METHOD FOR FLATTENING SURFACE OF AlN SINGLE CRYSTAL AND METHOD FOR MANUFACTURING AlN SINGLE CRYSTAL SUBSTRATE

PROBLEM TO BE SOLVED: To provide a method by which the surface flatness of an AlN single crystal substrate can be secured and the crystal quality can be improved. SOLUTION: When the AlN single crystal substrate is polished, alumina abrasive grains having an average particle diameter of, e.g., 0.1 μm are dispersed in an amount of 10 wt.%, a polishing liquid having a pH value of about 5-10 is used, and polishing is performed so that the average polishing amount becomes 1 μm. Thereafter, an annealing treatment comprising heating the AlN single crystal substrate at a temperature of ≥1,500°C, preferably, ≥1,600°C is performed. Thereby, the surface flatness of the AlN single crystal substrate is improved, and further, the processing deterioration layer formed by the polishing treatment is removed by the annealing treatment. Accordingly, when a device layer is formed on the substrate, a device layer having a mirror-like surface and a better crystal quality than that of a device layer formed on a substrate subjected to only the polishing treatment can be obtained. COPYRIGHT: (C)2006,JPO&NCIPI