Stacked Nanosheet Gate-All-Around Morphotropic Phase Boundary Field-Effect Transistors

Abstract

A material design method is proposed using ferroelectric (FE)-antiferroelectric (AFE) mixed-phase HfZrO₂ (HZO) to achieve performance improvements in morphotropic phase boundary (MPB) field-effect transistors (MPB-FETs), such as steep subthreshold swing (SS) and non-hysteretic on-current (I_on) enhancement. Capacitance (small-signal and quasi-static) and transient current measurements of MPB-FETs confirmed that near-threshold voltage (V_TH) capacitance amplification leads to I_on boosts under high-speed and low-power conditions. For the first time, two-stacked nanosheet (NS) gate-all-around (GAA) MPB-FETs with optimized HZO, demonstrating superior short channel effect (SCE) immunity with enhanced current drivability is fabricated. Bias temperature instability (BTI) analyses revealed over-10-year endurance at 0.6 V and 120 °C. The NS MPB-FETs achieved a 24.1% I_on gain, 82.5 mV operating voltage scalability, and a 30.7% AC performance improvement at V_DD = 0.6 V compared to control MOSFETs with HfO₂ high-k dielectric. Transconductance benchmarks with industrial logic technologies confirmed that the MPB with mixed HZO enables effective oxide thickness scaling without mobility degradation, making NS MPB-FETs an ideal choice for low-power / high-performance CMOS technology.

Keywords: HZO, morphotropic phase boundary; capacitance‐boosting; effective oxide thickness; field‐effect transistor; gate‐all‐around; high‐κ, hysteresis‐free; nanosheet.