Apparent depths of B and Ge deltas in Si as measured by secondary ion massspectrometry

The apparent depths of B and Ge deltas in Si were measured with secondary i on mass spectrometry using 1-4 keV O-2(+) beams at oblique incidence (40 de grees-80 degrees with respect to the surface normal). The real depths of th e Ge deltas were obtained via calibration against transmission electron mic roscopy (TEM). The measured centroids of the Ge delta peaks were 0.5+/-0.4 nm shallower than the red (TEM) depths, independent of angle and energy. Fo r B there was a clear angular dependency of the centroid position, but the energy dependency was virtually absent (viz., differential shift <0.2 nm/ke V/ion). Repeated analyses during a 2.5 year period showed a reproducibility in Ge delta peak position of 0.04 nm. Surprisingly, the slow but continuou s growth of the native surface oxide had no effect on the apparent Ge delta depths. The profile shift of B towards the surface was attributed to the h igh sputter rate during the surface transient and to B outdiffusion under o xygen bombardment. It was concluded that decreasing the beam energy did not reduce the B shift; the positive effect of a thinner surface transient lay er was nullified by a larger (equilibrium) oxygen concentration. In contras t, indiffusion of Ge compensated at all energies and angles the (apparent) Ge shift due to the transient high sputter rate. (C) 2000 American Vacuum S ociety. [S0734-211X(00)08702-3].