| 摘要: | 表面聲波感測器元件由於靈敏度高、體積小、高可靠度等優勢，被運用在氣體感測器、液體感測器、溫度及濕度感測器上，近幾年也開始應用於生醫、生物檢測上。隨著樣品體積逐漸縮小，感測器的靈敏度必須提升。隨著微奈米製造技術的進步，微結構提供較多的感測表面積以提升元件性能。本文利用微機電(MEMS)製程技術設計與製作一具有柱狀微結構之表面聲波元件，量測其元件特性，探討微結構來提升其表面聲波感測效能的可行性。 首先利用微影技術與乾蝕刻於石英基板上蝕刻出不同結構尺寸、數量與深度之微結構於感測區上，接著利用蒸鍍沉積金屬薄膜，經微影製程蝕刻出指叉電極，再利用舉離法在感測區上沉積鉻金屬薄膜當作負載。訊號量測使用高頻功率與雜訊量測系統，測量質量負載前與負載後其輸入電壓與輸出電壓跟頻率響應之關係，計算並繪出插入損失與頻率響應關係圖，探討在不同結構與蝕刻深度由質量負載造成中心頻率的偏移之結果。最後將實驗量測數據與模擬結果做比對分析，以期達到藉由模擬來預測實驗結果，減少實驗的次數來達到較佳的結構增加形態。 由實驗量測結果顯示無論是增加微結構物數量或是增加蝕刻深度都能達到中心頻率偏移量上升的效果，而又以結構物週期變小所造成的效益較增加蝕刻深度來的優秀，此結果與簡化微結構的模擬所提供之結論是互相呼應的，因此由模擬來預測實驗趨勢是可行的。 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. |
