Scatterometry for nanoimprint lithography

Abstract

Angular scatterometry is used to characterize the nanostructure parameters of two samples: a high dielectric contrast ∼100-nm period Al wire-grid polarizer (WGP), and a low dielectric contrast ∼130-nm period photoresist grating on a flexible polycarbonate substrate; both fabricated by nanoimprint lithography. The zero-order diffraction (reflection) is monitored for a large incident angle range from 8° to 80°. For the WGP, four wavelengths (244-, 405-, 633-, and 982-nm) are used to study the dependence of the scatterometry parametric determination as a function of the sample pitch to wavelength ratio (p/λ: 0.41–0.1). A 4-nm thick native Al2O3 layer was added to the scatterometry simulation and dramatically improved the cross-correlations between results at the different wavelengths. For the photoresist samples, the scatterometry results at 405 nm are compared with atomic force microscopy measurements and the master grating structure. The scatterometry results are sensitive to inhomogeneity of the sample and show a capability for classifying different types of macroscopic defects.