CHARACTERIZATION OF BURIED COBALT SILICIDE LAYERS IN SI BY MEVVA IMPLANTATION

Buried cobalt silicide layers have been formed by high-dose Co implant ation into Si with a metal vapor vacuum are (MEVVA) ion source using a n accelerating voltage of 70 kV. Annealing was performed by rapid ther mal annealing at various temperatures for various time intervals. The structures of the implanted samples were studied by cross-section tran smission electron microscopy and high-resolution electron microscopy o bservations and the electrical properties were studied by resistivity and Hall effect measurements. It is found that in the as-implanted sam ple a continuous CoSi2 layer had not been formed but the surface layer contained a high density of CoSi2 precipitates, either aligned A-type or twinned B-type. After rapid thermal annealing at 750 degrees C for 10 s and then at 1100 degrees C or 1200 degrees C for 5 s, a continuo us buried single-crystalline CoSi2 layer, about 60 nm thick, had been formed beneath a 40 nm Si layer. Both A-type and B-type CoSi2 precipit ates are present in the damaged layer below the buried CoSi2 layer for the 1100 degrees C annealed sample. There were no precipitates in the damaged layer beneath the silicide layer for the 1200 degrees C annea led sample. However, some threading dislocations were observed. The te mperature dependence of the resistivity of the CoSi2 layer has been fo und to follow the Matthiessen's rule with similar magnitude to that re ported by other researchers. However, in contrast to those reported in the literature, a surprisingly strong temperature dependence of the f lail coefficient has been observed with a large peak at about 100-110 K.