Abstract
Ferroelectric field effect transistors with a metal-ferroelectric- insulator-silicon (MFIS) structure have emerged as promising nonvolatile memory devices. In this work, metal (Al)/ferroelectric (PZT)/insulator/Si MFIS capacitors and field effect transistors using hafnium oxide (HfO2) and zirconium oxide (ZrO2) insulator layers were fabricated. After deposition, the HfO2 and ZrO2 insulator films were first annealed at 500oC and the PZT films were annealed at different temperatures of 400oC, 500oC, 600oC and 700oC. The variation of the memory window as a function of annealing temperature was studied. The maximum capacitance-voltage (C-V) memory window of Al/PZT/HfO2/p-Si capacitors with 500oC-annealed PZT was 3.97V at a sweep voltage of 8V and the similar value for Al/PZT/ZrO2/p-Si capacitors was 3.04V at a sweep voltage of 12V.The MFIS field effect transistors show normal IDS-VDS and IDS-VGS characteristics. The subthreshold slope of Al/PZT/HfO2/p-Si transistors is 286 mV/decade and the electron mobility is 86 cm2/V-sec. The MFIS transistors with ZrO2 insulator layer show poorer performances. The retention property of MFIS field effect transistors was also measured. The fabricated n-channel MFIS field effect transistors with Al/PZT/HfO2/Si structure exhibited a memory window larger than 0.5V after 11.6 days.