![]() For nanoscale CD metrology, angle- and or wavelength- dependant reflectometry is utilised, whereby the dependence of the reflected intensity of an incident beam (0 th order diffraction) can be fitted to an EM library, typically computed by rigorous coupled-wave analysis (RCWA) 17, 20, 21, 22, 23, 24, 25, 26. Ellipsometry is an example of a powerful scatterometry technique utilising elliptical phases which can determine thin-film optical constants and layer thicknesses down to several nanometres 19. This surface scattering response is then compared to a library of simulated data created by electromagnetic (EM) modelling techniques to fit the measured response to a computational prediction a method known as inverse problem solving. Scatterometry techniques use scattered light from a surface as a function of a variable such as angle-of-incidence or wavelength. However, for more complex structural determination, optical scatterometry has become a widely investigated and adopted technique 16, 17, 18. Simple spectroscopic techniques such as reflectivity, absorption, fluorescence or Raman scattering 14, 15 can be used to determine the amount of a material present which in turn can be related to film thickness. For this reason, a variety of non-imaging optical technologies are used for inspection having the advantage of being fast and non-destructive. They are hard to insert into a production, comparatively slow, require precise alignment and are potentially destructive. Traditional powerful CD technologies such as scanning electron microscopy (SEM) and atomic force microscopy (AFM) have serious drawbacks for such an application. For quality control purposes, inspection technologies are required to be compatible with these high-speed patterning technologies, i.e., fast and suitable for large area critical dimension (CD) measurements 10, 11, 12, 13. High-throughput NIL technologies such as roll-to-roll, roll-to-plate, and step-and-repeat enable high-volume production of such devices and surfaces 6, 7, 8, 9. Smart surfaces with nano- and micro- scale features find application in a wide variety of sectors in modern society: electronics 1, security 2, photonics 3, micro-optics, micro- fluidics 4 and biomedicine 5.
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