JP2004224663A - Apparatus for growing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a highly efficient growth apparatus which can increase a growth amount L and a magnification rate α of the diameter of a crystal, can grow the crystal without deteriorating the crystal quality, is simple in configuration and can reduce a production cost. <P>SOLUTION: The apparatus for growing the single crystal houses the raw material of the single crystal to be grown into a vessel, projects a portion of the inner wall surface of the vessel facing the raw material toward the raw material side as a pedestal to support a seed crystal and grows the single crystal on the seed crystal by heating and sublimating the raw material. The pedestal is provided with a conical guide which is connected with a small-diameter part thereof to the pedestal and is formed into a conical shape provided with a large-diameter part toward the inner wall surface of the vessel. A clearance is formed between the large-diameter part of the conical guide and the inner wall surface of the vessel. In the apparatus for growing the single crystal, the clearance between the large-diameter part of the conical guide and the inner wall of a crucible is 0.1 to 5 mm and the length in the height direction of the clearance is 0.1 to 20 mm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for growing a single crystal such as silicon carbide.
[0002]
[Prior art]
Silicon carbide single crystal (SiC) is excellent in thermal and chemical properties, and has excellent electrical properties such as a large band gap compared to Si semiconductors. Therefore, semiconductors for high-power, high-temperature, high-frequency devices It is attracting attention as a material. Large-sized bulk crystal growth for the purpose of manufacturing a hexagonal SiC wafer is performed by sublimation recrystallization in which a raw material is heated and sublimated to grow on a seed crystal (improved Lely method: described in J. Cryst. Growth 43 (1978) 209). This is generally done by:
FIG. 5 shows an example of the most common growth apparatus in recent years in the sublimation recrystallization method (hereinafter, referred to as “prior art 1”). The SiC seed crystal 3 is placed and fixed on the lid 2. When the SiC raw material 4 is heated and sublimated, the sublimation gas is recrystallized on the facing seed crystal 3, and the SiC single crystal 5 grows. By the way, as a SiC single crystal substrate for manufacturing a semiconductor device, a substrate having a diameter of about 2 inches is currently on the market. However, a SiC single crystal substrate having a larger diameter is required to improve mass productivity. I have.
[0003]
On the other hand, as shown in FIG. 6, there has been proposed a growth apparatus in which a pedestal protruding from a lid is formed and a seed crystal is placed and fixed on the pedestal (for example, see Patent Documents 1 and 2). In this apparatus, the seed crystal 3 is placed and fixed on a pedestal 7 formed at the center of the lower surface of the lid 2, so that a single crystal 5 growing on the seed crystal 3 and a polycrystal 6 deposited around the pedestal 7. Are delayed, and the diameter expansion rate α of the grown crystal is increased (hereinafter referred to as “prior art 2”).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 1-305898 [Patent Document 2]
JP 10-36195 A [Patent Document 3]
JP-A-2002-60297
[Problems to be solved by the invention]
However, in the prior art 1, since the seed crystal 3 is directly bonded to the lid 2, the polycrystal 6 deposited on the surface of the lid 2 around the seed crystal 3 and the single crystal 5 grown on the seed crystal 3 Contact. For this reason, there is a problem that the diameter expansion of the grown crystal is hindered.
Further, in the prior art 2, it is possible to delay the contact timing between the single crystal 5 and the polycrystal 6, but as the growth progresses, the single crystal and the polycrystal eventually come into contact as shown in FIG. However, there is a problem that the diameter of the grown crystal is prevented from further increasing.
On the other hand, it is well known that when a polycrystal comes into contact with a single crystal, strain is introduced from the interface toward the single crystal, and a defect called a macro defect (described in Physica B 185 (1993) 211) also occurs. . These phenomena are considered to cause the crystallinity of the grown crystal to be remarkably deteriorated, so that semiconductor-grade crystal quality cannot be achieved.
[0006]
In order to solve these problems, the present inventors have previously disclosed in Japanese Patent Application No. 2000-249634 (see Patent Document 3) that a single crystal can be separated and grown to improve crystal quality and promote diameter expansion. A growth apparatus has been proposed (hereinafter referred to as “prior art 3”). In this growth apparatus, the single crystal 5 is enlarged and grown on the seed crystal 3 while being separated from the polycrystal 6 by the guide member 8 as shown in FIG. By guiding the flow of the sublimation gas from the SiC raw material 4 by the guide member 8, the growth of the single crystal is predominantly caused, and the deposition of the polycrystal 6 is effectively delayed, so that the separation state can be grown for a long time. The feature is that it is possible. With this growth apparatus, a growth amount L = 12 cm and a diameter expansion rate α = 30 ° are achieved.
It is another object of the present invention to provide a high-efficiency growth apparatus that can increase the growth amount L and the crystal diameter expansion rate α and that can grow without deteriorating the crystal quality, has a simple configuration, and can reduce the production cost. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a single crystal growth apparatus of the present invention accommodates a raw material for a grown single crystal in a container, and projects a part of the inner wall surface of the container facing the raw material toward the raw material to form a seed crystal. In a device for growing a single crystal on the seed crystal by heating and sublimating the raw material as a supporting pedestal, connect the small-diameter portion of the cone-shaped guide to the pedestal and form the large-diameter portion conically toward the inner wall surface of the container. And a gap is formed between the large-diameter portion of the cone-shaped guide and the inner wall surface of the container.
In addition, the single crystal growth apparatus of the present invention sets the gap between the large diameter portion of the cone-shaped guide and the inner wall of the crucible to 0.1 to 5 mm, and sets the length of the gap in the height direction to 0.1 to 20 mm. It is characterized by the following.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a crystal growth apparatus used in the method of the present invention, which is an example of an apparatus for growing single-crystal silicon carbide (SiC) by sublimation recrystallization on a seed crystal by an improved Lely method.
The apparatus mainly includes a crucible 1 and a lid 2 constituting a container, a pedestal 7 projecting downward from the lid 2, and a cone-shaped guide 9. The crucible 1 is mainly composed of columnar and cylindrical graphite, and forms a quasi-enclosed space in which the upper part of the crucible is closed by a lid 2 also made of graphite. The silicon carbide (SiC) raw material 4 is loaded in the lower portion of the crucible 1, and the seed crystal 3 is mounted and fixed on the lower end surface of a pedestal 7 sufficiently protruding from the lid 2. I do. The diameter of the pedestal 7 is approximately 略 to の of the inner diameter of the crucible 1.
[0009]
The cone-shaped guide 9 has a conical structure in which a small-diameter portion is integrated with the pedestal 7, and a large-diameter portion is provided toward the inner wall surface of the container. The inner wall surface 10 of the crucible 1 is not in contact with the inner wall 10 at a distance of the gap d. The gap d is maintained at the inner wall surface of the crucible and the large-diameter portion of the cone-shaped guide 9 over the length h in the height direction. The gap d and its length h in the height direction are for controlling the amount of the raw material gas flowing into the space 11 around the pedestal of the lid 2.
[0010]
FIG. 2 shows the relationship between the gap d and the length h and the polycrystal precipitated in the space 11. As is clear from FIG. 2, by reducing the gap d and increasing the length h, the amount of gas flowing into the space 11 is reduced, and the deposition rate of the polycrystal 6 that precipitates in the space 11 around the pedestal 3 is reduced. Therefore, only the single crystal 5 precipitated in the cone-shaped guide 9 can be more efficiently grown.
[0011]
On the other hand, the change in the precipitation ratio of the single crystal 5 and the polycrystal 6 changes the spatial structure in the container, and the temperature distribution in the entire container such as the crucible 1 and the lid 2 changes. FIG. 3 illustrates the relationship between the surface shape of the single crystal, the gap d, and the length h. The surface shape of the growing single crystal 5 changes greatly from convex to flat. That is, when the gap d is narrow and the length h is long, the surface shape of the single crystal becomes convex, and conversely, when the gap d is wide and the length h is short, the surface shape of the single crystal becomes flat. This change in surface shape greatly affects the crystallinity. Generally, when the surface is flat, defects grow at the center of the crystal, and when the shape is convex, a large strain is generated from the center of the single crystal toward the outside. Therefore, in order to reduce the deposition rate of the polycrystal 6 that precipitates in the space 11 around the pedestal 3 and to form an appropriate surface shape, the gap d and the height h of the gap should be set in what range. Becomes important.
[0012]
From FIG. 2, it is desired that the gap d is narrow and the length h is long in order to reduce the deposition rate of the polycrystal 6. Further, from FIG. 3, the surface shape of the single crystal is markedly flattened when the gap d is 5 mm and the length h is around 0.1 mm, and conversely, when the gap d is 0.1 mm and the length h is around 20 mm. It can be seen that the convex shape becomes remarkable. From these facts, in order to reduce the deposition rate of the polycrystal 6 and to make the surface shape of the single crystal appropriate, the gap d should be in the range of 0.1 to 5 mm and the length h should be 0. It is desirable to set it in the range of 0.1 to 20 mm.
[0013]
The cone-shaped guide 9 has a shape spread at an angle θ with respect to the surface of the pedestal 7. As shown in FIG. 4, the spread angle θ of the cone-shaped guide 9 affects the magnification α of the single crystal 5, the surface shape, and the amount of polycrystal adhered to the inner wall of the guide. By increasing the angle θ, the magnification of the grown crystal can be increased, and a large-diameter crystal can be obtained by one-time growth. However, the rapid expansion of the diameter causes distortion of the crystal.
FIG. 4 is a diagram for explaining the relationship between the angle of spread θ of the cone-shaped guide 9 and the enlargement ratio, surface shape, and polycrystal adhesion on the inner wall of the cone-shaped guide.
According to FIG. 4, when the angle θ is 60 ° or more, the polycrystal 6 adheres to the inner wall of the cone-shaped guide 9 and the expansion of the single crystal 5 may be hindered. It is desirable that θ ≦ 60 °.
In addition, the change in the surface shape of the single crystal 5 due to the angle θ has a large effect of the gap d and the length h of the gap in the height direction or more, and considering the crystallinity, 20 ° ≦ θ ≦ 50 °. Is appropriate.
Furthermore, an appropriate enlargement ratio from the viewpoint of not giving a strain to the crystal, that is, not deteriorating the crystallinity, and increasing the efficiency of the crystal enlargement ratio is 30 ° ≦ θ ≦ 60 °.
Therefore, the angle θ of the spread of the cone-shaped guide 9 is appropriately set according to the purpose of use of the obtained single crystal, but in consideration of the above, the angle θ of the cone-shaped guide 9 becomes , 30 ° ≦ θ ≦ 50 °.
[0014]
As the silicon carbide raw material 4, SiC powder obtained by the Acheson method or chemical synthesis is usually used. As the seed crystal 3, a SiC single crystal obtained by the Acheson method or the Lely method, or a SiC single crystal grown from the Acheson crystal or the Lely crystal by the sublimation method is used. Seed crystal 3 has a thickness of 0.1 to 30 mm.
[0015]
The crystal is grown by heating the crucible in a high-purity Ar gas atmosphere using a high-frequency furnace, a resistance heating furnace, an infrared furnace, or the like. Is controlled while measuring with a color thermometer. At this time, the temperature of the seed crystal and the temperature of the raw material are controlled at 2000 to 2500 ° C., and the temperature gradient (Tb-Ta) between the raw material and the seed crystal is controlled at 0 to 20 ° C./cm. Crystal growth is started by reducing the pressure inside the growth apparatus after heating to the above-mentioned controlled temperature, and is performed by maintaining a constant pressure at 1 to 100 Torr. By performing growth under the above conditions using this apparatus, only the single crystal 5 grows on the seed crystal 3, and the polycrystal 6 is completely separated and deposited on the periphery of the pedestal 7.
[0016]
【Example】
As shown in FIG. 1, the crucible 1 has an inner diameter of 75 mm, the pedestal 7 protruding from the lid 2 is a column having a diameter of 45 mm and a height of 10 mm, and a seed crystal 3 having a diameter of 45 mm and a thickness of 1 mm is placed on the pedestal 7. It grew stuck. The cone-shaped guide 9 had an angle θ of 45 °, a gap d with the crucible 1 of 1 mm, and a height h of an outer peripheral surface of the cone-shaped guide 9 in a height direction of 2 mm. The seed crystal 3 was a disc-shaped hexagonal SiC single crystal prepared by a sublimation method, and the orientation of the growth plane was the (0001) plane. The crucible 1 was first supported in a high-frequency furnace, and the pressure in the furnace was reduced to 2 × 10 ⁻⁵ Torr. Thereafter, the pressure was increased to 700 Torr with high purity Ar, and the temperature of the seed crystal 3 was increased to 2200 ° C. After the temperature of the seed crystal 3 reached the target value, the inside of the furnace was decompressed to 10 Torr to start growth, and after holding for 70 hours, the pressure was raised to normal pressure and cooled, and the single crystal 5 was taken out. The single crystal 5 grew long with the growth amount L = 31 mm, and the diameter was expanded to φ = 63 mm. The aperture enlargement rate α is 45 °, which is the same as the angle θ of the cone-shaped guide 9. Furthermore, the surface shape of the single crystal was also appropriate. At this time, the amount of the polycrystal 6 precipitated around the pedestal was small and did not come into contact with the cone-shaped guide 9, and the single crystal 5 grew completely separated from the polycrystal 6.
[0017]
The diameter expansion rate α of the crystal depends on the angle θ of the cone-shaped guide 9, and as θ increases, the diameter expansion rate α of the single crystal 5 increases at the same angle. However, depending on the size of the crucible 1, the heating conditions, the growth atmosphere, and the temperature conditions, polycrystals adhere to the inner wall of the cone-shaped guide 9 at a high angle of θ> 60 ° or more, and it is difficult to grow the single crystal 5 alone. There was a case. Therefore, according to the growth conditions, while adjusting the polycrystal to the cone-shaped guide 9 so as not to deteriorate the crystallinity, θ is adjusted so that the diameter expansion rate α becomes the largest.
The angle θ of the conical guide 9 also affects the shape of the crystal growth surface. As θ approaches 0, the surface of single crystal 5 becomes smoother, and as θ approaches 90 °, the surface becomes convex in the growth direction.
[0018]
Also, the gap d between the cone-shaped guide 9 and the crucible 1 and the length h in the height direction of the outer peripheral surface that forms the distance between the cone guide 9 and the crucible 1 change the amount of the polycrystal 6 attached to the periphery of the pedestal. When the gap d is narrow and the length h of the gap in the height direction is increased, the adhesion of the polycrystal 6 is reduced. The attached amount of the polycrystal 6 affects the surface shape of the growing single crystal 5 in the same manner as the effect of the angle θ of the cone-shaped guide 9 described above.
[0019]
Since the surface shape affects the crystallinity of the single crystal 5, θ, d, and h are controlled to adjust the surface to an optimal shape in which the single crystal 5 can be prevented from being deteriorated.
As described above, it is possible to perform more efficient growth of the diameter while separating only the single crystal in a good quality state.
[0020]
【The invention's effect】
The present invention has the following effects.
(1) In a crystal growth apparatus in a sublimation recrystallization method in which a cone-shaped guide is attached to a base for fixing a seed crystal, a single crystal and a polycrystal are completely separated while increasing the diameter expansion rate α, and the crystal quality is improved. A growth apparatus capable of growing without deterioration is enabled.
(2) It enables long single crystal growth.
(3) It is possible to contribute to the growth efficiency and the mass productivity of single crystal wafers by enabling a high diameter expansion rate and a long growth crystal.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing a single crystal growing apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a relationship between a gap d and a length h and a polycrystal precipitated in a space 11;
FIG. 3 is a diagram illustrating a relationship between a gap d and a length h and a surface shape of a single crystal.
FIG. 4 is a diagram illustrating the relationship between the angle of spread θ of the cone-shaped guide, the magnification of the single crystal 5, the surface shape, and the attachment of polycrystal to the inner wall of the cone-shaped guide.
FIG. 5 is a front sectional view showing a conventional technique 1 in the sublimation recrystallization method.
FIG. 6 is a front sectional view showing Conventional Technique 2 in the sublimation recrystallization method.
FIG. 7 is a front sectional view showing a conventional technique 3 in the sublimation recrystallization method.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 crucible 2 lid 3 seed crystal 4 silicon carbide raw material 5 single crystal 6 polycrystal 7 pedestal 9 cone-shaped guide 10 inner wall 11 of crucible 11 space around pedestal θ angle of cone-shaped guide α single crystal diameter expansion rate L single crystal Growth amount d Gap between inner wall of crucible and cone guide h Length of gap in height direction

Claims (2)

A raw material for a growing single crystal is accommodated in a container, and a part of the inner wall surface of the container facing the raw material is protruded toward the raw material side to form a pedestal for supporting a seed crystal. In the apparatus for growing a single crystal, a cone-shaped guide having a small diameter portion of a cone-shaped guide connected to the pedestal and a large-diameter portion formed conically toward the inner wall surface of the container is provided, and the large-diameter portion of the cone-shaped guide is provided. A single crystal growing apparatus, wherein a gap is formed between the inner wall surface and the inner wall surface of the container. 2. The gap between the large diameter portion of the cone-shaped guide and the inner wall surface of the container is set to 0.1 to 5 mm, and the length of the gap in the height direction is set to 0.1 to 20 mm. Single crystal growth equipment.

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