High Sensitivity and Low Insertion Loss Surface Acoustic Wave Temperature Sensor Based on Pt/ScAlN/Mo/Si Structure

Modern intelligent industrial production has imposed more stringent demands on micro-electro-mechanical system (MEMS) sensors. Scandium aluminum nitride (ScAlN)-based surface acoustic wave (SAW) sensors not only exhibit strong stability and small size, but also demonstrate excellent temperature drift characteristics and low loss. This study proposes a multilayered architecture based on a fast-layer/slow-interlayer/fast-substrate configuration, using a Pt/ScAlN/Mo/Si material system to construct a temperature sensor. The performance of the Pt/ScAlN/Mo/Si resonator was analyzed using the finite element method (FEM) and the effects of ScAlN and Mo thickness on devices characteristics were discussed. The sensor was prepared based on our device simulation results and its performance was evaluated in the range of $20~^{\circ }$ C $\sim 155~^{\circ }$ C. The experimental results indicated that the sensor fabricated in this work has a temperature coefficient frequency (TCF) is approximately −38.84 ppm/°C and a sensitivity of −90.83 kHz/°C. In addition, the insertion loss (IL) varies very little with temperature, remaining at a consistent value of about −16.12 dB. In summary, the “fast-slow-fast” structure based on the Pt/ScAlN/Mo/Si material system is proposed in this work, which holds significant potential for enhancing the performance of SAW sensors.