TRANSIENT ENHANCED DIFFUSION FROM DECABORANE MOLECULAR ION-IMPLANTATION

Transient enhanced diffusion (TED) from implantation of 5 keV B10H14 a nd 0.5 keV B ions has been quantified and compared for nominal boron d oses of 10(14) and 10(15) cm(-2). Boron diffusivity during annealing w as extracted from secondary ion mass spectroscopy depth profiles of di ffused marker layers in boron doping-superlattices and the actual impl anted B dose was independently measured by nuclear reaction analysis. Comparable enhancements were observed from both ions. Transmission ele ctron microscopy analysis revealed that both boron- and decaborane-imp lanted samples were amorphized at a nominal 10(15) cm(-2) B dose. A co mparison with data from low energy Si implants revealed a similar depe ndence of diffusivity enhancement on implant dose. These findings are consistent with the understanding that TED is caused by the interstiti al supersaturation resulting from a number of excess interstitials app roximately equal to the number of implanted atoms which can become sub stitutional in the silicon lattice. Accordingly, no contribution to TE D is expected from the hydrogen in the B10H14 ions and none is observe d. Furthermore, there is no detectable effect in the diffusion profile s which can be attributed to a difference in the ion damage produced b y the decaborane molecule and the boron atom. In both cases the reduct ion in diffusivity enhancement is due only to proximity of the implant ation-induced excess interstitials to the wafer surface. (C) 1998 Amer ican Institute of Physics. [S0003-6951(98)04240-5].