Stress-Memorized HZO for High-Performance Ferroelectric Field-Effect Memtransistor

Abstract

A ferroelectric field-effect transistor (FeFET), capable of logic and memory functionalities in a single device, is a promising three-terminal memtransistor that enables high-performance in-memory computing for non Von Neumann architectures. Among all HfO2-based ferroelectric materials, HfZrO2 (HZO) has attracted the most attention due to the low process temperature of ≤500 °C; however, it has relatively weak polarization. Many prior works claimed that the way to improve HZO-based FeFET characteristics is to enhance HZO ferroelectric properties, while they did not account for the fundamental compromise on dielectric breakdown strength (BDS), transistor ON/OFF current (I ON/I OFF) ratio, and memory window (MW) due to the enhanced polarization. In this work, we propose an approach for controlling the ferroelectric orthorhombic phase (O phase) and the corresponding polarization in optimal value by engineering both the surface morphology and stress of HZO layer by a thermal expansion mismatch with a TiN/W stacked capping layer, to improve the BDS, I ON/I OFF ratio, and MW. Through electrode surface optimization and stress memorization we achieved an 18% HZO ferroelectricity increase with a high BDS value of ≥4.8 MV/cm. Our optimized FeFET shows good electrical characteristics and supports operation in an identical pulse programming (IPP) mode, showing good potentiation and depression nonlinearity (−0.84 and −2.04) with an asymmetry factor of 1.2. A simulation based on the proposed FeFET array demonstrates the high potential of application in an artificial neural network (ANN).

Technology Roadmap for Flexible Sensors

“…Promising neuromorphic devices include memristors, , spintronics, , synaptic transistors, − and memtransistive synapses (a combination of memristors and transistors), , with features including analog computing and parallel storage and processing, in stark contrast to conventional digital processers. Individual neuromorphic devices when integrated with sensors or embedded with sensing functions can preprocess sensory information in a delocalized manner, providing a promising route to edge computing.…”

Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications

“…Combining friction potential with semiconductor devices, the carrier transportation of the semiconductor channel can be directly controlled by mechanical stimulus. The integration of TENG tactile sensors with Extended Gate Field Effect Transistor or EGFET [ 73 , 74 ], Ferroelectric Field Effect Transistor or FeFET [ 75 , 76 , 77 ], Floating-Gate Field Effect Transistor or FGFET [ 78 , 79 , 80 ], Semi-Floating-Gate Field Effect Transistor or SFGFET [ 81 ] and other neuromorphic transistors [ 82 , 83 ] has been used to develop self-powered tactile perception systems. The external force applied on the TENG is converted into voltage spikes, which are then captured by the neuromorphic transistor, producing PSC responses.…”

High-Performance Ferroelectric Thin Film Transistors with Large Memory Window Using Epitaxial Yttrium-Doped Hafnium Zirconium Gate Oxide

“…To induce the orthorhombic phase in HZO thin films used as gate oxides, tensile strength must be applied through “stress memorization”. This process involves the deposition of films that exert tensile strength on HZO, followed by annealing and etching, which adds complexity to device fabrication . Moreover, nonuniform crystal orientation and the coexistence of multiple phases in HZO, as opposed to a singular phase, can elevate leakage currents across grain boundaries, subsequently diminishing ferroelectricity .…”

“…Moreover, nonuniform crystal orientation and the coexistence of multiple phases in HZO, as opposed to a singular phase, can elevate leakage currents across grain boundaries, subsequently diminishing ferroelectricity . Consequently, when HZO is used as a ferroelectric insulator in FeFETs, it is employed in conjunction with extra layers (e.g., Al 2 O 3 , NbO x , and ZrO 2 ). ,− Incorporating these extra layers results in an overall increase in the device thickness of the FeFETs and contributes to the complexity of the fabrication process compared with using a single layer of HZO.…”

“…This process involves the deposition of films that exert tensile strength on HZO, followed by annealing and etching, which adds complexity to device fabrication. 22 Moreover, nonuniform crystal orientation and the coexistence of multiple phases in HZO, as opposed to a singular phase, can elevate leakage currents across grain boundaries, subsequently diminishing ferroelectricity. 23 Consequently, when HZO is used as a ferroelectric insulator in FeFETs, it is employed in conjunction with extra layers (e.g., Al 2 O 3 , NbO x , and ZrO 2 ).…”