Integrated circuit field isolation process.

摘要

A method for forming a field oxide structure in an integrated circuit is disclosed. The resulting structure exhibits minimal bird's beak formation and has dimensions smaller than what can be achieved by straightforward lithography. The process includes formation of a pad oxide (e.g., 13) and an overlying silicon nitride layer (e.g., 27) (an optional polysilicon stress buffer layer (e.g., 15) may be sandwiched between the oxide and nitride.) An opening is lithographically created in the oxide/ nitride stack. Then the oxide is wet etched to create a small gap underneath the overlying nitride. Next a nitride spacer (e.g., 29) is formed within the opening. The spacer has a foot-like protrusion (e.g., 27) into the gap. Then a field oxide (e.g., 29) is grown within the opening defined by the spacer.