In Situ Formation of Ag Capping Layer for Preventing Oxidation in Copper Chemical Mechanical Polishing

Abstract

An Ag capping layer as a metal barrier was proposed to hinder the oxide formation of Cu, which is exposed after chemical mechanical polishing CMP . To simplify the process step, the in situ formation of the Ag barrier during the Cu CMP process was investigated using a displacement reaction at either the second step of Cu CMP or the buffing step. The Ag capping layer effectively disturbed the contact between oxygen and Cu, which led to preventing Cu oxidation. Moreover, through the capping formation at the buffing step, the depth of dishing was diminished to about 20 nm regardless of the linewidth.