Noise-free estimation of spatial line edge/width roughness parameters

Abstract

At present, the most widely used technique for Line Edge and Width Roughness (LER/LWR) measurement is based on the analysis of top-down CD-SEM images. However, the presence of noise on these affects importantly the obtained edge morphologies leading to biased LER/LWR measurements. In the last few years, significant progress has been made towards the acquisition of noise-free LER/LWR metrics. The output of all proposed methods is the noise-free rms value R q estimated using lines with sufficiently long lengths. Nevertheless, one of the recent advances in LER/LWR metrology is the realization that a single R q value does not provide a complete description of LER and a three parameter model has been introduced including the R q value at infinite line length, the correlation length ξ and the roughness exponent α. The latter two parameters describe the spatial fluctuations of edge morphology and can be calculated by the height height correlation function G(r) or the dependence of rms value R q on line length R q (L). In this paper, a methodology for noise free estimation of G(r) and R q (L) is proposed. Following Villarrubia et al. [Proc.SPIE5752, 480 (2005)], we obtain a formula for the noise free estimation of G(r) and assess its predictions by implementing and applying a modeling approach. Also, we extend appropriately the methodology of Yamagutchi et al. [Proc.SPIE6152, 61522D (2006)] to a large range of line lengths and show that it can provide a reliable noise free estimation of the whole R q (L) curve.Metrology, Inspection, and Process Control for Microlithography XXIII, edited Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 7272 72724B-4 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 7272 72724B-7 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

Effect of white noise on roughness measurements of self-affine fractals

“…However, the validity of this assumption has not been checked, and the influence of the correlated component must be clarified for reliable assessment of noise errors. Some previous studies have similarly ignored the correlated component [6,13,[17][18][19][20][21][22]. As the above assumption is widely accepted in fields of roughness measurement, an accurate theoretical equation related to the noise error is imminently required for roughness analysis.…”

Contact edge roughness in EUV lithography

“…The latter can degrade the electrical performance of the transistor due to the sensitive dependence of electrical characteristics (threshold voltage, off-current) on the channel length. Also, the possibility of the first two methods to provide noise-free spatial information about LWR has also been investigated [95]. The most widely used metric for the quantification of LER/LWR has been the standard deviation of the edge points from their mean value (rms value) σ LER :…”