28nm Planar Flow

Device Context and Integration Logic

The AA Pad Nitride Deposition step forms a mechanically robust and chemically resistant silicon nitride layer on top of the previously grown pad oxide, creating a composite pad stack that is essential for shallow trench isolation (STI) integration in the 28 nm planar technology node [P2].This pad nitride functions as the primary hard mask during subsequent STI trench etching, ensuring that the silicon substrate beneath active regions is protected from pl…

• [High] STI Stress-Induced Silicon Defects: Excessive intrinsic or thermally induced stress in the pad nitride can concentrate at trench edges and corners during subsequent oxidation and densification, driving dislocation formation along silicon slip planes and creating leakage paths when these defects intersect junction depletion regions, as described for STI stress mechanisms in [P1].