Transverse Deflection for Extreme Ultraviolet Pellicles

Defect control of extreme ultraviolet (EUV) masks using pellicles is challenging for mass production in EUV lithography because EUV pellicles require more critical fabrication than argon fluoride (ArF) pellicles. One of the fabrication requirements is less than 500 $\mathsf{\mu }\mathrm{m}$ transverse deflections with more than 88% transmittance of full-size pellicles (112 $\mathrm{m}\mathrm{m}$ $\times$ 145 $\mathrm{m}\mathrm{m}$) at pressure 2 $\mathrm{P}\mathrm{a}$. For the nanometer thickness (thickness/width length ($t/L$) = 0.0000054) of EUV pellicles, this study reports the limitation of the student’s version and shear locking in a commercial tool-based finite element method (FEM) such as ANSYS and SIEMENS. A Python program-based analytical-numerical method with deep learning is described as an alternative. Deep learning extended the ANSYS limitation and overcame shear locking. For EUV pellicle materials, the ascending order of transverse deflection was $\mathrm{R}\mathrm{u}<{\mathrm{M}\mathrm{o}\mathrm{S}\mathrm{i}}_2=\mathrm{S}\mathrm{i}\mathrm{C}<\mathrm{S}\mathrm{i}\mathrm{N}\mathrm{x}<{\mathrm{Z}\mathrm{r}\mathrm{S}\mathrm{r}}_2<\mathrm{p}$-$\mathrm{S}\mathrm{i}<\mathrm{S}\mathrm{n}$ in both ANSYS and a Python program, regardless of thickness and pressure. According to a neural network, such as the Taguchi method, the sensitivity order of EUV pellicle parameters was $Poisson’s ratio<Elastic modulus<Pressure<Thickness<Length$.