JP2009102187A - Crucible for growth of silicon carbide single crystal, method of manufacturing silicon carbide single crystal using the same, and silicon carbide single crystal ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crucible for the growth of a SiC single crystal for producing a high quality SiC single crystal wafer which is reduced in transfer defect and has a large diameter, with high reproducibility. <P>SOLUTION: In an apparatus for the growth of the SiC single crystal by a sublimation re-crystallization method, the whole of the crucible is composed of a 2 or more kinds of materials each having different thermal expansion coefficient and a crucible component material of a seed crystal holding part 4 to which the SiC seed crystal 1 is attached has thermal expansion coefficient substantially smaller than that of another part. At least one kind of a component material of the crucible is made from graphite and the thermal expansion coefficient of the seed crystal holding part 4 at 2,000°C is 5.0-5.5×10<SP>-6</SP>/°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crucible for growing a silicon carbide single crystal, a method for producing a silicon carbide single crystal using the same, and a silicon carbide single crystal ingot, and in particular, a high-quality and large-sized silicon carbide single crystal that serves as a substrate wafer of an electronic device. The present invention relates to a crucible for growing a silicon carbide single crystal suitable for obtaining an ingot, a method for producing a silicon carbide single crystal using the crucible, and a silicon carbide single crystal ingot.

  Silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material because of its physical and chemical properties such as excellent heat resistance and mechanical strength, and resistance to radiation. In recent years, the demand for SiC single crystal wafers as substrate wafers for short wavelength optical devices from blue to ultraviolet, high frequency / high voltage electronic devices, and the like has been increasing. However, a crystal growth technique that can stably supply a high-quality SiC single crystal having a large area on an industrial scale has not yet been established. Therefore, practical use of SiC has been hindered despite the semiconductor material having many advantages and possibilities as described above.

  Conventionally, on a laboratory scale scale, for example, a SiC single crystal was grown by a sublimation recrystallization method (Rayleigh method) to obtain a SiC single crystal of a size capable of producing a semiconductor element. However, with this method, the area of the obtained single crystal is small, and it is difficult to control its size and shape with high accuracy. Also, it is not easy to control the crystal polymorphism and impurity carrier concentration of SiC. In addition, a cubic SiC single crystal is grown by heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using chemical vapor deposition (CVD). In this method, a single crystal having a large area can be obtained. However, since the lattice mismatch with the substrate is about 20%, crystal defects such as stacking faults are easily generated, and it is difficult to obtain a high-quality SiC single crystal.

  In order to solve these problems, an improved Rayleigh method in which sublimation recrystallization is performed using a SiC single crystal as a seed crystal has been proposed (Non-patent Document 1) and has been implemented in many research institutions. In this method, since the seed crystal is used, the nucleation process of the crystal can be controlled, and the growth rate of the crystal can be controlled with good reproducibility by controlling the atmospheric pressure to about 100 Pa to 15 kPa with an inert gas.

  The principle of the improved Rayleigh method will be described with reference to FIG. The SiC single crystal serving as a seed crystal and the SiC crystal powder serving as a raw material are stored in a crucible (usually graphite) and heated to 2000 to 2400 ° C. in an inert gas atmosphere such as argon (133 to 13.3 kPa). At this time, the temperature gradient is set so that the seed crystal has a slightly lower temperature than the raw material powder. After sublimation, the raw material is diffused and transported in the direction of the seed crystal by a concentration gradient (formed by a temperature gradient). Single crystal growth is realized by recrystallization of the source gas that has arrived at the seed crystal on the seed crystal. At this time, the resistivity of the crystal can be controlled by adding an impurity gas in an atmosphere made of an inert gas or mixing an impurity element or a compound thereof in the SiC raw material powder. Typical substitutional impurities in SiC single crystals include nitrogen (n-type), boron (p-type), and aluminum (p-type). By using the modified Rayleigh method, it is possible to grow a SiC single crystal while controlling the crystal polymorphism (6H type, 4H type, 15R type, etc.), shape, carrier type and concentration of the SiC single crystal.

Currently, SiC single crystal wafers having a diameter of 2 inches (50.8 mm) to 3 inches (76.2 mm) are cut out from the SiC single crystals produced by the above-described improved Rayleigh method, and are used for epitaxial thin film growth and device fabrication. However, these SiC single crystal wafers contain 10 ⁴ cm ⁻² or more of dislocation defects that have a significant effect on device manufacturing yield and the like, which hinders high yield device manufacturing.

As described above, the SiC single crystal produced by the conventional technique contained a large amount of dislocation defects. It has been reported that these defects occur due to thermal stress of the crystal during crystal growth. Patent Document 1 describes that, during crystal growth, a growing SiC single crystal and a crucible member come into contact with each other to generate mechanical stress in the grown crystal, resulting in dislocation defects. In Patent Document 1, in order to prevent this contact, a guide member structure is installed in the crucible, and a gap of a specific size is provided between the guide member, the crucible and the seed crystal, and this gap is sublimated gas from the raw material. Flows to prevent contact between the grown crystal and the crucible member.
JP 2007-77017 A Yu. M. Tairov and VF Tsvetkov, Journal of Crystal Growth, Vol.52 (1981) pp.146-150

  Conventionally, with respect to preventing contact between the grown crystal and the crucible member, the object has been achieved by introducing various internal structures into the crucible, as in the method described in Patent Document 1. However, when a complicated internal structure as described in Patent Document 1 is provided in the crucible, the design freedom of the crucible is greatly impaired, and as a result, the size of the grown crystal is increased in size and quality. The crucible process design will be severely limited. Moreover, the complicated crucible internal structure caused an increase in the cost of the entire crucible and caused an increase in the cost of the manufactured SiC single crystal ingot.

  The present invention has been made in view of the above circumstances, and without using a complicated crucible internal structure, to minimize the stress acting on the growth crystal, to produce a high-quality SiC single crystal ingot at a low cost, The present invention provides a crucible for growing a SiC single crystal, a method for producing a SiC single crystal using the same, a SiC single crystal ingot, and the like.

The present invention
(1) A crucible used in a method for producing a SiC single crystal including a step of storing a seed crystal in a crucible and growing a silicon carbide (SiC) single crystal on the seed crystal by a sublimation recrystallization method. A SiC single crystal growth crucible, characterized in that the seed crystal holding part for holding silicon is made of a material having a thermal expansion coefficient of 4.5 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C. at 2000 ° C. ,
(2) The SiC single crystal growth according to (1), wherein the seed crystal holding part is composed of a material having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C. at 2000 ° C. Crucible for
(3) The SiC single crystal growth crucible according to any one of (1) and (2), wherein the constituent material of the seed crystal holding part is graphite,
(4) All the constituent materials of the crucible are graphite (1) or the crucible for growing a single crystal of crystal according to any one of (2),
(5) A crucible used in a method for producing a SiC single crystal including a step of storing a seed crystal in a crucible and growing the SiC single crystal on the seed crystal by a sublimation recrystallization method, wherein the entire crucible is thermally expanded. SiC single crystal growth characterized in that the material constituting the crucible of the seed crystal holding part, which is composed of two or more types of materials having different coefficients, has a smaller thermal expansion coefficient than other parts. Crucible for
(6) The SiC single crystal growth crucible according to (5), wherein a thermal expansion coefficient at 2000 ° C. of the crucible constituent material of the seed crystal holding part is 4.5 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. ,
(7) The SiC single crystal growth crucible according to (5), wherein a thermal expansion coefficient at 2000 ° C. of the crucible constituent material of the seed crystal holding portion is 5.0 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. ,
(8) A crucible for growing a SiC single crystal according to any one of (5) to (7), wherein at least one kind of constituent material of the crucible is graphite,
(9) The SiC single crystal growth crucible according to any one of claims (5) to (7), wherein all the constituent materials of the crucible are graphite.
(10) A crucible used in a method for producing a silicon carbide single crystal including a step of storing a seed crystal in a crucible and growing a silicon carbide single crystal on the seed crystal by a sublimation recrystallization method, wherein the entire crucible is The crucible-constituting material of the seed crystal holding part, which is composed of two or more materials having different thermal expansion coefficients and holds the seed crystal, has a substantially smaller thermal expansion coefficient than other parts, and the seed crystal holding part has The constituent material of the portion that is separated from the portion that is in contact with the seed crystal and the other portion and that is not in contact with the seed crystal of the seed crystal holding portion is more than the constituent material of the portion that is in contact with the seed crystal A crucible for growing a silicon carbide single crystal, characterized by having a small thermal expansion coefficient,
(11) The thermal expansion coefficient at 2000 ° C. of the constituent material in contact with the seed crystal of the seed crystal holding part is 4.5 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C. The crucible for SiC single crystal growth described,
(12) The constituent material of the portion in contact with the seed crystal of the seed crystal holding part has a thermal expansion coefficient at 2000 ° C. of 5.0 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less (10) The crucible for SiC single crystal growth described,
(13) The SiC single crystal growing crucible according to any one of (10) to (12), wherein at least one kind of constituent material of the crucible is graphite,
(14) The SiC single crystal growing crucible according to any one of (10) to (12), wherein all the constituent materials of the crucible are graphite.
(15) A method for producing a SiC single crystal comprising the steps of storing a seed crystal in a crucible and growing the SiC single crystal on the seed crystal by a sublimation recrystallization method, wherein the crucibles (1) to (14 ) A method for producing a SiC single crystal, characterized by using the crucible according to any one of
(16) A SiC single crystal ingot obtained by the production method according to (15), wherein the diameter of the ingot is 50 mm or more and 300 mm or less,
(17) The SiC single crystal ingot according to (16), wherein the basal plane dislocation density in the ingot is 1 × 10 ⁴ cm ⁻² or less,
(18) The SiC single crystal ingot according to (16), wherein the basal plane dislocation density in the ingot is 5 × 10 ³ cm ⁻² or less,
(19) SiC single crystal substrate obtained by cutting and polishing the SiC single crystal ingot according to any one of (16) to (18),
(20) A SiC epitaxial wafer obtained by epitaxially growing a SiC thin film on the SiC single crystal substrate according to (19),
(21) A thin film epitaxial wafer formed by epitaxially growing gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN) or a mixed crystal thereof on the SiC single crystal substrate according to (19),
It is.

  If the crucible for growing SiC single crystal of the present invention is used, a high-quality SiC single crystal ingot with few dislocation defects can be grown with good reproducibility and low cost by the improved Rayleigh method. By using a wafer and an epitaxial wafer cut out from such a SiC single crystal, it is possible to produce a high-frequency / high-voltage electronic device having excellent electrical characteristics and a short wavelength region light-emitting element having excellent optical characteristics.

  In the method for producing a SiC single crystal of the present invention, the crucible constituent material of the seed crystal holding portion that is made of two or more kinds of materials having different thermal expansion coefficients as the SiC single crystal growing crucible and that holds the seed crystal is substantially In particular, by having a smaller coefficient of thermal expansion than the other parts, the stress applied to the grown crystal during crystal growth can be minimized, and as a result, a SiC single crystal ingot and a wafer with few dislocation defects can be obtained.

  The effect of the present invention will be described with reference to FIG. The SiC single crystal growth crucible of the present invention is composed of two or more kinds of materials having different coefficients of thermal expansion, as schematically shown in FIG. 2 (a). The crucible constituent material of the seed crystal holding part has a substantially smaller thermal expansion coefficient than the other parts. Here, the SiC single crystal growth crucible of the present invention shown in FIG. 2 is composed of a seed crystal holding part that also serves as a lid and a crucible body, and when this crucible is used for SiC single crystal growth, FIG. As shown in (b), during crystal growth (crystal growth temperature: 2000 ° C. or higher), the difference in thermal expansion coefficient between the seed crystal holding part of the crucible and the other part (crucible body), the crucible body The inner wall has a shape that expands in the crystal growth direction. This is because the thermal expansion coefficient of the crucible body is larger than the thermal expansion coefficient of the constituent material of the seed crystal holding part, so that the crucible body tends to expand more at a high temperature than the seed crystal holding part. is there. The reason why the degree of expansion increases along the crystal growth direction is that a temperature gradient is applied. As shown in Fig. 2 (b), when the space in which the SiC single crystal can grow (crystal growth space) expands in the direction of crystal growth, contact between the grown crystal and the crucible body during crystal growth As a result, the stress applied to the grown crystal is minimized.

  When the seed crystal holding part and the crucible body are fixed by some mechanism, the expansion of the crystal growth space is further promoted, and the contact between the grown crystal and the crucible body is further suppressed. This is because the thermal expansion on the side close to the seed crystal holding part of the crucible body is suppressed by the seed crystal holding part having a small thermal expansion coefficient.

  In the above description, the case where the crucible for growing a SiC single crystal is composed of two types of materials having different thermal expansion coefficients has been described. If the same effect is obtained, the crucible has three or more types having different thermal expansion coefficients. There is no problem even if it is composed of the above materials. However, also in this case, it is necessary that the seed crystal holding part is made of a material having a substantially smaller thermal expansion coefficient than other parts. In the present invention, the crucible constituent material of the seed crystal holding part has a substantially smaller thermal expansion coefficient than other parts, for example, the constituent material of the seed crystal holding part in a part other than the seed crystal holding part Even when a material having a thermal expansion coefficient equal to or lower than that is partially used, if the same effect as that of the present invention can be obtained, in such a case, “the material constituting the crucible of the seed crystal holding portion may be different. "Having a smaller coefficient of thermal expansion than the portion of".

As described above, in the present invention, by using two or more kinds of materials having different thermal expansion coefficients as a crucible for growing a SiC single crystal, the growth crystal and the crucible member can be formed without using a complicated crucible internal structure. The contact can be suppressed and the stress exerted on the grown crystal can be minimized. By minimizing the stress applied to the grown crystal during crystal growth, dislocation defects in the SiC single crystal, particularly basal plane dislocations, can be reduced. It has been reported that basal plane dislocations deteriorate the reliability of diodes and transistors fabricated using SiC single crystals, and reduction is desired. In the SiC single crystal manufactured using the SiC single crystal growth crucible of the present invention, the basal plane dislocation density is as low as 1 × 10 ⁴ cm ⁻² or less, and further 5 × 10 ³ cm ⁻² or less. Suitable for the manufacture of high SiC devices.

Further, in the present invention, by using a material having a thermal expansion coefficient close to that of the SiC single crystal as the crucible material constituting the seed crystal holding portion, it is possible to further reduce the stress applied to the grown crystal during crystal growth. . This is because a large thermal stress is generated in the seed crystal and the SiC single crystal grown on it when there is a large difference in thermal expansion coefficient between the seed crystal holding part and the SiC single crystal during crystal growth. is there. The thermal expansion coefficient of SiC single crystal has been reported in several papers, and is estimated to be about 4.9 × 10 ^{−6 to} 5.4 × 10 ⁻⁶ / ° C. at 2000 ° C.

As a coefficient of thermal expansion of the material constituting the seed crystal holding part, at 2000 ° C., 4.5 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C., more preferably 5.0 × 10 ⁻⁶ / ° C. to 5.5 × 10 ^-6 / ℃ or less is desirable. When the thermal expansion coefficient at 2000 ° C is less than 4.5 × 10 ^-6 / ° C or more than 5.5 × 10 ^-6 / ° C, the difference in thermal expansion coefficient with the SiC single crystal becomes excessive, and dislocations caused by thermal stress, etc. Occurrence becomes remarkable.

  In another aspect of the present invention, the seed crystal holding part is composed of two or more kinds of materials and is divided into a part (ii) in contact with the seed crystal and a part (i) other than that (FIG. 2 (c) )reference). Materials that have different coefficients of thermal expansion are used for the parts that are in contact with the seed crystal and the other parts, and by this structure, the function that maximizes the difference in coefficient of thermal expansion with the crucible body And the function of minimizing the difference in thermal expansion coefficient from the SiC single crystal can be maintained almost independently. That is, a material having a thermal expansion coefficient substantially equal to that of the SiC single crystal is used for a portion in contact with the seed crystal, while a thermal expansion coefficient with the crucible body is used for a portion not in contact with the seed crystal. A material with a smaller coefficient of thermal expansion can be used so that the difference can be maximized.

Regarding the thermal expansion coefficient at 2000 ° C. of the constituent material of the part (ii) in contact with the seed crystal in the seed crystal holding part, 4.5 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C., preferably It should be 5.0 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. On the other hand, the thermal expansion coefficient of the portion (i) that is not in contact with the seed crystal of the seed crystal holding part is preferably 2.0 × 10 ⁻⁶ / ° C. or more and 6.0 × 10 ⁻⁶ / ° C. or less. If the temperature is less than 2.0 × 10 ^-6 / ° C, the difference in thermal expansion coefficient from the portion (ii) in contact with the seed crystal becomes too large, causing the crucible to unintentionally deform during crystal growth. There is a risk of it. Further, if it exceeds 6.0 × 10 ⁻⁶ / ° C., the difference in thermal expansion coefficient from the crucible body cannot be obtained sufficiently, and the effects of the present invention may not be obtained.

  It is desirable to use a graphite material as a part or all of the constituent material of the crucible. Graphite is the most preferable material as a crucible material for SiC single crystal growth from the viewpoint of its heat resistance, ease of machining, and unit cost of raw materials. Furthermore, in the graphite material, the thermal expansion coefficient can be controlled by controlling the microstructure, and in this sense, it is optimal as the crucible constituent material of the present invention.

In a SiC single crystal, in general, thermal stress is relaxed in the form of basal plane dislocation generation (stress is released). Therefore, when the grown crystal is subjected to high thermal stress during crystal growth, an increase in the basal plane dislocation density in the SiC single crystal is observed. For example, if the grown crystal comes into contact with the crucible during crystal growth, or if the difference in thermal expansion coefficient between the seed crystal holding part and the SiC single crystal is large, 1 × High-density basal plane dislocations exceeding 10 ⁴ cm ^-2 are introduced. On the other hand, in the SiC single crystal manufactured using the crucible of the present invention, such a phenomenon hardly occurs, and as a result, a low basal plane dislocation of 1 × 10 ⁴ cm ⁻² or less or 5 × 10 ³ cm ⁻² or less. Density is realized.

  The crucible for growing a SiC single crystal of the present invention is applied to a SiC single crystal growth method for producing a large-diameter single crystal using a seed crystal, such as an improved Rayleigh method. As shown in FIG. 1, the crucible contains the SiC raw material powder and the seed crystal inside, and is heated to 2000-2400 ° C. in an inert gas atmosphere such as argon. At this time, the temperature gradient is set so that the seed crystal has a slightly lower temperature than the raw material powder. After sublimation, the raw material is diffused and transported in the direction of the seed crystal by this temperature gradient. Single crystal growth is realized by recrystallization of the source gas that has arrived at the seed crystal on the seed crystal.

The SiC single crystal substrate manufactured using the SiC single crystal growth crucible of the present invention has a diameter of 50 mm or more and 300 mm or less, and therefore is industrially established when manufacturing various devices using this substrate. A conventional production line for semiconductor (Si, GaAs, etc.) substrates can be used, which is suitable for mass production. In addition, the SiC single crystal substrate produced according to the present invention has a basal plane dislocation density as low as 1 × 10 ⁴ cm ⁻² or less, which causes problems such as deterioration of device characteristics caused by basal plane dislocations. Less likely to occur than conventional ones. Furthermore, an SiC single crystal epitaxial wafer produced by growing an epitaxial thin film on this SiC single crystal substrate by a CVD method or the like, or GaN, AlN, InN, and mixed crystal thin film epitaxial wafers of the SiC single crystal substrate are used. Since the dislocation density of the crystal wafer is small, the crystal wafer has good characteristics (surface morphology, withstand voltage, etc. of the epitaxial thin film).

(Example 1)
Examples of the present invention will be described below. FIG. 3 shows an example of an apparatus for growing a SiC single crystal by a modified Rayleigh method using a seed crystal, which is a manufacturing apparatus used in the present invention. First, this single crystal growth apparatus will be briefly described. Crystal growth is performed by sublimating and recrystallizing SiC powder 2 as a raw material on SiC single crystal 1 used as a seed crystal. Seed crystal SiC single crystal 1 is attached to the inner surface of seed crystal holding portion 4 (usually made of graphite). The raw material SiC powder 2 is filled in the crucible body 3 (usually made of graphite). The crucible body 3 is placed inside a double quartz tube 5 by a graphite support rod 6 after a seed crystal holding part 4 to which a seed crystal is attached is arranged on the upper surface. A heat insulating felt 7 (usually made of graphite) for heat shielding is installed around the crucible body 3. The double quartz tube 5 can be highly evacuated (10 ⁻³ Pa or less) by the evacuation device 13, and the internal atmosphere can be pressure controlled by Ar gas. In addition, a work coil 8 is installed on the outer periphery of the double quartz tube 5 to heat the crucible body 3 and the seed crystal holding part 4 by flowing a high-frequency current, thereby heating the raw material and the seed crystal to a desired temperature. can do. The crucible temperature is measured using a two-color thermometer by providing an optical path having a diameter of 2 to 4 mm at the center of the felt covering the crucible main body and the seed crystal holding part, and extracting light from the crucible main body and the seed crystal holding part. The temperature of the lower surface of the crucible body is the raw material temperature, and the temperature of the upper surface of the seed crystal holding part is the seed crystal temperature.

Next, an example of manufacturing a SiC single crystal using this crystal growth apparatus will be described. First, a 4H type SiC single crystal wafer having a (000-1) C face with a diameter of 50 mm was prepared as a seed crystal, and attached to the inner surface of the graphite seed crystal holding part 4. In producing the seed crystal holding part 4, isotropic graphite having a thermal expansion coefficient of 2.6 × 10 ⁻⁶ / ° C. near normal temperature and 4.7 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. In the production of the graphite crucible body 3, isotropic graphite having a thermal expansion coefficient of 3.5 × 10 ⁻⁶ / ° C. near normal temperature and 5.8 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. The inner diameter of the graphite crucible main body 3 was 51.5 mm, and the raw material (SiC powder) 2 was filled inside. Next, the graphite crucible main body 3 filled with the raw material is closed with a seed crystal holding part 4 to which a seed crystal is attached, covered with a graphite felt 7, and then placed on a graphite support rod 6, and a double quartz tube 5 Installed inside. Then, after evacuating the inside of the quartz tube, current was passed through the work coil to raise the raw material temperature to 2000 ° C. Thereafter, Ar gas containing 10% nitrogen was introduced as an atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51.47 mm, and the height was about 16 mm. Moreover, when the side surface of the taken-out grown crystal was observed with the naked eye, it became a glossy overview, and there was no evidence of the grown crystal contacting the crucible inner wall during crystal growth.

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Also, for the purpose of evaluating the basal plane dislocation density existing in the grown crystal, the grown (single crystal) ingot was cut and polished to take out the (0001) Si plane wafer that was turned off by 8 ° in the [11-20] direction. It was. Thereafter, the wafer surface was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to the basal plane dislocation was examined with a microscope. As a result, an average value of 0.8 × 10 ⁴ cm ⁻² was obtained on the entire wafer surface.

Furthermore, using the above SiC single crystal wafer as a substrate, an SiC thin film was epitaxially grown. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 ° C., the flow rates of silane (SiH ₄ ), propane (C ₃ H ₈ ), and hydrogen (H ₂ ) are 5.0 × 10 ⁻⁹ m ^{3 /} sec and 3.3 × 10 respectively. ^-9 m ³ / sec, 5.0 × 10 ^-5 m ³ / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours and the film thickness was about 5 μm.

  After the epitaxial thin film was grown, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. I found it growing up.

Similarly, a (0001) Si surface SiC single crystal wafer with an off angle of 0 ° was cut out from the SiC single crystal and mirror-polished, and then a GaN thin film was formed thereon by metal organic chemical vapor deposition (MOCVD). Epitaxially grown. Growth conditions are: growth temperature 1050 ° C., trimethylgallium (TMG), ammonia (NH ₃ ), silane (SiH ₄ ), 54 × 10 ⁻⁶ mol / min, 4 liter / min, 22 × 10 ⁻¹¹ mol / min, respectively. Min shed. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type GaN was grown to a thickness of 3 μm.

  In order to examine the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. It was found that a very flat morphology was obtained over the entire surface of the wafer, and a high-quality GaN thin film was formed over the entire surface.

(Example 2)
As in Example 1, a 4H-type SiC single crystal wafer having a (000-1) C face with a diameter of 50 mm was produced as a seed crystal. Thereafter, this SiC single crystal wafer was attached to the inner surface of the graphite seed crystal holding unit 4 as a seed crystal. In producing the seed crystal holding part 4, isotropic graphite having a thermal expansion coefficient of 2.9 × 10 ⁻⁶ / ° C. near normal temperature and 5.2 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. In the production of the graphite crucible body 3, isotropic graphite having a thermal expansion coefficient of 3.5 × 10 ⁻⁶ / ° C. near normal temperature and 5.8 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. The inner diameter of the graphite crucible body 3 was 51.5 mm, and the raw material 2 was filled in the inside. Next, the graphite crucible main body 3 filled with the raw material is closed with a seed crystal holding part 4 to which a seed crystal is attached, covered with a graphite felt 7, and then placed on a graphite support rod 6, and a double quartz tube 5 Installed inside. Then, after evacuating the inside of the quartz tube, a current was passed through the work coil to raise the raw material temperature to 2000 ° C. Thereafter, Ar gas containing 10% nitrogen was introduced as an atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 0.75 mm / hour. The diameter of the obtained crystal was 51.48 mm, and the height was about 15 mm. Moreover, when the side surface of the taken-out grown crystal was observed with the naked eye, it became a glossy overview, and there was no evidence of the grown crystal contacting the crucible inner wall during crystal growth.

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Also, for the purpose of evaluating the basal plane dislocation density existing in the grown crystal, the grown (single crystal) ingot was cut and polished to take out the (0001) Si plane wafer that was turned off by 8 ° in the [11-20] direction. It was. Thereafter, the wafer surface was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to the basal plane dislocation was examined with a microscope. As a result, an average value of 3.8 × 10 ³ cm ⁻² was obtained on the entire wafer surface.

  Furthermore, as in Example 1, an SiC thin film and a GaN thin film were formed, but an epitaxial wafer having a good surface morphology was obtained.

(Example 3)
As in Example 1, a 4H-type SiC single crystal wafer having a (000-1) C face with a diameter of 50 mm was produced as a seed crystal. Thereafter, this SiC single crystal wafer was attached to the inner surface of the graphite seed crystal holding unit 4 as a seed crystal. When producing the seed crystal holding part 4, as shown in FIG. 2 (c), the seed crystal holding part 4 is divided into a part (ii) in contact with the seed crystal and a part (i) other than that, and each part has a thermal expansion coefficient. Different materials were used. As for the thermal expansion coefficient, in the part (ii) in contact with the seed crystal, isotropic graphite of 2.9 × 10 ⁻⁶ / ° C. near room temperature and 5.2 × 10 ⁻⁶ / ° C. at 2000 ° C. is used. In the portion (i) that does not come into contact, isotropic graphite of 2.6 × 10 ⁻⁶ / ° C. near normal temperature and 4.7 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. In the production of the graphite crucible body 3, isotropic graphite having a thermal expansion coefficient of 3.5 × 10 ⁻⁶ / ° C. near normal temperature and 5.8 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. The inner diameter of the graphite crucible body 3 was 51.5 mm, and the raw material 2 was filled in the inside. Next, the graphite crucible main body 3 filled with the raw material is closed with a seed crystal holding part 4 to which a seed crystal is attached, covered with a graphite felt 7, and then placed on a graphite support rod 6, and a double quartz tube 5 Installed inside. Then, after evacuating the inside of the quartz tube, a current was passed through the work coil to raise the raw material temperature to 2000 ° C. Thereafter, Ar gas containing 10% nitrogen was introduced as an atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51.48 mm, and the height was about 16 mm. Moreover, when the side surface of the taken-out grown crystal was observed with the naked eye, it became a glossy overview, and there was no evidence of the grown crystal contacting the crucible inner wall during crystal growth.

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Also, for the purpose of evaluating the basal plane dislocation density existing in the grown crystal, the grown (single crystal) ingot was cut and polished to take out the (0001) Si plane wafer that was turned off by 8 ° in the [11-20] direction. It was. Thereafter, the surface of the wafer was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to the basal plane dislocation was examined with a microscope, and an average value of 4.2 × 10 ³ cm ⁻² was obtained on the entire surface of the wafer.

  Furthermore, as in Example 1, an SiC thin film and a GaN thin film were formed, but an epitaxial wafer having a good surface morphology was obtained.

(Comparative example)
First, as in Example 1, a 4H-type SiC single crystal wafer having a (000-1) C face with a diameter of 50 mm was produced as a seed crystal. Thereafter, this SiC single crystal wafer was attached to the inner surface of the graphite seed crystal holding unit 4 as a seed crystal. In producing the seed crystal holding part 4, isotropic graphite having a thermal expansion coefficient of 3.5 × 10 ⁻⁶ / ° C. near normal temperature and 5.8 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. Further, in the production of the graphite crucible body 3, isotropic graphite having the same thermal expansion coefficient of 3.5 × 10 ⁻⁶ / ° C. near normal temperature and 5.8 × 10 ⁻⁶ / ° C. at 2000 ° C. was used. The inner diameter of the graphite crucible body 3 was 51.5 mm, and the raw material 2 was filled in the inside. Next, the graphite crucible main body 3 filled with the raw material is closed with a seed crystal holding part 4 to which a seed crystal is attached, covered with a graphite felt 7, and then placed on a graphite support rod 6, and a double quartz tube 5 Installed inside. Then, after evacuating the inside of the quartz tube, a current was passed through the work coil to raise the raw material temperature to 2000 ° C. Thereafter, Ar gas containing 10% nitrogen was introduced as an atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51.57 mm, and the height was about 16 mm. Further, when the side surface of the taken-out growth crystal was observed with the naked eye, a black layer considered to be graphite adhered to the side surface of the growth crystal at several sites. It was speculated that the black layer was attached because the grown crystal was in contact with the inner wall of the crucible during crystal growth.

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Also, for the purpose of evaluating the basal plane dislocation density existing in the grown crystal, the grown (single crystal) ingot was cut and polished to take out the (0001) Si plane wafer that was turned off by 8 ° in the [11-20] direction. It was. Thereafter, the wafer surface was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to the basal plane dislocation was examined with a microscope. As a result, an average value of 2.3 × 10 ⁴ cm ⁻² was obtained on the entire wafer surface.

Furthermore, SiC was epitaxially grown using the above SiC single crystal wafer as a substrate. The SiC epitaxial film growth conditions, the growth temperature of _{1500 ℃, SiH 4, C 3} H 8, the flow rate of H _2, respectively ^{5.0 × 10 -9 m 3 /sec,3.3×10 -9} m 3 /sec,5.0× 10 ^-5 m ³ / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours and the film thickness was about 5 μm.

  After the growth of the epitaxial thin film, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. As a result, surface defects thought to be caused by basal plane dislocations in the substrate were observed in some regions.

Similarly, a (0001) Si-plane SiC single crystal wafer having an off angle of 0 ° was cut out from the SiC single crystal and mirror-polished, and then a GaN thin film was epitaxially grown thereon by MOCVD. As growth conditions, a growth temperature of 1050 ° C., TMG, NH ₃ , and SiH ₄ were flowed at 54 × 10 ⁻⁶ mol / min, 4 liter / min, and 22 × 10 ⁻¹¹ mol / min, respectively. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type GaN was grown to a thickness of 3 μm.

  In order to investigate the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope, and dense portions of surface defects such as pits were observed at several locations on the wafer surface.

FIG. 1 is a diagram for explaining the principle of the improved Rayleigh method. FIG. 2 is a diagram illustrating the effect of the present invention. The seed crystal holding part and the crucible body, (a) the form at room temperature (before crystal growth), (b) the form at high temperature (during crystal growth), (c) the high temperature of the crucible of another aspect of the present invention (crystal (When grown) The seed crystal holding part is composed of a part in contact with the seed crystal and the other part, and the part in contact with the seed crystal is approximately the same thermal expansion coefficient as the SiC single crystal If you have). FIG. 3 is a configuration diagram showing an example of a single crystal growth apparatus used in the manufacturing method of the present invention.

Explanation of symbols

1 seed crystal (SiC single crystal)
2 Raw material for SiC powder
3 Crucible body (made of graphite)
4 Seed crystal holding part (made of graphite)
5 Double quartz tube
6 Support rod
7 Graphite felt
8 Work coil
9 Ar gas piping
10 Ar gas mass flow controller
11 Nitrogen gas piping
12 Mass flow controller for nitrogen gas
13 Vacuum exhaust system

Claims (21)

A crucible used in a method for producing a silicon carbide single crystal including a step of storing a seed crystal in a crucible and growing a silicon carbide single crystal on the seed crystal by a sublimation recrystallization method, the seed crystal holding the seed crystal A crucible for growing a silicon carbide single crystal, characterized in that the holding part is made of a material having a thermal expansion coefficient of 4.5 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C. at 2000 ° C. 2. The crucible for growing a silicon carbide single crystal according to claim 1, wherein the seed crystal holding part is made of a material having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. to 5.5 × 10 ⁻⁶ / ° C. at 2000 ° C. .   3. The crucible for growing silicon carbide single crystal according to claim 1, wherein the constituent material of the seed crystal holding part is graphite.   3. The crucible for growing a silicon carbide single crystal according to claim 1, wherein all the constituent materials of the crucible are graphite.   A crucible used in a method for producing a silicon carbide single crystal including a step of storing a seed crystal in a crucible and growing a silicon carbide single crystal on the seed crystal by a sublimation recrystallization method, wherein the entire crucible has a coefficient of thermal expansion Silicon carbide single crystal growth characterized in that the material constituting the crucible of the seed crystal holding part that holds the seed crystal is substantially smaller in thermal expansion coefficient than the other part. Crucible for use. 6. The crucible for growing silicon carbide single crystal according to claim 5, wherein a thermal expansion coefficient at 2000 ° C. of the crucible constituent material of the seed crystal holding part is 4.5 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. 6. The crucible for growing a silicon carbide single crystal according to claim 5, wherein the crucible constituent material of the seed crystal holding part has a thermal expansion coefficient at 2000 ° C. of 5.0 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less.   8. The crucible for growing a silicon carbide single crystal according to claim 5, wherein at least one constituent material of the crucible is graphite.   The crucible for growing a silicon carbide single crystal according to any one of claims 5 to 7, wherein all the constituent materials of the crucible are graphite.   A crucible used in a method for producing a silicon carbide single crystal including a step of storing a seed crystal in a crucible and growing a silicon carbide single crystal on the seed crystal by a sublimation recrystallization method, wherein the entire crucible has a coefficient of thermal expansion The crucible constituent material of the seed crystal holding part that is made up of two or more different materials and that holds the seed crystal has a substantially smaller thermal expansion coefficient than the other part, and the seed crystal holding part is a seed crystal The constituent material of the portion not in contact with the seed crystal of the seed crystal holding part, which is separated into the portion in contact with the other portion, has a smaller thermal expansion than the constituent material of the portion in contact with the seed crystal. A crucible for growing silicon carbide single crystal, characterized by having a coefficient. 11. The carbonization according to claim 10, wherein a thermal expansion coefficient at 2000 ° C. of a constituent material in contact with the seed crystal of the seed crystal holding part is 4.5 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. A crucible for growing silicon single crystals. 11. The carbonization according to claim 10, wherein a thermal expansion coefficient at 2000 ° C. of a constituent material in contact with the seed crystal of the seed crystal holding part is 5.0 × 10 ⁻⁶ / ° C. or more and 5.5 × 10 ⁻⁶ / ° C. or less. A crucible for growing silicon single crystals.   13. The crucible for growing a silicon carbide single crystal according to claim 10, wherein at least one constituent material of the crucible is graphite.   The crucible for growing silicon carbide single crystal according to any one of claims 10 to 12, wherein all the constituent materials of the crucible are graphite.   A method for producing a silicon carbide single crystal comprising a step of storing a seed crystal in a crucible and growing a silicon carbide single crystal on the seed crystal by a sublimation recrystallization method, wherein the crucible is any one of claims 1 to 14. A method for producing a silicon carbide single crystal, wherein the crucible according to claim 1 is used.   16. A silicon carbide single crystal ingot obtained by the production method according to claim 15, wherein the ingot has a diameter of 50 mm or more and 300 mm or less. 17. The silicon carbide single crystal ingot according to claim 16, wherein the basal plane dislocation density in the ingot is 1 × 10 ⁴ cm ⁻² or less. 17. The silicon carbide single crystal ingot according to claim 16, wherein the basal plane dislocation density in the ingot is 5 × 10 ³ cm ⁻² or less.   19. A silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal ingot according to any one of claims 16 to 18.   20. A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on the silicon carbide single crystal substrate according to claim 19.   20. A thin film epitaxial wafer obtained by epitaxially growing gallium nitride, aluminum nitride, indium nitride, or a mixed crystal thereof on the silicon carbide single crystal substrate according to claim 19.

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