Focused Ion Beam SIMS: Ion Images and End Point Detection.

A secondary ion mass spectrometer has been added to a liquid metal ion source instrument which was designed as a micro- machining apparatus. The SIMS performance exceeds or rivals any reports to date on similar devices, even though no compromises were made with the primary function of the apparatus. End-point detection for ion milling allows depth control within a few hundred angstroms, on micron sized raster fields. A sensitivity of 4x10 sup 5 cps/nA is routinely measured on sup 52 sub Cr sup + signals; similar count rates are also obtained from Al. Ion images on Cr or Al with sub-micron resolution with a 25micron field are obtained in as little as 10 sec. collection time. Features as small as 0.3micron can be defined by the secondary ion imaging, with the removal of only a few monolayers of material.