JP4224755B2 - Seed crystal fixation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing how the seed crystal.
[0002]
[Prior art]
As a substrate for manufacturing a silicon carbide semiconductor device, a substrate having a diameter of 2 inches is currently commercially available, but a higher quality substrate is required to improve the performance and yield of the semiconductor device. In order to improve the quality of silicon carbide substrates, high-quality silicon carbide bulk single crystals are required, and development of high-quality growth technology for silicon carbide bulk single crystals has been attempted by sublimation recrystallization. In particular, macro defects generated due to poor adhesion between the seed crystal and the seed crystal support part of the crucible for single crystal growth have become a problem. For example, Japanese Patent Laid-Open Nos. 9-110584 and 11-171691 The countermeasure method is disclosed. In any of these methods, the type of adhesive used for fixing the seed crystal and the seed crystal support portion and the post-treatment method are specified. The former is for carbonizing a polymer material at a high temperature, and the latter is for drying a mixture of carbohydrates, heat-resistant fine particles and a solvent at room temperature. In any of the methods, the effect of suppressing the macro defect is seen, but it is not perfect and a macro defect may occur.
[0003]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to suppress macro defects generated due to poor adhesion when the seed crystal and the seed crystal support are bonded during single crystal growth (for example, silicon carbide single crystal growth in the sublimation method). Thus, the quality of the single crystal can be improved.
[0004]
[Means for Solving the Problems]
According to the first aspect of the present invention, as a method for fixing the seed crystal in the entire single crystal growth, after removing the surface of the adhesion surface, the removal surface is adhered to the seed crystal support portion via the adhesive. In particular, according to the first aspect of the present invention, the adhesive force can be improved by defining the heat treatment conditions for drying and curing the adhesive. Therefore, the occurrence of macro defects due to poor adhesion can be suppressed.
[0005]
According to the second aspect of the present invention, as a method for fixing the seed crystal in the single crystal growth by the sublimation method, after removing the surface of the adhesion surface, the removal surface is adhered to the seed crystal support portion via the adhesive. In particular, according to the invention described in claim 2, the adhesive force can be improved by defining the heat treatment conditions for drying and curing the adhesive. Therefore, the occurrence of macro defects due to poor adhesion can be suppressed.
[0006]
According to the third aspect of the invention, in the first and second aspects of the invention, the surface of the adhesive surface is removed by mechanical polishing. Therefore, the occurrence of macro defects due to poor adhesion can be suppressed at a simple and low cost.
[0007]
According to the invention of claim 4, in the invention of claim 3, the diamond abrasive having a particle diameter of 3 μm or more is removed by mechanical polishing as the final step. Therefore, even when bonded on the silicon surface, the occurrence of macro defects due to poor bonding can be suppressed. In particular, it is effective in the growth of the 4H polymorph that is carbon surface growth.
[0008]
According to the invention of claim 5, in the invention of claims 1 and 2, the surface of the adhesive surface is removed by RIE. Therefore, it can be processed in the same process as the surface processing of the growth surface, and is simple. Also, in-plane uniformity is improved.
[0009]
According to the invention described in claim 6, in the invention of claims 1 and 2, the surface of the adhesive surface is removed by ion milling. Therefore, macro defects can be easily suppressed.
According to the seventh aspect of the present invention, in the first and second aspects of the present invention, the adhesive comprises carbon powder, a polymer material, and an organic solvent. Therefore, it is an adhesive having excellent heat resistance and can be grown at high temperatures. Moreover, the adhesive force at high temperature is large, and the occurrence of macro defects due to poor adhesion can be suppressed.
[0010]
According to the invention described in claim 8, in the invention of claim 7, the adhesive is made of carbon powder, phenol resin, phenol, and ethyl alcohol. Therefore, in addition to the above effects, it is commercially available as a carbon adhesive and can be easily obtained at low cost.
[0011]
According to the invention described in 請 Motomeko 9, a seed crystal and the single crystal silicon carbide single crystal is suitable for the growth of silicon carbide single crystal.
[0012]
According to the invention of claim 1 0, the raw material is silicon carbide powder, is suitable for the growth of silicon carbide single crystal by a sublimation method.
The invention of claim 1 1, which seed crystal is bonded to the silicon surfaces of the two silicon carbide single crystal substrate, the adhesive surface, a carbon surface on the growth surface both. This allows the 4H polymorph to grow without macro defects.
[0018]
In the present specification, when expressing the surface of single crystal silicon carbide, it should be expressed by adding a bar on a required number as originally described in the drawing (FIG. 8 and the like). However, because there are restrictions on the expression means, instead of the expression of adding a bar on the required number, “−” is added in front of the required number.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1-6 is explanatory drawing at the time of growing a single crystal from the seed crystal in this embodiment. In FIG. 6, a single crystal raw material (silicon carbide raw material powder) 23 is placed in a crucible 20 as a container, and a seed crystal 1 is fixed to a seed crystal support portion 22 in a lid 21 in the crucible 20. . In this way, the single crystal raw material 23 to be grown and the seed crystal 1 are arranged to face each other. In this state, raw material 23 is heated and sublimated to grow single crystal (silicon carbide single crystal) 3 from seed crystal (silicon carbide substrate) 1.
[0020]
Hereinafter, a method for growing a single crystal will be described in detail.
First, as shown in FIG. 1A, a silicon carbide single crystal substrate 1 to be a seed crystal is prepared. 1B, after forming thermal oxide films 2a and 2b on both surfaces of the silicon carbide single crystal substrate 1, the oxide films 2a and 2b are formed by hydrofluoric acid etching as shown in FIG. 2b is removed (sacrificial oxidation is performed).
[0021]
Next, as shown in FIG. 2, the silicon carbide single crystal substrate 1 that becomes a seed crystal is set in the polishing machine 10, and the side that becomes the bonding surface of the substrate 1 is mechanically polished by the diamond abrasive 13. Specifically, the polishing machine 10 includes a polishing board 11, a guide ring 14, and a sample fixing jig 15. Silicon carbide single crystal substrate 1 is arranged inside guide ring 14 and fixed by sample fixing jig 15. The bonded surface side of the silicon carbide single crystal substrate 1 thus fixed is pressed against the surface of the rotating polishing disk 11, and polishing is performed in this state. On the other hand, the diamond abrasive 13 is a mixture of diamond particles in a solvent such as water, and is supplied from the spray nozzle 12 to the surface of the polishing disc 11 at regular time intervals.
[0022]
As a result, as shown in FIG. 1 (d), one surface (bonding surface side) of silicon carbide single crystal substrate 1 to be a seed crystal is removed by a predetermined amount t1 by mechanical polishing. In this way, one surface 1a of the substrate 1 becomes the growth surface and the other surface becomes the bonding surface 1b.
[0023]
The finished state of the polished surface, for example, the surface roughness is not particularly limited, but it is preferably about the same as the surface roughness of the seed crystal support portion 22 in FIG. The surface roughness depends on the particle size of the diamond particles used. In the present embodiment, the surface polished by changing the particle size of diamond in three steps in the order of 9 μm, 3 μm, and 1 μm, or the surface polished in one step of 9 μm was used as an adhesive surface.
[0024]
Although the detailed mechanism for improving the adhesion when the polished surface is an adhesive surface is not clear, it is estimated as follows.
At the surface after the oxide film formed by chemical reaction such as thermal oxidation is removed by chemical etching, the surface atoms are terminated and the surface becomes inactive, and atomic bonding with the adhesive occurs. It is thought that it becomes difficult. On the other hand, the mechanically polished surface as described above has an exposed physically fractured surface, so the surface is active, and it is considered that the adhesive bond is likely to be easily bonded to the adhesive. Alternatively, when silicon carbide is polished with the diamond abrasive 13, a work-affected layer such as an amorphous layer or a strained layer remains on the surface of the polished surface, which may be a cause of surface activity. Presumed.
[0025]
When the mechanically-polished layer remains on the growth surface 1a opposite to the bonding surface 1b, that is, on the growth surface 1a on which the silicon carbide single crystal is grown, the work-affected layer deteriorates the quality of the grown crystal. Therefore, it is common to grow after removing the work-affected layer. For example, as described above, a method of removing the oxide film together with the work-affected layer by hydrofluoric acid etching after the formation of the thermal oxide film is widely used. If the work-affected layer is removed by such a method, the work-affected layer on the adhesion surface side is also removed at the same time, and the surface is inactive according to the above inference. Therefore, the adhesion surface side should be mechanically polished to adhere with good adhesion. I have to.
[0026]
Although the surface layer is removed by mechanical polishing in the above, the surface layer may be removed by other methods, for example, dry etching such as reactive ion etching (RIE) or ion milling.
[0027]
Returning to the description of the single crystal growth step and the polishing is completed, the lid 21 in the growth crucible of FIG. 6 is then removed. As shown in FIG. 3, a seed crystal support 22 is projected from the lid 21. The lid 21 (seed crystal support portion 22) is made of graphite.
[0028]
And the adhesive 30 is apply | coated to the seed crystal support part 22 of the cover body 21 so that thickness may become uniform. This adhesive 30 is originally for adhering graphite, carbon powder is mixed with phenol resin (polymer material), and phenol and ethyl alcohol are used as solvents. The adhesive 30 used this time is Nisshinbo Co., Ltd. ST-201. The coating thickness is preferably 50 μm or less, and the coating amount is preferably 5 to 10 mg / cm ² .
[0029]
Subsequently, as shown in FIG. 4, the seed crystal 1 from which the surface layer has been removed is brought into contact with the seed crystal support portion 22 via the adhesive 30. That is, the side of the seed crystal 1 from which the surface layer has been removed is brought into intimate contact with the adhesive 30 applied to the seed crystal support 22 and bonded together.
[0030]
Next, as shown in FIG. 5, the lid body 21 in contact with the seed crystal 1 through the adhesive 30 is set on the mounting table 41 in the thermostat 40, and a load is applied by the weight 42. Heat treatment is performed. This is for evaporating the solvent contained in the adhesive 30 and for curing the phenolic resin. Regarding the heat treatment for drying and curing the adhesive, as shown in FIG. 7, the heat treatment temperature and time were raised from room temperature to 80 ° C. in 1 hour, held at 80 ° C. for 4 hours, and from 80 ° C. to 120 ° C. The temperature is raised to 1 ° C. in 1 hour 20 minutes, held at 120 ° C. for 4 hours, heated from 120 ° C. to 200 ° C. over 4 hours, and finally held at 200 ° C. for 1 hour. Then, naturally cool. Since the above heat treatment is at a relatively low temperature of 200 ° C. and the atmosphere may be in the air, it can be performed in a thermostatic chamber or the like. Further, the adhesive force can be improved by using this temperature profile.
[0031]
In this example, the weight 42 is placed on the seed crystal 1 and pressed in FIG. 5 to improve the adhesion, which is more preferable. The weight 42 may be 200 g to 1000 g per 1 cm ² .
[0032]
Note that the heat treatment condition shown in FIG. 7 is one example, and of course, bonding can be performed under other conditions. However, since the above conditions are performed over a relatively long period of time in order to suppress the generation of bubbles when the solvent evaporates, it is preferable to spend more time than the above conditions.
[0033]
Moreover, although Nisshinbo Co., Ltd. ST-201 was used as the adhesive 30, it is good to use what mixed carbon powder and the polymeric material with the organic solvent, without being restricted to this.
[0034]
Since the seed crystal 1 and the seed crystal support portion 22 have been bonded, the lid 21 to which the seed crystal 1 is bonded is replaced with a graphite crucible containing silicon carbide raw material powder 23 as shown in FIG. The silicon carbide single crystal 3 is grown on the (crucible body) 20 under predetermined growth conditions. As a result of cutting out the crystal 3 after growth, polishing, and examining the crystal quality, no macro defect due to poor adhesion between the seed crystal 1 and the seed crystal support portion 22 was found.
[0035]
A macro defect is a cavity-shaped defect (hexagonal plate-shaped cavity) having a self-shape with a size of about 0.1 mm to 1 mm. The mechanism by which macro defects occur in the crystal due to poor adhesion is as described below. A. Stein, Physica B185 (1993) p. 211. Alternatively, M.M. Anikin et al., Materials Science Forum Vol. 264-268 (1998) p. Documents such as 45 are described.
[0036]
Due to the poor adhesion, a gap is formed between the seed crystal 1 and the seed crystal support portion 22, and a space path is formed between the bonding surface and the outside through the gap. Sublimation and recrystallization of the seed crystal occur in the void formed on the bonding surface, and the temperature gradient becomes a driving force, and the void advances from the seed crystal toward the grown crystal, resulting in a macro defect. Since the space path promotes the sublimation and recrystallization, the occurrence of macro defects is increased. Further, since the voids generated on the bonding surface are non-uniform, non-uniformity occurs in the presence or absence of contact between the seed crystal 1 and the seed crystal support 22, and the heat transfer between the seed crystal 1 and the seed crystal support 22 is different. Occurs. As a result, a temperature distribution is generated in the seed crystal plane, and the sublimation and recrystallization are promoted by the temperature gradient, and the occurrence of macro defects is similarly increased. If the bonding method according to the present embodiment is used, the seed crystal 1 and the seed crystal support portion 22 are in close contact with each other, and the voids as described above do not occur, so that no macro defect occurs.
[0037]
As described above, after the surface layer of the bonding surface of the seed crystal 1 is removed by mechanical polishing, the silicon carbide single crystal substrate (seed) is originally used with the adhesive (carbon adhesive) 30 for bonding graphite to each other. Crystal) 1 and graphite seed crystal support 22 are bonded with good adhesion.
[0038]
In addition, the present inventors have found that the crystallographic plane orientation of the bonded surface of silicon carbide affects the bonded state. That is, when comparing the (000-1) carbon surface and the (0001) silicon surface of the 6-type, 4H-type, 15R-type (hereinafter referred to as polymorph) α-type (000-1) carbon surface, the (0001) silicon surface Has found that the yield of bonding with good adhesion is low. The reason for this is not clear, but a difference in surface energy occurs between the (000-1) carbon surface and the (0001) silicon surface due to the difference in the outermost surface atoms, and there is a difference in adhesive force due to the difference in the interfacial energy with the adhesive. It is thought to occur.
[0039]
When growing a 4H polymorph crystal, the growth surface needs to be a (000-1) carbon surface, in which case the adhesion surface becomes a (0001) silicon surface, and the yield of adhesion with good adhesion decreases. The incidence of macro defects increases. When the above-mentioned mechanical polishing process of the bonding surface was changed to three stages of diamond particle size in the order of 9 μm, 3 μm, and 1 μm, the yield of adhesion with good adhesion was 50%, and the macro defect occurrence rate was 50%. On the other hand, when a crystal having 6H polymorphism is grown, the growth surface may be a (0001) silicon surface, and the bonding surface is a (000-1) carbon surface. Similarly, when the process of mechanical polishing of the bonded surface was changed to three stages of diamond particle size in the order of 9 μm, 3 μm, and 1 μm, the yield of adhesion with good adhesion was 100%, and the macro defect occurrence rate was 0%. . Therefore, in order to improve the yield of adhesion with good adhesion and reduce the macro defect generation rate when growing 4H polymorph crystals, the effect of changing the process of mechanical polishing of the bonded surface was investigated. When the surface polished in one step with a diamond particle size of 9 μm was used as an adhesive surface, the yield of adhesion with good adhesion was improved to 90%, and the macro defect occurrence rate was reduced to 10%. This is because, when the diamond particle size is 9 μm, the adhesion surface becomes rough and the contact area (exposed area) between the seed crystal support 22 and the adhesive 30 increases, and the surface orientation of the contact surface is (0001) silicon. This is presumably due to the addition of faces other than faces.
[0040]
In order to further improve the yield of adhesion with good adhesion and reduce the macro defect occurrence rate to 0% when growing 4H polymorph crystals, silicon carbide single crystal substrates 60 and 61 as shown in FIG. The (0001) silicon surfaces 60b and 61b are bonded together and joined to form a seed crystal as shown in FIG. 9, so that both the adhesion surface and the growth surface are (000-1) carbon surfaces. In order to bond (0001) silicon surfaces to each other, the polished surfaces are directly adhered and bonded together, and heat treatment is performed in an argon gas at 2000 ° C. to 2300 ° C., or a thermal oxide film is formed on the polished surfaces to form an oxide film And performing a heat treatment at 1000 ° C. to 1300 ° C. By this method, the seed crystal support portion 22 and the (000-1) carbon surface of the seed crystal 1 are bonded, the yield of bonding with good adhesion is improved, and the occurrence rate of macro defects can be reduced to 0%. In addition, the surface on which the silicon carbide single crystal 3 is grown becomes a (000-1) carbon surface, and a 4H polymorph crystal can be grown.
[0041]
Furthermore, in this embodiment, the quality determination of the fixed state of the seed crystal 1 is performed as follows.
After the seed crystal 1 and the seed crystal support 22 are brought into contact with each other through the adhesive 30, the adhesive 30 is dried and cured in this state (by the first heat treatment) in the temperature profile shown in FIG. As shown in FIG. 10, the adhesive 30 is set on the mounting table 51 in the atmosphere furnace 50, and the adhesive 30 is carbonized by the second heat treatment shown in FIG. 11 in an argon gas atmosphere. That is, the heat treatment shown in FIG. 11 is performed after the solvent contained in the adhesive 30 is evaporated and the phenol resin is cured by the heat treatment shown in FIG.
[0042]
In FIG. 11, the temperature is raised from room temperature to 300 ° C. in 2 hours, the temperature is raised from 300 ° C. to 500 ° C. in 8 hours, the temperature is raised from 500 ° C. to 800 ° C. in 4 hours, and 800 ° C. for 1 hour. Hold and then cool naturally. By this heat treatment, the phenol resin contained in the adhesive 30 is carbonized, and the adhesive layer becomes a mixed layer of carbon powder and carbonized layer.
[0043]
In addition, the process conditions shown in FIG. 11 are an example, and as long as the phenol resin is carbonized, heat treatment may be performed under other conditions. Further, the heat treatment atmosphere may be an atmosphere in which the seed crystal support portion 22 made of graphite is not oxidized, and may be, for example, in a vacuum or nitrogen gas.
[0044]
After the heat treatment is performed in this manner, the quality of the fixed state is determined by the presence or absence of cracks in the carbonized layer of the adhesive 30. In other words, when the adhesive state is good, when the adhesive layer (30) is visually observed through the transparent silicon carbide single crystal substrate (seed crystal) 1, the adhesive layer (30) is not changed and only a black layer is visible. It is. On the other hand, when the adhesive state is poor, cracks and voids are observed in the adhesive layer (30), and part of the seed crystal 1 and the adhesive layer (30) is peeled off, compared with the case where the adhesive state is good. Reflects a lot of light and looks bright.
[0045]
After the adhesion state is determined (evaluated) in this way, when the silicon carbide single crystal 3 is grown, if it is determined that the adhesion state is good, macro defects do not occur, and a high-quality silicon carbide single crystal 3 is obtained. However, when it was determined that the adhesion state was poor, many macro defects were generated, and the obtained silicon carbide single crystal 3 was of poor quality.
[0046]
If this discrimination method (fixed state evaluation method) is used, before the silicon carbide single crystal 3 is grown from the seed crystal 1, it is judged whether the seed crystal 1 and the seed crystal support portion 22 are in good or bad adhesion and after the growth. Therefore, it is possible to predict the presence or absence of the occurrence of macro defects, so that it is possible to greatly reduce the labor for finding good bonding conditions for obtaining a high-quality silicon carbide single crystal 3 free from macro defects.
[0047]
Once good bonding conditions are found, a high-quality silicon carbide single crystal 3 free from macro defects can be obtained without performing the heat treatment for determining the bonding state. However, it can be used not only as a method for finding an adhesion method before mass production (eg, finding the size of an abrasive) but also for quality control during mass production. That is, if heat treatment for determining the bonding state is performed, defective bonding products can be surely found before growth, so that the yield of high quality silicon carbide single crystal 3 can be obtained and the productivity can be improved.
[0048]
In the case where only the step of removing the work-affected layer introduced on the growth surface side on which the silicon carbide single crystal 3 of the seed crystal 1 is grown is performed, and the mechanical polishing of the bonding surface side is not performed, that is, after the formation of the thermal oxide film, After removing the oxide film together with the work-affected layer by acid etching (sacrificial oxidation), if the seed crystal 1 and the seed crystal support portion 22 are bonded as they are, the adhesion state is determined by the above heat treatment to indicate poor adhesion, cracks, It was confirmed that voids were generated. On the other hand, when the seed crystal 1 and the seed crystal support portion 22 are bonded after mechanical polishing is performed on the bonding surface side of the seed crystal 1 after the oxide film is removed, the bonding state is good when the bonding state is determined by the heat treatment. It was confirmed that no cracks or voids were generated. Further, when a single crystal was grown from the seed crystal bonded by the above two methods, many macro defects were generated in the former, but no macro defects were generated in the latter.
[0049]
From the above, it can be seen that the occurrence of macro defects after growth can be reliably predicted by the above-described method for determining the adhesion state (method for evaluating the fixed state of the seed crystal).
As described above, the present embodiment has the following features.
(A) As a method for fixing a seed crystal when growing a silicon carbide bulk single crystal by a sublimation method, a surface to be bonded to the seed crystal support portion 22 in the surface layer of the seed crystal 1 using a physical method such as mechanical polishing A step of removing the side, and a step of bonding the new surface 1b on the side from which the surface layer of the seed crystal 1 has been removed and the seed crystal support portion 22 are bonded via the adhesive 30. Therefore, seed crystal 1 can be adhered to seed crystal support portion 22 with good adhesion, and when silicon carbide bulk single crystal 3 is grown from seed crystal 1, the occurrence of macro defects due to poor adhesion can be suppressed. As a result, a high quality single crystal is obtained. Specifically, in the silicon carbide single crystal growth in the sublimation method, the adhesion and the yield when the seed crystal and the seed crystal support are bonded to each other are improved, the macro defects caused by the adhesion failure are eliminated, and the single crystal Quality can be improved.
[0050]
Here, when the step of removing the surface layer is mechanical polishing using a diamond abrasive, it is possible to suppress the occurrence of macro defects due to poor adhesion at a simple and low cost.
Further, when the particle diameter of the diamond abrasive used in the final step of the mechanical polishing process using the diamond abrasive is 3 μm or more (corresponding to the case where the diamond particle size is 9 μm in one step). Even when bonded on the silicon surface, the occurrence of macro defects due to poor bonding can be suppressed, and is particularly effective in the growth of the 4H polymorph that is the carbon surface growth.
[0051]
Further, when the adhesive 30 is composed of carbon powder, a polymer material, and an organic solvent, the adhesive 30 has excellent heat resistance and can be grown at a high temperature. Moreover, the adhesive force at high temperature is large, and the occurrence of macro defects due to poor adhesion can be suppressed. In particular, when the polymer material contained in the adhesive 30 is a phenol resin and the organic solvent is phenol and ethyl alcohol, the adhesive is made of carbon powder, phenol resin, phenol, ethyl alcohol, and is commercially available as a carbon adhesive. Can be used easily and can be obtained at low cost.
(B) As an evaluation method for discriminating the quality of the fixed state of the seed crystal 1, the seed crystal 1 and the seed crystal support 22 are brought into contact with each other through the adhesive 30, and the first heat treatment (for example, FIG. 7) is performed. The temperature of the adhesive 30 is dried and cured, and the adhesive 30 is carbonized by the second heat treatment (for example, the temperature profile of FIG. 11), and the presence or absence of cracks in the carbonized layer of the adhesive 30 is fixed. And a step of determining pass / fail. As described above, after carbonizing the adhesive 30 by heat treatment, it is possible to predict whether or not a macro defect has occurred before growth by determining whether the carbonized layer is cracked or not, thereby reducing the labor required until the growth. . In addition, it is possible to efficiently search for good bonding conditions with strong bonding strength.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining a seed crystal processing step in an embodiment.
FIG. 2 is a view for explaining a seed crystal processing step.
FIG. 3 is a view for explaining a step of bonding a seed crystal and a seed crystal support part.
FIG. 4 is a view for explaining a step of bonding a seed crystal and a seed crystal support part.
FIG. 5 is a view for explaining a step of bonding a seed crystal and a seed crystal support part.
FIG. 6 is a view for explaining a silicon carbide single crystal growth apparatus.
FIG. 7 is a diagram showing a temperature profile during heat treatment.
FIG. 8 is a cross-sectional view for explaining a step of bonding two silicon carbide single crystal substrates to form a seed crystal.
FIG. 9 is a cross-sectional view for illustrating a step of bonding two silicon carbide single crystal substrates to form a seed crystal.
FIG. 10 is a view showing a heat treatment apparatus for evaluation.
FIG. 11 is a diagram showing a temperature profile during heat treatment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Seed crystal, 3 ... Single crystal, 20 ... Crucible, 21 ... Lid body, 22 ... Seed crystal fixing | fixed part, 30 ... Adhesive agent.

Claims (11)

A method for fixing a seed crystal when growing a single crystal (3) from a seed crystal (1) fixed on a seed crystal support (22),
Removing the side of the surface layer of the seed crystal (1) that adheres to the seed crystal support (22);
Bonding the new surface (1b) on the side from which the surface layer of the seed crystal (1) has been removed and the seed crystal support (22) via an adhesive (30);
Consists of
In the step of bonding the new surface (1b) of the seed crystal (1) and the seed crystal support portion (22) via the adhesive (30), a heat treatment for drying and curing the adhesive (30),
Increasing the temperature from room temperature to 80 ° C. in 1 hour;
Holding at 80 ° C. for 4 hours;
Increasing the temperature from 80 ° C. to 120 ° C. in 1 hour and 20 minutes;
Holding at 120 ° C. for 4 hours;
Increasing the temperature from 120 ° C. to 200 ° C. in 4 hours;
Holding at 200 ° C. for 1 hour;
A seed crystal fixing method comprising the steps of: In the container (20), the single crystal raw material (23) to be grown and the seed crystal (1) fixed to the seed crystal support (22) are arranged to face each other, and the raw material (23) is heated and sublimated. A method for fixing the seed crystal when growing the single crystal (3) from the seed crystal (1),
Removing the side of the surface layer of the seed crystal (1) that adheres to the seed crystal support (22);
Bonding the new surface (1b) on the side from which the surface layer of the seed crystal (1) has been removed and the seed crystal support (22) via an adhesive (30);
Consists of
In the step of bonding the new surface (1b) of the seed crystal (1) and the seed crystal support portion (22) via the adhesive (30), a heat treatment for drying and curing the adhesive (30),
Increasing the temperature from room temperature to 80 ° C. in 1 hour;
Holding at 80 ° C. for 4 hours;
Increasing the temperature from 80 ° C. to 120 ° C. in 1 hour and 20 minutes;
Holding at 120 ° C. for 4 hours;
Increasing the temperature from 120 ° C. to 200 ° C. in 4 hours;
Holding at 200 ° C. for 1 hour;
A seed crystal fixing method comprising the steps of:   The method for fixing a seed crystal according to claim 1, wherein the step of removing the surface layer is mechanical polishing using a diamond abrasive.   4. The seed crystal fixing method according to claim 3, wherein a particle diameter of the diamond abrasive used in a final step of the mechanical polishing process using the diamond abrasive is 3 μm or more.   The seed crystal fixing method according to claim 1, wherein the step of removing the surface layer is reactive ion etching.   3. The seed crystal fixing method according to claim 1, wherein the step of removing the surface layer is ion milling.   The seed crystal fixing method according to claim 1 or 2, wherein the adhesive (30) is composed of carbon powder, a polymer material, and an organic solvent.   The seed crystal fixing method according to claim 7, wherein the polymer material contained in the adhesive (30) is a phenol resin, and the organic solvent is phenol and ethyl alcohol.   The seed crystal fixing method according to any one of claims 1 to 8, wherein the seed crystal (1) and the single crystal (3) are silicon carbide single crystals.   The seed crystal fixing method according to any one of claims 2 to 9, wherein the raw material (23) is silicon carbide powder. The seed crystal (1) is obtained by bonding the (0001) silicon surfaces of two silicon carbide single crystal substrates (60, 61), and is bonded to the seed crystal support portion (22) of the seed crystal surface. 11. The seed crystal according to claim 1, wherein both the surface (60 a) and the surface (61 a) on which the silicon carbide single crystal grows are (000-1) carbon surfaces. Fixing method .

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