JP2015093810A - Production method of silicon carbide single crystal and production apparatus of silicon carbide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a silicon carbide single crystal and a production apparatus of the silicon carbide single crystal capable of obtaining a high-quality silicon carbide single crystal.SOLUTION: A SiC single crystal is grown on a first seed crystal 50a comprising silicon carbide, and the SiC single crystal is cut to form a base end part 51c, a tip part 51a and an intermediate part 51b. Then, the intermediate part 51b is taken out, and the base end part 51c and the tip part 51a are bonded together to form a second seed crystal 50b, and the SiC single crystal is grown from a growth surface 52 thereof.

Description

  The present invention relates to a method for manufacturing a silicon carbide single crystal and an apparatus for manufacturing a silicon carbide single crystal.

  Silicon carbide (hereinafter also referred to as SiC) has excellent physical properties such as a band gap of about 3 times, a saturation drift velocity of about 2 times, and a breakdown electric field strength of about 10 times that of Si, and a large thermal conductivity. Therefore, it is expected as a material for realizing a next-generation high-voltage / low-loss semiconductor device that greatly surpasses the performance of currently used Si single crystal semiconductors.

  As one of methods for producing an SiC single crystal, a gas growth method such as an HTCVD method is known (for example, see Patent Document 1). In the gas growth method, as long as the source gas is continuously supplied to the seed crystal, a long SiC single crystal can be produced in theory. If the SiC single crystal can be grown long at high speed, the price can be reduced.

  However, in practice, it is necessary to take out the SiC single crystal when a predetermined length is reached due to restrictions on the apparatus. Therefore, it is necessary to repeatedly take out the SiC single crystal, place the seed crystal, and perform crystal growth.

  Here, the seed crystal is made of tabular SiC. When there is a temperature gradient on the surface (growth surface) of the seed crystal, for example, when there is a temperature gradient such that the peripheral part is high temperature and the central part is low temperature, the growth does not progress much in the high temperature part, and the growth does not proceed. When such growth proceeds and the shape of the growth surface coincides with the isothermal surface (convex curved surface), the entire growth surface grows.

  That is, when a plate-like seed crystal is used, the crystal grows in a state where the growth surface is not along the isothermal surface at the initial stage of growth. At this time, dislocation may occur in the SiC single crystal. In addition, it takes a certain time for the growth surface to be along the isothermal surface, which hinders shortening of the manufacturing time.

  Such a problem exists not only in the gas growth method but also in the sublimation method and the liquid phase method.

JP2012-240894A

  In view of the above circumstances, an object of the present invention is to provide a silicon carbide single crystal manufacturing method and a silicon carbide single crystal manufacturing apparatus capable of obtaining a high-quality silicon carbide single crystal.

  In a first aspect for achieving the above object, a silicon carbide single crystal is grown on a first seed crystal made of silicon carbide, and the silicon carbide single crystal is cut to form a base end on the first seed crystal side. And a tip portion on the growth surface side, the base end portion or the tip portion is used as a second seed crystal, and a silicon carbide single crystal is grown from the cut surface of the base end portion or the growth surface of the tip portion The present invention resides in a method for producing a silicon carbide single crystal.

  In the first aspect, the growth of the SiC single crystal for the second and subsequent times starts from the second seed crystal. The second seed crystal grows last time and has a growth surface having the same shape as the isothermal surface. Therefore, when crystal growth is performed from the second seed crystal after the second time, crystal growth can be performed from the growth surface along the isothermal surface. Thereby, a high quality silicon carbide single crystal can be manufactured. Further, it does not take a certain time for the growth surface to follow the isothermal surface, and the manufacturing time can be shortened accordingly.

  According to a second aspect of the present invention, in the method for manufacturing a silicon carbide single crystal according to the first aspect, the silicon carbide single crystal is cut at two cutting planes to form the base end portion, the tip end portion, and the intermediate portion. Forming a portion, taking out the intermediate portion, and joining the cut surfaces of the base end portion and the tip end portion to each other.

  In the second aspect, the intermediate portion can be taken out as a silicon carbide single crystal and used as a material such as a silicon carbide wafer.

  According to a third aspect of the present invention, in the method for manufacturing a silicon carbide single crystal according to the second aspect, the silicon carbide single crystal is cut along an off-angle of the silicon carbide single crystal. It is in.

  In the third aspect, an off-wafer can be manufactured without generating a useless portion from the silicon carbide single crystal.

  According to a fourth aspect of the present invention, in the method for producing a silicon carbide single crystal according to the first aspect, after the cut surface of the base end portion as the second seed crystal is etched, carbonization is performed from the cut surface. A silicon carbide single crystal is produced by growing a silicon single crystal.

  In the fourth aspect, since etching can be performed and crystal growth can be resumed, the trouble of polishing the growth surface can be omitted, and the manufacturing process can be simplified.

  According to a fifth aspect of the present invention, there is provided growth means for growing a silicon carbide single crystal on a first seed crystal disposed in a container, and a group on the first seed crystal side by cutting the silicon carbide single crystal. A silicon carbide unit comprising cutting means for forming an end portion and a tip portion on the growth surface side, and installation means for disposing the base end portion or the tip portion as a second seed crystal in the container. It is in the crystal production equipment.

  In the fifth aspect, when crystal growth is performed from the second seed crystal for the second time and thereafter, crystal growth can be performed from the growth surface along the isothermal surface. Thereby, a high quality silicon carbide single crystal can be manufactured. Further, it does not take a certain time for the growth surface to follow the isothermal surface, and the manufacturing time can be shortened accordingly.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a silicon carbide single crystal which can obtain a high quality silicon carbide single crystal, and the manufacturing apparatus of a silicon carbide single crystal are provided.

It is sectional drawing of the manufacturing apparatus which concerns on this embodiment. It is sectional drawing of the manufacturing apparatus which shows the manufacturing process in this manufacturing method. It is sectional drawing of the manufacturing apparatus which shows the manufacturing process in this manufacturing method. It is the schematic which expanded the intermediate part of the SiC single crystal. It is sectional drawing to which the principal part of the manufacturing apparatus which shows the manufacturing process by this manufacturing method was expanded. It is sectional drawing to which the principal part of the manufacturing apparatus which shows the manufacturing process by this manufacturing method was expanded.

  A SiC single crystal manufacturing apparatus (hereinafter simply referred to as a manufacturing apparatus) according to this embodiment will be described. FIG. 1 is a cross-sectional view of the manufacturing apparatus.

  The manufacturing apparatus I is for growing a SiC single crystal in bulk by a high temperature gas growth method. The manufacturing apparatus I includes a raw material gas supply means 1 for supplying a raw material gas, a pedestal 10 that supports a seed crystal made of SiC (hereinafter referred to as a first seed crystal 50a), and a heat insulating container 20 that houses the pedestal 10 therein. The airtight container 30 for housing the heat insulating container and the coil 40 (heating means) for heating the heat insulating container 20 are provided.

  The raw material gas supply means 1 includes a raw material gas supply device 2 for silicon carbide and a pipe line 3 serving as a flow path for the raw material gas supplied from the raw material gas supply device 2. The pipe 3 is provided with a supply port 4 on the upper surface in the vertical direction, and supplies the raw material gas from the raw material gas supply device 2 to the first seed crystal 50a described later from the supply port 4.

The source gas is not particularly limited as long as SiC is deposited on the first seed crystal 50a. For example, SiH ₄ or C ₃ H ₈ gas, and further a source gas composed of H ₂ gas as a carrier gas can be used.

  The pedestal 10 supports the first seed crystal 50a made of SiC. The pedestal 10 includes a columnar support portion 11 that supports the first seed crystal 50 a and a shaft portion 12 connected to the upper surface of the support portion 11 in the vertical direction. The support portion 11 has a support surface 13 that faces the supply port 4 of the conduit 3 described above. In the pedestal 10, the first seed crystal 50 a is bonded to the support surface 13. The material of the support portion 11 is not particularly limited, but may be formed of graphite or silicon carbide.

  The base 10 can be moved up and down in the vertical direction by the moving mechanism 14. That is, the entire pedestal 10 can be moved up and down by the moving mechanism 14 moving the shaft portion 12 up and down. A source gas is supplied from the supply port 4 to the first seed crystal 50 a bonded to the support surface 13. For this reason, the first seed crystal 50a is grown by being supplied with the source gas while being moved upward by the pedestal 10.

  Note that the pedestal 10 is not necessarily movable up and down, and may be fixedly disposed in the sealed container 30.

  The heat insulating container 20 is a container that accommodates the pedestal 10 therein, and is formed of a heat insulating material. Although there is no limitation in particular as a heat insulating material, For example, an alumina, a zirconia, pyrolytic carbon, graphite (graphite) etc. can be utilized.

  The heat insulating container 20 is formed in a cylindrical shape and has an internal space 21. The heat insulating container 20 is placed on the opening edge of the supply port 4 of the pipeline 3, and the internal space 21 communicates with the pipeline 3 via the supply port 4.

  The pedestal 10 is accommodated in the internal space 21 of the heat insulating container 20. The shaft portion 12 of the pedestal 10 is inserted through an insertion hole 33 of a lid 32 formed on the upper surface of the sealed container 30. As described above, since the pedestal 10 can move up and down, the support portion 11 can move up and down in the internal space 21.

  The sealed container 30 is a container that houses the heat insulating container 20 therein. The material is not particularly limited, and for example, quartz or metal can be used. Further, a discharge path 31 is formed in the sealed container 30, and the raw material gas supplied from the supply port 4 is discharged from the discharge path 31.

  Further, the airtight container 30 has an upper opening 34 closed by a lid 32. The lid 32 can be formed from the same material as that of the sealed container 30. During the production of the SiC single crystal, the sealed container 30 is hermetically closed by the lid 32, while the lid 32 is opened during operations such as recovery of the grown SiC single crystal, installation of new seed crystals, and maintenance, These operations are performed.

  The heating means heats the inside of the heat insulating container 20. The temperature in the heat insulating container 20 is set by the heating means. Specifically, the coil 40 can be used as a heating means.

  The coil 40 performs induction heating on the heat insulating container 20. Although not particularly illustrated, the coil 40 is connected to an AC power supply and supplied with a high-frequency AC current. The coil 40 is used as a main heat source which makes the temperature in the heat insulation container 20 high temperature, for example, 1500 degreeC or more. Although not particularly illustrated, when the sealed container 30 made of metal is used, the coil 40 is disposed inside the sealed container 30 and outside the heat insulating container 20.

  Although not particularly shown, the support portion 11 of the pedestal 10 is provided with a cooling mechanism so that the first seed crystal 50a can dissipate heat.

  Although not particularly illustrated, the manufacturing apparatus I includes cutting means for cutting the SiC single crystal grown on the first seed crystal 50a, and installation means for newly placing the cut one on the base 10. May be. Details of these will be described later.

  In the SiC single crystal manufacturing apparatus I having the above-described configuration, the inside of the heat insulating container 20 is set to a high temperature by the coil 40. On the other hand, the first seed crystal 50a is set to a relatively low temperature by the cooling mechanism of the base 10. Then, by supplying the source gas to the first seed crystal 50a, the SiC single crystal grows on the first seed crystal 50a. At this time, the first seed crystal 50 a grows while being pulled upward by the pedestal 10.

  Next, the manufacturing method of the SiC single crystal of this embodiment performed by the manufacturing apparatus I mentioned above is demonstrated. FIG. 2 is a cross-sectional view of the manufacturing apparatus showing the manufacturing process in this manufacturing method.

  First, the SiC single crystal 51 is grown on the first seed crystal 50a. Specifically, a source gas containing SiC is supplied from the source gas supply device 2 to the first seed crystal 50 a in the sealed container 30. When the crystal is grown from the surface of the first seed crystal 50a to a certain length, the shape of the growth surface 52 becomes the same convex curved surface shape as the isothermal surface, and the entire growth surface 52 grows. Then, SiC single crystal 51 grows until length L is reached while maintaining the shape of growth surface 52. The length L here is the maximum length of the SiC single crystal 51 that can be manufactured by the manufacturing apparatus I.

  In the growth process of the present embodiment, the SiC single crystal 51 is grown while pulling the support portion 11 upward (in the direction opposite to the source gas supply port 4) by the moving mechanism 14. The support portion 11 is pulled up at the same speed (substantially the same speed) as the growth speed of the SiC single crystal 51. Therefore, the relative position of the surface (growth surface 52) of SiC single crystal 51 with respect to supply port 4 is always constant.

  For example, the moving mechanism 14 is used to position the surface of the first seed crystal 50a in the vicinity of the supply port 4 (see FIG. 1). Thereafter, the SiC single crystal 51 grows, but the support portion 11 is pulled upward in accordance with the growth rate. Therefore, the growth surface 52 of the SiC single crystal 51 is at the same position as the vicinity of the supply port 4 where the surface of the original first seed crystal 50a was located as shown in FIG. That is, the growth surface 52 does not protrude from the supply port 4 into the pipe 3.

  Next, the SiC single crystal 51 is cut. In the present embodiment, the SiC single crystal 51 is cut along two cut surfaces. The cut surfaces are a lower cut surface 53 on the tip side (growth surface 52 side) of the SiC single crystal 51 and an upper cut surface 54 on the base end side (first seed crystal 50a side) of the SiC single crystal 51. By cutting the SiC single crystal 51 at these two cut surfaces, a tip end portion 51a, a base end portion 51c, and an intermediate portion 51b between them are formed.

  The means for cutting the SiC single crystal 51 is not particularly limited, and for example, a multi-wire saw, a diamond blade, a peripheral blade cutting machine, or the like can be applied. Further, the SiC single crystal 51 may be taken out from the hermetic container 30 and cut by a cutting means, or the SiC single crystal 51 is supported by the pedestal 10 by a cutting means provided integrally with the manufacturing apparatus I. You may make it cut | disconnect.

  Further, the length L is a range smaller than the limit length that allows the SiC single crystal 51 to be pulled up, and can be appropriately changed in consideration of the device configuration, the size of the SiC single crystal, and the like. The method for detecting that the SiC single crystal 51 has reached the length L is not particularly limited, and the distance by which the SiC single crystal 51 is pulled up, the supply amount of the source gas, the parameters correlated therewith, etc. are not shown. This can be done by having the control device detect and calculate.

  Next, the intermediate part 51b of the cut SiC single crystal 51 is taken out. The intermediate portion 51b is used as a SiC single crystal material such as a SiC wafer.

  Next, of the cut SiC single crystal 51, the tip 51a having the growth surface 52 is defined as a second seed crystal 50b. Specifically, the lower cut surface 53 of the distal end portion 51a and the upper cut surface 54 of the proximal end portion 51c are joined.

  FIG. 3 is a cross-sectional view of the manufacturing apparatus showing the manufacturing process in this manufacturing method. As shown in the figure, the tip portion 51a and the base end portion 51c of the SiC single crystal 51 are joined, and the tip portion 51a having the growth surface 52 is newly arranged on the pedestal 10 as the second seed crystal 50b. Yes.

  Joining of the front-end | tip part 51a and the base end part 51c can be performed with the following method, for example. That is, the adhesive layer 55 is formed between the lower cut surface 53 of the distal end portion 51a and the upper cut surface 54 of the proximal end portion 51c. As the adhesive layer 55, a paste obtained by wet-mixing carbon powder having a particle size of about several μm and silicon powder with alcohol or the like can be used. The distal end portion 51a and the proximal end portion 51c sandwiching the adhesive layer 55 are put in a heat treatment apparatus, heated to a predetermined temperature and pressure, pressurized, and then pressed. After maintaining this state for a predetermined time, the inside of the apparatus is returned to room temperature and normal pressure. As a result, the carbon powder and the silicon powder react to generate SiC, and at the same time, sintering of the generated SiC proceeds to firmly join the distal end portion 51a and the proximal end portion 51c.

  In addition, it is not limited to the joining method as mentioned above, The method of adhere | attaching the front-end | tip part 51a and the base end part 51c with an adhesive agent etc. may be used. Further, the manufacturing apparatus I may be provided with a mechanism (installation means) for taking out the intermediate part 51b from the manufacturing apparatus I and bonding the cut distal end part 51a and proximal end part 51c.

  In cutting, the lower cut surface 53 and the upper cut surface 54 are preferably parallel to each other. As a result, the lower cut surface 53 and the upper cut surface 54 can be bonded without gaps, so that the joining is facilitated and the physical stability is also improved.

  Furthermore, after joining the lower cut surface 53 and the upper cut surface 54, the step around the joined surface may be polished. Then, as a final finish used as the second seed crystal 50b, the growth surface 52 may be subjected to sacrificial oxidation, reactive ion etching, chemical mechanical polishing, or the like. Thereafter, the surface may be cleaned using an organic solvent, an acidic solution, an alkaline solution, or the like.

  As described above, after the tip 51a having the growth surface 52 is used as the new second seed crystal 50b, the SiC single crystal 51 is grown on the second seed crystal 50b (not shown). Specifically, the pedestal 10 is pulled downward until the second seed crystal 50b (growth surface 52) reaches the vicinity of the supply port 4, and an SiC single crystal is formed on the second seed crystal 50b in the same manner as the first crystal growth. Grow 51.

  Thereafter, every time the length of the SiC single crystal 51 reaches the length L, the SiC single crystal 51 is continuously cut by repeating the cutting of the SiC single crystal 51 and the rearrangement of the second seed crystal 50b as described above. (Intermediate portion 51b) can be obtained.

  According to the SiC single crystal manufacturing method according to the present embodiment described above, the growth of the SiC single crystal from the second time onward starts from the second seed crystal 50b. The second seed crystal 50b has a growth surface 52 that has been grown last time and has the same shape as the isothermal surface. Therefore, when the crystal is grown from the second seed crystal 50b for the second time or later, the crystal can be grown from the growth surface 52 along the isothermal surface.

  That is, even when the SiC single crystal 51 reaches the length L and is taken out from the manufacturing apparatus I and the next SiC single crystal 51 is grown, it is not necessary to perform growth from the first seed crystal 50a having a flat plate shape. It becomes.

  In the case of crystal growth from a plate-like seed crystal, there is a problem that dislocations occur because the growth surface does not conform to the isothermal surface in the initial stage, but this production method reduces the occurrence of such dislocations. As a result, a high-quality SiC single crystal 51 can be manufactured. Further, it does not take a certain time for the growth surface to follow the isothermal surface, and the manufacturing time can be shortened accordingly.

  Further, when cutting SiC single crystal 51, it is preferable that lower cut surface 53 and upper cut surface 54 be aligned with the off angle of SiC single crystal 51. FIG. 4 is an enlarged schematic view of the intermediate portion 51 b of the SiC single crystal 51.

  4A shows an intermediate portion 51b when the lower cut surface 53 and the upper cut surface 54 are at angles different from the off-angle of the SiC single crystal 51, and FIG. 4B shows the lower cut surface 53 and the upper cut surface. This is intermediate portion 51 b when cut surface 54 has the same angle as the off-angle of SiC single crystal 51.

  The intermediate part 51b shown in FIG. 4 (a) has a substantially cylindrical shape. Therefore, when an off-wafer is produced along the off-angle θ, a useless removal portion (D area indicated by oblique lines) for cutting out occurs.

  On the other hand, as shown in FIG. 4B, the intermediate part 51b (SiC single crystal 51) has an off angle θ. In this case, the intermediate portion 51b is cut out by cutting the SiC single crystal 51 along the off angle θ. From the intermediate part 51b, a SiC wafer is produced by cutting along a plurality of cutting surfaces 57 forming an off angle θ.

  Therefore, as shown in FIG. 4B, the lower cut surface 53 and the upper cut surface 54 preferably form the same angle as the off angle θ. Thereby, the removal part which becomes useless when producing an off-wafer from the intermediate part 51b can be eliminated.

<Other embodiments>
As mentioned above, although the example which joins the cut | disconnected SiC single crystal was demonstrated as embodiment of this invention, this invention is not limited to this, A various change is possible in the range which does not change the summary of this invention.

  For example, the tip 51 a of the SiC single crystal 51 may be joined to the support surface of the base 10. 5 (a) to 5 (b) and FIGS. 6 (a) to 6 (b) are enlarged cross-sectional views of the main part of the manufacturing apparatus showing the manufacturing process in this manufacturing method.

  As shown in FIG. 5A, after the first SiC single crystal 51 is grown, the SiC single crystal 51 is cut. Specifically, the SiC single crystal 51 is cut at the lower cut surface 53 to form the tip 51a.

  Next, although not particularly illustrated, the remaining SiC single crystal 51 and the first seed crystal 50a are removed from the pedestal 10.

  Next, as shown in FIG. 5B, the tip 51a of the SiC single crystal 51 is bonded to the support surface 13 of the base 10 to form a new second seed crystal 50b. Then, a SiC single crystal 51 is grown on the second seed crystal 50b.

  According to such an embodiment, since only the tip 51a of the SiC single crystal 51 is used as the second seed crystal, a longer SiC single crystal is grown as the second seed crystal 50b becomes shorter. Can do.

  Further, as shown in FIGS. 6A to 6B, after the first SiC single crystal 51 is grown, the SiC single crystal 51 is cut. Specifically, cutting is performed along the upper cut surface 54 so that the base end portion 51c remains. The remaining base end portion 51c is used as the second seed crystal 50b.

  Then, etching with hydrogen gas or high temperature etching is applied to the base end portion 51c, and then a SiC single crystal is grown on the surface.

  According to such an embodiment, since the crystal growth can be resumed by performing etching or the like, the trouble of polishing the growth surface can be omitted, and the manufacturing process can be simplified. In addition, since the second seed crystal 50b is formed using the base end portion 51c of the SiC single crystal 51 already bonded to the support surface 13 of the pedestal 10, the step of bonding the SiC single crystal can be omitted.

  The present invention is not limited to the gas growth method, and can also be applied to a method for producing an SiC single crystal by a sublimation method or a liquid phase method. That is, even by these methods, crystal growth can be performed from a growth surface having the same shape as that of the isothermal surface.

  The present invention can be used in the industrial field for producing silicon carbide single crystals.

I Silicon carbide single crystal production apparatus 1 Raw material gas supply means 10 Base 20 Heat insulation container 30 Sealed container 40 Coil (heating means)
50a First seed crystal 50b Second seed crystal 51 Single crystal 51a Tip 51b Intermediate 51c Base 52 52 Growth surface

Claims (5)

Growing a silicon carbide single crystal on a first seed crystal made of silicon carbide;
Cutting the silicon carbide single crystal to form a base end portion on the first seed crystal side and a tip end portion on the growth surface side;
A method for producing a silicon carbide single crystal, wherein the base end portion or the tip end portion is used as a second seed crystal, and a silicon carbide single crystal is grown from a cut surface of the base end portion or a growth surface of the tip end portion. . In the manufacturing method of the silicon carbide single crystal of Claim 1,
Cutting the silicon carbide single crystal at two cutting planes to form the base end, the tip, and an intermediate portion;
The intermediate part is taken out, and the cut surfaces of the base end part and the tip end part are joined to each other. A method for producing a silicon carbide single crystal, comprising: In the manufacturing method of the silicon carbide single crystal of Claim 2,
Cutting the silicon carbide single crystal along an off angle. A method for producing a silicon carbide single crystal. In the manufacturing method of the silicon carbide single crystal of Claim 1,
A method for producing a silicon carbide single crystal, comprising: etching a cut surface of the base end portion as the second seed crystal, and then growing a silicon carbide single crystal from the cut surface. A growth means for growing a silicon carbide single crystal on the first seed crystal disposed in the container;
Cutting means for cutting the silicon carbide single crystal to form a base end portion on the first seed crystal side and a tip end portion on the growth surface side;
An apparatus for producing a silicon carbide single crystal, comprising: an installation means for disposing the base end portion or the tip end portion as a second seed crystal in the container.

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