CMOS-based biosensors with an independent double-gate FinFET

Abstract

A novel biosensor based on an independent double-gate FinFET is demonstrated for the first time. It features a silicon nanowire implemented on a bulk substrate, a floating gate for charge sensing, and a control gate for current driving. The detection of charged polymers and DNA is demonstrated for the diagnosis of breast cancer.Introduction Silicon nanowire field effect transistors (SiNW FETs) have great potential in biosensor applications due to their highly sensitive label-free detection of biomolecules [1][2][3][4]. For the commercialization of SiNW FET biosensors, the SiNW should meet the requirements of CMOS compatibility, good uniformity, simple fabrication, and a low fabrication cost. As shown in the Table 1, the various SiNW fabrication techniques introduced thus far still have weaknesses. In this work, we used a simple one-route deep reactive-ion-etching (RIE) process to fabricate SiNW FET biosensors uniformly on a conventional bulk silicon substrate. The SiNW FET biosensors are realized using independent double-gate (IDG) FinFETs. Thus, the monolithic integration of CMOS circuitry and biosensors can be realized on the same plane (Fig. 1). The proposed biosensor facilitates the label-free detection of charged molecules such as polymers and DNA. Device FabricationThe process flow shown in Fig. 2 is similar to that of the well-known IDG FinFET process [5] except for the SiNW formation. A bulk silicon substrate was used as the starting material. Silicon nitride was deposited as a stopping layer for the subsequent chemical-mechanical polishing (CMP). A SiNW was formed by means of the photo-resist ashing and deep RIE procedure known as the Bosch process [6]. As shown in Fig. 3, the SEM and TEM images show that the SiNW is completely separated from the bulk substrate. To isolate each device, shallow trench isolation (STI) processes which consist of channel stop implantation, STI oxide deposition, a subsequent oxide blanket etch-back by CMP, and oxide recess by HF are employed. An 8-nm thick oxide was grown, and an n+ in situ doped poly-Si layer was subsequently deposited. Through the use of CMP, the initially connected single poly-Si gate was separated into double gates. After gate

A Novel Dielectric Modulated Gate-Stack Double-Gate Metal-Oxide-Semiconductor Field-Effect Transistor-Based Sensor for Detecting Biomolecules

“…The sensitivity of different DG-MOSFET-based biosensors is discussed in [ 16 , 17 ]. Different FET-based biosensors are reported in [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Makarona et al [ 25 ] fabricated metal-insulator-semiconductor (MIS) devices, including self-assembled molecular monolayers (SAM).…”