JP2007019160A - Manufacturing method of silicon carbide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of obtaining a desired 4H silicon carbide single crystal by controlling the transformation of crystal polymorph. <P>SOLUTION: The manufacturing method of a silicon carbide single crystal is to subject a silicon carbide single crystal to vapor phase epitaxy by bringing Si containing stock gas and C containing stock gas to reaction on a seed crystal substrate. In the method, the seed crystal is a 15R silicon carbide single crystal, and the 4H silicon carbide single crystal is subjected to vapor phase epitaxy by bringing the Si containing stock gas and the C containing stock gas to reaction at a temperature of 1,700°C or higher with a C/Si ratio of 1.0 or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method capable of easily and reliably producing a desired 4H-type silicon carbide single crystal.

  Silicon carbide is used as an environmentally resistant semiconductor material because it is very stable thermally and chemically and has excellent heat resistance and mechanical strength. Silicon carbide is known to have a crystalline polymorphic structure. This crystal polymorphism is a phenomenon that takes many different crystal structures even if the chemical composition is the same. When the molecule in which the Si and C are bonded in the crystal structure is considered as one unit, this unit structure molecule Is caused by the difference in the periodic structure when stacked in the c-axis direction ([0001] direction) of the crystal.

  Representative crystal polymorphs include 2H, 3C, 4H, 6H and 15R. Here, the first number represents the repetition period of the lamination, the alphabet represents the crystal system, H represents the hexagonal system, R represents the rhombohedral system, and C represents the cubic system. Each crystal structure has different physical and electrical characteristics, and application to various uses is considered using the difference. 6H, 4H, and 15R types are used for semiconductor devices. Since the 4H type has desirable characteristics for power devices compared to the 6H type, it has recently been attracting attention as a semiconductor crystal material for power devices. .

  Conventionally, as a method for growing a silicon carbide single crystal, various methods such as a vapor phase growth method, an atchison method, and a solution growth method are known. As a method for manufacturing a large single crystal for a semiconductor device, A sublimation recrystallization method called an improved Lerry method is mainly used (see, for example, Patent Document 1).

  This sublimation recrystallization method uses silicon carbide powder as a raw material, and a vapor composed of Si and C sublimated from the raw material in a semi-closed space is transported by diffusing in an inert gas and set at a lower temperature than the raw material. This is a method that utilizes the phenomenon of supersaturation and condensation on the crystal.

JP 7-330493 A

  However, it is known that a single crystal produced by the above-described sublimation recrystallization method has a hollow penetrating defect called a micropipe defect. Further, in the sublimation recrystallization method, if the seed crystal is in the 4H form, a 4H form single crystal can be easily grown on the seed crystal, but the 4H form single crystal is difficult to obtain and is relatively difficult to obtain. There is a need for a method of growing a 4H-type silicon carbide single crystal using an easy 6H-type or 15R-type hydrocarbon single crystal as a seed crystal.

  The present invention solves such problems, uses a CVD method in which process control and defect control are relatively easy as compared with a sublimation recrystallization method, and uses a 15R type silicon carbide single crystal or a 6H type silicon carbide single crystal as a seed crystal. It is an object to provide a method capable of obtaining a 4H-type silicon carbide single crystal having a desired crystal structure using

  In order to solve the above problems, according to a first invention, a silicon carbide single crystal including vapor-phase growth of a silicon carbide single crystal by reacting a Si-containing source gas and a C-containing source gas on a seed crystal substrate. In this manufacturing method, the seed crystal is a 15R-type silicon carbide single crystal, and a Si-containing source gas and a C-containing source gas are reacted at a temperature of 1700 ° C. or more at a C / Si ratio of 1.0 or less to form a 4H-type silicon carbide single crystal. The crystal is grown in a vapor phase.

  In order to solve the above problems, according to a second invention, a silicon carbide single crystal including vapor-phase growth of a silicon carbide single crystal by reacting a Si-containing source gas and a C-containing source gas on a seed crystal substrate. In the manufacturing method, the seed crystal is a 6H-type silicon carbide single crystal, nitrogen atoms are ion-implanted into the seed crystal substrate to give lattice distortion between the atoms, and then the amorphous layer formed on the surface layer portion is removed, Next, the Si-containing raw material gas and the C-containing raw material gas are reacted at a temperature of 1700 ° C. or higher at a C / Si ratio of 1.0 or lower to cause 4H-type silicon carbide single crystal to vapor-phase grow.

  According to the present invention, since the crystal is grown by the CVD method, it can be carried out at a lower temperature than the sublimation recrystallization method, the crystal growth process control and defect control are easy, and the acquisition is relatively easy. From the 15R type or 6H type hydrocarbon single crystal, the 4H type hydrocarbon single crystal can be easily and reliably made.

  Hereinafter, the method for producing a silicon carbide single crystal of the present invention will be specifically described. First, the structure of the manufacturing apparatus used for the manufacturing method of the silicon carbide single crystal of this invention is demonstrated with reference to FIG. This manufacturing apparatus includes a reaction tube arranged horizontally, and a sample stage 2 is arranged in the reaction tube 1 by a support bar 3. Cooling water is supplied to the outside of the reaction tube 1 through branch tubes 4 and 5, and a coil 6 is wound around the outer periphery, and the sample stage 2 is induction-heated by flowing a high-frequency current through the coil 6. be able to. A branch pipe 7 serving as a gas inlet is provided on one side of the reaction tube 1, the other end of the reaction tube 1 is sealed by a flange 8, and a branch pipe 9 serving as a gas outlet is provided on the flange 8. .

A method for producing a silicon carbide single crystal using this production apparatus will be described. First, the seed crystal 10 is placed on the sample stage 2 in the reaction tube 1, the inside of the reaction tube 1 is evacuated and replaced with a carrier gas (for example, hydrogen gas), and a high-frequency current is passed through the coil to heat the sample stage 2. The temperature of the seed crystal 10 is raised to 1700 ° C. or higher, preferably 1750 to 2000 ° C. Next, a Si-containing source gas, a C-containing source gas, and a carrier gas are supplied from the branch pipe 7 and reacted on the seed crystal 10 to vapor-phase grow a silicon carbide single crystal. SiH ₂ Cl ₂ , SiH ₄ , SiHCl ₃ or the like can be used as the Si-containing source gas, and C ₂ H ₂ , C ₃ H ₈ , CH ₄ or the like can be used as the C-containing source gas, As the carrier gas, hydrogen, Ar, or the like can be used. The ratio of the Si-containing source gas to the C-containing source gas is 1.0 or less in terms of the C / Si ratio.

  In the method of the present invention, a 15R-type or 6H-type silicon carbide single crystal that is relatively easily available can be used as a seed crystal. When a 15R silicon carbide single crystal is used as a seed crystal, polymorph transformation can be performed by the above method to obtain a 4H type silicon carbide single crystal. Here, when the temperature is lower than 1700 ° C., it does not transform into 4H type, and when the C / Si ratio is higher than 1.0, it transforms into 3C type.

  On the other hand, when a 6H type silicon carbide single crystal is used as a seed crystal, the above method does not cause polymorphic transformation and a 6H type silicon carbide single crystal is formed, and a 4H type silicon carbide single crystal cannot be obtained. However, the 6H type silicon carbide single crystal is subjected to a pretreatment that gives lattice strain between atoms of the 6H type silicon carbide single crystal and removes the amorphous layer formed on the surface layer portion, thereby transforming the 6H type silicon carbide single crystal into a polymorphic form. A silicon carbide single crystal can be obtained. In order to give lattice distortion between atoms, for example, nitrogen atoms having an atomic radius smaller than C are implanted by using an ion implantation apparatus. The removal of the amorphous layer is performed by a normal etching process such as dry etching.

  If a conventional sublimation recrystallization method is used, a polymorphic transformation from a 15R-type seed crystal to a 4H-type single crystal may be achieved, but this polymorphic transformation is observed only on the C plane and does not occur on the Si plane. On the other hand, according to the present invention, polymorphic transformation can be performed not only on the C plane but also on the Si plane. Furthermore, although the sublimation recrystallization method tends to cause micropipe defects in the obtained single crystal, the method of the present invention allows crystal growth at a lower temperature than the sublimation recrystallization method. It is possible to suppress the occurrence of pipe defects.

Example 1
A 15R type silicon carbide single crystal substrate (polarity: C plane) was used as a seed crystal. This substrate was ultrasonically cleaned with alcohol, etched with an HF aqueous solution, washed with running pure water, and then dried. This seed crystal was placed on a sample stage (manufactured by BN) of the apparatus shown in FIG. 1 and heated by high frequency induction heating. The heating temperature was measured with a thermocouple provided with a support rod, and the temperature was controlled. Hydrogen gas was used as the carrier gas, C ₂ H ₂ diluted with hydrogen gas was used as the C-containing source gas, and SiH ₂ Cl ₂ diluted with hydrogen gas was used as the Si-containing source gas. A single crystal was grown at a temperature of 1750 ° C. with a C / Si ratio = 0.5.

  The obtained single crystal thin film was evaluated for SiC crystal polymorphism by reciprocal space mapping using a thin film X-ray diffractometer (Philips X 'Pert MRD). An X-ray lens was used on the incident side of the measurement optical system, and a 0.27 ° collimator was used on the light receiving side. The results of this X-ray diffraction are shown in FIGS. FIG. 2 shows the measurement results of a 15R-type silicon carbide single crystal that is a seed crystal. FIG. 3 shows the measurement results of 4H type silicon carbide single crystal, and shows a representative peak position of 2θ = 34.84 in 4H (101). FIG. 4 shows the result of the single crystal obtained in Example 1, and it can be seen that a 4H-type silicon carbide single crystal was formed by having a peak at 2θ = 34.87.

Example 2
A seed crystal sample was grown in the same manner as in Example 1 except that the polarity of the 15R type silicon carbide single crystal was changed from the C plane to the Si plane. As is apparent from the results shown in FIG. 5, it was found that a 4H type silicon carbide single crystal was formed also on the Si surface.

Comparative Example 1
Crystal growth was performed in the same manner as in Example 1 except that the seed crystal sample was changed from the 15R type silicon carbide single crystal to the 6H type silicon carbide single crystal. The produced single crystal was in the same 6H form as the seed crystal.

Example 3
Crystal growth was performed in the same manner as in Example 1 except that the reaction was performed at a C / Si ratio of 1.0. A 4H type silicon carbide single crystal was formed on the 15R type silicon carbide single crystal.

Comparative Example 2
Crystal growth was performed in the same manner as in Example 1 except that the reaction was performed at a C / Si ratio of 1.5. A 3C type silicon carbide single crystal was formed on the 15R type silicon carbide single crystal.

Example 4
Crystals were grown in the same manner as in Example 1 except that the heating temperature was 1700 ° C. A 4H type silicon carbide single crystal was formed on the 15R type silicon carbide single crystal.

Comparative Example 3
Crystals were grown in the same manner as in Example 1 except that the heating temperature was 1600 ° C. Si was formed on the 15R silicon carbide single crystal.

Example 5
A 6H silicon carbide single crystal was used as a seed crystal sample. Nitrogen atoms were implanted at 1E14 / cm ² using a 400 keV ion implanter. Thereafter, the thickness of the surface layer portion of 0.5 μm was polished with a dry etching apparatus. Crystal growth was performed under the same conditions as in Example 1, and it was found that a 4H-type silicon carbide single crystal was produced.

1 is a schematic diagram showing the configuration of a manufacturing apparatus used in the method for manufacturing a silicon carbide single crystal of the present invention. It is a graph which shows the measurement result of the X-ray diffraction of a 15R type silicon carbide single crystal. It is a graph which shows the measurement result of the X-ray diffraction of 4H type silicon carbide single crystal. It is a graph which shows the measurement result of the X-ray diffraction of the silicon carbide single crystal obtained by the method of this invention. It is a graph which shows the measurement result of the X-ray diffraction of the silicon carbide single crystal obtained by the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Sample stand 3 Support rod 4 Branch tube 5 Branch tube 6 Coil 7 Branch tube 8 Flange 9 Branch tube 10 Seed crystal

Claims (2)

  A method for producing a silicon carbide single crystal comprising reacting a Si-containing source gas and a C-containing source gas on a seed crystal substrate to vapor-phase grow a silicon carbide single crystal, wherein the seed crystal is a 15R-type silicon carbide single crystal. A silicon carbide characterized in that a 4H silicon carbide single crystal is vapor-phase grown by reacting a Si-containing source gas and a C-containing source gas at a temperature of 1700 ° C. or higher at a C / Si ratio of 1.0 or lower. A method for producing a single crystal.   A method for producing a silicon carbide single crystal comprising reacting a Si-containing source gas and a C-containing source gas on a seed crystal substrate to vapor-phase grow a silicon carbide single crystal, wherein the seed crystal is a 6H-type silicon carbide single crystal. The crystal is a crystal, and nitrogen atoms are ion-implanted into the seed crystal substrate to give lattice distortion between the atoms. Then, the amorphous layer formed on the surface layer is removed, and then the Si-containing source gas and the C-containing source gas are heated to 1700 ° C. or higher. A method for producing a silicon carbide single crystal, wherein the 4H-type silicon carbide single crystal is vapor-phase grown by reacting at a temperature of C / Si at a ratio of 1.0 or less.

Images