24 May 2004 Toward a complete description of linewidth roughness: a comparison of different methods for vertical and spatial LER and LWR analysis and CD variation
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Proceedings Volume 5375, Metrology, Inspection, and Process Control for Microlithography XVIII; (2004); doi: 10.1117/12.535153
Event: Microlithography 2004, 2004, Santa Clara, California, United States
Abstract
Line edge (or width) roughness (LER or LWR) of photoresists lines consists a serious issue in shrinking the CDs of the gates to dimensions of a few tens of nanometers. In this paper, we address the problem of the reliable LER characterization as well as the association of LWR with the CD variations. The complete LER characterization requires more parameters than the rms value σ since the latter neglects the spatial aspects of LER and does not predict the dependence on the length of the measured line. The further spatial LER descriptors may be the correlation length ξ and the roughness exponent α, which can be estimated through various methods. One aim of the present work is to perform a systematic comparative study of these methods using model edges generated by a roughness algorithm, in order to show their advantages and disadvantages for a reliable and accurate determination of the spatial LER parameters. In particular, we compare the results from (1) the study of the height-height correlation function (HHCF), (2) the Fourier (or power spectrum, PS) analysis and (3) the variation of rms value σ with measured line edge L [σ(L) curve]. It is found that the HHCF can be considered approximately a rescaled version of σ(L) and that the value of σ becomes almost independent on the measured edge length for lengths larger than ten times the correlation length. As regards the PS, it is shown that the finite length of the edge may affect harmfully the reliable estimation of α and ξ. Finally, we confirm theoretically and generalize an experimental observation regarding the relationship between LWIR and the σ of the CD variations within a die of a wafer. It is shown that they behave in a complimentary way as line length increases so that the sum of their squares remains constant and equal to the square of the LWR σ of the infinite line.
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Vassilios Constantoudis, George P. Patsis, Leonardus Hendrikus Albertino Leunissen, Evangelos Gogolides, "Toward a complete description of linewidth roughness: a comparison of different methods for vertical and spatial LER and LWR analysis and CD variation", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); doi: 10.1117/12.535153; https://doi.org/10.1117/12.535153
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KEYWORDS
Line edge roughness

Picosecond phenomena

Line width roughness

Critical dimension metrology

Edge roughness

Correlation function

Scanning electron microscopy

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