JP2015048277A - Silicon carbide substrate and production method of silicon carbide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a silicon carbide single crystal capable of obtaining a high-quality silicon carbide single crystal, and to provide a silicon carbide substrate used therefor.SOLUTION: A silicon carbide substrate 100 has a first principal surface P1 and a second principal surface P2 positioned on the opposite side to the first principal surface P1. In a cross section vertical to the first principal surface P1, the width D1 of the first principal surface P1 is larger than the width D2 of the second principal surface P2.

Description

  The present invention relates to a silicon carbide substrate and a method for manufacturing a silicon carbide single crystal.

  In recent years, silicon carbide semiconductor devices have attracted attention as power semiconductor devices. This is because by using a silicon carbide material for a semiconductor device, a higher breakdown voltage and a lower on-resistance can be expected as compared with a semiconductor device using a silicon material which is currently mainstream. Along with this, there is an increasing demand for high-quality silicon carbide single crystals that serve as base substrates for semiconductor devices. Currently, such a silicon carbide single crystal is manufactured by a sublimation recrystallization method (see, for example, International Publication No. 2011/065239 (Patent Document 1)).

International Publication No. 2011/065239

  In a method for manufacturing a silicon carbide single crystal using a sublimation recrystallization method, a silicon carbide single crystal is grown on a seed crystal (that is, a silicon carbide substrate) fixed on a pedestal. The technique disclosed in Patent Document 1 suppresses generation of relatively large crystal defects such as micropipe defects by uniformly fixing the seed crystal and the pedestal.

  However, in order to fully utilize the potential of the silicon carbide material and improve the performance of the silicon carbide semiconductor device, it is necessary to suppress the occurrence of finer defects (for example, dislocation defects).

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide a method for producing a silicon carbide single crystal capable of obtaining a high-quality silicon carbide single crystal and a carbonization used therefor. It is to provide a silicon substrate.

  A silicon carbide substrate according to an embodiment of the present invention has a first main surface and a second main surface located on the opposite side of the first main surface, and in a vertical cross section with respect to the first main surface, The width of the first main surface is larger than the width of the second main surface.

  And the manufacturing method of the silicon carbide single crystal which concerns on embodiment of this invention has the 1st main surface and the 2nd main surface located in the other side of the 1st main surface, The 1st main surface A step of preparing a silicon carbide substrate in which the width of the first main surface is larger than the width of the second main surface in a cross section perpendicular to the surface; and a step of bonding the second main surface and the pedestal with an adhesive; And a step of growing a silicon carbide single crystal on a first main surface of the silicon carbide substrate bonded to the pedestal.

  According to the silicon carbide substrate and the method for manufacturing a silicon carbide single crystal according to the embodiment of the present invention, a silicon carbide single crystal having high crystal quality can be grown.

It is typical sectional drawing illustrating a part of manufacturing method of the silicon carbide single crystal which concerns on this Embodiment. It is typical sectional drawing illustrating a part of manufacturing method of the silicon carbide single crystal which concerns on this Embodiment. It is typical sectional drawing illustrating a part of manufacturing method of the conventional silicon carbide single crystal. It is typical sectional drawing illustrating a part of manufacturing method of the conventional silicon carbide single crystal. It is typical sectional drawing which shows an example of the silicon carbide substrate which concerns on this Embodiment. It is typical sectional drawing which shows another example of the silicon carbide substrate which concerns on this Embodiment. It is a schematic plan view showing an example of a silicon carbide substrate according to the present embodiment. It is typical sectional drawing illustrating a part of manufacturing method of the silicon carbide single crystal which concerns on this Embodiment. It is typical sectional drawing illustrating a part of manufacturing method of the silicon carbide single crystal which concerns on this Embodiment. It is a flowchart which shows the outline of the manufacturing method of the silicon carbide single crystal which concerns on this Embodiment.

  Hereinafter, the present embodiment will be described in more detail. In the drawings of the present application, the same or corresponding parts are denoted by the same reference numerals, and the same description will not be repeated. For crystallographic description, individual planes are indicated by () and collective plane {}, respectively. In addition, a negative crystallographic index is usually expressed by adding a “-” (bar) above a number, but in this specification a negative sign is added before the number. It shall be expressed as

[Description of Embodiment of Present Invention]
First, an outline of an embodiment of the present invention (hereinafter also referred to as “this embodiment”) will be described in the following (1) to (9).

  The present inventor conducted intensive research to solve the above problems, and as a result, the adhesive used for bonding the silicon carbide substrate, which is a seed crystal, and the pedestal protrudes from the bonding surface, and the silicon carbide single crystal is formed. A method for efficiently preventing adhesive wraparound by obtaining knowledge that it is a factor causing fine crystal defects by wrapping around the surface to be grown, and conducting further research based on this knowledge As a result, the present invention has been completed. That is, the silicon carbide substrate according to the present embodiment has the following configuration.

  (1) The silicon carbide substrate according to the present embodiment has a first main surface P1 and a first main surface P1 having a first main surface P1 and a second main surface P2 located on the opposite side of the first main surface P1. In a vertical cross section with respect to, the width D1 of the first main surface P1 is larger than the width D2 of the second main surface P2.

  In the silicon carbide substrate having the above-described configuration, the second main surface is formed by using the second main surface P2 as a surface to be bonded to the pedestal 2 and using the first main surface P1 as a surface for growing a silicon carbide single crystal. Even when the adhesive 3 protrudes from between the P2 and the pedestal 2, the adhesive 3 does not wrap around the first main surface P <b> 1 that is the growth surface of the silicon carbide single crystal. . Therefore, it is possible to prevent the occurrence of fine crystal defects due to the wraparound of the adhesive 3.

  In addition, even if the adhesive 3 protrudes, it does not go around on the first main surface P1, so that the space between the second main surface P2 and the pedestal 2 is bonded by intentionally protruding the adhesive 3. It can be confirmed that it is filled with the agent 3. That is, it is possible to easily determine whether the adhesion state between the silicon carbide substrate and the base 2 is good or bad.

  (2) The thickness T of the silicon carbide substrate is preferably 0.2 mm or more and 5 mm or less. Thereby, the wraparound of the adhesive 3 can be prevented more reliably. A silicon carbide substrate having a thickness in the above range can also be used as a device substrate. That is, the silicon carbide semiconductor device can be directly manufactured by performing epitaxial growth on first main surface P1.

  (3) The difference between the width D1 of the first main surface P1 and the width D2 of the second main surface P2 is preferably 0.1 mm or more and 10 mm or less. Thereby, the wraparound of the adhesive 3 can be prevented more reliably.

  (4) The silicon carbide substrate has a side surface SD that connects the first main surface P1 and the second main surface P2, and in the vertical cross section, the side surface SD is 30 ° with respect to the perpendicular of the first main surface P1. It is preferable to have the following crossing angle θ. Thereby, the wraparound of the adhesive 3 can be prevented more reliably.

  (5) The first main surface P1 and the second main surface P2 each have an outer peripheral portion connected to the side surface SD, and in a region surrounded by the outer peripheral portion C1 of the first main surface P1 in plan view. It is preferable that the outer peripheral portion C2 of the second main surface P2 is included. Thereby, it is possible to reliably prevent the adhesive 3 from wrapping around the entire circumference of the first main surface P1.

  (6) It is preferable that the outer peripheral portion C1 of the first main surface P1 and the outer peripheral portion C2 of the second main surface P2 are concentric. Thereby, the wraparound of the adhesive 3 can be more reliably prevented over the entire circumference of the first main surface P1.

  (7) The method for manufacturing a silicon carbide single crystal according to the present embodiment includes a first main surface P1 and a second main surface P2 located on the opposite side of the first main surface P1. A step S1 of preparing a silicon carbide substrate 100 in which the width D1 of the first main surface P1 is larger than the width D2 of the second main surface P2 in a cross section perpendicular to the main surface P1, and the second main surface P2 and the base 2 with an adhesive 3 and a step S3 of growing the silicon carbide single crystal 11 on the first main surface P1 of the silicon carbide substrate 100 bonded to the base 2.

  According to said manufacturing method, generation | occurrence | production of the fine crystal defect resulting from the adhesive agent 3 can be prevented by using the silicon carbide substrate 100 which has said structure. Therefore, a silicon carbide single crystal having high crystal quality can be manufactured.

  (8) It is preferable that the adhesive 3 contains a carbon adhesive. Thereby, since silicon carbide substrate 100 and adhesive 3 both contain carbon atoms (C), the adhesion between silicon carbide substrate 100 and adhesive 3 can be improved.

  (9) Thickness T of silicon carbide substrate 100 is preferably not less than 0.5 mm and not more than 5 mm. Silicon carbide substrate 100 having a thickness in the above range is useful as a seed crystal. That is, it is excellent in handling property in the bonding work with the base 2 or the like. Moreover, when the thickness of the silicon carbide substrate 100 occupies the above range, the wraparound of the adhesive 3 can be more reliably prevented.

[Details of the embodiment of the present invention]
Hereinafter, although the silicon carbide substrate and silicon carbide single crystal manufacturing method according to the present embodiment will be described in more detail, the present embodiment is not limited thereto.

<Embodiment 1>
<Silicon carbide substrate>
FIG. 5 is a schematic cross-sectional view showing an example of silicon carbide substrate 100 of the present embodiment. As shown in FIG. 5, silicon carbide substrate 100 of the present embodiment has first main surface P1 and second main surface P2 located on the opposite side of first main surface P1. In the cross section perpendicular to the first main surface P1, the width D1 of the first main surface P1 is larger than the width D2 of the second main surface P2.

  3 and 4 are schematic cross-sectional views illustrating a method for manufacturing a silicon carbide substrate (seed crystal) and a silicon carbide single crystal in the prior art. As shown in FIG. 3, silicon carbide substrate 300 in the prior art has a surface on which a silicon carbide single crystal is grown and an adhesive surface with pedestal 2 are substantially the same in a cross section perpendicular to the surface on which the silicon carbide single crystal is grown. It has a width. For this reason, as shown in FIG. 4, when bonding the silicon carbide substrate 300 and the pedestal 2 using the adhesive 3, if the adhesive 3 protrudes from the bonding surface, the adhesive 3 grows a silicon carbide single crystal. It will wrap around on the surface to be made. Thereafter, the adhesive 3 is heated and carbonized, so that it remains on the growth surface as carbonized dirt. When a silicon carbide single crystal is grown on silicon carbide substrate 300 in this state, fine crystal defects are generated in the silicon carbide single crystal due to carbonized dirt.

  Further, in the prior art, if the amount of the adhesive 3 is reduced in order to prevent the adhesive 3 from wrapping around, the adhesion between the silicon carbide substrate 300 and the pedestal 2 becomes uneven, and macro defects (for example, micropipe defects, for example) ) May occur.

  Here, the amount of generation of fine crystal defects can be estimated by measuring, for example, etch pit density (EPD).

  On the other hand, as shown in FIG. 1, silicon carbide substrate 100 of the present embodiment has a width D1 of first main surface P1 larger than width D2 of second main surface P2. Therefore, as shown in FIG. 2, even when the adhesive 3 protrudes from the bonding surface when the second main surface P <b> 2 is bonded to the base 2 using the adhesive 3, the adhesive 3 is not It cannot wrap around the main surface P1. Therefore, carbonized dirt derived from the adhesive 3 does not occur on the first main surface P1. Thereby, a silicon carbide single crystal having high crystal quality can be grown on first main surface P1. In addition, by positively protruding the adhesive 3 during the bonding operation, it is possible to reliably determine whether the bonded state is good or bad.

  The silicon carbide substrate of the present embodiment may have a cross-sectional shape as shown in FIG. 6, for example, in addition to the cross-sectional shape shown in FIG. The silicon carbide substrate 200 shown in FIG. 6 also has high crystal quality on the first main surface P1 because the width D1 of the first main surface P1 is larger than the width D2 of the second main surface P2. Single crystals can be grown.

  In the present embodiment, the off angle (inclination) from the {0001} plane of the first principal plane P1 (that is, the off angle from the (0001) plane or the (000-1) plane) is 15 ° or less is preferable, and 5 degrees or less is more preferable.

  Thickness T of silicon carbide substrate 100 in the present embodiment is preferably not less than 0.2 mm and not more than 5 mm. This is because when the thickness of the substrate is 0.2 mm or more, the adhesive 3 can be more reliably prevented from wrapping around. On the other hand, if the thickness of the substrate exceeds 5 mm, it is not preferable from the viewpoint of material cost. Silicon carbide substrate 100 having a thickness in the above range can also be used as a device substrate. When silicon carbide substrate 100 is used as a seed crystal, thickness T of silicon carbide substrate 100 is preferably not less than 0.5 mm and not more than 5 mm, more preferably not less than 0.7 mm and not more than 2 mm. This is because having such a thickness improves handling properties in bonding work and the like.

  The difference between the width D1 of the first main surface P1 and the width D2 of the second main surface P2 is preferably 0.1 mm or more and 10 mm or less. This is because, when the difference is 0.1 mm or more, the adhesive 3 can be more reliably prevented from wrapping around. If the difference exceeds 10 mm, it is not preferable from the viewpoint of material cost. This is because the portion corresponding to the above-mentioned difference in the first main surface P1 disappears by proximity sublimation when the silicon carbide single crystal is grown, so that it does not substantially function as a growth surface and is a waste portion. Because it becomes. More preferably, the difference is 0.5 mm or more and 5 mm or less. Note that the width D3 of the bonding surface of the base 2 preferably satisfies the relationship of D1 ≧ D3 ≧ D2.

  Silicon carbide substrate 100 has a side surface SD that connects first main surface P1 and second main surface P2, and in a vertical cross-section as shown in FIG. 5, side surface SD is formed on first main surface P1. It is preferable to have an intersection angle (θ in FIG. 5) of 30 ° or less with respect to the perpendicular. When the crossing angle θ exceeds 30 °, when the first main surface P1 and the second main surface P2 are subjected to chemical mechanical polishing (CMP), the polishing pad becomes an edge portion (first main surface P1). In the vicinity of the connecting portion between the surface SD and the side surface SD), the processing efficiency may be reduced. The crossing angle θ is more preferably 20 ° or less.

  FIG. 7 is a plan view of silicon carbide substrate 100 as viewed from the second main surface P2 side. As shown in FIG. 7, in silicon carbide substrate 100, first main surface P1 and second main surface P2 each have outer peripheral portion C1 and outer peripheral portion C2 connected to side surface SD, and in plan view, It is preferable that the outer peripheral portion C2 of the second main surface P2 is included in the region surrounded by the outer peripheral portion C1 of the first main surface P1. This is because the adhesive 3 can be reliably prevented from wrapping around the entire circumference of the first main surface P1.

  Furthermore, it is preferable that the outer peripheral part C1 of the first main surface P1 and the outer peripheral part C2 of the second main surface P2 are concentric. Here, “concentric” indicates that the circumscribed circle of the outer peripheral portion C1 and the circumscribed circle of the outer peripheral portion C2 are concentric circles. As shown in FIG. 7, the silicon carbide substrate usually has an orientation flat portion OF and is not completely circular, but the circumscribed circle of the outer peripheral portion C1 and the circumscribed circle of the outer peripheral portion C2 are concentric circles. Therefore, it can be considered that the outer peripheral portion C1 and the outer peripheral portion C2 are concentric. And by having such a structure, the surroundings of the adhesive agent 3 can be prevented over the perimeter of the 1st main surface P1.

<Embodiment 2>
<Method for producing silicon carbide single crystal>
The second embodiment is a method of manufacturing a silicon carbide single crystal using the silicon carbide substrate described in the first embodiment. FIG. 10 is a flowchart schematically showing a method for manufacturing a silicon carbide single crystal according to the present embodiment. As shown in FIG. 10, the method for manufacturing a silicon carbide single crystal of the present embodiment includes a step S1, a step S2, and a step S3. Hereinafter, each step will be described.

<Process S1>
In step S1, the first main surface P1 has a first main surface P1 and a second main surface P2 located on the opposite side of the first main surface P1, and the first main surface is perpendicular to the first main surface P1. Silicon carbide substrate 100 in which width D1 of P1 is larger than width D2 of second main surface P2 is prepared. That is, silicon carbide substrate 100 described in the first embodiment is prepared. Here, the thickness T of the prepared silicon carbide substrate 100 is preferably not less than 0.5 mm and not more than 5 mm, and more preferably not less than 0.7 mm and not more than 2 mm.

  Silicon carbide substrate 100 according to the present embodiment can be prepared, for example, by the following method. That is, after grinding a silicon carbide ingot (not shown) into a cylindrical shape, a silicon carbide substrate is obtained by slicing, and the side surface of the silicon carbide substrate is chamfered, for example, to obtain FIG. A silicon carbide substrate having the cross-sectional shape shown in FIG. 6 can be prepared. Since this method has high dimensional accuracy, the difference between the width D1 and the width D2 and the crossing angle θ can be easily controlled.

  Silicon carbide substrate 100 can also be prepared by the following method. That is, the silicon carbide ingot is grown such that the diameter of the ingot increases as the ingot grows. Thereby, the silicon carbide substrate having the cross-sectional shape shown in FIG. 5 can be manufactured by slicing the ingot as it is without grinding it into a cylindrical shape. Since this method does not require grinding, it is preferable because the process load is small. Of course, chamfering or the like can be performed on the silicon carbide substrate obtained by this method.

  It is preferable that processing for increasing the surface roughness is performed on the second main surface P2 serving as an adhesive surface with the base 2. This is because the adhesive strength with the pedestal 2 is improved. This processing can be performed, for example, by polishing the second main surface P2 using abrasive grains having a sufficiently large particle diameter. Here, the abrasive preferably includes particles having a particle diameter of 16 μm or more. That is, in the particle size distribution, it is preferable to include a component having a particle size of 16 μm or more. The average particle diameter of the abrasive is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 30 μm or less, and further preferably 12 μm or more and 25 μm or less. Here, the “average particle diameter” means a 50% volume average particle diameter (that is, d50) by a laser diffraction / scattering method.

  The abrasive grains are preferably diamond particles. Moreover, it is more preferable that the abrasive grains are used by being dispersed in a slurry. That is, the above polishing is preferably performed using a diamond slurry. A diamond slurry containing diamond particles having an average particle size of 5 μm or more and 50 μm or less and having a component having a particle size of 16 μm or more in the particle size distribution is generally easily available.

  Instead of performing the step of increasing the surface roughness of the second main surface P2 as described above, the second main surface P2 having a sufficiently large surface roughness is formed from the beginning, and this surface is polished. You may use without. Specifically, second main surface P2 of silicon carbide substrate 100 formed by slicing with a wire saw may be used without polishing. That is, an as-sliced surface that is a surface formed by slicing and not polished after that may be used as the second main surface P2. In slicing with a wire saw, it is preferable to use the above-mentioned abrasive grains.

<Process S2>
Step S2 will be described with reference to FIGS. Step S2 is a step of bonding second main surface P2 of silicon carbide substrate 100 and pedestal 2 with adhesive 3. As described above, since the silicon carbide substrate 100 in which the width D1 of the first main surface P1 is larger than the width D2 of the second main surface P2 is used in the present embodiment, the adhesive 3 is the first It is possible to prevent wraparound on the main surface P1.

  Pedestal 2 preferably contains carbon (C) on a surface to be bonded to silicon carbide substrate 100 (hereinafter also referred to as a holding surface). The material of the base 2 is, for example, graphite. The holding surface of the pedestal 2 is preferably flat. Therefore, for example, it is preferable that a process for improving flatness such as polishing is performed on the holding surface.

  Referring to FIG. 1, adhesive 3 is arranged between silicon carbide substrate 100 and pedestal 2. Here, the adhesive 3 preferably includes a carbon adhesive. The carbon adhesive is an adhesive in which carbon powder is dispersed in a solvent, and the solvent is volatilized by heat treatment, so that an adhesive layer consisting essentially of carbon can be formed. Since such a carbon adhesive contains carbon, the adhesiveness with the silicon carbide substrate 100 and the base 2 is high and suitable. As a specific example of the carbon adhesive, for example, a carbon resin mixed with a phenol resin and phenol and ethyl alcohol as solvents may be exemplified.

  Although FIG. 1 illustrates an example in which the adhesive 3 is disposed on the holding surface of the pedestal 2, the adhesive 3 may be disposed between the silicon carbide substrate 100 and the pedestal 2. It may be disposed on the second main surface P2 of the silicon substrate 100, may be disposed on the holding surface of the base 2, or may be disposed on both of them.

  Next, second main surface P2 of silicon carbide substrate 100 and pedestal 2 are brought into contact with each other with adhesive 3 interposed therebetween. Preferably, this contact is performed such that the two are pressed against each other at a temperature of 50 ° C. to 120 ° C. and a pressure of 0.01 Pa to 1 MPa. Further, in the present embodiment, the adhesive state is confirmed by pressing the two together so that the adhesive 3 protrudes from between the silicon carbide substrate 100 and the pedestal 2, and the two are securely and uniformly bonded. Can do. Such an operation is possible because the adhesive 3 does not wrap around the first main surface P1.

  Subsequently, the adhesive 3 is preferably pre-baked. The prebake temperature is preferably 150 ° C. or higher.

  Furthermore, the adhesive 3 is preferably heated and carbonized after pre-baking. By this heating, adhesive 3 is cured to become an adhesive layer, and silicon carbide substrate 100 is bonded and fixed to pedestal 2.

  The heating is preferably performed at a temperature of 800 ° C. to 1800 ° C., for a time of 1 hour to 10 hours, at a pressure of 0.13 kPa to atmospheric pressure, and in an inert gas atmosphere. As the inert gas, for example, helium, argon, or nitrogen gas is used.

<Process S3>
Step S3 is a step of growing silicon carbide single crystal 11 on first main surface P1 of silicon carbide substrate 100 bonded to pedestal 2. First, referring to FIG. 8, raw material 10 made of silicon carbide powder is stored in crucible 20. Next, the base 2 is attached to the crucible 20 so that the first main surface P <b> 1 faces the inside of the crucible 20. At this time, the base 2 may function as a lid of the crucible 20 as shown in FIG.

  Next, silicon carbide single crystal 11 is grown on first main surface P <b> 1 of silicon carbide substrate 100 by a sublimation recrystallization method. That is, the silicon carbide single crystal 11 can be grown by sublimating the raw material 10 in the direction indicated by the arrow in the drawing and depositing the sublimate on the first main surface P1. The temperature in this sublimation recrystallization method is, for example, 2100 ° C. or higher and 2500 ° C. or lower. The pressure in the sublimation recrystallization method is preferably 1.3 kPa or more and atmospheric pressure or less, and more preferably 13 kPa or less in order to increase the growth rate.

  At this time, as shown in FIG. 8, silicon carbide single crystal 11 is deposited on the entire surface of first main surface P1 in the early stage of crystal growth. However, since the edge portion of silicon carbide substrate 100 approaches and sublimates toward the pedestal 2 side (broken line arrow in FIG. 8), the edge portion gradually disappears, and finally, as shown in FIG. The width D1 of the first main surface P1 is substantially the same as that of the second main surface P2, and the silicon carbide single crystal 11 is grown thereon.

  Therefore, the protruding adhesive 3 from between the silicon carbide substrate 100 and the base 2 also disappears together with the edge portion. Thereby, the adhesive 3 does not flow and reach the first main surface P1 which is a growth surface at a high temperature during crystal growth, and a high-quality crystal can be grown.

  Also, from an economic viewpoint, it is not preferable to make the width D1 of the first main surface P1 excessively larger than the width D2 of the second main surface P2, and the width D1 of the first main surface P1 and the second main surface P1 are not preferable. The difference from the width D2 of the surface P2, that is, “D1-D2” is preferably 0.1 mm or more and 10 mm or less, and more preferably 0.5 mm or more and 5 mm or less.

  Hereinafter, although this Embodiment is described in detail using an Example, this Embodiment is not limited to these.

<Example 1>
First, a substrate sliced from a silicon carbide ingot is chamfered to have a polytype 4H and a plane orientation (000-1), the diameter (width D1) of the first main surface P1 is 105 mm, A silicon carbide substrate 100 according to Example 1 having a diameter (width D2) of main surface P2 of 100 mm and a thickness T of 1.5 mm was obtained. Silicon carbide substrate 100 has an orientation flat portion OF in a plan view, and the diameter here indicates the diameter of a circle circumscribing each main surface.

  Next, a pedestal 2 made of graphite was prepared. The holding surface of the graphite pedestal 2 was polished with diamond slurry.

Next, an adhesive 3 containing a phenol resin, phenol, ethyl alcohol, formaldehyde, moisture, and a solid carbon component was prepared. Then, the second main surface P2 and the base 2 were brought into contact with each other with the adhesive 3 interposed therebetween. The application amount of the adhesive 3 was about 25 mg / cm ² and the thickness was about 40 μm. The contact was performed at 100 ° C. and 0.1 MPa.

  Next, the adhesive 3 was pre-baked. Specifically, heat treatment was sequentially performed at 80 ° C. for 4 hours, 120 ° C. for 4 hours, and 200 ° C. for 1 hour.

  Subsequently, the adhesive 3 was heated. This heating was performed at 1150 ° C. for 1 hour in an 80 kPa helium gas atmosphere. By this heating, adhesive 3 was carbonized, an adhesive layer was formed, and silicon carbide substrate 100 and pedestal 2 were bonded and fixed.

  Next, the raw material 10 which is silicon carbide powder was accommodated in the crucible 20 made of graphite. Further, the pedestal 2 was attached to the crucible 20 so that the first main surface P <b> 1 faces the inside of the crucible 20 and the pedestal 2 functions as a lid of the crucible 20.

  Next, silicon carbide single crystal 11 was grown on first main surface P1 by a sublimation recrystallization method. The growth conditions were temperature: 2400 ° C., pressure: 1.7 kPa, and time: 300 hours.

<Comparative Example 1>
Except for obtaining the silicon carbide substrate 300 according to Comparative Example 1 in which the diameters of the first main surface P1 and the second main surface P2 are both 100 mm, in the same manner as in Example 1, by the sublimation recrystallization method, Silicon carbide single crystal 11 was grown on first main surface P1.

<Evaluation>
The substrate obtained by slicing the silicon carbide single crystal obtained in Example 1 and Comparative Example 1 was immersed in a potassium hydroxide (KOH) melt, the surface was etched, and the surface was subjected to a normalsky differential interference microscope. EPD was measured by observing and counting the number of etch pits.

  As a result, in Example 1, compared with Comparative Example 1, the EPD at the initial stage of growth was reduced by 20%. This reason is considered to be because the fine crystal defect resulting from the adhesive agent 3 wrapping around on the 1st main surface P1 was suppressed.

  As described above, the embodiments and examples have been described, but it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2 Pedestal 3 Adhesive 11 Silicon carbide single crystal 10 Raw material 20 Crucible 100, 200, 300 Silicon carbide substrate P1 First main surface P2 Second main surface D1, D2, D3 Width T Thickness θ Crossing angle SD Side surface C1, C2 Outer part OF Orientation flat part

Claims (9)

A first main surface and a second main surface located on the opposite side of the first main surface;
A silicon carbide substrate, wherein a width of the first main surface is larger than a width of the second main surface in a cross section perpendicular to the first main surface.   The silicon carbide substrate according to claim 1, wherein a thickness of the silicon carbide substrate is not less than 0.2 mm and not more than 5 mm.   The silicon carbide substrate according to claim 1 or 2, wherein a difference between a width of the first main surface and a width of the second main surface is not less than 0.1 mm and not more than 10 mm.   The silicon carbide substrate has a side surface connecting the first main surface and the second main surface, and in the vertical cross section, the side surface is 30 ° or less with respect to a perpendicular of the first main surface. The silicon carbide substrate according to any one of claims 1 to 3, wherein the silicon carbide substrate has an intersection angle. Each of the first main surface and the second main surface has an outer peripheral portion connected to the side surface,
The silicon carbide substrate according to claim 4, wherein, in a plan view, an outer peripheral portion of the second main surface is included in a region surrounded by the outer peripheral portion of the first main surface.   The silicon carbide substrate according to claim 5, wherein an outer peripheral portion of the first main surface and an outer peripheral portion of the second main surface are concentric. A first main surface and a second main surface located on the opposite side of the first main surface, wherein a width of the first main surface is equal to the first main surface in a cross section perpendicular to the first main surface; A step of preparing a silicon carbide substrate larger than the width of the main surface of 2;
Bonding the second main surface and the pedestal with an adhesive;
A step of growing a silicon carbide single crystal on the first main surface of the silicon carbide substrate bonded to the pedestal.   The method for producing a silicon carbide single crystal according to claim 7, wherein the adhesive includes a carbon adhesive.   The method for manufacturing a silicon carbide single crystal according to claim 7 or 8, wherein the thickness of the silicon carbide substrate is not less than 0.5 mm and not more than 5 mm.

Images