Hole-Patterned Pellicles: A Structural Approach for Improved Extreme Ultraviolet Transmittance and Mechanical Behavior

Abstract

To sustain high-throughput extreme ultraviolet (EUV) lithography, pellicles with high transmittance are essential. As conventional methods-such as material optimization and membrane thinning-have reached their practical limits, alternative strategies are now required. In this study, we investigate an alternative hole-patterned pellicle architecture that introduces a geometric degree of freedom beyond that of continuous-film architectures. EUV transmittance measurements show that transmittance increases with open ratio (OR), following the absorption-limited trend predicted by an OR-based upper bound model, while exhibiting a measurable deviation at higher OR. To provide structural insight into this deviation, pseudo-spectral time domain (PSTD) simulations were performed under scanner-relevant numerical aperture and illumination conditions, solely to extract qualitative angular redistribution trends associated with hole geometry. Lithographic aerial-image simulations indicate that pattern distortion effects emerge only under highly coherent illumination and are suppressed as radius sigma sigma r increases. Mechanical characterization using bulge tests reveals distinct pressure-deflection behavior in hole-patterned membranes compared with continuous films, including earlier pressure saturation and modified burst-failure statistics. Although a modest reduction in mean burst pressure is observed, the hole-patterned membranes exhibit a narrower failure distribution, reflecting altered defect sensitivity. Taken together, the results demonstrate how periodic perforation influences transmittance behavior and mechanical response, providing design-relevant trends that complement existing material- and thickness-based pellicle optimization approaches.