Predictive simulation of transient activation processes in boron-doped silicon structures

Abstract

A physically-based continuum diffusiodclustering model has been applied to the simulation of transient activationheactivation of ion implanted boron. This work is aimed at the optimization and development of post-implant thermal cycles for minimal dopant diffusion with peak activation. This model has been successfully applied to the simulation of several new structures exhibiting partial deactivation of the implanted boron.source/drain regions of MOS devices. Further work with this full cluster system has shown , for a range of conditions, that several of the boron cluster species are in or near equilibrium with one another. This observation has allowed for the reduction of the full system to a system of three different boron clusters, while still maintaining virtually all of the physics inherent to this modeling approach. Details of these systems are shown in Figures 2 and 3. This reduced version of the model incorporating charge state effects is shown capable of accurately modeling diffusion and activation over a range of boron concentrations and anneal temperatures.

Diffusion of Boron near Projected Ranges of B and BF2 Ions Implanted in Silicon

“…The peak profile of 11 B remains almost intact and TED produces the diffusion tail of 11 B. 10 B is demonstrated to diffuse from the bulk into the region of immobile 11 B. However, only a minor increase in 10 B concentration is shown around the immobile peak of 11 B, where a significant 10 B uphill diffusion occurs at 850 C. This implies that 10 B TED around the peak region of 11 B is retarded.…”

“…Interestingly, the TED of 10 B is significant between the diffusion tail and projected range of 11 B, where the diffusion of 11 B is almost invisible. On the basis of published studies, 9,10) the clustering of boron with interstitials determines the concentration of mobile 11 B. Accordingly, the accumulation of 10 B in front of the 11 B diffusion tail in fact indicates the formation of BICs.…”

“…11 B þ implantation caused 10 B accumulation between the tail diffusion region and projected range of 11 B at 750 C. The retardation of TED was also observed near the projected range of the implanted 11 B. The 10 B accumulation in front of the 11 B diffusion tail revealed a band of BICs because it disappeared at 850 C. For samples implanted with BF 2 þ , BIC formation was suppressed near the EOR region because only a peak of 10 B was observed at the EOR dislocations. The surface proximity effect reduced the density of EOR dislocations at low BF 2 þ energies.…”

Process modeling for future technologies

“…As the defects recombine and cluster, they can also interact with dopants. Dopants can form mobile defect-dopant pairs or immobile higher-order clusters [21][22][23][24][25][26]. All of these interactions can create a vastly complex system, with a large number of reaction rates, binding energies, and diffusivities that have to be parameterized.…”

A Simplified Picture for Transient Enhanced Diffusion of Boron in Silicon

“…There have been several attempts in the literature to develop a comprehensive physical picture for TED, [2][3][4][5] and such attempts have been incorporated into various widely used profile simulators. 6 However, the existing models suffer important deficiencies.…”