Reduction of boride enhanced diffusion in MeV-implanted silicon

Abstract

We demonstrated that implantation of MeV Si ions into a Si substrate can suppress boride-enhanced diffusion (BED) normally associated with a high B concentration layer. In this study, a molecular-beam-epitaxy grown Si layer with a B concentration of 1021/cm3 over a 10 nm region capped with 100 nm Si was used as a source of BED. A sequence of four B delta-doped layers with 100 nm Si spacers was grown prior to the source layer to monitor the diffusion. Half of the sample was implanted with 1 MeV Si ions at a dose of 1016/cm2, followed by annealing at 800, 900, and 1000 °C for different periods of time. For control samples without the MeV Si implant, BED was observed with enhancements of around 40 while the MeV Si-implanted sample showed a reduced, yet nonvanishing, BED with an enhancement of around 8 after annealing at 800 °C for 1 h. Both BED and suppressed BED with MeV implant show transient behavior with decay after annealing for long periods of time. The effect of high energy implant on B diffusion from surface deposited B layer was also discussed.