Influence of Al Oxide Film on Thermocompression Bonding of Au Wire to Evaporated Al Film

This study is concerned with the influence of Al surface condition on the thermocompression bondability of Au wires to Al electrode on IC’s. Au wires were connected to Al electrodes on IC’s by “nail-head bonding” after various Al surface treatments. The bondability was evaluated by measuring the wire pull strength and the fraction P of the number of failures at Au-Al bonds to the total number of failures. The dependence of P on applied load W was derived theoretically with a parameter named “critical load W0” to take into consideration the difference in Al surface conditions as follows:(This article is not displayable. Please see full text pdf.) \ oindentwhere K and E2 are constants. This relationship was also found to hold experimentally with different values of W0 for various surface treatments. The characterization of Al surface was carried out by using ESCA. W0 was found to depend on the intensity ratio of the metal Al to the oxidized Al peak, this ratio being determined mainly by the Al oxide film thickness.