Effective model-based mask fracturing for mask cost reduction

Abstract

The use of aggressive resolution enhancement techniques like multiple patterning and inverse lithography (ILT) has led to expensive photomasks. Growing mask write time has been a key reason for the cost increase. Moreover, due to scaling, e-beam proximity effects can no longer be ignored. Model-based mask fracturing has emerged as a useful technique to address these critical challenges by allowing overlapping shots and compensating for proximity effects during fracturing itself. However, it has been shown recently that heuristics for model-based mask fracturing can be suboptimal by more than 1.6× on average for ten real ILT shapes, highlighting the need for better heuristics. In this work, we propose a new model-based mask fracturing method that significantly outperforms all the previously reported heuristics. The number of ebeam shots of our method is 23% less than a state-of-the-art prototype version of capability within a commercial EDA tool for ebeam mask shot decomposition (PROTO-EDA) for ten ILT mask shapes. Moreover, our method has an average runtime of less than 1.4s per shape.