AlN/Sapphire-Based SAW Resonators With Q Over 10000 for Temperature Sensors

Abstract

A surface acoustic wave (SAW) resonator with quality factors (Q) of 3526/10 205 at the resonant/antiresonant frequencies (fr/fa) has been fabricated on thick metal-organic chemical vapor deposition (MOCVD)-grown (0002) aluminum nitride (AlN) films (4 μm) on sapphire. The impact of device parameters on Q of resonators, including aspect ratio of length to width (L/W), number of interdigital transducers (IDTs), and IDT metal thickness, has been investigated. The high Q is obtained due to the large L/W value of 12, which can enhance the acoustic energy superimposition of IDTs, and the thick AlN film (4 μm), which can reduce the negative impact of seed layer. Moreover, the temperature coefficient of frequency (TCF) values of -46.52/-46.09 ppm/°C for fr/fa with temperatures ranging from -50 °C to 250 °C and a high Q of 4027 at 250 °C of the resonator have been demonstrated for temperature sensor application.