19 March 2015 Metrology of 50nm HP wire-grid polarizer: a SEM-scatterometry comparison
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The capabilities and limitations of angular scatterometry for a structure pitch much less than the optical wavelength are experimentally investigated using a 100-nm pitch Al-wire grid polarizer on a SiO2 substrate. Three CW laser sources of wavelengths (244 nm, 405 nm and 633 nm) are used to measure the 0-order diffraction (reflection) across an incident angle range of 8° to 80°. The grating profile is defined by seven parameters (pitch, bottom linewidth, top linewidth, fused silica undercut, Al thickness, horizontal and vertical extent of top rounding). Rigorous coupled wave analysis (RCWA) simulations show that the reflectivity versus angle results are sensitive to changes in all of these parameters. The simulations act as a baseline library for the scatterometry measurements. Fitting the experimental curves with the corresponding simulation parameters results in a determination of the grating profile. As expected the shorter wavelength measurements provide the most sensitivity, but good precision is obtained at all three wavelengths. The measurements are in good agreement with destructive cross section scanning electron microscopy measurements.
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Ruichao Zhu, Alexander Munoz, S. R. J. Brueck, Shrawan Singhanl, and S. V. Sreenivasan "Metrology of 50nm HP wire-grid polarizer: a SEM-scatterometry comparison", Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 94241W (19 March 2015); doi: 10.1117/12.2087273; https://doi.org/10.1117/12.2087273

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