JP5803519B2 - Method and apparatus for producing SiC single crystal - Google Patents

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for a SiC single crystal by a solution method.

  SiC single crystals are very thermally and chemically stable, excellent in mechanical strength, resistant to radiation, and have excellent physical properties such as higher breakdown voltage and higher thermal conductivity than Si single crystals. . Therefore, it is possible to realize high power, high frequency, withstand voltage, environmental resistance, etc. that cannot be realized with existing semiconductor materials such as Si single crystal and GaAs single crystal, and power devices that enable high power control and energy saving. Expectations are growing as next-generation semiconductor materials in a wide range of materials, high-speed and large-capacity information communication device materials, in-vehicle high-temperature device materials, radiation-resistant device materials, and the like.

  Conventionally, as a method for growing a SiC single crystal, a gas phase method, an Acheson method, and a solution method are typically known. Among the vapor phase methods, for example, the sublimation method has a defect that a grown single crystal is liable to cause a lattice defect such as a hollow through defect called a micropipe defect or a stacking fault and a crystal polymorphism, but the crystal growth. Because of its high speed, conventionally, most of SiC bulk single crystals have been manufactured by a sublimation method, and attempts have been made to reduce defects in grown crystals. In the Atchison method, since silica and coke are used as raw materials and heated in an electric furnace, it is impossible to obtain a single crystal with high crystallinity due to impurities in the raw materials.

  In the solution method, the Si melt or the alloy is melted into the Si melt in the graphite crucible, C is dissolved in the melt from the graphite crucible, and the SiC crystal layer is formed on the seed crystal substrate placed in the low temperature portion. It is a method of growing by precipitation. In the solution method, since crystal growth is performed in a state close to thermal equilibrium as compared with the gas phase method, the reduction of defects can be most expected. For this reason, several methods for producing SiC single crystals by the solution method have recently been proposed.

  In general, there may be a work-affected layer such as dislocation or a natural oxide film on the surface layer of a seed crystal substrate on which a SiC single crystal is grown. Before the SiC single crystal is grown in a solution method, It is disclosed to perform meltback to dissolve and remove these (Patent Document 1).

JP 2007-284301 A

  In the method described in Patent Document 1, meltback can be performed only before the growth of the SiC single crystal, and defects generated during the growth of the SiC single crystal cannot be melted.

  Accordingly, there is a need for a SiC single crystal manufacturing method and manufacturing apparatus that can perform meltback even during the growth of the SiC single crystal.

In the present invention, the seed crystal holding shaft holds the Si-C solution heated so as to have a temperature gradient in which the temperature decreases from the inside toward the surface in the crucible by a heating device arranged around the crucible. A method for producing a SiC single crystal by a solution method, wherein a SiC single crystal is grown by bringing a SiC seed crystal into contact with the seed crystal as a base point,
During the growth of the SiC single crystal, the temperature gradient in the surface region from the inside of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature, and the seed crystal and the SiC single crystal grown from the seed crystal are used as the starting point. A method for producing a SiC single crystal, comprising melt-backing the contained single crystal.

The present invention also includes a crucible containing a Si-C solution;
A heating device arranged around the crucible;
A seed crystal holding shaft arranged to be movable in the vertical direction,
The SiC seed crystal held on the seed crystal holding shaft is brought into contact with a Si-C solution heated so as to have a temperature gradient that decreases from the inside toward the surface, and a SiC single crystal is grown from the seed crystal as a starting point. An apparatus for producing a SiC single crystal by a solution method,
During the growth of the SiC single crystal, the temperature gradient in the surface region from the inside of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature, and the seed crystal and the SiC single crystal grown from the seed crystal are used as the starting point. The SiC single crystal manufacturing apparatus includes means for melting back the single crystal.

  According to the present invention, meltback can be performed even during the growth of the SiC single crystal.

It is a cross-sectional schematic diagram showing an example of the basic composition of the SiC single crystal manufacturing apparatus which can be used in this invention. It is a cross-sectional schematic diagram of the SiC single crystal manufacturing apparatus which can arrange | position and remove an additional heat insulating material on the crucible upper surface which can be used in 1st Embodiment. It is a cross-sectional schematic diagram of the SiC single crystal manufacturing apparatus which can be used in 2nd Embodiment and can change the position of the heating apparatus arrange | positioned around the crucible and / or the periphery of a crucible. It is a cross-sectional schematic diagram of the SiC single crystal manufacturing apparatus provided with the heating apparatus which can be used in 3rd Embodiment in the vicinity on the liquid level of a Si-C solution which can heat a Si-C solution from a liquid level. . It is a cross-sectional schematic diagram of the SiC single crystal manufacturing apparatus provided with the heating apparatus which can be used in 4th Embodiment in the circumference | surroundings of a seed crystal holding shaft which can heat a seed crystal holding shaft. SiC single crystal production capable of immersing a single crystal including a seed crystal and a SiC single crystal grown from the seed crystal up to the reverse temperature gradient region of the Si-C solution, which can be used in the fifth embodiment It is a cross-sectional schematic diagram of an apparatus. It is a cross-sectional schematic diagram of the SiC single crystal manufacturing apparatus provided with the S-shaped graphite heater which can be used in 3rd Embodiment and can heat a Si-C solution from a liquid level.

  In the present invention, the seed crystal holding shaft holds the Si-C solution heated so as to have a temperature gradient in which the temperature decreases from the inside toward the surface in the crucible by a heating device arranged around the crucible. A method for producing a SiC single crystal by a solution method in which a SiC single crystal is grown by bringing a SiC seed crystal into contact with the seed crystal as a starting point. During the growth of the SiC single crystal, the surface of the surface is formed from the inside of the Si-C solution. The temperature gradient of the region is changed to a constant temperature or a temperature gradient that increases the temperature, and a single crystal including the seed crystal and the SiC single crystal grown from the seed crystal (hereinafter referred to as a grown single crystal) is melted back. It is a manufacturing method of a SiC single crystal containing.

  According to the manufacturing method of the present invention, at any timing during the growth of the SiC single crystal, the temperature gradient of the surface region from the inside of the Si-C solution is changed to a constant temperature or a temperature gradient that rises in temperature. The grown single crystal can be melted back by lowering the SiC saturation in the Si-C solution in the surface region. Further, according to the production method of the present invention, it is possible to melt back the seed crystal before growing the SiC single crystal.

  In the present specification, as described above, the growth single crystal refers to a single crystal including a seed crystal and an SiC single crystal grown from the seed crystal. This is expressed in this way because meltback is performed during the growth of the SiC single crystal from the seed crystal as a base point. According to the present invention, it is possible to dissolve a crystal part in which dislocations or defects generated in the surface layer part of the grown crystal are generated and proliferated. When the thickness of the grown crystal is very thin, not only the dislocations and defects contained in the surface layer portion but also the underlying seed crystal substrate can be dissolved simultaneously.

  According to the manufacturing method of the present invention, since a crystal part where dislocations and defects generated during the growth of the SiC single crystal have occurred can be melted, it is possible to obtain a SiC single crystal with few dislocations and defects. it can. Following the meltback, the growth of the SiC single crystal can be continued, and the meltback and the growth of the SiC single crystal can be repeated a plurality of times. As a matter of course, melt back by the manufacturing method can be performed during the growth of the SiC single crystal, and the melt back method of the manufacturing method according to the present invention can be applied to the seed crystal substrate before the growth of the SiC single crystal. Alternatively, a conventional method for melting back a seed crystal substrate may be used.

  In this specification, the term “meltback” refers to removing a seed crystal or a surface layer of an SiC single crystal grown from a seed crystal as a starting point by dissolving it in an Si—C solution. In general, a surface layer of a seed crystal substrate on which a SiC single crystal is grown may have a work-affected layer such as a dislocation or a natural oxide film, which is dissolved before the SiC single crystal is grown. This removal is effective for growing a high-quality SiC single crystal. In the present invention, it is possible to remove dislocations, defects and the like that can occur in a growing SiC single crystal that could not be removed conventionally.

  The thickness dissolved by meltback is generally about 1 μm to 1 mm, although it depends on the thickness of the layer containing dislocations and defects in order to sufficiently remove the layer containing dislocations and defects that may occur during growth. Or about 1 micrometer-100 micrometers are preferable.

  The meltback can be performed by forming a temperature gradient in the Si—C solution in the vicinity of the growth single crystal, in which the temperature is constant or increases from the inside of the Si—C solution toward the surface of the solution. When performing SiC single crystal growth, a temperature gradient is formed in which the temperature decreases from the inside of the Si-C solution of the seed crystal substrate toward the surface of the solution, but this temperature gradient is changed to a constant or increasing temperature gradient. Thus, the grown single crystal can be melted back. The temperature gradient increasing from the inside of the Si—C solution toward the surface of the solution is preferably 0 to 50 ° C./cm in the range of 10 mm, 8 mm, 6 mm, 4 mm, 3 mm, 2 mm, 1 mm, and the like from the solution surface. -20 ° C / cm is more preferable.

  In the present specification, the region from the inside to the surface of the Si—C solution is a region near the liquid surface of the Si—C solution for growing the SiC single crystal from the seed crystal or for melting back the grown single crystal. An area. The region from the inside to the surface of the Si-C solution can be a region between the surface of the Si-C solution, for example, a depth of about 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, or 10 mm, and is a grown single crystal. It can be a region in the vicinity of, for example, a region between the surface of the Si—C solution and a depth of about 10 μm, 50 μm, or 100 μm.

  FIG. 1 shows an example of a basic configuration of an SiC single crystal manufacturing apparatus that can be used to carry out the manufacturing method according to the present invention. The illustrated SiC single crystal manufacturing apparatus 100 includes a crucible 10 containing a Si—C solution 24 in which C is dissolved in a Si or Si / X melt, and the Si—C solution 24 is formed from the inside of the Si—C solution 24. A temperature gradient that lowers the temperature toward the surface of the solution 24 is formed, and the seed crystal substrate 14 held at the tip of the seed crystal holding shaft 12 that can be raised and lowered is brought into contact with the Si-C solution 24, so that the seed crystal substrate 14 is A SiC single crystal can be grown as a base point. It is preferable to rotate the crucible 10 and the seed crystal holding shaft 12 about the axis of the seed crystal holding shaft 12.

  The Si-C solution 24 is prepared by charging a raw material into a crucible and dissolving C in a Si or Si / X melt prepared by heating and melting. X is one or more kinds of metals, and is not particularly limited as long as it can form a liquid phase (solution) in thermodynamic equilibrium with SiC (solid phase). Examples of suitable metals X include Ti, Mn, Cr, Ni, Ce, Co, V, Fe and the like. For example, in addition to Si, Cr, Ni, or the like can be charged into the crucible to form a Si—Cr solution, a Si—Cr—Ni solution, or the like. Moreover, by making the crucible 10 into a carbonaceous crucible such as a graphite crucible or an SiC crucible, C is dissolved in the melt by melting the crucible 10 to form an Si-C solution. In this way, undissolved C does not exist in the Si—C solution 24, and waste of SiC due to precipitation of the SiC single crystal in the undissolved C can be prevented. The supply of C may be performed by, for example, a method of injecting hydrocarbon gas or charging a solid C supply source together with the melt raw material, or combining these methods with melting of a crucible. Also good.

  The surface temperature of the Si—C solution 24 is preferably 1800 to 2200 ° C. with little variation in the amount of C dissolved in the Si—C solution.

  The temperature of the Si—C solution can be measured using a thermocouple, a radiation thermometer, or the like. Regarding the thermocouple, from the viewpoint of high temperature measurement and prevention of impurity contamination, a thermocouple in which a tungsten-rhenium strand coated with zirconia or magnesia glass is placed in a graphite protective tube is preferable.

  The seed crystal holding shaft 12 is a graphite shaft that holds the seed crystal substrate on its end face, and a graphite shaft having an arbitrary shape such as a columnar shape or a prismatic shape can be used.

  The outer periphery of the crucible 10 can be covered with a heat insulating material 18 for heat insulation. You may accommodate these in the quartz tube 26 collectively. A heating device 22 is disposed around the heat insulating material 18. The heating device can be, for example, a high frequency coil. The high-frequency coil can be composed of, for example, a multi-stage configuration such as an upper coil and a lower coil that can be independently controlled.

  Since the crucible 10, the heat insulating material 18, and the heating apparatus 22 become high temperature, they can be disposed inside the water-cooled chamber. The water-cooled chamber can be provided with a gas inlet and a gas outlet in order to adjust the atmosphere in the apparatus.

  The temperature of the Si—C solution 24 usually tends to form a temperature distribution in which the surface temperature is lower than the inside of the Si—C solution 24 due to radiation or the like. In addition, when the heating device 22 is a high-frequency coil including an upper coil and a lower coil, a predetermined temperature is adjusted from the inside of the Si-C solution 24 to the surface region by adjusting the outputs of the upper coil and the lower coil. A decreasing temperature gradient can be formed. The temperature gradient is preferably 50 ° C./cm or less, more preferably 40 ° C./cm or less, in the range of 10 mm, 8 mm, 6 mm, 4 mm, 3 mm, 2 mm, 1 mm, etc. from the solution surface.

  C dissolved in the Si-C solution 24 is dispersed by diffusion and convection. The vicinity of the lower surface of the seed crystal substrate 14 is more than the inside of the Si—C solution 24 due to output control of the heating device 22, heat radiation from the surface of the Si—C solution 24, heat removal through the seed crystal holding shaft 12, and the like. A temperature gradient can be formed that results in a low temperature. When C dissolved in the solution having high solubility at high temperature reaches the vicinity of the seed crystal substrate having low solubility at low temperature, a supersaturated state is obtained, and a SiC single crystal can be grown on the seed crystal substrate using this supersaturation as a driving force. .

  There are several methods for melting back the grown single crystal at an arbitrary timing when the SiC single crystal is grown in this way. This will be described below with reference to the drawings.

(First Embodiment of the Manufacturing Method)
In the first embodiment of the manufacturing method according to the present invention, the crucible has a heat insulating material around it, and during the growth of the SiC single crystal, the thickness of the heat insulating material at the top of the crucible is increased, By changing the temperature gradient that decreases from the inside toward the surface to a constant temperature or a temperature gradient that increases the temperature, the SiC saturation in the Si-C solution in the region from the inside to the surface is decreased, and the grown single crystal is formed. It can be melted back.

  As shown in FIG. 2, a heat insulating material 28 can be further disposed on the heat insulating material 18 at the top of the crucible 10 during the growth of the SiC single crystal. When the heat insulating material 28 is further arranged on the heat insulating material 18 at the upper part of the crucible, the heat insulating effect by the heat insulating material is improved, and particularly the temperature of the surface of the Si-C solution 24 is increased. The temperature gradient of the Si—C solution that decreases in temperature toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution that decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, the Si—C solution 24 in the region from the inside in the vicinity of the seed crystal substrate 14 to the surface region. It is possible to melt back the grown single crystal by lowering the SiC saturation degree.

  The meltback can be terminated by removing the heat insulating material 28 from the upper part of the heat insulating material 18, and the temperature gradient of the Si-C solution is changed again to a temperature gradient in which the temperature decreases from the inside toward the surface, and SiC is changed. Single crystals can also be grown.

  The method of arranging and removing the heat insulating material 28 can be performed manually or automatically. For example, the heat insulating material 28 can be moved up and down by an elevator having an elevating means. Further, two or more heat insulating materials may be used by being stacked, or heat insulating materials having several thicknesses are prepared as the heat insulating material 28, and a heat insulating material having a desired thickness according to a target temperature gradient is prepared. You may choose to use it.

(Second Embodiment of the Manufacturing Method)
In the second embodiment of the manufacturing method according to the present invention, the Si-C solution when growing the SiC single crystal has a temperature gradient in which the temperature decreases from the inside toward the surface, and from the inside to the deep part. Is heated to have a temperature gradient that decreases toward
Change the temperature gradient of the Si-C solution that moves above the center of heating in the crucible and decreases in temperature from the inside to the surface, to a constant temperature or temperature gradient that increases in temperature from the inside to the surface. The grown single crystal can be melted back by reducing the SiC saturation in the Si—C solution from the inside to the surface region.

  Since the Si—C solution 24 accommodated in the crucible is heated by the heating device 22 arranged around as shown in FIG. 3, the Si—C solution near the center of the heating device 22. Is most likely to be heated, and heat is likely to escape from the lower part of the crucible, so that a temperature gradient that decreases in temperature from the inside of the Si-C solution to the surface of the solution is usually formed, and from the inside of the Si-C solution 24. It is easy to form a temperature gradient in which the temperature decreases toward the deep part of the solution. That is, there is a heating center inside the Si—C solution 24, and a temperature gradient can be formed in which the temperature is relatively low at the surface and deep portions and the temperature is relatively high inside.

  In the present embodiment, as shown in FIG. 3, the heating device 22 arranged around the crucible 10 can be moved in the vertical direction with respect to the crucible 10 during the growth of the SiC single crystal. When the heating device 22 is moved upward with respect to the crucible 10, the heating center in the crucible can be moved upward in the crucible, so that a temperature gradient in which the temperature decreases from the inside toward the deep portion in the SiC solution 24. By moving upward, the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution 24 that decreases in temperature from the inside toward the surface in the vicinity of the seed crystal substrate 14, the Si—C solution in the region from the inside to the surface is changed to a constant temperature or a temperature gradient that increases in temperature. The SiC saturation in 24 can be reduced, and the grown single crystal can be melted back.

  The meltback can be terminated by moving the heating device 22 moved upward, and the temperature gradient of the Si-C solution is changed again to a temperature gradient that decreases from the inside toward the surface. Thus, a SiC single crystal can be grown.

  The method of moving the heating device 22 up and down can be performed manually or automatically. For example, the heating device 22 can be moved up and down by an elevator having an elevator.

  In this embodiment, since the temperature gradient in the Si-C solution in the vicinity of the growth single crystal can be continuously changed, not only the growth single crystal can be melted back, but also the growth rate of the SiC single crystal can be increased. It can also be changed continuously.

  In another method, as shown in FIG. 3, during the growth of the SiC single crystal, the crucible 10 containing the Si—C solution 24 is moved in the vertical direction with respect to the heating device 22 arranged around the crucible 10. be able to. When the crucible 10 is moved downward with respect to the heating device 22, the heating center in the crucible can be moved upward in the crucible, so that a temperature gradient in which the temperature decreases from the inside toward the deep portion in the SiC solution 24. By moving upward, the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution 24 in the vicinity of the seed crystal substrate 14, which decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, Si—C in the region from the inside to the surface is obtained. The SiC saturation in the solution 24 can be reduced, and the grown single crystal can be melted back.

  The meltback can be terminated by moving the crucible 10 moved downward, and the temperature gradient of the Si-C solution 24 is changed again to a temperature gradient that decreases from the inside toward the surface. Thus, a SiC single crystal can be grown.

  The method of moving the crucible 10 up and down can be performed manually or automatically. For example, the crucible 10 can be moved up and down by an elevator having an elevator.

  Further, both the heating device 22 and the crucible 10 are simultaneously moved up and down to change the temperature gradient of the Si—C solution, the temperature of which decreases from the inside toward the surface, to a constant temperature or a temperature gradient of increasing the temperature. The crystals may be melted back.

(Third embodiment of the manufacturing method)
In the third embodiment of the manufacturing method according to the present invention, the Si-C solution is heated by a liquid surface heating device disposed on the liquid surface of the Si-C solution, so that the region of the surface region is changed from the inside of the Si-C solution. The grown single crystal can be melted back by changing the temperature gradient to a constant temperature or a temperature gradient increasing in temperature to reduce the SiC saturation in the Si-C solution from the inside to the surface region.

  As shown in FIG. 4, a liquid surface heating device 30 is disposed near the surface of the Si—C solution 24, and the Si—C solution 24 is heated from the liquid surface by the liquid surface heating device 30 during the growth of the SiC single crystal. can do. Thereby, the temperature gradient of the surface region of the Si—C solution 24 increases, and the temperature gradient of the Si—C solution 24 that decreases in temperature from the inside toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature. .

  The liquid level heating device 30 can be any heating device as long as it is arranged in the crucible and can heat the Si-C solution 24 from the liquid level. For example, the Si-C as shown in FIG. In the vicinity of the liquid surface of the solution 24, a graphite heater 34 having a ring-shaped cross section and having an S-shaped cross section and having a high frequency coil heater 36 can be used. The graphite heater 34 may have other shapes such as an L shape.

  By changing the temperature gradient of the Si—C solution 24 that decreases in temperature from the inside toward the surface in the vicinity of the seed crystal substrate 14, the Si—C solution in the region from the inside to the surface is changed to a constant temperature or a temperature gradient that increases in temperature. The SiC saturation in 24 can be reduced, and the grown single crystal can be melted back.

  By turning off the output of the liquid surface heating device 30, the meltback can be terminated, and the temperature gradient of the Si-C solution 24 is changed again to a temperature gradient that decreases in temperature from the inside toward the surface. Single crystals can also be grown.

  In the present embodiment, not only is it possible to melt back the grown single crystal, but also the liquid surface can be heated. Therefore, in the liquid surface of the Si—C solution 24 when the growth of the single crystal is resumed after melt back. An abrupt temperature drop can be suppressed, and generation of polycrystals near the liquid surface can be suppressed.

(Fourth Embodiment of the Manufacturing Method)
In the fourth embodiment of the manufacturing method according to the present invention, the seed crystal holding shaft is heated by a seed crystal holding shaft heating device arranged around the seed crystal holding shaft, and heat conduction is performed through the seed crystal holding shaft. Suppressing heat removal from the Si-C solution and changing the temperature gradient from the inside of the Si-C solution to the surface region to a constant temperature or a temperature gradient increasing in temperature to change the Si-C solution from the inside to the surface region. The grown single crystal can be melted back by reducing the SiC saturation in it. The grown single crystal can be melted back by changing the temperature gradient substantially only in the vicinity of the grown single crystal to lower the saturation of the Si—C solution near the grown single crystal.

  As shown in FIG. 5, a seed crystal holding shaft heating device 32 is disposed around the seed crystal holding shaft 12, and the seed crystal holding shaft 12 is heated by the seed crystal holding shaft heating device 32 during the growth of the SiC single crystal. Thus, heat removal from the Si-C solution 24 due to heat conduction through the seed crystal holding shaft 12 can be reduced.

  By reducing heat removal from the Si-C solution 24 through the seed crystal holding shaft 12, the SiC saturation in the Si-C solution 24 in the region from the inside to the surface can be reduced, and the grown single crystal is melted. Can be back.

  By turning off the output of the seed crystal holding shaft heating device 32, the meltback can be terminated, and the temperature gradient of the Si-C solution 24 in the region from the inside to the surface is lowered again from the inside toward the surface. The SiC single crystal can be grown by changing the temperature gradient.

  The seed crystal holding shaft heating device 32 can be any heating device that can be arranged and heated around the seed crystal holding shaft 12, and can be, for example, a high-frequency heater, a resistance heater, or the like.

  In this embodiment, not only can the grown single crystal be melted back, but the temperature gradient of the Si—C solution is not directly changed by heating from the heating device, but heat removal via the seed crystal holding shaft is used. Therefore, the degree of saturation of the Si—C solution only in the vicinity of the grown single crystal can be reduced, the temperature variation of the Si—C solution can be further reduced, and the occurrence of polycrystals can be suppressed.

(Fifth Embodiment of the Manufacturing Method)
In the fifth embodiment of the manufacturing method according to the present invention, the heating device arranged around the crucible has a temperature gradient that decreases in temperature from the inside toward the surface in the crucible, and from the inside toward the deep part. The SiC seed crystal substrate held on the seed crystal holding shaft is brought into contact with the Si-C solution heated so as to have a temperature gradient that decreases in temperature, and a SiC single crystal is grown from the seed crystal substrate as a base point. A method for producing a SiC single crystal by a method,
During the growth of the SiC single crystal, at least a part of the grown single crystal can be immersed in a region having a temperature gradient in which the temperature decreases from the inside toward the deep portion, and the grown single crystal can be melted back.

As shown in FIG. 6, the Si—C solution 24 is heated so as to have a temperature gradient in which the surface temperature is lower than the inside and a temperature in the deep part is lower than the inside,
During the growth of the SiC single crystal, at least a part of the grown single crystal can be immersed in a region having a temperature gradient in which the temperature is constant or decreases from the inside toward the deep portion.

  The growing single crystal can be melted back by immersing at least a part of the growing single crystal from the inside to a region having a constant temperature in the deep part or a temperature gradient in which the temperature decreases. This is because the SiC saturation in the SiC solution in the vicinity of the grown single crystal is lowered by immersing the grown single crystal up to the above region.

  A region having a temperature gradient in which the immersion depth of the grown single crystal can be changed according to the range where the grown single crystal is to be melted back, such as the lower surface, the lower surface, and the side surface of the grown single crystal, and the temperature decreases from the inside toward the deep portion. It is possible to adjust the range of the grown single crystal that reaches.

  By returning the grown single crystal to the original position, the meltback can be completed and the SiC single crystal can be grown.

  In this embodiment, no additional device is required, which is advantageous in terms of cost.

  In FIG. 6, it is preferable that a relationship of t ≧ d is satisfied, where d is the immersion depth from the surface of the Si—C solution to the lower surface of the grown single crystal, and t is the thickness of the grown single crystal. As a result, the Si—C solution 24 is placed on the seed crystal holding shaft 12 while the grown single crystal is immersed and melted back from the inside to the deep region of the Si—C solution 24 having a constant temperature or a temperature gradient that lowers the temperature. Can be prevented from coming into contact with each other, and generation of polycrystals can be suppressed.

  In order to obtain the relationship of t ≧ d, the Si—C solution 24 is heated so as to have a temperature distribution such that the distance from the surface of the Si—C solution 24 to the heating center is smaller than the thickness t of the grown single crystal. can do. Alternatively, in order to obtain a relationship of t ≧ d, a seed crystal in which the thickness t of the grown single crystal is larger than the distance from the surface of the Si—C solution 24 to the heating center can be prepared.

  In any of the first to fifth embodiments, the seed crystal substrate may be heated in advance and then contacted with the Si-C solution. When a low-temperature seed crystal substrate is brought into contact with a high-temperature Si—C solution, heat shock dislocation may occur in the seed crystal. Heating the seed crystal substrate before bringing the seed crystal substrate into contact with the Si—C solution is effective for preventing thermal shock dislocation and growing a high-quality SiC single crystal. The seed crystal substrate can be heated by heating the seed crystal holding shaft. Alternatively, the Si—C solution may be heated to a temperature at which the SiC single crystal is grown after bringing the seed crystal into contact with a relatively low temperature Si—C solution. This case is also effective for preventing heat shock dislocation and growing a high-quality SiC single crystal.

The present invention also includes a crucible containing a Si-C solution;
A heating device arranged around the crucible;
A seed crystal holding shaft arranged to be movable in the vertical direction,
The SiC seed crystal held on the seed crystal holding shaft is brought into contact with a Si-C solution heated so as to have a temperature gradient that decreases from the inside toward the surface, and a SiC single crystal is grown from the seed crystal as a starting point. An apparatus for producing a SiC single crystal by a solution method,
During the growth of the SiC single crystal, the temperature gradient in the surface region from the inside of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature, and the seed crystal and the SiC single crystal grown from the seed crystal are used as the starting point. The SiC single crystal manufacturing apparatus includes means for melting back a single crystal including the crystal (hereinafter referred to as a grown single crystal).

  According to the manufacturing apparatus of the present invention, at any timing during the growth of the SiC single crystal, the temperature gradient of the surface region from the inside of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature, The grown single crystal can be melted back by lowering the SiC saturation in the Si-C solution in the surface region. Moreover, according to the manufacturing apparatus which concerns on this invention, it is also possible to melt back a seed crystal before growing a SiC single crystal.

  According to the manufacturing apparatus of the present invention, since dislocations and defects generated during the growth of the SiC single crystal can be dissolved, a SiC single crystal with few dislocations and defects can be obtained. Following the meltback, the growth of the SiC single crystal can be continued, and the meltback and the growth of the SiC single crystal can be repeated a plurality of times. As a matter of course, the meltback means by the present manufacturing apparatus is applied during the growth of the SiC single crystal, and the meltback means provided in the manufacturing apparatus according to the present invention is applied to the seed crystal substrate before the growth of the SiC single crystal. Or a conventional melt-back means for the seed crystal substrate may be used in combination.

  The definitions related to the growth single crystal and meltback described above in relation to the manufacturing method according to the present invention and the related description, and the explanation related to an example of the basic configuration of the SiC single crystal manufacturing apparatus that can be used are The same applies to the apparatus.

  There are several methods for melting back the grown single crystal at an arbitrary timing when growing the SiC single crystal. This will be described below with reference to the drawings.

(First embodiment of the manufacturing apparatus)
A first embodiment of a manufacturing apparatus according to the present invention is shown in FIG.

  As shown in FIG. 2, the first embodiment of the manufacturing apparatus includes means for further arranging a heat insulating material 28 on the heat insulating material 18 on the upper part of the crucible 10 during the growth of the SiC single crystal. If the heat insulating material 28 is further arranged on the heat insulating material 18 at the upper part of the crucible, the heat insulating effect by the heat insulating material is improved, and particularly the temperature of the surface of the Si-C solution 24 is increased. The temperature gradient of the Si-C solution 24 that decreases in temperature toward the temperature can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, in the Si—C solution in the region from the inside to the surface. SiC saturation can be reduced, and the grown single crystal can be melted back.

  The first embodiment of the manufacturing apparatus also includes means for removing the heat insulating material 28 from the top of the heat insulating material 18. The meltback can be terminated by removing the heat insulating material 28 from the upper part of the heat insulating material 18, and the temperature gradient of the Si-C solution is changed again to a temperature gradient in which the temperature decreases from the inside toward the surface, and SiC is changed. Single crystals can also be grown.

  The means for arranging and removing the heat insulating material 28 can be any manual or automatic means. For example, the heat insulating material 28 can be moved up and down by an elevator having a lifting means. Moreover, you may have a means to use two or more heat insulating materials in piles, or prepare the heat insulating material which has some thickness as the heat insulating material 28, and set desired thickness according to the target temperature gradient. You may have a means to select the heat insulating material to have.

(Second embodiment of the manufacturing apparatus)
A second embodiment of the manufacturing apparatus according to the present invention is shown in FIG.

  As shown in FIG. 3, since the Si—C solution 24 accommodated in the crucible 10 has a configuration that is heated by the heating device 22 disposed around, the Si—C solution 24 is located near the center of the heating device 22. Since a certain Si-C solution is most easily heated and heat is likely to escape from the lower part of the crucible, the Si-C solution is usually formed while forming a temperature gradient in which the temperature decreases from the inside of the Si-C solution toward the surface of the solution. It is easy to form a temperature gradient in which the temperature decreases from the inside of the solution 24 toward the deep part of the solution. That is, there is a heating center inside the Si—C solution 24, and a temperature gradient can be formed in which the temperature is relatively low at the surface and deep portions and the temperature is relatively high inside.

  In this embodiment, as shown in FIG. 3, it is possible to have means for moving the heating device 22 arranged around the crucible 10 in the vertical direction with respect to the crucible 10 during the growth of the SiC single crystal. . When the heating device 22 is moved upward with respect to the crucible 10, the heating center in the crucible can be moved upward in the crucible, so that a temperature gradient in which the temperature decreases from the inside toward the deep portion in the SiC solution 24. By moving upward, the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution 24 that decreases in temperature from the inside toward the surface in the vicinity of the seed crystal substrate 14, the Si—C solution in the region from the inside to the surface is changed to a constant temperature or a temperature gradient that increases in temperature. The SiC saturation in 24 can be reduced, and the grown single crystal can be melted back.

  The meltback can be terminated by moving the heating device 22 moved upward, and the temperature gradient of the Si-C solution is changed again to a temperature gradient that decreases from the inside toward the surface. Thus, a SiC single crystal can be grown.

  The means for moving the heating device 22 up and down can be any manual or automatic means, for example, it can have means for moving the heating device 22 up and down by an elevator having lifting means.

  In this embodiment, since the temperature gradient in the Si-C solution in the vicinity of the growth single crystal can be continuously changed, not only the growth single crystal can be melted back, but also the growth rate of the SiC single crystal can be increased. It can also be changed continuously.

  In the variation of the second embodiment, as shown in FIG. 3, a crucible containing a Si—C solution 24 with respect to a heating device 22 arranged around the crucible 10 during the growth of a SiC single crystal. 10 has means for moving up and down. When the crucible 10 is moved downward with respect to the heating device 22, the heating center in the crucible can be moved upward in the crucible, so that a temperature gradient in which the temperature decreases from the inside toward the deep portion is changed to the Si—C solution 24. The temperature gradient of the Si—C solution that decreases in temperature from the inside toward the surface in the vicinity of the seed crystal substrate 14 can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution 24 in the vicinity of the seed crystal substrate 14, which decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, Si—C in the region from the inside to the surface is obtained. The SiC saturation in the solution 24 can be reduced, and the grown single crystal can be melted back.

  The meltback can be terminated by moving the crucible 10 moved downward, and the temperature gradient of the Si-C solution 24 is changed again to a temperature gradient that decreases from the inside toward the surface. Thus, a SiC single crystal can be grown.

  The means for moving the crucible 10 up and down can be performed manually or automatically by any method. For example, the crucible 10 can be moved up and down by an elevator having a lifting means.

  Further, both the heating device 22 and the crucible 10 are simultaneously moved up and down to change the temperature gradient of the Si—C solution, the temperature of which decreases from the inside toward the surface, to a constant temperature or a temperature gradient of increasing the temperature. You may have a means to melt back the crystal.

(Third embodiment of the manufacturing apparatus)
FIG. 4 shows a third embodiment of the manufacturing apparatus according to the present invention.

  As shown in FIG. 4, the third embodiment of the present manufacturing apparatus includes a liquid surface heating device 30 disposed on the vicinity of the liquid surface of the Si—C solution 24. During the growth of the SiC single crystal, the liquid surface heating device 30 heats the Si—C solution 24 from the liquid surface so that the temperature gradient in the region of the surface from the inside of the Si—C solution 24 becomes a constant temperature or a temperature gradient that rises. Can be changed.

  By changing the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, in the Si—C solution in the region from the inside to the surface. SiC saturation can be reduced, and the grown single crystal can be melted back.

  The liquid level heating device 30 can be any heating device as long as it is arranged in the crucible and can heat the Si-C solution 24 from the liquid level. For example, the Si-C as shown in FIG. In the vicinity of the liquid surface of the solution 24, a graphite heater 34 having a ring-shaped cross section and having an S-shaped cross section and having a high frequency coil heater 36 can be used. The graphite heater 34 may have other shapes such as an L shape.

  By turning off the output of the liquid surface heating device 30, the meltback can be completed, and the temperature gradient of the Si-C solution is changed again to a temperature gradient that decreases in temperature from the inside toward the surface. Crystals can also be grown.

  In the present embodiment, not only is it possible to melt back the grown single crystal, but also the liquid surface can be heated. Therefore, in the liquid surface of the Si—C solution 24 when the growth of the single crystal is resumed after melt back. An abrupt temperature drop can be suppressed, and generation of polycrystals near the liquid surface can be suppressed.

(Fourth embodiment of the manufacturing apparatus)
FIG. 5 shows a fourth embodiment of the manufacturing apparatus according to the present invention.

  As shown in FIG. 5, the fourth embodiment of the manufacturing apparatus includes a seed crystal holding shaft heating device 32 disposed around the seed crystal holding shaft 12. During the growth of the SiC single crystal, the seed crystal holding shaft 12 is heated by the seed crystal holding shaft heating device 32 to suppress heat removal from the Si-C solution 24 due to heat conduction through the seed crystal holding shaft 12. The temperature gradient of the Si—C solution that decreases in temperature from the inside in the vicinity of the seed crystal substrate 14 toward the surface can be changed to a constant temperature or a temperature gradient that increases in temperature.

  By changing the temperature gradient of the Si—C solution in the vicinity of the seed crystal substrate 14 that decreases in temperature from the inside toward the surface, to a constant temperature or a temperature gradient that increases in temperature, in the Si—C solution in the region from the inside to the surface. SiC saturation can be reduced, and the grown single crystal can be melted back.

  By turning off the output of the seed crystal holding shaft heating device 32, the meltback can be terminated, and the temperature gradient of the Si-C solution 24 in the region from the inside to the surface is lowered again from the inside toward the surface. The SiC single crystal can be grown by changing the temperature gradient.

  The seed crystal holding shaft heating device 32 can be any heating device that can be arranged and heated around the seed crystal holding shaft 12, and can be, for example, a high-frequency heater, a resistance heater, or the like.

  In this embodiment, not only can the grown single crystal be melted back, but the temperature gradient of the Si—C solution is not directly changed by heating from the heating device, but heat removal via the seed crystal holding shaft is performed. Since it uses, the dispersion | variation from the predetermined temperature of the Si-C solution of the growth single crystal vicinity can be suppressed smaller, and generation | occurrence | production of a polycrystal can be suppressed.

(Fifth embodiment of the manufacturing apparatus)
A fifth embodiment of the manufacturing apparatus according to the present invention is shown in FIG.

The fifth embodiment of the manufacturing apparatus is
A crucible containing a Si-C solution;
A heating device arranged around the crucible;
A seed crystal holding shaft arranged to be movable in the vertical direction,
The SiC seed crystal held on the seed crystal holding shaft is heated to have a temperature gradient in which the temperature decreases from the inside toward the surface and a temperature gradient in which the temperature decreases from the inside toward the deep portion. A SiC single crystal manufacturing apparatus by a solution method, which is brought into contact with a solution and grows a SiC single crystal based on a seed crystal.
During the growth of the SiC single crystal, there is provided means for immersing at least a part of the grown single crystal to a region having a temperature gradient in which the temperature decreases from the inside toward the deep part, and melt-back the grown single crystal.

As shown in FIG. 6, in the fifth embodiment of the manufacturing apparatus, the Si—C solution 24 has a temperature gradient in which the surface temperature is lower than that in the interior and the temperature in the deep portion is lower than in the interior. Heated to have
During the growth of the SiC single crystal, there is provided means for immersing at least a part of the grown single crystal to a region having a temperature gradient in which the temperature decreases from the inside toward the deep portion.

  The growing single crystal can be melted back by immersing at least a part of the growing single crystal from the inside to a region having a constant temperature in the deep part or a temperature gradient in which the temperature decreases. This is because the SiC saturation in the SiC solution in the vicinity of the grown single crystal is lowered by immersing the grown single crystal up to the above region.

  The fifth embodiment of the manufacturing apparatus has means for changing the immersion depth of the grown single crystal depending on the range where the grown single crystal is to be melted back, such as the lower surface, the lower surface, and the side surface of the grown single crystal. Means are provided for adjusting the range of the growing single crystal reaching the region having a temperature gradient in which the temperature decreases toward the deep part.

  The fifth embodiment of the manufacturing apparatus can also end the meltback by returning the grown single crystal to the original position, and can grow the SiC single crystal.

  The fifth embodiment of the manufacturing apparatus is advantageous in terms of cost because no additional apparatus is required.

  Further, as shown in FIG. 6, the manufacturing apparatus according to the fifth embodiment is such that the immersion depth from the surface of the Si—C solution to the lower surface of the grown single crystal is d, and the thickness of the grown single crystal is t. , T ≧ d is preferably included. As a result, the Si—C solution 24 is placed on the seed crystal holding shaft 12 while the grown single crystal is immersed and melted back from the inside to the deep region of the Si—C solution 24 having a constant temperature or a temperature gradient that lowers the temperature. Can be prevented from coming into contact with each other, and generation of polycrystals can be suppressed.

  The manufacturing apparatus according to the fifth embodiment has a temperature distribution such that the distance from the surface of the Si-C solution 24 to the heating center is smaller than the thickness t of the grown single crystal in order to obtain a relationship of t ≧ d. The Si-C solution 24 can be heated to have. Further, in the manufacturing apparatus according to the fifth embodiment, in order to obtain the relationship of t ≧ d, the thickness t of the grown single crystal is larger than the distance from the surface of the Si—C solution 24 to the heating center. A seed crystal can also be arranged.

  In any of the manufacturing apparatuses 1 to 5 according to the above embodiments, the seed crystal substrate may be heated in advance, and then the seed crystal substrate may be brought into contact with the Si—C solution. When a low-temperature seed crystal substrate is brought into contact with a high-temperature Si—C solution, heat shock dislocation may occur in the seed crystal. Heating the seed crystal substrate before bringing the seed crystal substrate into contact with the Si—C solution is effective for preventing thermal shock dislocation and growing a high-quality SiC single crystal. The seed crystal substrate can be heated by heating the seed crystal holding shaft. Moreover, after making a seed crystal contact a comparatively low temperature Si-C solution, you may have a means to heat a Si-C solution to the temperature which makes a crystal grow. This case is also effective for preventing heat shock dislocation and growing a high-quality SiC single crystal.

  The SiC single crystal manufacturing method and manufacturing apparatus according to the present invention are not limited to the manufacturing methods and manufacturing apparatuses according to the first to fifth embodiments. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The production method and production apparatus according to the present invention were evaluated as to whether or not the seed crystal substrate could be melt-backed by the following examples and comparative examples. In this example and the comparative example, for the sake of convenience, the possibility of meltback was evaluated using a seed crystal substrate instead of the grown single crystal, but the results are the same even when the grown single crystal is used. The possibility of meltback is based on the criteria that when the thickness of the seed crystal substrate is not reduced or changed, the meltback is possible, and when the thickness of the seed crystal substrate is increased, the crystal grows without being meltbacked. Judged.

(Common conditions)
Conditions common to Examples 1 to 5 and Comparative Examples 1 to 3 are shown. In each example, using the single crystal manufacturing apparatus shown in FIGS. 1 to 5, a graphite crucible having an inner diameter of 40 mm and a height of 185 mm for accommodating the Si—C solution, and a heat insulating material having a thickness of 10 mm are arranged around the graphite crucible. Then, Si / Cr / Ni / Ce was charged as a melt raw material at an atomic composition percentage of 50: 40: 4: 6. The air inside the single crystal production apparatus was replaced with argon. A high-frequency coil including a high upper coil and a lower coil was used as a heating device disposed around the crucible. The raw material in the graphite crucible was melted by energizing and heating the high frequency coil to form a Si / Cr / Ni / Ce alloy melt. Then, a sufficient amount of C was dissolved from the graphite crucible into the Si / Cr / Ni / Ce alloy melt to form a Si—C solution.

  In Examples 1-4 and Comparative Examples 1-2, a SiC single crystal having a disc-shaped 4H-SiC single crystal having a thickness of 1 mm and a diameter of 12 mm and having an offset angle of 0 ° with respect to the c-plane is prepared. And used as a seed crystal substrate. In Example 5, a 4H-SiC single crystal having a rectangular parallelepiped shape having a length of 5 mm, a width of 5 mm, and a thickness of 15 mm was used as a seed crystal, and the lower surface had a 0 ° offset angle with respect to the c-plane. In Comparative Example 3, a 4H—SiC single crystal having a rectangular parallelepiped shape having a length of 5 mm, a width of 5 mm, and a thickness of 5 mm was used as a seed crystal, and the seed crystal having a lower surface having an offset angle of 0 ° with respect to the c-plane was used. .

  Using a cylindrical graphite shaft having a length of 20 cm and a diameter of 12 mm as a seed crystal holding shaft, the upper surface of the seed crystal substrate was bonded to the end surface of the graphite shaft using a graphite adhesive.

  The temperature of the surface of the Si—C solution is increased to 1920 ° C. by adjusting the outputs of the upper coil and the lower coil, and the temperature gradient from the inside of the solution in the range of 8 mm from the solution surface to the solution surface is 1 ° C. / The temperature was controlled to have a temperature gradient that decreased at 2 ° C./mm from a depth of 8 mm to a depth of 10 mm while having a temperature gradient that decreased in mm. That is, it had a temperature distribution with a heating center at a depth of 8 mm from the solution surface. The temperature was measured using a thermocouple in which a tungsten-rhenium strand capable of raising and lowering was placed in a graphite protective tube.

(Comparative Example 1)
The single crystal manufacturing apparatus shown in FIG. 1 is used, and the position of the lower surface of the seed crystal coincides with the liquid surface of the Si-C solution while keeping the lower surface of the seed crystal adhered to the graphite shaft in parallel with the Si-C solution surface. The seed crystal was placed in position and contacted with the Si-C solution, and held for 10 hours. During this time, the Si-C solution did not contact the graphite shaft.

  Next, the graphite shaft was raised, and the seed crystal substrate was separated from the Si-C solution and the graphite shaft and collected. From the seed crystal substrate as a starting point, 1 mm thick crystal growth was observed in the vertical direction on the lower surface of the seed crystal, and the seed crystal substrate was not melted back.

(Example 1)
Using the single crystal manufacturing apparatus shown in FIG. 2, an additional 5 mm thick heat insulating material is arranged on the heat insulating material arranged on the crucible upper part, the total thickness of the heat insulating material on the crucible upper part is 15 mm, and the output of the high frequency coil is lowered. The temperature at the surface of the Si—C solution was maintained at 1920 ° C. At this time, the temperature gradient from the inside of the solution in the range of 8 mm from the solution surface to the solution surface had a temperature gradient in which the temperature increased at 1 ° C./mm. The conditions other than these were the same as the conditions shown in Comparative Example 1, and the seed crystal substrate was brought into contact with the Si—C solution.

  When the seed crystal substrate was separated from the Si-C solution and the graphite shaft and recovered, the seed crystal substrate was melted and the thickness was reduced, and the seed crystal substrate was melted back.

(Example 2)
Using the single crystal manufacturing apparatus shown in FIG. 3, the graphite crucible was moved 20 mm downward relative to the high-frequency coil, and the heating center in the graphite crucible was moved 20 mm upward. At this time, while adjusting the output of the high frequency coil to maintain the temperature at the surface of the Si—C solution at 1920 ° C., the temperature gradient from the inside of the solution in the range of 8 mm from the solution surface toward the solution surface is 0 ° C./mm. Met. Conditions other than these were the same as those shown in Comparative Example 1, and the seed crystal substrate was brought into contact with the Si-C solution.

  When the seed crystal substrate was separated from the Si-C solution and the graphite shaft and recovered, the seed crystal substrate was melted and reduced in thickness and melted back.

(Comparative Example 2)
The graphite crucible was moved upward by 10 mm with respect to the high frequency coil, and the heating center in the graphite crucible was moved downward by 10 mm. At this time, while adjusting the output of the high-frequency coil to maintain the temperature at the surface of the Si—C solution at 1920 ° C., the temperature gradient from the inside of the solution in the range of 8 mm from the solution surface toward the solution surface is 1 ° C./mm. It had a temperature gradient that decreased in temperature. Conditions other than these were the same as those shown in Comparative Example 1, and the seed crystal substrate was brought into contact with the Si-C solution.

  When the seed crystal substrate was separated from the Si-C solution and the graphite axis and recovered, 1.1 mm thick crystal growth was observed with the seed crystal substrate as a base point, and the seed crystal substrate was not melted back.

(Example 3)
7 is a graphite heater having a ring shape in the vicinity of the surface of the Si-C solution and having an S-shaped cross section and a high-frequency coil heater as a liquid surface heating device using the single crystal manufacturing apparatus shown in FIG. The heater was arranged so that the distance from the liquid surface of the Si—C solution on the lower surface of the ring-shaped heater was 16 mm, and the Si—C solution was heated from the liquid surface. At this time, while adjusting the output of the high-frequency coil to maintain the temperature at the surface of the Si-C solution at 1920 ° C., the temperature gradient from the inside of the solution in the range of 8 mm from the solution surface toward the solution surface is 1.5 ° C. It had a temperature gradient that increased in temperature at / mm. The conditions other than these were the same as the conditions shown in Comparative Example 1, and the seed crystal substrate was brought into contact with the Si—C solution.

  When the seed crystal substrate was separated from the Si-C solution and the graphite shaft and recovered, the seed crystal substrate was melted and reduced in thickness and melted back.

Example 4
The single crystal production apparatus shown in FIG. 5 is used, and the upper part of the seed crystal holding shaft is heated using a high frequency heater as the seed crystal holding shaft heating apparatus 32, so that the saturation of the Si—C solution in the vicinity of the seed crystal is lowered. The output of the high frequency coil which is the heating device 22 was lowered, and the temperature on the surface of the Si—C solution was maintained at 1920 ° C. The conditions other than these were the same as the conditions shown in Comparative Example 1, and the seed crystal substrate was brought into contact with the Si—C solution.

  When the seed crystal substrate was separated from the Si-C solution and the graphite shaft and recovered, the seed crystal substrate was melted and reduced in thickness and melted back.

(Example 5)
Using the single crystal manufacturing apparatus shown in FIG. 6, a rectangular parallelepiped seed crystal having a length of 5 mm, a width of 5 mm, and a thickness of 15 mm is used as a seed crystal substrate, and the lower surface of the seed crystal is brought to a depth of 8 mm from the surface of the Si—C solution. Soaked. The other conditions were the same as those shown in Comparative Example 1.

  When the seed crystal substrate is in contact with the Si-C solution, the thickness of the seed crystal substrate is larger than the immersion depth, so that the Si-C solution is wetted up to the graphite axis, and the Si-C solution is in contact with the graphite axis. There wasn't.

  When the seed crystal substrate was separated from the Si-C solution and the graphite shaft and recovered, the seed crystal substrate was melted and reduced in thickness and melted back. Since the Si-C solution did not contact the graphite shaft, the generation of polycrystals could be suppressed.

(Comparative Example 3)
As the seed crystal substrate, a rectangular parallelepiped seed crystal having a length of 5 mm, a width of 5 mm, and a thickness of 5 mm was used, and the lower surface of the seed crystal was immersed to a depth of 1 mm. The other conditions were the same as those shown in Comparative Example 1.

  When the seed crystal substrate was separated from the Si-C solution and the graphite axis and recovered, crystal growth was observed with the seed crystal substrate as a starting point, and the seed crystal substrate was not melted back.

DESCRIPTION OF SYMBOLS 100 Single crystal manufacturing apparatus 10 Graphite crucible 12 Graphite shaft 14 Seed crystal substrate 18 Heat insulating material 22 Heating device 24 Si-C solution 26 Quartz tube 28 Heat insulating material 30 Liquid surface heating device 32 Seed crystal holding shaft heating device 34 S-shaped liquid surface Heater 36 High-frequency coil provided in liquid level heater

Claims (20)

A SiC seed crystal held on a seed crystal holding shaft in a Si-C solution heated to have a temperature gradient decreasing from the inside toward the surface in the crucible by a heating device arranged around the crucible A SiC single crystal by a solution method, wherein a SiC single crystal is grown from the seed crystal as a base point,
During the growth of the SiC single crystal, the temperature gradient in the region from the inside to the surface of the Si-C solution was changed to a constant temperature or a temperature gradient increasing in temperature, and the seed crystal and the seed crystal were grown as a starting point. look including to melt back the single crystal and a SiC single crystal,
During the growth of the SiC single crystal or during the meltback, the Si-C solution does not contact the seed crystal holding shaft.
A method for producing a SiC single crystal. The crucible has a heat insulating material around the crucible;
The temperature gradient of the region from the inside to the surface of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature by increasing the thickness of the heat insulating material at the top of the crucible. The manufacturing method of the SiC single crystal of description. The Si-C solution when growing the SiC single crystal has a temperature gradient that decreases in temperature from the inside toward the surface, and a temperature gradient that decreases in temperature from the inside toward the deep part. Is heated,
The temperature gradient in the region from the inside to the surface of the Si-C solution is changed to a constant temperature or a temperature gradient that increases in temperature by moving the position of the heating center in the crucible upward. 2. A method for producing a SiC single crystal according to 1.   The method for producing a SiC single crystal according to claim 3, wherein the position of the heating center in the crucible is moved upward by moving the heating device upward with respect to the crucible.   The method for producing an SiC single crystal according to claim 3, wherein the position of the heating center in the crucible is moved upward by moving the crucible downward with respect to the heating device.   Changing the temperature gradient of the region from the inside to the surface of the Si-C solution to a constant temperature or a temperature gradient increasing in temperature is achieved by the liquid surface heating device disposed on the liquid surface of the Si-C solution. The manufacturing method of the SiC single crystal of Claim 1 performed by heating C solution.   Changing the temperature gradient from the inside to the surface region of the Si-C solution to a constant temperature or a temperature gradient increasing in temperature is achieved by the seed crystal holding shaft heating device disposed around the seed crystal holding shaft. The manufacturing method of the SiC single crystal of Claim 1 performed by heating a holding shaft and suppressing the heat removal from the said Si-C solution via the said seed crystal holding shaft. The crucible was heated by the heating device arranged around the crucible so as to have a temperature gradient in the crucible that decreases in temperature from the inside toward the surface, and a temperature gradient in which the temperature decreases from the inside toward the deep part. A method for producing a SiC single crystal by a solution method, wherein a SiC single crystal held on a seed crystal holding shaft is brought into contact with a Si-C solution, and a SiC single crystal is grown from the seed crystal as a base point.
During the growth of the SiC single crystal, a region having a temperature gradient in which at least a part of the single crystal including the seed crystal and the SiC single crystal grown with the seed crystal as a base point is decreased in temperature from the inside toward the deep portion. by immersing up, it looks including to melt back the single crystal comprising said seed crystal and the grown SiC single crystal the seed crystal as a base point,
During the growth of the SiC single crystal or during the meltback, the Si-C solution does not contact the seed crystal holding shaft.
A method for producing a SiC single crystal.   The SiC single crystal grown from the seed crystal and the seed crystal as a base point, rather than the immersion depth from the surface of the Si-C solution of the single crystal including the seed crystal and the SiC single crystal grown from the seed crystal as a base point The method for producing a SiC single crystal according to claim 8, wherein the thickness of the single crystal including The melt containing the back was growing a SiC single crystal after manufacturing method of SiC single crystal according to any one of claims 1-9. A crucible containing a Si-C solution;
A heating device arranged around the crucible;
A seed crystal holding shaft arranged to be movable in the vertical direction,
The SiC seed crystal held on the seed crystal holding shaft is brought into contact with the Si-C solution heated so as to have a temperature gradient that decreases from the inside toward the surface, and the SiC single crystal is used as a base point. An apparatus for producing a SiC single crystal by a solution method for growing a crystal,
During the growth of the SiC single crystal, the temperature gradient in the region from the inside to the surface of the Si-C solution was changed to a constant temperature or a temperature gradient increasing in temperature, and the seed crystal and the seed crystal were grown as a starting point. for example Bei a means to melt back the single crystal and a SiC single crystal,
Control means for preventing the Si-C solution from coming into contact with the seed crystal holding shaft during the growth of the SiC single crystal or during the meltback.
SiC single crystal manufacturing equipment. The crucible has a heat insulating material around the crucible;
The meltback means,
A means for changing the thickness of the heat insulating material at the top of the crucible, and a means for changing the thickness of the heat insulating material during the growth of the SiC single crystal, thereby increasing the thickness of the heat insulating material at the top of the crucible. Means for changing the temperature gradient of the region from the inside to the surface of the Si-C solution to a constant temperature or a temperature gradient that increases in temperature.
The apparatus for producing a SiC single crystal according to claim 11 , comprising: The Si-C solution when growing the SiC single crystal has a temperature gradient that decreases in temperature from the inside toward the surface, and a temperature gradient that decreases in temperature from the inside toward the deep part. Is heated,
The meltback means,
Means for moving above the position of the heating center in the crucible to change the temperature gradient in the region from the inside to the surface of the Si-C solution to a constant temperature or a temperature gradient increasing in temperature;
The apparatus for producing a SiC single crystal according to claim 11 , comprising: Elevating means for moving the heating device in the vertical direction;
Means for moving the heating device upward with respect to the crucible by the elevating means to change the temperature gradient from the inside to the surface area of the Si-C solution to a constant temperature or a temperature gradient increasing in temperature. ,
The SiC single crystal manufacturing apparatus according to claim 13 , comprising: Elevating means for moving the crucible up and down;
By moving the crucible downward with respect to the heating device by the elevating means, the temperature gradient in the region from the inside to the surface of the Si-C solution is changed to a constant temperature or a temperature gradient increasing in temperature. means,
The SiC single crystal manufacturing apparatus according to claim 13 , comprising: The meltback means,
The liquid surface heating means disposed on the surface of the Si-C solution, and the Si-C solution is heated from the surface by the liquid surface heating means during the growth of the SiC single crystal. Means for changing the temperature gradient in the region from the inside to the surface to a constant temperature or a temperature gradient that increases in temperature;
The apparatus for producing a SiC single crystal according to claim 11 , comprising: The meltback means,
A seed crystal holding shaft heating means disposed around the seed crystal holding shaft, and the seed crystal holding shaft is heated by the seed crystal holding shaft heating means during the growth of the SiC single crystal, thereby holding the seed crystal. Means for suppressing heat removal from the SiC solution via the shaft, and changing the temperature gradient in the region from the inside to the surface of the Si-C solution to a constant temperature or a temperature gradient increasing in temperature;
The apparatus for producing a SiC single crystal according to claim 11 , comprising: A crucible containing a Si-C solution;
A heating device arranged around the crucible;
A seed crystal holding shaft arranged to be movable in the vertical direction,
The SiC seed crystal held on the seed crystal holding shaft has a temperature gradient that decreases in temperature from the inside toward the surface, and is heated so as to have a temperature gradient that decreases in temperature from the inside toward the deep portion. A SiC single crystal production apparatus by a solution method, which is brought into contact with a -C solution and grows a SiC single crystal based on the seed crystal,
During the growth of the SiC single crystal, a region having a temperature gradient in which at least a part of the single crystal including the seed crystal and the SiC single crystal grown with the seed crystal as a base point is decreased in temperature from the inside toward the deep portion. was immersed to, e Bei means for melt-back the single crystal and a grown SiC single crystal the seed crystal and the seed crystal as a base point,
Control means for preventing the Si-C solution from coming into contact with the seed crystal holding shaft during the growth of the SiC single crystal or during the meltback.
SiC single crystal manufacturing equipment. The meltback means controls the depth from the surface of the Si—C solution to the inside where the slope of the temperature gradient of the Si—C solution changes to be in a range smaller than the thickness of the seed crystal. The apparatus for producing a SiC single crystal according to claim 18 , comprising: The apparatus for producing an SiC single crystal according to any one of claims 11 to 19 , further comprising means for growing the SiC single crystal after the meltback.

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