No abstract

Ferroelectric random-access memories based on conventional perovskite materials are non-volatile but suffer from lack of CMOS compatibility, scalability limitation, and a destructive reading scheme. On the other hand, ferroelectric tunnel junctions based on CMOS compatible hafnium oxide are a promising candidate for future non-volatile memory technology due to their simple structure, scalability, low power consumption, high operation speed, and non-destructive read-out operation. Herein, we report an efficient strategy based on the interface-engineering approach to improve upon the tunneling electroresistance effect and data retention by depositing bilayer oxide heterostructure (Al2O3/Hf0.5Zr0.5O2) using atomic layer deposition (ALD) on Ge substrate which is treated in-situ ALD chamber with H2-plasma before film deposition. Integrating a thin ferroelectric layer i.e. Hf0.5Zr0.5O2 (8.4 nm) with a thin interface layer i.e. Al2O3 (1 nm) allowed us to reduce the operation (read and write) voltage to 1.4 V, and 4.3 V, respectively, while maintaining a good tunneling electroresistance or ON/OFF ratio above 10. Furthermore, an extrapolation to 1000 years at room temperature gives a residual ON/OFF ratio of 4.

The emerging field of ferroelectric hafnium zirconium oxide has garnered increased attention recently for its wide array of applications from nonvolatile memory and transistor devices to nanoelectromechanical transducers. Atomic layer deposition is one of the preferred techniques for the fabrication of hafnium zirconium oxide thin films, with a standard choice of oxidizer being either O3 or H2O. In this study, we explore various oxidizing conditions and report on the in situ treatment of hydrogen plasma after every atomic layer during the deposition of hafnium zirconium oxide to increase the virgin state polarization. Three different oxidization methods were utilized during the fabrication of the Hf0.5Zr0.5O2 films: H2O, O2 plasma, and O2 plasma followed by H2 plasma. The 10 and 8 nm thick films oxidized with only O2 plasma result in initially anti-ferroelectric films. Comparatively, the addition of H2 plasma after every O2 plasma step results in films with strong ferroelectric behavior. Peak shifting of the GIXRD pattern suggests that the sequential O2-H2 plasma films tend more to the orthorhombic phase as compared to the O2 plasma and H2O oxidized films.

This paper reports a 30 nm-thick integrated nano-electro-mechanical resonator based on atomically engineered ferroelectric hafnium zirconium oxide (Hf0.5Zr0.5O2) film. A 10 nm-thick Hf0.5Zr0.5O2 layer is atomically engineered through capping with 10 nm-thick titanium nitride (TiN) layer and rapid thermal annealing to promote the orthorhombic crystal phase with strong ferroelectric properties. The resulting metal-ferroelectric-metal (MFM) membrane is then patterned to create an integrated nano-electro-mechanical resonator with an overall thickness of 30 nm and a planar-to-vertical aspect ratio exceeding 104:1. Benefiting from large electrostrictive effects in ferroelectric Hf0.5Zr0.5O2, the 30 nm-thick nanomechanical resonator is excited into flexural resonance at 195 kHz with a very large vibration amplitude of ∼100 nm. The transmission response of the nano-electro-mechanical resonator is extracted, using a two-port apodization of the TiN electrodes, showing quality factors (Q) of 15 and 3300 at atmospheric and 10−7 Torr ambient pressures, respectively. Finally, the structural robustness of the MFM nano-membrane is explored through the application of a ∼24 μm deflection, using a point-force by a micro-probe, highlighting the extended elasticity despite the small thickness and ultra-high aspect ratio. The atomic-level thickness, fully integrated operation, high Q, and structural robustness of the Hf0.5Zr0.5O2-based nano-membrane resonator promise its potential for the realization of highly integrated transducers for chip-scale classical and quantum information processing and sensing applications.

Using a tiered deposition approach, Hf1-xZrxO2 (HZO) films with varying atomic layer deposition (ALD) cycles from 36 to 52 cycles were grown on Ge, Ir, and TiN substrates in single runs and annealed at 500 °C. 40 ALD cycle films grown on Ir exhibit a switched polarization (Psw) of 13 μC/cm2, while those grown on Ge and TiN did not exhibit measurable Psw values until 44 and 52 ALD cycles, respectively. High-resolution cross-sectional transmission electron microscopy confirmed these results; the ferroelectric films are crystalline with defined lattice fringes, while non-ferroelectric films remain amorphous. 52 ALD cycle 1:1 HZO grown on Ge had the highest Psw of all the films fabricated at 39 μC/cm2, while the 1:1 HZO grown on TiN displayed continuous wake-up and no fatigue up to 1010 cycles with the Psw increasing from <1 μC/cm2 to 21 μC/cm2.