ION-INDUCED TOPOGRAPHY, DEPTH RESOLUTION, AND ION YIELD DURING SECONDARY ION MASS-SPECTROMETRY DEPTH PROFILING OF A GAAS/ALGAAS SUPERLATTICE - EFFECTS OF SAMPLE ROTATION

Effects of sample rotation and sputtering conditions on the depth resolution and ion yield during secondary ion mass spectrometry (SIMS) sputter depth profiles have been studied on bulk GaAs and a GaAs (5 nm)/Al0.3Ga0.7As(5 nm) superlatice. Profiles without sample rotation with 1.0-7.0 keV O2+ show a rapid degradation of the depth resolution with increasing sputter depth. Profiles with Ar+ show only slight degradation. Scanning electron microscope (SEM) studies indicate that degradation is associated with development of periodic surface ripples. The wavelength of the ripples is energy dependent and increases with increasing ion impact energy. With sample rotation, no degradation of the depth resolution is observed and SEM micrographs indicate that surfaces sputtered with rotation are smooth. In addition, with 3.0 keV O2+ significant changes in the secondary ion yield of AsO+ from bulk GaAs are observed at a depth of approximately 200 nm. No changes are observed with sample rotation. Our results demonstrate that sample rotation during SIMS depth profiling prevents and can reverse the development of surface topography that both degrades depth resolution and changes secondary ion yield. Thus, interpretation and quantitation of SIMS analysis is facilitated.