Qualitative and quantitative analysis of acoustomigration effects in SAW-devices

Low-loss surface acoustic wave (SAW) filters are widely used in modern mobile phones, especially for front-end applications. Therefore high power durability of the SAW-structure is required. In order to develop an appropriate metallization the mechanism of acoustomigration has to be investigated in more detail. For this purpose, we designed a two-port test resonator which enables us to investigate acoustomigration in thin films. With a standard measuring procedure to quantify the power durability of metallization it is possible to investigate acoustomigration effects in thin layers systematically. For a better understanding of acoustomigration, we analysed the defect structure by different microscopy techniques as a function of the driving power, testing time and temperature. By in situ tests it was possible for the first time to investigate the growing of extrusions and cracks in real time on a submicron scale. We found a correlation between the loading and the measured number of extrusions as well as the frequency shift of the SAW device.