JP2003176200A - Seed crystal for growing silicon carbide single crystal, silicon carbide single crystal ingot, and methods for manufacturing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seed crystal for growing a silicon carbide single crystal ingot with which the silicon carbide single crystal for cutting out the wafers of the single crystal silicon carbide each having a very low defect density and a large diameter is manufactured, and to provide the single crystal silicon carbide ingot obtained by using the same and methods for manufacturing them. <P>SOLUTION: A mask layer consisting of carbon is formed on a seed crystal by photolithography, and the silicon carbide single crystal is epitaxially grown across the mask. Further, during the growth of the single crystal, a new mask layer is formed by the photolithography while epitaxially growing the silicon carbide single crystal across the mask, and furthermore the silicon carbide single crystal is epitaxially grown across the new mask. The epitaxial growth process is carried out at least once. The position of the mask part of the each mask layer is arranged so that images projected on the surface of the seed crystal cover the surface of the seed crystal completely when the mask part of the each mask layer is projected onto the surface of the seed crystal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seed crystal for growing a silicon carbide single crystal and a method for producing the same, and more particularly to the production of a large single crystal ingot with extremely few defects such as micropipes and edge defects. The present invention relates to a seed crystal and a method for producing the same, which are made possible, and to a silicon carbide single crystal ingot using the seed crystal and a method for producing the same. A silicon carbide single crystal ingot manufactured using this seed crystal is used as a substrate wafer for blue light emitting diodes, electronic devices characterized by high breakdown voltage and high frequency operation, and the like.

[0002]

2. Description of the Related Art Silicon carbide (SiC) has excellent heat resistance and mechanical strength, and also has excellent semiconductor characteristics exceeding that of silicon, which is a typical general-purpose semiconductor material. Therefore, it has a short wavelength range from blue to ultraviolet. As a substrate wafer for optical devices, high-frequency high-voltage electronic devices, etc., research aiming at industrial stable production thereof has been activated in recent years. However,
Even at present, the defect density is still high, which is one of the major obstacles to practical use. The existence of micro hollow defects called micropipes is known as a typical defect, and it has already been reported that it causes fatal effects such as causing leakage current when the device is manufactured. (Eg PG Neudeck et al., IEEE Electron
Device Letters, Vol.15 (1994) pp.63-65). Also,
In recent years, there is an increasing tendency to report that defects such as edge dislocations and screw dislocations existing in ingots may also cause device leakage current. Therefore, although there is an industrial demand for the production of a large-diameter, high-quality SiC single crystal ingot in which such defect groups are minimized, the crystal growth technology that enables this is still not fully established. It has not been done.

Generally, a SiC single crystal ingot is manufactured by a method called an improved Rayleigh method (Yu.
M. Tairov and VF Tsvetkov, Journal of Crystal G
rowth, Vol.52 (1981) pp.146-150). In this method, Si
Using a C single crystal wafer as a seed crystal, a raw material SiC crystal powder was filled in a crucible mainly made of graphite,
In an atmosphere of an inert gas such as argon (133 Pa-13.
3 kPa) and heated to 2000-2400 ° C.
At this time, the seed crystal and the raw material powder are arranged so that a temperature gradient in which the seed crystal is on a lower temperature side than the raw material powder is formed, whereby the raw material is sublimated, and then diffused and transported in the seed crystal direction,
After that, the SiC sublimation gas that has arrived on the seed crystal is recrystallized on the seed crystal, whereby single crystal growth is realized.

By such an improved Rayleigh method, SiC
When manufacturing a single crystal ingot, it is known that the defect group already existing in the seed crystal has a property of being taken over during growth. In order to remove these defect groups, edge dislocations, screw dislocations, micropipes due to polymorphic crystals peculiar to this system called heterogeneous polytypes, generation of crystal grains whose crystal orientation is greatly disturbed, etc. It is necessary to repeat stable crystal growth so that the generation of such new defect groups does not occur at all. By repeating this stable growth operation, the edge dislocations in the crystal move to the peripheral portion of the crystal, and finally the dislocation centers escape to the outside of the crystal, so that the edge dislocation density in the crystal decreases. Also in the micropipe, a huge Burgers vector at the center of the screw dislocation, which is supposed to be the cause of the formation, is decomposed into a screw dislocation group having a Burgers vector equal to or less than the critical value, and the void portion disappears. At present, there is no effective method other than this method.

As a crystal that can be used as a seed crystal having an extremely low defect density, the existence of a crystal fragment called a Rayleigh crystal produced by the Rayleigh method is conventionally known. However, the size of this crystal piece is only 10 to 15 mm in diameter at most, which is 2 to 4 inches (about 50 to 100 mm) which is industrially desired.
Far less than the diameter. Therefore, in view of the above-mentioned circumstances, in practice, starting from the above Rayleigh crystal, carefully expanding the aperture diameter so as not to newly generate a defect by repeating stable crystal growth, the desired 2 to 4 inches (about Fifty
The present situation is that a large-diameter ingot is manufactured by a method of manufacturing a large-diameter high-quality ingot by setting the diameter to 100 mm). Furthermore, even if this method succeeds in expanding the diameter, it is not possible to ignore the probability that a large number of new defects will occur in the ingot due to growth instability due to accidental factors such as sudden changes in growth conditions. There is a need to. That is, when such growth instability occurs and the defect density increases, it is necessary to repeat stable crystal growth again until the defect density decreases to the original level, which hinders efficient industrial production. I will end up.

For this reason, a silicon carbide ingot having a particularly large diameter and a high-quality ingot with a defect density as small as possible does not depend on the defect density of the seed crystal and is excessively and repeatedly grown stably. There has been a strong desire for a new method that enables manufacturing without the need for.

[0007]

As described above, when stable growth is realized, most of various defects existing in the SiC single crystal existed in the seed crystal but succeeded to the grown crystal. (Takahashi et al., Journa
l of Crystal Growth, Vol.167 (1996) pp.596-606). Therefore, in order to realize a large-diameter ingot with an extremely small defect density, ideally, it is necessary to prepare a large-diameter seed crystal having no defects. However, at present, there is no method for efficiently producing such a seed crystal.

Therefore, in view of the above circumstances, the present invention provides a high-quality large-diameter seed crystal capable of manufacturing a large-diameter ingot having an extremely small defect density, a single crystal silicon carbide ingot using the same, and a method for manufacturing these. It is provided.

[0009]

The gist of the present invention is as follows. That is, (1) a seed crystal used for producing a silicon carbide single crystal ingot by a crystallization method, wherein the seed crystal made of a silicon carbide single crystal contains a mask portion containing carbon and an opening portion. A seed crystal for growing a silicon carbide single crystal, comprising a plurality of layers.

(2) The seed crystal for growing a silicon carbide single crystal according to (1), wherein the mask layers each independently have a thickness of 1 to 100 μm.

(3) The seed crystal for growing a silicon carbide single crystal according to (1) or (2), wherein the widths of the mask portions are each independently 10 to 100 μm.

(4) The mask aperture ratio (aperture area / mask area) of the mask layer is independently 0.0.
The seed crystal for growing a silicon carbide single crystal according to any one of (1) to (3), which is 5 to 2.

(5) Any one of (1) to (4), wherein the projection image obtained when the mask portion is projected on the seed crystal growth surface completely shields the seed crystal growth surface. A seed crystal for growing a silicon carbide single crystal according to one item.

(6) A method for producing a seed crystal for growing a silicon carbide single crystal according to any one of (1) to (5), wherein the crystal growth surface of the seed crystal comprising the silicon carbide single crystal. To form a mask layer composed of a mask portion and an opening, to perform silicon carbide epitaxial growth over the mask layer, to form a new mask layer during the growth, and to continue the silicon carbide epitaxial growth at least. A method for producing a seed crystal for growing a silicon carbide single crystal, characterized in that the seed crystal is grown once.

(7) The mask layer is formed by a method of forming a shield on a seed crystal by photolithography, depositing a thin film containing carbon on the shield, and then removing the shield. The method for producing a seed crystal for growing a silicon carbide single crystal according to 6).

(8) A method for producing a silicon carbide single crystal ingot, which comprises a step of growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method, wherein (1)-
A method for producing a silicon carbide single crystal ingot, which comprises using the seed crystal for growing a silicon carbide single crystal according to any one of (5).

(9) A silicon carbide single crystal ingot obtained by the manufacturing method according to (8), wherein the ingot has a diameter of 50 mm or more.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a seed crystal used for producing a silicon carbide single crystal ingot by a crystallization method,
A seed crystal for growing a silicon carbide single crystal, a seed crystal for growing a silicon carbide single crystal, and a plurality of mask layers each including a mask portion including carbon and an opening portion, and a method for producing the seed crystal, A silicon carbide single crystal ingot comprising the seed crystal and a method for producing the same.

In the present invention, a mask layer mainly made of carbon is formed on the seed crystal by using, for example, a photolithography technique, and a SiC single crystal is grown through the mask, while the single crystal is growing. Then, the step of forming a new mask layer by photolithography and performing epitaxial growth of a silicon carbide single crystal through the mask is repeated at least once, and at this time, a projection image of the mask portion of each mask layer onto the seed crystal surface. By arranging each mask layer so as to completely cover the surface of the seed crystal, a seed crystal for growing a SiC single crystal having almost no micropipe defects can be obtained. By using this seed crystal to grow an SiC single crystal by a sublimation recrystallization method such as an improved Rayleigh method, it becomes possible to easily manufacture a high-quality SiC single crystal ingot with extremely few micropipe defects. .

FIG. 1 shows the outline of the present invention. In this figure,
Regarding the case of performing SiC single crystal growth on the {0001} plane, an example is shown in which the crystal growth surface is completely covered by two mask layers. First, the first mask layer mainly made of carbon is formed on the surface of the SiC seed crystal by using photolithography. The seed crystal used at this time may include many micropipe defects. As the photolithography, a generally used method is sufficient, but for example, a positive type photosensitive agent called a photoresist is first uniformly applied and prebaked on the surface of the SiC seed crystal. By exposing this surface to ultraviolet rays through a photomask on which a desired pattern is formed in advance, and then developing it,
A pattern is formed in which all the exposed parts are removed.
When a carbon thin film is uniformly vacuum-deposited on the patterned SiC seed crystal surface and then the residual resist is peeled off, all the carbon thin film layer formed on the residual resist is also removed, and finally the photo resist is removed. The SiC seed crystal surface of the substrate is exposed only in a portion corresponding to the mask portion of the mask, and a patterned surface (mask layer) covered with a carbon thin film can be obtained in all other portions (FIG. 1).
(A)).

Next, a SiC single crystal is epitaxially grown over the mask layer on the surface of the SiC seed crystal patterned by the mask layer made of the carbon thin film.
Here, as the epitaxial growth method, either a physical vapor deposition method (Physical Vapor Transport method) or a chemical vapor deposition method (Chemical Vapor Deposition method) may be used, but the former method is more preferable. It is advantageous in that high-speed growth is possible. However, it is necessary to control conditions such as the growth rate so that three-dimensional nucleation and step bunching do not occur during crystal growth (for example, Y. Khlebnikov et al., Journal of Crystal.
Growth, Vol.233 (2001) p.112). In the initial stage of epitaxial growth, SiC single crystal growth occurs in the opening of the mask layer in a direction substantially parallel to the c-axis. As the growth progresses thereafter, however, the crystal growth in the direction directly above the c-axis occurs immediately above the mask. Progresses, eventually covering the entire surface of the patterned seed crystal (Fig. 1
(B)). At this time, in the opening of the mask layer, since defect groups such as micropipes existing in the seed crystal are inherited, the defect density is maintained almost the same as that in the seed crystal. As disclosed in Japanese Patent No. 262599, a micropipe defect is hardly generated in a space portion on a mask portion, and crystal growth with extremely low defect density is realized by a stable growth mechanism peculiar to epitaxial growth. . Almost similar results have recently been reported by Y.
As reported by Khlebnikov et al. (Y. Khlebnikov et al., Journal of Crystal Growth,
Vol.233 (2001) p.112).

Subsequently, the second mask layer is formed on the main crystal surface as described above, and the defect group remaining in the opening is removed (FIG. 1 (c)). The details will be described below.
First, a mask layer mainly composed of carbon and an opening portion is formed on the main crystal surface by photolithography in the same manner as described above. The mask layer may be formed directly on the main crystal surface, but when the surface undulation is severe, the crystal surface may be polished to form a mirror flat surface as a pretreatment. The polishing treatment is mainly mechanical polishing using a polishing liquid containing diamond abrasive grains, but in order to suppress the generation of defects during subsequent crystal growth as much as possible, the surface damage layer should be removed by etching with molten KOH or the like. Is preferred.
On the flat surface thus formed, the mask formation and the single crystal epitaxial growth are carried out by the same method as the previous time. At that time, the second mask layer to be formed has the mask portion whose opening is the opening of the first mask layer. Place it so that it completely covers the part. By this operation, the projected image of the mask portion of each mask layer completely shields the seed crystal surface. When the epitaxial growth is performed through the mask thus manufactured, the crystal growth is continued from the crystal portion formed by the first epitaxial growth and having a very low defect density, so that even in the opening portion of the second mask layer. There are already very few defects, and as a result, a high quality seed crystal having a small defect density over almost the entire surface of the crystal on which the crystal is grown is produced.

The shape of the photomask may be any pattern such as a mesh shape or a grid shape, but from the viewpoint of ease of manufacturing the photomask, a simple shape is preferable. The material of the mask layer preferably contains carbon, more preferably graphite, in consideration of heat resistance and reaction resistance during growth of the SiC single crystal.

The thickness of the mask layer formed of the carbon-containing mask portion and the opening is 1 to 100.
μm is desirable. Where the mask layer thickness is 1
When the thickness is less than 100 μm, the function as a mask is insufficient due to variations in the thickness of the mask layer and the like, which is not preferable. On the other hand, when the thickness exceeds 100 μm, it is too large to form such a mask layer. It requires time and is not industrially preferable.

Further, the aperture ratio (area of the opening / area of the mask) of the above-mentioned mask layer is preferably 0.05 to 2.0. If the aperture ratio is less than 0.05, it may be difficult to inherit the growth orientation from the seed crystal portion, and polycrystals or the like may easily occur on the mask portion. On the other hand, if it exceeds 2.0, The portion covered with the mask portion becomes small, and the masking effect of the micropipe defects by the mask layer may be reduced.

Further, if the width of the mask portion is less than 10 μm, the growth in the direction perpendicular to the c-axis is not performed for a sufficient length, and the micropipe defect cannot be completely suppressed. Therefore, it becomes difficult to obtain the effects of the present invention. Further, when the width of the mask portion exceeds 100 μm, it becomes difficult to cover the entire area of the mask due to the growth in the direction perpendicular to the c-axis, and defects such as voids occur right above the central portion of the mask portion. Not preferable.

Furthermore, the present invention provides the Si obtained as described above.
This is a method for producing an ingot by using a C single crystal growing seed crystal by a sublimation recrystallization method such as the improved Rayleigh method described in detail above. By this method, a high-quality single crystal ingot with extremely low defect density over almost the entire surface can be manufactured.

Takahashi et al., Journal of Crystal Growth, Vo
As shown in l.181 (1997) pp.229-240, (0
001) Area layer defects may occur, but SiC single crystal growth is performed by the sublimation recrystallization method using the seed crystal of the present invention to produce a sufficiently thick single crystal ingot, and In most of the region, crystal growth progresses substantially parallel to the c-axis, so that the above-mentioned surface defect does not occur.

Finally, the present invention is basically independent of the diameter of the seed crystal and is effective for seed crystals of any diameter, but in particular, a large single crystal growth seed crystal having an diameter of 50 mm or more, and A very large effect can be obtained for a single crystal ingot. In order to manufacture such a large-sized ingot, conventionally, as described above, a high-quality single crystal having a small diameter and few defects such as micropipe density is carefully expanded to a diameter of 50 mm. Alternatively, if the micropipe density increases in the middle of the process, stable growth can be repeated until the micropipe density drops to a predetermined value. According to the method of the present invention, eg, shown in FIG.
A seed crystal for growing a high-quality single crystal having an extremely low defect density can be obtained only by performing the single crystal epitaxial growth only twice, and the growing seed obtained in the production of the single crystal ingot by the modified Rayleigh method. The use of crystals makes it possible to easily produce a high-quality single crystal ingot with a very low defect density.

As described above, according to the manufacturing method of the present invention,
Regardless of the defect density of the seed crystal, a large diameter S with very few defects without repeating excessive stable growth as in the past.
It becomes possible to easily produce a high-quality large-diameter seed crystal for producing an iC single crystal ingot.

[0031]

EXAMPLES Examples of the present invention will be described below.

FIG. 2 shows an outline of the growth apparatus. Caliber is about 5
A 4 ° off hexagonal SiC single crystal wafer having a 1 mm (= 2 inch) c-axis tilted by 4 ° in the <11-20> direction was used as a seed crystal wafer. Next, a graphite mask layer was formed on the surface of the seed crystal wafer by photolithography. FIG. 2B shows the mask shape. The mask layer is composed of a mask portion (28) and an opening portion (29), the thickness of the mask layer is 5 μm, the diameter of the circular opening portion is 30 μm, and the distance between the centers of adjacent opening circles is between the circle centers of the opening portions. The distance (30) was set to 80 μm (mask opening ratio: about 0.1).
2). This seed crystal was attached to the inner surface of a graphite lid, and a raw material high-purity SiC wafer (23) was placed opposite to the lower part of the graphite crucible (21), which was then sealed and covered with a heat-insulating graphite felt (25). Then, it was heat-insulated and installed inside the water-cooled double quartz tube (24). A work coil (27) is installed on the outer circumference of the double quartz tube (24), and the graphite crucible (21) is heated by passing a high-frequency current to heat the raw material and the seed crystal to a desired temperature. be able to. After evacuating the inside of the quartz tube, evacuation equipment Ar
Ar gas was flown in through the gas pipe (26) to replace the atmosphere, and while maintaining the pressure in the quartz tube at about 80 kPa, the raw material temperature was raised to about 2350 ° C., and then the growth pressure was 1.
Epitaxial growth was carried out by reducing the pressure to 3 kPa and maintaining the growth at that temperature for about 1 hour. Growth rate is about 2μ
It was below m / min.

Next, the obtained single crystal surface was mirror-finished by mechanical polishing using a polishing liquid containing diamond abrasive grains, and the single crystal surface was slightly etched with molten KOH heated to 500 ° C. A mask layer made of graphite was newly formed on the surface of this wafer by photolithography. The mesh-shaped mask layer formed at this time was moved in parallel with the opening so as to completely cover the opening of the mask used for the initial growth. Hereinafter, epitaxial growth was performed under substantially the same conditions as in the initial growth to produce a seed crystal for growing a SiC single crystal.

Using the thus obtained seed crystal for growing a SiC single crystal, a SiC single crystal ingot was manufactured by a sublimation recrystallization method using a general improved Rayleigh method. That is, after filling a graphite crucible with a raw material made of high-purity SiC powder, the graphite crucible was sealed with a lid equipped with the seed crystal obtained above, covered with a graphite felt, and subjected to a heat treatment, followed by double treatment. It was installed inside a quartz tube. After evacuating the inside of the quartz tube, Ar gas was introduced to replace the atmosphere, and the raw material temperature was set to 200 while maintaining the quartz tube pressure at about 80 kPa.
Raised to 0 ° C. Then, the growth pressure of 1.3 kPa
While reducing the pressure over about 30 minutes, the raw material temperature was raised to the target temperature of 2400 ° C., and the growth was maintained at that temperature for about 20 hours to carry out single crystal growth. At this time, the temperature gradient in the crucible was 15 ° C / cm. The obtained crystal had a diameter of 53 mm and a growth rate of about 1 mm / hour.

From the ingot thus obtained,
A 1 ° thick 4 ° off {0001} face wafer was taken out, and after polishing, the wafer surface was etched with molten KOH.
As a result of microscopic observation, it was found that the number of etch pits corresponding to various defects was approximately 800 / cm ² .

As a comparative example, using a seed crystal wafer having a defect density almost equal to that of the SiC seed crystal wafer used in producing the above-mentioned single crystal growing seed crystal, direct sublimation recrystallization was performed under exactly the same conditions. A silicon carbide single crystal ingot was manufactured by the method, a 4 ° -off {0001} plane wafer with a thickness of about 1 mm was taken out, and similarly, after polishing, the wafer surface was etched with molten KOH and observed under a microscope. Was approximately 2000 pieces / cm ² . That is, about 6 by using the seed crystal of the present invention.
A defect density reduction of 0% was achieved.

Further, a comparison was made between the present invention and an ingot manufacturing method for preventing defects by repeating the conventional stabilizing process. Using the SiC seed crystal wafer used when the seed crystal for growing a single crystal described above and the seed crystal wafer having a defect density almost equal to each other, single crystal growth by a conventional sublimation recrystallization method without setting a mask is performed. Carried out. The growth conditions are the same as above. A 4 ° off {0001} plane wafer was cut out from this ingot, and single crystal growth using this wafer and 4 ° off {0001}
The cutout of the surface wafer was repeated about 19 times thereafter for a total of 20 times. After that, the same as above, 4 mm thick
Off {0001} plane wafer was cut out, and after polishing, the wafer surface was etched with molten KOH and observed under a microscope. As a result, the number of etch pits was 1500 over almost the entire surface.
The number was about 1 piece / cm ² . That is, in the conventional method, a total of 2
In the present invention, a high-quality single crystal ingot that cannot be realized by repeating the single crystal growth and the seed crystal wafer slicing step 0 times is used in the present invention by forming a mask of only two layers and accompanying the single crystal growth twice. It was proved to be possible.

[0038]

INDUSTRIAL APPLICABILITY As described above, the seed crystal of the present invention can be easily prepared, and by using the seed crystal of the present invention in the production of a silicon carbide single crystal ingot by the improved Rayleigh method, defects can be produced. A high-quality silicon carbide single crystal with extremely low density can be grown with good reproducibility and homogeneity. By using such a silicon carbide single crystal wafer, a blue light emitting element having excellent optical characteristics and a high breakdown voltage / environment resistant electronic device having excellent electric characteristics can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram outlining a method for producing a seed crystal of the present invention.

2A is a schematic view of a growth apparatus for performing epitaxial single crystal growth, and FIG. 2B is an example of a carbon mask pattern used in photolithography.

[Explanation of symbols]

11 Mask part 12 SiC seed crystal 13 Micropipe defect 21 Graphite crucible 22 Seed crystal with mask 23 High Purity SiC Wafer for Raw Material 24 Water-cooled double quartz tube 25 Graphite felt for heat insulation 26 Vacuum exhaust device Ar gas pipe 27 work coil 28 Mask 29 opening 30 Distance between centers of adjacent opening circles

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masakazu Katsuno             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division (72) Inventor Hirokatsu Yashiro             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division F-term (reference) 4G077 AA02 BE08 DA02 DA19 EA02                       EA03 ED01 HA02 SA04

Claims (9)

[Claims] 1. A seed crystal used for producing a silicon carbide single crystal ingot by a sublimation recrystallization method, wherein a seed crystal made of a silicon carbide single crystal comprises a mask portion containing carbon and an opening. A seed crystal for growing a silicon carbide single crystal, comprising: 2. The seed crystal for growing a silicon carbide single crystal according to claim 1, wherein the mask layers each independently have a thickness of 1 to 100 μm. 3. The seed crystal for growing a silicon carbide single crystal according to claim 1, wherein the width of the mask portion is 10 to 100 μm independently of each other. 4. The mask aperture ratio (aperture area / mask area) of the mask layer is independently 0.05 to 0.05.
The seed crystal for growing a silicon carbide single crystal according to any one of claims 1 to 3, which is 2. 5. The projection image obtained when the mask portion is projected onto the seed crystal growth surface completely shields the seed crystal growth surface. The seed crystal for growing a silicon carbide single crystal described. 6. A method for producing the seed crystal for growing a silicon carbide single crystal according to claim 1, wherein the mask portion is provided on the crystal growth surface of the seed crystal made of the silicon carbide single crystal. Forming a mask layer composed of the opening and the opening, performing silicon carbide epitaxial growth through the mask layer, forming a new mask layer during the growth, and continuing the silicon carbide epitaxial growth at least once. A method for producing a seed crystal for growing a silicon carbide single crystal, comprising: 7. The mask layer is produced by a method of forming a shield on a seed crystal by photolithography, depositing a thin film containing carbon thereon, and then removing the shield. 7. The method for producing a seed crystal for growing a silicon carbide single crystal according to item 6. 8. A method for producing a silicon carbide single crystal ingot, which comprises a step of growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method, wherein the seed crystal is used.
A method for manufacturing a silicon carbide single crystal ingot, which comprises using the seed crystal for growing a silicon carbide single crystal according to any one of 1. 9. A silicon carbide single crystal ingot obtained by the manufacturing method according to claim 8, wherein the ingot has a diameter of 50 mm or more.