| 摘要 |
Reflective and scanning CDI for identifying errors in mask patterns and defects on mask blanks. Providing a set-up for scanning the mask in reflection mode with low and/or high NA. Illuminating the mask pattern with EUV light at 2 to 35°. Detecting the diffracted light beam with a position sensitive detector. Analyzing the detected intensities using ptychographic algorithms and thereby obtaining a high resolution image of the sample of arbitrary patterns. Analyzing the detected intensities for intensity variations deviating from the normal intensity distribution caused by the periodic mask pattern in order to detect defects on the mask. This novel technique may be referred to as differential CDI. For periodically structured masks, a fast inspection can be executed by steps of multiples of period, which should give the same diffraction pattern. The investigation for only the deviation from the normal diffraction pattern allows rapid identification of periodic mask pattern defects. |
