Ferroelectric La‐Doped ZrO₂/Hf_xZr_1−xO₂ Bilayer Stacks with Enhanced Endurance

Abstract

Hafnium zirconate (HZO) is investigated in metal-ferroelectric-metal capacitors as a function of Hf/(Hfþ Zr) atomic ratio, the presence of a thin ZrO 2 seed layer, and/or by doping HZO with La 3þ . It is demonstrated that a longer endurance is achieved with Hf-rich HZO by introducing a ZrO 2 seed layer. The endurance is further improved by introducing La 3þ in the Hf-rich HZO layer of the bilayer stack, which offers a higher 2P r in the pristine state compared with a stoichiometric HZO doped with the same amount of La 3þ . Both ZrO 2 underlayer and La 3þ doping of HZO are shown to play a decisive role in promoting the formation of an orthorhombic and tetragonal phase at the expense of a detrimental monoclinic phase.

Energy-Efficient Annealing Process of Ferroelectric Hf0.5Zr0.5O2 Capacitor Using Ultraviolet-LED for Green Manufacturing

“…Next, X-ray diffraction analysis was performed for the samples annealed by UV-LED at 450℃ for 15 s. First, we measured the grazing incidence x-ray diffraction (GIXRD) pattern and performed Rietveld refinement, which can be utilized to analyze the composition of the m-, o-, and t-phases in the HZO thin film [27][28][29][30][31].…”

“…Therefore, UV-LED annealing is preferable for energy-and time-efficient annealing process to HL annealing. Also, it was indicated that the energy consumption was not largely affected by the maximum input power because the ramp-up time was roughly in inverse proportion to the maximum input power.Next, X-ray diffraction analysis was performed for the samples annealed by UV-LED at 450℃ for 15 s. First, we measured the grazing incidence x-ray diffraction (GIXRD) pattern and performed Rietveld refinement, which can be utilized to analyze the composition of the m-, o-, and t-phases in the HZO thin film[27][28][29][30][31].Fig.12shows the measured GIXRD pattern and the fitting curve obtained by Rietveld refinement. The incidence angle was fixed at 0.5°, and 2θ was ranged between 15 and 90° with 0.05° step.…”

Electrical Investigation of Wake-Up in High Endurance Fatigue-Free La and Y Doped HZO Metal–Ferroelectric–Metal Capacitors

“…HZO is being explored for both FEFET [6]- [8] and FERAM [4], [9], [10] applications. Ferroelectricity in HZO has been demonstrated with Si [11], Al [11] as well as La [12]- [14]dopants. In undoped form, the coercive field of HZO layers is within ~0.9-1.2MV/cm range, which drops with addition of dopants in the layers to 0.5-0.7MV/cm [12].…”

Improvement of the Ferroelectric Response of La-Doped Hafnium Zirconium Oxide Employing Tungsten Oxide Interfacial Layer with Back-End-of-Line Compatibility

“…Ensuring the reliability of device operation necessitates achieving a sufficiently high endurance device cycle with enough ferroelectric response . Although pure HZO exhibits a satisfactory ferroelectric response, it faces issues such as early breakdown and fatigue. , These challenges stem from the intrinsic vulnerability of HZO to reduction, potential generation of oxygen vacancies (V o ), and monoclinic phase evolution. , Therefore, pure HZO has been considered to be inappropriate for actual device applications.…”

“…To address these application issues, various dopants have been explored for the HZO layer. Among them, trivalent lanthanum (La 3+ ) has shown promising characteristics in terms of endurance and polarization. , La-doped HZO (La:HZO) generally showed lower initial two remanent polarization (2P r ) values and a larger wake-up effect, , likely caused by tetragonal phase stabilization in the presence of La dopant. Nevertheless, a delicate control of La dopant concentration allowed one to achieve a higher endurance cycle for device operation and maximum 2P r . , The La acceptor doping effect could mitigate the n-type nature of HZO, lowering the Fermi level, which decreased the leakage current and improved the endurance properties.…”