Formation and Reduction of Embedded Contamination Defects Detected after FEOL Poly Patterning

Embedded contamination (EC) is a significant contributor to front-end-of-line (FEOL) defects detected at Poly Conductor (PC) Bright Field (BF) PLY (Process Limited Yield) inspection after poly patterning. There are two types of EC defects found in PC PLY after poly line formation. A small percentage of them has relatively larger size than ground rule and is believed to be related to particle residue incoming to or fallen during polysilicon deposition. The vast majority of the ECs are small and appear first at post poly deposition Dark Field (DF) PLY inspection as poly bumps. Subsequent PC lithographic pattering and plasma etch modification transform the poly bumps into ECs as detected in PC BF PLY. No appreciable correlation of these small bumps was found to any of the prior level partition BF PLY defects through the defect source analysis (DSA). Larger EC was found to be effectively removed with improved wet clean and the use of cryogenic aerosol clean prior to well anneal process. Small EC was found to be reduced by proper control and minimization of STI height and divot, as well as the processing procedure and environment change.