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Gate leakage mechanisms in strained Si devices

Lookup NU author(s): Liang Yan, Dr Sarah Olsen, Dr Mehdi Kanoun, Professor Anthony O'Neill



This is the final published version of an article that has been published in its final definitive form by American Institute of Physics, 2006.

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This work investigates gate leakage mechanisms in advanced strained SiSiGe metal-oxide-semiconductor field-effect transistor (MOSFET) devices. The impact of virtual substrate Ge content, epitaxial material quality, epitaxial layer structure, and device processing on gate oxide leakage characteristics are analyzed in detail. In state of the art MOSFETs, gate oxides are only a few nanometers thick. In order to minimize power consumption, leakage currents through the gate must be controlled. However, modifications to the energy band structure, Ge diffusion due to high temperature processing, and SiSiGe material quality may all affect gate oxide leakage in strained Si devices. We show that at high oxide electric fields where gate leakage is dominated by Fowler-Nordheim tunneling, tensile strained Si MOSFETs exhibit lower leakage levels compared with bulk Si devices. This is a direct result of strain-induced splitting of the conduction band states. However, for device operating regimes at lower oxide electric fields Poole-Frenkel emissions contribute to strained Si gate leakage and increase with increasing virtual substrate Ge content. The emissions are shown to predominantly originate from surface roughness generating bulk oxide traps, opposed to Ge diffusion, and can be improved by introducing a high temperature anneal. Gate oxide interface trap density exhibits a dissimilar behavior and is highly sensitive to Ge atoms at the oxidizing surface, degrading with increasing thermal budget. Consequently advanced strained SiSiGe devices are inadvertently subject to a potential tradeoff between power consumption (gate leakage current) and device reliability (gate oxide interface quality). © 2006 American Institute of Physics.

Publication metadata

Author(s): Yan L, Olsen SH, Kanoun M, Agaiby R, O'Neill AG

Publication type: Article

Publication status: Published

Journal: Journal of Applied Physics

Year: 2006

Volume: 100

Issue: 10

Date deposited: 15/09/2016

ISSN (print): 0021-8979

ISSN (electronic): 1520-8850

Publisher: American Institute of Physics


DOI: 10.1063/1.2374191

Notes: Article no. 104507 6 pages


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