Quantitative trace metal analysis of silicon surfaces by ToF-SIMS

Volumetric relative sensitivity factors (RSFs) are determined for Cr-52, Fe-56 and Ni-58 in an O-2(+)-formed silicon oxide using a 12 keV Ga+ primary ion beam, and the influence of matrix oxygen content on these RSF values is evaluated. A multivariate expression for Si-2(+)-referenced RSP values as a function of oxygen content is developed. This expression indicates that 12 keV Ga+ ion beam RSF values for Cr-52, Fe-56 and Ni-58 in O-2(+)-formed oxide at 1.0 nm depth are in excellent agreement with well-established 8 keV O-2(+) RSF values in a silicon matrix. Because calculated RSF values for O-2(+)-formed oxide at 1.0 nm depth and native silicon oxide are almost equivalent, time-of-flight (ToF) SIMS metal RSF values and detection limits in native oxide for a Ga+ liquid metal ion source are predicted, using the well-established 8 keV O-2(+) RSF values for metals in a silicon matrix. Time-of-flight SIMS silicon surface detection limits of 5 x 10(6) to 5 x 10(8) atoms cm(-2) @ 0.5 nm are predicted for most metals of interest to the semiconductor community. (C) 1998 John Wiley & Sons, Ltd.