JP2004284869A - Method for manufacturing nitride single crystal and manufacturing apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently manufacture a high-quality single crystal with a large diameter and no defect in the process of manufacturing a nitride single crystal by a sublimation method. <P>SOLUTION: In the method for manufacturing a nitride single crystal by growing on a seed crystal 7 on a susceptor 8 by a sublimation method, the face of the susceptor 8 where the seed crystal 7 is to be stuck is inclined at 0.1 to 2.0° with respect to the horizontal plane. Or the growing plane of the seed crystal 7 is preferably inclined at 0.1 to 0.8° from the crystallographic orientation with respect to the horizontal plane. Further, it is also preferable to dispose the discharge port 6 of the environmental gas in the inclination direction of the susceptor and that the flow F of the sublimated gas is made almost same as the inclination of the surface of the susceptor 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for producing a single crystal of a nitride of a group III element such as aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN).
[0002]
[Prior art]
Among nitrides of group III elements, aluminum nitride is expected to be used as a substrate for GaN-based semiconductor devices because of its high thermal conductivity and lattice matching with gallium nitride.
Heretofore, as a method for producing this kind of nitride single crystal, several methods have been known, and among them, the sublimation method is considered promising.
[0003]
FIG. 6 shows a conventional apparatus for producing a nitride single crystal by this sublimation method. In the figure, reference numeral 1 denotes a heating furnace. The heating furnace 1 includes an induction heating coil 2 and a heating furnace main body 3, and a container-shaped graphite crucible 4 is provided in the heating furnace main body 3. At the bottom of the heating furnace 1, an atmosphere gas inlet 5 is formed, and at the top of the heating furnace 1, an atmosphere gas outlet 6 is formed.
[0004]
A susceptor 8 to which a seed crystal 7 is attached is fixed to an upper portion of the heating furnace 1. The susceptor 8 is a plate-shaped member made of graphite or the like. The surface on which the seed crystal 7 is attached is horizontal, and the surface of the seed crystal 7 is also horizontal (sometimes called just direction).
Then, at the bottom of the graphite crucible 4, a nitride powder or a sintered body as the raw material 9 is disposed. Next, after the inside of the heating furnace 1 is evacuated, an atmospheric gas such as nitrogen is introduced from the inlet 5 for the atmospheric gas at the bottom. The induction heating coil 2 is operated to heat the nitride powder and the sintered body, the susceptor 8 and the seed crystal 7 which are the raw material 9 in the graphite crucible 4. Atmosphere gas in the heating furnace 1 is exhausted from a discharge port 6 in the upper part of the heating furnace 1.
[0005]
By this heating, the nitride powder or the like of the raw material 9 at the bottom of the crucible 4 melts and sublimates, and the sublimation gas adheres to the surface of the seed crystal 7 to grow the crystal. At this time, in order to control the crystallization speed of the crystal growth in the seed crystal 7, the temperature of the susceptor 8 and the sublimation speed of the sublimation gas sublimated from the raw material 9 are optimized.
[0006]
By the way, during the crystal growth by such a sublimation method, the temperature distribution in the crucible 4 is highest near the wall surface of the crucible 4 and lowest in the center thereof. For this reason, the amount of the sublimation gas sublimated from the crucible 4 becomes uneven. This phenomenon becomes more remarkable as the size of the crucible increases. When an attempt is made to produce a large-diameter nitride single crystal, a large crucible is required, and the non-uniformity of the amount of sublimation gas is further increased.
[0007]
For this reason, the gas phase in the heating furnace 1 is in a turbulent state at the crystal growth temperature (2100 to 2200 ° C.), and the crystal nuclei are randomly deposited on the seed crystal 7 in the process of depositing the crystal nuclei on the seed crystal 7. (In the crystal growthological expression, it is called a Wolmer-Weber growth mode.), And in the subsequent crystal growth process, the vapor phase / crystal interface grows in a rough state (in the crystal growthological expression, three-dimensional). Therefore, the obtained single crystal has a defect that many defects are introduced.
Prior art documents relating to a method for producing a nitride single crystal such as aluminum nitride include the following.
[0008]
[Patent Document 1]
JP-A-10-053495 [Non-Patent Document 1]
Glen A. Slack and T.S. F. McNelly, Journal of Crystal Growth, 34 (1976) 263-279.
[Non-patent document 2]
R. Schlesser and Z. Sitar, Journal of Crystal Growth, 234 (2002) 349.
[0009]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to make it possible to efficiently produce a single crystal of good quality and large diameter without defects in the obtained single crystal when producing a nitride single crystal by a sublimation method.
[0010]
[Means for Solving the Problems]
To solve this problem,
The invention according to claim 1 is a manufacturing method for growing a nitride single crystal on a seed crystal on a susceptor by a sublimation method, wherein the surface on which the seed crystal of the susceptor is attached is 0.1 to 2.0 with respect to a horizontal plane. This is a method for producing a nitride single crystal, characterized in that it is tilted.
[0011]
The invention according to claim 2 is characterized in that the growth plane of the seed crystal is inclined from the crystallographic orientation by 0.1 to 0.8 degrees with respect to the horizontal plane, and the nitride single crystal according to claim 1 is manufactured. Is the way.
The invention according to a third aspect is the method for producing a nitride single crystal according to the first or second aspect, wherein the flow of the atmospheric gas is made substantially coincident with the inclination of the surface of the susceptor.
[0012]
The invention according to claim 4 is a manufacturing apparatus for growing a nitride single crystal on a seed crystal on a susceptor by a sublimation method, wherein the surface on which the seed crystal is attached is inclined at 0.1 to 2.0 degrees with respect to a horizontal plane. An apparatus for producing a nitride single crystal, wherein the susceptor is used.
[0013]
The invention according to claim 5 is characterized in that a seed crystal whose growth surface is inclined by 0.1 to 0.8 degrees with respect to a horizontal plane from a crystallographic orientation is used as a seed crystal. Is an apparatus for producing a nitride single crystal.
The invention according to claim 6 is the apparatus for producing a nitride single crystal according to claim 4 or 5, wherein the outlet of the atmospheric gas of the heating furnace is provided in the inclination direction of the susceptor.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
FIG. 1 shows an example of an apparatus for producing a nitride single crystal according to the present invention. The same components as those shown in FIG.
[0015]
In the apparatus of the example shown in FIG. 1, as shown in FIG. 1A, the surface on which the seed crystal 7 of the susceptor 8 fixed on the upper part of the heating furnace 1 is inclined with respect to the horizontal plane. The surface of the seed crystal 7 attached to the susceptor 8 is also inclined.
[0016]
Further, as shown in FIG. 1 (b), the outlet 6 of the atmosphere gas formed on the upper part of the heating furnace 1 is provided with the susceptor 8 so that the flow of the atmosphere gas flows along the inclined surface of the surface of the susceptor 8. It is formed at a position in the inclination direction. The outlet 6 has a rectangular shape and a length in the longitudinal direction is substantially the same as the outer diameter of the susceptor 8, and is formed on the side of the susceptor 8.
[0017]
In addition, as shown in FIG. 1 (c), the atmosphere gas inflow ports 5 formed at the bottom of the heating furnace 1 are radially dispersed at three places at the bottom, and are uniformly heated from the entire bottom. Atmosphere gas flows into the furnace 1.
Due to such arrangement of the inlet 5 and the outlet 6, the flow F of the sublimated gas sublimated from the crucible 4 flows smoothly along the inclination direction of the seed crystal 7 as shown in the figure.
[0018]
FIG. 2 is an enlarged view of the susceptor 8 and the seed crystal 7 in FIG. The surface 8a of the susceptor 8 is inclined such that the inclination angle α is 0.1 to 2.0 degrees with respect to the horizontal plane. The surface 7a of the seed crystal 7 is also inclined at an inclination angle β of 0.1 to 0.8 degrees. Specifically, the surface of the seed crystal 7 is inclined from the (0001) plane, which is a crystallographically low index plane, by 0.1 to 0.8 degrees in the azimuth (1100) direction. As shown, many fine steps 10 are formed on the surface. In FIG. 2, each of the inclination angles α and β is drawn larger than the actual angle for understanding.
[0019]
When a nitride single crystal was grown on seed crystal 7 using such a manufacturing apparatus, the seed crystal 7 was tilted by 0.1 to 0.8 degrees from the low index plane of seed crystal 7, as shown in FIG. As shown, a step 10 composed of a low index surface is formed, along which the sublimation gas flows. For this reason, crystal nuclei adhere to the step 10 to grow in-plane (step growth), and the single crystal 11 grows, and two-dimensional uniform crystal growth (Frank van der Melbe growth) is performed. Thus, a high-quality nitride single crystal free from defects can be manufactured.
[0020]
The inclination angle in the present invention has an error of about ± 0.05 degrees from the viewpoint of the processing accuracy of the susceptor 8 and the seed crystal 7, and is a value that takes this error into account.
Further, it goes without saying that the present invention is not limited to aluminum nitride and can be applied to the production of other nitride single crystals. Further, the present invention can be applied to the production of a carbide single crystal.
Further, the crucible 4 and the susceptor 8 are preferably made of graphite whose surfaces are covered with boron nitride (BN), silicon nitride (SiN), or the like, to preferably prevent the reaction with the sublimation gas.
[0021]
Hereinafter, specific examples are shown, but the present invention is not limited to these specific examples.
In the following specific examples, SiC and AlN single crystals belonging to a hexagonal system are used as seed crystals, but similar results can be obtained with other hexagonal or trigonal single crystals.
[0022]
(Example 1)
An AlN single crystal was produced using the apparatus having the structure shown in FIG. As the raw material 9, a lump obtained by sintering 99.99% AlN powder was used and placed on the bottom of the graphite crucible 4. As the seed crystal 7, a SiC single crystal inclined from the (0001) plane, which is a crystallographically low index plane, in the azimuthal (1100) direction having an inclination angle β of 0.1 ° was used. The susceptor 8 used had a surface inclination angle α of 0.1 degree.
[0023]
The temperature of the raw material 9 was heated to about 20 ° C. higher than the decomposition temperature of AlN, 2200 ° C., and the temperature of the seed crystal 7 was heated to 1950 ° C. and maintained at this temperature for 20 hours. At this time, a nitrogen gas is used as an atmosphere gas, and the flow rate thereof is introduced from the inlet 5 so that the internal pressure becomes 500 torr, so that the gas flows smoothly along the inclination direction of the susceptor. I did it.
[0024]
After a lapse of 20 hours, a single crystal having a thickness of 20 mm had grown on the seed crystal 7. This single crystal was colorless and transparent, and had a crystal structure corresponding to AlN of wurtzite by X-ray diffraction. The lattice constant was c = 4.97 ° and a = 3.11 °. It was confirmed that the single crystal had no small-angle grain boundaries. Regarding the crystallinity, the rocking curve half width of 2θ-ω scan of X-ray diffraction was about 70 seconds.
[0025]
(Example 2)
As the seed crystal 7, a SiC single crystal inclined from the (0001) plane, which is a crystallographically low index plane, in the azimuth (1100) direction having an inclination angle β of 0.3 ° is used. An AlN single crystal was prepared in the same manner as in Example 1, except that an inclination angle α of 0.3 ° was used. However, the growth time was 18 hours.
[0026]
The obtained single crystal was a pale yellow transparent crystal having a thickness of about 15 mm. As a result of X-ray diffraction, the bulk growth portion was AlN, and the lattice constants were c = 4.98 ° and a = 3.10 °. The rocking curve half width of 2θ-ω scan of X-ray diffraction was about 55 seconds.
[0027]
(Example 3)
This example shows a comparative example using the manufacturing apparatus having the structure shown in FIG. In the apparatus shown in FIG. 4, Example 1 is different from the apparatus shown in FIG. 1 in that the formation position of the atmospheric gas discharge port 6 is opposite to that of the manufacturing apparatus shown in FIG. This is different from the device used in 2. In such an apparatus, the flow F of the sublimation gas is in a direction opposite to the direction in which the susceptor 8 is inclined.
[0028]
The plane orientation inclination angle β of the seed crystal 7 was set to 0.3 degrees, and the inclination angle α of the surface of the susceptor 8 was set to about 0.5 degrees. Except for this, the crystal was grown for 20 hours under the same conditions as in Example 1.
As a result, a light gray blue transparent crystal having a thickness of about 23 mm was obtained. As a result of X-ray diffraction, the bulk growth portion was AlN, and the lattice constants were c = 4.96 ° and a = 3.10 °. The half width of the rocking curve of the 2θ-ω scan of the X-ray diffraction was about 205 seconds.
[0029]
Further, when the obtained crystals were observed by an electron microscope, fine precipitates were found in the crystals. It was presumed that this precipitate deteriorated the crystallinity. From this, it is considered that the sublimation gas hit the corner of the step 10 on the surface of the seed crystal 7 and the crystal nucleus generation was gathered at the corner by the so-called Berg effect, causing heterogeneous crystal growth.
[0030]
(Example 4)
An AlN single crystal was produced in the same manner as in Example 1. The temperature of the raw material was 2210 ° C. and the seed crystal temperature was 1995 ° C. Crystal growth was performed for 20 hours with the outer diameter of the susceptor 8 set to 20 mm, the inclination angle β of the seed crystal 7 set to about 0.3 degrees, and the inclination angle α of the surface of the susceptor 8 set to 0.5 degrees.
[0031]
As a result, the grown single crystal had an outer diameter of about 20 mm from the outer diameter of the susceptor 8 and was about 30 mm in the final growth part. From microscopic observation and X-ray analysis, the growth portion was an AlN single crystal, and the lattice constant was c = 4.96 ° and a = 3.11 °. The half width of the rocking curve of the 2θ-ω scan of X-ray diffraction was about 60 seconds, indicating that the crystal had extremely good crystallinity.
[0032]
(Example 5)
Using the manufacturing apparatus used in Example 1, an AlN single crystal was produced. The raw material temperature was 2210 ° C. and the seed crystal temperature was 1995 ° C. The outer diameter of the susceptor 8 was about 20 mm, the inclination angle α of the susceptor 8 was 1.5 degrees, the inclination angle β of the seed crystal 7 was about 1.0 degrees, and the growth time was 20 hours.
[0033]
As a result, the obtained crystal was a grayish transparent crystal having a thickness of about 27 mm. However, the crystallinity was poor, the half-width of the X-ray rocking curve was 370 seconds, and the lattice constants were c = 4.99 ° and a = 3.12 °. Such low crystallinity is interpreted as follows. That is, since the inclination angle β of the surface of the seed crystal 7 is as large as 1.0 degree, the shape of the step 10 that will be exposed on the surface has a small step width, and the in-plane growth of the AlN crystal nucleus (two-dimensional) It is presumed that growth or lateral growth) was suppressed and, as a result, three-dimensional growth was achieved.
[0034]
Based on these specific examples and other experimental results, the crystallinity of the AlN single crystal obtained using the inclination angle α of the susceptor 8 and the inclination angle β of the seed crystal 7 as parameters is summarized in FIG. Here, those having a rocking curve half width of 100 seconds or less were regarded as having good crystallinity, and are indicated by ○. Similarly, those having a half width of more than 100 seconds are regarded as having poor crystallinity, and are indicated by Δ. Further, those having poor crystallinity obtained by a manufacturing apparatus in which the atmosphere gas outlet 6 was provided on the side opposite to the direction of inclination of the susceptor 8 as in Example 3 were indicated by x.
[0035]
From the results shown in FIG. 5, the susceptor tilt angle α is 0.1 to 2 degrees and the seed crystal tilt angle β is 0.1 to 0.8 degrees to produce an AlN single crystal having good crystallinity. It turns out that it is a range.
[0036]
【The invention's effect】
As described above, according to the present invention, steps are formed on the seed crystal surface, and the steps enable two-dimensional growth, so that a smooth gas-phase / crystal interface is obtained, and A nitride single crystal such as AlN having crystallinity can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a nitride single crystal manufacturing apparatus of the present invention.
FIG. 2 is a schematic configuration diagram showing an enlarged main part of the device.
FIG. 3 is an explanatory view showing a state of crystal growth in the present invention.
FIG. 4 is a schematic configuration diagram of an apparatus for manufacturing a single crystal of a comparative example used in Example 3 of the specific example.
FIG. 5 is a chart showing the results of a specific example.
FIG. 6 is a schematic configuration diagram of a conventional nitride single crystal manufacturing apparatus.
[Explanation of symbols]
6 ... outlet, 7 ... seed crystal, 8 ... susceptor

Claims (6)

In a manufacturing method for growing a nitride single crystal on a seed crystal on a susceptor by a sublimation method, a surface on which the seed crystal of the susceptor is attached is inclined by 0.1 to 2.0 degrees with respect to a horizontal plane. A method for producing a nitride single crystal. 2. The method for producing a nitride single crystal according to claim 1, wherein a growth surface of the seed crystal is inclined from the crystallographic orientation by 0.1 to 0.8 degrees with respect to a horizontal plane. The method for producing a nitride single crystal according to claim 1, wherein the flow of the atmospheric gas is made substantially coincident with the inclination direction of the surface of the susceptor. In a manufacturing apparatus for growing a nitride single crystal on a seed crystal on a susceptor by sublimation, a susceptor in which the surface on which the seed crystal is attached is inclined by 0.1 to 2.0 degrees with respect to a horizontal plane is used. Characteristic nitride single crystal manufacturing equipment. 5. The apparatus for producing a nitride single crystal according to claim 4, wherein a seed crystal whose growth surface is inclined by 0.1 to 0.8 degrees with respect to a horizontal plane from a crystallographic orientation is used. . The apparatus for producing a nitride single crystal according to claim 4, wherein an outlet of the atmosphere gas of the heating furnace is provided in an inclined direction of the susceptor.

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