Improvement in Long-Term and High-Temperature Retention Stability of Ferroelectric Field-Effect Memory Transistors With Metal–Ferroelectric–Metal–Insulator–Semiconductor Gate-Stacks Using Al-Doped HfO2 Thin Films

摘要

Nonvolatile memory characteristics of the ferroelectric field-effect transistors (FeFETs) were investigated by introducing the metal-ferroelectric-metal-insulator-semiconductor (MFMIS) gate-stacks, employing Al-doped HfO2 (Al:HfO2) ferroelectric thin films. The obtained memory window (MW) of the MFMIS FETs increased from 1.0 to 2.8 V by increasing the areal ratios of the metal-insulator-semiconductor (MIS) to the metal-ferroelectric-metal (MFM) (S-I/S-F) from 8 to 32. The device with an S-I/S-F ratio of 16 exhibited a 3-order-of-magnitude on/off memory margin even with a program pulse duration of 500 ns. The long-term data retention was also verified by improving the tolerance against the depolarization field by introducing the MFMIS gate-stacks, which can use fully saturated polarization. The temperature-dependent memory performance and operational reliabilities of the MFMIS-FETs were also investigated at high temperatures to exploit fully the thermal stability of the Al:HfO2. The obtained MWs were not markedly degraded for a retention time of 10(4) s from room temperature (RT) to 80 C.