The Stop Oxide layer prevents halogen-based etch chemistry from attacking the underlying Pad Nitride during a-Si mandrel removal [P1].
The "Stop Oxide Deposition" step acts as a critical etch-stop and protection layer positioned between the underlying Pad Nitride and the subsequent amorphous Silicon (a-Si) hardmask layer used for fin patterning [P1][P2]. In advanced multi-patterning schemes like self-aligned double patterning (SADP), the a-Si layer acts as a sacrificial mandrel which must be sel…
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