SIMS (Secondary Ion Mass Spectrumetry)
Secondary Mass Ion
Spectrometry (SIMS) is a powerful analytical technique sensitive to most
elements, with the ability to detect dopant or impurity species at concentrations
as low as parts per billion (ppb). SIMS uses a focussed primary ion beam to
sputter/etch material from a sample. The sputtered material may be ionized by
the process and is extracted to form a secondary ion beam which is then focused
and mass analyzed. Through the use of appropriate reference samples, it is
possible to quantify this data.
The use of an ion beam
to remove material from a sample for analysis is present in a number of
analytical methods. With SIMS, the ion beam is typically O2+ or Cs+ depending
on the sample and analysis required. This ion beam impacts the surface of the
sample and produces, via sputtering, charged sample ions which are ejected from
the sample. These secondary ions are collected and mass analysed to produce depth
profile data. As a result, it is possible to analyse species of interest with respect
to layer thickness. The impact energy of the primary ions with respect to the sample
makes profiling at the micron level possible at the expense of chemical information.
