為了防止人類受到有毒氣體的傷害並保護環境，有毒氣體的檢測變得越來越重要。作為多年來一直被認為是有效的感測材料氧化物之一的半導體金屬也已被廣泛研究。
本研究中一開始先利用微機電系統（MEMS）技術在六吋矽晶圓上首先在濕氧下生長出低應力的介電層，並以沉積方式製作出金屬指叉狀感測電極與微加熱器，最後使用ICP-RIE在元件背面蝕刻出懸空結構。接著，我們在微加熱器上施加電壓，之後再以熱顯像儀觀察溫度的增益變化，以便在不同溫度設定下進行接下來的量測實驗。在感測材料的合成部分，我們利用sol-gel法合成出α-Fe2O3奈米粒子，比較在不同退火溫度下的薄膜有何差異特性，結果顯示隨退火溫度升高晶粒尺寸也隨之變大。在400°C下退火一個小時，其α-Fe2O3感測層表面可獲得較多孔洞且擁有高表面積，有利於氣體的吸附。最後，在量測方面，先在大氣下做阻值的穩定化的動作，以確保元件在後續量測中所得出的結果是建立在穩定的基準層面之上。在各種氣體比較下，發現α-Fe2O3奈米薄膜對於NOx的存在有較優秀的響應值與較快的響應/恢復時間。而在工作溫度200°C及濃度50 ppb的NO環境下，其最大的響應值為48%，且具備可再現性，並擁有53.54%的穩定性。

To prevent human beings from being harmed by toxic gases and to protect the environment, the detection of toxic gases becomes increasingly important. Therefore, the environmentally-friendly materials such as semiconductor metal oxides, have been considered as effective sensing materials for many years and have been extensively studied.
First, a micro-electromechanical system (MEMS) technology was used to grow a low-stress dielectric layer under wet oxygen on a six-inch silicon wafer, and to deposit metal afterward to fabricate interdigital sensing electrodes and micro heating element. Finally, inductively-coupled reactive ion etching (ICP RIE) was used to etch the backside of the device to render a suspended structure. Before carrying out the measurement, a voltage was applied to the microheater to increase the temperature while a thermal imager was used to monitor the temperature change. To prepare the sensing material, the sol-gel method was adopted to synthesize α-Fe2O3 nanoparticles and the variations in the characteristics of the films prepared at different annealing temperatures were assessed. The result showed that the grain size increases with the annealing temperature. Specifically, conducting the annealing at 400 °C for an hour would yield the α- Fe2O3 sensing film surface with more porous holes and a higher surface area layer, which is conducive for gas adsorption.
Finally, before initiating the measurement task, the initial resistance value should be stabilized first in the atmosphere to ensure the subsequent gas sensing readings are gathered on a reliable basis. With various gases sensed and duly compared, it is found that NOx appears to have a better sensing response and faster response/recovery times for α- Fe2O3 nano-films while subjecting the sensor to NO with a concentration of 50 ppb at operating temperature 200°C would show that a maximum response of 48%, reliable reproducibility, and stability of 53.54%.

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