Impact of Sputter Deposition Parameters on the Leakage Current Behavior of Aluminum Nitride Thin Films

In microelectromechanical systems, piezoelectric aluminum nitride (AlN) thin films are commonly used as functional material for sensing and actuating purposes. This is due to excellent dielectric properties as well as a high chemical and thermal stability of AlN. In this work, we investigate the leakage current behavior (i.e. IV characteristic and charging behavior) of AN thin films sputter deposited at varying plasma powers (300 W - 800 W) and deposition pressures (4 mu bar - 8 mu bar) up to an electric field of 0.5 MV/cm. First results show a Poole-Frenkel behavior for all samples with an increase in leakage current by orders of magnitude as the degree of c-axis orientation decreases. In addition, the discharging curves (i.e. meaning the current discharge after an applied constant electric field) agree well with the empirical Curie - von Schweidler Law (I(t) = I-0 + I-1.t(-n)) and an increase of the parameter I-1 with temperature is observed. I-1 shows qualitatively the same behavior as the overall stored charge. Furthermore, the results show a strong negative correlation between the parameters n and the time constant tau(1/2) (i.e. defined as the time after which half the stored charge has decayed), proofing that n is a good indicator for the decay time of the stored charge.