A Comparative study of electromigration of Al thin films deposited on low dielectric polyimide and SiO2 substrates

摘要

The electromigration characteristics of Al filmsdeposited onto low dielectric polyimide and CVD-SiO2 have beeninvestigated. The polyimides used in this study were DuPont PI-2734 and Toray BG-2480.500 nm Al-0.5%Cu-1%Si thin filmswere deposited onto polyimides and LPCVD-SiO2 by DCmagnetron sputtering. All lines were tested at constant voltage, at atemperature of 225℃, and a current density of 1.85MA/cm2. Theelectromigration reliability of Al lines onto polyimides was worsethan that onto SiO2. Joule heating was the main cause of thedegradation of electromigration reliability in the Al lines depositedonto polyimides. Since the thermal conductivity of polyimide isabout one order lower than that of SiO2, joule heating was moresignificant in Al/polyimide during electromigration test and thetemperature increase of Al lines on polyimide decreased theelectromigration life.