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

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-K gate dielectric (HfO2) or silicon dioxide. The high density array of nanowires (up to 7 or 8 x 20 SiNWs in the vertical and horizontal direction, respectively) provides for high drive currents (1.3 mA/mu m, normalized to an average NW diameter of 30 nm at V-SG = 3 V, and V-d = 50 mV, for a standard structure with 7 x 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 I-on/I-off ratios >10(6) 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 10 mu S) 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 d(NW) similar to 15-30 nm) in order to be fully depleted and provide also high surface to volume ratios for high sensitivities. (C) 2014 Elsevier B.V. All rights reserved