Electrical characterization of high performance, liquid gated vertically stacked SiNW-based 3D FET biosensors

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2014-04-03
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Buitrago, Elizabeth
Badia, Monserrat Fernández-Bolaños
Georgiev, Yordan M.
Yu, Ran
Lotty, Olan
Holmes, Justin D.
Nightingale, Adrian M.
Guerin, Höel M.
Ionescu, Adrian M.
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Elsevier
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Abstract
A 3D vertically stacked silicon nanowire (SiNW) field effect transistor featuring a high density array of fully depleted channels gated by a backgate and one or two symmetrical platinum side-gates through a liquid has been electrically characterized for their implementation into a robust biosensing system. The structures have also been characterized electrically under vacuum when completely surrounded by a thick oxide layer. When fully suspended, the SiNWs may be surrounded by a conformal high-κ gate dielectric (HfO2) or silicon dioxide. The high density array of nanowires (up to 7 or 8 × 20 SiNWs in the vertical and horizontal direction, respectively) provides for high drive currents (1.3 mA/μm, normalized to an average NW diameter of 30 nm at VSG = 3 V, and Vd = 50 mV, for a standard structure with 7 × 10 NWs stacked) and high chances of biomolecule interaction and detection. The use of silicon on insulator substrates with a low doped device layer significantly reduces leakage currents for excellent Ion/Ioff ratios >106 of particular importance for low power applications. When the nanowires are submerged in a liquid, they feature a gate all around architecture with improved electrostatics that provides steep subthreshold slopes (SS < 75 mV/dec), low drain induced barrier lowering (DIBL < 20 mV/V) and high transconductances (gm > 10 μS) while allowing for the entire surface area of the nanowire to be available for biomolecule sensing. The fabricated devices have small SiNW diameters (down to dNW ∼ 15–30 nm) in order to be fully depleted and provide also high surface to volume ratios for high sensitivities.
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Keywords
ISFET , Sensor , FinFET , SiNW , GAA , Ion sensitive field effect transistor , Biomolecules , Gate dielectrics , Hafnium oxides , Leakage currents , Nanowires , Sensors , Silicon on insulator technology , Biomolecule interactions , Drain-induced barrier lowering , Electrical characterization , High surface-to-volume ratio , Silicon-on-insulator substrates , Liquids
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BUITRAGO, E., BADIA, M. F.-B., GEORGIEV, Y. M., YU, R., LOTTY, O., HOLMES, J. D., NIGHTINGALE, A. M., GUERIN, H. M. & IONESCU, A. M. 2014. Electrical characterization of high performance, liquid gated vertically stacked SiNW-based 3D FET biosensors. Sensors and Actuators B: Chemical, 199, 291-300. http://www.sciencedirect.com/science/article/pii/S092540051400375X