Following the Pad Oxide Etch, the contact hole bottom must be perfectly clean to form an optimal ohmic contact with the subsequent Ti deposition T1.The preceding fluorocarbon-based dry etch leaves behind carbon-rich polymeric residues (CFx) and chemically damaged silicon surfaces P3.If not removed, these residues act as tunneling barriers, exponentially increasing specific contact resistivity T1.Therefore, this ashing and strip/clean step is specifically designed to eliminate plasma-induced poly