Accuracy Improvement of Shot Leveling and Focusing with Interferometry for Optical Lithography

Abstract
This paper describes a new algorithm of shot-by-shot leveling using laser interferometry for a high resolution stepper system (wave amplitude uniform method). This unifies the interference fringe and can improve the accuracy of the height and tilt detection deviation. The effect of the WAUM was verified by simulation. The maximum offset deviation for tilt and height was proved to be ±2.4 µ rad and ±0.03 µ m respectively. The performance was evaluated with an Al processed wafer and tilt offset deviation was proved to be ±6.4 µ rad.