Fea of Thermo-Mechanically Induced Cracks in IMD

Thermo-mechanical stability in back-end-of-line (BEOL) interconnect structures remains as one of the BEOL integration challenges as coefficient of thermal expansion (CTE) mismatch between interconnect metal and dielectric materials resulted in significant thermal stress that often leads to cracks in BEOL structures. These cracks further pose reliability concerns as the cracks may continue to propagate under subsequent thermal loading. Hence, this paper discusses the use of finite element analysis (FEA) along with limited experimental investigation to study the thermo-mechanical stress during BEOL fabrication process and a more conservative approach in evaluating the various process/design factors to reduce the occurrence of inter-metal dielectric (IMD) cracks.