Chemical mechanical polishing on cobalt-based barrier through dual functionality of salicylhydroxamic acid between the removal of copper and corrosion inhibition

Abstract

As integrated circuits continue to shrink, Co has been introduced into Cu interconnect structures as a barrier material. However, achieving an optimized removal rate ratio between Cu and Co in simple slurry formulation for the chemical mechanical polishing (CMP) of Cu interconnects with Co-based barrier layers remains a significant challenge. In this study, we identified the dual functionality of salicylhydroxamic acid (SHA) in Cu CMP and achieved a 1:1 selective removal rate ratio between Cu and Co. When used in conjunction with H₂O₂, SHA achieves the target remove rate (RR) for the barrier layer (Cu RR = 163 Å/min, Co RR = 155 Å/min) while maintaining a low static etch rate (SER) of 1.84 Å/min and excellent surface quality (Sq = 1.61 nm). SHA can adsorb onto the surface of oxidized Cu through O atoms, forming a protective layer that inhibits corrosion. Under mechanical friction, SHA molecules on elevated surface regions detach and react with Cu²⁺, facilitating Cu removal. Meanwhile, SHA molecules adsorbed on lower surface regions remain intact. The synergistic action of SHA enables simultaneous Cu removal and corrosion protection, effectively replacing traditional complexing agents and inhibitors, thus simplifying the formulation of polishing solutions.