2-Bit/Cell Operation of Hf_0.5Zr_0.5O₂Based FeFET Memory Devices for NAND Applications

Abstract

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. INDEX TERMS FeFET memory, Hf 0.5 Zr 0.5 O 2 , 2-bit/cell, write schemes, retention, endurance. SHUAIZHI ZHENG received the B.S. degree in chemistry and the M.S. degree in inorganic chemistry from Beijing Normal University, China, in 2005 and 2008, respectively, and the academic degree of Doctor of Natural Sciences from the

Back-End, CMOS-Compatible Ferroelectric Field-Effect Transistor for Synaptic Weights

“…Moreover, the ability to integrate the synaptic design between any metal level of the BEOL increases the flexibility in the design of neuromorphic circuits. Recently, analog synaptic behavior has been shown in a hafnia-based FeFET with indium gallium zinc oxide (IGZO) and poly-Si channels fabricated in the BEOL. ,,, The combination of a hafnia-based ferroelectric with an oxide channel is expected to alleviate the known issues associated with Si-based FeFETs such as unintended low- k interfacial layers formed at the Si interface. On Si-based channels, buffer layers have been used as a solution, but they have the disadvantage of reducing the effective field over the ferroelectric layer. − For neuromorphic applications, the absolute resistance should be in the megohm range and the relative change in resistance ideally within a window of 8 up to 20–50 .…”

A Simple Strategy to Realize Super Stable Ferroelectric Capacitor via Interface Engineering

“…Since ferroelectricity was discovered and reported for the first time in HfO 2 ‐based thin films in 2011, [ 1 ] various studies have focused on this material because of its superior ferroelectricity in relative thin films and compatibility with advanced complementary metal–oxide–semiconductor processes, which are very advantageous in terms of device design and fabrication. [ 2 ] For this reason, the use of HfO 2 ‐based ferroelectric thin films in the field of nonvolatile ferroelectric memories such as ferroelectric‐field effect transistors, ferroelectric‐ramdom acess memory, neuromorphic devices, [ 3–7 ] energy storage capacitors [ 8 ] and piezoelectric devices [ 9 ] are receiving great interest. Specifically, high‐performance, nonvolatile ferroelectric memory, and neuromorphic applications require high remanent polarization ( P r ) characteristics to achieve a large memory window and a uniform level of ferroelectric properties over multiple operating cycles for the high‐reliability characteristics of the memory device.…”

Electric Field Gradient‐Controlled Domain Switching for Size Effect‐Resistant Multilevel Operations in HfO2‐Based Ferroelectric Field‐Effect Transistor

“…The write variability and retention properties of the presented 2-bit/cell HZO-FeFET memory are comparable or even better than those of the traditional multilevel HfO 2 -based FeFET memories. [22,23,30] Those excellent memory performances demonstrate the feasibility of operating multilevel memory cell in HZO-FeFETs by the proposed write scheme.…”

“…For example, the 2-bit/cell operations of Hf 0.5 Zr 0.5 O 2 (HZO)-FeFETs have been demonstrated for high-density storage by utilizing two NAND architecture compatible write schemes. [23] Besides, HfO 2 -based FeFETs have been extensively investigated to mimic the brain synapses for neuromorphic applications, such as the optimization of potentiation and depression properties, and the realization of more analog states. [24][25][26] In these studies, the multiple nonvolatile memory states are determined by the multidomain switching or subloop operations of FE-HfO 2 thin films, requiring the coexistence of multi-ferroelectric domains.…”

“…Single domain switching (only two memory states) has been observed in Si-doped HfO 2 -FeFETs with a gate length of 30 nm. [22,28] To improve the multilevel capability in the highly scaled device, film engineering and nonplanar device structures have been reported, [23,[30][31][32] but more efforts are still needed for the practical applications. Moreover, the risk of reliable operation might exist due to the intrinsic stochasticity of individual domain switching and the variation among domains.…”