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Koh S.-M.,National University of Singapore | Zhou Q.,National University of Singapore | Thanigaivelan T.,Varian Semiconductor | Henry T.,Varian Semiconductor | And 2 more authors.
Technical Digest - International Electron Devices Meeting, IEDM | Year: 2011

We report a new technique of achieving reduced nickel silicide contact resistance in strained n-FETs, where a pre-silicide Aluminum (Al) implant was introduced, and the Al profile was controlled/engineered by Carbon (C). C suppresses Al diffusion during silicidation, hence retaining high concentration of Al within the NiSi. Incorporating Al within NiSi reduces the Schottky barrier height for n-Si:C contact, leading to 18 % I On improvement for Si:C S/D nFETs with no compromise on short channel effects. © 2011 IEEE.


Zhou Q.,National University of Singapore | Zhou Q.,University of Electronic Science and Technology of China | Koh S.-M.,National University of Singapore | Tong Y.,National University of Singapore | And 3 more authors.
Journal of the Electrochemical Society | Year: 2012

We investigated Si:C SD stressors having a retrograde carbon profile formed by carbon ion implantation and solid phase epitaxy (SPE). The retrograde carbon profile features a 30-nm-thick buried silicon carbon (Si:C) layer that is spatially decoupled from a 10-nm-thick surface layer with high phosphorus concentration. Retrograde carbon profile can increase the dopant activation rate in the Si:C SD stressors and achieves more than 30% reduction of sheet resistance (R s) when SPE temperature is lower than 800°C. Samples with retrograde carbon profile have a lower R s for a given substitutional carbon concentration compared to the uniform carbon profile samples. Nickel monosilicide (NiSi) formed on Si:C SD with a retrograde carbon profile has a R s which ∼10 lower than that formed on Si:C with uniform C profile. © 2012 The Electrochemical Society.


Zhou Q.,National University of Singapore | Zhou Q.,University of Electronic Science and Technology of China | Koh S.-M.,National University of Singapore | Thanigaivelan T.,Varian Semiconductor | And 2 more authors.
IEEE Transactions on Electron Devices | Year: 2013

We demonstrate a novel technique to reduce the nickel silicide (NiSi) contact resistance Rcon in strained n-channel MOSFETs (n-FETs) with silicon carbon (Si:C) stressors, where a presilicide aluminum (Al) implant is performed and the Al profile is found to be affected by carbon (C). Al diffusion during silicidation is retarded by the presence of C and a high Al concentration is retained within the NiSi:C film, which is considered to be the main reason for electron barrier height ΦBn reduction in NiSi:C contacts. Ge preamorphization implant prior to Al implant further reduces the ΦBn to 0.44 eV. Integration of this technique in n-FETs with Si:C stressors achieves a 50% reduction in source/drain series resistance and 12% enhancement in saturation drive current. Negligible impact on the device short-channel effects is observed. When Al segregates at the NiSi/Si interface, the hole barrier height ΦBp is lowered, and such an Al profile can be used for the p-FETs. Al profile engineering shows a promise as a single-metal-silicide solution for selective Rcon optimization in CMOS. © 1963-2012 IEEE.


Koh S.-M.,National University of Singapore | Ng C.-M.,Globalfoundries | Liu P.,Globalfoundries | Mo Z.-Q.,Globalfoundries | And 8 more authors.
IWJT-2010: Extended Abstracts - 2010 International Workshop on Junction Technology | Year: 2010

We report the first demonstration of a contact technology employing a combination of low energy Aluminum (Al) ion implantation and pulsed laser anneal (PLA) to form nickel silicide (NiSi) with low hole effective Schottky barrier height (ΦB p) on Si. First, the Al implant energy is reduced over prior work to ensure compatibility with thinner NiSi contacts. Second, the effect of PLA on silicide contact formation is investigated. Third, we show that increasing Al concentration at the silicide/Si interface while keeping the Al concentration within the silicide low is vital for reducing ΦB p. Successful implementation of the contact technology leads to ∼77 % reduction in ΦB p, achieving a low ΦB p of 0.104 eV. This opens up new options to lower ΦB p with reduced thermal budget for future technology generations.


Koh S.-M.,National University of Singapore | Wong H.-S.,National University of Singapore | Gong X.,National University of Singapore | Ng C.-M.,Globalfoundries | And 5 more authors.
Journal of the Electrochemical Society | Year: 2010

An integration scheme for realizing strained n-channel metal-oxide- semiconductor field-effect transistors (nFETS) with embedded silicon-carbon (e-Si:C) source/drain (S/D) stressors formed in close proximity to the channel was demonstrated. The stressors are termed channel-proximate (CP) Si:C S/D stressors, whose proximity to the channel improves their effectiveness in contributing to tensile strain in the channel region. Numerical simulation was performed using the finite-element method to assess the strain enhancement due to CP Si:C S/D. Key process development and material characterization were performed to understand the interaction between dopants and substitutional carbon concentration Csub. Unstrained control nFETs, nFETs with conventional Si:C S/D formed after spacers, and nFETs with CP Si:C S/D were fabricated. The nFET with CP Si:C S/D stressors achieved a drive current Ion enhancement of ∼19 and ∼8% over unstrained nFET and nFET with conventional Si:C S/D, respectively. The impact of channel orientation on I on enhancement was also investigated. © 2010 The Electrochemical Society.


Koh S.-M.,National University of Singapore | Wang X.,Singapore Institute of Manufacturing Technology | Thanigaivelan T.,Varian Semiconductor | Henry T.,Varian Semiconductor | And 3 more authors.
Journal of Applied Physics | Year: 2011

We investigate the tuning of Schottky barrier height (SBH) of nickel silicide formed by pulsed excimer laser anneal of nickel on silicon implanted with aluminum (Al). A wide range of laser fluence was investigated, and it has been found that laser fluence influences the distribution of Al within the silicide and at the silicide/silicon interface. This in turn affects the effective whole SBH (φB p) at the silicide/silicon junction. High Al concentration at the silicide/silicon interface and high temperature for nano-second duration to achieve Al activation while keeping the Al concentration within the silicide low is vital for achieving low φB p. We demonstrate the achievement of one of the lowest reported φB p of ∼0.11 eV. This introduces a new option for forming nickel silicide contacts with reduced contact resistance at low thermal budget for possible adoption in future metal-oxide-semiconductor transistor technologies. © 2011 American Institute of Physics.

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