Nondestructive picosecond-ultrasonic characterization of Mo/Si extreme ultraviolet multilayer reflection coatings
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720-1772 (United States)
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
- Department of Material Science and Mineral Engineering, University of California, Berkeley, California 94720 (United States)
We have used noncontact, nondestructive picosecond-ultrasonic techniques to characterize Mo/Si multilayer reflection coatings for extreme ultraviolet (EUV) lithography. Using our alternating-pump technique, we successfully excited and detected the two lowest frequency localized acoustic-phonon surface modes. By measuring their vibration frequencies simultaneously, we can extract the two key parameters for EUV reflector performance: d (bilayer thickness) and {gamma} (thickness ratio of Mo layer to the bilayer) of the Mo/Si multilayers. To demonstrate the utility of this technique, we measured the surface-mode frequencies and extracted the values of d and {gamma} for six mirrors. Good agreement with the results of at-wavelength EUV reflectometry was found. Damage to coatings caused by the pump and probe laser beams was also studied, and found to be negligible given our data-acquisition time. (c) 1999 American Vacuum Society.
- OSTI ID:
- 20217903
- Journal Information:
- Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena, Vol. 17, Issue 6; Other Information: PBD: Nov 1999; ISSN 0734-211X
- Country of Publication:
- United States
- Language:
- English
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