JP5267177B2 - Method for manufacturing silicon carbide single crystal substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon carbide single crystal substrate having a smooth and high-quality surface, and a method for manufacturing the substrate. <P>SOLUTION: The method for manufacturing a silicon carbide single crystal substrate includes: a step (A) of preparing a silicon carbide single crystal substrate having a principal plane on which mechanical polishing is performed; a step (B) of performing chemical mechanical polishing on the principal plane of the silicon carbide single crystal substrate so as to finish the principal plane to a mirror finished surface by using a first polishing slurry in which a first abrasive grain is dispersed in a first solution obtained by dissolving an oxidant in solvent wherein the oxidant includes at least one substance selected from among hydrogen peroxide, ozone, permanganate, peracetic acid, perchlorate, periodic acid, periodate and hypochlorite; and a step (C) of performing chemical mechanical polishing on the principal plane having been finished to the mirror finished surface by using a second polishing slurry in which a second abrasive grain is dispersed in a second solution containing neither hydrogen peroxide, ozone, permanganate, peracetic acid, perchlorate, periodic acid, periodate nor hypochlorite. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a silicon carbide single crystal substrate and a method for manufacturing the same, and more particularly to polishing a silicon carbide single crystal substrate.

  A silicon carbide semiconductor has a breakdown electric field, an electron saturation drift velocity, and a thermal conductivity larger than those of a silicon semiconductor. For this reason, research and development have been actively conducted to realize a power device that can operate at a higher temperature and higher speed than conventional silicon devices by using a silicon carbide semiconductor. In particular, the development of high-efficiency switching elements that are used as power sources for driving motors of electric motorcycles, electric vehicles, hybrid cars, and the like has attracted attention. In order to realize such a power device, a silicon carbide substrate for epitaxially growing a high-quality silicon carbide semiconductor layer is necessary.

  In addition, there is an increasing need for a blue laser diode as a light source for recording information at a high density and a white diode as a light source replacing a fluorescent lamp or a light bulb. Such a light-emitting element is manufactured using a gallium nitride semiconductor, and a silicon carbide single crystal substrate is used as a substrate for forming a high-quality gallium nitride semiconductor layer.

  A silicon carbide single crystal substrate for such applications requires high processing accuracy in terms of the flatness of the substrate, the smoothness of the substrate surface, and the like. However, since silicon carbide single crystal generally has high hardness and excellent corrosion resistance, the workability in producing such a substrate is poor, and it is difficult to obtain a silicon carbide single crystal substrate with high smoothness.

  In general, a smooth surface of a semiconductor single crystal substrate is formed by polishing. When polishing a silicon carbide single crystal, the surface is mechanically polished using abrasive grains such as diamond harder than silicon carbide as an abrasive to form a flat surface. However, fine scratches corresponding to the grain size of the diamond abrasive grains are introduced on the surface of the silicon carbide single crystal substrate polished with the diamond abrasive grains. In addition, a work-affected layer having mechanical strain is generated on the surface of the silicon carbide single crystal substrate. For this reason, the smoothness of the surface of the silicon carbide single crystal substrate is not sufficient as it is, and a high-quality silicon carbide semiconductor layer cannot be formed on the surface of the silicon carbide single crystal substrate.

  In manufacturing a semiconductor single crystal substrate, CMP (Chemical Mechanical Polishing) is conventionally used as a method of smoothing the surface of a semiconductor substrate after mechanical polishing. CMP uses a chemical reaction such as oxidation to change the workpiece to oxide, etc., and uses abrasive grains that are softer than the workpiece to remove the generated oxide with abrasive grains. It is the method of grind | polishing the surface of this. This method has the advantage that a very smooth surface can be formed without introducing any strain on the surface of the workpiece. Patent Document 1 discloses that the surface of a silicon carbide single crystal substrate after mechanical polishing is smoothed by CMP using silica slurry.

  However, when only the silica slurry is used as in Patent Document 1, the reactivity of the slurry is low, so it takes a long time to form a smooth surface. Further, since the silicon carbide single crystal substrate is polished by applying pressure, the longer the CMP time, the more likely to cause problems such as defects in the substrate and chipping.

  In order to solve this problem, for example, Patent Document 2 discloses that an oxidizing agent is added to a polishing slurry for CMP of a silicon carbide single crystal substrate. According to Patent Document 2, by performing CMP in a state where an oxidizing agent is present on the polishing surface, the polishing rate is increased, and a hard material such as silicon carbide can be efficiently polished even at a low processing pressure.

JP-A-2005-260218 JP 2001-205555 A

  The method using a polishing slurry containing an oxidizing agent as described in Patent Document 2 is very excellent as a method for efficiently polishing a silicon carbide single crystal substrate. However, the inventors of the present invention used such a polishing slurry to finish the surface of the silicon carbide single crystal substrate to a mirror surface by CMP, and epitaxially grew a silicon carbide semiconductor layer or a gallium nitride semiconductor layer on the smoothed silicon carbide single crystal substrate. However, problems such as unevenness and scratch-like crystal defects appear on the surface of the grown silicon carbide semiconductor layer.

  An object of the present invention is to solve such problems and to provide a silicon carbide single crystal substrate for growing a silicon carbide semiconductor layer or the like having a smooth and high-quality surface and a method for manufacturing the same.

  The method for producing a silicon carbide single crystal substrate of the present invention comprises a step (A) of preparing a silicon carbide single crystal substrate having a main surface subjected to mechanical polishing, hydrogen peroxide, ozone, permanganate, peracetic acid. First abrasive particles dispersed in a first solution in which an oxidizing agent containing at least one selected from perchlorate, periodic acid, periodate and hypochlorite is dissolved in a solvent. Using a polishing slurry, subjecting the main surface of the silicon carbide single crystal substrate to chemical mechanical polishing and finishing the main surface into a mirror surface (B), hydrogen peroxide, ozone, permanganate, peracetic acid, The mirror surface was finished by using a second polishing slurry in which second abrasive grains were dispersed in a second solution containing none of perchlorate, periodic acid, periodate and hypochlorite. And (C) performing chemical mechanical polishing on the main surface.

  In a preferred embodiment, the first abrasive grains and the second abrasive grains are silicon oxide abrasive grains.

  In a preferred embodiment, the chemical mechanical polishing in the steps (B) and (C) is continuously performed on the same polishing pad.

  In a preferred embodiment, the mirror-finished main surface after the step (B) has a step structure derived from a single crystal structure of silicon carbide.

  In a preferred embodiment, the main surface subjected to the chemical mechanical polishing after the step (C) has a step structure derived from a single crystal structure of silicon carbide.

  In a preferred embodiment, the silicon carbide single crystal substrate is a single crystal substrate having a hexagonal crystal structure, and an off angle with respect to the C axis of the (0001) plane of the main surface is within 4 °.

  The silicon carbide single crystal substrate of the present invention is manufactured using the manufacturing method defined in any of the above.

  According to the present invention, CMP is performed on the surface of the silicon carbide single crystal substrate using the first polishing slurry containing an oxidizing agent having a high oxidation ability, so that the time required for finishing the main surface into a mirror surface can be shortened. It is possible to manufacture a silicon carbide single crystal substrate having a high-quality mirror surface under typical processing conditions. In addition, since the main surface finished to a mirror surface is further polished using the second polishing slurry not containing an oxidizing agent having a high oxidizing ability contained in the first polishing slurry, an oxide of silicon carbide is formed on the main surface. It does not remain. Therefore, a high-quality silicon carbide semiconductor layer or gallium nitride semiconductor layer having no defects can be formed on the main surface of the silicon carbide single crystal substrate.

(A) And (b) is a typical top view and sectional drawing of the conventional silicon carbide single crystal substrate in which the silicon carbide semiconductor layer was formed. It is a flowchart which shows one Embodiment of the manufacturing method of the silicon carbide single crystal substrate by this invention. (A)-(c) is process sectional drawing in one Embodiment of the manufacturing method of the silicon carbide single crystal substrate by this invention. It is a figure which shows an example of the structure of a peroxometalate ion.

  The inventor of the present application causes defects in a silicon carbide semiconductor layer grown on a silicon carbide single crystal substrate when CMP is performed using a polishing slurry containing a strong oxidizing agent as described in Patent Document 2. Were examined in detail.

  FIG. 1 (a) schematically shows the surface of a silicon carbide single crystal substrate on which a silicon carbide semiconductor layer is formed by such a method, and FIG. 1 (b) infers the state of its cross section. A schematic diagram is shown. As shown in FIGS. 1A and 1B, silicon carbide semiconductor layer 61 is formed on main surface 51 </ b> S of silicon carbide single crystal substrate 51. When silicon carbide semiconductor layer 61 was observed with a microscope, scratch-like crystal defects 61a extending in a direction unrelated to the crystal orientation of silicon carbide single crystal substrate 51 and main surface 51S of silicon carbide single crystal substrate 51 were generated. A triangular defect 61b in which a heterogeneous phase was grown due to the point defect was observed.

  However, when the main surface 51S of the silicon carbide single crystal substrate 51 is analyzed by an ordinary surface analysis method such as optical microscope observation or X-ray photoelectron spectroscopy before the growth of the silicon carbide semiconductor layer 61, scratch-like crystal defects 61a and triangles It was not possible to detect scratches, foreign matters, altered layers, and the like that cause the shape defect 61b.

  Since such a defect in silicon carbide semiconductor layer 61 is considered to reflect the state of main surface 51S on which silicon carbide semiconductor layer 61 is formed, after polishing by CMP using a polishing slurry containing an oxidizing agent. This is because the deteriorated layer 52 that is so thin that it cannot be detected by normal surface analysis is partially formed or remains on the main surface 51S of the silicon carbide single crystal substrate 51, thereby inhibiting the epitaxial growth of the silicon carbide semiconductor layer 61. It is guessed that there is not. Further, it is considered that the altered layer 52 is not silicon oxide. This is because silicon oxide is etched with hydrofluoric acid or the like for removing a natural oxide film or the like generated on main surface 51S of silicon carbide single crystal substrate 51 before forming silicon carbide semiconductor layer 61. .

  As a result of detailed examination, it is surmised that the generation of the deteriorated layer 52 is caused by using a polishing slurry containing a strong oxidizing agent. As described above, CMP polishes an object to be polished using chemical reaction and mechanical polishing. Since the polishing slurry containing a strong oxidizing agent has a high oxidizing ability, it oxidizes a portion of silicon carbide extending from the outermost surface of the silicon carbide single crystal substrate to a certain extent inside, and an oxide containing silicon, carbon and oxygen (Si—C—O ) Is considered to be generated. However, in mechanical polishing with abrasive grains, the inside cannot be scraped from the surface to the extent that the generated oxide is completely removed, so it is considered that the oxide remains as the altered layer 52 after polishing. It is considered that this oxide does not remain uniformly on the surface of the substrate, but partially remains depending on scratches caused by diamond abrasive grains generated on the substrate before polishing by CMP.

  On the other hand, when a silicon carbide single crystal substrate is polished by CMP using a polishing slurry that does not contain a strong oxidizing agent as disclosed in Patent Document 1, since the polishing slurry does not contain a strong oxidizing agent, silicon carbide Only the vicinity of the outermost surface of the single crystal substrate is oxidized. For this reason, it is considered that oxides generated by mechanical polishing with abrasive grains are completely removed, and no excess oxide remains after polishing by CMP.

  Based on such estimation, in the present invention, after polishing the surface of the silicon carbide single crystal substrate by CMP using a polishing slurry containing a strong oxidizing agent, further CMP is performed using a polishing slurry containing no strong oxidizing agent. As a result, the oxide containing silicon, carbon and oxygen remaining on the substrate surface, that is, the altered layer, is removed. As a result, the main surface of the silicon carbide single crystal substrate can be mirror-finished in a practical time using a polishing slurry containing a strong oxidizer, and conventionally removed using a polishing slurry that does not contain a strong oxidizer. The oxide remaining on the substrate surface that was not obtained can be removed, and a silicon carbide single crystal substrate having a main surface finished as a mirror surface free from foreign matter can be obtained. Hereinafter, embodiments of a method for manufacturing a silicon carbide single crystal substrate according to the present invention will be described in detail.

  FIG. 2 is a flowchart showing an embodiment of a method for manufacturing a silicon carbide single crystal substrate according to the present invention. 3A to 3C show process cross-sectional views in the manufacturing process of the silicon carbide single crystal substrate. First, as shown in step S11 and FIG. 3A, silicon carbide single crystal substrate 10 subjected to mechanical polishing is prepared. Silicon carbide single crystal substrate 10 includes a main surface 10S finished to at least a mirror surface. A work-affected layer 11 in which stress is generated by mechanical polishing is generated on the surface of the main surface 10S. The surface roughness Ra of the surface 11S of the work-affected layer 11 is preferably about 1 μm or less. Usually, the work-affected layer 11 has a thickness comparable to the surface roughness, and the work-affected layer 11 has a thickness of, for example, 1 μm or less.

  The surface orientation of main surface 10S of silicon carbide single crystal substrate 10 is not particularly limited, and the method of this embodiment can be suitably used for silicon carbide single crystal substrate 10 of any orientation. However, the present invention is particularly suitably used for the production of a silicon carbide single crystal substrate having a hard surface, which has been difficult to form a high-quality mirror surface by a conventional method. Specifically, the silicon carbide single crystal of the silicon carbide single crystal substrate 10 has a hexagonal crystal structure and is preferably 2H—SiC, 4H—SiC, 6H—SiC, or the like, and is preferably 4H—SiC or 6H—SiC. It is particularly preferred. Off angle θ with respect to the C axis of (0001) plane of main surface 10S of silicon carbide single crystal substrate 10 is 10 ° or less, and is appropriately selected according to the type of semiconductor formed on silicon carbide single crystal substrate 10. . The smaller the offset angle, the slower the polishing rate by CMP using a polishing slurry that does not contain a strong oxidizer. The present invention is based on the silicon carbide single crystal substrate 10 having such a surface, specifically, the off angle θ. It is possible to mirror-finish silicon carbide single crystal substrate 10 having an angle of 4 ° or less in a practical time, and the quality of the silicon carbide semiconductor layer formed on the obtained mirror surface is high. The silicon carbide single crystal substrate 10 may be other than a hexagonal crystal structure, and can be applied to a cubic crystal structure, for example. Specifically, silicon carbide single crystal substrate 10 may be 3C—SiC.

  In this embodiment, only one main surface 10S of silicon carbide single crystal substrate 10 is finished as a mirror surface, but the other main surface 10R may be finished as a mirror surface. In this case, for example, CMP may be performed on the main surface 10S and the main surface 10R in each step described below.

  Next, as shown in step S12, the work-affected layer 11 is removed by CMP, and the main surface 10S of the silicon carbide single crystal substrate 10 is finished to a mirror surface. The first polishing slurry used for CMP includes a first solution in which an oxidizing agent is dissolved in a solvent, and first abrasive grains dispersed in the solution. The oxidizing agent preferably has a high oxidizing ability and is at least selected from hydrogen peroxide, permanganate, ozone, peracetic acid, perchlorate, periodic acid, periodate and hypochlorite. It is preferable to include one kind. For example, periodic acid disclosed in JP 2007-27663 A can be used. Among these, hydrogen peroxide is preferable because it does not contain a heavy metal element, is inexpensive, easily available, and has low toxicity.

Further, the first polishing slurry contains transition metal ions and further contains peroxometalate ions in which the peracid ions ((O ₂ ) ²⁻ ) generated from the oxidant described above are coordinated to the transition metal ions. Is preferred. It is considered that the peroxometalate ion is bonded to the silicon carbide oxide and the activation energy of the oxidation-reduction reaction of the silicon carbide oxide is reduced, so that the reaction rate of the oxidation reaction can be increased. FIG. 4 schematically shows an example of peroxometalate ions. The peracid ion is a bidentate ligand as shown in FIG. 4, and FIG. 4 shows a pentadentate peroxometalate ion in which two peracid ions are coordinated. The peroxometalate ion promotes the oxidation reaction of silicon carbide if at least one peracid ion is arranged.

  The metal species of the peroxometalate ion is preferably at least one selected from the group consisting of Ti, V, Nb, Ta, Mo and W. For example, very efficient polishing can be performed by using a solution containing vanadic acid and hydrogen peroxide as described in JP-A-2008-179655.

  As the first abrasive grains contained in the first polishing slurry, abrasive grains made of silicon oxide, aluminum oxide, cerium oxide, titanium oxide, or the like can be used. Among these, it is preferable to use silicon oxide abrasive grains such as colloidal silica and fumed silica in that the first abrasive grains are easily dispersed uniformly in the above solution.

  Water is usually used as the solvent. In addition, an acid such as hydrochloric acid or acetic acid or an alkali such as sodium hydroxide is added to the first polishing slurry in order to adjust the pH of the solution so as to exhibit the activity and appropriate reactivity of the oxidant and peroxometalate ion. It may be added to the solution.

Providing a first polishing slurry described above, pressed against the polishing table to the main surface 10S side of the silicon carbide single crystal substrate 10 for example by abrasive surface pressure of 50g weight / cm ² to 1000 g heavy / cm ^2, rotating the polishing platen The main surface 10S of the silicon carbide single crystal substrate 10 is polished while supplying the first polishing slurry onto the polishing surface plate at a rate of, for example, about 1 ml / min. The supply amount of the first polishing slurry depends on the size of the polishing surface plate, the size of the silicon carbide single crystal substrate 10 to be polished, and the number of substrates. By performing the polishing for several hours to several tens of hours, the work-affected layer 11 generated on the main surface 10S is oxidized by the oxidizing agent in the first polishing slurry, and the generated oxide containing silicon, carbon, and oxygen is the first. It is mechanically shaved by one abrasive grain. Thereby, silicon carbide single crystal substrate 10 in which work-affected layer 11 is completely removed and main surface 10S is flattened to a mirror finish is obtained. As shown in FIG. 3B, at this time, the work-affected layer 11 is completely removed, but a thin deteriorated layer 52 of oxide containing silicon, carbon, and oxygen that cannot be confirmed by surface observation partially remains. ing.

  However, main surface 10S as a whole has high flatness and smoothness, and step structure 10d derived from silicon carbide single crystal, which is a step at the atomic level, appears on the surface of main surface 10S. Surface roughness Ra of main surface 10S of silicon carbide single crystal substrate 10 finished to a mirror surface by CMP is preferably 1 nm or less.

  Next, as shown in step S <b> 13, CMP is further performed on main surface 10 </ b> S of silicon carbide single crystal substrate 10 finished to a mirror surface using the second polishing slurry.

  The second polishing slurry includes a second solution and second abrasive grains dispersed in the second solution. The second solution contains a strong oxidant as described above, specifically hydrogen peroxide, permanganate, ozone, peracetic acid, perchlorate, periodic acid, periodate and hypochlorite. None of these are included. It also does not contain peroxometalate ions. Water is usually used as the solvent.

  The same thing as a 1st abrasive grain can be used for a 2nd abrasive grain. Specifically, abrasive grains made of silicon oxide, aluminum oxide, cerium oxide, titanium oxide, or the like can be used. As long as it is chosen from these, the 1st abrasive grain and the 2nd abrasive grain may differ. However, similarly to the first abrasive grains, from the viewpoint of dispersion, it is preferable to use silicon oxide abrasive grains such as colloidal silica and fumed silica.

  Such a second polishing slurry is prepared, and the main surface 10S finished as a mirror surface of the silicon carbide single crystal substrate 10 is further subjected to CMP. The main surface 10S on which the deteriorated layer 52 is generated is subjected to CMP using a second polishing slurry that does not contain a strong oxidizing agent, so that the deteriorated layer 52 is further oxidized and the oxide is contained in the second polishing slurry in the second polishing slurry. Polished and removed by abrasive grains. At this time, since the second polishing slurry does not contain a strong oxidizing agent, only the vicinity of the outermost surface of the deteriorated layer 52 remaining on the main surface 10S is oxidized. For this reason, during the CMP by the second polishing slurry, the altered layer 52 is removed without newly producing the altered layer 52, and the altered layer 52 is completely removed.

  The above-described CMP using the first polishing slurry and the CMP using the second polishing slurry are preferably performed continuously on the same polishing pad. Here, “continuous” means that after the above-described CMP using the first polishing slurry, CMP using the second polishing slurry is performed without replacing the polishing pad with another one. When the CMP using the first polishing slurry and the CMP using the second polishing slurry are performed on different polishing pads, the contact state between the silicon carbide single crystal substrate 10 and the polishing pad is caused by a slight difference in shape between the polishing pads. This is because there is a possibility that a local pressure is applied to main surface 10S of silicon carbide single crystal substrate 10 to cause scratches on main surface 10S.

  The components of the second solution are preferably the same as the components of the first solution except that they do not contain the strong oxidizing agent and peroxometalate ions described above. As described above, when the CMP using the first polishing slurry and the CMP using the second polishing slurry are continuously performed on the same polishing pad, the first solution of the first polishing slurry and the second solution of the second polishing slurry are used. This is to prevent the components of the first solution and the components of the second solution from reacting with each other and producing solids that adversely affect polishing, because there is a possibility of contact with the two solutions.

  The polishing conditions for CMP using the second polishing slurry can be the same as the polishing conditions for the first polishing slurry. However, since the deteriorated layer 52 is thin as described above, by performing polishing for several tens of minutes to several hours, as shown in FIG. 3C, the silicon carbide single crystal of the main surface 10S from which the deteriorated layer 52 has been removed is shown. A substrate 10 is obtained. In CMP using the second polishing slurry, the surface roughness of the main surface 10S hardly changes. For this reason, main surface 10S finished to a mirror surface by planarization obtained by CMP is maintained, and surface roughness Ra of main surface 10S of silicon carbide single crystal substrate 10 after CMP using the second polishing slurry is maintained. Is 1 nm or less. Further, a step structure 10d derived from a silicon carbide single crystal that is an atomic level step is maintained on the surface of main surface 10S.

  Silicon carbide single crystal substrate 10 thus obtained has a major surface 10S with a flat surface and a mirror surface with a surface roughness Ra of 1 nm or less. Further, the deteriorated layer 52 does not remain on the main surface 10S. Therefore, a high-quality silicon carbide semiconductor layer or gallium nitride semiconductor layer free from scratch-like crystal defects 61a and triangular defects 61b can be formed on main surface 10S of silicon carbide single crystal substrate 10.

  Also, since CMP is performed on the surface of the silicon carbide single crystal substrate using the first polishing slurry containing an oxidizing agent having a high oxidizing ability, the time required to finish the main surface to a mirror surface can be shortened, and practical processing conditions A silicon carbide single crystal substrate having a high-quality mirror surface can be manufactured.

(Experimental Example) To the colloidal silica slurry 1, an aqueous peroxide solution having a concentration of 30 mass% was added as an oxidizing agent at a ratio of 0.25 to prepare a first polishing slurry. Using this first polishing slurry, a 4H—SiC single crystal substrate having a diameter of 2 inches was polished by CMP. The off angle θ of the principal surface with respect to the C-axis of the (0001) plane is 4 °. The main surface is polished with diamond abrasive grains having a particle size of 1 μm or less, and the surface roughness Ra is 2 nm. The single crystal substrate was polished by pressing the substrate against a polishing platen at a polishing surface pressure of 500 g weight / cm ² and rotating the polishing platen at 30 rpm. The polishing surface plate is a buffing machine having a diameter of 15 inches. Polishing was performed under these conditions for 4 hours to obtain a silicon carbide single crystal substrate having a main surface finished to a mirror surface (surface roughness Ra is 1 nm or less).

  Thereafter, the first polishing slurry was replaced with a second polishing slurry containing only the colloidal silica slurry 1, and polishing was performed for 30 minutes under the same conditions using the same polishing surface plate. When a silicon carbide semiconductor layer was grown on this substrate by the CVD method, no defects were found.

  (Comparative Example) A silicon carbide single crystal substrate having the same conditions as in the example was prepared, and the main surface was polished by CMP using the first polishing slurry in the example under the same conditions as in the example, and finished to a mirror surface. A silicon carbide single crystal substrate having a main surface was obtained. When a silicon carbide semiconductor layer was grown on the main surface by the CVD method, many scratch-like defects were observed.

(Summary of experimental results)
From the result of the experimental example, by performing the CMP using the second polishing slurry not containing the strong oxidant, the altered layer of the silicon carbide single crystal substrate after the CMP using the first polishing slurry containing the strong oxidant is removed. It can be seen that a high-quality silicon carbide semiconductor layer can be formed.

  The present invention is preferably used for manufacturing a silicon carbide single crystal substrate for manufacturing various semiconductor elements.

DESCRIPTION OF SYMBOLS 10, 51 Silicon carbide single crystal substrate 10d Step structure 10S, 10R Main surface 11 Work-affected layer 61 Silicon carbide semiconductor layer 61a Scratch

Claims (6)

A step (A) of preparing a silicon carbide single crystal substrate having a main surface subjected to mechanical polishing;
An oxidizing agent containing at least one selected from hydrogen peroxide, ozone, permanganate, peracetic acid, perchlorate, periodic acid, periodate and hypochlorite is dissolved in a solvent. Using the first polishing slurry in which the first abrasive grains are dispersed in one solution, subjecting the main surface of the silicon carbide single crystal substrate to chemical mechanical polishing (B), and finishing the main surface into a mirror surface;
The second abrasive grains were dispersed in the second solution containing neither hydrogen peroxide, ozone, permanganate, peracetic acid, perchlorate, periodic acid, periodate, or hypochlorite. A method of manufacturing a silicon carbide single crystal substrate, comprising: (C) performing chemical mechanical polishing on the main surface finished to the mirror surface using a second polishing slurry.   The method for manufacturing a silicon carbide single crystal substrate according to claim 1, wherein the first abrasive grains and the second abrasive grains are silicon oxide abrasive grains.   The method for producing a silicon carbide single crystal substrate according to claim 1 or 2, wherein the chemical mechanical polishing in the steps (B) and (C) is continuously performed on the same polishing pad.   4. The silicon carbide single crystal substrate according to claim 1, wherein the mirror-finished main surface after the step (B) has a step structure derived from a single crystal structure of silicon carbide. 5. Production method.   5. The method for producing a silicon carbide single crystal substrate according to claim 4, wherein the main surface subjected to the chemical mechanical polishing after the step (C) has a step structure derived from a single crystal structure of silicon carbide. The silicon carbide single crystal substrate prepared in the step (A) is a single crystal substrate having a hexagonal crystal structure, and an off angle with respect to the C axis of the (0001) plane of the main surface is within 4 °. 6. A method for producing a silicon carbide single crystal substrate according to any one of 5 above.

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