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).