Ferroelectric, Analog Resistive Switching in Back-End-of-Line Compatible TiN/HfZrO₄/TiO_x Junctions

Due to their compatibility with complementary metal–oxide–semiconductor technologies, hafnium-based ferroelectric devices receive increasing interest for the fabrication of neuromorphic hardware. Herein, an analog resistive memory device is fabricated with a process developed for back-end-of-line integration. A 4.5 nm-thick HfZrO4 (HZO) layer is crystallized into the ferroelectric phase, a thickness thin enough to allow electrical conduction through the layer. A TiOx interlayer is used to create an asymmetric junction as required for transferring a polarization state change into a modification of the conductivity. Memristive functionality is obtained, both in the pristine state and after ferroelectric wake-up, involving redistribution of oxygen vacancies in the ferroelectric layer. The resistive switching is shown to originate directly from the ferroelectric properties of the HZO layer.