Improved Stability of BEOL-Compatible Highly Scaled Ultrathin InZnO Channel Ferroelectric Thin-Film Transistor With TiO₂ Interfacial Layer

In this study, we investigated the impact of inserting an interfacial layer (IL) between the InZnO channel and ZrO2/HfO2 superlattice (SL) ferroelectric (FE) gate-stack on the performance and stability of highly scaled FE thin-film transistors (FeTFTs). FeTFTs with various channel lengths (50–750 nm) were characterized to reveal the impact of two IL (i.e., TiO2 and Al2O3) on device characteristics. All the memory window (MW) contours of FeTFTs with a pulsewidth of 1 ms–100 ns and an amplitude of 2.5–5 V have been investigated. The FeTFT with TiO2 IL demonstrated impressive stability in MW ( $\boldsymbol {\Delta } $ MW/MW $_{{1}\text {st cy}\text {cle}}~\boldsymbol {\le } ~3.6$ %) up to 108 cycles for a program/erase voltage of $\boldsymbol {\pm }3$ V and pulsewidth of $1~\boldsymbol {\mu } $ s. It was suggested that the FeTFT with a higher dielectric constant $(k)$ TiO2 IL may reduce the electrical field and depolarization field at the interface between the channel and gate dielectric, as well as improve interfacial quality, thereby enhancing the reliability of FeTFTs.