Alpha-ERDA analysis of the energy distribution of oxygen ions implanted into silicon with plasma immersion ion implantation

Plasma immersion ion implantation was used to implant
oxygen ions into silicon with applied voltage pulses of -40 kV and 2.5
ms lenght. Positive ions, O2+ and O+, with a continuous energy distribution
between 0 and 40 keV were implanted. Between 3x104 and 3x105 pulses, corresponding
to nominal doses from 2x1016 to 2x1017/cm2 were used. The resulting oxygen
depth profiles were measured with elastic recoil detection analysis (ERDA)
using 13.4 MeV a particles. Rutherford backscattering was used to determine
possible co-implanted contaminations. The obtained depth profiles were
simulated using a linear supersposition of calculated single-energy profiles.
The results obtained for the energy distribution of the incident ions are
compared with calculations obtained from a theoretical model, and the agreement
is very good. The incident flux is found to be composed of 34(5)% O2+ and
66(5)% O+ ions with an Fe contamination of ca. 0.5%.