Patent ID: 7763547

Claim:
A method, comprising: forming a resist mask above a dielectric layer stack comprising a low-k dielectric layer formed on an etch stop layer having a first thickness, said dielectric layer stack being formed on a substrate; etching an opening through said low-k dielectric layer and to said etch stop layer based on a first plasma ambient of a first etch chemistry that is selective to said low-k dielectric layer; removing said resist mask on the basis of a second oxygen-containing plasma ambient of a second etch chemistry, said second etch chemistry including, at least after an initialization phase, an etchant that removes material of said etch stop layer; and maintaining said second etch chemistry after removing said resist mask to effect a controlled reduction in a thickness of said etch stop layer corresponding to a difference between the first thickness and a predefined target thickness for the etch stop layer after exposure to said second etch chemistry.