Robust Ferroelectricity and Suppressed Leakage Current in Ultrathin (≤4 nm) HfO2/ZrO2 Nanolaminates With Ru-TiN Asymmetric Electrodes

Thinner hafnia-based ferroelectric (FE) films are critical for lower operation voltages, easy integration into advanced CMOS technology nodes, and higher densities. In this work, we report systematic engineering of FE capacitors based on ultrathin ( $\le 4$ nm) Hf ${}_{{0}.{5}}$ Zr ${}_{{0}.{5}}$ O2 (HZO) films. We demonstrate that: 1) at ultrathin thickness scale, the HZO nanolaminate (NL) film shows $\ge 10\times $ improvement in leakage current compared to the traditional solid solution (SS) film; 2) the use of Ru bottom electrode (BE) can efficiently enhance the ferroelectricity while greatly limiting the wake-up effect in ultrathin HZO films; and 3) robust ferroelectricity ( $2{P}_{\text {r}}\sim {35} {\boldsymbol {\mu } }$ C/cm ${}^{{2}}\text {)}$ with reliable ret- ention ( $\ge 10^{{5}}$ s at room temperature (RT) and $85~^{\circ }$ C) and endurance ( $\ge 2\times 10^{{12}}$ cycles by recovery) are achieved in the 3.5 nm HZO NL film with Ru-TiN asymmetric electrodes. Our results pave the way for HZO FEs toward low-voltage memory and next-generation computing applications.