Interfacial Void Structure of Au/Sn/Al Metallizations on Ga--Al--As Light-Emitting Diodes

Proc. Int. Conf. Metallurgical Coatings, San Diego, California, U.S.A., Apr. 1980. Electron microscopy was used to study the cause of an erratic adhesion problem which occurred between Au/Sn/Al metallizations and Ga--Al--As during the fabrication of light-emitting diodes. A cross-sectional study revealed that the metallization layer was actually separated from much of the Ga--Al--As surface by a complex void structure which was a potential source for poor adhesion. Rapid grain boundary diffusion of tin into gold at room temp. was found to be the origin of the observed void structure. Furthermore, the occurrence of an interfacial crack, a major feature of the void structure, was attributed to interdiffusion-induced high tensile stresses which caused the separation of the metallization layer from the Ga--Al--As substrate. 11 ref.--AA