PROGRAMMABLE READ-ONLY MEMORY CELL AND METHOD OF FABRICATION

摘要

A programmable read-only memory cell includes a semiconductor substrate (20) having an n-type epitaxial layer (22) embodying a collector region for an NPN transistor which also includes a base region (28), a p-type base contact region (21) and an n-type emitter region (32). Located on the emitter region (32) is an anti-fuse structure incorporating a region of undoped polycrystalline silicon (37) and an n-type doped polysilicon region (34). Metal contacts (50, 51) are provided for the anti-fuse structure and the base contact region (21). Programming is effected by applying a relatively low current through the undoped polycrystalline silicon region (37) which switches from a high to a low resistance condition. The cell enables production of a high density PROM and is fabricated on a chip together with CMOS devices by steps compatible with CMOS processing technology.