JP5397503B2 - Single crystal growth equipment - Google Patents

Description

  The present invention relates to a single crystal growth apparatus for growing a single crystal such as silicon carbide and a method for producing a single crystal such as silicon carbide.

  Silicon carbide (SiC) has excellent thermal and chemical characteristics, and is known as a semiconductor material that has a forbidden band width larger than that of silicon (Si) semiconductors and has excellent electrical characteristics. A single crystal silicon carbide substrate is used to manufacture a silicon carbide semiconductor device or the like that takes advantage of the characteristics. A single crystal silicon carbide substrate is obtained by slicing a bulk silicon carbide single crystal, and an improved Rayleigh method (sublimation method) is widely used as a method for growing the silicon carbide single crystal. Currently, silicon carbide substrates with a diameter of up to 100 mm are commercially available. However, since the single crystal is not sufficiently large and long, the productivity is not high and the cost is high. In addition, since the crystal defect density is still high, it is required to further reduce the crystal defect density as a single crystal silicon carbide substrate used for manufacturing a semiconductor device.

  In the modified Rayleigh method for forming a silicon carbide single crystal, when a polycrystal contacts the periphery of the growing single crystal, strain is introduced from the polycrystal to the single crystal, resulting in a large amount of crystal defects and an increase in the quality of the single crystal. Deteriorate significantly. As a method for avoiding this problem, for example, a method of separating a single crystal and a polycrystal using a single crystal polycrystal separation guide has been proposed (for example, Patent Document 1).

  In addition, when a single crystal polycrystal separation guide is provided as in Patent Document 1 to grow a long single crystal, polycrystal is deposited on the inner wall of the single crystal polycrystal separation guide, and the single crystal and polycrystal are completely separated. It is known that there will be a problem that it cannot be separated. In order to solve this problem, a method of growing a long single crystal of high quality by providing a gas path at the lower end of the single crystal polycrystal separation guide and controlling the flow of the source gas has been proposed ( For example, Patent Document 2).

JP 2002-60297 A (pages 5-7) JP 2005-53739 A (7th to 12th pages)

However, in the single crystal growth method in which a gas path is provided at the lower end of the single crystal polycrystal separation guide as in Patent Document 2 and the flow of the raw material gas is controlled, if an attempt is made to lengthen the single crystal, single crystal polycrystal Polycrystals are deposited in the gas path at the lower end of the separation guide to block the gas path at the lower end of the single crystal polycrystal separation guide, or the gas path between the single crystal polycrystal separation guide and the single crystal is blocked. In some cases, the lengthening of the single crystal may be hindered.
When the gas path at the lower end of the single crystal polycrystal separation guide is blocked by the polycrystal precipitation, the polycrystal is likely to be deposited on the inner wall of the single crystal polycrystal separation guide. In addition, if the gas path between the single crystal polycrystal separation guide and the single crystal is blocked by the precipitation of the polycrystal, convection of the source gas occurs inside the guide for separation, or separation occurs due to the convection of the source gas. In some cases, the etching guide is etched and a hole is formed in the separation guide, so that the source gas flows outside the single crystal polycrystal separation guide that does not contribute to single crystal growth.
Thus, even in the single crystal growth method disclosed in Patent Document 2, there is a case where the lengthening of the single crystal is hindered.

  The present invention has been made to solve the above-described problems, and has a large diameter, long length, and few defects by suppressing the precipitation of polycrystals and growing the single crystals separately from the polycrystals. The object is to obtain a single crystal.

  A single crystal growth apparatus according to the present invention includes a crucible having a filling portion for filling a raw material, a lid that serves as a lid for the crucible, and a seed crystal that is provided on the lid so as to face the filling portion. A pedestal, a single crystal polycrystal separation guide provided from the crucible toward the pedestal, and an upper surface provided on an upper portion of the filling portion provided to face the single crystal polycrystal separation guide. The single crystal polycrystal separation guide is provided with a raw material gas rectifying guide which is a radiation surface for radiant heating from below.

  According to the present invention, the single crystal polycrystal separation guide is kept at a higher temperature than the seed crystal, and the source gas is concentrated on the seed crystal, so that the precipitation of the polycrystal on the single crystal polycrystal separation guide can be prevented. Only crystals can be grown long and large in diameter.

It is a cross-sectional schematic diagram which shows the principal part of the single-crystal growth apparatus in Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows a part of single crystal growth apparatus in Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows the principal part of the single-crystal growth apparatus in Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows the principal part of the single crystal growth apparatus during the single crystal growth in Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows the principal part of the single crystal growth apparatus in the single crystal growth in Embodiment 2 of this invention. It is a cross-sectional schematic diagram which shows the principal part of the single crystal growth apparatus in the single crystal growth in Embodiment 3 of this invention. It is a cross-sectional schematic diagram which shows the principal part of the single crystal growth apparatus in the single crystal growth in Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view showing the main part of a single crystal growth apparatus according to Embodiment 1 for carrying out the present invention. In FIG. 1, a digging portion and its opening are formed in one of the crucibles 10 having a cylindrical outer shape and made of graphite, and a raw material is filled in the back side of the digging portion as viewed from the opening. Therefore, a filling portion 13 having an inner diameter smaller than the inner diameter of the dug portion is formed. Since there is a difference between the inner diameter of the digging portion and the inner diameter of the filling portion 13, a surface called a radiation surface 15 is formed at the boundary between the digging portion and the filling portion 13.
The opening is covered with a graphite lid 20 having the same outer diameter as that of the crucible 10, and a seed crystal is placed in the center of the lid 20 toward the back of the crucible 10. A pedestal 21 which is a protrusion for fixing is formed. The outer diameter of the pedestal 21 is formed to be equal to the inner diameter of the filling portion 13.

In the digging portion of the crucible 10, a graphite single crystal polycrystal is formed from the back side of the outer periphery of the digging portion of the crucible 10 toward the position where the tip of the pedestal 21 is arranged when the lid 20 is covered. A crystal separation guide 30 is arranged. The diameter of the single crystal polycrystal separation guide 30 is designed so that the gap with the pedestal 21 is about 2 mm in the upper part and larger in the lower part.
Here, the crucible 10, the lid 20, and the single crystal polycrystal separation guide 30 all have a symmetrical shape when viewed from above with the axis 1 at the center of the crucible 10 as the center.

Next, a method for manufacturing a single crystal using the main part of the single crystal growth apparatus shown in FIG. 1 will be described.
First, as shown in FIG. 2, single crystal silicon carbide seed crystal 40 is attached to the tip of pedestal 21 of lid 20. Subsequently, as shown in FIG. 3, the filling portion 13 is filled with a silicon carbide raw material 50. Moreover, the crucible 10 is covered with the lid 20 to which the seed crystal 40 is attached.
Subsequently, the main part of the single crystal growth apparatus shown in FIG. 3 is evacuated and replaced with high-purity argon (Ar) gas. Next, the main part of the single crystal growth apparatus shown in FIG. 3 installed in a high-purity argon gas atmosphere is heated by heating means such as an induction coil (not shown). At this time, the temperature of the filling portion 13 filled with the silicon carbide raw material 50 is set to a temperature at which silicon carbide sublimates (2000 to 2500 ° C.), and the temperature of the lid 20 to which the seed crystal 40 is attached is changed to the silicon carbide raw material 50. Set lower than the temperature of. By reducing the pressure of the Ar atmosphere, the gas obtained by sublimating the silicon carbide raw material 50 reaches the 40 parts of the seed crystal, and single crystal growth starts.

  Here, the single crystal polycrystal separation guide 30 is radiantly heated from the radiation surface 15 made of graphite around the filling portion 13, and the temperature of the single crystal polycrystal separation guide 30 is set to a seed crystal placed on the pedestal 21. Higher than 40. By setting the temperature in this way, the single crystal 60 can be grown downward from the seed crystal 40 as shown in FIG. 4 without precipitating the polycrystal in the single crystal polycrystal separation guide 30. it can. Excess source gas that does not contribute to the single crystal growth flows around the pedestal 21 via the gap between the single crystal polycrystal separation guide 30 and the pedestal 21, and adheres as the polycrystal 70 around the pedestal 21.

  Thus, according to the single crystal growth apparatus and single crystal growth method in the present embodiment, the inner diameter of filling portion 13 into which silicon carbide raw material 50 is placed is the same as the diameter of pedestal 21 to which seed crystal 40 is attached. Since the temperature of the single crystal polycrystal separation guide 30 that is radiantly heated by the radiation surface 15 is higher than that of the seed crystal 40, the source gas sublimated from the silicon carbide raw material 50 efficiently moves toward the seed crystal 40 and separates the single crystal polycrystal. Since it is difficult for polycrystals to precipitate in the guide 30 for use, a long and large-diameter single crystal can be manufactured.

In the present embodiment, an example of a single crystal growth apparatus in which the diameter of the pedestal 21 is equal to the inner diameter of the filling portion 13 has been described. However, the diameter of the pedestal 21 and the inner diameter of the filling portion 13 need not be exactly equal. However, it may be the same or less. In addition, as for the position of the lower end of the single crystal polycrystal separation guide 30, an example of the outermost periphery is shown at the lowermost end of the digging portion of the crucible 10, but the position may be higher to some extent than the lowermost portion, and to some extent from the outermost periphery. It may be inside.
Moreover, in this Embodiment, although the radiation surface 15 provided in the circumference | surroundings of the filling part 13 showed the horizontal example, the radiation surface 15 does not need to be horizontal and may incline. It is more preferable that the inclination of the radiating surface 15 is close to the inclination of the single crystal polycrystal separation guide 30 because the radiating surface 15 and the lower surface of the single crystal polycrystal separation guide 30 are more opposed to each other.

Embodiment 2. FIG.
FIG. 5 is a schematic cross-sectional view showing the main part of the single crystal growth apparatus during single crystal growth in the second embodiment for carrying out the present invention. In FIG. 5, the digging portion of the crucible 10 and the filling portion 13 have the same inner diameter, and a graphite material gas rectifying guide 31 is provided on the top of the filling portion 13. The upper surface of the source gas rectifying guide 31 is a radiation surface 15, which is formed to face the single crystal polycrystal separation guide 30. Since other than these are the same as those in the first embodiment, description thereof is omitted. Here, the raw material gas rectifying guide 31 has a point-symmetrical shape as viewed from above with respect to the central axis of the crucible 10, and the seed crystal 40 is installed at the uppermost opening diameter of the raw material gas rectifying guide 31. It is equal to the diameter of the base 21. The single crystal growth method in this embodiment is performed in the same manner as in Embodiment 1 using the single crystal growth apparatus of this embodiment.

  According to the single crystal growth apparatus of the present embodiment, the temperature of the single crystal polycrystal separation guide 30 that is radiantly heated by the radiation surface 15 is higher than that of the seed crystal 40 as in the single crystal growth apparatus of the first embodiment. Therefore, since the source gas sublimated from the silicon carbide source material 50 can be efficiently suppressed toward the seed crystal 40 and the polycrystal is deposited on the single crystal polycrystal separation guide 30, a long and large-diameter single crystal can be formed. Can be grown. Moreover, since the internal volume of the filling part 13 can be enlarged, many silicon carbide raw materials 50 can be filled, and it becomes advantageous by lengthening.

Embodiment 3 FIG.
FIG. 6 is a schematic cross-sectional view showing the main part of the single crystal growth apparatus during single crystal growth in the third embodiment for carrying out the present invention. 6 is the same as FIG. 5 except that the single crystal polycrystal separation guide 30 of FIG. The single crystal growth method is the same as that of the second embodiment. The folded structure portion 32 of the single crystal polycrystal separation guide 30 is provided almost all around the shaft 1 and there is no gap in the circumferential direction other than the path for vacuuming.

  Since the single crystal growth apparatus of the present embodiment includes the single crystal polycrystal separation guide 30 having the folded structure portion 32, radiant heat from the single crystal polycrystal separation guide 30 to the lid 20 is suppressed, The temperature rise of the lid 20 can be suppressed. Further, the single crystal polycrystal separation guide 30 is heated by the radiant heat from the source gas rectifying guide 31 as in the second embodiment, and in addition to having the folded structure portion 32, the heat from the folded structure portion 32 is provided. The single crystal polycrystal separation guide 30 can be heated to a higher temperature by conduction heat from the crucible 10 via the reflection and folding structure portion 32, so that the temperature difference between the seed crystal 40 and the single crystal polycrystal separation guide 30 is further increased. can do. Therefore, a longer and larger-diameter single crystal can be manufactured.

  Further, when a graphite flexible sheet 33 is attached to the lower surface of the folded structure portion 32 as shown in FIG. 7, the heat reflection from the folded structure portion 33 described above can be further increased. The temperature difference between the guide portions of 40 and the single crystal polycrystal separation guide 30 can be further increased, and a long and large diameter single crystal can be manufactured.

  In addition, since the single crystal polycrystal separation guide 30 made of graphite, the raw material gas rectifying guide 31 and the folded structure portion 32 shown in the first to third embodiments are at a high temperature, they may be sublimated or etched by the raw material gas. is there. In order to prevent this deterioration, the reliability of the apparatus can be further improved by coating the single crystal polycrystal separation guide 30, the raw material gas rectifying guide 31 and the folded structure portion 32 with tantalum carbide. Single crystals can be produced.

DESCRIPTION OF SYMBOLS 10 Crucible, 13 Filling part, 15 Radiation surface, 20 Lid body, 21 Base, 30 Guide for single crystal polycrystal separation, 31 Source gas rectification guide, 32 Folding structure part, 33 Flexible sheet made of graphite, 40 seed crystal, 50 Carbonization Silicon raw material, 60 single crystal, 70 polycrystal.

Claims (4)

A crucible having a filling portion for filling raw materials;
A lid that serves as a lid for the crucible;
A pedestal for attaching a seed crystal provided on the lid facing the filling portion;
A single-crystal polycrystal separation guide provided from the crucible toward the pedestal;
A raw material gas rectifier provided on an upper portion of the filling portion, the upper surface of which is provided to face the single crystal polycrystal separation guide and is a radiation surface for radiatively heating the single crystal polycrystal separation guide from below. A single crystal growth apparatus comprising a guide. The single crystal growth apparatus according to claim 1, wherein the raw material gas rectifying guide is provided with an opening through which a gas sublimated from the raw material passes, and the diameter of the opening is equal to or smaller than the diameter of the pedestal. The single crystal growth apparatus according to claim 1, wherein the single crystal polycrystal separation guide includes a folded portion. The single crystal growth apparatus according to claim 3, further comprising a graphite flexible sheet on a lower surface of the folded portion.