Method for optical inspection of nanoscale objects based upon analysis of their defocused images and features of its practical implementation
Journal
OPT EXPRESS
Date
2013.10.07
Abstract
A microscopic method to inspect isolated sub 100 nm scale structures made of silicon is presented. This method is based upon analysis of light intensity distributions at defocused images obtained along the optical axis normal to a sample plane. Results of experimental measurements of the objects ？ calibrated lines (height 50 nm, length 100 μm, width range 40-150 nm with 10 nm step) on top of monocrystalline silicon substrate are presented. It is demonstrated that processing of the defocused images allows one to distinguish between objects with 10 nm change in width. Results of comparison between experimental and simulated data are presented. It is shown that taking into account spherical aberrations of the imaging system provides better agreement between experimental and simulation results. Accuracy limit of the objects widths measurements with the optical method is discussed.