Silicon@ substrate mfr. for DRAM components - comprises forming silicon@ mirror wafer and subjecting it to two=stage heat treatment process, then removing surface layer

A process is disclosed for mfg. a silicon substrate for a semiconductor device, in which a silicon mirror wafer is formed and subjected to a two-stage heat treatment process, involving firstly a high temp. and secondly a lower temp.. A surface layer of the silicon mirror wafer is removed after carrying out the two-stage heat treatment procedure. A layer which is 0.2-20 microns thick is removed from the surface of the wafer. Before forming the mirror wafer, a monocrystalline Si blank is formed from a melt by the crystal pulling technique and heat-treated to give a uniform distribution of the thermal donor atoms. The blank is then cut into discs which are formed into mirror wafers and heat treated. USE/ADVANTAGE - The process is of particular use for mfg. Si wafers for DRAM components. The silicon substrate produced has improved properties compared with those produced by other techniques, and a satisfactory intrinsic getter effet is achieved.