Comparative studies on ferroelectric switching kinetics of sputtered Hf0.5Zr0.5O2 thin films with variations in film thickness and crystallinity

Abstract

Ferroelectric Hf0.5Zr0.5O2 (HZO) thin film capacitors with Pt/HZO/TiN structures were characterized to investigate the effects of oxygen partial pressure (PO2) and film thickness on the ferroelectric properties and switching dynamics of sputter-deposited HZO thin films. The PO2 during deposition and the film thickness varied from 0% to 1.5% and from 20 to 30 nm, respectively. The ferroelectric remnant polarization (2Pr) was 24.8 μC/cm2 for the 20-nm-thick HZO thin film deposited at a PO2 of 0% and decreased with increasing PO2 and film thickness due to variation in the amount of ferroelectric orthorhombic phase. The 2Pr of the 30-nm-thick HZO film deposited at a PO2 of 1% was 9.60 μC/cm2. The switching times and related parameters of the HZO films were estimated and analyzed by Kolmogorov–Avrami–Ishibashi and nucleation-limited switching (NLS) models. The NLS model provided better fitting results over the full range of polarization switching. The switching times could be modulated with variations in PO2 and film thickness from 0.46 to 1.58 μs. The activation field for polarization reversal increased with increasing PO2, and the degree of PO2 dependence was higher for a thinner film.

Interplay between oxygen defects and dopants: effect on structure and performance of HfO2-based ferroelectrics

“…Findings were analogous in Hf 0.5 Zr 0.5 O 2 films deposited via physical vapour deposition, as in the case of Lee et al 48 and Ryu et al 49 Both groups demonstrated that increasing oxygen partial pressure during deposition suppresses the ferroelectric properties in the layers and again favours the stabilization of the m-phase. Since PVD layers are most likely free of carbon contaminants, the stabilization of the ferroelectric phase together with the increase in leakage current led them to conclude that V O are generated in the films for low oxygen supply.…”

“…87,88 Recently, switching kinetics started to be addressed by more research groups and some studies looked at how the switching behaviour can be affected from the oxygen content in the examined layers. As an example, Ryu et al 49 studied the switching of PVD grown Hf 0.5 Zr 0.5 O 2 thin films when varying the oxygen partial pressure from 0 to 1%. By means of the nucleation limited switching model, they calculated an increasing activation energy (E act ) for increasing oxygen content.…”

“…97 V O were shown to have a strong influence on field cycling behaviour as observed Table 3 Summary of the activation energy for polarization switching as experimentally calculated. 18,49 Oxygen poor and oxygen rich stand for the minimum and the maximum oxygen supply during deposition, respectively…”

Fabrication Strategies of Metal–Ferroelectric–Insulator–Silicon Gate Stacks Using Ferroelectric Hf–Zr–O and High-k HfO2 Insulator Layers for Securing Robust Ferroelectric Memory Characteristics

“…Furthermore, the ferroelectric polarization switching characteristics are critically determined by the relative amounts of various crystalline phases included within the FLs, 55 which are significantly influenced by such process parameters as the types of adjacent layers underneath the FL and atomic compositions of the FLs. Thus, as a second concern, the variations in the crystallinity and crystalline phases of the FLs were examined in terms of important control parameters to improve the device operations of MFIS capacitors.…”

Back‐End CMOS Compatible and Flexible Ferroelectric Memories for Neuromorphic Computing and Adaptive Sensing

“…The switching times in HZO films of different thicknesses prepared under different O 2 pressure were investigated by Ryu et al [ 87 ] A comparative study based on KAI and NLS switching models showed that NLS model can provide better fitting over the full range of polarization switching. The switching times could be modulated from 0.46 to 1.58 μs by varying the partial O 2 pressure during deposition and film thickness.…”