The dependence of arsenic transient enhanced diffusion on the silicon substrate temperature during ultralow energy implantation

The redistribution of As during high-temperature annealing has been investi gated as a function of the Si(100) substrate temperature (-120 degrees C, 25 degrees C, and +300 degrees C) during 2.5 keV implantation (to 1.5x10(15 )atoms/cm(2)). Each implant produced a damaged near-surface region, the ext ent of which varied with implant temperature. Samples implanted at each tem perature were annealed in a nitrogen ambient with a few percent oxygen for 10 s at 550, 925, and 975 degrees C. The changes in implant damage and dopa nt distributions both prior to and following annealing were investigated us ing medium energy ion scattering and secondary ion mass spectrometry. Trans ient enhanced diffusion (TED) of the dopant was observed for all implant te mperatures after 925 degrees C annealing with the 25 degrees C implant show ing the deepest diffusion. Between 925 and 975 degrees C annealing, the As diffusion rate in the 300 degrees C exceeded that of the 25 degrees C impla nt. Significantly, the -120 degrees C implant displayed less TED of As comp ared to the higher temperature implants following annealing at 975 degrees C. The results indicate that the diffusion is affected by the nature of the post-implant damage and the high arsenic concentrations. (C) 2000 American Institute of Physics. [S0003-6951(00)03005-9].