Analysis of Alkali Elements in Insulators Using a CAMECA IMS-6f

SIMS analysis of insulators is difficult because charging of the sample affects the trajectories of primary and secondary ions. Analysis of alkali elements in insulators is additionally complicated by the mobility of the species of interest under the influence of an electric field. Magnetic sector analyzers also present difficulties in providing charge neutralization because of the high electric field required to inject ions into the analyzer. Coating of the sample with a conductive film or grid has often been needed to provide a meaningful analysis. However, coating the sample adds a contaminant source that complicates alkali analysis, especially at the concentrations of interest to the semiconductor industry. This paper provides, for a magnetic sector instrument, a method which requires no coating or sample preparation prior to analysis. If the electron penetration depth is matched to the thickness of the oxide layer, results show that SiO sub 2 layers from 0.3 to 1.36microns thick can be easily and repeatably analyzed fro alkali elements using this approach.