2 June 2003 Novel diffraction-based spectroscopic method for overlay metrology
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A spectroscopic, diffraction based technique is proposed in this paper as an alternative solution for overlay metrology in technology nodes below 90 nanometers. This novel technique extracts alignment error from broadband diffraction efficiency of specially designed diffraction targets in real-time. Feasibility of the technique is studied for a front-end process flow by measuring grating targets printed on a series of wafers which were intentionally mis-processed to introduce inter-die (grid) level programmed overlay errors. Correlation to conventional imaging overlay measurements is demonstrated. Short term and long term data sets demonstrate sub-half-nanometer in 3-sigma statistical parameters that characterize the diffraction overlay system, repeatability, reproducibility, Tool-Induced-Shift and tool-to-tool matching. The resulting total measurement uncertainty for this technique is thus demonstrated to be in the sub-nanometer range.
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Weidong Yang, Weidong Yang, Roger Lowe-Webb, Roger Lowe-Webb, Silvio Rabello, Silvio Rabello, Jiangtao Hu, Jiangtao Hu, Je-Yi Lin, Je-Yi Lin, John D. Heaton, John D. Heaton, Mircea V. Dusa, Mircea V. Dusa, Arie J. den Boef, Arie J. den Boef, Maurits van der Schaar, Maurits van der Schaar, Adolph Hunter, Adolph Hunter, "Novel diffraction-based spectroscopic method for overlay metrology", Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); doi: 10.1117/12.483476; https://doi.org/10.1117/12.483476

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