Site-specific SIMS backside analysis

Abstract For maximum SIMS depth resolution for any layer in a sample, the depth profile should begin only as far from the layer as necessary to establish a constant implant concentration of the primary ion beam species. Depth resolution and detection limit can be severely degraded if it is necessary to sputter through an over layer having non uniform sputtering properties or containing a high level of the impurity of interest prior to reaching the layer of interest. A SIMS backside analysis method based on mechanical polishing is extended to allow site-specific SIMS backside depth profile analysis. Optical microscopy employing a red filter was used to allow direct viewing of the site to be depth profiled both during polishing and in situ during SIMS analysis. Depth profile analyses were performed on 100 μm ×100 μm device test structures. Sample charging resulting from insulator layers present in these device test structures was alleviated using a modified sample mounting technique. Backside SIMS depth profile analysis using an O2+ primary ion beam having an impact energy of 1.25 keV was used to determine if boron had penetrated a thin SiO2 layer.