JP2011018772A - Susceptor for silicon carbide single crystal film forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a susceptor that enables an SiC epitaxial film with uniform characteristics to be formed by preventing a gap from being formed between a bottom surface of a counterbore of SiC deposits on a bottom surface of the counterbore of the susceptor and a backside of an SiC single-crystal substrate in a silicon carbide single crystal film-forming device that forms a thin film of SiC single crystal by epitaxial growth.SOLUTION: The susceptor 7 on which the silicon carbide single crystal substrate is mounted includes the counterbore bottom surface 10a on which the silicon carbide single crystal substrate is mounted, a circumferential sidewall surrounding a circumferential edge of the stored substrate, and a ring-shaped groove 11 dug in a thickness direction of the susceptor along the circumferential sidewall, wherein the susceptor is provided with the counterbore 10 satisfying y+z<x<y+2z and 0 (mm)<z≤4 (mm) for a diameter (x) of the silicon carbide single crystal substrate, a diameter (y) of the counterbore bottom surface, and a groove width (z).

Description

  The present invention relates to a susceptor used in a silicon carbide single crystal film forming apparatus for producing a thin film by epitaxially growing a silicon carbide single crystal.

  Silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material because it is excellent in heat resistance and mechanical strength and is physically and chemically stable. In recent years, the demand for SiC single crystal substrates has increased as a substrate for high-frequency, high-voltage electronic devices.

  When manufacturing power devices, high-frequency devices, etc. using a SiC single crystal substrate, a SiC thin film is epitaxially grown on the substrate using a method called thermal CVD (thermochemical vapor deposition) or ion implantation is usually used. In general, a dopant is directly implanted by a method. In the latter case, annealing at a high temperature is required after the implantation, so that the former thin film formation by epitaxial growth is frequently used (see Patent Documents 1 and 2).

  In recent years, the hot wall CVD method has become mainstream as a method of epitaxial growth, and its general configuration is shown in FIG. In the configuration of FIG. 1, a heat insulating material 2 is placed in a quartz tube 1, and further a graphite 3 is placed therein, and this graphite is heated by an outer induction heating coil 4. The SiC single crystal substrate 5 is placed on the graphite 3, and the introduced source gas is heated and decomposed, whereby SiC is epitaxially grown on the SiC single crystal substrate 5 to form a SiC thin film. is there. Previously, it was common to place a SiC single crystal substrate on graphite as shown in FIG. 1, but in this case, since the source gas is consumed from the upstream (gas supply side), the downstream (gas The film thickness of the epitaxially grown thin film becomes smaller or the variation of the doping value with respect to the set value becomes larger as it becomes the (discharge side). Therefore, recently, a SiC single crystal substrate is placed in a susceptor (see Patent Documents 3 and 4), the susceptor is placed in graphite, and the susceptor is rotated to determine the substrate surface with respect to characteristics such as the film thickness and doping value of the epitaxially grown film. A method for improving the uniformity has been adopted. The method is shown in FIG. FIG. 2 shows a sectional view of only the SiC single crystal substrate 5, the graphite 3, and the susceptor 7. A depression is formed in the graphite 3, and a susceptor 7 enters the depression. Although details of the rotation mechanism are not shown in FIG. 2, a hole is formed in the center of the depression of the graphite 3, and a rotation rod is passed through the depression to connect to the susceptor 7. A method of blowing up and rotating the susceptor 7 is generally employed. However, the structure near the upper surface of the susceptor holding the SiC single crystal substrate is almost the same regardless of the rotation mechanism. A side view (sectional view) and a top view of the susceptor 7 are shown in FIGS. 3 and 4, respectively. A counterbore 8 for holding a SiC single crystal substrate is formed on the susceptor 7, and the diameter of the counterbore 8 is usually about 2 to 3 mm larger than the diameter of the substrate for easy handling of the substrate. It has become. 3 and 4 show the susceptor in the case where there is one SiC single crystal substrate. However, even if there are a plurality of SiC single crystal substrates, the susceptor becomes large and the number of SiC single crystal substrates accommodated increases. Other than that, the structure does not change.

JP 2008-270682 A JP-A-2005-223143 JP 2007-173467 A JP 2005-109408 A Japanese Unexamined Patent Publication No. 2006-351865 JP-A-10-87394 Japanese Patent Laid-Open No. 2002-9002

  When epitaxial growth is performed using the susceptor as described above, the diameter of the spot facing 8 is larger than the diameter of the SiC single crystal substrate, so that SiC is deposited in a ring shape on the bottom face of the spot facing that is not covered with the substrate. . Usually, since the growth of about 10 to 20 μm is performed in one epitaxial growth, the same thickness is also deposited on the bottom face of the recess, and after about several times of growth, the thickness is about 50 to 100 μm. Deposits will remain. On the other hand, when setting the SiC single crystal substrate on the counterbore 8, it is difficult to always place it on the part without deposits, even if it can be placed on the part without deposits, A situation occurs where the substrate moves due to force or expansion during heating, and one end of the substrate rides on the deposit. FIG. 5 shows a schematic diagram in which a SiC single crystal substrate rides on a SiC deposit 9 deposited in a ring shape on the bottom surface of the spot facing 8. In the state as shown in FIG. 5, when the substrate is set with a part of the SiC single crystal substrate 5 on board, or the SiC single crystal substrate 5 moves and one end thereof rides on the deposit 9. It happens when it happens. When the height of the deposit 9 is 100 μm, a gap of about 50 μm is generated between the front surface of the counterbore at the center of the SiC single crystal substrate and the back surface of the substrate. If such a gap occurs, the temperature non-uniformity in the SiC single crystal substrate surface will increase, and the epitaxial growth film thickness and doping values that are sensitive to the growth temperature will also vary widely in the substrate surface. Become. Specifically, for example, when a 2 inch SiC single crystal substrate is used, these variations are expressed by standard deviation / average value (σ / mean), and the film thickness is 5 to 10%, and the doping value is 10 to 10. 15%. In order to make the device yield practical, this variation is required to be 5% or less in terms of film thickness and about 5 to 10% in terms of doping value. On the other hand, as one of the solutions to the above problem, it is conceivable to remove the deposit 9 on the bottom face of the spot facing each time the epitaxial growth is completed. However, in the case of SiC, the deposit adheres strongly, so it is completely removed. This is difficult and also affects productivity.

  Therefore, it is a SiC epitaxial growth substrate that is expected to be applied to devices in the future. However, as long as the current susceptor is used, an epitaxial substrate with in-plane distribution of basic characteristics such as epitaxial film thickness and doping value is used. Will do. Therefore, the characteristics of a device manufactured using such an epitaxial substrate also vary, and the yield decreases.

  The present invention has been made in view of the above-described problems, and in a silicon carbide single crystal film forming apparatus for producing a thin film by epitaxially growing a SiC single crystal, the SiC deposits deposited on the bottom surface of the counterbore of the susceptor are used. Another object of the present invention is to provide a silicon carbide single crystal film forming apparatus susceptor in which a gap is generated between the bottom face of the counterbore and the back surface of the SiC single crystal substrate, thereby preventing deterioration in uniformity of characteristics of the formed SiC epitaxial film.

  The present invention solves the above-mentioned problem by adopting a susceptor structure having a groove on the bottom face of the counterbore formed along the peripheral side wall of the counterbore in the concave counterbore formed on the susceptor to hold the SiC single crystal substrate. It was found and completed.

That is, the present invention
(1) A susceptor used for a silicon carbide single crystal film forming apparatus for epitaxially growing a silicon carbide single crystal to produce a thin film and mounting a silicon carbide single crystal substrate, the susceptor comprising a silicon carbide single crystal substrate A counterbore having a circular concave shape to be accommodated, the counterbore having a counterbore bottom surface on which the silicon carbide single crystal substrate is placed, a peripheral side wall surrounding the periphery of the stored substrate, and a thickness direction of the susceptor along the peripheral side wall A ring-shaped groove dug, and the relationship between the diameter x of the silicon carbide single crystal substrate, the diameter y of the counterbore bottom surface, and the groove width z,
y + z <x <y + 2z
And
0 (mm) <z ≤ 4 (mm)
A susceptor for a silicon carbide single crystal film forming apparatus,
(2) The distance S from the bottom surface of the groove to the counterbore bottom is:
0 (μm) <S <600 (μm)
A susceptor for a silicon carbide single crystal film forming apparatus according to (1) above, and
(3) The silicon carbide single-piece according to (1) or (2), wherein a distance L from the counterbore bottom to the susceptor top is within a range of ± 50 μm with respect to the thickness of the silicon carbide single-crystal substrate to be accommodated. A susceptor for a crystal deposition apparatus,
It is.

  According to the present invention, even if a SiC single crystal is epitaxially grown to repeatedly produce a silicon carbide single crystal film, excess deposits that could not be grown on the silicon carbide single crystal substrate are accumulated in grooves provided on the periphery of the substrate. Since the bottom face of the counterbore can always be kept flat, a high-quality SiC single crystal thin film with excellent uniformity of in-plane distribution with respect to the film thickness and doping value of the epitaxially grown film can be manufactured with high yield.

Sectional drawing which shows the structure of the general hot wall CVD method. Sectional drawing which shows the relationship between a hot wall part (graphite) and a susceptor in the general hot wall CVD method. Sectional drawing of the conventional susceptor used for a hot wall CVD method. The top view of the conventional susceptor used for a hot wall CVD method. Sectional drawing which shows the state in which a part of SiC single-crystal substrate got on the SiC deposit deposited in the ring shape on the susceptor at the time of using the conventional susceptor. (A) is a top view of the susceptor of this invention, (b) is A-A 'sectional drawing. Explanatory drawing which shows the shape of the spot facing in the susceptor of this invention. The figure explaining an example at the time of putting a SiC single crystal substrate on the susceptor of this invention. The figure explaining the other example at the time of putting a SiC single crystal substrate on the susceptor of this invention. The graph which shows the relationship between the diameter y of the counterbore bottom and the groove width z which support the SiC single crystal substrate in a counterbore when the present invention is applied to a susceptor for a 2-inch substrate. The figure which shows in-plane distribution of the film thickness of the 2-inch SiC single crystal epitaxial film formed into a film using the susceptor of this invention. The figure which shows the in-plane distribution of the doping density of the 2-inch SiC single crystal epitaxial film formed into a film using the susceptor of this invention. The figure which shows in-plane distribution of the film thickness of the 3-inch SiC single crystal epitaxial film formed into a film using the susceptor of this invention. The figure which shows the in-plane distribution of the doping density of the 3-inch SiC single-crystal epitaxial film formed into a film using the susceptor of this invention. The figure which shows the in-plane distribution of the film thickness of the 2-inch SiC single crystal epitaxial film formed into a film using the conventional susceptor. The figure which shows the in-plane distribution of the doping density of the 2-inch SiC single crystal epitaxial film formed into a film using the conventional susceptor.

The specific contents of the present invention will be described.
First, a method for producing a SiC single crystal thin film by epitaxially growing a SiC single crystal on a SiC single crystal substrate will be described. As a general method, an SiC single crystal substrate 5 is set on a susceptor 7 (FIG. 2), and this susceptor 7 is placed in a graphite 3 to be induction-heated in a growth furnace 6 (FIG. 1) (FIG. 1, 2). After the inside of the growth furnace is evacuated, hydrogen gas is introduced to adjust the pressure to 1 × 10 ^{4 to} 3 × 10 ⁴ Pa. Thereafter, the temperature of the graphite 3 is increased while keeping the pressure constant, and the SiC single crystal substrate is etched in hydrogen chloride by introducing hydrogen or hydrogen chloride at about 1400 to 1500 ° C. for 10 to 30 minutes. This operation is for removing a deteriorated layer on the surface of the SiC single crystal substrate due to polishing or the like to obtain a clean surface. Thereafter, the temperature is raised to 1500 to 1600 ° C. which is a SiC growth temperature, and SiH ₄ and C ₂ H ₄ which are raw material gases are introduced to start the growth of SiC. The SiH ₄ gas flow rate is 40-50 cm ³ / min, and the C ₂ H ₄ gas flow rate is 30-40 cm ³ / min. In this case, the SiC growth rate (thickness increase rate) is 6 to 7 μm / hr. This growth rate is determined in consideration of productivity because the normally required SiC epitaxial growth film has a thickness of about 10 to 20 μm. SiC is grown for a predetermined time, and when a desired film thickness is obtained, the introduction of SiH ₄ and C ₂ H ₄ gas is stopped, and the temperature is lowered while only hydrogen gas is allowed to flow. After the temperature falls to room temperature, the introduction of hydrogen gas is stopped. Next, the inside of the growth furnace 6 is evacuated, an inert gas is introduced into the growth furnace 6 (replacement of the growth chamber with an inert gas), the inside of the growth furnace 6 is returned to atmospheric pressure, and then the susceptor 7 is taken out. The extracted susceptor 7 accommodates the SiC single crystal substrate 5, and a film in which the SiC single crystal is epitaxially grown is formed on the surface of the SiC single crystal substrate 5.

  Next, FIG. 6A shows a top view of the susceptor of the present invention used in the SiC single crystal film forming apparatus for producing a thin film by epitaxially growing the SiC single crystal as described above. FIG. 6B shows a cross-sectional view of the susceptor AA ′ in FIG. The susceptor of the present invention has two recesses. That is, two of a counterbore 10 for holding the SiC single crystal substrate and a ring-shaped groove 11 formed along the inner peripheral side wall of the counterbore and having a bottom surface lower than the counterbore bottom surface 10a. It is a recess.

  In Patent Document 5 and Patent Document 6, particularly, a case where vapor phase growth is performed on a silicon single crystal substrate (silicon wafer), similar to the above, a groove is formed in the inner peripheral portion of the concave counterbore of the susceptor. Yes. Of these, the groove 8 shown in FIG. 2 of Patent Document 6 is provided to make it easier to attach the silicon wafer to a special counterbore portion having a protruding portion 6 in which the peripheral side wall of the counterbore protrudes toward the substrate side. It has been done. Further, the groove 5 shown in FIG. 1 of Patent Document 5 is provided to prevent the silicon wafer from sticking to the counterbore side wall when the semiconductor integrated circuit is manufactured by vapor phase growth. However, the silicon wafer support (the counterbore bottom surface) inside the counterbore is larger than the silicon wafer. Therefore, the object of the present invention cannot be achieved with the grooves of Patent Document 5 and Patent Document 6. In the present invention, the peripheral side wall of the spot facing does not protrude toward the substrate side, and excess deposits that could not be grown on the silicon carbide single crystal substrate by a groove as described later can be efficiently stored. A working effect can be obtained.

  Further, Patent Document 7 relates to a susceptor used in a thin film forming apparatus such as a CVD furnace for growing a silicon layer on a semiconductor substrate. Unnecessary silicon is deposited in a spot facing portion partially exposed at the orientation flat portion of the semiconductor substrate. In order to prevent the adhesion between the semiconductor substrate and the counterbore part main surface from being deteriorated, it is disclosed to provide a groove along the outer peripheral edge in the counterbore part. However, in the susceptor, since the surface of the semiconductor substrate is set lower than the upper surface of the outer periphery of the susceptor, there is no problem when a silicon layer having a low growth temperature is formed, but a SiC single crystal whose growth temperature is much higher than that of silicon. In the case of epitaxial growth, SiC is deposited at the corners of the side wall of the susceptor counterbore, and the SiC single crystal substrate is fixed to the susceptor by the SiC precipitate, or the SiC precipitate becomes an obstacle. The SiC single crystal substrate cannot be taken out. Further, although the silicon film is not re-evaporated in the film formation of silicon, the SiC precipitates are most evaporated and adhere to the SiC single crystal substrate below the SiC precipitates to cause surface defects.

  Therefore, in the present invention, the distance (depth of the counterbore) L between the susceptor upper surface 12 and the counterbore bottom surface 10a that supports the SiC single crystal substrate in the counterbore 10 is about the thickness of the SiC single crystal substrate used. . That is, L is preferably the same as the thickness of the SiC single crystal substrate or the range of the thickness of the SiC single crystal substrate ± 50 μm. Usually, L is about 400 μm.

FIG. 8 shows a cross-sectional view when a SiC single crystal substrate is placed on the susceptor of the present invention. As is clear from FIG. 8, the diameter of the SiC single crystal substrate 5 is larger than the diameter y of the counterbore bottom surface 10a supporting the SiC single crystal substrate in the counterbore 10, and the outer periphery of the SiC single crystal substrate 5 is Since there is the groove 11, the SiC deposit 13 is deposited on the groove 11, and the adhesion between the SiC single crystal substrate 5 and the counterbore bottom surface 10a supporting the SiC single crystal substrate is always kept good. As a result, the temperature uniformity is improved in the plane of the SiC single crystal substrate. However, in practice, the SiC single crystal substrate 5 is moved by centrifugal force or the like while the susceptor is rotating, and the center of the SiC single crystal substrate and the counterbore center of the susceptor generally do not coincide as shown in FIG. When the SiC single crystal substrate 5 moves as shown in FIG. 9, if the counterbore bottom 10a supporting the SiC single crystal substrate in the counterbore 10 is exposed, SiC is deposited on the exposed portion. . That is, as described above, in the subsequent film formation, a gap is formed between the SiC single crystal substrate to be installed and the support surface 10a due to the SiC deposit. Therefore, in the present invention, as shown in FIG. 9, even if the SiC single crystal substrate 5 is moved, in order for the SiC deposit 13 to be deposited only on the groove 11, the diameter of the SiC single crystal substrate 5 is set to x. When the diameter of the bottom face 10a of the counterbore supporting the SiC single crystal substrate in the spot face 10 is y and the width of the groove 11 is z,
y + z <x <y + 2z [1]
Need to be. When x is equal to or less than y + z, when the SiC single crystal substrate 5 moves as described above, the counterbore bottom surface 10a that supports the SiC single crystal substrate is exposed. On the other hand, if x is the same as y + 2z as in Patent Document 7, when epitaxially growing a SiC single crystal, SiC is deposited and adhered between the SiC single crystal substrate and the side face or upper surface of the counterbore part. It will be. When x exceeds y + 2z, the SiC single crystal substrate 5 does not enter the counterbore 10 of the susceptor. Therefore, it is preferable that there is an appropriate gap between x and y + 2z. Specifically, it is more preferable that (y + 2z) −x be equal to or greater than the film thickness of the SiC single crystal epitaxial growth film.

Furthermore, regarding the width z of the groove 11,
0 (mm) <z ≤ 4 (mm) ... [2]
Must be in the range. If the value of the width z of the groove 11 is increased to exceed 4 mm, the area of the SiC single crystal substrate on the groove 11 increases (the protruding portion of the SiC single crystal substrate 5 not in contact with the counterbore bottom 10a increases). Therefore, the substrate temperature at that portion is greatly lowered, and the uniformity within the substrate surface is lowered with respect to the substrate temperature. A more preferable range of the width z of the groove 11 is
1 (mm) ≤ z ≤ 4 (mm) ... [3]
It is. If the value of the groove width z is reduced to less than 1 mm, the opening of the groove 11 is reduced, and it may be difficult for the SiC deposit to enter the bottom of the groove 11. In that case, SiC is deposited on the side wall of the groove 11, and as the film formation is repeated, the value of z is further reduced, which may make it difficult to set the SiC single crystal substrate. That is, the number of repeated film formations is reduced. Therefore, in consideration of productivity, the groove width is more preferably 1 mm or more.

Taking the case of a 2-inch substrate (x = 50.8 mm) as an example, the relationship between y and z is shown in FIG. From the relationship of the above formula [1],
(xy) / 2 <z <xy ... [4]
10 and satisfying the above equation [2], the three of z = 50.8−y, z = (50.8−y) / 2, and z = 4 in FIG. The inside of the triangle surrounded by a straight line is a combination of y and z that provides the effects of the present invention.

The distance S (FIG. 7) between the bottom surface of the groove 11 and the counterbore bottom surface 10a that supports the SiC single crystal substrate in the counterbore 10 is
0 (μm) <S <600 (μm)
It is more preferable that it is in the range. When the film formation is repeated and repeated, the height of the SiC deposit 13 is increased, and SiC is deposited higher than the counterbore bottom surface 10a that supports the SiC single crystal substrate of the counterbore 10, and the SiC single crystal substrate 5 Is placed on the susceptor while on the SiC deposit 13. If it becomes like this, the adhesiveness of the SiC single crystal substrate 5 and the spot face 10a of the spot facing 10 will worsen, and the uniformity of the temperature distribution in the surface of the SiC single crystal substrate 5 will fall. In order to avoid this inconvenience, the distance S (step) may be increased. However, when the distance S exceeds 600 μm, heat radiation from the portion increases, and the uniformity of the temperature distribution on the surface of the SiC single crystal substrate 5 may decrease. Considering productivity, more preferably,
400 (μm) ≦ S ≦ 500 (μm)
It is.

  The material of the susceptor is usually a carbon material such as graphite (graphite), but a material other than graphite such as a high melting point material, a graphite coated high melting point material, or a high melting point material coated graphite may be partially used. For example, in order to avoid generation of hydrocarbons due to graphite heating in hydrogen, a susceptor in which TaC is coated on graphite is also used.

(Example 1)
From a SiC single crystal ingot for a 2 inch (50.8 mm) wafer, it was sliced and subjected to rough grinding and normal polishing with diamond abrasive grains to produce a SiC single crystal substrate having a 4H type polytype with a thickness of 400 μm. A SiC single crystal was epitaxially grown on the Si surface of the SiC single crystal substrate to produce a thin film. The off-angle of the SiC single crystal substrate is 8 °. The structure of the susceptor used is that y shown in FIG. 8 is 48 mm and z is 2 mm, and the bottom surface of the groove shown in FIG. 7 and the bottom face of the counterbore that supports the SiC single crystal substrate in the counterbore are shown. The distance S is 450 μm, and the distance L between the susceptor upper surface 12 and the counterbore bottom surface 10a is 400 μm. Note that this susceptor is used after it has been grown 20 times from the new condition under the same conditions as described below, and during this time, the SiC deposit on the susceptor is not removed.

As a film forming procedure, the SiC single crystal substrate was placed in this susceptor, set in a growth furnace, the inside of the growth furnace was evacuated, and a pressure of 1.0 was applied while introducing hydrogen gas at 150,000 cm ³ / min. Adjusted to × 10 ⁴ Pa. Thereafter, the susceptor was rotated, the temperature of the growth furnace was raised while keeping the pressure constant, and after reaching 1550 ° C., hydrogen chloride was flowed at 1000 cm ³ / min and the substrate was etched for 20 minutes. After etching, the temperature was raised to 1600 ° C., SiH ₄ flow rate of _{^{40cm 3 / min, C 2 H}} 4 flow rate 30 cm ³ / min (C / Si molar ratio = 1.5), 10 cm a N ₂ flow for doping ³ / The SiC single crystal epitaxial thin film was grown to a thickness of 10 μm. The growth rate at this time was about 7 μm / hr.

  FIG. 11 shows the in-plane distribution of the film thickness and FIG. 12 shows the in-plane distribution of the doping of the substrate formed by epitaxially growing the SiC single crystal in this way. The variation in the in-plane distribution of the film thickness expressed in σ / mean was 2.3%, and the variation in the in-plane distribution of doping was 4.0%, which was good. In particular, since the variation in data at the edge of the SiC single crystal substrate is small, in the susceptor of the present invention, the SiC single crystal caused by the SiC deposit caused by repeated deposition of the SiC single crystal thin film is caused. It can be seen that the surface temperature non-uniformity of the crystal substrate is suppressed.

(Example 2)
The SiC single crystal was epitaxially grown on the Si surface of a 3 inch (76 mm) SiC single crystal substrate (thickness 400 μm) having a 4H type polytype that had been sliced, roughened, and normally polished as in Example 1. A thin film was prepared. The off-angle of the SiC single crystal substrate is 8 °. The film forming conditions such as the film forming procedure and temperature are the same as those in the first embodiment. The structure of the susceptor used is that y shown in FIG. 8 is 72.5 mm, z is 3 mm, and the bottom surface of the groove shown in FIG. 7 and the bottom face of the counterbore that supports the SiC single crystal substrate in the counterbore The distance S between the susceptor upper surface 12 and the counterbore bottom surface 10a is 375 μm. Note that this susceptor is used after it has been grown 10 times under the same conditions as described below from a new state, and during that time, SiC deposits on the susceptor are not removed.

  FIG. 13 shows the in-plane distribution of the film thickness and FIG. 14 shows the in-plane distribution of the doping of the SiC single crystal epitaxially grown film after film formation. The in-plane distribution variation of the film thickness expressed in σ / mean is 4.4%, and the in-plane distribution variation of doping is 6.6%. In this case as well, the data variation at the edge of the SiC single crystal substrate is reduced. It was.

(Examples 3 to 7)
The SiC single crystal was epitaxially grown on the Si surface of a 2 inch (50.8 mm) SiC single crystal substrate (thickness 400 μm) having a 4H type polytype that had been sliced, roughened, and normally polished as in Example 1. A thin film was prepared. The off-angle of the SiC single crystal substrate is 8 °. The film forming conditions such as the film forming procedure and temperature are the same as those in Example 1. In addition, the susceptor is used after it has been grown 10 times under the same conditions as in Example 1 from a new state, and during that time, the SiC deposit on the susceptor is not removed. Table 1 summarizes the structure of the susceptor used, the in-plane distribution of the film thickness expressed in σ / mean, and the in-plane distribution of doping in the SiC single crystal epitaxially grown film after film formation. The definitions of x, y, z, S and L in Table 1 are the same as those in the first embodiment.

  From Example 3, when the distance S between the bottom surface of the groove and the bottom surface of the counterbore that supports the SiC single crystal substrate in the counterbore increases, the surface temperature of the SiC single crystal substrate becomes non-uniform due to heat radiation from that portion. In addition, the variation in the in-plane distribution of doping tends to be large, although it is an allowable range in which the effects of the present invention can be obtained. Further, in Example 5, the in-plane distribution of film thickness and the in-plane distribution of doping were good. However, since S is as shallow as 100 μm, if the number of depositions is further increased, the top surface of the SiC deposit begins to be higher than the bottom face of the counterbore that supports the SiC single crystal substrate, and the SiC single crystal substrate and the bottom face of the counterbore are closely attached. As a result, the in-plane distribution of the film thickness and the in-plane distribution variation of the doping increase. Therefore, with respect to S, 400 to 500 μm is more preferable, particularly from the in-plane distribution of the film thickness, the in-plane distribution of doping, and the film formation efficiency.

  For Example 6, the in-plane distribution of film thickness and the in-plane distribution of doping were good. However, within the scope of the present invention, since z was small, there was a tendency that the SiC single crystal substrate was difficult to be accommodated in the susceptor due to SiC deposits adhering to the sidewalls of the grooves. In particular, when the number of film formations was further increased, the above tendency became remarkable. In Example 7, z is larger than that in Example 6, so that it does not take time to store the SiC single crystal substrate in Example 6 in the susceptor. Therefore, regarding z, 1-4 mm is more preferable.

  When L is ± 50 μm with respect to a 400 μm thick substrate, a good SiC single crystal epitaxially grown film is obtained. For example, when L was set to 325 μm under the same conditions as in Example 7, a good film could not be obtained, for example, the substrate was too lifted from the upper surface of the susceptor, resulting in large variations in film thickness. On the other hand, when L was 475 μm, the substrate was too low from the upper surface of the susceptor, SiC was deposited on the corners of the side wall of the susceptor, and defects were generated in the film obtained by the re-evaporation. .

(Comparative Example 1)
As a comparative example, on the Si surface of a 2 inch (50.8 mm) SiC single crystal substrate (thickness 400 μm) having a 4H-type polytype that was sliced, roughly ground, and normally polished in the same manner as in Example 1, SiC single Crystals were epitaxially grown to produce a thin film. The off-angle of the SiC single crystal substrate is 8 °. The film forming conditions such as the film forming procedure and temperature are the same as in Example 1, but the susceptor used is a conventional type (x = 50.8 mm, y = 51 mm, z = 0 mm, S) with no groove 11 on the bottom face. = 0 µm, L = 400 µm), and after the growth was performed 20 times from a new state, SiC deposits were not removed during that time. FIG. 15 shows the in-plane distribution of the film thickness and FIG. 16 shows the in-plane distribution of the doping of the SiC single crystal epitaxially grown film after film formation. The in-plane distribution variation of the film thickness expressed by σ / mean is 6.0%, and the in-plane distribution variation of doping is 11.8%, which is worse than that of Example 1. In particular, from the comparison between FIG. 12 and FIG. 16, it can be seen that the value at the end of the SiC single crystal substrate varies greatly in FIG. This indicates that the temperature of this part of the SiC single crystal substrate has decreased, and this occurred because the SiC single crystal substrate is on top of the SiC deposit resulting from the 20th growth. It is.

(Comparative Examples 2 to 5)
A SiC single crystal is epitaxially grown on a Si surface of a 2 inch (50.8 mm) SiC single crystal substrate (thickness 400 μm) having a 4H type polytype that has been sliced, roughed, and normally polished as in Example 1. A thin film was prepared. The off-angle of the SiC single crystal substrate is 8 °. The film forming conditions such as the film forming procedure and temperature are the same as those in Example 1. In addition, the susceptor is used after it has been grown 20 times under the same conditions as in Example 1 from a new state, and during that time, the SiC deposit on the susceptor is not removed. Table 2 summarizes the structure of the susceptor used and the variations in the in-plane distribution of the film thickness and the in-plane distribution of the doping expressed in σ / mean for the epitaxially grown SiC single crystal film.

  Comparative Example 2 is an example in which z exceeds the upper limit of the present invention. Since the groove width of the counterbore bottom is too large and the heat dissipation from that part is large, the in-plane distribution of film thickness and doping The variation in in-plane distribution is large. In addition, Comparative Example 3 is a case where y + z = x, and Comparative Examples 4 and 5 are a case where y + z> x. Since a susceptor after 20 growths has already been performed, a SiC single crystal substrate is used during that time. Because of SiC deposits attached to the edge or the bottom of the counterbore that supports the substrate, the adhesion between the SiC single crystal substrate and the bottom surface of the counterbore deteriorates, and the surface temperature non-uniformity of the SiC single crystal substrate increases. The variation is large. In particular, Comparative Example 5 is a case where the counterbore bottom is larger than the single crystal substrate, and has the same configuration as Patent Document 5.

  According to the present invention, in a SiC single crystal film forming apparatus for epitaxially growing a SiC single crystal on a SiC single crystal substrate, the present invention relates to a thin film obtained by epitaxial growth of a SiC single crystal, with respect to the film thickness and doping value within the substrate surface. It is possible to provide a SiC single crystal substrate having a uniform SiC distribution and having a high quality SiC single crystal epitaxial film. Therefore, if an electronic device is formed on such a SiC single crystal substrate, device characteristics and yield are improved. In the present embodiment, the result when only one SiC single crystal substrate is set is shown, but the effect is the same even when the susceptor is increased and the number of SiC single crystal substrates is increased.

DESCRIPTION OF SYMBOLS 1 Quartz tube 2 Thermal insulation material 3 Graphite 4 Induction heating coil 5 SiC single crystal substrate 6 Growth chamber 7 Susceptor 7a Upper surface of susceptor 8 Counterbore 9 SiC deposit 10 Counterbore 10a Counterbore bottom surface 11 supporting the SiC single crystal in the pocket Groove 12 Upper surface of susceptor 13 SiC deposit

Claims (3)

A susceptor used for a silicon carbide single crystal film forming apparatus for epitaxially growing a silicon carbide single crystal to form a thin film and mounting a silicon carbide single crystal substrate, the susceptor being a circular shape that accommodates the silicon carbide single crystal substrate The counterbore has a concave counterbore, and the counterbore is dug in the thickness direction of the susceptor along the counterbore bottom surface on which the silicon carbide single crystal substrate is placed, the peripheral side wall surrounding the periphery of the accommodated substrate, and the peripheral side wall. A ring-shaped groove, and the relationship between the diameter x of the silicon carbide single crystal substrate, the diameter y of the counterbore bottom, and the groove width z is
y + z <x <y + 2z
And
0 (mm) <z ≤ 4 (mm)
A susceptor for a silicon carbide single crystal film-forming apparatus, characterized in that: The distance S from the bottom surface of the groove to the counterbore bottom is:
0 (μm) <S <600 (μm)
The susceptor for a silicon carbide single crystal film forming apparatus according to claim 1.   3. The susceptor for a silicon carbide single crystal film forming apparatus according to claim 1, wherein a distance L from the counterbore bottom surface to the susceptor upper surface is within a range of ± 50 μm with respect to a thickness of the silicon carbide single crystal substrate to be accommodated. .

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