Fabrication technology of high-frequency and high-power durable surface acoustic wave devices for mobile terminals

Abstract

The addition of Ti, Ge, and Zn to sputtered Al electrodes is investigated, to obtain both high-power durability and fine-dimensional control in high-frequency surface acoustic wave (SAW) devices. Ti is more effective than Ge, Zn or conventional Cu. The improvement in the electrode durability at a high SAW power is related to the grain refinement and the static stress incorporated by addition of Ti, Ge, Zn, and Cu by sputter deposition. For Ti addition to Al, dry etching (reactive ion etching) with gases containing BCl₃ can be more easily performed than in the case of Cu addition. By using RIE and dyed UV positive-type resist, the line-width deviation of 1.2-μm electrodes can be improved to the small value of 95 nm, which is 40% of that in the conventional wet-etched case.