Optimization of Triple Periodic Bilayer Stacks and Aerial Image Performance Analysis

EUV lithography uses 13.5 nm wavelength incident light. For all materials, the absorption of EUV wavelength cannot be neglected. Therefore, EUV lithography system employs a reflective system. In order to to increase the reflectivity rate, We optimize triple periodic bilayer stacks for 13.5 nm EUV- lithography with a 4 × demagnification and an Numerical Aperture (NA) of 0.5. The optimization is performed using multi-objective Genetic Algorithms (GA). Selected bilayer stacks are further investigated by adding a 9.5 nm dense line absorber. The aerial images are calculated and the lithographic performance of these mask designs are evaluated in terms of threshold, NILS, EL and DOF.