Following the Backside Contact IIP and subsequent Ashing/Clean steps, the exposed silicon and dielectric surfaces on the wafer backside are highly reactive and susceptible to metallic contamination P4.The LS/Aperture Grid Barrier Deposition step deposits a conformal refractory metal/metal-nitride stack (typically Ti/TiN) to line these backside trenches and contact holes before the bulk Light Shield (LS) / Aperture Grid metal is deposited A1.This step is distinct from the front-end Ta-based Botto