Conference Paper

Computational nanometrology of line-edge roughness: noise effects, cross-line correlations and the role of etch transfer

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... While a single number is often used to characterize LER or LWR, that one number does not capture all interesting features of a rough edge or width. 6,7 The power spectral density (PSD) analysis of edge or line roughness offers more detailed information 6 and is useful for process monitoring 8,9 and understanding aspects of transistor performance. 10 It is difficult to accurately estimate the power spectrum of a rough edge or line from a low-dose SEM image because of the artifacts that corrupt those images. ...
... 10 It is difficult to accurately estimate the power spectrum of a rough edge or line from a low-dose SEM image because of the artifacts that corrupt those images. 6,7 Therefore, new techniques to automate the estimation of edge geometries and to improve the accuracy of power spectrum density estimates are potentially useful for semiconductor manufacturing. ...
... The above methodology is applied to the SEM images of the SAQP steps described in Sec. 2. 41 The results for the c-factor quantifying the left/right edge correlations are shown in The results for the c-factor-function quantifying the crossline correlations of line centers are shown in Fig. 15 versus line distances in pitches. These reveal that (a) doubling and quadrupling of pattern density increases cross-line correlations with number of pitches, (b) the noticed increase is calculated in pitches. ...
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Line edge (or width) roughness (LER or LWR) of photoresists lines constitutes a serious issue in shrinking the critical dimensions (CD) of the gates to dimensions of a few tens of nanometers. In this article, 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 (a) the study of the height–height correlation function (HHCF), (b) the Fourier [or power spectrum (PS)] analysis, and (c) 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 of 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 harmfully affect the reliable estimation of α and ξ. Finally, we confirm theoretically and generalize an experimental observation [Leunissen etal, Microelectron. Eng. (to be published)] regarding the relationship between LWR 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. © 2004 American Vacuum Society.
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The function of a component part can be profoundly affected by its surface topography. There are many examples in nature of surfaces that have a well-controlled topography to affect their function. Examples include the hydrophobic effect of the lotus leaf, the reduction of fluid drag due to the riblet structure of shark skin, the directional adhesion of the gecko foot and the angular sensitivity of the multi-faceted fly eye. Surface structuring is also being used extensively in modern manufacturing. In this way many properties can be altered, for example optical, tribological, biological and fluidic. Previously, single line (profile) measurements were adequate to control manufacture of surfaces, but as the need to control the functionality of surfaces increases, there is a growing need for three-dimensional (areal) measurement and characterisation techniques. For this reason there has been considerable research, development and standardisation of areal techniques. This book will present the areal framework that is being adopted by the international community. Whereas previous books have concentrated on the measurement aspects, this book concentrates on the characterisation techniques, i.e. how to interpret the measurement data to give the appropriate (functional) information for a given task. The first part of the book presents the characterisation methods and the second part case studies that highlight the use of areal methods in a broad range of subject areas - from automobile manufacture to archaeology. © 2013 Springer-Verlag Berlin Heidelberg. All rights are reserved.
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The measurement of line-edge roughness (LER) has recently become a major topic of concern in the litho-metrology community and the semiconductor industry as a whole, as addressed in the 2001 International Technology Roadmap for Semiconductors (ITRS) roadmap. The Advanced Metrology Advisory Group (AMAG, a council composed of the chief metrologists from the International SEMATECH (ISMT) consortium"s Member Companies and from the National Institute of Standards and Technology (NIST) has begun a project to investigate this issue and to direct the critical dimension scanning electron microscope (CD-SEM) supplier community towards a semiconductor industry-backed solution for implementation. The AMAG group has designed and built a 193 nm reticle that includes structures implementing a number of schemes to intentionally cause line edge roughness of various spatial frequencies and amplitudes. The lithography of these structures is in itself of interest to the litho-metrology community and will be discussed here. These structures, along with several other photolithography process variables, have been used to fabricate a set of features of varying roughness value and structure which span the LER process space of interest. These references are, in turn, useful for evaluation of LER measurement capability. Measurements on different CD-SEMs of major suppliers were used to demonstrate the current state of LER measurement. These measurements were compared to roughness determined off-line by analysis of top-down images from these tools. While no official standard measurement algorithm or definition of LER measurement exists, definitions used in this work are presented and compared in use. Repeatability of the measurements and factors affecting their accuracy were explored, as well as how CD-SEM parameters can affect the measurements.