JPH061699A - Device for producing silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To continuously generate a sublimated vapor and to produce a high- quality silicon carbide single crystal by successively using plural silicon carbide sintered compacts as the sublimation source. CONSTITUTION:Plural silicon carbide sintered compacts 11 and 12 are respectively put in the holes 21 and 22 of a material holder 20. The holder 20 on a crucible 30 contg. a seed crystal on its bottom is slid on the upper end of the side wall 32 of the crucible 30 to oppose the sublimating surface of the sintered compact 12 to the seed crystal. The sintered compact 11 is heated by heaters 50 and 51 and continuously sublimated. The holder 20 is slid at about the time when sublimation is finished to introduce the sintered compact 12 into the crucible 30, and sublimation is continued. Consequently, the crystal growth condition is stabilized, and a constant-quality long-sized single crystal 15 is obtained. Besides, since the sintered compact residue is not mixed into the single crystal, the quality of the obtained single crystal 15 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuous sublimation of a silicon carbide raw material to produce a long silicon carbide single crystal having stable quality.

[0002]

2. Description of the Related Art Silicon carbide single crystals are usually produced by a sublimation method using silicon carbide powder as a raw material. The silicon carbide powder is housed in a crucible together with a seed crystal and heated to a temperature of 2000 to 2400 ° C in an inert atmosphere.
The vapor sublimated from the silicon carbide powder by heating comes into contact with the seed crystal, and a single crystal having a uniform crystal orientation grows on the seed crystal.

A graphite crucible has been conventionally used. 20-30 at the bottom or top of the graphite crucible
About g of silicon carbide powder is put and a seed crystal is arranged on the opposite side. For example, as shown in FIG. 1, when the silicon carbide powder 2 is put in the upper part of the crucible 1, the inside of the crucible 1 is partitioned by the porous graphite plate 3, and the seed crystal 4 is arranged at the bottom of the crucible 1. Then, the heater 5 surrounding the crucible 1 heats and sublimates the silicon carbide powder 2 with a predetermined temperature gradient to grow the single crystal 4 on the seed crystal. As the heater 5, a resistance heating method, a high frequency induction heating method, or the like is adopted.
When silicon carbide powder is put in the lower part of the crucible, a seed crystal may be attached to the upper lid of the crucible.

Under this condition, the crucible was set in an inert gas atmosphere with a pressure of 760 Torr or less, and a temperature gradient was set so that the seed crystal side became lower than the raw material side.
Maintain a high temperature atmosphere of 00 ° C. As a result, the raw material silicon carbide powder is sublimated, and Si, Si ₂ C, SiC
_2. Steam such as SiC pours onto the seed crystal. From these vapors, a silicon carbide single crystal grows on the surface of the seed crystal at a growth rate of about 0.5 to 2 mm / hour. When the crystal growth step is completed, if the silicon carbide powder contained in the crucible as a raw material is preset to an amount such that the total amount is sublimated within the crystal growth time, most of the silicon carbide is sublimated and consumed. Then, soot-like carbon remains inside the crucible.

[0005]

The sublimation reaction of silicon carbide does not generate a large amount of sublimation gas proportional to the amount of silicon carbide powder contained in the crucible. When the amount of silicon carbide powder stored in the crucible exceeds the sublimation condition, undecomposed silicon carbide tends to remain as a solidified body inside the raw material powder layer. The remaining silicon carbide suppresses the subsequent sublimation reaction and becomes a cause of hindering the generation of steam. Therefore, one step of crystal growth is determined according to the characteristics such as temperature distribution and pressure determined by the manufacturing apparatus and the conditions of the controllable range. From this, in order to continuously grow a single crystal under stable conditions, it is necessary to set the same sublimation condition of the raw material at the time of crystal growth.

In order to maintain the sublimation conditions continuously and the same, a method of continuously supplying silicon carbide powder as a raw material can be considered. However, since soot-like carbon remains in the crucible after sublimation of silicon carbide, it is impossible to continuously supply the silicon carbide powder for a long time. Further, in the structure for continuously supplying the raw material, it is inevitable that an opening will be generated. The opening is not suitable for the crucible structure in which sublimation vapor is required not to leak to the outside. It also causes disturbance of the generated sublimation vapor flow.

The present invention has been devised to solve such a problem, and a plurality of silicon carbide sintered bodies are intermittently sequentially fed into the crucible in accordance with the progress of sublimation, whereby the sublimation vapor is produced. The objective is to make the generation of silicon carbide continuous and to grow a silicon carbide single crystal under stable conditions.

[0008]

In order to achieve the object, a silicon carbide single crystal production apparatus of the present invention contains a crucible having a seed crystal attached to one side and a plurality of silicon carbide sintered bodies, A raw material holder movably provided on the other side of the crucible and a heater surrounding the outer periphery of the crucible, so that the sublimation surface of the silicon carbide sintered body drawn into the crucible faces the seed crystal. The silicon carbide sintered body is sequentially drawn into the crucible by the movement of the raw material holder.

[0009]

[Operation] In the present invention, a plurality of silicon carbide sintered bodies are prepared as sublimation raw materials. This sintered body is manufactured by the same sintering method as the method for obtaining a normal ceramics sintered body. Alternatively, as shown in FIG. 2, silicon carbide powder 7 is housed in a graphite container 6 having a cylindrical volume and heated to 500 to 1000 ° C. in an inert gas atmosphere to perform disc-shaped sintering. You can also get a body. As shown in FIG. 3, the plurality of silicon carbide sintered bodies 11 and 12 are respectively housed in the hole portions 21 and 22 formed in the raw material holder 20, and the silicon carbide sintered body 11 is placed inside the crucible 30 at the sublimation position. It is set in a chamber 40 provided with a heat insulating lining so as to face the crystal growth surface. Raw material holder 20
Slides in the chamber 40 as indicated by arrow D.

The crucible 30 has a side wall 32 having a step formed at the upper end on which the porous graphite plate 31 is mounted. The porous graphite plate 31 prevents the residue of the sintered body from dropping onto the crystal growth surface when the silicon carbide sintered body 11 is sublimated or at the end of sublimation. The hole 21 of the raw material holder 20 at the sublimation position is closed by the upper lid 33. The raw material holder 20 is arranged in contact with the upper end of the side wall 31 or at least in a very close position so that the sublimation vapor 13 does not leak to the outside of the crucible 30.

The outer circumference of the crucible 30 is a cylindrical heater 50.
It is surrounded by. The heater 51 is also arranged above the silicon carbide sintered body 11 at the sublimation position. The heater 50 is vertically divided into a plurality of blocks,
By controlling the current supplied to each block, the crucible 30 is provided with a predetermined temperature gradient in the vertical direction. Specifically, the silicon carbide sintered body 11 side is set to a high temperature and the seed crystal side is set to a low temperature.

The chamber 40 is evacuated through the exhaust port 41, and an inert gas is introduced into the chamber 40 through the air supply port 42. The interior of the chamber 40 is cleaned by repeating exhaustion and air supply, and an inert gas atmosphere suitable for sublimation and crystal growth of silicon carbide is adjusted. Next, the silicon carbide sintered body 11 is heated by the heaters 50 and 51,
Sublimation steam 13 is generated. The sublimation vapor 13 permeates the porous graphite plate 31 and flows down in the crucible 30.
The single crystal 15 grows on the seed crystal arranged at the bottom of the.

When the sublimation of the main component of the silicon carbide sintered body 11 is completed, the raw material holder 20 is slid to draw the next silicon carbide sintered body 12 into the crucible 30. At this time, the residue of the silicon carbide sintered body 11 that has been sublimated is discharged to the outside of the crucible 30 as the raw material holder 20 moves. Since the silicon carbide sintered body 12 that has been drawn in is already in a high temperature state, it immediately starts sublimation. Then, the sublimation vapor 13 is generated for a certain period of time.
In this way, the sublimation vapor 13 is constantly obtained by continuously introducing the plurality of silicon carbide sintered bodies 11 and 12 into the crucible 30 at regular time intervals. as a result,
The crystal growth is performed under stable conditions, and the single crystal 15 having a constant quality is obtained.

The positional relationship between the seed crystal and the silicon carbide sintered body can be reversed as shown in FIG. In this case, a seed crystal is attached to the upper part of the crucible 30 and the raw material holder 3 containing a plurality of silicon carbide sintered bodies 11 and 12 is housed.
Place 0 at the bottom. Raw material holder 30 is slid in the direction indicated by arrow D when the sublimation of silicon carbide sintered body 11 is completed, as in the case of FIG. 3. In this positional relationship, the residue of the silicon carbide sintered body 11 is the raw material holder 30.
Therefore, the porous graphite plate 31 can be omitted. The silicon carbide sintered bodies 11 and 12 are housed in the recesses 23 and 24 formed in the raw material holder 20.

In the example of FIGS. 3 and 4, a slide type raw material holder 30 is adopted. However, the present invention is not limited to this, and as long as a plurality of silicon carbide sintered bodies are intermittently introduced into the crucible, other types of raw material holders can be adopted. For example,
A rotary disk having a plurality of concentric circular holes or recesses for accommodating the silicon carbide sintered body may be incorporated, and the rotary disk may be intermittently rotated as the silicon carbide sintered body is consumed by sublimation. .

[0016]

[Example] 50 g of silicon carbide powder was placed in a graphite cylindrical container having a diameter of 25 mm, and 1000 to 1000 in an inert gas atmosphere.
Heat-sintered at a temperature of 1500 ℃ for about 1 hour, diameter 25mm
And a cylindrical silicon carbide sintered body having a thickness of 10 mm was obtained. As the crucible 30, a graphite crucible having an inner diameter of 25 mm was used. In the crucible 30, the seed crystal was placed on the pedestal 34 of the lower lid, and the porous graphite plate 31 was attached to the upper end of the side wall 32. Then, the raw material holder 20 containing the silicon carbide sintered bodies 11 and 12 in the holes 21 and 22 was slidably arranged on the upper portion of the crucible 30. The peripheral portions of the silicon carbide sintered bodies 11 and 12 are supported by the shoulders of the raw material holder 20, and in the state of being pulled into the crucible 30, the porous graphite plate 31 and the upper lid 33 are provided.
Is set in the closed space.

An inert gas is introduced into the chamber 40 with the silicon carbide sintered body 11 being drawn into the crucible 30,
The silicon carbide sintered body 11 and the crucible 30 were heated by the heaters 50 and 51. Crucible 30 is 2000-2400
When the temperature reached ℃, sublimation of the silicon carbide sintered body 11 started. The sublimation vapor 13 passed through the porous graphite plate 31 and was poured onto the seed crystal to grow as a single crystal 15. After continuing sublimation for 3 hours, the raw material holder 20 was slid in the direction of arrow D, and a new silicon carbide sintered body 12 was drawn into the crucible 30. From this point, sublimation was continued for another 3 hours to grow crystals. Crystal growth of about 3 mm was observed from the silicon carbide sintered body 11, and further the silicon carbide sintered body 1
After sublimating No. 2, crystal growth of about 6 mm was confirmed. From this, it is about 3 mm per silicon carbide sintered body.
It can be seen that the crystal growth of Further, the obtained single crystal had a uniform and stable quality without any influence caused by switching the sublimation raw material from the silicon carbide sintered body 11 to the silicon carbide sintered body 12.

[0018]

As described above, in the present invention, a plurality of silicon carbide sintered bodies are sequentially fed into the crucible to make sublimation continuous. Therefore, sublimation vapor is continuously poured onto the crystal growth surface under the same conditions, crystal growth is continuously performed, and a long single crystal is manufactured. Moreover, since the fresh raw material is always supplied, it is possible to prevent the conventional residue from being mixed into the product single crystal, and to obtain a high-quality silicon carbide single crystal.

[Brief description of drawings]

FIG. 1 Conventional single crystal production apparatus using silicon carbide powder as a raw material

FIG. 2 An example of using silicon carbide powder as a sintered body

FIG. 3 is a single crystal manufacturing apparatus in which a silicon carbide sintered body and a seed crystal are arranged above and below a crucible according to the present invention.

FIG. 4 is an apparatus for producing a single crystal in which a seed crystal and a silicon carbide sintered body are arranged above and below a crucible according to the present invention.

[Explanation of Codes] 11,12 Silicon Carbide Sintered Body 13 Sublimation Steam
15 Single Crystal 20 Raw Material Holder 21, 22 Hole 23, 24 for Receiving Silicon Carbide Sintered Body Recess 30 Crucible
31 porous graphite plate 32 side wall 33 upper lid 34 pedestal
40 chamber 50,51 heater

Claims (1)

[Claims] 1. A crucible having a seed crystal attached to one side and a plurality of silicon carbide sintered bodies are accommodated, and a sublimation surface of the silicon carbide sintered body drawn into the crucible faces the seed crystal. As described above, the raw material holder movably provided on the other side of the crucible and the heater surrounding the outer periphery of the crucible are provided, and the silicon carbide sintered body is sequentially drawn into the crucible by the movement of the raw material holder. An apparatus for producing a silicon carbide single crystal, which is characterized in that: