| 摘要 |
<p>Inspection of photomasks for defects in phase-shifters is enhanced using optical techniques based on multiple modified radiation collection techniques, which allows allow for errors in phase-shifters to be more accurately detected. The system includes an illumination system (105), at least on collection system (107R, 107T), and a data analysis section (108). In one embodiment, the intensities of two slightly defocused images of phase objects corresponding to the same photomask location are compared. In a second embodiment, radiation having two Zernike point spread functions is used to obtain two slightly different phase sensitive images. Data collected and analyzed by the data analysis section (108) using this method provides much greater sensitivity to phase objects and errors in phase objects than prior art inspection systems. Embodiments include both scanning-type and projector type optical architectures and may utilize radiation transmitted or reflected by a sample.</p> |
