JP6133127B2 - SiC single crystal and method for producing the same - Google Patents

Description

  The present invention relates to a SiC single crystal and a method for manufacturing the same, and more specifically, a method for manufacturing a SiC single crystal capable of efficiently reducing both edge dislocations and basal plane dislocations, and by such a method. It relates to the obtained SiC single crystal.

In recent years, SiC single crystals have attracted attention as power semiconductor applications. However, since there are still high-density dislocations in the SiC single crystal, a method for producing a single crystal with fewer dislocations is required for its practical use. The main dislocation species in SiC are micropipes, threading-type screw dislocations (hereinafter also simply referred to as “spiral dislocations”), basal plane dislocations, threading-type edge dislocations (hereinafter simply referred to as “edge dislocations”). Is mentioned.
The crystal structure of the SiC single crystal used for power semiconductors is hexagonal. Therefore, the micropipe and the screw dislocation have a Burgers vector in the c-axis direction. On the other hand, basal plane dislocations and edge dislocations have Burgers vectors in the a-axis direction.

  Recently, as the quality of SiC has been improved, the micropipes that have been regarded as the most problematic in the past have almost been eradicated. As for the screw dislocations, if the extension direction is changed to the basal plane inward direction by so-called a-plane growth and then c-plane offset growth is performed, it can be discharged out of the crystal relatively easily (Patent Document 1). ).

  Thus, a reduction method is being established for dislocations having a Burgers vector in the c-axis direction. However, methods for reducing basal plane dislocations and edge dislocations having a Burgers vector in the a-axis direction have not been established, and usually remain at a high density as compared with spiral dislocations.

On the other hand, in Patent Documents 2 and 3, in the case where the cutting of the seed crystal from the SiC single crystal and the growth of the single crystal on the growth surface of the seed crystal are repeated N times, the (n-1) th growth time The angle difference between the offset direction in and the offset direction during the n-th growth is changed in the range of 45 ° to 135 °.
The document describes that a single crystal with few micropipes and dislocations can be obtained by such a method.

  In Patent Documents 2 and 3, the angular difference in the offset direction between the immediately preceding growth processes is limited to a predetermined range. However, there is no limitation on the offset direction that can be taken in the total number of N growth steps, and the offset direction can be set in all the {0001} in-plane directions. Therefore, in the method described in this document, there is a limit to the reduction of basal plane dislocations and edge dislocations for reasons described later (the direction of dislocation discharge is not constant). Further, in Patent Document 3, the offset angle of the growth surface is large, and the screw dislocations are extremely reduced in the upstream portion of the offset, which may cause heterogeneous polymorphism.

Further, Patent Document 4 describes a method of repeating growth by changing the offset angle to be smaller when repeating offset growth. Further, this document shows that the offset direction is matched within a range of ± 45 ° with respect to the immediately preceding offset direction.
However, this document does not presuppose changing the offset direction. Therefore, in the method described in this document, there is a limit to the reduction of basal plane dislocations and edge dislocations for the reasons described later (a discharge effect cannot be obtained for all dislocations).

Japanese Patent Laid-Open No. 2003-119097 JP 2003-321298 A JP 2006-225232 A JP 2012-116676 A

The problem to be solved by the present invention is to provide a method for producing a SiC single crystal capable of efficiently reducing both edge dislocations and basal plane dislocations.
Another object of the present invention is to provide a SiC single crystal obtained by such a method.

In order to solve the above-described problems, the gist of a method for producing an SiC single crystal according to the present invention is as follows.
(1) The method for producing the SiC single crystal is as follows:
(A) a seed crystal cutting step of cutting a c-plane growth seed crystal having a growth plane offset angle of 1 ° to 30 ° from a single crystal;
(B) A c-plane growth step that repeats n times (n ≧ 2) a c-plane growth step of growing a new single crystal on the growth surface as a c-plane is provided.
(2) The offset direction of the growth surface of the seed crystal is changed in the {0001} plane at least once among the n repetitions.
(3) The maximum angle difference in the offset direction of the growth surface of the seed crystal is 120 ° or less.
However, the “maximum angle difference in the offset direction” means the offset direction of the growth surface during the k-th (1 ≦ k ≦ n) c-plane growth and the m-th (1 ≦ m ≦ n, m ≠ k) c. The maximum value of the difference in angle between the growth surface and the offset direction during surface growth.

The first of the SiC single crystals according to the present invention is:
Of the three dislocations having any one of the three <11-20> Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as a basal plane dislocation, and
(B) The gist is that at least a part of the remaining two dislocations mainly exists as edge dislocations.

The second of the SiC single crystals according to the present invention is:
Of the three dislocations having any one of the three <11-20> Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as an edge dislocation, and
(B) The gist is that at least a part of the remaining two dislocations mainly exists as basal plane dislocations.

Furthermore, the third of the SiC single crystal according to the present invention is:
Of the three dislocations having any one of the three <11-20> Burgers vectors in the crystallographically equivalent direction, the gist is to have at least a portion where two dislocations mainly exist .

When repeating the cutting of a seed crystal for c-plane growth from a SiC single crystal and the c-plane growth of the single crystal on the growth surface of the seed crystal, the offset direction of the growth surface is changed at least once, and all If the maximum angle difference in the offset direction is limited to 120 ° or less throughout the process, edge dislocations and basal plane dislocations can be efficiently reduced.
this is,
(A) Every time the growth is performed by changing the offset direction, only dislocations having a specific Burgers vector are preferentially discharged downstream in the offset direction, and
(B) The offset direction does not become the opposite direction throughout the entire growth process, or because the components in the opposite direction are sufficiently small, the dislocations that have been discharged out of the single crystal return to the center direction of the single crystal. Because there is no
it is conceivable that.

It is the transmission topograph image (left figure: (10-10) plane diffraction image, right figure: (0-110) plane diffraction image) of the same area | region whose offset direction of a growth surface is a [2-1-10] direction. It is a schematic diagram of the process used as dislocation distribution like FIG. It is the reflection topograph image (left figure: (11-28) plane diffraction image, right figure: (2-2010) plane diffraction image) of the same area | region whose offset direction of a growth surface is a [1-100] direction. FIG. 3 is a schematic diagram showing a process of dislocation distribution as shown in FIG. It is a schematic diagram for demonstrating the change range of an offset direction.

It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 1st Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 2nd Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 3rd Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 4th Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 5th Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 6th Embodiment of this invention. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 7th Embodiment of this invention. It is a schematic diagram for demonstrating the change range of an offset direction. It is process drawing of the manufacturing method of the SiC single crystal which concerns on the 8th Embodiment of this invention. It is a schematic diagram for demonstrating the change range of an offset direction.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Definition of terms]
“C-plane” refers to the {0001} plane.
“A plane substantially parallel to the c-plane” refers to a plane having an offset angle of 30 ° or less with respect to the c-plane.
“C-plane growth” refers to growing a single crystal using a plane substantially parallel to the c-plane as a growth plane.

The “growth plane” refers to a plane whose normal vector has a growth component of the single crystal in the surface of the seed crystal or single crystal.
“Growth direction” refers to the direction of macro growth of the entire single crystal. For example, when the growth surface is composed of a single plane, the growth direction is a direction perpendicular to the growth surface.
“Offset angle” refers to an angle formed by a normal vector of a certain surface and a normal vector of a {0001} surface.
The “offset direction” refers to a direction parallel to a vector obtained by projecting the normal vector of the growth surface onto the {0001} plane.
The “downstream side in the offset direction” refers to the side on which the front end of a vector obtained by projecting the normal vector of the growth surface onto the {0001} plane faces.
The “upstream side in the offset direction” refers to the side opposite to the side on which the tip of the vector obtained by projecting the normal vector of the growth plane onto the {0001} plane is facing.
“The most upstream part in the offset direction” means a region where the uppermost {0001} plane exists in the growth direction crystallographically.

“Growth plane offset direction (or offset angle)” means that the growth plane of the seed crystal is composed of a single plane or a plurality of planes, and has the most upstream portion in the offset direction at the end of the growth plane (in particular, offset This refers to the substrate (when the main growth direction of the crystal and the c-axis direction is an angle of 1 ° or more), and the main offset direction (or offset angle) of the growth surface.
The “maximum angle difference in the offset direction” means the offset direction of the growth surface during the k-th (1 ≦ k ≦ n) c-plane growth and the m-th (1 ≦ m ≦ n, m ≠ k) c-plane growth. The maximum value of the difference in angle between the offset direction of the growth surface at the time.

"Main offset direction (offset angle)"
(A) When the growth surface consists of a single plane, the offset direction (offset angle) of the single plane,
(B) When the growth surface is composed of a plurality of planes, the offset direction (offset angle) of the plane having the largest area,
(C) When the growth surface includes a curved surface, the offset direction (offset angle) of the apex portion in the region of 50% of the central portion when considering the apex of the square of 10 mm square on the plane perpendicular to the growth direction ) Average,
Say.
In the case where the growth surface of the seed crystal is composed of a plurality of planes and has the most upstream portion in the offset direction at the approximate center of the growth surface (in particular, the angle between the main direction of the crystal and the c-axis direction is 1 ° The “main offset direction (offset angle)” means the offset direction (or offset angle) of each area of each plane. When the boundary line between planes changes due to repeated c-plane growth, it refers to the offset direction (or offset angle) of each further subdivided region (see FIGS. 13 and 15).

The “basal plane dislocation” is
(A) a screw dislocation whose dislocation line is parallel to the {0001} plane and whose Burgers vector is parallel to the {0001} plane;
(B) an edge dislocation whose dislocation line is parallel to the {0001} plane and whose Burgers vector is parallel to the {0001} plane; or
(C) Mixed rearrangement of (a) and (b).

“Through-type edge dislocation (hereinafter also simply referred to as“ edge dislocation ”)” means that the dislocation line is substantially perpendicular to the {0001} plane and the Burgers vector is parallel to the {0001} plane. An edge dislocation.
“Threading type screw dislocation (hereinafter also simply referred to as“ screw dislocation ””) is a screw dislocation in which the dislocation line is substantially perpendicular to the {0001} plane and the Burgers vector is perpendicular to the {0001} plane. Say.
“The part where (specific dislocations) exist mainly”
(A) a region in which 80% or more of dislocations having a crystallographically equivalent Burgers vector are dislocations having a Burgers vector in a specific direction, or
(B) a region in which 80% or more of the dislocations having a Burgers vector in a specific direction are specific dislocation species;
(Hereinafter, such a region is also referred to as a “localized region”).
“Having at least a part (the unevenly distributed region)” means that when a single crystal is divided into regions having a size of 5 mm ² , one or more of the divided regions are unevenly distributed regions.

[2. Manufacturing method of SiC single crystal]
The manufacturing method of the SiC single crystal which concerns on this invention is equipped with the following structures.
(1) The method for producing the SiC single crystal is as follows:
(A) cutting a seed crystal for c-plane growth having an offset angle of 1 ° or more and 30 ° or less from a single crystal;
(B) a c-plane growth step that repeats n times (n ≧ 2) a step of growing a new single crystal on the growth surface as a c-plane.
(2) The offset direction of the growth surface of the seed crystal is changed in the {0001} plane at least once among the n repetitions.
(3) The maximum angle difference in the offset direction of the growth surface of the seed crystal is 120 ° or less.
However, the “maximum angle difference in the offset direction” means the offset direction of the growth surface during the k-th (1 ≦ k ≦ n) c-plane growth and the m-th (1 ≦ m ≦ n, m ≠ k) c. The maximum value of the difference in angle between the growth surface and the offset direction during surface growth.

[2.1. Seed crystal cutting process]
First, a c-plane growth seed crystal having a growth plane offset angle of 1 ° to 30 ° is cut out from the single crystal (seed crystal cutting step).
If the offset angle of the growth surface of the seed crystal is too small, the dislocation discharging effect cannot be obtained. Accordingly, the offset angle of the growth surface needs to be 1 ° or more. In order to prevent the occurrence of heterogeneous polymorphism due to the formation of facets at a plurality of locations or in a wide area in the initial stage of growth, the offset angle of the growth surface is preferably 2 ° or more.
When a wafer having the same offset angle as that of the seed crystal is taken out from the growth crystal, the yield is highest. By setting the offset angle to 4 °, the dislocation discharge effect can be obtained more easily, and at the same time, a wafer having an offset angle of 4 °, which is a general wafer standard, can be obtained with a high yield. With such a wafer, an epitaxial film with less step bunching can be formed.

On the other hand, if the offset angle becomes too large, a larger growth height is required to completely discharge the dislocations out of the single crystal. Therefore, the offset angle needs to be 30 ° or less. Further, when the offset angle is less than 20 °, the screw dislocation density in the upstream portion of the offset is unlikely to decrease, and the heterogeneous polymorphism hardly occurs. Furthermore, since the general standard of the wafer offset angle is 4 to 8 °, if the offset angle of the seed crystal is 10 ° or less, the yield of wafer removal can be increased.
In the case where the offset angle of the growth surface is 20 ° or more and 30 ° or less, at least the facet forming portion on the upstream side of the offset (region corresponding to the length of about one fifth of the length of the seed crystal in the offset direction) In order to maintain the density of screw dislocations for polymorph control, the offset angle is preferably partially less than 20 °.
The offset direction of the growth surface of the seed crystal will be described later.

In the repeated c-plane growth step, the seed crystal used for the second and subsequent c-plane growth is cut out from the single crystal obtained in the immediately preceding c-plane growth step.
On the other hand, the single crystal for cutting out the first seed crystal for c-plane growth is not particularly limited, and various single crystals can be used.

As a single crystal for cutting out the first seed crystal for c-plane growth,
(1) a single crystal obtained by the c-plane growth method,
(2) A single crystal obtained by growing a single crystal on the growth surface (a-plane growth) using a seed crystal (B) having an offset angle of 60 ° to 90 ° on the growth surface,
and so on.
Unlike the c-plane grown crystal, the a-plane grown crystal has almost no screw dislocations, so the entanglement with the basal plane dislocation is reduced, and the basal plane dislocation easily extends linearly in the offset direction, thereby efficiently discharging the dislocation. be able to. A single crystal obtained by repeating a-plane growth in directions orthogonal to each other (repeated a-plane grown crystal) has a lower density of other dislocation species than a simple a-plane grown crystal. Therefore, the a-plane grown crystal (including the repeated a-plane grown crystal) is suitable as a single crystal for cutting out the first seed crystal.

  Further, the offset direction of the seed crystal for the first c-plane growth is preferably substantially perpendicular to the growth direction for obtaining a single crystal for cutting the seed crystal for the first c-plane growth. This is because the dislocation density exposed on the seed crystal surface is smaller when the offset direction is perpendicular to the final a-plane growth direction.

The growth surface of the seed crystal is
(A) one having a single or plural planes so as to have the most upstream portion in the offset direction at the end thereof, or
(B) What is constituted by a plurality of planes so as to have the most upstream portion in the offset direction at its approximate center,
Either may be sufficient.
In the latter case, the set of planes having different offset directions constituting the growth surface of the seed crystal is preferably 3 or more and 11 or less. If the set of planes is set to 2 or less, there is a place where a region where the rotation angle of the offset direction change exceeds 120 ° occurs depending on the region. In addition, since the most upstream part in the offset direction is not a point but a line, an unstable linear facet is generated at the initial stage of growth, so that heterogeneous polymorphism is also likely to occur.
On the other hand, if the set of planes having different offset directions is set to 12 or more, the change in the offset direction is 30 ° at the maximum in all regions, and the effect of the change in the offset direction cannot be obtained.

[2.2. c-plane growth process]
Next, a new single crystal is grown on the c-plane on the growth surface of the cut seed crystal. The method for growing the single crystal is not particularly limited, and various methods can be used. Examples of single crystal growth methods include sublimation reprecipitation, CVD, and solution.

Even if the growth surface of the seed crystal is a flat surface, the most advanced surface of the single crystal that is being grown (the growth surface of the single crystal) follows an isothermal surface, and thus is not usually a flat surface. In order to efficiently reduce the edge dislocations and the screw dislocations, the c-plane growth process requires that the offset direction change angle and the maximum angle difference are also in the offset direction of the seed crystal growth surface even in the growth surface of the single crystal during the growth. It is preferable to grow a new single crystal on the growth surface so as to be maintained equal to the maximum angle difference.
Here, “equivalent” means that the maximum angle difference in the offset direction in a region of 50% of the growth surface in the middle of growth is ± 20% or less with respect to the maximum angle difference in the offset direction of the growth surface of the seed crystal. Say.

As a method of growing while maintaining the maximum angle difference in the offset direction of the growth surface of the single crystal within a predetermined range,
(1) A method in which a soaking plate is disposed above the growth crystal and the single crystal is grown so that the growth surface of the single crystal is maintained substantially parallel to the growth surface of the seed crystal.
(2) A method of growing a single crystal so that the growth surface of the single crystal is maintained substantially parallel to the growth surface of the seed crystal by moving the growth crucible up and down with respect to the heater or the like during the growth. ,
(3) The radial distribution of heat dissipation from the back surface of the seed crystal holding member is adjusted during growth using the heat dissipation control member, and the growth surface of the single crystal is maintained substantially parallel to the growth surface of the seed crystal. A method of growing a single crystal,
and so on.

[2.3. Repeat count]
As will be described later, when a single crystal is grown on a growth surface having a specific offset direction, dislocations having a Burgers vector in a specific direction can be preferentially discharged out of the single crystal. In order to obtain such an effect, the number of repetitions n of seed crystal cutting and c-plane growth needs to be n ≧ 2. The number of repetitions n is more preferably n ≧ 3. In order to reduce edge dislocations and basal plane dislocations, the larger the number of repetitions n, the better.

Burgers vectors of edge dislocations and basal plane dislocations existing in the SiC single crystal are each one of three crystallographically equivalent <11-20> directions (positive and negative are the same). have.
When a single crystal is grown on a growth surface having a specific offset direction in a c-plane, and the growth height is sufficiently larger than the diameter of the seed crystal, a Burgers vector in a specific direction is obtained by a single c-plane growth. Dislocations possessed can be completely discharged out of the crystal.

However, in practice, the growth height cannot be increased without limit. Therefore, as the diameter of the seed crystal increases or the offset angle of the growth surface of the seed crystal increases, it is more difficult to completely discharge dislocations having a Burgers vector in a specific direction to the outside of the crystal by one c-plane growth. Become.
Therefore, in such a case, it is preferable that the c-plane growth in the same offset direction is repeated a plurality of times simultaneously with changing the offset direction so as to satisfy the conditions described later. Further, when it is difficult to take out a new seed crystal having a largely different offset direction from the grown crystal due to insufficient growth height, it is preferable to change the offset direction in small increments.

[2.4. Offset direction]
[2.4.1. Relationship between change of offset direction and reduction of dislocation density]
Both basal plane dislocations and edge dislocations (penetrating edge dislocations) can be converted to each other. Therefore, if edge dislocations are converted into basal plane dislocations, when crystals are grown substantially parallel to the c-axis direction, they can be discharged out of the crystal as in the case of spiral dislocations (through-type screw dislocations).
However, the Burgers vectors for edge dislocations and basal plane dislocations are not oriented in a single direction (c-axis direction) as in the case of spiral dislocations, but are three crystallographically equivalent Burgers vectors in the a-axis direction. Can take. Therefore, the conversion rate of edge dislocations to basal plane dislocations, the rate at which basal plane dislocations remain as basal plane dislocations without being converted to edge dislocations, and the discharge out of the crystal accompanying this, In addition to the optimum magnitude of the offset angle, there is an optimum offset direction depending on the direction of each Burgers vector.

  Specifically, if the direction of the Burgers vector for edge dislocations and basal plane dislocations is more parallel to the offset direction of the growth surface during growth, it becomes a basal plane dislocation and downstream in the offset direction. When there is a strong tendency to be discharged and it is oriented more vertically, it becomes difficult to be discharged due to edge dislocation. Below, the difference in dislocation conversion and ease of discharge due to the difference in Burgers vector orientation is shown.

FIG. 1 shows a transmission topographic image of a region in which the growth plane offset direction is the [2-1-10] direction. These are topographic images obtained by two crystallographically equivalent diffractions ((10-10) plane diffraction and (0-110) plane diffraction) for the same region. In the (10-10) plane diffraction image on the left side, basal plane dislocations extending almost parallel to the [2-1-10] direction which is the offset direction are observed. On the other hand, the basal plane dislocation is not observed in the (0-110) plane diffraction image on the right side although it is the same region (corresponding to the basal plane dislocation in the (10-10) plane diffraction image on the left side). (Show the dotted line with dotted lines).
In the (0-110) plane diffraction, the diffraction g vector is the [0-110] direction, and the dislocation having the Burgers vector in the direction parallel to the [2-1-10] direction perpendicular thereto is extinguished. It is a condition. This suggests that the basal plane dislocation observed in the left (10-10) plane diffraction image has a Burgers vector in the [2-1-10] direction.
Also, the lower the screw dislocation density, the stronger the tendency for such a dislocation structure in which Burgers vectors are biased. When the screw dislocation density exceeded 100 / cm ² , no clear tendency was observed. This is because the basal plane dislocation entangled with the screw dislocation (pinning effect of dislocation) becomes remarkable.

FIG. 2 shows a process of dislocation distribution as shown in FIG. In the seed crystal, there exist dislocations having three equivalent <11-20> Burgers vectors (FIG. 2 (a): edge dislocation, FIG. 2 (a '): basal plane dislocation). And they are exposed on the surface.
Since the offset direction of the growth surface is the [2-1-10] direction, the dislocation having the Burgers vector in the [2-1-10] direction parallel to the offset direction is the basis at the interface between the seed crystal and the growth crystal. It becomes a plane dislocation.
On the other hand, dislocations having Burgers vectors in the [1-210] and [11-20] directions that form an angle of 60 ° with the offset direction become edge dislocations (FIGS. 2B and 2B ′). .
The basal plane dislocations tend to be oriented and discharged in the offset direction, and the edge dislocations remain in the crystal while extending in the c-axis direction (FIG. 2 (c)).

FIG. 3 shows a reflection topographic image of a region where the growth plane offset direction is the [1-100] direction. These are topographic images of (11-28) plane diffraction and (2-2010) plane diffraction obtained for the same region.
In the (11-28) plane diffraction image on the left side, many edge dislocations are recognized as indicated by white circles. On the other hand, in the (2-2010) plane diffraction image on the right side, most of the edge dislocations disappear even though they are in the same region (the edge dislocation in the (11-28) plane diffraction image on the left side. The part corresponding to is indicated by a dotted white circle).

In (2-2010) plane diffraction, the g vector of diffraction is the [1-100] direction on the paper surface, and the edge dislocation having a Burgers vector in a direction parallel to the [11-20] direction perpendicular thereto is expressed. The diffraction conditions disappear. Therefore, most of the edge dislocations observed in the (11-28) plane diffraction image on the left side have a Burgers vector in the [11-20] direction.
Also, the lower the screw dislocation density, the stronger the tendency for such a dislocation structure in which Burgers vectors are biased. When the screw dislocation density exceeded 100 / cm ² , no clear tendency was observed.

FIG. 4 shows a process of dislocation distribution as shown in FIG. In the seed crystal, there exist dislocations having three equivalent <11-20> Burgers vectors (FIG. 4 (a): edge dislocation, FIG. 4 (a ′): basal plane dislocation). And they are exposed on the surface.
Since the offset direction of the growth plane is the [1-100] direction, at the interface between the seed crystal and the growth crystal, the [2-1-10] direction and the [1- A dislocation having a Burgers vector in the 210] direction becomes a basal plane dislocation.
On the other hand, a dislocation having a Burgers vector in the [11-20] direction that forms an angle of 90 ° with the offset direction becomes an edge dislocation (FIGS. 4B and 4B ′).
The basal plane dislocations tend to be oriented and discharged in the offset direction, and the edge dislocations remain in the crystal while extending in the c-axis direction (FIG. 4C). In the upper part of the grown crystal, the basal plane dislocation is completely discharged from this region, and only the dislocation having the Burgers vector in the [11-20] direction remains (FIG. 4D).

  From these facts, in order to obtain the effect of discharging out of the crystal for all edge dislocations and basal plane dislocations, it is not necessary to repeat growth in a single offset direction, but to combine growth in different offset directions. It is effective to repeat growth. The three directions of Burgers vectors that are crystallographically equivalent differ in direction every 60 ° (or 120 ° unless positive and negative are distinguished). When repeating the growth, it is preferable to change the offset direction so as to act on these three types of Burgers vectors.

  However, if there is no restriction on the angular range of the direction when changing the offset direction, the basal plane dislocation that was being ejected out of the crystal during a certain c-plane growth may cause the basal plane dislocation in the next different c-plane growth. In some cases, the extension direction is changed to the inner side of the crystal and the dislocation density cannot be reduced. This is because when two offset directions having different directions are compared, the extension direction of dislocations is more likely to change in the reverse direction as the components in the opposite directions increase. Since basal plane dislocations are converted to edge dislocations relatively easily, they are difficult to be discharged out of the crystal at a low growth height like spiral dislocations. Therefore, the angle range in the offset direction becomes more important.

[2.4.2. Change range of offset direction]
FIG. 5 is a schematic diagram for explaining a change range in the offset direction.
For example, an edge dislocation (or basal plane dislocation) having a Burgers vector parallel to the [11-20] direction is more easily converted to a basal plane dislocation as the offset direction is closer to the [11-20] direction ( Or, the basal plane dislocation remains.) As a result, the dislocation having such a barber vector is discharged very efficiently downstream in the offset direction during the growth process of the single crystal.

As the offset direction deviates from the [11-20] direction, dislocations having Burgers vectors parallel to the [11-20] direction are less likely to be discharged.
However, if the offset direction is within a range of ± 30 ° from the [11-20] direction, dislocations having Burgers vectors parallel to the [11-20] direction are located downstream of the offset direction in the growth process of the single crystal. It is discharged efficiently.

On the other hand, as the offset direction exceeds ± 30 ° from the [11-20] direction and approaches 60 °, dislocations having Burgers vectors parallel to the [11-20] direction are gradually discharged downstream in the offset direction. It becomes difficult.
Further, when the offset direction is inclined by about 60 ° or more from the [11-20] direction, the dislocation having a Burgers vector parallel to the [11-20] direction exists as an edge dislocation, or a basal plane dislocation. Is converted into edge dislocations and almost no discharge occurs.
Further, when the offset direction is tilted 90 ° from the [11-20] direction, almost no discharge occurs. When the offset direction exceeds 120 °, dislocations having Burgers vectors parallel to the [11-20] direction are gradually increased again. After being activated, dislocations begin to be discharged in the reverse direction ([-1-120] direction).

Therefore, if the components in the opposite direction are not generated between the offset directions, or if the components in the opposite direction are reduced, the dislocations that are turned downstream in the offset direction during growth in a certain offset direction may be It is possible to avoid turning in the opposite direction when growing in the offset direction.
That is, edge dislocations and basal plane dislocations can be efficiently reduced by satisfying the following two conditions regarding the offset direction.
(A) The growth direction of the seed crystal is changed in the offset direction within the {0001} plane at least once among the n repetitions.
(B) The maximum angle difference in the offset direction of the growth surface of the seed crystal is 120 ° or less.

Even when the maximum angular difference in the offset direction is small, dislocations having Burgers vectors parallel to at least one of the three <11-20> directions crystallographically equivalent are activated. At least one of the three types of dislocations can be reduced.
As the maximum angle difference in the offset direction increases, two or more of the three types of dislocations are activated. In order to efficiently discharge two or more kinds of dislocations, the maximum angle difference in the offset direction is preferably 30 ° or more. The maximum angle difference in the offset direction is more preferably 60 ° or more. When two <1-100> directions having an angle difference of 60 ° are selected as offset directions, the three <11-20> directions each have an inclination of 30 ° with respect to at least one offset direction.

When the maximum angle difference in the offset direction is 120 °, three types of dislocations can be efficiently discharged out of the crystal. In particular, if the offset direction of the growth surface of the seed crystal is changed between three adjacent <11-20> directions ± 30 °, three types of dislocations can be efficiently discharged out of the crystal. it can. However, as the maximum angular difference in the offset direction increases, a higher growth height is required to repeatedly cut out a seed crystal having a growth surface having a predetermined area or more.
Therefore, the maximum angle difference in the offset direction is preferably 90 ° or less.

[2.4.3. Specific example of changing the offset direction]
The offset direction in each c-plane growth process and the change order of the offset direction are not particularly limited as long as the above-described conditions are satisfied.

[A. Specific Example 1]
In the example shown in FIG. 5A, the offset direction is set between the [2-1-10] direction and the [-12-10] direction. When the offset direction is represented by a rotation angle θ with reference to the x-axis ([1-100] direction), the offset direction θ in FIG. 5A is in a range of θ = 30 ° to 150 °.
In this case, out of n repetitions, at least one c-plane growth in which the offset direction θ is 30 ° ([2-1-10] direction) and the offset direction θ is 150 ° ([-12-10]). Direction), at least one c-plane growth is performed.

When the c-plane growth is performed three times or more, the offset direction θ of the remaining c-plane growth process can be arbitrarily selected according to the purpose.
For example, if at least one c-plane growth with an offset direction θ of 90 ° ([11-20] direction) ± 30 ° is performed, three types of dislocations can be efficiently discharged out of the crystal.
Moreover, when the offset direction θ is set between 30 ° ([2-1-10] direction) and 90 ° ([11-20] direction), two types of dislocations are generated depending on the magnitude of the offset direction θ. The reduction rate can be adjusted.

[B. Specific Example 2]
On the other hand, in the example shown in FIG. 5B, the offset direction θ is set in a range of θ = −15 ° to 105 °. In this case, among the n repetitions, at least one c-plane growth with an offset direction θ of −15 ° and at least one c-plane growth with an offset direction θ of 105 ° are performed.
In the c-plane growth of θ = −15 °, dislocations having a Burgers vector parallel to the [1-210] direction are mainly discharged out of the crystal. On the other hand, in the c-plane growth of θ = 105 °, dislocations having a Burgers vector parallel to the [11-20] direction are mainly discharged out of the crystal.

When the c-plane growth is performed three times or more, the offset direction θ of the remaining c-plane growth process can be arbitrarily selected according to the purpose.
For example, when at least one c-plane growth with an offset direction θ of 30 ° ([2-1-10] direction) ± 30 ° is performed, three types of dislocations can be efficiently discharged out of the crystal.
Moreover, when the offset direction θ is set between 30 ° ([2-1-10] direction) and 90 ° ([11-20] direction), two types of dislocations are generated depending on the magnitude of the offset direction θ. The reduction rate can be adjusted.

[C. Specific Example 3]
Further, in the example shown in FIG. 5C, the offset direction θ is set in a range of θ = −60 ° to 60 °. In this case, among the n repetitions, at least one c-plane growth in which the offset direction θ is −60 ° and at least one c-plane growth in which the offset direction θ is 60 ° are performed.
In the c-plane growth of θ = −60 °, dislocations having Burgers vectors parallel to the [1-210] direction and the [−1-120] direction are discharged almost uniformly from the crystal. Similarly, in the c-plane growth of θ = 60 °, dislocations having Burgers vectors parallel to the [11-20] direction and the [2-1-10] direction are discharged out of the crystal almost equally. .

When the c-plane growth is performed three times or more, the offset direction θ of the remaining c-plane growth process can be arbitrarily selected according to the purpose.
For example, when at least one c-plane growth with an offset direction θ of 0 ° ([1-100] direction) ± 30 ° is performed, two types of dislocations out of the crystal are selectively out of the crystal. Can be discharged.

[D. Other specific examples]
Although not shown, the offset direction θ may be set in a range of θ = 0 ° to 90 °. In this case, of the n repetitions, at least one c-plane growth with an offset direction θ of 0 ° and at least one c-plane growth with an offset direction θ of 90 ° are performed.
In the c-plane growth of θ = 0 °, two types of dislocations having directions parallel to the [2-1-10] direction and the [1-210] direction, respectively, are discharged almost uniformly out of the crystal. On the other hand, in the c-plane growth of θ = 90 °, dislocations having a Burgers vector parallel to the [11-20] direction are mainly discharged out of the crystal.

[3. SiC single crystal]
As described above, when the method according to the present invention is used or applied, the dislocation species discharged out of the crystal can be arbitrarily selected according to the magnitude of the offset direction θ.
That is, when the offset direction θ is optimized within the range of the maximum angle difference of 120 ° or less in the offset direction, only a part of the three types of dislocation species is selectively discharged out of the crystal, or all the dislocations The seed can be discharged out of the crystal.

For example, using the method according to the present invention, of the three dislocations having any one of three <11-20> direction Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as a basal plane dislocation, and
(B) A SiC single crystal having at least a portion where the remaining two dislocations mainly exist as edge dislocations can be produced.

In such a substrate taken out from the SiC single crystal, the direction of the basal plane dislocation is aligned. Therefore, by adjusting the pattern of the device and the direction of the basal plane dislocation (for example, the basal plane dislocation is prevented from being exposed to the gate oxide interface by making the gate oxide interface of the transistor parallel to the basal plane dislocation) Device characteristics can be improved.
Further, a substrate having a basal plane dislocation Burgers vector and an offset direction perpendicular to the offset angle and having a relatively small offset angle can be taken out. When an epitaxial film is formed on this, all of the basal plane dislocations harmful to the device can be converted into edge dislocations (the edge dislocations exist as edge dislocations because of the low off-angle). Thereby, the SiC substrate without a basal plane dislocation is obtained.
Such a SiC single crystal can be manufactured, for example, by performing at least one c-plane growth with θ = 90 °.

Alternatively, of the three dislocations having any one of the three <11-20> Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as an edge dislocation, and
(B) A SiC single crystal having at least a portion where the remaining two dislocations mainly exist as basal plane dislocations can be produced.

When a substrate having an offset direction parallel to the direction of the Burgers vector of edge dislocations and a relatively small offset angle is taken out from such a SiC single crystal and an epitaxial film is formed thereon, most of the basal plane dislocations are formed. Can be converted into edge dislocations. Thereby, an SiC substrate having an extremely small basal plane dislocation density can be obtained.
Such a SiC single crystal can be manufactured, for example, by performing at least one c-plane growth with θ = 0 °.

Alternatively, a SiC single crystal having at least part of a portion where two dislocations mainly exist among three dislocations having any one of three <11-20> Burgers vectors crystallographically equivalent Can be manufactured. In this case, both of the two dislocations can be produced by either an SiC single crystal having edge dislocations or an SiC single crystal in which one of the two dislocations is a basal plane dislocation.

In the substrate taken out from the SiC single crystal in which both of the two dislocations are edge dislocations, there is no basal plane dislocation. Therefore, a bipolar device with little forward deterioration can be easily manufactured. In addition, since the edge dislocation density is also reduced as compared with the prior art, the reliability of transistors and diodes can be improved, and the leakage current can be greatly reduced.
In a SiC single crystal in which one of the two dislocations is a basal plane dislocation, the direction of the basal plane dislocation is aligned. Therefore, the device characteristics can be improved by adjusting the pattern of the device and the direction of the basal plane dislocation. In addition, since the edge dislocation density is significantly smaller than that of the prior art, the reliability can be further improved and the leakage current can be further reduced.

An SiC single crystal in which both of the two dislocations are edge dislocations can be produced, for example, by performing c-plane growth with θ = 90 ° until a specific dislocation species is completely discharged out of the crystal. it can.
An SiC single crystal in which one of the two dislocations is a basal plane dislocation, for example, by performing at least one c-plane growth with θ = 90 ° and at least one c-plane growth with θ = 120 °. Can be manufactured.

  Further, when a SiC single crystal is manufactured using the method according to the present invention, if a seed crystal having a low density of screw dislocations having a Burgers vector in the c-axis direction is used, the entanglement between the basal plane dislocation and the screw dislocation is reduced. , Dislocations can be reduced more efficiently.

[4. Action]
When repeating the cutting of a seed crystal for c-plane growth from a SiC single crystal and the c-plane growth of the single crystal on the growth surface of the seed crystal, the offset direction of the growth surface is changed at least once, and all If the maximum angle difference in the offset direction is limited to 120 ° or less throughout the process, edge dislocations and basal plane dislocations can be efficiently reduced.
this is,
(A) Every time the growth is performed by changing the offset direction, only dislocations having a specific Burgers vector are preferentially discharged downstream in the offset direction, and
(B) The offset direction does not become the opposite direction throughout the entire growth process, or because the components in the opposite direction are sufficiently small, the dislocations that have been discharged out of the single crystal return to the center direction of the single crystal. Because there is no
it is conceivable that.

Example 1
FIG. 6 shows a process chart of the method for manufacturing the SiC single crystal according to the first embodiment of the present invention.
FIG. 6A shows a schematic diagram of a SiC single crystal before c-plane growth. In the crystal, there are edge dislocations (indicated by “⊥” in FIG. 6; the same applies hereinafter) having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 90 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface as a c-plane, θ = 90 as shown in FIG. Edge dislocations having a Burgers vector in the 90 ° direction are converted into basal plane dislocations (indicated by an arrow and a spiral wound around the arrow in FIG. 6, the same applies hereinafter).

When the c-plane growth of θ = 90 ° is continued, the basal plane dislocation is gradually discharged downstream ([11-20] direction) in the offset direction, as shown in FIG. 6C. When the c-plane growth at θ = 90 ° is further continued, the basal plane dislocation is completely discharged downstream in the offset direction as shown in FIG. 6 (d). The plane dislocation is indicated by a broken line.
6B to 6D may be performed by one c-plane growth, or may be performed by repeating seed crystal cutting and c-plane growth a plurality of times.

FIG. 6 (e) shows a schematic diagram of the SiC single crystal obtained in FIG. 6 (d). In this case, of the three crystallographically equivalent directions, only the edge dislocation having the Burgers vector in the θ = 90 ° direction disappears.
When a seed crystal for c-plane growth with θ = 150 ° is cut out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 150 ° as shown in FIG. Edge dislocations with directional Burgers vector are converted to basal plane dislocations.

When the c-plane growth of θ = 150 ° is continued, the basal plane dislocation is gradually discharged downstream ([-12-10] direction) in the offset direction, as shown in FIG. When the c-plane growth at θ = 150 ° is further continued, the basal plane dislocation is completely discharged downstream in the offset direction as shown in FIG. 6 (h).
6E to 6H may be performed by a single c-plane growth, or may be performed by repeating seed crystal cutting and c-plane growth a plurality of times.

FIG. 6 (i) shows a schematic diagram of the SiC single crystal obtained in FIG. 6 (h). In this case, of the three crystallographically equivalent directions, only the edge dislocation having the Burgers vector in the θ = 30 ° direction remains.
When a seed crystal for c-plane growth with θ = 30 ° is cut out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 30 ° as shown in FIG. Edge dislocations with directional Burgers vector are converted to basal plane dislocations.

When the c-plane growth at θ = 30 ° is continued, the basal plane dislocations are gradually discharged downstream ([2-1-10] direction) in the offset direction, as shown in FIG. 6 (k). When the c-plane growth at θ = 30 ° is further continued, the basal plane dislocation is completely discharged downstream in the offset direction as shown in FIG.
6 (i) to 6 (l) may be performed by a single c-plane growth, or may be performed by repeating seed crystal cutting and c-plane growth a plurality of times.

As the SiC seed crystal used in the present embodiment, when the density of the screw dislocation having the Burgers vector in the c-axis direction is small, the dislocation can be discharged out of the crystal more efficiently. This is because the interaction with the basal plane dislocation decreases as the density of the screw dislocation decreases.
When a so-called a-plane grown crystal grown in a direction substantially perpendicular to the c-axis direction is used as a seed crystal, basal plane dislocations are most easily discharged because there are almost no screw dislocations. In this case, since the dislocations in the seed crystal exist mainly as basal plane dislocations, they do not start from edge dislocations as shown in FIG. 6A, but are shown in FIG. 2A ′ or FIG. As shown in FIG. 6B, all start from a basal plane dislocation as shown in FIG.

Even if a single crystal grown in a direction substantially parallel to the c-axis direction and having a relatively small screw dislocation density (the density of screw dislocations is 100 / cm ² or less) is used as a seed crystal, Is discharged. However, as the density of screw dislocations increases, the rate of discharge decreases.
On the other hand, when a single crystal having a screw dislocation density exceeding 100 / cm ² is used as a seed crystal, the basal plane dislocation is entangled with the screw dislocation and hardly discharged.

When the offset angle of the growth surface of the seed crystal is set to 8 °, the conversion rate and the discharge rate of edge dislocations to basal plane dislocations are increased. Moreover, the conversion rate of the stacking fault in the seed crystal obtained by a-plane growth to the screw dislocation can be reduced.
Furthermore, if the offset angle is changed to a normal wafer standard (for example, 4 °) and the c-plane growth is performed after the dislocation is sufficiently reduced, the wafer can be taken out from the grown crystal with a high yield.

(Example 2)
FIG. 7 shows a process diagram of a method for producing an SiC single crystal according to the second embodiment of the present invention.
FIG. 7A shows a schematic diagram of an SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 90 ° is cut out from such a SiC single crystal and a new single crystal is grown on the growth surface, Burgers in the θ = 90 ° direction are obtained as in Example 1. Edge dislocations having vectors are converted into basal plane dislocations and discharged downstream ([11-20] direction) in the offset direction (FIGS. 7B to 7D).

FIG. 7 (e) shows a schematic diagram of the SiC single crystal obtained in FIG. 7 (d). In this case, of the three crystallographically equivalent directions, only the edge dislocation having the Burgers vector in the θ = 90 ° direction disappears.
When a seed crystal for c-plane growth with θ = 0 ° is cut out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 30 ° as shown in FIG. Most of the edge dislocations having Burgers vector in the direction of θ = −30 ° are converted into basal plane dislocations. When the growth is continued, as shown in FIG. 7G to FIG. 7H, the basal plane dislocation is in the direction closer to the downstream side in the offset direction ([2-1-10] direction and [1-210]). Direction).

FIG. 7 (i) shows a schematic diagram of the SiC single crystal obtained in FIG. 7 (h). In this case, out of three crystallographically equivalent directions, the edge dislocation having the Burgers vector in the θ = 90 ° direction disappears and has Burgers vectors in the θ = 30 ° direction and the θ = −30 ° direction. Most of the edge dislocations have also disappeared.
In order to take out a wafer having an <11-20> offset direction, which is a general wafer standard, from such a SiC single crystal with a high yield, an offset growth in the <11-20> direction is finally performed. In this case, when a seed crystal for c-plane growth with θ = 30 ° is cut out and a new single crystal is grown on the growth surface, the remaining θ = 30 ° as shown in FIG. Edge dislocations with directional Burgers vector are converted to basal plane dislocations. When the growth is continued, the basal plane dislocation is completely discharged downstream in the offset direction, as shown in FIGS. 7 (k) to 7 (l).

  The difference according to the type of SiC seed crystal used in this example and the size of the offset angle is the same as in Example 1.

(Example 3)
FIG. 8 shows a process diagram of a method for producing an SiC single crystal according to the third embodiment of the present invention.
FIG. 8A shows a schematic diagram of a SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 90 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface with c-plane growth, as in Example 1, θ = 90 ° Edge dislocations having a Burgers vector in the direction are converted into basal plane dislocations and discharged downstream ([11-20] direction) in the offset direction (FIGS. 8A to 8D).

FIG. 8E shows a schematic diagram of the SiC single crystal obtained in FIG. In this case, of the three crystallographically equivalent directions, only the edge dislocation having the Burgers vector in the θ = 90 ° direction disappears.
When a seed crystal for c-plane growth with θ = 60 ° is cut out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 30 ° as shown in FIG. Most of the edge dislocations with directional Burgers vector are converted to basal plane dislocations. If the growth is continued, as shown in FIGS. 8G to 8H, the basal plane dislocations are discharged in the direction closer to the downstream side in the offset direction ([2-1-10] direction).

FIG. 8 (i) shows a schematic diagram of the SiC single crystal obtained in FIG. 8 (h). In this case, of the three crystallographically equivalent directions, the edge dislocation having the Burgers vector in the θ = 90 ° direction disappears, and the majority of the edge dislocation having the Burgers vector in the θ = 30 ° direction also disappears. ing.
In order to take out a wafer having an <11-20> offset direction, which is a general wafer standard, from such a SiC single crystal with a high yield, an offset growth in the <11-20> direction is finally performed. In this case, when a seed crystal for c-plane growth with θ = 30 ° is cut out and a new single crystal is grown on the growth surface, as shown in FIG. 8 (j), the remaining θ = 30 ° Edge dislocations having a Burgers vector in the direction and part of the edge dislocations having a Burgers vector in the direction of θ = −30 ° are converted into basal plane dislocations. If the growth is continued, the basal plane dislocation is completely discharged in the downstream direction of the offset direction, as shown in FIGS. 8 (k) to 8 (l).

  The difference according to the type of SiC seed crystal used in this example and the size of the offset angle is the same as in Example 1.

Example 4
FIG. 9 shows a process diagram of a method for producing an SiC single crystal according to the fourth embodiment of the present invention.
FIG. 9A shows a schematic diagram of a SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 0 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface as a c-plane, θ = Most of the edge dislocations having Burgers vectors of 30 ° and θ = −30 ° directions are converted into basal plane dislocations. If the growth is continued, as shown in FIG. 9C to FIG. 9D, the basal plane dislocation is in the direction closer to the downstream side in the offset direction ([2-1-10] direction and [1-210]). Direction).

FIG. 9 (e) shows a schematic diagram of the SiC single crystal obtained in FIG. 9 (d). In this case, of the three crystallographically equivalent directions, most of the edge dislocations having Burgers vectors in the directions of θ = 30 ° and θ = −30 ° disappear and have Burgers vectors in the direction of θ = 90 °. Edge dislocations mainly remain.
When a seed crystal for c-plane growth with θ = 90 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 90 ° as shown in FIG. Edge dislocations with directional Burgers vector are converted to basal plane dislocations. If the growth is continued, as shown in FIGS. 9G to 9H, the basal plane dislocations are discharged downstream in the offset direction ([11-20] direction).

  The difference according to the type of SiC seed crystal used in this example and the size of the offset angle is the same as in Example 1.

(Example 5)
FIG. 10 shows a process diagram of a method for producing an SiC single crystal according to the fifth embodiment of the present invention.
FIG. 10A shows a schematic diagram of a SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 0 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface as a c-plane, θ = 30 ° as in Example 4. Most of the edge dislocations having Burgers vector in the θ = −30 ° direction are converted into basal plane dislocations, and directions close to the downstream side in the offset direction ([2-1-10] direction and [1-210] direction) (FIG. 10 (b) to FIG. 10 (d)).

FIG. 10 (e) shows a schematic diagram of the SiC single crystal obtained in FIG. 10 (d). In this case, of the three crystallographically equivalent directions, most of the edge dislocations having Burgers vectors in the directions of θ = 30 ° and θ = −30 ° have disappeared.
In order to take out a wafer having an <11-20> offset direction, which is a general wafer standard, from such a SiC single crystal with a high yield, an offset growth in the <11-20> direction is finally performed. In this case, if a seed crystal for c-plane growth with θ = 30 ° is taken out and a new single crystal is grown on the growth surface, the remaining θ = 30 ° as shown in FIG. Edge dislocations with directional Burgers vectors are converted to basal plane dislocations.

When the growth is continued, the basal plane dislocation is discharged downstream ([2-1-10] direction) in the offset direction, as shown in FIGS. 10 (g) to 10 (h). At this time, most of the edge dislocations having the Burgers vector in the θ = 90 ° direction and a part of the edge dislocations having the Burgers vector in the θ = −30 ° direction remain.
However, when the rotation angle at the time of changing the offset direction is as small as 30 °, seed crystals having different offset directions can be extracted from the grown crystal with a high yield. In addition, in a seed crystal with few screw dislocations in the seed crystal, when a region (not shown) in which a screw dislocation can be generated is introduced upstream of the offset in order to suppress the occurrence of heterogeneous polymorphism, it is newly added by changing the offset direction. The region where the screw dislocation can be introduced can be reduced.

  The difference according to the type of SiC seed crystal used in this example and the size of the offset angle is the same as in Example 1.

(Example 6)
FIG. 11 is a process diagram of a method for producing an SiC single crystal according to the sixth embodiment of the present invention.
FIG. 11A shows a schematic diagram of an SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions.
When a seed crystal for c-plane growth with θ = 0 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface as a c-plane, θ = 30 ° as in Example 4. Most of the edge dislocations having the Burgers vector in the θ = −30 ° direction are converted into basal plane dislocations and discharged downstream in the offset direction ([2-1-10] direction and [1-210] direction). (FIG. 11 (b) to FIG. 11 (d)).

FIG. 11 (e) shows a schematic diagram of the SiC single crystal obtained in FIG. 11 (d). In this case, of the three crystallographically equivalent directions, most of the edge dislocations having Burgers vectors in the directions of θ = 30 ° and θ = −30 ° have disappeared.
When a seed crystal for c-plane growth with θ = 60 ° is taken out from such a SiC single crystal and a new single crystal is grown on the growth surface, θ = 90 as shown in FIG. Most of the edge dislocations having the Burgers vector in the ° direction and θ = 30 ° direction are converted into basal plane dislocations. When the growth is continued, as shown in FIGS. 11 (g) to 11 (h), the basal plane dislocation is in the direction closer to the downstream side in the offset direction ([11-20] direction and [2-1-10]). Direction).

FIG. 11 (i) shows a schematic diagram of the SiC single crystal obtained in FIG. 11 (h). In this case, of the three crystallographically equivalent directions, most of the edge dislocations having the Burgers vector in the θ = 30 ° direction disappear and have Burgers vectors in the θ = 90 ° and θ = −30 ° directions. Some of the edge dislocations remain.
In order to take out a wafer having an <11-20> offset direction, which is a general wafer standard, from such a SiC single crystal with a high yield, an offset growth in the <11-20> direction is finally performed. In this case, a c-plane growth seed crystal with θ = 30 ° is cut out and a new single crystal is grown on the growth surface. In this case, there are almost no edge dislocations newly converted into basal plane dislocations. However, since the rotation angle for changing the offset direction is as small as 30 ° with respect to the immediately preceding c-plane growth, seed crystals having different offset directions can be extracted from the grown crystal with a high yield.

  The difference according to the type of SiC seed crystal used in this example and the size of the offset angle is the same as in Example 1.

(Example 7)
FIG. 12 shows a process diagram of a method for producing an SiC single crystal according to the seventh embodiment of the present invention.
FIG. 12A shows a schematic diagram of an SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions. The growth surface of the seed crystal is three planes with θ = 30 °, 150 °, and 270 °, respectively (the upper right region in the figure is θ = 30 °, the upper left region is θ = 150 °, and the lower central region is θ = 270 °). In the present example, the c-axis direction of the single crystal and the growth direction are substantially the same, but each plane has an offset angle.

When a new single crystal is grown on the growth plane on the c-plane, edge dislocations having Burgers vectors in the θ = 30 ° direction are converted into basal plane dislocations in the region where θ = 30 ° (FIG. 12B). ), And is discharged downstream in the offset direction ([2-1-10] direction) in the region (FIG. 12C).
Similarly, in the region where θ = 150 °, the edge dislocation having the Burgers vector in the θ = 150 ° direction is converted into the basal plane dislocation, and the downstream side in the offset direction in the region ([-12-10] direction). To be discharged.
Similarly, in the region where θ = 270 °, the edge dislocation having the Burgers vector in the θ = 270 ° direction is converted into the basal plane dislocation, and the downstream side in the offset direction ([−1-120] direction) in that region. To be discharged.

as a result,
(A) In the region of θ = 30 °, only the edge dislocations having Burgers vectors in the [-12-10] direction and the [-1-120] direction are
(B) In the region of θ = 150 °, only edge dislocations having Burgers vectors in the [2-1-10] direction and the [-1-120] direction are
(C) In the region of θ = 270 °, only edge dislocations having Burgers vectors in the [2-1-10] direction and [-12-10] direction are
Each remains.

FIG. 12D shows the growth plane of the SiC single crystal obtained in FIG. 12C with three planes with θ = 90 °, 210 °, and 330 ° (the region in the center in the figure is θ = 90 °, the lower left region is θ = 210 °, and the lower right region is θ = 330 °).
When a new single crystal is grown on the growth surface, in the region where θ = 90 °, the edge dislocation having a Burgers vector in the θ = 90 ° direction is converted into a basal plane dislocation (FIG. 12 (e)). It is discharged downstream ([11-20] direction) in the offset direction in that region (FIG. 12 (f)).
Similarly, in the region where θ = 210 °, the edge dislocation having the Burgers vector in the direction of θ = 210 ° is converted into the basal plane dislocation and discharged downstream in the offset direction ([−2110] direction) in that region. Is done.
Similarly, in the region where θ = 330 °, the edge dislocation having the Burgers vector in the direction of θ = 330 ° is converted into the basal plane dislocation, and downstream in the offset direction ([1-210] direction) in that region. Discharged.

As a result, within the region of θ = 90 °,
(A) In the region where θ = 30 ° in FIG. 12 (a), only the edge dislocation having the Burgers vector in the [-12-10] direction is
(B) In the region where θ = 150 °, only the edge dislocation having a Burgers vector in the [2-1-10] direction is
Each remains.
Similarly, in the regions of θ = 210 ° and θ = 330 °, edge dislocations having Burgers vectors in different directions depending on the regions remain.

FIG. 13 shows the range of change in the offset direction in each region on the single crystal. Although the change range of the offset direction in each region is different, the change range is 60 ° in any region.
In FIG. 12A, when θ of the plane constituting the growth surface is changed in a range of θ = 30 °, 150 °, 270 ° to ± 15 °, or in FIG. When θ of the plane constituting the growth surface changes in the range of θ = 90 °, 210 °, 330 ° to ± 15 °, there is some change in the rate of change from edge dislocation to basal plane dislocation. However, almost the same effect can be obtained. The difference depending on the type of SiC seed crystal used in this example is the same as in Example 1.

(Example 8)
FIG. 14 shows a flow chart of a method for manufacturing a SiC single crystal according to the eighth embodiment of the present invention.
FIG. 14A shows a schematic diagram of an SiC single crystal before c-plane growth. In the crystal, there are edge dislocations having Burgers vectors in three crystallographically equivalent directions. The growth surface of the seed crystal has three planes with θ = 0 °, 120 °, and 240 °, respectively (the right region in the figure is θ = 0 °, the upper left region is θ = 120 °, and the lower left region is θ = 240 °). In the present example, the c-axis direction of the single crystal and the growth direction are substantially the same, but each plane has an offset angle.

When a new single crystal is grown on c-plane on the growth surface, most of the edge dislocations having Burgers vectors in the θ = 30 ° direction and θ = 330 ° direction are basal plane dislocations in the region where θ = 0 °. (FIG. 14B) and discharged downstream in the offset direction ([2-1-10] direction and [1-210] direction) in the region (FIG. 14C).
Similarly, in the region where θ = 120 °, most of the edge dislocations having Burgers vectors in the θ = 90 ° direction and θ = 150 ° direction are converted into basal plane dislocations, and the downstream side in the offset direction in the region ([11-20] direction and [-12-10] direction).
Similarly, in the region where θ = 240 °, most of the edge dislocations having Burgers vectors in the directions of θ = 210 ° and θ = 270 ° are converted into basal plane dislocations, and downstream in the offset direction in the region ( [-2110] direction and [-1-120] direction).

as a result,
(A) In the region of θ = 0 °, edge dislocations having a Burgers vector mainly in the [11-20] direction are
(B) In the region of θ = 120 °, edge dislocations having a Burgers vector mainly in the [2-1-10] direction are
(C) In the region of θ = 240 °, an edge dislocation having a Burgers vector in the [1-210] direction is
Each remains.

FIG. 14 (d) shows the growth plane of the SiC single crystal obtained in FIG. 14 (c) as three planes with θ = 60 °, 180 °, and 300 ° (the upper right region in the figure is θ = 60). Degrees of left and right regions are θ = 180 °, and the lower right region is θ = 300 °.
When a new single crystal is grown on the growth plane on the c-plane, in the region where θ = 60 °, most of the edge dislocations having Burgers vectors in the directions of θ = 30 ° and θ = 90 ° become basal plane dislocations. It is converted (FIG. 14 (e)) and discharged downstream in the offset direction ([2-1-10] direction and [11-20] direction) in that region (FIG. 14 (f)).
Similarly, in the region where θ = 180 °, most of the edge dislocations having Burgers vectors in the θ = 150 ° direction and the θ = 210 ° direction are converted into basal plane dislocations, and the downstream side in the offset direction in the region ([-12-10] direction and [-2110] direction).
Similarly, in the region where θ = 300 °, edge dislocations having Burgers vectors in the θ = 270 ° direction and θ = 330 ° direction are converted into basal plane dislocations, and the downstream side in the offset direction ([1 -210] direction and [-1-120] direction).

As a result, edge dislocations having a Burgers vector in the [2-1-10] direction are almost discharged in the region where θ = 0 ° in FIG. . In addition, edge dislocations having Burgers vectors in the [1-210] direction and [11-20] direction are also reduced to some extent.
In the region where θ = 120 °, edge dislocations having a Burgers vector in the [11-20] direction are almost discharged. Further, edge dislocations having Burgers vectors in the [2-1-10] direction and [-12-10] direction are also reduced to some extent.
Similarly, in the region of θ = 180 ° and θ = 300 °, edge dislocations having Burgers vectors in different directions depending on the region are mainly reduced.

FIG. 15 shows the change range in the offset direction in each region on the single crystal. Although the change range of the offset direction in each region is different, the change range is 60 ° in any region.
In FIG. 14A, when θ of the plane constituting the growth surface is changed in the range of θ = 0 °, 120 °, 240 ° to ± 15 °, or in FIG. When θ of the plane constituting the growth surface changes in the range of θ = 60 °, 180 °, 300 ° to ± 15 °, there is a slight change in the rate of change from edge dislocation to basal plane dislocation. However, almost the same effect can be obtained. The difference depending on the type of SiC seed crystal used in this example is the same as in Example 1.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  The SiC single crystal according to the present invention, the manufacturing method thereof, and the SiC substrate can be used for the semiconductor material of an ultra-low power loss power device and the manufacturing thereof.

Claims (13)

The manufacturing method of the SiC single crystal provided with the following structures.
(1) The method for producing the SiC single crystal is as follows:
(A) a seed crystal cutting step of cutting a c-plane growth seed crystal having a growth plane offset angle of 1 ° to 30 ° from a single crystal;
(B) A c-plane growth step that repeats n times (n ≧ 2) a c-plane growth step of growing a new single crystal on the growth surface as a c-plane is provided.
(2) The offset direction of the growth surface of the seed crystal is changed in the {0001} plane at least once among the n repetitions.
(3) The maximum angle difference in the offset direction is 120 ° or less.
However, the “maximum angle difference in the offset direction” means the offset direction of the growth surface during the k-th (1 ≦ k ≦ n) c-plane growth and the m-th (1 ≦ m ≦ n, m ≠ k) c. The maximum value of the difference in angle between the growth surface and the offset direction during surface growth.   The method for producing a SiC single crystal according to claim 1, wherein the maximum angle difference in the offset direction is 30 ° or more.   The method for producing a SiC single crystal according to claim 1 or 2, wherein the maximum angle difference in the offset direction is 90 ° or less.   The method for producing a SiC single crystal according to any one of claims 1 to 3, wherein n ≧ 3. 5. The repetitive c-plane growth step is to change the offset direction of the growth surface of the seed crystal between three adjacent <11-20> directions ± 30 °. The manufacturing method of the SiC single crystal of any one. The single crystal for cutting out the seed crystal for the first c-plane growth is a single crystal manufactured using a seed crystal (B) having an offset angle of 60 ° to 90 ° on the growth surface. 5. The method for producing a SiC single crystal according to any one of 5 to 5.   The offset direction of the seed crystal for the first c-plane growth is substantially perpendicular to a growth direction for obtaining the single crystal for cutting out the seed crystal for the first c-plane growth. A method for producing a SiC single crystal.   The c-plane growth step is performed such that the maximum angle difference in the offset direction of the growth surface of the single crystal during the growth is maintained equal to the maximum angle difference in the offset direction of the growth surface of the seed crystal. The method for producing a SiC single crystal according to any one of claims 1 to 7, wherein a new single crystal is grown thereon.   The method for producing a SiC single crystal according to any one of claims 1 to 8, wherein at least an area having an offset angle of less than 20 ° is provided upstream of the seed crystal in the offset direction.   The method for producing a SiC single crystal according to any one of claims 1 to 9, wherein the growth surface of the seed crystal is configured by a plurality of planes so that the most upstream portion in the offset direction is provided at the approximate center thereof. .   The method for producing an SiC single crystal according to claim 10, wherein a set of planes having different offset directions constituting the growth surface of the seed crystal is 3 or more and 11 or less. A SiC single crystal having the following configuration.
(1) The SiC single crystal is
Of the three dislocations having any one of the three <11-20> Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as a basal plane dislocation, and
(B) the remaining two dislocations that Yusuke at least in part moieties present primarily as edge dislocations.
(2) The SiC single crystal has a density of screw dislocations having a Burgers vector in the c-axis direction of 100 pieces / cm ² or less. A SiC single crystal having the following configuration.
(1) The SiC single crystal is
Of the three dislocations having any one of the three <11-20> Burgers vectors crystallographically equivalent,
(A) one dislocation mainly exists as an edge dislocation, and
(B) the remaining two dislocations that Yusuke at least in part moieties present primarily as basal plane dislocations.
(2) The SiC single crystal has a density of screw dislocations having a Burgers vector in the c-axis direction of 100 pieces / cm ² or less.

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