Characterization of buried cobalt silicide layers in Si by MEVVA implantation

Abstract

Buried cobalt silicide layers have been formed by high-dose Co implantation into Si with a metal vapor vacuum arc (MEVVA) ion source using an accelerating voltage of 70 kV. Annealing was performed by rapid thermal annealing at various temperatures for various time intervals. The structures of the implanted samples were studied by cross-section transmission electron microscopy and high-resolution electron microscopy observations and the electrical properties were studied by resistivity and Hall effect measurements. It is found that in the as-implanted sample a continuous CoSi 2 layer had not been formed but the surface layer contained a high density of CoSi 2 precipitates, either aligned A-type or twinned B-type. After rapid thermal annealing at 750 °C for 10 s and then at 1100 °C or 1200 °C for 5 s, a continuous buried single-crystalline CoSi 2 layer, about 60 nm thick, had been formed beneath a 40 nm Si layer. Both A-type and B-type CoSi 2 precipitates are present in the damaged layer below the buried CoSi 2 layer for the 1100 °C annealed sample. There were no precipitates in the damaged layer beneath the silicide layer for the 1200 °C annealed sample. However, some threading dislocations were observed. The temperature dependence of the resistivity of the CoSi 2 layer has been found to follow the Matthiessen's rule with similar magnitude to that reported by other researchers. However, in contrast to those reported in the literature, a surprisingly strong temperature dependence of the Hall coefficient has been observed with a large peak at about 100–110 K.