JP2018168051A - Manufacturing apparatus of silicon carbide single crystal ingot and manufacturing method of silicon carbide single crystal ingot - Google Patents

Abstract

To provide a manufacturing apparatus capable of manufacturing a high quality SiC single crystal ingot having less defect in a large-diameter single crystal growth by suppressing degradation of a heat insulator during a crystal growth, and a manufacturing method of SiC of single crystal ingot using the manufacturing method.SOLUTION: Provided are a manufacturing apparatus of a SiC single crystal ingot, the manufacturing apparatus being capable of exhausting sublimation gas leaking from a graphite crucible through a gap formed between a graphite shield member and an outer surface of a peripheral wall part by interposing the shield member interposed at least between the outer side surface of the peripheral wall part of the graphite crucible and an inner surface of the peripheral wall part covering the outer surface of the peripheral wall part, and a manufacturing method of the SiC single crystal ingot using the same manufacturing apparatus.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a silicon carbide single crystal ingot manufacturing apparatus and a silicon carbide single crystal ingot manufacturing method. Specifically, the present invention relates to a silicon carbide single crystal ingot manufacturing apparatus capable of suppressing deterioration of a heat insulating material during manufacture of a silicon carbide single crystal ingot, and a method for manufacturing a silicon carbide single crystal ingot using the same.

  Since silicon carbide (SiC) has excellent semiconductor characteristics, it has attracted much attention as a wafer material for manufacturing a power device for high power control. In particular, development of SiC power devices such as SiC Schottky barrier diodes and MOSFETs (Metal Oxide-Semiconductor Field Effect Transistors) fabricated from SiC single crystal wafers is underway, withstand voltage exceeding 1000V, and Various power control devices have been developed, including an inverter for large power control with low power loss at the time of conversion because it can exhibit the advantage of reducing the on-resistance during conduction.

  An SiC single crystal ingot for obtaining an SiC single crystal wafer is currently manufactured by a sublimation recrystallization method called an improved Rayleigh method, or a method called a sublimation method, which is technically synonymous. It is general (refer nonpatent literature 1).

  In order to stably realize a SiC power device having excellent withstand voltage characteristics and long-term operation reliability of the device, it is necessary to sufficiently reduce the defect density of the SiC single crystal ingot. For example, the defects of the SiC single crystal wafer that affect the power device characteristics include micropipe defects and basal plane dislocations that are edge dislocations on the (0001) basal plane. In particular, the former is a defect having a structure in which a hole having a diameter of several μm or more penetrates in a dislocation core portion. In order to obtain a SiC single crystal wafer, a SiC single crystal thin film is epitaxially grown on a SiC single crystal substrate cut out from an ingot. In such a case, it is known that if such a defect remains in the thin film portion after the epitaxial thin film is produced, the reverse breakdown voltage characteristics and the like are significantly deteriorated (see Non-Patent Document 2). As described above, in the SiC single crystal wafer, it is important to reduce the defect density as much as possible for application as a power device.

  One of the causes of the above defects is that when a 4H type SiC single crystal suitable for power devices is grown, other types of polytype crystals such as 6H and 15R are generated and mixed. In addition to the above, silicon droplets, foreign matters and the like may be mixed (see Non-Patent Document 3). When such a growth disturbance occurs, the atomic arrangement of the 4H-type SiC crystal is disturbed, so that a large amount of micropipes, dislocation defects, and the like are generated during the growth. With the progress of sublimation growth technology in recent years, SiC single crystal wafers have reached a large diameter of 150 mm, and the entire growth process for growing large SiC single crystals from which such large diameter wafers can be taken out. Therefore, there is a demand for a manufacturing method that can realize stable growth conditions without causing the above-described growth disturbance.

  In the sublimation method, a SiC raw material and a seed crystal are charged into a crucible which is a heat-resistant container made of graphite, and single crystal growth is performed using a sublimation phenomenon of SiC at a high temperature of about 2000 ° C. or more (see Non-Patent Document 1). ). At this time, it is customary that the temperature environment in the crucible optimal for growth is achieved by devising a heat insulating material arranged around the crucible (see Patent Document 1). Regarding the heat insulating material, the temperature distribution inside the crucible is determined by giving a special structure (see Patent Document 2), and in the sublimation recrystallization method, it is important to obtain a high-quality SiC single crystal. Part of it. In addition, a susceptor that generates heat upon receiving high-frequency induction is placed on the outer periphery of the crucible, and the temperature environment in the crucible is optimized by a comprehensive hot zone structure including the susceptor and heat insulating material. (See Patent Document 3).

  By the way, in a general sublimation method, since a SiC raw material and a seed crystal are arranged to face each other in a graphite crucible (see, for example, Patent Document 1), the crucible is basically divided into a plurality of parts. Are formed by joining together. For example, this seam is usually provided by fitting each part with a screw structure or the like to assemble a desired crucible structure. The crucible assembled in this manner is covered with a heat insulating material made of carbon fiber or a molded heat insulating material infiltrated with a molding resin, and heated to a high temperature exceeding 2000 ° C. to grow a SiC single crystal. .

  However, from the seam of the crucible, the internal pressure of the SiC sublimation gas generated by the thermal decomposition of the raw material increases at the growth temperature, so that the sublimation gas leaks toward the outside of the crucible. The leaked sublimation gas penetrates into the heat insulating material covering the crucible or stays in the vicinity of the surface of the heat insulating material and solidifies preferentially at a portion where the temperature is lower than the inside of the crucible. The heat insulation characteristic of the heat insulating material changes or deteriorates, and changes the temperature distribution inside the crucible. In particular, when the SiC single crystal is increased in diameter, the amount of charged raw material is increased, so that the amount of sublimation gas generated during growth is also increased, and the change in heat insulation characteristics as a heat insulating material is increased. In such a case, the temperature distribution inside the crucible changes, the single crystal growth becomes unstable, and a different polytype other than the desired polytype is generated, so that the crystal quality is liable to deteriorate.

  In order to avoid the deterioration of the heat insulating material as described above, it is effective that the seam of the crucible is brought into close contact with, for example, a heat resistant adhesive so that the sublimation gas does not leak from the inside. However, if the crucible is completely sealed in this way, the pressure inside the crucible of the sublimation gas generated at a high temperature increases, and on the contrary, a growth disturbance in which a different phase such as a silicon droplet is crystallized (see Non-Patent Document 4). (See Non-Patent Document 3), and this causes the crystal quality to deteriorate, such as the occurrence of defects.

  On the other hand, a gap of a predetermined size is provided between the crucible and the heat insulating material, and the sublimation gas leaked from the crucible is conveyed to the outside of the heat insulating material by using the flow of the atmospheric gas in this space. A method for preventing deterioration of the heat insulating material is known (see Patent Document 4). According to such a method, it is possible to improve the controllability of optimum heating conditions during crystal growth and enable the growth of a silicon carbide single crystal having a good crystal quality, but the large diameter of the SiC single crystal. In order to cope with the increase in the amount of sublimation gas generated as a result of conversion, there is room for further study.

JP 2002-308697 A JP 2008-74662 A Special Table 2003-523918 JP 2011-219295 JP

Yu. M. Tairov and V. F. Tsvetkov, Journal of Crystal Growth, vol.52 (1981) p.146 G. Wahab, A. Ellison, A. Henry and E. Janzen, Appl. Phys. Lett., Vol.76 (2000) p.2725. Fujimoto, Journal of Japanese Society for Crystal Growth Vol.42 (2015) p.148. R. C. Glass, D. Henshall, V. F. Tsvetkov and C. H. Carter, Jr, phys. Stat. Sol. (B) 202 (1997) p.149.

  As mentioned above, even in the growth of large-diameter SiC single crystals, the inside of the crucible can be maintained in a state suitable for the growth of high-quality SiC single crystals, avoiding deterioration over time in the heat insulating properties of the heat insulating material during the growth process. Therefore, a method that can realize stable growth is desired.

  Therefore, the present invention can suppress deterioration of the heat insulating material during the growth of the SiC single crystal, and in particular, a high-quality SiC single crystal ingot with few defects even in the growth of a large-diameter single crystal having a diameter of 100 mm or more. It is an object of the present invention to provide a silicon carbide single crystal ingot production apparatus capable of producing a silicon carbide single crystal ingot and a method for producing a silicon carbide single crystal ingot using the same.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have at least between the outer surface of the peripheral wall portion of the graphite crucible and the inner surface of the peripheral wall insulating material covering the outer surface of the peripheral wall portion. By interposing a graphite shielding member, the sublimation gas leaked from the graphite crucible is discharged to the outside of the heat insulating material through a gap formed between the graphite shielding member and the outer surface of the peripheral wall of the graphite crucible. The present inventors have found that a high-quality SiC single crystal ingot having a small defect density can be produced by suppressing the deterioration of the insulating material during growth, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) A graphite crucible having a crucible body loaded with a silicon carbide raw material and a crucible lid to which a seed crystal is attached, a heat insulating material disposed around the graphite crucible, and heating the graphite crucible A silicon carbide single crystal ingot producing apparatus for producing a silicon carbide single crystal ingot by a sublimation recrystallization method in which a silicon carbide raw material is heated to generate a sublimation gas and recrystallized on a seed crystal. And
At least a graphite shielding member is interposed between the outer surface of the peripheral wall portion of the graphite crucible and the inner surface of the peripheral wall heat insulating material covering the outer surface of the peripheral wall portion, and the sublimation gas leaked from the graphite crucible is shielded from the graphite shield. Through the gap formed between the member and the outer surface of the peripheral wall portion of the graphite crucible, the heat is discharged from the upper wall portion side and / or the bottom wall portion side of the graphite crucible to the outside of the heat insulating material. Production apparatus for silicon carbide single crystal ingot,
(2) The graphite shielding member has a bottom wall shielding portion interposed between the bottom wall portion outer surface of the graphite crucible and the inner surface of the bottom wall heat insulating material covering the bottom wall outer surface, The apparatus for producing a silicon carbide single crystal ingot according to (1), wherein the sublimation gas leaked from the graphite crucible is discharged to the outside of the heat insulating material from the upper wall portion side of the graphite crucible through the gap,
(3) The upper wall heat insulating material covering the outer surface of the upper wall portion of the graphite crucible has a central opening, and the graphite shielding member is disposed on the inner surface of the upper wall heat insulating material and the graphite crucible. Sublimation leaking from the graphite crucible, having an upper wall shielding portion that is interposed between the outer wall surface of the wall portion and extends to cover the inner peripheral side surface of the central opening to form a cylindrical exhaust port The apparatus for producing a silicon carbide single crystal ingot according to (2), wherein the gas is discharged from the cylindrical exhaust port communicating with the gap to the outside of the heat insulating material,
(4) The heating apparatus according to any one of (1) to (3), wherein the heating apparatus is an induction heating type heating apparatus, and the graphite shielding member has a thickness smaller than a high-frequency penetration depth used in the heating apparatus. Production apparatus for silicon carbide single crystal ingot,
(5) The apparatus for producing a silicon carbide single crystal ingot according to any one of (1) to (4), which produces a silicon carbide single crystal ingot having a diameter of 100 mm or more.
(6) A graphite crucible having a crucible body loaded with a silicon carbide raw material and a crucible lid body to which a seed crystal is attached, a heat insulating material disposed around the graphite crucible, and heating the graphite crucible A silicon carbide single crystal ingot is manufactured by a sublimation recrystallization method in which a silicon carbide raw material is heated to generate a sublimation gas and recrystallized on a seed crystal using a silicon carbide single crystal ingot manufacturing apparatus equipped with a heating device A silicon carbide single crystal ingot manufacturing method comprising:
At least, a sublimation gas leaked from the graphite crucible is interposed between the graphite crucible with a graphite shielding member interposed between the outer surface of the peripheral wall of the graphite crucible and the inner surface of the peripheral wall heat insulating material covering the outer surface of the peripheral wall. Silicon carbide is discharged from the top wall side and / or bottom wall side of the graphite crucible through the gap formed between the shielding member and the outer peripheral surface of the peripheral wall of the graphite crucible. Manufacturing method of single crystal ingot,
It is.

  In the apparatus for producing a silicon carbide single crystal ingot in the present invention, since the heat insulating material covering the crucible can be prevented from deteriorating during crystal growth, the temperature distribution in the crucible can be optimally maintained, high quality with few defects, A SiC single crystal ingot can be easily manufactured. In particular, it is effective in the production of a SiC single crystal ingot having a large diameter of 100 mm or more in diameter, and if a SiC single crystal wafer manufactured from a large diameter SiC single crystal substrate cut out from such a SiC single crystal ingot is used, A power device for power control having extremely high performance and excellent reliability can be manufactured with high efficiency.

FIGS. 1A and 1B are schematic views for explaining an example of a SiC single crystal ingot manufacturing apparatus (heating apparatus not shown) according to the present invention. FIG. 2 is a schematic diagram for explaining another example of the graphite crucible. FIG. 3 is a schematic diagram for explaining the configuration of a single crystal growth apparatus using a sublimation recrystallization method (improved Rayleigh method). FIG. 4 is a schematic diagram for explaining a conventional SiC single crystal ingot manufacturing apparatus (heating apparatus not shown).

The present invention will be described in detail below.
The present invention relates to a graphite crucible having a crucible body loaded with a silicon carbide (SiC) raw material and a crucible lid body to which a seed crystal is attached, a heat insulating material disposed around the graphite crucible, and the graphite A SiC single crystal ingot manufacturing apparatus that includes a heating device for heating a crucible, heats an SiC raw material, generates a sublimation gas, and recrystallizes on a seed crystal by a sublimation recrystallization method. The sublimation gas leaked from the graphite crucible by interposing a graphite shielding member between at least the outer peripheral surface of the peripheral wall portion of the graphite crucible and the inner surface of the peripheral wall heat insulating material covering the outer peripheral surface of the graphite crucible, Through a gap formed between the shield member and the outer peripheral surface of the peripheral wall of the graphite crucible, the heat can be discharged from the top wall side and / or the bottom wall side of the graphite crucible to the outside of the heat insulating material.

  In general, a graphite crucible is easily loaded with a SiC raw material or a seed crystal for crystal growth, or for the purpose of increasing a crystal growth region between these SiC raw material and a seed crystal, for example, the above-mentioned It is divided into two or more crucible members by dividing the crucible body into two crucible members, such as a crucible lid body and a crucible body, or by further dividing the crucible body into an upper body and a lower body. These crucible members are joined together to form a crucible. At that time, the joint part of the crucible member is screwed into a male screw and female screw structure, or mechanically joined to each other between the ground surfaces, using a heat-resistant adhesive, etc. Can be bonded, but at least one seam is not bonded with an adhesive so that the sublimation gas can leak out so that the sublimation gas pressure inside the crucible at the crystal growth temperature does not rise excessively. Further, it is usually mechanically coupled by a screw structure or fitting.

  FIGS. 1A and 1B show an example of an apparatus for producing an SiC single crystal ingot according to the present invention (a heating apparatus is not shown). These are examples of the graphite crucible 5 in which the joint portion between the lower surface side of the crucible lid body 3 and the upper surface side of the crucible body 4 is screwed by a screw structure, and a male screw is formed on the lower surface side of the crucible lid body 3. A female screw is formed on the upper surface side of the crucible body 4. Then, the graphite shielding member 11 is interposed between the outer peripheral surface of the peripheral wall portion of the graphite crucible 5 and the inner surface of the peripheral wall heat insulating material 6 covering the outer peripheral surface of the peripheral wall portion. The sublimation gas leaked from the joint between the peripheral wall heat insulating material 6, the bottom wall heat insulating material 7 and the upper wall heat insulating material 8 is passed through a gap formed between the graphite shielding member 11 and the outer surface of the peripheral wall portion of the graphite crucible. To prevent the sublimation gas from flowing out to at least the inner surface of the peripheral wall heat insulating material 6. it can.

  FIG. 2 shows an example of a graphite crucible 5 having a structure different from that shown in FIG. 1. The seam between the lower surface side of the crucible lid 3 and the upper surface side of the crucible body 4 is made complementary to each other. It can also be fitted. Further, the crucible body 4 may be divided into an upper body 4a and a lower body 4b, and these seam portions may be fitted in complementary shapes as shown in FIG. May be screwed together. Even in the case of the graphite crucible 5 as shown in FIG. 2, the seam between the crucible lid 3 and the crucible body 4 and the seam of the crucible body 4 (the seam between the upper body 4a and the lower body 4b). The sublimation gas leaked from the gas is discharged to the outside of the heat insulating material 9 through a gap formed between the graphite shielding member 11 and the outer peripheral surface of the graphite crucible 5 (in this example, as will be described later, the graphite crucible is described later). It is possible to prevent the sublimation gas from flowing out to at least the inner surface of the peripheral wall heat insulating material 6.

  The graphite shielding member 11 in the present invention is disposed between at least the outer peripheral surface of the graphite crucible 5 and the inner surface of the peripheral wall heat insulating material 6 covering the outer peripheral surface of the graphite crucible 5. The sublimation gas leaked from the outer surface can be blocked from flowing out to the peripheral wall heat insulating material 6 side, and the sublimation gas is formed between the graphite shielding member 11 and the outer surface of the peripheral wall portion of the graphite crucible 5. As long as it can be discharged from the upper wall side of the graphite crucible 5 or from the bottom wall side through the gap, it can be discharged from both, for example, FIG. As shown in b), the graphite shielding member 11 has a bottom wall shielding portion between the outer surface of the bottom wall portion of the graphite crucible 5 and the inner surface of the bottom wall heat insulating material 7 covering the outer surface of the bottom wall portion. 11a, whether the sublimation gas passes through the gap, the upper wall side of the graphite crucible 5 So as to be discharged to the heat insulating material externally, sublimation gas is preferably set to prevent the outflow of the bottom wall heat insulating material 7 side.

  Among these, FIG.1 (b) is an example of the manufacturing apparatus which open | released without covering the upper wall part outer surface of the graphite crucible 5 with a heat insulating material, but the graphite crucible 5 is like FIG.1 (a). You may make it cover the upper wall part outer surface with the upper wall heat insulating material 8. FIG. In that case, the graphite shielding member 11 has an upper wall shielding portion 11b located between the inner side surface of the upper wall heat insulating material 8 and the upper wall portion outer side surface of the graphite crucible 5. Generally, the upper wall heat insulating material 8 is used for the purpose of measuring the temperature of the crucible lid 3 or for the purpose of lowering the temperature of the central portion of the seed crystal 1 as compared with the peripheral portion by heat release. Since the central opening 10 is provided, it is preferable that one end of the upper wall shielding part 11b is extended so as to cover the inner peripheral side surface of the central opening 10 formed in the upper wall heat insulating material 8, and It is preferable that the end of the wall shielding part 11 b forms the cylindrical exhaust port 12 in the central opening 10. Thereby, the graphite shielding member 11 in the example of FIG. 1 has the bottom wall shielding portion 11a on the outer surface of the bottom wall portion of the graphite crucible 5, and the upper wall shielding on the outer surface of the upper wall portion of the graphite crucible 5. The outer surface of the graphite crucible 5 (upper wall portion outer surface, peripheral wall portion outer surface and bottom wall portion outer surface) and the inner surface of the heat insulating material 9 (upper wall heat insulating material inner surface, peripheral wall heat insulation) The gap formed between the inner side surface of the material and the inner side surface of the bottom wall heat insulating material communicates with the cylindrical exhaust port 12, and the sublimation gas leaked from the graphite crucible 5 flows into the insulating material 9 from the cylindrical exhaust port 12. It is possible to prevent the sublimation gas from being discharged to the outside and flowing out to the inner surface of the heat insulating material.

  In addition, the discharge location of the sublimation gas discharged through the gap formed between the graphite shielding member 11 and the outer peripheral surface of the graphite crucible 5 is not limited to these examples. You may make it discharge | emit from the wall part side to the exterior of the heat insulating material 9, or you may make it discharge | emit it to the exterior of the heat insulating material 9 from the bottom wall part side.

  For such a graphite shielding member 11, for example, a single graphite block is cut out and processed in accordance with the shape of the graphite crucible 5, and the seam provided with the bottom wall shielding portion 11 a is processed. You may make it produce as a cylindrical member with the bottom of the integral part which does not exist. Further, if necessary, a plate-like graphite member corresponding to the outer surface of the upper wall portion of the graphite crucible 5 is prepared, and drilling processing corresponding to the central opening portion 10 of the upper wall heat insulating material 8 is performed on this. Furthermore, a cylindrical graphite member for forming the cylindrical exhaust port 12 is prepared, and these are joined to the above-mentioned cylindrical member with a bottom with a heat-resistant adhesive or the like so as to provide the upper wall shielding part 11b. Good. Alternatively, a plate-like graphite member that forms the bottom wall shielding portion 11a by cutting out a cylindrical graphite member corresponding to the outer surface of the peripheral wall portion of the graphite crucible 5 from the graphite block, or the upper wall shielding portion as described above You may make it join each graphite member which forms 11b with a heat resistant adhesive agent. Here, as the heat-resistant adhesive, for example, a commercially available heat-resistant adhesive for carbon bonding such as trade name ST-201 manufactured by Nisshinbo Co., Ltd. can be used. In addition to such a heat-resistant adhesive, for example, an adhesive obtained by dissolving a polymer material such as a phenol resin in an organic solvent such as ethyl alcohol, or an adhesive obtained by mixing carbon powder with these. An agent or the like can also be used. In order to increase the adhesive strength, an adhesive may be applied to the graphite member and heat treatment at about 200 ° C. or higher may be performed.

  Moreover, as for the thickness of the graphite shielding member 11, for example, a material having a thickness of at least 0.5 mm may be used so that the graphite shielding member 11 is not damaged during handling during transportation of the apparatus. On the other hand, the upper limit of the thickness is not particularly limited when the heating device uses an electric heating method (resistance heating method), but when an induction heating method heating device is used, the thickness of the graphite shielding member is It is better to make it thinner than the penetration depth of the high frequency used in the heating device.

Here, regarding high-frequency penetration depth, when high-frequency electromagnetic waves are applied to a graphite material such as a graphite crucible or a graphite shielding member, an eddy current is generated near the surface and heated by its Joule heat. In addition, the eddy current decreases exponentially from the surface to the depth due to the skin effect. Therefore, the depth to the point where the eddy current is reduced to 0.368 times the strength at the surface can be defined as the penetration depth. This penetration depth δ (cm) is expressed by the following equation.

  Here, ρ is the electrical resistivity (μΩ · cm), μ is the relative magnetic permeability (1 for non-magnetic materials), and f is the frequency (Hz) of the electromagnetic wave (for example, see Best System Homepage: http: / /www.best-system-t3.com/). In the case of an industrial isotropic carbon material, when a typical electric resistance value of 15 μΩ · m at room temperature is adopted and an electromagnetic wave of 10 kHz is applied, the penetration depth is about 1.9 cm (= 19 mm). . The penetration depth needs to use electrical resistivity at a high temperature (2000 ° C. or higher) at which crystal growth is performed, but an industrial carbon material can be approximated as having almost no large temperature dependency although it depends on the material ( For example, the lightweight standard synthesis center: https://www.nmij.jp/~nmijclub/netsu/docimgs/1-iwashita.pdf), it is possible to evaluate with a calculated value δ at room temperature. If the temperature change of the electrical resistivity cannot be ignored, correction that reflects the value at the growth temperature may be performed as appropriate.

  If the thickness of the graphite shielding member is greater than or equal to the penetration depth of the high frequency, the graphite shielding member itself becomes the main heating element, and the structure of this shielding member may affect the temperature distribution in the crucible optimally. There is. If it is a frequency (generally about 7 to 10 kHz) in a commonly used induction heating type heating apparatus, it depends on the electrical resistivity value of the graphite material, but considering the penetration depth of the high frequency, a graphite shielding member The thickness needs to be sufficiently smaller than the penetration depth. In the above case, the thickness is preferably about 15 mm or less, but the preferable thickness of the graphite shielding member is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 5 mm or less. As described above, when an electric heating type heating device is used, the upper limit of the thickness of the graphite shielding member 11 is not particularly limited. For example, the upper limit of the thickness of the graphite shielding member 11 can be set to the same level as that of an induction heating type heating device. .

  In the SiC single crystal ingot producing apparatus according to the present invention, the graphite shielding member as described above is interposed between at least the outer peripheral surface of the peripheral wall of the graphite crucible and the inner surface of the peripheral heat insulating material covering the outer peripheral surface of the peripheral wall. Other than this, it can be the same as a known manufacturing apparatus. In the present invention, the sublimation gas leaked from the graphite crucible is discharged to the outside of the heat insulating material through a gap formed between the graphite shielding member and the outer peripheral surface of the graphite crucible, and at least the peripheral wall heat insulating material. It is possible to prevent the sublimation gas from flowing out to the inner surface of 6, and to avoid the characteristic deterioration of the heat insulating material. Preferably, as shown in FIG. 2, the graphite shielding member 11 is interposed between the outer surface of the bottom wall portion of the graphite crucible 5 and the inner surface of the bottom wall heat insulating material 7 covering the outer surface of the bottom wall portion. Or a bottom wall shielding portion 11a to be used, and as shown in FIG. 1, the upper wall portion outer surface of the graphite crucible 5 and the inner surface of the upper wall heat insulating material 8 covering the outer surface of the upper wall portion By having an upper wall shielding part interposed therebetween, the sublimation gas can be prevented from flowing out to the inner side surfaces of all of these heat insulating materials 9, and deterioration of the characteristics of the heat insulating material 9 can be avoided. Therefore, for example, the optimum temperature distribution in the crucible can be maintained from the start to the end of the growth, and the SiC having a large diameter such as a diameter of 100 mm (4 inches) or more or 150 mm (6 inches) or more. This is particularly effective when a large amount of SiC raw material is charged in the crucible to produce a single crystal ingot.

  In addition, on a large-diameter SiC single crystal substrate cut out from the large-diameter SiC single crystal ingot obtained as described above, an SiC single crystal thin film is epitaxially grown by, for example, chemical vapor deposition (CVD). By doing so, an epitaxial wafer having very few defects such as basal plane dislocations can be produced in substantially the entire region of the substrate. By using such an epitaxial wafer, it is possible to efficiently obtain various power devices having excellent power conversion characteristics.

  Hereinafter, although the present invention is explained based on an example, the present invention is not limited to these contents.

Example 1
First, an outline of the production of a SiC single crystal ingot by the sublimation recrystallization method will be described. FIG. 3 shows a general example of a single crystal growth apparatus using a sublimation recrystallization method. A seed crystal 1 made of an SiC single crystal substrate is attached to the inner wall surface of a graphite crucible lid 3 that forms a crucible 5, and an SiC raw material (SiC powder) 2 is a graphite crucible body that also forms the crucible 5. 4 is filled. The graphite crucible 5 thus configured is installed on the graphite support rod 18 inside the double quartz tube 13 and is used to eliminate the temperature non-uniformity in the circumferential direction at a rotational speed of less than 1 rpm. 5 is a rotatable mechanism, and always rotates at a substantially constant speed during crystal growth. Around the graphite crucible 5, a heat insulating material (heat insulating heat insulating material) 9 for heat shielding is installed. The double quartz tube 13 can be highly evacuated (10 ⁻³ Pa or less) by the evacuation device 14, and the internal atmosphere can be pressure controlled by argon gas. In addition, a work coil 15 is installed on the outer periphery of the double quartz tube 13, and the graphite crucible 5 is heated by flowing a high-frequency current to heat the SiC raw material 2 and the seed crystal 1 to a desired temperature. Can do. The crucible temperature 5 is measured by providing an optical path 16 having a diameter of 2 to 4 mm at the center in the upper direction of the double quartz tube 13, and a heat insulating material heat removal hole (center opening) provided on the outer surface of the crucible lid 3. Radiant light is extracted from 10 and the two-color thermometer 17 is used. In the present invention, a graphite shielding member is located between the graphite crucible 5 and the heat insulating material 9, but this is not shown in FIG. 3 and will be described in detail below.

  That is, in Example 1, a {0001} 4H type SiC single crystal substrate having a diameter of 102 mm and a thickness of 1.5 mm is prepared as the seed crystal 1, and the (000-1) plane (C plane) is the growth plane. It was affixed on the inner surface of the crucible lid 3 so as to be. Then, as shown in FIG. 1A, the lower surface side of the crucible lid body 3 and the upper surface side of the crucible body 4 are screwed into the crucible body 4 loaded with SiC powder as the SiC raw material 2 by a screw structure. In addition, a seam portion was formed so that the sublimation gas could leak. The graphite crucible 5 composed of the crucible lid 3 and the crucible body 4 has a thickness of 15 mm for all of the peripheral wall portion, the bottom wall portion, and the upper wall portion.

  As for the graphite shielding member 11, a bottomed cylindrical member having a bottom wall shielding portion 11a and having a seamless wall was manufactured from a single graphite block in accordance with the shape of the graphite crucible 5. In addition, a plate-like graphite member corresponding to the outer surface of the upper wall portion of the graphite crucible 5 is prepared, a hole is drilled in the center, and a cylinder having a size corresponding to the opening formed by the drilling process A graphite member was prepared and bonded with a commercially available heat-resistant adhesive for carbon bonding (ST-201 manufactured by Nisshinbo Co., Ltd.) to form the upper wall shielding part 11b. Then, the graphite crucible 5 is accommodated in the bottomed cylindrical member, and the upper wall shielding portion 11b is bonded using the above-described heat-resistant adhesive for carbon bonding, and then the peripheral wall heat insulating material 6 made of carbon felt and the bottom wall, respectively. The heat insulating material 7 and the upper wall heat insulating material 8 are arranged, and as shown in FIG. 1A, the graphite shielding is provided between the outer surface of the graphite crucible 5 and the inner surface of these heat insulating materials 9. The member 11 was interposed. The electrical resistivity of the graphite material (graphite block, plate-like, and cylindrical graphite members) that forms the graphite shielding member 11 used here is 9 μΩm. Further, the thickness of the graphite shielding member 11 is 5 mm, which is thinner than the penetration depth (about 15 mm) of the high-frequency current (9.8 kHz) flowing through the work coil 15. Moreover, the thickness of the carbon felt-made heat insulating material 9 is 10 mm, and a central opening 10 is formed in the upper wall heat insulating material 8, and the diameter is formed by the end of the upper wall shielding portion 11 b so as to cover the inner peripheral side surface. A cylindrical exhaust port 12 having a height of 25 mm and a height of 15 mm from the outer surface of the upper wall portion of the graphite crucible 5 was formed.

  The graphite crucible 5 covered with the heat insulating material 9 and the upper wall shielding part 11 in this way was placed on the graphite support rod 18 in the double quartz tube 13. Then, after evacuating the double quartz tube 13, an electric current was passed through the work coil 15 to raise the surface temperature of the crucible lid 3 to 1700 ° C. Thereafter, a mixed gas of high-purity argon gas (purity 99.9995%) and high-purity nitrogen gas (purity 99.9995%) is introduced as an atmospheric gas, and the pressure in the double quartz tube 13 is maintained at about 80 kPa while maintaining the pressure in the crucible lid 3. The surface temperature was raised to the target temperature of 2250 ° C. The nitrogen concentration in the atmospheric gas was 7%. Thereafter, the pressure was reduced to 1.3 kPa as a growth pressure over about 30 minutes. At this time, the temperature gradient between the SiC raw material 2 and the seed crystal 1 in the crucible is about 20 ° C./cm. Then, crystal growth was performed with a growth time of 100 hours, and then immediately cooled.

  The diameter of the obtained SiC single crystal ingot was about 102.3 mm, the growth surface shape was a gentle convex shape, and the height near the crystal center at the tip of crystal growth was about 34 mm. Moreover, when the outer peripheral side surface of the ingot, the crystal growth end surface, and the back surface of the seed crystal (opposite side of the crystal growth end surface) were observed visually and with a stereomicroscope, no macro defects such as subgrain boundaries were generated, and the grown crystal Confirmed that good crystal quality equivalent to that of the seed crystal was realized.

Further, the obtained SiC single crystal ingot was ground, cut and polished to have a diameter of 100 mm and a thickness of 0.35 mm, and the crystal c axis (hexagonal <0001> axis) was <11−. A 4-degree off-wafer was produced that was inclined 4 degrees in the 20> direction. When the wafer was taken out from the top of the ingot, that is, from the crystal growth end, the entire surface of the wafer was composed of 4H type polytype. Further, the wafer was heated to 500 ° C. and immersed in molten KOH (potassium hydroxide) for about 3 minutes for etching to form dislocation pits. Among the pits that appeared, the number of shell-shaped etch pits (P. Wu, Journal of Crystal Growth, Vol. 312 (2010) p. 1193) corresponding to the basal plane dislocation was measured over the entire wafer surface. As a result, the basal plane dislocation density per unit area was obtained, and an extremely small density value of 67 / cm ² was realized on the entire surface of the 100 mm wafer.

(Comparative Example 1)
As shown in FIG. 4, without using the graphite shielding member 11, the outer surface of the graphite crucible 5 and the inner surface of the heat insulating material 9 are in contact with each other. The thickness of all of the part, the bottom wall part, and the upper wall part is 20 mm (that is, the heating conditions of the graphite to be induction-heated are the same as those in Example 1). Crystal growth was performed in the same manner.

The diameter of the obtained SiC single crystal ingot was about 101.9 mm. When the ingot was observed in detail, the shape of the growth surface was slightly concave on the periphery of the ingot. The thickness was about 29 mm. Subgrain boundaries are generated in the periphery of the ingot, and when examined in detail using a Raman spectroscopic device, it was found that a 6H-type different polytype was mixed. Further, as in Example 1, a 4 degree off wafer having a diameter of 100 mm and a thickness of 0.35 mm was produced from the top of the ingot, and the basal plane dislocation density was evaluated by the molten KOH etching method as in Example 1, The shell-like etch pit density was extremely high at the periphery of the wafer, and a basal plane dislocation density of 569,000 pieces / cm ² was obtained.

(Thickness evaluation test of graphite shielding member)
In order to examine the influence of the thickness of the graphite shielding member due to induction heating, a test production of a SiC single crystal ingot was performed as follows. The seed crystal used is a 4H type SiC single crystal substrate made of a {0001} substrate having a diameter of 153 mm and a thickness of 2.5 mm, and the crucible lid so that the (000-1) plane (C plane) is the growth plane. 3 was affixed to the inner surface. Then, with respect to the crucible main body 4 loaded with SiC powder as the SiC raw material 2, the lower surface side of the crucible lid 3 and the upper surface side of the crucible main body 4 are screwed together by a screw structure in the same manner as in Example 1. A seam portion was formed so that the sublimation gas could leak.

  With respect to the graphite shielding member 11, a seamless integral part including a bottom wall shielding portion 11 a from a single graphite block is formed in accordance with the shape of the graphite crucible 5 including the crucible lid body 3 and the crucible body 4. A bottomed cylindrical member was used. As shown in FIG. 1B, the graphite crucible 5 described above is accommodated in the bottomed cylindrical member, and a carbon felt peripheral wall heat insulating material 6 and a bottom wall heat insulating material 7 each having a thickness of 15 mm are disposed. Further, the outer surface of the upper wall portion of the graphite crucible 5 is opened without being covered with a heat insulating material, and a graphite shielding member 11 is interposed between the outer surface of the graphite crucible 5 and the inner surface of these heat insulating materials 9. It was made to be. Here, the outer peripheral surface of the upper wall portion of the graphite crucible 5 was projected with a length of 30 mm so that the peripheral wall heat insulating material 6 and the graphite shielding member 11 had the same height.

  In this evaluation test, as shown in Table 1 below, the total thickness of the graphite crucible 5 and the graphite shielding member 11 is 25 mm (both the peripheral wall portion side and the bottom wall portion side), The thickness of each was changed. The thickness of the upper wall portion of the graphite crucible 5 (thickness of the crucible lid 3) was fixed at 25 mm. The graphite crucible 5 covered with the heat insulating material 9 and the upper wall shielding portion 11 in this way is placed on the graphite support rod 18 in the double quartz tube 13, and the crystal growth conditions are the same as in the first embodiment. Then, crystal growth was performed with a growth time of 140 hours.

  After the growth, it is immediately cooled, the ingot is taken out, and the surface is observed visually and with a stereomicroscope. Also, in the same manner as in Example 1, a four-degree off-wafer with a diameter of 150 mm is produced and melted by KOH etching. The basal plane dislocation density was obtained by counting shell-like etch pits. The results are summarized in Table 1.

As shown in Table 1, in the manufacturing apparatus having the structure shown in FIG. 1 (b), when the thickness of the graphite shielding member 11 is 5 mm or less, the convex SiC single crystal having a gentle growth surface is formed. Reflecting that the ingot was obtained and the growth was good, it can be seen that a SiC single crystal ingot with a very small basal plane dislocation density of about 100 / cm ² and few defects was obtained. On the other hand, when the thickness of the graphite shielding member 11 is 10 mm or more, ingot production by high frequency heating has a tendency that the concave shape of the shape of the growth end face becomes gradually stronger, and a different polytype other than the 4H type such as 6H and 15R is mixed. Appears. This is because the thickness of the graphite shielding member 11 protruding from the outer surface of the upper wall portion of the graphite crucible 5 is increased, and heat generation at the shielding member 11 portion due to high frequency induction is increased. This is thought to be due to the fact that the temperature distribution is greatly changed. When the thickness of the graphite shielding member 11 is 15 mm, or particularly when the thickness of the graphite shielding member 11 is 20 mm, the obtained SiC single crystal ingot is obtained. In this case, various kinds of defects such as micropipes were generated in an excessive amount due to the mixing of different polytypes, so that the dislocation density by KOH etching could not be evaluated accurately. Further, from the result when the thickness of the graphite shielding member 11 is 15 mm, the calculated value of the penetration depth (about 15 mm) is obtained, but it is good when the fluctuation of the electrical resistance value at high temperature is taken into consideration. In order to obtain the growth stability, it is preferable that the value is sufficiently smaller than 15 mm, and that it is required to be 10 mm or less industrially.

  From the results shown above, with the production apparatus of the present invention, an excessive increase in the sublimation gas pressure in the crucible can be avoided, and the property deterioration of the heat insulating material due to the sublimation gas can be suppressed, and a stable large-diameter SiC unit can be obtained. Crystalline ingots can be produced. Therefore, it is possible to stably manufacture a SiC single crystal wafer having a low defect density without mixing different types of polytypes.

1: seed crystal, 2: silicon carbide raw material, 3: crucible lid, 4: crucible body, 4a: upper body, 4b lower body, 5: graphite crucible, 6: peripheral wall heat insulating material, 7: bottom wall heat insulating material, 8: upper wall heat insulating material, 9: heat insulating material, 10: central opening, 11: graphite shielding member, 11a: bottom wall shielding portion, 11b: upper wall shielding portion, 12: cylindrical exhaust port, 13: double quartz Tube: 14: vacuum exhaust device, 15: work coil, 16: optical path, 17: two-color thermometer, 18: graphite support rod.

Claims (6)

A graphite crucible having a crucible main body loaded with a silicon carbide raw material and a crucible lid body to which a seed crystal is attached, a heat insulating material disposed around the graphite crucible, and a heating device for heating the graphite crucible A silicon carbide single crystal ingot for producing a silicon carbide single crystal ingot by a sublimation recrystallization method in which a silicon carbide raw material is heated to generate a sublimation gas and recrystallized on a seed crystal,
At least a graphite shielding member is interposed between the outer peripheral surface of the peripheral wall of the graphite crucible and the inner surface of the peripheral heat insulating material covering the outer peripheral surface of the graphite crucible, and the sublimation gas leaked from the graphite crucible is made of the graphite crucible. Through the gap formed between the shielding member and the outer peripheral surface of the peripheral wall of the graphite crucible, the heat is discharged from the upper and / or bottom wall side of the graphite crucible to the outside of the heat insulating material. An apparatus for producing a silicon carbide single crystal ingot.   The graphite shielding member has a bottom wall shielding portion interposed between an outer side surface of the bottom wall portion of the graphite crucible and an inner side surface of the bottom wall heat insulating material covering the outer surface of the bottom wall portion. The apparatus for producing a silicon carbide single crystal ingot according to claim 1, wherein the sublimation gas leaked from the gas is discharged from the upper wall side of the graphite crucible to the outside of the heat insulating material through the gap.   The upper wall heat insulating material covering the outer surface of the upper wall portion of the graphite crucible has a central opening, and the graphite shielding member is disposed on the inner surface of the upper wall heat insulating material and outside the upper wall portion of the graphite crucible. A sublimation gas leaked from the graphite crucible, having an upper wall shielding portion that is interposed between the side surface and extends to cover the inner peripheral side surface of the central opening to form a cylindrical exhaust port, The apparatus for producing a silicon carbide single crystal ingot according to claim 2, wherein the silicon carbide single crystal ingot is discharged from the cylindrical exhaust port communicating with the gap to the outside of the heat insulating material.   The silicon carbide single crystal ingot according to any one of claims 1 to 3, wherein the heating device is an induction heating type heating device, and the graphite shielding member has a thickness thinner than a high-frequency penetration depth used in the heating device. Manufacturing equipment.   The apparatus for producing a silicon carbide single crystal ingot according to any one of claims 1 to 4, wherein the silicon carbide single crystal ingot having a diameter of 100 mm or more is produced. A graphite crucible having a crucible body loaded with a silicon carbide raw material and a crucible lid body to which a seed crystal is attached, a heat insulating material disposed around the graphite crucible, and a heating device for heating the graphite crucible A silicon carbide single crystal ingot is produced by a sublimation recrystallization method in which a silicon carbide raw material is heated to generate a sublimation gas and recrystallized on a seed crystal using a silicon carbide single crystal ingot production apparatus equipped with A method for producing a single crystal ingot, comprising:
At least, a sublimation gas leaked from the graphite crucible is interposed between the graphite crucible with a graphite shielding member interposed between the outer surface of the peripheral wall of the graphite crucible and the inner surface of the peripheral wall heat insulating material covering the outer surface of the peripheral wall. Silicon carbide is discharged from the top wall side and / or bottom wall side of the graphite crucible through the gap formed between the shielding member and the outer peripheral surface of the peripheral wall of the graphite crucible. A method for producing a single crystal ingot.

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