2026/07/27 by Ting Wei Chen
paper · doi:10.1088/1402-4896/ae90fc
Abstract Attenuated phase-shift masks (attPSMs) are widely used in extreme ultraviolet (EUV) lithography to enhance image contrast and process margins for advanced via patterning. The complex optical response of absorber materials introduces coupled phase and amplitude modulation that can generate unintended side-lobe exposure, particularly in dense layouts. In this work, EUV aerial images formed by attPSMs are numerically investigated using a coherent Fourier-optics framework. Two representative absorber responses corresponding to low-absorption (Ru-like) and higher-absorption (TaBN-like) materials are compared within a common absorber thickness, mask geometry, and imaging configuration. Imaging performance is evaluated using aerial-image metrics including via-center intensity, side-lobe intensity, and edge-normalized image log-slope (NILS). The simulations indicate that lower-attenuation absorbers preserve higher spatial-frequency content and produce larger threshold-defined openings, whereas stronger attenuation suppresses parasitic side-lobe intensity and provides improved robustness against focus and dose variations. These results highlight the importance of evaluating EUV absorber materials from a holistic imaging perspective within the simplified coherent imaging framework adopted here.