Development of Extreme Ultraviolet Pellicles Based on Yttrium Core with Amorphous Carbon Capping Layer

Abstract

Yttrium offers exceptional intrinsic extreme ultraviolet (EUV) transmittance and emissivity for next-generation pellicles. However, its severe oxidation susceptibility limits its practical implementation. In this study, we demonstrate that amorphous carbon (a-C) capping layers effectively preserve metallic Y, whereas plasma-enhanced atomic-layer-deposited SiNx causes catastrophic oxidation. Our standalone a-C/Y/a-C film achieves 86.8% EUV transmittance and exhibits remarkable thermal stability, maintaining approximate to 400 degrees C peak temperature for over 1000 cycles under 1 W/cm(2) absorbed power. Transmission electron microscopy analysis of the freestanding membrane revealed substantial fluorine penetration throughout the Y core during back-etching, driven by a strong Y-F thermodynamic affinity. Despite the compositional change, the film retained its robust thermal performance. These results establish a-C-capped Y as a viable high-powered EUV pellicle, demonstrating that strategic material design can overcome intrinsic oxidation challenges while delivering the optical and thermal properties required for advanced lithography.