Nitrogen Implantation and Diffusion in Crystalline Germanium: Implantation Energy, Temperature and Ge Surface Protection Dependence

Abstract

In the present work nitrogen (N2+) has been implanted in crystalline germanium at a constant dose and its diffusion has been studied as a function of implantation energy, annealing temperature and various capping layers deposited on substrate surface. Nitrogen diffusion in germanium appears to be, as in the case of silicon, anomalous toward the capping layer/germanium interface not obeying the second Fick's law. In addition, it appears independent on the capping layer composition. As the implantation energy increases, characteristic nitrogen pileups appear in the region beyond the former amorphous/crystalline interface, attributed to the formation of nitrogen-Ge point defects (in particular interstitials) clusters. There is an evidence that N diffusion in Ge is related to the presence of Ge interstitials gradients maintained during post-implantation annealing between the capping layer/Ge interface and the region beyond the former amorphous/crystalline interface of the substrate. This unique diffusion behavior of N could find applications in Ge based MOS (Metal-Oxide-Semiconductor) technology as proposed in the body of the present article.

Phosphorous Diffusion in N2+-Implanted Germanium during Flash Lamp Annealing: Influence of Nitrogen on Ge Substrate Damage and Capping Layer Engineering

“…This accumulation (more intense at 850 • C) is reflected in the characteristic "kink" of Figs. 9b and 10b, and has been also observed in the case of our N monodpoing study 22 and our N/P RTA co-diffusion experiment at 550-650…”

Strong Diffusion Suppression of Low Energy-Implanted Phosphorous in Germanium by N2 Co-Implantation

“…In addition to the experimental study of N diffusion (Ref. 14), this is also supported by the studies of arsenic and phosphorous diffusion when co-implanted with fluorine in Ge. 9,18 In the later works the formation of FI clusters in the presence of an interstitial P50 ECS Solid State Letters, 4 (6) P47-P50 (2015) supersaturation at the EOR region has been verified experimentally as well as by theoretical calculations.…”

“…Consequently this hypothesis hardly justifies the EOR "kink" formation in the distributions of both species after annealing, which is also observed in the case of nitrogen (Ref. 14) but not observed in the case of phosphorous single-doping diffusion in Ge (Fig. 1).…”

“…15,16 During annealing an interstitial gradient is maintained between the EOR region and Al 2 O 3 /Ge interface, which act as a sink, being the driving force for N anomalous diffusion. 14 In parallel, nitrogen clustering with part of Ge excess interstitials prevents their absorption by the Al 2 O 3 /Ge interface and leads to the formation of the characteristic "kink" of N distribution at the EOR region.…”

“…14 The nitrogen profile within the former amorphous Ge layer remains almost immobile, which lead to a constant dose loss of ∼ 10% for all temperatures examined.…”