Power Durability Enhancement and Failure Analysis of TC-SAW Filter With Ti/Cu/Ti/Cu/Ti Electrodes

In response to the rapid development of wireless communication, enhancement of temperature stability and power durability for surface acoustic wave (SAW) devices is both scientifically and technologically important in the 5G era. This paper discusses the utilization of 5-layer electrode Ti/Cu/Ti/Cu/Ti to the development of high power and low loss temperature-compensated surface acoustic wave (TC-SAW) filters. By modulating the microstructure of 5-layer electrode, the power durability can be increased to 1.7 times that of the conventional 3-layer electrode, while the life time to failure can be enhanced by 104 times. Through the cross section analysis of devices before and after power test, it is found that the deformation mainly concentrates on the bottom edge of electrode, whose result matches well with finite element method (FEM) simulation. The enhancement of power durability can be attributed to high resistance to cyclic stress in the bottom fine grain area. Furthermore, substrate failure areas due to Ti diffusion were also observed, which may be caused by the high temperature due to the current concentration around the electrode deformation. Our results show that the 5-layer electrode configuration is a promising solution for high power TC-SAW filter without deterioration of radio frequency performance and temperature coefficient of frequency.