Abstract
Signamization is an automated process to optimize the NA and σ settings of a stepper for a given combination of critical features and CD tolerances, basing on the E-D Forest methodology 1 . Using the computer program developed by the author, an optimization process takes approximately 10 seconds per CD feature. Hence, it requires less than 3 minutes to optimize the combination of up to 14 CD features. Because of the rapid turnaround of this powerful tool, optimization can be explored extensively. It has been used on a variety of feature combinations using disk and annular illuminations, binary intensity mask and phase-shifting mask. This paper deals mainly with reporting the findings, which consist of expected outcomes as well as surprises. For example, single features optimize at relatively low NA. Adding even a less critical feature raises the optimized NA significantly. Signamization is a strong function of feature size and shape, in addition to sensitivity to feature combination mentioned above. Adding or subtracting a bias on a mask feature can affect the NA or σ setting favorably or otherwise.