New approaches for scatterometry-based metrology for critical distance and overlay measurement and process control

摘要

Communication between lithography and metrology is becom-ning increasingly demanding in advanced nodes. This is where the re-nquirements for metrology become extremely tight. This work is dedicatednto the search for “clean” metrology that is required to address these re-nquirements. Metrology measurements are obtained via an angle-resolvednscatterometry-based platform (called YieldStar). Details of the technologynbehind YieldStar were thoroughly discussed by Vanoppen et al. in 2010.nIn this current work, measurement limits are challenged to test resolutionnand measurement uncertainty for overlay, critical dimension (CD), andnsidewall angle (focus). Results indicate an atomic-scale performance ofndeep subnanometers. Two different sizes of scatterometry-based overlayntargets are evaluated and compared using a technique called the similar-nity index. A CD reconstruction model is tested for cross talk of underlyingnthin-film layers, specifically the case where one of the underlying layersnis anisotropic. A systematic approach is taken to increase the complex-nity of a CD reconstruction model in steps to evaluate the capability ofnhandling birefringence effects of anisotropic material in the model. CDnmetrology data (1-D and 2-D/hole layers) are compared to CD scanningnelectron microscope data. Focus measurements are also extended fornproduct wafers, and focus precision is evaluated. In addition, CD metrol-nogy monitor wafer applications, such as hotplate monitoring and overlaynmetrologymonitor wafer application for scanner stability andmatchedma-nchine overlay, are tested