Study of polarization aberration measurement using SPIN method

High-NA and immersion projection systems require RETs (Resolution Enhancement Techniques) that utilize polarized illumination. Therefore measuring aberrations that is dependent on illumination polarization (polarization aberration) also becomes important. Generally, metrology for polarization aberration measurement consists of polarizer, resulting in a large-scale apparatus and rising cost. Therefore, a simple and accurate metrology method is desired, one that can be easily installed then removed after testing. We have investigated a simple and accurate metrology method for polarization aberration measurement using Canon SPIN. Through this work, we developed a new theory, entitled BLP (Birefringence measurement by Linear Polarization of light), to characterize birefringence of the lens by rotating linear polarization illumination. One of the merits of BLP is its applicability to most of the conventional metrologies for lens aberration measurement. In this paper, we have used SPIN method for BLP evaluation. We confirmed the accuracy of BLP by achieving 1.0 correlation coefficient with Jones theory for Retardance and Fast-Axis of birefringence. We also evaluated the validity of Pseudo-Jones-Pupil (PIP), which was generated from SPIN-BLP analysis, for imaging performance simulation.. This resulted in identical imaging performance with the original Jones pupil for resolution and LRCD. As a polarization aberration monitor SPIN can be used for qualification, periodic monitor and evaluation of image performance in the field. Another advantage of SPIN is its portability. Therefore we also consider usage of SPIN as a machine-to-machine calibration tool.