Secondary ion mass spectrometry depth profiling of amorphous polymer multilayers using O2 + and Cs+ ion bombardment with a magnetic sector instrument

Thin planar polymer films are model systems in a number of fields, including nanoand biotechnology. In contrast to reciprocal space techniques such as reflectivity or diffraction, secondary ion mass spectrometry SIMS can provide depth profiles of tracer labeled polymers in real space directly with sufficient depth resolution to characterize many important aspects in these systems. Yet, continued improvements in characterization methods are highly desirable in order to optimize the trade-offs between depth resolution, mass resolution, detection sensitivity, data acquisition time, and artifacts. In this context, the utility of a magnetic sector SIMS instrument for amorphous polymer film analysis was evaluated using model polymer bilayer systems of polystyrene PS with poly methyl methacrylate PMMA , PS with poly 2-vinylpyridine , and poly cyclohexyl methacrylate PCHMA with PMMA. Deuterium-labeled polystyrene embedded in PS or PCHMA at concentrations ranging from 5% to 20% v /v was used as tracer polymer. Analysis conditions for a magnetic sector SIMS instrument CAMECA IMS-6f were varied to achieve a depth resolution of 10 nm, high signal/noise ratios, and high sensitivity, while minimizing matrix effects and sample charging. Use of Cs+ and O2 + primary ions with detection of negative and positive secondary ions, respectively, has been explored. Primary beam impact energy and primary ion species have been shown to affect matrix secondary ion yields. Sputtering rates have been determined for PS and PMMA using both primary ion species and referenced to values for intrinsic 100 silicon Si under identical analysis conditions. © 2006 American Vacuum Society. DOI: 10.1116/1.2172948