JPH03295898A - Method and device for growing silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To obtain a large, long and high-quality SiC single crystal by using a split graphite crucible also used as a heating element and consisting of the upper crucible outer cylinder, crucible bottom and expansion crucible outer cylinder to be arranged between them. CONSTITUTION:An SiC single crystal substrate 23 is fixed at the mounting part 22 of a graphite lid 19. The crucible 28 consists of the graphite upper crucible outer cylinder 18, expansion crucible outer cylinder 21 and crucible bottom 20. A powder 26 contg. SiC as the raw material is placed in the crucible 28, and the distance 30 between the growth surface 27 of the substrate and the powder 26 is adjusted by the length of the cylinder 21. The powder 26 is heated, the sublimated SiC is deposited on the substrate 23 to grow a lumpy SiC single crystal 24. When the crystal growth is successively carried out, the residue after crystal growth in the crucible 28 is removed, fresh raw powder 26 is charged, the distance between the growth surface 29 and raw powder 26 surface is adjusted by the length of the outer cylinder 21, and a crystal is again grown.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for growing a silicon carbide single crystal. Specifically, the present invention relates to a method and apparatus for growing silicon carbide single crystals that efficiently grow large-area, long, and high-quality silicon carbide single crystals at low cost that are useful for applications such as blue light emitting diodes as semiconductor electronic materials. .

(Prior Art) Conventionally known bulk silicon carbide single crystal growth methods include the Acheson method, the Rayleigh method, and the sublimation recrystallization method (improved Rayleigh method). Among these, the sublimation recrystallization method is currently mainly used as a growth method useful for semiconductor materials.

The apparatus shown in FIG.
Page 81 [IEEE 1'RANSACTION O
N ELECTRON DEVICES, VOL, E
D-30, No. 4 (1983) 277-281, in which numeral 1 is a crucible made of graphite with a circular cross section, and 2 is a crucible placed in the center of Luppo 1. 3 is a raw material mounting table made of porous graphite provided in the lower half between the crucible 1 and the cylindrical body 2; 4 is the crucible 1 and the cylindrical body 2;
5 is a growth chamber formed inside the cylindrical body 2; 6 is a pedestal made of graphite disposed at the bottom of the growth chamber 5; 7 is a pedestal 6; A silicon carbide single crystal substrate is placed on top of the crucible 1, and the crucible 1 is heated by a high-frequency induction heating coil (not shown) placed outside the crucible 1, and the raw material 4 sublimates, passing through the cylindrical body 2 into the growth chamber. The sublimated gas that has reached the substrate 7 hits the substrate 7, which is slightly lower in temperature than the raw material 4, and recrystallizes on the surface of the substrate 7, thereby growing a silicon carbide single crystal. However, since the gas for recrystallization cannot be replenished once all the raw materials have sublimated, there is a limit to how large or long a single crystal can be made. Furthermore, when the raw materials are replaced and the growth is performed again, the single crystal growth surface approaches the raw material as the single crystal grows, so the length of the crucible is limited. It becomes impossible to create a temperature gradient. Therefore, this method has a problem in that silicon carbide single crystal cannot be easily grown for a long time.

Furthermore, the apparatus shown in FIG.
This figure shows a conventional device disclosed in the above issue. A silicon carbide raw material 10 stored in a space 11 formed between a bottomed cylindrical storage section 9 made of graphite and a wall 12 arranged concentrically inside the cylindrical storage section is exposed to a high frequency wave (not shown). The sublimated gas that is heated by the induction heating coil reaches the growth chamber 13 . The sublimated gas hits the single crystal substrate holding portion 17 of the substrate holder 16 attached to the sliding member 15 having the sliding mechanism 14 and is recrystallized on the surface.
A lumpy single crystal grows. The height from the lower surface of the single crystal substrate 17 held by the substrate holder 16 to the surface of the raw material 10 can be arbitrarily adjusted by the sliding mechanism 14. It is true that using this method, it is possible to lengthen the silicon carbide single crystal while keeping the distance from the single crystal growth surface to the raw material constant by sliding the substrate holder as the bulk single crystal grows larger, but this method However, there are still problems in increasing the size and length of silicon carbide single crystals inexpensively and efficiently, such as the need for larger equipment and the need for greater skill in the growth method.

(Problems to be Solved by the Invention) As mentioned above, there are still problems in manufacturing large and long silicon carbide single crystals at low cost with the conventional technology, so the present invention solves the following problems:
It is an object of the present invention to provide a silicon carbide single crystal growth method and apparatus for solving these problems and producing a large, long, and high quality silicon carbide single crystal at low cost.

(Means for Solving the Problems) The above object is achieved in a method of growing a silicon carbide single crystal on a silicon carbide single crystal substrate by heating and sublimating a raw material made of silicon carbide powder by a sublimation recrystallization method. After growing a silicon carbide single crystal using a graphite crucible whose length can be changed, the raw material charged inside the crucible is replaced, and the crucible is removed from the single crystal growth surface. A method for growing a silicon carbide single crystal, comprising adjusting the length of the crucible so that the distance to the surface of the raw material is a predetermined distance, and performing crystal growth again by a sublimation recrystallization method at least once. achieved by.

The above object also includes a crucible that also serves as a heating element made of graphite, a crucible lid made of graphite that covers the upper end opening of the crucible, a heating means for heating the crucible, and a vacuum or inert gas In a silicon carbide single crystal growth apparatus having a vacuum system for controlling the atmosphere, the graphite crucible includes an upper crucible outer cylinder, a crucible bottom, and an additional crucible outer cylinder detachably disposed between the two. This is achieved using a silicon carbide single crystal growth apparatus characterized by being of a split type.

(Function) The silicon carbide single crystal growth method of the present invention involves heating and sublimating a raw material powder made of silicon carbide, and placing the silicon carbide single crystal at a slightly lower temperature than the raw material powder in a crucible cover made of graphite that covers the upper part of the crucible. A silicon carbide single crystal is deposited and grown from sublimated silicon carbide gas on a crystal substrate, but after removing the residue of the raw material after growth, regrowth is performed from the crystal growth surface before regrowth. The distance to the surface of the raw material replaced can be set to a predetermined distance because the length of the melt can be changed. This predetermined distance is a space for the single crystal to continue growing when it grows long and large, and at the same time, it maintains the single crystal growth surface at a slightly lower temperature than the raw material powder for silicon carbide single crystal growth by the sublimation method. This is the distance required to create the temperature gradient necessary for

The present invention will be described in more detail based on embodiments.

FIG. 1 shows an example of a single crystal growth apparatus suitably used in the silicon carbide single crystal growth method of the present invention.

As shown in FIG. 1, the graphite crucible 28 used in the single crystal growth apparatus includes an upper crucible outer cylinder 18 made of graphite having a circular cross-sectional shape, and a crucible in the crystal growth direction. It is composed of an additional crucible outer cylinder 21 used to adjust the length of the crucible, and a crucible bottom 20 for holding silicon carbide raw material powder 26. Then, the sublimated silicon carbide gas flows out of the crucible 28 from the upper crucible outer cylinder 18 and the additional crucible outer cylinder 21, and from the crucible outer cylinder 18 or the additional crucible outer cylinder 21 and the crucible bottom 20. They are connected by a connecting portion 25 that prevents unevenness in crucible temperature. The connecting portion 25 is made of a structure that satisfies the conditions of the above-mentioned joint portion, such as (1) screw-in type, (2) sliding type, and (2) fitting type. In addition,
At the upper end opening of the upper crucible outer cylinder 18, a graphite crucible lid body 19 having a portion 22 for attaching a silicon carbide single crystal substrate at the center of the inner surface is attached. It is installed like a rice field.

To grow a single crystal using the crucible shown in FIG. 1, first, a silicon carbide single crystal substrate 23 is attached to a portion 22 of the graphite lid 19 for attaching the silicon carbide crystal substrate.

A crucible 28 made of graphite and composed of an upper crucible outer cylinder 18, an additional crucible outer cylinder 21, and a crucible bottom 20 stores powder 26 containing silicon carbide as a raw material. Here, the distance 30 from the single crystal substrate growth surface 27 to the surface of the raw material powder 26 is adjusted by the length of the additional crucible outer cylinder 21. of course,
Even if this additional crucible outer cylinder 21 is not used, for example, the upper crucible outer cylinder 18 and the crucible can be separated by a distance of 3 by the bottom 20.
It is sufficient if 0 is a predetermined distance.

Thus, the silicon carbide gas that has been sublimed by heating the raw material by the heating means is deposited on the silicon carbide single crystal substrate 23 which is at a slightly lower temperature, and a bulk silicon carbide single crystal 24 can be grown. To continue crystal growth, first, the residue after crystal growth is removed from the melter 28, and new raw material powder 26 containing silicon carbide is introduced into the melter 28 for crystal growth. The lumpy silicon carbide single crystal 24 that is to be regrown to become larger or longer can be left integrated with the lid 19 used for the initial crystal growth or attached to the silicon carbide single crystal of a new crucible lid 19. Part 2
2 and placed on the upper crucible outer cylinder 18. The distance 30 from the single crystal growth surface 29 to the surface of the silicon carbide raw material powder 26 is set to a predetermined distance by adjusting the length of the additional crucible outer cylinder 21. This predetermined distance 30 is between 5 and 25 m.
m, preferably 10 to 20 mm; if it is short, the growth of the single crystal is likely to be inhibited, and if it is long, it is difficult to create the necessary temperature gradient.

Thus, by heating the crucible 28 with a heating means such as a high-frequency induction heating coil, silicon carbide gas can be deposited on the single crystal growth surface 29 to lengthen the silicon carbide single crystal 24. Silicon single crystals are, for example, Extended Abstracts on Site Seventeenth Conference on Solid State Devices and Materials, Tokyo, 1985.
Pages 249-252 [Extend CD abstract
ucts of the 17th, Confere
ncc on Devices and Mater
ials, Tokyo, 1985゜pp249-2
As described in No. 521, it is known that crystals grow in the direction perpendicular to the crystal growth direction, and it is also possible to increase the size in the radial direction. Also, IEE Transactions on Electron Devices, Volume, Eday-30, Number 4 (1983) 277-281
Page [IEEE TI? ANSACTIONON E
LECTRON DEVICES, VOL, ED-3
0, No. 4 (1983) 277-2811, the crystallinity of a single crystal grown on a silicon carbide substrate is improved compared to a silicon carbide single crystal substrate, and by growing the crystal for a long time, the crystallinity gradually improves. It is known that the crystallinity of a single crystal can be easily improved by growing a silicon carbide single crystal long using this method.

On the other hand, since the concentration of impurities tends to be uneven near the growth interface during regrowth, it is desirable to use silicon carbide powder from which impurities have been removed or high-purity silicon carbide powder as the silicon carbide raw material powder 26 used. .

Also, in a crucible configured as shown in Figure 1. Crucible lid 1
A small amount of unnecessary polycrystalline silicon carbide adheres to 9, but it does not grow to the extent that it inhibits single crystal growth.

By repeating the above-mentioned regrowth method several times, a practical large, long, and high quality silicon carbide single crystal can be grown simply, inexpensively, and efficiently. In addition, as long as the size of the growth apparatus allows, growth can be performed as many times as possible by adding additional crucible extension outer cylinders 21 or by using crucible extension outer cylinders 21 with different lengths, and the number of repeated growths can be reduced. There are no restrictions.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Using a single crystal growth crucible configured as shown in Figure 1,
An attempt was made to grow silicon carbide single crystals. The connection portion 25 between the upper crucible outer cylinder 18, the additional crucible outer cylinder 21, and the crucible bottom 20 is screwed. First, the silicon carbide single crystal substrate 23 used for the initial growth is a shaped single crystal obtained as a by-product in the process of industrially manufacturing a silicon carbide abrasive material or a single crystal obtained by a sublimation recrystallization method. Cut and polished crystals were used. The size is approximately 10-15 mm.

Further, as the silicon carbide raw material powder 26, a commercially available silicon carbide abrasive material was vacuum heat-treated at about 2000° C. for 10 minutes. The silicon carbide powder 26 that has been pretreated as described above is put into the container 28, and the single crystal substrate 23 is attached to the single crystal substrate mounting portion 22 of the crucible lid 19, which is attached to one hole of the upper crucible outer cylinder 18. growth surface 2 of the single crystal substrate.
The distance 30 from 7 to the surface of the raw material powder 26 was adjusted to 15 mm, and the melt 28 was heated to about 2350°C by high-frequency induction heating in an inert gas atmosphere, so that the growth rate was about 0°5.
Crystal growth was attempted by adjusting the atmospheric pressure so that the rate was ~1.5 mm/hour. As a result, the diameter is 13 mm and the length is 1
A 0 mm silicon carbide single crystal was obtained. In order to continue growing, the residue of the raw material 26 is taken out of the crucible 28,
After replacing the new raw material 26 and adjusting the distance from the crystal growth surface 29 of the single crystal 24 to 15 mm, growth was attempted again under the same crystal growth conditions as above, and as a result, the diameter was 18 mm. A silicon carbide single crystal with a length of 18 mm was obtained. The same growth continued until the diameter reached 23.
1. A bulk silicon carbide single crystal with a length of 25 mm was obtained. At this time, the polycrystal around the single crystal 24 did not grow to the extent that it inhibited the growth of the single crystal.

In addition, the crystal defect density at the interface of repeated growth is 8X1
04 pieces/C♂, which is sufficient for practical use as a semiconductor electronic material. Furthermore, the crystal defect density was improved as the crystal grew, reaching 4 x 104 defects/C♂.

(Effects of the Invention) As described above, the present invention uses a crucible whose length can be changed, and after forming a silicon carbide single crystal, replaces the silicon carbide raw material powder charged in the crucible, and Since this method adjusts the distance from the single crystal growth surface to the raw material surface to a predetermined distance and repeats single crystal growth, it is possible to grow large, long, and high quality silicon carbide single crystals simply, inexpensively, and efficiently. This patent is characterized by the supply of silicon carbide single crystal wafers that are useful for various applications including blue light emitting diodes using silicon carbide single crystals.

The present invention also provides that the graphite crucible that also serves as a heating element is of a split type, consisting of an upper crucible outer cylinder, a crucible bottom, and an additional crucible outer cylinder that is detachably disposed between the two. Since this is a silicon carbide single crystal growth apparatus with special characteristics, it is suitable for use in the single crystal growth method described above, and despite such a simple configuration, it is possible to easily grow large and long silicon carbide single crystals. It can be grown cheaply and efficiently.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a silicon carbide single crystal growth apparatus of the present invention in a use stage, and FIGS. 2 and 3 are cross-sectional views of a conventional silicon carbide single crystal growth apparatus. 18... Upper crucible outer cylinder, 19... Crucible lid body, 2
0... The bolt is the bottom, 21... The extension bolt is the outer cylinder, 22
...Single crystal substrate mounting part, 23...Silicon carbide single crystal substrate, 24...Silicon carbide single crystal, 25...Trust connection part,
26...Silicon carbide raw material powder, 27...Single crystal substrate growth surface, 29...Single crystal growth surface.

Claims (2)

[Claims] (1) In a method of growing a silicon carbide single crystal on a silicon carbide single crystal substrate by heating and sublimating a raw material made of silicon carbide powder using the sublimation recrystallization method, it is possible to change the length of the crucible in the crystal growth direction. After growing a silicon carbide single crystal using a graphite crucible, the raw material loaded in the crucible is replaced, and the distance from the single crystal growth surface to the surface of the raw material is a predetermined distance. 1. A method for growing a silicon carbide single crystal, comprising adjusting the length of a crucible and growing the crystal again by a sublimation recrystallization method at least once. (2) A crucible made of graphite that also serves as a heating element, a crucible lid made of graphite that covers the upper opening of the crucible, a heating means for heating the crucible, and a vacuum or inert gas atmosphere controlled by inserting the crucible. In a silicon carbide single crystal growth apparatus having a vacuum system, the graphite crucible is divided into an upper crucible outer cylinder, a crucible bottom, and an additional crucible outer cylinder detachably disposed between the two. A silicon carbide single crystal growth device characterized by a shape.