Paper AS-ThP6
Using a Dual-Beam SIMS to Study Nano-scale Metallic Thin Films and Biological Samples

Thursday, October 18, 2007, 5:30 pm, Room 4C

Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) offers high sensitivity and mass resolution. It is used widely in both research laboratories and industry. While TOF-SIMS is a well established surface analyzing method, high resolution depth-profile analysis is often desired in semiconductor industry, nano-structure manufacturing and engineering. Using a TRIFT II dual-gun system, which is equipped with a Au_n⁺ gun as primary beam and an Argon gun as sputter beam, we studied a series of samples that consist of multilayer, nano-scale metallic thin films. Depth profiling is carried at different sputter energies (500eV-5keV) and the resolution is compared for these different sputter energies. Using the imaging capability of TOF-SIMS, the image of the crater after sputtering is obtained and the ion mixing at interface is studied. The result is compared with TRIM simulations. One great advantage that TOF-SIMS offers over other types of mass spectroscopy like MALDI is sub-micron spatial resolution. MALDI is the primary method used in mass spectroscopic imaging of biological samples like cells and tissue sections. Though MALDI offers a wide mass range, the spatial resolution, limited by the matrix crystal size and laser beam spot size, is often tens of microns. SIMS high spatial image is a well suited complement to MALDI image. The argon sputtering, though primarily used to study inorganic samples, was recently used to expose cell inner structures for electron microscopy images. Using the dual-beam system, we studied a prostate tissue section. The sputtering rate is determined, and depth-profiles are correlated to interior cell structures in the SIMS image.