JP2014043367A - METHOD FOR MAKING SiC SINGLE CRYSTAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for making an SiC single crystal by which an SiC single crystal is grown using a solution growth method, and at the time, the height of a step formed on a crystal growth surface can be reduced.SOLUTION: When an SiC single crystal is grown by developing a step comprising SiC on the crystal growth surface of an SiC seed crystal in a material solution using a liquid phase growth method, at least a part of step bunching is dissolved by applying external force to the material solution in order to flow the material solution in a direction opposite to the developing direction of the step.

Description

  The present invention relates to a method for producing a SiC single crystal by growing a SiC seed crystal.

  SiC (silicon carbide) is a thermally and chemically very stable semiconductor material. SiC has a forbidden band width of about 2 to 3 times and a dielectric breakdown voltage of about 10 times that of silicon (Si), which is currently widely used as a substrate material for electronic devices and the like. For this reason, the SiC single crystal is expected as a substrate material for power devices exceeding the devices using silicon.

  As a method for producing an SiC single crystal, there are a method of growing an SiC seed crystal in a gas phase (so-called vapor phase growth method) and a method of growing an SiC seed crystal in a liquid phase (so-called liquid phase growth method). Are known. Since the liquid phase growth method performs crystal growth in a state close to thermal equilibrium as compared with the vapor phase growth method, it is considered that a high-quality SiC single crystal can be obtained (for example, see Patent Document 1).

  By the way, during crystal growth, a number of steps are formed on the crystal growth surface of the SiC single crystal. It is difficult to control the height of this step as desired. When a SiC single crystal is used as a substrate for various devices, it may not be preferable that a step having a high height is formed on the surface of the SiC single crystal. In such a case, the SiC single crystal It was necessary to smooth the crystal growth surface by cutting or the like.

JP 2000-264790 A

  The present invention has been made in view of the above-described circumstances, and it is possible to grow a SiC single crystal by a liquid phase growth method and reduce the height of a step formed on a crystal growth surface. An object is to provide a manufacturing method.

  As a result of diligent research, the inventors of the present invention have solved the step bunching generated on the crystal growth surface of the SiC single crystal by growing the SiC single crystal under a specific condition by the liquid phase growth method. It has been found that the height of the step formed on the surface can be reduced.

  That is, the method for producing a SiC single crystal according to the present invention that solves the above-described problem comprises a step of forming SiC on the crystal growth surface of a SiC seed crystal by a liquid phase growth method in a raw material solution containing silicon (Si) and carbon (C). A crystal growth step of growing a SiC single crystal by developing the step, wherein the crystal growth step applies an external force to the raw material solution and causes the raw material solution to flow along a direction opposite to the progress direction of the step, It is a method comprising a smoothing step for solving at least a part of step bunching on the crystal growth surface.

  According to the manufacturing method of the present invention including such a method, the surface of the SiC single crystal in which step bunching occurs and relatively large irregularities are formed can be substantially smoothed by the smoothing step. For this reason, according to the manufacturing method of the SiC single crystal of the present invention, it is possible to obtain an SiC single crystal having a substantially smooth surface without performing polishing or cutting.

The method for producing a SiC single crystal of the present invention preferably includes any one of the following (1) to (4), and more preferably includes a plurality of (1) to (4).
(1) The crystal growth step includes a bunching step of causing step bunching on the crystal growth surface by causing the raw material solution to flow along the progress direction of the step.
(2) In the bunching step, a macro step made of SiC single crystal and having a height exceeding 70 nm is formed by the step bunching.
(3) In the bunching step, a macro step having a height of 80 nm or more is formed by the step bunching.
(4) In the bunching step, a macro step having a height of 100 nm or more is formed by the step bunching.

  As a result of diligent research, the inventors of the present invention have grown a seed crystal under a specific condition by a liquid phase growth method, thereby generating step bunching and crystallizing a single crystal while forming a high step. I have found that it can grow.

  That is, according to the SiC single crystal manufacturing method of the present invention having the above (1), step bunching can be generated in the bunching step, so that the single crystal can be grown while forming a high step. Is possible. In addition, by performing the bunching process before the smoothing process, it is possible to perform crystal growth while progressing a step having a high height, and thereafter to substantially smooth the crystal growth surface. In this case, the flow direction of the raw material solution with respect to the crystal growth surface of the seed crystal may be switched to two directions different by 180 °. For example, if the flow direction of the raw material solution is set in the same direction as the step progress direction of the SiC single crystal and then the direction opposite to the step progress direction, it is possible to obtain a SiC single crystal with few defects and a smooth surface.

  According to the method for producing a SiC single crystal of the present invention including any one of the above (2) to (4), a SiC single crystal with few defects can be easily produced as described later.

  The SiC single crystal obtained by the production method of the present invention can be used as a substrate for various devices or the like, or can be used as a seed crystal.

  According to the manufacturing method of the present invention, a SiC single crystal can be grown by a liquid phase growth method, and the height of the step formed on the crystal growth surface at that time can be reduced.

It is explanatory drawing which represents typically the relationship of the step progress direction, terrace surface, and step height in the SiC single crystal during crystal growth. It is explanatory drawing which represents typically the single crystal growth apparatus used in embodiment. It is explanatory drawing which represents typically the crucible in the manufacturing method of the SiC single crystal of Test 1, the flow direction of a raw material solution, and the position of a seed crystal. It is explanatory drawing which represents typically the position of the position adjustment element in the manufacturing method of the SiC single crystal of Test 1, a crucible, and a seed crystal. It is explanatory drawing which represents typically a mode that the off angle was formed in the (0001) plane of a SiC single crystal. It is a graph showing the step height in the AB position of the atomic force microscope image of the SiC single crystal of test 1a, and the said atomic force microscope image. It is a graph showing the step height in the CD position of the atomic force microscope image of the SiC single crystal of test 1b, and the said atomic force microscope image. It is a graph showing the time-dependent change of the step height in SiC single crystal 1a and 1b during crystal growth. 2 is an X-ray topography image obtained by imaging a seed crystal and an SiC single crystal at the initial stage of crystal growth by the method of Reference Test 1 at the same location. FIG. 13 is an X-ray topography image obtained by imaging the seed crystal used in Reference Test 1 at the same location as in FIGS. 11 and 12. FIG. 13 is an X-ray topography image obtained by imaging a SiC single crystal at the initial stage of crystal growth by the method of Reference Test 1 at the same position as in FIGS. 10 and 12. 12 is an X-ray topography image obtained by imaging the SiC single crystal of Reference Test 1 at the same location as in FIGS. 10 and 11. Relationship between conversion rate of threading screw dislocation (%) in SiC single crystals of Reference Tests 1 to 3 and the minimum step height in each SiC single crystal and the off-angle formed in the SiC seed crystal in Reference Tests 1 to 3 It is a graph showing. It is a laser microscope image of the SiC single crystal of Reference Test 1. It is a laser microscope image of the SiC single crystal of Reference Test 2. It is a laser microscope image of the SiC single crystal of Reference Test 3. It is explanatory drawing which represents typically the step of the SiC single crystal obtained based on FIG. It is a graph showing the relationship between the step height and off angle in each SiC single crystal of Reference Tests 1-3. It is a graph showing the relationship between the terrace width | variety and off angle in each SiC single crystal of the reference tests 1-3. It is explanatory drawing which represents the cross section of a SiC seed crystal typically. It is explanatory drawing which represents typically a mode that the macro step is advancing on the crystal growth surface of a SiC seed crystal. It is explanatory drawing which represents typically a mode that the macro step is advancing on the crystal growth surface of a SiC seed crystal. It is explanatory drawing which represents typically the SiC single crystal which carried out the crystal growth, developing the macro step formed with the manufacturing method of the SiC single crystal of this invention. It is explanatory drawing which represents typically the relationship between the height (h) of a macrostep, the step progress rate ( _Vstep ) of a _macrostep , terrace width (w), and the growth rate ( _vspiral ) of a screw dislocation. It is the microscope image which imaged the SiC single crystal of the reference test 4 using the Nomarski type | mold differential interference microscope.

  In the SiC single crystal growth method of the present invention, a solution containing silicon element and carbon element is used as the raw material solution. The SiC seed crystal is brought into contact with this raw material solution, and at least the solution in the vicinity of the SiC seed crystal is brought into a supercooled state. Thus, the C concentration of the raw material solution is supersaturated in the vicinity of the SiC seed crystal, and an SiC single crystal is grown (mainly epitaxial growth) on the SiC seed crystal. In the liquid phase growth method, since crystal growth proceeds in an environment close to a thermal equilibrium state, it is possible to obtain a high-quality SiC single crystal with a low density of defects such as stacking faults. In addition, the material of a raw material solution is not specifically limited, A general thing can be used. For example, Si or Si alloy can be used as the Si source of the raw material solution. Specifically, Si is the main component and selected from Ti, Cr, Sc, Ni, Al, Co, Mn, Mg, Ge, As, P, N, O, B, Dy, Y, Nb, Nd, and Fe. Or an alloy solution to which at least one kind is added. As the C source of the raw material solution, a hydrocarbon gas such as graphite, glassy carbon, SiC, methane, ethane, propane, acetylene, and a carbide of the element X described below (X = Li, Be, B, Na, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Br, Sr, Y, Zr, Nb, Mo, Ba, Hf, Ta, W, La, Ce, Sm, Eu, Ho, At least one selected from Yb, Th, U, Pu) can be used. As the SiC seed crystal, various crystal polymorphs represented by 4H—SiC and 6H—SiC can be used.

  In any case, by flowing the raw material solution along the direction opposite to the step progress direction in the SiC single crystal, at least part of the step bunching existing on the crystal growth surface is solved and the crystal growth surface is substantially smoothed. Is possible. In addition, by making the flow direction of the raw material solution in a direction along the step progress direction of the SiC single crystal, it is possible to generate step bunching and form a high step on the crystal growth surface. By the way, in this specification, making the flow direction of the raw material solution a direction along the step progress direction of the single crystal means making the flow direction of the raw material solution a direction parallel or substantially parallel to the step progress direction. . The crossing angle between the flow direction of the raw material solution and the step progress direction may be within ± 15 °. The crossing angle between the flow direction of the raw material solution and the step progress direction is preferably within 10 °, and more preferably within ± 5 °.

  In the present specification, the flow of the raw material solution refers to forced flow rather than convection. That is, generally, in the liquid phase growth method, since a temperature gradient or the like is formed in the raw material solution, convection of the raw material solution may occur even when the raw material solution is not forced to flow by an external force. In the production method of the present invention, the raw material solution is forced to flow to such an extent that the convection is canceled. The method for forcibly flowing the raw material solution is not particularly limited. For example, when crystal growth is performed in a raw material solution contained in a container such as a crucible, external force is indirectly applied to the raw material solution in the container by applying external force to the container and rotating or vibrating the container. And forced flow may be generated. Alternatively, the raw material solution may be forced to flow by applying a magnetic field directly to the raw material solution. In addition, it can be paraphrased that the raw material solution flows is that the position of at least one of the raw material solution in the liquid tank and the crystal growth surface of the seed crystal changes relative to the other. That is, it is possible to perform crystal growth while changing the position of the seed crystal itself while relatively changing the position of the raw material solution and the seed crystal.

  Further, the step height h in this specification refers to the distance between the terrace surfaces P1 and P2 shown in FIG. More specifically, the step height can be described as follows. As shown in FIG. 1, the terrace surface in any step S1 (that is, the tip surface in the crystal growth direction of the SiC seed crystal itself) is defined as a terrace surface P1, and a straight line passing through the terrace surface P1 is defined as a straight line L1. Further, the terrace surface of another step S2 adjacent to the front side in the step progress direction of the step S1 is P2, and a straight line passing through the terrace surface P2 is a straight line L2. In this case, the height of step S1 corresponds to the distance between the straight line L1 and the straight line L2. In the present specification, a step having a height exceeding 70 nm is called a macro step.

(Embodiment)
(Test 1)
Hereinafter, the SiC single crystal of the present invention and the manufacturing method thereof will be described with specific examples.

  A SiC single crystal was produced using a high frequency heating graphite hot zone furnace. FIG. 2 is an explanatory view schematically showing this single crystal growth apparatus. The single crystal growth apparatus 20 includes a carbon crucible 21, a heating element 22 that heats the crucible 21, a holding element 23 that can freely change its position relative to the inside of the crucible 21, and a crucible that rotates the crucible 21. It has the drive element 24 and the chamber (not shown) which accommodates these. The crucible 21 has a bottomed, generally cylindrical shape that opens upward. The inner diameter of the crucible 21 is 45 mm and the depth is 50 mm. The heating element 22 is an induction heating type heater. The heating element 22 has a coiled conductor 25 and a lead wire (not shown) that connects the conductor 25 and a power source (not shown). The conducting wire 25 is wound around the outer side of the crucible 21 to form a coil coaxial with the crucible 21. The holding element 23 includes a rod-shaped dip shaft portion 26 and a dip shaft drive portion (not shown) that drives the dip shaft portion 26. The diameter of the dip shaft portion 26 is 10 mm, and one end portion (the lower end portion in FIG. 2) in the longitudinal direction of the dip shaft portion 26 is branched into two. A holding portion 28 capable of holding the SiC seed crystal 1 is formed at each tip. The holding element 23 is held by a position adjusting element 3 described later.

  In Test 1, using this single crystal growth apparatus, the SiC seed crystal 1 was dipped in the raw material solution 29 in the crucible 21 and was grown while being pulled based on the TS Seed (Top Seed Solution Growth) method. .

  Specifically, the crucible drive element 24 was used to rotate the crucible 21 in one direction, and as shown in FIG. 3, the flow of the raw material solution 29 was formed in the crucible 21 in one direction as indicated by an arrow in the figure. More specifically, Si (purity 11N, manufactured by Tokuyama Corporation) is heated by the heating element 22 in the carbon crucible 21 to elute C contained in the crucible 21 into the Si melt in the crucible 21. Thus, a raw material solution 29 was obtained. As pretreatment, the SiC seed crystal and Si were ultrasonically cleaned in advance in methanol, acetone, and purified water (18 MΩ / cm), respectively.

  The set temperature of the heating element 22 in the single crystal growth apparatus 20 is 1700 ° C., and a temperature gradient is formed in the crucible 21 in the vertical direction in FIG. 2 (the liquid surface-bottom direction of the crucible 21) at 21 ° C./cm. It was done. That is, the raw material solution 29 accommodated in the crucible 21 has the highest temperature in a portion located in the vicinity of the conducting wire 25 and adjacent to the inner surface 21 a of the crucible 21. The closer to the center of the crucible 21 (the farther it is from the inner surface 21a of the crucible), or the farther away from the lead wire 25 in the axial direction of the crucible 21, that is, the vertical direction shown in FIG. With the temperature gradient formed in the raw material solution 29 in the crucible 21 in this way, while supplying high purity (99.9999% by volume) argon gas into the chamber, SiC seed crystal 1 (hereinafter simply referred to as seed crystal 1). The dip shaft portion 26 holding the above was inserted into the crucible 21.

The holding element 23 includes the dip shaft portion 26 and the position adjusting element 3 shown in FIG. More specifically, the dip shaft portion 26 is held by the position adjusting element 3 and is movable with respect to the radial direction of the crucible 21 and the rotational axis L ₀ direction. Can be placed. The position adjusting element 3 is arranged above the crucible 21 and has a substantially plate shape, an x-direction guide 30x attached to the xy table 30, and a y-direction attached to the x-direction guide 30x. It has a guide portion 30y and a z-direction guide portion 30z attached to the xy table 30.

  As shown in FIG. 4, the x-direction guide part 30x and the y-direction guide part 30y each have a substantially bowl shape. The x-direction guide unit 30 x is fixed to the xy table 30. One end of the y-direction guide 30y is slidably attached to the x-direction guide 30x. Therefore, the y-direction guide portion 30y can slide along the longitudinal direction of the x-direction guide portion 30x (the arrow x direction in FIG. 4). An x-direction drive unit 31x is interposed between the y-direction guide unit 30y and the x-direction guide unit 30x. The x-direction drive unit 31x includes a first motor (not shown) and a first transmission mechanism (not shown) that converts the rotational motion of the first motor into a linear motion in the x direction and transmits the linear motion to the y-direction guide unit 30y. In addition, the y-direction guide unit 30y is automatically slid in the x direction.

  A dip shaft portion 24a is attached to the y-direction guide portion 30y. The dip shaft portion 24a is slidable along the longitudinal direction of the y-direction guide portion 30y (the arrow y direction in FIG. 4). A y-direction drive unit 31y is interposed between the y-direction guide unit 30y and the dip shaft unit 24a. The y-direction drive unit 31y includes a second motor (not shown) and a second transmission mechanism (not shown) that converts the rotational motion of the second motor into a linear motion in the y-direction and transmits the linear motion to the dip shaft portion 24. The dip shaft 24 is automatically slid in the y direction.

  A z-direction guide portion 30z is attached to the xy table 30. The z-direction guide part 30z is slidable along the z direction (up and down direction in FIG. 2). A z-direction drive unit 31z is interposed between the xy table 30 and the z-direction guide unit 30z. The z-direction drive unit 31z includes a third motor (not shown) and a second transmission mechanism (not shown) that converts the rotational motion of the third motor into a linear motion in the z direction and transmits the linear motion to the xy table. The table is automatically slid in the z direction. The dip shaft 24, the x-direction guide 30x, and the y-direction guide 30y also slide up and down following the xy table 30.

The longitudinal direction x of the x-direction guide portion 30x and the longitudinal direction y of the y-direction guide portion 30y are directions that intersect each other (a direction that is substantially orthogonal in Test 1), and the dip shaft portion 24a is parallel to the xy table 30. It can move freely on the surface, that is, on the xy plane. The longitudinal direction of the dip shaft portion 24a is a direction intersecting the longitudinal direction y of the y-direction guide portion 30y and the longitudinal direction x of the x-direction guide portion 30x (a direction substantially orthogonal in Test 1), and as described above, The shaft portion 24a is slidable in the height direction (depth direction of the crucible 21: z-axis direction). Therefore, the seed crystal 1 held by the dip shaft portion 24a can move in the crucible 21 in the x-axis direction and the y-axis direction, and in a direction substantially orthogonal to the xy table (z-axis direction, shown in FIG. 2). It can also be moved in the vertical direction. That is, in the crystal manufacturing apparatus used in Test 1, the seed crystal 1 can be arranged over substantially the entire region in the crucible 21. The dip shaft portion 24a is, x-direction driving unit 31x, the y-direction drive unit 31y and the z-direction drive unit 31z, it is movable on about the rotation axis _{L 0} of the crucible 21 xy plane in an arc direction. In other words, dip shaft portion 24a is capable of revolving on a xy plane about the rotation axis L ₀ of the crucible 21.

  Further, a motor 39 is attached to the dip shaft portion 24a. The motor 39 moves in the x-axis direction, the y-axis direction, and the z-axis direction together with the dip shaft portion 24a. The motor 39 can drive the dip shaft 24a to rotate (spin). In this crystal manufacturing apparatus, the raw material solution (SiC solution) 29 can also be flowed by rotating (revolving and / or rotating) the dip shaft portion 24a. That is, the motor 39, the x-direction drive unit 31x, the y-direction drive unit 31y, the z-direction drive unit 31z, and the dip shaft portion 24a can be used as a solution flow element.

As the seed crystal 1, a 4H—SiC single crystal (10 mm × 10 mm × thickness 0.35 mm) manufactured by a vapor phase growth method (sublimation method) was used. As shown in FIG. 5, an offset surface facing the [11-20] direction was cut and formed on the crystal growth surface of the seed crystal 1, that is, the (0001) plane. The off angle at this time was 1.25 °. Two seed crystals 1 were prepared and attached to each holding portion 28 as shown in FIG. At this time, the crystal growth surface that formed an off-angle among the various crystals 1 faced the raw material solution 29 in the crucible 21. Then, the dip shaft driving portion was caused to advance the dip shaft portion 26 toward the inside of the crucible 21, and the seed crystal 1 was immersed in the raw material solution 29. The SiC crystal grew on the surface of the seed crystal 1 by cooling the raw material solution 29 in the vicinity of the seed crystal 1 having a low temperature. Note that crystal growth was performed based on an accelerated crucible rotation technique (accelerated crucible rotation technique). That is, the crucible 21 was rotated by the crucible driving element 24 during crystal growth. By this rotation of the crucible 21, the raw material solution 29 in the crucible 21 flowed in the same direction as the rotation direction of the crucible 21 (FIG. 3). In addition, two seed crystals (seed crystal 1 a and seed crystal 1 b) are disposed in the crucible 21, and the various crystals 1 a and 1 b are disposed on the outer side in the radial direction of the crucible 21 than the rotation axis L _{0 of the} crucible 21. . For this reason, the raw material solution 29 also flowed in the vicinity of the crystal growth surface of the seed crystal 1.

  By the way, as described above, off-angles directed in the [11-20] direction are formed on the surfaces of the two seed crystals 1a and 1b. For this reason, the step progress direction of the SiC single crystal grown on the various crystals 1a and 1b is guided in the [11-20] direction. On the other hand, the raw material solution 29 flows in the vicinity of the seed crystal 1a so as to be approximately in the same direction as the step progress direction, and in the vicinity of the seed crystal 1b, it is approximately opposite to the step progress direction. Flowed. At this time, the rotational speed (maximum speed) of the crucible 21 was about 20 rpm.

  The x-direction guide portion 30x, the y-direction guide portion 30y, and the dip shaft portion 26 are formed with scales along the respective longitudinal directions. It is possible to grasp the coordinates in the crucible 21 of the seed crystal 1 fixed to the dip shaft portion 26 and eventually the dip shaft portion 26 by the scales of the x direction guide portion 30x, the y direction guide portion 30y and the dip shaft portion 26. Thus, it is possible to arrange the seed crystal 1 at a desired position in the crucible 21 with high reproducibility.

  The flow direction and flow rate of the raw material solution in the crucible 21 can be calculated based on, for example, the number of revolutions of the crucible 21, the amount of the raw material solution, the temperature, and the like. Then, by appropriately adjusting the positions of the dip shaft portion 26 and the seed crystal 1 based on the flow direction of the raw material solution obtained by detection or calculation, the step progress direction of the SiC single crystal on the seed crystal 1 and the raw material solution The flow direction can be opposite or the same direction.

  The step progress direction of the SiC single crystal on the SiC seed crystal 1a and the flow direction of the raw material solution 29 are substantially the same direction, and the step progress direction of the SiC single crystal on the SiC seed crystal 1b and the flow direction of the raw material solution 29 are approximately the same. While maintaining the reverse direction, crystal growth was continued, and SiC single crystals were grown on the crystal growth surfaces of the seed crystals 1a and 1b at a temperature lower than that of the raw material solution 29. The growth temperature at this time was 1700 ° C. The flow rate of the raw material solution 29 was 8.6 cm / s.

Twenty minutes after the start of growth (that is, after contact between the seed crystal 1 and the raw material solution 29), the dip shaft portion 26 is moved upward by the dip shaft drive unit, and two seed crystals 1 (that is, SiC single crystals) that have undergone crystal growth. ) Was pulled up from the raw material solution 29. The two SiC single crystals 10 pulled up were etched with a mixed solution of HNO ₃ and HF (HNO ₃ : HF = 2: 1) in order to remove the raw material solution remaining on the surface. The SiC single crystal of Test 1 was obtained through the above steps. Of these, the one using 1a as the seed crystal is called the SiC single crystal of Test 1a, and the one using 1b as the seed crystal is called the SiC single crystal of Test 1b. In both the SiC single crystal of Test 1a and the SiC single crystal of Test 1b, crystal growth accompanied by step progress occurred.

  Using an atomic force microscope (AFM), the heights of the steps formed in the SiC single crystal of Test 1a and the SiC single crystal of Test 1b were measured. The measurement results are shown in FIGS. Specifically, the upper diagram of FIG. 6 represents the height distribution of the surface of the SiC single crystal of Test 1a, and the lower diagram of FIG. 6 represents the height profile between AB in the upper diagram. The upper diagram of FIG. 7 represents the height distribution of the surface of the SiC single crystal of Test 1b, and the lower diagram of FIG. 7 represents the height profile between C and D in the upper diagram. As shown in FIG. 6, in the SiC single crystal of Test 1a in which the flow direction of the raw material solution and the step progress direction were substantially the same direction, the average height of the step was 103 nm, and the macro step with a high step height was Was formed. On the other hand, as shown in FIG. 7, in the SiC single crystal of Test 1b in which the flow direction of the raw material solution and the step progress direction were approximately opposite directions, the average height of the step was 66 nm. A large step was not formed as in the SiC single crystal.

  FIG. 8 shows a graph representing the change over time of the step heights in SiC single crystals 1a and 1b during crystal growth. As shown in FIG. 8, with respect to the SiC single crystal of Test 1a in which the flow direction of the SiC solution 29 and the step progress direction are the same direction, the crystal growth proceeds (that is, the crystal growth proceeds). Step height). That is, step bunching progressed and a step (macro step) with a high step height was formed. On the other hand, for the SiC single crystal of Test 1b in which the flow direction of the SiC solution 29 and the step progressing direction were opposite, the step height decreased as the crystal growth time passed. That is, step bunching was solved and the crystal growth surface was smoothed. As described above, according to the crystal growth method of the present invention, it is possible to reduce the step bunching on the crystal growth surface (dissolve the step bunching) and smooth the crystal growth surface. Further, according to the crystal growth method of the present invention, the formation of step bunching on the crystal growth surface can be advanced, and a single crystal can be grown while forming a macro step. A single crystal in which defects such as threading screw dislocations are converted into defects on the basal plane can be obtained.

  In Test 1, the raw material solution 29 was caused to flow by rotating the crucible 21, but the raw material solution 29 may be caused to flow, for example, by rotating or reciprocating the dip shaft portion 26 in the raw material solution 29. it can. In this case, a shaft drive element (for example, a motor) for driving the dip shaft portion 26 and a shaft transmission portion (for example, a gear or rack and pinion) for transmitting the driving force of the shaft drive element to the dip shaft portion 26 If a mechanism, a pulley mechanism, a crankshaft, etc.) are provided, the dip shaft portion 26 can be automatically driven.

  By the way, when a macro step is advanced on the threading screw dislocation in the seed crystal when the SiC single crystal is grown, defects extending in the crystal growth direction (for example, threading screw dislocation, threading edge dislocation, etc.) It can be converted into defects substantially parallel to the surface (stacking defects on the basal plane or basal plane dislocations) or the like. That is, by the SiC single crystal manufacturing method of the present invention, crystal growth is performed while flowing the raw material solution along the step progress direction, thereby causing step bunching on the crystal growth surface of the SiC single crystal and thus forming a macro step. can do. Then, a SiC single crystal with reduced defects such as threading screw dislocations can be obtained by advancing macro steps on the defects. Then, by the SiC single crystal manufacturing method of the present invention, by growing the crystal while flowing the raw material solution along the reverse direction of the step progress direction, defects such as threading screw dislocations are reduced, and the surface is It is possible to obtain a smoothed SiC single crystal.

[Relationship between step height and penetration helix conversion rate]
(Reference test 1)
In the SiC single crystal manufacturing method of Reference Test 1, the cutting process was performed so that the off angle formed on the (0001) plane of the SiC seed crystal was 1.25 °, and the raw material solution was applied to the crystal growth surface. This is the same method as the SiC single crystal manufacturing method of Test 1 except that the forced flow in one direction is not performed. The SiC single crystal of Reference Test 1 was obtained by the SiC single crystal manufacturing method of Reference Test 1.

(Reference test 2)
The SiC single crystal manufacturing method of Reference Test 2 is the same as the SiC single crystal manufacturing method of Reference Test 1 except that the off-angle formed on the (0001) plane of the seed crystal is 2 °. Is the method. The SiC single crystal of Reference Test 2 was obtained by the SiC single crystal manufacturing method of Reference Test 2.

(Reference test 3)
The SiC single crystal manufacturing method of Reference Test 3 is the same method as the SiC single crystal manufacturing method of Reference Test 1 except for the off-angle angle. Specifically, the off angle formed in the seed crystal in Reference Test 3 was 4 °. The SiC single crystal of Reference Test 3 was obtained by the SiC single crystal manufacturing method of Reference Test 3.

(Reference test 4)
The SiC single crystal manufacturing method of Reference Test 4 is the same method as the SiC single crystal manufacturing method of Reference Test 1 except for the off-angle angle. Specifically, the off angle formed in the seed crystal in Reference Test 4 was 0.75 °. The SiC single crystal of Reference Test 4 was obtained by the SiC single crystal manufacturing method of Reference Test 4.

(Reference evaluation test)
[Conversion rate of threading screw dislocation]
Using the X-ray topography method using synchrotron radiation X-rays, the SiC single crystals of the above-described Reference Tests 1 to 3 were observed, and defects remaining in each SiC single crystal were evaluated. In addition, the defect was evaluated by the same method for the seed crystal before crystal growth. For the X-ray topography method, a photon factory BL-15C was used as the beam line. The wavelength was 0.150 nm and the reflection surface was (11-28).

  FIG. 9 is an X-ray topographic image obtained by imaging the seed crystal and the SiC single crystal at the initial stage of crystal growth by the method of Reference Test 1 at the same location. More specifically, the image shown on the left in FIG. 9 is an X-ray topography image of the seed crystal, and the image shown on the right in FIG. 9 is an X-ray topography image of the SiC single crystal of Reference Test 1 in the early stage of crystal growth. It is. There are many threading screw dislocations TSD represented by point-like contrast in the seed crystal before growth. Most of the threading screw dislocations TSD are converted into a linear contrast extending in the step progress direction in the grown crystal. From the results of TEM observation, it has been clarified that the defect having such a contrast is a flank type stacking fault SF accompanied by partial dislocation. From this result, it can be seen that, according to the production method of Reference Test 1, threading screw dislocations existing in the seed crystal can be converted into basal plane stacking faults.

  10 to 12 are X-ray topographic images obtained by imaging the seed crystal, the SiC single crystal in the initial stage of crystal growth by the method of Reference Test 3, and the SiC single crystal of Reference Test 3 at the same location. More specifically, the image shown in FIG. 10 is an X-ray topographic image of a seed crystal. The image shown in FIG. 11 is an X-ray topographic image of the SiC single crystal of Reference Test 3 at the initial stage of crystal growth. The image shown in FIG. 12 is an X-ray topographic image of the SiC single crystal of Reference Test 3. As shown in FIGS. 10 and 11, in the SiC single crystal of Reference Test 3 in which the off-angle is larger than that of Reference Test 1, most threading screw dislocations TSD are converted into stacking faults SF in the initial stage of growth. Then, as shown in FIG. 12, the SiC single crystal obtained by the manufacturing method of Reference Test 3 is formed with many steps, which are traces of the progress of steps, and most threading screw dislocations TSD and stacking faults SF have disappeared. . From this result, it is understood that the threading screw dislocation existing in the seed crystal can be converted into the stacking fault of the basal plane also by the manufacturing method of Reference Test 3 in which the off-angle is increased.

  By visually counting an arbitrary 1 mm × 5 mm area selected from the X-ray topography image obtained by the above method, the number of threading screw dislocations of the seed crystal used in each reference test, and each reference test The number of threading screw dislocations in the SiC single crystal obtained in step 1 was measured. And the conversion rate (%) of the threading screw dislocation by each reference test was calculated by setting the number of threading screw dislocations in various crystals used in each reference test as 100% by number. The results are shown in FIG.

  As shown in FIG. 13, as the off-angle increases, the conversion rate (%) from threading screw dislocations to stacking faults increases.

[Relationship between step height and off angle]
Using a confocal laser microscope, the height of the step formed on the SiC single crystal obtained in each reference test was measured. Specifically, Olympus Corporation LEXT OLS-3100 was used as a confocal laser microscope, and each SiC single crystal was imaged from the terrace surface side. FIG. 14 shows a laser microscope image of the SiC single crystal of Reference Test 1, FIG. 15 shows a laser microscope image of the SiC single crystal of Reference Test 2, and FIG. 16 shows a laser microscope image of the SiC single crystal of Reference Test 3. . The shading of each image shown in FIGS. 14 to 16 indicates the height of the step. The step progress direction is a vertical direction (light color side → dark color side direction) in each figure. As shown in FIGS. 14 to 16, many bunched steps are formed in the SiC single crystals of the reference tests 1 to 3. And since these many steps are arranged in stripes, it can also be seen that the steps have progressed in these SiC single crystals. It can also be seen that the height of each step is Reference Test 3> Reference Test 2> Reference Test 1. As an example, FIG. 17 shows an explanatory diagram schematically showing steps of a SiC single crystal obtained based on a laser microscope image of the SiC single crystal of Reference Test 1 shown in FIG. From these figures, the step height and terrace width of the SiC single crystals of Reference Tests 1 to 3 were read. The relationship between the step height and the off angle in each SiC single crystal of Reference Tests 1 to 3 is shown in FIG. 18, and the relationship between the terrace width and the off angle in each SiC single crystal of Reference Tests 1 to 3 is shown in FIG. As shown in FIG. 18, a step having a higher step height was formed as the off-angle increased. For this reason, it is thought that the SiC single crystal containing many steps (macro step) with a high step height can be obtained, so that an off angle is large.

  FIG. 13 shows the relationship between the off-angle formed in the seed crystal in Reference Tests 1 to 3 and the minimum step height in each SiC single crystal shown in FIG. 18 together with the conversion rate of threading screw dislocations. As shown in FIG. 13, there is a positive correlation between the conversion rate of threading screw dislocations and the minimum step height in the SiC single crystal. The larger the minimum step height value, the higher the conversion rate of threading screw dislocations. It turns out that becomes high. In the SiC single crystal of Reference Test 1 having an off angle of 1.25 ° and a minimum step height of 80 nm, 90% or more of threading screw dislocations were converted. Further, in the SiC single crystal of Reference Test 3 having an off angle of 4 ° and a minimum step height of 100 nm, 99% or more of threading screw dislocations were converted. Thus, by forming a macro step having a high step height, the conversion rate of threading screw dislocations into stacking faults is greatly improved.

  Note that in the method for producing a SiC single crystal of the present invention, not all steps may be macro steps. If at least one macro step is formed, it is possible to improve the conversion rate of threading screw dislocations and obtain a SiC single crystal with few threading screw dislocations. Of course, if a large number of macrosteps are formed as described above (for example, when the minimum step height is 100 nm or more as in Reference Test 3), a SiC single crystal with significantly reduced threading screw dislocations. Can be obtained. That is, according to the method for producing a SiC single crystal of the present invention, it is possible to obtain a SiC single crystal having no threading screw dislocation by appropriately adjusting the number and height of macro steps. For reference, as shown in FIG. 19, the larger the off-angle, the smaller the terrace width.

  The larger the number of macro steps, the better. This is because if a plurality of macro steps progress on one threading screw dislocation, the frequency at which the threading screw dislocation is converted increases. The number of preferred macrosteps can be expressed as the density of preferred macrosteps based on the following calculation:

  As described above, in the SiC single crystal of Reference Test 3, almost 100% of threading screw dislocations were converted. The thickness of the SiC single crystal (the thickness of the grown crystal) was 20 μm. Since the minimum height of the macrostep at this time was 100 nm (0.1 μm), almost all of the threading screw dislocations in the SiC single crystal occur when the phenomenon of the macrostep progressing on the crystal growth surface occurs 200 times or more. Is considered to convert. In other words, it is considered that the threading screw dislocation is almost certainly converted if the macro step advances 200 times or more on one threading screw dislocation. Since the crystal growth surface of the SiC seed crystal of Reference Test 3 was 1 cm × 1 cm, it can be said that the particularly preferable macrostep density (linear density) is 200 pieces / cm or more. Actually, if the linear density of the macrostep is 100 pieces / cm or more, the majority of threading screw dislocations are converted. That is, it can be said that the preferable linear density of the macro step is 100 pieces / cm or more. The linear density of the macrostep is more preferably 250 pieces / cm or more, and further preferably 500 pieces / cm or more. In addition, since the average macrostep linear density ρ in the SiC single crystal in which threading screw dislocation conversion occurred was about 1000 pieces / cm, the macrostep linear density ρ was particularly 1000 pieces / cm or more. Preferably, it can be said that it is more preferable that it is 2000 pieces / cm or more.

  For reference, the number of macro steps here refers to the number of macro steps at an arbitrary point in the crystal growth. The number of macro steps approximates the number of striped steps remaining on the SiC single crystal. The number of striped steps may be regarded as the number of steps. Further, the size of the crystal growth surface in the SiC seed crystal approximates the size of the crystal growth surface in the SiC single crystal. Therefore, it is possible to measure the macro step density by measuring the density of the striped step remaining on the crystal growth surface of the SiC single crystal. The number of striped steps remaining on the crystal growth surface of the SiC single crystal can be measured under a laser microscope.

  By the way, the number or density of the preferable macro steps described above can also be expressed as follows.

The average height of the macro step is h (cm), the growth thickness of the SiC single crystal is t (cm), the linear density of the macro step, that is, how many stripe-shaped steps are present per unit length (1 cm). Let ρ (1 / cm) and the average _macrostep interval W _ave be 1 / ρ (cm).

A case where a macro step progresses on the crystal growth surface will be considered by paying attention to an arbitrary point A on the crystal growth surface. When the SiC single crystal grows to a thickness t, the macro step passes n = t / h (times) on the point A. Further, in order for the macro step to pass n times on the point A, the macro step needs to progress toward the point A from a point separated from the point A by n × W _ave (cm). That is, if the length of the SiC single crystal in the step progress direction is y (cm), the thickness t (cm) grows, which means that the length of the SiC seed crystal in the step progress direction is t / This means that the percentage of y has grown.

Further, if the number of macro step passages required for threading screw dislocation conversion is N, the SiC single crystal needs to grow by a thickness of N × h. Further, in order for the macrostep to pass through the threading screw dislocation N times, the _{macrostep at} a distance of N × W _ave (cm) from the threading screw dislocation needs to pass through the threading screw dislocation. That is, the macro step needs to be advanced by N × W _ave (cm) or more.

The average macrostep linear density ρ is 1000 / cm. The preferred height of the macro step is 0.1 μm as described above. For this reason, considering the above formula, the growth thickness of the SiC single crystal is preferably 100 × 0.1 μm = 10 μm or more in order for the macrostep to progress 100 times or more on one threading screw dislocation. . A more preferable growth thickness is 20 μm or more. Moreover, the preferable progress distance (cm) of a macro step is 100 * _Wave = 100 * 1 / (rho) = 100 * 1/1000 = 1 / 10cm = 1mm.

  In addition, in order to convert many threading screw dislocations, it is preferable that the macrosteps progress continuously over a wide area. The total length of the X-ray topography image shown in FIG. 12 is about 1000 μm. The macro step is formed over the entire area of the image, and the linear density thereof is the above-described preferable range, that is, 100 / cm or more. For this reason, it can be said that it is preferable that a macro step continues over 1 mm or more with a linear density of 100 pieces / cm or more (more preferably 200 pieces / cm). The longer the macrosteps are continuous, the longer is preferable. For this reason, it is considered that the macro step is preferably continuous over 3 mm or more at a linear density of 100 pieces / cm or more (more preferably 200 pieces / cm), and preferably continuous over 5 mm or more.

  Further, in order to reduce the total number of threading screw dislocations in the SiC single crystal, it is preferable that the macrostep progresses on many threading screw dislocations. That is, it is preferable to enlarge the region where the macro step progresses on the crystal growth surface of the seed crystal. For example, when the macro step advances the entire crystal growth surface, the total number of threading screw dislocations remaining in the SiC single crystal can be greatly reduced. The growth area of the macro step on the crystal growth surface is preferably 30 area% or more, more preferably 50 area% or more, when the (0001) crystal growth surface in the SiC single crystal is 100 area%. . It should be noted that the region where the above-described regular striped steps are generated on the surface of the SiC single crystal (crystal growth surface) can be regarded as a region where the macro step has advanced. As described above, since the crystal growth surface in the SiC seed crystal and the crystal growth surface in the SiC single crystal can be regarded as the same area, the crystal growth surface of the SiC single crystal obtained by the manufacturing method of the present invention. It is possible to measure the progress region of the macro step by measuring the area of the region where the striped step remains on the crystal growth surface. In order to advance the macro step over the entire crystal growth surface of the SiC seed crystal, for example, it is preferable to provide an off angle on the crystal growth surface of the seed crystal as in Reference Test 1, but the method is not limited to this method.

  Thus, although the reason which can obtain a SiC single crystal with few defects by advancing a macro step is not clear, it estimates as follows.

Threading screw dislocations TSD extending in a direction substantially perpendicular to the (0001) plane as shown in FIG. 20, by progress macro step _{S m} as described above, as shown in FIG. 21, 22 (0001) plane ( That is, it is considered that the stacking fault SF extends in a direction substantially parallel to the base surface).

As shown by arrows in FIGS. 20 to 22, the direction in which each step S progresses (step progress direction) when the SiC single crystal grows is a direction substantially parallel to the (0001) plane. On the other hand, the growth direction of threading screw dislocation TSD is substantially perpendicular to the (0001) plane. That is, the step progress direction and the growth direction of threading screw dislocation TSD are substantially orthogonal. Therefore, at the time of crystal growth of the SiC seed crystal 1 having a macro step S _m, the macro step S _m as shown in FIG. 21 to the crystal growth while passing over the threading screw dislocations TSD. Then, as shown in FIG. 22, the growth direction of threading screw dislocation TSD changes to a direction substantially parallel to the (0001) plane, and is converted into a stacking fault SF. The reason why such a phenomenon occurs is not clear, but is considered to be related to the step height. That is, the growth direction of threading screw dislocation TSD and the step growth direction of the SiC single crystal are substantially orthogonal. Therefore, when the height of the step formed on the crystal growth surface (0001) is large (i.e., if the step is the macro step _{S m),} bending threading screw dislocations TSD by the image force (image force) It is considered that it is easily converted into a stacking fault SF on the base surface. Conversion In other words, in the manufacturing method of the SiC single crystal of the present invention, a macro step S _m is formed on the seed crystal 1, only it needs to develop this macro step S _m the upper threading screw dislocations TSD, the threading screw dislocations TSD can do. In the conventional crystal growth method, it is said that the crystal growth is good so as not to form the step S having a high height. Therefore, according to the conventional crystal growth method, only a low step S height is formed, not macro step S _m is formed, is considered that it could not be converted to threading screw dislocations TSD.

  Further, as shown in FIG. 23, when the crystal growth of the SiC single crystal 10 is further continued after the conversion of the threading screw dislocation TSD into the stacking fault SF occurs, the layer containing the threading screw dislocation TSD derived from the seed crystal 1 ( A first layer 11), a second layer 12 formed continuously with the first layer 11 and containing a stacking fault SF, and formed with a first layer 11 continuously with the second layer 12. In comparison, the SiC single crystal 10 having the third layer 13 and the third layer 13 with less threading screw dislocation TSD can be obtained. This is because the stacking fault SF is a basal plane defect and is not inherited in the crystal growth direction. The second layer 12 has a smaller number of threading screw dislocations TSD and a larger number of stacking faults SF than the first layer 11. Since the third layer 13 is a portion grown after the threading screw dislocation TSD is converted into the stacking fault SF, the number of threading screw dislocations TSD is greatly reduced as compared with the first layer 11, and the stacking fault SF The number is also greatly reduced. Therefore, by cutting out the third layer 13 from the SiC single crystal 10, it is possible to obtain the SiC single crystal 10 with very little threading screw dislocation TSD. Further, depending on the use of the SiC single crystal 10, the number of defects penetrating through the crystal growth direction of the SiC single crystal 10 may be reduced, and a threading screw dislocation TSD is formed in a part of the SiC single crystal 10 in the crystal growth direction. It may be present. In such a case, the SiC single crystal 10 obtained by the manufacturing method described above can be used as it is.

  Thus, when manufacturing a SiC single crystal, there exists an advantage which can manufacture a SiC single crystal without a threading screw dislocation (or very few threading screw dislocations) comparatively easily in a short time. Moreover, if the SiC single crystal with few threading screw dislocations obtained in this way is used as a seed crystal, it is possible to grow a SiC single crystal with few threading screw dislocations by a general liquid phase method or gas phase method. It is. In other words, according to the manufacturing method of the present invention in which step bunching is performed on a SiC single crystal, macrosteps can be formed on the crystal growth surface of the SiC single crystal, and as a result, an SiC single crystal with few threading screw dislocations can be easily and shortly formed. It is possible to manufacture in time.

By the way, as described above, when the growth rate of the screw dislocation is larger than the step progress rate, the step does not progress, and the screw dislocation remains and spiral growth occurs. Therefore, as shown in FIG. 24, when the height of the macro step is h, the step progress rate of the macro step is V _step , the terrace width is w, and the growth rate of the screw dislocation is v _spiral , The conditions are expressed as follows:

V _spiral <(h × v _step ) / w
In the reference test, V _spiral = 9 μm / hour and v _step = 500 μm / hour. Substituting these into the above equation results in 0.018 <h / w. This is a condition for the step to progress during the crystal growth of the SiC single crystal. In the case of Reference Test 1 (minimum step height 80 nm, off angle 1.25 °, threading screw dislocation conversion rate 90%), w = 8.5 μm. Is approximately 70 nm <h. In such a range, it is considered that conversion of threading screw dislocation by macro step occurs. That is, if a macro step having a height exceeding 70 nm is formed in the step formation process, an SiC single crystal with reduced threading screw dislocations can be obtained.

  The higher the macrostep height, the higher the conversion rate of threading screw dislocations into stacking faults. Therefore, considering the mirror image force, it is preferable that the height of the macro step is high. Specifically, the height of the macro step is preferably 80 nm or more, and more preferably 100 nm or more. By growing a SiC single crystal using a second seed crystal in which at least one macrostep is formed, preferably a plurality of such macrosteps, it is possible to obtain a SiC single crystal with greatly reduced threading screw dislocations.

[Relationship between step height and step progress]
The microscope image which imaged the SiC single crystal of Test 4 using the Nomarski type | mold differential interference microscope (Leica DM4000 M) is shown in FIG. As shown in FIG. 25, many hillocks (hillocks: non-step-like bumps) generated by spiral growth due to threading screw dislocation were observed on the growth surface of the SiC single crystal of Reference Test 4. From this result, it can be seen that spiral growth occurs in the SiC single crystal of Reference Test 4 in preference to the progress of the step, and in the SiC single crystal of Reference Test 4, threading screw dislocation conversion occurs, It is suggested that many have not occurred. In other words, in the manufacturing method of Reference Test 4, macrosteps are formed in the seed crystal, but the number is small compared to Reference Test 1 and the like, and the threading screw dislocation conversion frequency is also low compared to Reference Test 1. It is done.

  That is, in the SiC single crystal manufacturing method of Reference Test 1 to Reference Test 3, many macro steps, which are steps exceeding 70 nm in height, are formed in the macro step forming process, and the macro steps progress on many threading screw dislocations. On the other hand, in the SiC single crystal manufacturing method of Reference Test 4, the steps formed in the macrostep forming process are mostly less than 70 nm in height, and the number is considered to be relatively small. That is, it is understood that when the macro step is formed by forming the off angle, the off angle is preferably set to 1 ° or more.

  (Others) The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications within a range not departing from the gist. For example, before the crystal growth step, a step (preparation step) for guiding the step progress direction to the flow direction of the raw material solution by crystal growth of a seed crystal that does not form an off-angle while flowing the raw material solution is provided. May be. The single crystal obtained in this preparation step may be used as a seed crystal for the crystal growth step.

  In addition, the flow direction of the raw material solution in the crystal growth process may not completely match the step progress direction of the single crystal. For example, the step progress in a part of the single crystal may be different from the step progress direction in the other part, or a part of the raw material solution may flow in a direction different from the other part.

(Appendix)
The crystal growth step in the method for producing an SiC single crystal of the present invention includes a smoothing step, but it is also possible to perform only the bunching step without performing the smoothing step. That is, it is possible to grasp the following technical idea from the description of the present specification.

(Additional item 1)
Including a crystal growth step of growing a SiC single crystal by causing a step made of SiC to progress on a crystal growth surface of a SiC seed crystal by a liquid phase growth method in a raw material solution containing silicon (Si) and carbon (C),
The crystal growth process includes a bunching process in which step bunching is generated on the crystal growth surface by applying an external force to the raw material solution and causing the raw material solution to flow along the progress direction of the step. .

(Appendix 2)
The SiC according to claim 1, wherein the crystal growth step includes a smoothing step of solving at least part of the step bunching on the crystal growth surface by causing the raw material solution to flow along a direction opposite to the step progress direction. A method for producing a single crystal.

1: SiC seed crystal 10: SiC single crystal 11: First layer 12: Second layer 13: Third layer
TSD: threading screw dislocation SF: stacking fault
h: Step height P1, P2: Terrace surface S _m : Macro step 20: Single crystal growth apparatus 21: Crucible 22: Heating element 23: Holding element 24: Crucible drive element 25: Conductor 26: Dip shaft 27: Dip shaft Drive unit 28: Holding unit 29: Raw material solution

Claims (5)

Including a crystal growth step of growing a SiC single crystal by causing a step made of SiC to progress on a crystal growth surface of a SiC seed crystal by a liquid phase growth method in a raw material solution containing silicon (Si) and carbon (C),
The crystal growth step includes a smoothing step of solving at least a part of step bunching on the crystal growth surface by applying an external force to the raw material solution and causing the raw material solution to flow along a direction opposite to the progress direction of the step. A method for producing a SiC single crystal.   2. The method for producing an SiC single crystal according to claim 1, wherein the crystal growth step includes a bunching step of causing step bunching on the crystal growth surface by causing the raw material solution to flow along the progress direction of the step.   3. The method for producing a SiC single crystal according to claim 2, wherein in the bunching step, a macro step made of an SiC single crystal and having a height exceeding 70 nm is formed by the step bunching.   The method for producing an SiC single crystal according to claim 3, wherein in the bunching step, a macro step having a height of 80 nm or more is formed by the step bunching.   5. The method for producing an SiC single crystal according to claim 3, wherein in the bunching step, a macro step having a height of 100 nm or more is formed by the step bunching.