Performance of a new ion optics for quasisimultaneous secondary ion, secondary neutral, and residual gas mass spectrometry

Abstract

We have constructed an electron impact postionizing optics for sputtered neutrals which can be used on quadrupole mass filters for combined secondary neutral mass spectrometry (SNMS), positive and negative secondary ion mass spectrometry (SIMS), and residual gas analysis (RGA). In the SNMS mode, residual gas and secondary ion suppression exceeds 106, and the signal-to-background ratio is better than 104. Detection limits better than 30 ppm are shown using primary ion beam (3 keV Ar+) doses of 80 μAs per amu scan. The sensitivity in the SNMS mode exceeds that of SIMS only if the secondary ion fraction of the sputtered particle flux is in the order of 10−5, which is excessively low. As a first application, we have quantitatively determined secondary neutral and ion fluxes as well as oxygen concentrations on oxygen loaded Si(100) surfaces by purely mass spectroscopic experiments.