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 beam 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 degrees C, 30 min in N-2). It was found that the CoSi2 layer quality strongly depends on the pixel dwell time and the implantation temperature. Only for properly chosen parameters continuous CoSi2 layers could be obtained. Scanning electron microscopy and Rutherford backscattering/channelling investigations were carried out combined with a special preparation technique for structures 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 results show that the irradiation damage increases with the dwell-time. The Si top layer was amorphized for longer dwell-times although the substrate temperature was always above the critical temperature for amorphization of about 270 degrees C according to the model of Morehead and Crowder. For the high current density of a focused ion beam (1-10 A/cm(2)) the damage creation rate is higher than the rate of dynamic annealing. (C) 1999 Elsevier Science B.V. All rights reserved.