Process for manufacture of fast recovery diodes

摘要

A high speed or fast recovery diode having soft turn-off characteristics has gold atoms diffused in a silicon wafer to reduce minority carrier lifetime. The gold atom density gradient is relatively high across the thickness of the wafer. A novel process is used to form the gold atom density gradient in which a shallow surface layer of phosphorus is diffused into the wafer and the shallow phosphorus diffusion is removed from one of the wafer surfaces. Gold is then plated onto the wafer and is sintered into the wafer through the phosphorus-free surface with a high gradient since gold atoms will not penetrate the wafer where the thin phosphorus coating remains.