Cu Electrochemical Polishing for RDL Process of FOWLP and Effects of Cu Overburden Profiles

Abstract

Cu electrochemical polishing for planarization in the redistribution layer (RDL) process and the effects of Cu overburden profiles on Cu electrochemical polishing were investigated. Despite the fact that Cu electrochemical polishing is a feasible alternate planarization method, there are issues with obtaining void and bump-free overburden profiles associated with overpolishing for wide trenches. To ensure uniform electrochemical polishing for all width patterns, Cu overburdens were tuned by changing leveler additive concentration, resulting in bumps on the trenches. Uniform Cu overburden polishing was observed at similar overburden areas for all width patterns. The Cu electrochemical polishing results indicated that overburden on trenches and on interlayer dielectrics were important for uniform Cu overburden electrochemical polishing.