JP2003095797A - Method of producing single crystal material and method of manufacturing electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a thick and high-quality silicon carbide single crystal, and to provide a method of manufacturing an electronic device using the same. SOLUTION: The method of producing the single crystal material includes a process for forming a cavity 2 at the inside of a silicon carbide single crystal substrate 1, and a process for sublimating silicon carbide from the first surface of the substrate 1, which the first surface faces a space of the cavity 2, and crystallizing the sublimated silicon carbide on the second surface of the substrate 1, which the second surface faces the first surface while putting the cavity 2 between them, by setting the temperature of the first surface of the substrate 1 higher than that of the second surface of the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a single crystal material and a method for manufacturing an electronic device, and more particularly to a method for manufacturing a high quality silicon carbide single crystal and a method for using such a silicon carbide single crystal. The electronic device manufacturing method.

[0002]

2. Description of the Related Art A method utilizing sublimation called an improved Rayleigh method is used for producing a silicon carbide single crystal. In the single crystal produced by this method, different polytypes are mixed, fatal defects called micropipes penetrating the wafer, slip dislocations, edge dislocations, and subgrain structures in which the crystal orientation is slightly deviated. It contains many flaws.

In order to reduce these defects, technological developments such as reviewing single-crystal growth conditions and devising crucible structure are in progress, but single-crystal substrates of a level capable of producing electronic devices such as semiconductor devices are still available. Not obtained. Therefore, when manufacturing a semiconductor device using a silicon carbide single crystal, a high quality epitaxial layer was grown on a single crystal substrate, and various processing was performed on this high quality epitaxial layer.

However, the epitaxial layer takes over the defects of the single crystal substrate, and many defects are present inside. Therefore, in the semiconductor device obtained by this method, problems such as deterioration of breakdown voltage and increase of leak current occur. Further, it has been pointed out that when an ultra-high voltage semiconductor device is manufactured, it takes a very long time to grow a thick epitaxial layer, resulting in poor productivity and high cost.

[0005]

The present invention has been made in view of the above problems, and is a method for producing a single crystal capable of producing a thick and high-quality silicon carbide single crystal, and such a silicon carbide. It is an object to provide a method for manufacturing an electronic device using a single crystal.

[0006]

In order to solve the above problems, a step of forming a cavity inside a silicon carbide single crystal material, and a first surface of the silicon carbide single crystal material facing a space in the cavity. At a temperature higher than that of the second surface of the silicon carbide single crystal material facing the first surface with the cavity sandwiched between the second surface and the silicon carbide sublimated from the first surface. And a step of crystallizing on a surface thereof.

The present invention also provides the step of forming a cavity inside the silicon carbide single crystal material, and the first surface of the silicon carbide single crystal material facing the space in the cavity with the cavity sandwiched therebetween. No. 1 second of the silicon carbide single crystal material facing the surface
Forming a silicon carbide single crystal region by sublimating silicon carbide from the first surface and crystallizing the sublimated silicon carbide on the second surface at a temperature higher than that of the surface; And a step of producing an electronic device having a single crystal region.

Further, according to the present invention, the step of forming a groove in a silicon carbide single crystal substrate and the temperature of the first side wall of the groove is higher than that of the second side wall of the groove facing the first side wall,
Forming a silicon carbide single crystal region by sublimating silicon carbide from the first side wall and crystallizing the sublimated silicon carbide on the second side wall; and an electronic device including the silicon carbide single crystal region. And a method of manufacturing an electronic device.

The "electronic device" referred to here is a high breakdown voltage semiconductor device, a light emitting diode, a semiconductor laser, and an LS.
It means a device using electric conduction such as a semiconductor device such as I or an electronic device having a microlens.

In the present invention, the cavity has, for example, a plurality of recesses formed in a silicon carbide single crystal material, the silicon carbide single crystal material is heated in a reducing atmosphere, and the silicon carbide single crystal is surrounded by the plurality of recesses. It can be formed by closing the openings of the plurality of recesses by fluidizing the material and connecting the plurality of recesses.

In the present invention, the number of cavities formed in the silicon carbide single crystal material is not particularly limited. That is, the number of cavities may be one or plural.
Similarly, the number of grooves formed in the silicon carbide single crystal substrate is not particularly limited, and may be one or plural. When forming a plurality of cavities, there is no particular limitation on the positional relationship between the cavities. For example, the cavities may be arranged in parallel or perpendicular to the direction forming the temperature gradient. Also, the atmosphere in the cavity is
The atmosphere outside the silicon carbide single crystal material may be the same or different. For example, the inside of the cavity may be an atmosphere that promotes sublimation, and the outside of the silicon carbide single crystal material may be an atmosphere that suppresses sublimation. For example, when the cavity is formed in a low pressure reducing atmosphere (for example, a hydrogen atmosphere of 20 Torr) and then heated under a higher pressure (for example, normal pressure), sublimation and crystallization in the cavity are caused. Volatilization from the outer surface of the silicon carbide single crystal material can be suppressed while proceeding.

In the present invention, before the step of forming the high-quality silicon carbide single crystal region or the step of crystallizing the high-quality silicon carbide single crystal region, between the space inside the cavity and the space outside the silicon carbide single crystal material in the silicon carbide single crystal material. You may form the hole which connects. In this case, sublimation and crystallization of silicon carbide can be performed while controlling the atmosphere in the cavity through the holes formed in the silicon carbide single crystal material. For example, sublimation and crystallization of silicon carbide can be performed while supplying an inert gas or a reducing gas inside the cavity. Moreover, sublimation and crystallization of silicon carbide can be performed while supplying a gas containing a silicon source and a carbon source into the cavity.

When forming the above-mentioned holes, sublimation and crystallization of silicon carbide may be further performed while supplying a gas containing P-type or N-type impurities into the cavity. In this case, if sublimation and crystallization of silicon carbide are performed while alternately supplying a gas containing a P-type impurity and a gas containing an N-type impurity into the cavity, a P-type high-quality silicon carbide single crystal is obtained. A laminated structure of a crystal region and an N-type high-quality silicon carbide single crystal region can be formed. In this case, for example, it is possible to obtain a semiconductor device including a doping region having a super junction structure. Further, when forming the above-mentioned holes, sublimation and crystallization of silicon carbide may be performed while supplying a gas containing an impurity having a conductivity type opposite to that of the silicon carbide single crystal material. Alternatively, sublimation and crystallization of silicon carbide may be performed while supplying a gas containing impurities having the same conductivity type as that of the silicon carbide single crystal material.

The supply of these gases can be performed in the same manner even when the groove is formed in the silicon carbide single crystal substrate.

In the present invention, any crystal plane may be exposed on the first surface and the second surface. Similarly, the first
Any crystal plane may be exposed on the side wall and the second side wall. For example, the (0001) plane may be exposed,
The (11-20) plane may be exposed. Furthermore, 4H
The (03-38) plane of -SiC may be exposed, and 6
The (01-14) plane of H-SiC may be exposed.
Further, the first surface and the second surface may be parallel to each other or may not be parallel to each other. Similarly, the first side wall and the second side wall may or may not be parallel to each other.

According to the method of the present invention, the first surface is heated to a temperature higher than that of the second surface to sublimate silicon carbide from the first surface and to crystallize the sublimated silicon carbide on the second surface. In addition to the step, the method further includes a second recrystallization step in which the third surface is heated to a temperature higher than that of the fourth surface to sublimate silicon carbide from the third surface and crystallize the sublimated silicon carbide on the fourth surface. You can In this case, the first surface and the fourth surface may be the same and the second surface and the third surface may be the same. Alternatively, the first surface, the second surface, the third surface, and the fourth surface may be different from each other.

Similarly, the method of the present invention comprises a first side wall and a second side wall.
In addition to the first recrystallization step of subliming silicon carbide from the first sidewall and crystallizing the sublimated silicon carbide on the second sidewall at a temperature higher than that of the sidewall, the third sidewall is more A second recrystallization step of sublimating silicon carbide from the third sidewall and crystallizing the sublimated silicon carbide on the fourth sidewall can be further included at the high temperature. In this case, the first side wall and the fourth side wall may be the same and the second side wall and the third side wall may be the same. Alternatively, the first side wall, the second side wall, the third side wall and the fourth side wall may be different from each other.

When the method of the present invention further comprises a second recrystallization step in addition to the first recrystallization step, each of these recrystallization steps may be carried out once, or the recrystallization steps are alternately repeated. You can go.

When the present invention is applied to the manufacture of a semiconductor device, a high quality silicon carbide single crystal region can be used as a channel region. When a plurality of cavities are formed and the present invention is applied to manufacture of a semiconductor device, a region corresponding to a pillar portion between cavities does not have an active region of the semiconductor device formed therein, but an element isolation region. You may use as. When the present invention is applied to the manufacture of a semiconductor device, cavities may be left in the completed semiconductor device, or polishing may be performed until the cavities disappear at any stage of the manufacturing process.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals, and duplicated description will be omitted.

(First Embodiment) FIGS. 1A to 1C.
FIG. 4 is a cross-sectional view schematically showing a method for manufacturing a single crystal material according to the first embodiment of the present invention.

In the method according to the present embodiment, first, as shown in FIG.
As shown in (a), a silicon carbide single crystal material 1 as a base material
The cavity 2 is formed in the inside of the. The method of forming the cavity 2 will be described in detail later.

Next, silicon carbide single crystal material 1 is heated so that a part of the surface of silicon carbide single crystal material 1 facing the space in cavity 2 becomes higher in temperature than the surface facing the surface.
For example, in the figure, heating is performed so that the lower side has a higher temperature than the upper side. The size of the cavity 2 in the temperature gradient direction can be arbitrarily selected, and can be set within a range of several hundred nm to several mm, for example. The temperature on the high temperature side must be at least about 1600 ° C. at which sublimation occurs, and for example, about 2000 to 24 where sublimation of silicon carbide occurs actively.
Set to around 00 degrees. The temperature gradient between the high temperature side and the low temperature side is set to, for example, about 1 to 20 ° C / cm.

When such a temperature gradient is formed, the cavity 2
Silicon carbide sublimes from the relatively high temperature surface facing the inner space, and the sublimated silicon carbide diffuses in the direction indicated by arrow 3 and crystallizes on the relatively low temperature surface. Sublimation above /
With the progress of crystallization (that is, recrystallization), the surface of relatively high temperature recedes, and the surface of relatively low temperature grows a high-quality silicon carbide single crystal region with reduced defects. As a result, the position of the cavity 2 is changed from the state of FIG. 1 (a) to that of FIG. 1 (b).
And the state of FIG. 1C are sequentially changed. That is, cavity 2 moves inside silicon carbide single crystal material 1 from the low temperature side to the high temperature side. The moving speed of the cavity 2 depends on the heating temperature, the temperature gradient, and the size of the cavity 2 in the direction of the temperature gradient. Under the above temperature conditions, it is usually about 1 to 200 μm /
Move at the speed of h. As described above, almost the entire silicon carbide single crystal material 1 can be improved in quality.

As described above, in this embodiment, the cavity 2 is formed in the silicon carbide single crystal material 1 and the silicon carbide is recrystallized inside the silicon carbide single crystal material 1 to improve the quality of the single crystal. ing. Therefore, almost all of the sublimated silicon carbide is used for growing the high-quality silicon carbide single crystal region. Therefore, a thicker high quality silicon carbide single crystal region can be more easily formed as compared with the case of growing a high quality epitaxial layer on a single crystal substrate. Further, in the present embodiment, since cavity 2 is isolated from the external space of silicon carbide single crystal material 1, impurities in the external space to the high quality silicon carbide single crystal region are contained in the high quality silicon carbide single crystal region. Will not be mixed in. Further, in the present embodiment, as compared with the case where silicon carbide is sublimated from one of a pair of silicon carbide single crystal substrates arranged to face each other in the chamber and the sublimated silicon carbide is crystallized on the other. Since recrystallization is carried out in a remarkably narrow reaction space, undesired turbulent flow in the reaction space, undesired crystallization other than on the low temperature side surface, etc. are suppressed. Therefore, according to this embodiment, a thick and extremely high-quality silicon carbide single crystal can be manufactured.

In the present embodiment, the method for forming the cavity 2 inside the silicon carbide single crystal material 1 is not particularly limited, and for example, the method described below can be used.

FIGS. 2A to 2C are schematic views showing a method of forming a cavity that can be used in the method of manufacturing a single crystal material according to the first embodiment of the present invention. 2A is a perspective view, FIG. 2B is a sectional view of the structure shown in FIG. 2A, and FIG. 2C is shown in FIGS. 2A and 2B. It is sectional drawing of the structure obtained by giving a predetermined process to a structure.

In forming the cavity 2, first, referring to FIG.
As shown in (a) and (b), a silicon carbide single crystal material 1
RIE (Reactive Ion Etch) on the surface of
ing) method or the like to form the concave portions 6 periodically. Next, the structure shown in FIGS. 2A and 2B is subjected to a high temperature treatment in a reducing atmosphere such as a hydrogen atmosphere. When such a high temperature treatment is performed, fluidization occurs on the surface of the silicon carbide single crystal material 1, whereby the openings of the recesses 6 are closed and the recesses 6 are connected to each other. As a result, as shown in FIG. 2C, a cavity 2 is formed inside the silicon carbide single crystal material 1.

For example, radius R = 0.25 μm and depth L =
Cylindrical recesses 6 of 2.3 μm are periodically formed so that the distance D between adjacent recesses 6 is 0.78 μm, and then, for example, hydrogen atmosphere under high temperature and low pressure of 1600 to 1850 ° C. and 20 Torr. In the case where the heat treatment is performed for about 30 minutes, a huge flat plate-shaped cavity 2 having a size T = 0.7 μm in the vertical direction in the figure is formed (the thickness of the flat plate-shaped cavity 2 is T = 27). given by .83R ³ / D ^2). Also, <11
When the cavity 2 is formed by this method in a (0001) plane wafer having an off angle in the −20> direction, the opposing surfaces of the cavity 2 automatically become the (0001) plane having the off angle.

This method is applied to Applied Physics Vol. 69.
No. 10 (2000) pp. The method for forming a cavity in a Si single crystal reported in 1187-1191 is applied to the formation of a cavity in a silicon carbide single crystal.

According to the above cavity forming method, it is possible to form the cavity 2 for high quality control with good controllability. In addition, since the cavity 2 having various shapes such as a flat plate shape, a rod shape, and a spherical shape can be formed by appropriately changing the formation pitch or the arrangement of the concave portions 6, it can be selected according to the structure of the semiconductor device to be manufactured. is there.

The cavity 2 can be formed by a method other than that described with reference to FIGS. For example, cavity 2 can be formed by forming a recess on the surface of a silicon carbide single crystal base material and bonding another silicon carbide single crystal base material on the surface. In this case, the silicon carbide single crystal material 1 is composed of a pair of silicon carbide single crystal base materials,
It is possible to obtain substantially the same effect as described above. In this case, the carbide crystal material on the high temperature side does not necessarily have to be a single crystal, and may be a polycrystal.

In the present embodiment, silicon carbide single crystal material 1 may have any shape. For example, as the silicon carbide single crystal material 1, a (0001) plane wafer cut out from a silicon carbide ingot grown in the <0001> direction,
A (0001) plane wafer with an off angle in the <11-20> direction, a (000-1) plane wafer, a (000-1) plane wafer with an off angle in the <11-20> direction, (11-2
0) plane wafer, 4H-SiC (03-38) plane wafer,
A 6H-SiC (01-14) plane wafer can be used.

When these wafers are used as the silicon carbide single crystal material 1, a flat plate-shaped cavity 2 parallel to the wafer surface may be formed. Further, as the silicon carbide single crystal material 1, (000
When a 1) plane wafer is used, as described in the fourth embodiment, instead of the cavity 2, a groove may be formed in which the side wall is the (11-20) plane. Further, <0001> direction, <11-20> direction, 4H-SiC <03-38>
Direction, a wafer cut out from each of the silicon carbide ingots grown in the 6H-SiC <01-14> direction may be used. In a wafer having an off-angle to a (0001) plane wafer or a (000-1) plane wafer, step flow growth occurs at the surface of the cavity where crystallization occurs, so that the appearance of different polytypes is suppressed. Effects such as flattening and filling of micropipes can be expected. In addition, the (11-20) plane wafer and 4H-SiC (0
In the 3-38) plane wafer and the 6H-SiC (01-14) plane wafer, since the silicon carbide single crystal has a periodic array on the surface where crystallization occurs in the cavity, it is different even if the off angle is not provided. The appearance of polytypes is suppressed and a flat surface is easily obtained. The (0001) plane wafer has sidewalls (11
In the case of forming a groove to be the −20) plane, (11
-20) A temperature gradient is set perpendicularly to the plane, and the cavity is moved in a direction perpendicular to the thickness direction of the wafer to achieve high quality.

The silicon carbide single crystal material 1 that is the base does not necessarily have to be in the form of a wafer, but a cavity is formed at one end of a cylindrical ingot and a temperature gradient is set toward the other end. High quality may be achieved. Further, by changing the direction of the temperature gradient, the moving direction of the cavity 2 can be changed, and the quality of the inside of the ingot can be improved throughout. When it is desired to form the silicon carbide single crystal material 1 after quality improvement into a complete wafer shape without the cavity 2, the back surface side may be polished until the remaining cavity 2 disappears.

In the first embodiment described above, one cavity 2 is formed in the silicon carbide single crystal material 1, but the number of cavities 2 formed in the silicon carbide single crystal material 1 is not particularly limited.
For example, the plurality of cavities 2 may be arranged in a direction perpendicular to the direction forming the temperature gradient.

Further, although the cavity 2 has a flat plate shape in the first embodiment, the shape of the cavity 2 is not particularly limited. For example, the cavity 2 may be square or spherical.

Further, in the first embodiment, the cavity 2 is moved from the upper side to the lower side in the drawing, but thereafter, the cavity 2 may be further moved from the lower side to the upper side. That is, the high temperature side and the low temperature side may be reversed. in this case,
Since recrystallization is repeated, higher quality can be achieved. When the cavity 2 is, for example, a square or a sphere, the cavity 2 may be moved from the upper side to the lower side in the figure, and then the cavity 2 may be further moved to the right side or the left side in the figure. In this case, the quality of almost the entire silicon carbide single crystal material 1 can be improved even though the shape of the cavity 2 is square or spherical.

(Second Embodiment) In the above-described first embodiment, the formation of one cavity 2 inside the silicon carbide single crystal material 1 has been mainly described. In the second embodiment described below, a plurality of cavities 2 are formed inside the silicon carbide single crystal material 1.

FIGS. 3A to 3C are sectional views schematically showing a method for producing a single crystal material according to the second embodiment of the present invention.

In the method according to this embodiment, first, as shown in FIG.
As shown in (a), a plurality of cavities 2 are formed inside the silicon carbide single crystal material 1. Here, two cavities 2a and 2b are formed as the cavity 2. The method of forming the cavities 2a and 2b will be described in detail later.

Next, for example, in the figure, the silicon carbide single crystal material 1 is heated so that the lower side has a higher temperature than the upper side. When such a temperature gradient is formed, recrystallization similar to that described in the first embodiment proceeds in each of the region surrounding the cavity 2a and the region surrounding the cavity 2b. As a result, the positions of the cavities 2a and 2b are as shown in FIG.
The state of (a) is sequentially changed to the state of FIG. 3 (b) and the state of FIG. 3 (c). That is, the cavities 2a and 2b move inside the silicon carbide single crystal material 1 from the low temperature side to the high temperature side. As described above, almost the entire silicon carbide single crystal material 1 can be improved in quality.

As described above, in the present embodiment, the silicon carbide single crystal material 1 is provided with the plurality of cavities 2a and 2b, and the temperature gradient is formed along the arrangement direction thereof. Therefore, as compared with the method according to the first embodiment, it is possible to complete the quality improvement in a shorter time or to form a higher quality high quality silicon carbide single crystal region.

In this embodiment, the method for forming the cavities 2a and 2b inside the silicon carbide single crystal material 1 is not particularly limited, and, for example, the method described below can be used.

FIGS. 4 (a) to 4 (c) are diagrams schematically showing a method of forming a cavity that can be used in the method of manufacturing a single crystal material according to the second embodiment of the present invention. 4A is a perspective view, FIG. 4B is a sectional view of the structure shown in FIG. 4A, and FIG. 4C is shown in FIGS. 4A and 4B. It is sectional drawing of the structure obtained by giving a predetermined process to a structure.

In forming the cavity 2, first, referring to FIG.
As shown in (a) and (b), a silicon carbide single crystal material 1
Recesses 6 are periodically formed on the surface of the substrate by RIE or the like. Here, the recess 6 is formed deeper than the recess 6 shown in FIGS. Next, the structure shown in FIGS. 4A and 4B is subjected to high temperature treatment in a reducing atmosphere such as a hydrogen atmosphere. In the structure shown in FIGS. 4A and 4B, since the deep recesses 6 are formed, not only the openings of the recesses 6 but also the intermediate portions are formed when the recesses 6 are connected by performing the above high temperature treatment. Will be blocked. As a result,
As shown in (c), a plurality of cavities 2 a and 2 b are formed inside the silicon carbide single crystal material 1.

The number of the cavities 2 formed by the above method depends on the depth L of the recess 6. For example, radius R =
Cylindrical recesses 6 having a depth of 0.25 μm and a depth L of 5 μm are periodically formed so that the distance D between adjacent recesses 6 is D = 0.78 μm, and then, for example, 1600 to 1850 ° C.
When the heat treatment is performed for about 30 minutes in a hydrogen atmosphere at a high temperature and a low pressure of 20 Torr, two cavities 2 are formed. Further, for example, three cavities 2 are formed when the depth of the recess 6 is 7 μm, and four cavities 2 are formed when the depth of the recess 6 is 9 μm.

(Third Embodiment) FIGS. 5A to 5F.
FIG. 6 is a diagram schematically showing a method for producing a single crystal material according to a third embodiment of the present invention. 5A is a perspective view, and FIGS. 5B to 5F are sectional views. Further, FIG. 5B is a sectional view of the structure shown in FIG.

In the method according to this embodiment, first, as shown in FIG.
As shown in (a) and (b), a silicon carbide single crystal material 1
The concave portions 6a and 6b are periodically formed by the RIE method or the like on the surface of. Here, the recesses 6b located at both ends are formed to have a larger diameter than the recesses 6a located between them. Next, with respect to the structure shown in FIGS.
Perform high temperature treatment in a reducing atmosphere such as a hydrogen atmosphere. By this high temperature treatment, the recesses 6a and 6b are connected to each other and the opening of the recess 6a is closed. However, in the structure shown in FIGS. 5A and 5B, since the recess 6b having the larger diameter is formed on both sides of the recess 6a having the smaller diameter, the opening of the recess 6b is not completely closed. Slit-shaped holes 7 are left at those positions. As described above, FIG.
As shown in (c), a cavity 2 is formed inside the silicon carbide single crystal material 1, and a slit-shaped hole 7 that connects the cavity 2 and the external space of the silicon carbide single crystal material 1 is formed. It Here, although the slit-shaped hole 7 is formed in the peripheral portion of the cavity 2 here, the hole 7 may be formed in the central portion in order to facilitate introduction of gas from the outside.

In this embodiment, recrystallization is performed while controlling the atmosphere inside the cavity 2 from outside the silicon carbide single crystal material 1. This makes it possible to intentionally control the surface reaction that occurs during recrystallization to suppress the generation of defects and suppress or promote the incorporation of impurities. In addition, it is possible to increase or decrease the moving speed of the cavity 2 by controlling the pressure and the atmosphere. In particular, if the inside of the cavity 2 is made into a reducing atmosphere such as hydrogen, fluidization of the surface that causes crystallization is promoted, and it becomes possible to further improve the quality. Also,
By supplying SiH ₄ gas as a silicon supply source and C ₃ H ₈ gas as a carbon supply source in the cavity 2 at a predetermined ratio, the ratio between the surface etching rate by sublimation and the recrystallization rate can be controlled. Higher quality can be achieved. Further, by increasing the ratio of C ₃ H ₈ gas serving as a carbon supply source, nitrogen incorporation can be suppressed and a single crystal having a low impurity concentration can be manufactured. Furthermore, T as a P-type doping gas
By supplying MA (trimethylaluminum) as nitrogen as an N-type doping gas, a P-type region or an N-type region can be formed in the silicon carbide single crystal material 1 in a free shape.

In the third embodiment described above, the cavity 2
Although a slit is formed as the hole 7 that connects the outer space of the silicon carbide single crystal material 1 with the slit 7, the shape of the hole 7 is not limited to this. In addition, in the present embodiment, FIG.
Although the hole 7 and the cavity 2 are formed by the method described with reference to (c), the method of forming the hole 7 and the cavity 2 is not limited to this. For example, after forming cavity 2 by the method described with reference to FIGS. 2A to 2C, part of silicon carbide single crystal material 1 may be removed to form hole 7.

The method according to the third embodiment can be applied to the manufacture of various electronic devices. For example, when the method according to the third embodiment is used, an excellent semiconductor substrate can be obtained and therefore an excellent semiconductor device can be manufactured.

FIGS. 6A to 6C are sectional views schematically showing an example of a semiconductor substrate that can be manufactured by using the method for manufacturing a single crystal material according to the third embodiment of the present invention. . In addition,
Here, a low-concentration n-type layer (n ⁻ ) is used as the silicon carbide single crystal material 1 that is the base material.

The semiconductor substrate shown in FIG. 6A has a laminated structure of a p-type layer and an n-type layer as a high-quality silicon carbide single crystal region (or doping region) 8. This laminated structure can be used as a Super Junction structure. When the method for producing a single crystal material according to the third embodiment is used, the structure shown in FIG. 6 (a) allows the gas supplied from the external space of the silicon carbide single crystal material 1 into the cavity 2 through the hole 7. It can be obtained by performing the above-mentioned high temperature treatment while alternately switching between the P-type doping gas and the N-type doping gas. That is, it is possible to form the doping region 8 at the same time as the quality improvement process of the single crystal. As the doping gas, for example, TMA (trimethylaluminum) can be used for the P type and nitrogen can be used for the N type.

In the semiconductor substrate shown in FIG. 6B, a high-quality silicon carbide single crystal region (or a doping region) 8 having a conductivity type opposite to that of the base silicon carbide single crystal material 1 is formed. It has a mold layer. In the structure shown in FIG. 6B, the conductivity type of the base silicon carbide single crystal material 1 is the conductivity type as the gas supplied from the external space of the silicon carbide single crystal material 1 into the cavity 2 through the hole 7. However, it can be obtained by performing the above high temperature treatment while supplying a doping gas opposite thereto.

In the semiconductor substrate shown in FIG. 6C, the high-quality silicon carbide single crystal region (or doping region) 8 is an n-type having the same conductivity type as that of the base silicon carbide single crystal material 1. Have layers. In the structure shown in FIG. 6C, the conductivity type and the conductivity type of the base silicon carbide single crystal material 1 are used as the gas supplied from the outer space of the silicon carbide single crystal material 1 into the cavity 2 through the holes 7. It can be obtained by performing the above high temperature treatment while supplying the same doping gas.

According to this embodiment, it is possible to improve the quality of the single crystal and form the doped region 8 at the same time. When the structure shown in FIGS. 6A to 6C is subjected to heat treatment in an oxidizing atmosphere, an oxide film is formed on the inner walls of the cavity 2 and the hole 7, so that these doping regions 8 are separated by the dielectric material. SOI (SiC on Insula)
(tor) region, and a device with high speed and low power consumption can be formed. Furthermore, the large area SON (SiCon N
In the case of an
The characteristics exceeding the I structure can be obtained.

(Fourth Embodiment) In the first to third embodiments described above, the method mainly using the cavity 2 has been described. In the fourth embodiment described below, a groove is used instead of the cavity 2.

FIGS. 7A to 7C are sectional views schematically showing an example of a method for manufacturing a semiconductor device using the method for manufacturing a single crystal material according to the fourth embodiment of the present invention. In this method, first, as shown in FIG. 7A, a groove 2 is formed on the surface of a silicon carbide single crystal substrate 1. In addition, here
As the silicon carbide single crystal substrate 1, one having an n ⁻ type layer formed on an n ⁺ type layer is used, and the groove 2 is formed on the surface of the n ⁻ type layer. In addition, (0
The (001) plane is exposed and the (11-20) plane is exposed on the side wall of the groove.

Next, the ambient temperature is set so that a temperature difference is generated between the opposite side walls of the groove 2. Here, in the figure, the left side wall is heated so as to have a higher temperature than the right side wall. As a result, as shown in FIG. 7A, silicon carbide is sublimated from the left side wall, and the sublimated silicon carbide is crystallized on the right side wall to form high quality silicon carbide single crystal region 8a.
Is formed.

After the heat treatment is performed for a predetermined time, the temperature gradient is reversed and the heat treatment is further performed for a predetermined time. That is, in the figure, the right side wall is heated so as to have a higher temperature than the left side wall. As a result, FIG.
As shown in (b), silicon carbide is sublimated from the right side wall, and the sublimated silicon carbide is crystallized on the left side wall to form high quality silicon carbide single crystal region 8b.

After that, the insulating film 9, the gate electrode 10, the source electrode 11, the drain electrode 12 and the like are formed. As described above, as shown in FIG. 7C, the vertical MO having the high-quality silicon carbide single crystal regions 8a and 8b as the channel regions.
Obtain the SFET device structure.

According to this embodiment, the channel regions 8a,
Since 8b is improved in quality, it is possible to realize a low-loss vertical MOSFET having a large channel mobility. If the quality of only the channel regions 8a and 8b is to be improved, the heat treatment time may be very short. In addition, even when the quality of the entire region between the grooves 2 is improved,
Since it is only necessary to move the groove 2 by sublimation / crystallization by a thermal gradient within a minute area sandwiched between the grooves 2, high quality can be achieved by heat treatment for a relatively short time.
Although the epitaxial growth method is not used in the above embodiment, it is possible to combine the method described above with the epitaxial growth method. For example, an n ⁻ -type substrate manufactured by a sublimation method is n ⁻ -typed by an epitaxial growth method.
A mold layer may be formed and the above-described purification method may be applied thereto to further improve the quality of the epitaxial layer.

Further, in the above-described embodiment, the manufacturing of a specific semiconductor device as an electronic device has been described, but the present invention is not limited to the high breakdown voltage semiconductor device, and other devices such as a light emitting diode, a semiconductor laser, and an LSI. It is also applicable to semiconductor devices. In addition, since high-purity silicon carbide containing almost no impurities is transparent, if the cavity is convex or concave, a substance having a refractive index different from that of silicon carbide is enclosed in the cavity to achieve high accuracy. A micro lens can be obtained. Therefore, an electronic device having such a microlens can be obtained.

Further, in the above-described embodiment, the case where the cavity 2 is left without being embedded to form the large area SON structure has been described, but the cavity 2 can be used for other purposes. For example, if a semiconductor element is formed on a high-quality portion of a silicon carbide single crystal material, an oxide film is formed on the surface facing the space inside the cavity, and a liquid is enclosed in the cavity, this is used as a heat pipe. Can be used.
In this case, the temperature rise of the semiconductor element can be suppressed.

[0066]

As described in detail above, in the present invention, a cavity or groove is formed in a silicon carbide single crystal material or a silicon carbide single crystal substrate, and silicon carbide is formed inside the silicon carbide single crystal material or the silicon carbide single crystal substrate. Sublimation and crystallization of the single crystal improves the quality of the single crystal. Therefore, for example, it is possible to manufacture an extremely high quality silicon carbide single crystal in various thicknesses from a very thin film form to a bulk form like a substrate. That is, according to the present invention, a method for producing a single crystal capable of producing a thick and high-quality silicon carbide single crystal, and a method for producing an electronic device using such a silicon carbide single crystal are provided.

[Brief description of drawings]

1A to 1C are cross-sectional views schematically showing a method for manufacturing a single crystal material according to a first embodiment of the present invention.

2A to 2C are diagrams schematically showing a method for forming a cavity that can be used in the method for producing a single crystal material according to the first embodiment of the present invention.

3 (a) to 3 (c) are cross-sectional views schematically showing a method for manufacturing a single crystal material according to a second embodiment of the present invention.

4A to 4C are diagrams schematically showing a method of forming a cavity that can be used in the method of manufacturing a single crystal material according to the second embodiment of the present invention.

5 (a) to (f) are diagrams schematically showing a method for producing a single crystal material according to a third embodiment of the present invention.

6A to 6C are cross-sectional views schematically showing an example of a semiconductor substrate that can be manufactured by using the method for manufacturing a single crystal material according to the third embodiment of the present invention.

7A to 7C are cross-sectional views schematically showing an example of a method for manufacturing a semiconductor device using the method for manufacturing a single crystal material according to the fourth embodiment of the present invention.

[Explanation of symbols]

1. Silicon carbide single crystal material or silicon carbide single crystal substrate 2 ... Cavity 2a ... cavity 2b ... cavity 3 ... Arrow 6 ... recess 6a ... Groove with small radius 6b ... Groove with large radius 7 ... hole 8 ... Doping region 8a ... High quality silicon carbide single crystal region 8b ... High-quality silicon carbide single crystal region 9 ... Insulating film 10 ... Gate electrode 11 ... Source electrode 12 ... Drain electrode

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Claims (6)

[Claims] 1. A step of forming a cavity inside a silicon carbide single crystal material, and a first surface of the silicon carbide single crystal material facing a space in the cavity facing the first surface across the cavity. A temperature higher than that of the second surface of the silicon carbide single crystal material, sublimating silicon carbide from the first surface and crystallizing the sublimated silicon carbide on the second surface. And a method for producing a single crystal material. 2. The step of forming the cavity comprises forming a plurality of recesses in the silicon carbide single crystal material, and heating the silicon carbide single crystal material in a reducing atmosphere to surround the plurality of recesses. And fluidizing the silicon carbide single crystal material to close the openings of the plurality of recesses and connect the plurality of recesses to each other. Production method. 3. Prior to the step of crystallizing, a step of forming a hole in the silicon carbide single crystal material for connecting a space inside the cavity and a space outside the silicon carbide single crystal material is further formed. The single crystal according to claim 1 or 2, wherein the step of crystallizing is performed while the atmosphere inside the cavity is controlled from the outside of the silicon carbide single crystal material through the hole. Material manufacturing method. 4. The step of sublimating silicon carbide from the second surface and crystallizing the sublimated silicon carbide on the first surface by setting the second surface at a higher temperature than that of the first surface. Claim 1 characterized in that it is included.
A method for manufacturing the single crystal material according to claim 3. 5. A step of forming a cavity inside the silicon carbide single crystal material, and a first surface of the silicon carbide single crystal material facing a space in the cavity facing the first surface across the cavity. The silicon carbide single crystal obtained by sublimating silicon carbide from the first surface and crystallizing the sublimated silicon carbide on the second surface at a higher temperature than the second surface of the silicon carbide single crystal material described above. A method of manufacturing an electronic device, comprising: a step of forming a region; and a step of manufacturing an electronic device including the silicon carbide single crystal region. 6. A step of forming a groove in a silicon carbide single crystal substrate, the first side wall of the groove having a temperature higher than that of a second side wall of the groove facing the first side wall, Forming a silicon carbide single crystal region by sublimating silicon carbide and crystallizing the sublimated silicon carbide on the second sidewall; and a step of manufacturing an electronic device including the silicon carbide single crystal region. A method of manufacturing an electronic device, comprising: