Transient effects in SIMS analysis of Si with Cs + at high incidence angles: Secondary ion yield variations

Abstract

Secondary ion mass spectrometry (SIMS) depth profile analysis of Si wafers using 1 keV Cs + primary ions at large incidence angles (80°) is plagued by unusually strong transient effects (variations in both sputter and ion yields). Analysis of a native oxide terminated Si wafer with and without the aid of an O 2 leak, and an Ar + pre-sputtered wafer revealed correlations between the implanted Cs content and various secondary ion intensities consistent with that expected from a resonance charge transfer process (that assumed by the electron tunneling model). Cs concentrations were defined through X-ray photoelectron spectroscopy of the sputtered surface from SIMS profiles terminated within the transient region. These scaled with the surface roughening occurring under these conditions and can be explained as resulting from the associated drop in sputter rates. An O induced transient effect from the native oxide was also identified. Characterization of these effects allowed the reconstruction of the XPS derived Cs concentration profiles, which in turn, allowed enhancement effects resulting from O and Cs to be approximated.