Long-lifetime beryllium-based EUV pellicle membrane

An EUV pellicle is essential for protecting EUV photomasks from particle contamination and is now used in the mass production of EUV lithography. Various materials have been considered for pellicle membranes, with carbon nanotube membranes being particularly promising for the next generation. However, they reportedly face durability concerns against hydrogen radicals in scanner environments. Enhancing such protective performance by capping (coating) often reduces EUV transmittance. This paper proposes beryllium as a material that effectively balances these properties. NGK Insulators has created the world's first ultra-thin beryllium membrane, achieving over 90% EUV transmittance and excellent durability under conditions equivalent to 600W EUV power (30W/cm²) in a hydrogen atmosphere, enduring EUV irradiation for over 50,000 wafers. Additionally, we confirmed that beryllium complies with international safety standards, addressing toxicity concerns.