JP2011046578A - Method for producing single crystal body and method for producing free-standing single-crystal substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a single crystal body by which reduction in air-tightness in a production device for a single crystal body is suppressed, and to provide a method of producing a free-standing single-crystal substrate. <P>SOLUTION: The method of producing a single crystal by a vapor phase growth method comprises: a step where a group IIIB element metal is melted to form a melt 11 of the group IIIB element metal; a step where a feed pipe 5 for feeding a halogen gas is inserted into the melt 11, a bubble 7 smaller than an inside diameter that of the feed pipe 5 is fed inside the melt 11 to extract the halide gas of the group IIIB element; and a step where a nitrogen-containing gas and the halide gas of the group IIIB element are fed to the surface of a seed substrate 3, and the nitrogen-containing gas and the halide of the group IIIB element are reacted on the seed substrate 3 to grow a single crystal body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a single crystal and a method for manufacturing a single crystal free-standing substrate by growing the single crystal by vapor phase epitaxy.

  Nitride objects such as GaN and AlGaN are used in, for example, light-emitting elements such as light-emitting diodes (LEDs) and semiconductor lasers (LDs), electronic devices such as power devices such as transistors and power FETs (Field Effect Transistors), and the like. , Expansion of use is expected.

  However, group IIIB nitride single crystals such as GaN and AlGaN have a high melting point and a high equilibrium vapor pressure of N (nitrogen), which makes it difficult to produce a bulk single crystal from the liquid phase. is there. Therefore, a single crystal body of a group IIIB nitride object is vapor-phase grown on a seed substrate and used as a free-standing substrate for various devices. The self-supporting substrate means a substrate that can be handled as a solid material without being deformed or damaged by its own weight when handled.

  For example, Patent Document 1 discloses that gallium chloride, which is a gas for growing a gallium nitride thick film, is produced by bubbling hydrogen chloride gas into a gallium melt, and then gallium nitride gas and ammonia gas are reacted to make the gallium nitride self-supporting. A method of making a substrate is described.

JP 2007-126320 A

  As a method for efficiently producing a gallium nitride single crystal free-standing substrate, for example, a gallium nitride single crystal is produced in a bulk shape (thickness of 10 mm or more), and a plurality of free-standing single crystal substrates are cut out from the single crystal. When trying to introduce the method, the method of Patent Document 1 has insufficient reaction efficiency between the gallium melt and hydrogen chloride gas, and it has been difficult to produce a bulk gallium nitride single crystal.

  In the method described above, there are many hydrogen chloride gases that have not been used in the production of gallium nitride. Hydrogen chloride gas has an effect of etching gallium nitride in a high temperature atmosphere exceeding 1000 ° C. Therefore, unreacted hydrogen chloride gas remains in the gallium nitride manufacturing apparatus, so that the surface of the growing gallium nitride is exposed and the growth rate of gallium nitride is reduced.

  The present invention has been completed in view of the above-mentioned conventional problems, and improves the reaction efficiency between a Group IIIB element metal melt used for growth of a Group IIIB nitride single crystal and a halide gas. Another object of the present invention is to provide a method for producing a single crystal.

  A method for producing a single crystal according to an embodiment of the present invention is a method for producing a single crystal by a vapor phase growth method, comprising melting a group IIIB element metal to form a group IIIB element metal melt. A supply pipe for supplying a halogen gas is put into the melt, and bubbles smaller than the inner diameter of the supply pipe are supplied into the melt from a plurality of locations to extract the group IIIB element halide gas. Supplying a nitrogen-containing gas and a group IIIB element halide gas onto a seed substrate, and reacting the nitrogen-containing gas and the group IIIB element halide on the seed substrate to form a single crystal And growing.

  It is preferable that the supply pipe has a plurality of gas outlets to the melt at the tip, and the gas outlet is smaller than the inner diameter of the supply pipe.

  The inner diameter of the gas outlet is preferably 0.1 to 1% of the inner diameter of the supply pipe.

  The tip of the supply pipe is preferably inclined with respect to the inner diameter direction of the supply pipe.

  The vapor phase growth method is preferably a hydride vapor phase growth method.

  A method for manufacturing a single crystal free-standing substrate according to an embodiment of the present invention includes a step of cutting a plurality of self-supporting substrates from a single crystal obtained by the method for manufacturing a single crystal.

  According to the method for producing a single crystal of the present invention, a supply pipe for supplying halide gas is put into the melt, and bubbles smaller than the inner diameter of the supply pipe are supplied into the melt from a plurality of locations. Since it has a step of extracting the halide gas of the group IIIB element, the halide gas and the group IIIB element metal melt are increased by increasing the gas-liquid interface area and the contact time between the halide gas and the group IIIB element metal melt. The reaction efficiency of can be greatly improved. As a result, unreacted halide gas is removed, the growth rate of the single crystal body can be increased as compared with the conventional case, and a bulk single crystal body can be manufactured.

FIG. 1 is a schematic cross-sectional view showing an example of a vapor phase growth apparatus used in the method for producing a single crystal of the present invention. (A) is the expanded sectional view of the site | part near the gas outlet of the vapor phase growth apparatus shown in FIG. 1, (b) is the top view which looked at the site | part near the gas outlet from the bottom. FIG. 3 is a schematic cross-sectional view showing an example of a vapor phase growth apparatus used in the method for producing a single crystal of the present invention.

  FIG. 1 is a schematic cross-sectional view showing an example of a vapor phase growth apparatus for producing a single crystal of the present invention. In FIG. 1, 1 is a vapor phase growth apparatus, 2 is a holder, 3 is a seed crystal substrate (seed substrate) for crystal growth, 4 is a container for storing a group IIIB element metal, 5 is a halogen gas supply pipe, 5a Is a halogen gas supply pipe of group IIIB, 7 is a bubbling halogen gas, 8 is an inert gas supply pipe, 9 is a nitrogen-containing gas supply pipe, 10 is a heater, 11 Represents a melt of a group IIIB element metal, respectively.

  As shown in FIG. 2, which is an enlarged view of the distal end portion of the halogen gas supply pipe 5, a plurality of gas emission ports 5b that are fine holes are formed at the distal end portion 5a of the halogen gas supply pipe 5 in FIG.

  In FIG. 2, the gas outlet 5b is provided in the filter. In addition, in FIG. 2, it is provided not only on the bottom surface of the halogen gas supply pipe 5, but also on the side surface of the halogen gas supply pipe 5, so that the halogen gas can be sufficiently supplied.

  The diameter of the gas outlet 5 a is smaller than the inner diameter of the halogen gas supply pipe 5. Specifically, the diameter of the gas outlet 5b is preferably small enough to be 0.1 to 1% of the inner diameter of the supply pipe 5. Further, it is preferable that 10,000 to 20,000 gas outlets 5a exist in the filter. Thus, since the gas outlet 5a is small, the surface area of the emitted halogen gas bubble is small, and since there are a plurality of gas outlets, it can be injected into many bubbles and the melt. Therefore, the reaction efficiency of the group IIIB element metal can be sufficiently improved.

  The pitch of the plurality of gas outlets 5a is preferably 10 μm or more. Thereby, the coupling | bonding of the bubbles supplied from the adjacent gas emission port 5a can be suppressed.

  The tip 5a shown in FIG. 2 may be a filter different from the halogen gas supply pipe 5 as shown in FIG. 1, or the gas outlet 5b may be directly provided in the halogen gas supply pipe 5. The tip 5a is preferably formed by a filter separate from the halogen gas supply pipe 5 because it can be replaced even if the gas outlet 5b deteriorates due to long-term use.

  Any filter can be used as long as it can be put into a high-temperature Group IIIB element metal melt, and a graphite filter is particularly preferable. The graphite filter has corrosion resistance to high-temperature halogen gas and low wettability to a Group IIIB element metal melt.

  The thickness of the filter is preferably about 1 to 10 mm in consideration of ease of handling.

  The thickness of the filter is preferably uniform. Specifically, it is desirable that the error of the filter thickness is suppressed to ± 1% or less. Furthermore, for the same reason, it is desirable that the pore diameter distributed in the filter is uniform.

The halogen gas supply pipe 5 is preferably a member having high temperature resistance (about 800 ° C.) and corrosion resistance against halogen gas, and specifically, quartz, Al ₂ O ₃ , SiC and the like can be mentioned.

  In FIG. 1, the seed substrate 3 is described here using an example using a group IIIB nitride single crystal. Specifically, a gallium nitride compound semiconductor such as GaN or AlGaN, AlN, or the like can be used. When the group IIIB nitride single crystal is a GaN single crystal, examples of the seed substrate 3 include sapphire, SiC, GaN single crystal, AlN single crystal, or a mixed crystal of GaN single crystal and AlN single crystal. it can. Among them, GaN single crystals, AlN single crystals, or mixed crystals of GaN single crystals and AlN single crystals are preferably used. The thickness of the seed substrate 3 for growth is about 0.3 to 0.6 mm. The diameter of the seed substrate 3a for growth is 20 mm to 60 mm.

  In FIG. 1, the substrate 2 is provided on the holding body 2. Graphite can be used for the holder 2, but when corrosive ammonia is used as the source gas, the surface of the holder 2 is coated with one or more selected from the group consisting of SiC, BN and TaC. It is preferable. Examples of the coating method include a CVD method and a sputtering method. Thereby, the corrosion resistance of the holding body 2 is improved. PBN is preferable among BN. PBN is pyrogenic boron nitride (pyrolytic BN (p-BN)). Further, it is desirable to provide a mechanism (susceptor rotating shaft 2a) for rotating the seed substrate 2 held around the central axis of the holding body 2 so as to rotate during crystal growth. Thereby, the uniformity of the crystal growing on the seed substrate 3 can be improved. In addition, as rotation speed, it is possible to select from the range of about 2 rpm-50 rpm, for example.

  1 and 2, the case where the growth surface of the single crystal body is arranged and grown on the seed substrate 3 so as to face the vertical direction is not limited to this. For example, As shown in FIG. 3, a growth apparatus will be described in which a single crystal is grown so that the growth surface is directed downward with respect to the vertical direction. Comparing the vapor phase growth apparatus shown in FIG. 1 and FIG. 3, the metal melt droplets scattered from the IIIB halide gas supply pipe 6 toward the crystal surface due to the bubbles that bounced on the surface of the metal melt. The vapor phase growth apparatus shown in FIG. 1 is preferable because it has a structure that is difficult to scatter.

  The production method of the present invention will be specifically described below. In the following description, gallium is used as the group IIIB element metal and hydrogen chloride is used as the halogen gas. However, the present invention is not limited to these.

(Process 1)
The production method of the present invention includes a step of melting a group IIIB element metal to form a melt. Specifically, gallium metal is melted at a temperature of about 800 ° C. in the gallium container 4. For this purpose, the gallium container 4 may be heated by heating the heater 10 to a predetermined temperature.

(Process 2)
Next, the hydrogen chloride supply pipe 5 is put into the gallium melt 11. At this time, the hydrogen chloride supply pipe 5 is preferably installed such that the gas outlet 5 b is as far away from the liquid surface of the gallium melt 11 as possible. Thereby, since the hydrogen chloride bubble 7 can stay in the melt 11 for a long time, the reaction efficiency between hydrogen chloride and the gallium melt can be improved.

  The hydrogen chloride supply pipe 5 has a plurality of gas outlets 5b as described above formed at the tip thereof. By supplying a plurality of hydrogen chloride bubbles 7 from the plurality of gas outlets 5b, each of the bubbles 7 In this case, the area in contact with the melt 11 is increased, and the reaction efficiency between hydrogen chloride and the gallium melt can be improved.

(Process 3)
The gallium chloride gas thus generated is supplied from the gallium chloride supply pipe 6 to the seed substrate 3, and ammonia gas is supplied as a nitrogen-containing gas from the nitrogen-containing gas supply pipe 9 to the seed substrate 3 and mixed. By setting the temperature to a predetermined temperature, a single crystal of GaN can be grown on the surface of the seed substrate 3 at a high speed. The pressure during the reaction is usually atmospheric pressure (normal pressure) in the HPVE method.

  In step 3, it is preferable that the central axis of the gallium chloride supply pipe 6 and the susceptor rotating shaft 2a do not overlap. By arranging the gallium chloride supply pipe 6 and the susceptor rotating shaft 2a in this way, a single crystal having a uniform film thickness can be produced.

  The heating in the above steps is performed using a heater 10 provided around the outer periphery of the vapor phase growth apparatus 1. The heater on the holder 2 side may heat the holder 2 and the seed substrate 3 by setting the temperature to 500 to 1000 ° C. when forming a low-temperature buffer layer or the like, and 1000 to 1300 ° C. when starting single crystal growth. The low-temperature buffer layer is necessary when a sapphire substrate is used as the growth seed substrate 3, and is formed at a thickness of 10 to 100 nm. Note that when the low-temperature buffer layer is formed, the gas composition is the same as that for growing the single crystal 3b.

  As the vapor phase growth method, a hydride vapor phase growth method (HVPE method) is preferably used. Other vapor phase growth methods include metal organic vapor phase growth (MOVPE), sublimation, etc., but the HVPE method is used because of its high growth rate, good quality, and ease of producing nitrided bodies. preferable. Hereinafter, an example using the HVPE method will be described.

The source gas supplied into the vapor phase growth apparatus 1 for growing a nitride body is ammonia (NH ₃ ) gas, gallium chloride (GaCl) gas, or the like. Further, nitrogen (N ₂ ) gas, hydrogen (H ₂ ) gas, silane (SiH ₄ ) gas, or the like may be included.

  The flow rate ratio between the ammonia gas and the hydrogen chloride gas supplied to the gallium vessel 4 is preferably such that the flow rate of the ammonia gas is about 15 to 80 times the flow rate of the hydrogen chloride gas. By setting this ratio, the growth rate of the GaN single crystal can be increased, and the growth of columnar crystals that increase dislocations in the GaN single crystal can be suppressed.

  In the manufacturing method of the present invention, it is preferable to flow an etching gas for removing by-products along the inner wall surface of the vapor phase growth apparatus 1. Examples of the etching gas include hydrogen halides such as hydrogen chloride, hydrogen boride, hydrogen bromide, and hydrogen fluoride. By causing the etching gas to flow along the inner wall surface of the growth apparatus, by-products attached to the inner wall surface can be removed. Moreover, since the possibility that the etching gas flows into the seed substrate 3 along the inner wall surface is low, it is possible to reduce the occurrence of single crystal growth suppression.

The single crystal obtained by the production method of the present invention as described above has a large thickness of 1 mm or more (preferably 10 mm or more, most preferably 25 mm or more), and an average dislocation density of 1 × 10 ⁹ cm ⁻² or less. A low quality product is obtained.

  According to the above manufacturing method, generation of unreacted halogen gas can be suppressed, so that a single crystal body (so-called ingot) having high crystallinity, small crystal quality variation, and large thickness can be manufactured. . In this manner, a plurality of single crystal substrates can be cut out by dicing from a single crystal having a large thickness and a small variation in crystal quality within the single crystal.

  In the case of a normal HVPE method, a single self-supporting single crystal substrate can be produced, but when the single crystal is to be grown thicker, the unreacted halogen gas is increased in the thickness of the single crystal. Conventionally, there has been a problem that a single crystal having a large thickness and excellent crystallinity cannot be obtained as a result of inhibiting film formation. However, the method for producing a single crystal of the present invention solves such problems.

  The obtained single crystal is processed into a substrate shape by, for example, the following method.

  First, the outer periphery of a single crystal grown using a diamond grindstone is ground to a predetermined outer diameter. Next, with a wire saw that cuts the crystal by reciprocating the wire while dripping diamond or SiC abrasive grains into a brass wire with a slurry, the single crystal is fixed to a predetermined thickness. Cut into a wafer shape (for example, 0.6 mm).

  And after rough-polishing both surfaces of a single crystal wafer using a diamond abrasive grain or a SiC abrasive grain, the surface used in a device process is mirror-polished using colloidal silica, and a single crystal wafer substrate is obtained.

  From the above, it is possible to manufacture a bulk-type and high-quality single crystal substrate suitable for epitaxial growth of gallium nitride compound semiconductors applied to optical elements and electronic elements.

  Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention.

  Furthermore, the vapor phase growth apparatus 1 is not limited to the shape as shown in FIG. 1, but can be applied to an apparatus for growing a nitride body in the vapor phase, and the source gas is also limited to the materials shown in the embodiments. However, it can be applied to a source gas capable of growing a nitride body.

[Example]
Examples are shown below, but the present invention is not limited to the contents of these Examples.

Example 1
In the HVPE apparatus, a supply pipe (made of quartz, inner diameter of supply pipe: 5 mm) with a carbon filter having a gas outlet having a diameter of 10 μm attached to the tip was placed in the gallium melt, and hydrogen chloride gas was bubbled.

  The ratio (reaction efficiency) of the amount of hydrogen chloride gas used for the reaction of gallium chloride to the amount of hydrogen chloride gas injected into the gallium melt from the supply pipe was 98%.

(Comparative Example 1)
The supply pipe of Example 1 with the carbon filter removed was installed on the gallium melt, and hydrogen chloride gas was allowed to flow from the supply pipe.

  The reaction efficiency of hydrogen chloride gas was 70%.

(Comparative Example 2)
The supply pipe of Example 1 with the carbon filter removed was placed in the gallium melt as in Example 1, and hydrogen chloride gas was bubbled.

  The reaction efficiency of hydrogen chloride gas was 85%.

  As described above, the reaction efficiency of the hydrogen chloride gas in Example 1 was larger than the reaction efficiency of the hydrogen chloride gas in Comparative Examples 1 and 2, and there was little hydrogen chloride gas remaining in the apparatus. Therefore, the growth rate of the gallium nitride single crystal was high, and a bulk gallium nitride single crystal of 25 mm or more that could not be produced in Comparative Examples 1 and 2 could be produced.

1: vapor phase growth apparatus 2: holder 3: seed crystal substrate for growth (seed substrate)
4: IIIB group element metal container 5: halogen gas supply pipe 5a: tip of halogen gas supply pipe,
6: Group IIIB halide gas supply pipe 7: Bubbled halogen gas 8: Inert gas supply pipe 9: Nitrogen-containing gas supply pipe 10: Heater 11: Group IIIB element metal melt

Claims (5)

A method for producing a single crystal by vapor deposition,
Melting a group IIIB element metal to form a group IIIB element metal melt;
A step of inserting a supply pipe for supplying a halogen gas into the melt and supplying bubbles smaller than the inner diameter of the supply pipe into the melt from a plurality of locations to extract a halide gas of a group IIIB element When,
Supplying a nitrogen-containing gas and a Group IIIB element halide gas onto a seed substrate, and reacting the nitrogen-containing gas and the Group IIIB element halide on the seed substrate to grow a single crystal. When,
A method for producing a single crystal comprising: The supply pipe has a plurality of gas outlets to the melt at its tip,
The method for producing a single crystal body according to claim 1, wherein the gas outlet is smaller than an inner diameter of the supply pipe.   The method for producing a single crystal according to claim 2, wherein the diameter of the gas outlet is 0.1 to 1% of the inner diameter of the supply pipe.   4. The method for producing a single crystal according to claim 1, wherein the vapor phase growth method is a hydride vapor phase growth method. A method for manufacturing a single crystal free-standing substrate, in which a plurality of self-supporting substrates are cut out from the single crystal obtained by the method for manufacturing a single crystal according to claim 1.

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