High-speed position tracking for nanohandling inside scanning electron microscopes

This paper describes a new position tracking system that uses the scanning electron microscope as a fast, high-resolution sensor system. The position tracking system works similar to an optical encoder using a specially structured pattern as scale. Thus, with low computational overhead, an accuracy below 10 nm is achieved in a tungsten cathode-based microscope. The tracking system is virtually immune to changes in contrast, brightness, magnification and, to a certain extend, to defocusing. With a customized, external scan generator and scanning algorithm, the bottleneck of image acquisition can be bypassed and the position tracking system can reach update rates of more than 1 kHz. Furthermore, measurements can be conducted over long working ranges of up to 200 mum without losing precision.