Advanced failure analysis methods and microstructural investigations of wire bond contacts for current microelectronic system integration

The paper demonstrates that new failure modes can be analyzed and understood if an improved comprehensive flow in diagnostics involving non-destructive failure localization, ion-beam-supported target preparation, high-resolution electron microscopy and ultra-sensitive surface analytics are implemented in the physical failure analysis chain. For illustration, the potential of combining new non-destructive lock-in-thermography (LIT) and, 2D/3D-X-Ray inspection to localize fine pitch wire bond failures inside moulded packages will be shown. In addition to non-destructive methods, the increasing demands related to current ldquophysics of failurerdquo approaches in reliability aspects require ultra-high-resolution microstructure investigations. Corrosive failing of the intermetallic Au₄Al formed in the Au bond/Al pad contact is discussed. Results are presented based on preparation with focused ion beam (FIB) device followed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowing analysing the corrosion process. Further application of time-of flight secondary ion mass spectroscopy (ToF-SIMS) verified the presence of low concentrated contaminations as a root cause.