Pattern fidelity improvement by considering the underlying patterns at defocus

Abstract

The model-based OPC is considered in 0.13um and beyond generation. However, the accuracy of model-based OPC is based on the measurement of test patterns on bare silicon wafers using the optimized exposure condition. The through pitch patterns and systematic patterns should be contained in the test patterns design. Experiments showed that that the accuracy of model would be constrained if the underlying pattern effects would not be considered. The CD performance at the defocus and process window would also suffer since not considering the underlying pattern effects. This CD performance at defocus level and process window will be worse at damascene process. In this paper, we propose a hybrid OPC to cover these issues. In this work, we can use a simple method to investigate the underlying impact on the target layer on which we want to implement OPC to improve the pattern fidelity. We can observe the impact of underlying layer by studying the CD of critical patterns at de-focus level. This experiment provides us the CD data for considering the underlying impact without relying on theoretical foundation. With the hybrid OPC, we can find the exposure latitude has been improved.