JP6488607B2 - Manufacturing method of single crystal SiC wafer - Google Patents

Description

  The present invention relates to a method for manufacturing a single crystal SiC wafer.

  Silicon carbide (SiC) includes β-type SiC having a cubic crystal structure (also referred to as “3C-SiC”) and α-type SiC having a hexagonal crystal structure. In SiC, there are many types of crystal structure isomers such as 6H, 4H, and 2H due to the difference in the repetition period of the layered arrangement of Si and C. Since SiC has a wide band gap of 2.2 to 3.3 eV, it is expected as a semiconductor material for various semiconductor devices.

  However, the technology for growing a single crystal SiC ingot by the sublimation method or the Czochralski method and cutting out the single crystal SiC wafer from the ingot is currently limited to a wafer diameter of 150 mm, and the diameter can be further increased. Absent. This is because the SiC ingot generates a larger thermal stress than the Si ingot, and as a result, the large-diameter ingot is distorted. Therefore, large-diameter single crystal SiC wafers having a diameter of 200 mm or 300 mm have not yet been put into practical use.

  Therefore, a technique for epitaxially growing a single crystal SiC layer on a silicon wafer having a large diameter of 300 mm or more has been studied. The crystal growth temperature of SiC generally requires a temperature of 1500 ° C. or higher for α-type SiC and 1300 ° C. or higher for β-type SiC. Therefore, α-type single crystal SiC cannot be directly epitaxially grown on a silicon wafer having a melting point of 1414 ° C. by a general CVD method. In addition, although β-type SiC can be epitaxially grown at a temperature lower than the melting point of silicon, it is close to the melting point. Therefore, during epitaxial growth, silicon atoms in the silicon wafer easily diffuse into the SiC layer, and voids are formed near the interface. The problem is that the crystallinity is poor.

  In Patent Document 1, a polycrystalline or amorphous SiC layer is formed as a buffer layer on a silicon wafer by a low temperature CVD method in which the temperature of the silicon wafer is about 1050 ° C., and then the temperature of the silicon wafer is about 1350. A method for growing a β-type single crystal SiC layer on the SiC layer at a temperature of ° C is described. In addition, Patent Document 2 recognizes that it is difficult to directly form a β-type single crystal SiC layer on a silicon wafer at 1250 ° C. or higher. A method is described in which a SiC layer is formed as a buffer layer by carbonization at a low temperature of 200 ° C., and then the temperature of the silicon wafer is 1200 ° C., and a β-type single crystal SiC layer is vapor-phase epitaxially grown on the SiC layer. .

JP 59-203799 A JP 7-31347 A

  Patent Document 1 and Patent Document 2 are techniques for forming a β-type single crystal SiC layer on a silicon wafer via a buffer layer, and do not directly form a β-type single crystal SiC layer on silicon. For this reason, there is a problem that a buffer layer forming step is required and the manufacturing process becomes complicated. Moreover, since the buffer layer formed in Patent Document 1 is polycrystalline or amorphous, it is expected that the single crystal SiC layer formed on this buffer layer has poor crystallinity. In addition, the carbonization treatment at a low temperature as reported in Patent Document 2 does not sufficiently modify the surface of the silicon wafer, and causes defects such as dislocations. Therefore, single crystal SiC formed on such a buffer layer is used. The layer is also expected to be poorly crystalline.

  In view of the above-described problems, an object of the present invention is to provide a method for manufacturing a single crystal SiC wafer that can cope with an increase in diameter and can obtain a single crystal SiC wafer having high crystallinity.

  In order to achieve this object, a technique for epitaxially growing a single crystal SiC layer having high crystallinity on the silicon wafer is required even when the temperature of the silicon wafer is set to a temperature lower than the melting point of silicon. Although it is necessary to give the energy required for epitaxial growth of β-type single crystal SiC with high crystallinity to the reaction field on the silicon wafer, when the temperature of the silicon wafer is lower than the melting point of silicon, the single crystal SiC layer is Even if the single crystal SiC layer can be grown using the buffer layer forming technique as described in Patent Documents 1 and 2, as described in Patent Documents 1 and 2, the crystallinity must be low. Here, the inventor does not give the energy required for epitaxial growth of highly crystalline β-type single crystal SiC to the reaction field only in the form of heating of the silicon wafer, but in the form of ions of the source gas in the form of ions. The idea was to give it in the form of acceleration and irradiation toward the wafer. In other words, as a result of giving a predetermined amount of source gas ion acceleration energy to the reaction field, it has been found that even if the temperature of the silicon wafer is maintained below the melting point of silicon, a highly crystalline β-type single crystal SiC layer can be epitaxially grown. It was.

  From the viewpoint of the crystal structure, it is a β-type single crystal SiC layer that can directly grow on the surface of the silicon wafer. In order to form an α-type single crystal SiC layer on a silicon wafer, a β-type single crystal SiC layer is first grown on the silicon wafer, and an α-type single crystal SiC layer is grown on the β-type single crystal SiC layer. There is a need. The present inventor adopts a method of accelerating and irradiating the source gas toward the silicon wafer in the form of ions, so that even if the temperature of the silicon wafer is maintained below the silicon melting point, It was also found that an α-type single crystal SiC layer having high crystallinity can be grown.

The gist configuration of the present invention completed based on the above findings is as follows.
(1) a first step of epitaxially growing a single crystal SiC layer on a silicon wafer;
A second step of removing the silicon wafer to obtain a single crystal SiC wafer comprising the single crystal SiC layer;
A method for producing a single crystal SiC wafer having
In the first step, while maintaining the temperature of the silicon wafer at a temperature lower than the melting point of silicon, the source gas containing carbon and silicon is ionized, and the ions are accelerated to irradiate the silicon wafer. A method for manufacturing a single crystal SiC wafer.

(2) In the first step, by epitaxially growing a β-type single crystal SiC layer on the silicon wafer,
The method for producing a single crystal SiC wafer according to (1) above, wherein a β type single crystal SiC wafer comprising the β type single crystal SiC layer is produced.

  (3) The method for producing a single crystal SiC wafer according to (2), wherein the temperature of the silicon wafer is maintained at 800 to 1000 ° C. in the first step.

(4) In the first step, a β-type single crystal SiC layer is epitaxially grown on the silicon wafer, and subsequently an α-type single crystal SiC layer is epitaxially grown on the β-type single crystal SiC layer.
After the second step, the β-type single crystal SiC layer is removed to manufacture an α-type single crystal SiC wafer made of the α-type single crystal SiC layer. Method.

  (5) In the first step, the temperature of the silicon wafer is maintained at 800 to 1000 ° C. during the growth of the β-type single crystal SiC layer, and is maintained at 1000 to 1300 ° C. during the growth of the α-type single crystal SiC layer. The manufacturing method of the single crystal SiC wafer as described in said (4).

(6) Prior to the first step, the silicon wafer is carbonized, and a surface layer portion of the silicon wafer is a β-type single crystal SiC layer,
In the first step, by epitaxially growing an α-type single crystal SiC layer on the β-type single crystal SiC layer of the silicon wafer,
The manufacturing method of the single crystal SiC wafer as described in said (1) which manufactures the alpha type single crystal SiC wafer which consists of this alpha type single crystal SiC layer.

  (7) The method for producing a single crystal SiC wafer according to (6), wherein the temperature of the silicon wafer is maintained at 1000 to 1300 ° C. in the first step.

  (8) In the first step, the acceleration energy of silicon ions is set to 7 eV or more and less than 7 keV, and the acceleration energy of carbon ions is set to 3 eV or more and less than 3 keV, according to any one of (1) to (7) above. A method for producing a single crystal SiC wafer.

(9) In the first step,
The silicon wafer is fixed to a wafer fixing base in the chamber,
After depressurizing the chamber, the source gas is introduced into the chamber,
(1) to (1) to accelerate the ions in the plasma toward the silicon wafer while generating the plasma of the source gas by applying a pulse voltage to the silicon wafer after heating the silicon wafer. The method for producing a single crystal SiC wafer according to any one of (8).

  The method for producing a single crystal SiC wafer of the present invention can cope with an increase in diameter and can provide a single crystal SiC wafer having high crystallinity.

It is a model cross section explaining the manufacturing method of the single crystal SiC wafer by a 1st embodiment of the present invention. It is a model cross section explaining the manufacturing method of the single crystal SiC wafer by the 2nd Embodiment of this invention. It is a model cross section explaining the manufacturing method of the single crystal SiC wafer by the 3rd Embodiment of this invention. It is a schematic diagram of the plasma ion irradiation apparatus used in each embodiment of the present invention.

  The method for producing a single crystal SiC wafer according to the present invention includes a first step of epitaxially growing a single crystal SiC layer on a silicon wafer, and removing the silicon wafer to obtain a single crystal SiC wafer comprising the single crystal SiC layer. In the first step, while maintaining the temperature of the silicon wafer at a temperature lower than the melting point of silicon, the source gas containing carbon and silicon is ionized, and the ions are accelerated to accelerate the silicon. It is characterized by irradiating the wafer. Hereinafter, preferred embodiments of the present invention will be described.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIG. First, in the first step, the β-type single crystal SiC layer 12 is epitaxially grown on the silicon wafer 10 (FIGS. 1A and 1B). Next, in the second step, the silicon wafer 10 is removed to obtain a β-type single crystal SiC wafer 100 composed of the β-type single crystal SiC layer 12 (FIGS. 1C and 1D).

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. First, in the first step, the β-type single crystal SiC layer 12 is epitaxially grown on the silicon wafer 10, and then the α-type single crystal SiC layer 14 is epitaxially grown on the β-type single crystal SiC layer 12 (FIGS. 2A to 2 ( C)). Next, in the second step, the silicon wafer 10 is removed (FIG. 2D). After this second step, the β-type single crystal SiC layer 12 is removed to obtain an α-type single crystal SiC wafer 200 composed of the α-type single crystal SiC layer 14 (FIGS. 2E and 2F).

  The purpose of this embodiment is to obtain an α-type single crystal SiC wafer. The α-type single crystal SiC layer cannot be directly grown on the surface of the silicon wafer, but can be grown on the β-type single crystal SiC layer. . Therefore, in the present embodiment, the β-type single crystal SiC layer 12 is first formed on the silicon wafer 10.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, prior to the first step (epitaxial growth step of single crystal SiC), the silicon wafer 10 is carbonized so that the surface layer portion of the silicon wafer 10 becomes a β-type single crystal SiC layer 10A (FIG. 3A). , (B)). Next, as a first step, the α-type single crystal SiC layer 14 is epitaxially grown on the β-type single crystal SiC layer 10A of the silicon wafer 10 (FIG. 3C). Next, in the second step, the silicon wafer 10 including the β-type single crystal layer 10A is removed to obtain an α-type single crystal SiC wafer 300 composed of the α-type single crystal SiC layer 14 (FIG. 3D, (E)).

  In the second embodiment, the β-type single crystal SiC layer is formed by epitaxial growth, whereas in the present embodiment, the β-type single crystal SiC layer is formed by carbonizing the silicon wafer 10.

(Detailed description of each process in each embodiment)
A silicon wafer 10 prepared in FIGS. 1 (A), 2 (A), and 3 (A) is a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method). Can be sliced with a wire saw or the like. In order to obtain a high gettering capability, carbon and / or nitrogen may be added to the silicon wafer 10. Furthermore, for voltage control during plasma processing, a predetermined concentration of an arbitrary dopant may be added to the silicon wafer 10 to form a so-called n-type or p-type substrate.

  In addition, in order to epitaxially grow a single crystal SiC layer by regularly arranging silicon and carbon, a substrate that does not include COP (Crystal Originated Particle) that is a void formed by aggregation of vacancies that are point defects may be used. preferable. The “silicon wafer not including COP” in the present invention means a silicon wafer in which COP is not detected by the observation evaluation described below. That is, first, a silicon wafer cut out from a single crystal silicon ingot grown by the CZ method is subjected to SC-1 cleaning (that is, ammonia water, hydrogen peroxide water, and ultrapure water are 1: 1: 15). The surface of the silicon wafer after cleaning is observed and evaluated using a Surface Scan SP-2 manufactured by KLA-Tencor as a surface defect inspection device, and a bright spot defect estimated to be a surface pit. (LPD: Light Point Defect) is specified. At this time, the observation mode is an Oblique mode (oblique incidence mode), and surface pits are estimated based on the detected size ratio of the Wide Narrow channel. The LPD thus identified is evaluated whether it is a surface pit using an atomic force microscope (AFM). By this observation and evaluation, a silicon wafer in which no surface pits are observed is referred to as a “silicon wafer not including COP”.

  The diameter of the silicon wafer 10 is preferably 200 mm or more, and more preferably 300 mm or more. Since the diameter of the silicon wafer 10 and the diameter of the obtained single crystal SiC wafer match, the larger the diameter of the silicon wafer 10, the larger the single crystal SiC wafer can be obtained.

  In the step of epitaxially growing the β-type single crystal SiC layer 12 or the α-type single crystal SiC layer 14 on the silicon wafer 10 (FIG. 1B, FIG. 2B, FIG. 3C, FIG. 3C), silicon While maintaining the temperature of the wafer 10 at a temperature lower than the melting point of silicon, it is important to ionize a source gas containing carbon and silicon and accelerate the ions to irradiate the silicon wafer 10.

  An embodiment of an apparatus for realizing this method will be described with reference to FIG. The plasma ion irradiation apparatus 40 includes a plasma chamber 41, a gas inlet 42, a vacuum pump 43, a pulse voltage application unit 44, a wafer fixing table 45, and a heater 46.

  First, the silicon wafer 10 is placed and fixed on the wafer fixing table 45 in the plasma chamber 41. Next, the inside of the plasma chamber 41 is depressurized by the vacuum pump 43, and then the source gas is introduced into the plasma chamber 41 from the gas inlet 42. Subsequently, after the wafer fixing table 45 is heated by the heater 46, a negative voltage is applied in a pulsed manner to the wafer fixing table 45 (and the silicon wafer 10) by the pulse voltage applying means 44. As a result, plasma of a source gas containing carbon and silicon can be generated, and ions of the source gas included in the generated plasma can be accelerated and irradiated toward the silicon wafer 10. The irradiated silicon ions and carbon ions react on the silicon wafer, and single crystal SiC grows epitaxially.

  As the source gas, one or more of methane, ethane, propane and the like can be used as a carbon source, and one or more of monosilane, dichlorosilane, trichlorosilane, silicon tetrachloride and the like are used as a silicon source. be able to.

  The degree of vacuum in the plasma chamber 41 is set to 5 Pa or less. This is because when the pressure exceeds 5 Pa, the plasma is not stabilized and the plasma state cannot be maintained.

  Here, the pulse voltage applied to the silicon wafer 10 is 10 V or more and 1 kV or less. This is because when the voltage is less than 10 V, the bond energy between silicon and carbon becomes insufficient, and the SiC layer may not be formed. On the other hand, if it exceeds 1 kV, silicon or carbon is injected from the silicon wafer surface to the inner side, and there is a possibility that the SiC layer cannot be formed.

  The frequency of the pulse voltage determines the number of times that the silicon wafer 10 is irradiated with ions. The frequency of the pulse voltage is preferably 10 Hz to 10 kHz. Here, by setting the frequency to 10 Hz or more, the ion irradiation variation can be absorbed and the ion irradiation amount is stabilized. Moreover, the plasma formation by glow discharge is stabilized by setting it as 10 kHz or less.

  The pulse width of the pulse voltage determines the time during which the silicon wafer 10 is irradiated with ions. The pulse width is preferably 1 μs to 1000 μs. By setting it to 1 microsecond or more, the silicon wafer 10 can be stably irradiated with ions. Moreover, the plasma formation by glow discharge is stabilized by setting it as 1000 microseconds or less.

  In each embodiment, the energy required for epitaxial growth of β-type single crystal SiC having high crystallinity is realized by the sum of thermal energy applied to the silicon wafer 10 and acceleration energy of ions irradiated on the silicon wafer 10. . That is, by maintaining the temperature of the silicon wafer 10 at a temperature lower than the melting point of silicon, the shortage of thermal energy is compensated by the acceleration energy of ions.

  In each embodiment, when the β-type single crystal SiC layer is epitaxially grown (FIGS. 1B and 2B), the silicon ion acceleration energy is set to 7 eV while maintaining the temperature of the silicon wafer at 800 to 1000 ° C. It is preferable that the acceleration energy of carbon ions be 3 eV or more. By setting the ion acceleration energy in this way, even in the temperature range below the melting point of the silicon wafer, the shortage of thermal energy is compensated for by the ion acceleration energy, and a highly crystalline β-type single crystal SiC layer is formed. Can be formed. If the temperature of the silicon wafer is 800 ° C. or higher, the ion acceleration energy does not need to be higher than the preferred upper limit described later. When the temperature of the silicon wafer is made higher, the required ion acceleration energy becomes smaller. In addition, since the acceleration energy ratio of silicon ions and carbon ions is 7: 3, it becomes possible to irradiate silicon ions and carbon ions at the same depth on the silicon wafer surface, and the SiC layer is applied to the silicon wafer surface. It can be formed stably.

  In each embodiment, when the α-type single crystal SiC layer is epitaxially grown (FIGS. 2C and 3C), the acceleration energy of silicon ions is set to 7 eV while maintaining the temperature of the silicon wafer at 1000 to 1300 ° C. It is preferable that the acceleration energy of carbon ions be 3 eV or more. By setting the ion acceleration energy in this way, even in the temperature range below the melting point of the silicon wafer, the shortage of thermal energy is compensated by the ion acceleration energy, so that α type single crystal SiC having high crystallinity is obtained. Layers can be formed. Since the energy required for the growth of the α-type single crystal SiC layer is higher than the energy required for the growth of the β-type single crystal SiC layer, the temperature of the silicon wafer is higher than when the β-type single crystal SiC is grown. Set. If the temperature of the silicon wafer is 1000 ° C. or higher, the ion acceleration energy does not need to be higher than the preferred upper limit described later.

  In each embodiment, the acceleration energy of silicon ions and the acceleration energy of carbon ions are preferably less than 3 keV, and more preferably less than 1 keV. In the case of 3 keV or more, there is a possibility that excessive damage may be given to the silicon wafer 10, and a phenomenon that ions are implanted into the silicon wafer occurs, and there is a possibility that the SiC layer cannot be epitaxially grown on the surface.

  The acceleration energy of ions is mainly controlled by the applied voltage. Also, as supplementary control, adjust the resistance between the wafer and the pulse application device (resistance of the fixed base, resistance between the fixed base and the pulse application device), or adjust the timing of voltage application. Then, the distance between the plasma region and the wafer is adjusted. The acceleration energy of ions can be measured by processing a monitoring wafer for a short time and grasping the concentration distribution of silicon and carbon in the depth direction from the wafer surface to the inside by SIMS analysis.

  The film thicknesses of the β-type single crystal SiC layer 12 in FIG. 1B and the α-type single crystal SiC layer 14 in FIGS. 2C and 3C are preferably 300 μm or more. If it is 300 micrometers or more, these single-crystal SiC layers can be utilized as a wafer. Note that the β-type single crystal SiC layer 12 in FIG. 2B and the β-type single crystal SiC layer 10A in FIG. 3B are merely for forming an α-type single crystal SiC layer thereon. The film thickness may be about 10 nm to 1 μm.

  The carbonization treatment of the silicon wafer 10 in FIG. 3B may be performed by a known or arbitrary method. For example, carbon gas such as propane gas, methane gas, and ethane gas and hydrogen gas as a carrier gas are introduced into the heat treatment furnace, and the temperature of the silicon wafer 10 is set to 1000 to 1300 ° C. in a carbon atmosphere for 1 to 60 minutes. Perform carbonization.

  The removal of the silicon wafer 10 in FIGS. 1C and 2D can be performed by treatment with an alkaline solution or an acidic solution capable of dissolving silicon. Examples of the alkaline solution include a mixed solution of potassium hydroxide and sodium hydroxide, and examples of the acidic solution include a mixed solution of hydrofluoric acid and nitric acid. The silicon portion in FIG. 3D can be removed in the same manner.

  The removal of the β-type single crystal SiC layer 12 in FIG. 2E can be performed by arbitrary grinding and / or polishing such as CMP processing. The removal of the β-type single crystal SiC layer 10A in FIG. 3D can be similarly performed.

  The β-type single crystal SiC layer 12 shown in FIG. 1C and the α-type single crystal SiC layer 14 shown in FIGS. 2E and 3D are formed on the front and back surfaces by an arbitrary method such as CMP. About 0.01 to 10 μm is ground and / or polished to obtain the final wafer thickness.

  According to each embodiment described above, a single crystal SiC wafer with high crystallinity can be obtained. Moreover, since the single crystal SiC layer formed on the silicon wafer is used as a wafer, a single crystal SiC wafer having a large diameter of 200 mm or more, further 300 mm or more can be preferably manufactured.

Example 1
According to the procedure of FIG. 1, a β-type single crystal SiC wafer having a diameter of 300 mm was produced using the apparatus of FIG.

First, a COP-free silicon single crystal ingot grown by the CZ method is sliced and processed to obtain a 300 mm diameter, p-type (111) silicon wafer (resistivity: 0.01 Ωcm, oxygen concentration: 1.3 × 10 ¹⁸ atoms). / Cm ³ ).

  While the temperature of the silicon wafer is 900 ° C., methane gas and monosilane gas are flowed into the plasma chamber, the pressure in the chamber is 0.05 Pa, the pulse voltage is 750 V, the frequency is 320 Hz, and the pulse width is 183 μsec. A β-type single crystal SiC layer was epitaxially grown to 500 μm. The acceleration energy of silicon ions was 105 eV, and the acceleration energy of carbon ions was 45 eV.

  Subsequently, the silicon wafer was dissolved in a solution obtained by diluting a mixed solution of potassium hydroxide and sodium hydroxide with pure water. Next, the front and back surfaces of the β-type single crystal SiC layer were ground and polished. The grinding and polishing allowance was 2 μm. In this way, a β-type single crystal SiC wafer having a thickness of 498 μm and a diameter of 300 mm was obtained.

  As a result of evaluating the crystallinity of the obtained wafer using the PL method, XPS method and TEM observation, it was confirmed that cubic SiC could be produced.

(Example 2)
According to the procedure of FIG. 2, an α-type single crystal SiC wafer having a diameter of 300 mm was produced using the apparatus of FIG.

  A silicon wafer similar to that in Example 1 was prepared. With the temperature of the silicon wafer set to 900 ° C., methane gas and monosilane gas are flowed into the plasma chamber, the pressure in the chamber is 0.07 Pa, the pulse voltage is 890 V, the frequency is 290 Hz, and the pulse width is 168 μsec. A β-type single crystal SiC layer was epitaxially grown by 0.5 μm. The acceleration energy of silicon ions was 125 eV, and the acceleration energy of carbon ions was 53 eV.

  Subsequently, an α-type single crystal SiC layer was epitaxially grown by 500 μm on the β-type single crystal SiC layer under the same conditions except that the temperature of the silicon wafer was 1200 ° C.

  Subsequently, the silicon wafer was dissolved in a solution obtained by diluting a mixed solution of potassium hydroxide and sodium hydroxide with pure water. Next, the β-type single crystal SiC layer was removed by grinding and polishing. Next, the front and back surfaces of the α-type single crystal SiC layer were ground and polished. The grinding and polishing allowance was 3 μm. Thereafter, the surface of the α-type single crystal SiC layer was polished to obtain an α-type single crystal SiC wafer having a thickness of 497 μm and a diameter of 300 mm.

  As a result of evaluating the crystallinity of the obtained wafer using the PL method, XPS method and TEM observation, it was confirmed that hexagonal 4H—SiC could be produced.

(Example 3)
According to the procedure of FIG. 3, an α-type single crystal SiC wafer having a diameter of 300 mm was produced using the apparatus of FIG.

  A silicon wafer similar to that in Example 1 was prepared. Propane gas and hydrogen gas were introduced into the heat treatment furnace, and the carbon wafer was carbonized for 3 minutes at a temperature of 1200 ° C. in a carbon atmosphere. The surface layer portion 20 nm of the silicon wafer became a β-type single crystal SiC layer.

  In a state where the temperature of the silicon wafer is 1200 ° C., methane gas and monosilane gas are flowed into the plasma chamber, the pressure in the chamber is 0.1 Pa, the pulse voltage is 940 V, the frequency is 270 Hz, and the pulse width is 140 μsec. An α-type single crystal SiC layer was epitaxially grown by 500 μm on the β-type single crystal SiC layer. The acceleration energy of silicon ions was 132 eV, and the acceleration energy of carbon ions was 56 eV.

  Subsequently, the silicon portion was dissolved with a solution obtained by diluting a mixed solution of potassium hydroxide and sodium hydroxide with pure water. Next, the β-type single crystal SiC layer was removed by grinding and polishing. Next, the front and back surfaces of the α-type single crystal SiC layer were ground and polished. The grinding and polishing allowance was 3 μm. In this way, an α-type single crystal SiC wafer having a thickness of 497 μm and a diameter of 300 mm was obtained.

  As a result of evaluating the crystallinity of the obtained wafer using the PL method, XPS method and TEM observation, it was confirmed that hexagonal 4H—SiC could be produced.

(Comparative example)
An α-type SiC single crystal ingot grown by the sublimation method was sliced and processed to obtain an α-type SiC wafer having a diameter of 100 mm. On this α-type SiC wafer, an α-type single crystal SiC layer was epitaxially grown by 10 μm by a general CVD method in a state where the temperature of the wafer was 1580 ° C. The single crystal SiC layer obtained here should have high crystallinity.

(Evaluation)
Table 1 shows the results of evaluating the surface integrity using a laser scattering type defect inspection apparatus. In each of the examples and comparative examples, the number of defects having a size of 10 μm or more (pieces / cm ² ) was obtained for three wafers. From Table 1, it can be seen that in Examples 1 to 3, the same high crystallinity as in Comparative Example 1 was obtained.

  The method for producing a single crystal SiC wafer of the present invention can cope with an increase in diameter and can provide a single crystal SiC wafer having high crystallinity.

DESCRIPTION OF SYMBOLS 10 Silicon wafer 10A β type single crystal SiC layer 12 β type single crystal SiC layer 14 α type single crystal SiC layer 100 β type single crystal SiC wafer 200,300 α type single crystal SiC wafer 40 Plasma ion irradiation apparatus 41 Plasma chamber 42 Gas Introduction port 43 Vacuum pump 44 Pulse voltage application means 45 Wafer fixing base 46 Heater

Claims (7)

A first step of epitaxially growing a single crystal SiC layer on a silicon wafer;
A second step of removing the silicon wafer to obtain a single crystal SiC wafer comprising the single crystal SiC layer;
A method for producing a single crystal SiC wafer having
In the first step,
The silicon wafer is fixed to a wafer fixing base in the chamber,
After reducing the pressure in the chamber, a source gas containing carbon and silicon is introduced into the chamber,
While heating the silicon wafer, while maintaining the temperature of the silicon wafer at a temperature below the melting point of silicon, by applying a negative voltage to the silicon wafer in a pulsed manner, while generating plasma of the source gas, A method for producing a single crystal SiC wafer, comprising accelerating ions of the source gas contained in the plasma and irradiating the silicon wafer. In the first step, by epitaxially growing a β-type single crystal SiC layer on the silicon wafer,
The manufacturing method of the single crystal SiC wafer of Claim 1 which manufactures the beta type single crystal SiC wafer which consists of this beta type single crystal SiC layer.   The method for producing a single crystal SiC wafer according to claim 2, wherein the temperature of the silicon wafer is maintained at 800 to 1000 ° C. in the first step. In the first step, a β-type single crystal SiC layer is epitaxially grown on the silicon wafer, and then an α-type single crystal SiC layer is epitaxially grown on the β-type single crystal SiC layer.
The method for producing a single crystal SiC wafer according to claim 1, wherein after the second step, the β type single crystal SiC layer is removed to produce an α type single crystal SiC wafer comprising the α type single crystal SiC layer. .   The temperature of the silicon wafer is maintained at 800 to 1000 ° C. during the growth of the β-type single crystal SiC layer and maintained at 1000 to 1300 ° C. during the growth of the α-type single crystal SiC layer in the first step. 4. A method for producing a single crystal SiC wafer according to 4. Prior to the first step, the silicon wafer is carbonized, and the surface layer of the silicon wafer is a β-type single crystal SiC layer,
In the first step, by epitaxially growing an α-type single crystal SiC layer on the β-type single crystal SiC layer of the silicon wafer,
The manufacturing method of the single crystal SiC wafer of Claim 1 which manufactures the alpha type single crystal SiC wafer which consists of this alpha type single crystal SiC layer.   The method for producing a single crystal SiC wafer according to claim 6, wherein the temperature of the silicon wafer is maintained at 1000 to 1300 ° C. in the first step.