Single mask trench fred with enlarged Schottky area

摘要

A single mask process is described for making a trench type fast recovery process. The single mask defines slots in a photoresist for locally removing strips of nitride and oxide from atop silicon and for subsequently etching trenches in the silicon. A boron implant is carried out in the bottoms of the trenches to form local P/N junctions. The oxide beneath the nitride is then fully stripped in the active area and only partly stripped in the termination area in which the trenches are wider spaced than in the active area. Aluminum is then deposited atop the active area and in the trenches, but is blocked from contact with silicon in the active area by the remaining nitride layer.