Improved diffraction-based overlay metrology by use of two dimensional array target

Yi-Sha Ku; Hsiu-Lan Pang; Weite Hsu; Deh-Ming Shyu

doi:10.1117/12.825524

21 August 2009 Improved diffraction-based overlay metrology by use of two dimensional array target

Yi-Sha Ku, Hsiu-Lan Pang, Weite Hsu, Deh-Ming Shyu

Proceedings Volume 7405, Instrumentation, Metrology, and Standards for Nanomanufacturing III; 74050C (2009) https://doi.org/10.1117/12.825524
Event: SPIE NanoScience + Engineering, 2009, San Diego, California, United States

Abstract

We report results of theoretical modeling into a scatterometry-based method relevant to overlay measurement. A set of two array targets were designed with intentional offsets difference, d and d+20 nm, between the top and bottom grid arrays along the X and Y directions. The correlation of bi-azimuth measurements is the first critical issue been taken into account. The method linearizes the differential values of scatterometry signatures at the first diffraction order with respect to designed offsets, and hence permits determination of overlay using a classical linear method. By evaluating the process variations (eg. CD, roundness and thickness) on overlay measurement error, a set of two overlay target design were optimized to minimize the correlation of bi-azimuth measurements and maximize the measurement sensitivity.

Citation Download Citation

Yi-Sha Ku, Hsiu-Lan Pang, Weite Hsu, and Deh-Ming Shyu "Improved diffraction-based overlay metrology by use of two dimensional array target", Proc. SPIE 7405, Instrumentation, Metrology, and Standards for Nanomanufacturing III, 74050C (21 August 2009); https://doi.org/10.1117/12.825524

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KEYWORDS

Overlay metrology

Diffraction

Scatterometry

Signal processing

Critical dimension metrology

Photoresist materials

Diffraction gratings

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