Numerical modeling of absorber characteristics for EUVL

Abstract

The characteristics of various potential absorbers, such as Cr, Ta, and TaN materials were quantitatively investigated by calculating the optical contrast and geometrical width variation of pattern image of 25-nm-width transferred through the exposure system. The intrinsic absorber performance was evaluated by the numerical modeling of the reflectivity on the mask and the aerial image intensity on the wafer. The reflectivity on the mask was calculated for various absorber thicknesses (40-70 nm) using Fresnel equation. For the calculation of the aerial image intensity of pattern features with various absorbers, SOLID-EUV, which is capable of rigorous electromagnetic field computation, was employed. It could be reasonably concluded that the TaN absorber model showed superior optical characteristics compared to other absorber systems, whereas the best performance on the geometrical characteristics was found in the Ta absorber system.