Effect of Microstructute on Dewetting Evolution in Polycrystalline Au Thin Film

12-nm-thick Au films on silicon nitride coated Si substrates were annealed at elevated temperatures in a high vacuum or forming gas, and the changes in film morphology and microstructure were investigated. The microstructure was observed using SEM and in-situ TEM, and the crystal structure was analyzed using an automatic crystal orientation and phase mapping system (ASTAR) in TEM. In situ observation of the Au films showed rapid growth of fine grains from the very early stage of annealing, followed by holes formation at grain boundary junctions, and the holes grew and coalescenced. Annealing at a lower temperature of 400 degrees C showed that the holes grew with faceted edges that were parallel to the low surface energy crystal planes, while holes at a higher temperature occurred with rounded edges. These morphological and crystallographic evolutions of Au film during dewetting are discussed in detail in view of the diffusion mechanism and surface energy.