The surface transient in Si for SIMS with oblique low-energy O-2(+) beams

The surface transient in Si and SiGe for secondary ion mass spectrometry (S IMS) analysis with low-energy and obliquely incident O-2(+) beams was studi ed. In particular, the transition width (z(tr), the depth at which equilibr ium secondary Si+ intensity was reached) was measured for various impact en ergies (0.56 keV less than or equal to E-p less than or equal to 2 keV) and incidence angle (45 degrees < theta < 77 degrees to the surface normal). F or E-p < 700 eV and theta > 60 degrees, the transition widths for relativel y fresh surfaces were 3-4 nm, offering good conditions for ultra-shallow SI MS analysis. At E-p = 1 keV and theta = 60 degrees, the differences in z(tr ) between various secondary ions (Si+, SiO+, Ge+ and GeO+) were marginal an d only O+ and Si-2(+) ions reached equilibrium significantly earlier. We fo und that z(tr) is about twice the mean penetration depth of the primary ion s. In addition, the thickness of the native oxide of Si wafers was measured as a function of the storage time in air. It varied from 0.6 nm after 1 day t o 1.5 nm after 2 Sears. Copyright (C) 1999 John Wiley & Sons, Ltd.