Role of Indium Underlays in the Prevention of Thermal Grooving in Thin Gold Films

摘要

Thin gold films are potentially important for metallizations in microelectronic devices because of the high activation energy of gold for electrotransport. A high activation energy ensures a longer lifetime of microelectronic devices compared with those in which aluminum metallizations are used. When electromigration is no longer the principal failure mechanism, other failure mechanisms, caused by d.c. stressing, might become important. One possibility is grain boundary grooving. Preliminary studies have shown that grain boundary grooving in thin gold films is prevented by inserting an indium underlay between the gold film and the substrate. The objective of this work was to investigate the mechanisms for the prevention of grain boundary grooving in In/Au composite films during isothermal annealing. Microstructures were characterized in terms of grain size, grain size distribution, preferred orientation and surface morphology utilizing transmission electron microscopy (TEM), cross-sectional TEM, scanning electron microscopy and X-ray diffraction. The chemical reactions and the distribution of the phases were monitored by selected area diffraction in TEM, and by Auger electron spectroscopy sputter profiling.