Development of a Porous Patterned Membrane with a Large Field Size for EUV Pellicles

Abstract

EUV lithography plays a critical role in semiconductor manufacturing, and EUV pellicles are essential for preventing defects caused by photomask contamination during semiconductor production. As closed film-type membranes face limitations, interest in porous structures, such as carbon nanotubes (CNTs), is growing. Our team has been developing breathable porous silicon nitride (SiN) membranes with hole patterns. We explored wet etching techniques using KOH and TMAH for silicon etching, alongside dry etching technology for deep silicon etching. Although we attempted to create large field-size membranes, fabricating larger membranes proved difficult. So we investigated the contour of the silicon-etched side and improved the abnormal step height at the membrane edges. In a bulge test, we confirmed that the maximum deflection was 27.3 μm, and the maximum pressure difference sustained was 7 Pa. Remarkably, the membrane did not fracture during the bulge test. Specifically, a 40 nm SiN membrane with 100 nm hole patterns exhibited a 3.0 percentage point increase in transmittance compared to the 79% of a typical closed-type membrane.