Aging Effects in Gold Thermocompression Bonds to Complex Metallizations

The times to failure of Au thermocompression bonds to Au-Mo-Al and to Au-Ti-Al multilayer films were determined as a function of temperature over the range of 125-400°C and compared with the time to failure of gold bonds to aluminum films. A 500-Å Ti intermediate film was found to be ineffective as a barrier to reaction between gold and aluminum. On the other hand, a 500-Å Mo film was effective, providing increased time to failure over that observed for bonds to Au-Ti-Al and Al films. No failures were observed after 2000 hours at 400°C when gold wire bonds were made to an Au/Mo/Al metallization having 1000 Å of molybdenum as the intermediate layer.