Electrical Characterisation of HfZrO2 Ferroelectric Tunnel Junctions for Neuromorphic Application

International audience; Ferroelectric Tunnel Junctions (FTJ), which can modulate their electro-resistance depending on the polarisation configuration, have demonstrated multi-state, synaptic behaviour [1]. Hf0.5Zr0.5O2 (HZO) based FTJs are an ideal solution for the industrial implementation of brain inspired computing thanks to the low annealing temperature of HZO and its full compatibility with industrial processes. In this work, we present the development of HZO-based FTJs on silicon substrates and their electrical characterisation. A TiN/HZO/Al2O3/TiN structure was fabricated by reactive magnetron sputtering with 11 nm of HZO crystallised using rapid thermal annealing [2,3]. The dielectric layer of Al2O3 was formed from the deposition of Al and the scavanging of oxygen from the HZO layer, leading to increased conductance and enhancing the asymmetry of the junction to reach higher electro-resistance values. The structural properties were investigated by X-ray reflectometry and grazing incidence X-ray diffraction. Positive-Up-Negative-Down measurements with engineered pulse parameters along with quasi-static current-voltage measurements were conducted to evaluate and control the ferroelectric switching of the devices together with their electro-resistance. Cycling measurements were carried out to investigate the evolution of the polarisation and of the resistance ratio until breakdown. Dominant conduction mechanisms across the junction were evaluated by means of in temperature current-voltage measurements and modelling. References: [1] Boyn, S., Grollier, J., Lecerf, G. et al., Nat Commun 8, 14736 (2017). [2] Bouaziz, J. et al., APL Materials 7, 081109 (2019). [3] Bouaziz, PR Romeo, N Baboux, B VilquinACS Applied Electronic Materials 1, 1740-1745 (2019)