Hiroyuki Sumiya

Quantitative SIMS analysis of nitrogen using in situ internal implantation

Abstract The peak concentration of nitrogen implanted into a silicon wafer was determined by the in situ internal standard implantation of 14 N + followed by the SIMS depth profiling analysis of 30 Si 14 N − . Quantification was done as follows. As an internal standard, the N ions with a known fluence were directly implanted into the sample using a SIMS instrument. The depth profile of 30 Si 14 N − was then measured. The standard deviation of the projected range in the depth distribution, ΔRP, and the ion intensity for each peak was carefully measured. The actual concentration of nitrogen for the internal implant was calculated from its measured ΔRP value and the fluence. The nitrogen concentration for the original implant was then evaluated by comparing the ion intensity ratio of the internal implant peak to the original implant peak with their concentration ratio. The concentration thus estimated was in good agreement with the actual concentration. The ΔRP values measured from the depth profiles were also compared to the theoretical ones.

A Lithium Liquid Metal Ion Source with a Sealed-Cone-Type Reservoir

A sealed-cone-type liquid metal ion source (LMIS) suitable for lithium has been designed. It consists of a conical metal reservoir, a ceramic lid atop the reservoir covering the ion material, a tungsten filament, and a tungsten-needle emitter. The sealed-cone-type LMIS has good efficiency in heating and any contamination of the ion source due to the deposition of the source material is minimal. The chemical reaction of Li2CrO4 with Si was used to produce the Li liquid metal ion because it does so more easily than the heating of the Li metal does. The use of the Li primary ion in the secondary ion mass spectrometry (SIMS) analysis increased the yield of negative ions, which is similar to the case of the Cs primary ion. The use of light lithium ions improves beam focusing, which in turn increases the sensitivity of element analysis and ion imaging of a microarea.

Depth profiling by combined SIMS-ESDMS analysis : a new surface analytical technique

Electron-stimulated desorption mass spectrometry (ESDMS), a new technique based on the mass analysis of ions desorbed by a high-energy (several keV) electron beam, has analytical features that complement SIMS. The ESDMS has high sensitivity in the surface analysis of both adsorbates and the first one or two monolayers of substrate constituents. The variations in ESDMS signal intensities and in the sampling surface depth with time were negligible even in a one-monolayer sample. Using this combined SIMS-ESDMS technique, depth profiling analysis was performed for several different metal layers deposited on wafers and for a boron-implanted wafer. The sample depth was changed by sputtering with an ion beam, and the surface analysis at each depth was done by ESDMS with the ion beam off. The ion profiles by SIMS-ESDMS closely coincided with the SIMS profiles. The SIMS-ESDMS technique should be particularly useful for thin layered samples, because the signal-to-noise ratio can be improved by accumulating the ESDMS signals for as long as required without changing the sampling depth under continuous bombardment by the electron beam.