JP2010126392A - Method for producing nitride single crystal body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a nitride single crystal body from which a large diameter nitride single crystal substrate can be obtained. <P>SOLUTION: The method for producing the nitride single crystal body is the one for forming a bulky nitride single crystal body 7 on a seed substrate 5 by a vapor deposition method. The method includes: a process for heating the seed substrate 5; and a process for supplying a raw gas to the seed substrate 5 from a direction A parallel to or inclined from the seed substrate 5 and supplying the same raw gas as the raw gas supplied from the direction A to the seed substrate from such a direction B that the angle between the seed substrate 5 and itself is different from the angle between the seed substrate 5 and the direction A while rotating the seed substrate 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nitride single crystal manufacturing method for producing a bulk nitride single crystal on the surface of a seed substrate, and in particular, a light emitting element such as a light emitting diode (LED) or a semiconductor laser (LD), a transistor, The present invention relates to a method for manufacturing a nitride single crystal applied to an electronic device such as a power device such as a power FET (Field Effect Transistor).

  Nitride single crystals such as GaN and AlGaN have a high melting point and a high equilibrium vapor pressure of N (nitrogen), making it difficult to produce a bulk single crystal from the liquid phase. Therefore, a thin film made of nitride is vapor-phase grown on the seed substrate, and the thin film is used for various devices.

In recent years, a substrate of a self-standing nitride single crystal has been put into practical use by a vapor phase growth method such as a hydride vapor phase growth method (HVPE method) (see, for example, Patent Document 1). . Such a self-standing nitride single crystal substrate is very useful because a nitride single crystal semiconductor can be stacked thereon by, for example, metal organic chemical vapor deposition (MOCVD). is there.
Japanese Patent Laid-Open No. 2000-12900

  The nitride single crystal substrate is obtained by cutting out from a nitride single crystal grown by a vapor phase growth method. However, in the obtained nitride single crystal, the generation of crystal defects (dislocations) and the cracking of nitrided objects become prominent, so a nitride single crystal substrate (size larger than 2 inches) larger than the seed substrate is not It has not been obtained yet.

  Accordingly, the present invention has been completed in view of the above-described conventional problems, and an object thereof is to provide a method for producing a nitride single crystal capable of obtaining a large-diameter nitride single crystal substrate. It is.

  The method for producing a nitride single crystal according to the present invention is a method for producing a nitride single crystal in which a bulk nitride single crystal is produced on a seed substrate by vapor deposition, and the seed substrate is heated. A source gas is supplied to the seed substrate from a direction A that is parallel to or inclined with respect to the seed substrate while rotating the seed substrate, and an angle formed with the seed substrate from a direction B different from the direction A Supplying the same source gas as the source gas to the seed substrate.

  The vapor deposition method is preferably a hydride vapor deposition method.

  The seed substrate is preferably a nitride single crystal.

  The direction A is preferably directed upward of the seed substrate.

  The direction B is preferably a direction perpendicular to the seed substrate.

  The main surface of the seed substrate is preferably a (001) plane.

  According to the present invention, in the method for producing a nitride single crystal by a vapor phase growth method, while rotating the seed substrate, a direction A parallel or inclined with respect to the seed substrate and an angle formed with the seed substrate are By supplying the same source gas to the seed substrate from the two directions of the direction A and the direction B different from the direction A, the concentration distribution of the source gas capable of crystal growth can be realized even on the side surface of the grown crystal, and only in the vertical direction. Instead, crystal growth in the lateral direction becomes possible. Therefore, a nitride single crystal substrate having a larger diameter than that of the seed substrate can be obtained.

  The seed substrate is preferably a nitride single crystal. Both the seed substrate and the single crystal to be grown are the same nitride single crystal, the difference in lattice constant or the difference in thermal expansion is small, and by supplying the same source gas from two directions, Since dislocations combine and disappear in the single crystal growth step, a nitride single crystal having a lower dislocation density than the seed substrate can be obtained.

  The direction A is preferably directed upward of the seed substrate. Thereby, the source gas can be directly supplied to the single crystal grown above the seed substrate, and the growth of the side surface can be increased. As a result, a large-diameter nitride single crystal substrate can be obtained.

  The direction B is preferably a direction perpendicular to the seed substrate. Thereby, since the source gas can be supplied with high density to the growth surface of the seed substrate, the nitride single crystal can be rapidly grown.

  The main surface of the seed substrate is preferably (001). As a result, the growth rate is fast and the facet surface is easily formed.

  The method for producing a nitride single crystal of the present invention will be described below.

  FIG. 1 is a cross-sectional view of a vapor phase growth apparatus S used for manufacturing a nitride single crystal according to the present embodiment. FIG. 2 shows a nitride single crystal 7 grown on a seed substrate 5 in FIG. 1 is a cross-sectional view of a vapor phase growth apparatus S. FIG.

  In FIG. 1, S is a vapor phase growth apparatus, 1a and 1b are upper surface material supply tubes, 2a and 2b are heaters, 3 is a quartz tube, 4a and 4b are side surface material supply tubes, 5 is a seed substrate, and 6 is a susceptor. . In FIG. 2, 7 indicates a nitride single crystal. 1 and 2, the upper surface material supply pipes 1 a and 1 b supply a material gas from a direction perpendicular to the seed substrate 5. Further, the side raw material supply pipes 4 a and 4 b supply the raw material gas from a direction parallel to the seed substrate 5.

  The present invention is a method for manufacturing a nitride single crystal in which a bulk nitride single crystal 7 is formed on a seed substrate 5. Here, the bulk shape means a thickness of 1 mm or more.

  In the production method of the present invention, a nitride single crystal is grown by vapor phase growth. A hydride vapor phase growth method is preferably used as the method for manufacturing the nitride object of the present embodiment. In addition, examples of the vapor phase growth method include a metal organic vapor phase growth method (MOVPE method), a sublimation method, etc., but the growth rate is fast, the quality is good, and a bulk nitride single crystal is easily produced. The hydride vapor phase growth method is preferable for the reason.

  In the manufacturing method of the present invention, for example, a vapor phase growth apparatus S as shown in FIG. 1 is used.

  As shown in FIG. 1, a seed substrate 5 is placed in a vapor phase growth apparatus S while being supported by a susceptor 6, and a nitride single crystal 7 as shown in FIG. 2 is grown by using the manufacturing method of the present invention. Can be made.

  In the manufacturing method of the present invention, the seed substrate 5 is first heated. Specifically, the heaters 2a and 2b in the vapor phase growth apparatus S are heated to 700 ° C. or higher. The heaters 2a and 2b set the temperature to 1000 to 1300 ° C. during single crystal growth to heat the susceptor 6 and the seed substrate 5.

  Examples of the shape of the seed substrate 5 include a disc shape, a rectangular shape, and a truncated pyramid shape. When the seed substrate 5 is disc-shaped, the diameter is 50 to 100 mm and the thickness is 0.1 to 1 mm.

  The main surface of the seed substrate is preferably a growth surface, and specific examples include (001) surface and (100) surface. In particular, the (001) plane is preferable because the growth rate is fast and the facet plane is easily formed.

  Specifically, a nitride semiconductor such as GaN, AlGaN, or AlN can be used as the seed substrate 5. Moreover, sapphire, SiC, etc. can also be used. Among these, a nitride semiconductor is preferable as the seed substrate 5 because the difference in lattice constant from the nitride single crystal to be grown is small and the occurrence of dislocations is small.

  In the manufacturing method of the present invention, while the seed substrate 5 is rotated, the source gas is supplied to the seed substrate 5 from the direction A parallel or inclined with respect to the seed substrate 5, and the source gas is supplied from the direction B perpendicular to the seed substrate 5. A step of supplying the same source gas as the gas to the seed substrate 5. This process will be described with reference to FIGS. FIG. 3 is an enlarged cross-sectional view showing a part of the vapor phase growth apparatus S of FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the vapor phase growth apparatus S having a raw material supply pipe having a different form from the vapor phase growth apparatus S of FIG. Specifically, FIG. 3 shows a case where the source gas is supplied to the seed substrate 5 from the direction A parallel to the seed substrate 5, and FIG. 4 shows that the source gas is seeded from the direction A inclined with respect to the seed substrate 5. The case where it supplies to the board | substrate 5 is shown, respectively. 3 and 4 shows a state in the middle of growing the nitride single crystal 7. 3 and 4, the source gas is supplied from the direction B perpendicular to the seed substrate 5. The direction B is preferably a direction perpendicular to the seed substrate 5, but is not limited to this in the present invention. The direction B is different from the direction A in the angle formed with the seed substrate 5 and the seed substrate 5. As long as the raw material gas can be supplied to the surface.

  The angle formed by the direction A and the direction B is preferably 45 ° or more. Thereby, the nitride single crystal can be grown not only in the vertical direction but also in the horizontal direction.

  Here, there is no problem if the “direction parallel to the seed substrate” and the “direction perpendicular to the seed substrate” are within an error range of ± 5 °. Further, the “direction inclined with respect to the seed substrate” refers to a direction inclined by 5 to 45 ° with respect to the seed substrate 5. Further, “to the seed substrate 5” means “to the main surface (growth main surface) of the seed substrate 5”.

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

  When hydrogen chloride gas is used, hydrogen chloride is reacted with gallium metal at a temperature of about 800 ° C. in the vapor phase growth apparatus S and supplied as gallium chloride (GaCl) gas. The ammonia single crystal 8 is grown on the surface of the seed substrate 5 by supplying ammonia gas to the mixture and supplying it to the seed substrate 5. The flow rate ratio of ammonia gas to hydrogen chloride gas is such that the flow rate of ammonia gas is about 15 to 30 times the flow rate of hydrogen chloride gas. By setting the ratio to about 15 to 30 times, the growth rate of the GaN single crystal can be increased, and the growth of the columnar crystal can be suppressed to suppress the increase of dislocations in the GaN single crystal.

  A specific example of producing a GaN single crystal will be described with reference to FIG. Gallium chloride gas is supplied from the upper surface material supply pipe 1a and the side surface material supply pipe 4a, and ammonia, which is another material gas, is supplied from the upper surface material supply pipe 1b and the side surface material supply pipe 4b. In this case, in both directions A and B, gallium chloride gas and ammonia are supplied, and the same raw material gas is supplied.

  Since the seed substrate 5 is rotated by the susceptor, even if different source gases are supplied from the upper surface source supply pipes 1a and 1b and further different source gases are supplied from the side surface source supply pipes 4a and 4b, the seed substrate is rotated by rotation. The material gas can be supplied evenly and evenly. In addition, the rotation speed of the seed substrate 5 is 5-50 rpm.

  In this way, since the same source gas is supplied from the direction A and the direction B to the seed substrate 5 and the growing nitride single crystal 7, the nitride single crystal 7 is not only vertically oriented but also laterally oriented. A large-diameter GaN single crystal substrate can be obtained.

  On the contrary, when the source gas is different in the direction A and the direction B such that gallium chloride gas is supplied from the upper surface material supply pipes 1a and 1b and ammonia is supplied from the side surface material supply pipes 4a and 4b, Since the gallium chloride residence time becomes shorter, it becomes difficult to grow a GaN single crystal in the lateral direction, and a large-diameter GaN single crystal substrate cannot be obtained.

  Also, when ammonia is supplied from the upper surface material supply pipes 1a and 1b and gallium chloride gas is supplied from the side surface material supply pipes 4a and 4b, the large-diameter GaN is used because the gas is not mixed uniformly in the vicinity of the GaN crystal. It becomes impossible to obtain a single crystal substrate.

  The direction A is preferably located above the seed substrate 5, that is, so as to face the nitride single crystal 7 that is being grown. Thereby, the source gas can be directly supplied to the single crystal grown above the seed substrate, and the growth of the side surface can be increased. As a result, a large-diameter nitride single crystal substrate can be obtained.

  In FIG. 4, the direction A is inclined with respect to the seed substrate 5 as described above. In FIG. 4, gallium chloride gas is supplied from the upper surface material supply pipe 1a and the slope material supply pipe 8a, and ammonia, which is another material gas, is supplied from the upper surface material supply pipe 1b and the slope material supply pipe 8b. Even in this case, gallium chloride gas and ammonia are supplied in both directions A and B, and the same source gas is supplied in both directions A and B, so that nitride single crystal 7 is grown not only in the vertical direction but also in the horizontal direction. Can be made. Thereby, a large-diameter GaN single crystal substrate can be obtained.

  In the present invention, the direction A is preferably a direction parallel to the seed substrate 5 rather than a direction inclined with respect to the seed substrate 5. When the direction A is parallel to the seed substrate 5, the nitride single crystal 7 can be greatly grown in the lateral direction, so that a larger-diameter GaN single crystal substrate can be obtained.

  The nitride single crystal substrate can be taken out from the nitride single crystal 7 grown on the seed substrate 5 by the following method, for example.

  First, the nitride single crystal 7 grown on the seed substrate 5 is taken out of the vapor phase growth apparatus S together with the seed substrate 5, and the outer periphery of the nitride single crystal 7 is ground to a desired size. For example, a diamond grindstone is used for grinding. Then, both surfaces of the ground nitride single crystal 7 are polished. For polishing, for example, rough polishing is performed using diamond abrasive grains or SiC abrasive grains, and then the surface is mirror-polished using, for example, colloidal silica.

  From the above, a nitride single crystal substrate applied to an optical element and an electronic element can be manufactured.

  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.

Examples of the method for producing a nitride single crystal according to the present invention will be described below.
Example 1
A single crystal of GaN was manufactured using the vapor phase growth apparatus S shown in FIG. A seed substrate 5 made of a disk-shaped GaN single crystal having a diameter of 52 mm, a thickness of 0.4 mm, and a main surface of (001) plane was used. The growth surface of the seed substrate 5 is placed on a susceptor 6 made of graphite having an outer diameter of 60 mm and a thickness of 20 mm and coated with 0.2 mm of SiC, which is installed in the quartz tube 3 (inner diameter 85 mm) as the vapor phase growth apparatus S. Was fixed to face upward.

  Next, the heaters 2a and 2b were energized to heat the inside of the quartz tube, and the susceptor 6 was rotated at 10 rpm while controlling the temperature of the seed substrate 5 to about 1100 ° C. GaCl gas was supplied in an amount of 30 cc / min from the raw material supply pipe 1a and the side surface raw material supply pipe 4a. At almost the same time, ammonia gas was supplied in an amount of 800 cc / min from the raw material supply pipe 1b and the side surface raw material supply pipe 4b. Thereby, the growth of a single crystal of GaN was started, and the crystal was grown to a growth thickness of 30 mm. The outer diameter of the obtained single crystal of GaN was 62 mm.

  After the completion of the crystal growth, a single crystal of GaN was taken out from the vapor phase growth apparatus S, and peripheral grinding was performed using a diamond grindstone. Thereafter, a plurality of GaN single crystals obtained by grinding the outer periphery were cut into a thickness of 0.6 mm with a wire saw using a wire having diamond abrasive grains fixed thereon, to obtain a GaN single crystal substrate.

  Next, both sides of the GaN single crystal substrate cut out by a wire saw are roughly polished using diamond abrasive grains, and further, by using colloidal silica, the surface used for crystal growth is mechanochemically polished and mirror-finished, A GaN single crystal substrate wafer having a diameter of 56 mm and a thickness of 0.4 mm could be produced.

The GaN single crystal substrate produced as described above had a larger diameter than the original seed substrate 5. Further, when the wafer surface of the GaN single crystal substrate was observed with an X-ray topographic image, the average dislocation density was 5 × 10 ⁵ cm ⁻² .
(Example 2)
Using the GaN substrate obtained in Example 1 as a seed substrate, a GaN single crystal having a thickness of 30 mm was grown by the same method as in Example 1, and then cut and polished, and GaN having a diameter of 56 mm and a thickness of 0.4 mm. A single crystal substrate was produced.

When the wafer surface of the GaN single crystal substrate produced as described above was observed with an X-ray topographic image, the average dislocation density was 2 × 10 ⁴ cm ⁻² .
(Comparative Example 1)
A wafer of a GaN single crystal seed substrate was produced by the same process as in Example 1 except that the raw material gas was not supplied from the side raw material supply tubes 4a and 4b. As a result, a GaN single crystal body having an outer diameter of 50.2 mm and a thickness of 30 mm was obtained, but the substrate outer diameter after cutting and polishing was 49 mm as a result, which was larger than the original seed substrate 5. Was not obtained.
(Comparative Example 2)
When sapphire was used as the seed substrate 5, the grown GaN single crystal cracked when the growth thickness exceeded 1 mm.

It is sectional drawing of the vapor phase growth apparatus S used for manufacture of the nitride single crystal of this Embodiment. FIG. 2 is a cross-sectional view of the vapor phase growth apparatus S of FIG. 1 in which a nitride single crystal 7 is grown on a seed substrate 5. FIG. 2 is an enlarged sectional view showing a part of the vapor phase growth apparatus S of FIG. 1. FIG. 2 is an enlarged cross-sectional view showing a part of a vapor phase growth apparatus S having a raw material supply pipe different from the vapor phase growth apparatus S of FIG. 1.

Explanation of symbols

S: Vapor growth apparatus 1a: Upper surface material supply tube 1b: Upper surface material supply tube 2a: Heater 2b: Heater 3: Quartz tube 4a: Side surface material supply tube 4b: Side surface material supply tube 5: Seed substrate 6: Susceptor 7: Nitriding Single crystal 8a: slope raw material supply pipe 8b: slope raw material supply pipe A: direction A
B: Direction B

Claims (6)

A nitride single crystal manufacturing method for producing a bulk nitride single crystal on a seed substrate by vapor deposition,
Heating the seed substrate;
While rotating the seed substrate, a source gas is supplied to the seed substrate from a direction A that is parallel or inclined with respect to the seed substrate, and an angle formed with the seed substrate from a direction B different from the direction A Supplying the same source gas to the seed substrate;
A method for producing a nitride single crystal comprising:   2. The method for producing a nitride single crystal according to claim 1, wherein the vapor phase growth method is a hydride vapor phase growth method.   The method for producing a nitride single crystal according to claim 1, wherein the seed substrate is a nitride single crystal.   4. The method for producing a nitride single crystal according to claim 1, wherein the direction A is directed upward of the seed substrate. 5.   The method for producing a nitride single crystal according to claim 1, wherein the direction B is a direction perpendicular to the seed substrate.   The method for producing a nitride single crystal according to claim 1, wherein a main surface of the seed substrate is a (001) plane.