JP6958042B2 - Single crystal substrate, manufacturing method of single crystal substrate and silicon carbide substrate - Google Patents

Description

The present invention relates to a single crystal substrate, a method for producing a single crystal substrate, and a silicon carbide substrate.

Silicon carbide (SiC) is a wide bandgap semiconductor having a bandgap (2.36 to 3.23 eV) that is more than twice that of Si, and is attracting attention as a material for high withstand voltage devices.

However, unlike Si, SiC has a high crystallization temperature, so that it is difficult to prepare a single crystal ingot by a method of pulling up from a liquid phase similar to that of a Si substrate. Therefore, a method of forming a SiC single crystal ingot by a sublimation method has been proposed, but in such a sublimation method, it is very difficult to form a substrate having a large diameter and few crystal defects. On the other hand, among SiC crystals, cubic SiC (3C-SiC) can be formed at a relatively low temperature, and therefore, a method of epitaxial growth on a substrate has been proposed.

As one of the methods for manufacturing a SiC substrate using this epitaxial growth, a heteroepitaxial technique for growing 3C-SiC on a Si substrate in the gas phase has been studied. For example, Non-Patent Document 1 discloses that an offset substrate in which the [001] direction is tilted by about 4 ° in the [001] direction is used in the Si (100) substrate, and SiC is epitaxially grown on the surface thereof. .. As a result, it is possible to reduce crystal defects called anti-phase boundary (APB) in the SiC growth layer.

Further, Patent Document 1 includes a groove including a bottom portion of the (001) plane and a facet composed of the (111) plane, the (-1-11) plane, the (-111) plane, and the (1-11) plane. A semiconductor device including a semiconductor substrate, a semiconductor buffer layer provided on the semiconductor substrate, and a first semiconductor layer provided on the semiconductor buffer layer is disclosed.

Journal of Crystal Growth 78 (1986) 538-544.

Japanese Unexamined Patent Publication No. 2006-196631

However, conventional offset substrates and semiconductor substrates provided with grooves cannot sufficiently reduce crystal defects. In particular, when the SiC growth layer to be grown on the substrate is thin, this tendency becomes remarkable. Therefore, it is necessary to thicken the SiC growth layer, which leads to a decrease in manufacturing efficiency.

An object of the present invention is a single crystal substrate capable of forming a silicon carbide growth layer having few crystal defects even when the silicon carbide growth layer to be grown is thin, a method for producing a single crystal substrate capable of efficiently producing such a single crystal substrate, and a method for producing the single crystal substrate. The present invention is to provide a silicon carbide substrate having a high quality silicon carbide growth layer.

The above object is achieved by the following invention.
The single crystal substrate of the present invention has a plurality of grooves having a first crystal plane and a second crystal plane facing the first crystal plane on the inner surface and an extension direction of <110>, and between the grooves. A base substrate comprising a flat surface provided on the
The silicon carbide base film provided on the flat surface and
It is characterized by having.

As a result, the silicon carbide growth layer can be grown using the silicon carbide base film as a seed layer, so that the silicon carbide growth layer can be efficiently and stably grown from the silicon carbide base film toward the groove. As a result, a higher quality silicon carbide growth layer can be obtained even when the silicon carbide growth layer to be grown is thin.

In the single crystal substrate of the present invention, the flat surface is preferably a Si {100} surface.
As a result, the flat surface and the groove can be formed with high accuracy, so that crystal defects can be more efficiently eliminated or reduced even when the silicon carbide growth layer to be grown is thin.

In the single crystal substrate of the present invention, the flat surface is preferably a surface in which the Si {100} surface is inclined at an angle of more than 0 ° and less than 54.7 ° in the <110> direction.

As a result, crystal defects can be eliminated or reduced not only on the groove but also on the flat surface. As a result, a high-quality silicon carbide growth layer with fewer crystal defects can be formed.

In the single crystal substrate of the present invention, the angle formed by the flat surface and the first crystal plane is preferably an angle larger than the angle formed by the flat surface and the Si {111} surface.

As a result, crystal defects can be associated with each other with a higher probability and disappear or be reduced.

In the single crystal substrate of the present invention, the base substrate preferably contains silicon, polycrystalline silicon carbide or diamond.
This makes it possible to form a higher quality silicon carbide growth layer.

The method for producing a single crystal substrate of the present invention is a method for producing a single crystal substrate of the present invention.
A step of preparing a masked base material including a single crystal base material and a mask provided on a part of the surface of the single crystal base material, and
The step of forming the silicon carbide base film on the surface of the single crystal base material, and
The step of etching the single crystal base material to form the groove, and
The step of removing the mask and
It is characterized by having.
As a result, the single crystal substrate can be efficiently manufactured.

The silicon carbide substrate of the present invention includes the single crystal substrate of the present invention.
The silicon carbide growth layer formed on the single crystal substrate and
It is characterized by having.

As a result, a silicon carbide substrate having a semiconductor layer capable of forming a power device can be obtained by taking advantage of the wide band gap of the silicon carbide growth layer and the small number of crystal defects.

It is a vertical sectional view of the silicon carbide substrate which concerns on this embodiment. It is a perspective view which shows the single crystal substrate contained in the silicon carbide substrate shown in FIG. It is a perspective view which shows only the base substrate included in the single crystal substrate shown in FIG. It is an enlarged view of the silicon carbide substrate shown in FIG. 1, and is the figure which shows typically an example of a crystal defect. It is a figure for demonstrating embodiment of the manufacturing method of the single crystal substrate of this invention. It is a figure for demonstrating embodiment of the manufacturing method of the single crystal substrate of this invention. It is a figure for demonstrating embodiment of the manufacturing method of the single crystal substrate of this invention. It is a figure for demonstrating embodiment of the manufacturing method of the single crystal substrate of this invention. It is a figure for demonstrating embodiment of the manufacturing method of the single crystal substrate of this invention.

Hereinafter, the single crystal substrate, the method for producing the single crystal substrate, and the silicon carbide substrate will be described in detail based on the preferred embodiments shown in the accompanying drawings.

<Silicon carbide substrate>
First, an embodiment of the silicon carbide substrate of the present invention will be described.

FIG. 1 is a vertical cross-sectional view of the silicon carbide substrate 10 according to the present embodiment.
The silicon carbide substrate 10 (the embodiment of the silicon carbide substrate of the present invention) includes the single crystal substrate 1 (the embodiment of the single crystal substrate of the present invention) and the silicon carbide growth layer 4 formed on the single crystal substrate 1. ,have. The silicon carbide growth layer 4 is used as a semiconductor layer capable of forming a power device described later, for example, by taking advantage of its wide band gap and few crystal defects.

Examples of the silicon carbide growth layer 4 include a semiconductor layer made of cubic silicon carbide (3C-SiC). Cubic silicon carbide has a wide bandgap value of 2.36 eV or more, high thermal conductivity and high dielectric breakdown electric field, and is therefore particularly preferably used as a wide bandgap semiconductor for power devices. The silicon carbide growth layer 4 is not limited to the semiconductor layer composed of 3C-SiC, and may be a semiconductor layer composed of 4H-SiC or 6H-SiC.

Then, by using the single crystal substrate 1 described later, a high-quality silicon carbide growth layer 4 with few crystal defects can be formed.

Examples of the power device manufactured by using the silicon carbide substrate 10 include a transistor and a diode for a step-up converter. Specific examples thereof include MOSFETs (metal-oxide-semiconductor field-effect transistors), insulated gate bipolar transistors (IGBTs), and Schottky barrier diodes (SBDs).

Hereinafter, the single crystal substrate 1 will be described in more detail.
(Single crystal substrate)
FIG. 2 is a perspective view showing a single crystal substrate 1 included in the silicon carbide substrate 10 shown in FIG. Further, FIG. 3 is a perspective view showing only the base substrate 2 included in the single crystal substrate 1 shown in FIG.

The single crystal substrate 1 has a base substrate 2 and a silicon carbide base film 3 provided on the base substrate 2. Such a single crystal substrate 1 is used, for example, as a base for epitaxially growing the silicon carbide growth layer 4 using the silicon carbide base film 3 as a seed layer.

− Base substrate −
The base substrate 2 is not particularly limited as long as it is a single crystal substrate, but for example, these crystals are formed on a silicon substrate, a polycrystalline silicon carbide substrate, a diamond substrate, a sapphire substrate, a quartz substrate, or an arbitrary substrate. It is a composite substrate.

Of these, the base substrate 2 preferably contains silicon, polycrystalline silicon carbide, or diamond, and is more preferably composed of a crystal material containing these as the main material. All of such base substrates 2 contain cubic crystals and are suitable as a base for growing silicon carbide. Therefore, by using such a base substrate 2, a higher quality silicon carbide growth layer 4 can be formed.

The thickness of the base substrate 2 is appropriately set so as to have a mechanical strength sufficient to withstand the handling of the step of forming the silicon carbide growth layer 4, but as an example, it is preferably about 100 μm or more and 2 mm or less.

As an example, the base substrate 2 shown in FIG. 1 is a single crystal silicon substrate whose main surface is a Si (001) surface. The lower surface 2a of the base substrate 2 is a flat surface of the Si (001) surface. On the other hand, the upper surface 2b of the base substrate 2 includes a plurality of flat surfaces 21 made of Si (001) surfaces and a plurality of grooves 22 whose extending direction is the [110] direction. That is, on the upper surface 2b, the plurality of flat surfaces 21 extending in the [110] direction and the plurality of grooves 22 extending in the [110] direction are alternately arranged in a direction orthogonal to the [110] direction. .. As a result, the upper surface 2b has a concave-convex shape in which convex portions (peaks) having the flat surface 21 as the top surface and concave portions (valleys) formed of the grooves 22 are alternately arranged along the [1-10] direction. It is a face.

Here, each groove 22 has a V-shaped cross-sectional shape. That is, each groove 22 includes a first crystal plane 221 and a second crystal plane 222 facing the first crystal plane 221 on the inner surface. Each groove 22 extends in the [110] direction while maintaining a V-shaped cross-sectional shape composed of the first crystal plane 221 and the second crystal plane 222. The fact that the first crystal plane 221 and the second crystal plane 222 face each other means that both are located on the inner surface of the groove 22 and are located on opposite sides of the bottom of the groove 22. say.

The opening angle θ of the groove 22, that is, the angle formed by the first crystal plane 221 and the second crystal plane 222 is preferably more than 70.6 °. The groove 22 having such an opening angle θ efficiently eliminates or reduces crystal defects in the silicon carbide crystal when silicon carbide is epitaxially grown on the single crystal substrate 1 including the groove 22 on the upper surface 2b. be able to. As a result, a high-quality silicon carbide growth layer 4 can be obtained.

Here, FIG. 4 is an enlarged view of the silicon carbide substrate 10 shown in FIG. 1, which schematically shows an example of crystal defects.

In the groove 22, as described above, the first crystal plane 221 and the second crystal plane 222 face each other. In the example shown in FIG. 4, the crystal defect 91 originating from the first crystal plane 221 extends in parallel with the Si (111) plane. On the other hand, the crystal defect 92 originating from the second crystal plane 222 extends in parallel with the Si (1-11) plane. Then, the crystal defect 91 and the crystal defect 92 meet at the meeting point 93 and disappear. In this way, in the silicon carbide growth layer 4 grown on the single crystal substrate 1 having the groove 22, the crystal defects 91 and 92 that grow in different directions can be associated with each other and disappear or be reduced.

If the opening angle θ of the groove 22 is less than the lower limit value, the opening angle θ is too narrow, so that the probability that the crystal defects 91 and 92 meet is reduced, and the crystal defects 91 and 92 cannot be sufficiently reduced. There is a risk.

Further, the opening angle θ of the groove 22 is more preferably 100 ° or more and 176 ° or less, further preferably 150 ° or more and 175 ° or less, and particularly preferably 166 ° or more and 174 ° or less. Thereby, the crystal defects 91 and 92 can be eliminated or reduced more efficiently. If the opening angle θ of the groove 22 exceeds the upper limit value, the effect of providing the groove 22 is diminished, so that the probability that the crystal defects 91 and 92 meet is reduced, and the crystal defects 91 and 92 are sufficiently satisfied. It may not be possible to reduce it.

The opening angle θ of the groove 22 can be adjusted according to the width of the groove 22, the formation time of the groove 22, and the like. For example, by widening the width of the groove 22, the opening angle θ of the groove 22 can be increased, while by narrowing the width of the groove 22, the opening angle θ of the groove 22 can be reduced. Further, since the groove 22 can be deepened by lengthening the formation time of the groove 22, the opening angle θ of the groove 22 can be reduced, while the groove 22 can be formed by shortening the formation time of the groove 22. Since 22 can be made shallow, the opening angle θ of the groove 22 can be increased.

As described above, such a groove 22 extends in the [110] direction. Further, the base substrate 2 has a plurality of grooves 22, which are arranged in a direction orthogonal to the [110] direction.

On the other hand, the base substrate 2 according to the present embodiment has a Si (001) surface as a flat surface 21 provided between adjacent grooves 22 as described above. By providing such a flat surface 21, the upper surface 2b of the base substrate 2 becomes a surface on which the groove 22 can be easily machined. Therefore, the flat surface 21 and the groove 22 are arranged alternately and with high accuracy. It becomes a surface having. Such an upper surface 2b can more efficiently eliminate or reduce crystal defects even when the film thickness of the silicon carbide growth layer 4 to be grown on the single crystal substrate 1 is thin.

Further, the flat surface 21 according to the present embodiment is a region for forming the above-mentioned silicon carbide base film 3. That is, by providing the flat surface 21, the silicon carbide base film 3 can be stably provided adjacent to the groove 22. As a result, the silicon carbide growth layer 4 can be grown using the silicon carbide base film 3 as a seed layer, so that the silicon carbide growth layer 4 can be efficiently and stably grown from the silicon carbide base film 3 toward the groove 22. Can be done. As a result, even when the silicon carbide growth layer 4 to be grown is thin, a higher quality silicon carbide growth layer 4 can be obtained.

The flat surface 21 may be parallel to or non-parallel to the lower surface 2a (back surface). When they are parallel to each other, it is easy to provide the silicon carbide base film 3 having a uniform thickness on the flat surface 21, so that the silicon carbide growth layer 4 that grows toward the groove 22 also has few crystal defects. Be done.

Further, the angle α formed by the flat surface 21 and the first crystal plane 221 is preferably larger than the angle formed by the flat surface 21 and the Si (1-11) surface. Since the Si (1-11) plane is a plane parallel to the crystal defect, the angle formed by the flat surface 21 and the first crystal plane 221 is set to be larger than the angle formed by the Si (1-11) plane. By setting, crystal defects can be associated with each other with a higher probability and disappear or be reduced.

Further, the angle formed by the flat surface 21 and the second crystal plane 222 is the same as the angle formed by the flat surface 21 and the first crystal plane 221.

Further, although FIG. 1 illustrates an example in which the flat surface 21 is a Si (001) surface, the flat surface 21 is not limited to this surface, and the Si (001) surface is inclined at a predetermined angle. It may be a surface. As an example, a surface in which the Si (001) surface is inclined in the [110] direction at an angle of more than 0 ° and less than 54.7 ° can be mentioned. By making the surface inclined in this way a flat surface 21, crystal defects can be eliminated or reduced not only in the groove 22 but also in the flat surface 21. As a result, a high-quality silicon carbide growth layer 4 with fewer crystal defects can be formed.

The inclination angle from the Si (001) plane is more preferably 1 ° or more and 15 ° or less, and further preferably 2 ° or more and 10 ° or less. As a result, the above effect becomes more remarkable, and the quality of the silicon carbide growth layer 4 can be further improved.

The period C of the groove 22 (see FIG. 4), that is, the total of the width W2 of the groove 22 and the width W1 of the flat surface 21 is not particularly limited, but is preferably 0.1 μm or more and 100 μm or less, preferably 0.2 μm. It is more preferably 20 μm or less. By setting the period C of the groove 22 within the above range, crystal defects can be more efficiently eliminated or reduced even when the film thickness of the silicon carbide growth layer 4 grown on the single crystal substrate 1 is thin.

The width W2 of the groove 22 is preferably 5% or more and 95% or less, and more preferably 30% or more and 85% or less of the period C of the groove 22. By setting the ratio of the width W2 of the groove 22 to the period C of the groove 22 within the above range, the balance between the width W2 of the groove 22 and the width W1 of the flat surface 21 is optimized. As a result, even when the film thickness of the silicon carbide growth layer 4 to be grown on the single crystal substrate 1 is thin, crystal defects can be eliminated or reduced more efficiently.

When the single crystal constituting the base substrate 2 is a cubic crystal, for example, (001) plane, (010) plane, (001) plane, (-100) plane, (0-10) plane, (00-) plane. 1) The surfaces and the like are surfaces equivalent to each other. Therefore, the Si (001) plane in the present specification can be replaced with these equivalent planes. That is, since the Si (001) plane in the present invention is not limited to that plane, the Si {100} plane is typically described when these equivalent planes are described together. Although the specification of the present application describes that there is a predetermined relationship between the Si (001) plane and other planes and directions, when the Si (001) plane is replaced with a plane equivalent thereto. Will be replaced with respect to other aspects and directions so that the predetermined relationships described above are maintained.

Similarly, for example, the (111) plane, the (-111) plane, the (1-11) plane, the (11-1) plane, the (-1-11) plane, the (-11-1) plane, and the like are equivalent to each other. This is the aspect. Therefore, the Si (111) plane and the Si (1-11) plane in the specification of the present application can be replaced with these equivalent planes. Therefore, in the present application, these equivalent planes are typically described together. Described as Si {111} plane. Although the specification of the present application describes that there is a predetermined relationship between the Si (111) plane or Si (1-11) plane and the other plane or direction, the Si (111) plane or Si (11) plane or Si ( 1-11) When a surface is replaced with an equivalent surface, other surfaces and directions are also replaced so that the predetermined relationship described above is maintained.

Similarly, for example, the [110] direction, the [101] direction, the [011] direction, the [1-10] direction, the [10-1] direction, the [01-1] direction, and the like are equivalent directions to each other. Therefore, the [110] direction and the [1-10] direction in the specification of the present application can be replaced with these equivalent directions. Therefore, in the present application, when these equivalent directions are collectively described, <110 is typically used. > Describe as direction. Although the specification of the present application describes that there is a predetermined relationship between the [110] direction and the [1-10] direction and other surfaces and directions, the [110] direction and the [1-10] direction are described. ] When the direction is replaced with the direction equivalent to it, other faces and directions are also replaced so that the predetermined relationship described above is maintained.

-Silicon carbide base film-
The silicon carbide base film 3 is provided on the flat surface 21 of the upper surface 2b of the base substrate 2. The silicon carbide base film 3 may be, for example, a carbide film obtained by modifying the surface of a silicon single crystal substrate, or is a silicon carbide film obtained by forming SiC on the upper surface of the base substrate 2. May be good. Further, the silicon carbide base film 3 may be provided only on a part of the flat surface 21.

The crystal structure of the silicon carbide base film 3 is not particularly limited, but is, for example, cubic SiC (3C-SiC). Crystals other than 3C-SiC, for example, 4H-SiC and 6H-SiC may be used.

The thickness of the silicon carbide base film 3 is not particularly limited, but is preferably 1 nm or more and 100 nm or less, more preferably 2 nm or more and 50 nm or less, and further preferably 3 nm or more and 10 nm or less. By setting the thickness of the silicon carbide base film 3 within the above range, the thickness becomes necessary and sufficient as the seed layer.

If the thickness of the silicon carbide base film 3 is less than the lower limit, the thickness of the silicon carbide base film 3 may be insufficient as a seed layer. On the other hand, if the thickness of the silicon carbide base film 3 exceeds the upper limit value, the thickness of the silicon carbide base film 3 becomes too thick. Therefore, depending on the conditions of epitaxial growth and the like, the influence of the silicon carbide base film 3 may affect the silicon carbide growth. There is a risk that it will reach layer 4.

Further, the thickness of the silicon carbide base film 3 is measured by, for example, a measuring method using an optical method such as an ellipsometry method, or the cross section of the single crystal substrate 1 is observed with an electron microscope, an optical microscope, or the like. It is obtained by a method such as measuring the thickness of the silicon carbide base film 3 on the observation image.

Further, the silicon carbide base film 3 is preferably a single crystal as a whole, but is not necessarily limited to that, and may be a polycrystal, a microcrystal, or an amorphous crystal.

The silicon carbide base film 3 may be provided not only on the flat surface 21 but also in the groove 22, that is, at least a part of the first crystal plane 221 and the second crystal plane 222, but the flat surface is preferable. It is provided only on 21. As a result, the silicon carbide base film 3 provided at a constant density can be used as a seed layer to grow crystals toward the inside of the groove 22, so that crystals with fewer crystal defects can be grown. As a result, a higher quality silicon carbide growth layer 4 can be obtained.

<Manufacturing method of single crystal substrate>
Next, an embodiment of the method for manufacturing a single crystal substrate of the present invention will be described.

5 to 9 are diagrams for explaining embodiments of the method for manufacturing a single crystal substrate of the present invention, respectively.

The method for manufacturing the single crystal substrate 1 according to the present embodiment includes a step of preparing a masked base material 120 including a single crystal base material 100 and a first mask 110 provided on a part of the surface thereof, and a single crystal. It includes a step of providing a second mask 30 on the surface of the base material 100, a step of etching the single crystal base material 100 to form a groove 22, and a step of removing the first mask 110. According to such a manufacturing method, the single crystal substrate 1 can be efficiently manufactured. Hereinafter, each step will be described in sequence.

[1] First, the single crystal base material 100 is prepared. Since the single crystal base material 100 is a raw material for the base substrate 2, for example, the same single crystal material as the base substrate 2 described above can be mentioned.

Next, a mask coating 110'is provided on the surface of the single crystal base material 100. Here, first, a mask coating film 110'is formed so as to cover the entire surface of the single crystal base material 100 (see FIG. 5). The mask coating 110'is composed of a material having resistance to the etching treatment of the single crystal base material 100 described later. Examples of such a material include silicon oxide and silicon nitride.

Next, a photosensitive coating is formed on the surface of the mask coating 110'. Then, the photosensitive film is exposed and developed to perform patterning. As a result, the resist film 130 provided only in the target region can be obtained (see FIG. 5).

Next, the mask coating film 110'is etched through the patterned resist film 130. As a result, the region of the mask film 110'that is not covered by the resist film 130 is etched. As a result, the first mask 110 provided in the region corresponding to the groove 22 to be formed in the step described later is obtained (see FIG. 6). Then, a masked base material 120 including the single crystal base material 100 and the first mask 110 provided on a part of the surface thereof can be obtained.
After that, the resist film 130 is removed.

[2] Next, as shown in FIG. 7, a second mask 30 is formed on the surface of the single crystal base material 100. The second mask 30 is formed in a region of the surface of the single crystal base material 100 that is not covered by the first mask 110. The second mask 30 may be formed on the surface of the first mask 110, but is omitted in FIG. 7.

The method for forming the second mask 30 is not particularly limited, but for example, a method of forming the second mask 30 by modifying (carbonizing) the surface of the single crystal base material 100, or forming silicon carbide on the upper surface of the single crystal base material 100. And the like.

The carbonization treatment is performed by heating the single crystal base material 100 in a carbon-based gas atmosphere. According to the carbonization treatment, a part of the single crystal base material 100 is converted into silicon carbide, so that the second mask 30 having higher crystallinity than other methods can be formed.

The carbon-based gas atmosphere is composed of a processing gas containing a carbon-based gas. The carbon-based gas is not limited as long as it contains carbon, but for example, in addition to ethylene (C ₂ H ₄ ), acetylene (C ₂ H ₂ ), propane (C ₃ H ₈ ), and methane (CH ₄ ). , Ethane (C ₂ H ₆ ), normal butane (n-C ₄ H ₁₀ ), isobutane (i-C ₄ H ₁₀ ), neopentane (neo-C ₅ H ₁₂ ) and other hydrocarbon gases. One or a combination of two or more of them can be used.

Further, it may be a mixed gas of these hydrocarbon-based gases and other gases. Examples of other gases include hydrogen silicate gas, silicon chloride gas, silicon carbide gas and the like.

Further, any gas such as a carrier gas may be mixed with these treated gases. Examples of the carrier gas include hydrogen, nitrogen, helium, argon and the like. When a carrier gas is used, the concentration of the carbon-based gas in the processing gas is appropriately set according to the rate of carbonization treatment and the like, but as an example, it is preferably 0.1% by volume or more and 30% by volume or less. It is more preferably 0.3% by volume or more and 5% by volume or less.

The heating temperature of the single crystal base material 100 in the carbonization treatment is preferably 500 ° C. or higher and 1400 ° C. or lower, more preferably 800 ° C. or higher and 1300 ° C. or lower, and further preferably 950 ° C. or higher and 1200 ° C. or lower. .. The heating time of the single crystal base material 100 in the carbonization treatment is preferably 0.5 minutes or more, more preferably 1 minute or more and 120 minutes or less, and 3 minutes. It is more preferably 90 minutes or less.

By setting the heating conditions within the above range, the second mask 30 having the thickness as described above can be formed. Further, by optimizing the applied thermal energy, the conversion rate to silicon carbide is optimized, so that a high-quality second mask 30 can be formed.

Further, the carbonization treatment may be carried out in any of a normal pressure atmosphere, a pressurized atmosphere and a reduced pressure atmosphere, but preferably in a state where the processing gas is introduced while exhausting the processing chamber containing the single crystal base material 100. You just have to do it. As an example, the amount of carbon-based gas introduced into the processing gas is 10 sccm or more and 100 sccm or less.

On the other hand, in the film forming process of silicon carbide, a vapor phase film forming method such as a CVD method or a vapor deposition method is used.

[3] Next, the single crystal base material 100 is subjected to an etching treatment. As a result, the groove 22 is formed.
In this etching process, the upper surface of the single crystal base material 100 is etched so that the lower part of the first mask 110 (the region facing the first mask 110) is removed.

Examples of such an etching process include a process of heating a masked base material 120 provided with a second mask 30 at a sublimation temperature of Si or higher. As a result, the Si atoms contained in the single crystal base material 100 are easily sublimated, and are discharged to the outside through the gap between the single crystal base material 100 and the first mask 110. As a result, the lower part of the first mask 110 is etched to form the groove 22 as shown in FIG.

Although the heating temperature is slightly different depending on the pressure in the space where the single crystal base material 100 is placed, it is a temperature at which Si atoms can sublimate and is below the melting point of Si, and is 900 ° C. or higher and 1400 ° C. or lower. It may be in the range. The heating time is set in a timely manner according to the heating temperature, but the time of exposure to the heating temperature is preferably 0.5 minutes or more and 60 minutes or less.

Further, the heating of the base material 120 with a mask may be performed in a normal pressure atmosphere or a pressurized atmosphere, but is preferably performed in a reduced pressure atmosphere or a reducing atmosphere. As a result, sublimation of Si atoms is promoted and oxidation is prevented, so that the etching treatment can be performed while suppressing the denaturation of the single crystal base material 100.

The pressure in this depressurized atmosphere is not particularly limited as long as it is less than atmospheric pressure, but is, for example, 0.5 Pa or less.
As described above, the groove 22 is formed below the first mask 110.

Etching is suppressed in the region where the second mask 30 is formed on the upper surface of the single crystal base material 100. Therefore, the flat surface 21 described above is formed in this region.

Further, in the etching treatment, instead of the above heat treatment, a treatment of exposing the masked base material 120 provided with the second mask 30 to the etching gas may be used.

[4] Next, the first mask 110 is removed.
For the removal of the first mask 110, for example, an etching process is used.

As described above, the single crystal substrate 1 shown in FIG. 9 is obtained. The second mask 30 shown in FIG. 9 can be used as the silicon carbide base film 3 shown in FIG. 1 described above. Therefore, the second mask 30 may be removed, but may be left without being removed.

<Manufacturing method of silicon carbide substrate>
Next, an example of a method for manufacturing the silicon carbide substrate 10 shown in FIG. 1 will be described.

The silicon carbide substrate 10 is manufactured by epitaxially growing the silicon carbide growth layer 4 on the single crystal substrate 1. The silicon carbide base film 3 functions as a seed layer for epitaxially growing the silicon carbide growth layer 4.

The silicon carbide growth layer 4 grows with the silicon carbide base film 3 as a seed layer by, for example, storing the single crystal substrate 1 in the treatment chamber and heating the single crystal substrate 1 while introducing the raw material gas. As a result, the silicon carbide substrate 10 shown in FIG. 1 is obtained.

The raw material gas includes a mixed gas obtained by mixing a gas containing carbon and a gas containing silicon in a predetermined ratio, a gas containing carbon and silicon in a predetermined ratio, a gas containing silicon, and a gas containing carbon. Examples thereof include a plurality of mixed gases obtained by mixing a gas containing silicon and a gas containing carbon and silicon at a predetermined ratio.

Among these, as the gas containing carbon, for example, in addition to ethylene (C ₂ H ₄ ), acetylene (C ₂ H ₂ ), propane (C ₃ H ₈ ), methane (CH ₄ ), ethane (C ₂ H ₆₎ ), butane _{(n-C 4 H 10)} , isobutane _{(i-C 4 H 10)} , include neopentane _{(neo-C 5 H 12)} or the like, singly or in combination of two or more of these Can be used.

Examples of the gas containing silicon include monosilane (SiH ₄ ), disilane (Si ₂ H ₆ ), trisilane (Si ₃ H ₈ ), tetrasilane (Si ₄ H ₁₀ ), dichlorosilane ( _{Si H 2} Cl ₂ ), and the like. Examples thereof include tetrachlorosilane (SiCl ₄ ), trichlorosilane (SiHCl ₃ ), hexachlorodisilane (Si ₂ Cl ₆ ), and one or more of these can be used in combination.

Further, examples of the gas containing carbon and silicon include methylsilane (SiH ₃ CH ₃ ), dimethylsilane (SiH ₂ (CH ₃ ) ₂ ), trimethylsilane (SiH (CH ₃ ) ₃ ), and the like. One type or a combination of two or more types can be used.

Further, the heating temperature in the epitaxial growth, that is, the temperature of the single crystal substrate 1 during the epitaxial growth is preferably 600 ° C. or higher and 1400 ° C. or lower, more preferably 800 ° C. or higher and 1350 ° C. or lower, and 950 ° C. or higher and 1100 ° C. The following is more preferable. The heating time in the epitaxial growth is appropriately set according to the target thickness of the silicon carbide growth layer 4.

The pressure in the processing chamber in the epitaxial growth is not particularly limited ^{, but is preferably 1 × 10 -4} Pa or more and atmospheric pressure (100 kPa) or less, and ^{more preferably 1 × 10 -3} Pa or more and 10 kPa or less.

By epitaxially growing the silicon carbide growth layer 4 on the silicon carbide base film 3 as described above, the silicon carbide substrate 10 having the high quality silicon carbide growth layer 4 can be efficiently obtained.

Such a high-quality silicon carbide substrate 10 is suitably used as a semiconductor substrate capable of manufacturing, for example, a high-performance power device.

The single crystal substrate, the method for producing the single crystal substrate, and the silicon carbide substrate according to the present invention have been described above based on the illustrated embodiments, but the present invention is not limited thereto. For example, the single crystal substrate and the silicon carbide substrate according to the present invention may each have an arbitrary element added to the above-described embodiment. Further, the method for producing a single crystal substrate according to the present invention may be one in which an arbitrary step is added to the above-described embodiment.

Next, specific examples of the present invention will be described.
1. 1. Manufacture of Silicon Carbide Substrate (Example 1)
<1> First, a 6-inch (diameter 150 mm, thickness 0.625 mm) silicon wafer having a Si (001) surface as a main surface was prepared as a single crystal base material. Then, the surface was washed with hydrofluoric acid or the like.

Next, a mask film was formed on the entire surface of the silicon wafer. Subsequently, after forming a resist film on the mask film, the mask film was etched. As a result, a masked base material having a first mask patterned in a desired shape was obtained.

<2> Next, a second mask was formed on the surface of the base material with a mask. In forming the second mask, ethylene gas was used, and the surface of the silicon wafer was carbonized by heating at 1000 ° C. for 60 minutes.

<3> Next, the masked base material provided with the second mask was subjected to an etching treatment. As a result, a base substrate in which grooves extending in the [011] direction and flat surfaces were alternately arranged was obtained. In this etching treatment, the masked base material was heated at 1000 ° C. for 30 minutes in a reduced pressure atmosphere.

<4> Next, the first mask was removed by an etching process. As a result, a single crystal substrate provided with a base substrate and a second mask was obtained.

<5> Next, a silicon carbide growth layer was epitaxially grown on the obtained single crystal substrate. As a result, a silicon carbide substrate was obtained. In the epitaxial growth, ethylene gas and dichlorosilane gas were used as raw material gases, and the silicon carbide growth layer was obtained by heating at 1000 ° C. for 2 hours.

(Examples 2 to 16)
A silicon carbide substrate was obtained in the same manner as in Example 1 except that the production conditions were changed as shown in Table 1 or Table 2.

(Comparative Examples 1 and 2)
As shown in Table 1, a silicon carbide substrate was obtained in the same manner as in Example 1 except that the production conditions were changed so that a flat surface was not formed.

(Comparative Example 3)
A silicon carbide substrate was obtained in the same manner as in Example 1 except that the groove forming process was omitted.

2. Evaluation of Silicon Carbide Substrate The density of crystal defects was measured for the silicon carbide substrates obtained in each Example and each Comparative Example. The density of crystal defects was measured by observing the surface of the central portion of the silicon carbide substrate with an atomic force microscope (AFM).

Next, assuming that the density of crystal defects of the silicon carbide substrate obtained in Comparative Example 3 was 1, the relative value of the density of crystal defects of the silicon carbide substrate obtained in each Example and each Comparative Example was calculated. Then, the calculation result was evaluated against the following evaluation criteria.

<Evaluation criteria for crystal defect density>
⊚: Relative value of crystal defect density is less than 0.5 ○: Relative value of crystal defect density is 0.5 or more and less than 0.75 Δ: Relative value of crystal defect density is 0.75 or more Less than 1 ×: The relative value of the density of crystal defects is 1 or more. The evaluation results are shown in Tables 1 and 2.

As is clear from Table 1, it was found that the silicon carbide substrates obtained in each example had a relatively low density of crystal defects even if the silicon carbide growth layer was thin. From this, it was confirmed that according to the present invention, a silicon carbide growth layer having a thin film thickness and high quality can be produced.

1 ... Single crystal substrate, 2 ... Base substrate, 2a ... Bottom surface, 2b ... Top surface, 3 ... Silicon carbide base film, 4 ... Silicon carbide growth layer, 10 ... Silicon carbide substrate, 21 ... Flat surface, 22 ... Grooves, 30 ... Second mask, 91 ... Crystal defect, 92 ... Crystal defect, 93 ... Meeting point, 100 ... Single crystal base material, 110 ... First mask, 110'... Mask coating, 120 ... Masked base material, 130 ... Resist film , 221 ... 1st crystal plane, 222 ... 2nd crystal plane, C ... period, W1 ... width, W2 ... width, α ... angle, θ ... opening angle

Claims (5)

A plurality of grooves having a first crystal plane and a second crystal plane facing the first crystal plane on the inner surface and extending in the <110> direction, and a flat surface provided between the grooves. With a base substrate,
The silicon carbide base film provided on the flat surface and
It is a manufacturing method of a single crystal substrate having
A step of preparing a masked base material including a single crystal base material and a mask provided on a part of the surface of the single crystal base material, and
The step of forming the silicon carbide base film on the surface of the single crystal base material, and
A step of etching the single crystal base material to form the groove in a region facing the mask, and a step of forming the groove.
The step of removing the mask and
A method for producing a single crystal substrate. The method for manufacturing a single crystal substrate according to claim 1, wherein the flat surface is a Si {100} surface. The method for manufacturing a single crystal substrate according to claim 1, wherein the flat surface is a surface in which the Si {100} surface is inclined at an angle of more than 0 ° and less than 54.7 ° in the <110> direction. The method for manufacturing a single crystal substrate according to claim 2 or 3, wherein the angle formed by the flat surface and the first crystal plane is larger than the angle formed by the flat surface and the Si {111} surface. The method for producing a single crystal substrate according to any one of claims 1 to 4, wherein the base substrate contains silicon, polycrystalline silicon carbide, or diamond.

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