Stress Phenomena In Times Of Porous Low-k Dielectrics

Abstract

Since the introduction of copper as an interconnect material into the Back End of Line (BEoL) stack approximately ten years ago, the biggest challenge for reducing the RC values is the reduction of the k‐value of the dielectric. Significant reduction can only be reached by the introduction of new ILD material. These new materials are very challenging with respect to all investigated BEoL reliability phenomena such as electromigration (EM), stress migration (SM) and time dependent dielectric breakdown (TDDB).In this paper we are going to give an overview over the reliability robustness challenges due to the introduction of porous dielectrics. Besides these general aspects we accentuate on how the general SM performance suffers from the introduction of the new material. Within this particular context we will show possible solutions for stress migration margin losses. It was not obvious before that the introduction of electromigration improvement options such as surface silicidation or metal capping of the copper line also significantly improves SM performance.