Post etch killer defect characterization and reduction in a self-aligned double patterning technology

This paper identifies post etch killer defects, e.g., core bridging, small particle and tiny bridging, and investigates the possible solutions in a SADP module. Among the killer defect adders, core bridging and small particle are commonly observed after the oxide core removal by BOE. Core bridging adder is a carbon-containing polymeric by-product during nitride spacer open; by introducing additional diluted HF (DHF) treatment could effectively eliminate such bridging adder. Small particle adder is found to peel from the poly-Si hard mask-1 (HM1) damaged location, where is eroded during the wafer backside cleaning. It is useful for suppressing the formation of small particle by skipping the wafer backside cleaning process. Tiny bridging adder is block of etched poly-Si HM1 causing short between lines. One possibility of blocked etch adder creating is the fine micromasking formed on the opening of BARC during poly-Si HM1 etching. The effective suppression of tiny bridging adder is using high energetic F-/O-radicals to break through the micromasking in the poly-Si HM1 patterning. The reductions of above killer defects successfully boost up the sorting yield in our 45 nm charge-trapping flash memory.