On the Nature of Zero Temperature Coefficient of Resistance of RuO₂ thin Film Resistor Formation using in situ Annealing

Thin film RuO₂ resistors with a temperature coefficient of resistance (TCR) around 0±20 ppm/°C were reproducibly deposited on ceramic alumina substrates using reactive direct-current (dc) magnetron sputtering at room temperature followed in situ annealing of the film at 250 °C in oxygen for 60 min. The electrical resistance of the films was monitored in real time and temperature during the in situ annealing. The TCR of the films was irreversible during increasing and decreasing temperature. Auger electron spectroscopy depth profiling on the film with a near zero TCR fabricated in such a way revealed layerlike structure of the resistors. The top region of the film was near stoichiometric, whereas the bottom region was oxygen deficient.