Picosecond ultrasonic characterization of Mo/Si multilayers for extreme ultraviolet lithography

Nen-Wen Pu; Seongtae Jeong; Rian Zhao; Jeffrey Bokor

doi:10.1117/12.351136

25 June 1999 Picosecond ultrasonic characterization of Mo/Si multilayers for extreme ultraviolet lithography

Nen-Wen Pu, Seongtae Jeong, Rian Zhao, Jeffrey Bokor

Proceedings Volume 3676, Emerging Lithographic Technologies III; (1999) https://doi.org/10.1117/12.351136
Event: Microlithography '99, 1999, Santa Clara, CA, United States

Abstract

We have used picosecond ultrasonic techniques as a nondestructive detection tool to characterize Mo/Si multilayer reflectors for EUV. The lowest two localized acoustic-phonon surface modes were simultaneously observed in our samples with various d and (Gamma) values. The vibration frequencies of these surface modes depend both on d and (Gamma) , and can be used to extract these two parameters. We mapped the thickness profile of a linearly graded Mo/Si multilayer sample with 2 percent d-variation from the two edges towards the center. The dependence of the vibration frequencies on (Gamma) was also studied theoretically and experimentally, and was found to be separable from the dependence on d.

Citation Download Citation

Nen-Wen Pu, Seongtae Jeong, Rian Zhao, and Jeffrey Bokor "Picosecond ultrasonic characterization of Mo/Si multilayers for extreme ultraviolet lithography", Proc. SPIE 3676, Emerging Lithographic Technologies III, (25 June 1999); https://doi.org/10.1117/12.351136

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