Large area pulsed laser deposition of memristive Pr0.7Ca0.3MnO3 heterostructures for neuromorphic computing

Abstract

Heterostructures of the perovskite Pr_0.7Ca_0.3MnO₃ (PCMO) and a tunnel oxide such as AlO_x are highly interesting memristive devices for emulating synaptic properties in neuromorphic circuits. Future chip generations with these memristive elements requires PLD systems which enables PCMO growth on a full wafer. To address the issue of plume broadening in this study, a slit system was used to localize the deposition region, thereby eliminating the need for excessive scanning. This study investigates the effect of the slit system and process gas pressure on plume broadening. This investigation has been used to parameterize a simulation software to assess the effectiveness of different movement speeds and to develop strategies for homogeneous deposition, adjustable to a chosen film thickness in the order of twenty nanometers. We used these strategies to fabricate area dependent switching memory cells on a standard 4″ Si wafer using the material combination of Pr_0.7Ca_0.3MnO₃ and AlO_x. The influence of the aluminum oxide thickness on the switching shows that the IV loop starts to exhibit a hysteresis for AlO_x thicknesses ≥ 3 nm. An increase in AlO_x thickness leads to an increase in resistance and capacitive charging. An additional thermal treatment reduces the resistance and the switching voltage and increases the ratio between low resistive and high resistive state. Devices without thermal treatment of the PCMO are compatible for back end of line processing of standard CMOS technology.