Ferroelectric FETs With 20-nm-Thick HfO₂ Layer for Large Memory Window and High Performance

Hafnium oxide (HfO₂)-based ferroelectric field-effect transistor (FeFET) is an attractive device for nonvolatile memory. However, when compared to the well-established flash devices, the memory window (MW) of FeFETs reported so far is rather limited, which might be an obstacle to practical applications. In this article, we report on FeFETs fabricated in the 28-nm high- metal gate (HKMG) bulk technology with 90 and 80 nm for the channel length and width, respectively, which show a large MW of nearly 3 V. This is achieved by adopting 20-nm-thick HfO₂ films in the gate stack instead of the usually employed 10-nm-thick films. We show that such a thickness increase leads to only a moderate increase of the switching voltages, and to a significantly improved resilience of the memory characteristics upon the parasitic charge trapping. The devices display a good retention at high temperatures and endure more than 10⁵ bipolar cycles, thus supporting this technology for a future generation of FeFET memories