Czochralski-type (001) wafers were implanted with 100keV As+ to a dose of 1015/cm2 in order to produce a continuous amorphous layer which extended to a depth of about 120nm. The implantation conditions were such that the peak As concentration was below the As clustering threshold. A second As+ or Ge+ implantation was then performed at 30keV, to doses of 2 x 1011, 5 x 1015 and 1016/cm2. All of the samples were annealed at 800C for 1h. The second implant was designed to be contained within the amorphous region which was created by the first implant. The second As+ implant was also designed to provide the additional As which was required to exceed the critical concentration for clustering at the projected range. Of the 3 samples with dual As+ implants, the clustering threshold was exceeded for the 2 lower doses, while the SiAs precipitation threshold was exceeded at the highest dose. In the case of the dual As+/Ge+ implants, the clustering and precipitation thresholds were not attained. Because the As and Ge were similar in mass, the extent of damage created by them was comparable. The implanted and annealed specimens were analyzed by using secondary-ion mass spectroscopy and transmission electron microscopy. The differences in defect evolution and transient-enhanced As diffusion, beyond the end-of-range region between As+ and Ge+ implanted and annealed samples, was used to isolate the effects of As clustering and precipitation. The results showed that point defects which were introduced during clustering and/or precipitation did not contribute to the enhanced As diffusion; although these defects coalesced to form extended defects at the projected range. Damage beyond the end-of-range region nevertheless caused enhanced As diffusion.

Transient Enhanced Diffusion and Defect Microstructure in High-Dose, Low-Energy As+-Implanted Si. V.Krishnamoorthy, K.Moller, K.S.Jones, D.Venables, J.Jackson, L.Rubin: Journal of Applied Physics, 1998, 84[11], 5997-6002