Engineering Ferroelectric HZO With n+-Si/Ge Substrates Achieving High 2Pr =84 μC/cm2 and Endurance >1E11
Journal
IEEE Access
Journal Volume
12
Start Page
71598
End Page
71605
ISSN
2169-3536
Date Issued
2024
Author(s)
Abstract
Metal-Ferroelectric-Metal (MFM) devices possessing high remanent polarizations (2Pr ) of 84 and 73μ C/cm2 are demonstrated with nearly epitaxially grown Hf0.5Zr0.5O2 (HZO) films on (001) n+-Si(3E19/cm3) and n+-Ge(3E20/cm3) substrates, respectively, which are higher than MFM devices with HZO films grown on amorphous SiO2 and partially crystallized TiN underlayers/substrates. The HZO superlattice films by sequential ZrO2/HfO2 plasma-enhanced atomic layer deposition (PEALD) process show high crystallinity in TEM images of all devices; however, the measured 2Pr values are quite different, ranging from 84 to 33μ C/cm2. The high-resolution scanning transmission electron microscopy (HR-STEM) images of HZO films on n+-Si and n+-Ge show the polarization axis of o-phase is well-aligned with the growth direction which is consistent with observed high 2Pr values. Much lower interfacial energy at o-phase/Si(Ge) interfaces than m-(t-)phase/Si(Ge) by density functional theory (DFT) calculations indicates that o-phase is greatly stabilized in the HZO films on n+-Si(Ge) substrates. Strong 2Pr of 51 and 47μ C/cm2 are measured after 1E9 and 1E11 endurance cycles for HZO films on n+-Si and n+-Ge substrates, respectively. This study shows epitaxial ferroelectric HZO films could be achieved by using small misfit substrates with the thermal budget as low as 450°C.
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Type
journal article