Effects of local CD error on lithography performance

Effects of mask CD error on lithography performance are estimated as the metric “dose-MEF”. The mask CD error is classified into three categories in accordance with the spatial frequency (global, local and LER). In the global CD error, the CD is constant within the range where the OPE reaches. The local CD error has the spatial frequency that is nearly equal to OPE range. The LER has very small spatial frequency by comparison with OPE range. The effects of local CD error and LER are estimated by using Monte Carlo Simulation because of randomness. For dense pattern, dose-MEF for local error is half of that for global error. Further, dose-MEF for LER is so small that this effect is negligible. Therefore, specifications for mask CD error must be decided by considering dose-MEF for each category.