Development and optimization of metal silicide EUV pellicle for 400W EUV lithography

Abstract

In the extreme ultraviolet lithography (EUVL) process, extreme ultraviolet (EUV) pellicles serve as thin, transparent membranes that shield the photomask (reticle) from particle contamination, thereby preserving photomask pattern integrity, reducing chip failure risks, and enhancing production yields. The production of EUV pellicles is highly challenging due to their mechanical fragility at nanometer-scale thicknesses and the need to endure the rigorous conditions of the EUVL environment, which include high temperatures and hydrogen radicals. Consequently, extensive research has been conducted on a variety of materials, such as carbon-based and silicon-based substances, for the development of EUV pellicles. This study explores the feasibility of implementing molybdenum silicide (MoSix) pellicles for high-power EUVL applications. We successfully fabricated MoSix pellicles in two dimensions: a 10 mm x 10 mm sample and a full-size 110 mm x 144 mm pellicle. We then evaluated their optical, mechanical, thermal, and chemical properties, as well as their lifespan. The pellicles demonstrated over 90% transmittance and less than 0.02% reflectance. The films exhibited a deflection of 300 μm under a 2 Pa differential pressure and an ultimate tensile strength (UTS) exceeding 2 GPa. The thermal emissivity was measured at 0.3. Additionally, the durability of the pellicles was validated through exposure to 20,000 wafers using a 400W EUV power (offline test: 20W/cm²). The transmittance variations of the pellicles were evaluated by comparing the measurements obtained before and after exposure to 400W EUV power.