Active low temperature oxidation as a route to minimize electrode–oxide interface reactions in nanoscale capacitors

Abstract

The electrical characteristics of reactive metal–oxide interfaces are largely dependent on the thermodynamics and kinetics of interfacial reactions that may occur during synthesis and further processing conditions. Such reactions may lead to undesirable properties such as increased loss tangent, frequency dispersion, or asymmetric capacitance. Metals such as Ni are being explored as electrodes in various electronic packaging as well as on-chip decoupling capacitors and this presents a challenge to advance processing routes that render utilization of high-dielectric constant oxide thin films. In this work, we demonstrate that photon-assisted oxidation enables a unique low temperature processing route to synthesize reduced loss (Ba,Sr)TiO3 thin film based capacitors with Ni bottom electrodes. Our results show a decrease in the dielectric loss tangent in photon-assisted oxidized films compared to conventionally re-oxidized at an applied field of 0.33 MV/cm, tan δ of 0.08 versus 0.63, respectively. Leakage currents showed a significant decrease, 7.8 A/cm2 for conventional re-oxidation versus 0.046 A/cm2 for photon assisted, at an applied field of 0.33 MV/cm. The results are of relevance to processing reactive materials wherein athermal routes are necessary to avoid interfacial reactions.