JP2006143497A - Apparatus for manufacturing silicon carbide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing a silicon carbide single crystal, wherein the temperature distribution at a section for arranging a raw material for sublimation can be kept uniformly. <P>SOLUTION: The apparatus for manufacturing the silicon carbide single crystal has a vessel for accommodating the raw material for sublimation and a seed crystal arrangement part provided opposite to the raw material for sublimation, which are used for manufacturing the silicon carbide single crystal by recrystallizing the sublimated silicon carbide on a seed crystal. The vessel for accommodating the raw material for sublimation has a heat-insulating part at the bottom part of a part for accommodating the raw material for sublimation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing a silicon carbide single crystal.

  Silicon carbide single crystal is attracting attention as a substrate material for manufacturing semiconductor devices such as power devices, and further higher quality and larger size are demanded from current technological trends. One method for producing this silicon carbide single crystal is a method (an improved Rayleigh method) for growing a silicon carbide single crystal by a sublimation method. In the improved Rayleigh method, in order to increase the crystal size and improve the productivity, it is required to efficiently sublimate the raw material powder so that the temperature distribution in the raw material powder is as uniform as possible.

  Here, as shown in FIG. 11, a conventional silicon carbide single crystal manufacturing apparatus 110 has a container (crucible) 111 that can accommodate a sublimation raw material 104, a detachable attachment to the container 111, and a seed crystal 105. And a lid 112 that enables it. Moreover, in order to keep the inside of the container 111 at a high temperature, the outer periphery of the silicon carbide single crystal manufacturing apparatus 110 is covered with a heat insulating material 109. Further, in order to observe the temperature of the sublimation raw material 104 during crystal growth, a temperature measurement window 108 formed by providing a hole in the heat insulating material 109 is disposed below the container 111 (in the direction of gravity). Then, the sublimation raw material 104 is filled in the container 111, heated by a heating means (not shown) provided outside, and the sublimated silicon carbide is recrystallized on the seed crystal 105 to produce a silicon carbide single crystal. Is done.

  However, in the configuration of the conventional silicon carbide single crystal manufacturing apparatus 110, heat escapes from the temperature measurement window 108. Therefore, the temperature of the sublimation raw material 104 increases in the region near the temperature measurement window 108 of the sublimation raw material 104. There was a tendency to remain and solidify without sublimation. Further, since the temperature distribution in the sublimation raw material 104 is not uniform, the sublimation speed is not uniform, and this tends to adversely affect the quality of crystals.

Several techniques have been proposed as means for solving the above-mentioned problems (for example, refer to Patent Document 1). It has been difficult to effectively prevent the release of.
JP 7-330493 A

  In view of the above, there has been a demand for an apparatus capable of maintaining a uniform temperature distribution in the sublimation raw material placement portion of the silicon carbide single crystal production apparatus. That is, there has been a demand for a silicon carbide single crystal production apparatus capable of efficiently growing a silicon carbide single crystal and finally obtaining a large and high-purity silicon carbide single crystal.

The present invention relates to the following items:
(1) A container for containing a sublimation raw material for producing a silicon carbide single crystal by recrystallizing sublimated silicon carbide on a seed crystal, and a seed crystal arrangement portion provided facing the sublimation raw material A silicon carbide single crystal manufacturing apparatus comprising: a container for storing the sublimation raw material, comprising a heat insulating portion including a heat insulating layer at a bottom of the sublimation raw material storage portion.

(2) The silicon carbide single crystal manufacturing apparatus according to (1), wherein a member having a lower thermal conductivity than that of the container that houses the sublimation raw material is provided as the heat insulating layer in the heat insulating portion.

(3) The silicon carbide single crystal manufacturing apparatus according to (2), wherein the member having a lower thermal conductivity than the container for storing the sublimation raw material is 50% or less of the thermal conductivity of graphite at a high temperature in the sublimation method. .

(4) The silicon carbide single crystal manufacturing apparatus according to (1), wherein a gap is provided as the heat insulating layer in the heat insulating portion.

(5) When the height in the vertical direction of the silicon carbide single crystal manufacturing apparatus is L and the maximum thickness of the heat insulating portion is T, T / L is 0.01 or more. 4) The silicon carbide single crystal production apparatus according to any one of 4).

(6) The silicon carbide according to (1), wherein S2 / S1 is 0.2 or more and 1.1 or less when the projected area of the sublimation raw material powder is S1 and the projected area of the heat insulating layer is S2. Single crystal manufacturing equipment.

  ADVANTAGE OF THE INVENTION According to this invention, the silicon carbide single crystal manufacturing apparatus which can maintain the temperature distribution of the sublimation raw material arrangement | positioning part uniform is provided. That is, according to the present invention, there is provided a silicon carbide single crystal production apparatus capable of efficiently growing a silicon carbide single crystal and finally obtaining a large and high-purity silicon carbide single crystal.

  As a result of diligent research, the inventors of the present invention have provided a heat insulating portion provided with a heat insulating layer made of a member having a low thermal conductivity or a gap between the sublimation raw material powder and the temperature observation window at the bottom of the container that contains the sublimation raw material. It has been found that the heat flow from the sublimation raw material powder to the observation window can be suppressed by providing. Hereinafter, embodiments of the present invention will be described with reference to the drawings. Needless to say, the present invention is not limited to the following embodiments. Moreover, what has the same function attaches | subjects the same code | symbol, and abbreviate | omits description.

  As shown in FIG. 1, a silicon carbide single crystal manufacturing apparatus 10 according to an embodiment of the present invention includes a container 11 that can contain a sublimation raw material 4, a detachable attachment to the container 11 and a seed crystal 5. And a lid 12 that enables it. Furthermore, heat insulating materials 9a, 9b, and 9c are disposed on the outer periphery of the silicon carbide single crystal manufacturing apparatus 10, and a temperature measurement window 8 of the container 11 is provided below the container 11 (in the direction of gravity). . Further, a heat insulating part 6 is provided between the sublimation raw material 4 and the temperature observation window 8 at the bottom of the container 11.

  Here, the container 11 is not particularly limited as long as it can form a silicon carbide sublimation atmosphere inside the container 11. For example, a crucible can be used as the container 11, and the material thereof is preferably graphite, and more preferably a material whose thermal expansion coefficient is substantially the same as that of the seed crystal. From the viewpoint of easily storing the sublimation raw material 4, it is preferable that the container 11 and the lid 12 are detachably and integrally formed. As the joining means, any joining means may be used as long as the airtightness inside the container 11 is maintained. Examples of the joining means include screwing means as shown in FIG.

  Moreover, as the lid | cover 12, what makes the seed crystal 5 of a silicon carbide single crystal installable, the thing whose material is graphite is preferable, and what has a thermal expansion coefficient substantially the same as a seed crystal is further more preferable.

  The heat insulating part 6 is not particularly limited as long as it can control the release of heat from the temperature observation window, but preferably includes a heat insulating layer 6a and a heat insulating part forming member 6b. The heat insulating layer 6 a is formed by, for example, disposing a member having a lower thermal conductivity than the gap or the container 11 in the heat insulating portion 6. The heat insulating part forming member 6b can be the same member as the container 11. As the member having a lower thermal conductivity than the container 11, it is convenient to arrange a member having a thermal conductivity of 50% or less, more preferably 20% or less, of the thermal conductivity of graphite at a high temperature in the sublimation method. The lower limit of the thermal conductivity is not particularly limited, but is about 10% of the thermal conductivity of graphite at a high temperature in the sublimation method. In addition, the thermal conductivity of graphite is 20-40 W / mk.

  As shown in FIG. 2A, when the height in the longitudinal direction (gravity direction) of the silicon carbide single crystal manufacturing apparatus 10 is L and the maximum thickness of the heat insulating layer 6a is T, T / L is It is convenient that it is 0.01% or more, more preferably 8% or more.

  Further, as shown in FIG. 2B, when the projected area of the sublimation raw material 4, that is, the internal area of the container 11 is S1, and the projected area of the heat insulating layer 6a is S2, S2 / S1 is 20%. It is preferable that it is 110% or less.

  A method for attaching the heat insulating portion 6 is not particularly limited as long as a soaking effect can be obtained. For example, as shown in FIG. 3, the heat insulating portion is provided in a hollow portion provided at the bottom of the container 11 and having a thread on the inner wall. The method of attaching 6 to a screw-in type is mentioned.

  Next, the operational effects of the first embodiment will be described in comparison with a conventional silicon carbide single crystal manufacturing apparatus. FIG. 12 is a diagram showing the heat flow in the conventional (without voids) silicon carbide single crystal manufacturing apparatus 110. In the normal sublimation method, the side wall of the container 111 (crucible) is mainly heated by induction heating. The heat is transferred to the side wall and bottom of the container 111, and part of the heat is transferred to the sublimation raw material 104, but most of the remaining heat escapes from the temperature measurement window 108 to the outside.

  However, as shown in FIG. 4, according to the first embodiment, most of the heat transferred to the bottom of the container 11 is transferred to the sublimation raw material 4, so that the sublimation raw material 4 can be heated more uniformly. Become. That is, since the sublimation raw material 4 is effectively sublimated, the silicon carbide single crystal 6 grows efficiently, and finally a large and high-purity silicon carbide single crystal is obtained.

(Modification of the embodiment)
Next, a modification of the embodiment will be described:
In the said embodiment, the heat insulation part 6 was set as the structure attached to the container 11 by screwing type. However, the attachment method of the heat insulation part 6 is not limited to a screwing type. For example, as shown in FIGS. 5 and 6, the lid 12 may be removed and the heat insulating portion 6 may be disposed on the bottom of the container 11 through the opening of the container 11.

  Moreover, the cross-sectional shape of the heat insulation part demonstrated by embodiment is not restrict | limited in particular. Therefore, the cross-sectional shape of the heat insulating portion can be the shape shown in FIGS.

  That is, as shown in FIG. 7, the heat insulation part 26 provided with the heat insulation layer 26a which is the cross-sectional shape which rotated the character D 90 degree clockwise can be arrange | positioned. With such a configuration, the effect of concentrating radiant heat at the center of the bottom of the crucible is obtained by the concave lens effect. Moreover, as shown in FIG. 8, the heat insulation part 36 provided with the protrusion-shaped heat insulation part formation member 36b and the heat insulation layer 36a which were each provided along the isothermal line in a raw material powder is arrange | positioned, and the temperature distribution in a raw material powder Can also be achieved. As shown in FIG. 9, it is possible to increase the soaking effect by arranging the heat insulating portion 46 formed so that the thickness of the heat insulating portion forming member 46 b is thick at the center of the container 11. As shown in FIG. 10, it is possible to increase the soaking effect by arranging a heat insulating portion 56 including a heat insulating layer 56 a formed in a step shape so as to be thick at the center of the container 11.

(Method for producing silicon carbide single crystal)
As mentioned above, although the embodiment of the silicon carbide single crystal manufacturing apparatus of this invention was described, the manufacturing method of a silicon carbide single crystal is provided as another form of this invention.
That is, as another embodiment of the present invention, the sublimation raw material is housed in a container containing the sublimation raw material, the seed crystal is disposed substantially opposite to the sublimation raw material, and the sublimated raw material is sublimated on the seed crystal. A method for producing a silicon carbide single crystal that is recrystallized to grow a silicon carbide single crystal, which is formed integrally with the aforementioned container at the bottom of a container that contains the sublimation raw material when sublimating the sublimation raw material. There is provided a method for producing a silicon carbide single crystal in which a heat insulating portion having a heat insulating layer is disposed.

  When implementing this manufacturing method, it is preferable to use the above-mentioned silicon carbide single crystal manufacturing apparatus described with reference to the embodiment and its modifications.

A conventionally known material can be used as a raw material for sublimation. As a sublimation raw material, for example, a high purity tetraethoxysilane polymer is used as a silicon source, a resol type phenol resin is used as a carbon source, and a mixture obtained by uniformly mixing these is heated and fired in an argon atmosphere. Silicon carbide powder can be used. A conventionally known single crystal can be used as the seed crystal of the silicon carbide single crystal.
The heating conditions such as the heating temperature of the sublimation raw material are not particularly limited, and can be appropriately set by those skilled in the art based on known techniques.

(Silicon carbide single crystal)
The silicon carbide single crystal of the present invention is produced by the aforementioned method for producing a silicon carbide single crystal:
In the silicon carbide single crystal of the present invention, crystal defects (pipe defects) evaluated by etching with molten alkali are preferably 100 pieces / cm ² or less, more preferably 50 pieces / cm ² or less. It is particularly preferable that the number of particles / cm ² or less.
The total content of metal impurity elements in the silicon carbide single crystal is preferably 10 ppm or less.

  The silicon carbide single crystal obtained by the present invention is free from crystal defects such as polycrystals, polymorphs, and micropipes, and is extremely high quality. Therefore, the silicon carbide single crystal is excellent in dielectric breakdown characteristics, heat resistance, radiation resistance, etc. It is particularly suitably used for electronic devices such as wafers and optical devices such as light emitting diodes.

  As described above, according to the silicon carbide single crystal production apparatus of the present invention, a high-quality silicon carbide single crystal can be produced easily and efficiently without being damaged such as cracks.

(Examples 1-6)
First, the silicon carbide single crystal manufacturing apparatus (Examples 1-6) of FIG. 1 provided with the heat insulation part of the conditions shown in Table 1 was prepared. Next, the apparatus of FIG. 1 was heated by providing heating means provided outside the apparatus (not shown). And the temperature of the center part (A point in a figure) of a container bottom part and the side wall vicinity (B point in a figure) of a container bottom part was measured. From the obtained measured values, the distance from point A was plotted on the X axis, and the temperature difference between points A and B was plotted on the Y axis in FIG.

(Comparative Example 1)
Experiments were performed in the same manner as in Examples 1 to 6 except that a conventional silicon carbide single crystal manufacturing apparatus (Comparative Example 1) without the heat insulating portion of FIG. 11 was used. The obtained experimental results are summarized in Table 1.

  In the embodiment, the temperature at the center (point A) is higher than that of the comparative example, and the bottom temperature is made uniform. And when the heat conductivity of a heat insulation layer is 20% of a crucible material, and when a space | gap is arrange | positioned as a heat insulation layer, a temperature distribution has a substantially the same effect. However, when the thermal conductivity of the heat insulating layer is 50% or less of the crucible material (graphite), when the thickness of the heat insulating layer (void) is small (1% or less compared to the crucible thickness), when the area is small (inside the crucible) The soaking effect is reduced to 20% or less of the area).

The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 10 concerning embodiment of this invention is shown. (A) The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 10 concerning embodiment of this invention is shown.

(B) A1-A1 schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 10 concerning embodiment of this invention is shown.
The schematic sectional drawing which shows the method of attaching the heat insulation part 6 to the silicon carbide single crystal manufacturing apparatus 10 concerning embodiment of this invention is shown. The flow of the heat in the silicon carbide single crystal manufacturing apparatus 10 concerning embodiment of this invention is shown. The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 80 concerning the modification of embodiment of this invention is shown (the 1). The schematic sectional drawing which shows the method of attaching the heat insulation part 6 to the silicon carbide single crystal manufacturing apparatus 10 concerning the modification of embodiment of this invention is shown. The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 20 concerning the modification of embodiment of this invention is shown (the 2). The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 30 concerning the modification of embodiment of this invention is shown (the 3). The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 40 concerning the modification of embodiment of this invention is shown (the 4). The schematic sectional drawing of the silicon carbide single crystal manufacturing apparatus 50 concerning the modification of embodiment of this invention is shown (the 5). The schematic sectional drawing of the conventional silicon carbide single crystal manufacturing apparatus 110 is shown. The heat flow in the conventional silicon carbide single crystal manufacturing apparatus 110 is shown. The temperature distribution inside a silicon carbide single crystal manufacturing apparatus is shown.

Explanation of symbols

4, 104 ... Raw materials for sublimation 5, 105 ... Seed crystals 6, 26, 36, 46, 56, 86, 106 ... Heat insulation parts 6a, 26a, 36a, 46a, 56a, 86a ... Heat insulation layers 6b, 26b, 36b, 46b , 56b, 86b ... heat insulating portion forming member 8, 108 ... temperature observation window 9, 109 ... heat insulating material 10, 110 ... silicon carbide single crystal 10, 20, 30, 40, 50, 60, 80, 110 ... silicon carbide single Crystal manufacturing apparatus 11, 111 ... container 12, 112 ... lid (seed crystal placement part)

Claims (6)

A container for containing a sublimation raw material for producing a silicon carbide single crystal by recrystallizing sublimated silicon carbide on a seed crystal, and a seed crystal arrangement portion provided facing the sublimation raw material A silicon carbide single crystal manufacturing apparatus,
The container for storing the sublimation raw material includes a heat insulating portion including a heat insulating layer at the bottom of the sublimation raw material storage portion.   The silicon carbide single crystal manufacturing apparatus according to claim 1, wherein a member having a lower thermal conductivity than that of the container containing the sublimation raw material is provided as the heat insulating layer in the heat insulating portion.   3. The silicon carbide single crystal production according to claim 2, wherein the member having a lower thermal conductivity than the container for containing the sublimation raw material is 50% or less of the thermal conductivity of graphite at a high temperature in the sublimation method. apparatus.   The silicon carbide single crystal manufacturing apparatus according to claim 1, wherein a gap is provided as the heat insulating layer in the heat insulating portion.   The T / L is 0.01 or more, where L is the height in the vertical direction of the silicon carbide single crystal manufacturing apparatus and T is the maximum thickness of the heat insulating layer. 4. The silicon carbide single crystal production apparatus according to any one of 4 above.   The carbonization according to claim 1, wherein S2 / S1 is 0.2 or more and 1.1 or less, where S1 is a projected area of the sublimation raw material powder and S2 is a projected area of the heat insulating layer. Silicon single crystal production equipment.

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