Post Cu CMP Cleaning of Polyurethane Pad Debris

Abstract

Polyurethane (PU) pad debris is identified as one of the major polish residue defects in Cu CMP processes when a barrier pad is conditioned. AES analysis of the debris confirms the organic nature of such defects while FT-IR analysis reveals the characteristic peaks of polyurethane from the pad debris. Hybrid cleans (i.e. acidic plus basic cleans) and basic cleans can both remove the pad debris effectively. The efficiency of basic-only cleans can be improved by increasing time and/or chemistry concentration in the brush modules. The PU pad can endure harsh chemical environments at both low and high pH without any detectable decomposition or morphological changes. The advantages and disadvantages of acidic vs. basic cleans are discussed and the cleaning mechanisms of pad debris PR are elucidated.