A systematic study of the surface roughening and sputter rate variations occurring during SIMS ultrashallow depth profile analysis of Si with Cs +

Abstract

Sputter rate variations and surface roughening occurring during the initial stages of secondary ion mass spectrometry ultrashallow depth profiling of Si with Cs + are examined for a range of primary ion incident energies (0.25–5.0 keV) and incident angles (40–80°). Sputter rate variations were derived over the 4.15–36.4 nm range through the analysis of a Boron delta layered structure. A reduction in the sputter rate with sputtering time was noted, with the variation increasing with decreasing primary ion energy and increasing incident angle. From this data set, a relation expressing these sputter rate variations as a function of the primary ion energy and incident angle was derived which, in turn, allows for depth and intensity scale corrections to be carried out. Surface roughening culminating in ripple formation was also observed using atomic force microscopy. These were observed under conditions resulting in excessive sputter rate variations.