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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.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Weidong Yang, Roger Lowe-Webb, Silvio Rabello, Jiangtao Hu, Je-Yi Lin, John D. Heaton, Mircea V. Dusa, Arie J. den Boef, Maurits van der Schaar, and Adolph Hunter "Novel diffraction-based spectroscopic method for overlay metrology", Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003);

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