Schematics showing the process of forming NiSi/n-Si contact devices (a) without and (b) with (NH4)2S treatment. 15 nm of nickel was deposited and annealed for 30 s at 450 °C in N2 ambient after the treatment. This formed nickel monosilicide (NiSi) for both contact devices.
(a) X-ray diffraction (XRD) phase analysis of nickel-silicided samples that were treated with (NH4)2S solution prior to nickel deposition. A general area detector diffraction system (GADDS) equipped with a two-dimensional (2D) detector and Cu Kα radiation (λ = 0.15418 nm) was used. (b) 2D Debye diffraction rings with uniformly distributed intensity indicate a polycrystalline film with randomly orientated mono-nickel silicide grains that correspond to NiSi (002), (111), (112), (202), (103), and (013) lattice planes.
(a) Sheet resistance of nickel silicide films as a function of annealing temperatures for blanket samples with and without 1 h of pre-silicide (NH4)2S treatment. (b) Secondary ion mass spectroscopy (SIMS) analysis of blanket samples with and without pre-silicide (NH4)2S treatment. The inset shows an obvious segregation of S at the NiSi/Si junction for the blanket sample that received 20 min of heated sulfide treatment.
(a) Low magnification and (b) high magnification transmission electron microscopy (TEM) images of the nickel silicide film annealed for 30 s at 450 °C and which received (NH4)2S pre-silicide treatment.
(a) Current-voltage (I-V) characteristics of contact devices with and without 1 h of room temperature (NH4)2S treatment prior to nickel deposition. (b) Multi-temperature current-voltage (I-V) characteristics of a NiSi/Si contact device which received 1 hour of room temperature (NH4)2S treatment prior to nickel silicidation.
Richardson plot for the extraction of the effective electron Schottky barrier height for the contact device that received 1 h of room temperature pre-silicide (NH4)2S treatment.
Cumulative distribution plot of Is for contact devices with and without 1 h of pre-silicide (NH4)2S treatment at room temperature.
(a) Current-voltage (I-V) characteristics of contact devices with and without 20 min of pre-silicide (NH4)2S treatment heated at 60 °C. (b) Box plots of Is for contact devices with and without (NH4)2S treatment.
Energy band diagrams of the NiSi/Si contact devices (a) without and (b) with S donor-like traps in the depletion region. The trap level (Et ) is at 0.275 eV below the conduction band, VR is the applied reverse bias, EF , EC, and EV are the Fermi energy level, conduction, and valence band edge, respectively. For the sulfide-treated junction, thermionic emission (TE), generation (G), and trap-assisted tunneling (TAT) mechanisms may participate in the carrier transport under reverse bias.
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