Device Feasibility of Ferroelectric Field‐Effect Transistors Using Al‐Doped HfO2 Gate Insulator Deposited with H2O Oxygen Precursor during Atomic Layer Deposition Process

Abstract

Metal–ferroelectric–metal (MFM) capacitors with Pt‐/Al‐doped HfO2 (Al:HfO2)/TiN structures are characterized to demonstrate the ferroelectricity of the Al:HfO2 thin films deposited by atomic layer deposition with H2O precursor at various annealing conditions. When the crystallization annealing temperature increases from 750 to 850 °C, the value of ferroelectric remnant polarization (2Pr) 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:HfO2 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:HfO2 thin film prepared with PMA at 850 °C as a ferroelectric gate insulator, which exhibits a maximum value of 2Pr 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 × 104 and 2.0 × 104 after a lapse of retention time of 105 s and after repeated program operations of 104 cycles, respectively.