Interlayer-engineered local epitaxial templating induced enhancement in polarization (2P$_r$ > 70$\mu$C/cm$^2$) in Hf$_{0.5}$Zr$_{0.5}$O$_2$ thin films

Abstract

In this work, we report a high remnant polarization, 2Pr >70$\mu$C/cm$^2$ in thermally processed atomic layer deposited Hf0.5Zr0.5O2 (HZO) film on Silicon with NH3 plasma exposed thin TiN interlayer and Tungsten (W) as a top electrode. The effect of interlayer on the ferroelectric properties of HZO is compared with standard Metal-Ferroelectric-Metal and Metal-Ferroelectric-Semiconductor structures. X-Ray Diffraction shows that the Orthorhombic (o) phase increases as TiN is thinned. However, the strain in the o-phase is highest at 2 nm TiN and then relaxes significantly for the no-TiN case. HRTEM images reveal that the ultra-thin TiN acts as a seed layer for the local epitaxy in HZO potentially increasing the strain to produce a 2X improvement in the remnant polarization. Finally, the HZO devices are shown to be wake-up-free, and exhibit endurance >10^6 cycles. This study opens a pathway to achieve epitaxial ferroelectric HZO films on Si with improved memory performance.