JPH07330493A - Method for growing 4h type silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To obtain a 4H type SiC single crystal by using the (0001) C face of 15R type SiC as a seed crystal in a sublimation recrystallization method of SiC. CONSTITUTION:The seed crystal S is produced by shaping and polishing the planar amorphous 15R type SiC single crystal and executing face decision by a steam oxidation method, then subjecting the single crystal to acid washing with HF and drying. The seed crystal is then mounted by directing the (0001) Si face of the seed crystal 5 toward the side of a crucible cap 3 and directing the (0001) C face as a crystal growth face 6 in a direction opposite to the crucible cap 3. SiC raw material powder 2 is packed into the crucible 1 and the crucible cap 3 holding the seed crystal 5 in the mounting part 4 is put on the crucible 1 packed with the SiC powder 2 and thereafter, the crucible is arranged in a vessel in which vacuum is maintainable. The inside of the system is evacuated to a high vacuum and an inert gaseous atmosphere of a pressure 10 to 20Torr is generated and thereafter, the crucible 1 is heated to sublimate the SiC powder 2 at 2300 to 2400 deg.C, by which the SiC crystal is grown at a crystal growth rate 0.6 to 1.2mm/ hour on the growth surface of the seed crystal kept at 2150 to 2250 deg.C slightly lower than the temp. of the SiC powder and the 4H type SiC single crystal is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 4H type silicon carbide single crystal useful for power devices and the like (H indicates that the crystal form is hexagonal, and 4 indicates 4 layers of atomic lamination in the crystal c-axis direction. Represents a crystal structure which is one cycle in (1).

[0002]

2. Description of the Related Art A silicon carbide single crystal is a material attracting attention as an environment resistant device and a power device because it has a chemically stable and semiconductor-like physical property which is not found in silicon. As a method for producing a large single crystal for a semiconductor device, a sublimation recrystallization method called an improved Rayleigh method is a main method. Further, there are many crystal structures in a silicon carbide single crystal, and the main ones are 6H type, 4H type and 15R type (15 indicates that stacking in the crystal c-axis direction is 15 periods, and R is It shows that it is a rhombohedral structure.). Among them, 6H type silicon carbide single crystal has been used as a material for blue light emitting diodes. The 4H-type silicon carbide single crystal has more desirable characteristics for power devices than the 6H-type, and therefore has recently attracted attention as a semiconductor crystal material for power devices.

In the sublimation recrystallization method, if the seed crystal is the 4H type, a 4H type single crystal can be easily grown on it. However, the 4H type silicon carbide single crystal contains a Si compound and a C compound. Since it cannot be obtained by a process for producing an abrasive material called an Asochin method which is synthesized at a high temperature, a 4H-type silicon carbide single crystal is grown using the 6H-type or 15R-type silicon carbide single crystal obtained by the Asochin process as a seed crystal. Need a way.

In sublimation recrystallization, as a method for separately producing the 6H-type and 4H-type single crystals, for example, Japanese Patent Laid-Open No. 4-1
In No. 2096, a 6H type silicon carbide single crystal (0
A method of growing a desired silicon carbide single crystal using a 001) carbon face and under crystal growth conditions convenient for 4H and 6H type silicon carbide single crystal growth is disclosed. Further, JP-A-2-48495 discloses a method of growing a 4H type silicon carbide single crystal by appropriately adjusting the crystal growth conditions. Indeed, using this method, 4H and 6H type silicon carbide single crystals can be produced.
The resulting single crystal polytype is highly dependent on the crystal growth conditions. Further, JP-A-5-51299 discloses that a 4H-type silicon carbide single crystal can be produced by growing a crystal by a sublimation recrystallization method on a seed crystal having an oxide film. This method is simple as a method for producing a 4H type silicon carbide single crystal,
The above-mentioned sublimation recrystallization method of silicon carbide exposed to high temperature cannot be said to be a reliable method for producing a 4H-type single crystal because the oxide film disappears by sublimation.

[0005]

As described above, the conventional silicon carbide single crystal growth method cannot simply and reliably produce a 4H type silicon carbide single crystal. Therefore, an object of the present invention is to provide a method for easily and surely producing a 4H-type silicon carbide single crystal.

[0006]

Means for Solving the Problems The above-mentioned object is to sublimate a silicon carbide raw material powder in an inert gas atmosphere in a crucible made of graphite, and to place it on a silicon carbide substrate (seed crystal) at a temperature slightly lower than that of the raw material. In a sublimation recrystallization method for growing a silicon carbide single crystal on a substrate, 15R type silicon carbide (0
001) is achieved by a 4H-type silicon carbide single crystal growth method characterized by using a carbon face.

[0007]

In the method for growing a silicon carbide single crystal of the present invention, the silicon carbide raw material powder is sublimated in a graphite crucible in an inert gas atmosphere, and is placed in a graphite crucible lid that covers the upper part of the crucible, and is slightly separated from the raw material. A silicon carbide single crystal is deposited and grown from a sublimated silicon carbide gas on a low-temperature silicon carbide seed crystal.
By using the (0001) carbon face of the silicon carbide in the form of 4H, a silicon carbide single crystal of the 4H form can be easily grown.

First, in the sublimation recrystallization method, if a 6H-type silicon carbide single crystal is used as a seed crystal for the purpose of growing a 4H-type single crystal, the 4H-type single-crystal growth condition is greatly influenced. It is hard to say that a silicon carbide single crystal can be grown. When the (0001) carbon face of a 15R type silicon carbide single crystal is used as a seed crystal, a 4H type single crystal can be easily obtained without being largely influenced by crystal growth conditions. On the other hand, if the 15R type (0001) silicon surface is used as a seed crystal, a 4H type crystal cannot be obtained.

The crystal growth conditions in the sublimation recrystallization method using 15R type as a seed crystal in the present invention are preferably such that the temperature of the seed crystal is 2150 ° C to 2250 ° C and the temperature of the raw material powder of silicon carbide is 2300 ° C to 2400. ℃,
More preferably, in addition to the above temperature conditions, the inert gas atmosphere pressure is set to 10 to 20 Torr and the crystal growth rate is set to 0.
It is suitable for the purpose of 4H-type single crystal growth to adjust the temperature of the seed crystal and the raw material powder and the atmospheric pressure so as to be 6 to 1.2 mm / h.

[0010]

【Example】

Example 1 Hereinafter, the present invention will be described in detail based on embodiments. Figure 1
Shows an example of a sublimation method silicon carbide crystal growth apparatus suitably used in the present invention. The crucible used in the single crystal growth apparatus is a bottomed crucible 1 made of graphite and the crucible 1 having a mounting portion (seed crystal mounting portion 4) for mounting a silicon carbide seed crystal 5.
And a crucible lid 3 made of graphite that covers the opening of the crucible 1. The crucible 1 and the outer peripheral surface of the crucible lid 3 and the upper and lower sides thereof are covered with a heat insulating material 7 made of felt made of graphite. (Not shown) can be evacuated and the internal atmosphere can be changed from atmospheric pressure to several T with an inert gas such as argon gas.
It is contained in a container (not shown) that can be controlled to orr. The crucible is heated by the heating means, and the temperature of the crucible can be measured by a radiation thermometer through measurement holes 8 provided on the upper and lower sides and the side wall of the crucible.

The seed crystal in the present invention will be described below.
For the seed crystal 5, a plate-shaped amorphous 15R type silicon carbide single crystal obtained as a by-product when industrially manufacturing a silicon carbide abrasive is shaped and polished, and surface determination is performed by a steam oxidation method. What was dried after acid cleaning with hydrofluoric acid was used. The steam oxidation used for surface determination was performed with a seed crystal of 1150.
Heat treatment was performed for 3 hours in an atmosphere heated to 90 ° C. and flowing pure oxygen containing saturated steam at 90 ° C., and the thick surface of the oxide film was determined to be a carbon surface.

The (0001) silicon surface of the seed crystal 5 pretreated as described above is directed to the crucible lid 3 side, that is, the (0001) carbon surface is directed to the opposite side of the crucible lid 3 as the crystal growth surface 6. I attached it. A silicon carbide raw material powder 2 is housed in a bottomed crucible 1 and a seed crystal 5 is attached to a seed crystal mounting portion 4.
After covering the crucible lid 3 held in the above with the crucible 1 containing the silicon carbide powder 2, the crucible lid 3 is placed in a container capable of holding a vacuum, and the inside of the system is evacuated to a high vacuum by a vacuum evacuation device to be inert. A gas is introduced to make an inert gas atmosphere, and then the crucible 1 is heated by a heating means to sublimate the silicon carbide powder 2 to form a silicon carbide single crystal on the seed crystal growth surface 6 at a temperature slightly lower than that of the silicon carbide powder 2. Crystal 9 was grown. Regarding the crystal growth conditions, the temperature of the seed crystal was 2200 ° C. and the temperature of the silicon carbide raw material powder was 2300 ° C. At this time, the temperature gradient from the seed crystal to the raw material was about 20 ° C./cm. When the inert gas atmosphere pressure was 10 Torr, the crystal growth rate was about 0.8 mm / h. As a result, out of 20 bulk single crystals formed by performing 20 times of crystal growth, the ratio of the number of bulk single crystals having a complete 4H form was 95% (19), and the remaining 5%. Was a 6H-type massive single crystal.

The crystal growth conditions of the present invention are not limited to the growth conditions of the above embodiment, and as described above, the seed crystal temperature is 2150 ° C. to 2250 ° C. and the silicon carbide raw material powder temperature is 2300. C. to 2400.degree. C., inert gas atmosphere pressure 10 to 20 Torr, and crystal growth rate 0.
If the growth is performed in the range of 6 to 1.2 mm / h, the same effect as above can be obtained.

Example 2 In the apparatus shown in FIG. 1, as a seed crystal 5, a 15R type silicon carbide single crystal substrate cut out from a 15R type silicon carbide single crystal produced by a sublimation recrystallization method and polished was used. 0
Crystal growth was carried out with the 001) carbon surface as the crystal growth surface 6. The crystal growth condition is that the seed crystal temperature is 2250 ° C.
The temperature of the silicon carbide raw material powder was set to 2340 ° C. At this time, the temperature gradient from the seed crystal to the raw material was about 15 ° C./cm. As a result, the crystal form of the grown bulk single crystal is 4H.
It was in shape.

[0015]

As described above, according to the present invention, a silicon carbide raw material powder is sublimated in an inert gas atmosphere in a graphite crucible, and a silicon carbide substrate (seed crystal) is slightly lower than the raw material. In the sublimation recrystallization method in which a silicon carbide single crystal is grown on, a seed crystal of 15R type silicon carbide (00
01) A silicon carbide single crystal growth method characterized by using a carbon surface. Therefore, by using this method,
A 4H type silicon carbide single crystal can be simply and surely obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a silicon carbide single crystal growth apparatus by a sublimation recrystallization method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bottom crucible, 2 ... Silicon carbide powder, 3 ... Crucible lid, 4 ... Seed crystal attachment part, 5 ... Seed crystal, 6 ... Seed crystal growth surface.

Claims (2)

[Claims] 1. Sublimation in which a silicon carbide raw material powder is sublimated in a graphite crucible in an inert gas atmosphere, and a silicon carbide single crystal is grown on a silicon carbide substrate (seed crystal) slightly lower than the raw material. In the recrystallization method, a (0001) carbon face of 15R type silicon carbide is used as a seed crystal, and a 4H type silicon carbide single crystal growth method is characterized. 2. The temperature of the seed crystal is 2150 ° C. to 225.
The temperature of the silicon carbide raw material powder is set to 0 ° C.
00 ° C. to 2400 ° C., the inert gas atmosphere pressure is 10 to 20 Torr, and the crystal growth rate is 0.6 to
It is 1.2 mm / h, The 4H type silicon carbide single crystal growth method of Claim 1 characterized by the above-mentioned.