Paper BI-MoA8
Fabrication of Nanowire FETs for pH Sensing

Monday, October 31, 2011, 4:20 pm, Room 108

Sensors for measuring pH are very important for understanding reactions of biological species such as proteins, enzymes and cells. While traditional sensors based upon such techniques as infrared spectroscopy, fluorescence and others have low sensitivity and slow response time, more recent nanowire field effect transistor sensors offer improved sensitivity and response time due to smaller size and increased surface areas. [1, 2]

We have fabricated nanowire FET sensors using conventional CMOS semiconductor processes. The nanowires were patterned by electron beam lithography and reactively ion etched into 30 nm thick silicon on insulator (SOI) substrates. The gate sensing surface is comprised of a hafnium oxide/ silicon dioxide stack covering the nanowire, while the source/drain regions are comprised of boron activated SOI with nickel-platinum silicide contacts. The resulting 16 nm wide nanowire devices show high sensitivity for pH measurements. The FET drain current increases by a factor of eight per unit change in pH, while the subthreshold slope is ~ 77 mV/decade. The sensors operate at a reduced sensing voltage of 0.5 V, making them promising candidates for low power, bio-medical applications.

[1] E. Stern, J. Klemic, et al., Nature, 445 (2007) 519

[2] S. Zafar, C. D’Emic, et al, to be published