Temperature Cross-Sensitivity of AlN-Based Flexural Plate Wave Sensors

In this paper, we investigate the temperature cross-sensitivity of aluminum nitride (AlN)-based flexural plate wave devices for sensing applications in contact with liquids. In our improved device topology, the interdigital transducers are designed as a buried electrode, and thus, are electrically shielded, enabling full immersion of the sensor into the liquid. The fabricated devices showed a mass sensitivity of 240 cm2/g for loading with deionized water which is in good agreement with the theoretical predictions. The temperature coefficient of frequency (TCF) was evaluated for devices with initially compressive and tensile stressed AlN layers. Devices with compressive film stress exhibited a TCF of −62 ppm/K to −28 ppm/K, while the devices with tensile film stress showed an increased TCF of −391 ppm/K to −72 ppm/K. It is shown that variations in in-plane tension are mainly accountable for the increased TCF, while the lower TCF is primarily caused by material softening.

在本文中，我们研究了用于液体接触传感应用的氮化铝（AlN）基弯曲板波器件的温度交叉敏感性。在我们改进的器件拓扑结构中，叉指换能器被设计为埋入式电极，因此受到电屏蔽，使得传感器能够完全浸入液体中。所制造的器件在加载去离子水时显示出240 cm²/g的质量灵敏度，这与理论预测非常吻合。对具有初始压应力和张应力氮化铝层的器件评估了频率温度系数（TCF）。具有压应力薄膜的器件表现出 -62 ppm/K至 -28 ppm/K的TCF，而具有张应力薄膜的器件则显示出 -391 ppm/K至 -72 ppm/K的升高的TCF。结果表明，面内张力的变化是TCF升高的主要原因，而较低的TCF主要是由材料软化引起的。