探討垂直矽奈米線延伸式閘極離子感測場效電晶體

Study of Vertical Silicon-Nanowire Extended-Gate Ion-Sensitive Field Effect Transistor

王瑞興(Rui-Xing Wang)

指導教授 ： 林致廷

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002593

摘要

定點照顧檢驗系統 (POCT) 是下一代醫療健保系統的趨勢之一。定點照顧系統的建立需要有高靈敏度、成本低等優點的電化學感測器。而延伸式閘極離子感測場效應電晶體 (EGISFET) 是其中一種電化學感測器，EGISFET在許多方面皆優於離子感測場效應電晶體 (ISFET)，然而解析度與靈敏度之間的取捨，一直都是EGISFET很大的問題。故有著高解析度且高靈敏的EGISFET陣列感測器，是許多研究人員的最大目標。在我的研究中，我們製作出不同高度的垂直矽奈米線延伸式閘極離子感測場效應電晶體(SiNW-EGISFET)，不同高度的垂直矽奈米線是利用金屬輔助化學蝕刻做出，在蝕刻過程中會用到的金屬奈米網格是由我們重複使用的陽極氧化鋁翻印而成，過程中的材料與蝕刻方法，所花的成本相對於傳統方法都低很多。最後我們使用曝光顯影定義出感測區範圍。我們使用COMSOL模擬來獲得電雙層電容/靈敏度增加率與矽奈米線高度的關係。經量測後發現，SiNW-EGISFET的pH靈敏度皆大於平面結構且趨勢與COMSOL模擬結果相同。為了探究實驗結果背後的數學關係，我們推導出了一個簡單的模型，模型結果趨勢也與實驗結果相同。我們認為在奈米線間擴散層的重疊是靈敏度增加的原因。基於這項研究，我們可以在無法縮小奈米結構間距的情況下，繼續增加感測器靈敏度。這對於建立能應用在定點照顧檢驗系統的高靈敏度感測器有非常大的幫助。

關鍵字

垂直矽奈米線 ； 延伸式閘極離子感測場效應電晶體 ； 離子感測場效應電晶體 ； 陽極氧化鋁 ； 金屬輔助化學蝕刻 ； 電雙層 ； pH靈敏度

並列摘要

Point-of-Care Testing (POCT) is one of the future trends in the next-generation healthcare system. POCT requires electrochemical sensors with characteristics, such as high sensitivity, cost efficient, etc. Extended-gate ion-sensitive field-effect transistor (EGISFET) is one of the electrochemical sensors for biochemical sensing. Nevertheless, in EGISFET there is a trade-off between pixel-resolution and sensitivity. In my thesis, vertical silicon nanowire (SiNW) EGISFET with different heights are fabricated. SiNW with different heights are produced by metal-assisted chemical etching (MACE). The metal nanomesh utilized in MACE is replicated from a reused anodic aluminum oxide (AAO) template. By photo-lithography the sensing area on the SiNW sensing membrane is defined. A COMSOL simulation of relationship between capacitance of electric double layer/enhanced sensitivity ratio and heights of SiNW have been performed. The transfer characteristics of such SiNW EGFET pH sensors exhibit a higher sensitivity than that of the conventional planar EGISFET for the different pH solutions and is basically in accordance with the COMSOL simulation results. In order to obtain the mathematical relationship behind the experiment results, a rudimentary derivation has been performed. The trend of derivation is also in accordance with the experiment results. We believe that the high sensitivity originates from the extension of diffuse layers between SiNW as opposed to planar structures. This development has considerable potentials and provides opportunities for realization of chemical/biological sensor array with high pixel-resolution and high sensitivity.

並列關鍵字

silicon nanowire (SiNW) ； Extended-gate ion-sensitive field-effect transistor (EGISFET) ； anodic aluminum oxide (AAO) ； metal-assisted chemical etching (MACE) ； electric double layer (EDL) ； pH sensitivity

參考文獻

[1] W. Jung, J. Han, J-W Choi, C. H. Ahn, Point-of-care testing (POCT) diagnostic systems using microfluidic lab-on-a-chip technologies. Microelectronic Engineering 132, 46-57, 2015.

[2] Agnieszka A.Zuber, Elizaveta Klantsataya, Akash Bachhuka, Comprehensive Nanoscience and Nanotechnology (Second Edition) 3, 105-126, 2019.

[3] R. Yan, S. Qiu, L. Tong, Y. Qian, Review of progresses on clinical applications of ion selective electrodes for electrolytic ion tests: From conventional ISEs to graphene-based ISEs. Chemical Speciation Bioavailability 28, 72–77, 2016.

[4] P. Bergveld, Development of an Ion-Sensitive Solid-State Device for Neurophysiological Measurements. IEEE Transactions On Bio-Medical Engineering BME-17, 70-71, 1970.

[5] L. Bousse, S. Mostarshed, B. van der Schoot, and N. F. de Rooij, Comparison of the hysteresis of Ta2O5 and Si3N4 pH-sensing insulators, Sensors and Actuators B 17, 157, 1994.