JP4110611B2 - Single crystal manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal manufacturing apparatus used for growing a single crystal such as silicon carbide.
[0002]
[Prior art]
A silicon carbide single crystal is useful as a semiconductor substrate used in a semiconductor device such as a power element, and has been conventionally produced by a sublimation method. In the sublimation method, a raw material powder and a single crystal growth substrate are arranged facing each other in a graphite crucible, the raw material powder is heated and sublimated, introduced onto the single crystal growth substrate, and recrystallized. At this time, the temperature in the crucible is controlled so that the single crystal growth substrate has a lower temperature than the other portions, so that the single crystal can easily grow on the single crystal growth substrate.
[0003]
Also, as described in JP-A-8-295595, there is one in which a shielding plate is provided between the raw material powder and the single crystal growth substrate. FIG. 4 shows an example. In the figure, the crucible 2 of the single crystal manufacturing apparatus 1 is filled with silicon carbide powder as a raw material powder 4 at the bottom, and carbonized on the lower surface of the lid 3 facing this. A single crystal growth substrate 6 made of silicon single crystal is bonded with an adhesive 5. A disc-shaped shielding plate 7 is disposed between the raw material powder 4 and the single crystal growth substrate 6 to protect the single crystal growth substrate 6 from the radiant heat of the raw material powder 4.
[0004]
[Problems to be solved by the invention]
However, when the single crystal 8 is grown using the above-described conventional apparatus, there is a problem that the central portion of the grown single crystal 8 is thermally etched and a depression is generated as shown in the figure. This is because when the temperature of the shielding plate 7 itself rises, the temperature of the central portion of the single crystal 8 rises due to thermal radiation from the shielding plate 7 and induces thermal etching, which hinders the growth of the grown crystal. Yes.
[0005]
Accordingly, an object of the present invention is to provide a single crystal manufacturing apparatus capable of preventing the central portion of a growth crystal from being thermally etched and obtaining a long growth crystal.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the single crystal manufacturing apparatus of the present invention has a raw material powder and a single crystal growth substrate facing each other in a crucible, and a shielding plate is provided between the raw material powder and the single crystal growth substrate. And a single crystal is grown on the single crystal growth substrate while protecting the single crystal growth substrate from radiant heat generated when the raw material powder is heated and sublimated. The shielding plate has a shape in which the central portion is recessed, and the distance between the single crystal growth substrate and the central portion of the shielding plate is larger than the distance between the single crystal growth substrate and the peripheral portion of the shielding plate. (Claim 1).
[0007]
When the shielding plate is provided, the single crystal growth substrate is not directly exposed to the radiant heat of the raw material powder, but when the shielding plate itself is at a high temperature, the grown crystal is thermally etched by the radiant heat. In the present invention, focusing on the fact that the central portion of the grown crystal is easily thermally etched and hinders lengthening, the structure of the shielding plate is changed to suppress the temperature rise of the grown crystal. Specifically, the distance between the central portion of the shielding plate and the single crystal growth substrate is larger than the peripheral portion in the central portion, the thermal radiation from the central portion is reduced, and the temperature of the central portion of the grown crystal is lowered. . Thus, thermal etching is prevented and a long single crystal can be obtained.
[0008]
The shielding plate is made of a fixed type and is made of two kinds of materials having different thermal conductivities, and the first material constituting the central portion of the shielding plate is more thermally conductive than the second material constituting the peripheral portion. (Claim 2). Specifically, the first material constituting the central portion of the shielding plate and a porous graphite, a second material which constitutes the peripheral portion and the graphite (claim 3). By configuring the central portion of the shielding plate with a material having low thermal conductivity such as porous graphite, the same effect of reducing thermal radiation from the central portion and preventing thermal etching can be obtained.
[0009]
The shielding plate may have a shape in which the central portion protrudes toward the raw material powder, and the thickness of the central portion may be greater than the thickness of the peripheral portion. By increasing the plate thickness, it is possible to suppress the temperature rise at the central portion of the shielding plate, reduce the heat radiation from the central portion, and obtain the same effect of preventing thermal etching.
[0010]
Specifically, the area ratio between the central portion and the peripheral portion of the shielding plate is preferably in the range of 1: 3 to 1:10. The central area where thermal etching occurs in the conventional apparatus configuration is usually about 1/10 to 1/3 of the total area of the crystal. Therefore, the area ratio between the central part and the peripheral part of the shielding plate is set within the above range. Then, thermal etching can be effectively prevented.
[0011]
The single crystal produced by the single crystal production apparatus of the present invention is specifically a silicon carbide single crystal (Claim 6), and the advantage of lengthening is great.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a first embodiment of the present invention. In the figure, a single crystal production apparatus 1 has a graphite crucible 2 having an upper end opening and a graphite lid 3 disposed so as to close the opening, and a raw material powder is placed at the bottom of the crucible 2. 4 is filled with silicon carbide powder. The lid 3 has a lower surface center portion protruding downward to form a base 3a for attaching a substrate. A seed crystal serving as a single crystal growth substrate 6 is bonded to the pedestal 3 a via an adhesive 5. As the seed crystal, for example, a silicon carbide single crystal grown by the Atchison method, the sublimation method, or the like can be used, and this is processed into a wafer shape having a diameter of about φ10 mm to φ100 mm.
[0013]
Below the single crystal growth substrate 6, a graphite shielding plate 7 is disposed so as to face each other at a predetermined interval. The shielding plate 7 is disc-shaped and is supported from below by a rod-like support member 7 a fixed to the bottom of the crucible 2 to protect the single crystal growth substrate 6 from being directly exposed to the radiant heat of the raw material powder 4. ing. The height of the shielding plate 7 is set so that a sufficient space for the growth of the single crystal 8 is formed below the single crystal growth substrate 6. Here, the space between the single crystal growth substrate 6 and the raw material powder 4 is set. It is arranged at almost the middle position. The size of the shielding plate 7 is normally set as appropriate within a range of about 0.9 to 9 times the diameter of the single crystal growth substrate 6. Generally, the magnification is increased when the diameter of the single crystal growth substrate 6 is small, and the magnification is decreased when the diameter is large. A predetermined interval is provided between the outer periphery of the shielding plate 7 and the crucible 2 so that the sublimation gas of the raw material powder 4 can reach the single crystal growth substrate 3 from the periphery of the shielding plate 7.
[0014]
In the present embodiment, the shielding plate 7 has a shape in which the central portion 71 is recessed with respect to the peripheral portion 72 so that the distance from the single crystal growth substrate 6 is larger than the peripheral portion 72 at the central portion 71 of the shielding plate 7. To. Thus, by increasing the distance between the central portion 71 of the shielding plate 7 and the single crystal 8, there is an effect of suppressing thermal etching of the central portion of the single crystal 8. Here, the area ratio between the central portion 71 and the peripheral portion 72 is usually in the range of about 1: 3 to 1:10. The central area where thermal etching occurs in the conventional apparatus configuration is usually about 1/10 to 1/3 of the total crystal area. Therefore, if the area ratio of the central portion 71 and the peripheral portion 72 is within the above range, An effect is obtained. Further, the difference in distance between the central portion 71 and the single crystal growth substrate 6 in the peripheral portion 72 (step difference between the upper surface of the central portion 71 and the upper surface of the peripheral portion 72) is usually about 2 to 10 mm, and is appropriately selected within this range. be able to.
[0015]
In the case of growing a single crystal using the above apparatus, the raw material powder 4 and the single crystal growth substrate 6 are arranged facing each other in the crucible 2, and the crucible 2 is heated to a predetermined temperature by a heating device (not shown). The raw material powder 4 is sublimated. The inside of the crucible 2 is an inert gas atmosphere such as argon gas, and the pressure is about 0.1 to several Torr. The temperature of the raw material powder 4 is about 2000 to 2500 ° C., and the single crystal growth substrate 6 is provided with a temperature gradient in the crucible 2 so that the temperature is lower than that of the raw material powder 4. The sublimation gas of the raw material powder 4 reaches the single crystal growth substrate 6 from the periphery of the shielding plate 7, and the single crystal 8 grows on the single crystal growth substrate 6 having a relatively low temperature.
[0016]
In the present embodiment, since the shielding plate 7 has a shape in which the central portion 71 is recessed, the radiant heat from the central portion 71 of the shielding plate 7 is reduced. Therefore, since the temperature rise of the center part of the single crystal 8 facing this can be suppressed and thermal etching can be prevented, the growing single crystal 8 can be made long.
[0017]
FIG. 2 shows a second embodiment of the present invention. In this Embodiment, the shielding board 7 is made into flat form, and the center part 71 is comprised with the porous carbon (porous graphite) which is a 1st material . The peripheral part 72 is made of graphite which is the second material . In this way, by configuring the central portion 71 with porous carbon having a low thermal conductivity, heat radiation from the central portion 71 of the shielding plate 7 to the single crystal growth substrate 6 can be reduced. Therefore, the same effect of preventing the central portion of the single crystal 8 from thermal etching and lengthening the single crystal 8 can be obtained. Note that the area ratio between the central portion 71 and the peripheral portion 72 is the same as that in the first embodiment, and may be appropriately set in the range of 1: 3 to 1:10.
[0018]
FIG. 3 shows a third embodiment of the present invention. In the present embodiment, the shielding plate 7 has a shape in which the central portion 71 protrudes downward so that the thickness of the central portion 71 is larger than the thickness of the peripheral portion 72. With such a configuration, since the thermal conduction in the central portion 71 is lower than the peripheral portion 72, it is possible to reduce radiant heat from the central portion 71 of the shielding plate 7. Therefore, the same effect of preventing the central portion of the single crystal 8 from thermal etching and lengthening the single crystal 8 can be obtained. Note that the area ratio between the central portion 71 and the peripheral portion 72 is the same as that in the first and second embodiments, and is usually set as appropriate within a range of 1: 3 to 1:10. The plate thickness is preferably about 7 to 10 mm at the peripheral portion 72 and about 1.5 to 5 times that at the central portion 71.
[0019]
【Example】
(Example 1)
An experiment for actually growing a single crystal was performed using the apparatus shown in FIG. A wafer-like silicon carbide single crystal having a diameter of 25 mm and a thickness of 1 mm was used as the single crystal growth substrate 6 and attached to a pedestal 3 a provided on the lower surface of the lid 3. The shielding plate 7 has a diameter of 80 mm, a plate thickness of 10 mm, a diameter of the central portion 71 is 30 mm, and a step between the central portion 71 and the peripheral portion 72 is 5 mm. The distance between the single crystal growth substrate 6 and the central portion 71 of the shielding plate 7 was 40 mm, and the distance between the single crystal growth substrate 6 and the peripheral portion 72 of the shielding plate 7 was 35 mm.
[0020]
The bottom part of the crucible 2 was filled with a sufficient amount of silicon carbide powder as a raw material powder 4 for growth, and a lid 3 having a single crystal growth substrate 6 attached to the upper end opening was fixed. This was placed in a heating device (not shown), exhausted by a vacuum exhaust system (not shown), and replaced with an argon gas atmosphere. Next, the raw material powder 4 is heated to about 2300 ° C. and the single crystal growth substrate 6 is heated to about 2230 ° C., and the pressure is reduced to about 1 Torr to sublimate the raw material powder 4. Grew. Then, heating was stopped and argon gas was introduced.
[0021]
At this time, the single crystal 8 grew at a growth rate of 0.5 to 0.6 mm / hour, and no decrease in the growth rate over time was observed. Further, the grown single crystal 8 has a high growth rate at the central portion and is grown in a substantially convex shape, and a phenomenon that the central portion is thermally etched is not observed. From the above, it was confirmed that by changing the shape of the shielding plate 7, thermal etching can be prevented and the length can be increased.
[0022]
(Example 2)
An experiment for actually growing a single crystal was performed using the apparatus shown in FIG. A single crystal is grown in the same manner as in Example 1 except that the shielding plate 7 (diameter 80 mm, plate thickness 10 mm), the central portion 71 is made of porous carbon having a diameter of 30 mm, and the peripheral portion 72 is made of graphite. I let you. As a result, it was confirmed that the grown single crystal 8 has a substantially convex shape, no thermal etching is observed, and can be elongated.
[0023]
(Example 3)
An experiment for actually growing a single crystal was performed using the apparatus shown in FIG. The shield plate 7 has a diameter of 80 mm, and a plate thickness of 20 mm at the central portion 71 (diameter 30 mm) and 10 mm at the peripheral portion 72. Other than that, a single crystal was grown in the same manner as in Example 1. As a result, it was confirmed that the grown single crystal 8 has a substantially convex shape, no thermal etching is observed, and can be elongated.
[0024]
(Comparative Example 1)
For comparison, an experiment for actually growing a single crystal was performed using the apparatus shown in FIG. The shielding plate 7 had a diameter of 80 mm and a plate shape with a plate thickness of 10 mm, and the distance between the shielding plate 7 and the single crystal growth substrate 6 was 35 mm. Other than that, a single crystal was grown in the same manner as in Example 1.
[0025]
At this time, the single crystal 8 grew at a growth rate of 0.4 to 0.5 mm / hour, and a growth rate decrease with the passage of time was not observed, but the growth rate was slightly lower than those of Examples 1 to 3 above. . Further, the grown single crystal 8 had a slow growth rate at the center and was grown in a substantially concave shape, and a thermal etching phenomenon was observed at the center.
[0026]
As described above, the length of the single crystal can be increased by the single crystal manufacturing apparatus of the present invention. 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 manufacturing apparatus showing a first embodiment of the present invention.
FIG. 2 is an overall cross-sectional view of a single crystal manufacturing apparatus showing a second embodiment of the present invention.
FIG. 3 is an overall cross-sectional view of a single crystal manufacturing apparatus showing a third embodiment of the present invention.
FIG. 4 is an overall cross-sectional view of a conventional single crystal manufacturing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Single crystal manufacturing apparatus 2 Crucible 3 Lid 3a Base 4 Raw material powder 5 Adhesive 6 Single crystal growth substrate 7 Shielding plate 71 Central part 72 Peripheral part 8 Single crystal

Claims (6)

A raw material powder and a single crystal growth substrate are arranged opposite to each other in a crucible, a shielding plate is provided between the raw material powder and the single crystal growth substrate, and the single crystal is taken from the radiant heat generated when the raw material powder is heated and sublimated. In a single crystal manufacturing apparatus for growing a single crystal on the single crystal growth substrate while protecting the growth substrate, the shielding plate is shaped so that a central portion is recessed, and the single crystal growth substrate and the central portion of the shielding plate are Is made larger than the distance between the single crystal growth substrate and the peripheral portion of the shielding plate. The raw material powder and the single crystal growth substrate are placed facing each other in the crucible, and a fixed shielding plate is provided between the raw material powder and the single crystal growth substrate, so that radiation heat generated when the raw material powder is heated and sublimated. In the single crystal manufacturing apparatus for growing a single crystal on the single crystal growth substrate while protecting the single crystal growth substrate, the shielding plate is composed of two kinds of materials having different thermal conductivities, and the center of the shielding plate A single crystal manufacturing apparatus , wherein the first material constituting the portion is made of a material having a lower thermal conductivity than the second material constituting the peripheral portion . The first material constituting the central portion of the shielding plate is a porous graphite, a single crystal manufacturing apparatus of the second claim 2, wherein the material is graphite which constitutes the peripheral portion of the shielding plate. A raw material powder and a single crystal growth substrate are arranged opposite to each other in a crucible, a shielding plate is provided between the raw material powder and the single crystal growth substrate, and the single crystal is taken from the radiant heat generated when the raw material powder is heated and sublimated. In the single crystal manufacturing apparatus for growing a single crystal on the single crystal growth substrate while protecting the growth substrate, the shielding plate is shaped so that the central portion protrudes toward the raw material powder side, and the central plate of the shielding plate An apparatus for producing a single crystal, characterized in that the thickness is larger than the thickness of the peripheral portion. The single crystal manufacturing apparatus according to any one of claims 1 to 3, wherein an area ratio of a central portion and a peripheral portion of the shielding plate is 1: 3 to 1:10. The single crystal manufacturing apparatus according to any one of claims 1 to 5, wherein the single crystal is a silicon carbide single crystal.

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