Assessment of Heat Deformation and Throughput for Selecting Mask Substrate Material for Extreme Ultraviolet Lithography

Abstract

In order to determine the selection of the extreme ultraviolet (EUV) mask substrate, an assessment model based on the temperature profile along the substrate thickness is proposed. Regarding the glass ceramic materials, thermal deflection and displacement due to thermal expansion are compared as functions of the heat transfer coefficient between the mask and the stage. Displacement is small although the thermal deflection is large in the region where the heat transfer coefficient is sufficiently high. Marginal EUV power density used for 35 nm node is determined by the substrate material and exposure conditions. Throughput estimated by EUV power density and exposure conditions depends on the substrate material. It was shown that a throughput of 60 wafer per hour (wph) is possible under conditions equivalent to low pressure in a helium environment.