Effect of Cu Content in Al IDT Electrode on Nonlinearity of SAW Device

This study reports the effect of varying copper (Cu) concentrations in the aluminum-copper (AlCu) alloy used in the interdigital transducer (IDT) electrodes of surface acoustic wave (SAW) resonators on nonlinearity and power durability. Finite element method (FEM) simulations were conducted to investigate the strain distribution in the IDT electrodes, which is one of causes of nonlinearity. The strain was significant at the bottom of the electrodes, suggesting that reinforcement of the part is important. In order to investigate the effect of Cu content, two test groups were prepared. The first test group had Cu distributed uniformly in AlCu electrode, while the second test group had Cu concentrated at the bottom of the electrode. As predicted by the FEM simulation, the second test group SAW resonator demonstrated excellent power durability and better nonlinearity.