关键词：NE特征;强度测量;散焦相位成像;电磁边缘效应
摘 要：The edges of absorbing regions used to de ne features on photomasks have inherent elec- tromagnetic di raction e ects that limit the focus tolerance during projection printing. In this work it is shown that the thin mask boundary layers used to characterize these e ects can be directly measured by capturing through-focus aerial images, a routine procedure for local quality inspection during mask fabrication. The Transport of Intensity phase imaging method is used to recover quantitative phase from a stack of intensity images, the phase near feature edges directly corresponding to edge e ects at the mask. We discover that the Transport of Intensity solver produces errors in the solved phase near sharp corners due to strong curl e ects in the power  ow, and an iterative solver is developed to remedy the artifacts. Using the improved algorithm, polarization-dependent edge e ects are observed experimentally in the quantitative phase images for both OMOG and ATT-PSM masks. The measured edge e ects correspond to 20nm wide imaginary valued boundary layers for ATT- PSM, and half that for OMOG masks, values which agree with those predicted by full-wave simulations in literature. Finally, the TIE is extended for the case of general illumination, and it is shown that the phase can be recovered from intensity measurements at a single focal plane by illumination patterning.