New Metallization Concepts for High Power SAW Devices

Stress induced mass transport (acoustomigration) is the dominant failure mechanism in surface acoustic wave (SAW) devices. A strong microstructure damage of the metal finger electrodes by void and hillock formation results in an irreversible degradation of the electrical characteristics of the device. Copper based metallizations were applied to SAW technique using LiNbO3 and quartz substrates to fabricate SAW structures for high power application. Power durability and lifetime of the Cu interdigital transducers (IDTs) were studied using a special power SAW test structure in comparison with an Al/Ti-metallization. In addition to incumbent fingers a novel copper damascene technique was developed to realize embedded copper finger structures, which offer some new SAW features. Experimental results generally show a much higher rf power durability and lifetime of the copper metallizations under comparable loading conditions and a good quality of SAW excitation using embedded Cu-IDTs. Siegfried Menzel Marcela Pekarčiková Daniel Reitz Hagen Schmidt Matthias Hofmann Stefan Baunack Horst Wendrock Thomas Gemming Manfred Weihnacht Klaus Wetzig