Study on Pt-Rh Composite Thin Film Electrode for High Temperature Saw Device

Abstract

In order to improve the maximum operating temperature of surface acoustic wave (SAW) devices, the major challenge comes from the bearing capacity of the thin film electrode at high temperature. Traditional pure metal such as Pt and Ir are prone to oxidation, agglomeration and recrystallization in high temperature environment. In this paper, Pt-Rh thin films were observed by scanning electron microscope (SEM) at extremely high temperature, which verified that Pt-Rh has excellent high temperature resistance. Therefore, Pt-Rh was used as the electrode layer material, and a resistance wire of 5μm width was designed and fabricated to imitate the interdigital transducer (IDT) of SAW device. The change of resistance value of the film electrode prepared with different electrode layer structure and different passivation protection layer at high temperature were observed by four-line method. A new ZrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /Pt-Rh(10%)/Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> /Pt-Rh(10%)/Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> composite thin film electrode is proposed. The maximum operating temperature can reach 1600°C and can work stably for 0.93h at 1500°C. This is of great significance for the preparation of high temperature SAW devices.