Optimized Multigrid Strategy for Accurate Flare Modeling with Three-Dimensional Mask Effect in Extreme-Ultraviolet Lithography

摘要

Extreme-ultraviolet (EUV) lithography has many critical challenges regarding its implementation in the semiconductor industry. One of the main challenges is flare, the unwanted total integrated light scattering at the wafer level, which reduces the critical dimension and imaging performance. Therefore, EUV flare has been intensively studied and has been compensated by a rule-based method for many years. However, there are few results with regard to developing more accurate and feasible flare-modeling techniques to enable us to satisfy the criteria of the sub-22 nm half pitch (HP) technology node and beyond. In this work, we studied an improved flare-modeling technique considering the interaction of scattered EUV light with a three-dimensional EUV mask topography in order to obtain an accurate flare distribution and an optimized multigrid strategy for generating a flare map over the full-field scale. Also, we proposed a flare-modeling technique based on the pedestal model, which we developed using novel effective reflection coefficients in order to achieve sufficient accuracy. Such an approach is thought to be needed instead of the conventional pattern density approach in preparation for upcoming advanced HP technology nodes or for different absorber materials and illumination angles. Lastly, the need for a flare map shift to compensate for the mask defocus error is introduced and some flare evaluations of mask patterns used in the exposure-dose-monitoring technique were performed.