Passivation layer effects on power durability of SAW duplexer

The power durability of the ladder-type SAW filter was investigated with various electrode materials and passivation layers. Among the aluminum alloys, the Al-2%Cu electrode showed the longest lifetime. In addition, the Al-2%Cu/Ti structure electrode showed about 27 times longer lifetime than that of Al-0.5%Cu IDT at an input power level of 31 dBm. The passivation layer effects on the power durability were examined by using SiO₂, Si₃N₄, and AlN thin film layer. The 300 nm thick SiO₂ layer suppressed the migration of aluminum and prevented from shorting out IDT electrodes effectively. The lifetime of SiO₂-coated Al-2%Cu IDT could be about 30,000 hr at an input power level of 31 dBm.