28nm Planar Flow

Device Context and Integration Rationale

The AA Amorphous Carbon Deposition step is inserted in the STI module after pad oxide, pad nitride, and hardmask formation to introduce a sacrificial yet mechanically robust pattern transfer layer that can decouple lithographic pattern fidelity from aggressive trench etch requirements [A1].In a planar 28 nm flow, STI etching demands high anisotropy and selectivity against underlying oxide and nitride, and amorphous carbon serves as an intermediate h…

• [High] Film Density and Etch Resistance Loss: Excessive structural disorder or unintended heteroatom incorporation increases free volume in the amorphous carbon network, lowering density and weakening resistance to plasma etching, which can cause premature hardmask erosion during STI transfer, as governed by sp²/sp³ bonding balance principles [P1].- [Medium] Intrinsic Stress‑Induced Pattern Distortion: High ion energy during deposition can densify the film through subplantation but sim…