| dc.description.abstract | Due to the high sensitivity, small size and high reliability, surface acoustic wave (SAW) device has been used as a sensor in many fields, such as gas sensors, liquid sensors, temperature sensors, and humidity sensors. It is also used as biomedicine and biological sensors in recent years. In such applications, as the sample size reduces, the sensitivity of the sensor has to be improved. Incorporating micro/nano-structures into the sensors is a promising approach. The high surface-to-volume ratio of micro/nano-structures provides more surface area of sensing to improve the performance of the device. In this study, we use MEMS fabrication techniques to fabricate micro-pillars on the SAW device, characterize its performance, and study the impacts of micro-structures in improving the SAW sensor performance.
First, we use photolithography and dry etching to fabricate micro-pillar arrays on the quartz substrate with different pillar diameters, lengths, and the array patterns. Then, a metal film is deposited and patterned to make the inter-digital transducers. Finally, chromium is deposited in the sensing area by lift-off as the mass loading material. An oscillating voltage is then apply to the SAW device, and the output voltage is measured by HF power measurement system. The insertion loss frequency response can be obtained. From the shift of the center frequency after loading, the mass of the loading can be determined. The experimental results is analyzed and compared with the simulation results.
The experimental data show that either increasing the micro-structure density or deepening the micro-structure etching depth, the shift of center frequency will increase. In addition, increasing the micro-structure density is better than deepening the micro-structure etch depth. The result was consistent with the simplified numerical simulation. | en_US |