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.

Line Edge Roughness Characterization of Sub-50nm Structures Using CD-SAXS: Round-Robin Benchmark Results



Chengqing C. Wang, J C. Roberts, Robert Bristol, B Bunday, Ronald L. Jones, Eric K. Lin, Wen-Li Wu, John S. Villarrubia, Kwang-Woo Choi, James S. Clarke, Bryan J. Rice, Michael Leeson


he need to characterize line edge and line width roughness in patterns with sub-50 nm critical dimension challenges existing platforms based on electron microscopy and optical scatterometry. The development of x-ray based metrology platforms provides a potential route to characterize a variety of parameters related to line edge roughness by analyzing the diffracted intensity from a periodic array of test patterns. In this study, data from a series of photoresist line/space patterns featuring programmed line width roughness measured by critical dimension small angle x-ray scattering (CD-SAXS) is presented. For samples with periodic roughness, CD-SAXS provides the wavelength and amplitude of the periodic roughness through satellite diffraction peaks. In addition, the rate of decay of intensity, termed an effective Debye-Waller factor, as a function of scattering vector provides a measure of the fluctuation in line volume.CD-SAXS data are compared to analogous values obtained from CD-SEM. Correlations between the techniques exist, however significant differences are observed for the current samples. C-AFM data reveal large fluctuations in both line height and line width, providing a potential explanation for the observed disparity between CD-SEM and CD-SAXS.


line edge roughness, scatterometry, small angle x-ray scattering


Wang, C. , Roberts, J. , Bristol, R. , Bunday, B. , Jones, R. , Lin, E. , Wu, W. , Villarrubia, J. , Choi, K. , Clarke, J. , Rice, B. and Leeson, M. (2007), Line Edge Roughness Characterization of Sub-50nm Structures Using CD-SAXS: Round-Robin Benchmark Results, SPIE, [online], (Accessed June 13, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 1, 2007, Updated February 17, 2017