Sub-nanometer ZrO2 capping Hf0.5Zr0.5O2 thin films for BEOL-compatible ferroelectric tunnel junction with giant electroresistance

Abstract

Here, we report a high-performance ferroelectric tunnel junction (FTJ) built with thermal atomic layer deposition-processed 2.9 nm-thick Hf0.5Zr0.5O2 (HZO) and a 0.6 nm-thick ZrO2 capping layer atop by implementing a post-deposition-annealing at 400 °C. Ultrathin ZrO2/HZO ferroelectrics (FE) exhibit a high remnant polarization (Pr) of 18.3 μC/cm2 and superior endurance and retention, resulting from the formation of a high-ratio orthorhombic-phase in FE with the aid of a ZrO2 capping layer. The FTJ in the W/ZrO2/HZO/Pt structure delivers giant tunnel electroresistance ratios of up to 5.6 × 106, in attribution to the robust polarization of ultrathin FE and the formation of a WOx interfacial layer. Under 10 ns single-pulse programming, FTJ is capable of multiple distinct stable resistance states and can survive up to 4.3 × 106 bipolar switching cycles with a large memory window of over 3000. The results demonstrate a viable and simple processing for HZO-based BEOL-compatible FTJ, which would be of significance for practical application in integrating HZO-based embedded memory.