Role of Additive in Alkaline Slurries for Co CMP

Cobalt has been considered as one of the most promising candidates for use as a barrier metal in current generation integrated circuits. The present work investigated the polishing and electrochemical behavior of cobalt in an alkaline slurry containing a chelator based on a derivative of ethylene diamine tetraacetic acid (EDTA) in the absence of any oxidant. The key experimental variables investigated include abrasive concentration, surfactant concentration, chelator concentration and pH. Synergistic effect of these additives was investigated by orthogonal experimental. The results show that the removal rate of cobalt can be controlled at low silica abrasive concentration by regulating pH and chelating agent concentration. Moreover, the addition of a non-ionic surfactant can enhance the surface quality of cobalt.