Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during initial annealing, due to Si interstitials being emitted from the region of the implant damage. The structural source of these interstitials has not previously been identified. Quantitative transmission electron microscopy measurements of extended defects are used to demonstrate that TED is caused by the emission of interstitials from specific defects. The defects are rodlike defects running along 〈110〉 directions, which consist of interstitials precipitating on {311} planes as a single monolayer of hexagonal Si. We correlate the evaporation of {311} defects during annealing at 670 and 815 °C with the length of the diffusion transient, and demonstrate a link between the number of interstitials emitted by the defects, and the flux of interstitials driving TED. Thus not only are {311} defects contributing to the interstitial flux, but the contribution attributable to {311} defect evaporation is sufficient to explain the whole of the observed transient. The {311} defects are the source of the interstitials.

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Copper centers in copper-diffused n-type silicon measured by photoluminescence and deep-level transient spectroscopy Appl. Phys. Lett. 101, 042113 (2012) Bonding and diffusion of nitrogen in the InSbN alloys fabricated by two-step ion implantation Appl. Phys. Lett. 101, 021905 (2012) Shift of Ag diffusion profiles in CdTe by metal/semiconductor interfaces Appl. Phys. Lett. 100, 171915 (2012) Diffusion of co-implanted carbon and boron in silicon and its effect on excess self-interstitials Implanted B and P dopants in Si exhibit transient enhanced diffusion ͑TED͒ during annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, transmission electron microscopy measurements of implantation damage were combined with B diffusion experiments using doping marker structures grown by molecular-beam epitaxy ͑MBE͒. Damage from nonamorphizing Si implants at doses ranging from 5ϫ10 12 to 1ϫ10 14 /cm 2 evolves into a distribution of ͕311͖ interstitial agglomerates during the initial annealing stages at 670-815°C. The excess interstitial concentration contained in these defects roughly equals the implanted ion dose, an observation that is corroborated by atomistic Monte Carlo simulations of implantation and annealing processes. The injection of interstitials from the damage region involves the dissolution of ͕311͖ defects during Ostwald ripening with an activation energy of 3.8Ϯ0.2 eV. The excess interstitials drive substitutional B into electrically inactive, metastable clusters of presumably two or three B atoms at concentrations below the solid solubility, thus explaining the generally observed immobile B peak during TED of ion-implanted B. Injected interstitials undergo retarded diffusion in the MBE-grown Si with an effective migration energy of ϳ3.5 eV, which arises from trapping at substitutional C. The concept of trap-limited diffusion provides a stepping stone for understanding the enormous disparity among published values for the interstitial diffusivity in Si. The population of excess interstitials is strongly reduced by incorporating substitutional C in Si to levels of ϳ10 19 /cm 3 prior to ion implantation. This provides a promising method for suppressing TED, thus enabling shallow junction formation in future Si devices through dopant implantation. The present insights have been implemented into a process simulator, allowing for a significant improvement of the predictive modeling of TED.

The density of amorphous Si has been measured. Multiple Si implants, at energies up to 8.0 MeV, were made through a contact mask to produce alternating amorphous/crystalline Si stripes with amorphous thicknesses up to ∼5.0 μm. For layers up to 3.4 μm (5 MeV), the amorphous Si is constrained laterally and deforms plastically. Above 5 MeV, plastic deformation of the surrounding crystal matrix is observed. Height differences between the amorphous and crystalline regions were measured for as-implanted, thermally relaxed, and partially recrystallized samples using a surface profilometer. Combined with ion channeling measurements of the layer thickness, amorphous Si was determined to be 1.8±0.1% less dense than crystalline Si (4.90×1022 atom/cm3 at 300 K). Both relaxed and unrelaxed amorphous Si show identical densities within experimental error (<0.1% density difference).