3 May 2016 Two-dimensional low-coherence interferometry for the characterization of nanometer wafer topographies
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Within this work a scan-free, low-coherence interferometry approach for surface profilometry with nm-precision is presented. The basic setup consist of a Michelson-type interferometer which is powered by a super-continuum light-source (Δλ= 400-1700 nm). The introduction of an element with known dispersion delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height differences on a sample. In order to enable scan-free measurements, the interference signal is spectrally decomposed with a grating and imaged onto a two-dimensional detector. One dimension of this detector records spectral, and therefore height information, while the other dimension stores the spatial position of the corresponding height values.

In experiments on a height standard, it could be shown that the setup is capable of recording multiple height steps of 101 nm over a range of 500 m with an accuracy of about 11.5 nm. Further experiments on conductive paths of a micro-electro-mechanical systems (MEMS) pressure sensor demonstrated that the approach is also suitable to precisely characterize nanometer-sized structures on production-relevant components. The main advantage of the proposed measurement approach is the possibility to collect precise height information over a line on a surface without the need for scanning. This feature makes it interesting for a production-accompanying metrology.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ch. Taudt, Ch. Taudt, T. Baselt, T. Baselt, B. Nelsen, B. Nelsen, H. Aßmann, H. Aßmann, A. Greiner, A. Greiner, E. Koch, E. Koch, P. Hartmann, P. Hartmann, "Two-dimensional low-coherence interferometry for the characterization of nanometer wafer topographies", Proc. SPIE 9890, Optical Micro- and Nanometrology VI, 98900R (3 May 2016); doi: 10.1117/12.2227887; https://doi.org/10.1117/12.2227887

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