Failure analysis of TaN thin film resistors for microwave circuits

The failure manifestations of TaN thin film resistors for microwave circuits are that resistances become larger or even breaker failures occur. In order to investigate the failure mechanism of TaN thin film resistors, the resistance changing analysis under varied voltages and morphologies are studied by the home-made testing system and metallographic microscope in the working process. The results showed that thermal gradient fields were both formed from midst to the two ends and from surface to downward of TaN thin film resistors. The thermal gradient fields resulted in the oxidation of TaN thin films and then the increasing of resistances. When the TaN films in the middle positions on the vertical direction of current had almost changed into Ta₂O₅ films, the failures of TaN thin film resistors finally occurred. The improvement measures are also given in this paper. It can be concluded that thermal gradient field oxidation is the main failure cause of TaN thin film resistors on work.