Papers by Keyword: Nickel Silicide

Abstract: Low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and scanning tunnelling microscopy (STM) were used to study the reactive diffusion of one monolayer of silicon deposited at room temperature onto a Ni (111) substrate. We have done isochronal and isothermal kinetics by AES, and we observed in both cases a kinetics blockage on a plateau corresponding to around one third of a silicon monolayer. STM images and LEED patterns both recorded at room temperature just after annealing, reveal formation of an ordered hexagonal superstructure corresponding probably to a two-dimensional surface silicide.

Abstract: The Diffusion and Solubility of B Implanted in δ-Ni₂Si and Nisi Layers Is Studied by SIMS. it Is Observed that both Diffusion and Solubility Are Higher in δ-Ni₂Si than Nisi. the Redistribution of B during Ni Silicidation Is Also Studied. the SIMS Profiles Show the Presence of Concentration Step in the Middle of the Final Nisi Layer. this Profile Shape Is Explained in Light of the Results Obtained in Preformed Silicides. the Proposed Model Is Supported by Redistribution Simulations that Can Reproduce the Main Features of the Profile.

Abstract: Trenched implanted vertical JFETs (TI-VJFETs) with self-aligned gate and source contacts were fabricated on commercial 4H-SiC epitaxial wafers. Gate regions were formed by aluminium implantation through the same silicon oxide mask which was used for etching mesa-structures. Self-aligned nickel silicide source and gate contacts were formed using a silicon oxide spacer formed on mesa-structure sidewalls by anisotropic thermal oxidation of silicon carbide followed by anisotropic reactive ion etching of oxide. Fabricated normally-on 4H-SiC TI-VJFETs demonstrated low gate leakage currents and blocking voltages exceeding 200 V.

Abstract: 3.3 kV rated 4H-SiC diodes with nickel monosilicide Schottky contacts and 2-zone JTE regions were fabricated on commercial epitaxial wafers having a 34 m thick blocking layer with donor concentration of 2.2×1015 cm-3. The diodes were fabricated with and without additional field stop rings to investigate the impact of practically realizable stopper rings on the diode blocking characteristics. The field stop ring was formed by reactive ion etching of heavily doped epitaxial capping layer. The diodes with field stop rings demonstrated significantly higher yield and reduction of reverse leakage current. The diodes demonstrated blocking voltages in excess of 4.0 kV and very low change of leakage current at ambient temperatures up to 200 °C.

Abstract: In this paper we demonstrate the recovery of Ohmic contacts formed on C-face 4H-SiC following high temperature post-processing. After a typical high-κ dielectric anneal in O2 for 3 minutes at 650 °C, replacing the metallization stack is revealed to significantly reduce the damage produced in the I-V characteristics. Using C-AFM we have also studied the mechanisms responsible for Ohmic contact formation, presenting a possible relationship between changes in the SiC crystal orientation and the establishment of Ohmic behaviour.

Abstract: The unique capabilities of atom probe tomography (APT) to characterize internal interfaces and layer chemistry with sub-nanometer scale resolution in three dimensions have been recently opened up to materials with poor electrical conductivity by the use of ultrafast laser pulses. The progress in sample preparation (focused ion beam) as well as in instrument performance enable now the analysis of relatively large volumes with typical diameters of 100 to 200 nm and depths of several hundred nm (this corresponds to an increase by several order of magnitude compared to the former instrument) of site specific samples. In this work, APT is used to study the effects of Pt on the formation and stability of Ni silicides. The precise location of this alloy element has been determined at the nanometer scale: In particular, APT allows us to quantify the amount of Pt in the grain boundaries (GB) of Ni2Si for about 100 different grain boundaries and thus to better characterize the GB diffusion and segregation.

Abstract: Nickel silicide/silicon/silica composite nanostructure, i.e., Ni31Si12/Si/SiO2, was synthesized successfully by a coevaporation method, using nickel formate and SiO powder as the source materials. The structure of product was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscope (HRTEM). The results indicated that the product had a rod morphology, which consisted of three parts with different morphologies and crystallographic structures. The top of the rod was a polycrystalline nickel silicide (Ni31Si12) nanoball with average diameter of 100 nm; the middle part was a single-crystal Si short rod with average diameter of 80 nm; the bottom part was an amorphous silicon oxide nanowire with average diameter of 60 nm. A possible growth mechanism of the composite nanorod was briefly discussed

Abstract: Thin Ni/Al and Ni/Ga layers of different atomic ratios were codeposited onto Si(001) at room temperature followed by subsequent annealing. Influence of annealing temperature on morphology and composition of ternary disilicide NiSi2-xAlx and NiSi2-xGax layers was investigated by transmission electron microscopy. Addition of Al or Ga leads to a decrease of the disilicide formation temperature from 700°C down to at least 500°C. Depending on the composition closed, uniformly oriented NiSi2-xAlx and NiSi2-xGax layers were observed after annealing at 900°C, whereas reaction of a pure Ni film with Si leads to the island formation with a mixture of A- and B-type orientations.

Abstract: Nickel- and Platinum-silicide nanodots with an areal density of the order of ~1011cm-2 were successfully formed on thermally-grown SiO2 through a process of ultrathin metal film formation on self-assembled Si quantum dots (QDs) on SiO2 and subsequent remote H2 plasma exposure. Chemical shifts in photoemission spectra of core lines and changes in valence band spectrum and work function value with the remote H2-plasma treatment show that silicidation of pre-grown Si-QDs is promoted by the remote H2-plasma treatment. Electrical separation among so-prepared nanodots was verified from the surface potential change after applying a dc bias between the AFM tip and the sample surface. From temporal decay in the surface potential after electron injection to the nanodots, we confirmed that silicide nanodots have superior charge retention to that of Si nanodots with almost the same size as expected in a deeper potential well for electrons in silicide dots than pure Si-QDs. In the application of silicide nanodots to a floating gate in MOS capacitors, distinct hysteresis characteristics caused by charging and discharging of several electrons per dot were verified by capacitance-voltage measurements.

Abstract: Nickel silicide Schottky contacts were formed on 4H-SiC by consecutive deposition of a titanium adhesion layer, 4 nm thick, and nickel, 100 nm thick, followed by annealing at temperatures from 600 to 750 °C. It was found that contacts with barrier heights of 1.45 eV, consisting mainly of NiSi phase, formed in the 600-660 °C temperature range, while annealing at around 750 °C led to the formation of Ni2Si phase with barrier heights of 1.1 eV. Annealing at intermediate temperatures resulted in the nucleation of Ni2Si grains embedded in the NiSi film which were directly observed by micro-Raman mapping. It was concluded that the thermodynamically unfavourable NiSi phase appeared in the 600-660 °C temperature range due to the fact that the solid state chemical reaction between Ni and SiC at these temperatures is controlled by nickel diffusion through the titanium barrier.