Physical mechanisms of transient enhanced dopant diffusion in ion-implanted silicon
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)
- Bell Laboratories, Lucent Technologies, Breinigsville, Pennsylvania 18031 (United States)
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) 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 (MBE). Damage from nonamorphizing Si implants at doses ranging from 5{times}10{sup 12} to 1{times}10{sup 14}/cm{sup 2} evolves into a distribution of {l_brace}311{r_brace} interstitial agglomerates during the initial annealing stages at 670{endash}815{degree}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 {l_brace}311{r_brace} defects during Ostwald ripening with an activation energy of 3.8{plus_minus}0.2 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 {approximately}3.5 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 {approximately}10{sup 19}/cm{sup 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. (Abstract Truncated)
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 496650
- Journal Information:
- Journal of Applied Physics, Vol. 81, Issue 9; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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