JP2004131376A - Silicon carbide single crystal, and method and apparatus for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a large diameter silicon carbide single crystal with few crystal defects stably at a high growth rate on a seed crystal substrate by suppressing fluctuation of components of a sublimate gas by controlling an atmospheric gas when the silicon carbide single crystal is grown by a sublimation method. <P>SOLUTION: A growth crucible 2 is disposed inside an outer crucible 1. During the growth of the silicon carbide single crystal, a silicon raw material 22 is continuously fed from outside into a space between the growth crucible 2 and the outer crucible 1. By vaporizing the silicon raw material 22, the atmospheric gas surrounding the growth crucible 2 is constituted of a silicon gas. The solid silicon raw material 22 is fed from outside. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a silicon carbide (SiC) single crystal, a method for manufacturing the same, and an apparatus for manufacturing a silicon carbide single crystal, and in particular, a method for manufacturing a silicon carbide single crystal having few defects such as micropipes, good quality, and a large diameter. It is about.

A silicon carbide single crystal expected as a semiconductor material is usually produced by a sublimation method using silicon carbide powder as a raw material. In the sublimation method, the raw material silicon carbide powder and the seed crystal substrate are placed facing each other inside a growth crucible made of graphite, and the silicon carbide raw material is heated to 1800 to 2400 ° C. in an inert gas atmosphere. The silicon carbide sublimation gas generated by heating reaches the seed crystal substrate held in a temperature range suitable for crystal growth and precipitates as a single crystal.

In the sublimation method, as components of the sublimation gas from the silicon carbide raw material, Si, Si ₂ C, SiC ₂ , SiC and the like are generated, and a part of these sublimation gases are deposited on the seed crystal substrate, A silicon carbide single crystal grows. The growth of a silicon carbide single crystal by this sublimation method is a process of sublimation and precipitation of a solid compound, so that 1) the growth rate is slow, and 2) if the growth rate is increased, crystal defects and polycrystallization are likely to occur. There was a problem.

In addition, the sublimation gas component in the growth process of the silicon carbide single crystal is the sublimation and decomposition process of the raw material silicon carbide powder, the mutual reaction of the sublimation gas component in the gas phase, and the contact reaction with graphite on the inner wall of the growth crucible. Fluctuates due to various factors. Alternatively, when the silicon carbide raw material is heated, silicon having a high vapor pressure tends to gasify, and carbon tends to remain as a residue. For this reason, with the passage of time, the silicon component in the silicon carbide raw material decreases before the carbon component, and the gas component in the sublimation gas changes. This is also one of the fluctuation factors of the sublimation gas component. In addition, changes in the sublimation temperature of the raw material, the raw material composition, the temperature distribution in the reaction crucible, and the like over time are also considered to be a variation factor of the sublimation gas component.

Variations in the sublimation gas component in the region near the surface of the seed crystal substrate on which the single crystal grows may cause crystal defects to be incorporated into the silicon carbide crystal, or polymorphism and anisotropic growth (so-called polycrystallization). It is thought that this is a factor that decreases the crystallinity of the single crystal. For this reason, in order to obtain a high-quality silicon carbide single crystal, it is important to control the fluctuation factors of these sublimation gas components.

In the growth of conventional silicon carbide single crystals, the growth rate is lowered to reduce the crystal defect occurrence rate, or the growth duration is shortened so that the fluctuation of the sublimation gas composition does not become too large. Measures were taken. However, in these, the quality and stability of the silicon carbide single crystal obtained by the sublimation method cannot be said to be sufficient.

Therefore, the following improvements of the sublimation method have been proposed. For example, as a method of suppressing fluctuations in the sublimation gas component, a silicon raw material and a carbon raw material are separately disposed, and a silicon component is formed by reacting the gas component generated from the silicon raw material with the carbon raw material, and the silicon carbide is sublimated. And a method of forming a silicon carbide single crystal is proposed (for example, refer to Patent Document 1). However, even with this method, the essential drawback of the sublimation method is that the gas composition changes with sublimation. Moreover, the manufacturing process of a single crystal becomes a two-step, and manufacturing time becomes comparatively long time.

Also, silicon is heated and evaporated in the reaction crucible, the silicon vapor reacts with the carbon vapor evaporated from the inner wall of the reaction crucible, the reaction gas is moved to the silicon carbide precipitation chamber, and the inner wall is carbonized. A method of depositing a silicon single crystal is also known (for example, see Patent Document 2). However, this method has a drawback that the growth rate of the silicon carbide single crystal is slow because carbon has a lower vapor pressure than silicon.
JP-A-6-316499 Japanese Patent Publication No.51-8400

As described above, at present, an effective method for growing a silicon carbide single crystal having good crystallinity by controlling the factors that cause the sublimation gas component to change has not been established. In the growth of a silicon carbide single crystal by the sublimation method, the present invention suppresses fluctuations in the components of the sublimation gas by controlling the atmospheric gas, and enables a large-diameter silicon carbide single crystal with few crystal defects to be stable and fast. An object is to provide a method of growing on a seed crystal substrate at a growth rate.

That is, the present invention
(1) A growth crucible made of graphite is provided with a low temperature portion and a high temperature portion, a seed crystal substrate made of a silicon carbide (SiC) single crystal is placed in the low temperature portion of the growth crucible, and a silicon carbide raw material is placed in the high temperature portion. In a method for producing a silicon carbide single crystal in which a sublimation gas sublimated from a silicon carbide raw material is deposited on a seed crystal substrate to grow a silicon carbide single crystal, the atmosphere gas surrounding the growth crucible is composed of silicon (Si) gas Is a method for producing a silicon carbide single crystal.

The present invention also provides
(2) The vapor pressure of silicon gas in the growth crucible (referred to as “silicon gas pressure in crucible”) is the equilibrium vapor pressure of silicon gas in the sublimation gas of the silicon carbide raw material (referred to as “silicon gas pressure in sublimation gas”). The method for producing a silicon carbide single crystal according to the above (1), wherein the silicon carbide single crystal is grown while maintaining at least the same as the above.

The present invention also provides
(3) A growth crucible is installed in the outer crucible, a silicon raw material is continuously supplied from the outside between the growth crucible and the outer crucible, and the silicon raw material is evaporated between the growth crucible and the outer crucible. The method for producing a silicon carbide single crystal according to the above (1) or (2), wherein the crystal is grown.

The present invention also provides
(4) A growth crucible made of graphite is provided with a low temperature part and a high temperature part, a seed crystal substrate made of a silicon carbide (SiC) single crystal is placed in the low temperature part of the growth crucible, and a silicon carbide raw material is placed in the high temperature part In a method for producing a silicon carbide single crystal in which a sublimation gas sublimated from a silicon carbide raw material is deposited on a seed crystal substrate to grow a silicon carbide single crystal, the growth crucible is installed in the outer crucible, and the growth crucible and the outer crucible A silicon carbide single crystal manufacturing method characterized in that a silicon carbide single crystal is grown while continuously supplying a silicon raw material from outside and evaporating the silicon raw material between a growth crucible and an outer crucible.

The present invention also provides
(5) The method for producing a silicon carbide single crystal according to (4), wherein a solid silicon raw material is supplied from the outside.

The present invention also provides
(6) The method for producing a silicon carbide single crystal according to (5) above, wherein the solid silicon raw material is a powder having a diameter of 0.2 to 5 mm.

The present invention also provides
(7) The method for producing a silicon carbide single crystal according to any one of (4) to (6), wherein the silicon raw material is supplied at a rate of 0.5 to 20 mg / second.

The present invention also provides
(8) The temperature of the place where the silicon raw material between the growth crucible and the outer crucible is charged is set to 1900 ° C. or higher, and the silicon carbide unit according to any one of (4) to (7) above It is a manufacturing method of a crystal.

The present invention also provides
(9) The pressure of the atmospheric gas surrounding the growth crucible is 1.33 × 10 ^{2 to} 4.0 × 10 ⁴ Pa, as described in any one of (4) to (8) above A method for producing a silicon carbide single crystal.

The present invention also provides
(10) The method for producing a silicon carbide single crystal according to (9) above, wherein the pressure of the atmospheric gas surrounding the growth crucible is set to 6.65 × 10 ^{3 to} 2.0 × 10 ⁴ Pa. .

The present invention also provides
(11) The method for producing a silicon carbide single crystal as described in (9) to (10) above, wherein the growth rate of the silicon carbide single crystal is 1 mm / hour or more.

The present invention also provides
(12) Silicon carbide produced by the method for producing a silicon carbide single crystal according to any one of (1) to (11) above, wherein the micropipe density is 10,000 pieces / cm ² or less. Single crystal.

The present invention also provides
(13) A low temperature part and a high temperature part are provided in a growth crucible made of graphite, a seed crystal substrate made of a silicon carbide single crystal is installed in the low temperature part of the growth crucible, a silicon carbide raw material is installed in the high temperature part, and silicon carbide In a silicon carbide single crystal manufacturing apparatus in which a sublimation gas sublimated from a raw material is deposited on a seed crystal substrate to grow a silicon carbide single crystal, a growth crucible is installed in the outer crucible, and an external space between the growth crucible and the outer crucible. An apparatus for producing a silicon carbide single crystal, characterized in that a supply means for continuously supplying a silicon raw material from is provided.

The present invention also provides
(14) Production of a silicon carbide single crystal as described in (13) above, wherein a supply means for supplying a solid silicon raw material at a rate of 0.5 to 20 mg / sec is provided by a quantitative supply device. Device.

The present invention also provides
(15) The production of a silicon carbide single crystal as described in (13) or (14) above, wherein a space is provided between the seed base on which the seed crystal substrate of the growth crucible is mounted and the cover plate. Device.

According to the method and apparatus for manufacturing a silicon carbide single crystal according to the present invention, crystal defects in the obtained silicon carbide single crystal can be reduced. For example, the micropipe density in a silicon carbide single crystal grown using the present invention can be 10,000 pieces / cm ² or less. Furthermore, the growth rate, which was limited by the conventional sublimation method, can be set to 1.0 mm / hour or more while maintaining good crystal quality, and further to 2.0 mm / hour or more by optimizing the conditions. Production efficiency can be improved.

FIG. 1 shows an example of an apparatus for producing a silicon carbide single crystal according to the present invention. An embodiment of the present invention will be described with reference to FIG. In FIG. 1, 1 is an outer crucible and 2 is a growth crucible. The growth crucible 2 is installed in the outer crucible 1. The growth crucible 2 has a cover plate 3 and a seed base 4. The cover plate 3 may also serve as the seed table 4. The material of the growth crucible 2 is graphite. The material of the outer crucible 1, the cover plate 3 and the seed table 4 is also preferably graphite. When high purity is required for the graphite material, it is preferable to use graphite that has been purified by halogen gas. The lower part in the growth crucible 2 has a size capable of storing a sufficient amount of the silicon carbide raw material 11 during crystal growth.

In the present invention, crystal growth of silicon carbide is performed as follows using the silicon carbide single crystal manufacturing apparatus shown in FIG. First, a seed crystal substrate 5 made of a silicon carbide single crystal is mounted on the lower surface of the seed table 4. For the mounting, a mechanical coupling method, a bonding method by adhesion, or the like can be used. As the seed crystal substrate 5 to be mounted, a seed crystal substrate obtained by processing a single crystal obtained by the Atchison method, the Rayleigh method, the sublimation method, or the method of the present invention into a plate shape can be used. The (0001) plane is generally used as the crystal plane direction of the substrate. A seed crystal substrate processed by shifting the direction of the crystal plane from the (0001) plane can also be used. In addition, a sufficient amount of powdered silicon carbide raw material 11 is placed in the lower part of the growth crucible 2. In order to obtain a silicon carbide single crystal having a high specific resistance for semiconductor use, it is preferable to use a silicon carbide raw material 11 having a high purity such as a purity of 8 nines. By the growth of the silicon carbide single crystal of the present invention, the silicon carbide single crystal 6 grows on the surface of the seed crystal substrate 5 facing downward.

A high frequency induction coil 7 is installed outside the outer crucible 1 as a heating device for heating the outer crucible 1 and the growth crucible 2. This heating apparatus is an apparatus that heats the silicon carbide raw material 11 in the growth crucible 2 to a temperature of, for example, 1900 ° C. or higher at which sublimation gas is generated. The heating device may be a resistance heating type. The outer crucible 1 is covered with a heat insulating material 8 made of, for example, carbon fiber in order to maintain a high temperature state. In order to realize a desired temperature distribution in the growth crucible 2 by using a portion where the silicon carbide raw material 11 is installed as a high temperature portion and a portion where the seed crystal substrate 5 is installed as a low temperature portion, for example, a high frequency induction coil In the heating method according to No. 7, a method can be used in which the high-frequency induction coil 7 is divided into upper and lower parts and the current flowing through each high-frequency induction coil is controlled independently. Alternatively, a method of adjusting the winding density of the high-frequency induction coil 7 in the vertical direction can also be used. As for the temperature of the outer crucible 1, for example, temperature measuring holes 9 are provided in the heat insulating material 8 covering the bottom surface and the cover plate of the outer crucible 1, and the radiation thermometer 10 is used through the temperature measuring holes 9. The temperature of the surface of the crucible 1 can be measured. Based on the temperature measurement result, the temperature distribution of the growth crucible 2 can be brought into a desired state by adjusting the position of the high frequency induction coil 7 and the current flowing through the high frequency induction coil 7.

Here, during the growth of the silicon carbide single crystal, the high temperature portion where the silicon carbide raw material 11 is installed is set to a temperature of 1900 ° C. or more, preferably 2300 ° C. or more, and the low temperature portion where the seed crystal substrate 5 is installed is It is desirable to set in the range of 1500-2500 ° C, preferably in the range of 2000-2400 ° C. However, in order to stably grow the silicon carbide single crystal on the seed crystal substrate, the temperature of the silicon carbide raw material usually needs to be higher by 100 ° C. than the temperature of the seed crystal substrate.

In the growth of the silicon carbide single crystal, by heating the silicon carbide raw material in the growth crucible to 1900 ° C. or higher, preferably 2300 ° C. or higher, the vapor pressure of the sublimation gas from the silicon carbide raw material becomes sufficiently high. The crystal growth rate can be increased. When the temperature of the seed crystal substrate is lower than 1500 ° C., the grown crystal is likely to be mixed with polymorphism or may not grow as a single crystal. Further, when the temperature of the seed crystal substrate is higher than 2500 ° C., various crystal defects are likely to occur, and polymorphism is likely to occur.

In the present invention, the atmospheric gas surrounding the growth crucible 2 is composed of silicon (Si) gas during the growth of the silicon carbide single crystal. In the present invention, the growth crucible 2 is installed in the outer crucible 1, a silicon raw material is continuously supplied from the outside between the growth crucible 2 and the outer crucible 1, and the silicon raw material is inserted between the growth crucible 2 and the outer crucible 1. By continuously growing the silicon carbide single crystal while evaporating the gas, the atmosphere gas surrounding the growth crucible 2 can be composed of silicon gas.

Supplied from the outside with silicon material as follows. In FIG. 1, 21 is a raw material container for continuously supplying the silicon raw material 22 from the outside, 23 is an extrusion-type fixed supply device, and 24 is a vibrator. A silicon raw material 22 is placed in the raw material container 21. The silicon raw material 22 is in a form that can use a quantitative supply device described later. The material of the raw material container 21 may be any material that can be processed into a predetermined shape and does not contain impurities in the silicon raw material 22. For example, a metal such as stainless steel can be used. In FIG. 1, an extrusion type quantitative supply device 23 is attached to the raw material container 21. The fixed amount supply device is provided for the purpose of supplying a fixed amount of silicon raw material 22 between the growth crucible 2 and the outer crucible 1, that is, supplying a predetermined amount of silicon raw material in a predetermined time.

In the present invention, the supply amount of the silicon raw material 22 from the outside is such that the vapor pressure of the silicon gas surrounding the growth crucible in the outer crucible 1 (referred to as “crucible silicon gas pressure”) is in the sublimation gas in the growth crucible 3. The amount is higher than the silicon gas pressure, that is, an amount capable of continuously maintaining an excessive silicon gas state. The silicon gas pressure in the sublimation gas obtained in the present invention is the equilibrium vapor pressure of the silicon component gas in the carbon-silicon carbide mixed system. For example, when the temperature of the silicon carbide raw material in the growth crucible is 2100 ° C., about 61 Pa or more Therefore, the silicon raw material is continuously supplied from the outside so as to maintain the crucible outer peripheral silicon gas pressure at a higher level.

Since the graphite growth crucible is not gas-tight at a high temperature close to 2000 ° C., the silicon gas surrounding the growth crucible permeates through the graphite wall of the growth crucible 2 and diffuses into the growth crucible. Therefore, by making the crucible outer peripheral silicon gas pressure excessive as described above, the silicon gas pressure in the crucible can be continuously maintained in an excess state than the silicon gas pressure in the sublimation gas.

The pressure of the silicon gas generated by evaporation and evaporation of the silicon raw material in the outer crucible is equal to the atmospheric gas pressure in the growth chamber 51, but is gradually exhausted to the outside of the single crystal growth apparatus through the chamber 51. By supplying the silicon raw material into the outer crucible 1 at a rate corresponding to this, an excessive silicon gas state can be maintained in the atmosphere surrounding the growth crucible 2 in the outer crucible 1. In reality, the rate at which the silicon gas is discarded outside the single crystal growth apparatus varies depending on the holding pressure in the growth chamber 51, the diffusion rate of the silicon gas, the shape of the crucible, and the like. It is necessary to determine the supply amount experimentally. The supply amount of a general silicon raw material is preferably set to such an extent that the silicon raw material is supplied into the outer crucible at a rate of 0.5 to 20 mg / second.

The structure of the quantitative supply device is not limited as long as the silicon raw material can be supplied at the above supply amount, and any of a screw feeder, a quantitative extrusion device, a vibration supply device, and the like can be used. As shown in FIG. 1, it is preferable to install a fixed amount supply device equipped with a vibrator 24 for vibrating the raw material container because supply can be performed smoothly. It is preferable to supply the silicon raw material as a solid because the mechanism of the quantitative supply device can be simplified. Although it is possible to quantitatively supply the molten silicon raw material, it is necessary to devise a method for maintaining the molten state, heating the supply path, or quantitatively.

The form of the solid silicon raw material used in the present invention is preferably a powder suitable for quantitative supply. For example, pulverized material, spherical polysilicon or the like may be used. The silicon raw material powder preferably has an average particle size of 0.2 mm or more. If it is less than 0.2 mm, it tends to rise at the time of supply or adhere to the inner wall of the supply introduction pipe 31 and the supply tends to become unstable. On the other hand, the upper limit of the diameter of the silicon raw material is almost determined from the impact on the growth crucible by the supplied silicon raw material and the evaporation efficiency. For example, a powder having a powder diameter exceeding 5 mm cannot be used. The solid silicon raw material is preferably a powder having a diameter of 0.2 to 5 mm. In particular, when the quantitative supply device is an extrusion type, the shape is preferably spherical from the viewpoint of facilitating transfer, and the average particle size is preferably 1 to 2 mm.

In order to supply the silicon raw material 22 from the raw material container 21 into the outer crucible 1, it is connected by a graphite introduction pipe 31. An introduction tube made of quartz glass or silicon carbide can also be used depending on temperature conditions, and an introduction tube made of a metal such as stainless steel can also be used at a sufficiently low temperature. The introduction pipe can also be composed of these composite materials. Further, when there is a discharge from the high frequency induction coil, it is preferable to protect with an insulator (for example, ceramic or quartz glass) in order to prevent it.

The outer crucible 1 incorporating these growth crucibles 2, the high frequency induction coil 7, the introduction pipe 31 and the like are installed in a growth chamber 51 in which the atmosphere can be controlled. In the growth chamber 51, an exhaust device 52 is connected to the gas outlet side, and a gas introduction line 53 via a gas purifier 54 is connected to the gas inlet side. A mass flow controller 55 is installed in the middle of the gas introduction line 53. An inert gas such as argon (Ar) is supplied as an atmospheric gas in the growth chamber 51 from the gas introduction line 53 to the growth chamber 51 during the growth of the silicon carbide single crystal, and is discharged through the exhaust device 52. By adjusting the mass flow controller 55 and the exhaust device 52, the amount of gas introduced into the growth chamber 51 and the amount of exhaust from the growth chamber 51 can be controlled, and the pressure in the growth chamber 51 can be controlled to a predetermined value. .

As shown in FIG. 1, the silicon raw material supplied into the outer crucible 1 evaporates and fills the space between the outer crucible 1 and the growth crucible 2. The place where the silicon raw material between the growth crucible and the outer crucible is charged is not particularly limited because the silicon raw material can be suitably evaporated and evaporated if the temperature at that place is 1900 ° C. or higher. At a temperature of 1900 ° C. or higher, which is the growth temperature of silicon carbide by a general sublimation method, the equilibrium vapor pressure when silicon vaporizes is 2.7 × 10 ⁴ Pa or higher. Part of the silicon gas generated excessively by evaporation of the silicon raw material between the outer crucible 1 and the growth crucible 2 is released into the growth chamber 51 through the introduction pipe 31. Further, since the graphite growth crucible is not gas-tight at a high temperature close to 2000 ° C., the remaining silicon gas in the outer crucible 1 permeates through the graphite wall of the growth crucible 2 and diffuses into the growth crucible. Maintain or increase the silicon gas pressure in the crucible.

The pressure in the growth chamber 51 and the pressure in the outer crucible 1 are equal because they are connected by the introduction pipe 31. The atmosphere gas surrounding the growth crucible 2 in the outer crucible 1 is composed of silicon gas by evaporation of the silicon raw material supplied from the outside. Further, the silicon gas in the outer crucible 1 permeates through the graphite wall of the growth crucible 2 and diffuses into the growth crucible. Therefore, if the thickness of the graphite material of the growth crucible and the temperature distribution of the growth crucible are the same, the silicon gas pressure in the crucible 2 in the growth crucible 2 can be controlled by the pressure in the growth chamber 51. That is, when the pressure in the growth chamber 51 is increased, the silicon gas pressure in the crucible is also increased. However, it is necessary that a silicon raw material sufficient for the crucible outer peripheral silicon gas pressure in the outer crucible 1 to be equal to the holding pressure of the growth chamber is continuously supplied into the outer crucible 1 from the outside.

During the growth of the silicon carbide single crystal, maintaining the silicon gas pressure in the crucible in the growth crucible 2 equal to or higher than the silicon gas pressure in the sublimation gas from the silicon carbide raw material 11 can improve the quality of the silicon carbide single crystal. Desirable for improvement. Therefore, it is desirable to set the pressure in the growth chamber 51 to be high. However, when the pressure in the growth crucible for growing the silicon carbide single crystal is increased, the growth rate of the silicon carbide single crystal due to the diffusion of the sublimation gas decreases. Therefore, it is necessary to set the pressure of the atmospheric gas surrounding the growth crucible in the growth chamber 51 so that the crystallinity and growth rate of the silicon carbide single crystal are optimized.

The pressure of the atmospheric gas surrounding the growth crucible when growing the silicon carbide single crystal can be performed within a range from a high pressure reduction to a level slightly higher than normal pressure, that is, 1.33 to 1.33 × 10 ⁵ Pa. is there. In particular, in order to efficiently generate sublimation gas from the silicon carbide raw material, it is preferable to set the pressure to 1.33 × 10 ^{2 to} 4.0 × 10 ⁴ Pa. Furthermore, in order to efficiently perform the single crystal growth, it is preferable that the pressure at the time of growing the silicon carbide single crystal is 6.65 × 10 ^{3 to} 2.0 × 10 ⁴ Pa.

According to the present invention, the growth rate of the silicon carbide single crystal can be increased by setting the pressure of the atmospheric gas surrounding the growth crucible during the growth of the silicon carbide single crystal to 1.33 × 10 ^{2 to} 4.0 × 10 ⁴ Pa. A silicon carbide single crystal having a micropipe density of 10,000 pieces / cm ² or less can be produced at 1 mm / hour or more. Furthermore, by setting the pressure to 6.65 × 10 ^{3 to} 2.0 × 10 ⁴ Pa, the growth rate of silicon carbide can be set to 2 mm / hour or more. Thus, when the growth rate of the silicon carbide single crystal is 1 mm / hour, preferably 2 mm / hour or more, the growth of the silicon carbide single crystal can be carried out efficiently.

In the growth of the silicon carbide single crystal of the present invention, impurity doping of the silicon carbide single crystal can be performed as necessary. For example, it is possible to dope impurities into a silicon carbide single crystal by using a silicon raw material doped with impurities in advance or by supplying a doping element as a gas.

FIG. 2 shows another example of the silicon carbide single crystal manufacturing apparatus according to the present invention. FIG. 2 shows a case where the cover plate 3 also serves as the seed table 4 and the silicon carbide seed crystal substrate 5 is attached to the cover plate 3 in the growth crucible of the silicon carbide single crystal manufacturing apparatus shown in FIG. FIG. Even with such an apparatus, the present invention can be implemented.

(Function)
The mechanism by which the present invention suppresses the occurrence of crystal defects in a silicon carbide single crystal is presumed as follows. In the sublimation gas from the silicon carbide raw material, it is considered that gas components such as unreacted Si, Si ₂ C and SiC ₂ reach a certain equilibrium vapor pressure in addition to silicon carbide (SiC). However, since the graphite growth crucible is not gas-tight at a high temperature close to 2000 ° C., if there is a difference in vapor pressure between the inside and outside of the growth crucible, the gas inside easily passes through the graphite wall of the crucible. In the normal sublimation method, the vapor pressure of the sublimation gas outside the growth crucible is almost zero, so the sublimation gas inside the growth crucible leaks to the outside, and the vapor pressure tends to be lower than the equilibrium vapor pressure. is there.

In the crystal growth of compound semiconductors, in order to keep the stoichiometric composition (so-called stoichiometry) of the constituent elements of the crystal constant, it is necessary to keep the vapor pressure of the constituent elements having a high dissociation pressure high during the crystal growth. It is known to be effective. If crystal growth is performed with the vapor pressures of the constituent elements being equal, elements with high dissociation pressure will have a low rate of incorporation into the solid during crystal growth, generating vacancies in the crystal and the accompanying small lattices. There is a high possibility that distortion occurs and induces dislocations and stacking faults in the growing crystal. In single crystal growth of silicon carbide, silicon corresponds to a constituent element having a high separation pressure.

In the present invention, since the atmosphere gas surrounding the growth crucible is composed of silicon gas, contrary to the case of the normal sublimation method, silicon gas having a high dissociation pressure diffuses from outside the growth crucible into the growth crucible through the growth crucible wall. Thus, the vapor pressure of the silicon gas in the growth crucible (silicon gas pressure in the crucible) tends to be equal to or more excessive than the silicon gas pressure in the sublimation gas. For this reason, it is thought that generation | occurrence | production of the crystal defect accompanying the growth of the silicon carbide single crystal by the conventional sublimation method can be suppressed significantly.

In Example 1, a silicon carbide single crystal was grown using the silicon carbide single crystal manufacturing apparatus shown in FIG. First, the center part of the growth crucible bottom side surface of a seed crucible seed base (made of graphite, thickness 9 mm) formed from a seed crystal substrate obtained by processing a 6H-SiC single crystal having a (0001) plane to a diameter of 40 mm and a thickness of 1.0 mm It was attached by gluing. The growth crucible is a bottomed cylinder with an inner diameter of 52 mm and a height of 116 mm, and the material is graphite. A silicon carbide powder raw material (about 172 g) was placed from the bottom bottom of the growth crucible to a height of about 52 mm. Further, a seed stand was attached so that the lower end surface of the seed crystal was positioned 32 m above it. The growing crucible was placed in the center inside the outer crucible. The outer crucible is a cylinder with a bottom with an inner diameter of 75 mm and a height of 157 mm, and the material is graphite. A silicon raw material introduction pipe is attached to the upper cover of the outer crucible, and its inner diameter is 5 mm. As the silicon raw material, 100 g of high-purity spherical polysilicon for semiconductor (purity 8 nines, average particle size 1.5 mm) was put in a 100 g raw material container. The silicon raw material was supplied from the raw material container between the outer crucible and the growth crucible through a graphite introduction pipe using a vibration type quantitative supply device.

The growth crucible and the introduction tube were installed in a growth chamber that can be depressurized. After reducing the pressure in the growth chamber to 1.33 × 10 ⁻¹ Pa, argon gas was introduced to atmospheric pressure to replace the growth atmosphere. Next, the temperature of the outer crucible was raised to about 2400 ° C. in about 30 minutes, and a heat treatment was performed to remove gas adhering to the crucible and the like. Next, while maintaining the temperature of the lower part of the outer crucible at about 2440 ° C. and the temperature of the upper part of the outer crucible at 1900 ° C., the argon atmosphere is reduced to 2.7 × 10 ⁴ Pa while introducing argon into the growth chamber. Then, the silicon raw material was continuously supplied between the growth crucible and the outer crucible at a supply rate of 0.12 g / min, and crystal growth was performed for 5 hours while evaporating.

After the completion of growth, the growth crucible was released. A single crystal was grown on the seed crystal substrate of the seed base of the growth crucible. The grown silicon carbide single crystal had a diameter of about 50 mm at the tip and a grown length of 7.0 mm.

Next, the silicon carbide powder raw material in the growth crucible was newly replaced, and a silicon carbide single crystal was again grown on the grown crystal. Settings such as temperature and pressure used for growth are the same as for the first growth. Crystal growth was performed again for 5 hours.

】 After the second growth, the growth crucible was released again. The silicon carbide single crystal grown in the second growth had a diameter of about 50 mm at the tip and a grown length of 6.0 mm. The grown single crystal was cut along the growth direction, the cross section was polished by polishing and observed with a microscope. As a result, there was no inclusion in the grown single crystal. Further, from the peak position by Raman spectroscopic measurement, it was confirmed that the grown crystal was 6H silicon carbide and was a single crystal having no other polymorphic contamination.

In addition, when the single crystal was cut perpendicularly to the growth direction and the cross section was observed with a microscope, the density of inherent defects called micropipes that accompany silicon carbide growth was about 10 ⁵ / cm ^{2 in} the seed crystal. In the single crystal at the time of growing 5 mm from the seed crystal, it was about 10 ³ pieces / cm ² and decreased to about 1/100. Furthermore, it was observed that the density of the micropipes decreased as the single crystal grew.

(Comparative Example 1)
In Comparative Example 1, a silicon carbide single crystal was grown using the apparatus shown in FIG. In order to match the temperature conditions and the like, the same crucible and seed crystal as in Example 1 were used, and the temperature and pressure were set in the same manner as in Example 1. However, the silicon raw material was not supplied from the outside even after maintaining the temperature at the growth temperature and then reducing the argon atmosphere to 2.7 × 10 ⁴ Pa. The crystal growth time was also 5 hours as in Example 1.

After the completion of growth, the growth crucible was released. Polycrystals were grown over the entire surface of the seed crystal substrate of the growth base of the crucible. The grown polycrystalline silicon carbide had a diameter of about 50 mm at the tip and a grown length of 6.5 mm. As a result of cutting along the growth direction of the grown crystal, polishing the cross section by polishing and observing under a microscope, it was found that polycrystallization occurred from directly above the seed crystal substrate.

Also in Example 2, the silicon carbide single crystal was grown using the apparatus shown in FIG. The same crucible and seed crystal as in Example 1 were used. The growth process was the same as in Example 1. However, the temperature at the lower part of the outer crucible during the growth was maintained at about 2480 ° C., the temperature at the upper part of the outer crucible was maintained at 1980 ° C., and the argon atmosphere in the growth chamber was maintained at 1.5 × 10 ⁴ Pa during the growth. Crystal growth was performed for 5 hours while dropping the silicon raw material in the same manner as in Example 1.

The grown silicon carbide single crystal had a diameter of about 50 mm at the tip and a grown length of 10.5 mm.

Next, the silicon carbide powder raw material in the growth crucible was newly replaced, and a silicon carbide single crystal was again grown on the grown crystal. Settings such as temperature and pressure used for growth are the same as for the first growth. Crystal growth was performed again for 5 hours.

】 After the second growth, the growth crucible was released again. The silicon carbide single crystal grown by the second growth had a diameter of about 50 mm at the tip and a grown length of 10.2 mm. The grown single crystal was cut along the growth direction, the cross section was polished by polishing and observed with a microscope. As a result, there was no inclusion in the grown single crystal. Further, from the peak position by Raman spectroscopic measurement, it was confirmed that the grown crystal was 6H silicon carbide and was a single crystal having no other polymorphic contamination.

Further, the single crystal was cut perpendicularly to the growth direction and the cross section was observed with a microscope, and the density of the micropipe was confirmed to be about 15 / cm ² in the single crystal at the time of growing 15 mm from the seed crystal. .

In the growth of a silicon carbide single crystal by the sublimation method, the fluctuation of the components of the sublimation gas is suppressed by controlling the atmospheric gas, and a large-diameter silicon carbide single crystal with few crystal defects can be stably grown at a high growth rate. A method of growing on a seed crystal substrate can be provided.

It is a figure which shows an example of the manufacturing apparatus of the silicon carbide single crystal which concerns on this invention. It is a figure which shows another example of the manufacturing apparatus of the silicon carbide single crystal which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer crucible 2 Growing crucible 3 Cover plate 4 Seed base 5 Silicon carbide seed crystal substrate 6 Grown silicon carbide single crystal 7 High frequency induction coil 8 Heat insulating material 9 Temperature measuring hole 10 Radiation thermometer 11 Silicon carbide raw material 21 Raw material container 22 Silicon raw material DESCRIPTION OF SYMBOLS 23 Extrusion type | formula quantitative supply apparatus 24 Vibrator 31 Introducing pipe 51 Growth chamber 52 Exhaust apparatus 53 Gas introduction line 54 Gas refiner 55 Mass flow controller

Claims (15)

A low temperature portion and a high temperature portion are provided in a growth crucible made of graphite, a seed crystal substrate made of a silicon carbide (SiC) single crystal is placed in the low temperature portion of the growth crucible, a silicon carbide raw material is placed in the high temperature portion, and silicon carbide In a method for producing a silicon carbide single crystal in which a sublimation gas sublimated from a raw material is deposited on a seed crystal substrate to grow a silicon carbide single crystal, the atmosphere gas surrounding the growth crucible is composed of silicon (Si) gas. A method for producing a silicon carbide single crystal. The vapor pressure of silicon gas in the growth crucible (referred to as “silicon gas pressure in crucible”) is equal to or higher than the equilibrium vapor pressure of silicon gas in the sublimation gas of the silicon carbide raw material (referred to as “silicon gas pressure in sublimation gas”). The method for producing a silicon carbide single crystal according to claim 1, wherein the silicon carbide single crystal is grown while maintaining the temperature. A growth crucible is installed in the outer crucible, a silicon raw material is continuously supplied from the outside between the growth crucible and the outer crucible, and a silicon carbide single crystal is grown while the silicon raw material is evaporated between the growth crucible and the outer crucible. The method for producing a silicon carbide single crystal according to claim 1 or 2, wherein: A low temperature portion and a high temperature portion are provided in a growth crucible made of graphite, a seed crystal substrate made of a silicon carbide (SiC) single crystal is placed in the low temperature portion of the growth crucible, a silicon carbide raw material is placed in the high temperature portion, and silicon carbide In a method for producing a silicon carbide single crystal in which a sublimation gas sublimated from a raw material is deposited on a seed crystal substrate to grow a silicon carbide single crystal, a growth crucible is installed in the outer crucible, and an external portion is provided between the growth crucible and the outer crucible. A method for producing a silicon carbide single crystal, comprising continuously supplying a silicon raw material from, and growing the silicon carbide single crystal while evaporating the silicon raw material between a growth crucible and an outer crucible. The method for producing a silicon carbide single crystal according to claim 4, wherein a solid silicon raw material is supplied from the outside. 6. The method for producing a silicon carbide single crystal according to claim 5, wherein the solid silicon raw material is a powder having a diameter of 0.2 to 5 mm. The method for producing a silicon carbide single crystal according to any one of claims 4 to 6, wherein the silicon raw material is supplied at a rate of 0.5 to 20 mg / sec. The method for producing a silicon carbide single crystal according to any one of claims 4 to 7, wherein a temperature at a place where a silicon raw material is introduced between the growth crucible and the outer crucible is 1900 ° C or higher. The silicon carbide single crystal production according to any one of claims 4 to 8, wherein the pressure of the atmospheric gas surrounding the growth crucible is set to 1.33 x 10 ^{2 to} 4.0 x 10 ⁴ Pa. Method. The method for producing a silicon carbide single crystal according to claim 9, wherein the pressure of the atmospheric gas surrounding the growth crucible is set to 6.65 × 10 ^{3 to} 2.0 × 10 ⁴ Pa. The method for producing a silicon carbide single crystal according to claim 9 or 10, wherein the growth rate of the silicon carbide single crystal is 1 mm / hour or more. A silicon carbide single crystal produced by the method for producing a silicon carbide single crystal according to any one of claims 1 to 11, wherein the micropipe density is 10,000 pieces / cm ² or less. A growth crucible made of graphite is provided with a low temperature portion and a high temperature portion, a seed crystal substrate made of silicon carbide single crystal is placed in the low temperature portion of the growth crucible, a silicon carbide raw material is placed in the high temperature portion, and sublimation from the silicon carbide raw material is performed. In a silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal by depositing the sublimation gas on a seed crystal substrate, a growth crucible is installed in the outer crucible, and the silicon raw material is externally provided between the growth crucible and the outer crucible. An apparatus for producing a silicon carbide single crystal, characterized in that a supply means for continuously supplying is provided. 14. The apparatus for producing a silicon carbide single crystal according to claim 13, wherein a supply means for supplying a solid silicon raw material at a rate of 0.5 to 20 mg / second is provided by a constant supply device. 15. The apparatus for producing a silicon carbide single crystal according to claim 13, wherein a space is provided between a seed base on which a seed crystal substrate of a growth crucible is mounted and a cover plate.

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