Dwell-time dependence of the defect accumulation in focused ion beam synthesis of CoSi2

Cobalt disilicide microstructures were formed by 70 keV Co2+ focused ion be am implantation into Si(111) at substrate temperatures of about 400 degrees C and a subsequent two step annealing (600 degrees C, 60 min and 1000 degr ees C, 30 min in N-2). It was found that the CoSi2 layer quality strongly d epends on the pixel dwell time and the implantation temperature. Only for p roperly chosen parameters continuous CoSi2 layers could be obtained. Scanni ng electron microscopy and Rutherford backscattering/channelling investigat ions were carried out combined with a special preparation technique for str uctures which are smaller than the analysing beam. The quality of the CoSi2 layers which is correlated to the damage was investigated as a function of dwell-time (1-250 mu s) and target temperature (355-415 degrees C). The re sults show that the irradiation damage increases with the dwell-time. The S i top layer was amorphized for longer dwell-times although the substrate te mperature was always above the critical temperature for amorphization of ab out 270 degrees C according to the model of Morehead and Crowder. For the h igh current density of a focused ion beam (1-10 A/cm(2)) the damage creatio n rate is higher than the rate of dynamic annealing. (C) 1999 Elsevier Scie nce B.V. All rights reserved.