SEMINAIRE LMGP - 25.05.2021 - Rony MIDAHUEN

" Wafer-scale fabrication of biologically sensitive Si nanowire FET: from pH sensing to electrical detection of DNA hybridization "

Rony MIDAHUEN
Ph.D. student,
UGA IMEP, CEA LETI, LMGP

Abstract

For several decades, the race towards the miniaturization and the complexification of electronic functions have led to the integration of innovative materials to maintain the required performance in terms of response time and power consumption. The development of biosensors, which is a subject of an intensive research activity, does not make exception to the rule. Indeed, the coupling of chemical functionalization and nanomaterials (Si nanowires in our case) open exciting new opportunities for the realization of ultra-scaled sensors, ultrasensitive and selective, used for the detection of chemical and biological species. In this context, our work aims to develop a biologically sensitive Silicon nanowire based FET capable of ultrasensitive charge detection. Here, we give a proof of principle with pH sensing and electrical detection of DNA molecule hybridization. Our bioFETs are based on conventional “top-down” CMOS compatible technology. We explored several designs (nanowires (NW), nanoribbons (NR), and honeycomb (HC) structures) with opening access scaled down to only 120 nm. After device fabrication, IDS-VBG output characteristics show a conventional n-type FET behavior with an ION/IOFF value higher than 105, as well as an increase of threshold voltage (Vt) as the NW width is reduced. We used a capacitive coupling in our dual-gated SiNW bioFETs to obtain an enhanced pH sensitivity up to 600 mV/pH. Finally, we successfully detected a 2 μM target DNA molecules through the positive Vt shift that it induced on the output characteristics when a greater number of negative charges –carried by the target DNA strands– is brought through hybridization, in the sensing site of our n-type FET biosensors.