Towards Epitaxial Ferroelectric HZO on n⁺-Si/Ge Substrates Achieving Record 2Pr = 84 μC/cm² and Endurance > 1E11

Abstract

Nearly epitaxially grown ferroelectric Hf <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (HZO) films on (001) n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si(3E19/cm 3) and n+ -Ge(3E20/cm 3) substrates exhibit record remanent polarization (2P r) of 84 and 73$\mu$C/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively, which are higher than that on amorphous SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ($\alpha$-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) and partially crystallized TiN underlayers. HZO films on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si and n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Ge also show high coercive field (2E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> ) of 8.8 and 5.8 MV/cm, respectively. Superlattice HZO films by plasma-enhanced atomic layer deposition (PEALD) show that c-axis is well-aligned with the growth direction in scanning transmission electron microscopy (STEM) images, consistent with observed high 2Pr of epitaxial HZO films on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si(Ge). The density functional theory (DFT) indicates o-phase is greatly stabilized in the HZO films on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> - Si(Ge) substrates due to low interfacial energy at o-phase/Si(Ge) interfaces as compared to m-(t-)phase/Si(Ge). After 1E9 and 1E11 endurance cycles, the HZO on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si and n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Ge substrates have record finial 2P r of 51 and 47 $\mu$C/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. Our study demonstrates the way to achieve single crystalline ferroelectric HZO films by using small misfit substrates without interfacial layers. The thermal budget is as low as 450°C.