Ferroelectric, Analog Resistive Switching in BEOL Compatible TiN/HfZrO4/TiOx Junctions

Thanks to their compatibility with CMOS technologies, hafnium based ferroelectric devices receive increasing interest for the fabrication of neuromorphic hardware. In this work, 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 TiO_x 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, in the pristine state as well as 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.