Effect of Ammonium Citrates as an Auxiliary Complexing Agent in TSV Copper Film CMP

Abstract

The removal rate of slurry is the key factor of CMP for through-silicon vias copper film. Currently, in the study of slurry, the synergistic effect of some additives can produce the effect of “1 + 1＞2.” It is widely used in semiconductor and microelectronics industries to develop novel slurry. In this paper, ammonium citrates were served as a crucial chemical additive in through silicon via Cu film slurries. Through electrochemical measurements, X-ray photoelectron spectroscopy, Ultraviolet–visible, and LSCM tests, it was revealed that ammonium citrates could react with cupric ions to form a stable water-soluble Cu-ammonium citrates complex, which can accelerate the chemical dissolution of Cu surface during the CMP process, and it was also found that the complexing effect was weaker than glycine. Moreover, various tests on Cu wafers showed that a high Cu removal rate (RR) and ideal surface quality could be realized when ammonium citrates were used as an auxiliary complexing agent in glycine-based Cu film slurries. The purpose of the study is to find an auxiliary chemical additive that can improve the performance of slurry in the manufacturing process of Cu film and other materials used in integrated circuits.