| 摘要 |
PROBLEM TO BE SOLVED: To lessen COP and haze of the surface of a wafer by a method wherein a temperature drop rate is made lower than a certain value from a maximum temperature to a prescribed temperature in a heat treatment. SOLUTION: A temperature drop rate from a maximum temperature to a temperature of 700 deg.C or so in a heat treatment is set lower than about 20 deg.C/sec. When a wafer is heat-treated at high temperatures in a reducing atmosphere that contains hydrogen, the surface of the wafer is liable to be stepped, but the surface of the wafer gets flatter due to the fact that the surface energy of the wafer becomes stable by the migration effect when a temperature drop rate is set smaller. Therefore, a wafer temperature is slowly decreased at a drop rate of about 20 deg.C/sec or below from a maximum temperature to about 700 deg.C in a heat treatment. No migration occurs in the surface of a wafer at a temperature of 700 deg.C or below, so that it is considered that it does not affect the haze level of a wafer even if a wafer temperature is made to drop quickly after the wafer temperature gets lower than 700 deg.C. By this setup, both COP and haze of a wafer surface can be lessened at the same time.
|
