Stable thin film resistors using double layer structure

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Abstract
Highly stable bilayer thin film resistors, which consist of an underlying layer of tantalum nitride and of a capping layer of ruthenium oxide, were developed by taking advantage of the desired characteristics of two different materials in a single system. The resistors fabricated in such a way were highly stable under power loading or thermal cycling. Resistors with one digit temperature coefficient of resistance (TCR) could be easily controlled by the layer thickness ratio of the tantalum nitride to the ruthenium oxide and the ex situ annealing temperature or duration. Auger electron spectroscopy depth profile on the thin films indicates that the ruthenium oxide layer is well defined for the as-deposited form. Nevertheless, interdiffusion takes place after thermal treatment of the bilayer which is used to tune the temperature coefficient of resistance and to stabilize the resistance of the resistors.