Effect of Insertion of Dielectric Layer on the Performance of Hafnia Ferroelectric Devices

Abstract

Hafnia-based ferroelectric (FE) devices have attracted significant attention as nonvolatile memory devices due to their compatibility with complementary metal–oxide–semiconductor processes. Among them, the FE tunnel junction (FTJ) has been considered as the next-generation of nonvolatile memory devices owing to its neuromorphic characteristics and nondestructive read operation as well as the high-density integration. However, degradation of ferroelectricity in a thin hafnia film causes a reduced tunneling electroresistance (TER) ratio. In this work, we inserted a TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer into the metal–FE–metal capacitor to provide an asymmetric structure for FTJ operations and recorded the enhanced remnant polarization with enhanced ferroelectricity. In this study, a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{P}_{r}$ </tex-math></inline-formula> value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$44.4~\mu \text{C}$ </tex-math></inline-formula> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a notable TER ratio of 11.6 were observed for 6-nm thick hafnia films with 1-nm thick TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films.