Effects of Liner Metal and CMP Slurry Oxidizer on Copper Galvanic Corrosion

Abstract

In-situ electrochemical measurements during polishing and in static were performed for copper and barrier metals in two kinds of copper slurries using a rotating disk electrode apparatus. Current density during polishing in the slurry using APS as oxidizer is larger than in H2O2 as oxidizer for all metals. This is due to the strong reactivity of APS on the exposed metal surface. Potential of Ru during polishing is larger than that of Cu. This means Ru is more noble than Cu and the possibility of Cu galvanic corrosion is high in APS slurry. In the case of Ta, Cu is more noble than Ta, so Cu is stable. In H2O2 slurry, Ru and Cu potential is almost same and current density is low, so Cu is stable. However, abrupt potential change of copper was detected by dipping exposed barrier metal window in all slurries. This indicates Cu could generate corrosion.