Impact of buried capping layer on TDDB physics of advanced interconnects

In Cu/SiOC interconnects, the incorporation of a thin (100/spl Aring/) buried capping layer (BCL) extends the lifetime beyond 10 years when extrapolated to the operating conditions of 105/spl deg/C and 0.5 MV/cm. A thicker (800/spl Aring/) BCL, however, initiates Ta barrier rupture due to thermomechanical stress and degrades lifetime performance. For the first time, three distinctively different failure mechanisms of structures with and without BCL are identified: Cu drift into the bulk SiOC; along the capping layer/SiOC interface; and through the ruptured Ta barrier into the BCL. We demonstrate that BCL engineering is a realizable and potentially promising technique to improve the electrical reliability of advanced interconnects.