In MEMS (micro electromechanical system) devices, piezoelectric aluminum nitride (AlN) thin films are commonly
used as functional material for sensing and actuating purposes. Additionally, AlN features excellent dielectric properties
as well as 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
thin AlN films is of utmost importance for the realization of advanced device concepts.
In this study, we present results on the transversal dielectric strength of 100 nm AlN thin films deposited by dc
magnetron sputtering. The dielectric strength was measured using a time-zero approach, where the film is stressed using
a fast voltage ramp up to the point of breakdown. The measurements were performed using different contact pad sizes,
different voltage ramping speeds and device temperatures, respectively. In order to achieve statistical significance, at
least 12 measurements were performed for each environment parameter set and the results analyzed using the Weibull
The results show, that the breakdown field in positive direction rises with the pad size, as expected. Furthermore, lower
breakdown fields with increasing temperatures up to 300°C are observed with the mean field to failure following an
exponential law typical for temperature activated processes. The activation energy was determined to 27 meV, allowing
an estimation of the breakdown field towards even higher temperatures. In negative field direction no breakdown
occurred, which is attributed to the metal-insulator-semiconductor configuration of the sample and hence, the larger
depletion layer forming in the silicon dominates the observed current behavior.