Frequency-domain modeling-free learning control for wafer stages with transient improvement by adaption

Precise patterns exposed by the most complicated machine called lithography in high-performance integrated circuits cannot be done without the capability of precise position. Due to the repetitive work demand, a method of FRF(frequency response function)-based modeling-free iterative learning control has been proposed for nano-scaled tracking of wafer stages with high dynamics and external disturbances. The proposed method is aimed at leaving out the modeling process to avoid modeling error and additional expenditure with no need for complex matrix calculation. In an attempt to deal with the adverse effects of iteration transient and random disturbances, an adaptive parameter is designed.