JP3251687B2 - Manufacturing method of semiconductor single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hexagonal semiconductor single crystal produced by a sublimation method or a solution method.

[0002]

2. Description of the Related Art Since SiC is very stable both thermally and chemically, it has been studied as an environment-resistant element material that can withstand high temperature and high pressure. On the other hand, SiC has attracted attention as a short-wavelength light emitting element material because of its energy gap of 2.3 eV or more. SiC has several crystal structures such as a hexagonal type (hexagonal system), a cubic type (cubic system), and a rhombohedral type (trigonal system). Among them, in particular, single crystal of 6H type (hexagonal type having six molecules in one cycle) and 4H type (hexagonal type having four molecules in one cycle) have an energy gap of about 3 eV.
Therefore, it is expected as a material for a blue LED.

[0003] The manufacture of blue LEDs is a journal
Of Applied Physics 50 (1979) pp
8215-8225 [Journal of Applied Physic
s 50 (1979) pp 8215 <8225] or liquid phase epitaxial method (LPE method) or Japanese Journal of Applied Physics 19 (19
80) ppL353-L856 [Japanese Journal of
As reported in Applied Physics 19 (1980) L353 <L856], it is performed by a chemical reaction deposition method (CVD method), and in each case, an LED is placed on a 6H SiC single crystal substrate (0001) surface. Being manufactured.

As described above, the hexagonal SiC single crystal substrate plays an important role as a growth substrate for a blue LED. Conventionally, as a method for growing a hexagonal-type SiC single crystal substrate, a sublimation method in which a SiC raw material powder is sublimated and deposited on a low temperature side has been used. For example, Applied Physics Letter 58 (1991) pp. 56-58 [AppliedPhy
sics Letter 58 (1991) pp56 <58]. The inventors of the present invention have made a crystal having a large diameter by utilizing the fact that the crystal diameter increases with the crystal growth length in order to increase the crystal diameter by the sublimation method. However, in this method, as the crystal length becomes longer, the spread of the diameter becomes smaller, and it is difficult to obtain a large-diameter substrate. Further, the inventors have found that the growth surface becomes concave as the crystal length increases, and a high-quality substrate cannot be obtained.

[0005]

As described above, when growing a hexagonal-type single crystal SiC single crystal by the sublimation method, the growth must be sufficiently long to obtain a large-diameter substrate. However, in this case, when the growth length is increased, the growth surface of the crystal becomes concave, and there is a problem that the increase in the diameter of the crystal eventually stops. Further, the obtained crystal has a problem that it has many crystal defects and cannot be trusted in terms of quality. Further, the above-described problem exists in various hexagonal-type semiconductor single crystals other than SiC.

The present invention has been made in view of the above problems, and has as its object to provide a method for producing a large-diameter hexagonal-type semiconductor single crystal in which a crystal growth surface is prevented from becoming concave and crystal defects are reduced.

[0007]

In order to solve the above problems, a method for producing a semiconductor single crystal according to the present invention comprises growing a hexagonal single crystal on a seed crystal composed of a hexagonal single crystal by a bulk growth method. In the method for producing a semiconductor single crystal to be formed, a side surface in contact with a main growth surface of the seed crystal is
The present invention is characterized in that a seed crystal having only a plane inclined from both the (0001) plane and the (1-100) plane is used.

[0008]

As a result of the study of the present inventors, the most important point of the growth surface being concave is that hexagonal-type crystal, for example, α-SiC, has a lower crystal orientation rate depending on the plane orientation than other crystals. Strongly, I found that a plane called a facet appeared. Figure 11 shows the (0001) plane as the main growth plane.
The facet 111 when the (1-100) plane is the side surface is shown. We believe that this phenomenon is <0001>, or <1-100
> Since the growth rate of the azimuth is very slow,
I thought that facets would appear as a result of trying to extend parallel to the (0001) plane or the (1-100) plane. This facet 111
Appears at a growth rate faster than that of the main growth surface, and the growing single crystal has a bulge at its periphery rather than at the center (112 is a bulge at the periphery). The main growth surface of the resulting single crystal was found to be concave at the center.

In order to prevent the appearance of the facet, the present inventors can achieve the object by inclining the side surface in contact with the main growth surface of the seed crystal from any of the (0001) plane and the (1-100) plane. Was found.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail.

A first embodiment of the present invention will be described. FIG. 1 is a schematic diagram of a sublimation single crystal manufacturing apparatus which is one of the bulk growth methods. 11 is a seed crystal, 12 is porous graphite, 13 is a crucible, 14 is a crucible lid, and 15 is a raw material powder. In this embodiment, a hexagonal-type SiC single crystal was grown.

FIG. 2 shows a hexagonal type SiC seed crystal 11.
Shows the relationship between the crystal type and the main growth surface. FIG. 3 is a diagram showing the shape of the SiC seed crystal 11. The growth main surface of the seed crystal 11 was a {000-1} plane ((0001) carbon plane), and was shaped into a circle having a diameter of 10 mm. In addition, all sides were machined into a conical shape with a crushed head so as to be at 45 ° to the {000-1} plane. The raw material was sublimated on the seed crystal 11 using the apparatus shown in FIG. 1 with the wider surface of the seed crystal 11 as the growth surface, to grow a SiC single crystal. The growth conditions were a seed crystal temperature of 2300 ° C.
The raw material temperature was 2500 ° C. and the growth pressure was 50 torr. A SiC single crystal having a length of about 20 mm was grown for a growth time of 20 hours.

FIG. 4 shows a SiC single crystal 41 grown according to the present invention as a comparative example, in which the main growth surface is a {000-1} plane ((0001) carbon plane) and a part of the side surface is a (1-100) plane. A cross-sectional view of an SiC single crystal 43 grown under the same conditions as in the first embodiment using a columnar seed crystal 42 of FIG.

In the case of the comparative example (FIG. 4B), the grown S
The iC single crystal 43 became barrel-shaped, and the diameter stopped expanding. In addition, the growth surface became concave with a recess of about 3 mm at the center, and a crystal abnormality such as transition and twinning occurred due to stress due to abnormal growth of the circumferential portion. On the other hand, in the present invention (FIG. 4A), the SiC single crystal 41 grows conically. For this reason, the present invention has a larger crystal diameter, and can manufacture a large-diameter substrate. In addition, the growth main surface was almost no concave, and it was possible to suppress an increase in defects due to abnormal growth of the circumferential portion, thereby improving the crystal quality.

FIG. 5 shows the growth principal surface of the seed crystal of the present invention as (0
001) Indicates the angle of the side surface when the surface is set. Side (1-100)
It is desirable to incline at least 3 ° or more with respect to the plane (90 ° with respect to the (0001) plane) (region A in the figure). By using such a seed crystal, the generation of facets can be suppressed, and the growth main surface can be prevented from becoming concave. Therefore, a hexagonal single crystal having a large diameter and few crystal defects can be grown. Next, a second embodiment of the present invention will be described. In this embodiment, the growth principal plane is (11-20) plane,
An SiC single crystal was grown using an iC seed crystal. The apparatus used was the one shown in FIG. 1 and the growth conditions were the same as in the first embodiment.

FIG. 6 shows α-6HSiC of the seed crystal of this embodiment.
A diagram showing the relationship between the crystal type and the (11-20) plane, which is the main growth plane,
FIG. 7 shows the angles of the side surfaces when the principal growth surface is the (11-20) plane. When the main growth surface is the (11-20) plane, the side is (1-100)
The plane and the (0001) plane appear at 30 °, 90 °,
The angle is 150 °, and it is only necessary to incline 3 ° or more from each of these planes (region A in the figure).

In this embodiment, the growth main surface is formed in a circular shape having a diameter of 10 mm, the side surface is inclined by 60 ° from the growth main surface, and a conical seed crystal whose head is crushed is used. A SiC single crystal having a growth length of 20 mm was grown as a plane. In this embodiment, the SiC single crystal could be grown conically in the same manner as in the first embodiment. In addition, no facets appeared in the circumferential portion, and no concave growth surface occurred. Next, a third embodiment of the present invention will be described. In this embodiment, the main growth surface is
A SiC single crystal was grown using the (1-100) plane SiC seed crystal. The apparatus used was the one shown in FIG. 1 and the growth conditions were the same as in the first embodiment.

FIG. 8 shows the α-6HSiC of the seed crystal of this embodiment.
A diagram showing the relationship between the crystal type and the (1-100) plane, which is the main growth surface,
FIG. 9 shows the angles of the side surfaces when the main growth surface is the (1-100) plane. When the main growth surface is (1-100), the side is (1-100)
Plane and (0001) plane appear at 60 °, 90 °,
The angle is 120 °, and it is only necessary to incline 3 ° or more from each of these planes (region A in the figure).

In this embodiment, the growth principal surface is formed in a circular shape having a diameter of 10 mm, the side surface is inclined by 45 ° from the growth principal surface, and a conical seed crystal whose head is crushed is used. A SiC single crystal having a growth length of 20 mm was grown as a plane. In this embodiment, the SiC single crystal could be grown conically in the same manner as in the first embodiment. In addition, no facets appeared in the circumferential portion, and no concave growth surface occurred.

Next, a fourth embodiment of the present invention will be described. In this embodiment, the main surface of the SiC seed crystal used in the first, second, and third embodiments is further polished, and a SiC single crystal is used by using a seed crystal whose growth main surface is a plane shifted by 5 ° from each main surface. A crystal was grown. The growth apparatus shown in FIG. 1 was used, and the growth conditions were the same as in the first embodiment. In this embodiment, since the growth rates of the main growth surface and the side surface hardly change, the crystal shape spreads from the seed crystal to a natural conical shape, and a good single crystal can be obtained.

Next, a fifth embodiment of the present invention will be described. In the present embodiment, a solution method which is one of bulk growth methods
From the above solution, an SiC single crystal was deposited and grown on the SiC seed crystal. FIG. 10 shows a growth apparatus used in this embodiment. C
Alternatively, a Si solvent 102 is stored in a crucible 101 made of SiC, and the highest temperature part in the solvent is set to 1800 ° C.
Temperature is set to 1700 ° C., and 100H growth is performed. C in the crucible and Si as a solvent precipitate on the SiC seed crystal 103, and a single crystal grows. In this case, as in the first embodiment, the seed crystal was processed into a conical shape with its head crushed by tilting the main growth surface to the (0001) plane and the side surfaces by 45 ° from the main growth surface. The larger surface of the seed crystal is used as the main growth surface and the SiC seed crystal
A SiC single crystal of about 10 mm was grown thereon. Also in the present embodiment, it is possible to significantly increase the diameter of the crystal as compared with the case of using a seed crystal having a (1-100) plane on the side surface,
No growth surface was concave.

Next, a sixth embodiment of the present invention will be described. In this embodiment, a single crystal of hexagonal gallium nitride was grown by the sublimation method. At present, gallium nitride cannot obtain a very large crystal as a seed crystal, so it is necessary to use a fine crystal as a seed. In this embodiment, a seed crystal was used in which the principal growth surface was a (0001) plane, and the side surface was machined into a conical shape with a squashed head inclined at 45 ° from the principal growth surface. Both sides are inclined from the (1-100) plane. The growth apparatus was almost the same as that used in Example 1. The growth temperature was 1300 ° C. for the raw material, the seed crystal was 1200 ° C., and the pressure was several Torr in an N ₂ atmosphere. Also in this example, the diameter of the grown single crystal was significantly increased, and the growth surface was not concave, and the quality was improved.

In each of the above embodiments, the growth principal surface is a circular seed crystal, but the growth surface is not particularly limited, such as a triangle, a square, a polygon, and an ellipse. In the case of a triangle, square, or polygon, even if the seed crystal is columnar, the side surface in contact with the main growth surface can be only a plane inclined from any of the (0001) plane and the (1-100) plane. In each of the above embodiments, the crystal temperature and the temperature gradient can be freely changed and used.

[0024]

As described above, by using the present invention, it is possible to manufacture a hexagonal-type semiconductor single crystal substrate having a large diameter and having a small crystal defect by preventing the crystal growth surface from becoming concave. In addition, it is possible to suppress an increase in defects due to abnormal growth where the facet collides, thereby improving the quality of the crystal.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a sublimation single crystal manufacturing apparatus used in first, second, third, fourth and sixth embodiments of the present invention.

FIG. 2 is a diagram showing a (0001) plane of a hexagonal crystal.

FIG. 3 is a diagram showing a shape of a seed crystal used in the first embodiment of the present invention.

FIG. 4 is a diagram showing a comparison between a SiC single crystal grown in the first embodiment of the present invention and a conventional example.

FIG. 5 is a diagram showing an angle of a side surface of a seed crystal when a main growth surface is a (0001) plane.

FIG. 6 is a diagram showing a (11-20) plane of a hexagonal crystal.

FIG. 7 is a diagram showing an angle of a side surface of a seed crystal when a growth main surface is a (11-20) plane.

FIG. 8 is a diagram showing a (1-100) plane of a hexagonal crystal.

FIG. 9 is a diagram showing an angle of a side surface of a seed crystal when a growth main surface is a (1-100) plane.

FIG. 10 is a schematic diagram of a solution-processed single crystal manufacturing apparatus used in a fifth embodiment of the present invention.

FIG. 11 is a diagram showing facets appearing in a circumferential portion when a main growth surface is a (0001) surface and side surfaces are a (1-100) surface.

[Explanation of symbols]

 11. Seed crystal 12. Porous graphite 13. Crucible 14. Crucible lid 15. Raw material powder 101. Graphite crucible 102. Si solvent 103. Seed crystal

Claims (4)

(57) [Claims] 1. A method for producing a semiconductor single crystal in which a hexagonal-type single crystal is grown on a seed crystal made of a hexagonal-type single crystal by a bulk growth method, wherein a side surface in contact with a growth main surface of the seed crystal has a (0001) plane. And (1-1
00) so that it has only a plane inclined from any plane
A method of manufacturing a semiconductor single crystal, characterized by using a seed crystal whose side surface is processed . 2. The method according to claim 1, wherein the hexagonal type single crystal is a SiC single crystal.
Crystal or gallium nitride single crystal
The method for producing a semiconductor single crystal according to claim 1. 3. The method according to claim 1, wherein the hexagonal single crystal is SiC single crystal.
A crystal, wherein the main growth surface of the seed crystal is a (0001) plane;
(1-100) plane or (11-20) plane,
The sides are from (0001) plane and (1-100) plane, respectively.
Characterized by having only a surface inclined by 3 mm or more.
Item 2. The method for producing a semiconductor single crystal according to Item 1. 4. The seed crystal is processed into a conical shape with a crushed head.
The method according to any one of claims 1 to 3, wherein
A method for manufacturing a semiconductor single crystal.