Transient enhanced diffusion and defect microstructure in high dose, low energy As+ implanted Si

Abstract

(001) CZ silicon wafers were implanted with As+ at 100 keV to a dose of 1×1015/cm2 in order to produce a continuous amorphous layer to a depth of about 120 nm. Furthermore, the implant condition was such that the peak arsenic concentration was below the arsenic clustering threshold. Subsequently, a second As+ or Ge+ implant was performed at 30 keV to doses of 2×1015/cm2, 5×1015/cm2 and 1×1016/cm2, respectively, into the as-implanted samples. All of the samples were annealed at 800 °C for 1 h. The second implant was designed to be contained within the amorphous region created by the initial implant. The second As+ implant was also designed to provide the additional arsenic needed to exceed the critical concentration for clustering at the projected range. Of the three samples with the dual As+ implant the clustering threshold was exceeded for the two 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 reached. Since arsenic and germanium are similar in mass the extent of damage created by these implants would be comparable. The implanted and annealed specimens were analyzed using secondary ion mass spectroscopy and transmission electron microscopy. The difference in the defect evolution and the transient-enhanced diffusion of arsenic beyond the end-of-range region between the As+ and Ge+ implanted and annealed samples was used to isolate the effects of arsenic clustering and precipitation. The results showed that point defects induced during clustering and/or precipitation did not contribute to the enhanced diffusion of arsenic although these defects did coalesce to form extended defects at the projected range. However, damage beyond the end-of-range region did cause enhanced diffusion of arsenic.

Comparison of arsenic diffusion in Si1−xGex formed by epitaxy and Ge+ implantation

“…Krishnamoorthy et al 10 have reported increased arsenic diffusion in silicon due to damage beyond the end of range defects created by an arsenic implant, which might explain the increased arsenic diffusion seen in our ion beam synthesized Si 1Ϫx Ge x layers. Furthermore, Jones et al 11 reported that low-temperature amorphizing implants led to dislocation loops which did not hamper the flow of interstitials across the amorphous/crystalline interface.…”

Effect of Elevated Implant Temperature on Amorphization and Activation in As-implanted Silicon-on-insulator Layers

“…For example, As concentrations (peak values of 2 x 10 21 /cm 3 for the lowest dose implant) are substantially above the expected solid solubility limit of 1-3 x 10 20 /cm 3 [5], and As clustering is non-negligible [6]. Reflectance Wavelength, nm Figure 1.…”

Thermal activation of As implanted in bulk Si and separation by implanted oxygen

“…Experiments suggest that a large fraction of electrically inactive As atoms are either in substitutional lattice sites in the form of As clusters, 11 or, for high dopant concentrations, coherent crystalline precipitates. 12,13 The latter are expected to be present both in bulk Si and SIMOX, although the clusters containing vacancies should be favored in SIMOX compared to bulk Si due to the higher vacancy concentration in this type of substrate.…”