JP2000044383A - Growth unit for single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growth unit designed to afford a continuous and large- diameter single crystal through raising the radial growth rate of the single crystal. SOLUTION: This growth unit has such a scheme that, a silicon carbide single crystal substrate 5 serving as a seed crystal is placed opposite to silicon carbide powder 4 as feedstock in a crucible 2; between the substrate 5 and the silicon carbide powder 4, a heat-shielding member 6 enclosing the substrate 5 so that a gas is passable under the substrate 5 and defining a space inside where a single crystal grows is set up to ensure a silicon carbide single crystal 7 to be grown while shielding the substrate 5 from the radiant heat emitted from the silicon carbide powder 4; wherein the heat-shielding member 6 is tapered so that its diameter becomes larger downward, that is, the diameter of the above-mentioned space becomes larger toward the side of the silicon carbide powder 4, thereby ensuring the radial growth of the single crystal to be greater through suppressing the change in the temperature gradient in the vicinity of the side face of the silicon carbide single crystal 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single crystal growing apparatus used for growing a single crystal such as silicon carbide.

[0002]

2. Description of the Related Art Silicon carbide single crystals have excellent electrical and mechanical properties and are useful as substrate materials for semiconductor devices. As a method for producing a silicon carbide single crystal, a sublimation method is generally used. A seed crystal and a raw material powder are arranged opposite to each other in a graphite crucible, and the raw material powder is heated and a sublimated gas is introduced onto the seed crystal. I do. A temperature difference is provided in the crucible so that the seed crystal is lower in temperature than the raw material powder, and the sublimation gas is recrystallized on the lower temperature seed crystal to grow a single crystal.

In order to efficiently grow a single crystal by the sublimation method, it is effective to control the temperature, the atmospheric pressure, the flow of the sublimation gas, and the like in the crucible, and various apparatuses have been conventionally proposed. For example, JP-A-8-295595 discloses an apparatus in which a heat shielding member is provided between a raw material powder and a seed crystal in order to keep the temperature of the seed crystal low. Referring to FIG. 8, the crucible 2 of the single crystal growing apparatus 1 is filled with a silicon carbide raw material powder 4 at the bottom, and a silicon carbide single crystal substrate 5 serving as a seed crystal is placed on a pedestal 3a opposed thereto. Are joined. Between the raw material powder 4 and the silicon carbide single crystal substrate 5, a bottomed cylindrical heat shielding member 9 is arranged so as to surround the lower part of the silicon carbide single crystal substrate 5, and carbonized by radiant heat of the raw material powder 4. The silicon single crystal substrate 5 is protected. By providing heat shielding member 9 in this manner, it is possible to suppress a rise in temperature of silicon carbide single crystal substrate 5, increase the temperature difference, and grow silicon carbide single crystal 7 efficiently.

Japanese Patent Laid-Open Publication No. Hei 8-325099 discloses a concentrated pipe having an inner diameter gradually decreasing upward between a container in which raw material powder is stored and a lid in which seed crystals are arranged. An interposed device is disclosed, and a sublimation gas is concentrated and guided on a seed crystal, thereby enabling efficient growth of a single crystal.

[0005]

By the way, in order to enhance the effect of mass production of semiconductor devices using a silicon carbide substrate, a silicon carbide single crystal substrate having a larger diameter is required.
However, in the above-described conventional method, a long silicon carbide single crystal can be obtained by increasing the growth rate in the direction perpendicular to the surface of the seed crystal, but the effect of increasing the diameter is small. For this reason, in order to obtain a single crystal having a large diameter, it was necessary to repeatedly grow a single crystal on a seed crystal cut out from the grown single crystal and gradually increase the diameter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a single crystal growth apparatus capable of increasing the radial growth rate of a growing single crystal to obtain a long single crystal having a large diameter.

[0007]

In order to solve the above-mentioned problems, a single crystal growing apparatus of the present invention comprises a seed crystal and a raw material powder arranged in a vessel so as to face each other. And a heat shielding member is provided between the raw material powder and the single crystal to grow on the seed crystal while protecting the seed crystal from radiant heat when the raw material powder is heated and sublimated. The heat shielding member surrounds the seed crystal in a gas-flowable manner to form a space in which a single crystal grows, and the diameter of the single crystal growth space is from the seed crystal side toward the raw material powder side. (Claim 1).

When the heat shielding member is installed so as to surround the single crystal growth space, and a temperature difference is provided between the heat shielding member and the seed crystal, the temperature of the seed crystal becomes relatively low. A single crystal grows. At this time, a temperature difference occurs not only in the direction perpendicular to the seed crystal surface but also in the radial direction,
Single crystals also grow in the radial direction. Moreover, since the heat shielding member of the present invention has a shape in which the diameter of the single crystal growth space increases from the seed crystal side toward the raw material powder side, even if the single crystal grows in the radial direction. A sufficient distance is maintained between the heat shielding member and the single crystal, and the radial growth rate does not decrease. Therefore, the growth rate in the vertical and radial directions can be increased, and a long single crystal having a large diameter can be obtained.

Preferably, the spread angle of the heat shielding member is in a range of 5 ° to 80 °. If the spread angle of the heat shielding member is less than 5 °, the spread angle of the grown crystal is small and the effect of increasing the diameter is small. On the other hand, if it exceeds 80 °, the spread angle does not increase, and there is no further effect of increasing the aperture.

The spread angle of the heat shielding member can be changed in two stages (claim 3). When it is desired to change the spread angle of the grown crystal during the growth, for example, when controlling the diameter of the grown crystal finally obtained, the spread angle of the heat shielding member may be changed. The spread angle of the heat shielding member may be changed continuously (claim 4).

[0011] It is also possible to adopt a structure in which a member for closing an opening between the heat shielding member and the side wall of the container is arranged on the outer periphery of the raw material side end (claim 5). Thereby, the gas in which the raw material powder has sublimated reaches between the heat shielding member and the side wall of the container, and it is possible to prevent the polycrystal from adhering to the heat shielding member or the side wall of the container. By preventing the polycrystal from adhering to these sites, the amount of sublimation gas contributing to single crystal growth increases, the single crystal growth rate increases, and the growth efficiency increases.

The space between the heat shielding member and the side wall of the container can be filled. Also in this case, the sublimation gas of the raw material powder can be prevented from reaching the heat shielding member or the side wall of the container and the polycrystal can be prevented from adhering to the side wall of the container, thereby increasing the single crystal growth rate. Growth efficiency.

[0013] In the structure of the sixth aspect, the heat shielding member and the container may have an integral structure. By integrating the heat shielding member and the container, the number of parts can be reduced, and the cost can be reduced.

[0014] The heat shielding member may have a configuration in which a widened side wall portion and a bottom wall portion parallel to the seed crystal surface are separated. The heat shielding member is divided into a side wall portion and a bottom wall portion,
The structure is simplified and the manufacturing cost can be reduced.

The heat shielding member is preferably made of, for example, graphite (claim 9) and is excellent in heat insulation and heat resistance. The single crystal produced by the single crystal growth apparatus of the present invention is specifically a silicon carbide single crystal (Claim 10), which has a large advantage due to a large diameter.

[0016]

FIG. 1 shows a first embodiment of the present invention. In the figure, a single crystal growth apparatus 1 has a bottomed cylindrical graphite crucible 2 serving as a container for single crystal growth, and a graphite lid 3 closing an upper end opening. Crucible 2
Is filled with silicon carbide powder 4 as a raw material powder, and pedestal 3 is formed by projecting a lower surface center portion of lid 3.
The silicon carbide single crystal substrate 5 serving as a seed crystal is joined to a. The silicon carbide single crystal substrate 5 is formed, for example, by processing a silicon carbide single crystal grown by Acheson method, sublimation method or the like into a wafer having a diameter of about 10 mm to 100 mm, and affixing the base 3a with an adhesive. Can be

A heat shielding member 6 is provided between silicon carbide single crystal substrate 5 and silicon carbide powder 4 so as to surround the outer periphery of silicon carbide single crystal substrate 5 and the space below silicon carbide single crystal substrate 5. It is arranged. The heat shielding member 6 is formed of a hollow container that expands in a tapered shape downward, and forms a sufficient space for growing a single crystal therein, and has a larger diameter toward the lower side. The growth of the single crystal in the radial direction is not hindered. The heat shielding member 6 is made of a material having excellent heat insulation properties, for example, graphite since the inside of the crucible 2 has a high temperature because of its high heat insulation. An opening 61 having a diameter slightly larger than the outer diameter of silicon carbide single crystal substrate 5 is formed on the upper end surface of heat shielding member 6, and the inner periphery of opening 61 is spaced apart from the outer periphery of silicon carbide single crystal substrate 5 by a predetermined distance. Are arranged to face each other. A plurality of gas flow holes 62 are formed in the lower end surface of heat shield member 6, and the sublimation gas of silicon carbide powder 4 can reach silicon carbide single crystal substrate 5 through gas flow holes 62. . The heat shielding member 6
The crucible 2 is formed by a flange 61 provided on the outer periphery of the upper end surface.
Is fixed to the inner wall.

When a single crystal is grown using the above apparatus, the crucible 2 is filled with the silicon carbide powder 4 and the silicon carbide single crystal substrate 5 is joined to the pedestal 3a. Attach to Next, the inside of the crucible 2 is evacuated, an inert gas such as an argon gas is introduced, and the atmosphere pressure is adjusted to be about 0.1 to several Torr. Further, crucible 2 is heated to a predetermined temperature by a heating device (not shown) to sublime silicon carbide powder 4 and generate a sublimation gas. At this time, the power introduced into the heating device is adjusted so that the temperature of raw material powder 4 is in the range of about 2000 to 2500 ° C., and crucible 2 is set so that silicon carbide single crystal substrate 5 has a lower temperature than silicon carbide powder 4. A temperature gradient is provided inside. The generated sublimation gas as a raw material passes through gas flow holes 62 of heat shield member 6, enters the single crystal growth space in heat shield member 6, and reaches silicon carbide single crystal substrate 5.

Here, a temperature gradient is provided in crucible 2 in the vertical direction in the figure, and silicon carbide single crystal 7 grows on silicon carbide single crystal substrate 5 at a relatively low temperature. In general, the growth amount and growth direction of a single crystal depend on the temperature near the growth surface,
Although it depends on the temperature gradient and the amount and flow of the sublimation gas, the main one is the temperature gradient near the growth surface.The greater the temperature gradient, the higher the degree of supersaturation of the sublimation gas, and the larger the growth amount per unit time. Become. When the heat shielding member 6 is not provided, the temperature gradient is only in the vertical direction and not in the radial direction. Therefore, the growth direction of the silicon carbide single crystal 7 is only in the direction perpendicular to the surface of the silicon carbide single crystal substrate 5 as a seed crystal. Does not grow in the radial direction. On the other hand, when heat shielding member 6 is provided, temperature of heat shielding member 6 rises due to heat radiation from silicon carbide powder 4, and the upper surface and side surfaces of heat shielding member 6 and the silicon carbide single crystal 7 at a high temperature become higher. Since a temperature gradient occurs in the radial direction due to the temperature difference, silicon carbide single crystal 7 can grow not only in the vertical direction but also in the radial direction.

However, in the case of the heat shield member 9 having a constant inner diameter as in the conventional apparatus shown in FIG. 8, the distance between the silicon carbide single crystal 7 and the heat shield member 9 becomes smaller as it grows in the radial direction. And the temperature gradient changes. In other words, when the distance is reduced, heat radiation from heat shielding member 9 is more greatly received, so that the temperature of the side surface of silicon carbide single crystal 7 increases. As a result, the temperature gradient near the side surface of silicon carbide single crystal 7 is reduced, and the growth amount in the radial direction is reduced. On the other hand, the heat shielding member 6 of the present invention has a shape that expands in a tapered shape downward, and is configured such that the inner single crystal growth space expands radially downward. ing. Therefore, even if grown in the radial direction, silicon carbide single crystal 7
The distance between the heat shield member 9 and the heat shield member 9 can be kept substantially constant, and the temperature gradient does not change, so that the growth can be continued in the radial direction.

Here, the shape of the heat shielding member 6 is the same as that shown in FIG.
The shape is not limited to this, and it is sufficient that the inner diameter increases downward, and the single crystal growth space formed in the heat shielding member 6 expands radially downward. Further, as shown in FIG. 2 as a second embodiment of the present invention, the spread angle θ of the heat shielding member 6 is preferably set in a range of 5 ° to 80 °. If the spread angle of the heat shielding member 6 is less than 5 °, the spread angle of the grown crystal is small and the effect of increasing the diameter is small. On the other hand, if it exceeds 80 °, the spread angle does not increase, and there is no further effect of increasing the aperture.

As shown in FIG. 3 as a third embodiment of the present invention, the spread angle of the heat shielding member 6 can be changed in two stages. Here, the spread angle of the upper portion of the heat shielding member 6 is θ1, and the spread angle of the lower portion is θ2.
<Θ2 is set so that the growth amount in the radial direction increases as the silicon carbide single crystal 7 grows downward. As described above, when it is desired to control the diameter of the finally grown crystal, for example, by changing the spread angle of the heat shielding member 6 stepwise, the spread angle of the grown crystal can be changed during the growth. it can. The spread angle of the heat shielding member is
Of course, it can be changed continuously. Another example of the shape of the heat shielding member 6 is shown below.

As shown in FIG. 4 as a fourth embodiment of the present invention, the heat shielding member 6 is formed between the side wall of the crucible 2 and the outer periphery of the end face (lower end face in the figure) on the silicon carbide powder 4 side. A configuration in which the gas shielding member 8 is arranged so as to close the formed annular opening may be adopted (claim 5). Gas shielding member 8 is made of, for example, graphite, and closes an opening between heat shielding member 6 and crucible 2 to prevent the sublimation gas of silicon carbide powder 4 from reaching above. This allows
Polycrystal can be prevented from adhering to the outer wall of the heat shielding member 6 and the inner wall of the crucible 2 and the sublimation gas contributing to the growth of the single crystal is increased, so that the single crystal growth rate is increased and the efficiency is improved. Single crystal growth is possible.

As shown in FIG. 5 as a fifth embodiment of the present invention, the heat shielding member 6 has a crucible having a single crystal growth space in which the diameter of the single crystal growth is tapered downward. The heat shield member 6 may be formed in a thick cylindrical shape that matches the inner diameter of the crucible 2 so as to fill the space between the crucible 2 and the side wall. Even in this case, the fourth
As in the first embodiment, it is possible to prevent the sublimation gas of silicon carbide powder 4 from reaching the space between heat shielding member 6 and crucible 2 and adhering the polycrystal. Therefore, the amount of sublimation gas contributing to single crystal growth is increased, the single crystal growth rate is increased, and efficient single crystal growth is possible.

As shown in FIG. 6 as a sixth embodiment of the present invention, the heat shielding member 6 and the crucible 2 may be integrated. In the present embodiment, the heat shield member 6 has a single crystal growth space in which the diameter is increased in a tapered shape downward,
It is formed in a thick cylindrical shape whose outer diameter matches the outer diameter of the crucible 2 and is provided integrally with the upper part of the crucible 2. Thus, by integrating the heat shielding member 6 and the crucible 2,
In addition to improving the single crystal growth efficiency by filling the space between the crucibles 2, the cost can be reduced by reducing the number of parts.

As shown in FIG. 7 as a seventh embodiment of the present invention, the heat shielding member 6 is formed by expanding the side wall portion 6a.
And a lower end surface portion 6b as a bottom wall portion parallel to the surface of silicon carbide single crystal substrate 5 as a seed crystal. These side wall portions 6a and lower end surface portions 6b
Are fixed to the inner wall of the crucible 2 respectively. By dividing the side wall portion 6a and the lower end surface portion 6b in this manner, the structure of the heat shielding member 6 can be simplified, and the manufacturing cost can be reduced.

As described above, according to the single crystal growth apparatus of the present invention, the growth rate in the direction perpendicular to the seed crystal surface and in the radial direction can be increased, and the silicon carbide is long and has a large diameter. A single crystal can be obtained. In addition, the single crystal manufacturing apparatus of the present invention is not limited to the growth of silicon carbide single crystal,
Any single crystal, such as cadmium sulfide, which can be grown by the sublimation method can be used.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a single crystal growth apparatus showing a first embodiment of the present invention.

FIG. 2 is an overall sectional view of a single crystal growth apparatus showing a second embodiment of the present invention.

FIG. 3 is an overall sectional view of a single crystal growth apparatus showing a third embodiment of the present invention.

FIG. 4 is an overall sectional view of a single crystal growing apparatus showing a fourth embodiment of the present invention.

FIG. 5 is an overall sectional view of a single crystal growing apparatus showing a fifth embodiment of the present invention.

FIG. 6 is an overall sectional view of a single crystal growing apparatus showing a sixth embodiment of the present invention.

FIG. 7 is an overall sectional view of a single crystal growing apparatus showing a seventh embodiment of the present invention.

FIG. 8 is an overall sectional view of a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal growth apparatus 2 Crucible (vessel) 3 Lid 3a Pedestal 4 Silicon carbide powder (raw material powder) 5 Silicon carbide single crystal substrate (seed crystal) 6 Heat shielding member 7 Silicon carbide single crystal (single crystal) 8 Gas shielding member (Member for closing the opening) 9 Heat shielding member

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroo Tosao 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Eiji Kitaoka 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Co., Ltd. Inside DENSO (72) Inventor Naohiro Sugiyama 41-Cho, Yokomichi, Nagakute-machi, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. F-term in Toyota Central Research Laboratory, Inc. (reference) 4G051 AA01 AA11 4G077 AA02 BE08 DA18

Claims (10)

[Claims] 1. A seed crystal and a raw material powder are arranged in a container so as to face each other, a heat shielding member is provided between the seed crystal and the raw material powder, and radiant heat generated when the raw material powder is heated and sublimated. In a single crystal growing apparatus for growing a single crystal on the seed crystal while protecting the seed crystal from, the heat shielding member,
A space in which a single crystal grows is formed by surrounding the seed crystal so as to allow gas to flow therethrough, and the diameter of the single crystal growth space increases in shape from the seed crystal side toward the raw material powder side. A single crystal growth apparatus characterized by the above-mentioned. 2. The single crystal growing apparatus according to claim 1, wherein the spread angle of the heat shielding member is 5 ° to 80 °. 3. The single crystal growth apparatus according to claim 1, wherein the spread angle of the heat shielding member changes in two stages. 4. The single crystal growth apparatus according to claim 1, wherein the spread angle of the heat shielding member changes continuously. 5. The single crystal growth apparatus according to claim 1, wherein a member that closes an opening between a side wall of the container and an outer periphery of an end of the heat shielding member on the raw material side is arranged. 6. The single crystal growing apparatus according to claim 1, wherein a space between the heat shielding member and a side wall of the container is filled. 7. The single crystal growing apparatus according to claim 6, wherein the heat shielding member and the container have an integral structure. 8. The single crystal growth apparatus according to claim 1, wherein the heat shielding member has a widened side wall portion and a portion parallel to the seed crystal surface. 9. The single crystal growth apparatus according to claim 1, wherein said heat shielding member is made of graphite. 10. The single crystal growth apparatus according to claim 1, wherein said single crystal is a silicon carbide single crystal.