As patterning technology advances beyond 45-nm half-pitch, the process window shrinks dramatically even with advanced resolution enhancement techniques. Beam focus represents one of the process parameters that have significant contribution to overall critical feature dimension error budget. In building of an optical model for proximity correction, the final model quality strongly depends on matching the focus used in the simulation to the experimental focus conditions. In this paper, a new method to determine the best beam focus for matching the experimental data is presented. The accuracy of the method will be verified using actual test pattern measurements.

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