Impact of film thickness and temperature on the dielectric breakdown behavior of sputtered aluminum nitride thin films

In micromachined devices, piezoelectric aluminum nitride (AIN) thin films are commonly used as functional material for sensing and actuating purposes. Additionally, AIM features a high chemical and thermal stability, making it also a good choice for passivation purposes for microelectronic devices. With those aspects and current trends towards minimization in mind, the dielectric reliability of ultra-thin AIN films is of utmost importance for the realization of advanced device concepts. In this study, we present a systematic analysis of the transversal dielectric strength of sputtered AIN thin films of varying film thickness (i.e. 70 nm to 400 nm) up to 300 degrees C. Using a time-zero approach, the dielectric strength is measured by applying a voltage ramp to stress the film up to the point of breakdown. The results are subsequently analyzed using the Weibull approach. For temperatures T> 180 degrees C, the characteristic breakdown field E-b,E-0 follows the relationship E-b,E-0 similar to T-2, while showing a weak temperature dependence below, thus indicating a transitory regime between thermally induced breakdown at higher T and electrically induced breakdown at lower T. It is shown, that the characteristic breakdown field increases at lower film thickness which is in good correlation with a corresponding decrease in leakage current (C) 2015 Elsevier B.V. All rights reserved.