Predicting the thermomechanical distortion of extreme ultraviolet lithography reticles for preproduction and production exposure tools

摘要

The thermomechanical distortion of extreme ultraviolet lithography (EUVL) reticles during exposure may lead to significant image placement (IP) errors. As throughput requirements for high-volume manufacturing (HVM) increase, the necessary illumination power levels rise, resulting in further distortion of the reticle. The thermal response of the EUVL reticle is predicted using finite element models for a typical HVM exposure tool. The effect of increasing the EUV source power on reticle heating is investigated by comparing the thermal distortion expected in exposure tools using different throughput values corresponding to the α tool, β tool, and the HVM exposure tool (γ tool). The effect of imperfect contact between the EUVL reticle and the chuck surface on the IP errors due to thermal distortion is studied for different effective contact area ratios. Also, an alternative design concept is proposed, aimed at providing a solution to the microparticle trapping problem (between the reticle and the chuck).