Patent ID: 6406977
Filing Date: 2002-06-18
Classification: H01L

Abstract:
An isolation region forming method comprising the sequential steps of:forming an oxide layer over a substrate; forming a silicon nitride layer over the oxide layer, the silicon nitride layer and oxide layer having a pattern of openings extending therethrough to expose portions of the underlying substrate; etching the exposed portions of the underlying substrate to form openings extending into the substrate, each opening defining a periphery, and the etching forming lateral walls of the oxide and silicon nitride layers with the lateral walls defining a portion of the periphery of the openings; after etching the exposed portions of the underlying substrate, wet etching the silicon nitride layer to remove portions of the silicon nitride layer while leaving other portions of the silicon nitride layer over the substrate, the wet etching removing the silicon nitride layer at a rate of about 55 Angstroms per minute; after etching the exposed portions of the underlying substrate, removing portions of the oxide layer to extend the lateral walls of the oxide layer outwardly from the periphery of the openings and to undercut the silicon nitride layer; and after the wet etching and removing the portions of the oxide layer, and while leaving the other portions of the silicon nitride layer over the substrate, forming oxide within the openings in the substrate, the oxide within the openings forming at least portions of isolation regions.