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

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. Al‐doped HfO2 ferroelectric thin films prepared by atomic layer deposition with H2O oxygen source are verified to be feasible as ferroelectric gate insulators for nonvolatile memory field‐effect transistors (FETs) with metal–ferroelectric–metal–insulator–semiconductor (MFMIS) gate stack. The MFMIS–FET fabricated with optimum conditions exhibits robust retention and endurance performance due to good ferroelectric and interfacial properties of the MFMIS gate stack.