Compensation of Contact Nature-Dependent Asymmetry in The Leakage Current of Ferroelectric Sc_xAl_1−x N Thin-Film Capacitors

Abstract

This paper reports on the fabrication, characterization, and leakage current analysis of Scandium-doped Aluminum Nitride (ScAlN) thin-film ferroelectric capacitors. Different thicknesses and Sc-doping levels are taken into account and the capacitors are measured with the Polarization Up-Polarization Down (PUND) scheme, showing an asymmetry in the output currents for positive and negative applied voltages due to leakage. The problem is addressed with considerations on the contact-nature (Schottky barrier, ohmic contact) of the metal-ferroelectric interfaces and on the presence of a very thin layer of native oxide on the ScAlN top surface. Moreover, a simple alternative measuring setup is shown, with clear explanation on why and how it is able to give symmetry to the measured ferroelectric capacitor characteristics, making a further step towards the understanding and commercial employment of such a high-polarization ferroelectric and post-CMOS compatible material.