Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Accurate Reflectometry for Extreme-Ultraviolet Lithography at the National Institute of Standards and Technology

Published

Author(s)

S Grantham, Charles Tarrio, Thomas B. Lucatorto

Abstract

The most demanding application of extreme ultraviolet (EUV) multilayer optics is in lithography. The optics in current alpha-class tools are large, and the multilayer coatings must have both optimized reflectance and extremely high uniformity. At NIST we have recently commissioned a very large sample chamber at the Synchrotron Ultraviolet Radiation Facility (SURF III) storage ring. This dedicated reflectometer is capable of carrying out complete surface maps of alpha- and beta-class tools for the extreme-ultraviolet lithography (EUVL) community.We have conducted a rigorous characterization of the system by varying the output spectrum of SURF III in conjunction with multiple filter and detector combinations. This exercise has resulted in an accurate model of the effects of out-of-band radiation and scattering on the measured reflectivity. The model can be directly applied to raw data measured under any typical operating conditions to reduce the uncertainty of our measurements to 0.3%.We will report the findings of the characterization along with the resulting model and sample measurements, which show that the requisite accuracy and precision in reflectivity required for beta-class tools has been achieved. We will also present measurements of large-sized curved multilayer samples. Finally, we will report on an upgrade to the beamline's monochromator, which is currently in progress. This will improve the stability that will yield the wavelength precision needed for all planned EUVL tools.
Citation
Journal of Vacuum Science and Technology B
Volume
20
Issue
No. 6

Keywords

extreme-ultraviolet, lithography, metrology, multilayer mirror

Citation

Grantham, S. , Tarrio, C. and Lucatorto, T. (2002), Accurate Reflectometry for Extreme-Ultraviolet Lithography at the National Institute of Standards and Technology, Journal of Vacuum Science and Technology B (Accessed February 24, 2024)
Created November 30, 2002, Updated October 12, 2021