Back-End-of-Line Compatible HfO$_{\text{2}}$/ZrO$_{\text{2}}$ Superlattice Ferroelectric Capacitor With TiO$_{\text{2}}$ Seed Layer for Enhanced Ferroelectricity

In this study, the influence of TiO $_{\text{2}}$ seed layers in ferroelectric capacitors with HfZrO $_{\textit{x}}$ (HZO) solid-solution and HfO $_{\text{2}}$ /ZrO $_{\text{2}}$ superlattice structures has been explored. Due to the insertion of the TiO $_{\text{2}}$ seed layer, significant enhancement in ferroelectric properties and reduction in coercive field ( $\textit{E}_{\text{c}}$ ) has been achieved. In addition, samples with the TiO $_{\text{2}}$ seed layer exhibit decent ferroelectricity at a low crystalline annealing temperature of 300 $^{\circ}$ C, making them compatible with back-end-of-line (BEOL) processes. Especially, the HfO $_{\text{2}}$ /ZrO $_{\text{2}}$ superlattice ferroelectric thin film with a 1-nm TiO $_{\text{2}}$ seed layer exhibits outstanding remnant polarization (2 $\textit{P}_{\text{r}}$ ) of approximately 51.4 $\mu$ C/cm $^{\text{2}}$ with a low $\textit{E}_{\text{c}}$ of 0.9 MV/cm, reducing the operating voltage to 1.2 V, and demonstrating stable endurance larger than 10 $^{\text{9}}$ cycles. This study presents a robust approach with BEOL process compatibility for enhancing both the ferroelectric properties and the reliability of future ferroelectric devices.