The preceding steps in the integration flow removed the Deep Trench Isolation (DTI) oxide and nitride hard masks, leaving the silicon substrate exposed in the active areas P2.Before transitioning to the Shallow Trench Isolation (STI) module, which begins with the deposition of a silicon nitride (SiN) and silicon oxide (SiO) hard mask stack, the silicon surface must be absolutely pristine P2.Any residual contaminants, such as metallic impurities, organic residues, or uncontrolled native oxides le