| 摘要 |
PROBLEM TO BE SOLVED: To obtain a single crystal substrate excellent in surface roughness, having extremely small face sagging and smooth surface by keeping average roughness in the center line of a substrate surface, face sagging of the substrate and sagging of the substrate to thickness direction to a specific value. SOLUTION: In this substrate, average roughness in the center line of a substrate surface is set to <=0.3 nm and face sagging of the substrate is set to a value within 20 μm from the periphery of the substrate and sagging of the substrate to thickness direction is set to 1 μm. Such substrate is obtained by cutting single crystal ingot to afford a plate-like wafer, polishing the wafer to a desired thickness by both-face lap, attaching a formed body for polishing the wafer until, a desired thickness by both-face lap, attaching a formed body for polishing consisting mainly of silica (silicon dioxide) and having 0.2-1.5 g/cm<3> bulk density, 10-400 m<2> /g BET specific surface area and 0.001-0.5 μm average particle diameter to a polishing apparatus to afford a surface plate, pressing the wafer to the surface plate for polishing and polishing the wafer. The single crystal substrate includes especially preferably an oxide substrate of lithium borate or lithium tantalate. |
