New model of defect formation caused by retainer ring in chemical mechanical polishing

Defect formation by retainer ring pressure in chemical mechanical polishing (CMP) was investigated. It was found that a higher retainer ring pressure causes more defects. The mechanism underlying this finding was considered to be the agglomeration of abrasive particles mixed with polished polymers from the retainer ring. Such agglomeration is accelerated by increasing the retainer ring pressure. This ring pressure exerts stress onto particles and also polishes the polymers from the ring. Lowering the retainer ring pressure and also changing the ring material from polymers, which are easy to polish, to tough materials are effective for minimizing the density of defects in CMP.