Method of characteristic signatures matching through discrepancy-enhanced library generation process

Shih-Chun Wang; Yi-Sha Ku; Chun-Hung Ko; Nigel Smith

doi:10.1117/12.616383

15 September 2005 Method of characteristic signatures matching through discrepancy enhanced library generation process

Shih-Chun Wang, Yi-Sha Ku, Chun-Hung Ko, Nigel Smith

Proceedings Volume 5908, Optical Information Systems III; 59081D (2005) https://doi.org/10.1117/12.616383
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Scatterometry is an optical measurement technology based on the analysis of light scattered, or diffracted, from a periodic array of features. It is not an optical imaging technique, but rather a model-based metrology that determines measurement results by comparing measured light scatter against a model of theoretical scatter 'signatures'. Conventional algorithms take the average of the difference between the experimental and modeled signatures across the full detection range, and calculate a fitting quality score parameter for the fit, eg. as a RMSE (Root Mean Square Error), MSE (Mean Square Error) or SD (Square Distance). This study reports a novel method for efficiently and accurately determining grating profiles using characteristic signature matching in a discrepancy-enhanced library generation process. Using light scattering theory, such as rigorous coupled wave theory, a series of scattering signatures vs. scattering angles or wavelengths are generated based on the designed grating parameters, eg. CD (Critical Dimension), thickness and Line:Space ratio. This method selects characteristic portions of the signatures wherever their measurement sensitivity exceeds the preset criteria and reforms a characteristic signature library for quick and accurate matching. This method does not need to modify existing measurement hardware or the grating target. It saves a great percentage of storage memory in the computer system, and also increases the measurement sensitivity.

Citation Download Citation

Shih-Chun Wang, Yi-Sha Ku, Chun-Hung Ko, and Nigel Smith "Method of characteristic signatures matching through discrepancy enhanced library generation process", Proc. SPIE 5908, Optical Information Systems III, 59081D (15 September 2005); https://doi.org/10.1117/12.616383

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