Actinic EUV metrology for 1D and 2D patterns

Feature sizes on EUV photomasks are rapidly shrinking to accommodate higher resolution patterns and sub-resolution features. However, as feature size decreases on the mask, EUV scattering becomes increasingly sensitive to Mask 3D effects, which depend on the 3D absorber profile. Therefore, there is an increasing need to accurately measure and control the 3D profile of etched absorber structures on EUV photomasks. Furthermore, EUV radiation is an ideal probe for measuring an EUV photomask, due to its short wavelength, high reflectivity near normal incidence, and sensitivity to all EUV optical effects. We present a method for measuring the sidewall angle (SWA) EUV photomasks using EUV scatterometry, along with an experimental demonstration of the method on the EUV Tech ENK tool.