Applied Surface Science, Vol.179, No.1-4, 30-37, 2001
Depth profiling of electrically non-conductive layered samples by RF-GDOES and HFM plasma SNMS
The work is intended to compare the capabilities of two similar depth profiling techniques to analyse electrically nonconductive samples. In order to get a better evaluation of the depth resolution, various multilayer sandwiches, such as SiO2/ TiO2 and Si3N4/SiO2 deposited on glass substrates have been investigated. Optimised depth profiles are presented for both methods, glow discharge optical emission spectrometry (GDOES) and radiofrequency mode (known as "HFM" in the SNMS literature) of plasma secondary neutral mass spectrometry (SNMS). The optimisation procedure, necessary to get the best set of plasma parameters, which result in the optimal depth resolution, is also described for one selected sample. Additionally, sputtering crater profilometry was carried out in order to check out the flatness of the sputtered crater. The influence of the thickness of the sample substrate on the sputtering rate is discussed. Finally, advantages and disadvantages of the use of these two depth profiling methods, especially for the non-conductive samples, are concluded from this comparative study. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of a cross-sectioned sample was carried out in order to get supplementary information.
Keywords:rf-glow discharge;HFM plasma SNMS;non-conductive layered samples;depth resolution;crater shape;ToF-SIMS