Single bit cell SRAM failure due to titanium particle

Abstract

A single bit cell SRAM failure with shorted bit line (BL) and bit line bar (BLB) storage nodes were analyzed. Instead of using top down deprocessing to localize the defect, a modified approach incorporating Atomic Force Probe (AFP) and STEM dark field imaging of a thick sample were used. Using the modified approach the single bit cell failure was found to be due to a titanium particle on the spacer of a transistor that shorted the polysilicon gate and active silicon.