JP4103183B2 - Method for producing silicon carbide single crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon carbide (SiC) single crystal in which micropipe defects are blocked.
[0002]
[Prior art]
When a SiC single crystal is produced by an improved Rayleigh method using a SiC single crystal as a seed crystal, a hollow through hole with a diameter of sub-μm to several μm called a micropipe defect (hollow through defect) grows substantially along the growth direction. Is inherent in. Since the micropipe defect adversely affects the electrical characteristics of the device, the SiC single crystal having the micropipe defect is not suitable for a substrate for device formation. For this reason, reducing micropipe defects is an important issue.
[0003]
As a method for reducing micropipe defects, methods disclosed in US Pat. No. 5,679,153 and JP-A-5-262599 have been proposed.
The method shown in US Pat. No. 5,679,153 utilizes the fact that micropipe defects are blocked during epitaxial growth when crystal growth is performed by liquid phase epitaxy using SiC melting in silicon. A seed crystal having a micropipe defect (defect density: 50 to 400 cm) ^-2 ) Epitaxial layer with reduced micropipe defects (defect density: 0 to 50 cm) ^-2 ) Is growing.
[0004]
In the method disclosed in Japanese Patent Laid-Open No. 5-262599, by using a plane perpendicular to the (0001) plane as a seed crystal growth plane, a single crystal in which hexagonal etch pits are not observed at the time of alkali etching, that is, a microcrystal. A single crystal having no pipe defects is grown on a seed crystal.
[0005]
[Problems to be solved by the invention]
Both of the above two methods grow a new single crystal on the seed crystal and reduce micropipe defects in the growth layer.
For this reason, in the former method, in order to obtain a portion free from micropipe defects, an epitaxial layer of 20 to 75 μm or more must be grown by the liquid phase epitaxy method. There is a problem that defects exist. Further, when single crystal growth is performed again by the sublimation method using the epitaxial layer formed in this way as a seed crystal, since the portion where the micropipe defect is closed is thin, the closed portion is sublimated and microscopically again. There is a possibility that an opening of a pipe defect may occur, and there is a problem that it is difficult to prepare a seed crystal sample and to optimize the sublimation growth conditions.
[0006]
On the other hand, the latter method is effective in suppressing the occurrence of micropipe defects, but since new stacking faults are introduced into the grown single crystal, anisotropy occurs in the electrical characteristics of the substrate, There is a problem that it is not suitable as a substrate for electronic devices.
The present invention has been made in view of the above problems, and can prevent micropipe defects existing in a silicon carbide single crystal from being blocked rather than suppressing generation and inheritance of micropipe defects in a new growth layer. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the following technical means are adopted.
In the first aspect of the invention, a silicon carbide single crystal having a micropipe defect is prepared, and a heat treatment is performed by saturating the inside of the micropipe defect with a silicon carbide vapor species to form a silicon carbide single crystal. And a step of increasing the temperature of the silicon carbide single crystal and a step of decreasing the temperature of the silicon carbide single crystal from the increased temperature in the heat treatment step. It is characterized by doing.
[0008]
Thus, the micropipe defect which exists in a silicon carbide single crystal can be obstruct | occluded by heat-processing by making the inside of a micropipe defect saturated with a silicon carbide vapor seed | species. Furthermore, in the heat treatment step, by repeating the step of raising the temperature of the silicon carbide single crystal and the step of lowering the temperature of the silicon carbide single crystal from the raised temperature, the equilibrium vapor due to the temperature difference at the time of raising the temperature again Since silicon carbide is resublimated by the amount of pressure and dislocation coalescence is advanced at the time of lowering the temperature again, the vapor pressure component of the lowering temperature can be efficiently recrystallized to close the micropipe defects.
[0009]
For example, the above-described effect can be obtained by repeating the temperature increase / decrease in the temperature of the silicon carbide single crystal within the range of 1800 to 2500 ° C.
It should be noted that by repeating the temperature increase / decrease, the process in which the silicon carbide single crystal becomes high temperature / low temperature is repeated, but each temperature of the repeated high temperature process and each temperature of the low temperature process are sequentially decreased. Then, the micropipe defect can be blocked more efficiently.
[0010]
Further, at least a part of the surface of the silicon carbide single crystal may be covered with a coating material in order to efficiently bring the micropipe defect into a saturated state with the silicon carbide vapor species. In this case, as the coating material, either SiC having the same crystal form as the silicon carbide single crystal or SiC having a different crystal form can be applied. However, when the silicon carbide single crystal material is hexagonal, cubic or rhombohedral Silicon carbide is suitable. Moreover, a SiC polycrystal, a SiC sintered body, amorphous SiC, a carbon material, a metal material, a metal carbide, a metal nitride, and a metal oxide can also be applied as a coating material.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below.
FIG. 1 is a schematic cross-sectional view of a heat treatment apparatus used to close micropipe defects 1a of a substrate crystal (silicon carbide single crystal) 1.
The heat treatment apparatus includes a crucible 2 having an open top and a lid 3 that covers the opening of the crucible 2. The crucible 2 and the lid 3 are made of graphite.
[0012]
The crucible 2 contains silicon carbide 4 as a raw material for stably performing heat treatment for closing the micropipe defect 1a with good reproducibility. The substrate crystal 1 is supported with the lower surface of the lid 3 as a mounting surface. When the opening of the crucible 2 is covered with the lid 3, the substrate crystal 1 is disposed opposite to the silicon carbide 4. It is like that. Hereinafter, the mounting surface side of both surfaces of the substrate crystal 1 is referred to as a mounting surface side surface, and the opposite side of the mounting surface is referred to as a non-mounting surface side surface.
[0013]
Although not shown in FIG. 1, a resistance heating element made of graphite is disposed on the outer periphery of the crucible 2, and the temperature inside the crucible 2, specifically the temperature of the substrate crystal 1, is formed by this resistance heating element. The temperature of silicon carbide 4 can be adjusted. Although not shown, the crucible 2 is placed in a container capable of adjusting the atmospheric pressure, and an inert gas or the like can be introduced into the crucible 2 or the atmospheric pressure can be adjusted.
[0014]
As shown in FIG. 1, the non-mounting surface side of the substrate crystal 1 is covered with a coating material 5. This coating material 5 is formed by, for example, a chemical vapor deposition (CVD) method, a molecular beam epitaxy (MBE) method, a vapor phase growth method such as a sputter vapor deposition method or a sublimation method, or a liquid phase growth method such as a liquid phase epitaxy (LPE) method. Deposited on the substrate crystal 1.
The covering material 5 may be either SiC having the same crystal form as that of the substrate crystal 1 or SiC having a different crystal form. However, when the material of the substrate crystal 1 is a hexagonal silicon carbide single crystal, cubic or rhombohedral crystal Silicon carbide is suitable. In particular, when the crystal form of the substrate crystal 1 is 6H—SiC, 3C—SiC, 4H—SiC, and 15R—SiC are suitable as the coating material 5, and when 4H—SiC, 3C—SiC, 6H -SiC and 15R-SiC are suitable as the coating material 5.
[0015]
In addition, as the coating material 5, SiC polycrystalline body, SiC sintered body, amorphous SiC, carbon material (eg, graphite, carbon nanotube, fullerene, etc.), metal material (eg, W, Mo, etc.), metal carbide (eg, TaC, HfC, etc.), metal nitride (eg, tungsten nitride, etc.), metal oxide (eg, zirconia, alumina, etc.) can also be applied.
[0016]
When the coating material 5 is made of cubic silicon carbide (3C—SiC), in addition to the above-described deposition method, for example, an organic material in which an organosilicon polymer such as polymethylcarbosilane or the like is dissolved is dissolved. After the solvent is uniformly applied to the substrate crystal 1 and the organic solvent is dried, it is vacuum or Ar, N ₂ You may thermally decompose at 600-1500 degreeC in non-oxidizing atmospheres.
[0017]
In FIG. 1, the non-mounting surface side surface of the substrate crystal 1 is covered with the coating material 5, but at least one of both surfaces of the substrate crystal 1 may be covered with the coating material 5. Need not be. Further, the coating material 5 may be formed on the substrate crystal 1 prior to the heat treatment described later, but may be grown on the surface of the substrate crystal 1 during the heat treatment step. The covering material 5 can be selected in the range of several tens of nanometers to several millimeters, but considering the degree of freedom of heat treatment conditions for blocking micropipe defects and the manufacturing cost, it is selected in the range of several micrometers to several hundred micrometers. It is preferable to do.
[0018]
Further, the thickness of the substrate crystal 1 can be arbitrarily selected, but if the substrate crystal 1 is made thicker, it is possible to form a larger number of micropipe defects 1a at a time, and if the substrate crystal 1 is too thin, the substrate crystal 1 is deformed or damaged. In view of the fact that there is a possibility of operability during the manufacturing process, it is desirable that the thickness be at least 100 μm.
[0019]
After the substrate crystal 1 configured in this manner is placed in the heat treatment apparatus shown in FIG. 1, heat treatment is performed.
At this time, as temperature conditions for the heat treatment, if the temperatures of the silicon carbide raw material 4 and the substrate crystal 1 are To (° C.) and Ts (° C.), respectively, these temperatures change as shown in the heat treatment temperature profile shown in FIG. Let
[0020]
Specifically, the temperature To of the silicon carbide raw material 4 is raised to a temperature approximately equal to or higher than the sublimation temperature of silicon carbide, and the temperature is maintained for a predetermined time, and then lowered according to the time. .
The temperature Ts of the substrate crystal 1 is raised to a relatively high predetermined temperature (for example, 1800 to 2500 ° C.), then lowered to a relatively low temperature from the predetermined temperature, and further raised and lowered repeatedly. Change the temperature. That is, the temperature Ts of the substrate crystal 1 is changed between a high temperature and a low temperature by performing a thermal cycle of repeatedly performing a high temperature process and a low temperature process. In addition, in this figure, although what raised / lowered temperature twice is shown, it can also be repeated more than that. Further, a time during which the temperature is constant may be provided during the transition from the high temperature to the low temperature and during the transition from the low temperature to the high temperature, and it is not always necessary to raise or lower the temperature. Further, the high temperature process and the low temperature process are repeated, but it is not necessary to set the temperatures of the repeated high temperature process and the low temperature process to the same temperature. For example, the arrows (ΔT1, ΔT2) in this figure As shown, the temperature may be lowered in order. Further, the number of thermal cycles can be selected as appropriate depending on the temperature of Ts and the temperature increase / decrease rate for shifting to a high temperature / low temperature process. However, considering the manufacturing cost, the total number of heat cycles is 3 to 48. Time is desirable.
[0021]
The atmospheric pressure conditions are 1 × 10 ^-8 ~ 1x10 ⁹ Applicable in the range of Pa.
2 and 3 show the state of the substrate crystal 1 before and after the above heat treatment. As shown in these drawings, the micropipe defect 1 a having an opening on the surface of the substrate crystal 1 is blocked from at least one direction of the surface of the substrate crystal 1. At this time, the length by which the micropipe defect 1a was blocked could be made larger than 75 μm from the surface of the substrate crystal 1. In this figure, the closed hole 7 remains, but the closed hole 7 is gradually closed according to the heat treatment time and the number of repetitions of temperature increase / decrease. In some cases, the micropipe defect 1a can be substantially eliminated.
[0022]
Thus, the micropipe defect 1a in the substrate crystal 1 can be closed by the heat treatment that satisfies the above temperature condition and atmospheric pressure condition.
The mechanism by which the micropipe defect 1a is blocked is estimated as follows.
In the micropipe defect 1a, it is considered that a screw dislocation core having a large Burgers vector becomes a hollow through-hole in order to relax large elastic strain energy (FC Frank. Acta. Cryst. 4 (1951). ) 497).
[0023]
It is estimated that the blocking phenomenon of the micropipe defect 1a is a phenomenon opposite to the mechanism of the micropipe defect 1a. The blockage estimation model of the micropipe defect 1a will be described based on the schematic diagram shown in FIG. In FIG. 4, locations corresponding to the states of the substrate crystal 1 shown in FIGS. 5A to 5F are indicated by (a) to (f), respectively.
[0024]
First, as shown in FIG. 5A, consider a case where a substrate crystal 1 including a micropipe defect 1 a on which a 3C—SiC epitaxial film is formed as a coating material 5 is placed on a graphite lid 3. In this state, when placed in the heat treatment apparatus shown in FIG. 1 and heat treatment is performed at an appropriate temperature and pressure condition, as shown in FIG. 5B, in order to maintain the equilibrium vapor pressure at that temperature, the micropipe From the periphery of the defect 1a, the 3C-SiC film and the graphite of the lid, Si, SiC ₂ , Si ₂ Vapor species such as C sublimate as shown by the arrows in the figure.
[0025]
After that, although the reason is not yet clear, dislocation movement becomes easy at the interface with the lid 3 and the interface with the 3C-SiC film, and is coupled / disappeared with other dislocations. As shown in FIG. 4, the elastic strain is relieved mainly from the vicinity 8 of the interface. At that location, it is possible to realize at least one of elimination of surface energy disadvantage due to the formation of the surface by crystallization rather than hollow holes having a surface, or reduction of free energy by crystallization. There is an energy gain, and as shown in FIG. 5 (d), it is presumed that recrystallization has progressed at that point.
[0026]
The micropipe defect 1a can be obtained by coating at least one surface of the silicon carbide single crystal 1 having the micropipe defect 1a of the present embodiment with the coating material 5 (including the case where the silicon carbide single crystal 1 is only placed on the lid 3) and performing a heat treatment. It is presumed that it played the role of reducing the Burgers vector of (spiral dislocation), and as a result, the micropipe defect 1a was blocked.
[0027]
In the present embodiment, the temperature of the substrate crystal 1 is repeatedly changed between high and low temperatures during the heat treatment. Therefore, when the temperature is raised again, as shown in FIG. As shown in FIG. 5F, dislocation coalescence progresses and elastic strain is relaxed, and only the vapor pressure of the temperature lowering is efficiently recrystallized.
[0028]
For this reason, compared with the case where a high temperature process and a low temperature process are not repeated, the micropipe defect 1a can be block | closed more efficiently.
By cutting out a region where the micropipe defect 1a does not exist (for example, a substrate parallel to the (0001) plane or an off-angle substrate) from the substrate crystal 1 thus obtained, there is substantially no micropipe defect 1a. The substrate crystal 1 can be obtained. If the substrate crystal 1 thus obtained is processed and chemically cleaned and then used in a device, a high-performance, high withstand voltage, high frequency, high speed, environmentally resistant device can be produced. Moreover, it can be provided again as a seed crystal for the sublimation method. In addition, it was confirmed by experiment that the micropipe defect 1a once closed is stable in terms of energy. For this reason, even if a silicon carbide single crystal is grown on the seed crystal by a sublimation method or the like using the micropipe defect 1a as a closed single crystal seed crystal, the micropipe defect 1a does not occur again. A silicon carbide single crystal (for example, a substrate for device formation) free from many micropipe defects 1a can be cut out from a single crystal ingot obtained by performing high-quality long single crystal growth.
[0029]
In addition, since the micropipe defect 1a can be closed in the substrate crystal 1, it is necessary to require a great deal of labor for the substrate enlargement process, that is, many growth experiments for sequentially expanding the substrate diameter while maintaining high quality. The manufacturing cost is greatly reduced.
The crystal form of the substrate crystal 1 can be applied to any of 6H polymorph, 4H polymorph, and others.
[0030]
Further, as the substrate crystal 1, not only a plane (just plane) parallel to the (0001) plane but also an off-angle substrate tilted at an angle from the (0001) plane, for example, has the same effect.
Furthermore, in the examples described later, the substrate crystal 1 will be described by taking a case where the thickness is 1 mm or less as an example. In particular, when the present invention is applied to a single crystal ingot, a large number of substrates free from micropipe defects 1a can be obtained at one time, which is effective as an industrial process.
[0031]
As shown in FIG. 1, as a heat treatment apparatus for closing micropipe defects, a case has been described in which the substrate crystal 1 is disposed above the crucible 2 where the lid 3 is located and the silicon carbide 4 is disposed below. The present invention can also be applied to other devices, for example, the case where the silicon carbide 4 is disposed on the upper part of the crucible 2 and the substrate crystal 1 is disposed on the lower part. Although the vertical heat treatment apparatus has been described, the present invention can also be applied to a horizontal heat treatment apparatus. Further, the same effect can be obtained even when a conventionally known high-frequency induction heating method is used.
[0032]
Although single crystal growth of silicon carbide has been described, the above method can be applied to other crystals, for example, materials having hollow through defects such as ZnS.
[0033]
【Example】
Hereinafter, examples in the present embodiment will be specifically described.
(Example 1)
First, the defect density is about 40 cm. ^-2 A 6H polymorphic substrate crystal 1 having a thickness of 300 μm having a micropipe defect 1a is prepared, and a 3C-SiC epitaxial film is formed on the surface of the substrate crystal 1 as a coating material 5 by a CVD method to a thickness of about 20 μm. Formed.
[0034]
When observed using a differential interference microscope, a polarizing microscope, and a scanning electron microscope, the opening of the micropipe defect 1a was completely covered with the 3C-SiC epitaxial film. The (0001) just plane is used as the surface of the substrate crystal 1, and the 3C-SiC epitaxial film is formed with the (111) plane as the growth plane.
[0035]
Next, the substrate crystal 1 is placed in the heat treatment apparatus shown in FIG. 1, and the atmospheric pressure is 1.333 × 10 6 as a micropipe defect closing step. ² Heat treatment was performed at Pa (1 Torr) for 6 hours. At this time, the temperature of the silicon carbide raw material 4 was raised to 2300 ° C. and then held at that temperature. Further, the temperature of the substrate crystal 1 is increased to 2280 ° C., then the temperature is decreased to 2230 ° C., the temperature is increased again to 2280 ° C., and then the temperature is decreased to 2230 ° C. The temperature was changed repeatedly between high and low temperatures. The temperature increase temperature in the repetition was about 3.3 ° C./min, and the temperature decrease rate was about 0.4 ° C./min. After the heat treatment step, the temperature of the substrate crystal 1 was lowered with time.
[0036]
The single crystal ingot obtained through these steps was cut in parallel to the growth direction, the cut surface was polished, and observed with a microscope in a transmission bright field. As a result, all the micropipe defects 1 a existing in the substrate crystal 1 were blocked from both sides of the surface of the substrate crystal 1. And 65% of the micropipe defects 1a were 20 μm or less in length.
[0037]
Further, in order to remove the silicon carbide crystal (growth crystal 6) formed during the heat treatment, the substrate crystal 1 was polished in parallel with the (0001) plane and observed with an orthogonal polarization microscope. As a result, the characteristic birefringence interference pattern observed around the micropipe defect 1a was no longer shown in the portion where the micropipe defect 1a was blocked. For this reason, it can be said that the micropipe defect 1a once closed is stable in terms of energy.
[0038]
(Example 2)
First, the defect density is about 40 cm. ^-2 A 6H polymorphic substrate crystal 1 having a thickness of 300 μm and having a micropipe defect 1a is prepared. A (0001) just plane is adopted as the surface of the substrate crystal 1. The substrate crystal 1 is not particularly formed with a coating film in advance.
[0039]
Next, the substrate crystal 1 is placed in the heat treatment apparatus shown in FIG. 1, and the atmospheric pressure is 1.333 × 10 6 as a micropipe defect closing step. ² Heat treatment was performed at Pa for 6 hours. At this time, the temperature of the silicon carbide raw material 4 was raised to 2300 ° C. and then held at that temperature. Further, the temperature of the substrate crystal 1 is raised to 2280 ° C., lowered to 2230 ° C., raised to 2280 ° C., then lowered to 2230 ° C. The temperature was changed repeatedly between high and low temperatures. The temperature increase temperature in the repetition was about 3.3 ° C./min, and the temperature decrease rate was about 0.4 ° C./min. After the heat treatment step, the temperature of the substrate crystal 1 was lowered with time.
[0040]
The single crystal ingot obtained through these steps was cut in parallel to the growth direction, the cut surface was polished, and observed with a microscope in a transmission bright field. As a result, 50% of the micropipe defects 1 a existing in the substrate crystal 1 were blocked from at least one direction of the surface of the substrate crystal 1. And 30% of the micropipe defects 1a were 20 μm or less in length.
[0041]
Further, in order to remove the silicon carbide crystal formed during the heat treatment, the substrate crystal 1 was polished in parallel with the (0001) plane and observed with an orthogonal polarization microscope. As a result, the characteristic birefringence interference pattern observed around the micropipe defect 1a was no longer shown in the portion where the micropipe defect 1a was blocked.
In addition, when the surface of the substrate crystal 1 was observed carefully, it was found that a layer having a crystal color different from that of the mother crystal constituting the substrate crystal 1 was formed. As a result of identifying this layer by Raman scattering spectroscopy, it was found to be 3C-SiC.
[0042]
That is, in the initial stage of the growth of the sublimation method, it is considered that the heterogeneous polymorph (3C—SiC) is formed on the surface of the substrate crystal 1 and then the micropipe defect 1a is blocked by continuously performing heat treatment. It is done.
On the other hand, even in the region where the 3C—SiC layer was not formed in the sublimation growth layer, it was observed that the micropipe defect 1a was blocked from the mounting surface of the substrate crystal 1. This indicates that heat treatment in the micropipe defect 1a in a saturated state of the SiC vapor species is effective to block the micropipe defect 1a.
[0043]
As described above, even when the opening at one end of the micropipe defect 1a is not blocked, the micropipe defect 1a is saturated with SiC vapor species and subjected to heat treatment by a sublimation method. 1a can be occluded.
(Example 3)
First, the defect density is about 40 cm. ^-2 A 6H polymorphic substrate crystal 1 having a thickness of 300 μm having a micropipe defect 1a is prepared, and a 3C-SiC epitaxial film is formed on the surface of the substrate crystal 1 as a coating material 5 by a CVD method to a thickness of about 20 μm. Formed.
[0044]
When observed using a differential interference microscope, a polarizing microscope, and a scanning electron microscope, the opening of the micropipe defect 1a was completely covered with the 3C-SiC epitaxial film. The (0001) just plane is used as the surface of the substrate crystal 1, and the 3C-SiC epitaxial film is formed with the (111) plane as the growth plane.
[0045]
Next, the substrate crystal 1 is placed in the heat treatment apparatus shown in FIG. 1, and the atmospheric pressure is 1.333 × 10 6 as a micropipe defect closing step. ² Heat treatment was performed at Pa for 6 hours. At this time, the temperature of the silicon carbide raw material 4 was raised to 2300 ° C. and then held at that temperature. Further, after raising the temperature of the substrate crystal 1 to 2280 ° C., the temperature was lowered to 2250 ° C., the temperature was raised again to 2260 ° C., the temperature was lowered to 2230 ° C., and the temperature was further raised to 2240 ° C. The temperature was lowered to 2210 ° C., and the temperature was raised and lowered in order of decreasing temperature, and the temperature was changed to high and low. The temperature increase rate in repetition was about 0.7 ° C./min, and the temperature decrease rate was about 0.25 ° C./min. After the heat treatment step, the temperature of the substrate crystal 1 was lowered with time.
[0046]
The single crystal ingot obtained through these steps was cut in parallel to the growth direction, the cut surface was polished, and observed with a microscope in a transmission bright field. As a result, all the micropipe defects 1 a existing in the substrate crystal 1 were blocked from both sides of the surface of the substrate crystal 1. And 80% of the micropipe defects 1a were 20 μm or less in length.
[0047]
Further, in order to remove the silicon carbide crystal formed during the heat treatment, the substrate crystal 1 was polished in parallel with the (0001) plane and observed with an orthogonal polarization microscope. As a result, the characteristic birefringence interference pattern observed around the micropipe defect 1a was no longer shown in the portion where the micropipe defect 1a was blocked.
In this way, the micropipe defect 1a can be more efficiently closed by lowering the temperature of the repeated high temperature process and the temperature of the low temperature process in order.
[0048]
(Comparative example)
First, the defect density is about 40 cm. ^-2 A 6H polymorphic substrate crystal 1 having a thickness of 300 μm having a micropipe defect 1a is prepared, and a 3C-SiC epitaxial film is formed on the surface of the substrate crystal 1 as a coating material 5 by a CVD method to a thickness of about 20 μm. Formed.
[0049]
When observed using a differential interference microscope, a polarizing microscope, and a scanning electron microscope, the opening of the micropipe defect 1a was completely covered with the 3C-SiC epitaxial film. The (0001) just plane is used as the surface of the substrate crystal 1, and the 3C-SiC epitaxial film is formed with the (111) plane as the growth plane.
[0050]
Next, the substrate crystal 1 is placed in the heat treatment apparatus shown in FIG. 1, and the atmospheric pressure is 1.333 × 10 6 as a micropipe defect closing step. ² Heat treatment was performed at Pa (1 Torr) for 6 hours. At this time, the temperature of the silicon carbide raw material 4 was raised to 2300 ° C. and then held at that temperature. Further, after the temperature of the substrate crystal 1 was raised to 2230 ° C., the temperature was maintained.
[0051]
The single crystal ingot obtained through these steps was cut in parallel to the growth direction, the cut surface was polished, and observed with a microscope in a transmission bright field. As a result, all the micropipe defects 1 a existing in the substrate crystal 1 were blocked from both sides of the surface of the substrate crystal 1. And 35% of the micropipe defects 1a were 20 μm or less in length.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heat treatment apparatus used for producing a silicon carbide single crystal according to an embodiment of the present invention.
FIG. 2 is a diagram showing a silicon carbide single crystal 1 whose surface is coated with a coating material 5;
FIG. 3 shows a state of silicon carbide single crystal 1 after heat treatment.
FIG. 4 is a diagram showing a heat treatment temperature profile;
FIG. 5 is a diagram for explaining a blocking mechanism of a micropipe defect 1a.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon carbide single crystal (substrate crystal), 1a ... Micro pipe defect, 2 ... Crucible,
3 ... Cover material, 4 ... Silicon carbide raw material, 5 ... Coating material, 6 ... Growth crystal, 7 ... Closure hole,
8: Near the interface.

Claims (1)

Preparing a silicon carbide single crystal having micropipe defects;
Capping the micropipe defects present in the silicon carbide single crystal by performing a heat treatment in a saturated state with silicon carbide vapor species in the micropipe defects,
In the heat treatment step, the step of raising the temperature of the silicon carbide single crystal and the step of lowering the temperature of the silicon carbide single crystal from the raised temperature are repeated. Crystal production method.

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