Qualification of extrinsics in BEOL - the new challenge

Extrinsic failure behavior of vias and dielectrics in the backend of line (BEOL) has been studied using dedicated test structures on a large scale. Via fails after (unbiased) stress were detected utilizing a test set-up and program that allows the readout of more than 10⁹ individual vias per wafer. The isolation behavior of intra and inter level BEOL dielectrics was studied by performing breakdown tests on various types of complex via/metal line structures covering layout areas above 1cm² per wafer. Extrinsic failures of vias and dielectrics were linked to process or design marginalities. The study of both, resistance and isolation related defects allows a comprehensive assessment of the electrical defect density (eDD) in the BEOL to enable process and design improvements to ensure a “zero defect” product roadmap.