Dopant contrast in the helium ion microscope: Contrast mechanism

Abstract

With the continued miniaturisation of semiconductor devices, there is an increasing need for nanoscale characterisation. Dopant mapping in a Low Voltage Scanning Electron Microscope (LV-SEM) was identified as a potential technique to fulfil this need, provided that a small enough probe size (∼0.1 nm) could be achieved. It has been shown that He ion beams in Helium Ion Microscopes (HeIM) can be focussed to probe sizes as small as 0.24 nm. As the image in both LV-SEM and HeIM is formed by secondary electrons it is not surprising that HeIM exhibits dopant contrast as recently demonstrated. In this paper we describe similarities and differences between HeIM dopant contrast and SEM dopant contrast and explore implications for the contrast mechanism.