CPI assessment using a novel characterization technique based on bump-assisted scratch-indentation testing

Integration of compliant and brittle ultralow-k (ULK) interlayer dielectric (ILD) materials in advanced backend-of-line (BEOL) layer stacks requires a careful characterization of the mechanical stability of the BEOL stack to assure reliability during chip packaging and under field condition. We present a novel experimental technique which applies normal and shear forces on Cu pillars to test the stability of BEOL layer stacks beneath individual pillars. Critical forces and displacements are recorded with high sensitivity. The test directly verifies if the BEOL withstands the applied stress levels or if mechanical failure occurs.