DEPTH PROFILING BY COMBINED SIMS-ESDMS ANALYSIS - A NEW SURFACE ANALYTICAL TECHNIQUE

Electron-stimulated desorption mass spectrometry (ESDMS), a new techni que based on the mass analysis of ions desorbed by a high-energy (seve ral keV) electron beam, has analytical features that complement SIMS. The ESDMS has high sensitivity in the surface analysis of both adsorba tes and the first one or two monolayers of substrate constituents. The variations in ESDMS signal intensities and in the sampling surface de pth with time were negligible even in a one-monolayer sample. Using th is combined SIMS-ESDMS technique, depth profiling analysis was perform ed for several different metal layers deposited on wafers and for a bo ron-implanted wafer. The sample depth was changed by sputtering with a n ion beam, and the surface analysis at each depth was done by ESDMS w ith the ion beam off. The ion profiles by SIMS-ESDMS closely coincided with the SIMS profiles. The SIMS-ESDMS technique should be particular ly useful for thin layered samples, because the signal-to-noise ratio can be improved by accumulating the ESDMS signals for as long as requi red without changing the sampling depth under continuous bombardment b y the electron beam. (C) 1997 by John Wiley & Sons, Ltd.