Patent ID: 7291563

Claim:
A method of etching a substrate, comprising: forming a masking feature projecting from a substrate; the feature having a top, opposing sidewalls, and a base; depositing a layer comprising Si x C y F z over the feature where “x” is from 0 to 0.2, “y” is from 0.3 to 0.9, and “z” is from 0.1 to 0.6; etching the Si x C y F z -comprising layer and etching upper portions of the feature opposing sidewalls effective to laterally recess the upper portions of the feature opposing sidewalls proximate the feature top relative to lower portions of the feature opposing sidewalls proximate the feature base; and after said etching of the Si x C y F z -comprising layer and said etching of upper portions of the feature sidewalls, etching the substrate using the masking feature as a mask.