Load-Life Tests of Cr-SiO Cermet Thin-Film Resistors

Cr-SiO cerment thin films have been used to fabricate microminiature resistors which are compatible in size with monolithic circuits. Teh stability of these resistors under thermal and power stresses of up to 200°C ambient temperature and 80 mw/mil2 power density has been investigated. At 200°C and with 20 mw/mil2, dissipated on 1 mil x 5 mil resistors of 150 ohms, the resistance changes observed on stabilized Cr-SiO films were less than 0.2% after 1000 hours; however, the reliability of these resistors was found to depend on the contact metal. Degradation of the Cr-SiO/metal contact was observed with al terminals. The incidence and magnitude of this degradation are a function of storage temperature, dc load, and polarity, and can be related to the formation of a high-resistance region at the anodic al/Cr-SiO contact. This degradation does not occur when Cu or au films are used to terminate the resistors, and these devices can disspate 20 mw/mil2 at 200°C without resistance changes.