A SIMS STUDY OF THE ALTERED LAYER IN SI USING O-18(2) PRIMARIES AT VARIOUS ANGLES OF INCIDENCE

The phenomenon of impurity segregation in Si under oxygen bombardment is closely linked with the formation of an oxidized altered layer in t he near surface region. O-2(18) isotopes have beenused to study the ev olution of the altered layer. Si was bombarded with a 14 keV O-2+(18) beam at various angles from normal incidence to 60-degrees in 5-degree s increments. The crater bases were subsequently depth-profiled using a 3 keV Xe+ beam to reveal the oxygen distribution. The layers produce d from normal to 20-degrees incidence beam appeared to be completely o xidized. The thickness of the layer remained constant from normal to 1 0-degrees and then decreased slightly. Above 20-degrees, however, the altered layer appeared not to be fully oxidized and the oxygen content decreased with increasing angle. It was possible to correlate the shr inking thickness of the oxide layer, and subsequently the substoichiom etric oxygen content at more oblique angles, with a reduction in the a mount of diffusional oxygen available, which is governed by the sputte r rate.