Photomask Critical Dimension Metrology with Deep-Ultraviolet Microscope

A deep-ultraviolet (UV) microscope can output critical dimension (CD) that is consistent with an aerial image on a wafer even if the cross-sectional profile of the pattern on a photomask is varied. According to theoretical calculation, CD measured by the deep-UV microscope depends on global transmissivity, and so does the aerial image on a wafer if the cross-sectional profile is varied. The results of simulation and experiment indicate that offset between CD measured by deep-UV microscope and CD determined by the aerial image is constant despite variation of the cross-sectional profile.