Improved electromigration reliability of surface acoustic wave devices using Ti/Al-Mo/Ti/Al-Mo electrodes

Abstract

In order to obtain both high electromigration (EM) reliability and fine-dimensional control in high-frequency surface acoustic wave (SAW) devices, 4-layered Ti/Al-Mo/Ti/Al-Mo electrode films were investigated on 128° Y-X LiNbO 3 substrates by sputtering deposition. The results indicated that the 4-layered films had an improved EM reliability compared to conventional Al-0.5wt.%Cu films. Their lifetime is approximately three times longer than that of the Al-0.5wt.%Cu films tested at a current density of 5 × 10 7 A/cm 2 and a temperature of 200°C. Moreover, the 4-layered films were easily etched in reactive ion etching and fine-dimensional control was realized during the pattern replication for high-frequency SAW devices. For the 4-layered films, an optimum Mo quantity and sputtering parameters were very significant for high EM reliability.