Effect of 2-Mercapto-1-methylimidazole on the Dual Action of Chemical Mechanical Polishing of Cu and Ta

Abstract

When chemical mechanical polishing (CMP) of tantalum (Ta)-based barrier layers is done through silicon via (TSV), it is necessary to control the rate selection of copper (Cu) and Ta to prevent the formation of dishing pit formation due to the rapid removal rate (RR) of copper in the via compared to tantalum outside the via. This paper selected 2-mercapto-1-methylimidazole (TAMZ) as an inhibitor, which has the dual effect of reducing the RR of Cu and increasing the RR of Ta. The experimental results show that the rate selection ratio of Cu and Ta is up to 2.12:1, the inhibition rate of TAMZ on Cu is up to 98.37%, and it can control Cu–Ta galvanic corrosion; the mechanism of TAMZ on Cu and Ta was studied by XPS, SEM, AFM, and other experiments. Theoretical calculation found that TAMZ formed chemical bonds with the metal surface mainly through N and S atoms and could be adsorbed on the surface of Cu and Ta by mixed adsorption, which clarified the inhibition mechanism of TAMZ from a microscopic perspective.