Quantitative secondary ion mass spectrometry analysis of the native oxide on silicon wafers

Abstract

Quantitative analysis of the native oxide on silicon wafers has been investigated by secondary ion mass spectrometry (SIMS) combined with an encapsulation method. In the encapsulation technique, the sample surface is covered with a thin film whose material is identical to that of the substrate of the sample, and the analysis of the interface between the thin film and the original sample surface is performed. This technique enables quantitative analysis of the top surface of the original sample. The present study describes the optimization of the encapsulating film thickness, the reproducibility of the oxygen determination and the oxygen enhancement effects at the interface between the encapsulation film and the original sample surface. Results indicate that the minimum encapsulating film thickness is ∽130 nm when using a 14.5 keV Cs+ primary ion beam. The highest oxygen areal density that can be determined with good accuracy at the interface between the encapsulation film and the original silicon surface was 8×1014 atoms cm-2. © 1997 John Wiley & Sons, Ltd.