BioFET Technology: Aggressively Scaled pMOS FinFET as Biosensor

Abstract

We report for the first time on a BioFET sensor using FinFETs with 10nm wide fins built in a 300 mm pilot line. Our minimally modified finfet process uses a `Replacement Gate' strategy whereby the Si gate is pulled at the end of the process to form the cavity that holds the electrolyte. We used a pMOS FinFET as our electrolytic gate typically has a high work function of 5.0 eV. Changing the pH or binding biomolecules to the gate dielectric surface changes the threshold voltage (VT). Measuring the VT shift provides high sensitivity due to our high-quality gate dielectric. The median voltage referred 1/f noise of only ~500 μV2μm2/Hz (at 1Hz, at threshold), is significantly lower than other reported bioFETs. We obtain a pH sensitivity near the Nernstian limit of 57 mV/pH for HfO2. Drift of the sensor has been found to be adequate at -1 mV/hour. Finally, we have verified our device to act as a biomolecular transducer. We find the VT shift due to surface bound biomolecules for DNA grafting and PNA-DNA hybridization to be as expected from simulation. Based on our quantification of transduction and simulations we project which single molecule signal-to-noise ratios could ultimately be obtained in the future.