FinFET for high sensitivity ion and biological sensing applications

Mihai Adrian Ionescu, Livio Lattanzio, Sara Rigante
2011
Journal paper

Abstract

A double-gate (DG) fin field effect transistor (FinFET) is discussed as new label-free ion and biological sensor. Simulations as function of channel doping, geometrical dimensions, operation point and materials investigated the device response to an external potential difference which provides a body threshold voltage modulation. The simulation results presented in this work clearly state the key features for an ultrasensitive FET based sensor: an enhancement low doped and partially gated transistor operating in weak-moderate inversion regime. The optimized sensitivity, obtained when the width of the fin is equal to the gate height (W-NW similar to h(g)), reaches a value of 85% for an extraction current, I-d, of 0.1 mu A. These results pave the way for the fabrication process of an innovative CMOS compatible sensing system. (C) 2011 Elsevier B.V. All rights reserved.

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Junctionless silicon nanowire transistors for the tunable operation of a highly sensitive, low power sensor

Matthieu Berthomé, Elizabeth Buitrago Godinez, Montserrat Fernandez-Bolanos Badia, Mihai Adrian Ionescu

Silicon nanowire (SiNW) field effect transistors (FETs) have been widely investigated as biological sensors for their remarkable sensitivity due to their large surface to volume ratio (S/V) and high selectivity towards a myriad of analytes through functionalization. In this work, we propose a long channel (L > 500 nm) junctionless nanowire transistor (JNT) SiNW sensor based on a highly doped, ultrathin body field-effect transistor with an organic gate dielectric epsilon(r) = 1.7. The operation regime (threshold voltage V-th) and electrical characteristics of JNTs can be directly tuned by the careful design of the NW/Fin FET. JNTs are investigated through 3D Technology Computer Aided Design (TCAD) simulations performed as a function of geometrical dimensions and channel doping concentration N-d for a p-type tri-gated structure. Two different materials, namely, an oxide and an organic monolayer, with varying dielectric constants er provide surface passivation. Mildly doped N-d = 1 x 10(19) cm(-3), thin bodied structures (fin width F-w < 20 nm) with an organic dielectric (epsilon(r) = 1.7) were found to have promising electrical characteristics for FET sensor structures such as V-th similar to 0 V, high relative sensitivities in the subthreshold regime S > 95%, high transconductance values at threshold g(m),(Vfg=0V) > 10 nS, low subthreshold slopes SS similar to 60 mV/dec, high saturation currents I-d,I-max similar to 1-10 mu A and high I-on/I-off > 10(4)-10(10) ratios. Our results provide useful guidelines for the design of junctionless FET nanowire sensors that can be integrated into miniaturized, low power biosensing systems. (c) 2013 Elsevier B.V. All rights reserved.

Elsevier2013

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A 3D vertically stacked silicon nanowire (SiNW) and Fin field effect transistor (FET) featuring a high density array (7 or 8 x 20 SiNWs, > 4 Fins vertically stacked) of fully depleted, ultra-thin (SiNWs diameters similar to 15-30 nm, Fin width/height fw similar to 30 nm/fh similar to 150 nm), long (> 2 mu m) and suspended channels has been successfully fabricated for the first time by a top-down, complementary metal oxide semiconductor (CMOS) compatible process on silicon on insulator (SOI) substrates for biosensing applications. SiNW and FinFETs continue to draw interest as biological sensors for their outstanding sensitivity due to their large surface to volume ratios (S/V), high selectivity towards a myriad of analytes through surface functionalization and the possibility for label free, direct monitoring of biological activities. In this paper we describe different strategies and limitations for the successful development and fabrication of a 3D Si nanostructure FET using conventional clean-room fabrication techniques and their integration into heterogeneous systems. The vertical stacking allows for higher utilization of the Si substrate, high output currents (1.3 mA/mu m, normalized to a 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 for biomolecule interaction as the number of conduction channels increases. Also, as the NWs/Fins are suspended, their entire surface area is exposed to the sensing analyte. The configuration of the 3D sensor furthermore offers excellent electrostatic control of the channels by the possibility of applying symmetric or asymmetric gate potentials to tune the sensitivity and optimize the power consumption. Our fabrication scheme is competitive in terms of scaling and NW density in comparison to bottom-up and other top-down approaches with the advantage of using a CMOS-compatible, high yield (> 90%), reproducible and robust processes. (C) 2013 Elsevier B. V. All rights reserved.

Elsevier2014

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Elsevier2014