JP2003277193A - SiC WAFER WITH EPITAXIAL FILM, METHOD FOR PRODUCING THE SAME, AND SiC ELECTRONIC DEVICE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an SiC wafer with an epitaxial film which hardly contains defects and dislocations in the wafer and the film, a method for producing the same, and an SiC electronic device having a low curren on resistance and nearly free from the generation of leak current in the backward direction. <P>SOLUTION: In a first growth process, a first growth crystal is produced by using a surface having an offset angle of ≤20° from ä1-100} plane or a surface having an offset angle of ≤20° from ä11-20} plane as the first growth surface, and in continuous growth process, the n-th growth crystal is produced by using a surface inclined from (n-1)-th growth plane at an angle of 45 to 90° and inclined from ä0001} plane at an angle of 60 to 90° as the n-th growth surface. In the film-forming processes mentioned above, an SiC wafer 3 is produced by exposing a film-forming surface 35 from the N-th growth crystal obtained when n=N, and an epitaxial film 30 is formed on the film-forming surface 35. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to Si having an epitaxial film.
The present invention relates to a C wafer, a method of manufacturing the C wafer, and an electronic device using the SiC wafer.

[0002]

2. Description of the Related Art Conventionally, SiC using a SiC single crystal
Semiconductors are expected as candidate materials for next-generation power devices to replace Si semiconductors. In order to realize a high performance SiC power device, it is an essential condition to reduce the reverse leakage current and the like generated in the SiC semiconductor. According to the research reports so far, it is considered that defects such as micropipe defects, screw dislocations, edge dislocations, and stacking faults generated in the above-mentioned SiC single crystal cause the reverse leakage current of the SiC semiconductor. ing. In addition, for the use of the above-mentioned power device, especially, an S film having an epitaxial film is used.
An iC wafer is used. Therefore, it is desired to develop a SiC wafer with an epitaxial film that does not contain the above defects not only in the SiC single crystal but also in the epitaxial film.

As shown in FIG. 4, a SiC single crystal has a {0001} plane (c-plane) and a {0001} plane as major plane orientations.
{1-100} plane (a plane) perpendicular to the plane and {11-2
0} surface (a surface). Generally, as a method for obtaining the SiC wafer with the epitaxial film, first,
Si that exposes a hexagonal {0001} plane or a plane within an offset angle of 10 ° from the {0001} plane as a seed crystal plane
Using the C seed crystal, the above-mentioned SiC single crystal is grown on the seed crystal plane by a sublimation reprecipitation method or the like, so-called c-plane growth is performed, and a grown SiC bulk single crystal is obtained.

Next, from the SiC bulk single crystal, {000
A SiC wafer is produced in which a surface within an offset angle of 10 ° from the 1} surface is exposed as a film formation surface. Then, a surface treatment such as polishing is applied to the film formation surface to form an epitaxial film into which impurities of desired elements and densities are introduced to obtain a SiC wafer with an epitaxial film.

However, as described above, the {0001} plane is used as a seed crystal plane and is grown in the <0001> direction.
The bulk single crystal (c-plane grown crystal) has a problem that very many micropipe defects, screw dislocations, and edge dislocations occur in a direction substantially parallel to the <0001> direction. Furthermore, when a SiC wafer is produced from this c-plane grown crystal and an epitaxial film is formed, dislocations exposed on the surface of the SiC wafer are inherited in the epitaxial film. As a result, dislocations having substantially the same density as that of the SiC wafer exist in the epitaxial film, which adversely affects various device characteristics.

On the other hand, in Japanese Unexamined Patent Publication No. 5-262599, an inclination of a SiC single crystal from the {0001} plane is 60 to 60.
The plane of 120 ° (preferably 90 °) is used as the seed crystal plane,
A method of growing a seed crystal by a-plane growth to obtain a grown crystal (a-plane grown crystal) is disclosed. It was also clarified that the a-plane grown crystal does not contain micropipe defects or screw dislocations.

[0007]

However, in the above a-plane grown crystal, edge dislocations having Burgers vectors parallel to and orthogonal to the <0001> direction and stacking faults in the {0001} plane are substantially parallel to the growth direction. Exists in high density. Therefore, when a SiC wafer is produced from this a-plane grown crystal and an epitaxial film is formed, dislocations are inherited from the high density edge dislocations contained in the a-plane grown crystal in the epitaxial film. Thus, the SiC wafer with an epitaxial film containing dislocations at a high density in the epitaxial film has a high on-resistance and generates a reverse leakage current.
May adversely affect device operation.

The present invention has been made in view of the above-mentioned conventional problems, and it is an SiC wafer and a SiC wafer with an epitaxial film containing few defects and dislocations in the epitaxial film, a method for manufacturing the same, and a low on-resistance. The present invention aims to provide a SiC electronic device in which a reverse leakage current is hardly generated.

[0009]

According to a first aspect of the present invention, bulk SiC is obtained by growing a SiC single crystal on a seed crystal made of a SiC single crystal.
A method for producing a C single crystal, producing an SiC wafer from the SiC single crystal, forming an epitaxial film on the film formation surface of the SiC wafer, and producing an SiC wafer with an epitaxial film, wherein the producing method is N (N is a natural number), which includes a number of times (N is a natural number of N ≧ 2) of growth steps and a film forming step of forming an epitaxial film after the growth steps. If it is expressed as an ordinal number starting from 1 and ending with N), in the first growth step where n = 1, from the {1-100} plane, an angle less than 20 ° or from the {11-20} plane Using a first seed crystal in which a surface having an offset angle of 20 ° or less is exposed as a first growth surface, Si is formed on the first growth surface.
A C single crystal is grown to form a first grown crystal, and n = 2.
3 ,. ． ． , The Nth continuous growth step, the inclination is 45 to 90 ° from the (n−1) th growth plane, and {000
An n-th seed crystal having a plane inclined by 60 to 90 ° from the 1} plane as the n-th growth surface was prepared from the (n-1) -th growth crystal, and a SiC single crystal was formed on the n-th growth surface of the n-th seed crystal. A crystal is grown to produce an nth grown crystal, and in the film forming step, n = N
A method for manufacturing a SiC wafer with an epitaxial film, characterized in that a SiC wafer having a film formation surface exposed from the Nth grown crystal is formed, and an epitaxial film is formed on the film formation surface of the SiC wafer. There is (claim 1).

In the first growth step of the present invention, the {1-100} plane or the {11-20} plane, which is within the offset angle of 20 ° from the so-called a-plane, is used as the first growth plane. Therefore, the first grown crystal grows in the direction orthogonal to the first growth plane, which corresponds to so-called a-plane growth. Therefore, the micropipe defects and screw dislocations do not occur in the first grown crystal. However, micropipe defects, screw dislocations, edge dislocations, and composite dislocations thereof exist in the first seed crystal used in the first growth step. Therefore, edge dislocations having Burgers vectors parallel to and orthogonal to the <0001> direction due to these defects are present in the first growth crystal inherited from the surface of the first growth surface. At this time, the edge dislocations are present so as to extend in a direction parallel to the growth direction of the first grown crystal.

Next, in the above continuous growth step, the inclination is 45 to 90 ° from the (n-1) th growth plane and {000
The plane inclined by 60 to 90 ° from the 1} plane, that is, almost the a plane
The n-th seed crystal used as the growth surface is prepared from the (n-1) -th growth crystal, and the SiC single crystal is grown on the n-th growth surface to prepare the n-th growth crystal. Therefore, the edge dislocations contained in the (n-1) th grown crystal are barely exposed on the surface of the nth seed crystal, so that the edge dislocations hardly occur in the nth grown crystal. Further, the growth of the SiC single crystal in the above continuous growth step occurs in the direction of substantially a-plane growth. Therefore, micropipe defects and screw dislocations do not occur in the grown crystal in the continuous growth process. Further, the continuous growth step can be performed once (when N = 2) or repeated a plurality of times. The so-called dislocation density of the obtained grown crystal can be exponentially decreased each time the number of continuous growth steps is increased.

Next, in the film forming step, a SiC wafer having a film forming surface exposed from the Nth grown crystal of n = N is prepared, and an epitaxial film is formed on the film forming surface of the SiC wafer. To do. Here, the Nth grown crystal is a grown crystal obtained by the first growth step and the continuous growth step,
It contains almost no micropipe defects, screw dislocations and edge dislocations. Therefore, the defects and dislocations are hardly exposed on the film formation surface of the SiC wafer, and the defects and dislocations are rarely inherited in the epitaxial film.

As described above, according to the present invention, it is possible to provide a method for manufacturing an SiC wafer and an SiC wafer with an epitaxial film in which defects and dislocations are scarcely contained in the SiC wafer.

In the present invention, {1-100},
{11-20} and {0001} represent so-called plane indices of crystal planes. In the above surface index, the "-" symbol is usually added above the number, but in this specification and the drawings, it is added to the left side of the number for convenience of document preparation. Also, <0001>, <11-20>, and <1-100
> Represents the direction in the crystal, and the handling of the "-" symbol is the same as the above-mentioned plane index.

According to a second aspect of the present invention, a bulk SiC single crystal is manufactured by growing a SiC single crystal on a seed crystal made of a SiC single crystal, and a SiC wafer is produced from the SiC single crystal to obtain the SiC wafer. In a method for manufacturing an SiC wafer with an epitaxial film by forming an epitaxial film on a film formation surface, the manufacturing method comprises (N + α) times (N is a natural number of N ≧ 2, and α is a natural number) of growth steps. And a film forming step of forming an epitaxial film after the growing step, where each growing step in the growing step is represented as an nth growing step (n is a natural number and starts from 1 and ends with N + α) , N = 1, in the first growth step,
A surface with an offset angle of 20 ° or less from the {1-100} surface,
Alternatively, using a first seed crystal in which a face having an offset angle of 20 ° or less from the {11-20} face is exposed as a first growth face, a SiC single crystal is grown on the first growth face to form a first growth crystal. Produced, n = 2, 3 ,. ． ． , Nth time, in the first continuous growth step, 4 times from the (n-1) th growth surface.
5 to 90 °, and 60 to 90 ° from the {0001} plane
The n-th seed crystal whose inclined surface is the n-th growth surface is the (n-1) th crystal.
And a SiC single crystal is grown on the nth growth surface of the nth seed crystal to produce an nth growth crystal.
= N + 1, N + 2 ,. ． ． , N + α times, in the second continuous growth step, 0 to 45 from the (n−1) th growth surface.
An n-th seed crystal having a surface inclined at an angle of 60 ° to 90 ° from the {0001} plane as an n-th growth surface from the (n-1) -th growth crystal, and the n-th growth of the n-th seed crystal is performed. SiC on the surface
A single crystal is grown to produce an nth grown crystal, and in the above film forming step, a SiC wafer having a film formation surface exposed from the (N + α) th grown crystal with n = N + α is prepared.
A method for manufacturing an SiC wafer with an epitaxial film is characterized in that an epitaxial film is formed on the film formation surface of the C wafer (claim 2).

In the first growth step of the present invention, similarly to the first invention, the {1-100} plane or the {11} plane is used.
Offset angle 2 from the so-called a-plane, which is the −20} plane
The surface within 0 ° is the first growth surface. Therefore, the first grown crystal grows in the direction orthogonal to the first growth plane, which corresponds to so-called a-plane growth. Therefore, the micropipe defects and screw dislocations do not occur in the first grown crystal. However, similar to the first invention, micropipe defects, screw dislocations, edge dislocations, and composite dislocations thereof exist in the first seed crystal used in the first growth step. Therefore, edge dislocations having Burgers vectors parallel to and orthogonal to the <0001> direction due to these defects are present in the first growth crystal inherited from the surface of the first growth surface. At this time, the edge dislocations are present so as to extend in a direction parallel to the growth direction of the first grown crystal.

Next, in the first continuous growth step,
Similar to the first aspect of the present invention, 45 from the (n-1) th growth surface
An n-th seed crystal having a surface inclined by ~ 90 ° and inclined by 60-90 ° from the {0001} plane, that is, an a-plane is the n-th growth surface was prepared from the (n-1) -th growth crystal. A SiC single crystal is grown on the growth surface to produce an nth grown crystal. Therefore, the edge dislocations contained in the (n-1) grown crystal are
Since it is barely exposed on the surface of the n-th seed crystal,
The edge dislocation hardly occurs in the n-th grown crystal.
In addition, the growth of the SiC single crystal in the first continuous growth step occurs in the direction of substantially a-plane growth. Therefore, the first
Micropipe defects and screw dislocations do not occur in the grown crystal in the continuous growth process. Further, like the first aspect of the invention, the first continuous growth step can be performed once (when N = 2) or can be repeated a plurality of times. The so-called dislocation density of the obtained grown crystal can be exponentially decreased each time the number of times of the first continuous growth step is increased.

Next, n = N + 1, N + 2 ,. ． ． , (N
In the second continuous growth step, which is the + αth time,
-1) An n-th seed crystal having a plane inclined by 0 to 45 ° from the growth plane and 60 to 90 ° from the {0001} plane as the nth growth plane was prepared from the (n-1) th growth crystal, and A SiC single crystal is grown on the nth growth surface of the nth seed crystal to produce an nth growth crystal. Therefore, in the second continuous growth step, the (N + α) th grown crystal having the same quality as the Nth grown crystal can be produced. Then, in the second continuous growth step, an n-th seed crystal having a surface having a smaller inclination of 0 to 45 ° than the (n-1) th growth surface as the nth growth surface is formed from the (n-1) th growth crystal. I am making it. Therefore, when producing the n-th seed crystal from the (n-1) th grown crystal, it is not necessary to grow the (n-1) th grown crystal high. Therefore, the time and cost for producing the nth grown crystal can be reduced. Further, the second continuous growth step can be performed once (when α = 1) or can be repeated a plurality of times.

Next, in the film forming step, n = N +
A SiC wafer having a film formation surface exposed from the α-th (N + α) -grown crystal is produced, and an epitaxial film is formed on the film formation surface of the SiC wafer. Here, the (N + α) th growth crystal includes the first growth step, the first continuous growth step, and the second growth step.
It is a grown crystal obtained by the continuous growth process and contains almost no micropipe defects, screw dislocations and edge dislocations. Therefore, the defects and dislocations are hardly exposed on the film formation surface of the SiC wafer, and the defects and dislocations are rarely inherited in the epitaxial film.

As described above, according to the present invention, as in the first aspect of the present invention, it is possible to provide a method for manufacturing an SiC wafer and an SiC wafer with an epitaxial film in which defects and dislocations are scarcely contained in the epitaxial wafer.

Incidentally, also in the present invention, as in the above first invention, {1-100}, {11-20} and {000
1} represents a so-called crystal plane index. In the above surface index, the "-" symbol is usually added above the number, but in this specification and the drawings, it is added to the left side of the number for convenience of document preparation. Also, <0001>, <11-
20> and <1-100> represent directions in the crystal,
The handling of the "-" symbol is the same as the above-mentioned surface index.

A third invention is an SiC wafer with an epitaxial film, which is produced by the first or second invention described above (claim 9).

As described above, the SiC wafer with an epitaxial film produced by the first or second invention is of high quality, containing almost no micropipe defects, screw dislocations and edge dislocations. Therefore, it is very effective as a material for next-generation power devices.

A fourth invention is a SiC electronic device manufactured by using the above-mentioned third invention (claim 10).

SiC with epitaxial film of the third invention
As described above, the wafer has a high quality with almost no micropipe defects, screw dislocations and edge dislocations. Therefore, the SiC electronic device has excellent device characteristics of low on-resistance and very little reverse leakage current.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the first growth plane is a plane having an offset angle of 20 ° or less from a {1-100} plane or a {11-20} plane, which is {1-100}.
Alternatively, the concept includes the {11-20} plane. Here, the first growth plane is preferably a {1-100} plane or a {11-20} plane. In this case, the first growth is performed in the <1-100> or <11-20> direction (a-plane growth). Therefore, it is possible to more effectively reduce the penetrating defects in the <0001> direction included in the first grown crystal.

In the continuous growth step and the first continuous growth step, the nth growth plane is inclined by 80 ° to 90 ° with respect to the (n-1) th growth plane and is 80 degrees from the {0001} plane.
It is preferable that the surface is inclined by 90 °. In this case, edge dislocations having Burgers vectors parallel and orthogonal to the <0001> direction can be more effectively reduced.

Further, before growing the SiC single crystal on each growth surface, it is preferable to remove the deposits and work-affected layers on the surface of each growth surface. In this case, it is possible to prevent dislocations that are inherited by the grown crystals from the growth surfaces due to the deposits and work-affected layers. As a method for removing the above-mentioned deposits and work-affected layers, for example, polishing,
Chemical cleaning, Reactive Ion Etching
(RIE), sacrificial oxidation, etc.

Further, it is preferable to use a sublimation reprecipitation method for growing the SiC single crystal on the above various crystals. In this case, a sufficient growth height can be obtained,
A SiC wafer with an epitaxial film having a large diameter can be manufactured. Note that SiC that can be used in the present invention
The single crystal growth method is not limited to the sublimation reprecipitation method, and any method capable of growing a bulk single crystal with a sufficient growth height can be applied. For example, Mater. Sci. Eng. B
Vol. 61-62 (1999) 113-120, the chemical vapor deposition method in the temperature range over 2000 degreeC can also be used.

The thickness of each crystal is preferably 1 mm or more (claim 4). In this case, it is possible to prevent dislocations and stacking faults that occur in the grown crystal due to the stress due to the difference in thermal expansion between the seed crystal and the object fixing the seed crystal. That is, by sufficiently increasing the thickness of the seed crystal, it is possible to prevent the stress from distorting the lattice constituting the seed crystal and causing dislocations and stacking faults in the grown crystal. Further, especially when the area A of the growth surface of the seed crystal exceeds 500 mm ² , the thickness of the seed crystal needs to be made larger than 1 mm. If the minimum necessary thickness at this time is tseed, ts
The equation of eded = A ^1/2 × 2 / π is given. The seed crystal and the grown crystal are concepts including all seed crystals and all grown crystals in the present invention.

The film-forming surface is a surface having an offset angle of 0.5 ° to 20 ° from the {0001} surface, {1-100}
A surface with an offset angle of 20 ° or less from the surface, or {11-2
It is preferable that the angle is 20 ° or less from the 0 plane. In this case, generation of micropipe defects, screw dislocations and edge dislocations in the epitaxial film can be almost suppressed. Note that {00
When the surface having an offset angle of less than 0.5 ° from the 01} plane is used as the film formation surface, it may be difficult to form the epitaxial film.

Further, in forming the above-mentioned epitaxial film,
It is preferable to use the CVD method, the PVE method, or the LPE method (claim 6). Here, the CVD method is based on Chemi.
cal vapor deposition (chemical vapor deposition) method, the PVE method is a physical vapor deposition method.
The por epitaxy method, the LPE method is a liquid phase epitaxy method.
y (liquid phase epitaxy) method. In this case, the film thickness and the impurity concentration in the film, which are important design parameters in device fabrication, can be easily controlled.

Further, 1 × 10 ^{13 is formed on the} epitaxial film.
It is preferable to contain impurities of about 1 × 10 ²⁰ / cm ³ (claim 7). In this case, the impurities play a role of donors or acceptors, and the SiC wafer with the epitaxial film can be used as a semiconductor device or the like. When the content of the impurities is less than 1 × 10 ¹³ / cm ³ , the impurities cannot supply a sufficient amount of carriers, and the device characteristics of the SiC wafer with the epitaxial film may deteriorate. . On the other hand, 1
If it exceeds x10 ²⁰ / cm ³ , the impurities may aggregate, resulting in the generation of dislocations and stacking faults in the epitaxial film.

Further, the above-mentioned impurities are constituent elements thereof,
It is preferable to contain at least one of nitrogen, boron and aluminum (claim 8). In this case, the epitaxial film can be a p-type or n-type semiconductor. Therefore, the SiC wafer with the epitaxial film can be used as a semiconductor device such as a diode.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) As shown in FIGS. 1 to 3, a method for manufacturing an SiC wafer with an epitaxial film according to the present embodiment comprises growing a SiC single crystal on a seed crystal made of a SiC single crystal to form a bulk SiC single crystal. This is a method of manufacturing, producing a SiC wafer from the SiC single crystal, and forming an epitaxial film on the SiC wafer to produce an SiC wafer with an epitaxial film. This manufacturing method is performed N times (N is N
A growth step of a natural number of ≧ 2 and a film formation step of forming an epitaxial film after the growth step, and each growth step in the growth step is the n-th growth step (n is a natural number and starts from 1 to N). Ordinal number ending with).

First, as shown in FIG. 1, in the first growth step in which n = 1, a surface of an offset angle of 20 ° or less from the {1-100} plane is exposed as a first growth surface 15 of the first type. The crystal 1 is used to form Si on the first growth surface 15.
A C single crystal is grown to produce a first grown crystal 10 (first
Growth process).

Next, as shown in FIGS. 1 and 2, n = 2
In the continuous growth step as the second growth step,
45-90 ° tilt from the first growth surface 15 and {000
The second seed crystal 2 having the plane inclined by 60 to 90 ° from the 1} plane as the second growth plane 25 was prepared from the first growth crystal 10 and
A second single crystal 20 is produced by growing a SiC single crystal on the second growth surface 25 of the seed crystal 2 (continuous growth step).

Then, as shown in FIGS. 2 and 3, in the film forming step, a SiC wafer 3 having a film forming surface 35 exposed from the second grown crystal 20 with n = 2 is prepared, and the SiC wafer is prepared. The epitaxial film 30 is formed on the film forming surface 35 of 3 (film forming step).

This example will be described in detail below. In this example, as shown in FIGS. 1 to 5, by growing a SiC single crystal on a seed crystal made of a SiC single crystal by a sublimation reprecipitation method,
A SiC wafer was prepared from this SiC single crystal and
An epitaxial film is formed on the C wafer. In this example, N = 2, that is, an example including two growth steps as described above.

First, SiC grown by the sublimation reprecipitation method
A single crystal was prepared. As shown in FIG. 4, the SiC single crystal has {0001} planes and {000} planes as main plane orientations.
It has a {1-100} plane and a {11-20} plane perpendicular to the 1} plane. In addition, the direction perpendicular to the {0001} plane is the <0001> direction, and the direction perpendicular to the {1-100} plane is the <0001> direction.
1-100> direction, the direction perpendicular to the {11-20} plane is <
11-20>. As shown in FIG. 1, the SiC single crystal was cut so that the {1-100} plane of the SiC single crystal was exposed as the first growth surface 15, and the first growth surface 15 was further processed and polished. Further, the surface of the first growth surface 15 is chemically cleaned to remove deposits, and RIE (React
iv Ion Etching), by sacrificial oxidation,
The work-affected layer caused by cutting and polishing was removed, and this was designated as the first seed crystal 1. The thickness of the first seed crystal 1 is 3 mm.

Next, as shown in FIG. 5, the first seed crystal 1 and the SiC raw material powder 82 were placed in the crucible 8 so that they face each other. At this time, the first seed crystal 1 was fixed to the inner surface of the lid 85 of the crucible 8 with an adhesive. Then, the crucible 8 is set to 2100 to 240 in a reduced pressure inert atmosphere.
Heated to 0 ° C. At this time, the temperature of the SiC raw material powder 82 side was set to be 20 to 200 ° C. higher than the temperature of the first seed crystal 1 side. As a result, the SiC raw material powder 82 in the crucible 8 is sublimated by heating, and the first raw material at a temperature lower than that of the SiC raw material powder 82
A first grown crystal 10 was obtained by depositing on the seed crystal 1 (first growing step).

Next, as shown in FIGS. 1 and 2, the first grown crystal 10 is tilted by 90 ° from the first grown surface 15,
And a plane inclined by 90 ° from the {0001} plane, that is, {11-
A second seed crystal 2 having a 20} plane as a second growth surface 25 was prepared in the same manner as the first seed crystal 1. Then, this second seed crystal 2 was grown in the same manner as the first seed crystal 1 to obtain a second grown crystal 20 (continuous growth step).

Next, as shown in FIGS. 2 and 3, the SiC wafer 3 in which the plane having the offset angle x from the {0001} plane is exposed as the deposition surface 35 from the second grown crystal 20.
Cut out. On the film-forming surface 35 of this SiC wafer 3, the same processing, polishing, chemical cleaning,
Surface treatment such as RIE and sacrificial oxidation was performed. And CV
The epitaxial film 30 is formed on the film formation surface 35 of the SiC wafer 3 by the D method, and the SiC with the epitaxial film is formed.
Wafer 4 was produced (film forming step). Specifically, SiH ₄ gas and C ₃ H ₈ gas are used as source gases at 5 ml / min.
And H ₂ gas as a carrier gas at 10 l / mi
n was introduced into each reaction tube, and the temperature of the susceptor holding the SiC wafer 3 was set to 1550 ° C. to form a film. In this example, the offset angle x was 5 ° and the atmospheric pressure was 30 kPa.

Next, in order to examine the defect density contained in the epitaxial film 30 of the SiC wafer 4 with the epitaxial film manufactured as described above, the epitaxial film was subjected to KOH etching, and the number of etch pits generated by this was performed. Was measured. As a result, the number of etch pits corresponding to dislocations was 10 ² to 10 ³ / cm ² , which was extremely small.

The operation and effect of this example will be described below. In the first growth step of this example, the {1-100} plane is the first growth plane 15. Therefore, the first grown crystal 10 grows in the direction orthogonal to the first growth surface 15, which corresponds to so-called a-plane growth. Therefore, the micropipe defect and the screw dislocation do not occur in the first grown crystal 10. However, defects such as micropipe defects, screw dislocations, edge dislocations, and composite dislocations thereof exist in the first seed crystal. Therefore, the first grown crystal 10
Edge dislocations having Burgers vectors parallel and orthogonal to the <0001> direction are present therein, inherited from the surface of the first growth surface. At this time, the edge dislocations are present so as to extend in a direction parallel to the growth direction of the first grown crystal.

In the above continuous growth step, the second kind in which the second growth surface 25 is a surface inclined by 90 ° with respect to the first growth surface 15 and 90 ° with respect to the {0001} surface, that is, the {11-20} surface. Crystal 2 is produced. Therefore, the edge dislocations contained in the first grown crystal 10 are hardly exposed on the surface of the second seed crystal 2. Therefore, the second growth surface 25
Even if a SiC single crystal is grown on top, edge dislocations inherited from the second seed crystal 2 are almost excluded from the second grown crystal 20. In the continuous growth step, the second
Seed crystal 2 grows in the direction of approximately a-plane growth. Therefore, micropipe defects and screw dislocations do not occur in the second grown crystal 20.

In the film forming step, the SiC wafer 3 in which the surface having the offset angle of 5 ° is exposed from the {0001} surface of the second grown crystal 20 is manufactured. for that reason,
On the film formation surface 35 of the SiC wafer 3, there is almost no edge dislocation having Burgers vectors parallel and orthogonal to the <0001> direction. Therefore, edge dislocations, which are dislocations having a Burgers vector orthogonal to the <0001> direction, do not occur in the epitaxial film 30. Also,
Micropipe defects and screw dislocations, which are defects having Burgers vectors parallel to the <0001> direction, do not occur.

In the present example, the first growth surface 1
5 and before depositing a SiC single crystal on the second growth surface 25, or before forming the epitaxial film 30 on the film formation surface 35, deposits and work-affected layers are removed. Therefore, due to the above-mentioned deposits and work-affected layers, each growth surface 15, 2
It is possible to prevent dislocations which are inherited from each growth crystal 10, 20 or the epitaxial film 35 from the film formation surface 35 or the film formation surface 35.

Further, the thickness of each of the various crystals is set to 1 mm or more. Therefore, it is possible to prevent dislocations and stacking faults occurring in the grown crystals 10 and 20 due to the stress due to the difference in thermal expansion between the various crystals 1 and 2 and the lid 65 in contact with the seed crystal.

As described above, according to this example, it is possible to provide the SiC wafer and the SiC wafer with the epitaxial film, which contains almost no defects and dislocations in the epitaxial film, and the manufacturing method thereof.

In this example, N = 2 and the continuous growth step is performed only once, but it may be repeated a plurality of times. That is, in the continuous growth process of this example, the {11-20} plane was used as the second growth plane 25 to obtain the second growth crystal 20. From this second grown crystal 20, the second
90 ° inclined from the growth plane 25 and 9 from the {0001} plane
A plane inclined by 0 °, that is, a {1-100} plane is used as a third growth plane in the third growth step, and a SiC single crystal is grown on this to produce a third growth crystal. Further, the continuous growth step can be repeated from the third growth crystal to the fourth growth step, the fifth growth step, ..., And the (N−1) th step. In this case, the so-called dislocation density of the grown crystal obtained here can be exponentially reduced each time the number of continuous growth steps is increased.

(Embodiment 2) As shown in FIGS. 3 and 6 to 8, a method for manufacturing an SiC wafer with an epitaxial film according to the present embodiment is carried out by growing a SiC single crystal on a seed crystal made of a SiC single crystal and performing bulk formation. -Shaped SiC single crystal is manufactured, and the SiC
This is a method for producing a SiC wafer from a single crystal and forming an epitaxial film on the film formation surface of the SiC wafer to produce an SiC wafer with an epitaxial film. This manufacturing method includes (N + α) times of growth steps (N is a natural number of N ≧ 2, and α is a natural number), and a film forming step of forming an epitaxial film after the growth step. Each growth step in the growth steps is represented as an nth growth step (n is a natural number and is an ordinal number starting from 1 and ending with N + α).

First, as shown in FIG. 6, in the first growth step where n = 1, as in Example 1, {1-1
Using the first seed crystal 1 in which a surface having an offset angle of 20 ° or less from the {00} plane is exposed as the first growth surface 15, a SiC single crystal is grown on the first growth surface 15 to form the first growth crystal 10. Fabricate (first growth step).

Next, as shown in FIGS. 6 and 7, n = 2
In the first continuous growth step as the second growth step, which is the same as in Example 1, 45 to 9 from the first growth surface 15
A second seed crystal 5 having a second growth plane 55 having a plane inclined by 0 ° and 60 to 90 ° from the {0001} plane was prepared from the first growth crystal 10, and the second seed crystal 5 was formed into the second seed crystal 5 described above. Growth surface 55
A SiC single crystal is grown on top to produce a second grown crystal 50 (first continuous growth step).

Next, as shown in FIGS. 7 and 8, n = 3
In the second continuous growth step as the third growth step, the inclination is 0 to 45 ° from the second growth surface 55, and {000
The third seed crystal 6 having the surface inclined by 60 to 90 ° from the 1} plane as the third growth surface 65 was prepared from the second growth crystal 50, and
A SiC single crystal is grown on the third growth surface 65 of the seed crystal 6 to produce a third growth crystal 60 (second continuous growth step). Then, as shown in FIGS. 3 and 7, in the film forming step, the SiC wafer 3 having the film forming surface 35 exposed from the third growth crystal 60 with n = 3 is manufactured, and the SiC wafer 3 is formed.
The epitaxial film 30 is formed on the film forming surface 35 of the wafer 3 (film forming step).

This example will be described in detail below. In this example, as shown in FIGS. 3 and 6 to 8, a SiC single crystal is grown on a seed crystal made of a SiC single crystal by a sublimation reprecipitation method, and a SiC wafer is produced from this SiC single crystal. An epitaxial film is formed on the SiC wafer. In this example, N = 2 and α as described above.
An example including a total of three growth steps of = 1 is shown.

First, SiC grown by the sublimation reprecipitation method
Prepared. The above-mentioned SiC single crystal was cut so that the {1-100} plane of this SiC single crystal was exposed as the first growth surface 15, and in the same manner as in Example 1, a first seed crystal 1 having a thickness of 3 mm was produced. Further, in the same manner as in Example 1, the above SiC raw material powder was deposited on this first seed crystal 1, and
A grown crystal 10 was obtained (first growing step).

Next, as shown in FIGS. 6 and 7, a plane tilted from the first grown crystal 10 by 90 ° from the first growth plane 15 and 90 degrees from the {0001} plane, that is, {11-2
Example 2 of the second seed crystal 2 having the 0} plane as the second growth plane 55
Was prepared in the same manner as in. Then, this second seed crystal 5 was further grown in the same manner as the first seed crystal 1 to obtain a second grown crystal 50 (first continuous growth step). Here, the second grown crystal 50 was grown to about half the height of the first grown crystal.

Next, as shown in FIG. 7 and FIG. 8, a surface inclined from the second growth crystal 50 by the angle y with respect to the second growth surface 55 and with an angle of 90 ° from the {0001} plane is formed into the third growth surface 65.
The third seed crystal 6 having the following structure was produced in the same manner as the first and second seed crystals. Then, the third seed crystal 6 was further grown in the same manner as the first and second seed crystals to obtain a third grown crystal 60 (second continuous growth step). In addition, the angle y
Can be arbitrarily determined within a range of 0 to 45 °, and is set to 0 ° in this example.

Next, as shown in FIGS. 3 and 8, the SiC wafer 3 in which the surface having the offset angle z from the {0001} plane is exposed as the film formation surface 35 from the third grown crystal 60.
Cut out. Then, as in the first embodiment, this S
The epitaxial film 30 was formed on the film forming surface 35 of the iC wafer 3 to prepare the SiC wafer 4 with the epitaxial film (film forming step). In this example, the offset angle z
Was 5 °.

When the defect density contained in the epitaxial film 30 of the SiC wafer 4 with the epitaxial film produced as described above was examined in the same manner as in Example 1, the number of etch pits corresponding to dislocations was It was about the same as the SiC wafer 4 with the epitaxial film produced in Example 1, and was very small. Also, according to the manufacturing method of this example, similarly, the SiC wafer 4 with the epitaxial film having a very low defect density can be obtained.

Further, in the second continuous growth step of this example, an angle y = 0 ° from the second growth surface 55, that is, a plane parallel to the second growth surface 55 and inclined by 90 ° from the {0001} plane is formed. The third growth surface 65 is used. Therefore, it is not necessary to grow the second grown crystal 50 high in the second growth step. Therefore, the third seed crystal 6 can be manufactured in a short time and at low cost, and the time and cost for finally manufacturing the SiC wafer 4 with the epitaxial film can be reduced.

In this example, the first and second continuous growth steps are performed once with N = 2 and α = 1. However, these steps may be repeated a plurality of times. By repeating the first continuous growth step, the so-called dislocation density of the obtained grown crystal can be exponentially reduced, as in the continuous growth step of Example 1. Here, if the dislocation density is sufficiently reduced, a seed crystal with a very low dislocation density can be obtained in the second continuous growth step even with a small angle y.

(Embodiment 3) In this embodiment, the {1-100} plane is used as the film formation surface and the S with the epitaxial film is formed.
The example which produced the iC wafer is shown. First, a second grown crystal 20 was prepared in the same manner as in Example 1, and the {1-100} plane was exposed as the film formation surface 35 from the second grown crystal 20.
The iC wafer 3 was cut out. The surface treatment is performed on the film formation surface 35 of the SiC wafer 3 in the same manner as in the first embodiment to form C.
An epitaxial film 30 was formed by the VD method to produce a SiC wafer 4 with an epitaxial film. Also in this case, similarly to Example 1, the SiC wafer 4 with the epitaxial film having a very low defect density could be obtained.

(Embodiment 4) In this embodiment, the {11-20} plane is used as the film formation surface and the S with the epitaxial film is formed.
The example which produced the iC wafer is shown. First, the second grown crystal 20 was prepared in the same manner as in Example 1, and the {11-20} plane was exposed as the film formation surface 35 from the second grown crystal 20.
The iC wafer 3 was cut out. The surface treatment is performed on the film formation surface 35 of the SiC wafer 3 in the same manner as in the first embodiment to form C.
An epitaxial film 30 was formed by the VD method to produce a SiC wafer 4 with an epitaxial film. Also in this case, similarly to Example 1, the SiC wafer 4 with the epitaxial film having a very low defect density could be obtained.

(Embodiment 5) This embodiment shows an example in which the SiC wafer with the epitaxial film is manufactured by the PVE method. First, as in the first embodiment, Si having a surface having an offset angle of 5 ° from the {0001} surface exposed as the film formation surface 35
A C wafer 3 was produced, and the film formation surface 35 was surface-treated. Then, the epitaxial film 30 was formed on the film formation surface 35 of the SiC wafer 3 by the PVE method, and the SiC wafer 4 with the epitaxial film was produced. Specifically, T
The SiC wafer 3 and a high-purity polycrystalline SiC plate are placed to face each other in an aC-coated graphite crucible, and the crucible is set to about 1 in a reduced pressure inert atmosphere (Ar, atmospheric pressure 100 Pa).
The temperature was raised to 800 ° C. At this time, a temperature gradient (5 to 10 ° C./cm) was set so that the temperature of the SiC wafer 3 was lower than that of the polycrystalline SiC plate. Also in this case, an SiC wafer with an epitaxial film having a very low defect density could be obtained as in Example 1.

(Embodiment 6) This embodiment shows an example in which the SiC wafer with the epitaxial film is manufactured by the LPE method. First, as in the first embodiment, Si having a surface having an offset angle of 5 ° from the {0001} surface exposed as the film formation surface 35
A C wafer 3 was produced, and the film formation surface 35 was surface-treated. Then, the epitaxial film 30 was formed on the film formation surface 35 of the SiC wafer 3 by the LPE method to produce the SiC wafer 4 with the epitaxial film. In particular,
The SiC wafer 3 was fixed to the bottom of a high-purity graphite crucible having impurities of less than 1 ppm, and impurities of 10 p were contained in the crucible.
High-purity Si powder of less than pb is filled and 1800 in a high-pressure inert atmosphere (Ar, atmosphere pressure 1.0 MPa).
Heated at ° C. Also in this case, an SiC wafer with an epitaxial film having a very low defect density could be obtained as in Example 1.

Example 7 In this example, an SiC wafer with an epitaxial film containing nitrogen as an impurity in the above epitaxial film was produced. First, similarly to Example 1, a SiC wafer 3 having a {0001} plane exposed as a film formation surface 35 was prepared, and the film formation surface 35 was subjected to a surface treatment. Next, in the above film forming step, when an epitaxial film is formed by the CVD method in the same manner as in Example 1, the flow rate of N ₂ gas is 0.5 ml / min (0.5 scc).
m). In this way, an SiC wafer 4 with an epitaxial film containing nitrogen as an impurity in the epitaxial film 30 was produced. At this time, the concentration of impurities contained in the epitaxial film 30 is 1.5 × 1.
It was 0 ¹⁶ to 1 × 10 ¹⁸ / cm ³ . Also in this case, an SiC wafer with an epitaxial film having a very low defect density could be obtained as in Example 1.

(Embodiment 8) This example shows an example in which a SiC wafer with an epitaxial film containing aluminum as an impurity in the above epitaxial film was produced. First, similarly to Example 1, a SiC wafer 3 having a {0001} plane exposed as a film formation surface 35 was prepared, and the film formation surface 35 was subjected to a surface treatment. Next, in the film forming step,
(CH ₃ ) ₃ Al gas at a flow rate of 0.01 ml when forming the epitaxial film 30 by the CVD method in the same manner as
/ Min (0.01 sccm), and a SiC wafer 4 with an epitaxial film containing aluminum as an impurity in the epitaxial film 30 was produced. Also in this case, an SiC wafer with an epitaxial film having a very low defect density could be obtained as in Example 1.
The impurity concentration contained in the epitaxial film 30 at this time was 1 × 10 ¹⁸ / cm ³ to 2 × 10 ¹⁸ / cm ³ .

Example 9 In this example, an SiC wafer with an epitaxial film containing boron as an impurity in the above epitaxial film was produced. First, Example 1
Similarly to, the SiC wafer 3 in which the {0001} plane was exposed as the film formation surface 35 was produced, and the film formation surface 35 was subjected to a surface treatment. Next, in the film forming step, when the epitaxial film 30 is formed by the CVD method in the same manner as in Example 1, the flow rate of B ₂ H ₆ gas is 0.001 ml / min.
(0.001 sccm) was introduced, and a SiC wafer 4 with an epitaxial film containing boron as an impurity in the epitaxial film 30 was produced. Also in this case, similarly to Example 1, the SiC wafer 4 with the epitaxial film having a very low defect density could be obtained. At this time, the concentration of impurities contained in the epitaxial film 30 is 2
It was × 10 ^{18 to} 3 × 10 ¹⁸ / cm ³ .

Example 10 This example shows an example in which a Schottky barrier diode is formed on the SiC wafer with an epitaxial film obtained in Example 1. First, a SiC wafer 4 with an epitaxial film was prepared in the same manner as in Example 1. A Schottky barrier diode was produced on this SiC wafer 4. Specifically, Ni was vapor-deposited as an ohmic electrode, heat-treated in a vacuum atmosphere at 900 ° C., and then a Schottky electrode was vapor-deposited. Next, the reverse-direction and forward-direction current-voltage characteristics of this Schottky barrier diode were measured. The results are shown in FIGS. 9 and 10. Note that FIG. 9 shows the reverse current −
FIG. 10 shows a voltage characteristic, and FIG.

As is known from FIG. 9, in the Schottky barrier diode, the reverse leakage current I
_R is 10 ⁻⁷ A / cm ⁻² or less (V _R <200 V),
Very few. Further, as is known from FIG. 10, the rising of the forward current I _F is very steep, that is, the on-resistance is very small. As described above, a high-performance electronic device can be provided by using the SiC wafer with the epitaxial film.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first growth step according to Example 1.

FIG. 2 is an explanatory view showing a continuous growth process according to the first embodiment.

FIG. 3 is an explanatory view showing a film forming process according to the first and second embodiments.

FIG. 4 is an explanatory view showing main plane orientations of a SiC single crystal according to Example 1.

5 is a SiC according to Example 1 by a sublimation recrystallization method. FIG.
Explanatory drawing which shows the growth method of a single crystal.

FIG. 6 is an explanatory diagram showing a first growth step according to Example 2.

FIG. 7 is an explanatory diagram showing a first continuous growth step according to Example 2.

FIG. 8 is an explanatory view showing a second continuous growth step according to Example 2.

9 is an S with an epitaxial film according to Example 10. FIG.
Explanatory drawing which shows the electric current-voltage characteristic of the reverse direction in the electronic device which used the iC wafer.

FIG. 10 is an explanatory diagram showing forward current-voltage characteristics in an electronic device using an SiC wafer with an epitaxial film according to Example 10.

[Explanation of symbols]

1. ． ． First seed crystal, 15. ． ． First growth plane, 10. ． ． First grown crystal, 2. ． ． Second seed crystal (continuous growth process), 25. ． ． Second growth surface (continuous growth process), 20. ． ． Second growth crystal (continuous growth step), 3. ． ． SiC wafer, 35. ． ． Deposition surface, 30. ． ． Epitaxial film, 4. ． ． SiC wafer with epitaxial film, 5. ． ． Second seed crystal (first continuous growth step), 55. ． ． Second growth surface (first continuous growth step), 50. ． ． Second grown crystal (first continuous growth step), 6. ． ． Third seed crystal (second continuous growth step), 65. ． ． Third growth surface (second continuous growth step), 60. ． ． Third growth crystal (second continuous growth step),

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tadashi Ito             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Masami Naito             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 4G077 AA02 BE08 DA02 DB04 DB07                       EA02 ED04 ED05 FG11 HA06                       HA12

Claims (10)

[Claims] 1. SiC on a seed crystal made of SiC single crystal
A single crystal is grown to produce a bulk SiC single crystal,
In a method for producing a SiC wafer from the SiC single crystal and forming an epitaxial film on the film formation surface of the SiC wafer to produce an SiC wafer with an epitaxial film, the producing method is performed N times (N is N ≧ N 2 growth step and a film forming step of forming an epitaxial film after the growth step, and each growth step in the growth step is performed by n-th growth step (n is a natural number and starts from 1 Ordinal number that ends), in the first growth step where n = 1, a surface having an offset angle of 20 ° or less from the {1-100} plane or a surface having an offset angle of 20 ° or less from the {11-20} plane. Using the exposed first seed crystal as the first growth surface, a SiC single crystal is grown on the first growth surface to prepare a first growth crystal, and n = 2, 3 ,. ． ． , N-th continuous growth step, the inclination is 45 to 90 ° from the (n−1) th growth plane and 60 to 9 from the {0001} plane.
The n-th seed crystal having the surface inclined at 0 ° as the n-th growth surface is designated as (n-
1) A grown single crystal is grown, and a SiC single crystal is grown on the nth growth surface of the nth seed crystal to form an nth grown crystal. A SiC wafer having a film-forming surface exposed from a grown crystal is prepared, and the S
A method of manufacturing an SiC wafer with an epitaxial film, comprising forming an epitaxial film on the above-mentioned film formation surface of an iC wafer. 2. SiC on a seed crystal made of SiC single crystal
A single crystal is grown to produce a bulk SiC single crystal,
In a method for producing an SiC wafer from the SiC single crystal and forming an epitaxial film on the film formation surface of the SiC wafer to produce an SiC wafer with an epitaxial film, the producing method is (N + α) times (N is N is a natural number of 2 and α is a natural number, and includes a growth step of forming an epitaxial film after the growth step, and each growth step in the growth steps is the n-th growth step (n is a natural number). And an ordinal number starting from 1 and ending at N + α), in the first growth step where n = 1, {1-10
A plane with an offset angle of 20 ° or less from the 0 plane, or {1
The first seed crystal was grown on the first growth surface by using a first seed crystal in which a surface having an offset angle of 20 ° or less from the 1-20} plane was exposed as the first growth surface. , N = 2, 3 ,. ． ． , Nth first continuous growth step, the angle is 45 to 90 ° from the (n-1) th growth surface.
An n-th seed crystal having a plane inclined at an angle of 60 to 90 ° from the {0001} plane as the n-th growth surface was prepared from the (n-1) -th growth crystal, and the n-th growth surface of the n-th seed crystal was formed. A SiC single crystal is grown on the nth grown crystal to produce n = N + 1,
N + 2 ,. ． ． , N + α times, in the second continuous growth step, a surface inclined at an angle of 0 to 45 ° from the (n−1) th growth surface and at an angle of 60 to 90 ° from the {0001} plane is defined as the nth growth surface. A seed crystal is produced from the (n-1) th growth crystal, and a SiC single crystal is grown on the nth growth surface of the nth seed crystal to produce the nth growth crystal. A SiC wafer with an epitaxial film, characterized in that a SiC wafer having a film formation surface exposed from a (N + α) th growth crystal in which n = N + α is formed, and an epitaxial film is formed on the film formation surface of the SiC wafer. Wafer manufacturing method. 3. The method for producing an SiC wafer with an epitaxial film according to claim 1, wherein a sublimation reprecipitation method is used for growing the SiC single crystal on the various crystals. 4. The method according to claim 1, wherein
The method for producing a SiC wafer with an epitaxial film, wherein the thickness of each of the various crystals is 1 mm or more. 5. The method according to any one of claims 1 to 4,
The film-forming surface has an offset angle of 0.
A SiC wafer with an epitaxial film, which is a surface having an angle of 5 ° to 20 °, a surface having an offset angle of 20 ° or less from a {1-100} plane, or a surface having an offset angle of 20 ° or less from a {11-20} plane. Manufacturing method. 6. The method according to any one of claims 1 to 5,
The epitaxial film is formed by CVD method, PVE
Method, or a method for manufacturing an SiC wafer with an epitaxial film, characterized by using the LPE method. 7. The method according to any one of claims 1 to 6,
1 × 10 ¹³ to 1 × 10 ²⁰ / cm in the above epitaxial film
^A method for producing a SiC wafer with an epitaxial film, which comprises containing the impurity of ³ . 8. The Si with an epitaxial film according to claim 7, wherein the impurity contains at least one of nitrogen, boron and aluminum as a constituent element thereof.
C wafer manufacturing method. 9. A SiC wafer with an epitaxial film, which is manufactured by the manufacturing method according to any one of claims 1 to 8. 10. An S manufactured by using the SiC wafer with an epitaxial film according to claim 9.
iC electronic device.