JP4193681B2 - Gallium phosphide single crystal production equipment - Google Patents

Description

  The present invention relates to an apparatus for producing a gallium phosphide single crystal using a liquid sealing pulling method (LEC method).

  A gallium phosphide (GaP) single crystal used as a visible light emitting diode (LED) substrate is grown by the LEC method.

  An example of a conventional GaP single crystal manufacturing apparatus is shown in a sectional view in FIG. 4 is a cross-sectional view showing the heating graphite heater of FIG.

  The GaP single crystal manufacturing apparatus by the LEC method is composed of a high-pressure vessel (1) that can withstand a pressure of about 100 atm. Usually, the GaP single crystal is produced in a high-pressure vessel (1) such as nitrogen or argon at 50 atm. Performed in an inert gas atmosphere. At the center of the high-pressure vessel (1), a heat insulating cylinder (10) and a quartz crucible (2) surrounded by a heating graphite heater (3a) are arranged, and a single crystal pulling shaft (8) is disposed above. Is provided.

  As shown in FIG. 4, the graphite heater (3a) for heating has an upper cylindrical portion (31a) and a lower cylindrical portion (32a) with different diameters formed integrally, and the upper cylindrical portion (31a) has an upper portion (33a). ), A slit portion (34a) having a slit, and a lower portion (35a), and a lower cylindrical portion (32a) is formed to protrude downward from a bottom portion (36a) of the upper cylindrical portion (34a). Of these, only the slit portion (34a) of the upper cylindrical portion contributes to heat generation. The slit portion (34a) is formed in a zigzag shape with the vertical direction as the longitudinal direction, and functions as a heating element.

  Usually, by designing the bottom part (36a) of the upper cylindrical part (31a) and the bottom of the quartz crucible (2) as close as possible, the heat retention of the graphite heater (3a) is improved and the atmosphere gas of 50 atmospheres Prevents temperature fluctuations due to convection and keeps the solid-liquid interface where the growing GaP single crystal (6) is in contact with the GaP melt (5) stable, enabling the growth of long GaP single crystals Yes.

  In order to perform crystal growth while keeping the temperature distribution in the quartz crucible (2) constant and maintaining the temperature gradient near the solid-liquid interface from the beginning to the end of crystal growth, A push-up shaft (11) that pushes up the quartz crucible (2) is provided below so as to maintain the liquid upper surface at a fixed position with respect to the graphite heater (3a).

When crystal growth is performed with a GaP single crystal manufacturing apparatus, first, a raw material gallium phosphide (GaP) polycrystal is put in a quartz crucible (2), and any of n-type impurities S, Te and Si is added. To do. On top of that, B ₂ O ₃ which is a sealing agent (4) for preventing volatile decomposition of phosphorus at the time of melting the raw material is placed, and a graphite heater (3a) is used in a high-pressure inert gas atmosphere such as argon or nitrogen. And heating to a melting point of GaP of 1465 ° C. or higher. After melting the raw material, the seed crystal (7) attached to the pulling shaft (8) is lowered and immersed in the surface of the GaP melt located under the sealant (4), then the melt temperature is lowered, and the quartz crucible The GaP single crystal (6) is grown by rotating (2) and pulling up the seed crystal (7) while rotating it.

  The obtained single crystal (6) is subjected to cylindrical grinding to adjust the outer shape, and then cut into a wafer having a thickness of about 300 to 500 μm with a wire saw or an inner peripheral cutting machine. Wafers are inspected for electrical characteristics, crystal defects, appearance stains, scratches, etc., and wafers that pass the standards are used as products.

  In the GaP single crystal (6) obtained by the above-described method, a lineage failure in which dislocations are accumulated on the straight line portion or the bottom portion of the crystal or a polycrystallization failure due to the development of lineage occurs. Further, solidification that causes a sudden mass increase signal to enter a crystal mass sensor (not shown) that monitors the crystal mass during the crystal growth and stops the growth occurs.

  The cause of the lineage failure in which dislocations accumulate linearly, or the failure of polycrystallization due to the development of lineage occurs because the solid-liquid interface shape is entirely or partially concave with respect to the melt. Dislocations having the property of propagating perpendicular to the surface are accumulated at concave portions. Therefore, in order to suppress the accumulation of dislocations, the convexity of the solid-liquid interface may be set to an appropriate level.

  Until now, as described in Japanese Patent Application Laid-Open No. 2003-212698, the growth of GaP single crystals having a diameter of about 50 mm is based on the convexity data obtained by measuring the obtained solid-liquid interface shape. In addition, it has been proposed to obtain an appropriate degree of convexity of the solid-liquid interface to reduce poor polycrystallization.

With increasing demand for LEDs, a large-diameter GaP substrate having a diameter of 65 to 80 mm is required. The diameter of a quartz crucible for growing a large diameter GaP single crystal having a diameter of 65 to 80 mm is generally about 130 mm, and the diameter of the graphite heater for heating, that is, the diameter of the upper cylindrical portion (31a) is 140 to 170 mm. However, in order to grow a large-diameter GaP single crystal having a diameter of 65 to 80 mm, if the quartz crucible is simply enlarged to about 130 mm, even if the temperature of the quartz crucible bottom is adjusted, only the convexity of the small solid-liquid interface can be obtained. It is not possible to prevent a lineage failure in which dislocations accumulate on a line or a polycrystallization failure in which dislocation accumulation has developed.
Japanese Patent Laid-Open No. 2003-212698

  The present invention suppresses the occurrence of lineage defects in which dislocations accumulate on a line and polycrystallization failure in which dislocation accumulation further develops when a GaP single crystal having a diameter of 65 to 80 mm is manufactured by the LEC method. The purpose is to improve the yield of.

The GaP single crystal manufacturing apparatus of the present invention includes a graphite heater in which an upper cylindrical portion and a lower cylindrical portion having different diameters are integrally formed. The upper cylindrical portion is provided with a slit portion that functions as a heating element, and is liquid-sealed. In an apparatus for producing a GaP single crystal having a diameter of 65 to 80 mm by a pulling method, the vertical length from the lower end of the slit portion of the upper cylindrical portion of the graphite heater to the lower end of the lower cylindrical portion is set to The height is 31.5% or more and 36% or less , and the height of the lower cylindrical portion is 12 % or more and 17% or less with respect to the height of the entire graphite heater.

  The present invention is preferably applied to a GaP single crystal manufacturing apparatus in which the entire graphite heater has a height of 228 to 232 mm.

  According to the present invention, when producing a GaP single crystal having a diameter of 65 to 80 mm by the LEC method, it is possible to remarkably reduce the occurrence of lineage failure in which dislocations are accumulated on the line and polycrystallization failure in which dislocation accumulation is further developed. And the yield of GaP single crystal can be improved.

  In general, if the space under the graphite heater below the lower end of the slit portion of the upper cylindrical portion is made large, the lower portion of the graphite heater does not contribute to heat generation. Since the temperature gradient in the vicinity of the solid-liquid interface increases, it is known that the convexity of the solid-liquid interface increases. However, if the space under the graphite heater is made too large, the temperature fluctuation due to the convection of the atmospheric gas at 50 atm becomes large, and it is possible to produce a long single crystal while keeping the solid-liquid interface stable during crystal growth. Have difficulty. The present inventors have obtained the knowledge that it is effective to adjust the space under the graphite heater in order to obtain an appropriate degree of convexity at the solid-liquid interface and enable stable crystal growth. The present invention has been reached.

The GaP single crystal manufacturing apparatus of the present invention includes a graphite heater in which an upper cylindrical portion and a lower cylindrical portion having different diameters are integrally formed, from the lower end of the slit portion of the upper cylindrical portion of the graphite heater to the lower end of the lower cylindrical portion. The vertical length is 31.5% or more and 36% or less with respect to the overall height of the graphite heater, and the height of the lower cylindrical portion is 12 % or more and 17 with respect to the overall height of the graphite heater. % Or less .

  That is, in the present invention, the upper cylindrical portion and the lower cylindrical portion are integrally formed, thereby reducing the temperature fluctuation by convection by constricting the space by the lower cylindrical portion, and lower than the lower end of the slit portion of the upper cylindrical portion. By increasing the space under the graphite heater in Fig. 1, the heat retention near the bottom of the quartz crucible is reduced and the temperature gradient near the solid-liquid interface during crystal growth is increased. By regulating the vertical length from the lower end of the slit part to the lower end of the lower cylindrical part and the height of the lower cylindrical part, the convexity of the solid-liquid interface is properly controlled, and lineage failure and polycrystallization failure Is decreasing.

  The shape of the graphite heater may be composed of three or more cylindrical portions, but two cylinders are used in order to achieve the minimum object and minimize the increase in manufacturing cost due to the processing of the graphite heater. It is desirable to consist of parts.

  If the length in the vertical direction from the lower end of the slit portion to the lower end of the lower cylindrical portion is less than 32% of the total height of the graphite heater, the convexity of the solid-liquid interface becomes insufficient, resulting in poor lineage and polycrystallization. It is not preferable because defects frequently occur. On the other hand, if it exceeds 36%, the degree of convexity becomes excessive, and an abrupt mass increase signal enters the crystal mass sensor that monitors the crystal mass during the crystal growth, so that solidification that causes the growth to stop is likely to occur.

  If the height of the lower cylindrical portion is less than 12% with respect to the total height of the graphite heater, the convexity becomes excessive and solidification tends to occur, which is not preferable. On the other hand, if it exceeds 17%, the convexity becomes insufficient, which is not preferable.

  The overall height of the graphite heater can be changed as necessary. However, the GaP single crystal production apparatus by the LEC method is composed of a high-pressure vessel that can withstand a pressure of about 100 atm. Usually, the production of GaP single crystal is performed in an inert gas atmosphere such as nitrogen or argon at 50 atm. It will be limited by the height of the high-pressure vessel used. In order to produce a GaP single crystal having a diameter of 65 to 80 mm using the above-described generally used quartz crucible, the overall height of the graphite heater is preferably 228 to 232 mm.

(Example 1)
The graphite heater (3) whose sectional view was shown in FIG. 2 was used. The total height (T) of the graphite heater is 230 mm ± 2 mm, the vertical length (F1) from the lower end of the slit portion (34) to the lower end of the lower cylindrical portion (32) is 73 mm, and the height of the lower cylindrical portion ( S1) was 38 mm. That is, F1 is 31.5 to 32% with respect to T, and S1 is 16 to 17% with respect to T.

  Crystal growth of a GaP single crystal having a diameter of 65 to 80 mm was performed three times by a normal LEC method using the GaP single crystal manufacturing apparatus whose sectional view is shown in FIG.

  As a result, a single crystal (6) having an average mass of 1860 g was obtained, and the incidence of defective lineage and defective polycrystallization was 9%. Moreover, the bottom part of the single crystal ingot which becomes a standard of the solid-liquid interface shape during the growth of the single crystal had a shape with a center of 5 to 9 mm with respect to the periphery.

(Example 2)
Crystal growth was performed four times in the same manner as in Example 1 except that the vertical height difference (F1) from the lower end of the slit to the lower end of the lower cylindrical portion was 83 mm. In addition, F1 was 35 to 36% with respect to T.

  As a result, a single crystal (6) having an average mass of 1860 g was obtained, and the incidence of defective lineage and defective crystallization was 0%. In addition, the bottom of the single crystal ingot, which is a measure of the solid-liquid interface shape during single crystal growth, had a shape with a center of 6 to 7 mm with respect to the periphery.

(Example 3)
Crystal growth was performed twice in the same manner as in Example 1 except that the height (S1) of the lower cylindrical portion was 28 mm. S1 was 12% with respect to T.

  As a result, a single crystal (6) having an average mass of 1860 g was obtained, and the incidence of defective lineage and defective crystallization was 0%. In addition, the bottom of the single crystal ingot, which is a measure of the solid-liquid interface shape during single crystal growth, had a shape with a center protruding 5 to 7 mm from the periphery.

(Comparative Example 1)
The graphite heater (3a) whose sectional view was shown in FIG. 4 was used. Crystal growth was carried out 12 times in the same manner as in Example 1 except that the height (S2) of the lower cylindrical portion was 49.5 mm. In addition, S2 was 21-22% with respect to T.

  As a result, a single crystal (6) having an average mass of 1860 g was obtained, and the incidence of defective lineage and defective crystallization was 36%. In addition, the bottom of the single crystal ingot, which is a measure of the solid-liquid interface shape during single crystal growth, had a shape with a center of 2 to 4 mm with respect to the periphery.

The results of the above examples and comparative examples are summarized in Table 1. From the results of Table 1, in the examples according to the present invention, the occurrence of lineage and polycrystallization failure is significantly reduced as compared with the comparative example.

It is sectional drawing which shows one Example of the GaP single crystal manufacturing apparatus of this invention. It is sectional drawing which shows the graphite heater for a heating of FIG. It is sectional drawing which shows an example of the conventional GaP single crystal manufacturing apparatus. It is sectional drawing which shows the graphite heater for a heating of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure vessel 2 Quartz crucible 3, 3a Graphite heater 31, 31a Upper cylinder part 32, 32a Lower cylinder part 34, 34a Slit part 4 Sealant 5 GaP melt 6 GaP single crystal 7 Seed crystal 8 Pulling shaft 9 Quartz cap 10 Insulation tube 11 Lifting shaft T Height of graphite heater F1, F2 Vertical height difference from lower end of slit to lower end of lower cylindrical portion S1, S2 Height of lower cylindrical portion

Claims (1)

Equipped with a graphite heater in which upper and lower cylindrical parts with different diameters are integrally formed. The upper cylindrical part is provided with a slit part that functions as a heating element, and is phosphorylated with a diameter of 65 to 80 mm by a liquid sealing pulling method. In the apparatus for producing a gallium single crystal, the vertical length from the lower end of the slit portion of the upper cylindrical portion of the graphite heater to the lower end of the lower cylindrical portion is 31.5% or more with respect to the height of the entire graphite heater. An apparatus for producing a gallium phosphide single crystal, characterized in that it is 36% or less , and the height of the lower cylindrical portion is 12 % or more and 17% or less with respect to the overall height of the graphite heater.

Images