Depth resolution in sputter depth profiling-characterization of a third batch of tantalum pentoxide on tantalum certified reference material by AES and SIMS
✍ Scribed by Seah, M. P.; Spencer, S. J.; Gilmore, I. S.; Johnstone, J. E.
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 318 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0142-2421
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✦ Synopsis
Depth profiles have been made for a new batch of the certified reference material, BCR 261, of ~30 nm and 100 nm of anodic tantalum pentoxide layers on tantalum foil. Atomic force microscopy studies show that the preparation method traditionally used provides an excellent substrate root-mean-square (rms) smoothness of 1.5 Å. This goes part of the way to explain the exceptionally good interface resolutions readily obtained with this material using AES. Further AES measurements, in the pulse counting mode, show that the same excellent depth resolution is obtained as previously (1.6 nm at 100 nm depth). Interestingly, the background of inelastic primary electrons under the oxygen peak increased with a characteristic length of only 4.0 nm at the interface for a 5 keV electron beam. Measurement of the ion-induced emission at the oxygen Auger electron energy, or in a broad range around this energy, shows that this signal can be used to monitor the ion beam stability and the presence of the oxide without the electron beam, although the signal levels are smaller than for AES. This emission is attributed to O -ions being detected through the electron spectrometer. Measurements using time-of-flight SIMS with a 12 keV Ga Y beam for analysis and 2 keV Ar Y or SF 5 Y beams for depth profiling show that the material may be used to characterize aspects of SIMS instrumental performance, in addition to AES and XPS, at a very high level of quality. The optimum interface resolutions obtained are better than 1.0 nm, with trailing edge decay lengths down to 0.33 nm. The use of molecular ions gives excellent depth resolution, comparable to the 0.8 nm depth resolution of AES at its best.