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Increased lithographic performance has been the key enabler for the continued reduction of minimum device feature sizes down to 0.25 micrometers and beyond. However, this increase in performance has been accompanied by the added fabrication complexity of the various types of lithographic reticles. In addition to having submicrometer sized features, advanced optical masks are three dimensional in nature with high aspect ratio features of different materials in close proximity to each other. Lithographic process latitude, which determines the ultimate feasibility of that process, is critically dependent upon the level of measurement and control of these mask features. Standard reference materials are needed in order to improve the accuracy of the mask measurements, but do not yet exist. To initiate progress in this area, a set of test reticles has been fabricated to serve as in-house calibration standards and to study various phenomena affecting three-dimensional submicron dimensional metrology for advanced optical masks. The first member of the set, known as the Lateral Resolution Tester (LRT), contains chromium features on unetched quartz (opaque and partially transparent) having linewidths as narrow as 200 nm. The PSM Feature Tester contains many types of phase-shifting mask patterns with varying lateral dimensions. The Herschel Tester contains various phase-shifting apertures of different depths and widths. All of the patterns and concepts used in the set have been brought together in order to produce a new PSM metrology test/calibration mask known as the PSM Round Robin Reticle (RRR). The types of patterns as well as the techniques used to measure them are presented. The RRR will also be used as the test vehicle for a round robin comparison of measurements taken with metrology tools at different mask shops and to determine optimum designs for future PSM metrology calibration standards.
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