Patent ID: 6207538
Filing Date: 2001-03-27
Classification: H01L

Abstract:
A method for forming both n and p wells in a semiconductor substrate using a single photolithography masking step, a non-conformal oxide layer and a chemical-mechanical polish step, comprising the steps of:a) forming a screen oxide layer on a semiconductor substrate;b) forming a barrier layer on said screen oxide layer;c) coating a photoresist layer over said barrier layer;d) exposing said photoresist layer and developing said photoresist layer to form a photoresist mask having an opening to said barrier layer where first wells are to be formed;e) etching away said exposed barrier layer to expose said underlying screen oxide layer to form a first opening in said barrier layer over regions of the substrate where first wells will be formed;f) implanting impurities of a first conductivity type into said substrate to form first well regions;g) removing said photoresist layer;h) forming a non-conformal oxide layer over said first well regions and said barrier layer; said non-conformal oxide layer formed using a high density plasma chemical vapor deposition (HDPCVD) process using a sputter/deposit process;i) chemical-mechanical polishing said non-conformal oxide layer stopping at the barrier layer;j) removing said barrier layer using a selective etch, to form second openings in the remaining non-conformal oxide layer over areas where second well will be formed in said substrate;k) using the remaining non-conformal oxide as a mask, implanting impurities of the second conductivity type through said second openings to form second wells; andl) removing the remaining non-conformal oxide layer and said screen oxide layer.