26 March 1993 Coherence probe metrology for phase-shift masks: initial results
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Abstract
Coherence probe metrology (CPM) is a unique optical imaging technology which allows non- contact three dimensional measurements of sub-micron features. This technology has been applied to CD and overlay metrology on semiconductor wafers. CPM technology employs a Linnik interferometer to collect 3-D information, measuring both the amplitude and phase of an image. This makes CPM a promising technology for phase shift mask metrology. This paper gives a technical description covering the theory of the coherence probe microscope. Cross-sectional CPM images of phase shift mask features are presented, showing the ability to image quartz and PMMA shifter structures. Initial metrology performances for feature width and shifter thickness are presented. Linearity of CD is examined. Results are shown for shifter only and rim shifter masks. Shifter thickness measurement precision is compared for envelope-only and phase based signal measurement algorithms.
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Mark Allen Neil, Mark Allen Neil, Robert J. Monteverde, Robert J. Monteverde, Stephen D. Kirkish, Stephen D. Kirkish, } "Coherence probe metrology for phase-shift masks: initial results", Proc. SPIE 1809, 12th Annual BACUS Symposium on Photomask Technology and Management, (26 March 1993); doi: 10.1117/12.142131; https://doi.org/10.1117/12.142131
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