Chemical-mechanical polishing of SiCOH-based low-k dielectrics

Abstract

Material and integration issues related to direct Cu/Ta CMP with low-k SiCOH are investigated. Polish rates of SiCOH vary significantly with the degree of post-deposition curing, and are independent upon the mechanical hardness of SiCOH but proportional to concentration of Si-O bonds with conventional oxide slurry. Soft pad yield higher polish rates than hard pad. Slurries with special proprietary chemistry and/or less amount of abrasives result in reduced polish non-uniformity, lower defectivity, and tighter resistance distribution. Decrease in breakdown strength and increase in leakage current are observed on post-CMP porous SiCOH. Such degradation in reliability can be recovered, depending on the SiCOH porosity and the slurries used. SiCOH polish mechanism is proposed and issues and challenges for SiCOH, especially porous SiCOH CMP are discussed. Copyright The Electrochemical Society.