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 roduced by co-implantation of helium ions was investigated. The implantation of 1 MeV platinum ions at different doses ranging from 5 x 10(11) to 5 x 10(12) cm(-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 13 MeV introducing different profiles of radiation defects were applied to enhance and shape the diffusion of platinum atoms performed by 20 min annealing at 725 degrees C in vacuum, The distribution of in-diffused platinum was studied by monitoring the acceptor level of substitutional platinum Pt-s(-0) (E-C - E-T- = 0.23 eV) 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 Pt-s distribution is given by the profile of radiation damage produced by helium ions while the amount of in-diffused Pt-s, can be controlled by the dose of platinum implantation. It is also shown that all extra annealing at 685 degrees C performed prior to helium implantation substantially increases the amount of ill-diffused platinum. (c) 2004 Elsevier B.V. All rights reserved.