Investigation of SAW-induced acoustomigration effects in Cu- and Al-based metallizations

Surface acoustic wave (SAW) filter devices are successfully used for a variety of applications in telecommunication at low power levels. Shrinking sizes, raising frequencies and higher power levels lead now to new requirements regarding the device power capability since the metal electrodes tend to fatigue under high load due to acoustomigration effects. A lot of work was done to study the influence of several Al alloys and layered systems on the power durability usually by loading an existent layout with high power. By contrast, we have started our comparative investigations with in-situ experiments on different test metallizations, in order to gain a deeper insight into the acoustomigration phenomena and the basic mechanisms. These observations gave the experimental counterpart to the theoretical work on modeling the SAW stress fields. First results show clear differences in the migration behavior of Cu-based and Al-based metallization systems, with a significant higher power durability for the Cu systems