Following the anisotropic Silicon Etch step that defines the shallow trench boundaries, the wafer surface and trench sidewalls are inevitably coated with post-plasma etch residues, including silicon oxychloride passivating films and halogen-rich polymers P1.This specific Ashing & Strip/Clean step is critically positioned to eradicate these byproducts and restore the pristine crystalline silicon state of the trench before proceeding to Trench Sidewall Passivation and STI Liner Oxidation P1.Unlike