A MECHANICALLY POLISHED SILICON WAFER IS ETECHED TO REMOVE SURFACE DAMAGED MATERIAL AND GIVE A SMOOTH SURFACE BY ETCHING AT A TEMPERATURE OF FROM ABOUT 800 TO 1050*C. IN A GAS MIXTURE CONSISTING OF A CARRIER GAS OF H2, HE OR A MIXTURE THEREOF, A SMALL CONCENTRATION OF A GAS REACTIVE WITH SIO2 SUCH AS HF, CIF3 OR BRF5 AND A SMALL CONCENTRATION OF A GAS REACTIVE SILICON SUCH AS HBR, HI, HCL, CL2, BR2, OR I2.