JP6241254B2 - Single crystal manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a single crystal, and more particularly to a method for producing a single crystal capable of improving crystal quality.

  In recent years, the use of silicon carbide (SiC) as a semiconductor material has been actively studied. The large band gap of SiC can contribute to improving the performance of the semiconductor device. The manufacture of a SiC semiconductor usually requires a SiC single crystal substrate. A SiC single crystal substrate (wafer) can be formed by slicing a SiC single crystal (ingot).

  Generally, the flatness of a SiC single crystal substrate varies between lots (between SiC single crystals). That is, the SiC single crystal substrate may be warped or undulated, and the degree thereof usually includes variations even when the same SiC single crystal substrate manufacturing method is used.

  However, it is difficult to attach the seed crystal to a crucible lid (pedestal) when the warpage or undulation of the seed crystal is large.

  Japanese Patent Application Laid-Open No. 2005-314167 describes a seed crystal for growing a silicon carbide single crystal having a warp / swell of 10 μm or less on the surface in contact with the crucible lid. Further, it is described that the crystal growth surface of the seed crystal for silicon carbide single crystal growth is a concave surface.

JP 2005-314167 A

  However, in a seed crystal for growing a SiC single crystal, it is difficult to always suppress warping and undulation of the seed crystal to 10 μm or less due to an increase in the outer diameter of the seed crystal accompanying an increase in the diameter of the SiC epitaxial substrate. In this case, in the conventional method for producing a single crystal, when the seed crystal is warped or undulated, it cannot be fixed to the pedestal or even if it can be fixed, heat transfer becomes uneven, resulting in a highly crystalline silicon carbide single crystal. It is difficult to grow crystals.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a method for producing a single crystal, which can obtain a silicon carbide single crystal having high crystallinity even if a seed crystal having warpage or undulation is used.

  The method for producing a single crystal according to the present invention includes a step of preparing a seed substrate having a first surface, a pedestal having a second surface, and an adhesive for bonding the pedestal and the seed substrate, A step of fixing the seed substrate on the second surface of the pedestal using an adhesive so that the first surface and the second surface face each other, and a single crystal on the seed substrate fixed on the pedestal The seed substrate and the pedestal so that the sum of the SORI value of the first surface in the unloaded state and the SORI value of the second surface in the unloaded state is 70 μm or less. And are prepared.

  According to the present invention, a silicon carbide single crystal having high crystallinity can be obtained even if a seed crystal having warpage or undulation is used.

It is a plane schematic diagram for demonstrating the curvature (SORI) of a seed substrate. It is a cross-sectional schematic diagram for demonstrating the curvature (SORI) of a seed substrate. It is a plane schematic diagram for demonstrating the curvature (SORI) of a base. It is a cross-sectional schematic diagram for demonstrating the curvature (SORI) of a base. It is a cross-sectional schematic diagram for demonstrating the TTV value of a seed substrate. It is a flowchart of the manufacturing method of the single crystal which concerns on this Embodiment. It is sectional drawing for demonstrating the manufacturing method of the single crystal which concerns on this Embodiment. It is sectional drawing for demonstrating the manufacturing method of the single crystal which concerns on this Embodiment. It is sectional drawing for demonstrating the manufacturing method of the single crystal which concerns on this Embodiment. It is sectional drawing for demonstrating the manufacturing method of the single crystal which concerns on this Embodiment. It is sectional drawing for demonstrating the modification of the manufacturing method of the single crystal which concerns on this Embodiment. It is a schematic diagram for demonstrating the result of having measured the curvature amount of the seed substrate of an Example, and a base.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Description of Embodiment of Present Invention]
First, the outline of the embodiment of the present invention will be enumerated.

  (1) The method for manufacturing a single crystal according to the present embodiment includes a seed substrate 10 having a first surface (second main surface 10B) and a pedestal having a second surface (third main surface 20A). 20, a step of preparing an adhesive for bonding the base 20 and the seed substrate 10 (S10), a first surface (second main surface 10B) and a second surface (third main surface) 20A), the step of fixing the seed substrate 10 on the second surface of the pedestal 20 using the adhesive 30 (S20), and the seed substrate 10 fixed on the pedestal 20 In the step (S10) of preparing and preparing a crystal growth step (S30), the SORI value of the first surface (second main surface 10B) in the no-load state and the second surface (second surface) in the no-load state The seed substrate 10 and the pedestal 20 are prepared so that the sum of the SORI value of the main surface 20A) of No. 3 is 70 μm or less. The

  Here, the SORI value of the second main surface 10B as the first surface refers to the SORI value of the seed substrate 10 (details will be described later). The SORI value of the third main surface 20A as the second surface refers to the SORI value of the third main surface 20A of the pedestal 20 (details will be described later).

In this way, at least one of the second main surface 10B as the first surface of the seed substrate 10 and the third main surface 20A as the second surface of the pedestal 20 prepared in the step (S10). Even when warping or undulation occurs, the seed substrate 10 and the pedestal 20 can be fixed with good adhesion in the step (S20). Specifically, the adhesive 30 contracts when the adhesive 30 is transformed into the fixed layer 31 by the heat treatment in the step (S20), but the combination of the seed substrate 10 and the pedestal 20 in which the sum is 70 μm or less. By forming the seed substrate 10 and the pedestal 20 to be placed on the crucible 60 in the step (S30), at least the most region of the gap S generated between the second main surface 10B and the third main surface 20A is formed. It can be compensated by the fixed layer 31. By growing a single crystal on the first main surface 10A of the seed substrate 10 in the step (S30), a SiC single crystal with high crystallinity can be obtained. From a different point of view, even if the seed substrate 10 is prepared as a large-diameter substrate having a large SORI value of about 50 μm, for example, the pedestal in which the SORI value of the third main surface 20A is 20 μm or less. The single crystal growth in combination with 20 makes it possible to obtain a SiC single crystal with high crystallinity.

  Note that the gap S includes the second main surface 10B (the fifth main surface 11B when the coating film 11 (details will be described later) is formed on the second main surface 10B) and the second main surface 10B. The space which arises in the area | region where both surfaces do not surface-contact with 3 main surface 20A, this space may be open | released outside and may be a closed space.

  (2) In the method for producing a single crystal according to the present embodiment, in the step of preparing (S10), seed substrate 10 and pedestal 20 may be prepared so that the sum of SORI values is 50 μm or less. In this way, the void S can be more easily filled by the fixed layer 31, and a SiC single crystal with high crystallinity can be obtained.

  (3) In the method for producing a single crystal according to the present embodiment, in the preparing step (S10), seed substrate 10 and pedestal 20 may be prepared so that the sum of SORI values is 30 μm or less. In this way, the void S can be more easily filled by the fixed layer 31, and a SiC single crystal with high crystallinity can be obtained.

  (4) In the method for manufacturing a single crystal according to the present embodiment, the seed substrate 10 is preferably provided with a first surface (second main surface 10B) in a concave shape.

  That is, the seed substrate 10 is preferably provided with the first main surface 10A in a convex shape. In this way, it is possible to obtain a SiC single crystal with higher crystallinity than when the second main surface 10B has a convex shape (when the first main surface 10A has a concave shape). When the first main surface 10A of the seed substrate 10 becomes concave, distortion occurs in the portion, and defects are likely to occur. Further, since the defect is likely to occur even if the first main surface 10A is too convex, it is preferable that the radius of curvature of the ingot growth outermost surface is three times or more the diameter of the ingot.

  (5) In the method for manufacturing a single crystal according to the present embodiment, the pedestal 20 is preferably provided with a convex second surface.

  In this way, when the first main surface 10A of the seed substrate 10 has a convex shape, the gap S between the second main surface 10B and the third main surface 20A can be narrowed ( FIG. 11). As a result, the void S can be more easily filled with the fixed layer 31, and a SiC single crystal with high crystallinity can be obtained.

  (6) In the method for manufacturing a single crystal according to the present embodiment, the seed substrate 10 preferably has a TTV (Total Thickness Variation) value of 30 μm or less.

  When the TTV value exceeds 30 μm, for example, when a force is applied in a direction perpendicular to the first main surface 10A or the second main surface 10B, the force is not uniformly applied to the seed substrate 10, There has been a problem that the seed substrate 10 may come into contact with the mounting surface and one of the seed substrates 10 may jump up.

  On the other hand, in the step (S20) of fixing the seed substrate 10 using the adhesive 30 on the second surface of the pedestal 20 by using the seed substrate 10 having a TTV value of 30 μm or less, for example, the first substrate 10 of the seed substrate 10 is used. Even when a weight 51 (see FIG. 7) is placed on one main surface 10A and a load is applied, the load can be applied to the seed substrate 10 uniformly to some extent. Can be transformed into the fixed layer 31.

[Details of the embodiment of the present invention]
Next, details of the embodiment of the present invention will be described.

  First, the definition of the SORI value will be described with reference to FIGS. FIG. 1 and FIG. 2 are schematic diagrams for explaining the SORI value of the seed substrate 10. The SORI value is one of parameters for quantifying the degree of warpage of the substrate. The SORI value is the highest point of the first main surface 10A (in the example of FIG. 1) when the minimum square surface of the first main surface 10A of the seed substrate 10 is set to a reference height (minimum square surface height 2). , Represents the total value of the distance between the height at the position 3) and the reference height and the lowest point (position 4 in the example of FIG. 1) and the reference height. Since the SORI value represents a distance, it is always a positive value. The SORI value is calculated for the seed substrate 10 that is not clamped.

  The SORI value represents the degree of warpage in a certain measurement range. For example, the SORI value is determined between the position 3 of the seed substrate 10 and the other position 5 (range d). In the present embodiment, the SORI value of the seed substrate 10 is the maximum of the SORI values between any two points in the main surface (the first main surface 10A or the second main surface 10B) of the seed substrate 10. Refers to the SORI value.

  Further, since the SORI value of the first main surface 10A and the SORI value of the second main surface 10B facing each other are generally the same value, the SORI value of the seed substrate 10 is uniquely determined. If the SORI value of the first main surface 10A is different from the SORI value of the second main surface 10B, the SORI value of the seed substrate 10 is the SORI value of the first main surface 10A and the second main surface 10A. Of the SORI values of the surface 10B, this is a large SORI value.

  Further, from the definition of the SORI value described above, the size of the swell of the seed substrate 10 is always smaller than or equal to the SORI value of the seed substrate 10, so that the swell of the seed substrate 10 is defined by defining the upper limit value of the SORI value of the seed substrate 10. The upper limit of is defined.

3 and 4 are schematic diagrams for explaining the SORI value of the base 20. As in the case of the seed substrate 10 shown in FIGS. 1 and 2, when the least square surface of the third main surface 20A of the pedestal 20 is set to a reference height (minimum square surface height 6), the third It represents the sum of the distance between the height of the height and the reference of the main surface 2 position of 0A 7 distance between the position of the height of the height and the reference in (the highest point) 8 (minimum point). Since the SORI value represents a distance, it is always a positive value.

  The SORI value represents the degree of warpage in a certain measurement range. For example, the SORI value is determined from a position 7 of the pedestal 20 to another position 9 (range d). In the present embodiment, the SORI value of pedestal 20 refers to the maximum SORI value among the SORI values between any two points in third main surface 20A of pedestal 20. That is, the SORI value of the pedestal 20 refers to the maximum SORI value of the third main surface 20A as the second surface.

  The TTV value is one of parameters for quantifying the variation in the thickness of the seed substrate 10. For example, it is assumed that one of the first main surface 10A and the second main surface 10B facing each other of the seed substrate 10 is a flat surface (for example, the second main surface 10B). FIG. 5 shows a virtual seed substrate 10 in which the height of the first main surface 10A facing the second main surface 10B is determined so as to be equal to the thickness at each position of the seed substrate 10 at this time. When the maximum thickness of the virtual seed substrate 10 shown in FIG. 5 is T1, and the minimum thickness is T2, the TTV value is a value calculated as a difference between the maximum thickness and the minimum thickness (that is, T1-T2). The TTV value is calculated for the seed substrate 10 with the second main surface 10B clamped. The SORI value and the TTV value of the seed substrate 10 and the pedestal 20 in the no-load state can be measured and calculated by an arbitrary method. For example, the SORI value and the TTV value are calculated based on the amount of warpage measured using the light interference effect. be able to.

  Next, with reference to FIGS. 6-9, the manufacturing method of the silicon carbide (SiC) single crystal which concerns on this Embodiment is demonstrated. The method for producing a single crystal according to the present embodiment includes a step (S10) of preparing seed substrate 10, pedestal 20, and adhesive 30, and second main surface 10B as the first surface of seed substrate 10. Bonding the seed substrate 10 with the adhesive 30 on the third main surface 20A of the pedestal 20 so that the third main surface 20A as the second surface of the pedestal 20 faces (S20); A step (S30) of curing the adhesive 30 by heat treatment.

  First, the seed board | substrate 10, the base 20, and the adhesive agent 30 are prepared (process (S10)). The seed substrate 10 is a crystal made of SiC, and the crystal structure is preferably a hexagonal system. The crystal polymorph is preferably 4H or 6H. In this case, the surface orientation of the seed substrate 10 (the orientation of the lower surface in the drawing) preferably has an off angle smaller than 15 ° with respect to {0001}, and more preferably has an off angle smaller than 10 °. The TTV of the seed substrate 10 is preferably 30 μm or less, more preferably 20 μm or less.

  A coating film 11 containing carbon (see FIG. 7) may be formed on the second main surface 10B of the seed substrate 10. In this case, the second main surface 10B of the seed substrate 10 and the third main surface 20A of the pedestal 20 are bonded together using the coating film 11 and the adhesive 30.

  Specifically, the coating film 11 is an organic film in the present embodiment. This organic film is preferably formed from an organic resin. As the organic resin, for example, various resins such as an acrylic resin, a phenol resin, a urea resin, and an epoxy resin can be used, and a resin that is formed as a photosensitive resin that is crosslinked or decomposed by the action of light can also be used. it can. As the photosensitive resin, a positive type or negative type photoresist used for manufacturing a semiconductor device can be used, and since a coating technique by spin coating is established for these, the coating film 11 is used. Can be easily controlled. The spin coating method is performed as follows, for example.

  First, the seed substrate 10 is adsorbed to a holder (not shown). The seed substrate 10 is rotated by rotating the holder at a predetermined rotation speed. After the photoresist is dropped on the rotating seed substrate 10, the photoresist is applied thinly and uniformly by continuing the rotation for a predetermined time. In order to ensure uniformity over the entire surface of the seed substrate 10, for example, the rotation speed is 1000 rotations / minute to 10,000 rotations / minute, the time is 10 seconds to 100 seconds, and the coating thickness is 0.1 μm or more. .

  Next, the applied photoresist is dried to be solidified. Any method can be adopted as the drying method. The drying temperature and time can be appropriately selected depending on the photoresist material and the coating thickness. Preferably, the drying temperature is from 100 ° C. to 400 ° C., and the drying time is from 5 minutes to 60 minutes. For example, when the drying temperature is 120 ° C., the time required for drying (volatilization) is, for example, 15 minutes at a thickness of 5 μm, 8 minutes at a thickness of 2 μm, and 3 minutes at a thickness of 1 μm. Note that the coating film 11 can be formed by performing the above-described steps of application and drying once, but a thicker coating film 11 may be formed by repeating this process. In this way, the seed substrate 10 having the second main surface 10B covered with the coating film 11 can be prepared.

  The pedestal 20 is configured as a lid of a crucible 60 described later, and is made of, for example, a carbon material. The pedestal 20 is made of, for example, graphite. The pedestal 20 is bonded to the second main surface 10B of the seed substrate 10 in a step (S20) to be described later, and a third main surface 20A disposed toward the inside of the crucible 60, and a third main surface 20A and a fourth main surface 20B located on the opposite side.

  The seed substrate 10 and the pedestal 20 are prepared as a combination such that the sum of the SORI value of the seed substrate 10 and the SORI value of the pedestal 20 is 70 μm or less in an unloaded state. For example, as the pedestal 20 on which the seed substrate 10 having a SORI value of 60 μm is mounted, a pedestal 20 having a SORI value of 10 μm or less may be prepared. Preferably, the seed substrate 10 and the pedestal 20 are prepared as a combination such that the sum of the SORI value of the seed substrate 10 and the SORI value of the pedestal 20 is 50 μm or less, more preferably 30 μm or less. Is done.

  Here, the seed substrate 10 and the pedestal 20 need only have the sum of the respective SORI values within the above numerical range, regardless of the warped shapes of the second main surface 10B and the third main surface 20A. For example, when the second main surface 10B of the seed substrate 10 has a concave shape, the third main surface 20A of the pedestal 20 may be either a convex shape or a concave shape. In addition, when the second main surface 10B of the seed substrate 10 has a convex shape, the third main surface 20A of the pedestal 20 may be either a convex shape or a concave shape. When both the second main surface 10B of the seed substrate 10 and the third main surface 20A of the pedestal 20 are convex or concave (see FIG. 7), the seed substrate 10 and the pedestal 20 The maximum value of the gap S (the sum of the amounts of warpage) generated between the second main surface 10B and the third main surface 20A when bonding is the sum of the SORI values of the seed substrate 10 and the pedestal 20 70 μm or less. On the other hand, when one of the second main surface 10B of the seed substrate 10 and the third main surface 20A of the pedestal 20 is convex and the other is concave (see FIG. 11) (see FIG. 11), the seed substrate 10 is unloaded. And the pedestal 20 are bonded together, the maximum value of the gap S (the sum of the warpage amounts) generated between the second main surface 10B and the third main surface 20A is the respective SORI of the seed substrate 10 and the pedestal 20 The difference between the values is a value smaller than 70 μm.

  Further, in the seed substrate 10 and the pedestal 20, when the warped shape has a directional shape such as a saddle shape, the seed substrate 10 is formed so that the gap S is narrowed in consideration of the warped shape in addition to the SORI value. What is necessary is just to adjust suitably the direction which sticks the base 20 together.

  The adhesive 30 includes, for example, a resin that becomes non-graphitizable carbon when heated, diamond fine particles, and a solvent. Non-graphitizable carbon is carbon having an irregular structure that suppresses the development of a graphite structure when heated in an inert gas. Examples of the resin that becomes non-graphitizable carbon when heated include novolac resin, phenol resin, and furfuryl alcohol resin. The amount of diamond fine particles is preferably smaller than the amount of resin based on the number of moles of carbon atoms. The particle diameter of the diamond fine particles is, for example, not less than 0.1 μm and not more than 10 μm. The adhesive 30 may further include graphite fine particles in addition to the diamond fine particles. As the solvent, a solvent capable of dissolving and dispersing the above resin and carbohydrate is appropriately selected. The solvent is not limited to a single type of liquid, and may be a mixed liquid of a plurality of types of liquid. For example, a solvent containing alcohol that dissolves carbohydrates and cellosolve acetate that dissolves resin may be used. The adhesive 30 is provided to be curable at a predetermined temperature (for example, 1000 ° C. or higher).

  Next, with reference to FIGS. 7 and 8, seed substrate 10 is fixed on third main surface 20A as the first surface of pedestal 20 using adhesive 30 (step (S20)).

  Specifically, referring to FIG. 7, first, the fifth main surface of coating film 11 formed on second main surface 10B of seed substrate 10 via adhesive 30 (seed crystal fixing agent). The surface 11B and the third main surface 20A of the pedestal 20 are arranged to face each other (step (S21)). With reference to FIG. 8, the pressure is applied while heating, and the two are pressed against each other. The pressurizing process in the above process may be performed by any method, for example, by placing a weight 51 having a predetermined mass on the first main surface 10A of the seed substrate 10 via the protective sheet 50. Is called. In this step (S20), the adhesive 30 is not cured, and the seed substrate 10 and the base 20 are not completely fixed. Conversely, the adhesive 30 is softened by being heated to such an extent that it does not cure. As a result, the second principal surface 10B of the seed substrate 10 and the third principal surface 20A of the pedestal 20 are warped and the SORI value of the seed substrate 10 and the pedestal 20 When the sum with the SORI value is 70 μm or less, the gap S generated between both surfaces can be filled with the adhesive 30.

  Next, first, a first heat treatment is performed in a predetermined temperature range (step (S22)). This process (S22) is implemented using the hot plate 40 as a heating member, for example. The heat conducted from the hot plate 40 to the pedestal 20 is conducted to the adhesive 30 and the seed substrate 10 disposed on the third main surface 20A through the pedestal 20, and heats the adhesive 30 and the seed substrate 10. To do.

  The heating temperature in this step (S22) is a temperature at which the solvent contained in the adhesive 30 can be volatilized to some extent, for example, a predetermined temperature of 100 ° C. or higher and 400 ° C. or lower. The heat treatment time is, for example, not less than 5 minutes and not more than 60 minutes after reaching a predetermined temperature. In this way, the adhesive 30 can be temporarily cured.

  Next, the second heat treatment is performed in a higher temperature region continuously with the step (S22) (step (S23)). Specifically, it is carried out by a heat treatment method that enables heating to a predetermined temperature of, for example, 1000 ° C. or higher, preferably 2000 ° C. or higher. This step (S23) is performed using, for example, a lamp annealing apparatus. This heating is preferably performed in an inert gas.

By this step (S23), the coating film 11 is carbonized to become the carbon film 12. That is, the second main surface 10 B of the seed substrate 10 is a surface covered with the carbon film 12. Further, the adhesive 30 becomes the fixed layer 31 when the solvent contained in the adhesive 30 is volatilized and cured. Thus, referring to FIG. 9, seed substrate 10 is fixed on third main surface 20 </ b> A of pedestal 20 via fixing layer 31.

At this time, at least 90% of the main surface (second main surface 10 </ b> B) of the seed substrate 10 is fixed to the pedestal 20 via the fixed layer 31. If it says from a different viewpoint, the area | region (area | region where the space | gap has produced) which is not filled with the fixed layer 31 between 2nd main surface 10B of the seed substrate 10 and 3rd main surface 20A of the base 20 will be partially. May occur. Specifically, it is only necessary that the region has a substantially circular shape with an outer diameter of 5 mm or less and is arranged so as to be dispersed in the second main surface 10B. At this time, it is preferable that the number density of the said area | region in the 2nd main surface 10B is 0.5 piece / cm < ² > or less.

  Next, a single crystal is grown on the first main surface 10A of the seed substrate 10 fixed on the pedestal 20 via the fixed layer 31 (step (S30)). When a silicon carbide single crystal is manufactured using the silicon carbide seed substrate 10, a sublimation recrystallization method can be used as this growth method.

  That is, referring to FIG. 10, first, pedestal 20 to which seed substrate 10 is fixed is attached to crucible 60 in which raw material 61 is housed. Specifically, the base 20 is attached to the crucible 60 so that the seed substrate 10 faces the inside of the crucible 60. The crucible 60 is configured including, for example, a carbon raw material. A raw material 61 is stored in the crucible 60. Raw material 61 is, for example, silicon carbide powder. The crucible 60 is provided so as to be heated to a predetermined temperature, which will be described later, by a heating unit (not shown) disposed around the crucible 60.

  Next, the single crystal 70 can be grown by depositing a sublimate on the seed substrate 10 by sublimating the raw material 61. 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. As described above, the silicon carbide single crystal according to the present embodiment can be obtained.

  Next, the effect of the method for manufacturing a silicon carbide single crystal according to the present embodiment will be described. In the method for manufacturing a silicon carbide single crystal according to the present embodiment, in step (S10) of preparing seed substrate 10, pedestal 20, and adhesive 30, seed substrate 10 and pedestal 20 are seed substrates in an unloaded state. The sum of the SORI values of 10 and the sum of the SORI values of the pedestal 20 is 70 μm or less. Thereby, in the bonding step (S20), the gap (at least most of) generated between the seed substrate 10, the second main surface 10B, and the third main surface 20A of the base 20 is filled with the adhesive 30. Can do.

  As a result, since the seed substrate 10 and the pedestal 20 are fixed with good adhesion via the fixed layer 31, the SiC single crystal 70 having high crystallinity can be grown on the seed substrate 10.

  In addition, in order to prepare the seed substrate 10 having a TTV value of 30 μm or less in the step (S10) and perform the step (S20) using this, the load is applied to the seed substrate 10 using the weight 51 in the step (S20). The gap S can be filled with the adhesive 30 (fixed layer 31) in a state where the gap S is applied and narrowed. As a result, voids and defects (dislocations, etc.) are formed in the single crystal 70 grown on the seed substrate 10 due to the formation of voids S between the seed substrate 10 and the pedestal 20 in the step (S30). Can be suppressed.

At this time, in the step (S20), the gap S in the second main surface 10B was substantially circular with a diameter of 5 mm or less, and the number density in the second main surface 10B was dispersed at 0.5 pieces / cm ² or less. In the case of being provided as a region, voids, defects, and the like generated by the voids S in the single crystal 70 do not greatly progress and may be acceptable.

(Example)
Next, examples of the method for manufacturing a single crystal according to the present embodiment will be described.

  First, seed substrate 10, pedestal 20, and adhesive 30 were prepared according to the method for manufacturing a single crystal according to the present embodiment described above.

The seed substrate 10 was made of SiC, and an SiC substrate having an outer diameter of 100 mm was prepared. The pedestal 20 was prepared from graphite. FIG. 1 2 (a) shows the measurement result of the warpage amount for the first main surface 10A of the seed substrate 10. FIG. Figure 1 2 (b) shows the results of measurement of warpage of the third main surface 20A of the base 20. Here, the amount of warpage refers to the height of a measurement point with respect to a predetermined reference plane. Using the measurement results of the amount of warpage shown in FIG. 1 2 (a) and (b), was calculated SORI value of the seed substrate 10 and the pedestal 20.

Figure 1 2 (a) and (b) the region 1 in the warpage represents 10μm or less, region 2 warpage represents 20μm or less, region 3 warpage indicates 30μm or less. The SORI value of the seed substrate 10 was 30 μm. Moreover, 10 A of 1st main surfaces of the seed substrate 10 were convex shape. The SORI value of the third main surface 20A of the pedestal 20 was 20 μm. The third main surface 20A was concave. Moreover, the TTV value of the seed substrate 10 was 26 μm. The coating film 11 was prepared containing a novolac resin. The coating film 11 was applied onto the second main surface 10B of the seed substrate 10 using a spin coating method.

Next, the seed substrate 10 was fixed to the base 20 via the fixing layer 31. The adhesive 30 prepared what contains a phenol resin, phenol, ethyl alcohol, formaldehyde, moisture, and a solid carbon component. The application amount of the adhesive 30 was about 25 mg / cm ² and the thickness was about 40 μm. Specifically, on the hot plate 40, the seed substrate 10, the pedestal 20 and the fixed layer 31 are heated to a temperature of 100 ° C., and a pressure of 0.1 MPa is applied so that the seed substrate 10 and the pedestal 20 are pressed against each other. The board | substrate 10 and the base 20 were bonded together. Subsequently, heat treatment was sequentially performed on the hot plate 40 at 80 ° C. for 4 hours, 120 ° C. for 4 hours, and 200 ° C. for 1 hour. Next, heat treatment was performed in an 80 kPa helium gas atmosphere at a heating temperature of 1150 ° C. and a heating time of 1 hour. As a result, the seed substrate 10 and the pedestal 20 were fixed via the fixed layer 31.

  Next, the single crystal 70 was grown on the seed substrate 10 fixed to the pedestal 20. Specifically, the raw material 61 made of silicon carbide powder was placed in the crucible 60, and the pedestal 20 to which the seed substrate 10 was fixed was placed in the crucible 60. Next, heating was performed under the condition that the atmosphere pressure was 1 kPa as a mixed atmosphere of argon and nitrogen so that the crucible lower temperature was 2400 ° C. and the crucible upper temperature was 2100 ° C. The partial pressure ratio between argon and nitrogen was 10: 1. As a result of heating for 100 hours under these conditions, a silicon carbide single crystal ingot 70 having a diameter of 150 mm and a height of 30 mm could be produced.

The void density was evaluated for the single crystal 70 thus obtained. Evaluation of the void density in the single crystal 70 was measured using an ultrasonic microscope, and judged based on the contrast of the obtained image. As a result of the evaluation, the void was less than 5 cm ⁻² , and it was confirmed that the generation of the void was suppressed.

  Although the embodiments and examples of the present invention have been described above, the above-described embodiments can be variously modified. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10 seed substrate 10A first main surface 10B second main surface 11 coating film 11B fifth main surface 12 carbon film 20 pedestal 20A third main surface 20B fourth main surface 30 adhesive 31 fixing layer 40 hot Plate 50 Protective sheet 51 Weight 60 Crucible 61 Raw material 70 Single crystal

Claims (9)

Preparing a seed substrate having a first surface, a pedestal having a second surface, and an adhesive for bonding the pedestal and the seed substrate;
Fixing the seed substrate on the second surface of the pedestal using the adhesive so that the first surface and the second surface face each other;
And growing a single crystal on the seed substrate fixed on the pedestal,
In the preparing step, the seed substrate and the pedestal are arranged so that the sum of the SORI value of the first surface in the no-load state and the SORI value of the second surface in the no-load state is 70 μm or less. Be prepared ,
The method for producing a single crystal , wherein the SORI value of the first surface is larger than 10 μm . Providing a seed substrate having a first surface, a pedestal having a second surface, and an adhesive for adhering the pedestal and the seed substrate, and carbon on the first surface. A coating film containing is formed, and
Fixing the seed substrate on the second surface of the pedestal using the adhesive so that the first surface on which the coating film is formed and the second surface oppose each other; ,
And growing a single crystal on the seed substrate fixed on the pedestal,
In the preparing step, the seed substrate and the pedestal are arranged so that the sum of the SORI value of the first surface in the no-load state and the SORI value of the second surface in the no-load state is 70 μm or less. A method for producing a single crystal to be prepared. 3. The fixing step includes applying pressure to the seed substrate so that the adhesive and the seed substrate are pressed against each other while heating the adhesive and the seed substrate. A method for producing a single crystal as described in 1. above. The fixing step includes applying pressure to the seed substrate so that the adhesive and the seed substrate are pressed against each other while heating the adhesive and the seed substrate;
In the fixing step, the number density of voids having a diameter of 5 mm or less on the first surface is 0.5 / cm. ² The manufacturing method of the single crystal of Claim 1 or Claim 2 which is the following. 5. The method for producing a single crystal according to claim 1, wherein, in the preparing step, the seed substrate and the pedestal are prepared so that the sum is 50 μm or less. 5. The method for producing a single crystal according to claim 1 , wherein in the step of preparing, the seed substrate and the pedestal are prepared so that the sum is 30 μm or less. The seed substrate, the first surface is provided in the concave, the method for producing a single crystal according to any one of claims 1 to 6. The pedestal, the second surface is provided in a convex shape, method for producing a single crystal according to any one of claims 1 to 7. The seed substrate, TTV value is 30μm or less, The method for producing a single crystal according to any one of claims 1 to 8.

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