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24 May 2004 CD-SEM-based critical shape metrology of integrated circuits
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Abstract
With critical dimensions (CD) of integrated circuits shrinking to tens of nanometers, accurate metrology of three-dimensional feature shapes at different stages of the lithographic process becomes crucial to circuit performance. We propose Critical Shape Metrology (CSM), a CD-SEM-based technique that extracts accurate feature shape information from images obtained during routine in-line wafer inspection. Intensity profiles from CD-SEM images of known materials are compared in real time to profiles in an off-line generated Monte-Carlo SEM simulation library for the same materials with various model shapes. When the best match is found, metrics like bottom CD, top CD, sidewall angle, foot size and angle, and corner rounding can be obtained with high accuracy. The proposed technique takes advantage of the high resolution and throughput of low-voltage CD-SEMs, and does not require any additional tool calibration beyond the standard calibrations performed for conventional top-down CD metrology. While similar to optical scatterometry in concept, this technique allows for measurement of both isolated targets and dense arrays. Examples of performance on etched polysilicon and resist lines of different shapes are included and compared to SEM cross-sections and CD-AFM data.
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Dmitry V. Gorelikov, Jason Remillard, and Neal T. Sullivan "CD-SEM-based critical shape metrology of integrated circuits", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); https://doi.org/10.1117/12.536499
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