JP4513638B2 - Compound semiconductor crystal manufacturing equipment - Google Patents

Description

  The present invention relates to an improvement in a compound semiconductor crystal manufacturing apparatus, and more particularly to an improvement in a crystal manufacturing apparatus such as GaAs used for optical devices, electronic devices, and the like.

  Among compound semiconductor crystals, for example, a GaAs crystal is industrially manufactured by a pulling method (LEC method), a horizontal boat method (HB method, HGF method), a vertical boat method (VB method, VGF method), or the like. . In particular, in the pulling method and the vertical boat method, the cross section of the obtained crystal is the same circle as the device manufacturing substrate, so that the yield is improved and the large diameter is easy due to the symmetry of the crystal to be manufactured. Therefore, there are many advantages over the horizontal boat method as a method for producing a single crystal.

  The cross-sectional view of FIG. 2 schematically shows a compound semiconductor crystal manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. 11-335194. This apparatus includes, for example, a silicon carbide reaction tube 1 having an inner diameter of 170 mm, a thickness of 3 mm, and open ends at both ends. An Fe—Cr—Al-based heater 3 is disposed in the atmospheric air around the reaction tube 1 made of silicon carbide, and the heater 3 is separated into a plurality of zones, and the temperature of each zone is individually controlled. obtain.

  In the manufacturing apparatus as shown in FIG. 2, since the heater 3 is provided in the atmosphere outside the reaction tube 1, a low-cost iron-based heater can be used as described above. Since this type of resistance heater can be easily zoned in multiple stages, the temperature distribution can be controlled.

  Stainless steel flanges 9 are attached to both open ends of the silicon carbide reaction tube 1 in the manufacturing apparatus of FIG. A connecting portion between the silicon carbide reaction tube 1 and the stainless steel flange 9 has a Wilson seal structure, and a packing 12 is interposed to ensure airtightness. As the packing 12, an elastic body such as an O-ring is used, and specifically, a fluororesin or the like can be used in addition to rubber.

  Further, a jacket is attached to the flange 9, and the connecting portion between the silicon carbide reaction tube 1 and the flange 9 is cooled by circulating cooling water in the jacket, so that it is airtight when heated by the heater 3. Is configured to be maintained.

  In order to maintain the airtightness of the connection portion between the silicon carbide reaction tube 1 and the flange 9, in addition to using such a jacket, for example, the connection portion is forcibly air-cooled, or the heater and the connection portion. The distance may be sufficiently separated and air-cooled in an air atmosphere.

  An exhaust pipe insertion port 16 and a gas introduction pipe insertion port 17 are formed on the flange 9 attached to the upper part of the silicon carbide reaction tube 1. An exhaust pipe 18 for exhausting the inside of the silicon carbide reaction tube 1 to a vacuum is inserted into the exhaust pipe insertion port 16, and a gas is introduced into the silicon carbide reaction tube 1 into the gas introduction pipe insertion port 17. A gas introduction pipe 19 for introduction is inserted.

  On the other hand, in the center of the flange 9 attached to the lower part of the reaction tube 1 made of silicon carbide, a lower shaft 4 that can move up and down is installed, and a semiconductor crystal material is accommodated at the tip of the lower shaft 4. For this purpose, a crucible 2 is placed. A thermocouple insertion port 15 is formed in the flange 9 attached to the lower part of the silicon carbide reaction tube 1. A thermocouple 13 for measuring the temperature near the side surface of the crucible 2 is inserted into the thermocouple insertion port 15. It is also possible to provide a thermocouple port on the upper flange and insert the thermocouple into the crucible 2 from above. The temperature at the bottom of the crucible 2 may be measured by passing a thermocouple through the lower shaft 4. In addition to the thermocouple, a radiation thermometer can be used as the temperature measuring means.

For example, a 6-inch diameter single crystal of GaAs can be manufactured by the following VB method using the manufacturing apparatus of FIG. First, a seed crystal 55 made of a GaAs single crystal is put into a recess at the lower end of a crucible 2 having an inner diameter of 6 inches placed on the tip of the lower shaft 4. Next, in the crucible 2, for example, 20 kg of GaAs polycrystalline raw material and 300 g of boron oxide (B ₂ O ₃ ) 70 for sealing the surface of the raw material melt 60 are loaded.

  This crucible is installed in the reaction tube 1 made of silicon carbide, and a flange 9 is attached and sealed. Subsequently, the exhaust pipe 18 is used to evacuate the silicon carbide reaction tube 1 to a vacuum, and then the temperature is raised by the Fe—Cr—Al heater 3. During the temperature increase, nitrogen gas is introduced into the silicon carbide reaction tube 1 using the gas introduction pipe 19 and adjusted so that the pressure in the silicon carbide reaction tube 1 is about 2 atm when the temperature increase is completed. .

  The raw material melt 60 is formed by melting the GaAs polycrystalline raw material by heating with the Fe—Cr—Al heater 3. After adjusting the temperature of the seed crystal 55 to be around 1238 ° C., which is the melting point of GaAs, and the temperature of the side surface of the crucible 2 to be about 1250 ° C., as indicated by the arrows in FIG. The lower shaft 4 is moved downward at a speed of 2 mm / hr.

In this way, the GaAs single crystal 50 can be grown by slowly solidifying the raw material melt 60 upward from the seed crystal 55 placed in the lower end recess of the crucible 2.
JP 11-335194 A

  When the crucible 2 is heated by the heater 3 from the outside of the airtight reaction tube 1 as in the manufacturing apparatus of FIG. 2, the temperature distribution in the crucible 2 is blunted by the intervention of the reaction tube 1. Moreover, the reaction tube 1 must endure an internal pressure of about 2 atm at a high temperature exceeding 1000 ° C., and it is difficult to reduce the thickness of the reaction tube 1. In particular, when a reaction tube made of silicon carbide, which is preferable in terms of purity, is used, the reaction tube made of silicon carbide has a high thermal conductivity, so that the temperature distribution in the crucible 2 tends to be slowed down.

  On the other hand, if the temperature distribution in the crucible 2 is prevented from slowing down by further increasing the temperature in the high temperature portion of the Fe—Cr—Al heater 3 outside the hermetic reaction tube 1, the Fe—Cr—Al system is originally used. Since the heater 3 is used near the upper limit of the usable temperature, the oxidation of the heater 3 proceeds and the life is shortened.

  In view of the problems in the prior art as described above, an object of the present invention is to provide a compound semiconductor crystal manufacturing apparatus that can form a preferable temperature distribution for growing a compound semiconductor single crystal and can extend the life of a heater. It is said.

An apparatus for producing a compound semiconductor crystal according to the present invention comprises a reaction tube having an open end at least at one end, a first heating means disposed in an atmosphere around the outside of the reaction tube, and a reaction tube. A flange that is attached to the open end so as to be sealed, a crucible for containing a raw material of semiconductor crystal installed in the reaction tube, and a second heating means between the inner wall and the crucible inside the reaction tube. look-containing reaction tube between the first heating means and second heating means is characterized by being interposed.

  The crucible and the first and second heating means can be moved relative to each other. It is preferred that the first and second heating means can be moved relative to the crucible in synchronism with each other.

  Further, the reaction tube may be formed of silicon carbide, and the second heating means preferably includes any of carbon, pBN-coated carbon, and molybdenum silicide. A GaAs crystal can be preferably grown as the compound semiconductor crystal.

  According to the present invention, since the compound semiconductor crystal manufacturing apparatus includes the second heating means between the inner wall of the reaction tube and the crucible, a temperature distribution preferable for single crystal growth can be formed, and the reaction tube It is possible to avoid overheating the first heating means disposed in the surroundings in an air atmosphere, and the life of the manufacturing apparatus can be extended.

  The cross-sectional view of FIG. 1 schematically shows the main part of a compound semiconductor crystal manufacturing apparatus according to an embodiment of the present invention. The manufacturing apparatus in FIG. 1 is shown in a simplified manner as compared with FIG. 2, but the basic detailed structure can be configured in the same manner as the manufacturing apparatus in FIG. In FIG. 1, the same reference numerals as those in FIG. 2 represent the same or corresponding parts.

  Compared to FIG. 2, the characteristic configuration of the manufacturing apparatus of FIG. 1 is that the reaction tube heater 11 is included in addition to the reaction tube heater 3. As the reaction tube heater 3, an inexpensive Fe—Cr—Al heater can be used as in the case of FIG.

  On the other hand, since the heater 11 in the reaction tube is intended to heat the highest temperature portion of the crucible 12, it is preferably made of a material that can withstand higher temperatures. Moreover, since the semiconductor characteristics change if impurities generated from the heater 11 in the reaction tube are mixed into the compound semiconductor crystal, it is preferable to configure the heater 11 in the reaction tube with a material that does not generate such impurities.

  As such a material that can withstand high temperatures and does not generate impurities, carbon, pBN-coated carbon, molybdenum silicide, and the like can be preferably used for the heater 11 in the reaction tube.

  Thus, in addition to the heater 3 outside the reaction tube, by separately providing the heater 11 inside the reaction tube for heating the highest temperature region of the crucible 2, it becomes possible to control the sharp temperature distribution in the crucible 2, Overheating of the reaction tube heater 3 made of an inexpensive Fe—Cr—Al-based material can be avoided, and the lifetime can be significantly extended.

  When growing the compound semiconductor single crystal, the crucible 2 may be moved with respect to the reaction tube heater 3 and the reaction tube heater 11 by driving the lower shaft 4. The reaction tube heaters 11 may be moved relative to the crucible 2 in synchronization with each other. When the crucible 2 is moved, it is necessary to lengthen the reaction tube 1 corresponding to the moving distance. However, when the reaction tube heater 3 and the reaction tube heater 11 are moved in synchronization with each other, the reaction tube 1 is moved. The advantage of shortening can be obtained.

  As described above, according to the present invention, it is possible to provide a compound semiconductor crystal manufacturing apparatus capable of forming a temperature distribution preferable for single crystal growth and extending the lifetime.

It is typical sectional drawing which shows the manufacturing apparatus of the compound semiconductor crystal by this invention. It is a schematic sectional drawing which shows the manufacturing apparatus of the compound semiconductor crystal by a prior art.

Explanation of symbols

  1 reaction tube, 2 crucible, 3 reaction tube heater, 4 lower shaft, 9 flange, 11 reaction tube heater, 12 packing, 13 thermocouple, 15 thermocouple insertion port, 16 exhaust tube insertion port, 17 gas introduction tube Insertion port, 18 exhaust pipe, 19 gas introduction pipe, 50 compound semiconductor crystal, 55 seed crystal, 60 raw material melt, 70 liquid sealing material.

Claims (6)

An apparatus for producing a compound semiconductor crystal,
A reaction tube having an open end at least at one end; and
A first heating means disposed in an air atmosphere around the outside of the reaction tube;
A flange attached to the open end to seal the reaction tube;
A crucible for accommodating the raw material of the semiconductor crystal installed in the reaction tube;
A second heating means seen contains between inner its inner wall and the crucible of the reaction tube,
The apparatus for producing a compound semiconductor crystal , wherein the reaction tube is interposed between the first heating means and the second heating means .   2. The compound semiconductor crystal manufacturing apparatus according to claim 1, wherein the crucible and the first and second heating means can be relatively moved.   3. The compound semiconductor crystal manufacturing apparatus according to claim 2, wherein the first and second heating means can be moved relative to the crucible in synchronization with each other.   The said reaction tube is formed with silicon carbide, The manufacturing apparatus of the compound semiconductor crystal in any one of Claim 1 to 3 characterized by the above-mentioned.   5. The compound semiconductor crystal manufacturing apparatus according to claim 1, wherein the second heating unit includes any one of carbon, pBN-covered carbon, and molybdenum silicide. 6.   6. The compound semiconductor crystal manufacturing apparatus according to claim 1, wherein the compound semiconductor crystal is a GaAs crystal.

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