Concentric ring mask for controlling the shape of a planar PN junction

摘要

A mask for use in making a planar PN junction in a semiconductor device includes a central mask opening and a plurality of spaced apart concentric mask openings surrounding the central mask opening. The concentric mask openings each have a width less than a maximum dimension of the central mask opening. The central mask opening can be circular and the concentric mask openings can have a ring-shape. The mask can be used to form openings in a wafer layer for introducing an impurity to dope that wafer layer.