KR102163489B1 - Growth device for single crystal - Google Patents

Abstract

Provides a SiC single crystal growth device. According to the present invention, in the SiC single crystal growth apparatus applied to the growth of large-diameter silicon carbide (SiC) single crystals having a diameter of 4 inches or more, a crucible provided with an inner space into which a raw material is charged, a seed crystal support to which a seed crystal is attached, and the crucible A thermal insulation material and a quartz tube surrounding the, heating means for heating the crucible provided outside the quartz tube, and a temperature deviation reducing unit provided inside the crucible to reduce a temperature difference between the inner wall of the crucible and the center. .

Description

Silicon carbide (SiC) single crystal growth device {GROWTH DEVICE FOR SINGLE CRYSTAL}

The present invention relates to a silicon carbide (SiC) single crystal growth apparatus, and more particularly, by using porous graphite in the growth of large-diameter single crystal SiC having a diameter of 4 inches or more, the temperature difference between the inner wall of the crucible and the center is reduced. The present invention relates to a SiC single crystal growing apparatus capable of controlling cracks and defects to minimize the frequency of occurrence of cracks and defects, and finally to grow high-quality single crystals.

Conventionally, as a silicon carbide (SiC) single crystal growth method, a physical vapor transport method has the advantage of being able to manufacture high-quality silicon carbide with high yield, and is currently widely used. The growth method is largely classified into induction heating and resistance heating in detail in the heating method, and most of the growth methods mainly use induction heating methods that do not have significant restrictions on the target temperature and the time to reach the target temperature.

This method does not have a significant effect on the growth of single crystals having a diameter of 4 inches or less. However, in the application of the large-diameter single crystal SiC growth having a diameter of 4 inches or more, the application of the above method may cause various problems. That is, when the diameter of the single crystal increases, the size of the crucible also increases horizontally in proportion to this, so that the temperature difference between the inner wall of the crucible and the center of the crucible becomes large, and uniform sublimation of the raw material powder becomes impossible. Accordingly, since the grown ingot is not flat and the center is convex, it is difficult to implement a high-quality single crystal. In addition, the raw material powder that cannot be sublimated due to the low central temperature remains inside the crucible, ultimately reducing the yield of the ingot, and increasing the process time for growing a single crystal (see FIG. 7 ).

The present invention minimizes the frequency of occurrence of cracks and defects by controlling cracks and defects by reducing the temperature deviation between the inner wall of the crucible and the center by using porous graphite in the growth of large-diameter single crystal SiC having a diameter of 4 inches or more, Finally, we would like to provide a SiC single crystal growing apparatus capable of growing high quality single crystals.

According to an embodiment of the present invention, in the silicon carbide single crystal growing apparatus applied to the large-diameter silicon carbide single crystal growth having a diameter of 4 inches or more,

A crucible with an internal space into which raw materials are charged,

Seed crystal support to which the seed crystal is attached,

Insulation material and quartz tube surrounding the crucible,

Heating means provided outside the quartz tube to heat the crucible, and

A silicon carbide single crystal growth apparatus may be provided that is provided inside the crucible and includes a temperature deviation reducing part for reducing a temperature deviation between the inner wall part and the center of the crucible.

The temperature deviation reducing part is located on the inner wall of the crucible to surround the outer shell of the seed crystal, and the porous graphite for uniformly distributing the temperature between the inner wall of the crucible and the center by controlling radiant heat from the inner wall of the crucible in the crystal growth section. It can be made of layers.

The porous graphite layer may be formed by inserting and bonding porous graphite to an insertion groove formed in the inner wall of the crucible.

The insertion groove may be formed to be concave by a predetermined size from the inner wall portion toward the outer wall portion of the crucible.

The insertion groove may be formed with a predetermined length from the upper end of the inner wall portion to the lower portion of the crucible.

The purity of the porous graphite may be 99% or more.

The porosity of the porous graphite may be 70% or more.

The porous graphite may have a length of 0.5 to 1 mm.

In the crystal growth section, the inside of the crucible may be heated to a temperature of 2000° C. to 2300° C. by a heating means under atmospheric pressure so that the porous graphite can play a heat reflecting role by controlling radiant heat from the inner wall of the crucible.

According to this embodiment, in the growth of large-diameter single crystal SiC having a diameter of 4 inches or more, since it is possible to reduce the temperature deviation between the inner wall of the crucible and the center of the crucible by using porous graphite, it is possible to manufacture an ingot having a large radius of curvature. Hyperpolycrystalline separation is possible, the probability of generating cracks and defects can be minimized by reducing lattice distortion, and the quality of the finally grown single crystal ingot can be improved through process stabilization.

1 is a schematic cross-sectional view of a silicon carbide single crystal growing apparatus according to an embodiment of the present invention.
2 is a detailed view of porous graphite used in the single crystal growth apparatus according to an embodiment of the present invention.
3 is a cross-sectional view showing an upper portion of a crucible of a silicon carbide single crystal growing apparatus according to an exemplary embodiment of the present invention, and a view showing a temperature difference between an inner wall portion and a center of the crucible.
4 is a cross-sectional view showing an upper portion of a crucible of a silicon carbide single crystal growing apparatus according to the prior art, and a view showing a temperature difference between an inner wall portion and a center of the crucible.
5 is a photograph showing an ingot grown using porous graphite according to an embodiment of the present invention.
6 is a photograph showing an ingot grown without using porous graphite according to the prior art.
7 is a photograph of a simulation of the temperature inside the crucible according to the diameter of the reactor (crucible) when growing single crystals using the induction heating furnace method.In the drawing, the left side shows the case where the crucible diameter is 100 mm, and the right side shows the case where the crucible diameter is 150 mm. .

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the present invention. As those of ordinary skill in the art to which the present invention pertains can be easily understood, the embodiments to be described later may be modified in various forms without departing from the concept and scope of the present invention. As far as possible, the same or similar parts are indicated using the same reference numerals in the drawings.

The terminology used below is only for referring to specific embodiments, and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” specifies a specific characteristic, region, integer, step, action, element and/or component, and other specific characteristic, region, integer, step, action, element, component and/or group It does not exclude the existence or addition of

All terms including technical and scientific terms used below have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. The terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal meaning unless defined.

1 is a schematic cross-sectional view of a silicon carbide single crystal growing apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a silicon carbide (SiC) single crystal growing apparatus according to an embodiment of the present invention may be applied to a large-diameter silicon carbide single crystal having a diameter of 4 inches or more.

The SiC single crystal growth apparatus includes a crucible 200 provided with an internal space into which the raw material 100 is charged, a seed crystal support 600 to which the seed crystal 500 is attached, an insulating material 300 surrounding the crucible 200 and quartz. A heating means 700 provided outside the tube 400 and the quartz tube 400 to heat the crucible 200, and a temperature deviation provided inside the crucible to reduce a temperature deviation between the inner wall of the crucible and the center Includes a reduction part.

The crucible 200 is preferably made of a material having a melting point equal to or higher than the sublimation temperature of SiC. For example, it may be made of graphite or a material having a melting point equal to or higher than the sublimation temperature of SiC may be applied on the graphite material. Here, it is preferable to use a material that is chemically inert to silicon and hydrogen at a temperature at which the SiC single crystal is grown as the material applied on the graphite material.

The seed crystal pedestal 600 is a means for supporting the seed crystal 500 and is manufactured using high-density graphite. In addition, the seed crystal support 600 to which the seed crystal 500 is attached is mounted on the crucible 400 to form a single crystal on the seed crystal 600.

The insulating material 300 and the quartz tube 400 are provided outside the crucible 200 and maintain the temperature of the crucible 200 at the crystal growth temperature. At this time, since the crystal growth temperature of SiC is very high, it is preferable to use a graphite felt made of a tubular cylinder having a predetermined thickness by compressing graphite fibers as the heat insulating material 300. In addition, the insulating material 300 may be formed in a plurality of layers to surround the crucible 200.

The heating means 700 is provided outside the quartz tube 400, for example, a high frequency induction coil may be used. The crucible 200 is heated by flowing a high-frequency current through the high-frequency induction coil, and the raw material is heated to a desired temperature.

In addition, the temperature deviation reduction unit is located on the inner wall of the crucible 200 to surround the outer surface of the seed crystal 500, and controls radiant heat from the inner wall of the crucible 200 in a crystal growth section to control the crucible 200 It may be made of a porous graphite layer 800 for uniform temperature distribution between the inner wall portion and the central portion.

The porous graphite layer 800 may be formed by filling the insertion groove 210 formed on the inner wall of the crucible 200 with porous graphite.

The insertion groove 210 is the outer wall from the inner wall portion of the crucible 200 so that the porous graphite effectively controls radiant heat emitted from the inner wall portion of the crucible 200 to suppress the formation of polycrystals on the inner wall of the crucible 200. It is formed to be concave by a certain size toward the side, and may be formed by a certain length from the upper end of the inner wall portion of the crucible 200 to the lower side.

Accordingly, the size of the insertion groove 210 may be formed such that when the insertion groove 210 is filled with porous graphite, the inner surface of the porous graphite layer 800 is aligned with the inner wall portion of the crucible 200. .

Since the purity of the porous graphite is located inside the crucible 200, it must be 99% or higher so as to minimize contamination problems.

In addition, the porosity of the porous graphite must be 70% or more so as to sufficiently dissipate radiant heat from the inner wall of the crucible 200.

The porous graphite should be a fibrous material, and it is preferable that the length is 0.5 to 1 mm to avoid induction heating interference (see FIG. 2).

Hereinafter, the operation of the silicon carbide single crystal growth apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

In one embodiment of the present invention, a single crystal made of 4H-SiC is grown on the seed crystal by using a physical vapor transport (PVT) method. To this end, the raw material 100 is first charged into the crucible 200. The porous graphite of the porous graphite layer 800 according to an embodiment of the present invention is inserted into the insertion groove 210 formed on the inner wall of the crucible 200 and is positioned to surround the outer shell of the seed crystal 500. A seed crystal 500 made of SiC is prepared, and the seed crystal 500 is attached to the seed crystal support 600 using an adhesive. Subsequently, the seed crystal pedestal 600 to which the seed crystal 500 is attached is introduced into the SiC single crystal growing apparatus, and it is mounted on the inside of the crucible 200.

In addition, impurities contained in the crucible 200 are removed by heating for 2 to 3 hours at a temperature of less than 1000°C and a vacuum pressure. Thereafter, an inert gas, for example, argon (Ar) gas is injected to remove air remaining in the crucible 200 and between the crucible 200 and the heat insulating material 300. Here, it is preferable to repeat the purging process using an inert gas 2 to 3 times. Subsequently, after raising the pressure to atmospheric pressure, the crucible 200 is heated to a temperature of 2000° C. to 2300° C. using the heating means 700. Here, the reason for maintaining the atmospheric pressure is to prevent the occurrence of undesired crystal polymorphism at the beginning of crystal growth.

That is, first, the atmospheric pressure is maintained and the raw material 100 is heated to the growth temperature. At this time, the heat transfer is dominated by the effect of conduction by the skin heating. Then, the inside of the SiC single crystal growing apparatus is reduced to 1 torr to 20 torr and maintained at a growth pressure, while the raw material 100 is sublimated to grow a single crystal. In this case, radiation rather than conduction has a dominant effect on the temperature gradient of the seed crystal 500.

In the crystal growth period, the porous graphite of the porous graphite layer 800 serves as a kind of thermal reflection controlling radiant heat emitted from the inner wall of the crucible 200. Conventionally, as shown in FIG. 4, heat from the outer wall of the crucible is transferred to the inside as it is, so that the temperature difference between the outer shell of the crucible 200 and the center of the crucible 200 increases. However, according to an embodiment of the present invention, as shown in FIG. 3, the porous graphite filters the heat from the outer wall of the crucible 200 once to form the porous graphite layer 800 based on the porous graphite layer 800. The inside has a relatively uniform temperature distribution, and the outside of the porous graphite layer, that is, the inner wall of the crucible 200 increases in temperature due to the reflected heat, so that the formation of polycrystals on the inner wall of the crucible 200 can be suppressed.

In this way, in the silicon carbide growth, the crucible 200 is a heat source material and is heated and heated from room temperature to 2300°C or higher. Below 2000℃, the effect of conduction is dominant due to the skin effect of induction heating, but above 2000℃, the effect of radiation becomes more dominant. By using the porous graphite of the porous graphite layer 800, the radiant heat is more efficiently utilized to reduce the temperature deviation between the inner wall and the center of the crucible 200, and finally, a high-quality single crystal can be obtained.

[Example]

(Invention example)

5 is a photograph showing an ingot grown using porous graphite according to an embodiment of the present invention.

According to FIG. 5, it can be confirmed that the height difference between the central portion and the outer portion of the ingot is small due to the effect of the porous graphite in the porous graphite layer, and polycrystals are not formed on the outer shell of the ingot.

(Comparative example)

6 is a photograph showing an ingot grown without using porous graphite according to the prior art.

According to FIG. 6, in the ingot grown according to the prior art, the height difference between the center and the outer part of the crucible is relatively large due to the temperature difference between the inner wall and the center of the crucible. This may cause a warpage of the lattice structure inside the ingot, resulting in defects or cracks. In addition, since polycrystals are formed on the outer shell of the ingot and adhere to each other with the single crystal, it may cause a problem of cracking of the ingot due to stress relaxation during later processing.

100: raw material 200: crucible
300: insulation 400: quartz tube
500: seed crystal 600: seed crystal base
700: heating means 800: porous graphite layer

Claims (9)

In the silicon carbide single crystal growth apparatus applied to the large-diameter silicon carbide (SiC) single crystal growth having a diameter of 4 inches or more,
A crucible with an internal space into which raw materials are charged,
Seed crystal support to which the seed crystal is attached,
Insulation material and quartz tube surrounding the crucible,
Heating means provided outside the quartz tube to heat the crucible, and
A temperature deviation reducing part provided inside the crucible to reduce a temperature deviation between the inner wall part and the center of the crucible
Including,
The temperature deviation reducing part is located on the inner wall of the crucible to surround the outer shell of the seed crystal, and the porous graphite for uniformly distributing the temperature between the inner wall of the crucible and the center by controlling radiant heat from the inner wall of the crucible in the crystal growth section. Consists of layers,
The porous graphite layer is filled with porous graphite in the insertion groove formed on the inner wall of the crucible,
The size of the insertion groove is a silicon carbide single crystal growing apparatus formed such that when the insertion groove is filled with porous graphite, an inner surface of the porous graphite layer is formed to coincide with an inner wall portion of the crucible. delete delete The method of claim 1,
The insertion groove is a silicon carbide single crystal growing apparatus that is formed concave by a predetermined length from the inner wall portion toward the outer wall portion of the crucible. The method of claim 4,
The insertion groove is a silicon carbide single crystal growing apparatus formed by a predetermined length from the upper end of the inner wall portion of the crucible to the bottom. The method of claim 1,
A silicon carbide single crystal growth apparatus having a purity of 99% or more of the porous graphite. The method of claim 6,
A silicon carbide single crystal growth apparatus having a porosity of 70% or more of the porous graphite. The method of claim 7,
The porous graphite is a silicon carbide single crystal growth apparatus having a length of 0.5 to 1mm. The method according to any one of claims 4 to 8,
Silicon carbide single crystal growth apparatus in which the inside of the crucible is heated to a temperature of 2000° C. to 2300° C. by a heating means under atmospheric pressure so that the porous graphite can control radiant heat emitted from the inner wall of the crucible in the crystal growth section to serve as a heat reflection.

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