JP2011190129A - Apparatus for manufacturing silicon carbide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing a silicon carbide single crystal, which can provide a good-quality, large-diameter single crystal by reducing the temperature difference between the central portion and the peripheral portion of a growing crystal while maintaining the temperature gradient in the growing crystal being equal to or more than a predetermined value during the crystal growth. <P>SOLUTION: The manufacturing apparatus 1 of silicon carbide comprises a crucible 9 having a crucible body 5 accommodating a raw material 15 for sublimation, and a lid body 3 installed with a seed crystal attaching section 21 where a seed crystal is attached at a position opposing to the raw material 15 for sublimation, and is heated from the outer periphery of the crucible 9, wherein with respect to the seed crystal attaching section 21 of the lid body 3, a central portion 31 arranged on the inner peripheral side has a higher heat conductivity than an outer portion 32 arranged on the outer peripheral side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an apparatus for producing a silicon carbide single crystal.

  Conventionally, a single crystal wafer made of a single crystal has been widely used as a substrate for a semiconductor device, and a sublimation method is known as a method for producing this single crystal. In this sublimation method, it is known that a high-quality single crystal can be obtained by growing the crystal while keeping the convex curved shape downward (see, for example, Patent Document 1).

JP 2002-308699 A

  However, in the manufacturing method described in Patent Document 1, in the case of a single crystal having a large diameter, the temperature difference between the central portion and the outer peripheral portion of the grown crystal is large (for example, a temperature difference of 20 ° C. or more). There is a problem that a high-quality single crystal cannot be grown because the tensile stress inside the grown crystal becomes large or the outer peripheral edge of the seed crystal disappears due to heat in the initial stage of growth of the grown crystal.

  On the other hand, if the temperature gradient is made small in order to reduce the temperature difference between the central portion and the outer peripheral portion of the grown crystal, there is a problem that the downward curved shape cannot be maintained at the outer peripheral edge of the grown crystal. Therefore, it is necessary to set the temperature gradient to a predetermined value (for example, 1 ° C./cm) or more.

  Accordingly, an object of the present invention is to obtain a high-quality and large-diameter single crystal by reducing the temperature difference between the central portion and the outer peripheral portion of the grown crystal while maintaining a temperature gradient higher than a predetermined value in the grown crystal. An object of the present invention is to provide an apparatus for producing a silicon carbide single crystal.

  In order to solve the above-described problems, the present invention has the following features. The first feature of the present invention is that a crucible body (crucible body 5) containing a sublimation raw material (sublimation raw material 15) and a seed crystal in which a seed crystal (seed crystal 43) is attached at a position facing the sublimation raw material. An apparatus (silicon carbide) for producing a silicon carbide single crystal comprising a crucible (crucible 9) having a lid (lid 3) provided with a mounting part (seed crystal mounting part 21) and heated from the outer peripheral side of the crucible It is the manufacturing apparatus 1) of a single crystal, and the gist of the lid is that the thermal conductivity on the inner peripheral side is set larger than the thermal conductivity on the outer peripheral side.

  For the lid, the thermal conductivity on the inner peripheral side is set larger than the thermal conductivity on the outer peripheral side, and since it is heated from the outer peripheral side of the crucible, the temperature gradient from the inner peripheral side to the outer peripheral side is The side is gradual and the outer periphery is steep. Accordingly, since the temperature difference between the radial center and the outer peripheral edge of the lid can be reduced, the circumferential tensile stress in the single crystal is reduced, and the heat loss of the outer peripheral edge of the seed crystal in the initial stage of growth is reduced. Disappear. On the other hand, the temperature gradient at the outer peripheral edge of the grown crystal can be maintained at a predetermined value (for example, 1 ° C./cm) or more. Here, the growth crystal has a problem that it tends to be difficult to maintain a downwardly convex curved shape toward the outer peripheral side, and is most likely to have a concave shape at the outer peripheral edge. Accordingly, by maintaining the temperature gradient at the outer peripheral edge of the grown crystal at a predetermined value or higher, the shape of the entire grown crystal can be made to be a curved convex shape.

  In addition, it is necessary to set the temperature difference between the radial center and the outer peripheral edge of the lid to a predetermined value (for example, 20 ° C. or less).

  From the above, even when producing a single crystal with a large diameter, the temperature difference between the radial center of the lid and the outer peripheral edge can be reduced, and the temperature gradient can be set to a predetermined value or more. can do.

  The second feature of the present invention is that the thermal conductivity on the inner peripheral side is set larger than the thermal conductivity on the outer peripheral side for the seed crystal mounting portion (seed crystal mounting portion 21) of the lid (lid 3). This is the gist.

  The third feature of the present invention is that the seed crystal attachment portion (seed crystal attachment portion 21) of the lid (lid 3) is concentrically circular along the radial direction (center portion 31, outer portion 32). Among the plurality of annular portions, the thermal conductivity in the inner circumferential side annular portion (center portion 31) is set larger than the thermal conductivity in the outer circumferential side annular portion (outer portion 32). It is a summary.

  The gist of the fourth feature of the present invention is that the annular portion (center portion 31) on the inner peripheral side is formed over the entire thickness direction of the lid body (lid body 3).

  According to a fifth feature of the present invention, the seed crystal mounting portion (seed crystal mounting portion 21) includes a columnar central portion (center portion 31) disposed on the inner peripheral side and a cylindrical shape disposed on the outer peripheral side. The outer portion (outer portion 32) of the outer portion and the thermal conductivity of the central portion is 1.2 times or more than the thermal conductivity of the outer portion.

  According to the apparatus for producing a silicon carbide single crystal according to the present invention, the temperature difference between the central portion and the outer peripheral portion of the grown crystal is reduced while maintaining a temperature gradient of a predetermined value or more in the grown crystal, and the high-quality and large-diameter Can be obtained.

It is sectional drawing which shows the manufacturing apparatus of the silicon carbide single crystal which concerns on embodiment of this invention. It is a perspective view which shows the cover body of FIG. It is sectional drawing which shows the manufacturing apparatus of a general silicon carbide single crystal. It is the schematic which shows the isotherm in the vicinity of a seed crystal attachment part. It is the schematic which shows the isotherm in the seed-crystal attachment part where heat conductivity is medium. It is the schematic which shows the isotherm in the seed crystal attachment part with small heat conductivity. It is the schematic which shows the isotherm in the seed crystal attachment part with large heat conductivity. It is a graph which shows the relationship between the distance from the radial center in the seed crystal attaching part of FIGS. 5-7, and temperature. It is the schematic which shows the isotherm in the seed crystal attachment part which concerns on embodiment of this invention. It is a graph which shows the relationship between the distance from the radial center, and temperature in the seed crystal attaching part which concerns on a prior art example and this invention example.

  Hereinafter, details of an apparatus for producing a silicon carbide single crystal according to an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the overall configuration of the silicon carbide single crystal manufacturing apparatus, (2) the configuration of the lid, (3) the heat flow in the crucible, (4) the temperature distribution of the lid, (5) the action Effects, (6) Other embodiments will be described. It should be noted that the drawings are schematic, and the thicknesses and ratios of the material layers are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Also included in the drawings are portions having different dimensional relationships and ratios.

(1) Overall Configuration of Silicon Carbide Single Crystal Manufacturing Apparatus First, the overall configuration of a silicon carbide single crystal manufacturing apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a silicon carbide single crystal manufacturing apparatus 1 according to an embodiment of the present invention.

  The manufacturing apparatus 1 includes a crucible 9 having a lid 3, a crucible body 5, and a guide member 7, and a heat insulating material 11 that covers the outer periphery of the crucible 9. In addition, although the induction heating coil is wound around the outer peripheral side of the heat insulating material 11 as shown in FIG. 3 described later, it is omitted in FIG.

  The crucible body 5 has an upper end opened, and the opening is closed by the lid 3 and is made of graphite. A sublimation raw material 15 made of silicon carbide powder is accommodated in the bottom. When the sublimation raw material 15 is heated, sublimation gas is generated and guided to the seed crystal 43 (see FIG. 5) by the guide member 7.

  The lid body 3 is screwed into a screw portion at the upper end portion of the crucible body 5 so as to seal the opening at the upper end portion of the crucible body 5, and is made of graphite. A cylindrical seed crystal attachment portion 21 that protrudes downward is formed at the center of the lower surface 19 of the lid 3. A disc-shaped seed crystal 43 made of silicon carbide is attached to the lower surface of the seed crystal attachment portion 21.

  The heat insulating material 11 is disposed so as to cover the crucible 9, and temperature measurement holes 23 and 25 are formed in the upper surface of the heat insulating material 11 and the radial center of the subordinate.

(2) Configuration of Lid 3 Next, the configuration of the lid 3 will be described with reference to FIGS. FIG. 2 is a perspective view showing the lid 3 of FIG.

  The seed crystal attachment portion 21 provided on the lower surface 19 of the lid 3 is formed in a downwardly protruding cylindrical shape, and has a cylindrical central portion 31 disposed on the inner peripheral side, and an outer periphery of the central portion 31. It is comprised from the cylindrical outer side part 32 arrange | positioned at the side. The outer portion 32 is formed integrally with the lid body portion 33 of the lid body 3. In the present embodiment, the central portion 31 of the seed crystal attachment portion 21 is integrally provided over the entire thickness direction of the lid 3. And about the center part 31 and the outer side part 32 formed in these cyclic | annular parts, the heat conductivity in the center part 31 is set larger than the heat conductivity in the outer side part 32 and the lid body part 33. FIG. Specifically, the thermal conductivity in the central portion 31 is preferably set to 1.2 times or more of the thermal conductivity in the outer portion 32 and the main body portion 33. Note that the thermal conductivity of the lid 3 made of graphite and the seed crystal attachment portion 21 varies depending on the density of the graphite material.

(3) Heat Flow in Crucible 9 Next, the heat flow in the crucible 9 will be described with reference to FIGS. FIG. 3 is a cross-sectional view showing a general silicon carbide single crystal manufacturing apparatus, and FIG. 4 is a schematic view showing an isotherm in the vicinity of the seed crystal attachment portion.

  3, parts having the same configuration as in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. On the lower surface of the lid 103, a seed crystal mounting portion 121 having a convex shape is formed integrally with the lid 103. And the induction heating coil 141 wound helically is provided in the outer peripheral side of the heat insulating material 11. FIG.

  First, when a current is passed through the induction heating coil 141, the outer peripheral surfaces of the crucible body 5 and the lid 103 are heated by the induction heating h0, the lower high temperature portion H (L) is formed at the lower portion, and the upper high temperature portion H at the upper portion. (U) is formed.

  Since the temperature measurement hole 23 is formed in the center of the upper surface of the heat insulating material 11, the heat from the upper high temperature portion H (U) is directed outward from the temperature measurement hole 23 through the lid 103. Discharged. Therefore, as shown by the arrow in FIG. 4, a flow of heat h <b> 1 from the outer peripheral side toward the inner peripheral side is formed in the seed crystal attachment portion 121.

  On the other hand, since the heating amount for the sublimation raw material 15 is set larger than the heating amount for the seed crystal, the temperature in the lower high temperature portion H (L) is higher than the temperature in the upper high temperature portion H (U). Therefore, as shown by the arrow in FIG. 4, a flow of heat h <b> 2 from the lower side to the upper side is formed in the seed crystal attachment portion 121. By synthesizing these h1 and h2, a flow of heat h3 is formed in the seed crystal mounting portion 121 obliquely upward. Since the flow direction of the heat h3 is in the normal direction with respect to the isotherm t, the isotherm t in the vicinity of the seed crystal attachment portion 121 is formed in a downward curved shape as shown in FIG.

(4) Temperature distribution of the lid Next, the temperature distribution in the lid will be described with reference to FIGS. FIG. 5 is a schematic diagram showing an isotherm in a seed crystal attachment part having a medium thermal conductivity, and FIG. 6 is a schematic diagram showing an isotherm in a seed crystal attachment part having a low thermal conductivity. FIG. 7 is a schematic diagram showing an isotherm in the seed crystal mounting portion having a large thermal conductivity, and FIG. 8 is a graph showing the relationship between the distance from the radial center and the temperature in the seed crystal mounting portion in FIGS. It is.

  As shown in FIG. 5, a seed crystal 43 is attached under the seed crystal attachment portion 221 having a medium thermal conductivity. An upper high temperature portion H (U) is formed at the outer peripheral edge of the seed crystal mounting portion 221, and a temperature measurement hole 23 is formed in the heat insulating material 11. Accordingly, a heat flow h1 is formed from the upper high temperature portion H (U) toward the inner peripheral side of the seed crystal attachment portion 221 and through the temperature measurement hole 23 to the outside. Here, since the thermal conductivity of the seed crystal attachment portion 221 is medium, the interval between the isotherms T1 is also medium. Further, the temperature gradient from the center of the seed crystal attachment portion 221 toward the outer periphery is as shown by a solid line in FIG. The graph of FIG. 8 shows the temperature gradient along the arrow y direction on the lower surface of the seed crystal attachment portion 121 in FIG.

  On the other hand, as shown in FIG. 6, in the case of the seed crystal attachment portion 321 having a low thermal conductivity, the heat of the upper high temperature portion H (U) does not readily move to the inner peripheral side, so the interval between the isotherms T2 is The temperature gradient becomes steep as shown by the broken line in FIG.

  Further, as shown in FIG. 7, in the case of the seed crystal attachment portion 421 having a large thermal conductivity, the heat of the upper high temperature portion H (U) moves smoothly to the inner peripheral side, so that the interval between the isotherms T3 Becomes larger and the temperature gradient becomes gentler as shown by the one-dot chain line in FIG.

  Next, the temperature distribution of the seed crystal attachment part 521 according to this embodiment will be described. FIG. 9 is a schematic diagram showing an isotherm in the seed crystal mounting portion 521 according to the embodiment of the present invention, and FIG. 10 is a relationship between the distance from the radial center and the temperature in the seed crystal mounting portion according to the conventional example and the present invention example. It is a graph which shows.

  As schematically shown in FIG. 9, the seed crystal mounting portion 521 according to the present embodiment includes a seed crystal mounting portion 421 having a large thermal conductivity on the inner peripheral side and a low thermal conductivity on the outer peripheral side. The seed crystal attachment part 321 which is is arrange | positioned. That is, the seed crystal mounting portion 321 and the seed crystal mounting portion 421 are combined.

  Therefore, as shown by the solid line 50 in FIG. 10, in the seed crystal mounting portion 521 according to this embodiment, a portion having a small temperature gradient on the inner peripheral side and a portion having a large temperature gradient on the outer peripheral side are combined.

  In FIG. 10, the portion where the radius (r) of the horizontal axis becomes zero is the center in the radial direction of the seed crystal attachment portion 521, and goes toward the outer peripheral side of the seed crystal attachment portion 521 as the radius increases. The curve indicated by the alternate long and short dash line 51 corresponds to the curve having the medium thermal conductivity in FIG. On the other hand, in the solid line 50 according to the present embodiment, the inner peripheral portion is a portion where the thermal conductivity of FIG. 8 is large, and the outer peripheral portion is a portion where the thermal conductivity of FIG. 8 is small. Note that dT / dr in FIG. 10 is the tangential slope of the curves 50 and 51 and indicates the magnitude of the temperature gradient.

(5) Operational Effects Next, operational effects according to the present embodiment will be described.

(5-1) The silicon carbide single crystal manufacturing apparatus 1 according to this embodiment includes a crucible body 5 that houses a sublimation raw material 15 and a seed crystal attachment that attaches a seed crystal 43 to a position facing the sublimation raw material 15. The silicon carbide single crystal manufacturing apparatus 1 includes a crucible 9 having a lid 3 provided with a portion 21, and is heated from the outer peripheral side of the crucible 9, and includes a seed crystal attachment portion 21 of the lid 3. The thermal conductivity on the inner peripheral side is set larger than the thermal conductivity on the outer peripheral side.

  About the seed crystal attachment part 21, since the heat conductivity of the inner peripheral side is set larger than the heat conductivity of the outer peripheral side and is heated from the outer peripheral side of the crucible 9, the temperature gradient from the inner peripheral side toward the outer peripheral side The inner peripheral side is gentle and the outer peripheral side is steep. Therefore, since the temperature difference between the radial center and the outer peripheral edge in the seed crystal attachment portion 21 can be reduced, the circumferential tensile stress in the single crystal is reduced and the outer peripheral edge of the seed crystal 43 in the initial stage of growth. The loss of heat disappears. On the other hand, the temperature gradient at the outer peripheral edge of the grown crystal can be maintained at a predetermined value (for example, 1 ° C./cm) or more. Here, the growth crystal has a problem that it tends to be difficult to maintain a downwardly convex curved shape toward the outer peripheral side, and is most likely to have a concave shape at the outer peripheral edge. Accordingly, by maintaining the temperature gradient at the outer peripheral edge of the grown crystal at a predetermined value or higher, the shape of the entire grown crystal can be made to be a curved convex shape. Note that the temperature difference between the radial center and the outer peripheral edge of the seed crystal attachment portion 21 needs to be set to a predetermined value (for example, 20 ° C. or less).

  As described above, even when producing a single crystal having a large diameter, the temperature difference between the radial center and the outer peripheral edge of the seed crystal mounting portion 21 can be reduced and the temperature gradient can be set to a predetermined value or more, so that a high quality single crystal Crystals can be produced.

(5-2) The seed crystal mounting portion 21 of the lid 3 is defined by a central portion 31 and an outer portion 32 that are a plurality of concentric annular portions along the radial direction. Among the portions 32, the thermal conductivity in the inner peripheral side central portion 31 is set to be larger than the thermal conductivity in the outer peripheral side outer portion 32. For this reason, even when producing a single crystal having a large diameter, the temperature difference between the radial center and the outer peripheral edge of the seed crystal mounting portion 21 can be reduced and the temperature gradient can be set to a predetermined value or more, so A single crystal having a good shape can be manufactured.

(5-3) The central portion 31 on the inner peripheral side is formed over the entire thickness direction of the lid 3. Therefore, only the seed crystal attachment portion 21 can suppress the temperature gradient smaller than changing the thermal conductivity between the inner peripheral side and the outer peripheral side, and in the seed crystal attachment portion 21 while maintaining the temperature gradient at a predetermined value or more. The temperature difference between the radial center and the outer peripheral edge can be reduced. For this reason, it is possible to manufacture a high-quality single crystal having a downwardly convex curved shape.

(5-4) The seed crystal mounting portion 21 is composed of a columnar central portion 31 disposed on the inner peripheral side and a cylindrical outer portion 32 disposed on the outer peripheral side. The thermal conductivity is 1.2 times or more that of the outer portion 32.

  Thus, by setting the ratio of the thermal conductivity between the central portion 31 and the outer portion 32 specifically, maintaining the temperature gradient at a predetermined value or more, and the radial center in the seed crystal attachment portion 21 The temperature difference from the outer peripheral edge can be reliably reduced.

(6) Other Embodiments It should not be understood that the description and drawings that constitute part of the disclosure of the above-described embodiments limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the present embodiment, a columnar seed crystal mounting portion 21 that protrudes downward is formed at the center of the lower surface 19 of the lid 3, and the thermal conductivity between the inner peripheral side and the outer peripheral side of the seed crystal mounting portion 21 is determined. changed. However, the present invention is not limited to this, and the lower surface 19 of the lid 3 is formed to be flush with the center portion of the lower surface 19 as a seed crystal mounting portion to which a seed crystal is attached, and the entire lid 3 is formed. About, you may change the heat conductivity of the inner peripheral side of the cover body 3, and an outer peripheral side. For example, among the parts of the lid 3, the thermal conductivity of the inner peripheral part to which the seed crystal is attached may be reduced, while the thermal conductivity of the outer peripheral part to which the seed crystal is not attached may be increased.

  In this embodiment, although the case where the center part 31 was provided over the whole thickness direction of the cover body 3 was demonstrated, it is not limited to this, The thermal conductivity only for the thickness of the seed crystal attachment part 21 is shown. You can change it.

  In the present embodiment, as described with reference to FIGS. 1 and 2, the seed crystal attachment portion 21 is formed so as to protrude downward from the lower surface 19 of the lid body 3. It is good also considering the part which forms in the shape of a plane and the seed crystal 43 contacts as a seed crystal attachment part. In this case, the thermal conductivity on the inner peripheral side of the lid 3 at the portion where the seed crystal 43 abuts is increased, and the thermal conductivity on the outer peripheral side is decreased.

  Further, in the present embodiment, the seed crystal attachment portion 21 is divided into two parts, that is, the central portion 31 and the outer portion 32, but is not limited thereto, and the seed crystal attachment portion 21 is concentrically formed into three or more annular portions. It may be defined.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of silicon carbide single crystal 3 Lid body 5 Crucible body 9 Crucible 15 Raw material for sublimation 21 Seed crystal attachment part 31 Center part 32 Outer part 43 Seed crystal

Claims (5)

Carbonized with a crucible having a crucible body containing a sublimation raw material and a lid provided with a seed crystal attachment portion for attaching a seed crystal at a position facing the sublimation raw material, and heated from the outer peripheral side of the crucible An apparatus for producing a silicon single crystal,
An apparatus for producing a silicon carbide single crystal in which the thermal conductivity on the inner peripheral side of the lid is set larger than the thermal conductivity on the outer peripheral side.   2. The silicon carbide single crystal manufacturing apparatus according to claim 1, wherein a thermal conductivity on an inner peripheral side of the seed crystal attachment portion of the lid is set to be larger than a thermal conductivity on an outer peripheral side.   The seed crystal mounting portion of the lid is defined as a plurality of concentric annular portions, and among these annular portions, the thermal conductivity in the inner circumferential side annular portion is the thermal conductivity in the outer circumferential side annular portion. The apparatus for producing a silicon carbide single crystal according to claim 2, which is set to be larger than that.   The silicon carbide single crystal manufacturing apparatus according to claim 3, wherein the annular portion on the inner peripheral side is formed over the entire thickness direction of the lid. The seed crystal mounting part is composed of a columnar central part arranged on the inner peripheral side and a cylindrical outer part arranged on the outer peripheral side,
5. The apparatus for producing a silicon carbide single crystal according to claim 3, wherein the thermal conductivity of the central portion is 1.2 times or more of the thermal conductivity of the outer portion.

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