NH3-Plasma Treatment Induced Performance Enhancement of MoS2 Negative-Capacitance Transistors With Zr1−xAlxOy as Ferroelectric Layer Annealed at Low Temperature

Back-gate molybdenum disulfide (MoS2) negative-capacitance field-effect transistors (NCFETs) with $Zr_{{1}-{x}}$ AlxOy (ZAO)/Al2O3 as stacked gate dielectric are fabricated, and the impacts of the Al content and annealing temperature of the ferroelectric ZAO films on the transistor’s electrical properties are thoroughly examined. It is found that an optimal Al content of ~10% and a suitable annealing temperature of $\sim 400~^{\circ }$ C can yield MoS2 NCFETs with excellent performance of a low subthreshold swing (SS) of 46.8 mV/dec, an elevated on/off current ratio ( ${I} _{\text {ON}}$ / ${I} _{\text {OFF}}$ ) of $1.41\times 10^{{6}}$ , and a reduced hysteresis of 0.26 V. Moreover, a remote NH3 plasma is used to treat the surface of ZAO film and Al2O3 match layer, leading to further improvements of device performance: SS lowered to 38.2 mV/dec, ${I} _{\text {ON}}$ / ${I} _{ \text {OFF}}$ increased to $5.14\times 10^{{6}}$ , and hysteresis reduced to 0.06 V. The involved mechanisms are attributed to the passivation of oxygen vacancies within the thin film and dangling bonds at the surface of thin films by N incorporation, which enhances the ferroelectric properties and interfacial quality of the films and in turn enhances the negative capacitance (NC) effect and electrical performance of the relevant NCFETs. Therefore, using low-temperature annealed ZAO as a ferroelectric layer along with NH3-plasma treatment on both ferroelectric film and matching layer is an effective strategy to improve the performance of MoS2 NCFETs.