CHARACTERIZATION OF NI ON SI WAFERS - COMPARISON OF SURFACE-ANALYSIS TECHNIQUES

The need for improved characterization of materials used in the fabrication of semiconductor devices has been driven by the semiconductor industry's desire to increase device densities on substrate. This need is reflected in the analytical surface science community by efforts to develop methods for detection of trace impurities on semiconductor substrates at extremely low levels. With improvements in standard techniques continually occurring, and with new methods of trace analysis always being developed, it is important to assess the relative abilities of the suite of surface analysis techniques available for materials characterization and to develop well-characterized standard samples for these comparisons. This paper reports on a collaborative effort to review the capabilities of several approaches to trace surface analysis. As a test case, Ni contamination of Si wafers in the dose range 10(14)-10(10) cm-2 has been chosen. The emphasis of this paper will be on the capabilities of SARISA (surface analysis by resonant ionization of sputtered atoms) as an example of laser post-ionization secondary neutral mass spectrometry for the detection of contaminants in the near-surface region. Results on analyses of the same standard samples by other techniques will also be presented. These techniques include total reflection x-ray fluorescence and heavy ion backscattering spectrometry. The results of this comparison show that there are several techniques that can accurately determine metal contaminations on Si wafers in this concentration range and that the method of choice depends on other considerations, such as speed or accuracy of analysis.