Improved electromigration failure in Al based interconnects

Abstract

Electromigration (EM) failure in Al interconnects is significantly improved by inserting a WN film between Al and the interlayer dielectric: over 90% of test samples failed with the Al/TiN/Ti interconnects, whereas the failure rate of the Al film on WN is reduced to less than 13% under the stress conditions of 9 MA/cm(2) and 225 degrees C, and the EM lifetime is also much extended at the same conditions. Experimental results suggest that higher activation energy, no hillocks and compressive stress are responsible for the improved electromigration performance in the Al/WN interconnect.