Deep-subwavelength Nanometric Image Reconstruction using Fourier Domain Optical Normalization.

Abstract

Quantitative optical measurements of deep subwavelength, three-dimensional (3D), nanometric structures with sensitivity to sub-nanometer details address a ubiquitous measurement challenge. A Fourier domain normalization approach is used in the Fourier optical imaging code to simulate the full 3D scattered light field of nominally 15 nm-sized structures, accurately replicating the light field as a function of the focus position. Using the full 3D light field, nanometer scale details such as a 2 nm thin conformal oxide and nanometer topography are rigorously fitted for features less than one-thirtieth of the wavelength in size. The densely packed structures are positioned nearly an order of magnitude closer than the conventional Rayleigh resolution limit and can be measured with sub-nanometer parametric uncertainties. This approach enables a practical measurement sensitivity to size variations of only a few atoms in size using a high-throughput optical configuration with broad application in measuring nanometric structures and nanoelectronic devices.