Etching Rate Enhancement of Copper by Adding Sulfur Compounds in Chemical-Mechanical Polishing Slurries

Abstract

In the chemical mechanical polishing (CMP) process, we have discovered that the Cu etching rate can be enhanced without affecting the Cu slurry's pH by adding a small amount of the sulfur compounds MPS and Na2S2O3. Adding the sulfur compounds to the H2O2 slurry results in an increment in the oxidation reduction potential (ORP). The electrochemical model (mixed potential) showed that the ORP increment leads to enhancement of the Cu oxidizing reaction. Because XPS and Raman analysis of the Cu surface revealed that the Cu etching rate in CMP is limited by the Cu oxidizing reaction, we concluded that the Cu etching rate is enhanced by the addition of sulfur compounds to the Cu oxidizing reaction to increase the ORP increment.