Impact of Electrodes and Interfaces in Ferroelectric Switching of Sub-100nm Al_1-xSc_xN

Ferroelectric materials have garnered huge research interest in the last 50+ years as these materials possess a variety of interactions between electrical, mechanical, and thermal properties that can enable multiple functionalities. The reports of ferroelectric behavior in Aluminum Scandium Nitride (Al_1-xSc_xN) has widened the potential use of ferroelectric functionality in microelectronics beyond HfO_x based ferroelectrics. Particularly, Ferroelectric Field Effect Transistor (FeFET) is a compelling application of these materials that can enable novel logic and memory devices. However, most studies have reported Ferroelectricity in thick AlScN films and more work is needed to understand their behaviour in sub-100 nanometer thickness regime. Additionally, role of electrodes and interfacial layers when AlScN is integrated in FeFETs is not well-known. This work reports the role of electrodes in Ferroelectric Switching of sub -100 nm Al_1-xSc_xN (x≈22%) films. Sub-100nm Al_0.78Sc_0.22N has been deposited via reactive co-sputtering and impact of electrodes such as W, Ti/Ru and Sc has been studied in metal-insulator-metal and metal-insulator-p-Si configurations. We demonstrate the effects of rapid thermal annealing and its impact on polarization in these thin films. Notably, RTA can alter the film properties and modify interfaces. On Silicon substrates, we also report the role of oxynitride formation aided defect structures in ferroelectric switching of these III-V nitrides. True Ferroelectric switching has also been investigated through PUND (Positive Up and Negative Down) analysis accounting for leakage current induced effects on these AlScN thin films grown on different metals. The film microstructures have been investigated using TEM and EDX analysis that has been correlated with electrical test data on polarization. We believe this work is important for tailoring AlScN materials and interfaces to achieve the desired FeFETs performance.