The L28 STI CMP Dummy Pattern Study on Topography for Advanced Fixed Abrasive and High Selective Slurry

Abstract

The STI CMP performance was major determined by the uniformity of STI step height which was characterized by the ranges of within-die (WID) and within-wafer (WIW) thickness for both silicon nitride and trench oxide surface of isolation area. Currently, for 28nm generation, two advanced approaches for STI CMP were high selective slurry (HSS) and fixed abrasive (FA) CMP. For these two approaches, the design and layout of dummy were important to overcome the effect of various pattern densities and feature sizes. Therefore this research focused on the effect of dummy type for HSS and FA CMP. The result shows HSS CMP is the most robust process in STI CMP. The nitride thickness after HSS CMP shows good uniformity, 2~3 %, and is slightly affected by dummy type and PD of test key comparing with FA CMP.