7nm FinFET

Device Context and Integration Rationale

The Pad Oxidation Pre Clean step is inserted immediately after the Starting Wafer to establish a chemically pristine and electronically well-defined silicon surface prior to thermal pad oxide formation in the STI module [T1].At this position in the flow, the silicon surface may contain native oxide, adsorbed hydrocarbons, metallic contaminants, and weakly bonded surface states originating from wafer manufacturing, handling, and ambient exposure, all …

• [High] Native Oxide Residue Persistence: Incomplete dissolution of native silicon oxide leaves patchy oxide regions that locally modify oxidation kinetics during pad oxide growth, resulting in non-uniform Si/SiO₂ interface thickness and elevated interface trap density due to excess silicon or oxygen imbalance [T1][P4].- [High] Metallic Contamination Incorporation: Residual metal ions that are not fully complexed and removed during pre-clean can segregate at the growing Si/SiO₂ interfac…