Quantitative analysis of light elements (nitrogen, carbon, and oxygen) in sputtered tantalum films by Auger electron spectroscopy and secondary ion mass spectrometry (SIMS)

Abstract

The quantitative analysis of light elements (N, C, O) in sputtered tantalum films by Auger electron spectroscopy and secondary ion mass spectrometry (SIMS) via calibration with standards and electron microprobe analysis is described. The calibration standards were prepared by reactive sputtering, and the homogeneous distribution of the dopants (N, C, O) in these standards was established by SIMS and Auger in-depth profiling measurements. Although the electron microprobe could reproducibly detect the presence of low levels (< 5 at.%) of N, C, and O, the accuracy of quantitative electron microprobe measurements for these light elements in tantalum below ~5 at.% was questionable due to the lack of sufficiently accurate x-ray absorption coefficients. The accuracy of electron microprobe quantitative results above ~5 at.%, however, was estimated to be within plus or minus 10%. The analysis of nitrogen, carbon, and oxygen below ~5 at.% was accomplished by an extrapolation of the normalized Auger and SIMS data. SIMS detection limits for oxygen and carbon were in the ppM range and for nitrogen in the 0.1 at.% range depending on instrument background and amount of sample consumed. The Auger detection limits for N, C, and O were in the 0.3-0.4 at.% range.