Kinetics and Structure of Nickelide Contact Formation to Ingaas Fin Channels

The InGaAs high mobility channels are vowed as serious candidates for alternative channel materials for sub-10 nm technology nodes urging studies for analogous contacts to the dominant silicide contacts in the Si technology mainstream. The Ni-InGaAs (nickelide) contact technology has been demonstrated as a suitable self-aligned contact technology for InGaAs channels with record small specific contact resistivity. However, the majority studies on nickelide contact formation were conducted on planar InGaAs films and little studies focused on the contact metallurgy specific in nanoscale InGaAs nanowire or Fin channels. Here, we utilized a novel wafer bonding technique to transfer thin (50 nm) In_0.53Ga_0.47As layers onto SiO₂/Si substrates and Si transmission electron microscopy (TEM) frames. InGaAs Fins with variable widths, lengths, and orientations were fabricated through a combination of electron-beam lithography and top-down dry etching steps, followed by Ni contact deposition. Rapid thermal annealing and in-situ TEM thermal heating cycles were conducted to react Ni with the InGaAs channel and deduce the reaction kinetics, dynamics, and resultant nickelide and interface structures. We observed sharp and abrupt nickelide-InGaAs interfaces for Fin channels narrower than 250 nm whereas for wider Fins, multiple interfaces evolve due to multiple nickelide layer nucleation event per interface. A faster reaction rate for [100] oriented Fins was observed when compared with [110] oriented ones. When a simple analytical treatment is applied to the Fin geometry, the nickelide length was found to have a square root dependence of inverse channel width and inverse channel height, in excellent agreement with experimental data. From this dependency, we extracted a surface diffusion coefficient of 1.2x10^-15 ~ 2.6x10^-15 m²/s at a reaction temperature of 250 °C, which is 4-5 times larger than the extracted Fin ‘body’ diffusion coefficient. These results will be contrasted with those obtained for silicide reaction with Si nanowires, and the detailed structure, interface and reaction dynamics will be discussed.