Novel test strategy for statistical evaluation of defect density and reliability of contacts and vias

The increase of integration density has made interconnects even more critical for process yield and product reliability. In particular, contacts and vias (C/Vs) have become the main contributors to yield losses and device failures because of both size reduction and exponential growth of their number. Actually, it is important to note that not only open C/Vs but even resistive C/Vs on critical paths can impact the overall IC functionality. Conventional test structures used for monitoring interconnect defect density, like contact chains, can effectively detect open failures but they are totally inadequate to investigate the statistical occurrence of resistive elements. This paper presents a novel test methodology which allows the statistical occurrence of resistive C/Vs and their reliability to be easily evaluated, thus addressing the required failure analysis. Experimental results demonstrate the usefulness of the proposed approach.