Low-voltage operation and high endurance of 5-nm ferroelectric Hf0.5Zr0.5O2 capacitors

Abstract

In this letter, the ferroelectric (FE) properties of 5-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by atomic layer deposition have been investigated. By reducing the HZO film thickness to 5 nm, low-voltage operation (1.0 V) of the HZO-based capacitor was achieved while maintaining a remnant polarization (Pr) of about 10 μC/cm2 (i.e., 2Pr of 20 μC/cm2). Meanwhile, in order to form an orthorhombic phase, which is responsible for FE properties, a rapid thermal annealing process was performed after TiN top electrode deposition. The FE properties were realized after low temperature annealing (450 °C for 1 min), making them compatible with the back-end of the line. In addition, the low operating voltage and the suppression of an additional monoclinic phase formation by stress-induced crystallization induced a robust endurance (>1010 cycles at 1.2 V) of the 5-nm-thick HZO sample.

Back‐End‐of‐Line Compatible Low‐Temperature Furnace Anneal for Ferroelectric Hafnium Zirconium Oxide Formation

“…This is comparable with the result obtained by Kim et al. (about 10 8 @2.6 MV cm −1 ) for HZO films of the same thickness but annealed at 450 °C with RTA . Also for all other data points in Figure , no clear impact of the duration (60 s to 2 h) and the oven type (RTA and furnace) on endurance can be found.…”

“…This stage is attributed to a gradual decrease in the build‐in bias field due to a redistribution of defects (oxygen vacancies) and/or a partial phase transition of the dielectric material from the t‐phase to the o‐phase . During fatigue (or aging), 2 P r decreases again due to the generation of new defects like oxygen vacancies, which facilitate charge trapping and/or domain pinning …”

“…This ratio can be easily realized using common deposition techniques like atomic layer deposition (ALD) with a homogenous concentration throughout the film. 2) The FE properties of HZO films can be achieved at low process temperatures of about 400 °C . This is most likely due to the low crystallization temperature of ZrO 2 compared with other potential high‐k oxides .…”

“…It was shown that thin HZO films could be crystallized successfully in the desired FE phase by applying rapid thermal annealing (RTA) at 400 °C and even 300 °C for 30 or 60 s. Furthermore, phase transition kinetics were studied (at prior RTA crystallized films) during supplementary annealing at different temperatures and durations to simulate the thermal profile present during the formation of the interconnects, where high‐temperature processes (up to 400 °C) occur several times and last from some minutes to hours.…”

Phase field modeling of domain dynamics and polarization accumulation in ferroelectric HZO

“…Ferroelectric (FE) materials, particularly Zr doped HfO 2 (Hf 1-x Zr x O 2 :HZO 1 ) have drawn significant research interest in recent times due to CMOS process compatibility 2 , thickness scalability 3,4 as well as many promising attributes of ferroelectric field effect transistors 2,5 (FEFETs) for low-power logic [5][6][7][8] and non-volatile memories 9,10 applications. In addition, FEFETs can provide multiple non-volatile resistive states that harness the multi-domain FE characteristics, leading to the possibilities for multi-bit synapses 11,12 in a neuromorphic hardware 13 .…”