Fast Thermal Cycling - Enhanced Electromigratton Failures in Si/TiSi2W-Ti/Al-Si-Cu Multilayer Contacts

Failure mechanisms of TiSi2/W-Ti(15%)/Al-Si(l%)-Cu(2%) multilayer thin film contact to silicon shallow junction (0,25 μm) have been investigated. Both a fast temperature cycling (with 300 ms thermal cycle period) and a high constant temperature were used as means for the degradation processes acceleration. We have shown that stress time could be reduced by the factor of 10 or more if the temperature of adjacent contact region was cycled by a pulsed electrical current passed through the semiconductor region lying under the investigated contacts. Our data have also indicated that W-Ti barrier layer serves to reduce drastically the electromigration degradation of thin film contacts for failures caused by an increase in junction leakage on the one hand and on the other hand it serves to intensify the electromigration degradation caused by an increase in contact resistance. These distinctions have been explained through structural-morphological investigations of the contact layers surface morphology. They showed a reduction in size of crystallines of the sputter deposited Al-Si-Cu top layer with W-Ti barrier layer present.