Detecting Wire Bond Inter Layer Dielectric Crack by Dark Field Imaging

Wire bond in integrated circuit is one of the critical processes for package assembly. Wire bond ILD (InterLayer Dielectric) damages may occur during the mechanical event thereby causing electrical open or short to circuitry under the bond pad. [1, 2] To detect the ILD crack, the general cratering test is using chemicals to remove the ball bond and aluminum pad, following by the optical inspection for the visible cratering crack on bond pad surface. In this work, we will further discuss on failure analysis cases for ILD cracks occurring between the metal/ILD stacks underneath the bond pad. For thoss ILD cracks which are not able to be detected from fault isolation methods like OBIRCH (Optical Beam Induced Resistance Change), Photon Emission (PEM), A direct optical inspection way by dark field imaging was applied in this topic.