Molecular dynamics simulation of the regrowth of nanometric multigate Si devices

Abstract

We use molecular dynamics (MD) simulation techniques to study the regrowth of nanometric multigate Si devices, such as fins and nanowires, surrounded by free surfaces and interfaces with amorphous material. Our results indicate that atoms in amorphous regions close to lateral free surfaces or interfaces rearrange at a slower rate compared to those in bulk due to the discontinuity of the lateral crystalline template. Consequently, the recrystallization front which advances faster in the device center than at the interfaces adopts new orientations. Regrowth then proceeds depending on the particular orientation of the new amorphous/crystal interfaces. In the particular case of (110) oriented fins, the new amorphous/crystal interfaces are aligned along the (111) direction, which produces frequent twining during further regrowth. Based on our simulation results, we propose alternatives to overcome this defected recrystallization in multigate structures: device orientation along (100) to prevent the formation of limiting {111} I amorphous/crystal interfaces and presence of a crystalline seed along the device body to favor regrowth perpendicular to the lateral surfaces/interfaces rather than parallel to them. (C) 2012 American Institute of Physics. [doi :10.1063/1.3679126

Improved physical models for advanced silicon device processing

“…CMD simulations have reproduced the observed experimental behavior regarding the defected recrystallization of FinFET structures in Si [102], as shown in Fig. 8.…”

“…Stresses can be externally generated or appear as a result of the 2% volume expansion of amorphous Si with respect to crystal Si [108]. CMD simulations have shown that the anisotropic regrowth of the amorphous phase in thin film layers results in twin defects [102,109,110], and that when significant strains are present, a slow-down in zones with high shear strain produces the evolution of ledges that collapse and evolve into Frank partial loops [111].…”

“…5. This retardation of IV pair recombination near free surfaces causes the formation of twin defects in FinFET devices [87,102]. with more compact structures [103,104].…”

Visualising discrete structural transformations in germanium nanowires during ion beam irradiation and subsequent annealing

“…This is in full agreement with the molecular dynamics simulations obtained for Si nanowires. 27 These two processes result in formation of (111) stacking fault defects as well as epitaxial recovery of the rest of the nanowire including preexisting defects. The fact that the majority of the newly formed stacking faults are pinned to the nanowire surface suggests that the surface plays a predominant role in defect formation.…”

“…26 In comparison to planar substrates, it has already been predicted by molecular dynamics simulations that the recrystallisation process in nanowires can be largely influenced by the presence of interfaces which propagate the formation of stacking fault defects. 27 Simulations of the defect dynamics have also shown that such defects are pinned at the nanowire surface and can be a result of overlapping growth fronts.…”