Effect of Thermal Aging on the Electrical Resistivity of Thin Alloy Films

摘要

Multicomponent alloy films of sheet resistivity between 100 and 600 Ω/sq. have been fabricated on substrates at 300°C, and several substrate temperatures have been investigated for film resistivities of 250 Ω/sq. These films have been subjected to several thousand hours storage in air at elevated temperatures. When aged at 300°C, films of high resistivity increase in resistance until open, while films of low resistivity reach a resistance maximum, then decrease through a minimum, and finally increase in resistance until opening. The use of a protective overcoating of SiO enhances the film stability during extended storage. The normalized resistance of protected films always decreases, with the lower substrate temperature films exhibiting larger decreases. This normalized resistance decrease is accompanied by a linearly related increase in the temperature coefficient of resistance. The electrical properties of these films may be explained if we postulate that the conductivity is the result of several mechanisms, some resulting from normal metallic conduction through a defect film, whereas others result from activated charge transfer between adjacent grains. The electrical behavior of the protected films under thermal aging is the result of defect anneal and grain growth. For the unprotected films we must also introduce the concept of selective oxidation.