CONTACT-ELECTROMIGRATION-INDUCED LEAKAGE FAILURE IN ALUMINUM-SILICON TO SILICON CONTACTS.

Abstract

Si migration is observed in Al-Si contacts to both n plus and p plus silicon. Etch pits are found near the leading edges of the more positively biased contacts. Leakage failure is observed in n plus contacts, but despite the Si migration, no junction leakage increase is measurable in Al-Si to p plus Si contacts. In n plus contacts, the leakage mean time to failure (MFT) has an activation energy of 0. 83 eV and is inversely proportional to the current density at the leading edge of the contacts. A current crowding parameter and an effective current are defined which enable the prediction of MTF with contact and technology scaling. In a typical case, current crowding is so severe that at constant current, changes in contact length have little effect on MTF.