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Title: Smoothing of Diamond-Turned Substrates for Extreme Ultraviolet Illuminators

Abstract

Condenser optics in extreme ultraviolet lithography (EUVL) systems are subjected to frequent replacement as they are positioned close to the illumination source, where increased heating and contamination occur. In the case of aspherical condenser elements made by optical figuring/finishing, their replacement can be very expensive (several hundred thousand dollars). One approach to this problem would be to manufacture inexpensive illuminator optics that meet all required specifications and could be replaced at no substantial cost. Diamond-turned metal substrates are a factor of 100 less expensive than conventional aspherical substrates but have insufficient finish, leading to unacceptably low EUV reflectance after multilayer coating. In this work it is shown that, by applying a smoothing film prior to multilayer coating, the high spatial frequency roughness of a diamond-turned metal substrate is reduced from 1.76 to 0.27 nm rms while the figure slope error is maintained at acceptable levels. Metrology tests performed at various stages of the fabrication of the element demonstrated that it satisfied all critical figure and finish specifications as illuminator. Initial experimental results on the stability and performance of the optic under a real EUVL plasma source environment show no accelerated degradation when compared to conventional substrates.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15014372
Report Number(s):
UCRL-JRNL-201108
Journal ID: ISSN 0091-3286; OPEGAR; TRN: US200805%%394
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Optical Engineering
Additional Journal Information:
Journal Volume: 43; Journal Issue: 12; Journal ID: ISSN 0091-3286
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUMM MECHANICS, GENERAL PHYSICS; CONTAMINATION; DOLLARS; FABRICATION; HEATING; ILLUMINANCE; OPTICS; PERFORMANCE; PLASMA; ROUGHNESS; SPECIFICATIONS; STABILITY; SUBSTRATES

Citation Formats

Soufli, R, Spiller, E, Schmidt, M A, Robinson, J C, Baker, S L, Ratti, S, Johnson, M A, and Gullikson, E M. Smoothing of Diamond-Turned Substrates for Extreme Ultraviolet Illuminators. United States: N. p., 2003. Web.
Soufli, R, Spiller, E, Schmidt, M A, Robinson, J C, Baker, S L, Ratti, S, Johnson, M A, & Gullikson, E M. Smoothing of Diamond-Turned Substrates for Extreme Ultraviolet Illuminators. United States.
Soufli, R, Spiller, E, Schmidt, M A, Robinson, J C, Baker, S L, Ratti, S, Johnson, M A, and Gullikson, E M. 2003. "Smoothing of Diamond-Turned Substrates for Extreme Ultraviolet Illuminators". United States. https://www.osti.gov/servlets/purl/15014372.
@article{osti_15014372,
title = {Smoothing of Diamond-Turned Substrates for Extreme Ultraviolet Illuminators},
author = {Soufli, R and Spiller, E and Schmidt, M A and Robinson, J C and Baker, S L and Ratti, S and Johnson, M A and Gullikson, E M},
abstractNote = {Condenser optics in extreme ultraviolet lithography (EUVL) systems are subjected to frequent replacement as they are positioned close to the illumination source, where increased heating and contamination occur. In the case of aspherical condenser elements made by optical figuring/finishing, their replacement can be very expensive (several hundred thousand dollars). One approach to this problem would be to manufacture inexpensive illuminator optics that meet all required specifications and could be replaced at no substantial cost. Diamond-turned metal substrates are a factor of 100 less expensive than conventional aspherical substrates but have insufficient finish, leading to unacceptably low EUV reflectance after multilayer coating. In this work it is shown that, by applying a smoothing film prior to multilayer coating, the high spatial frequency roughness of a diamond-turned metal substrate is reduced from 1.76 to 0.27 nm rms while the figure slope error is maintained at acceptable levels. Metrology tests performed at various stages of the fabrication of the element demonstrated that it satisfied all critical figure and finish specifications as illuminator. Initial experimental results on the stability and performance of the optic under a real EUVL plasma source environment show no accelerated degradation when compared to conventional substrates.},
doi = {},
url = {https://www.osti.gov/biblio/15014372}, journal = {Optical Engineering},
issn = {0091-3286},
number = 12,
volume = 43,
place = {United States},
year = {Thu Nov 13 00:00:00 EST 2003},
month = {Thu Nov 13 00:00:00 EST 2003}
}