JP2000154097A - Liquid phase epitaxial growth method of silicon carbide crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the growth method that enables the growth of a high quality large SiC crystal which has no crystal defects causing defectiveness of device operation, such as micropipe or polytype inclusion within the crystal, and also, contains drastically reduced concentration of residual impurities greatly affecting electric characteristics of the crystal. SOLUTION: This growth method comprises, using an Si-C system melt that has a composition being between the peritectic point and eutectic point in the Si-C two component system phase diagram, as a raw material melt using an Si substrate having a SiC film formed on the substrate, as the growth substrate of an SiC crystal bringing the Si substrate side of the growth substrate into contact with the raw material melt to dissolve and remove the Si substrate and a part of the adjacent SiC film which part has inferior crystal properties and performing epitaxial growth of an SiC crystal on the residual SiC film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a SiC crystal expected as a material for a high-temperature operation device, a power device, a radiation-resistant device, and the like. The present invention relates to a liquid phase epitaxial growth method of a SiC crystal capable of growing a high-quality and large-sized SiC crystal having no crystal defects such as a mixture of types and having a greatly reduced residual impurity concentration that greatly affects the electrical characteristics of the crystal. It is.

[0002]

2. Description of the Related Art An SiC crystal, which is a wide gap semiconductor, has a large energy gap of about 3 eV and is physically and chemically stable due to a strong chemical bonding force, and is excellent in heat resistance and radiation resistance. Material. Furthermore, control of both p and n conductivity types is possible and carrier mobility
Because it is as large as a crystal, conventional Si, such as next-generation power transmission systems, electric trains, electric vehicles, and other high-voltage power devices, high-temperature operating devices, and radiation-resistant devices required in the fields of aviation, nuclear power, and space science, etc. Such semiconductor materials are most expected as materials for electronic devices that can be used under severe environments that cannot be realized due to their physical properties.

Since SiC does not have a melting point at normal pressure, it is very difficult to grow a bulk crystal. As an SiC crystal growing method, the Acheson method of reacting SiO ₂ and coke at a high temperature has been known for a long time. In this Acheson method, general industrial SiC crystals such as abrasives and refractory materials are produced.
A hexagonal plate-like single crystal of about m is obtained. However, in the Acheson method, it is impossible to control the growth of a single crystal, so that a large crystal with high purity cannot be grown without reproducibility.

On the other hand, the Rayleigh method (sublimation method) studied since the 1960s, that is, a method of sublimating and recrystallizing SiC powder in a graphite container at a high temperature of 2000 ° C. or more, also controls generation of crystal nuclei. Because of the difficulty, it was difficult to grow a large SiC crystal.

[0005] Under such technical background, a flat plate crystal is set in a low temperature part in a container, and the flat plate crystal is used as a seed crystal to form Si.
An improved Rayleigh method (sublimation method) for recrystallizing C sublimation gas was proposed in 1978 by Russia's Yu.M. Tairov and others, and has made great progress toward increasing the size of SiC crystals.

[0006] At present, an improved Rayleigh method generally used is a method in which a SiC powder 2 as a raw material is placed in one side of a cylindrical graphite vessel 1 as shown in FIGS. 4 (A) and 4 (B). A flat Si that is housed and has a seed crystal 3 on the other side
This is performed by disposing a C single crystal and heating the container 1 to about 2300 to 2700 K by a heating means (not shown) such as a high-frequency induction heating coil or a resistance heater in an inert gas atmosphere such as Ar.

Then, the gas sublimated from the raw material SiC powder by heating gathers in the seed crystal 3 at the lowest temperature in the vessel 1, and crystal growth is performed on the seed crystal 3, and the same as the seed crystal 3. A SiC bulk crystal 4 having a crystal orientation is obtained.

Further, in order to obtain a large-area SiC crystal, a Si crystal having a diameter of 6 inches or 8 inches, which is already in practical use, is applied as a substrate, and the Si crystal is grown by a vapor phase growth method such as a CVD method or an MBE method. A method of epitaxially growing a SiC film on a substrate has also been studied.

[0009]

By the way, when the above-mentioned improved Rayleigh method (sublimation method) is applied, a SiC crystal having a diameter of about 50 mm has been obtained at a research level, but has a certain degree of reproducibility in practice. The size of the obtained crystal is about 30 mm in diameter, which is a practical size of 5 mm.
It was difficult to grow large crystals of 0 mm or more with good reproducibility.

In addition, a SiC crystal grown by using the improved Rayleigh method has a significant effect on device characteristics, such as the presence of micropipes and polytypes, and must not be essentially present as a semiconductor substrate. There are defects. The micropipe causes a leak current in an electronic device, and a region where the micropipe exists cannot be used as a substrate material. Since the polytypes have different band gaps when the polytypes are different, a region where these polytypes exist cannot be applied to device fabrication.

In addition, the SiC powder usually used as a raw material in the improved Rayleigh method is generally synthesized by the Acheson method described above, and the purity of the SiC powder is at most 98.
%. Therefore, during the growth by the improved Rayleigh method, the impurity element contained in the raw material SiC powder also sublimes and is taken into the crystal. Therefore, the residual impurity concentration contained in the SiC crystal grown by this method is 10 ^17-
It is 10 ¹⁸ / cm ² or more. Since the high residual impurity concentration greatly affects the electric characteristics of the crystal, it is very difficult to obtain a crystal having desired electric characteristics as a material for an electronic device by the improved Rayleigh method.

As the raw material powder, a high-purity product synthesized by a method other than the Acheson method such as a gas phase synthesis method can be used. However, since the productivity of the raw material powder is low, the raw material cost is lower than that of the Acheson method. There is a problem that is more than twice as high,
Furthermore, even the SiC raw material powder obtained by a method other than the Acheson method has a purity of about 99.5%, and 6N (99.999) is expected as a raw material for growing semiconductor crystals.
9%) or 7N (99.9999%) is not sufficient purity.

On the other hand, in the vapor phase growth method using a Si crystal as a substrate, no crystal defects are observed in the micropipe, but the growth rate is at most 2-3 μm / h.
r. And several hundred to several thousand μm / hr.
Has a problem that the productivity is very inferior to the above. In addition, since the growth is performed at a temperature of about 1000 to 1100 ° C., the low-temperature stable type has an energy band gap of SiC.
At present, only the narrowest 3C type crystal among the poly types has been obtained.

In addition, since there is a difference in lattice constant between Si and SiC of about 20% and a coefficient of thermal expansion of about 8%, the resulting SiC film has voids near the interface with the Si substrate, and furthermore twins and anti-semiconductors. In some cases, crystal defects such as phase domains were included.

The present invention has been made in view of such a problem, and it is an object of the present invention to eliminate crystal defects such as micropipes and polytypes which cause device operation failure, and to prevent crystal defects. It is an object of the present invention to provide a liquid phase epitaxial growth method of SiC crystal capable of growing a high-quality and large-sized SiC crystal in which the concentration of residual impurities that greatly influences electrical characteristics is greatly reduced.

[0016]

That is, the invention according to claim 1 is based on the premise that a liquid phase epitaxial growth method of a SiC crystal is used, and the temperature between the peritectic point and the eutectic point shown in a two-component system phase diagram of Si—C. Is used as a raw material melt, the Si substrate on which the SiC film is formed is used as a SiC crystal growth substrate, and the Si substrate side of the growth substrate and the Si substrate are melted in a growth vessel. 3. The invention according to claim 2, wherein a SiC crystal is epitaxially grown on the remaining SiC film after contacting a liquid to dissolve and remove the Si substrate and a part of the SiC film having poor crystallinity adjacent thereto. Presupposes a liquid phase epitaxial growth method of a SiC crystal according to the first aspect of the present invention, and arranges a growth base material such that a Si substrate side is exposed on an upper side in a growth vessel and has a Si substrate on a lower side in the growth vessel. Raw materials and After the step of arranging graphite and heating the inside of the growth vessel to a temperature equal to or higher than the melting point of Si to obtain a Si-C-based melt, the growth vessel is turned upside down to remove the Si-C-based melt and the Si of the growth base material. Dissolving and removing the Si substrate of the growth substrate by bringing the substrate into contact with the substrate and setting the temperature distribution in the Si-C-based melt to be the lowest temperature on the growth substrate placement side; When the temperature of the melt is a predetermined temperature (1600
℃ or more), and after the C concentration in the Si-C-based melt reaches an equilibrium state, the temperature distribution in the Si-C-based melt is set so that the growth substrate arrangement side has the highest temperature. Dissolving and removing part of the SiC film having poor crystallinity of the growth base material, and dissolving and removing part of the SiC film having poor crystallinity. In the system melt, the Si-
A step of changing the temperature distribution in the C-based melt and epitaxially growing a SiC crystal on the remaining SiC film.

According to a third aspect of the present invention, there is provided a liquid-phase epitaxial growth method for SiC crystal, comprising:
A Si-C-based melt having a composition between the peritectic point and the eutectic point shown in the component system phase diagram is used as a raw material melt, and the Si substrate on which the SiC film is formed is used as a SiC crystal growth base material. After the SiC film of the growth substrate is melted and removed in the growth vessel to expose the SiC film, the SiC film of the growth substrate is brought into contact with the raw material melt to dissolve a part of the SiC film having poor crystallinity. A SiC crystal is epitaxially grown on the removed and remaining SiC film. The invention according to claim 4 is based on the liquid phase epitaxial growth method of SiC crystal according to the invention according to claim 3, Disposing the growth substrate such that the Si substrate side is exposed on the upper side of the inside, and disposing the Si raw material and graphite on the lower side of the growth container; and heating the inside of the growth container to a temperature equal to or higher than the melting point of Si. Melting Si substrate Obtaining a SiC KeiTorueki to expose the SiC film is removed by, the temperature of the SiC KeiTorueki reaches to a predetermined temperature (1600 ° C. or higher), and,
After the C concentration in the Si-C-based melt reaches an equilibrium state, the growth container is turned upside down to bring the Si-C-based melt into contact with the SiC film of the growth base material, A step of dissolving and removing a part of the SiC film having poor crystallinity by setting the temperature distribution in the liquid to be the highest on the growth substrate disposition side, and dissolving and removing a part of the SiC film having poor crystallinity. Thereafter, the temperature of the growth substrate is lowered so that the temperature of the Si-C-based melt is lower than that of the Si-C-based melt.
A step of changing the temperature distribution in the C-based melt and epitaxially growing a SiC crystal on the remaining SiC film.

The S according to the first to fourth aspects of the present invention.
According to the liquid phase epitaxial growth method of iC crystal, Si
A Si-C-based melt having a composition between the peritectic point and the eutectic point shown in the two-component system phase diagram of -C is used as a raw material melt, and a Si substrate on which a SiC film is formed is used as a growth substrate for SiC crystals. In addition, a SiC film having good crystallinity obtained by melting or dissolving and removing a Si substrate and a part of the SiC film having poor crystallinity adjacent to the Si substrate in the growth vessel is used as a seed crystal to form a SiC film on the SiC film. Because the crystal is grown epitaxially,
It is possible to easily obtain a SiC crystal which is larger than before and has few crystal defects such as micropipes.

Further, since the SiC film having good crystallinity from which the Si substrate has been removed is used as a seed crystal, the growth temperature of the Si—C-based melt can be set to 1600 ° C. or higher, which is higher than the melting point of Si. A polytype SiC crystal having a period of 4H (hexagonal) or 6H (hexagonal) required as a material can be easily and reliably obtained.

Further, since no SiC powder is used as a growth material, it is possible to obtain a SiC crystal having a lower residual impurity concentration than the SiC crystal obtained by the above-mentioned improved Rayleigh method (sublimation method), and to grow the same. The speed also depends on the growth temperature, the temperature gradient in the Si-C-based melt, and the like.
/ Hr. The above is one hundred times or more of the above-mentioned vapor phase growth method using a Si substrate, and it is possible to obtain a SiC crystal at high speed and with good reproducibility.

[0021]

Embodiments of the present invention will be described below in detail.

FIG. 3 is a diagram showing a two-component system of Si—C at normal pressure. As shown in this two-component system diagram, S
The melting point of i itself is 1414 ° C., but the binary system of Si—C has a peritectic point at 2545 ± 40 ° C. and 1404 ± 5
It has a eutectic point at ° C. The composition at the peritectic point is as follows:
%, C is 27 at%, and the composition at the eutectic point is as follows: Si is 99.25 ± 0.5 at%, C is 0.75 ± 0.5 at%.
%.

When an Si—C-based melt having a composition between the peritectic composition and the eutectic composition, for example, the melt initially in the state of point A in FIG. Becomes T, and after reaching point B on the liquidus line, the Si—C-based melt changes its composition along the liquidus line while crystallizing SiC crystals. Even if the composition of the Si—C-based melt changes along the liquidus line with the temperature drop, the crystal to be crystallized is always SiC. This state continues until the composition of the Si—C-based melt reaches the eutectic point. At a temperature lower than the eutectic point temperature, the liquid phase no longer exists, and S
It becomes a solid phase composed of a mixture of Si and SiC having a eutectic composition with iC.

In the above process, when a reaction of crystallizing a SiC crystal by a Si—C-based melt having a composition between the peritectic composition and the eutectic composition is performed on a seed crystal substrate, epitaxial growth occurs, and It becomes possible to grow a SiC crystal on the substrate.

At this time, in order to efficiently carry out the crystallization reaction of SiC on the seed crystal substrate, a temperature gradient at which the substrate side has the lowest temperature is set in the Si—C-based melt. The crystallization reaction is
This can be caused by lowering the temperature of the entire Si-C-based melt while maintaining this temperature gradient.
The graphite serving as a C supply source is disposed in the highest temperature portion in the system melt, and the seed crystal substrate is disposed in the lowest temperature portion in the Si-C melt. The crystallization reaction can also be caused by maintaining the temperature distribution of the Si-C-based melt. This is because when the C in the Si-C-based melt having reached the equilibrium concentration in the high temperature part reaches the low temperature part where the seed crystal substrate is installed by diffusion due to the difference in the C concentration in the melt, it becomes supersaturated, SiC is crystallized when trying to approach an equilibrium state at the temperature of the substrate portion, and epitaxial growth of SiC is performed on the seed crystal substrate kept at the lowest temperature (that is, a crystallization method using a temperature difference). Also, as another method, the solvent Si is evaporated while keeping the temperature distribution in the Si-C-based melt constant,
By setting the inside of the Si-C-based melt to a supersaturated state of C excess,
A crystallization reaction of iC can also be caused.

Among them, the crystallization method utilizing the above-mentioned temperature difference is a method for maintaining the temperature distribution of the Si-C-based melt at the substrate side low temperature-C supply source side high temperature. During the crystal growth, the temperature is always kept constant, and the growth is performed without evaporating the solvent Si. Therefore, not only can the generation of crystal defects such as a polytype change due to a temperature change be suppressed, but also the supply of C can be suppressed. It is possible to grow SiC until it disappears, and there is an advantage that a SiC crystal having a sufficient thickness can be obtained.

Hereinafter, a method of growing a SiC crystal by the temperature difference method using the Si substrate on which the SiC film is formed as a growth substrate (ie, a seed crystal substrate) for liquid phase epitaxial growth will be specifically described.

First, as shown in FIG. 1A, a growth substrate 10 composed of a Si substrate 11 and a SiC film 12 is arranged above a growth container 20 so that the Si substrate 11 side is exposed. In the lower side of the growth vessel 20, a Si polycrystal 31 which is melted to be a solvent and is a raw material of the Si-C-based melt and graphite 3 which is a raw material for supplying C to the melt.
2 are arranged respectively.

Next, the growth chamber 20 and heated to the melting point T _m above the temperature of the Si single by high-frequency induction heating method or a resistance heating method in an atmosphere such as Ar gas FIG 1 (B)
As shown in (1), a Si-C-based melt 30 is obtained. At this time, S
Installation of i polycrystals 31 and graphite 32, Si single melting point T _m above temperature (eg, T in FIG. 3) is heated to, installation of the growth substrate 10, Si substrate 11 it is necessary to adjust so as not to exceed the melting point T _m of a Si simple substance so as not to melt.

Next, as shown in FIG.
0, the Si—C-based melt 30 and the growth substrate 1
The Si substrate 11 is brought into contact with the Si substrate 11 to dissolve and remove it. However, S which becomes a seed crystal during epitaxial growth
In order to prevent the iC film 12 from being dissolved in the Si-C-based melt 30, the temperature distribution in the Si-C-based melt 30 should be set such that the temperature on the side where the growth base material 10 is disposed is the lowest. It costs.

Next, when the temperature of the Si—C-based melt 30 is 160
When the temperature reaches a predetermined temperature of 0 ° C. or higher and is sufficiently left until the C concentration in the Si—C-based melt 30 becomes substantially equilibrium, the temperature distribution in the Si—C-based melt 30 is changed to a growth base. The temperature on the growth substrate 10 side is increased so that the temperature on the side where the material 10 is disposed is the highest. By this heating process, the growth substrate 1
The C concentration near the position where the zero SiC film 12 is disposed is in an unsaturated state.
Part of 2 dissolves. In this step, the SiC film 12 having poor crystallinity near the interface with the Si substrate 11 was formed.
The C film is removed. At this time, the dissolution time of the SiC film 12 is appropriately set so that the SiC film 12 having a thickness necessary and sufficient for the subsequent epitaxial growth step can remain.

Next, after the SiC film having poor crystallinity is removed, the temperature on the side of the growth substrate 10 is lowered to reduce the Si-C film.
The temperature distribution in the Si—C-based melt 30 is changed so that the temperature on the growth substrate 10 side is the lowest in the system-based melt 30.

By this operation, the temperature distribution in the Si—C-based melt 30 becomes the lowest on the side where the growth base material 10 is disposed and the temperature on the side of the graphite 32 which is a C supply source. Epitaxial growth occurs on the SiC film 12 of the material 10, and SiC crystals can be obtained.

FIGS. 2A to 2C show that the Si substrate provided with the SiC film is used as a growth base material (ie, a seed crystal substrate) for liquid phase epitaxial growth, and the SiC film is formed by a temperature difference method.
It is a process explanatory view showing another method of growing a crystal.

First, as shown in FIG. 2A, the growth substrate 10 composed of the Si substrate 11 and the SiC film 12 is arranged above the growth container 20 so that the Si substrate 11 side is exposed. In the lower side of the growth vessel 20, a Si polycrystal 31 which is melted to be a solvent and is a raw material of the Si-C-based melt and graphite 3 which is a raw material for supplying C to the melt.
2 are arranged respectively.

Next, the growth vessel 20 and heated to Si single melting point T _m above temperature by high frequency induction heating method or a resistance heating method in an atmosphere such as Ar gas 2
As shown in (B), while obtaining the Si-C-based melt 30,
The SiC film 1 is obtained by melting and removing the Si substrate 11 of the growth base material 10.
Expose 2

Next, the temperature of the Si—C-based melt 30 is set to 160
When the temperature reaches a predetermined temperature of 0 ° C. or more and is sufficiently left until the C concentration in the Si—C-based melt 30 is substantially in an equilibrium state, as shown in FIG. To bring the Si—C-based melt 30 into contact with the SiC film 12 of the growth substrate 10,
The temperature distribution within 0 is raised so that the temperature on the growth substrate 10 side is the highest on the side where the growth substrate 10 is disposed. By this heating process, the C concentration in the vicinity of the growth base material 10 where the SiC film 12 is disposed becomes an unsaturated state, and a part of the SiC film 12 is dissolved to compensate for the insufficient C. In this step, the SiC film having poor crystallinity near the interface with the Si substrate 11 in the SiC film 12 is removed. At this time, the dissolution time of the SiC film 12 is appropriately set so that the SiC film 12 having a thickness necessary and sufficient for the subsequent epitaxial growth step can remain.

Next, after the SiC film having poor crystallinity is removed, the temperature on the growth substrate 10 side is lowered to reduce the Si-C film.
The temperature distribution in the Si—C-based melt 30 is changed so that the temperature on the growth substrate 10 side is the lowest in the system-based melt 30.

As a result of this operation, the temperature distribution in the Si—C-based melt 30 becomes the lowest on the growth substrate 10 side and the temperature on the graphite 32 side as the C supply source. Epitaxial growth occurs on the SiC film 12 of the material 10, and SiC crystals can be obtained.

[0040]

Embodiments of the present invention will be specifically described below.

[Example 1] First, in FIG. 1, the upper side of a growth vessel 20 made of graphite whose inner wall was coated with BN was placed.
As shown in FIG. 1A, a growth substrate 10 composed of a Si substrate 11 and a SiC film 12 is disposed so that the Si substrate 11 side is exposed, and a Si polycrystalline body 31 and a graphite are provided below a growth container 20. 32 were arranged respectively.

Next, the growth vessel 20 was heated in an Ar gas atmosphere at a high frequency induction heating temperature of 1430.degree. C. for the polycrystalline body 31 and graphite 32, and 1400.degree. C. for the growth substrate 10. The Si-C-based melt 3 in which the graphite 32 floats as shown in FIG.
0 was obtained.

Next, as shown in FIG.
0, the Si—C-based melt 30 and the growth substrate 1
The Si substrate 11 is brought into contact with the Si substrate 11 to dissolve and remove it. However, S which becomes a seed crystal during epitaxial growth
The temperature distribution in the Si-C-based melt 30 was set such that the temperature on the side where the growth base material 10 was disposed was the lowest so that the iC film 12 was not dissolved in the Si-C-based melt 30.

Next, when the temperature of the Si—C-based melt 30 is 160
When the temperature reaches a predetermined temperature (1700 ° C.) of 0 ° C. or more and is sufficiently left until the C concentration in the Si—C-based melt 30 becomes substantially equilibrium, the temperature in the Si—C-based melt 30 is reduced. The temperature of the growth base 10 side is increased to 1800 ° C. so that the distribution is the highest on the side where the growth base 10 is disposed.
By this heating process, the C concentration in the vicinity of the growth base material 10 where the SiC film 12 is disposed becomes an unsaturated state, and a part of the SiC film 12 is dissolved to compensate for the insufficient C.
In this step, the SiC film having poor crystallinity near the interface with the Si substrate 11 in the SiC film 12 is removed.
At this time, the SiC film 12 is formed so that the SiC film 12 having a thickness necessary and sufficient for the subsequent epitaxial growth process can remain.
Was set to 1 hour.

After removing the SiC film having poor crystallinity by these treatments, the temperature on the growth substrate 10 side is lowered, and the temperature on the side where the growth substrate 10 is disposed becomes lowest 1650 in the Si—C-based melt 30. ° C and set the Si-C-based melt 30
The temperature distribution inside was changed.

By this operation, the temperature distribution in the Si—C-based melt 30 becomes lowest on the side where the growth base material 10 is disposed, and becomes high on the graphite 32 side which is a supply source of C. The epitaxial growth occurred on the SiC film 12 of Example 1 and a SiC crystal was obtained.

[Example 2] First, FIG. 2 shows the upper side of a growth vessel 20 made of graphite whose inner wall was coated with BN.
As shown in FIG. 1A, a growth substrate 10 composed of a Si substrate 11 and a SiC film 12 is disposed so that the Si substrate 11 side is exposed, and a Si polycrystalline body 31 and a graphite are provided below a growth container 20. 32 were arranged respectively.

Next, the melting point of the simple Si (1414) is set in the growth vessel 20 by high frequency induction heating in an Ar gas atmosphere.
2C) to obtain a Si—C-based melt 30 as shown in FIG. 2B, and to melt and remove the Si substrate 11 of the growth base material 10 to form the SiC film 12. Exposed.

Next, when the temperature of the Si—C-based melt 30 is 160
When the temperature reaches a predetermined temperature (1700 ° C.) of 0 ° C. or higher and is sufficiently left until the C concentration in the Si—C-based melt 30 is substantially in an equilibrium state, the growth as shown in FIG. The container 20 is turned upside down, and the Si-C-based melt 30
And the SiC film 12 of the growth substrate 10
The temperature distribution on the growth substrate 10 side is set to 180 so that the temperature distribution in the Si-C-based melt 30 is the highest on the side where the growth substrate 10 is disposed.
Raise to 0 ° C. By this heating process, the growth substrate 1
The C concentration near the position where the zero SiC film 12 is disposed is in an unsaturated state.
Part of 2 dissolves. In this step, the SiC film 12 having poor crystallinity near the interface with the Si substrate 11 was formed.
The C film is removed. At this time, the dissolution time of the SiC film 12 was set to one hour so that the SiC film 12 having a sufficient and necessary thickness in the subsequent epitaxial growth step could remain.

After removing the SiC film having poor crystallinity by these treatments, the temperature on the growth base 10 side is lowered, and the temperature on the growth base 10 arrangement side becomes the lowest in the Si—C-based melt 30 1650. ° C and set the Si-C-based melt 30
The temperature distribution inside was changed.

By this operation, the temperature distribution in the Si—C-based melt 30 is lowest on the side where the growth substrate 10 is disposed, and high on the graphite 32 side which is a C supply source. The epitaxial growth occurred on the SiC film 12 of Example 1 and a SiC crystal was obtained.

[0052]

According to the liquid phase epitaxial growth method for SiC crystals according to the first to fourth aspects of the present invention, the composition has a composition between the peritectic point and the eutectic point shown in the binary phase diagram of Si-C. The Si-C-based melt is used as a raw material melt, the Si substrate on which the SiC film is formed is used as a growth base material for the SiC crystal, and a Si substrate and a SiC film adjacent to the Si substrate having poor crystallinity are formed in the growth container. The SiC film having good crystallinity obtained by melting or dissolving and removing the portion is used as a seed crystal to form S on the SiC film.
Since the iC crystal is grown epitaxially, it is possible to easily obtain a SiC crystal which is larger than the conventional one and has few crystal defects such as micropipes.

Further, since the SiC film having good crystallinity from which the Si substrate has been removed is used as a seed crystal, the growth temperature of the Si—C-based melt can be set to 1600 ° C. or higher, which is higher than the melting point of Si. A polytype SiC crystal having a period of 4H (hexagonal) or 6H (hexagonal) required as a material can be easily and reliably obtained.

Further, since no SiC powder is used as a growth material, it is possible to obtain a SiC crystal having a lower residual impurity concentration than the SiC crystal obtained by the above-mentioned improved Rayleigh method (sublimation method), and to grow the same. The speed also depends on the growth temperature, the temperature gradient in the Si-C-based melt, and the like.
/ Hr. The above is one hundred times or more of the above-mentioned vapor phase growth method using a Si substrate, and it is possible to obtain a SiC crystal at high speed and with good reproducibility.

[Brief description of the drawings]

FIGS. 1A to 1C are explanatory views showing steps of a liquid phase epitaxial growth method according to a first embodiment.

FIGS. 2A to 2C are explanatory views showing steps of a liquid phase epitaxial growth method according to a second embodiment.

FIG. 3 is a diagram of a two-component system of Si—C.

4 (A) and 4 (B) are process explanatory views of a conventional improved Rayleigh method (sublimation method).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Growth base material 11 Si substrate 12 SiC film 20 Growth container 30 Si-C-based melt 31 Si polycrystal 32 Graphite

Continued on the front page F term (reference) 4G077 AA03 BE08 CG03 CG07 EA01 EC08 ED04 ED06 EE04 QA06 QA12 QA26 QA38 QA73 5F053 AA03 AA32 AA33 BB04 BB05 BB08 BB09 BB15 DD02 FF01 GG01 HH01 PP01 PP02

Claims (4)

[Claims] 1. A liquid phase epitaxial growth method for a SiC crystal, comprising: a Si—C-based melt having a composition between a peritectic point and a eutectic point shown in a Si—C binary phase diagram as a raw material melt; SiC
The Si substrate on which the film is formed is used as a SiC crystal growth base material, and the raw material melt is brought into contact with the Si substrate side of the growth base material in a growth vessel to form a Si substrate and an adjacent SiC crystal having poor crystallinity. A liquid phase epitaxial growth method for a SiC crystal, wherein a SiC crystal is epitaxially grown on a remaining SiC film after dissolving and removing a part of the film. 2. A growth base is arranged so that the Si substrate side is exposed in the upper part of the growth vessel, and S is located in the lower part of the growth vessel.
i) a step of arranging the raw material and graphite; and heating the inside of the growth vessel to a temperature equal to or higher than the melting point of Si to obtain a Si-C-based melt. Contact with the Si substrate
Dissolving and removing the Si substrate of the growth base material by setting the temperature distribution in the system melt to be the lowest on the growth base arrangement side; and setting the temperature of the Si—C base melt to a predetermined temperature (1600). ℃ or more), and after the C concentration in the Si-C-based melt reaches an equilibrium state, the temperature distribution in the Si-C-based melt is set so that the growth substrate arrangement side has the highest temperature. Dissolving and removing a part of the SiC film having poor crystallinity by dissolving and removing a part of the SiC film having poor crystallinity; A step of changing the temperature distribution in the Si-C-based melt so that the growth substrate arrangement side becomes the lowest temperature in the system-based melt and epitaxially growing a SiC crystal on the remaining SiC film. The liquid phase epitaxy of a SiC crystal according to claim 1, Le growth method. 3. A liquid phase epitaxial growth method for SiC crystals, wherein a Si-C-based melt having a composition between a peritectic point and a eutectic point shown in a Si-C binary phase diagram is used as a raw material melt; SiC
The Si substrate on which the film is formed is used as a growth substrate for SiC crystals, and the SiC film as the growth substrate is melted and removed in a growth vessel to expose the SiC film. The raw material melt is brought into contact to dissolve and remove a part of the SiC film having poor crystallinity, and to remove Si on the remaining SiC film.
S characterized by epitaxially growing a C crystal
Liquid phase epitaxial growth method of iC crystal. 4. A growth base is arranged so that the Si substrate side is exposed above the growth vessel, and S is located below the growth vessel.
i) a step of arranging the raw material and graphite, and heating the inside of the growth vessel to a temperature equal to or higher than the melting point of Si to melt and remove the Si substrate as the growth base material, thereby exposing the SiC film and Si-C
A step of obtaining a system melt, after the temperature of the Si—C system melt reaches a predetermined temperature (1600 ° C. or higher) and the C concentration in the Si—C system melt reaches an equilibrium state, The growth vessel is turned upside down to bring the Si-C-based melt into contact with the SiC film of the growth substrate, and the temperature distribution in the Si-C-based melt is set so that the growth substrate-located side has the highest temperature. SiC with poor crystallinity
A step of dissolving and removing a part of the film; and a step of dissolving and removing a part of the SiC film inferior in crystallinity. 4. The SiC crystal according to claim 3, further comprising a step of changing a temperature distribution in the Si-C-based melt so as to be a low temperature and epitaxially growing a SiC crystal on the remaining SiC film. Liquid phase epitaxial growth method.