A comparison of donor mapping techniques using the scanning helium ion microscope and scanning electron microscope

Compared to scanning electron microscope (SEM) dopant contrast where energy filtering is required, this paper reports for the first time strong contrast from donor distributions using the scanning helium ion microscope (SHIM) that can be used to map n-type regions at high resolution without the need for energy filtering. The sensitivity limit is about 10¹⁷ donors cm^-3 if there were no p-type regions. Quantification problems are discussed and suggestions are given including improvements in detector design and lower beam voltage operation for the SHIM as a tool for high spatial resolution dopant characterisation.