In secondary ion mass spectrometry (SIMS), the sample is bombarded with a primary beam of ions. Secondary ions are emitted from the sample surface and these are mass analysed to provide detailed surface chemical information. The technique is sub-divided into three main categories, each having a specific purpose and characteristics.

Time of Flight SIMS (ToFSIMS) analysis is carried out with a combination of pulsed primary ion beam and time of flight mass spectrometer. The total ion dose used in the analysis is extremely low and the surface remains effectively undamaged. Elements and molecular species are detected which reveal the chemical and molecular structure of the surface.  Imaging and  Region Of Interest (ROI) modes provide the ability for retrospective analysis.

Dynamic SIMS utilises a rastered primary ion beam of usually O2+ or Cs+ in combination with a magnetic sector mass spectrometer. The beam progressively sputters successive layers in a defined area (from 500µm x 500µm to 10µm x 10µm) at a controlled rate. Depth profiles, images and mass spectra are produced which reveal the in-depth elemental structure and composition of materials with sensitivity in the range ppm – ppb for all elements.

In Ultra Low Energy SIMS (ULESIMS), a beam of O2+ or Cs+ with energy of 0.5keV – 2keV is used to produce shallow depth profiles of semiconductor materials or other flat substrates to examine elemental composition e.g dopant profiles and layer structures.