JP7392526B2 - Method for manufacturing silicon carbide single crystal substrate - Google Patents

Description

The present invention relates to a method for manufacturing a silicon carbide single crystal substrate.

Silicon carbide is a compound semiconductor material composed of silicon and carbon. Silicon carbide has a dielectric breakdown field strength ten times that of silicon and a band gap three times that of silicon, making it excellent as a semiconductor material. Furthermore, since it is possible to control p-type and n-type over a wide range, which is necessary for device fabrication, it is expected to be a material for power devices that exceeds the limits of silicon.

However, compared with silicon carbide semiconductors, which have been widely used in the past, it is difficult to obtain a silicon carbide single crystal substrate with a large area, and the manufacturing process is also complicated. For these reasons, silicon carbide semiconductors are difficult to mass produce and are expensive compared to silicon semiconductors. The high cost of silicon carbide semiconductors has been one of the factors preventing the spread of silicon carbide semiconductors.

Various efforts have been made to reduce the cost of silicon carbide semiconductors. For example, Patent Document 1 discloses a method for manufacturing a silicon carbide substrate, in which at least a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate having a density of micropipes of 30 pieces/cm ² or less are prepared, and the silicon carbide It is described that a step of bonding a single crystal substrate and the silicon carbide polycrystalline substrate is performed, and then a step of thinning the single crystal substrate is performed to manufacture a substrate in which a single crystal layer is formed on the polycrystalline substrate. ing.

Furthermore, Patent Document 1 discloses that before the step of bonding the single crystal substrate and the polycrystalline substrate, a step of implanting hydrogen ions into the single crystal substrate to form a hydrogen ion implantation layer is performed, and the single crystal substrate and the polycrystalline substrate are bonded together. After the process of bonding with the crystal substrate and before the process of thinning the single crystal substrate, heat treatment is performed at a temperature of 350°C or less, and the process of thinning the single crystal substrate is mechanically performed using a hydrogen ion implantation layer. A method for manufacturing a silicon carbide substrate is described, which includes a step of peeling off the substrate.

With this method, more silicon carbide bonded substrates can be obtained from one silicon carbide single crystal ingot.

JP2009-117533A

The silicon carbide bonded substrate manufactured by the method of Patent Document 1 uses silicon carbide single crystal and silicon carbide polycrystal. Silicon carbide single crystals for silicon carbide bonded substrates are produced by epitaxial growth of silicon carbide single crystals by sublimation method or chemical vapor deposition method (CVD method) on silicon carbide single crystal substrates obtained by sublimation method. It can be manufactured by

In addition, silicon carbide single crystal substrates manufactured by epitaxial growth are more sensitive to basal plane dislocations (BPD), which are killer defects in devices when silicon carbide devices are manufactured, than silicon carbide single crystal substrates manufactured by sublimation. It is considered to be superior in quality because it has less basal plane displacement.

However, in terms of cost, it is preferable to epitaxially grow a silicon carbide single crystal on a silicon carbide single crystal film-forming substrate manufactured by the sublimation method to form a thick film. The crystal substrate may warp. Warpage occurs in the silicon carbide single crystal substrate, so that, for example, when the silicon carbide single crystal substrate is transported to be bonded to a silicon carbide polycrystalline substrate, the silicon carbide single crystal substrate may be vacuum-adsorbed using a suction cup or the like. This has caused problems such as the inability to transport silicon carbide single crystal substrates, which has been a factor in lowering manufacturing yields.

Therefore, the present invention provides a silicon carbide single crystal substrate obtained by epitaxially growing a silicon carbide single crystal film on a silicon carbide single crystal film forming substrate, which can suppress the occurrence of warping of the silicon carbide single crystal substrate. An object of the present invention is to provide a method for manufacturing a silicon single crystal substrate.

The method for manufacturing a silicon carbide single crystal substrate of the present invention involves epitaxially growing a silicon carbide single crystal film on the surface of a silicon carbide single crystal film forming substrate having a dopant by chemical vapor deposition. In the method for manufacturing a silicon carbide single crystal substrate, a mixed gas containing a raw material gas and a dopant gas is supplied into a film forming chamber in which the silicon carbide single crystal film forming substrate is installed to form the silicon carbide single crystal film. The content of the dopant contained in the silicon carbide single crystal film forming substrate is -50% to +50% by adjusting the supply ratio of the mixed gas in the film forming step. The silicon carbide single crystal film having a dopant content of .

In the method for manufacturing a silicon carbide single crystal substrate of the present invention, in the film forming step, by further adjusting at least one of the supply amount of the mixed gas, the pressure in the film forming chamber, and the film forming temperature, The dopant content of the silicon carbide single crystal film may be adjusted.

In the method for manufacturing a silicon carbide single crystal substrate of the present invention, the film forming step is performed by forming the silicon carbide single crystal film while rotating the silicon carbide single crystal film forming substrate, and further comprising: The dopant content of the silicon carbide single crystal film may be adjusted by adjusting the rotation speed of the silicon carbide single crystal film forming substrate.

In the method for manufacturing a silicon carbide single crystal substrate of the present invention, the dopant gas may contain one or more selected from the group consisting of boron, aluminum, gallium, nitrogen, phosphorus, and vanadium.

In the supplementary method for manufacturing a silicon carbide single crystal substrate of the present invention, the dopant gas is nitrogen gas, and the mixed gas includes a silicon-based gas, a carbon-based gas, a hydrogen gas, a chlorine-based gas, and the nitrogen gas. , the ratio of the number of atoms of silicon atoms in the silicon-based gas, carbon atoms in the carbon-based gas, hydrogen atoms in the hydrogen gas, chlorine atoms in the chlorine-based gas, and nitrogen atoms in the nitrogen gas is Si:C:H: Cl:N may be within the range of 0.23:0.33:194.72:2.10:1.0 to 2.96.

In the method for manufacturing a silicon carbide single crystal substrate of the present invention, the film forming temperature in the film forming step may be 1000°C to 1800°C.

In the method for manufacturing a silicon carbide single crystal substrate of the present invention, a silicon carbide single crystal film is epitaxially grown on a silicon carbide single crystal substrate obtained by epitaxially growing a silicon carbide single crystal film on a silicon carbide single crystal film forming substrate. By setting the dopant content of -50% to +50% of the dopant content of the film-forming substrate, it is possible to suppress the occurrence of warping of the silicon carbide single crystal substrate.

A side view schematically showing an example of a film forming apparatus for forming a silicon carbide polycrystalline film by chemical vapor deposition (CVD) in a method for manufacturing a silicon carbide single crystal substrate according to an embodiment of the present invention. FIG. 1 is a side cross-sectional view schematically showing a silicon carbide single crystal growth substrate, a silicon carbide single crystal film, and a silicon carbide single crystal substrate in a method for manufacturing a silicon carbide single crystal substrate according to an embodiment of the present invention. 2 is a plan view showing a susceptor in a modification of the film forming apparatus shown in FIG. 1. FIG.

A method for manufacturing a silicon carbide single crystal substrate according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. Note that the present invention is not limited to the following embodiments.

The method for manufacturing a silicon carbide single crystal substrate of the present embodiment includes epitaxially growing a silicon carbide single crystal film on the surface of a silicon carbide single crystal film forming substrate having a dopant by chemical vapor deposition. The present invention can be applied to a method of manufacturing a silicon carbide single crystal substrate.

The method for manufacturing silicon carbide single crystal substrate 500 of the present embodiment is to supply a mixed gas containing a raw material gas and a dopant gas into a film forming chamber in which a silicon carbide single crystal film forming substrate is installed, and to form a silicon carbide single crystal film. This includes a film forming process of forming a film.

FIG. 1 shows a film forming apparatus 1000 which is an example of a film forming apparatus for forming a silicon carbide polycrystalline film by chemical vapor deposition in a method of manufacturing a silicon carbide single crystal substrate 500 according to an embodiment of the present invention. It is a sectional view showing typically. FIG. 2 shows a silicon carbide single crystal film forming substrate 100, a silicon carbide single crystal film 200, and a silicon carbide single crystal substrate 500 in each step in a method for manufacturing a silicon carbide single crystal substrate 500 according to an embodiment of the present invention. It is a side sectional view shown typically. FIG. 2(A) is a diagram showing a silicon carbide single crystal film forming substrate 100, and FIG. 2(B) is a diagram showing a silicon carbide single crystal substrate 500 obtained by the film forming process.

[Film forming process]
Next, a film forming process in the method for manufacturing silicon carbide single crystal substrate 500 of this embodiment will be described.

The film forming process is a process of forming a silicon carbide single crystal film 200 by epitaxial growth on the film forming target surface 100a of the silicon carbide single crystal film forming substrate 100. Through this step, a silicon carbide single crystal film 200 can be formed on the silicon carbide single crystal film forming substrate 100.

In addition, in the film forming process, as will be described later, by adjusting the supply ratio of the mixed gas, the dopant content can be reduced to -50% to +50% of the dopant content of the silicon carbide single crystal film forming substrate 100. A silicon carbide single crystal film 200 having the following structure is formed.

In addition, in the film forming process, the dopant in the silicon carbide single crystal film 200 can be further adjusted by adjusting at least one of the supply amount of the mixed gas, the pressure in the film forming chamber 1020 (described later), and the film forming temperature. The content may be adjusted.

Furthermore, in the method for manufacturing silicon carbide single crystal substrate 500 of this embodiment, silicon carbide single crystal film 200 may be formed while rotating silicon carbide single crystal film forming substrate 100. Further, in order to adjust the dopant content of the silicon carbide single crystal film 200, the rotation speed of the silicon carbide single crystal film forming substrate 100 may be adjusted.

Here, regarding the supply ratio of the mixed gas, which is a parameter for controlling the dopant content, the higher the ratio of the dopant gas for supplying the dopant, the higher the dopant content in the deposited silicon carbide single crystal film 200. tends to be higher. Further, the supply amount of the mixed gas, the pressure in the film forming chamber 1020, the film forming temperature, and the rotation speed of the silicon carbide single crystal film forming substrate 100 affect the film forming speed of the silicon carbide single crystal film 200.

As the silicon carbide single crystal film forming substrate 100 (FIG. 2(A)), it is possible to use, for example, a 4H-SiC single crystal wafer obtained by processing a bulk single crystal of silicon carbide created by a sublimation method or the like. can. Further, the shape of the silicon carbide single crystal film forming substrate 100 can be, for example, a circular parallel plate shape. Further, when forming a silicon carbide single crystal film 200 with a thickness of about 5 μm to 100 μm, the thickness of the silicon carbide single crystal film forming substrate 100 can be about 250 μm to 750 μm.

In addition, in this embodiment, when the silicon carbide single crystal film 200 is deposited on a susceptor 1090 (described later) and the silicon carbide single crystal film 200 is deposited while rotating the susceptor 1090, The silicon single crystal film forming substrate 100 has one surface to be film-formed (the film-forming surface 100a).

FIG. 1 is a diagram showing a film forming apparatus 1000, which is an example of a film forming apparatus that can be used in the method of manufacturing a silicon carbide single crystal substrate 500 of this embodiment. Note that the following description is an example of a film-forming procedure, and the configuration of the film-forming apparatus, conditions such as temperature, pressure, gas atmosphere, etc., procedures, etc. may be changed as long as there is no problem.

The film forming apparatus 1000 can form a silicon carbide single crystal film 200 on the silicon carbide single crystal film forming substrate 100 by chemical vapor deposition. As shown in FIG. 1, the film forming apparatus 1000 includes a casing 1010 serving as an exterior of the film forming apparatus 1000, and a film forming chamber 1020 for forming a silicon carbide single crystal film 200 on a silicon carbide single crystal film forming substrate 100. , an exhaust gas introduction chamber 1050 that introduces raw material gas and carrier gas discharged from the film forming chamber 1020 to a gas outlet 1040 (described later), a box 1060 that covers the exhaust gas introduction chamber 1050, and a film forming chamber 1060 from outside the box 1060. A carbon heater 1070 that heats the inside of the chamber 1020, a gas inlet 1030 that is provided at the top of the film forming chamber 1020 and that introduces source gas and carrier gas into the film forming chamber 1020, and a gas inlet 1030 that introduces source gas and carrier gas into the film forming chamber 1020. It has a gas exhaust port 1040 for discharging to the outside of the apparatus, a support 1080 that rotatably supports a susceptor 1090, and a susceptor 1090 on which a silicon carbide single crystal deposition substrate 100 is placed.

The support column 1080 has a holding mechanism (not shown) that holds the susceptor 1090 and a rotation mechanism (not shown) that rotates the susceptor 1090 during film formation. Further, the susceptor 1090 has a mounting part 1091 for the silicon carbide single crystal film forming substrate 100 formed on a flat plate, and a wall part 1092 standing up from the outer peripheral edge of the mounting part 1091. Since the susceptor 1090 has the wall portion 1092, even if the silicon carbide single crystal film forming substrate 100 tries to fly out to the outside due to centrifugal force when the susceptor 1090 rotates, it can be suppressed.

First, silicon carbide single crystal film forming substrate 100 is placed on mounting portion 1091 of susceptor 1090 (FIG. 1). Next, under a reduced pressure state, silicon carbide single crystal film forming substrate 100 is heated by heater 1070 to a film forming reaction temperature in an inert gas atmosphere such as Ar. When the preset reaction temperature for film formation (approximately 1000°C to 1800°C) is reached, the supply of inert gas is stopped and the pressure inside the film forming chamber 1020 is set at several kPa to several hundred kPa. A mixed gas such as a raw material gas and a carrier gas containing components of the silicon carbide single crystal film 200 is supplied. At this time, silicon carbide single crystal film 200 is formed while rotating susceptor 1090 in the direction of arrow A in FIG.

Note that the rotation speed of silicon carbide single crystal film forming substrate 100 can be approximately 0 rpm to 1000 rpm when using silicon carbide single crystal film forming substrate 100 of 4 inch φ size or 6 inch φ size.

Further, in order to adjust the dopant content of the silicon carbide single crystal film 200 formed in the film forming process, the pressure inside the film forming chamber 1020 can be set to about several kPa to several hundred kPa, and The temperature inside the film forming chamber 1020 can be 1000°C to 1800°C.

The source gas is not particularly limited as long as it can form the silicon carbide single crystal film 200, and Si-based source gas and C-based source gas that are generally used for forming the silicon carbide single crystal film 200 may be used. Can be used.

For example, as the silicon (Si)-based source gas, silane (SiH ₄ ) can be used, as well as monochlorosilane (SiH ₃ Cl), dichlorosilane (SiH ₂ Cl ₂ ), trichlorosilane (SiHCl ₃ ), and tetrachlorosilane. A chlorine-based Si raw material-containing gas (chloride-based raw material) containing Cl that has an etching effect, such as (SiCl ₄ ), can be used. Furthermore, for example, when using the above-mentioned silane gas, HCl may also be supplied together.

As the carbon (C)-based raw material gas, for example, hydrocarbons such as methane (CH ₄ ), propane (C ₃ H ₈ ), acetylene (C ₂ H ₂ ), etc. can be used. In addition to the above, trichloromethylsilane (CH ₃ Cl ₃ Si), trichlorophenylsilane (C ₆ H ₅ Cl ₃ Si), dichloromethylsilane (CH ₄ Cl ₂ Si), dichlorodimethylsilane ((CH ₃ ) ₂ SiCl ₂ ), chlorotrimethylsilane ((CH ₃ ) ₃ SiCl), and other gases containing both Si and C can also be used as the raw material gas.

As the carrier gas, a commonly used carrier gas can be used as long as it can spread the source gas onto the substrate without inhibiting film formation. For example, hydrogen (H ₂ ), which has excellent thermal conductivity and has an etching effect on silicon carbide, can be used.

Further, in order to control the conductivity type of the silicon carbide single crystal film 200, an impurity doping gas is simultaneously supplied. For example, N ₂ can be used when the conductivity type is n-type, and TMA (trimethylaluminum) can be used when the conductivity type is p-type.

The dopant gas is not limited to nitrogen and aluminum, but may be a gas containing one or more selected from the group consisting of boron, aluminum, gallium, nitrogen, phosphorus, and vanadium, for example.

In addition, dopant gases include boron trichloride (BCl3) and diborane (B ₂ H ₆ ) when the dopant is boron, and trimethylgallium (TMAL) and triethylgallium (TEGa) when the dopant is gallium. In the case of phosphorus, phosphine (PH ₃ ) can be used, and in the case of vanadium, vanadium tetrachloride (VCl ₄ ) can be used. When the dopant is nitrogen, ammonia (NH ₃ ) can be used in addition to nitrogen gas as the dopant gas.

Further, the dopant content in the silicon carbide single crystal film forming substrate 100 is not particularly limited, and the dopant content can be appropriately set based on a desired electrical resistance value, etc. When nitrogen is used as a dopant, for example, a silicon carbide single crystal film forming substrate 100 having a dopant content of about 6×10 ¹⁸ cm ⁻³ to 10×10 ¹⁸ cm ⁻³ can be used.

Note that the dopant that silicon carbide single crystal film forming substrate 100 has and the dopant that silicon carbide single crystal film 200 has may be the same or different.

When the dopant of silicon carbide single crystal film forming substrate 100 and the dopant of silicon carbide single crystal film 200 are different, both dopants substitute the same atoms, that is, silicon (Si) or carbon (C). Preferably, the dopant replaces either the same atom.

Furthermore, if different dopants are used in the silicon carbide single crystal film forming substrate 100 and the silicon carbide single crystal film 200, the warpage behavior in the silicon carbide single crystal substrate 500 may differ, so stable manufacturing management is possible. From this point of view, it is more preferable to use the same dopant, which makes it easy to predict the warpage behavior.

When forming the silicon carbide single crystal film 200, the above gases are appropriately mixed and supplied. Further, depending on the desired properties of the silicon carbide single crystal film 200, conditions such as the gas mixture ratio and supply amount may be changed during film formation. In addition, when forming the silicon carbide single crystal film 200, in order to grow a single crystal in the same orientation as the crystal of the silicon carbide single crystal film forming substrate 100, which is the film forming target, one film forming process is required. Instead of forming the film until the desired film thickness is reached, the film may be formed multiple times to obtain the desired film thickness.

The supply ratio of the above mixed gas is determined in order to adjust the dopant content. For example, the dopant gas is nitrogen gas, and the mixed gases include silicon gas, carbon gas, hydrogen gas, chlorine gas, nitrogen gas. When supplying, the ratio of the number of silicon atoms in the silicon-based gas, carbon atoms in the carbon-based gas, hydrogen atoms in the hydrogen gas, chlorine atoms in the chlorine-based gas, and nitrogen atoms in the nitrogen gas is Si:C:H. :Cl:N=0.23:0.33:194.72:2.10:1.0 to 0.23:0.33:194.72:2.10:2.96 I can do it.

That is, silane (SiH ₄ ) gas is used as the silicon-based gas, propane (C ₃ H ₈ ) gas and hydrogen (H ₂ ) gas are used as the carbon-based gas, hydrogen chloride (HCl) gas is used as the chlorine-based gas, and nitrogen (N) is used as the dopant gas. ₂ ) When supplying a mixed gas containing gas, SiH ₄ :C ₃ H ₈ :H ₂ :HCl:N ₂ =0.23:0.11:97.36:2.10:0.50~ 0.23:0.11:97.36:2.10:1.48.

Further, the amount of mixed gas supplied can be set to about 1 slm to 500 slm in total of the gases supplied into the film forming chamber 1020. Note that the unit of gas flow rate "slm" indicates standard liter/min, that is, the flow rate (L) per minute converted to standard conditions (0° C., 1 atm).

The silicon carbide single crystal film 200 can be formed on the heated silicon carbide single crystal film forming substrate 100 by a chemical reaction on the surface of the silicon carbide single crystal film forming substrate 100 or in the gas phase. Through the above film-forming process, a silicon carbide single-crystal substrate 500 (FIG. 2(B)) in which a silicon carbide single-crystal film 200 is formed on a silicon carbide single-crystal film-forming substrate 100 is obtained.

[Other processes]
As described above, the method for manufacturing silicon carbide single crystal substrate 500 of this embodiment can include the following steps. For example, in the step of heating the silicon carbide single crystal film forming substrate 100 that has been installed, the silicon carbide single crystal film forming substrate 100 before chemical vapor deposition is heated to prevent any reaction that may inhibit film formation from occurring. In order to create an inert atmosphere in the film forming chamber 1020 in which the crystal film forming substrate 100 is installed, an example is a process of flowing an inert gas such as argon.

In addition, as shown in FIG. 2(B), a silicon carbide single crystal substrate 500 obtained by forming a silicon carbide single crystal film 200 has a film formation target surface 100a of a silicon carbide single crystal film formation substrate 100. In addition, a silicon carbide film may be formed along the side surface of the silicon carbide single crystal film forming substrate 100. Therefore, after the film forming process, the diameter of silicon carbide single crystal substrate 500 may be adjusted by grinding or polishing the outer peripheral portion. Further, in order to eliminate warpage of silicon carbide single crystal substrate 500 or to obtain a desired thickness, grinding or polishing may be performed as necessary.

[Comparison with conventional silicon carbide single crystal substrate manufacturing method]
In conventional methods for manufacturing silicon carbide single crystal substrates, the resulting silicon carbide single crystal substrates may warp, and when manufacturing a bonded substrate with a silicon carbide polycrystalline substrate, vacuum suction may not be possible. This has caused problems such as the inability to transport the silicon carbide single crystal substrate, which has been a factor in lowering manufacturing yield.

Therefore, in order to solve the above problems, the inventors of the present invention conducted extensive research and through trial and error, and as a result, a silicon carbide single crystal film was epitaxially grown on a silicon carbide single crystal film forming substrate by chemical vapor deposition. In the film forming process, a silicon carbide single crystal substrate obtained by obtaining a silicon carbide single crystal film having a dopant content of -50% to +50% of the dopant content in the silicon carbide single crystal film forming substrate. It has been found that the occurrence of warpage can be suppressed. Furthermore, it has been found that the dopant content in the silicon carbide single crystal film to be formed can be adjusted by adjusting the supply ratio of the mixed gas.

In addition, since the amount of mixed gas supplied, the pressure inside the deposition chamber, the temperature inside the deposition chamber, and the rotation speed of the silicon carbide single crystal deposition substrate affect the growth rate of the silicon carbide single crystal film, It was found that the dopant content in the crystal film is affected.

That is, if there is a stress difference between the silicon carbide single crystal film forming substrate and the silicon carbide single crystal film formed, warping occurs. This stress difference is thought to be largely due to the difference in dopant content between the silicon carbide single crystal film forming substrate and the silicon carbide single crystal film.

Here, in the crystal structure of silicon carbide, the dopant substitutes at the C (carbon) site and forms a solid solution. When the dopant is nitrogen, the covalent bond radius is smaller than that of carbon, so the lattice constant increases as the dopant amount (dopant content) increases. Therefore, compared to the substrate for silicon carbide single crystal film formation, if the silicon carbide single crystal film is doped with a larger amount, the silicon carbide single crystal film will shrink, so the silicon carbide single crystal film will have a concave shape. Warping occurs. On the other hand, compared to the substrate for silicon carbide single crystal film formation, if the silicon carbide single crystal film has a smaller doping amount, the silicon carbide single crystal film will spread more. A convex warpage occurs.

In the method for manufacturing a silicon carbide single crystal substrate of the present embodiment, in the silicon carbide single crystal substrate obtained by epitaxially growing a silicon carbide single crystal film on a silicon carbide single crystal film formation substrate, warping of the silicon carbide single crystal substrate The occurrence of can be suppressed.

Note that the present invention is not limited to the embodiments described above, but includes other steps that can achieve the object of the present invention, and the present invention also includes the following modifications. In addition, in the following modified example, the same code|symbol is attached|subjected to the same structure as the embodiment mentioned above, and description is abbreviate|omitted.

In the embodiment described above, as shown in FIG. 1, the film forming apparatus 1000 is provided with one susceptor 1090, but the film forming apparatus 1000 may be provided with a plurality of susceptors. When a plurality of susceptors are provided, for example, as shown in FIG. 3, a stage 1100 on which a plurality of susceptors 1090 (four in FIG. 3) can be installed may be used.

The stage 1100 shown in FIG. 3 includes four susceptor installation sections 1110 and a susceptor rotation mechanism (not shown) that rotates the susceptor 1090 installed in the susceptor installation section 1110 in the direction of arrow D. A silicon carbide single crystal film forming substrate 100 is placed on the susceptor 1090 . Further, the stage 1100 is supported by a pillar 1080 of the film forming apparatus 1000, and is configured to rotate in the direction of arrow E.

That is, the susceptor 1090 and the stage 1100 rotate and revolve in opposite directions, thereby making the thickness of the silicon carbide film more uniform. Further, since a plurality of susceptors 1090 can be installed on stage 1100, a plurality of silicon carbide single crystal substrates 500 can be obtained at one time. Note that the directions of rotation of the susceptor 1090 and the stage 1100 indicated by arrows D and E in FIG. 3 and the rotational speeds of the susceptor 1090 and the stage 1100 can be set as appropriate.

Further, in the embodiment described above, a method of growing the silicon carbide single crystal film 200 by rotating the susceptor 1090 was exemplified, but the susceptor 1090 may also be rotated during the growth of the silicon carbide single crystal film 200. You don't have to let it happen. It is preferable to rotate the susceptor 1090 during the growth of the silicon carbide single crystal film 200 from the viewpoint of uniformity of the film thickness of the silicon carbide single crystal film 200 and uniformity of the dopant content by rotating the susceptor 1090.

In addition, the best configuration, method, etc. for carrying out the present invention have been disclosed in the above description, but the present invention is not limited thereto. That is, although the present invention has been specifically described mainly with respect to specific embodiments, there may be changes in shape, material, quantity, Various modifications can be made by those skilled in the art in other detailed configurations. Therefore, the descriptions in which the shapes, materials, etc. disclosed above are limited are provided as examples to facilitate understanding of the present invention, and are not intended to limit the present invention. Descriptions of names of members that exclude some or all of the limitations such as these are included in the present invention.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples in any way.

In this example, a silicon carbide single crystal substrate was manufactured using the film forming apparatus 1000 of the embodiment described above. Further, in this example, nitrogen was used as a dopant.

[Example 1]
(Manufacture of silicon carbide single crystal substrate)
In this example, nitrogen was used as a dopant. A silicon carbide single crystal film forming substrate for epitaxial growth of a silicon carbide single crystal was prepared by a sublimation method and had a diameter of 6 inches and a thickness of 350 μm, and had a nitrogen dopant content of 6×10 ¹⁸ per unit volume. A cm ^-3 4H-SiC single crystal wafer type was used.

Next, the inside of the film forming chamber was evacuated using an exhaust pump, and then the temperature inside the film forming chamber was raised to 1650° C. while supplying Ar gas to heat the silicon carbide single crystal film forming substrate.

After the temperature was raised to 1650° C., the supply of Ar gas was stopped, and gas such as raw material gas was supplied. Silane gas (SiH ₄ ), which is a silicon-based gas, propane gas (C ₃ H ₈ ), which is a carbon-based gas, as a raw material gas, hydrogen gas (H ₂ ), hydrogen chloride gas (HCl) as a purge gas, and nitrogen gas (N ₂ ) was used.

The supply ratio of the mixed gas was SiH ₄ :C ₃ H ₈ :H ₂ :HCl:N ₂ =0.23:0.11:97.36:2.10:1.02. The mixed gas was supplied at a total amount of 180 slm for 60 minutes, and while the substrate was rotated at 600 rpm, a silicon carbide single crystal film was epitaxially grown on the target surface of the silicon carbide single crystal film forming substrate. The pressure inside the film forming chamber during the film forming process was 25 kPa. Through the above steps, a silicon carbide single crystal substrate was obtained.

(Evaluation of silicon carbide single crystal substrate)
Regarding the manufactured silicon carbide single crystal substrate, the dopant content of the silicon carbide single crystal film, the film thickness of the silicon carbide single crystal film, and the amount of warpage of the silicon carbide single crystal substrate were evaluated.

The dopant content (nitrogen content) of the epitaxially grown silicon carbide single crystal film was measured using a secondary ion mass spectrometer (hereinafter sometimes referred to as D-SIMS). The nitrogen content in the silicon carbide single crystal film was measured to be 6×10 ¹⁸ cm ⁻³ , which was equivalent to the dopant content of the silicon carbide single crystal film forming substrate.

In addition, when the film thickness of the silicon carbide single crystal film was measured, the average film thickness of the epitaxially grown silicon carbide single crystal film was 50 μm, and the in-plane variation was 3% or less, and it was homogeneous, with low defects, and of high quality. We were able to obtain a silicon carbide single crystal film that has no problems as a semiconductor material.

In addition, the silicon carbide single crystal substrate obtained by forming a silicon carbide single crystal film was measured using a flatness measuring device to measure the difference between the maximum and minimum deviation of the central plane of the substrate from the reference plane. It was evaluated as If the amount of warpage is within ±100 μm, there is no possibility of problems such as conveyance errors or inability to obtain a reference plane in the bonding process with the silicon carbide polycrystalline substrate, and it was determined that the standard for the amount of warp is met. In addition, if the amount of warpage is a positive value here, it means that there is a concave warp with a depression on the silicon carbide single crystal film side, and if the amount of warpage is a negative value, it means that there is a convex warp that is concave on the silicon carbide single crystal film side. This shall indicate that there is a warpage in the form of a shape.

As a result of evaluating the amount of warpage, the amount of warpage of the silicon carbide single crystal substrate of Example 1 was 50 μm, which was an amount that would not cause any problem during the bonding process.

[Example 2 to Example 4, Comparative Example 1 to Comparative Example 3]
As Examples 2 to 4 and Comparative Examples 1 to 3, silicon carbide single crystal substrates were manufactured in the same manner as in Example 1, except that the supply ratio of the mixed gas was variously changed as shown in Table 1. did.

Regarding the silicon carbide single crystal substrates of Examples 1 to 4 and Comparative Examples 1 to 3, the supply ratio of the mixed gas in the film forming process and the atomic ratio of the supplied mixed gas are shown in Table 1. The atomic ratio indicates the ratio of the number of silicon atoms in silane gas, carbon atoms in propane gas, hydrogen atoms in hydrogen gas, chlorine atoms in chlorine-based gas, and nitrogen atoms in nitrogen gas.

In addition, regarding the manufactured silicon carbide single crystal substrate, the dopant content of the silicon carbide single crystal film, the film thickness of the silicon carbide single crystal film, and the amount of warpage of the silicon carbide single crystal substrate were evaluated in the same manner as in Example 1. .

Table 2 shows the evaluation results of silicon carbide single crystal substrates, including the nitrogen content, the nitrogen content of the silicon carbide single crystal film based on the silicon carbide single crystal film forming substrate (0), and the nitrogen content of the silicon carbide single crystal substrate. The amount of warpage is shown. The nitrogen content of the silicon carbide single crystal film is based on the silicon carbide single crystal film formation substrate (0), and the dopant content of the silicon carbide single crystal film is compared to the dopant content of the silicon carbide single crystal film formation substrate. It shows the calculated value of how much more or less it is. In other words, the nitrogen content in the silicon carbide single crystal film ((nitrogen content of the silicon carbide single crystal film - silicon carbide single crystal film formation Nitrogen content of silicon carbide single crystal film forming substrate)/Nitrogen content of silicon carbide single crystal film forming substrate x 100 (%)) was calculated.

(Evaluation results)
In the obtained silicon carbide single crystal substrates, the average film thickness of the silicon carbide single crystal film in both the example and the comparative example was 50 μm, and the in-plane variation was 3% or less.

Regarding the nitrogen content in the silicon carbide single crystal film when the nitrogen content of the silicon carbide single crystal film forming substrate is taken as the standard (0), in Examples 1 to 4, it is -50% to +50%, and the comparison In Examples 1 to 3, it was -60% to +83%.

Further, regarding the amount of warpage of the silicon carbide single crystal substrate, in Examples 1 to 4, the amount of warpage was −90 μm to +93 μm, and the amount of warpage was small. Further, in Examples 1 to 4, no problems occurred in the steps such as vacuum suction for transporting the silicon carbide single crystal substrate and acquisition of a reference surface for processing. On the other hand, in the silicon carbide single crystal substrates obtained in Comparative Examples 1 to 3, the amount of warpage was −101 μm to +120 μm, and the amount of warpage was large. Furthermore, in Comparative Examples 1 to 3, problems occurred in steps such as vacuum suction for transporting the silicon carbide single crystal substrate and acquisition of a reference surface for processing.

In Examples 1 to 4, which are exemplary embodiments of the present invention, it is possible to control the dopant concentration of the silicon carbide single crystal film by adjusting the supply ratio of the mixed gas in the film forming process. It has been shown that a silicon carbide single crystal substrate with a small amount of warpage can be obtained by setting the dopant content in the silicon single crystal film to -50% to +50% of the dopant content of the silicon carbide single crystal film forming substrate. It was done.

In addition, the silicon carbide single crystal substrate obtained in this way improves productivity by suppressing problems such as vacuum suction for transportation and obtaining a reference surface for processing, thereby reducing production costs. can be suppressed. In this example, nitrogen was used as the dopant, but by using other dopants, it is possible to suppress the amount of warpage in the resulting silicon carbide single crystal substrate.

100 Silicon carbide single crystal film forming substrate 200 Silicon carbide single crystal film 500 Silicon carbide single crystal substrate

Claims (4)

In a method for manufacturing a silicon carbide single crystal substrate, the silicon carbide single crystal substrate is obtained by epitaxially growing a silicon carbide single crystal film on the surface of a silicon carbide single crystal film forming substrate having a dopant by a chemical vapor deposition method,
The silicon carbide single crystal film forming substrate is a 4H-SiC single crystal wafer with a thickness of 250 μm to 750 μm and a 4 inch φ size or a 6 inch φ size,
A film forming step of supplying a mixed gas containing a source gas and a dopant gas into a film forming chamber in which the silicon carbide single crystal film forming substrate is installed to form the silicon carbide single crystal film,
the dopant gas is nitrogen gas,
The mixed gas includes a silicon-based gas, a carbon-based gas, a hydrogen gas, a chlorine-based gas, and the nitrogen gas,
The ratio of the number of atoms of silicon atoms in the silicon-based gas, carbon atoms in the carbon-based gas, hydrogen atoms in the hydrogen gas, chlorine atoms in the chlorine-based gas, and nitrogen atoms in the nitrogen gas is Si:C:H:Cl. :N=0.23:0.33:194.72:2.10: within the range of 1.0 to 2.96,
In the film forming step, by adjusting the supply ratio of the mixed gas, the silicon carbide having a dopant content of -50% to +50% of the dopant content of the silicon carbide single crystal film forming substrate is formed. A method for manufacturing a silicon carbide single crystal substrate , which comprises forming a single crystal film to obtain a silicon carbide single crystal substrate with a warpage within ±100 μm . In the film forming step, the dopant content of the silicon carbide single crystal film is further adjusted by adjusting at least one of the supply amount of the mixed gas, the pressure inside the film forming chamber, and the film forming temperature. The method for manufacturing a silicon carbide single crystal substrate according to claim 1. The film forming step is to form the silicon carbide single crystal film while rotating the silicon carbide single crystal film forming substrate,
The production of the silicon carbide single crystal substrate according to claim 1 or 2, wherein the dopant content of the silicon carbide single crystal film is further adjusted by adjusting the rotation speed of the silicon carbide single crystal film forming substrate. Method. The method for manufacturing a silicon carbide single crystal substrate according to any one of claims 1 to 3 , wherein the film forming temperature in the film forming step is 1000°C to 1800°C.

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