Radiation enhanced diffusion of implanted platinum in silicon guided by helium co-implantation for arbitrary control of platinum profile

The in-diffusion of platinum into a low-doped n-type float zone silicon guided and enhanced by radiation damage produced by co-implantation of helium ions was investigated. The implantation of 1MeV platinum ions at different doses ranging from 5x1011 to 5x1012cm-2 was used to produce a finite source for platinum diffusion. Single and multiple energy implantation of helium ions with energies 7, 9, 11 and 13MeV introducing different profiles of radiation defects were applied to enhance and shape the diffusion of platinum atoms performed by 20min annealing at 725oC in vacuum. The distribution of in-diffused platinum was studied by monitoring the acceptor level of substitutional platinum Pts-/0 (EC-ET=0.23eV) by deep level transient spectroscopy. Results show that the helium co-implantation significantly enhances platinum diffusion and allows its control up to the depths of hundreds of micrometers. The resulting Pts distribution is given by the profile of radiation damage produced by helium ions while the amount of in-diffused Pts can be controlled by the dose of platinum implantation. It is also shown that an extra annealing at 685oC performed prior to helium implantation substantially increases the amount of in-diffused platinum