Improved subthreshold swing of MoS₂ negative-capacitance transistor by fluorine-plasma treatment on ferroelectric Hf_0.5Zr_0.5O₂ gate dielectric

Abstract

In this work, the ferroelectricity of hafnium zirconium oxide (Hf0.5Zr0.5O2, HZO) is enhanced by fluorine (F)-plasma treatment, which is used to fabricate MoS2 negative-capacitance field-effect transistor. Measurements show that the subthreshold swing of the transistor is significantly reduced to 17.8 mV dec−1 over almost four orders of output current, as compared to its counterpart without the F-plasma treatment (37.4 mV dec−1). The involved mechanism is that during the F-plasma treatment, F atoms can be incorporated into the HZO bulk to passive its oxygen vacancies and interface traps, thus forming robust Zr–F and Hf–F bonds. Therefore, the F-plasma-treated HZO film exhibits much less oxygen vacancies than the untreated HZO film, which is beneficial to enhancing the amplification effect on the surface potential of the MoS2 channel during the NC operation.

Optimization of Subthreshold Swing and Hysteresis in Hf0.5Zr0.5O2-Based MoS2 Negative Capacitance Field-Effect Transistors by Modulating Capacitance Matching

“…Compared with traditional ferroelectric materials such as Pb­(Zr,Ti)­O 3 (PZT) and P­(VDF-TrFE), hafnium-based ferroelectric films show the advantages of high residual polarization strength ( P r ), high Curie temperature ( T c > 200 °C), high compatibility with CMOS process, good interface performance with semiconductor materials, and high dielectric constant . Ferroelectricity can be observed in the doped HfO 2 film with a thickness of less than 10 nm, − which makes it suitable for small-sized devices.…”