JP2020033208A - Tray, method for manufacturing semiconductor substrate, method for manufacturing semiconductor device, and semiconductor manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tray capable of making the temperature distribution of a semiconductor substrate uniform during epitaxial growth, a method for manufacturing a semiconductor substrate, a method for manufacturing a semiconductor device, and a semiconductor manufacturing device. A tray 10 has a counterbore 15 on which a silicon carbide substrate is placed. Of the bottom surface of the counterbore 15, the height of the upper surface of the slope portion 13 surrounding the upper surface of the concave shape portion 14 becomes linearly lower as the distance from the concave shape portion 14 increases. The tray 10 on which the silicon carbide substrate is placed is transported to the reaction vessel and installed so that the back surface of the silicon carbide substrate faces the bottom surface of the counterbore 15 on the counterbore 15. Then, a silicon carbide epitaxial film is epitaxially grown on the front surface of the silicon carbide substrate. [Selection diagram] Fig. 1

Description

  The present invention relates to a tray, a method of manufacturing a semiconductor substrate, a method of manufacturing a semiconductor device, and a semiconductor manufacturing apparatus.

  Conventionally, a manufacturing method for manufacturing a semiconductor substrate by epitaxially growing a semiconductor film made of silicon carbide on a silicon carbide (SiC) substrate has been known. In such a manufacturing method, for example, the shape of a tray installed inside a reaction vessel for epitaxially growing a semiconductor film made of silicon carbide on a silicon carbide substrate is changed from the center to the bottom of the recess accommodating the silicon carbide substrate. A manufacturing method has been proposed in which the shape becomes lower as it goes to the portion (for example, see Patent Document 1 below).

JP 2017-109900 A

  However, the above-described conventional technique has a problem that the temperature distribution of the semiconductor substrate cannot be made uniform during the epitaxial growth. For this reason, there are problems that the warpage of the semiconductor substrate increases and the occurrence of dislocations in the epitaxial layer increases.

  FIG. 16 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in a conventional manufacturing method. A tray 161 shown in FIG. 16 is a container for mounting a silicon carbide substrate 162 to be transported to a CVD (Chemical Vapor Deposition) apparatus in a conventional manufacturing method.

  Counterbore 161a for mounting silicon carbide substrate 162 is formed on tray 161. Counterbore 161a is formed according to the diameter and thickness of silicon carbide substrate 162 to be placed. When the silicon carbide substrate 162 is placed on the counterbore 161a, the bottom surface of the counterbore 161a facing the back surface of the silicon carbide substrate 162 is usually formed flat as shown in FIG.

  On the other hand, silicon carbide substrate 162 before epitaxial growth often warps so as to project toward the back surface (C surface), depending on the manufacturer and lot. To warp the silicon carbide substrate 162 so as to be convex toward the back surface side means that the silicon carbide substrate 162 warps such that, for example, the end of the back surface of the silicon carbide substrate 162 is separated from the bottom surface of the counterbore 161a. Since the warpage before the epitaxial growth is relatively small, a relatively large portion of the back surface of silicon carbide substrate 162 is in contact with the bottom surface of counterbore 161a.

  FIG. 17 is a cross-sectional view showing one example of a state where an epitaxial layer is formed on a silicon carbide substrate by a conventional manufacturing method. In FIG. 17, the same components as those shown in FIG. 16 are denoted by the same reference numerals, and description thereof will be omitted. A semiconductor substrate 170 shown in FIG. 17 is obtained by forming an epitaxial layer 171 by epitaxial growth on the front surface of a silicon carbide substrate 162 (see FIG. 16) placed on a tray 161 using a CVD apparatus.

  Since the epitaxial growth is performed at a high temperature of, for example, about 1600 [° C.], as the epitaxial growth proceeds, as shown in FIG. 17, the semiconductor substrate 170 warps so as to be convex on the front surface side. The term “the semiconductor substrate 170 warps so as to protrude toward the front surface side” means that the semiconductor substrate 170 warps such that, for example, the central portion of the back surface of the semiconductor substrate 170 is separated from the bottom surface of the counterbore 161a. This warpage is generally larger as the epitaxial layer 171 is thicker. Due to this warp, only a part (edge) of the back surface of the semiconductor substrate 170 comes into contact with the tray 161, and the unevenness of the temperature distribution in the surface of the semiconductor substrate 170 increases.

  When the bias of the temperature distribution in the surface of the semiconductor substrate 170 is increased, the warpage of the semiconductor substrate 170 that is convex toward the front surface side is further increased. When the warpage of the semiconductor substrate 170 increases, a trouble due to the warpage of the semiconductor substrate 170 occurs in the manufacture of a semiconductor device using the semiconductor substrate 170.

  For example, in order to manufacture a silicon carbide device, the semiconductor substrate 170 is transported and installed in various types of process equipment for semiconductor fine processing. At this time, if the warpage of the semiconductor substrate 170 is large, troubles such as a large dimensional error of the pattern in each microfabrication process and a problem that the semiconductor substrate 170 cannot be transported to the processing apparatus due to the large warpage occur.

  FIG. 18 is a top view showing an example of dislocation generated in a semiconductor substrate manufactured by a conventional manufacturing method. The dislocations 180 to 189 shown in FIG. 18 are observed by measuring the epitaxial layer 171 of the semiconductor substrate 170 manufactured by the conventional manufacturing method using the tray 161 by synchrotron radiation topography.

  Dislocations 180 to 189 are linear crystal defects (interface dislocations). When the bias of the temperature distribution in the surface of the semiconductor substrate 170 becomes large, a large number of dislocations 180 to 189 occur in the epitaxial layer 171 due to the stress generated in the epitaxial layer 171, separately from the above-mentioned trouble. For this reason, the quality of the semiconductor substrate 170 itself deteriorates, and the yield of the semiconductor device using the semiconductor substrate 170 decreases.

  Further, when the tray 161 having a flat bottom surface of the counterbore 161a is used, the silicon carbide substrate 162 (semiconductor substrate 170) placed on the tray 161 may come off from the counterbore 161a of the tray 161 during the epitaxial growth using the CVD apparatus. .

  Also, as in the above-mentioned Patent Document 1, even in a configuration in which the shape of the tray is such that the bottom surface of the dent becomes lower from the center to the end, the semiconductor substrate 170 protrudes toward the front surface during epitaxial growth. We cannot avoid warping to become Therefore, during the epitaxial growth, only a part of the semiconductor substrate 170 comes into contact with the tray 161, and there is a problem that the temperature distribution in the surface of the semiconductor substrate 170 becomes more uneven.

  The present invention provides a tray, a method of manufacturing a semiconductor substrate, a method of manufacturing a semiconductor device, and a semiconductor manufacturing apparatus capable of achieving a uniform temperature distribution of a semiconductor substrate during epitaxial growth in order to solve the above-described problems caused by the conventional technology. The purpose is to provide.

  In order to solve the above-described problems and achieve the object of the present invention, a tray according to the present invention is a tray on which the silicon carbide substrate is placed when epitaxially growing a silicon carbide epitaxial film on a main surface of the silicon carbide substrate. There is a counterbore on which the silicon carbide substrate is placed, and the height of the bottom surface of the counterbore in the annular region surrounding the central region of the bottom surface is linearly lower as the distance from the central region increases. It is characterized by becoming.

  Further, in the tray according to the present invention, in the above-described invention, the silicon carbide substrate is placed on the counterbore with the first main surface of the silicon carbide substrate facing the bottom surface of the counterbore. Wherein the silicon carbide epitaxial film is transported to a reaction vessel for epitaxially growing the silicon carbide epitaxial film on a second main surface opposite to the first main surface.

  In the tray according to the present invention, in the above-described invention, the depth of the shallowest portion in the counterbore is the thickness of the silicon carbide substrate before the silicon carbide epitaxial film is epitaxially grown, and the depth of the silicon carbide epitaxial film is And the amount of warpage of the silicon carbide substrate before the heat treatment is performed.

  Further, the tray according to the present invention is characterized in that, in the above-described invention, the central region of the bottom surface of the counterbore is a curved surface whose bottom surface becomes higher as it goes away from the center.

  Further, in the tray according to the present invention, in the above-described invention, the central region of the bottom surface of the counterbore has a depth and a depth corresponding to a warp amount of the silicon carbide substrate before the silicon carbide epitaxial film is epitaxially grown. It is characterized by a curved surface having a curvature.

  In the tray according to the present invention, in the above-described invention, the central region of the bottom surface of the counterbore is a curved surface having a depth of 5 μm or more and 100 μm or less. .

  Further, in the tray according to the present invention, in the above-described invention, the central region of the bottom surface of the counterbore is a circular region having a diameter of 0.3 times or more and 0.7 times or less the inner diameter of the counterbore. It is characterized by being.

  Further, in the tray according to the present invention, in the above-described invention, the inclination angle in the annular region on the bottom surface of the counterbore is an inclination angle according to a warp amount of the silicon carbide substrate on which the silicon carbide epitaxial film is epitaxially grown. It is characterized by being.

  The tray according to the present invention is characterized in that, in the above-described invention, an inclination angle of the annular region on the bottom surface of the counterbore is 0.3 degrees or more and 3 degrees or less.

  The tray according to the present invention is characterized in that, in the above-described invention, the tray is formed of carbon.

  The tray according to the present invention is characterized in that, in the above-described invention, at least the inside of the counterbore is coated with a high melting point material.

  Further, in the method for manufacturing a semiconductor substrate according to the present invention, in the first step, using a tray having a counterbore on which a silicon carbide substrate is mounted, the silicon carbide substrate is placed on the counterbore, One main surface is placed facing the bottom surface of the counterbore. The tray is characterized in that, in the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly as the distance from the central region increases. In the second step, the tray in which the silicon carbide substrate is placed in the counterbore in the first step with the first main surface of the silicon carbide substrate facing the bottom surface of the counterbore is transferred to a reaction vessel. And a silicon carbide epitaxial film is epitaxially grown on a second main surface of the silicon carbide substrate opposite to the first main surface inside the reaction vessel.

  Further, in the method for manufacturing a semiconductor device according to the present invention, in the first step, using the tray having the counterbore on which the silicon carbide substrate is placed, the silicon carbide substrate is placed on the counterbore, One main surface is placed facing the bottom surface of the counterbore. Further, the tray is characterized in that, in the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly as the distance from the central region increases. Further, in the second step, the tray on which the silicon carbide substrate is placed is transported and set in the counterbore by the first step, and the tray is placed inside the reaction container. A semiconductor substrate is manufactured by epitaxially growing a silicon carbide epitaxial film on a second main surface opposite to the one main surface. Further, in the third step, a predetermined element structure is formed on the semiconductor substrate manufactured in the second step.

  In addition, a semiconductor manufacturing apparatus according to the present invention includes a tray having a counterbore on which a silicon carbide substrate is placed, a reaction vessel in which the tray is installed, and a silicon carbide epitaxial layer on the silicon carbide substrate inside the reaction vessel. Growth means for epitaxially growing the film. Further, the tray is characterized in that, in the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly as the distance from the central region increases. The growth means may include a second main surface opposite to the first main surface of the silicon carbide substrate placed on the counterbore of the tray with a first main surface of the silicon carbide substrate facing a bottom surface of the counterbore. A silicon carbide epitaxial film is epitaxially grown on the main surface.

  During the epitaxial growth, the semiconductor substrate is warped so as to be convex toward the second main surface side mainly by bending the central portion, and at this time, the outer portion of the semiconductor substrate is hardly bent. Therefore, according to the above-described invention, during the epitaxial growth, the outer portion of the first main surface of the semiconductor substrate that warps so as to protrude toward the second main surface becomes farther away from the central region of the bottom surface of the tray. It touches an annular region that becomes linearly lower. Thereby, the contact amount between the semiconductor substrate and the tray can be increased, and the temperature distribution of the semiconductor substrate can be made uniform. Therefore, it is possible to suppress an increase in the warpage of the semiconductor substrate. Further, dislocation generated in the epitaxial layer of the semiconductor substrate can be suppressed.

  According to the tray, the method for manufacturing a semiconductor substrate, the method for manufacturing a semiconductor device, and the semiconductor manufacturing apparatus according to the present invention, the temperature distribution of the semiconductor substrate during the epitaxial growth is made uniform, the warpage of the semiconductor substrate is increased, There is an effect that dislocations generated in the epitaxial layer can be suppressed.

FIG. 1 is a diagram illustrating an example of the structure of a tray used in the method for manufacturing a semiconductor substrate according to the first embodiment. FIG. 2 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in the method for manufacturing a semiconductor substrate according to the first embodiment. FIG. 3 is a cross-sectional view showing one example of a state in which an epitaxial layer is formed on a silicon carbide substrate by the method for manufacturing a semiconductor substrate according to the first embodiment. FIG. 4 is a cross-sectional view illustrating an example of the warpage of the semiconductor substrate in the method of manufacturing a semiconductor substrate according to the first embodiment. FIG. 5 is a flowchart illustrating an example of the method for manufacturing a semiconductor substrate according to the first embodiment. FIG. 6 is a cross-sectional view illustrating an example of the diameter of the side wall and the concave portion of the tray used in the manufacturing method according to the first embodiment. FIG. 7 is a cross-sectional view illustrating an example of the counterbore depth of the tray used in the manufacturing method according to the first embodiment. FIG. 8 is a cross-sectional view illustrating an example of the depth of the concave portion of the tray used in the manufacturing method according to the first embodiment. FIG. 9 is a cross-sectional view illustrating an example of the angle of the slope of the tray used in the manufacturing method according to the first embodiment. FIG. 10 is a cross-sectional view illustrating another example of the structure of the tray used in the manufacturing method according to the first embodiment. FIG. 11 is a cross-sectional view illustrating still another example of the structure of the tray used in the manufacturing method according to the first embodiment. FIG. 12 is a top view illustrating an example of the structure of a tray having a plurality of counterbores used in the manufacturing method according to the first embodiment. FIG. 13 is a diagram illustrating an example of the structure of a tray used in the method for manufacturing a semiconductor substrate according to the second embodiment. FIG. 14 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in the method for manufacturing a semiconductor substrate according to the second embodiment. FIG. 15 is a cross-sectional view showing one example of a state where an epitaxial layer is formed on a silicon carbide substrate by the method for manufacturing a semiconductor substrate according to the second embodiment. FIG. 16 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in a conventional manufacturing method. FIG. 17 is a cross-sectional view showing one example of a state where an epitaxial layer is formed on a silicon carbide substrate by a conventional manufacturing method. FIG. 18 is a top view showing an example of dislocation generated in a semiconductor substrate manufactured by a conventional manufacturing method.

  Exemplary embodiments of a tray, a method of manufacturing a semiconductor substrate, a method of manufacturing a semiconductor device, and a semiconductor manufacturing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment 1)
A method for manufacturing a semiconductor substrate according to the first embodiment will be described. The semiconductor substrate manufactured by this manufacturing method has a silicon carbide epitaxial film epitaxially grown on the front surface (Si surface: second main surface) of the silicon carbide substrate, so that silicon carbide is formed on the front surface of the silicon carbide substrate. Is a substrate on which an epitaxial layer is formed.

  First, a tray having a counterbore (recess) for mounting a silicon carbide substrate, which is transported to a reaction vessel for epitaxial growth with the silicon carbide substrate mounted thereon, is provided. This tray is a tray in which, in the bottom surface of the counterbore for mounting the silicon carbide substrate, the height in an annular region surrounding the central region decreases linearly as the distance from the central region increases. A specific example of the structure of the tray will be described later (for example, see FIG. 1).

  Next, a silicon carbide (SiC) substrate is placed on the counterbore of the prepared tray such that the back surface (C surface: first main surface) of the silicon carbide substrate faces the bottom surface of the counterbore (first step). Then, the tray with the silicon carbide substrate placed on the counterbore is transported to the reaction vessel and placed therein, and a silicon carbide epitaxial film is epitaxially grown on the front surface of the silicon carbide substrate inside the reaction vessel (second step). Thereby, a semiconductor substrate having a silicon carbide epitaxial layer formed on the front surface of the silicon carbide substrate can be manufactured. A specific example of the method for manufacturing a semiconductor substrate according to the first embodiment will be described later (for example, see FIG. 5).

  The semiconductor manufacturing apparatus according to the first embodiment will be described. This semiconductor manufacturing apparatus includes the above-described tray, a reaction container in which the above-described tray is installed, a transport unit that transports and installs the above-described tray to the reaction container, and a front surface of the silicon carbide substrate inside the reaction container. Growth means for epitaxially growing a silicon carbide epitaxial film on the surface.

  This semiconductor manufacturing apparatus is, for example, a CVD (Chemical Vapor Deposition) apparatus. A CVD apparatus is an apparatus having a reaction vessel for performing chemical vapor deposition. The above-mentioned tray on which the silicon carbide substrate is placed is installed in the reaction vessel of the CVD apparatus. Further, the CVD apparatus includes a growth means for epitaxially growing a silicon carbide epitaxial film on the front surface of the silicon carbide substrate inside the reaction vessel. The growth means includes, for example, means for adjusting the pressure and temperature in the reaction vessel, means for introducing various gases into the reaction vessel, and the like.

  FIG. 1 is a diagram illustrating an example of the structure of a tray used in the method for manufacturing a semiconductor substrate according to the first embodiment. The tray 10 shown in FIG. 1 is a container for mounting a silicon carbide substrate to be transported to a reaction container of a CVD apparatus in the method for manufacturing a semiconductor substrate according to the first embodiment. For example, the tray 10 is installed on a susceptor (heating means) in a reaction vessel of a CVD apparatus. An upper surface structure 1 and a cross-sectional structure 2 in FIG.

  Here, the height direction of the tray 10 (the vertical direction of the sectional structure 2) is defined as the Z-axis direction. Further, directions orthogonal to the Z-axis direction and orthogonal to each other are defined as an X-axis direction and a Y-axis direction, respectively. The cross-sectional structure 2 is a cross-sectional structure that is parallel to the XZ plane and passes through the center of the tray 10, but each cross section is parallel to the Z-axis direction and passes through the center of the tray 10 (for example, a cross section that is parallel to the YZ plane). Is also the same as the cross-sectional structure shown in the cross-sectional structure 2.

  As shown in the upper surface structure 1, the tray 10 has a circular shape centered on the Z-axis direction when viewed from the upper surface side of the tray 10 (the positive direction of the Z-axis). Further, as shown in the top structure 1 and the cross-sectional structure 2, the tray 10 has a base 11, a side wall 12, a slope 13, and a concave portion 14. The base portion 11 is a portion serving as a bottom portion of the tray 10 when the tray 10 on which the silicon carbide substrate is placed is transported and installed in a reaction vessel of the CVD apparatus, that is, a portion of the tray 10 which is in contact with the bottom surface in the CVD apparatus. is there. The side wall 12, the slope 13, and the concave portion 14 are formed on the base 11.

  As shown in the upper surface structure 1, the side wall portion 12 has an annular shape (a donut shape) surrounding the inclined surface portion 13 with the center in the Z-axis direction as viewed from the upper surface side of the tray 10. As shown in the cross-sectional structure 2, the upper surface (the surface on the positive side of the Z axis) of the side wall portion 12 is parallel to the bottom surface of the tray 10 (the base portion 11).

  As shown in the upper surface structure 1, the slope portion 13 has a ring shape surrounding the concave portion 14 with the Z-axis direction as a center, as viewed from the upper surface side of the tray 10. As shown in the cross-sectional structure 2, the upper surface of the side wall portion 12 is inclined with respect to the bottom surface of the tray 10 (the base portion 11). Specifically, the shape of the slope portion 13 is such that, for example, as the distance from the center of the concave portion 14 (the center of the tray 10) increases on the XY plane, the height of the upper surface decreases linearly (linearly). . A low height means that the distance between the tray 10 and the bottom surface of the base 11 is short.

  As shown in the upper surface structure 1, the concave portion 14 has a circular shape centered on the Z-axis direction when viewed from the upper surface side of the tray 10. The concave portion 14 is a curved surface having a curved upper surface, as shown in the cross-sectional structure 2. Specifically, the upper surface of the concave portion 14 has a shape in which the center of the concave portion 14 on the XY plane (the center of the tray 10) is the lowest, and becomes higher as the distance from the center of the concave portion 14 on the XY plane increases. . Further, the upper surface of concave portion 14 is a curved surface having a constant curvature according to the warpage of a silicon carbide substrate described later.

  Here, the upper surface of the side wall portion 12 is higher than the inclined surface portion 13 and the concave portion 14. The counterbore 15 is a counterbore having the side wall portion 12 as a side surface and the concave portion 14 and the slope portion 13 as a bottom surface. A silicon carbide substrate can be placed on the counterbore 15.

  Thus, in tray 10 shown in FIG. 1, of the bottom surface of counterbore 15 on which the silicon carbide substrate is placed, the upper surface (annular shape) of slope 13 surrounding the upper surface (center region) of concave portion 14. Area) decreases linearly away from the central area. Further, the tray 10 shown in FIG. 1 has a curved surface in which the height of the central region (the upper surface of the concave portion 14) of the bottom surface of the counterbore 15 increases as the distance from the center increases. That is, the tray 10 shown in FIG. 1 has a counterbore 15 including a bottom surface in which a plurality of shapes are combined by using the top surfaces of the slope portion 13 and the concave portion 14 as bottom surfaces.

  The tray 10 is formed of a material having a high melting point, such as carbon (C), so as to withstand the processing by the CVD apparatus. Further, at least a portion of the tray 10 where the SiC epi film may be deposited may be coated with a material having a high melting point (a high melting point material). For example, tantalum carbide (TaC) or silicon carbide can be used as the high melting point material used for this coating. Thereby, the contact between tray 10 and the silicon carbide substrate can be improved.

  FIG. 2 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in the method for manufacturing a semiconductor substrate according to the first embodiment. In FIG. 2, the same parts as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Silicon carbide substrate 20 shown in FIG. 2 is a 4H-SiC substrate using, for example, 4H-SiC (four-layer periodic hexagonal silicon carbide) as a semiconductor material. Silicon carbide substrate 20 is a disk-shaped substrate having a diameter of about 4 inches and a thickness (thickness) of about 400 [μm], for example.

  Silicon carbide substrate 20 has a disk shape as described above, but may be warped so as to be convex on the back surface side as shown in FIG. To warp the silicon carbide substrate 20 so as to protrude to the back surface side means that the silicon carbide substrate 20 warps such that, for example, the end of the back surface of the silicon carbide substrate 20 is separated from the bottom surface of the counterbore 15. The warpage of silicon carbide substrate 20 is caused, for example, by a difference in stress between the front surface and the back surface of silicon carbide substrate 20 due to polishing or the like of silicon carbide substrate 20. Specifically, the front surface of silicon carbide substrate 20 is carefully polished with a whetstone having fine abrasive grains, and the back surface of silicon carbide substrate 20 is provided with abrasive particles for thinning silicon carbide substrate 20. Polishing with a coarse grindstone is performed. The difference between the polishing on the front surface and the polishing on the back surface causes a difference in stress between the front surface and the back surface. The amount of warpage (SORI) generated in silicon carbide substrate 20 is, for example, about 30 [μm] at the maximum.

  Here, the amount of warpage (SORI) of the substrate will be described. For example, a plane calculated from each point on the substrate by the least square method is defined as a least square plane. The distance between the least square plane and the highest point on the front surface of the substrate is d1. The distance between the least-squares plane and the lowest point on the front surface of the substrate is d2. At this time, the warpage amount (SORI) of the substrate can be defined by, for example, the total value (d1 + d2) of the distances d1 and d2.

  The concave portion 14 of the tray 10 has a curved surface whose upper surface is curved as described above. Then, the curvature of the upper surface of concave portion 14 is set to be close to the curvature of a bent portion (for example, see FIG. 4) of silicon carbide substrate 20. Therefore, when the warped silicon carbide substrate 20 is placed on the counterbore 15 with the back surface facing down, the back surface of the silicon carbide substrate 20 easily contacts the upper surface of the concave portion 14 as shown in FIG. The heat of the tray 10 is transmitted to the silicon carbide substrate 20 via the portion.

  In the example shown in FIG. 2, the back surface of the central portion of silicon carbide substrate 20 is in contact with the entire upper surface of concave shape portion 14. The central portion of silicon carbide substrate 20 is a circular portion including the center of silicon carbide substrate 20 on the XY plane. However, since the warpage of silicon carbide substrate 20 varies, the back surface of silicon carbide substrate 20 does not have to be in contact with the entire upper surface of concave portion 14. For example, it is preferable that the back surface of silicon carbide substrate 20 be in contact with 50% or more of the area of the upper surface of concave portion 14.

  FIG. 3 is a cross-sectional view showing one example of a state in which an epitaxial layer is formed on a silicon carbide substrate by the method for manufacturing a semiconductor substrate according to the first embodiment. In FIG. 3, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. A semiconductor substrate 30 shown in FIG. 3 is obtained by forming an epitaxial layer 31 by epitaxial growth on a front surface of a silicon carbide substrate 20 (see FIG. 2) placed on a tray 10 using a CVD apparatus.

  In chemical vapor deposition using a CVD apparatus, the temperature of the silicon carbide substrate 20 (semiconductor substrate 30) becomes high. Therefore, the semiconductor substrate 30 formed by the CVD apparatus is warped such that the front surface side is convex, that is, the warpage occurs in the direction opposite to the warpage of the silicon carbide substrate 20 shown in FIG. The term “the semiconductor substrate 30 warps so as to protrude toward the front surface side” means that the semiconductor substrate 30 warps such that, for example, the central portion of the back surface of the semiconductor substrate 30 is separated from the bottom surface of the counterbore 15. The principle of this warpage will be described. In the epitaxial growth, a compressive stress in a lateral direction (a direction parallel to the main surface of the silicon carbide substrate 20) is applied near the center of the epitaxial layer 31 which is an epitaxial film formed on the front surface of the silicon carbide substrate 20 (toward the outside). Force), and a slight tensile stress (force toward the center) in the lateral direction is applied near the end of the epitaxial layer 31. Thereby, the semiconductor substrate 30 is warped such that the front surface side is convex.

  For example, if the silicon carbide substrate 20 is warped so as to protrude to the rear surface side as shown in FIG. 2 before the epitaxial growth, the warp is gradually reduced during the epitaxial growth and the warp is eliminated. When the epitaxial growth further proceeds, the semiconductor substrate 30 is warped so as to be convex on the front surface side, the warpage gradually increases, and finally, for example, a state as shown in FIG. 3 is obtained. .

  On the other hand, as described above, the slope 13 of the tray 10 has a shape in which the upper surface decreases linearly as the distance from the center increases. Then, the angle (inclination) of the upper surface of the slope portion 13 is set to be the same angle as the outer portion of the semiconductor substrate 30 which is warped so as to project to the back surface side as shown in FIG. The outer portion of the semiconductor substrate 30 is an annular portion of the semiconductor substrate 30 excluding the central portion on the XY plane. Therefore, when the semiconductor substrate 30 is warped so as to be convex on the front surface side, the back surface of the semiconductor substrate 30 is more likely to come into contact with the upper surface of the inclined portion 13, and the heat of the tray 10 is reduced via the contact portion. It is transmitted to the semiconductor substrate 30.

  In the example shown in FIG. 3, the angle between the upper surface of the slope portion 13 and the rear surface of the outer portion of the semiconductor substrate 30 match. However, since the warpage of the semiconductor substrate 30 varies, the angle between the upper surface of the slope portion 13 and the rear surface of the outer peripheral portion of the semiconductor substrate 30 does not need to completely match.

  Further, when the epitaxial growth is completed before the semiconductor substrate 30 is warped such that it becomes convex on the front surface side, the semiconductor substrate 30 has no warpage or warpage remaining convex on the back surface side. State. Also in this case, the heat of the tray 10 is transmitted to the semiconductor substrate 30 via the contact portion because the back surface of the semiconductor substrate 30 is easily brought into contact with the upper surface of the concave portion 14 during the epitaxial growth.

  As shown in FIGS. 2 and 3, before the epitaxial growth in which silicon carbide substrate 20 is warped so as to be convex on the rear surface side, concave portion 14 in tray 10 is in contact with the central portion of silicon carbide substrate 20. (See FIG. 2). When the semiconductor substrate 30 is warped so as to be convex on the front surface side by epitaxial growth, the inclined surface portion 13 of the tray 10 can be easily brought into contact with the outer portion of the semiconductor substrate 30 (see FIG. 3).

  Therefore, the amount of contact between the semiconductor substrate 30 and the tray 10 during epitaxial growth can be increased. The contact amount between the semiconductor substrate 30 and the tray 10 during the epitaxial growth is, for example, an amount obtained by time-integrating the contact area between the semiconductor substrate 30 and the tray 10 during the epitaxial growth.

  By increasing the amount of contact between the semiconductor substrate 30 and the tray 10 during the epitaxial growth, it is possible to reduce the temperature change of the semiconductor substrate 30 during the epitaxial growth, thereby making the temperature distribution in the plane of the semiconductor substrate 30 uniform. it can. Since silicon carbide used for the semiconductor substrate 30 has good thermal conductivity, if approximately half of the semiconductor substrate 30 is in contact with the tray 10 during epitaxial growth, the temperature distribution in the plane of the semiconductor substrate 30 is sufficiently uniform. Can be

  By making the temperature distribution in the surface of the semiconductor substrate 30 uniform during the epitaxial growth, it is possible to suppress an increase in the warpage that becomes convex on the front surface side of the semiconductor substrate 30. For example, it is possible to prevent the semiconductor substrate 30 from warping more than the state shown in FIG.

  By suppressing the warpage of the semiconductor substrate 30 from increasing, it is possible to avoid the above-described trouble caused by the warpage of the semiconductor substrate 30 in the manufacture of a semiconductor device using the semiconductor substrate 30. Thereby, the manufacturing yield of the semiconductor device using the semiconductor substrate 30 can be improved. Alternatively, the reliability of the characteristics of the semiconductor device using the semiconductor substrate 30 can be improved.

  Further, by making the temperature distribution in the plane of the semiconductor substrate 30 during the epitaxial growth uniform, dislocations and the like generated in the epitaxial layer 31 of the semiconductor substrate 30 due to the stress in the epitaxial layer 31 caused by this temperature distribution are also suppressed. Can be. Therefore, the quality of the semiconductor substrate 30 itself can be improved. Therefore, the yield rate of the semiconductor device using the semiconductor substrate 30 can be improved.

  FIG. 4 is a cross-sectional view illustrating an example of the warpage of the semiconductor substrate in the method of manufacturing a semiconductor substrate according to the first embodiment. For example, as shown in FIG. 2, silicon carbide substrate 20 before epitaxial growth is in a state in which the back surface is warped so as to be convex, or in a state in which there is no warp. In addition, as shown in FIG. 4 (or FIG. 3), semiconductor substrate 30 obtained by forming epitaxial layer 31 by epitaxial growth on the front surface of silicon carbide substrate 20 has a front surface convex. It becomes a warped state like this.

  At this time, as shown in FIG. 4, the central portion 41 of the semiconductor substrate 30 is bent mainly, and the outer portion 42 around the central portion 41 of the semiconductor substrate 30 is parallel to the Z-axis direction. It is almost flat in cross section. For this reason, the slope portion 13 of the tray 10 is formed in an oblique planar shape in a cross section parallel to the Z-axis direction so as to easily contact the back surface of the outer portion 42 of the semiconductor substrate 30 warped by epitaxial growth.

  FIG. 5 is a flowchart illustrating an example of the method for manufacturing a semiconductor substrate according to the first embodiment. The method for manufacturing a semiconductor substrate according to the first embodiment is realized by, for example, each step shown in FIG.

  First, the silicon carbide substrate 20 is cleaned (Step S51). For the cleaning in step S51, for example, organic cleaning or RCA cleaning is used. At this time, in silicon carbide substrate 20, for example, a convex warp may be generated on the back side as shown in FIG. 2, or the warp may not be generated.

  Next, silicon carbide substrate 20 is placed on counterbore 15 of tray 10 described above (step S52 (first step)). At this time, silicon carbide substrate 20 is placed such that the back surface of silicon carbide substrate 20 faces the bottom surface of counterbore 15. By the step S52, for example, the state shown in FIG. 2 is obtained.

  Next, in step S52, the tray 10 on which the silicon carbide substrate 20 is placed on the counterbore 15 is transported to a reaction vessel of a CVD apparatus and installed, and a silicon carbide epitaxial film is epitaxially grown on the front surface of the silicon carbide substrate 20. (Step S53 (second step)). Thereby, silicon carbide epitaxial layer 31 is stacked on the front surface of silicon carbide substrate 20. By the step S53, for example, the state shown in FIG. 3 is obtained.

The epitaxial growth in step S53 is performed, for example, by introducing various gases into the reaction vessel and depositing silicon atoms and carbon atoms in the reaction vessel on the silicon carbide substrate 20 with the same crystal structure as the silicon carbide substrate 20. . At this time, for example, a source gas, an etching gas, a doping gas, and a carrier gas are introduced into the reaction vessel. As the source gas, for example, silicon hydride (SiH ₄ ) and propane (C ₃ H ₈ ) are used. As an etching gas, for example, hydrochloric acid (HCl) is used. As the doping gas, for example, nitrogen (N ₂ ) is used. As the carrier gas, for example, hydrogen (H ₂ ) gas of about 30 [slm] is used.

  At this time, for example, the flow rate of silicon hydride can be 54 [sccm], the flow rate of propane can be 21 [sccm], the flow rate of nitrogen can be 1.0 [sccm], and the flow rate of hydrochloric acid can be 162 [sccm]. The amount of nitrogen gas is adjusted so as to have a target doping concentration. The flow rate of hydrochloric acid may be changed to an arbitrary value between 0 [sccm] and 270 [sccm]. If the flow rate of hydrochloric acid is extremely increased, the growth rate of the silicon carbide epitaxial film decreases. Generally, in the case of a halide epitaxial film, the appropriate flow rate of hydrochloric acid is about three times the flow rate of silicon hydride.

  The epitaxial growth in step S53 is performed, for example, by setting the pressure inside the reaction vessel in which the silicon carbide substrate 20 is installed to about 20 [Torr], setting the temperature to about 1600 [° C.], and taking about 5 hours and 30 minutes. Done.

The silicon carbide epitaxial film epitaxially grown in step S53 is, for example, an n-type epitaxial film using a 4H-SiC material. Further, the silicon carbide epitaxial film formed in step S53 may be a p-type epitaxial film using a 4H—SiC material. In this case, in step S53, for example, trimethylaluminum (C ₆ H ₁₈ Al ₂ ) is used as the doping gas.

  The thickness of the silicon carbide epitaxial film (epitaxial layer 31) epitaxially grown in step S53 is, for example, about 260 [μm]. However, the thickness of the epitaxial layer 31 is not limited to about 260 [μm] and is determined according to, for example, a target breakdown voltage of a semiconductor device manufactured using the semiconductor substrate 30. The withstand voltage is a limit voltage at which the element does not malfunction or break down.

  Next, in step S53, the silicon carbide substrate 20, in which the silicon carbide epitaxial layer 31 is laminated on the front surface, that is, the semiconductor substrate 30, is taken out of the CVD apparatus (step S54), and a series of manufacturing methods of the semiconductor substrate 30 is completed. I do. At this time, in silicon carbide substrate 20, for example, a convex warpage occurs on the front side as shown in FIG. The semiconductor substrate 30 can be manufactured by the steps shown in FIG.

  FIG. 6 is a cross-sectional view illustrating an example of the diameter of the side wall and the concave portion of the tray used in the manufacturing method according to the first embodiment. The counterbore inner diameter D1 shown in FIG. 6 is the inner diameter of the counterbore 15 of the tray 10 as viewed from the Z-axis direction, that is, the inner diameter of the side wall portion 12 (or the outer diameter of the slope portion 13). Counterbore inner diameter D1 is determined to be larger than the diameter of silicon carbide substrate 20 placed on tray 10. For example, if the diameter of silicon carbide substrate 20 is about 4 inches, counterbore inner diameter D1 is determined to be larger than 4 inches.

  The diameter D2 shown in FIG. 6 is the diameter of the concave portion 14 as viewed from the Z-axis direction. That is, the counterbore inner diameter D1 corresponds to the inner diameter of the slope portion 13. The diameter D2 is, for example, in the range of about 0.3 times or more and 0.7 times or less the counterbore inner diameter D1 according to the ratio of the diameter of the central portion 41 and the outer portion 42 in the semiconductor substrate 30 shown in FIG. Is determined.

  Further, diameter D2 is determined to be smaller than the diameter of silicon carbide substrate 20 placed on counterbore 15. Thereby, outer portion 42 of silicon carbide substrate 20 placed on counterbore 15 can be positioned on slope 13.

  As an example, the diameter D2 can be approximately 50 [mm]. In this case, in the semiconductor substrate 30 after the epitaxial growth, a region outside a region having a radius of 25 [mm] from the center of the semiconductor substrate 30 contacts the slope portion 13.

  FIG. 7 is a cross-sectional view illustrating an example of the counterbore depth of the tray used in the manufacturing method according to the first embodiment. The counterbore depth D3 shown in FIG. 7 is the height difference between the upper surface of the side wall portion 12 and the boundary between the concave portion 14 and the slope portion 13, that is, the depth difference of the counterbore 15 of the tray 10 at the shallowest portion. Depth. Counterbore depth D3 is determined, for example, to a depth equal to or greater than the sum of the thickness of silicon carbide substrate 20 before epitaxial growth and the amount of warpage (SORI) of silicon carbide substrate 20 before epitaxial growth.

  For example, the thickness of silicon carbide substrate 20 before epitaxial growth is about 350 μm or more and 400 μm or less (400 μm in the above example), and the amount of warpage of silicon carbide substrate 20 before epitaxial growth is 100 μm. ] And about 110 [μm] or less. In this case, the counterbore depth D3 is determined to be, for example, a depth of 510 [μm] or more, for example, a depth of about 800 [μm].

  Thereby, even if silicon carbide substrate 20 is warped before epitaxial growth (see FIG. 2), the end of silicon carbide substrate 20 is prevented from protruding above the surface of tray 10 (the upper surface of side wall portion 12). it can. That is, the end portion of silicon carbide substrate 20 can be brought into a state where it is sufficiently sunk in counterbore 15. Therefore, even when the tray 10 rotates or revolves during epitaxial growth in which the amount of warpage or the direction of warpage of the silicon carbide substrate 20 changes, it is possible to prevent the silicon carbide substrate 20 from being misaligned (that is, coming off the counterbore 15). Can be.

  The counterbore depth D4 shown in FIG. 7 is the height difference between the upper surface of the side wall portion 12 and the lowest portion of the upper surface of the slope portion 13, that is, the deepest portion of the counterbore of the tray 10 (the outer portion of the counterbore). ) Depth. The counterbore depth D4 is deeper than the counterbore depth D3. As an example, when the counterbore depth D3 is about 800 [μm], the counterbore depth D4 can be about 900 [μm].

  FIG. 8 is a cross-sectional view illustrating an example of the depth of the concave portion of the tray used in the manufacturing method according to the first embodiment. The concave portion depth D5 shown in FIG. 8 is a height difference between the highest outer peripheral portion of the concave portions 14 and the lowest center of the concave portions 14, that is, the depth D5 of the concave portions 14. is there. The concave portion depth D5 is determined to be, for example, a depth within a range of 5 μm or more and 100 μm or less. As an example, the upper surface of the concave portion 14 may be curved with a constant curvature so that the concave portion depth D5 is about 10 [μm]. This is determined, for example, according to the general amount of warpage of new silicon carbide substrate 20.

  FIG. 9 is a cross-sectional view illustrating an example of the angle of the slope of the tray used in the manufacturing method according to the first embodiment. The inclination angle θ shown in FIG. 9 is an angle between the upper surface of the slope portion 13 and the direction of the bottom surface of the tray 10 (that is, the horizontal direction). The inclination angle θ is determined according to the amount of warpage of the semiconductor substrate 30 after the assumed epitaxial growth, and is determined to be, for example, an angle in a range of 0.3 degrees or more and 3 degrees or less.

  As an example, the inclination angle can be about 1 degree. However, since the amount of warpage of semiconductor substrate 30 varies depending on the manufacturer, lot, or the like of silicon carbide substrate 20, tilt angle θ is appropriately adjusted according to the amount of warpage expected in semiconductor substrate 30. That is, if the amount of warpage of the semiconductor substrate 30 is small, the inclination angle θ is reduced, and if the amount of warpage of the semiconductor substrate 30 is large, the inclination angle θ is increased.

  FIG. 10 is a cross-sectional view illustrating another example of the structure of the tray used in the manufacturing method according to the first embodiment. 10, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 10, the upper surface of the boundary between the slope portion 13 and the concave portion 14 may be formed so as not to be a corner, for example, to have a curved surface convex on the opposite side to the base 11. Good. Alternatively, the upper surface of the boundary between the slope portion 13 and the concave portion 14 may be formed so as to be a plane parallel to (ie, horizontal to) the base 11.

  Thereby, for example, a process in which silicon carbide substrate 20 (see FIG. 2) warped so as to be convex toward the rear surface side becomes semiconductor substrate 30 (see FIG. 3) that is warped so as to be convex toward the front surface side. In this case, the amount of contact between the semiconductor substrate 30 and the tray 10 can be increased.

  FIG. 11 is a cross-sectional view illustrating still another example of the structure of the tray used in the manufacturing method according to the first embodiment. In FIG. 11, the same portions as those shown in FIGS. 1 and 4 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 11, depending on the shape of the warp of the semiconductor substrate 30, the inclination angle of the upper surface of the inclined portion 13 (the inclined angle θ shown in FIG. 9) changes in two stages as the distance from the center of the inclined portion 13 increases. You may.

  For example, in the semiconductor substrate 30 shown in FIG. 11, the warpage of the portion 41b relatively far from the center of the center portion 41 is larger than the warpage of the portion 41a relatively close to the center of the center portion 41. On the other hand, in the tray 10 shown in FIG. 11, the inclination angle of a portion relatively close to the center of the upper surface of the inclined portion 13 is relatively small, and the inclination angle of a portion relatively far from the center of the upper surface of the inclined portion 13 is small. The angle is relatively large. Thereby, the contact amount between the semiconductor substrate 30 and the tray 10 during the epitaxial growth can be increased. Further, the inclination angle of the upper surface of the slope portion 13 may change in three or more steps as the distance from the center of the slope portion 13 increases. Further, in the configuration shown in FIG. 11, similarly to the configuration shown in FIG. 10, the upper surface of the boundary between the slope portion 13 and the concave portion 14 may be formed so as not to have a corner.

  FIG. 12 is a top view illustrating an example of the structure of a tray having a plurality of counterbores used in the manufacturing method according to the first embodiment. For example, when manufacturing a plurality of semiconductor substrates 30 collectively using a large-sized CVD apparatus, the tray 120 shown in FIG. 12 may be used. The tray 120 has a base 121 and counterbores 10a to 10h. The tray 120 is formed of a material having a high melting point, such as carbon, similarly to the tray 10. Further, the tray 120 may be coated with a material having a high melting point similarly to the tray 10.

  Base 121 is a portion serving as the bottom of tray 120 when tray 10 on which a silicon carbide substrate is placed is transported and installed in a reaction vessel of a CVD apparatus, that is, a part of tray 120 that contacts the bottom surface in the CVD apparatus. . The base 121 has a disk shape centered on the Z-axis direction. The counterbore portions 10a to 10h are formed on the base 121.

  Each of the counterbore portions 10a to 10h has the same shape as the side wall portion 12, the slope portion 13, and the concave portion 14 (see FIGS. 1, 10, and 11) of the tray 10 described above. That is, each of the counterbore portions 10 a to 10 h is obtained by replacing the base 11 of the tray 10 with the base 121.

  According to the tray 120 shown in FIG. 12, eight silicon carbide substrates 20 are loaded on the counterbore portions 10a to 10h, transported to a reaction vessel of a large-sized CVD apparatus and installed, and the eight semiconductor substrates 30 are put together. Can be manufactured. However, the shape of the base 121 and the number and arrangement of the counterbore portions provided on the base 121 are not limited to the example shown in FIG. 12, but can be determined according to the size of the CVD apparatus.

  A method for manufacturing a semiconductor device according to the first embodiment will be described. The semiconductor device manufactured by this manufacturing method is a semiconductor device manufactured using the semiconductor substrate 30 described above. A predetermined element structure is formed by a general method on a semiconductor substrate manufactured by the method for manufacturing a semiconductor substrate according to the first embodiment (first step and second step) (third step). Thus, a semiconductor device using the above-described semiconductor substrate 30 can be manufactured.

  The semiconductor device using the above-described semiconductor substrate 30 includes, for example, a diode using silicon carbide, a MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor), an IGBT (Insulated Gate Bipolar Transistor: Insulation). Gate type bipolar transistor).

  As described above, according to the first embodiment, silicon carbide substrate 20 can be placed on tray 10 and the silicon carbide epitaxial film formed on the front surface of silicon carbide substrate 20 can be epitaxially grown. . In the tray 10, the height of an annular region (upper surface of the slope 13) surrounding the central region (upper surface of the concave portion 14) of the bottom surface of the counterbore 15 decreases linearly as the distance from the central region increases. Shape.

  Here, as described with reference to FIG. 4, during the epitaxial growth, the semiconductor substrate 30 is warped so as to be convex on the front surface side mainly due to the bending of the central portion 41. 42 is hard to bend. Therefore, according to the first embodiment, during the epitaxial growth, the outer portion 42 of the semiconductor substrate 30 warped so as to protrude to the front surface side becomes more linear as the distance from the central region of the bottom surface of the tray 10 increases. Contact the lower annular area.

  Thereby, during epitaxial growth, the amount of contact between the semiconductor substrate 30 and the tray 10 that warps so as to protrude toward the front surface side can be increased, and the temperature distribution in the surface of the semiconductor substrate 30 can be made uniform. . Therefore, it is possible to suppress the warpage of the semiconductor substrate 30 from increasing. Therefore, for example, a trouble caused by a large warpage of the semiconductor substrate 30 is avoided, and the production yield of the semiconductor device using the semiconductor substrate 30 is improved, and the reliability of the characteristics of the semiconductor device using the semiconductor substrate 30 is improved. be able to.

  In addition, by making the temperature distribution in the plane of the semiconductor substrate 30 during the epitaxial growth uniform, dislocation or the like generated in the epitaxial layer 31 of the semiconductor substrate 30 due to the stress in the epitaxial layer 31 caused by this temperature distribution is also suppressed. Can be. Therefore, the quality of the semiconductor substrate 30 itself can be improved. Therefore, for example, the yield of a semiconductor device using the semiconductor substrate 30 can be improved.

  Further, according to the first embodiment, the central region (the upper surface of the concave portion 14) on the bottom surface of the counterbore 15 of the tray 10 is a curved surface that becomes higher as the distance from the center increases. Thus, before the epitaxial growth or at an early stage of the epitaxial growth, the contact amount between the silicon carbide substrate 20 (semiconductor substrate 30) and the tray 10 warped so as to be convex on the back surface side is increased, and The temperature distribution can be made uniform.

(Embodiment 2)
Next, the structure of the tray 10 used in the method for manufacturing a semiconductor substrate according to the second embodiment will be described. The difference between the tray 10 used in the method for manufacturing a semiconductor substrate according to the second embodiment and the tray 10 used in the method for manufacturing a semiconductor substrate according to the first embodiment is that It is a flattened point.

  FIG. 13 is a diagram illustrating an example of the structure of a tray used in the method for manufacturing a semiconductor substrate according to the second embodiment. In FIG. 13, the same parts as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 13, the tray 10 according to the second embodiment has a flat shape portion 16 instead of the above-described concave shape portion 14.

  As shown in the upper surface structure 1, the flat shape portion 16 has a circular shape when viewed from the upper surface side of the tray 10, like the concave shape portion 14. As shown in the sectional structure 2, the flat shape portion 16 has a shape in which the height of the upper surface of the tray 10 is constant on the XY plane. That is, the upper surface of the flat shape portion 16 is horizontal (parallel to the bottom surface of the tray 10) and flat.

  FIG. 14 is a cross-sectional view showing an example of a state where a silicon carbide substrate is placed on a tray used in the method for manufacturing a semiconductor substrate according to the second embodiment. 14, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. The upper surface of the flat portion 16 of the tray 10 according to the second embodiment is flat as described above. Therefore, when silicon carbide substrate 20 that is warped so as to protrude to the rear surface side is placed on counterbore 15 of tray 10, only the center of the rear surface of silicon carbide substrate 20 contacts the upper surface of flat shape portion 16.

  However, for example, when the warpage of the silicon carbide substrate 20 is relatively small, the warpage of the silicon carbide substrate 20 disappears at an early stage when the semiconductor substrate 30 is manufactured from the silicon carbide substrate 20, and thereafter, the silicon carbide substrate 20 is mainly And warp so that it becomes convex on the surface side. Therefore, the provision of the flat portion 16 in place of the concave portion 14 has little effect on the amount of contact between the tray 10 and the semiconductor substrate 30 when the semiconductor substrate 30 is manufactured.

  When the silicon carbide substrate 20 that is not warped is placed on the counterbore of the tray 10, the back surface of the silicon carbide substrate 20 contacts the entire upper surface of the flat shape portion 16. Therefore, the provision of the flat portion 16 in place of the concave portion 14 does not affect the amount of contact between the tray 10 and the semiconductor substrate 30 when the semiconductor substrate 30 is manufactured.

  FIG. 15 is a cross-sectional view showing one example of a state where an epitaxial layer is formed on a silicon carbide substrate by the method for manufacturing a semiconductor substrate according to the second embodiment. In FIG. 15, the same portions as those shown in FIGS. 3 and 14 are denoted by the same reference numerals, and description thereof will be omitted. In the tray 10 according to the second embodiment, similarly to the tray 10 according to the first embodiment, the slope 13 of the tray 10 has a shape such that the upper surface becomes lower as being away from the center.

  The angle of the upper surface of the slope portion 13 is set to be the same as the angle of the outer portion of the semiconductor substrate 30 that is warped so as to project toward the rear surface as shown in FIG. Therefore, when the semiconductor substrate 30 is warped to be convex on the rear surface side, the rear surface of the semiconductor substrate 30 is likely to be in contact with the upper surface of the slope portion 13.

  Further, in the manufacturing method according to the second embodiment, similarly to the configuration shown in FIG. 10, the upper surface of the boundary between the slope portion 13 and the flat shape portion 16 may be formed so as not to have a corner. Further, in the manufacturing method according to the second embodiment, similarly to the configuration shown in FIG. 11, the inclination angle of the upper surface of the slope portion 13 may change in a plurality of steps as the distance from the center of the slope portion 13 increases. . Further, the shape of the tray 10 in the manufacturing method according to the second embodiment may be applied to the counterbore portions 10a to 10h of the tray 120 shown in FIG.

  As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained.

  In the above, the present invention can be variously modified, and in the above-described embodiments, for example, the dimensions and the like of each part are variously set according to required specifications and the like. For example, although the method in which the tray 10 is set on the susceptor (heating means) in the reaction vessel of the CVD apparatus has been described, the heating means may be provided on the tray 10 itself.

  As described above, the tray, the method of manufacturing a semiconductor substrate, the method of manufacturing a semiconductor device, and the semiconductor manufacturing apparatus according to the present invention provide a method of epitaxially growing a silicon carbide epitaxial film formed on a front surface of a silicon carbide substrate. Useful.

DESCRIPTION OF SYMBOLS 1 Top surface structure 2 Cross-sectional structure 10,120 Tray 10a-10h Counterbore part 11,121 Base 12 Side wall part 13 Slope part 14 Concave part 15 Counterbore 16 Flat shape part 20 Silicon carbide substrate 30 Semiconductor substrate 31 Epitaxial layer 41 Central part 42 Outside part

Claims (14)

A tray on which the silicon carbide substrate is placed when epitaxially growing a silicon carbide epitaxial film on a main surface of the silicon carbide substrate,
Having a counterbore on which the silicon carbide substrate is mounted,
Of the bottom surface of the counterbore, the height in an annular region surrounding the central region of the bottom surface decreases linearly as the distance from the central region increases,
A tray characterized in that: The silicon carbide substrate is placed on the counterbore with the first main surface of the silicon carbide substrate facing the bottom surface of the counterbore,
The silicon carbide substrate is transported to a reaction vessel for epitaxially growing the silicon carbide epitaxial film on a second main surface opposite to the first main surface,
The tray according to claim 1, wherein:   The depth of the shallowest portion in the counterbore is the sum of the thickness of the silicon carbide substrate before the silicon carbide epitaxial film is epitaxially grown and the amount of warpage of the silicon carbide substrate before the silicon carbide epitaxial film is epitaxially grown. The tray according to claim 1, wherein:   The tray according to any one of claims 1 to 3, wherein the central region of the bottom surface of the counterbore is a curved surface that becomes higher as being away from the center.   The center region of the bottom surface of the counterbore is a curved surface having a depth and a curvature according to the amount of warpage of the silicon carbide substrate before the silicon carbide epitaxial film is epitaxially grown. Tray described in.   The tray according to claim 4, wherein the central region of the bottom surface of the counterbore is a curved surface having a depth of 5 μm or more and 100 μm or less.   The center area of the bottom surface of the counterbore is a circular area having a diameter of 0.3 to 0.7 times the inner diameter of the counterbore. The tray according to one of the above.   The inclination angle in the annular region of the bottom surface of the counterbore is an inclination angle according to a warp amount of the silicon carbide substrate on which the silicon carbide epitaxial film is epitaxially grown. The tray according to one of the above.   The tray according to claim 8, wherein an inclination angle in the annular region of the bottom surface of the counterbore is 0.3 degrees or more and 3 degrees or less.   The tray according to any one of claims 1 to 9, wherein the tray is formed of carbon.   The tray according to any one of claims 1 to 10, wherein the inside of the counterbore is coated with a high melting point material. A tray having a counterbore on which a silicon carbide substrate is placed, wherein, of the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly with distance from the central region. A first step of placing the silicon carbide substrate on the counterbore using a tray with the first main surface of the silicon carbide substrate facing the bottom surface of the counterbore;
The tray in which the silicon carbide substrate is placed on the counterbore by the first step is transported and installed in a reaction vessel, and inside the reaction vessel, a second side of the silicon carbide substrate opposite to the first main surface is provided. A second step of epitaxially growing a silicon carbide epitaxial film on the main surface;
A method for manufacturing a semiconductor substrate, comprising: A tray having a counterbore on which a silicon carbide substrate is placed, wherein, of the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly with distance from the central region. A first step of placing the silicon carbide substrate on the counterbore using a tray with the first main surface of the silicon carbide substrate facing the bottom surface of the counterbore;
The tray in which the silicon carbide substrate is placed on the counterbore by the first step is transported and installed in a reaction vessel, and inside the reaction vessel, a second side of the silicon carbide substrate opposite to the first main surface is provided. A second step of producing a semiconductor substrate by epitaxially growing a silicon carbide epitaxial film on the main surface;
A third step of forming a predetermined element structure on the semiconductor substrate produced in the second step;
A method for manufacturing a semiconductor device, comprising: A tray having a counterbore on which a silicon carbide substrate is placed, wherein, of the bottom surface of the counterbore, a height in an annular region surrounding a central region of the bottom surface decreases linearly with distance from the central region. Tray and
A reaction vessel in which the tray is installed,
Inside the reaction vessel, a second main surface opposite to the first main surface of the silicon carbide substrate placed on the counterbore of the tray with a first main surface of the silicon carbide substrate facing a bottom surface of the counterbore. Growth means for epitaxially growing a silicon carbide epitaxial film on the main surface;
A semiconductor manufacturing apparatus comprising:

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