CD-bias reduction in CD-SEM line-width measurement for the 32-nm node and beyond using the model-based library method

Chie Shishido; Maki Tanaka; Mayuka Osaki

doi:10.1117/12.813948

23 March 2009 CD-bias reduction in CD-SEM line-width measurement for the 32-nm node and beyond using the model-based library method

Chie Shishido, Maki Tanaka, Mayuka Osaki

Author Affiliations +

Proceedings Volume 7272, Metrology, Inspection, and Process Control for Microlithography XXIII; 72722C (2009) https://doi.org/10.1117/12.813948
Event: SPIE Advanced Lithography, 2009, San Jose, California, United States

Abstract

The measurement accuracy of critical-dimension scanning electron microscopy (CD-SEM) at feature sizes of 10 nm and below is investigated and methods for improving accuracy and reducing CD bias (the difference between true and measured CD values) are proposed. Simulations indicate that CD bias varies with feature size (CD) when the electron scatter range exceeds the CD. As the change in the CD-SEM waveform with decreasing CD is non-uniform, the CD bias in the results is strongly dependent on the algorithm employed to process the CD-SEM data. Use of the threshold method with a threshold level equal to 50% (Th = 50%) is shown to be effective for suppressing the dependence of CD bias on CD. Through comparison of experimental CD-SEM measurements of silicon line patterns (7-40 nm) with atomic force microscopy (AFM) measurements, it is confirmed that the threshold method (Th = 50%) is a effective as predicted, affording a largely invariant CD bias. The model-based library (MBL) method, which is theoretically capable of eliminating CD bias, is demonstrated to reduce the CD bias to near-zero levels. These experiments demonstrate the feasibility of next-generation CD-SEM for the measurement of feature sizes of the order of 10 nm and smaller.

Citation Download Citation

Chie Shishido, Maki Tanaka, and Mayuka Osaki "CD-bias reduction in CD-SEM line-width measurement for the 32-nm node and beyond using the model-based library method", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72722C (23 March 2009); https://doi.org/10.1117/12.813948

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