Reduced fatigue and leakage of ferroelectric TiN/Hf_0.5Zr_0.5O₂/TiN capacitors by thin alumina interlayers at the top or bottom interface

Abstract

Hf0.5Zr0.5O2 (HZO) thin films are promising candidates for non-volatile memory and other related applications due to their demonstrated ferroelectricity at the nanoscale and compatibility with Si processing. However, one reason that HZO has not been fully scaled into industrial applications is due to its deleterious wake-up and fatigue behavior which leads to an inconsistent remanent polarization during cycling. In this study, we explore an interfacial engineering strategy in which we insert 1-nm Al2O3 interlayers at either the top or bottom HZO/TiN interface of sequentially deposited metal-ferroelectric-metal capacitors. By inserting an interfacial layer while limiting exposure to the ambient environment, we successfully introduce a protective passivating layer of Al2O3 that provides excess oxygen to mitigate vacancy formation at the interface. We report that TiN/HZO/TiN capacitors with a 1-nm Al2O3 at the top interface demonstrate a higher remanent polarization (2Pr ~ 42 µC/cm2) and endurance limit beyond 108 cycles at a cycling field amplitude of 3.5 MV/cm. We use time-of-flight secondary ion mass spectrometry (ToF-SIMS), energy dispersive spectroscopy (EDS), and grazing incidence x-ray diffraction (GIXRD) to elucidate the origin of enhanced endurance and leakage properties in capacitors with an inserted 1-nm Al2O3 layer. We demonstrate that the use of Al2O3 as a passivating dielectric, coupled with sequential ALD fabrication, is an effective means of interfacial engineering and enhances the performance of ferroelectric HZO devices.

Enhanced Ferroelectricity in Hf‐Based Ferroelectric Device with ZrO2 Regulating Layer

“…[11] However, its low remnant polarization intensity and high annealing temperature have restricted its further development. [12] In order to improve the remanent polarization intensity of Hf-based ferroelectric materials, researchers generally insert an interface layer between the electrode and the ferroelectric layer, such as TiO 2 , [13,14] Al 2 O 3 , [15,16,17] HfO 2 , [18] ZrO 2 , [19,20] La 2 O 3 , [21] CeO x , [22] etc. Among them, there are reported works on the performance improvement of ZrO 2 layer in memory [23][24][25] and ZrO 2 has good lattice matching effect with HfO 2 , which was suitable as insert layer for improving performances of Hf-based devices.…”

Improved Polarization‐Retention‐Endurance in Hf0.5Zr0.5O2 Films by ZrO2 Capping via Electrostatic Effects

“…This high endurance is larger than the values reported in capped structures of polycrystalline films (Table 1). [6][7][8]10,12] The endurance map for ZrO 2 capping shows a similar result. At higher and lower than the optimal voltage values fatigue is larger due to faster degradation of device and to overall lower switchable polarization, respectively.…”

“…It has been claimed that the interface layer provides oxygen [6] and/or stress, [7] which helps to stabilize the ferroelectric orthorhombic phase in the doped HfO 2 film. Other interface layers such as RuO 2 , [8] Al 2 O 3 , [9][10][11] La 2 O 3 , [12] or ZrO 2 [13] have shown to improve the endurance properties at the expense of a reduced ferroelectric polarization. As it can be seen by relevant functional properties of results of literature summarized in Table 1, a variation among results exists.…”

Impact of HfO2 Dielectric Layer Placement in Hf0.5Zr0.5O2‐Based Ferroelectric Tunnel Junctions for Neuromorphic Applications

“…The difference arises from the formation of non-ferroelectric layers at the top or bottom interfaces due to the structural differences between the two devices, and the impact of the effective dead layer at all interfaces is stronger in the MIFS device. [61,62] To analyze the impact of structural differences on the ferroelectric layer in the two FTJs, The GIXRD was conducted in the two theta (2𝜃) range of 27°-35°. The HZO films in each case comprised a mixture of monoclinic, orthorhombic, and tetragonal phases.…”