NOR yield enhancement and downstream process variation reduction by STI CMP optimization

Abstract

Dual STI CMP step recombination was implemented to reduce the variation of the floating gate polysilicon thickness), resulting in less failure from poly foot. Initial qualification of the single oxide CMP showed elevated scratch count, which required DOE modeling with slurry flow rate and tool upgrades to reduce the scratch counts. Once qualified, the recombination showed numerous positive results at probe and post-assembly yield Additional benefits along with the variation reduction was the cycle time improvement along with the cost savings due to merging the dual CMP step into a single step. This change also enabled capacity improvement by qualifying it to run with other technologies and reduced Server SBL(Statistical Bin Limits) breaches driven by poly foot fails.