Coherence-length-constrained OPC for efficient mask segmentation in advanced lithography

The coherence length, defined as the maximum distance between two points that remain in optical correlation in a plane, determines the effective range of interference within an imaging system. This critical parameter depends on the wavelength, numerical aperture (NA), and partial coherence factor of the illumination pupil, establishing a physical boundary for imaging optimization through mask corrections in lithography. However, current optical proximity correction (OPC) methods tend to over-segment polygon edges, unnecessarily increasing mask complexity and computational cost with no improvements in image quality. Our simulations demonstrate that mask variations significantly affect the overall aerial image contours and critical dimension (CD) within the coherence length. Based on these insights, we propose a coherence-length-based OPC method that restricts segmentation to no more than three segments within the coherence length. This method is applicable to complex 2D patterns and effectively mitigates image ripples while maintaining comparable CD and exposure latitude (EL) performance. This study offers practical guidance for enhancing mask correction efficiency and simplifying mask fabrication in advanced lithography.