The process flow requires Pre Litho Cleaning immediately following the deposition of the SiO and SiN hard mask stack to prepare the surface for active area definition P1.This step ensures an ultra-clean, defect-free oxide surface prior to the spin-coating of anti-reflective coatings and photoresist for the Shallow Trench Isolation (STI) photolithography module P1.Unlike later pre-litho cleans that may occur over complex topography, this specific step addresses a planar deposited SiO hard mask th