Thermal and structural deformation and its impact on optical performance of projection optics for extreme ultraviolet lithography

Thermal and structural deformation of mirrors becomes an important consideration for extreme ultraviolet lithography (EUVL) when targeting features of 50 nm and below. Such deformation will contribute to the critical dimension control and decrease the performance of the designed system. Multilayer coated mirrors typically absorb 35%–40% of the in-band radiation, which results in the deformation of mirror figures and degrades the performance of the optics. We have employed several software packages to study these effects. This article presents the results for the EUVL production tool with wafer throughput of eighty 300 mm wafers per hour for the 35 nm technology generation.