懸空式焦電薄膜人體紅外線感測器之研究

Study on Human Infrared Sensors with Suspended Pyroelectric Film

林冠宇(Lin Kuan-Yu)

指導教授 ： 李佳言

國立屏東科技大學/工學院/材料工程研究所/碩士(2021年)

https://doi.org/10.6346/NPUST202100163

摘要

本研究利用微機電系統(MEMS)製程技術，設計並製作出懸空式焦電薄膜人體紅外線感測器，並針對懸空薄膜的厚度對人體紅外線感測器之影響做探討。懸空式焦電薄膜人體紅外線感測器係由矽基板、上下電極及感測層所組成。將單面拋光之P型矽(Si)基板經由低壓化學氣相沉積系統(LPCVD)將矽晶圓雙面沉積氮化矽(Si3N4)薄膜，利用電子束蒸鍍機(E-Beam)在拋光面沉積鉻(Cr)以及金(Au)，以濕式蝕刻定義出下電極圖型後，再以RF射頻濺鍍法(RF Sputtering)和濕式蝕刻定義出氧化鋅(ZnO)薄膜感測層範圍，並再次以電子束蒸鍍法沉積鉻(Cr)以及金(Au)並配合金屬剝離法(Lift-off)定義出上電極的圖型並進行退火，最後利用反應式離子蝕刻(RIE)於感測器背部進行乾式蝕刻來定義濕式蝕刻罩幕後，再以氫氧化鉀(KOH)進行濕式蝕刻，並計算蝕刻速率來形成不同厚度之懸空薄膜。
研究中以氧化鋅在結晶峰方向(002)有較強結晶峰值為基礎，選用功率為10 mW、波長為765 nm的紅外線雷射及人體作為信號源，於不同厚度之懸空薄膜下進行模擬與實驗，結果顯示在相同的頻率下，較薄的懸空薄膜有較佳的響應電壓及較高的穩定度，且於400 Hz的頻率下，此感測器有著最佳的響應電壓，並且懸空薄膜的厚度不影響感測範圍。

關鍵字

蝕刻 ； 人體紅外線感測器 ； 微機電系統 ； 焦電效應

並列摘要

The object of this study is on human infrared sensors with suspended pyroelectric film utilizing MEMS technology, and to discuss the influence of the suspended pyroelectric film’s thickness on the infrared sensors. The human infrared sensor’s structure consists of a silicon substrate, bottom electrodes, a sensing layer and top electrodes. The single-sided polished P-type Silicon substrate is deposited with Silicon Nitride (Si3N4) film on both sides utilizing Low-Pressure Chemical Vapor Deposition system (LPCVD), and then Electron Beam Evaporator (E-Beam) is used to deposit Chromium (Cr) and Gold (Au) on the polished side to form the bottom electrodes. RF sputtering and wet etching are used to define Zinc Oxide (ZnO) sensing layer. E-Beam is used again to deposit Cr and Au, to define the top electrodes. Finally, Reactive-Ion Etching (RIE) is used to form the etch mask of the backside of the substrate for the continuous wet etching to form the back cavity with KOH etchant.
Based on the strongest (002) peak of ZnO crystalline, an infrared laser of 10 mA power and 765 nm wavelength is used as the signal source. Simulation and experiments are performed with different thicknesses of suspended films. The simulated and experimental results show that thinner films perform better response voltage and higher stability at the same frequency. As the frequency is 400 Hz, the sensor has the highest response voltage. Finally, it is found that the available measurement range is not influenced by the film thickness.

並列關鍵字

Etching ； Human Infrared Sensor ； MEMS ； Pyroelectricity

參考文獻

[1] J. F. Chang, H. H. Kuo, I.C. Leu, M. H. Hon, 2002, “The effects of thickness and operation temperature on ZnO: Al thin film CO gas sensor,” Sensors and actuators B: Chemical, Vol. 84, No. 2-3, pp. 258-264.

[2] T. Prasada Rao, M. C. Santhoshkumar, 2009, “Effect of thickness on structural, optical and electrical properties of nanostructured ZnO thin films by spray pyrolysis,” Applied Surface Science, Vol. 255, No. 8, pp. 4579-4584.

[3] C. Y. Yen, S. R. Jian, G. J. Chen, C. M. Lin, H. Y. Lee, W. C. Ke, Y. Y. Liao, P. F. Yang, C. T. Wang, Y. S. Lai, Jason S. C. Jang, J. Y. Juang, 2011, “Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films,” Applied Surface Science, Vol. 257, No. 17, pp. 7900-7905.

[4] 廖偉珈，2009，可撓式氧化鋅焦電感測器之噴墨印刷技術，碩士論文，華梵大學，機電工程學系，新北。

[5] Richard P. Feynman, 1959, “There's Plenty of Room at the Bottom,” Caltech Engineering and Science, Vol. 23, No. 5, pp. 22-36.