Device feasibility of ferroelectric field-effect transistors using Al-doped HfO${}_2$ gate insulator deposited with H${}_2$O oxygen precursor during atomic layer deposition process

Metal-ferroelectric-metal (MFM) capacitors with Pt-/Al-doped HfO${}_2$ (Al:HfO${}_2$)/TiN structures are characterized to demonstrate the ferroelectricity of the Al:HfO${}_2$ thin films deposited by atomic layer deposition with H${}_2$O precursor at various annealing conditions. When the crystallization annealing temperature increases from 750 to 850 °C, the value of ferroelectric remnant polarization (2P${}_r$) increases from 11.5 to 17.1 µC cm${}^{-2}$ for the postmetallization annealing (PMA) process, whereas it increases from 8.1 to 11.4 µC cm${}^{-2}$ for the postdeposition annealing (PDA) process. The variations in crystallinity of Al:HfO${}_2$ and interfacial properties between the electrodes are analyzed to explore the physical origins to initiate the differences in electrical properties of the MFM capacitors. Using the Al:HfO${}_2$ thin film prepared with PMA at 850 °C as a ferroelectric gate insulator, which exhibits a maximum value of 2P${}_r$ and polarization switching time as short as 1 µs, the ferroelectric field-effect transistors (FeFETs) are fabricated with metal-ferroelectric-metal-insulator-semiconductor gate stack. The memory on/off ratios are secured to be 2.6 × 10${}^4$ and 2.0 × 10${}^4$ after a lapse of retention time of 10${}^5$ s and after repeated program operations of 10${}^4$ cycles, respectively. (© 2021 Wiley‐VCH GmbH)