Impact of nano-scale grain size on the properties of ZrSi2 EUV pellicles

Abstract

Extreme Ultraviolet (EUV) lithography requires pellicles with high transmittance and reduced thickness to minimize throughput reduction. However, as the pellicle thickness decreases, it leads to a degradation in mechanical properties and thermal stability, ultimately causing pellicle destruction. Therefore, enhancing both mechanical and thermal properties while maintaining high transmittance is an important issue for EUV pellicles. In this study, we evaluated the mechanical and thermal stability of ZrSi2 material with exceptional optical properties by controlling its microstructure at a constant thickness. A ZrSi2 thin film was deposited onto a SiNx free-standing membrane to fabricate a composite pellicle. The ZrSi2 composite pellicles with various grain sizes were produced through an annealing process. The ZrSi2 thin film exhibited an inverse Hall-Petch relationship at certain grain sizes. Additionally, thermal stability was confirmed to be reliable. By controlling the grain size, significant improvements in both mechanical properties and thermal stability of the ZrSi2 composite pellicles were achieved. This study demonstrates that controlling the grain size in ZrSi2 composite pellicles can enhance both their mechanical properties and thermal stability. The results demonstrate the potential of ZrSi2 material to address the challenges in EUV pellicle.