Proximity gettering of platinum in silicon following implantation with alpha particles at low doses

Platinum has been diffused into epitaxial n-type silicon at 600, 650, and 7 00 degrees C for 30 min following implantation with 3.3 MeV alpha particles . The doses employed were between 1 x 10(11) and 1 x 10(14) He+ cm(-2). The reafter the samples were characterised using DLTS (deep level transient spe ctroscopy). The samples diffused at 700 degrees C show only the deep level at 0.23 eV below the conduction band that is attributed to substitutional p latinum. DLTS profiling reveals a decoration of the region of maximal damag e by the platinum for lower doses while for higher ones the platinum concen tration is observed to decrease or vanish in this region. In addition, othe r deep levels may appear (so-called K-lines). As the implantation dose incr eases, so does the platinum concentration following diffusion at 700 degree s C at the shallow end of the DLTS working region. It is shown that by cont rolling the amount of implantation induced defects and the diffusion temper ature one can steer the amount of platinum that arrives in the region of ma ximal damage. The stability of the defect decoration has also been studied by varying the diffusion times at 700 degrees C from 10 to 50 min. For diff usion times longer than 30 min a reduction in the maximum platinum concentr ation is observed. It is assumed that the platinum diffuses further into th e bulk. (C) 2000 Elsevier Science S.A. All rights reserved.