A dopingless gate-all-around (GAA) gate-stacked nanowire FET with reduced parametric fluctuation effects

This paper proposes a gate-all-around silicon nanowire dopingless field-effect transistor (FET), utilizing a gate-stacked technique. The source and drain regions are formed by employing a charge plasma concept, with the application of appropriate work functions for metal contacts. The charge plasma approach reduces the need for doping control during fabrication, and thus reduces the thermal budget, while the gate-stacked structure solves the problem of scaling limitations with respect to the dielectric thickness (< 2 nm). The simulation results show that the proposed device, when compared with a conventional junctionless nanowire FET (JL-NWFET), possesses enhanced performance parameters, with improved immunity to short-channel effects. The random dopant fluctuations (RDFs) of the proposed device are analyzed and compared with those of a conventional JL-NWFET. The conventional device has a high doping concentration, and as a result suffers from higher RDFs, whereas the proposed dopingless device possesses lower RDFs. The process parameters used to measure sensitivity to RDFs include the radius, doping concentration and gate oxide thickness. When the radius of the nanowire is varied by 30%, changes in threshold voltage, on-state current and subthreshold slope of 66, 63 and 12%, respectively, are observed in the JL-NWFET, versus 5, 22.6 and 1.8% for the proposed dopingless device (CP-NWFET). Similar variations in doping concentration and gate oxide thickness are seen with the JL-NWFET, whereas the CP-NWFET is largely unaffected. Thus, the proposed gate-stacked dopingless CP-NWFET solves the issue of both doping control and scaling limitation of the gate oxide layer, which paves the way for easier fabrication, with exceptional immunity against parametric variations, making it a good candidate for future nanoscale devices.