Thermal desorption measurements were performed on (100)-oriented p-type wafers which had been implanted with 20keV He ions. The doses were chosen so as to produce crystal damage, while avoiding the formation of detectable bubbles. The He effusion kinetics, studied under both isothermal and constant heating-rate conditions, exhibited an effective activation energy heterogeneity which indicated the presence of various types of trap which were precursors of bubbles. The energy distribution data peaked at about 1.1eV, with an exponential decay towards higher energies and a width of about 0.2eV. A semi-quantitative mode was proposed which was based upon current understanding of the Si-He system. This accounted for He-filled nano-blister formation via interstitial He clustering and precipitation. The observed energy heterogeneity was attributed to variations in the He solution energy from these cavities, due to He-He and He-wall interactions.

Helium in Silicon - Thermal-Desorption Investigation of Bubble Precursors. F.Corni, C.Nobili, G.Ottaviani, R.Tonini, G.Calzolari, G.F.Cerofolini, G.Queirolo: Physical Review B, 1997, 56[12], 7331-8