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The stability and the evolution of electrical properties of high concentration arsenic ultra-shallow junctions in silicon have been studied with regard to their effect on the evolution of point defects. The activation of 2 keV 1 × 1015 cm-2 As implants was performed using millisecond sub-melt laser annealing at two different temperatures, 1100 and 1300 °C. The electrical deactivation upon subsequent thermal treatment at 700 °C was indirectly monitored through the diffusion of five 10 nm-wide boron layers aimed to detect the injection of self-interstitials coming from dopant clustering. Thermal treatments were repeated on samples implanted with Ge at condition similar to the As ones. The comparison helped to discriminate between interstitials coming from lattice damage evolution and dopant clustering. The results show the relevance of the laser annealing temperature in order to ensure junction stability in terms of active carrier concentration and junction depth.

The evolution of very high dose arsenic implants in silicon formed by plasma immersion ion implantation and deposition (PIIID) using a non-pulsed plasma source was studied over a time period of more than one year. The study focused on the effect of arsenolite micro-crystal formation, enhanced oxidation, and the significant As dose loss from as implanted samples at room temperature. The study was carried out combining analytical evidence from SIMS, XPS, INAA, SEM, and optical microscopy suggesting a two stage process of As dose loss, the first implying arsenolite crystal growth and the second an out-diffusion. In fact, comparison of samples fabricated using different PIIID parameters showed that crystal growth seems not to be the only process responsible for dose loss. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)