Impact of composition and structure of Al alloy electrodes to power durability of SAW devices

This paper reviews power durability of SAW filters in terms of its dependence on temperature and input power, and discusses how composition and structure of Al alloy electrodes affect power durability. First, the time to fail (TF) measurement is discussed. It is shown that change of the frequency response must be taken into account for the acceleration test. This is because excess temperature causes shift of the passband. Difference of the chip temperature with the environment must be also considered. Two types of four layer electrodes (AlMgCu/Ti/AlMgCu/Ti and AlScCu/Ti/AlScCu/Ti) are used for the discussion. Series of power durability tests are performed for 800 MHz and 1.9 GHz SAW devices, and we reveal how choice of the additives, their content and layer thicknesses influence behavior of the Al migration and affect the TF performances.