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).