Method for protecting sidewalls of etched openings to prevent via poisoning

A method for forming a protective oxide liner with improved critical dimension control in a subsequent photolithographic process comprising the steps of:

• providing at least one anisotropically etched opening extending through an anti-reflectance coating (ARC) layer and at least partially through an underlying insulating layer;
• conformally depositing an oxide liner over the at least one anisotropically etched opening such that the sidewalls and bottom portion therein including a surface penetrated by said at least one anisotropically etched opening are covered by said oxide liner;
• removing said oxide liner according to a chemical mechanical polishing (CMP) process from said surface while leaving the oxide liner covering the sidewalls and bottom portion prior to performing a photolitographic process;
• and,
• depositing layer of photoresist over said surface and photolithographically defining a pattern therein comprising openings situated substantially over the at least one anisotropically etched opening.