New CMP processes development and challenges for 7nm and beyond

Either new material or new integration usually requires a new CMP process. CMP is still growing for CMOS applications. And many newer applications are now also being developed beyond “traditional” CMP. In each new application, CMP's stop-on capability, high selectivity, with-in-wafer and with-in-chip uniformity control are increasingly seen as essential elements in gauging device integrity, and thus are critical to the successful implementation of a technology. This presentation discusses oxide CMP stop on SiN and new Si-poly CMP. Poor SiN quality in oxide CMP stop on SiN causes center residues and with-in-wafer SiN uniformity issue. Center residues is strong related with incoming step height, which affects CMP slurry removal rate on pattern wafer. New slurry application is required with good stopability or new stop hardmask is implemented. In Si-poly slurry evaluation, we demonstrate that the silica-based slurry has better selectivity, dishing, and nitride loss performance than the ceria-based slurry, but the process is heavily dependent on the incoming profile and topography. In further process improvement and optimization work will continue.