Programmable pupil correction method for photolithography illumination system

Abstract The off-axis illumination (OAI) technology is one of the resolution enhancement technologies, and it used to reduce critical dimension (CD) and increase depth of focus (DOF) which are the important performance parameters of photolithography machine. The performance of illumination modes has great effect on critical dimension uniformity (CDU), H–V bias and overlay accuracy. In order that the pupil characteristic parameters can always meet the requirements for a long time using, it is necessary to adopt the pupil correction technology for photolithography illumination system. Using experiments and photolithography performance simulation, a programmable pupil correction method based on correction fingers is studied. The correction algorithm and its operation process are analyzed in detail. The experimental results show that the energy distribution of corrected pupils is more balanced than the uncorrected ones. Furthermore, the simulation results indicate that the corrected pupil could improve the exposure patterns in different aspects. The proposed method could determine the fingers’ position easily, and could directly reflect the pupil performance requirements.