| Popis: |
Source Mask Optimization (SMO) is one of the most important techniques available for extending ArF immersion lithography1. However, imaging with a small k12 factor (~0.3 or smaller) is very sensitive to errors in the illumination pupil2. As a result, care must be taken to insure that the source solution from SMO can be produced by the real illuminator, which is subject to its own imaging constraints. One approach is to include an illuminator simulator in the SMO loop so that only realizable illumination pupils are considered during optimization. Furthermore, any illumination pupil predictor used in SMO should operate quickly compared to the imaging simulation if it is to avoid increasing the computational load. |
