KR20090021144A - Single-crystal sic, process for producing the same, and apparatus for producing single-crystal sic - Google Patents

Abstract

This invention provides a single-crystal SiC for use as a semiconductor device material or an LED material, and a process for producing the same, and an apparatus for producing a single-crystal SiC. In the single-crystal SiC, defects such as micropipes have been suppressed, and the single-crystal SiC has a high quality, is continuous, and has a large diameter. The process for producing a single-crystal SiC comprises the step of fixing an SiC seed single-crystal wafer onto a susceptor, and the step of externally continuously supplying a raw material for single-crystal SiC production onto the SiC seed single-crystal wafer and growing single-crystal SiC. The process is characterized in that the average temperature gradient of the susceptor, SiC seed single-crystal, and single-crystal SiC having a thickness increased with the growth thereof in the vertical direction (longitudinal direction) of the susceptor is not less than 0.5°C/mm and not more than 9°C/mm.

Description

SINGLE-CRYSTAL SiC, PROCESS FOR PRODUCING THE SAME, AND APPARATUS FOR PRODUCING SINGLE-CRYSTAL SiC}

TECHNICAL FIELD The present invention relates to a single crystal SiC used as a material for a semiconductor element or a material for an LED, a method for producing the same, and an apparatus for producing a single crystal SiC.

Single crystal SiC has a large binding energy of crystals, a large dielectric breakdown electric field, and a high thermal conductivity, and thus is useful as a material for harsh environmental devices and power devices. Moreover, since the lattice constant is close to the lattice constant of GaN, it is also useful as a substrate material for GaN-LED.

Conventionally, in the production of single crystal SiC, the Rayleigh method of subliming SiC powder in a graphite crucible and recrystallizing the single crystal SiC on the inner wall of the graphite crucible. An improved Rayleigh method of disposing epitaxially growing SiC seed single crystals, CVD method of transporting a gas source via a carrier gas onto a heated SiC seed single crystal and epitaxially growing a chemical reaction at the crystal surface, in a graphite crucible There is a sublimation proximity method in which SiC powder is epitaxially recrystallized on SiC seed single crystal while SiC powder and SiC seed single crystal are in close proximity.

In the present situation, however, these single crystal SiC manufacturing methods are all said to have problems. In the Rayleigh method, single crystal SiC having good crystallinity can be produced, but since crystals grow based on naturally occurring nucleation, shape control and crystal surface control are difficult, and there is a problem that a large diameter wafer cannot be obtained. .

In the improved Rayleigh method, a large diameter single crystal SiC ingot can be obtained at a high speed of about 100 µm / h. However, since the crystals are epitaxially grown in a spiral, a small hole penetrating through a crystal called a plurality of micropipes in the crystal is formed. There is a problem that occurs. In the CVD method, high-quality single crystal SiC with high purity and low defect density can be produced, but since the crystals are epitaxially grown using a lean gas source, the growth rate is slow to about 10 µm / h and a long single crystal SiC ingot is produced. There is a problem that cannot be obtained.

In the sublimation proximity method, high-purity SiC epitaxial growth can be realized with a relatively simple configuration, but there is a problem that it is impossible to obtain a long single crystal SiC ingot due to configuration limitations.

Recently, silicon dioxide ultrafine particles and carbon ultrafine particles are supplied as an inert carrier gas onto a heated SiC seed single crystal, and silicon dioxide is reduced to carbon on the SiC seed single crystal, thereby rapidly growing epitaxially monocrystalline SiC on the SiC seed single crystal. The method was invented (refer patent document 1). In this method, high quality single crystal SiC which suppresses defects such as micropipes can be obtained at high speed.

The manufacturing method disclosed in patent document 1 is similar to the Acheson process which is famous as a SiC manufacturing method for abrasives, in terms of using solid silicon dioxide ultrafine particles and solid carbon ultrafine particles as raw materials for producing single crystal SiC. The Acheson method is a method for producing single crystal SiC with volume shrinkage by heating silicic anhydride and a carbon source to 2,000 ° C or higher and reducing silicic anhydride to carbon. Since the Acheson method is complicated in reaction, SiC polycrystals of various polymorphs, sizes and directions are produced. On the other hand, the manufacturing method disclosed in patent document 1 is the direction of the single crystal SiC manufactured while accompanying volume shrinkage by supplying the raw material for single-crystal SiC manufacture which consists of ultra-fine silicon dioxide and ultrafine carbon particles on a heated and held SiC seed single crystal. The shape is controlled and the SiC single crystal is expected to be epitaxially arranged on the SiC seed single crystal.

In reality, however, in the production method disclosed in Patent Document 1, it is difficult to control the crystal growth of single crystal SiC. When 1 mol of solid silicon dioxide ultrafine particles and 3 mol of solid carbon ultrafine particles react in solid phase, 1 mol of SiC is produced by the reaction of Formula (1), and 2 mol of carbon monoxide gas is generated. This carbon monoxide gas is assumed to occur on the SiC seed single crystal in which the reaction proceeds.

SiO ₂ + 3C → SiC + 2CO ↑. (One)

Therefore, unless it is promptly removed from the SiC seed single crystal, the SiC seed single crystal and the reaction growth layer are divided by this carbon monoxide gas. As a result, it is thought that the cause is that the crystal arrangement information on the surface of the SiC seed single crystal is not transferred to the reaction growth layer.

[Patent Document 1] Japanese Patent No. 3505597

Disclosure of the Invention

Problems to be Solved by the Invention

This invention is made | formed in order to solve the said subject, The objective of this invention is providing the high quality long, large diameter single crystal SiC which suppressed defects, such as a micropipe, and its manufacturing method. Moreover, an object of this invention is to provide the manufacturing apparatus of single crystal SiC which can be used suitably for the said manufacturing method.

Means to solve the problem

The said subject was solved by the means as described in <1>, <4>, and <5>. It describes below with <2> and <3> which are preferable embodiment.

A method of manufacturing <1> single crystal SiC, the method comprising: fixing a SiC seed single crystal wafer to a susceptor; and growing a single crystal SiC by continuously supplying a raw material for producing single crystal SiC from the outside onto a SiC seed single crystal wafer; A method for producing single crystal SiC, wherein the average temperature gradient in the axial direction of the susceptor is 0.5 ° C./mm or more and 9 ° C./mm or less of the susceptor, SiC seed single crystal, and thickened with growth.

The manufacturing method of single crystal SiC as described in <1> whose <2> raw material for manufacturing said single crystal SiC is silica and carbon,

The manufacturing method of single crystal SiC as described in <1> or <2> whose <3> above-mentioned average temperature gradient is 0.5 degreeC / mm or more and 3 degrees C / mm or less,

<4> Single crystal SiC manufactured by the method in any one of <1>-<3>,

&Lt; 5 > A chamber having a crucible and a means for heating the crucible, a susceptor for fixing the SiC seed single crystal wafer in the crucible, and a means for supplying raw material for producing single crystal SiC to the SiC seed single crystal, wherein the susceptor can be controlled. The manufacturing apparatus of single-crystal SiC characterized by the above-mentioned.

Effects of the Invention

According to the present invention, it is possible to provide single crystal SiC having a high growth rate and low cost, a method for producing the same, and an apparatus for producing single crystal SiC.

The single crystal SiC obtained by the present invention has a low generation of micropipes and is of high quality. Moreover, according to this invention, the favorable single crystal SiC of large diameter can be provided.

1 is an example of an apparatus for producing the single crystal SiC of the present invention.

<Description of the code>

1: hermetic chamber

2: hermetically sealed crucible

3: high frequency induction heating coil

4: seed single crystal wafer

5: susceptor

6: supply line

7, 7 ': raw material reservoir

8, 8 ': regulating valve

9: growth layer

10: susceptor vertical direction

A: inert carrier gas

Best Mode for Carrying Out the Invention

The manufacturing method of single-crystal SiC of this invention includes the process of fixing a SiC seed single crystal wafer to a susceptor, and the process of continuously supplying the raw material for single-crystal SiC manufacture from outside to a SiC seed single crystal wafer, and growing single crystal SiC. The average temperature gradient in the axial direction of the susceptor of the single crystal SiC thickened as the acceptor, the SiC seed single crystal and grows is set to 0.5 ° C / mm or more and 9 ° C / mm or less.

Although average temperature gradient is 0.5 degreeC / mm or more and 9 degrees C / mm or less, it is preferable that they are 0.5 degreeC / mm or more and 3 degrees C / mm or less.

The average temperature gradient sets an average temperature gradient so that the growth layer of the SiC single crystal becomes a high temperature and the susceptor side becomes a low temperature.

By making an average temperature gradient into 0.5 degreeC / mm or more and 9 degrees C / mm or less, the single crystal SiC manufactured can be grown epitaxially. This is considered to be because crystal arrangement information on the surface of the SiC seed single crystal is transferred to the growth layer of the SiC single crystal.

In detail, since the average temperature gradient is made low on the susceptor side and high on the growth layer side, the temperature of the growth single crystal SiC surface is higher than that of the SiC seed single crystal surface. By setting the temperature gradient in this manner, the carbon monoxide gas, which is the reaction product, moves to the growth single crystal SiC surface quickly by thermal diffusion and is released into the crucible. That is, the generated carbon monoxide gas does not stay inside the growth single crystal SiC, and the SiC seed single crystal and the reaction growth layer are not divided by the carbon monoxide gas. As a result, it is considered that the crystal arrangement information on the surface of the SiC seed single crystal is well transmitted to the reaction growth layer.

However, when the temperature gradient is greater than 9 ° C / mm, the supersaturation degree of the surface of the SiC seed single crystal increases, and polymorphic nuclei irrelevant to the crystal arrangement information on the surface of the SiC seed single crystal are generated, and a single crystal cannot be obtained. On the other hand, when the temperature gradient is smaller than 0.5 ° C / mm, the growth rate decreases, and conversely, etching may occur.

In the present invention, the average temperature gradient can be measured as follows.

The temperature gradient is measured on the susceptor side (low temperature side) and the growth layer side (high temperature side), and this temperature difference is a value obtained by dividing the distance from the temperature sensor provided in the heat exchanger portion of the susceptor to the growth layer surface. Specifically, the temperature sensor is provided at a portion to which the heat exchanger of the susceptor is provided to measure the temperature, and the temperature is set at the low temperature side. In addition, the correlation between the temperature of the SiC seed single crystal surface and the temperature of the outer surface of the sealed crucible is measured in advance, and in practice, the temperature of the outer surface of the sealed crucible is measured with a radiation thermometer, and the calculated temperature is regarded as the temperature of the growth layer surface. It is set to the temperature on the high temperature side. From these temperatures and the distance from the temperature sensor to the susceptor surface, the thickness of the seed single crystal and the growth rate of the SiC single crystal, an average temperature gradient can be calculated.

In order to make an average temperature gradient into the said range, although any method can be used, it is preferable to control a temperature gradient by having a heat exchange function which a susceptor can control.

Specifically, the temperature on the high temperature side is fixed at the production temperature of single crystal SiC, and the temperature gradient adjustment can be exemplified by the temperature adjustment on the low temperature side (side to which the heat exchanger of the susceptor is applied). The temperature gradient can be adjusted by adjusting the contact area or heat exchange capacity of the susceptor and the heat exchanger, and controlling the temperature on the low temperature side.

In addition, when the manufacturing apparatus is used without a temperature gradient, the heat exchanger is stopped and a heat insulating material is inserted between the susceptor and the heat exchanger, whereby it can be used for other purposes without controlling the temperature gradient. Do.

It is preferable that the raw material for monocrystal SiC manufacture consists of silica and carbon.

The kind, particle diameter, particle shape, etc. of the silica particle used for this invention are not specifically limited, For example, the high purity silica obtained by the flame hydrolysis method etc. can be used suitably.

The kind, particle diameter, particle shape, etc. of the carbon particle used for this invention are not specifically limited, For example, commercially available high purity carbon black etc. can be used suitably.

The ratio of the continuous supply amount of the silica particles and the carbon particles is not particularly limited, and the desired composition ratio can be appropriately selected. You may mix and use 2 or more types of said silica particle and carbon particle. Moreover, the said silica particle and carbon particle may be pretreated as needed, or a trace amount of another component may be added.

The supply of the silica particles and the carbon particles onto the SiC seed single crystal wafer is not particularly limited as long as it is a method of supplying continuously without interruption, and any known method can be used. Specifically, there can be exemplified one that can transport the powder continuously like a commercially available powder feeder.

In addition, when supplying the raw material for single-crystal SiC production, in order to prevent oxygen mixing, it is preferable to set it as the sealing structure in which argon substitution and nitrogen substitution were carried out.

About the supply conditions of the said silica particle and the carbon particle on the SiC seed single crystal wafer, these raw material for single crystal SiC manufacture should just be supplied in the state mixed on the SiC seed single crystal wafer, Even if the raw material for manufacturing single crystal SiC is mixed previously, You may supply separately and mix on a SiC seed single crystal wafer.

Moreover, when doping in single crystal SiC, you may mix with the said raw material for single crystal SiC manufacturing as a solid supply source, and may mix the said doping component as a gas supply source in the atmosphere in a single crystal SiC manufacturing apparatus.

The type, size, and shape of the SiC seed single crystal wafer used in the present invention are not particularly limited, and can be appropriately selected depending on the type, size, and shape of the target single crystal SiC. For example, the SiC single crystal obtained by the improved Rayleigh method and the SiC seed single crystal wafer which pretreated this as needed can be used suitably.

In this invention, the structure of the single crystal SiC manufacturing apparatus used for obtaining single crystal SiC is not specifically limited. That is, a size, a heating method, a material, a raw material supply method, an atmosphere adjustment method, a temperature control method, etc. can be suitably selected according to the size and shape, a kind, and the kind and quantity of the raw material for monocrystal SiC manufacture, etc. of the target single crystal SiC.

In order to prevent oxygen mixing, the atmosphere of the device is preferably argon-substituted or nitrogen-substituted, and preferably a sealed structure.

In addition, the temperature for producing single crystal SiC is not particularly limited, and can be appropriately set according to the size and shape, type, and type and amount of the raw material for producing single crystal SiC. Preferable manufacturing temperature is the range of 1,600 degreeC-2,400 degreeC, and points out the temperature of the outside of a sealed crucible, for example. It is preferable that the manufacturing apparatus used for this invention is an apparatus which can control temperature in the said temperature range.

In the present invention, the heating method is not particularly limited, any heating method can be used, and high frequency induction heating or electric resistance heating can be exemplified.

It is preferable that the material of the susceptor holding the SiC seed single crystal wafer is made of graphite in consideration of the use temperature range, and a cooling mechanism for generating heat flow in the axial direction of the susceptor is preferably provided. Although the said cooling method is not specifically limited, It is preferable that it is designed so that a preferable temperature gradient can be selected respectively according to the size, shape, and kind of target single crystal SiC.

In the present invention, the apparatus for producing SiC single crystal has a chamber provided with a crucible and a means for heating the crucible, a susceptor for fixing the SiC seed single crystal wafer in the crucible, and a means for supplying a raw material for producing single crystal SiC to the SiC seed single crystal. It is especially preferable that it is a manufacturing apparatus of single-crystal SiC characterized by the fact that a acceptor has a controllable heat exchange function.

1 is an example of an apparatus for producing single crystal SiC of the present invention, in which a high frequency induction heating furnace is used.

A carbon sealed crucible 2 (100 mm in diameter and 150 mm in height) is disposed in the water-cooled sealed chamber 1, and a high frequency induction heating coil 3 is disposed outside the water-cooled sealed chamber.

A susceptor 5 for holding the SiC seed single crystal wafer 4 is inserted through the lower portion of the sealed crucible. This susceptor extends to the lower side of the hermetically sealed crucible and can be rotated by using a rotation mechanism (not shown) with the central axis of the susceptor as the rotation axis.

In addition, a controllable heat exchange function is provided at the lower end of the susceptor, which is not shown, and heat flow can be generated in the susceptor shaft direction 10. In addition, the heat flux can be adjusted.

In addition, the normal direction of the surface holding the SiC seed single crystal wafer on the upper end of the susceptor can be freely set up to an inclination of up to 45 ° in substantially parallel to the vertical direction of the susceptor.

At an upper portion of the sealed crucible, a feed pipe 6 for supplying raw material particles for producing single crystal SiC is inserted therethrough. In addition, the supply pipe is disposed outside the high frequency induction heating furnace, and is connected to a plurality of raw material reservoirs 7 and 7 ', each of which can be independently supplied, and an inert carrier gas supply source (not shown). have.

In the case of using a premixed raw material for producing single crystal SiC, one raw material storage tank is used. When mixing inside the supply pipe, silica and carbon powder are respectively filled in the raw material storage tank independently. After adjusting the supply amount from each storage layer with the control valves 8 and 8 ', by flowing the inert carrier gas A while adjusting the flow rate, the raw material for manufacturing single crystal SiC can be continuously supplied in an appropriate amount in the sealed crucible. . Although nitrogen gas, helium gas, argon gas, etc. can be illustrated as an inert carrier gas, nitrogen gas and argon gas are preferable, and argon gas can be used more suitably.

In this manner, the thicker single crystal SiC layer (growth layer) 9 is formed as the SiC seed single crystal wafer 4 grows.

The high frequency induction heating furnace is capable of controlling pressure by a vacuum exhaust system and a pressure regulator not shown, and is provided with an inert gas replacement mechanism not shown.

In addition, in the embodiment of FIG. 1, the supply pipe is disposed above and the susceptor is disposed below, but it is also possible to arrange the supply pipe in an inclined or transverse direction with respect to the susceptor within a range in which the operation of the present invention does not change. It is also possible.

Example

Hereinafter, embodiments of the present invention will be described.

Single-crystal SiC was manufactured on the following conditions using the said high frequency induction heating furnace.

An SiC seed single crystal wafer was fixed on top of the susceptor. The SiC seed single crystal wafers used here are both approximately 10 mm of amorphous single crystal SiC produced by the Rayleigh method and single-crystal SiC having a diameter of 2 centimeters produced by the improved Rayleigh method. Moreover, each of the just surface, the inclined surface, the C surface, and the Si surface was prepared as a seed single crystal and used.

Carbon (carbon black MA600 made by Mitsubishi Chemical Co., Ltd.) and silica (Aerosil 380 made by Nippon Aerosol), which are raw materials for producing single crystal SiC, were each independently filled in a raw material storage tank. In addition, each supply amount ratio was adjusted to silica / carbon = 1.5-5.0 (weight ratio). At this time, SiC powder may be supplied separately as needed.

After the vacuum treatment inside the high frequency induction furnace, the inside of the high frequency induction furnace was replaced with an inert gas (high purity argon or high purity nitrogen). Subsequently, the said carbonaceous sealing crucible was heated with the said high frequency induction heating coil, and it adjusted so that the SiC seed single crystal wafer surface temperature might be in the range of 1,600 degreeC-2,390 degreeC.

Subsequently, the susceptor on which the SiC seed single crystal wafer was fixed was rotated at a rotation speed of 0 rpm to 20 rpm. In this state, the inert carrier gas (high-purity argon or high-purity nitrogen) is adjusted to flow in a range of 0.5 l / min to 10 l / min, and the raw material for producing the single crystal SiC is lowered in the sealed crucible through the inside of the supply pipe. It was continuously supplied on the surface of the SiC seed single crystal wafer thus arranged, and monocrystalline SiC was produced for about 2 hours. As a result, single crystal SiC having a thickness of about 1 mm was obtained.

At this time, the heat exchange mechanism at the lower end of the susceptor is adjusted so that the average temperature gradient in the susceptor axis direction is 0.2 ° C / mm, 0.5 ° C / mm, 3 ° C / mm, 9 ° C / mm, and 10 ° C / mm. Single crystal SiC was produced, respectively.

A manufacturing result is demonstrated based on Table 1. When the average temperature gradient in the susceptor axis direction was 0.5 ° C / mm or more, the average growth rate was equivalent to 50 µm / h to 500 µm / h. However, on the condition that the said average temperature gradient is 0.2 degreeC / mm, a growth rate falls and in severe cases, it etched in reverse. Moreover, on the conditions whose average temperature gradient is 10 degrees C / mm, the obtained SiC becomes polycrystal which grew in columnar shape in the substantially normal direction of a SiC seed single crystal wafer, and was not epitaxially grown on the SiC seed single crystal wafer. Moreover, although epitaxial growth was made on the conditions of an average temperature gradient of 9 degree-C / mm, the generation amount of a micropipe increased. On the other hand, under the conditions of an average temperature gradient of 0.5 ° C./mm and 3 ° C./mm, it was possible to produce high-quality single crystal SiC that had no polycrystal mixed in the produced single crystal SiC and had few defects such as micropipes.

Average temperature gradient (℃ / mm) 0.2 0.5 3 9 10 Growth rate (μm / h) -50 to 100 50 to 500 50 to 500 50 to 500 50 to 500 Crystallinity Etching occurs Transparent monocrystalline Transparent monocrystalline Transparent monocrystalline Columnar polycrystalline flaw - Micro Pipe Less Micro Pipe Less Micro pipe plenty -

Claims (5)

As a method of manufacturing single crystal SiC, Fixing the SiC seed single crystal wafer to the susceptor, and It includes a step of growing a single crystal SiC by continuously supplying the raw material for producing single crystal SiC on the SiC seed single crystal wafer from the outside, A method for producing single crystal SiC, wherein the average temperature gradient in the axial direction of the susceptor is 0.5 ° C./mm or more and 9 ° C./mm or less of the susceptor, SiC seed single crystal, and thickened with growth. The method for producing single crystal SiC according to claim 1, wherein the raw materials for producing single crystal SiC are silica and carbon. The method for producing single crystal SiC according to claim 1 or 2, wherein the average temperature gradient is 0.5 ° C / mm or more and 3 ° C / mm or less. Single-crystal SiC manufactured by the method of any one of Claims 1-3. Means for heating the crucible and the chamber provided with the crucible, A susceptor for fixing the SiC seed single crystal wafer in the crucible, Means for supplying a raw material for producing single crystal SiC to the SiC seed single crystal, An apparatus for producing single crystal SiC, wherein the susceptor has a heat exchange function that can be controlled.

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