JPH061698A - Production of silicon carbide bulk single crystal - Google Patents

Abstract

PURPOSE:To obtain an SiC bulk single crystal excellent in crystallinity and homogeneity with good reproducibility by adding the silicon compd. of transition metal to an SiC powder and heating the mixture to grow an SiC single crystal on a seed crystal. CONSTITUTION:An SiC powder mixed with 1-10% of the silicon compd. of transition metal having 1800-2500 deg.C m.p. is filled in a graphite crucible 3. The crucible 3 is then closed with a lid 4 provided with a seed crystal 1 on its inner surface. The crucible 3 is set in a quartz tube 5 by a supporting rod 6, and the crucible 3 is covered with a heat shield 7. An inert gas is introduced into the tube 5 from the branch pipe 9 of a chamber 10, the SiC powder 2 is kept at 2100-2400 deg.C and the seed crystal 1 at 2000-2500 deg.C, the tube 5 us evacuated to <=10Torr by a vacuum pump 13, the condition is kept for 1-12 hr, and an SiC single crystal is grown on the seed crystal 1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a silicon carbide bulk single crystal. More specifically, it relates to a method for manufacturing a silicon carbide bulk single crystal using a sublimation recrystallization method.

[0002]

2. Description of the Related Art Silicon carbide (SiC) is a semiconductor material having a wide band gap (2.2 to 3.3 eV). In addition, it has the excellent characteristics that it is extremely stable thermally, chemically and mechanically and is resistant to radiation damage. On the other hand,
A device using a conventional semiconductor material such as silicon is difficult to use, especially under severe conditions such as high temperature, high output driving, and radiation irradiation. A semiconductor element using silicon carbide is expected to be applied in a wide range of fields as a semiconductor element that can be used even under such severe conditions.

However, a crystal growth technique capable of stably supplying a high-quality silicon carbide single crystal having a large area on an industrial scale has not been established yet. Therefore, although silicon carbide is a semiconductor material having many advantages and possibilities as described above, its practical use is hindered. Conventionally, in a laboratory scale, a silicon carbide single crystal was grown by, for example, a sublimation recrystallization method (Rayleigh method) to obtain a silicon carbide single crystal of a size usable for a semiconductor device. However, with this method, the area of the obtained single crystal is small, and it is difficult to control the size and shape with high accuracy. Further, it is not easy to control the crystal polymorphism and the impurity carrier concentration of silicon carbide.

There is also a method of growing a cubic silicon carbide single crystal by performing heteroepitaxial growth on a heterogeneous substrate such as silicon using a chemical vapor deposition method (CVD method). Although a large area single crystal can be obtained by this method, only a silicon carbide single crystal containing many defects (about 10 ⁷ / cm ² ) can be grown because the lattice mismatch with the substrate is about 20%. It is not easy to obtain a high quality silicon carbide single crystal.

In order to solve these problems, an improved Rayleigh method in which a sublimation recrystallization method is performed using a seed crystal has been proposed (Yu.M. Tairov and VFTsvetkov, J. Crystal G.
rowth, 52 (1981), pp.146-150). With this method,
A silicon carbide single crystal can be grown while controlling the crystal polymorphism and shape.

[0006]

Usually, in the sublimation recrystallization method using a seed crystal, the temperature of the seed crystal, the temperature gradient between the seed crystal and the raw material, and the pressure are controlled to obtain a hexagonal system (6H type, 4H
Type) and rhombohedral (15R type, 21R type) silicon carbide single crystals can be grown. However, in the sublimation recrystallization method using a seed crystal, Si, Si ₂ C, and SiC ₂ can be mentioned as molecular species involved in growth.
Due to the difference in vapor pressure of the molecular species and the high growth temperature of 2000 ° C. or higher, the proportion of the molecular species changes with the growth time. In particular, depletion of Si becomes a problem and a good quality silicon carbide single crystal cannot be grown. In order to solve this problem, in the improved sublimation recrystallization method, a method has been proposed in which silicon powder is added to the raw material silicon carbide powder to grow it (Japanese Patent Laid-Open No. 3-37195). Since the melting point is about 1400 ° C., while the growth temperature is 2000 ° C. or higher, the effect of adding silicon is only at the start of growth, and a homogeneous silicon carbide single crystal cannot be manufactured.

[0007]

According to the present invention, in a method for producing a silicon carbide bulk single crystal in which a silicon carbide single crystal is grown on a seed crystal by a sublimation recrystallization method, a transition metal of silicon is added to silicon carbide powder. There is provided a method for producing a silicon carbide bulk single crystal, which comprises adding a compound.

The silicon carbide powder used in the present invention may be a silicon carbide powder used in commercially available abrasives and the like, but a silicon compound of a transition metal and a high purity silicon carbide powder containing no transition metal may be used. desirable. As the silicon compound of the transition metal to be added next, a compound having a melting point of 1800 to 2500 ° C, preferably 1900 to 2400 ° C can be used. Examples of the method of adding the transition metal silicon compound include a method of using the transition metal silicon compound as it is, and a method of adding the transition metal and silicon to the silicon carbide powder and heat-treating at 1700 to 2200 ° C. . Examples of such transition metal silicon compounds include vanadium silicide, tungsten silicide, tantalum silicide, molybdenum silicide, niobium silicide, rhenium silicide, and zirconium silicide. The addition ratio of the silicon compound of the transition metal to the silicon carbide powder is 1 to 10
%, Preferably 2 to 6%. If the addition amount is 1% or less, the effect of adding the transition metal silicon compound does not appear, and the addition amount is 10%.
In the above case, an excessive silicon atmosphere is created and a good quality silicon carbide single crystal cannot be grown.

The seed crystal silicon carbide single crystal substrate used in the present invention can be manufactured by a known method. For example, a single crystal obtained as a by-product in the process of industrially manufacturing a silicon carbide abrasive may be used after being shaped and polished, and further polishing scratches removed by acid cleaning. In the present invention, a method for producing a silicon carbide bulk single crystal is a sublimation recrystallization method, and among them, an improved Rayleigh method is preferable. The diagram shown in FIG. 1 is an example of an apparatus for growing a silicon carbide single crystal by the improved Rayleigh method. Figure 1
The manufacturing method of the present invention will be described below based on.

First, a graphite crucible 3 is filled with silicon carbide powder containing a silicon compound of a transition metal as a raw material.
Next, a silicon carbide single crystal substrate 1, which is a seed crystal, is attached to the inner surface of the graphite crucible 3 with a lid 4 attached thereto. The graphite crucible 3 is installed inside the quartz tube 5 by the support rod 6,
The graphite crucible 3 is covered with a heat shield 7. Further, the temperature of the silicon carbide powder 2 in an inert gas atmosphere (for example, argon gas) is set to 2100 to 2400 ° C. and the seed crystal temperature is set to 2 although it changes depending on the kind of the silicon compound of the transition metal.
Set to 000 to 2500 ° C. Subsequently, the pressure is reduced to 10 Torr or less, and the silicon carbide single crystal is obtained by maintaining this state for 1 to 12 hours.

[0011]

The method for producing a bulk silicon carbide single crystal of the present invention is
It includes a step of growing a silicon carbide single crystal by a sublimation recrystallization method using a seed crystal, and adds a silicon compound of a transition metal having a high melting point to silicon carbide powder as a raw material to grow the bulk silicon carbide of high quality. Single crystal growth is possible. At this time, the vapor pressure of Si can be controlled by controlling the type of the silicon compound of the transition metal to be added and the temperature of the silicon carbide powder used as the raw material, and the molecular species involved in the growth that change with the growth can be kept constant. By keeping the growth in the above condition, it is possible to prevent foreign matters related to carbon from mixing in, and it is possible to form a good quality bulk silicon carbide single crystal with good reproducibility.

[0012]

【Example】

Example 1 will be described with reference to FIG. First, as a seed crystal, a substrate 1 made of a hexagonal 6H-type silicon carbide single crystal having a growth plane orientation in the (0001) direction was prepared. Then, the substrate 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. Also,
Inside the graphite crucible 3, 25 g of high-purity cubic silicon carbide powder as the raw material 2 and tungsten silicide (W
0.5 g of Si ₂ ; melting point 2160 ° C.) was filled. The silicon carbide powder used had a JIS grain size of # 250. The ratio of tungsten silicide to silicon carbide powder is 2%.

Next, a graphite crucible 3 filled with raw materials was
It was closed with a lid 4 to which a seed crystal was attached, and was placed inside a double quartz tube 5 with a support rod 6 made of graphite. The graphite crucible 3 was covered with a graphite felt 7. Then, argon gas (Ar) as an atmospheric gas was flowed from the branch pipe 9 of the stainless steel chamber 10 into the double quartz pipe 5. A
The flow rate of r gas was set to 1 liter / minute. Next, a high frequency current was passed through the work coil 8 to adjust the high frequency current so that the temperature of the silicon carbide powder 2 was 2300 ° C. and the temperature of the seed crystal was 2200 ° C. Then, the flow rate of Ar gas was adjusted and the inside of the double quartz tube 5 was decompressed using the vacuum pump 13. This depressurization is gradually performed from atmospheric pressure to 10 Torr over 20 minutes to 10 Torr.
The vacuum was maintained at r. By holding this state for 5 hours, a silicon carbide single crystal having a thickness of about 10 mm was grown.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman spectroscopy. As a result, a hexagonal 6H-type silicon carbide single crystal having a growth plane orientation of (0001) was grown. I found out that Growth rate is 2
It was found that the grown crystal was a high-quality silicon carbide single crystal, with the grown crystal being uniform from the seed crystal to the outermost growth surface and having few defects.

Furthermore, under the same conditions as above, tantalum silicide (Ta
Si ₂ ; melting point 2200 ° C. or zirconium silicide (Zr ₂
As a result of growing by adding Si: melting point 2100 ° C.), it was found that a similar homogeneous silicon carbide single crystal having excellent crystallinity was grown.

Embodiment 2 A description will be given with reference to FIG. First, inside a graphite crucible 3, a high-purity cubic silicon carbide powder 2 serving as a raw material 2 is placed.
5 g, 0.37 g of silicon powder and 0.
63 g was filled. As the silicon carbide powder, one having a JIS particle size of # 1000 was used. The graphite crucible 3 filled with the raw material was closed with a lid 4 to which no seed crystal was attached, and the graphite crucible 3 was placed inside a double quartz tube 5 by a graphite support rod 6. The graphite crucible 3 was covered with a graphite felt 7.
Then, argon gas (Ar) as an atmospheric gas was flowed from the branch pipe 9 of the stainless steel chamber 10 into the double quartz pipe 5. The flow rate of Ar gas was set to 1 liter / minute. Next, a high-frequency current is passed through the work coil 8 to adjust the high-frequency current so that the temperature of the silicon carbide powder 2 becomes 210.
The temperature was adjusted to 0 ° C. and kept for 20 minutes. By this treatment, molybdenum and silicon react to form molybdenum silicide (MoSi ₂ ; melting point 1950 ° C.). The ratio of molybdenum silicide to silicon carbide powder is 4%.

As a seed crystal, the growth plane orientation is (0001)
A substrate 1 made of a hexagonal 4H-type silicon carbide single crystal that is oriented was prepared. Then, the substrate 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. Next, the graphite crucible 3 filled with the raw material was closed by the lid 4 having the seed crystal attached thereto, and the graphite crucible 3 was placed inside the double quartz tube 5 by the graphite support rod 6. The graphite crucible 3 was covered with a graphite felt 7. Argon gas (Ar) is used as the atmosphere gas.
Was made to flow from the branch pipe 9 of the stainless steel chamber 10 into the double quartz pipe 5. The flow rate of Ar gas was set to 1 liter / minute. Next, a high-frequency current was passed through the work coil 8 to adjust the high-frequency current so that the temperature of the silicon carbide powder 2 was 2050 ° C. and the temperature of the seed crystal was 2100 ° C. Then, the flow rate of Ar gas was adjusted and the inside of the double quartz tube 5 was decompressed using the vacuum pump 13. The pressure was gradually reduced from atmospheric pressure to 1 Torr over 60 minutes, and the vacuum was maintained at 1 Torr. By holding this state for 5 hours, a silicon carbide single crystal having a thickness of about 5.5 mm grew.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman spectroscopy. As a result, a hexagonal 4H-type silicon carbide single crystal having a growth plane orientation of (0001) was grown. I found out that The growth rate was 1.1 mm / hr, and it was found that the grown crystal was a high-quality silicon carbide single crystal with more uniform defects on the seed crystal than the growth outermost surface.

Example 3 will be described with reference to FIG. First, as a seed crystal, a substrate 1 made of a hexagonal 6H-type silicon carbide single crystal having a growth plane orientation in the (0001) direction was prepared. Then, the substrate 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. Also,
Inside the graphite crucible 3, 25 g of high-purity cubic silicon carbide powder as the raw material 2 and tantalum silicide (TaSi) were used.
₂ ; 0.5 g of melting point 2200 ° C. and niobium silicide (Nb)
0.25 g of Si ₂ ; melting point 2160 ° C.) was charged. The silicon carbide powder used had a JIS particle size of # 100. The ratio of tantalum silicide and niobium silicide to the silicon carbide powder is 3%, respectively.

Next, a graphite crucible 3 filled with raw materials was
It was closed with a lid 4 to which a seed crystal was attached, and was placed inside a double quartz tube 5 with a support rod 6 made of graphite. The graphite crucible 3 was covered with a graphite felt 7. Then, argon gas (Ar) as an atmospheric gas was flowed from the branch pipe 9 of the stainless steel chamber 10 into the double quartz pipe 5. A
The flow rate of r gas was set to 1 liter / minute. Next, a high-frequency current was passed through the work coil 8 to adjust the high-frequency current so that the temperature of the silicon carbide powder 2 was 2100 ° C and the temperature of the seed crystal was 2050 ° C. Then, the flow rate of Ar gas was adjusted and the inside of the double quartz tube 5 was decompressed using the vacuum pump 13. This decompression is gradually performed from atmospheric pressure to 35 Torr over 60 minutes to obtain 35 Torr.
The vacuum was maintained at r. By holding this state for 6 hours, a silicon carbide single crystal having a thickness of about 4.2 mm was grown.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman spectroscopy. As a result, a hexagonal 6H-type silicon carbide single crystal having a crystal plane orientation in the (0001) direction was grown. I found out that The growth rate was 0.7 mm / hour, and it was found that the grown crystal was a high-quality silicon carbide single crystal with more uniform defects on the seed crystal than the growth outermost surface.

Comparative Example A silicon carbide single crystal was grown in the same manner as in Example 1 except that the silicon compound of the transition metal was not added to the raw material silicon carbide powder. In this silicon carbide single crystal, many hole structures and defects relating to carbon generated during growth were observed, and only a crystal having poor crystallinity was obtained.

Further, when a silicon carbide single crystal is grown by adding 2% of silicon, a uniform single crystal is obtained from the start of growth to about 2 mm, but a hole structure and defects are caused by the depletion of silicon during the growth. A large number of them were generated, and a uniform single crystal could not be obtained.

[0024]

According to the manufacturing method of the present invention, a high-quality silicon carbide single crystal, particularly a bulk silicon carbide single crystal, can be grown with good reproducibility and homogeneity by the sublimation recrystallization method using a seed crystal. it can. When such a silicon carbide single crystal is used as a growth substrate and a silicon carbide single crystal is grown on this substrate by a vapor phase epitaxial growth method, a blue emitting element and a silicon carbide semiconductor device having excellent electrical characteristics (for example, , Field effect transistors (FETs), complementary moss integrated circuits (C-MOS), and various power devices) can be manufactured. Moreover, since the above silicon carbide single crystal can be obtained with good reproducibility, the above various silicon carbide semiconductor devices having excellent electrical characteristics can be produced on an industrial scale with a high yield.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a crystal growth apparatus used in a manufacturing method of the present invention.

[Explanation of symbols]

 1 Silicon Carbide Single Crystal Substrate 2 Silicon Carbide Powder Containing Silicon Compound of Transition Metal 3 Graphite Crucible 4 Graphite Crucible Lid 5 Quartz Tube 6 Support Rod 7 Heat Shield 8 Work Coil 9 Branch Tube 10 Chamber 11 Branch Tube 12 Chamber 13 Vacuum pump

Claims (7)

[Claims] 1. A method for producing a silicon carbide bulk single crystal in which a silicon carbide single crystal is grown on a seed crystal by a sublimation recrystallization method, wherein a silicon compound of a transition metal is added to silicon carbide powder. Manufacturing method of silicon bulk single crystal. 2. The method for producing a silicon carbide bulk single crystal according to claim 1, wherein the melting point of the added transition metal silicon compound is 1800 to 2500 ° C. 3. The method for producing a silicon carbide bulk single crystal according to claim 1, wherein the transition metal silicon compound is a transition metal silicon alloy. 4. The method for producing a silicon carbide bulk single crystal according to claim 1, wherein the method for adding the silicon compound of the transition metal to the silicon carbide powder is to heat-treat a mixture of the transition metal, silicon and the silicon carbide powder. 5. The method for producing a silicon carbide bulk single crystal according to claim 3, wherein the transition metal silicon compound comprises vanadium silicide, tungsten silicide, tantalum silicide, molybdenum silicide, niobium silicide, rhenium silicide and zirconium silicide. 6. The method for producing a silicon carbide bulk single crystal according to claim 1, wherein one or more transition metal silicon compounds are added. 7. The method for producing a silicon carbide bulk single crystal according to claim 1, wherein the ratio of the silicon compound of the transition metal to the silicon carbide powder is 1 to 10%.