Implementation of phase shift focus monitor under modified illumination [photolithography]

For the convenience of practical use of phase shift focus monitor (PSFM), imaging characteristics of PSFM are investigated under modified illumination by optical image calculations and printing experiments. Although the mechanism of pattern shift is different from that in conventional high coherent illumination, sufficient sensitivity for precise focus monitoring is predicted by optical image calculation. By experiments, predicted characteristics are observed and similar sensitivity to that in conventional illumination is confirmed.