Engineering Ferroelectric HZO With n<sup>+</sup>-Si/Ge Substrates Achieving High 2<italic>P<sub>r</sub></italic>=84 <bold>μ</bold>C/cm<sup>2</sup> and Endurance >1E11
oleh: Zefu Zhao, Yun-Wen Chen, Yu-Rui Chen, C. W. Liu
| Format: | Article |
|---|---|
| Diterbitkan: | IEEE 2024-01-01 |
Deskripsi
Metal-Ferroelectric-Metal (MFM) devices possessing high remanent polarizations (<inline-formula> <tex-math notation="LaTeX">$2P_{r}$ </tex-math></inline-formula>) of 84 and <inline-formula> <tex-math notation="LaTeX">$73~\mu $ </tex-math></inline-formula>C/cm2 are demonstrated with nearly epitaxially grown Hf0.5Zr0.5O2 (HZO) films on (001) n+-Si(3E19/cm<inline-formula> <tex-math notation="LaTeX">$^{3}$ </tex-math></inline-formula>) and n+-Ge(3E20/cm<inline-formula> <tex-math notation="LaTeX">$^{3}$ </tex-math></inline-formula>) 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 <inline-formula> <tex-math notation="LaTeX">$2P_{r}$ </tex-math></inline-formula> values are quite different, ranging from 84 to <inline-formula> <tex-math notation="LaTeX">$33\mu $ </tex-math></inline-formula>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 <inline-formula> <tex-math notation="LaTeX">$2P_{r}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$2P_{r}$ </tex-math></inline-formula> of 51 and <inline-formula> <tex-math notation="LaTeX">$47~\mu $ </tex-math></inline-formula>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.