Nanometrology Using Through-Focus Scanning Optical Microscopy Method
Ravikiran Attota, Richard M. Silver
We present an initial review of a novel through-focus scanning optical microscopy (TSOM) imaging method that produces nanometer dimensional measurement sensitivity using a conventional bright-field optical microscope. In the TSOM method a target is scanned through the focus of an optical microscope, simultaneously acquiring optical images at different focal positions. The TSOM images are constructed using the through-focus optical images. A TSOM image is deemed unique under a given experimental condition and is sensitive to changes in the dimensions of a target in a distinct way. We use this characteristic for nanoscale dimensional metrology. This technique can be used to identify which dimension is changing between two nanosized targets and to determine the dimensions using a library-matching method. This methodology has potential utility for a wide range of target geometries and application areas, including, nanometrology, nanomanufacturing, defect analysis, process control, and biotechnology.