JPH09142995A - Production of p-type single crystal silicon carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a p-type SiC single crystal with high reproducibility at a low cost by using a mixture of SiC stock with Al2 O3 . SOLUTION: When an SiC single crystal is doped with Al in a sublimation- recrystallization method (Rayleigh method) by which SiC stock is sublimed and an SiC single crystal is grown on an SiC seed crystal substrate, the amt. of Al vaporized is reduced even at a high temp. of 2,000-2,500 deg.C by using a mixture of SiC powder with Al2 O3 as starting material in place of a mixture of SiC powder with Al power and uniform doping with Al is attained during growth. For example, a hexagonal SiC substrate 1 having <0001> direction as the orientation of a growth face is fixed as a seed crystal on the inside of the lid 4 of a graphite crucible 3, SiC power mixed with 1wt.% Al2 O3 is filled as starting material 2 into the crucible 3 and this crucible 3 is put in a double quartz tube 5. After evacuation, the tube 5 is heated to 2,000 deg.C, Ar is introduced and growth is carried out at 2,400 deg.C under 10Torr for 20hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon carbide single crystal, and more particularly to a method for growing a large-sized single crystal ingot of good quality which is used as a substrate wafer for blue light emitting diodes, electronic devices and the like.

[0002]

2. Description of the Related Art Silicon carbide (SiC) has attracted attention as an environment-resistant semiconductor material due to its physical and chemical properties such as excellent heat resistance and mechanical strength and resistance to radiation. Especially 6H
Type silicon carbide crystal has a forbidden band width of about 3 eV at room temperature,
Used as a blue light emitting diode material. 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 yet been established. Therefore, silicon carbide has been hampered in practical use despite the semiconductor material having many advantages and possibilities as described above.

Conventionally, on a laboratory scale, a silicon carbide single crystal is grown by, for example, a sublimation recrystallization method (Rayleigh method).
Thus, a silicon carbide single crystal having a size capable of manufacturing a semiconductor element has been obtained. However, in this method, the area of the obtained single crystal is small, and it is difficult to control the size and shape with high precision. Further, it is not easy to control the crystal polymorphism and impurity carrier concentration of silicon carbide.

In addition, a cubic silicon carbide single crystal is also grown by performing heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using a chemical vapor deposition method (CVD method). Although a large area single crystal can be obtained by this method, many defects are included due to the lattice mismatch with the substrate of about 20% (-10 ⁷ cm ^-2 ).
Only a silicon carbide single crystal can be grown, and it is not easy to obtain a high quality silicon carbide single crystal.

In order to solve these problems, an improved Rayleigh method of sublimation recrystallization using a seed crystal has been proposed (Yu.M. Tairov and VF Tsvetkov, Journal.
of Crystal Growth vol.52 (1981) pp.146-150). By using this method, a silicon carbide single crystal can be grown while controlling the crystal polymorphism and shape.

In the silicon carbide single crystal, nitrogen (N) is well known as an N type impurity, and boron (B) and aluminum (Al) are well known as P type impurities. B
Is easily incorporated into a silicon carbide single crystal, but its activation energy is large, so that it is not very practical.
Al is used for the type doping.

A silicon carbide single crystal was obtained by sublimation recrystallization.
As a method of doping l, conventionally, (1) a mixture of Al (aluminum) powder and silicon carbide powder (“Physical properties” May 1970 issue pp. 263-269), (2) silicon carbide powder in advance Obtained by heat-treating a mixture of Al and Al at a high temperature of about 1800 degrees Celsius (Japanese Patent Publication No. 6-45520), or (3) silicon carbide powder previously doped with Al as an impurity (G.Ziegler, et al., IEEE Transactions). on Ele
ctron Devices vol.ED-30 (1983) pp.277-281) was used as a raw material, and Al vaporized by heating and subliming under a low pressure of 1 to 100 Torr was doped during the growth of a silicon carbide single crystal.

[0008]

In the conventional method of the above (1), the growth temperature of the silicon carbide single crystal is 2000 to 250 degrees Celsius.
Since it is 0 ° C., which is much higher than the boiling point of Al (1,500 ° C. to 1,600 ° C.), only Al vaporizes while the temperature is raised to the growth temperature. Therefore, the concentration of Al is very high in the initial stage of growth of the silicon carbide single crystal, and the concentration of Al decreases as the growth progresses, and finally an N-type silicon carbide single crystal containing no Al grows. It was Furthermore, since vaporized Al adheres to the seed crystal surface before the growth temperature is reached, there is a problem that the crystallinity of the silicon carbide single crystal growing on the surface is lowered.

In the conventional method of (2) or (3), there is no commercially available silicon carbide powder as a raw material, which is obtained by heat-treating a mixture with Al, or is not sufficiently doped with Al. It is necessary to produce each before actual single crystal growth. Therefore, it is extremely difficult to reduce the manufacturing cost of the P-type silicon carbide single crystal by these methods.

The present invention has been made in view of the above circumstances, and provides a method for producing a P-type silicon carbide single crystal capable of producing a P-type silicon carbide single crystal with good reproducibility and at low cost. .

[0011]

In the method for producing single crystal silicon carbide of the present invention, a raw material made of silicon carbide is heated and sublimated and supplied onto a seed crystal made of a silicon carbide single crystal, and carbonized on the seed crystal. In the method of growing a silicon single crystal, a mixture of the above raw materials with Al ₂ O ₃ is used. That is, according to the present invention, as described in claim 1, in the sublimation recrystallization method of sublimating a silicon carbide raw material to grow a silicon carbide single crystal on a silicon carbide seed crystal substrate, Al ₂ O is added to the raw material.
_A method for producing a P-type silicon carbide single crystal, characterized in that a mixture of ₃ is used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the manufacturing method of the present invention, Al ₂ O
By using the silicon carbide powder mixed with ₃ as a raw material, the vaporization amount of Al, which has been a problem in the manufacturing method of the conventional method (1), can be suppressed to a low level even at a high temperature of 2000 to 2500 ° C. Uniform Al doping can be realized. Further, when compared with the production methods of the conventional methods (2) and (3), the powder of Al ₂ O ₃ having high purity can be easily obtained at a low price, so that the production cost of the crystal can be suppressed low.

[0013]

EXAMPLES The details of the present invention will be described below based on examples.

FIG. 1 shows a manufacturing apparatus used in the present invention, which is an example of an apparatus for growing single crystal silicon carbide by an improved Rayleigh method using a seed crystal.

First, the single crystal growth apparatus will be briefly described. Crystal growth is performed by sublimating and recrystallizing silicon carbide powder 2 as a raw material on silicon carbide single crystal substrate 1 used as a seed crystal. Seed silicon carbide crystal substrate 1 is attached to the inner surface of lid 4 of crucible 3 made of graphite. Silicon carbide powder 2 as a raw material is filled in a crucible 3 made of graphite. Such a graphite crucible 3 is installed inside a double quartz tube 5 by a graphite support rod 6. Around the graphite crucible 3, a graphite felt 7 for heat shielding is provided. The double quartz tube 5 is a vacuum exhaust device 1.
1, high vacuum exhaust (10 ^-5 Torr or less) can be performed, and the internal atmosphere can be guided from a Ar gas supply source (not shown) by a pipe 9 and pressure controlled by Ar gas controlled by the Ar gas mass flow controller 10. it can. A work coil 8 is provided around the outer periphery of the double quartz tube 5, and the graphite crucible 3 can be heated by flowing a high-frequency current to heat the raw material and the seed crystal to desired temperatures. The temperature of the crucible is measured by using a two-color thermometer by providing an optical path with a diameter of 2 to 4 mm at the center of the felt that covers the upper and lower parts of the crucible and extracting light from the upper and lower parts of the crucible. The temperature at the bottom of the crucible is the raw material temperature, and the temperature at the top of the crucible is the seed temperature.

Next, an example of the production of a silicon carbide single crystal using this crystal growth apparatus will be described.

First, as a seed crystal, the growth plane orientation is <00.
A substrate 1 made of hexagonal silicon carbide having a 01> direction was prepared. Then, the substrate 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. Further, the graphite crucible 3 was filled as a raw material 2 with 1% by weight of Al ₂ O ₃ mixed in silicon carbide powder.

Al ₂ O ₃ was obtained by pulverizing a commercially available granular material into powder having a roughness of about several tens of microns and then uniformly mixing it with the raw materials. Next, the graphite crucible 3 filled with the raw material is closed with a lid 4 fitted with a seed crystal, covered with a graphite felt 7, placed on a graphite support rod 6, and set inside a double quartz tube 5. did. And after evacuating the inside of the quartz tube,
An electric current was applied to the work coil to raise the raw material temperature to 2000 degrees Celsius. After that, Ar gas was introduced as an atmosphere gas, and the raw material temperature was raised to 2400 degrees Celsius which is a target temperature while maintaining the internal pressure of the quartz tube at about 600 Torr. The pressure was reduced to 10 Torr, which is the growth pressure, over about 30 minutes, and then the growth was continued for about 20 hours. The growth rate at this time was about 1 mm per hour.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, and it was confirmed that a hexagonal system silicon carbide single crystal had grown. Further, when the crystal was examined by secondary ion mass spectrometry, it was found that Al was approximately 1.2 × 10 ¹⁸ c from the seed crystal to the upper part of the growth.
It was found to be m ⁻³ doped. The maximum difference in the amount of doping between the upper part and the lower part was 30% or less. A in raw material
When the amount of l ₂ O ₃ charged was changed in the range of 0.27 to 2.7% and the amount of incorporation into the crystal was examined, it was found that the amount of incorporation increased almost in proportion to the square root of the amount of incorporation. all right. Furthermore, it was confirmed by electrical measurement (Hall measurement) that the crystal was P-type.

[0020]

As described above, according to the present invention,
By the improved Rayleigh method using a seed crystal, a P-type silicon carbide single crystal can be grown with good reproducibility and uniformity. If such a silicon carbide single crystal is used as a growth substrate and a silicon carbide single crystal thin film is grown on the substrate by a vapor phase epitaxial growth method, a blue light emitting device having excellent optical characteristics and an excellent electrical characteristic can be obtained. A high withstand voltage and environmental resistance electronic device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a single crystal growth apparatus used in a manufacturing method of the present invention.

[Explanation of symbols]

 1 ... Silicon carbide single crystal substrate (seed crystal) 2 ... Silicon carbide powder raw material 3 ... Graphite crucible 4 ... Graphite crucible lid 5 ... Double quartz tube 6 ... Support rod 7 ... Graphite felt 8 ... Work coil 9 ... Ar Gas pipe 10 ... Mass flow controller for Ar gas 11 ... Vacuum exhaust device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatoshi Kanaya 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside Nippon Steel Co., Ltd. Technology Development Division

Claims (1)

[Claims] 1. A sublimation recrystallization method in which a silicon carbide raw material is sublimated to grow a silicon carbide single crystal on a silicon carbide seed crystal substrate, wherein the raw material is mixed with Al ₂ O _3. A method for producing a P-type silicon carbide single crystal.