PECVD silicon and nitride postbond films for protecting bondpads,bonds and bondwires from corrosion failure

摘要

It was demonstrated experimentally that the ultimate strain ofPECVD thin-film silicon nitride coatings increased as the films weremade thinner, giving them better mechanical properties for protectingunderlying bulk Al structures such as bondwires, bond, and bondpads. Insections of under a micron, the films did not crack over Al bonds orbondwires during standard industrial temperature cycling. Temperatureramping tests indicated that 1000-A films had at least three times theultimate strain expected from bulk values. Film thickness was consistentaround bondwires and in the vicinity of the bonds from the plasmadeposition. The most susceptible part of the films was the area in theoccluded cavity under the foot of the bond. The spread of Almetallization corrosion under these films proceeded at a slower ratethan the thinner films due to their more favorable mechanicalproperties. The results of this project indicate that PECVD siliconnitride films are good candidates as protective films for mounted andbonded microelectronic or hybrid devices and have the potential ofoutperforming polymeric films by a wide margin