Reliability of p-Type Pi-Gate Poly-Si Nanowire Channel Junctionless Accumulation-Mode FETs

Abstract

In this study, p-type Pi-gate (PG) poly-Si nanowire channel junctionless accumulation-mode (JAM) field-effect transistors (FETs) were successfully fabricated and their reliability was investigated. The reliability of these PG JAM FETs was found to be dependent on the effective channel doping concentration (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch,eff</sub> ). Through a negative gate bias stress (NGBS) test, we found that degradation in the average subthreshold swing (A.S.S.) and shift in the threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> ) increases as the N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch,eff</sub> of the PG JAM FETs decreases. Furthermore, the PG JAM FETs with a lower N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch,eff</sub> show the more severe rate of deterioration in the transconductance (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) and ON current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ). By increasing N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch,eff</sub> to reduce the electric field ( E-field) on the gate oxide and tune the carrier transport mechanism in the poly-Si nanowire channel, a better immunity against the NGBS test in the p-type PG JAM FETs can be achieved under a gate overdrive voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GOD</sub> = V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> - V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH,initial</sub> = -3.5 V) to perform the NGBS test.