JP2014205593A - Silicon carbide single crystal and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon carbide single crystal which can suppress extension of a stacking fault and a manufacturing method of the silicon carbide single crystal.SOLUTION: A method of manufacturing a silicon carbide single crystal 2 includes a following step. A seed crystal 1 is prepared, which has a principal surface 1a and consists of silicon carbide. A silicon carbide single crystal 2 is grown on the principal surface 1a of the seed crystal 1 in an atmosphere gas including nitrogen. In a process for growing the silicon carbide single crystal 2, a silicon carbide single crystal region 2b is formed, of which nitrogen concentration is 2×10cmor less. The nitrogen concentration of the silicon carbide single crystal region 2b is lower than that of the seed crystal 1.

Description

  The present invention relates to a silicon carbide single crystal and a method for manufacturing the same, and more specifically to a silicon carbide single crystal capable of suppressing the growth of stacking faults and a method for manufacturing the same.

  In recent years, silicon carbide substrates have begun to be used for manufacturing semiconductor devices. Silicon carbide has a larger band gap than silicon. Therefore, a semiconductor device using a silicon carbide substrate has advantages such as high breakdown voltage, low on-resistance, and small deterioration in characteristics under a high temperature environment.

  For example, in D. Nakamura et al., “Ultra high-quality silicon carbide single crystals”, Nature, 430, 1009-1012, 26 August 2004 (Non-Patent Document 1), a-plane growth (so-called RAF (Repeated a-face ) Method) describes a method for producing high quality silicon carbide single crystals. When a stacking fault exists in the seed crystal, the growth crystal that grows on the seed crystal grows by step flow growth that inherits the crystal structure of the seed crystal, so that the stacking fault extends in the grown crystal. In the RAF method, stacking faults in the grown crystal are reduced by causing stacking faults to escape to the side surfaces of the grown crystal.

D. Nakamura et al., "Ultrahigh-quality silicon carbide single crystals", Nature, 430, 1009-1012, 26 August 2004

  However, even in the RAF method, reduction of stacking faults in the silicon carbide single crystal has not been sufficient.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a silicon carbide single crystal capable of suppressing the growth of stacking faults and a method for producing the same.

As a result of intensive studies on a method for reducing stacking faults of a silicon carbide single crystal grown on a seed crystal, the present inventors have obtained the following knowledge and found the present invention. For example, when a silicon carbide single crystal is grown on a seed crystal by a sublimation method, the silicon carbide single crystal is grown in an atmosphere containing nitrogen gas. Since the nitrogen atom substitutes for the carbon atom of the silicon carbide single crystal, the lattice of the silicon carbide single crystal grown on the seed crystal is distorted. By reducing the nitrogen concentration contained in the silicon carbide single crystal grown on the seed crystal, the lattice constant of the silicon carbide single crystal approaches the lattice constant of a pure silicon carbide single crystal containing no nitrogen element. Therefore, by reducing the nitrogen concentration contained in the silicon carbide single crystal grown on the seed crystal, the stability of stacking faults generated in the silicon carbide single crystal can be reduced. As a result of diligent research, the inventors have determined that the silicon carbide single crystal grown on the seed crystal has a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less, so that the stacking fault grows from the seed crystal onto the seed crystal. It was found that extension to a single crystal can be suppressed.

The method for producing a silicon carbide single crystal according to the present invention includes the following steps. A seed crystal having a main surface and made of silicon carbide is prepared. A silicon carbide single crystal is grown on the main surface of the seed crystal in an atmosphere gas containing nitrogen. In the step of growing the silicon carbide single crystal, a silicon carbide single crystal region having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less is formed. The nitrogen concentration in the silicon carbide single crystal region is lower than the nitrogen concentration in the seed crystal.

The silicon carbide single crystal according to the present invention has a first silicon carbide single crystal region and a second silicon carbide single crystal region. The first silicon carbide single crystal region has a first nitrogen concentration and has one or more stacking faults. The second silicon carbide single crystal region is in contact with the first silicon carbide single crystal region and has a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less. One or more terminations of stacking faults exist in the boundary region between the first silicon carbide single crystal region and the second silicon carbide single crystal region.

According to the silicon carbide single crystal and the method for producing a silicon carbide single crystal according to the present invention, the concentration of nitrogen contained in the silicon carbide single crystal region is 2 × 10 ¹⁹ cm ⁻³ or less. As a result, the lattice distortion of the silicon carbide single crystal is reduced and the stability of the stacking fault is reduced, thereby suppressing the stacking fault from extending from the seed crystal to the silicon carbide single crystal growing on the seed crystal. it can. As a result, it is possible to provide a silicon carbide single crystal capable of suppressing extension of stacking faults and a method for manufacturing the same.

  ADVANTAGE OF THE INVENTION According to this invention, the silicon carbide single crystal which can suppress extension of a stacking fault, and its manufacturing method can be provided.

It is a cross-sectional schematic diagram which shows schematically the manufacturing apparatus of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a flowchart which illustrates notionally the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating schematically the 1st process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating schematically the 1st example of the 2nd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating schematically the 2nd example of the 2nd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating schematically the 3rd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a figure which shows the 1st example of the relationship between nitrogen gas flow volume and time of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a figure which shows the 2nd example of the relationship between nitrogen gas flow volume and time of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a figure which shows the 3rd example of the relationship between nitrogen gas flow volume and time of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a photoluminescence imaging image for demonstrating schematically the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In the crystallographic description in this specification, the individual orientation is indicated by [], the collective orientation is indicated by <>, the individual plane is indicated by (), and the collective plane is indicated by {}. As for the negative index, “−” (bar) is attached on the number in crystallography, but in this specification, a negative sign is attached before the number. The angle is described using a system in which the omnidirectional angle is 360 degrees.

  With reference to FIG. 1, the structure of the apparatus for manufacturing the silicon carbide single crystal which concerns on this Embodiment is demonstrated.

  Referring to FIG. 1, silicon carbide single crystal manufacturing apparatus 100 according to the present embodiment mainly includes a crucible 10, a heating unit (not shown), and a reaction vessel 7. The crucible 10 is made of graphite, for example, and includes a seed crystal holding unit 4 and a raw material storage unit 5. The seed crystal holding unit 4 is for holding the seed crystal 1 made of single crystal silicon carbide. Raw material container 5 is for placing silicon carbide raw material 6 made of polycrystalline silicon carbide.

  The crucible 10 is housed inside the reaction vessel 7. The outer diameter of the crucible 10 is, for example, about 160 mm, the inner diameter is, for example, about 120 mm, and the height is, for example, about 200 mm. The heating part of the crucible 10 is, for example, an induction heating type heater or a resistance heating type heater, and is arranged so as to surround the outer periphery of the crucible 10. The heating unit is configured to be able to raise the temperature of the crucible 10 to the sublimation temperature of silicon carbide.

  At both ends of the reaction vessel 7, a gas introduction port 7 a for flowing an atmospheric gas into the reaction vessel 7 and a gas discharge port 7 b for discharging the atmospheric gas to the outside of the reaction vessel 7 are formed. . The silicon carbide single crystal manufacturing apparatus 100 includes a nitrogen gas supply unit for introducing nitrogen gas into the reaction vessel 7 through the gas inlet 7a, and a nitrogen gas flow rate control for controlling the flow rate of nitrogen gas in the reaction vessel 7. May have a part. The silicon carbide single crystal manufacturing apparatus 100 includes a helium gas supply unit for introducing helium gas into the reaction vessel 7 through the gas inlet 7a, and a helium gas flow rate control for controlling the flow rate of the helium gas in the reaction vessel 7. May have a part. The silicon carbide single crystal manufacturing apparatus 100 includes an argon gas supply unit for introducing argon gas into the reaction vessel 7 through the gas inlet 7a, and an argon gas flow rate control for controlling the flow rate of the argon gas in the reaction vessel 7. May have a part.

  A method for manufacturing a silicon carbide single crystal according to the present embodiment will be described with reference to FIGS.

  First, a silicon carbide seed crystal preparation step (S10: FIG. 2) is performed. Specifically, referring to FIGS. 1 and 3, seed crystal 1 made of, for example, polytype 4H hexagonal silicon carbide is fixed to seed crystal holding portion 4. Seed crystal 1 has a main surface 1 a and is arranged such that main surface 1 a faces silicon carbide raw material 6. As described above, seed crystal 1 having main surface 1a and made of silicon carbide is prepared. Silicon carbide raw material 6 is housed in raw material housing portion 5 and is, for example, silicon carbide powder.

Referring to FIG. 3, seed crystal 1 has stacking fault 3, and stacking fault 3 is exposed on main surface 1 a of seed crystal 1. The extension direction of the stacking fault 3 is, for example, a direction parallel to the (0001) plane. The concentration of nitrogen contained in seed crystal 1 is, for example, 1 × 10 ¹⁸ cm ⁻³ or more and 3 × 10 ¹⁹ cm ⁻³ or less, preferably 5 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ¹⁹ cm ⁻³ or less. . The diameter of seed crystal 1 is, for example, 100 mm, and preferably 100 mm or more. The main surface 1a of the seed crystal 1 is a surface that is turned off by an angle of about 10 ° or less with respect to the {0001} plane, for example. Preferably, the main surface 1a is a surface turned off by an angle of about 4 ° or less with respect to the (0001) surface, and more preferably a surface turned off by an angle of about 2 ° or less.

  Next, a silicon carbide single crystal growth step (S20: FIG. 2) is performed. The silicon carbide single crystal growth step may include a crucible temperature rising step and a reaction vessel decompression step. Specifically, referring to FIG. 1, crucible 10 in which seed crystal 1 and silicon carbide raw material 6 are arranged has a temperature (for example, a temperature at which silicon carbide crystal sublimates in an atmospheric gas containing helium gas and nitrogen gas, for example. 2100-2300 ° C). Next, by reducing the pressure in the reaction vessel 7 containing the crucible 10, the silicon carbide raw material 6 in the crucible 10 is sublimated and recrystallized on the main surface 1 a of the seed crystal 1. Silicon carbide single crystal 2 starts to grow on main surface 1a of crystal 1. The growth temperature at which silicon carbide single crystal 2 substantially grows is about 2200 ° C., for example, and the growth pressure is about 20 Torr (about 2.7 kPa), for example.

Referring to FIG. 4, in the silicon carbide single crystal growth step, silicon carbide single crystal 2 is formed as a silicon carbide single crystal region having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less. Specifically, the nitrogen concentration contained in the atmospheric gas is controlled so that the nitrogen concentration of silicon carbide single crystal 2 is 2 × 10 ¹⁹ cm ⁻³ or less. More specifically, the nitrogen gas concentration in the reaction vessel 7 is controlled while maintaining the temperature of the crucible 10 at about 2200 ° C. For example, when the growth temperature is 2200 ° C. and the growth pressure is 20 Torr, the nitrogen concentration in the reaction vessel 7 is set so that the flow rate of helium gas is 1.50 slm and the flow rate of nitrogen gas is 0.500 slm. Be controlled. Thereby, among the plurality of stacking faults 3 included in seed crystal 1, some stacking defects 3 a do not extend to silicon carbide single crystal 2, and other stacking faults 3 b extend to silicon carbide single crystal 2. In other words, among the plurality of stacking faults 3 included in the seed crystal 1, the terminal portion 8 of some stacking faults 3a is the boundary region 9 between the seed crystal 1 and the silicon carbide single crystal 2 (that is, the main surface 1a of the seed crystal 1). In the vicinity of.

Preferably, in the silicon carbide single crystal growth step, silicon carbide single crystal 2 as a silicon carbide single crystal region having a nitrogen concentration of 1 × 10 ¹⁹ cm ⁻³ or less is formed. Specifically, the concentration of nitrogen contained in the atmospheric gas is controlled so that the nitrogen concentration of silicon carbide single crystal 2 is 1 × 10 ¹⁹ cm ⁻³ or less. Preferably, the silicon carbide single crystal 2 as the silicon carbide single crystal region has a nitrogen concentration of 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ¹⁹ cm ⁻³ or less. By setting the nitrogen concentration of silicon carbide single crystal 2 to 1 × 10 ¹⁸ cm ⁻³ or more, polytype 4H of silicon carbide single crystal 2 can be stabilized. The nitrogen concentration of the silicon carbide single crystal as the silicon carbide single crystal region may be 9 × 10 ¹⁸ cm ⁻³ or less.

  The nitrogen concentration of silicon carbide single crystal 2 as the silicon carbide single crystal region is lower than the nitrogen concentration of seed crystal 1. Preferably, the nitrogen concentration of silicon carbide single crystal 2 as the silicon carbide single crystal region is not more than two-thirds of the nitrogen concentration of seed crystal 1, more preferably not more than one-third of the nitrogen concentration of seed crystal 1. It is. Specifically, when the growth temperature is 2100 to 2300 ° C., the growth pressure is 20 Torr, the flow rate of helium gas is 1.50 slm, and the flow rate of nitrogen gas is 0.015 slm or more and 0.500 slm or less. In addition, the nitrogen concentration in the reaction vessel 7 is controlled. Note that the nitrogen concentration of silicon carbide single crystal 2 grown on main surface 1a of seed crystal 1 is substantially proportional to the square root of the nitrogen concentration in the atmospheric gas.

  With reference to FIG. 7 to FIG. 9, the time change of the nitrogen gas flow rate (in other words, the nitrogen gas concentration) contained in the atmospheric gas in the reaction vessel 7 in the process of growing the silicon carbide single crystal will be described. As shown in FIG. 7, for example, the nitrogen gas flow rate A1 at the time T0 when the growth of the silicon carbide single crystal starts is 0.500 slm, and the nitrogen at the time T1 during the growth of the silicon carbide single crystal and the time T2 when the growth ends. The gas flow rate A1 may be a substantially constant flow rate. As shown in FIG. 9, for example, the nitrogen gas flow rate A3 at the time T0 when the growth of the silicon carbide single crystal starts is less than 0.500 slm, and the nitrogen gas flow rate A1 is set to 0 at the time T1 during the growth of the silicon carbide single crystal. It may be increased to 500 slm. Further, as shown in FIG. 8, the nitrogen gas flow rate A2 at the time T0 when the growth of the silicon carbide single crystal is started is larger than 0.500 slm, and the nitrogen gas flow rate A1 is set to 0.500 slm at the time T1 during the growth of the silicon carbide single crystal. It may be decreased.

  Referring to FIGS. 3 and 8, at the time T0 when the growth of the silicon carbide single crystal starts, the flow rate of nitrogen gas contained in the atmospheric gas is flow rate A2, and carbonization is performed on main surface 1a of seed crystal 1 in the state of flow rate A2. The growth of the silicon single crystal begins. Referring to FIGS. 5 and 8, the flow rate A2 of nitrogen gas contained in the atmospheric gas is, for example, 1.000 slm from the time T0 when the silicon carbide single crystal starts to the time T1 during the growth. The first silicon carbide single crystal region 2a of the silicon carbide single crystal 2 grows on the main surface 1a of the seed crystal 1 from the growth start time T0 to the growth time T1. When the flow rate of nitrogen gas contained in the atmospheric gas is large (that is, when the concentration of nitrogen contained in the atmospheric gas is high), the stacking faults present on the main surface 1a of the seed crystal 1 are deposited on the main surface 1a. The silicon carbide single crystal region 2a is inherited and extended.

  Referring to FIGS. 6 and 8, the nitrogen concentration of the atmospheric gas is reduced at time T1 during the growth of the silicon carbide single crystal. Specifically, the flow rate of nitrogen gas contained in the atmospheric gas is reduced from 1.000 slm to 0.500 slm, for example, while the flow rate of helium gas contained in the atmospheric gas is maintained at, for example, about 1.50 slm. Thereby, the extension of some stacking faults 3a out of stacking faults 3 extending to first silicon carbide single crystal region 2a is stopped. Subsequently, the growth of the silicon carbide single crystal is continued while maintaining the flow rate of the nitrogen gas contained in the atmospheric gas at, for example, 0.500 slm. Thereby, second silicon carbide single crystal region 2b in contact with first silicon carbide single crystal region 2a is formed.

  As shown in FIG. 6, the number of stacking faults contained in the silicon carbide single crystal region (second silicon carbide single crystal region 2b) grown in a state where the nitrogen gas flow rate is 0.500 slm is as follows. The number is less than the number of stacking faults included in the silicon carbide single crystal region (first silicon carbide single crystal region 2a) grown in a state of 000 slm. One or more terminal portions 8 of stacking fault 3 exist in boundary region 9 between first silicon carbide single crystal region 2a and second silicon carbide single crystal region 2b.

  Next, silicon carbide single crystal 2 grown on main surface 1 a of seed crystal 1 is taken out from crucible 10. Then, a plurality of silicon carbide substrates are obtained by slicing silicon carbide single crystal 2 with, for example, a wire saw.

Next, the structure of the silicon carbide single crystal according to the present embodiment will be described.
Referring to FIG. 6, silicon carbide single crystal 2 according to the present embodiment has a first silicon carbide single crystal region 2a and a second silicon carbide single crystal region 2b. The nitrogen concentration (first nitrogen concentration) of first silicon carbide single crystal region 2a is, for example, 3 × 10 ¹⁹ cm ⁻³ . First silicon carbide single crystal region 2 a has one or more stacking faults 3. Stacking fault 3 extends, for example, in a direction parallel to the (0001) plane of hexagonal silicon carbide constituting first silicon carbide single crystal region 2a.

Second silicon carbide single crystal region 2b is provided in contact with first silicon carbide single crystal region 2a. Nitrogen concentration in second silicon carbide single crystal region 2b is 2 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less. Preferably, the nitrogen concentration in second silicon carbide single crystal region 2b is lower than the nitrogen concentration in first silicon carbide single crystal region 2a. More preferably, the nitrogen concentration in second silicon carbide single crystal region 2b is not more than two-thirds of the nitrogen concentration in first silicon carbide single crystal region 2a. Preferably, when the nitrogen concentration distribution of silicon carbide single crystal 2 is measured along the <0001> axis direction, the maximum value of the nitrogen concentration in first silicon carbide single crystal region 2a is the second silicon carbide single crystal region. It is 1.5 times or more the minimum value of the nitrogen concentration in 2b.

  Silicon carbide single crystal 2 has a diameter W1 of 100 mm or more, preferably 150 mm or more. Preferably, silicon carbide single crystal 2 is polytype 4H silicon carbide. The nitrogen concentration in each of first silicon carbide single crystal region 2a and second silicon carbide single crystal region 2b can be measured by, for example, SIMS (Secondary Ion Mass Spectroscopy).

  In silicon carbide single crystal 2 according to the present embodiment, one or more termination portions 8 of stacking fault 3 exist in boundary region 9 between first silicon carbide single crystal region 2a and second silicon carbide single crystal region 2b. doing. A plurality of termination portions 8 of the stacking fault 3 may exist in the boundary region 9. The boundary region 9 is a region where the concentration of nitrogen contained in the silicon carbide single crystal 2 changes abruptly. In the boundary region 9, a part of the stacking fault 3 included in the first silicon carbide single crystal region 2 a is extended. Stop. The number of stacking faults 3 included in second silicon carbide single crystal region 2b is smaller than the number of stacking faults 3 included in first silicon carbide single crystal region 2a. Preferably, the number of stacking faults 3 included in second silicon carbide single crystal region 2b is 50% or less of the number of stacking faults 3 included in first silicon carbide single crystal region 2a, more preferably 10%. % Or less.

  As shown in FIG. 4, first silicon carbide single crystal region 2a of silicon carbide single crystal 2 of the present embodiment is seed crystal 1, and second silicon carbide single crystal region 2b is a silicon carbide single crystal. It may be region 2b. In this case, boundary region 9 between first silicon carbide single crystal region 2a and second silicon carbide single crystal region 2b becomes main surface 1a of seed crystal 1, and an end portion of a stacking fault is formed in the vicinity of main surface 1a. One or more 8 exists.

Next, the effect of the method for manufacturing the silicon carbide substrate according to the present embodiment will be described.
The method for manufacturing a silicon carbide single crystal according to the present embodiment includes the following steps. A seed crystal 1 having a main surface 1a and made of silicon carbide is prepared. Silicon carbide single crystal 2 is grown on main surface 1a of seed crystal 1 in an atmospheric gas containing nitrogen. In the step of growing silicon carbide single crystal 2, silicon carbide single crystal region 2b having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less is formed. Thereby, the lattice distortion of silicon carbide single crystal 2 is reduced and the stability of stacking fault 3 is reduced, so that stacking fault 3 extends from seed crystal 1 to seeded silicon carbide single crystal region 2b. Can be suppressed. As a result, silicon carbide single crystal 2 in which extension of stacking fault 3 is suppressed can be manufactured.

  According to the method for manufacturing a silicon carbide single crystal according to the present embodiment, the nitrogen concentration in silicon carbide single crystal region 2 b is lower than the nitrogen concentration in seed crystal 1. Thereby, the stability of stacking fault 3 in silicon carbide single crystal region 2b is lower than the stability of stacking fault 3 in seed crystal 1, so that silicon carbide in which stacking fault 3 grows from seed crystal 1 onto seed crystal 1 is achieved. Extension to the single crystal region 2b can be suppressed.

  Furthermore, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, the nitrogen concentration in the silicon carbide single crystal region is not more than two-thirds of the nitrogen concentration in the seed crystal. Thereby, extension of stacking fault 3 from seed crystal 1 to silicon carbide single crystal region 2b growing on seed crystal 1 can be effectively suppressed.

Furthermore, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, the nitrogen concentration in the silicon carbide single crystal region is 1 × 10 ¹⁹ cm ⁻³ or less. Thereby, extension of stacking fault 3 from seed crystal 1 to silicon carbide single crystal region 2b growing on seed crystal 1 can be effectively suppressed.

  Furthermore, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, the diameter of the silicon carbide single crystal is 100 mm or more. Thereby, a silicon carbide single crystal having a diameter of 100 mm or more can be manufactured.

  Furthermore, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, the main surface of the seed crystal is a surface off by an angle of 10 ° or less with respect to the (0001) plane. Thereby, it can suppress that a stacking fault newly arises in a growth crystal.

  Furthermore, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, the silicon carbide single crystal is polytype 4H silicon carbide. Thereby, a polytype 4H silicon carbide single crystal substrate can be manufactured.

  Further, in the method for manufacturing a silicon carbide single crystal according to the present embodiment, preferably, termination portion 8 of a stacking fault exists in the silicon carbide single crystal. Thereby, a silicon carbide single crystal in which extension of stacking faults has stopped can be manufactured.

The silicon carbide single crystal according to the present embodiment has first silicon carbide single crystal region 2a and second silicon carbide single crystal region 2b. First silicon carbide single crystal region 2a has a first nitrogen concentration and one or more stacking faults. Second silicon carbide single crystal region 2b is in contact with the first silicon carbide single crystal region and has a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less. One or more terminations 8 of stacking faults exist in the boundary region 9 between the first silicon carbide single crystal region and the second silicon carbide single crystal region. Thereby, silicon carbide single crystal 2 in which extension of stacking fault 3 is suppressed can be obtained.

  In the silicon carbide single crystal according to the present embodiment, preferably, the nitrogen concentration in the second silicon carbide single crystal region is lower than the nitrogen concentration in the first silicon carbide single crystal region. As a result, the stability of stacking fault 3 in second silicon carbide single crystal region 2b is lower than the stability of stacking fault 3 in first silicon carbide single crystal region 2a. Extension from silicon single crystal region 2a to silicon carbide single crystal region 2b can be suppressed.

  Furthermore, in the silicon carbide single crystal according to the present embodiment, preferably, the nitrogen concentration in second silicon carbide single crystal region is not more than two-thirds of the nitrogen concentration in first silicon carbide single crystal region. Thereby, extension of stacking fault 3 from first silicon carbide single crystal region 2a to silicon carbide single crystal region 2b can be effectively suppressed.

Furthermore, in the silicon carbide single crystal according to the present embodiment, preferably, the nitrogen concentration in the second silicon carbide single crystal region is 1 × 10 ¹⁹ cm ⁻³ or less. Thereby, extension of stacking fault 3 from first silicon carbide single crystal region 2a to second silicon carbide single crystal region 2b can be effectively suppressed.

  Furthermore, in the silicon carbide single crystal according to the present embodiment, preferably, the diameter of silicon carbide single crystal is 100 mm or more. Thereby, a silicon carbide single crystal substrate having a diameter of 100 mm or more can be manufactured.

  Furthermore, in the silicon carbide single crystal according to the present embodiment, preferably, the silicon carbide single crystal is polytype 4H silicon carbide. Thereby, a polytype 4H silicon carbide single crystal substrate can be obtained.

In the present embodiment, a silicon carbide single crystal region 2b is grown on main surface 1a of seed crystal 1 made of silicon carbide in six types of atmospheric gases described below, and from seed crystal 1 to silicon carbide single crystal region 2b. The proportion of stacking faults that did not extend (the rate at which stacking fault extension stopped) was investigated. First, the crucible 10 in which the silicon carbide raw material 6 and the seed crystal 1 were arrange | positioned was prepared. The crucible 10 was made of graphite. The outer diameter of the crucible 10 was 160 mm, the inner diameter was 120 mm, and the height was 200 mm. The seed crystal 1 was made of polytype 4H silicon carbide, and the diameter of the seed crystal 1 was 100 mm. The crucible 10 was heated to 2300 ° C. to grow a silicon carbide single crystal on the main surface 1 a of the seed crystal 1. The nitrogen concentration of the seed crystal 1 was 3 × 10 ¹⁹ cm ⁻³ . The main surface 1a of the seed crystal 1 was a surface off by 2 ° from the (0001) surface, a surface off by 4 °, a surface off by 10 °, and a surface off by 15 °.

The pressure of the atmospheric gas in the step of forming the silicon carbide single crystal region was 20 Torr, and the flow rate of helium gas and nitrogen gas included in the atmospheric gas were as follows. The helium gas flow rate of Comparative Example 1 was 1.50 slm, and the nitrogen gas flow rate was 1.000 slm. In Example 1 of the present invention, the helium gas flow rate was 1.50 slm, and the nitrogen gas flow rate was 0.500 slm. In Example 2 of the present invention, the helium gas flow rate was 1.50 slm, and the nitrogen gas flow rate was 0.075 slm. In Example 3 of the present invention, the helium gas flow rate was 1.50 slm, and the nitrogen gas flow rate was 0.045 slm. In Example 4 of the present invention, the helium gas flow rate was 1.50 slm, and the nitrogen gas flow rate was 0.030 slm. In Example 5 of the present invention, the helium gas flow rate was 1.50 slm, and the nitrogen gas flow rate was 0.015 slm. The nitrogen concentration of the silicon carbide single crystal region 2b (growth crystal) grown under the conditions of Comparative Example 1 and Invention Examples 1 to 5 is 3 × 10 ¹⁹ cm ⁻³ , 2 × 10 ¹⁹ cm ⁻³ , and 1 × 10 respectively. ^{19 cm -3, 9 × 10 18} cm -3, 7 × 10 18 cm -3, became 5 × 10 ¹⁸ cm ^-3. The nitrogen concentration contained in the grown crystal was measured by SIMS. In SIMS, the nitrogen concentration in a region from the surface to about 10 μm can be measured.

  Silicon carbide single crystal region 2b grown under the above conditions was taken out of crucible 10 together with seed crystal 1, and silicon carbide single crystal region 2b and seed crystal 1 were observed in a cross section perpendicular to main surface 1a of seed crystal 1. A photoluminescence imaging image was used for observation. An example of cross-sectional observation will be described with reference to FIG. For cross-sectional observation, a silicon carbide single crystal having a grown crystal grown under the conditions of Example 5 of the present invention was used. As shown in FIG. 10, a plurality of stacking fault groups existing in the seed crystal 1 stop extending at the boundary surface between the seed crystal 1 and the grown crystal. The ratio of the number of stacking faults extending in the grown crystal to the number of stacking faults present in the seed crystal 1 was calculated as the rate at which the stacking faults stopped extending. The growth direction of the growth crystal is substantially perpendicular to the main surface 1a of the seed crystal 1, and the main surface 1a is a surface that is off the (0001) plane.

With reference to Table 1, the result of the ratio at which the extension of stacking faults has stopped will be described. Note that there was almost no change in the rate at which the extension of stacking faults stopped due to the difference in off-angle. First, when the nitrogen concentration of the seed crystal 1 is the same as the nitrogen concentration of the growth crystal and the nitrogen concentration of the growth crystal is 3 × 10 ¹⁹ cm ⁻³ (in the case of Comparative Example 1), The rate at which the extension stopped at the interface between the seed crystal 1 and the grown crystal was 0%. That is, all the stacking faults of the seed crystal 1 were extended to the grown crystal. On the other hand, when the nitrogen concentration of the grown crystal was 2 × 10 ¹⁹ cm ⁻³ or less (in the case of Invention Examples 1 to 5), the rate at which the extension of stacking faults stopped was greater than 0%. In other words, when the nitrogen concentration of the grown crystal was 2 × 10 ¹⁹ cm ⁻³ or less, at least one of the stacking faults present in the seed crystal 1 stopped extending at the boundary surface. When the nitrogen concentration of the grown crystal was lower than the nitrogen concentration of the seed crystal, at least one of the stacking faults present in the seed crystal 1 stopped extending at the boundary surface.

When the nitrogen concentration of the grown crystal was 1 × 10 ¹⁹ cm ⁻³ or less and 9 × 10 ¹⁸ cm ⁻³ or more (in the case of Invention Examples 2 and 3), the rate at which the stacking fault extension stopped was 50% or more. Further, when the nitrogen concentration of the grown crystal was 7 × 10 ¹⁸ cm ⁻³ or less and 5 × 10 ¹⁸ cm ⁻³ or more (in the case of Invention Examples 4 and 5), the rate of stoppage of stacking faults was 90% or more .

When the main surface 1a of the seed crystal 1 is a surface that is off by 10 ° or less from the (0001) surface (specifically, a surface that is 2 ° off, 4 ° off, and 10 ° off), a stacking fault is newly generated in the grown crystal. Can be suppressed. On the other hand, when the main surface 1a of the seed crystal 1 is a surface that is 15 ° off from the (0001) plane, stacking faults are newly generated at a density of 1 × 10 ⁴ cm ⁻¹ or more in the grown crystal.

From the above results, when a silicon carbide single crystal region (growth crystal) having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less is formed, stacking faults existing in seed crystal 1 are extended to the silicon carbide single crystal region. It was confirmed that this can be suppressed. Further, it was confirmed that when the nitrogen concentration of the grown crystal is lower than the nitrogen concentration of the seed crystal, it is possible to suppress the stacking faults existing in the seed crystal 1 from extending into the silicon carbide single crystal region. Further, when a silicon carbide single crystal region (growth crystal) having a nitrogen concentration of 1 × 10 ¹⁹ cm ⁻³ or less is formed, it is effective that the stacking faults existing in the seed crystal 1 extend into the silicon carbide single crystal region. It was confirmed that it can be suppressed.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 seed crystal, 1a main surface, 2 silicon carbide single crystal, 2a first silicon carbide single crystal region, 2b second silicon carbide single crystal region (silicon carbide single crystal region), 3, 3a, 3b stacking fault, 4 Seed crystal holding part, 5 raw material accommodating part, 6 silicon carbide raw material, 7 reaction vessel, 7a gas inlet, 7b gas outlet, 8 terminal part, 9 boundary region, 10 crucible, 100 production equipment, A1, A2, A3 nitrogen Gas flow, W1 diameter.

Claims (13)

Preparing a seed crystal having a main surface and made of silicon carbide;
A step of growing a silicon carbide single crystal on the main surface of the seed crystal in an atmosphere gas containing nitrogen,
The step of growing the silicon carbide single crystal includes a step of forming a silicon carbide single crystal region having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less,
The method for producing a silicon carbide single crystal, wherein a nitrogen concentration in the silicon carbide single crystal region is lower than a nitrogen concentration in the seed crystal.   2. The method for producing a silicon carbide single crystal according to claim 1, wherein a nitrogen concentration of the silicon carbide single crystal region is not more than two-thirds of a nitrogen concentration of the seed crystal. 3. The method for producing a silicon carbide single crystal according to claim 1, wherein a nitrogen concentration in the silicon carbide single crystal region is 1 × 10 ¹⁹ cm ⁻³ or less.   The diameter of the said silicon carbide single crystal is a manufacturing method of the silicon carbide single crystal of any one of Claims 1-3 which is 100 mm or more.   5. The method for producing a silicon carbide single crystal according to claim 1, wherein the main surface of the seed crystal is a surface that is turned off by an angle of 10 ° or less with respect to the (0001) plane.   The method for producing a silicon carbide single crystal according to any one of claims 1 to 5, wherein the silicon carbide single crystal is polytype 4H silicon carbide.   The method for manufacturing a silicon carbide single crystal according to any one of claims 1 to 6, wherein a termination portion of a stacking fault exists inside the silicon carbide single crystal. A first silicon carbide single crystal region having a first nitrogen concentration and having one or more stacking faults;
A second silicon carbide single crystal region in contact with the first silicon carbide single crystal region and having a nitrogen concentration of 2 × 10 ¹⁹ cm ⁻³ or less,
A silicon carbide single crystal in which one or more terminal portions of the stacking fault exist in a boundary region between the first silicon carbide single crystal region and the second silicon carbide single crystal region.   The silicon carbide single crystal according to claim 8, wherein a nitrogen concentration in the second silicon carbide single crystal region is lower than a nitrogen concentration in the first silicon carbide single crystal region.   10. The silicon carbide single crystal according to claim 9, wherein a nitrogen concentration in said second silicon carbide single crystal region is not more than two-thirds of a nitrogen concentration in said first silicon carbide single crystal region. 11. The silicon carbide single crystal according to claim 8, wherein a nitrogen concentration of the second silicon carbide single crystal region is 1 × 10 ¹⁹ cm ⁻³ or less.   The diameter of the said silicon carbide single crystal is a silicon carbide single crystal of any one of Claims 8-11 which is 100 mm or more.   The silicon carbide single crystal according to any one of claims 8 to 12, wherein the silicon carbide single crystal is polytype 4H silicon carbide.