JP3843615B2 - Single crystal growth equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal growth apparatus used for growing a single crystal such as silicon carbide.
[0002]
[Prior art]
Silicon carbide single crystal has excellent electrical and mechanical properties and is useful as a substrate material for semiconductor devices. As a method for producing a silicon carbide single crystal, a sublimation method is generally used. In a graphite crucible, a seed crystal and a raw material powder are arranged to face each other, and a gas obtained by heating and sublimating the raw material powder is introduced onto the seed crystal. To do. A temperature difference is provided in the crucible so that the seed crystal is at a lower temperature than the raw material powder, and a single crystal is grown by recrystallizing the sublimation gas on the lower temperature seed crystal.
[0003]
In order to efficiently perform single crystal growth by the sublimation method, it is effective to control the temperature in the crucible, the atmospheric pressure, the flow of sublimation gas, and the like, and various apparatuses have been proposed. For example, Japanese Patent Laid-Open No. 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. When this structure is shown in FIG. 8, a crucible 2 of single crystal growth apparatus 1 is filled with silicon carbide raw material powder 4 at the bottom, and silicon carbide single crystal substrate 5 serving as a seed crystal is placed on pedestal 3a facing this. Are joined. Between the raw material powder 4 and the silicon carbide single crystal substrate 5, a bottomed cylindrical heat shielding member 9 is disposed so as to surround the lower side of the silicon carbide single crystal substrate 5, and carbonized from the radiant heat of the raw material powder 4. The silicon single crystal substrate 5 is protected. Thus, by providing the heat shielding member 9, it is possible to suppress the temperature rise of the silicon carbide single crystal substrate 5, increase the temperature difference, and grow the silicon carbide single crystal 7 efficiently.
[0004]
In JP-A-8-325099, a concentrating tube whose inner diameter is gradually reduced upward is interposed between a container body containing raw material powder and a lid body on which seed crystals are arranged. An apparatus is disclosed, and a sublimation gas is squeezed and concentrated on a seed crystal to enable efficient single crystal growth.
[0005]
[Problems to be solved by the invention]
By the way, in order to enhance the mass production effect of a semiconductor device using a silicon carbide substrate, a silicon carbide single crystal substrate having a larger diameter is required. However, in the 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 expanding the diameter is small. For this reason, in order to obtain a large-diameter single crystal, it was necessary to repeatedly grow the single crystal on the seed crystal cut out from the grown single crystal and gradually increase the diameter.
[0006]
An object of the present invention is to provide a single crystal growth apparatus that can increase the growth rate in the radial direction of a growing single crystal and obtain a long and large-diameter single crystal.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a single crystal growth apparatus of the present invention has a seed crystal and a raw material powder arranged in a container facing each other, and a heat shielding member is provided between the seed crystal and the raw material powder. Thus, a single crystal is grown on the seed crystal while protecting the seed crystal from radiant heat generated 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 a diameter of the single crystal growth space is directed from the seed crystal side to the raw material powder side. The side wall portion having a shape that increases as the portion extends and the portion that is parallel to the seed crystal surface are integrally provided (claim 1).
[0008]
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 single crystal is formed on the seed crystal that is relatively low in temperature. grow up. At this time, a temperature difference occurs not only in the direction perpendicular to the surface of the seed crystal but also in the radial direction, so that a single crystal grows in the radial direction. Moreover, since the heat shielding member of the present invention has such a shape that 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 direction and the radial direction can be increased, and a long and large single crystal can be obtained.
[0009]
The heat shielding member has a structure in which a gas flow hole is formed in a portion parallel to the seed crystal surface by separating a wide side wall portion and a bottom wall portion parallel to the seed crystal surface. (Claim 2). At this time, the position of the gas circulation hole is set such that the side wall portion of the heat shielding member can face the raw material powder surface through the gas circulation hole. Since the heat shielding member is divided into the side wall portion and the bottom wall portion, the structure is simplified and the manufacturing cost can be reduced.
Preferably, the spread angle of the heat shielding member is in the 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 the angle exceeds 80 °, the spread angle does not increase and there is no further effect of increasing the diameter.
[0010]
The spreading angle of the heat shielding member can be changed in two stages (claim 4 ). When it is desired to change the spread angle of the growth crystal during the growth, for example, when it is desired to control the diameter of the growth crystal to be finally obtained, the spread angle of the heat shielding member may be changed. The spread angle of the heat shielding member may be continuously changed (Claim 5 ).
[0011]
A member that closes the opening between the heat shielding member and the side wall of the container may be disposed on the outer periphery of the raw material side end (claim 6 ). Thereby, the gas which the said raw material powder sublimated reaches | attains between the said heat shielding member and the side wall of the said container, and it can prevent that a polycrystal adheres to the said heat shielding member or the side wall of the said container. By preventing the polycrystal from adhering to these parts, the sublimation gas contributing to the single crystal growth is increased, the single crystal growth rate is increased, and the growth efficiency is increased.
[0012]
A space between the heat shielding member and the side wall of the container can also be filled (claim 7 ). Even in this case, similarly to the fifth aspect, it is possible to prevent the sublimation gas of the raw material powder from reaching the heat shielding member or the side wall of the container and to adhere polycrystals, thereby increasing the single crystal growth rate. And increase the growth efficiency.
[0013]
In the above configuration according to claim 7, optionally as a unitary structure and the heat shield member and the container (claim 8). By integrating the heat shielding member and the container, the number of parts can be reduced and the cost can be reduced.
[0015]
The heat shielding member is preferably made of, for example, graphite (Claim 9) and excellent in heat insulation and heat resistance. In addition, as the single crystal produced by the single crystal growth apparatus of the present invention, specifically, a silicon carbide single crystal can be cited (Claim 10), and the advantage of increasing the diameter is great.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
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 that closes its upper end opening. The bottom portion of the crucible 2 is filled with silicon carbide powder 4 as a raw material powder, and a silicon carbide single crystal substrate 5 serving as a seed crystal is joined to a pedestal 3a formed by projecting the bottom center portion of the lid 3 It is. This silicon carbide single crystal substrate 5 is obtained by processing a silicon carbide single crystal grown by, for example, the Atchison method, the sublimation method or the like into a wafer shape having a diameter of about 10 mm to 100 mm, and is attached to the base 3a with an adhesive. It is done.
[0017]
Between the silicon carbide single crystal substrate 5 and the silicon carbide powder 4, a heat shielding member 6 is disposed so as to surround the outer periphery of the silicon carbide single crystal substrate 5 and the space below the silicon carbide single crystal substrate 5. It is. The heat shielding member 6 is formed of a hollow container body that expands in a tapered shape toward the lower side, forms a sufficient space for a single crystal to grow inside, and increases in diameter toward the lower side, The growth of the single crystal in the radial direction is not disturbed. Since the heat shielding member 6 is excellent in heat insulation and the inside of the crucible 2 becomes high temperature, it is made of a heat resistant material, for example, graphite. 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. It is arranged so as to face each other. A plurality of gas flow holes 62 are formed in the lower end surface of the heat shielding member 6, and the sublimation gas of the silicon carbide powder 4 can reach the silicon carbide single crystal substrate 5 through the gas flow holes 62. . The heat shielding member 6 is fixed to the inner wall of the crucible 2 by a flange portion 61 provided on the outer periphery of the upper end surface.
[0018]
When a single crystal is grown using the above apparatus, the silicon carbide powder 4 is filled in the crucible 2, the silicon carbide single crystal substrate 5 is bonded to the pedestal 3 a, and the lid 3 is attached to the crucible 2. . Next, the crucible 2 is evacuated, an inert gas such as argon gas is introduced, and the atmospheric pressure is adjusted to be about 0.1 to several Torr. Further, the crucible 2 is heated to a predetermined temperature by a heating device (not shown) to sublimate the silicon carbide powder 4 and generate sublimation gas. At this time, the electric power introduced into the heating device is adjusted so that the temperature of the raw material powder 4 is in the range of about 2000 to 2500 ° C. and the temperature of the silicon carbide single crystal substrate 5 is lower than that of the silicon carbide powder 4. A temperature gradient is provided inside. The generated raw material sublimation gas passes through the gas flow holes 62 of the heat shielding member 6, enters the single crystal growth space in the heat shielding member 6, and reaches the silicon carbide single crystal substrate 5.
[0019]
Here, a temperature gradient is provided in the crucible 2 in the vertical direction of the figure, and the silicon carbide single crystal 7 grows on the silicon carbide single crystal substrate 5 that is relatively low in temperature. Generally, the growth amount and growth direction of a single crystal depend on the temperature near the growth surface, the temperature gradient, the amount of sublimation gas and the flow, but the main is the temperature gradient near the growth surface, with a large temperature gradient. As the degree of supersaturation of the sublimation gas increases, the amount of growth per unit time increases. Without the heat shielding member 6, 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 that is the seed crystal. It does not grow in the radial direction. On the other hand, when the heat shielding member 6 is provided, the temperature of the heat shielding member 6 rises due to heat radiation from the silicon carbide powder 4, and the upper surface and side surfaces of the heat shielding member 6 and the silicon carbide single crystal 7 that are at a high temperature. Since the temperature difference causes a temperature gradient in the radial direction, the silicon carbide single crystal 7 can grow not only in the vertical direction but also in the radial direction.
[0020]
However, in the case of the heat shielding member 9 having a constant inner diameter as in the conventional apparatus of FIG. 8, the distance between the silicon carbide single crystal 7 and the heat shielding member 9 decreases as the diameter grows in the radial direction. The slope changes. That is, when the distance is reduced, the thermal radiation from the heat shielding member 9 is more greatly received, so that the temperature of the side surface of the silicon carbide single crystal 7 is increased. As a result, the temperature gradient in the vicinity of 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 internal single crystal growth space expands in the radial direction as it goes downward. ing. Therefore, even if grown in the radial direction, the distance between the silicon carbide single crystal 7 and the heat shielding 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.
[0021]
Here, the shape of the heat shielding member 6 is not limited to the shape of FIG. 1 described above, and the inner diameter increases downward, and the single crystal growth space formed in the heat shielding member 6 decreases in the radial direction toward the lower side. What is necessary is just to be comprised so that it may spread. In addition, as shown in FIG. 2 as a second embodiment of the present invention, the spreading angle θ of the heat shielding member 6 is preferably in the 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 the angle exceeds 80 °, the spread angle does not increase and there is no further effect of increasing the diameter.
[0022]
As shown in FIG. 3 as the third embodiment of the present invention, the spread angle of the heat shielding member 6 can be changed in two stages. Here, the upper spread angle of the heat shield member 6 is θ1, the lower spread angle is θ2, and θ1 <θ2, so that the growth amount of the growing silicon carbide single crystal 7 increases in the radial direction downward. As described above, when it is desired to control the diameter of the growth crystal to be finally obtained, the spread angle of the growth crystal can be changed during the growth by changing the spread angle of the heat shielding member 6 stepwise. it can. Of course, the spread angle of the heat shielding member can be continuously changed. Another example of the shape of the heat shielding member 6 is shown below.
[0023]
As shown in FIG. 4 as the fourth embodiment of the present invention, the annular shape formed between the outer periphery of the end surface (lower end surface in the figure) of the heat shielding member 6 on the silicon carbide powder 4 side and the side wall of the crucible 2. The gas shielding member 8 may be arranged so as to close the opening. The gas shielding member 8 is made of, for example, graphite, and closes the opening between the heat shielding member 6 and the crucible 2 to prevent the sublimation gas of the silicon carbide powder 4 from reaching above. As a result, it is possible to prevent polycrystals from adhering to the outer wall of the heat shielding member 6 and the inner wall of the crucible 2 and increase the sublimation gas contributing to the single crystal growth, thereby increasing the single crystal growth rate. Efficient single crystal growth is possible.
[0024]
As shown in FIG. 5 as a fifth embodiment of the present invention, the heat shielding member 6 has a single crystal growth space in which the diameter is increased in a tapered shape downward and the outer diameter is the inner diameter of the crucible 2. A space between the crucible 2 and the side wall of the crucible 2 can be filled with the heat shielding member 6 (Claim 6). Even in this case, as in the fourth embodiment, it is possible to prevent the sublimation gas of the silicon carbide powder 4 from reaching the space between the heat shielding member 6 and the crucible 2 and attaching polycrystals. it can. Therefore, the sublimation gas contributing to the single crystal growth is increased, the single crystal growth rate is increased, and efficient single crystal growth is possible.
[0025]
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 shielding member 6 is formed in a thick cylindrical shape having a single crystal growth space that expands downward in a tapered shape inside, and the outer diameter of which matches the outer diameter of the crucible 2. The crucible 2 is provided integrally with the crucible 2. Thus, by integrating the crucible 2 with the heat shielding member 6, it is possible to reduce the cost by reducing the number of parts, in addition to improving the single crystal growth efficiency by filling the space between the crucible 2.
[0026]
As shown in FIG. 7 as a seventh embodiment of the present invention, the heat shielding member 6 is a bottom wall portion that is parallel to the wide side wall portion 6a and the surface of the silicon carbide single crystal substrate 5 that is a seed crystal. It can also be set as the structure divided | segmented into the lower end surface part 6b. The side wall portion 6a and the lower end surface portion 6b are fixed to the inner wall of the crucible 2, respectively. Thus, by dividing the side wall portion 6a and the lower end surface portion 6b, the structure of the heat shielding member 6 can be simplified and the manufacturing cost can be reduced.
[0027]
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 a long and large diameter silicon carbide single crystal is obtained. Obtainable. The single crystal manufacturing apparatus of the present invention is not limited to the growth of a silicon carbide single crystal, and can be applied to any single crystal that can be grown by a sublimation method, such as cadmium sulfide.
[Brief description of the drawings]
FIG. 1 is an overall cross-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 cross-sectional view of a single crystal growth apparatus showing a third embodiment of the present invention.
FIG. 4 is an overall cross-sectional view of a single crystal growth apparatus showing a fourth embodiment of the present invention.
FIG. 5 is an overall cross-sectional view of a single crystal growth apparatus showing a fifth embodiment of the present invention.
FIG. 6 is an overall cross-sectional view of a single crystal growth apparatus showing a sixth embodiment of the present invention.
FIG. 7 is an overall cross-sectional view of a single crystal growth 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]
1 Single crystal growth equipment 2 Crucible (container)
3 Lid 3a Base 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 that closes the opening)
9 Heat shielding member

Claims (10)

In the container, the seed crystal and the raw material powder are placed facing each other, a heat shielding member is provided between the seed crystal and the raw material powder, and the seed crystal is removed from the radiant heat generated when the raw material powder is heated and sublimated. In a single crystal growth apparatus that grows a single crystal on the seed crystal while protecting it, the heat shielding member surrounds the seed crystal in a gas flowable manner to form a space in which the single crystal grows, A shape in which the diameter of the single crystal growth space increases from the seed crystal side toward the raw material powder side, and a side wall portion having the spread and a portion parallel to the seed crystal surface are integrally provided. Single crystal growth equipment. In the container, the seed crystal and the raw material powder are placed facing each other, a heat shielding member is provided between the seed crystal and the raw material powder, and the seed crystal is removed from the radiant heat generated when the raw material powder is heated and sublimated. In a single crystal growth apparatus that grows a single crystal on the seed crystal while protecting it, the heat shielding member surrounds the seed crystal in a gas flowable manner to form a space in which the single crystal grows, A shape in which the diameter of the single crystal growth space increases from the seed crystal side toward the raw material powder side, and a side wall portion having the spread and a portion parallel to the seed crystal surface are separated, and the seed crystal is separated. A gas flow hole is provided in a portion parallel to the surface, and the position of the gas flow hole is a position where a side wall portion of the heat shielding member can face the raw material powder surface through the gas flow hole. Single crystal Length devices. The single crystal growth apparatus according to claim 1 or 2 , wherein a spread angle of the heat shielding member is 5 ° to 80 ° . The single crystal growth apparatus according to claim 1 or 2 , wherein a spread angle of the heat shielding member is changed in two stages . The single crystal growth apparatus according to claim 1 or 2 , wherein a spread angle of the heat shielding member continuously changes . The single-crystal growth apparatus of Claim 1 or 2 which has arrange | positioned the member which closes the opening between the side walls of the said container in the outer periphery of the edge part by the side of the said raw material of the said heat shielding member . The single crystal growth apparatus according to claim 1, wherein a space between the heat shielding member and the side wall of the container is filled . The single crystal growth apparatus according to claim 7 , wherein the heat shielding member and the container have an integral structure .   9. The single crystal growth apparatus according to claim 1, wherein the heat shielding member is made of graphite.   10. The single crystal growth apparatus according to claim 1, wherein the single crystal is a silicon carbide single crystal.

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