Biosensor properties of SOI nanowire transistors with a PEALD Al$_{2}$O$_{3}$ dielectric protective layer

The properties of protective dielectric layers of aluminum oxide Al$_{2}$O$_{3}$ applied to prefabricated silicon-nanowire transistor biochips by the plasma enhanced atomic layer deposition (PEALD) method before being housed are studied depending on the deposition and annealing modes. Coating the natural silicon oxide with a nanometer Al$_{2}$O$_{3}$ layer insignificantly decreases the femtomole sensitivity of biosensors, but provides their stability in bioliquids. In deionized water, transistors with annealed aluminum oxide are closed due to the trapping of negative charges of $<$ (1–10) $\times$ 10$^{11}$ cm$^{-2}$ at surface states. The application of a positive potential to the substrate ($V_{\mathrm{sub}}$ $>$ 25 V) makes it possible to eliminate the negative charge and to perform multiple measurements in liquid at least for half a year.