Optical proximity effects correction at 0.25 um incorporating process variations in lithography

We study the optical proximity effect and its correction using empirically derived models for DUV lithography taking into account random process variations. The sensitivity of corrected configurations to different sources of process variation (exposure dose, defocus) is evaluated. For correction at a centered condition (optimum dose, zero defocus), problems may arise in ill-conditioned areas (inside corners of T-shape features, butting line-ends, etc.), when going away from the best focus and/or exposure dose, within the exposure/defocus window. Correction for sharp corners (aggressive correction) shows a stronger sensitivity to defocus than less corner sharpening (conservative correction). Furthermore, we study what types of design configurations tend to print poorly with process variations and investigate alternative correction optimization schemes that stabilize the printing performance in such areas. Various optimization alternatives to improve performance within the process window are evaluated.