Influence of surface chemical composition on the reliability of Al/Cu bond in electronic devices

Abstract Four chemically different copper surfaces, as revealed by ESCA, have been ultrasonically bonded to Al/Mg wires. The pull strength of the bond is influenced by this different chemical composition and is dramatically changed by stress conditions. A high temperature storage (200°C) is in this respect less effective then a water vapour pressure environment (121°C, 1.04 atm) especially if traces of halogens are there present. A thick (>40 A) Cu 2 O oxide layer on top of the copper used for the Al/Cu interconnections is found to cause large percentage of intermittance in resin encapsulated finite electronic devices. The failure percentage increases in stress conditions. The wire lift off does not occur, within the limit of practical use, when the thickness of the Cu 2 O overlayer on top of the copper used for the interconnection of the finite device, is of the order of 5 A. The interfacial chemistry is therefore shown to be a dominant factor in determining the reliability of the Al/Cu bond in operating conditions.