible 10 can be adjusted by adjusting the number of felt-like heat insulating materials constituting the upper heat insulating material 24 and the size of the opening corresponding to the heat radiating opening 11a. . Thereby, the growth rate of the single crystal and the shape of the ingot can be controlled.

  For example, if the number of felt heat insulating materials in the upper heat insulating material 24 is increased, the upward heat radiation from the furnace core tube 11 is reduced, so that the vertical temperature gradient is reduced. At that time, heat radiation from the furnace core tube 11 occurs intensively in the heat radiation opening 11a in the center, so that the temperature gradient in the radial direction increases. On the contrary, if the number of felt heat insulating materials of the upper heat insulating material 24 is reduced, the heat radiation to the upper side of the furnace core tube 11 is increased, so that the temperature gradient in the vertical direction is increased. At that time, since the heat radiation from the portion other than the heat radiation opening 11a becomes large on the upper surface of the furnace core tube 11, the temperature gradient in the radial direction becomes small.

  Here, the specific example of the manufacturing method of a SiC single crystal using the manufacturing apparatus of the single crystal which concerns on this Embodiment is demonstrated.

  First, the crucible 10 is prepared, the seed crystal 104 is attached to the base 103a of the lid 103, the raw material container 101 is filled with the SiC raw material 102, and the tapered guide 105 is further installed as shown in FIG. Thereafter, the crucible 10 and the furnace core tube 11 are installed on the mounting table 20 on which the graphite sheet 21 and the bottom heat insulating material 22 are mounted. And the felt-shaped heat insulating material is wound around the side surface of the furnace core tube 11 to form the side heat insulating material 23, and the upper surface of the furnace core tube 11 is covered with the felt-shaped heat insulating material to form the upper heat insulating material 24. Thereby, the structure shown in FIG. 1 is obtained.

  The furnace core tube 11 was made of graphite having a thickness of 3 mm. The graphite sheet 21 was about 0.4 mm thick and flexible. The bottom heat insulating material 22 was composed of three 7 mm thick felt-shaped heat insulating materials, and the side heat insulating material 23 was composed of four 7 mm thick felt heat insulating materials. The upper heat insulating material 24 is composed of 14 felt-like heat insulating materials having a thickness of 7 mm, and the number is adjusted according to the crystal to be grown.

Then, the mounting table 20 on which the crucible 10 is mounted is placed in a furnace, and the pressure in the furnace is evacuated (exhausted) to a level of 10 ⁻⁴ Pa. The furnace is filled with an inert gas such as argon, and the pressure in the furnace is maintained at 800 hPa. While maintaining the pressure in the furnace at 800 hPa, the temperature of the crucible 10 is heated to the SiC growth temperature (the bottom temperature in the crucible 10 is 2225 ° C. and the top temperature is 2100 ° C.) by induction heating. The frequency of the oscillator of the heating means was 10 kHz. In this case, the penetration depth of the induced current can be calculated as 1.7 cm.

  Subsequently, the pressure in the furnace is reduced to the SiC growth pressure (3.7 hPa) while maintaining the temperature of the crucible 10. When the pressure in the furnace reaches the growth pressure, the growth of the SiC single crystal on the seed crystal 104 starts.

  After a predetermined growth time (about 50 hours) has elapsed, the furnace is filled with argon, and the pressure in the furnace is increased to 800 hPa. Then, while maintaining the furnace pressure at 800 hPa, the temperature of the crucible 10 is lowered to room temperature over time (about 10 hours), and the grown SiC single crystal is taken out from the crucible 10.

  As a result of manufacturing the SiC single crystal under the above conditions by using the seed crystal 104 having a diameter of 40 mm, the inventor obtained a SiC single crystal having a height of 35 mm and a diameter of 50 mm. When the quality of the obtained SiC single crystal was evaluated by rocking curve measurement by X-ray diffraction, the full width at half maximum was 20 seconds or less, and it was confirmed that a high-quality single crystal was obtained.

  As described above, according to the single crystal manufacturing apparatus according to the present embodiment, the induction heating of the crucible 10 is performed with the lower end of the furnace core tube 11 positioned lower than the bottom of the crucible 10. It is possible to suppress current concentration at the outer edge portion of the bottom of 10 and to prevent an excessive temperature rise at that portion. Therefore, deterioration of the bottom heat insulating material 22 during the crystal growth can be prevented, and a high quality single crystal can be obtained.

  Further, by making the specific resistance of the furnace core tube 11 higher than the specific resistance of the crucible 10, and further reducing the thickness of the furnace core tube 11 to less than the penetration depth of the induction current in induction heating (preferably less than one third). Heat generation in the furnace core tube 11 is suppressed, and deterioration of the side heat insulating material 23, the upper heat insulating material 24, and the mounting table 20 can be suppressed.

  Furthermore, by using an inexpensive felt-like heat insulating material as the rapidly deteriorated bottom heat insulating material 22, an increase in cost due to replacement of the bottom heat insulating material 22 can be suppressed in order to maintain the reproducibility of the temperature distribution. Although the bottom heat insulating material 22 of the felt heat insulating material is unstable in shape and size, the reproducibility of the temperature distribution can be maintained high by disposing the mounting table 20 of the molded heat insulating material thereunder. Further, by interposing the graphite sheet 21 between the bottom heat insulating material 22 of the felt-like heat insulating material and the mounting table 20 for the molded heat insulating material, adhesion between the mounting table 20 and the bottom heat insulating material 22 can be prevented, and the bottom heat insulating material can be prevented. The replacement of the material 22 is facilitated and also useful for protecting the mounting table 20.

  Moreover, since the mounting table 20 has a three-stage structure as shown in FIG. It can be mounted on. And the heat | fever leakage from between the core tube 11 and the 2nd step part 202 can be suppressed by winding the side part heat insulating material 23 also on the 2nd step part 202 in which the furnace core tube 11 is mounted. . Moreover, the handling at the time of conveyance becomes easy by exposing the part of the 3rd step part 203 outside.

  The application of the present invention is not limited to the production of a SiC single crystal, but a single crystal such as AlN or GaN, which grows at a high temperature of about 2000 ° C. or higher (a temperature at which deterioration of the heat insulating material is a concern). Widely applicable to the manufacture of

<Embodiment 2>
As described above, the upper heat insulating material 24 covering the upper surface of the furnace core tube 11 is composed of a plurality of felt-shaped heat insulating materials, and the temperature gradient in the crucible 10 is adjusted according to the number of the heat insulating materials, thereby growing the single crystal growth rate. And the shape of the ingot can be controlled. The inventor made a comparison between the number of felt-like heat insulating materials used for the upper heat insulating material 24 and the number of 18 heat insulating materials.

  When the number of felt-like heat insulating materials is 8, the vertical temperature gradient in the crucible 10 (([crucible lower temperature] − [crucible upper temperature]) / [crucible height]) is 7. The temperature difference was 83 ° C./cm, and the temperature difference between the raw material 102 and the seed crystal 104 was too large. As a result, the obtained single crystal had a half-value width of about 60 seconds in the rocking curve measurement by X-ray diffraction, and was not high quality.

  On the other hand, when the number of felt-like heat insulating materials was 18, the vertical temperature gradient in the crucible 10 was 6.45 ° C./cm. The resulting single crystal had a high quality with a half-value width of 20 seconds or less in rocking curve measurement by X-ray diffraction.

  In either case, the crucible 10 provided with the tapered guide 105 was used, but almost no crystals grown on the surface of the tapered guide 105 were seen, and the crystal grew only from the surface of the seed crystal 104, and the single crystal portion was It was confirmed that it grew independently.

  Although the growth rate decreases when the temperature gradient in the vertical direction in the crucible 10 decreases, the growth rate can be increased by setting the temperature of the bottom of the crucible 10 high. In the above example, the temperature at the bottom of the crucible 10 at which a growth rate of 0.7 mm / h can be obtained was 2185 ° C. when the number of felt-like heat insulators in the upper heat insulator 24 was 8, but 18 Sometimes it was necessary to raise it to 2210 ° C. In that case, an ingot having a height of about 35 mm was obtained in 50 hours.

<Embodiment 3>
FIG. 4 is a diagram showing a configuration of a single crystal manufacturing apparatus according to the third embodiment. In the present embodiment, the mounting table 20 has a two-stage configuration including a first step part 201 having substantially the same diameter as the crucible 10 and a second step part 202 having a larger diameter. The side heat insulating material 23 is wound around the entire furnace core tube 11 and the mounting table 20, and the lower end of the side heat insulating material 23 is at the same height as the bottom of the mounting table 20.

  In the configuration of FIG. 4, the side surface of the side heat insulating material 23 having a stable shape is not exposed, so that it becomes difficult to carry the crucible 10 on the mounting table 20 and wind the side heat insulating material 23. Since the shape of the mounting table 20 becomes simple, the effect that the processing of the mounting table 20 becomes easy can be obtained. Also in the configuration of FIG. 4, it is obvious that the effect of suppressing deterioration of the heat insulating material and the heat insulating performance can be obtained in the same manner as in the first embodiment.

<Embodiment 4>
In the above embodiment, as the material for the mounting table 20 for mounting the crucible 10, a molded heat insulating material obtained by molding felt-like heat insulating material is used. However, sufficient heat resistance and shape / dimensional stability are provided. Other materials may be used as long as they are provided.

  FIG. 5 is a configuration diagram of the mounting table 20 according to the fourth embodiment. The mounting table 20 is obtained by alternately stacking graphite plates 204 (plate-like heat insulating materials) and graphite-made felt heat insulating materials 205 using graphite bolts 206 and nuts 207. The mounting table 20 also has a temperature measurement through hole 20a. Although FIG. 5 shows a mounting table 20 having a three-stage structure similar to that of the first embodiment, a two-stage structure as in the third embodiment may be used.

  Although the shape and dimensions are not stable only with the felt-like heat insulating material 205, the mounting table 20 having a stable shape and dimensions can be obtained by sandwiching and fixing the felt-like heat insulating material 205. Therefore, graphite plates 204 are used at least on the top and bottom of the mounting table 20. The graphite plate 204 is preferably made of a hard material similar to that of the crucible 10 and the furnace core tube 11, but it is not necessary to generate heat by induction heating. Therefore, it is preferable to use a material having a higher specific resistance than the furnace core tube 11.

  FIG. 6 is a top view illustrating a configuration example of the graphite plate 204. The graphite plate 204 is provided with an opening 204a for allowing the bolt 206 to pass therethrough and an opening 204b corresponding to the temperature measurement through hole 20a. A slit 204c cut in the radial direction is formed on the outer peripheral portion. The slit 204c functions so as to reduce the induced current generated in the graphite plate 204 during induction heating of the crucible 10.

  Since the graphite plate 204 and the felt-like heat insulating material 205 are less expensive than the molded heat insulating material, a reduction in manufacturing cost can be expected by configuring the graphite plate 204 using them.

  In the example of FIG. 5, the mounting table 20 has a laminated structure including only the graphite plate 204 and the felt-like heat insulating material 205, but a graphite sheet (adhesion prevention sheet) may be interposed therebetween. In this case, since the adhesion between the graphite plate 204 and the felt-like heat insulating material 205 is prevented, it is possible to replace only a part of the mounting table 20 when it deteriorates, and further reduction in manufacturing cost can be expected.

  10 crucible, 11 furnace core tube, 20 mounting table, 21 graphite sheet, 22 bottom heat insulating material, 23 side heat insulating material, 24 top heat insulating material, 101 raw material storage container, 102 raw material, 103 lid, 104 seed crystal, 105 tapered shape Guide, 204 graphite plate, 205 felt insulation, 206 bolts, 207 nuts.

Claims (16)

A conductive crucible;
Heating means for heating the crucible by induction heating;
A conductive furnace core tube disposed in the vicinity of the outer periphery of the crucible and covering the outer periphery of the crucible;
An apparatus for producing a single crystal, wherein when the crucible is heated by the heating means, the lower end of the furnace core tube is positioned lower than the bottom of the crucible. The single crystal manufacturing apparatus according to claim 1, wherein a specific resistance of the furnace core tube is higher than a specific resistance of the crucible. The single crystal manufacturing apparatus according to claim 2, wherein a specific resistance of the furnace core tube is in a range of 1200 μΩcm to 1300 μΩcm. The apparatus for producing a single crystal according to any one of claims 1 to 3, wherein a thickness of the furnace core tube is equal to or less than one third of a penetration depth of an induction current in the induction heating. A heat-insulating mounting table on which the crucible is mounted;
The single crystal manufacturing apparatus according to any one of claims 1 to 4, further comprising a bottom heat insulating material made of felt-like heat insulating material and interposed between the bottom of the crucible and the mounting table. The single attachment according to claim 5, further comprising an adhesion preventing sheet interposed between the mounting table and the bottom heat insulating material and preventing adhesion between the mounting table and the bottom heat insulating material due to heat when the crucible is heated. Crystal manufacturing equipment. The table above is
The single crystal manufacturing apparatus according to claim 5 or 6, wherein the apparatus is a molded heat insulating material formed by molding a felt-shaped heat insulating material. The table above is
The apparatus for producing a single crystal according to any one of claims 5 to 7, wherein a felt-like heat insulating material and a plate-like heat insulating material are alternately stacked and fixed. The table above is
An adhesion preventing sheet that is interposed between the felt-like heat insulating material and the plate-like heat insulating material and prevents the adhesion between the felt-like heat insulating material and the plate-like heat insulating material due to heat when the crucible is heated. 8. The apparatus for producing a single crystal according to 8. The table above is
A first step on which the crucible is placed on the upper surface;
10. The device according to claim 5, further comprising: a second step portion that is located under the first step portion, has a larger diameter than the first step portion, and on which the furnace core tube is placed. The manufacturing apparatus of the single crystal as described in one. The single crystal manufacturing apparatus according to claim 10, further comprising a side heat insulating material made of a felt heat insulating material and covering a side of the furnace core tube and the first and second stepped portions. The table above is
A third step portion located below the second step portion and having a larger diameter than the second step portion;
The single crystal manufacturing apparatus according to claim 11, wherein the side heat insulating material is installed so as not to cover a side of the third stepped portion. It consists of a felt-like heat insulating material, further comprising a side heat insulating material that covers the side of the furnace core tube,
The single crystal according to any one of claims 1 to 4, wherein when the crucible is heated by the heating means, a lower end of the side heat insulating material is positioned lower than a lower end of the furnace core tube. Manufacturing equipment. It further comprises a heat-insulating mounting table on which the crucible is mounted,
The said side part heat insulating material is a manufacturing apparatus of the single crystal of Claim 13 installed so that a part of said mounting stand may be exposed. The single crystal manufacturing apparatus according to any one of claims 1 to 14, further comprising an upper heat insulating material made of a felt-like heat insulating material and covering an upper surface of the furnace core tube. The crucible is
A container for storing single crystal raw materials;
A lid having a pedestal for placing a single crystal seed crystal;
The single crystal manufacturing apparatus according to any one of claims 1 to 15, further comprising a tapered guide provided on an inner surface of the container and configured to guide a gas obtained by sublimation of the raw material to the pedestal.

Images