Patent ID: 7314824

Claim:
A method, comprising: forming a low-k dielectric layer above a substrate; forming a substantially nitrogen-free ARC/capping layer with preselected optical characteristics and thickness on said low-k dielectric layer, wherein forming said substantially nitrogen-free ARC/capping layer comprises controlling at least one process parameter to obtain at least one layer characteristic that varies along the thickness of the substantially nitrogen-free ARC/capping layer; forming a resist layer on said substantially nitrogen-free ARC/capping layer; patterning said resist layer by a photolithography process, said ARC/capping layer acting as an anti-reflective layer during said photolithography process; forming a trench in said substantially nitrogen-free ARC/capping layer and said low-k dielectric layer using said patterned resist layer as an etch mask; depositing a conductive material to fill said trench; and removing excess conductive material and a portion of said substantially nitrogen-free ARC/capping layer to maintain a minimum layer thickness of said substantially nitrogen-free ARC/capping layer.