Single-crystal silicon-carbide substrate and polishing solution
View Patent ↗The present invention relates to a single-crystal silicon-carbide substrate provided with a principal surface having an atomic step-and-terrace structure containing atomic steps and terraces derived from a crystal structure, in which the atomic step-and-terrace structure has a proportion of an average line roughness of a front edge portion of the atomic step to a height of the atomic step being 20% or less.
1. A single-crystal silicon-carbide substrate comprising a polished principal surface having an atomic step-and-terrace structure, the atomic step-and-terrace structure comprising atomic steps and terraces derived from a crystal structure, wherein the atomic step-and-terrace structure has an average proportion of an average line roughness of a front edge portion of the atomic step to a height of the atomic step being 20% or less, and the average line roughness is measured from an AFM image in an area of 2 μm×1 μm.
2. The single-crystal silicon-carbide substrate according to claim 1 , wherein the polished principal surface is a surface on which a crystal is to be epitaxially grown to form a silicon-carbide semiconductor layer or a gallium-nitride semiconductor layer.
3. The single-crystal silicon-carbide substrate according to claim 1 , wherein a width of the terrace is substantially the same in each terrace.
4. The single-crystal silicon-carbide substrate according to claim 1 , wherein the front edge portion of the atomic step is a straight line having the average line roughness.
5. The single-crystal silicon-carbide substrate according to claim 1 , wherein the single-crystal silicon-carbide substrate is obtained by a process comprising:
polishing a surface of a single-crystal silicon-carbide substrate with a polishing pad in the presence of a polishing solution by moving the polishing pad relative to the surface,
wherein the polishing solution comprises: an oxidizing agent which comprises a transition metal having oxidation-reduction potential of 0.5 V or more, and
wherein the polishing pad and the polishing solution do not comprise an abrasive.
6. The single-crystal silicon-carbide substrate according to claim 5 , wherein a pH of the polishing solution is 11 or less.
7. The single-crystal silicon-carbide substrate according to claim 5 , wherein a pH of the polishing solution is 5 or less.
8. The single-crystal silicon-carbide substrate according to claim 5 , wherein a pH of the polishing solution is 3 or less.
9. The single-crystal silicon-carbide substrate according to claim 5 , wherein the oxidizing agent comprises a permanganate ion.
10. The single-crystal silicon-carbide substrate according to claim 5 , wherein the oxidizing agent comprises potassium permanganate or sodium permanganate.
11. The single-crystal silicon-carbide substrate according to claim 9 , wherein an amount of the permanganate ion in the polishing solution is 0.05 mass % or more and 5 mass % or less.
12. The single-crystal silicon-carbide substrate according to claim 9 , wherein an amount of the permanganate ion in the polishing solution is 0.1 mass % or more and 4 mass % or less.
13. The single-crystal silicon-carbide substrate according to claim 9 , wherein an amount of the permanganate ion in the polishing solution is 0.2 mass % or more and 3.5 mass % or less.
14. The single-crystal silicon-carbide substrate according to claim 1 , wherein the single-crystal silicon-carbide substrate is an on-axis substrate.
15. The single-crystal silicon-carbide substrate according to claim 1 , wherein the single-crystal silicon-carbide substrate is an on-axis 4H—SiC substrate.