Steep-Switching Fully Depleted Silicon-on-Insulator (FDSOI) Phase-Transition Field-Effect Transistor With Optimized HfO₂/Al₂O₃-Multilayer-Based Threshold Switching Device

摘要

The OFF-state resistance (R-OFF) and threshold voltage (V-T) of a HfO2-based threshold-switching (TS) device for phase-transition fully depleted silicon-on-insulator (FDSOI) device on silicon substrate can be improved, e.g., R-OFF is increased by implementing a multilayered HfO2/Al2O3 (rather than HfO2 layer only). The HfO2/Al2O3 layer with the atomic layer deposition (ADD) cycle ratio of 3:1 (i.e., Hf:Al = 3:1) shows approximately 3.47 x 10(11) Omega of average R-OFF and approximately 2.12 V of average V-T. Next, V-T can be modulated by adjusting the work function of the bottom electrode. We demonstrate that a high work function of the bottom electrode results in stronger built-in electric-field and tunneling, decreasing V-T and R-OFF. The Hf3Al1-based TS device with platinum electrode shows approximately 0.88 V of average V-T and approximately 2.81 x 10(9) Omega of average R-OFF. The phase-transition FDSOI device used in this work is fabricated by connecting the optimized TS device in series to the drain electrode of a baseline FDSOI device, whose channel length is 130 nm. The phase-transition FDSOI device shows the minimum subthreshold slope of 9 mV/decade owing to the abrupt resistive switching of the TS device. Additionally, it exhibits an increase in the ON/OFF-state current ratio by three times because of high R-OFF.