Papers by Keyword: Nickel Silicide

Abstract: A comparison between self-aligned process (using lift-off) and Ni-SALICIDE used in fabrication of ohmic contacts for SiC Power MOSFET is done. Both processes are demonstrated for 3.3 kV SiC VDMOS transistors fabricated on 100 mm substrates. It is shown that the Ni-SALICIDE process with first silicidation at 500 °C does not degrade the electrical properties of silicon dioxide; particularly, a degradation of the interlayer dielectric between source and gate is not evident. Additionally, this first silicidation is found to have a positive impact on the specific resistance of contacts formed on p-type SiC using NiAl2.6% as an ohmic metal.

Abstract: In this work, we demonstrate the possibility to achieve an ohmic contact using a low thermal budget applicable to backside processing after wafer thinning. The process window for laser annealing as a function of the thinning process is investigated. By laser melt annealing, we demonstrate the possibility for different silicide phases from pure nickel deposition on thinned 4H-SiC, formation of uniform carbon nanoclusters at the metal/SiC interface and recovery of thinning-induced defects. This has been demonstrated as a function of different thinning process and surface conditions.

Abstract: Ultraviolet (UV) monitoring is of great interest in the healthcare field to prevent excessive UV exposure risks. In the last years silicon carbide (SiC) has emerged as a suitable material for the fabrication of UV detectors. In this paper we propose a 4H-SiC Schottky photodiode with a continuous very thin Ni₂Si layer operating at 0V, properly designed for UV radiation monitoring.

Abstract: Ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performance. Ohmic contacts often require annealing under vacuum at over 1000 °C, whilst high-κ dielectrics are usually annealed in O₂ rich ambient at temperatures of 800 °C or less, affecting the specific contact resistivity (ρ_C) and RMS surface roughness. Therefore, protection of the Ohmic contacts during the annealing of a high-κ dielectric layer is a key enabling step in the realisation of high performance MOSFET structures. In order to prevent damage during the high-κ formation, a passivation layer capable of protecting the contacts during annealing is required. In this work we have investigated the suitability of PECVD silicon nitride as a passivation layer to protect Ohmic contacts during high temperature, oxygen rich annealing.

Abstract: This work presents experimental evidence of the formation mechanisms of few-layer graphene (FLG) films on SiC by nickel silicidation. FLG is formed by annealing of a 40 nm thick Ni layer on 6H-SiC at 1035^ºC for 60 s, resulting in a Ni₂Si layer which may be capped by any Ni that did not react during annealing. It has been proposed that FLG forms on top of the Ni during the high temperature stage. In contrast, during cooling, carbon atoms which were released during the silicidation reaction may diffuse back towards the Ni₂Si/SiC interface to form a second FLG film. After annealing, layer-by-layer de-processing was carried out in order to unequivocally identify the FLG at each location using Atomic force microscopy (AFM) and Raman spectroscopy.

Abstract: In this paper, Ni-silicide formed by co-sputtering of Ni and Ti on a boron cluster (BF₂, B₁₈H₂₂) implanted ultra-shallow source/drain for MOSFET (metal oxide semiconductor field effect transistor) is proposed. Ni and Ti with a TiN capping layer were deposited by co-sputtering on boron cluster implanted wafer. By analysis of its sheet resistance, interfacial structures, surface morphological stability, and phase formation after post-silicidation annealing, thermal stability of Ni-silicide was found to be improved a lot.

Abstract: Few-layers graphene films (FLG) were grown by local solid phase epitaxy on a semi-insulating 6H-SiC substrate by annealing Ni films deposited on the Si and C-terminated faces of the SiC. The impact of the annealing process on the final quality of the FLG films is studied using Raman spectroscopy. X-ray photoelectron spectroscopy was used to verify the presence of graphene on the sample surface. We also demonstrate that further device fabrication steps such as dielectric deposition can be carried out without compromising the FLG films integrity.

Abstract: The salicide (self-aligned silicide) technology involves selective wet etching step of non-reacted metal with respect to metal silicides. It was introduced in MOSFET fabrication due to the increase of the source, drain and gate resistances with the reduction of device dimensions. The introduction of a low resistive silicide layer on these areas has become mandatory to meet device specifications. NiSi has been widely considered for sub-65nm technology nodes due to its low resistivity, low silicon consumption and low formation temperature [1-2]. The two step annealing sequence is common in the industry for nickel silicide application to control the reverse linewidth effect. However, since Ni is the diffusing element in the NiSi reaction, a first high temperature rapid thermal anneal (RTA) will inadvertently result in Ni lateral diffusion under the spacer towards the gate causing electrical shorts. Indeed, a first low temperature anneal could seriously limit the nickel lateral diffusion and prevent this phenomenon. Minimizing thermal budget by means of reducing the temperature has also been proven to lower junction leakage current [3].

Abstract: Patterned Few Layers Graphene (FLG) films were grown by local solid phase epitaxy from nickel silicide supersaturated with carbon. The process was realised by annealing of thin Ni films deposited on the carbon-terminated surface of 6H-SiC semi-insulating wafer followed by wet processing to remove the resulting nickel silicide. Raman spectroscopy was used to investigate both the formation and subsequent removal of nickel silicide during processing. Characterisation of the resulting FLG films was carried out by Raman spectroscopy and Atomic Force Microscopy (AFM). The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 3 monolayers for initial Ni layers varying from 3 to 20 nm thick. AFM observations revealed process-induced surface roughening in FLG films, however, electrical conductivity measurements by Transmission Line Model (TLM) structures confirmed that roughness does not compromise the film sheet resistance.

Abstract: Semiconducting nanowires (NW) are implemented as the active channel of field effect transistor (FET) with linear and Schottky barrier source and drain contacts. Thermally activated axial intrusion of nickel silicides into the silicon NW from pre-patterned Ni reservoirs is used in the formation of nickel silicide/silicon contacts in SiNW FETs. In the present work, the kinetics of nickel silicide axial growth in SiNWs was analyzed in the framework of the model taking into account the balance between transition of Ni atoms from the Ni reservoir to the NW surface, diffusion transport of these Ni atoms from the contact area to the interfaces between different silicides and nickel silicide/Si interface, and corresponding reactions of Ni atoms with Si and the nickel silicides formed. Simultaneous growth of mono-and nickel rich silicide was described for different kinetic and geometrical parameters of the system. Critical parameters for transition from the linear to the parabolic dependences were introduced. The model was applied to the experimental results on nickel silicide growth in SiNWs of 25÷50 nm in diameters in a temperature range of 300÷440C°. The silicide intrusions were obtained by annealing of SiNWs with pre-patterned Ni electrodes in a rapid thermal annealing machine under nitrogen atmosphere for different temperatures and times up to 120 s. In most cases the intrusions consisted of two nickel silicides, Ni-rich and mono-silicide NiSi, as was confirmed by TEM and measuring the electrical resistance of the SiNW after full silicidation. The total intrusion length, L, and particular silicide lengths, showed various time dependences, from a linear (with low growth rates (1÷4nm/s)) to a square root, diffusion-type dependence (with higher rates (10÷15 nm/s)). This behavior is well described by the model developed.