Multistate Capability Improvement of BEOL Compatible FeFET by Introducing an Al2O3 Interlayer

The capability of multistate is critical for electronic synapses in neuromorphic computing. In this article, the multistate performance of the ferroelectric field-effect transistors (FeFETs) is investigated by inserting an Al
$_{\mathbf {{2}}}~\text{O}_{\mathbf {{3}}}$
interlayer (IL) into Hf
$_{\mathbf {{0}.{5}}}$
Zr0.5O2 film. The experimental results of characterization indicate that the grain sizes of the ferroelectric film can be effectively reduced by the Al
$_{\mathbf {{2}}}~\text{O}_{\mathbf {{3}}}$
IL. Benefiting from the refined grain sizes, both the proposed ferroelectric capacitor and FeFET show excellent multistate performance and linearity. The benchmark with other emerging synaptic devices demonstrates that the back-end-of-line (BEOL) compatible FeFETs behave noticeable synaptic performances, such as 160 conductance states, low nonlinearity (
$\alpha _{\mathbf {p}}$
= −1.83 and
$\alpha _{\mathbf {d}}$
= −1.39), high
$G_{\mathbf {\textit {max}}}$
/
$G_{\mathbf {\textit {min}}}$
(46.1), and low energy consumption (1.13 pJ).