High fluence retention of noble gases implanted in silicon

Abstract

Abstract Argon and xenon retention in silicon has been studied at implantation energies between 10 and 500 keV. The implantation distributions were determined by Rutherford backscattering. The steady state areal densities of the trapped noble gases were found to increase with increasing implantation energy. Sputtering of the implanted gas atoms limits the steady state surface concentration to about 2 at.% argon and 0.2 at.% xenon (estimated from a model calculation by introducing experimental data). The steady state peak concentrations become very large in the case of argon (maximum argon concentration (38 ± 4) at.%). At energies >100 keV the maximum areal densities of argon exceed 2 × 1017 atoms/cm2. This large impurity content results in gas agglomeration and blistering. Continuation of bombardment causes repeated formation and rupture of blisters as well as oscillations in argon content of the backing. From electron micrographs, electron microprobe analysis and talysurf measurements the thickness of the blister covers is found to be much smaller than the most probable projected range of the argon ions. All observations are consistent with the idea that formation and rupture of blisters results from the build-up of a high argon pressure. The integrated lateral stress is likely to cause blistering only indirectly in that it promotes agglomeration of the implanted gas.