Side-Gated silicon nanowire field-effect transistors for the detection of biological molecules

Abstract

Direct electrical detection of the binding of antibody and antigen of avian influenza (AI) virus was demonstrated through a side-gated silicon nanowire field-effect transistor derived from a double-gate FinFET. A simple detection method was employed in which the charge effect coming from the biomolecules was ob-served through the threshold voltage (VT) shift. Although the overall structure of the device is realized on a silicon-on-insulator (SOI) substrate, due to the presence of a local backgate, the proposed device is individual-ly addressable and the operating voltage is markedly low compared with similar nanowire-type biosensors with global backgates. Furthermore, its unique structure allows for the channel to be immune to the noise from the biomolecules which can be problematic for nanogap FET biosensors. Finally, it was demonstrated that the sensitivity of NW-FET sensors can be greatly enhanced when the same dopant type is used for both channel region and source and drain (S/D). This type of FET, known as accumulation mode (AM) FETs, functions under different operating principle compared with conventional inversion mode (IM) FETs. The improved sensitivity is attributed to the different conduction mechanism and current components of AM devices. The results have been verified through a direct comparison with a conventional IM device. The proposed device in this work is CMOS-compatible, highly reproducible, and monolithic integration with the readout circuits is achievable. Hence, this approach provides a step toward the large scale development of sensor chips for their potential use in medicine and biotechnology.