Improvement of lithographic performance and reduction of mask cost by simple OPC

An SMO whose optimized source shape and mask pattern can be simple is shown. However the simple solution can be competitive to a solution by complicated source shape and mask pattern. This technology is applied to cut pattern of 1 dimensional GDR layout of 20nm node and below. The simulation under ArF single exposure shows 16nm node of metal layer and 12nm node of gate layer can be resolved with rectangle mask patterns. For both layers bright field exposure is used and experimentally positive and negative tone developments are applied for metal layer (island patterns) and gate layer (cut patterns) respectively. The integrated process through SADP, etching, and so on is shown. It is found that the simple pattern has lower MEEF than the complicated ones. Applying simple mask pattern MEEF can be suppressed to be 3~4 even at 16nm node. The SEM images of the masks with simple and complicated shapes show that it is difficult to reproduce the complicated pattern accurately. We prepared mask data with various complexities of patterns and evaluated the writing time of an up-to-date EB writer. The time depends on the shot counts and a typical OPC pattern takes 4 times longer time than rectangle pattern. Since the cost of writing time is around 20% of the entire cost, the saved cost from OPC pattern to rectangle pattern becomes 15%. Regarding advanced node of mask with more complicated pattern it takes further longer time and there is an impact on other technologies of inspection or process. So the saved cost becomes huge.