JP6050053B2 - Method for producing SiC single crystal - Google Patents

Description

The present invention relates to the production how the SiC single crystal relates to the production how the wafer surface yields and the number of wafers yield higher SiC single crystal.

  At present, SiC is attracting attention as an alternative material for Si used in power semiconductors. In order to fabricate a high-performance SiC device using a SiC single crystal, it is necessary to use a single crystal having uniform electrical characteristics and a low defect density. However, in the growth process of the SiC single crystal, facet regions (growth mode: spiral growth) and non-facet regions (growth mode: step flow growth) having different growth modes are formed on the growing surface. Due to this difference in growth mode, variations in electrical characteristics (defect density) occur in the crystal.

There is a report (Patent Document 1) that the resistivity of the facet region is about 22% smaller than the resistivity of the non-facet region. This variation in resistivity within the wafer surface causes a reduction in device yield.
In addition, in a high-quality SiC single crystal, regions having partially different defect densities are generated (Patent Document 2). Such variations in wafer characteristics cause a reduction in the final device yield. Therefore, in order to obtain a wafer with small variation in characteristics and high yield, it is necessary to make the facet region as large as possible or as small as possible.

  Patent Documents 1 and 3 are related arts in which resistance is made uniform by growing while forming a facet region as large as possible. However, in SiC growth, as described in Patent Document 2, in the facet region, which is the most advanced part of the growth, there is a screw dislocation to inherit the polymorph of the base and suppress the inclusion of different polymorphs. Is essential. Therefore, in the methods of Patent Documents 1 and 3, since facets are formed on the entire surface of the crystal even if the electrical characteristics can be uniformed, in principle, it is necessary to keep the screw dislocations existing throughout the crystal. This is a technique that has a limit to high quality. The document also describes that when the growth rate of a single crystal becomes larger than a certain level, the movement of the step flow becomes unstable on a large facet surface, and heterogeneous polymorphism tends to occur.

In the experience of the present inventors, it is clear that the occurrence probability of heterogeneous polymorphism in the facet region is significantly higher than that in the non-facet region. Further, the movement of the growing facet region in the growth plane direction should be as small as possible. This is because when the facet formation position moves on the seed crystal with the change of the growth surface shape during single crystal growth, the presence of screw dislocations is required for each position as described above. This is because the quality of the single crystal must be lowered.
For the above reasons, it is desired that the facet is smaller and the movement in the growth plane direction is smaller.

  Patent Documents 4 to 8 are conventional techniques for keeping the facet area as small as possible. Patent Document 4 describes a method for reducing a facet region by offset growth. However, when the facet region is to be maintained within a region having a width of 10 mm from the outer periphery as described in the same document, it is necessary to greatly increase the offset angle. Alternatively, if the facet is to be greatly reduced at an offset angle of 8 ° as described in the same document, the growth with the growth surface kept extremely flat must be realized.

When the offset angle is greatly increased, the yield of the wafer is greatly reduced when the wafer is taken out from the single crystal ingot. In addition, it is extremely difficult to keep the flatness of the growth surface constantly throughout the growth.
In Patent Document 1 where the applicant is the same as Patent Document 4,
“When crystal growth is performed by inducing the {0001} facet near the outer periphery of the ingot by the method of Patent Document 4, thermal interaction with the inner wall of the crucible or graphite constituting the side wall is caused. As a result, the sublimation gas composition fluctuates easily, and the step supply mechanism becomes unstable due to these effects. . "
The problem is pointed out.

  In Patent Document 5, by making the carbon exposed area in the crucible excessive, the ratio of the step depth to the step height on the growth surface is made comparable to other regions in the central portion of the growth surface, A technique is described that does not substantially form facets. However, since the growth surface generally has a shape along the isothermal surface, it is difficult to realize a conical shape in which the curvature of the growth surface changes sharply by this method.

As described in the same document, according to the same technique, “the ratio of the step depth to the step height is in the range from 1 to 5 in the central portion, as in all the places near the other growth boundary surfaces. "
As a result, the growth surface has a very sharp conical shape.
And as the growth progresses, the SiC raw material is carbonized, and when the exposed carbon area in the crucible becomes excessive, the cone shape becomes sharper and the difference in the growth end face of the finally obtained single crystal ingot is extremely high. growing. In that case, the yield of the wafer is greatly reduced.

In Patent Documents 2 and 6-8, the temperature distribution in the single crystal growth region and the concentration of sublimation gas are asymmetrical, and the shape of the single crystal is also asymmetrical along with it. Describes a method for preventing the occurrence of heterogeneous polymorphism by suppressing the movement of the facet region from the surface. Thereby, the area of the region where the presence of the screw dislocations on the seed crystal can be reduced.
However, the difference in height of the growth end face of the finally obtained single crystal ingot becomes large, and the yield of the wafer is also greatly reduced. In particular, in order to make facets smaller, strong growth non-uniformity must be realized in the growth plane, but if growth continues as it is, it is difficult to make the growth height uniform in subsequent growth. It is.

JP 2010-254520 A JP 2004-323348 A US Application Publication No. 2011-0300323 JP 2008-001532 A JP 2011-256096 A JP 2009-051701 A JP 2011-011926 A JP2012-020893A

Problems to be solved by the present invention has high wafer surface yields and the number of wafers yield is that to provide a manufacturing how high SiC single crystal.

In order to solve the above 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 first growth step of growing a single crystal on the surface of the seed crystal while promoting the growth of the facet region from the initial growth stage to the middle growth stage, while suppressing the expansion of the facet region;
And a second growth step of further growing the single crystal so as to promote the growth of the non-faceted region and make the growth height uniform in a later stage of growth.
(2) The first growth step (and the second growth step) includes growing the SiC single crystal so as to satisfy the following equations (a) and (b). Here, the term “from the initial stage of growth to the middle stage of growth” refers to a period from the start of growth until the maximum value H ₁ of the growth height satisfies the formula (a). “Growth height” refers to the length from the bottom surface of the seed crystal to the growth surface.
H ₁ ≧ 0.5H ₂ (a)
However,
H ₁ is the maximum growth height at the end of the first growth step,
H ₂ is the maximum growth height at the end of the second growth step.
d ≦ 0.2D (b)
However,
d is the diameter of the circumscribed circle of the facet region at the end of the first growth step;
D is the diameter of the circumscribed circle of the SiC single crystal at the end of the second growth step.
(3) The second growth step includes growing the SiC single crystal so as to satisfy the following equation (c) in addition to the equations (a) and (b). Here, the “late growth period” refers to a period after the time when the growth height H ₁ satisfies the formula (a) and the expansion suppression of the facet region is finished.
H _min ≧ 0.8H _max (c)
However,
H _min is the minimum value of the growth height at the end of the second growth step,
H _max is the maximum value of the growth height at the end of the second growth process (= H ₂ ).

  (Delete)

From the initial growth stage to the middle growth stage, if the temperature of the facet region is lower than that of the non-facet region, or if the source gas concentration in the facet region is higher than that of the non-facet region, growth of the facet region and its neighboring regions is promoted. The As a result, the area of the facet region is reduced, and the yield in the wafer plane is improved.
Next, when the temperature difference or the source gas concentration difference between the facet region and the non-facet region is made uniform or reversed in the later stage of growth, the growth rate of the facet region becomes slower than that of the non-facet region. As a result, the growth height of the single crystal is made uniform, and the yield of the number of wafers is improved.

It is a schematic diagram for demonstrating the definition of the growth initial stage-the growth middle period, and the growth late stage. It is process drawing of the single crystal manufacturing apparatus which concerns on the 1st Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same. It is process drawing (upper figure: front sectional drawing, lower figure: bottom view) of the single crystal manufacturing apparatus which concerns on the 2nd Embodiment of this invention, and the manufacturing method of SiC single crystal using the same. It is process drawing (upper figure: front sectional drawing, lower figure: A-A 'line sectional drawing) of the single crystal manufacturing apparatus which concerns on the 3rd Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same. It is process drawing (upper figure: top view, lower figure: front sectional drawing) of the single crystal manufacturing apparatus which concerns on the 4th Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same.

It is process drawing (upper figure: front sectional drawing, lower figure: bottom view) of the single crystal manufacturing apparatus which concerns on the 5th Embodiment of this invention, and the manufacturing method of SiC single crystal using the same. It is process drawing (upper figure: front sectional drawing, lower figure: A-A 'line sectional drawing) of the single crystal manufacturing apparatus which concerns on the 6th Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same. It is process drawing (upper figure: top view, lower figure: front sectional drawing) of the single crystal manufacturing apparatus which concerns on the 7th Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same.

It is a schematic diagram of the manufacturing method of the SiC single crystal which concerns on this invention. It is a schematic diagram of the manufacturing method (1) of the conventional SiC single crystal. It is a schematic diagram of the manufacturing method (2) of the conventional SiC single crystal. It is a figure which shows the relationship between the ratio (d '/ D') of the diameter d 'of the facet area | region with respect to the diameter D' of a wafer, and a wafer surface retention.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Manufacturing method of SiC single crystal]
The method for producing a SiC single crystal according to the present invention includes a first growth step and a second growth step.

[1.1. First growth process]
The first growth step is a step of growing a single crystal on the surface of the seed crystal while promoting the growth of the facet region and suppressing the expansion of the facet region from the initial growth stage to the middle growth stage.
“Promoting the growth of the facet region” means growing while maintaining the radius of curvature of the facet region and the growth surface in the vicinity thereof relatively small. In this case, the growth height is non-uniform, but the expansion of the facet region is suppressed. As a result, the yield in the wafer surface (the ratio of the area of the high quality region to the total area of the wafer or the ratio of the area of the region having a uniform resistance value) is improved. In addition, when a later-described helical dislocation generation region is formed in the seed crystal, the facet region and the screw dislocation generation region can be grown in alignment.

In the first growth step (and the second growth step), specifically, the SiC single crystal is grown so as to satisfy the following equations (a) and (b) (see FIG. 1). That is, “from the initial stage of growth to the middle stage of growth” refers to a period from the start of growth until the maximum value H ₁ of the growth height satisfies the formula (a).
H ₁ ≧ 0.5H ₂ (a)
However,
H ₁ is the maximum growth height at the end of the first growth step,
H ₂ is the maximum growth height at the end of the second growth step.
H ₁ is preferably H ₁ ≧ 0.7H ₂ , more preferably H ₁ ≧ 0.9H ₂ .
d ≦ 0.2D (b)
However,
d is the diameter of the circumscribed circle of the facet region at the end of the first growth step;
D is the diameter of the circumscribed circle of the SiC single crystal at the end of the second growth step.
d is preferably d ≦ 0.15D, more preferably d ≦ 0.1D.

[1.2. Second growth process]
The second growth step is a step of further promoting the growth of the non-faceted region and further growing the single crystal so that the growth height becomes uniform in the later stage of growth.
“Non-faceted area” refers to an area other than the facet area.
“Promoting the growth of the non-faceted region” means growing so that the radius of curvature of the growth surface in the facet region and its vicinity is increased. In this case, the facet area is enlarged, but the growth height is made uniform.
When the maximum value H ₁ of the growth height at the end of the first growth process is optimized, the wafer number yield (predetermined size with respect to the total number of wafers cut out from the single crystal) is not reduced. The ratio of the number of wafers having the above size is improved.

Specifically, in the second growth step, the SiC single crystal is grown so as to satisfy the following formula (c) in addition to the formulas (a) and (b) described above (see FIG. 1). . The “late growth period” refers to a period after the time when the growth height H ₁ satisfies the formula (a) and the expansion suppression of the facet region is finished.
H _min ≧ 0.8H _max (c)
However,
H _min is the minimum value of the growth height at the end of the second growth step,
H _max is the maximum value of the growth height at the end of the second growth process (= H ₂ ).
H _min is preferably H _min ≧ 0.9H _max, more preferably H _min ≒ H _max.

[1.3. Facet area]
The present invention
(1) Using a seed crystal (c-plane growth substrate) whose growth plane is a {0001} plane (c-plane) or a plane slightly inclined with respect to the c-plane, the <0001> axis (c-axis) direction or a method of growing a crystal in a direction slightly inclined from the c-axis (c-plane growth method), and
(2) Using a {1-100} plane (m-plane) or a seed crystal (m-plane growth substrate) consisting of a plane slightly inclined with respect to the m-plane, the <1-100> axial direction or Method of growing crystal in a direction slightly inclined from the <1-100> axis (m-plane growth method)
It can be applied to any of these.

In the case of the c-plane growth method, the “facet region” refers to a region where {0001} plane facets are formed on the growth surface.
In the case of the m-plane growth method, the “facet region” refers to a region in which {1-100} facet is formed on the growth surface.

[1.4. Offset substrate and onset substrate]
In the c-plane growth method, “offset substrate” refers to a seed crystal (c-plane growth substrate) in which the inclination of the normal line of the {0001} plane with respect to the main growth axis direction is in the range of 1 to 15 °.
In the c-plane growth method, the “onset substrate” refers to a seed crystal (c-plane growth substrate) in which the inclination of the normal line of the {0001} plane is less than 1 ° with respect to the main growth axis direction.
In the m-plane growth method, the “offset substrate” refers to a seed crystal (m-plane growth substrate) in which the inclination of the normal line of the {1-100} plane is in the range of 1 to 15 ° with respect to the main growth axis direction. .
In the m-plane growth method, the “onset substrate” refers to a seed crystal (m-plane growth substrate) whose {1-100} plane normal has an inclination of less than 1 ° with respect to the main growth axis direction.
“Main growth axis direction” refers to a direction perpendicular to the bottom surface of the seed crystal.

[1.5. Spiral dislocation generation region]
When growing a single crystal using the c-plane growth method, heterogeneous polymorphism tends to occur. In order to suppress the generation of heterogeneous polymorphs, it is necessary to supply a relatively high density of screw dislocations to at least the facet region. When the seed crystal (c-plane growth substrate) is a normal-quality crystal including relatively high-density screw dislocations of several hundred to 1,000 pieces / cm ² , the screw dislocations contained in the seed crystal are contained in the grown crystal. Since it is inherited as it is, heterogeneous polymorphism is unlikely to occur. That is, a c-plane growth substrate made of a normal quality crystal can be used for crystal growth as it is.
On the other hand, when the c-plane growth substrate is a high-quality crystal with few screw dislocations (dislocation density: 100 / cm ² or less), the screw dislocations in the facet region are also insufficient, and heterogeneous polymorphism tends to occur. In such a case, on the upstream side in the offset direction of the c-plane growth substrate, a screw dislocation generation region capable of generating higher density screw dislocations is formed on the downstream side in the offset direction (region in which facets are not formed). Yes.
In the m-plane growth method, there is no problem of heterogeneous polymorphism caused by insufficient screw dislocations, so that it is not necessary to form a screw dislocation generation region.

“Upstream side in the offset direction” means a region in which the front end of a vector obtained by projecting a normal vector of the {0001} plane (or {1-100} plane) onto the growth plane faces (in other words, a facet at the start of growth). And a region in the vicinity thereof.
The spiral dislocation generation region may be any region that can generate a high-density spiral dislocation from the downstream side in the offset direction. In order to suppress the occurrence of heterogeneous polymorphism, the density of the screw dislocations generated from the screw dislocation generation region is preferably 10 times or more, more preferably 100 times or more of the downstream side in the offset direction. Further, the density of the screw dislocations generated from the screw dislocation generation region is preferably 100 / cm ² or more.
“Spiral dislocation generation region” refers to a region in which a screw dislocation generation source is intentionally formed on the surface of a c-plane growth substrate or a screw dislocation density outside the facet region. The area where the density is high.
If the growth conditions are optimized in the first growth step, the facet region and the screw dislocation generation region can be grown in alignment. Therefore, even when the area of the screw dislocation generation region is relatively small, the screw dislocation can be reliably supplied into the facet region.
Here, “matching the facet region and the screw dislocation generation region” means that the screw dislocation supplied from the screw dislocation generation region is supplied into the facet.

[1.6. Control of facet area and growth height]
The expansion of the facet region from the initial stage to the middle stage of growth and the uniformization of the growth height in the late stage of growth can be performed as follows.
(2) The first growth step includes
(A) forming a temperature distribution such that the temperature of the faceted region is lower than the temperature of the non-faceted region, and / or
(B) The growth of the facet region is promoted by forming a source gas concentration distribution so that the source gas concentration in the facet region is higher than the source gas concentration in the non-facet region.
(3) In the second growth step, the growth height is made uniform by reversing or homogenizing the temperature distribution and / or the source gas concentration distribution.

The inversion or homogenization of the temperature distribution or the source gas concentration may be performed after the single crystal is once cooled to room temperature after the first growth step. Further, when the inversion or homogenization method allows, the inversion or homogenization may be performed without cooling the single crystal to room temperature.
As a method for controlling the area of the facet region and the growth height, there are the following methods.

[A. First Method (Claim 6)]
The first method is a method applied when the seed crystal is an offset substrate (claim 5) for c-plane growth (claim 3). When the seed crystal is a high quality crystal, it is preferable to form a screw dislocation generation region at the upstream end portion in the offset direction.

First, in the first growth process,
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Making the temperature distribution near the growth surface asymmetric with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature on the upstream side in the offset direction of the seed crystal is lower than the temperature on the downstream side in the offset direction.
Next, in the second growth step,
Making the temperature distribution near the growth surface symmetric with respect to the central axis of the crucible, or
The single crystal is further grown in a state where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction.

When the crucible is arranged in a symmetrical position with respect to the heating furnace, the temperature distribution in the heating furnace and the crucible is usually symmetric with respect to the center of the heating furnace or the crucible. If a member that makes the temperature distribution asymmetric is inserted into such a heating furnace or crucible, the temperature distribution becomes asymmetric. At this time, if the temperature distribution is asymmetrical so that the upstream side in the offset direction of the seed crystal has a low temperature, the facet region and its vicinity can be preferentially grown.
When the crystal grows to some extent, the growth height can be made uniform by making the asymmetric temperature distribution uniform or reversed.

As a method for controlling the temperature distribution, specifically,
(A) a method of disposing an asymmetrical heat insulating material around the crucible (claim 7, FIG. 2);
(B) A method of inserting a heat dissipation control member on the back surface of the pedestal (claim 8, FIG. 3),
(C) Method of arranging a shielding plate on the growth surface side (Claim 9, FIG. 4)
and so on. Details of each method will be described later.

[B. Second Method (Claim 10)]
The second method is a method applied when the seed crystal is an offset substrate (claim 5) for c-plane growth (claim 3). When the seed crystal is a high-quality crystal, it is preferable to form a screw dislocation generation region at the upstream end portion in the offset direction (claim 4).

First, in the first growth process,
Placing the seed crystal in an asymmetric position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature on the upstream side in the offset direction of the seed crystal is lower than the temperature on the downstream side in the offset direction.
Next, in the second growth step,
Moving the single crystal to a position where the temperature distribution in the vicinity of the growth surface is more symmetrical with respect to the central axis of the crucible, or
The single crystal is further grown in a state where the single crystal is moved to a position where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction.

The central part of the heating furnace usually has a symmetrical temperature distribution. When the seed crystal is arranged at a position asymmetric with respect to this symmetric temperature distribution, the temperature distribution on the growth surface becomes asymmetric. At this time, if the seed crystal is arranged so that the temperature upstream of the offset direction becomes low, the facet region and its vicinity can be preferentially grown.
When the crystal grows to some extent, the growth height can be made uniform by moving the single crystal to a position where the temperature distribution becomes more symmetric or reverse.

[C. Third Method (Claim 11)]
The third method is a method applied when the seed crystal is an offset substrate (claim 5) for c-plane growth (claim 3). When the seed crystal is a high-quality crystal, it is preferable to form a screw dislocation generation region at the upstream end portion in the offset direction (claim 4).

First, in the first growth process,
Making the source gas concentration distribution in the vicinity of the growth surface asymmetric with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration upstream of the offset direction is higher than the source gas concentration downstream of the offset direction.
Next, in the second growth step,
Symmetrizing the source gas concentration distribution with respect to the central axis of the crucible, or
The single crystal is further grown in a state where the source gas concentration upstream of the offset direction is lower than the source gas concentration downstream of the offset direction.

The crucible usually has a symmetrical source gas concentration distribution. On the other hand, when a certain member is inserted into the crucible, the source gas concentration distribution becomes asymmetric. At this time, if the source gas concentration distribution is asymmetrical so that the upstream side in the offset direction of the seed crystal has a high concentration, the facet region and its vicinity can be preferentially grown.
When the crystal has grown to some extent, the height of the growth can be made uniform by symmetrizing or reversing the asymmetric material gas concentration distribution.

As a method for controlling the source gas concentration distribution, specifically,
Method of concentrating raw material gas (sublimation gas, gas having a composition similar to sublimation gas, etc.) at a specific location using a nozzle (Claim 12, FIG. 5)
and so on. Details of this method will be described later.

[D. Fourth Method (Claim 14)]
The fourth method is a method applied when the seed crystal is an onset substrate (claim 13) for c-plane growth (claim 3). When the seed crystal is a high-quality crystal, it is preferable to form a screw dislocation generation region at the upstream end portion in the offset direction (claim 4).

First, in the first growth process,
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature of the central portion of the seed crystal is lower than the temperature of the peripheral portion of the seed crystal.
Next, in the second growth step,
Reduce the temperature difference between the central part and the peripheral part, or
The single crystal is further grown in a state where the temperature of the central portion is higher than the temperature of the peripheral portion.

As a method for controlling the temperature distribution, specifically,
(A) a method using a heat dissipation control member (claim 15, FIG. 6),
(C) Method using a shielding plate (Claim 16, FIG. 7)
and so on. The other points are the same as those in the first method, and thus description thereof is omitted. Details of each method will be described later.

[E. Fifth Method (Claim 17)]
The fifth method is a method applied when the seed crystal is an onset substrate (claim 13) for c-plane growth (claim 3). When the seed crystal is a high-quality crystal, it is preferable to form a screw dislocation generation region at the upstream end portion in the offset direction (claim 4).

First, in the first growth process,
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration in the central portion of the seed crystal is higher than the source gas concentration in the peripheral portion of the seed crystal.
Next, in the second growth step,
Reduce the difference in the concentration of the source gas between the central portion and the peripheral portion, or
The single crystal is further grown in a state in which the source gas concentration in the central portion is lower than the source gas concentration in the peripheral portion.

As a method for controlling the source gas concentration distribution, specifically,
Method of concentrating source gas (sublimation gas, gas having a composition similar to sublimation gas, etc.) at a specific location using a nozzle (Claim 18, FIG. 8)
and so on. The other points are the same as in the third method, and thus the description thereof is omitted. Details of this method will be described later.

[F. Sixth Method (Claim 21)]
The sixth method is a method applied when the seed crystal is an offset substrate (claim 20) for m-plane growth (claim 19).

First, in the first growth process,
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Making the temperature distribution near the growth surface asymmetric with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature on the upstream side in the offset direction of the seed crystal is lower than the temperature on the downstream side in the offset direction.
Next, in the second growth step,
Making the temperature distribution near the growth surface symmetric with respect to the central axis of the crucible, or
The single crystal is further grown in a state where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction.
Since the other points of the sixth method are the same as those of the first method, description thereof will be omitted.

[G. Seventh Method (Claim 22)]
The seventh method is a method applied when the seed crystal is an offset substrate (claim 20) for m-plane growth (claim 19).

First, in the first growth process,
Placing the seed crystal in an asymmetric position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature on the upstream side in the offset direction of the seed crystal is lower than the temperature on the downstream side in the offset direction.
Next, in the second growth step,
Moving the single crystal to a position where the temperature distribution in the vicinity of the growth surface is more symmetric with respect to the central axis of the seed crystal, or
The single crystal is further grown in a state where the single crystal is moved to a position where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction.
Since the other points of the seventh method are the same as those of the second method, description thereof will be omitted.

[H. Eighth Method (Claim 23)]
The eighth method is a method applied when the seed crystal is an offset substrate (claim 20) for m-plane growth (claim 19).

First, in the first growth process,
Making the source gas concentration distribution in the vicinity of the growth surface asymmetric with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration upstream of the offset direction is higher than the source gas concentration downstream of the offset direction.
Next, in the second growth step,
Symmetrizing the source gas concentration distribution with respect to the central axis of the crucible, or
The single crystal is further grown in a state where the source gas concentration upstream of the offset direction is lower than the source gas concentration downstream of the offset direction.
Since the other points of the eighth method are the same as those of the third method, description thereof will be omitted.

[I. Ninth Method (Claim 25)]
The ninth method is a method applied when the seed crystal is an onset substrate (claim 24) for m-plane growth (claim 19).

First, in the first growth process,
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature of the central portion of the seed crystal is lower than the temperature of the peripheral portion of the seed crystal.
Next, in the second growth step,
Reduce the temperature difference between the central part and the peripheral part, or
The single crystal is further grown in a state where the temperature of the central portion is higher than the temperature of the peripheral portion.
Since the other points of the ninth method are the same as those of the fourth method, description thereof will be omitted.

[J. Tenth Method (Claim 26)]
The tenth method is a method applied when the seed crystal is an onset substrate (claim 24) for m-plane growth (claim 19).

First, in the first growth process,
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration in the central portion of the seed crystal is higher than the source gas concentration in the peripheral portion of the seed crystal.
Next, in the second growth step,
Reduce the difference in the concentration of the source gas between the central portion and the peripheral portion, or
The single crystal is further grown in a state where the source gas concentration in the central portion is lower than the source gas concentration in the peripheral portion.
Since the other points of the tenth method are the same as those of the fifth method, description thereof will be omitted.

[2. Specific examples of single crystal manufacturing apparatus and SiC single crystal manufacturing method]
Below, the specific example of the manufacturing method of the single crystal manufacturing apparatus for implementing the method mentioned above and a SiC single crystal using the same is demonstrated.

[2.1. Specific Example 1 (Claim 7)]
[2.1.1. Single crystal manufacturing equipment (1)]
FIG. 2 shows a process diagram of a single crystal manufacturing apparatus and a method of manufacturing a SiC single crystal using the same according to the first embodiment of the present invention.
In FIG. 2, the single crystal production apparatus 10a includes a crucible 12, two heaters (not shown), and a heat insulating material (not shown).

The crucible 12 is filled with SiC raw material powder (raw material gas supply source) 20. A seed crystal 22 is fixed to the inner surface of the upper lid 12a of the crucible 12 via a pedestal 12b. In the example shown in FIG. 2, the seed crystal 22 is an offset substrate for c-plane growth. Although not shown, a spiral dislocation generation region is formed at the end of the seed crystal 22 on the upstream side in the offset direction. Furthermore, the crucible 12 is placed on a rotatable support base 24.
The two heaters are respectively arranged on the upper side and the lower side with respect to the axial direction of the crucible 12 so that the temperature can be controlled independently. The crucible 12 is disposed at a symmetrical position with respect to the central axis of the heater. Furthermore, a heat insulating material having an asymmetric shape with respect to the crucible 12 is provided around the crucible 12.

[2.1.2. Method for producing SiC single crystal (1)]
In the case where an asymmetrical heat insulating material is provided, when the seed crystal 22 is arranged at a position symmetrical with respect to the central axis of the crucible 12 and the crucible 12 is arranged symmetrically with respect to the central axis of the heater, FIG. ), The isothermal surface is asymmetric with respect to the central axis of the crucible 12. Therefore, when the seed crystal 22 is arranged so that the temperature upstream of the offset direction of the seed crystal 22 is lower than the temperature downstream of the offset direction, and the single crystal 28 is grown on the surface of the seed crystal 22 in this state, the facet region (Not shown) can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 2B, when the support base 24 is rotated by 180 °, the temperature distribution in the vicinity of the growth surface is reversed. When heating is continued in this state, the single crystal 28 further grows so as to follow the isothermal surface. As a result, the growth height of the single crystal 28 is made uniform.

Instead of rotating the crucible 12 180 ° with the asymmetric heat insulating material attached, the asymmetric heat insulating material may be replaced with a heat insulating material having a symmetrical shape with respect to the crucible 12. When replaced with a symmetric insulation, the isothermal surface is symmetric with respect to the central axis of the crucible 12. That is, the non-uniform temperature distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
The rotation or replacement of the heat insulating material may be performed after the crucible 12 is cooled to room temperature, or may be performed without cooling.

[2.2. Specific Example 2 (Claim 8)]
[2.2.1. Single crystal manufacturing equipment (2)]
In FIG. 3, the process drawing (upper figure: front sectional drawing, lower figure: bottom view) of the single crystal manufacturing apparatus which concerns on the 2nd Embodiment of this invention, and the manufacturing method of a SiC single crystal using the same is shown.
In FIG. 3, the single crystal manufacturing apparatus 10b includes a crucible (not shown) and a heater (not shown).

The crucible is filled with SiC raw material powder (not shown), and a seed crystal 22 is fixed to the inner surface of the crucible upper lid 12a via a pedestal 12b. The crucible is disposed at a symmetrical position with respect to the central axis of the heater.
In the example shown in FIG. 3, the seed crystal 22 is an offset substrate for c-plane growth. Further, on the upstream side of the seed crystal 22 in the offset direction, a screw dislocation generation region 22a is formed.
Further, in the example shown in FIG. 3, an asymmetric heat dissipation control member 30 having a counterbore 30 a on one side is inserted on the back surface of the base 12 b for fixing the seed crystal 22. The heat dissipation control member 30 is inserted into the back surface of the pedestal 12b and is rotatable with respect to the pedestal 12b.

[2.2.2. Manufacturing method of SiC single crystal (2)]
When the heat radiation control member 30 having an asymmetric shape is inserted into the back surface of the pedestal 12b, the seed crystal 22 is disposed at a symmetrical position with respect to the central axis of the crucible (not shown), and the crucible is a heater ( When arranged symmetrically with respect to the central axis (not shown), the portion of the counterbore 30a is locally cooled.
Therefore, the seed crystal 22 is arranged so that the counterbore 30a comes to the upstream side of the seed crystal 22 in the offset direction (the portion where the spiral dislocation generation region 22a is formed), and the single crystal 28 is placed on the surface of the seed crystal 22 in this state. When grown, the facet region can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 3B, when the heat dissipation control member 30 is rotated 180 °, the temperature distribution in the vicinity of the growth surface is reversed. When heating is continued in this state, the single crystal 28 further grows so as to follow the isothermal surface. As a result, the growth height of the single crystal 28 is made uniform.

Instead of rotating the asymmetric heat radiation control member 30 by 180 °, the asymmetric heat radiation control member 30 may be removed and grown. When the asymmetrical heat dissipation control member 30 is removed (including filling the counterbore 30a), local cooling is alleviated. That is, the non-uniform temperature distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
The rotation or removal of the heat dissipation control member 30 may be performed after the crucible is cooled to room temperature or may be performed without cooling.

[2.3. Specific Example 3 (Claim 9)]
[2.3.1. Single crystal manufacturing equipment (3)]
FIG. 4 is a process diagram of an apparatus for producing a single crystal and a method for producing an SiC single crystal using the same according to a third embodiment of the present invention (upper view: front sectional view, lower view: sectional view along line AA ′) ).
In FIG. 4, the single crystal manufacturing apparatus 10 c includes a crucible 12, a heater (not shown), and a shielding plate 32.

The crucible 12 is filled with SiC raw material powder 20. A seed crystal 22 is fixed to the inner surface of the upper lid 12a of the crucible 12 via a pedestal 12b. In the example shown in FIG. 4, the seed crystal 22 is an offset substrate for c-plane growth. Although not shown, a spiral dislocation generation region is formed at the end of the seed crystal 22 on the upstream side in the offset direction.
The crucible 12 is disposed at a symmetrical position with respect to the central axis of a heater (not shown). Further, in the crucible 12, an asymmetric shielding plate 32 is disposed between the seed crystal 22 and the SiC raw material powder (raw material gas supply source) 20. The shielding plate 32 has a shape that can shield only one side of the seed crystal 22 (a shape that is asymmetric with respect to the seed crystal 22), and can rotate 180 ° within the crucible 12.

[2.3.2. Manufacturing method of SiC single crystal (3)]
In the case where the asymmetrical and rotatable shielding plate 32 is provided in the crucible 12, the seed crystal 22 is disposed at a symmetrical position with respect to the central axis of the crucible 12, and the crucible 12 is centered on the heater. The isothermal surface is asymmetric with respect to the central axis of the crucible 12. Therefore, when the seed crystal 22 is arranged so that the temperature upstream of the offset direction of the seed crystal 22 is lower than the temperature downstream of the offset direction, and the single crystal 28 is grown on the surface of the seed crystal 22 in this state, the facet region Can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 4B, when the shielding plate 32 is rotated by 180 °, the temperature distribution in the vicinity of the growth surface is reversed. When heating is continued in this state, the single crystal 28 further grows so as to follow the isothermal surface. As a result, the growth height of the single crystal 28 is made uniform.

Instead of rotating the asymmetric shielding plate 32 by 180 °, the asymmetric shielding plate 32 may be replaced with a shielding plate (not shown) having a symmetrical shape with respect to the crucible 12. When replaced with a symmetrical shielding plate, the isothermal surface is symmetric with respect to the central axis of the crucible 12. That is, the non-uniform temperature distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
Further, the shielding plate 32 may be rotated or replaced after the crucible 12 is cooled to room temperature, or may be performed without cooling.

[2.4. Specific Example 4 (Claim 12)]
[2.4.1. Single crystal manufacturing equipment (4)]
FIG. 5 shows process diagrams (upper view: plan view, lower view: front sectional view) of a single crystal manufacturing apparatus and a SiC single crystal manufacturing method using the same according to the fourth embodiment of the present invention.
In FIG. 5, the single crystal manufacturing apparatus 10 d includes a crucible (not shown), a heater (not shown), and a nozzle 34.

The crucible is filled with SiC raw material powder (not shown). A seed crystal 22 is fixed to the inner surface of the crucible upper lid 12a via a pedestal 12b. In the example shown in FIG. 5, the seed crystal 22 is an offset substrate for c-plane growth. Further, on the upstream side of the seed crystal 22 in the offset direction, a screw dislocation generation region 22a is formed.
The crucible is disposed at a symmetrical position with respect to the central axis of the heater. Further, in the crucible, a nozzle 34 is disposed between the seed crystal 22 and the SiC raw material powder. The nozzle 34 is for intensively supplying the source gas to a part of the growth surface of the seed crystal 22. The nozzle 34 is movable in the horizontal direction with respect to the growth surface of the seed crystal 22.

[2.4.2. Method for producing SiC single crystal (4)]
When the tip of the nozzle 34 is directed upstream of the seed crystal 22 in the offset direction, the source gas concentration upstream of the offset direction becomes higher than the source gas concentration downstream of the offset direction. When the single crystal 28 is grown on the surface of the seed crystal 22 in this state, the facet region can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 5B, when the nozzle 34 is moved downstream in the offset direction, the source gas concentration distribution in the vicinity of the growth surface is reversed. . If heating is continued in this state, the growth rate of the single crystal 28 on the downstream side in the offset direction increases. As a result, the growth height of the single crystal 28 is made uniform.

Instead of moving the nozzle 34 to the downstream side in the offset direction, the nozzle 34 may be removed. When the nozzle 34 is removed, the sublimation gas is supplied to the seed crystal 22 from the entire SiC raw material powder, so that the non-uniform raw material gas concentration distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
The rotation or removal of the nozzle 34 may be performed after the crucible 12 is cooled to room temperature, or may be performed without cooling.

[2.5. Specific Example 5 (Claim 15)]
[2.5.1. Single crystal manufacturing equipment (5)]
FIG. 6 shows a process diagram (upper view: front sectional view, lower view: bottom view) of a single crystal manufacturing apparatus and a SiC single crystal manufacturing method using the same according to the fifth embodiment of the present invention.
In FIG. 6, the single crystal manufacturing apparatus 10 e includes a crucible (not shown) and a heater (not shown).

The crucible is filled with SiC raw material powder (not shown), and a seed crystal 22 is fixed to the inner surface of the crucible upper lid 12a via a pedestal 12b. The crucible is disposed at a symmetrical position with respect to the central axis of the heater.
In the example shown in FIG. 6, the seed crystal 22 is an onset substrate for c-plane growth. The growth surface of the seed crystal 22 has a conical shape, and the center portion is upstream in the offset direction. Further, on the upstream side (center portion) of the seed crystal 22 in the offset direction, a screw dislocation generation region 22a is formed.
Further, in the example shown in FIG. 6A, a heat dissipation control member 30 having a counterbore 30a at the center is inserted in the back surface of the base 12b for fixing the seed crystal 22. The heat dissipation control member 30 can be replaced with a heat dissipation control member 30 ′ having a counterbore 30a ′ in the peripheral portion.

[2.5.2. Manufacturing method of SiC single crystal (5)]
When the heat radiation control member 30 is inserted on the back surface of the pedestal 12b, the seed crystal 22 is disposed at a position symmetrical to the central axis of the crucible (not shown), and the crucible is placed on the heater (not shown). When arranged symmetrically with respect to the central axis, the portion of the counterbore 30a is locally cooled.
Therefore, the seed crystal 22 is arranged so that the counterbore 30a comes to the upstream side of the seed crystal 22 in the offset direction (the portion where the spiral dislocation generation region 22a is formed), and the single crystal 28 is placed on the surface of the seed crystal 22 in this state. When grown, the facet region can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 6B, when the heat dissipation control member 30 is replaced with a heat dissipation control member 30 ′, the temperature distribution in the vicinity of the growth surface is reversed. . When heating is continued in this state, the single crystal 28 further grows so as to follow the isothermal surface. As a result, the growth height of the single crystal 28 is made uniform.

Instead of replacing the heat dissipation control member 30 with the heat dissipation control member 30 ′, the heat dissipation control member 30 may be removed and grown. Removing the heat dissipation control member 30 (including filling the counterbore 30a) alleviates local cooling, and as a result, the growth height of the single crystal 28 is made uniform.
Further, the replacement or removal of the heat dissipation control member 30 may be performed after the crucible is cooled to room temperature, or may be performed without cooling.

[2.6. Specific Example 6 (Claim 16)]
[2.6.1. Single crystal manufacturing equipment (6)]
FIG. 7 is a process diagram of an apparatus for producing a single crystal and a method for producing an SiC single crystal using the same according to a sixth embodiment of the present invention (upper view: front sectional view, lower view: sectional view along line AA ′) ).
In FIG. 7, the single crystal manufacturing apparatus 10 f includes a crucible 12, a heater (not shown), and a shielding plate 32.

The crucible 12 is filled with SiC raw material powder (raw material gas supply source) 20. A seed crystal 22 is fixed to the inner surface of the upper lid 12a of the crucible 12 via a pedestal 12b. In the example shown in FIG. 7, the seed crystal 22 is an onset substrate for c-plane growth. The growth surface of the seed crystal 22 has a conical shape, and the center portion is upstream in the offset direction. Further, on the upstream side (center portion) of the seed crystal 22 in the offset direction, a screw dislocation generation region 22a is formed.
The crucible 12 is disposed at a symmetrical position with respect to the central axis of a heater (not shown). Furthermore, a shielding plate 32 is disposed in the crucible 12 between the seed crystal 22 and the SiC raw material powder 20. The shielding plate 32 has a shape that can shield only the central portion of the seed crystal 22. The shielding plate 32 can be replaced with shielding plates 32 ′ and 32 ′ having a shape capable of shielding only the periphery of the seed crystal 22.

[2.6.2. Method for producing SiC single crystal (6)]
In the case where the shielding plate 32 covering the center portion of the seed crystal 22 is provided in the crucible 12, the seed crystal 22 is disposed at a symmetrical position with respect to the central axis of the crucible 12, and the crucible 12 is heated (not shown). The central part is locally cooled. Therefore, when the single crystal 28 is grown on the surface of the seed crystal 22 in this state, the facet region can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 7B, when the shielding plate 32 is replaced with the shielding plate 32 ', the temperature distribution in the vicinity of the growth surface is reversed. When heating is continued in this state, the single crystal 28 further grows so as to follow the isothermal surface. As a result, the growth height of the single crystal 28 is made uniform.

Instead of replacing the shielding plate 32 with the shielding plate 32 ′, the shielding plate 32 may be replaced with a shielding plate (not shown) that covers the entire surface of the seed crystal 22. If it is replaced with a shielding plate that covers the entire surface of the seed crystal 22, local cooling is alleviated. That is, the non-uniform temperature distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
The replacement of the shielding plate 32 may be performed after the crucible 12 is cooled to room temperature, or may be performed without cooling.

[2.7. Specific Example 7 (Claim 18)]
[2.7.1. Single crystal manufacturing equipment (7)]
FIG. 8 is a process diagram (upper view: plan view, lower view: front sectional view) of a single crystal manufacturing apparatus and a SiC single crystal manufacturing method using the same according to the seventh embodiment of the present invention.
In FIG. 8, the single crystal manufacturing apparatus 10 g includes a crucible (not shown), a heater (not shown), and a nozzle 34.

The crucible is filled with SiC raw material powder (not shown). A seed crystal 22 is fixed to the inner surface of an upper lid (not shown) of the crucible via a pedestal 12b. In the example shown in FIG. 8, the seed crystal 22 is an onset substrate for c-plane growth. The growth surface of the seed crystal 22 has a conical shape, and the center portion is upstream in the offset direction. Further, on the upstream side (center portion) of the seed crystal 22 in the offset direction, a screw dislocation generation region 22a is formed.
The crucible is disposed at a symmetrical position with respect to the central axis of the heater. Further, in the crucible, a nozzle 34 is disposed between the seed crystal 22 and the SiC raw material powder. The nozzle 34 is for intensively supplying the source gas to the central portion of the growth surface of the seed crystal 22. Further, the nozzle 34 can be replaced with a nozzle 34 ′ for intensively supplying the source gas to the peripheral portion of the growth surface of the seed crystal 22.

[2.7.2. Method for producing SiC single crystal (7)]
When the tip of the nozzle 34 is directed toward the upstream side of the seed crystal 22 in the offset direction (that is, the center portion of the seed crystal 22), the source gas concentration upstream of the offset direction becomes higher than the source gas concentration downstream of the offset direction. When the single crystal 28 is grown on the surface of the seed crystal 22 in this state, the facet region can be preferentially grown.

  When the growth height of the single crystal 28 reaches a predetermined height, as shown in FIG. 8B, when the nozzle 34 is replaced with the nozzle 34 ', the source gas concentration distribution in the vicinity of the growth surface is reversed. If heating is continued in this state, the growth rate of the single crystal 28 on the downstream side in the offset direction increases. As a result, the growth height of the single crystal 28 is made uniform.

The nozzle 34 may be removed instead of replacing the nozzle 34 with the nozzle 34 '. When the nozzle 34 is removed, the sublimation gas is supplied to the seed crystal 22 from the entire SiC raw material powder, so that the non-uniform raw material gas concentration distribution is made uniform. As a result, the growth height of the single crystal 28 is made uniform.
The replacement or removal of the nozzle 34 may be performed after the crucible is cooled to room temperature or may be performed without cooling.

[3. SiC single crystal]
The SiC single crystal according to the present invention has the following configuration.
(1) The SiC single crystal satisfies the following formula (c).
H _min ≧ 0.8H _max (c)
However,
H _min is the minimum value of the growth height of the SiC single crystal,
H _max is the maximum growth height of the SiC single crystal.
(2) The SiC single crystal satisfies the following equation (b ′) from the bottom surface to a position of 0.5 H _max .
d ′ ≦ 0.2D ′ (b ′)
However,
d ′ is the diameter of the circumscribed circle of the facet region in the wafer cut from the SiC single crystal,
D ′ is the diameter of the circumscribed circle of the wafer cut out from the SiC single crystal.
(3) The SiC single crystal is obtained by a c-plane growth method, and includes higher-density screw dislocations in the facet region than in the non-facet region.

As described above, when the growth is divided into two stages and the temperature of the facet region is lowered or the material gas concentration is increased from the initial growth stage to the middle growth stage, the single crystal satisfying the formula (b ′), that is, A single crystal in which the expansion of the facet region is suppressed is obtained.
Further, when the temperature distribution and / or the source gas concentration is made uniform or reversed in the later stage of growth after reaching a predetermined growth height, a single crystal satisfying the formula (c), that is, a single crystal having a uniform growth height is obtained. Crystals are obtained.

Further, when a SiC single crystal is manufactured by using the c-plane growth method, when a screw dislocation generation region is formed on the upstream side in the offset direction, a SiC single crystal containing high-density screw dislocations in the facet region is obtained.
The facet region only needs to contain a higher density of screw dislocations than the non-facet region. The dislocation density of the screw dislocations in the facet region is preferably 10 times or more, more preferably 100 times or more that of the non-facet region. Specifically, the screw dislocation density in the facet region is preferably 100 pieces / cm ² or more.

[4. Method for producing SiC single crystal and action of SiC single crystal]
In FIG. 9, the schematic diagram of the manufacturing method of the SiC single crystal which concerns on this invention is shown. FIG. 10 shows a schematic diagram of a conventional SiC single crystal manufacturing method (1). In FIG. 11, the schematic diagram of the manufacturing method (2) of the conventional SiC single crystal is shown.

As shown in FIGS. 10A and 10B, when a crystal is grown without locally reducing the temperature or concentrating the source gas, a single crystal having a uniform growth height can be obtained. Therefore, as shown in FIGS. 10C and 10D, the wafer number yield is increased.
However, since the facet area expands with the growth, the in-wafer yield decreases. In this case, as compared with the growth using a normal quality seed crystal containing many screw dislocations (FIG. 10C), a high quality seed crystal having no screw dislocations is provided with a screw dislocation generation region (FIG. 10D). )) Further reduces the in-wafer yield. This is because in order to suppress the occurrence of heterogeneous polymorphism, it is necessary to continue supplying screw dislocations to the expanding facet region, and for this purpose, it is necessary to increase the area of the screw dislocation generation region.

On the other hand, as shown in FIGS. 11A and 11B, when the crystal is grown while locally lowering the temperature or concentrating the source gas, the expansion of the facet region is suppressed. Therefore, as shown in FIGS. 11C and 11D, the in-wafer yield is increased. Further, since the expansion of the facet region is suppressed, even when the screw dislocation generation region is formed (FIG. 11 (d)), the size can be reduced. Therefore, the yield in the wafer surface is not greatly reduced.
However, since the growth height is non-uniform, the yield of the number of wafers decreases.

On the other hand, as shown in FIG. 9A, when the local temperature is lowered or the source gas is concentrated from the initial stage to the middle stage, the expansion of the facet region can be suppressed. Therefore, as shown in FIGS. 9C and 9D, the in-wafer yield is increased. Further, since the expansion of the facet region is suppressed, even when the screw dislocation generation region is formed (FIG. 9D), the size can be reduced. Therefore, the yield in the wafer surface is not greatly reduced.
Next, as shown in FIG. 9B, when the local temperature reduction or the concentration of the source gas is reversed or canceled in the later stage of growth, the growth height becomes uniform. Therefore, as shown in FIGS. 9C and 9D, the wafer number yield is also increased.

  In the present invention, from the initial stage to the middle stage of growth, the temperature on the upstream side in the offset direction of the growth surface is locally lowered and / or the concentration of the raw material gas is locally concentrated to grow the supersaturation degree locally. . On the other hand, in the late growth stage, the local temperature is lowered and / or the local concentration of the source gas concentration is canceled, or the local supersaturation degree on the growth surface is reversed and the growth is performed.

Thus, by locally increasing the degree of supersaturation on the upstream side in the offset direction of the growth surface, the area of the facet region having a different resistance value can be reduced, and the yield in the wafer surface can be improved. Furthermore, since the facet is fixed at a fixed position, the area of the screw dislocation generation region can be reduced even in the growth using a high-quality seed crystal having no screw dislocation, and the yield in the wafer plane is improved similarly. be able to.
In the later stage of growth, since the local increase in the degree of supersaturation is canceled, a single crystal having a uniform growth height can be obtained. As a result, the wafer yield is also improved.

  FIG. 12 shows the relationship between the ratio (d '/ D') of the diameter d 'of the facet region to the wafer diameter D' and the yield in the wafer surface. The facet region has different electrical characteristics because the nitrogen doping amount is different from that in the non-facet region. From FIG. 12, it can be seen that when d '/ D' is 0.2 or less, the in-wafer yield is 95% or more.

  The method according to the present invention can be applied not only to c-plane growth but also to m-plane growth. In the m-plane growth, a {1-100} plane facet is usually formed. Similarly to the c-plane growth, the {1-100} plane facet also has a nitrogen doping concentration outside the {1-100} plane facet. Different. Also, different orientation crystals tend to occur on {1-100} facets. From the above, as in the case of application of the present growth method to c-plane growth, effects of uniform dope concentration, suppression of different orientation crystals, and improvement in wafer yield can be obtained in m-plane growth.

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

20 SiC raw material powder (source gas supply source)
22 Seed crystal 28 Single crystal

Claims (26)

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 first growth step of growing a single crystal on the surface of the seed crystal while promoting the growth of the facet region from the initial growth stage to the middle growth stage, while suppressing the expansion of the facet region;
And a second growth step of further growing the single crystal so as to promote the growth of the non-faceted region and make the growth height uniform in a later stage of growth.
(2) The first growth step (and the second growth step) includes growing the SiC single crystal so as to satisfy the following equations (a) and (b). Here, the term “from the initial stage of growth to the middle stage of growth” refers to a period from the start of growth until the maximum value H ₁ of the growth height satisfies the formula (a) . “Growth height” refers to the length from the bottom surface of the seed crystal to the growth surface.
H ₁ ≧ 0.5H ₂ (a)
However,
H ₁ is the maximum growth height at the end of the first growth step,
H ₂ is the maximum growth height at the end of the second growth step.
d ≦ 0.2D (b)
However,
d is the diameter of the circumscribed circle of the facet region at the end of the first growth step;
D is the diameter of the circumscribed circle of the SiC single crystal at the end of the second growth step.
(3) The second growth step includes growing the SiC single crystal so as to satisfy the following equation (c) in addition to the equations (a) and (b). Here, the “late growth period” refers to a period after the time when the growth height H ₁ satisfies the formula (a) and the expansion suppression of the facet region is finished.
H _min ≧ 0.8H _max (c)
However,
H _min is the minimum value of the growth height at the end of the second growth step,
H _max is the maximum value of the growth height at the end of the second growth process (= H ₂ ). The manufacturing method of the SiC single crystal of Claim 1 further provided with the following structures.
(4) The first growth step includes
(A) forming a temperature distribution such that the temperature of the faceted region is lower than the temperature of the non-faceted region, and / or
(B) The growth of the facet region is promoted by forming a source gas concentration distribution so that the source gas concentration in the facet region is higher than the source gas concentration in the non-facet region.
(5) In the second growth step, the growth height is made uniform by reversing or homogenizing the temperature distribution and / or the source gas concentration distribution.   The method for producing a SiC single crystal according to claim 2, wherein the facet region is a {0001} facet region. The seed crystal has a screw dislocation generation region capable of generating a higher density of screw dislocations on the upstream side in the offset direction than on the downstream side in the offset direction,
4. The method for producing a SiC single crystal according to claim 3, wherein in the first growth step, the facet region and the screw dislocation generation region are made to coincide with each other. 5.   5. The method for producing a SiC single crystal according to claim 3, wherein the seed crystal is an offset substrate in which a normal of the {0001} plane is in a range of 1 to 15 ° with respect to a main growth axis direction. The first growth step includes
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Making the temperature distribution near the growth surface asymmetric with respect to the central axis of the crucible, and
In the state where the temperature upstream of the offset direction of the seed crystal is lower than the temperature downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Making the temperature distribution near the growth surface symmetric with respect to the central axis of the crucible, or
The method for producing an SiC single crystal according to claim 5, wherein the single crystal is further grown in a state where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction. (A) In the first growth step, a heat insulating material having an asymmetric shape with respect to the crucible is disposed around the crucible, and in the second growth step, the crucible is placed with the heat insulating material being disposed. Reversing the temperature distribution by rotating 180 °, or
(B) In the first growth step, a heat insulating material (A) having an asymmetric shape with respect to the crucible is disposed around the crucible, and in the second growth step, the heat insulating material (A) is The manufacturing method of the SiC single crystal of Claim 6 which makes the said temperature distribution uniform by replacing | exchanging for the heat insulating material (B) which has a symmetrical shape with respect to a crucible. (A) In the first growth step, an asymmetric heat dissipation control member having a counterbore on one side is inserted into the back surface of the pedestal for fixing the seed crystal, and in the second growth step, the heat dissipation control member is 180 By rotating the temperature distribution, or
(B) In the first growth step, an asymmetric heat dissipation control member having a counterbore on one side is inserted into the back surface of the base for fixing the seed crystal, and the heat dissipation control member is removed in the second growth step. The method for producing a SiC single crystal according to claim 6, wherein the temperature distribution is made uniform. (A) In the first step, a shielding plate having an asymmetric shape with respect to the seed crystal is disposed between the seed crystal and the source gas supply source, and in the second step, the shielding plate is 180 By rotating the temperature distribution, or
(B) In the first step, a shielding plate (A) having an asymmetric shape with respect to the seed crystal is disposed between the seed crystal and the source gas supply source, and in the second step, The method for producing an SiC single crystal according to claim 6, wherein the temperature distribution is made uniform by replacing the shielding plate (A) with a shielding plate (B) having a symmetrical shape with respect to the seed crystal. The first growth step includes
Placing the seed crystal in an asymmetric position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
In the state where the temperature upstream of the offset direction of the seed crystal is lower than the temperature downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Moving the single crystal to a position where the temperature distribution in the vicinity of the growth surface is more symmetric with respect to the central axis of the seed crystal, or
The SiC single crystal according to claim 5, wherein the single crystal is further grown in a state in which the single crystal is moved to a position where the temperature upstream of the offset direction is higher than the temperature downstream of the offset direction. Production method. The first growth step includes
The material gas concentration distribution in the vicinity of the growth surface is asymmetrical with respect to the central axis of the crucible, and
In the state where the source gas concentration upstream of the offset direction is higher than the source gas concentration downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Symmetrizing the source gas concentration distribution with respect to the central axis of the crucible, or
The method for producing an SiC single crystal according to claim 5, wherein the single crystal is further grown in a state where the source gas concentration upstream of the offset direction is lower than the source gas concentration downstream of the offset direction. (A) In the first growth step, the source gas is concentrated on the upstream side in the offset direction by using a nozzle, and in the second growth step, the nozzle is moved to the downstream side in the offset direction. Reverse the concentration distribution, or
(B) In the first growth step, a source gas is concentrated on the upstream side in the offset direction using a nozzle, and the nozzle is removed in the second growth step, thereby uniformizing the source gas concentration distribution. Item 12. A method for producing a SiC single crystal according to Item 11.   5. The method for producing an SiC single crystal according to claim 3, wherein the seed crystal is an onset substrate having an inclination of a normal line of a {0001} plane with respect to a main growth axis direction of less than 1 °. The first growth step includes
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature of the center part of the seed crystal is lower than the temperature of the peripheral part of the seed crystal,
The second growth step includes
Reduce the temperature difference between the central part and the peripheral part, or
The method for producing a SiC single crystal according to claim 13, wherein the single crystal is further grown in a state where the temperature of the central portion is higher than the temperature of the peripheral portion. (A) In the first growth step, a heat dissipation control member (A) having a counterbore in the center is inserted into the back surface of the pedestal for fixing the seed crystal. In the second growth step, the heat dissipation control member Replacing the temperature distribution by replacing (A) with a heat dissipation control member (B) having counterbore in the periphery, or
(B) In the first growth step, by inserting a heat dissipation control member having a counterbore in the center on the back surface of the pedestal for fixing the seed crystal, and removing the heat dissipation control member in the second growth step. The method for producing an SiC single crystal according to claim 14, wherein the temperature distribution is made uniform. (A) In the first step, a shielding plate (A) that covers the central portion of the seed crystal is disposed between the seed crystal and the source gas supply source, and in the second step, the shielding plate (A ) Is replaced with a shielding plate (B) that covers the periphery of the seed crystal, or the temperature distribution is reversed, or
(B) In the first step, a shielding plate (A) that covers the central portion of the seed crystal is disposed between the seed crystal and the source gas supply source, and in the second step, the shielding plate ( The method for producing an SiC single crystal according to claim 14, wherein the temperature distribution is made uniform by exchanging A) with a shielding plate (C) covering the entire surface of the seed crystal. The first growth step includes
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration at the center of the seed crystal is higher than the source gas concentration at the periphery of the seed crystal,
The second growth step includes
Reduce the difference in the concentration of the source gas between the central portion and the peripheral portion, or
The method for producing an SiC single crystal according to claim 13, wherein the single crystal is further grown in a state where the concentration of the source gas in the central portion is lower than the concentration of the source gas in the peripheral portion. (A) In the first growth step, the source gas is concentrated in the central portion of the seed crystal using a nozzle (A) for supplying the source gas to the central portion of the seed crystal, and the second growth step. The nozzle (A) is replaced with a nozzle (B) for supplying the source gas to the periphery of the seed crystal, and the source gas is concentrated on the periphery of the seed crystal using the nozzle (B). By reversing the source gas concentration distribution, or
(B) In the first growth step, the source gas is concentrated at the center of the seed crystal using a nozzle, and in the second growth step, the nozzle is removed to make the source gas concentration distribution uniform. The manufacturing method of the SiC single crystal of Claim 17.   The method for producing an SiC single crystal according to claim 2, wherein the facet region is a {1-100} facet region.   20. The method for producing a SiC single crystal according to claim 19, wherein the seed crystal is an offset substrate having an inclination of a normal of a {1-100} plane with respect to a main growth axis direction in a range of 1 to 15 °. The first growth step includes
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Making the temperature distribution near the growth surface asymmetric with respect to the central axis of the crucible, and
In the state where the temperature upstream of the offset direction of the seed crystal is lower than the temperature downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Making the temperature distribution near the growth surface symmetric with respect to the central axis of the crucible, or
The method for producing a SiC single crystal according to claim 20, wherein the single crystal is further grown in a state where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction. The first growth step includes
Placing the seed crystal in an asymmetric position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
In the state where the temperature upstream of the offset direction of the seed crystal is lower than the temperature downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Moving the single crystal to a position where the temperature distribution in the vicinity of the growth surface is more symmetric with respect to the central axis of the seed crystal, or
21. The SiC single crystal according to claim 20, wherein the single crystal is further grown in a state where the single crystal is moved to a position where the temperature on the upstream side in the offset direction is higher than the temperature on the downstream side in the offset direction. Production method. The first growth step includes
Making the source gas concentration distribution in the vicinity of the growth surface asymmetric with respect to the central axis of the crucible, and
In the state where the source gas concentration upstream of the offset direction is higher than the source gas concentration downstream of the offset direction, the single crystal is grown on the surface of the seed crystal,
The second growth step includes
Symmetrizing the source gas concentration distribution with respect to the central axis of the crucible, or
21. The method for producing a SiC single crystal according to claim 20, wherein the single crystal is further grown in a state where the source gas concentration upstream of the offset direction is lower than the source gas concentration downstream of the offset direction.   20. The method for producing an SiC single crystal according to claim 19, wherein the seed crystal is an onset substrate in which a normal to the {1-100} plane is less than 1 ° with respect to a main growth axis direction. The first growth step includes
Placing the seed crystal in a symmetrical position with respect to the central axis of the crucible;
Symmetrizing the temperature distribution near the growth surface with respect to the central axis of the crucible, and
The single crystal is grown on the surface of the seed crystal in a state where the temperature of the central part of the seed crystal is lower than the temperature of the peripheral part of the seed crystal,
The second growth step includes
Reduce the temperature difference between the central part and the peripheral part, or
The method for producing a SiC single crystal according to claim 24, wherein the single crystal is further grown in a state where the temperature of the central portion is higher than the temperature of the peripheral portion. The first growth step includes
The single crystal is grown on the surface of the seed crystal in a state where the source gas concentration at the center of the seed crystal is higher than the source gas concentration at the periphery of the seed crystal,
The second growth step includes
Reduce the difference in the concentration of the source gas between the central portion and the peripheral portion, or
The method for producing an SiC single crystal according to claim 24, wherein the single crystal is further grown in a state where the concentration of the source gas in the central portion is lower than the concentration of the source gas in the peripheral portion.

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