Development and fabrication of a charge sensor for a DNA sequencer based on an extremely small silicon nanowire

Nowadays one of the most promising methods for creating electronic charge sensors with subelectronic sensitivity and wide range of operating temperatures is the fabrication of a semiconductor nanowire. These are required for operation of such a device as an efficient, fast and inexpensive charge-type DNA sequencer. The aim of this work is to develop and manufacture electric charge sensors based on silicon nanowires with a thickness of less than 20 nm and a width of 30–50 nm with platforms formed on them for the immobilization of single molecules of DNA polymerase. The samples were fabricated on SOI substrates using photo- and electron lithography, ion-plasma etching and liquid etching, magnetron and electron beam sputtering. The formation of extremely small silicon nanowires with sites for the immobilization of polymerase molecules was implemented in three ways: 1) deposition of a single golden dot on a nanotransistor as a result of their exact alignment when the dot exposed; 2) formation of a single golden area and a nanowire channel by the shadow evaporaton method; 3) deposition of an extremely thin discontinuous granular gold film on the area of nanowire formed. Measurements of electron transport through fabricated nanotransistors showed that their resistances, which lie in the range of 1–2 GΩ, strongly depend on the gate voltage. The charge sensitivity of the sensors is less than 1 e/Hz^(1/2). According to estimates, this sensitivity is sufficient to detect a release of a proton upon insertion of a single nucleotide into DNA.