Reduced Topography After Stop on Nitride (SON) STI CMP Through Improved Post-Bulk Planarity for Diverse Layouts in Advanced Nodes

Abstract

Three methods for improving planarization in a ceria free, two step STI CMP process were investigated using patterned test wafers representing 2X nm technology. It was found that within die non-uniformity (WIDNU) after bulk CMP can be improved with (1) higher oxide overburden, (2) reduced bulk polish pressure and (3) intermittent polishing by up to 15, 30 and 41% respectively. Intermittent polishing consists of alternating polish and water rinse intervals with continuous conditioning. By combining these methods up to 33% lower WIDNU is achieved post-SON, while oxide dishing for large open areas on the scale of 0.1 and 1 mm is reduced by up to 43% and 46% respectively. All three methods only require minor process changes and may help silica slurry to replace common ceria slurry in certain applications where price, particle contamination, sustainability and supply risk are the deciding factors.