Development of a ToF version of the desktop MiniSIMS: instrument design and applications

The Millbrook MiniSIMS remains a unique concept in SIMS instrumentation, incorporating static, imaging and dynamic SIMS in a single compact desktop unit. The instrument is successfully being used in a wide range of applications, in which its low cost and high sample throughput are more important than the higher specification or flexibility in configuration of conventional instrumentation. The original MiniSIMS was designed around a quadrupole mass analyser, selected as the only type able at the time to meet the size and cost criteria appropriate to a desktop instrument. However, the sequential mass scanning needed to acquire a full spectrum is inefficient and the accepted static SIMS limit may often be exceeded during analysis of small areas. Therefore a time-of-flight (ToF) version has been developed in order to increase performance in areas where a low primary ion dose is critical to the analysis. Such analyses include organic species characterisation and the identification of small area surface contaminants. The instrument design is unconventional, utilising a continuous primary beam and a pulsed secondary ion beam. This allows a high duty cycle in comparison with conventional ToF-SIMS instruments (typically >10% compared to <0.1%), and also depth profiling with simultaneous continuous etching and ToF mass analysis. The use of such a spectrometer is thus ideally matched to the concept of a high-throughput instrument with static, imaging and dynamic SIMS capabilities. The instrumental design is described and data presented to compare the practical performance of the quadrupole and ToF versions of the instrument. Copyright (C) 2006 John Wiley & Sons, Ltd.