2-Bit/Cell Operation of Hf0.5Zr0.5O₂Based FeFET Memory Devices for NAND Applications

The multilevel memory performances of ferroelectric field effect transistor (FeFET) with Hf 0.5 Zr 0.5 O 2 (HZO) ferroelectric thin film are investigated. First, similar retention characteristics are observed for intermediate and saturated polarization states of HZO ferroelectric thin film, which enables memories for multi-bit data storage. And then, 2-bit/cell operation of HZO-based FeFET is demonstrated utilizing two NAND architecture compatible write schemes of varying program pulse amplitude and width. Low cycle-to-cycle variability, long retention to extrapolation of 10 years at 85°C, and endurance of 500 cycles are achieved for the both schemes. Moreover, the mechanism for multilevel memory operations of the FeFET is illustrated based on the polarization switching dynamics of HZO ferroelectric thin film.