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19 March 2015 Understanding the impact of CD-SEM artifacts on metrology via experiments and simulations
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Scanning Electron Microscopy (SEM) is widely used to measure Critical Dimensions (CD) in semiconductor lithography processes. Correlation between the CD-SEM metrology and target profile has drawing attention from metrology community [1]. In this paper, we use a recently developed CD-SEM simulator [2-3] to investigate some artifacts of SEM metrology. The simulation consists of two parts. First part is a stochastic resist modeling for lines and spaces through pitch, exposure dose and focus. Second part is CD-SEM simulation. Both CD and LWR extracted from experimental CD-SEM images were used to train the SEM model. Two types of artifacts were found to be metrology dependent: the first artifact is that a CD-SEM measures CD at various heights across pitch for the same SEM threshold. The second artifact is a misleading CD measurement for trenches not fully developed. By overlapping the CD-SEM simulation with 3D lithography simulation, correlation between CD-SEM metrology and target 3D profile is studied. Finally, a Process Window (PW) analysis based on both experiment and simulation is presented, using the simulated features and SEM images to correct the experimental PW.
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Chao Fang, Alessandro Vaglio Pret, Mark D. Smith, John J. Biafore, Stewart A. Robertson, and Joost Bekaert "Understanding the impact of CD-SEM artifacts on metrology via experiments and simulations", Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 94242A (19 March 2015);

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