探討感測層奈微米結構對離子感測場效電晶體靈敏度的影響

Effects of Submicron Structures in Sensing Membranes for Ion-Sensitive Field Effect Transistor

蔡承佑(Chen-Yu Tsai)

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(2021年)

https://doi.org/10.6342/NTU202102765

摘要

延伸式閘極離子感測器(EGISFET)是一種穩定且堅固的電化學感測器，這類的元件時常被應用於生物化學效應的感測，其發源於傳統離子感測器(ISFET)，但卻擁有較佳的穩定性與耐用性。雖然EGISFET已是一個發展許久且十分具有應用性的元件，EGISFET的感測靈敏性卻有其極限，此即為能斯特極限(Nernst limit)。因此，在我的論文中，我們便利用solid-state dewetting效應以及metal-assisted chemical etching的蝕刻方式嘗試於矽基板上製造簡單可控的奈米孔洞的結構，再將其作為EGISFET的延伸式閘極，並探討不同的奈米孔洞結構對元件靈敏度的提升效果。在本研究中，我們利用solid-state dewetting效應沉積一層奈米金屬顆粒於矽基板上，將其作為遮罩並再利用metal-assisted chemical etching的蝕刻方式蝕刻出奈米孔洞，之後便用掃描式電子顯微鏡觀察其孔洞分布，再將此結構作為延伸式閘極連接至MOSFET上，並量測元件對於不同pH值溶液的pH靈敏度。其pH靈敏度的提升主要與electrical double layer與site-binding現象有關。在量測與分析之後，我們確認了利用這樣的奈米孔洞結構能有有效提升元件靈敏度，並且於特定情況下得以超越能斯特極限。

關鍵字

pH靈敏度 ； 延伸式閘極離子感測器(EGISFET) ； 奈米孔洞狀結構 ； 固態除潤 ； 金屬輔助化學蝕刻(MACE) ； 電雙層 ； 氧化層結合點位

並列摘要

Extended-gate ISFETs (EGISFET) is a kind of robust, stable electrochemical sensor that is able to detect numerous biochemical reactions, it spawned from the device of ISFET but possess better stability and durability. Although it is a powerful device, it has its sensitivity limit, which can be predicted by the Nernst equation. In our research, we focus on how to simply utilize the effect of solid-state dewetting and metal-assisted chemical etching (MACE) to fabricate a tunable, cost-effective Si nanopore structure. After the realization of a Si nanopore structure, we would use the device as the sensing membrane of EGISFET, and discuss the relationship between the sensitivity improvements for Si nanopore structures with several different characteristics. As for the manufacture process, solid-state dewetting effect is utilize to deposit a layer of metal nanodroplets onto the Si substrate. This layer of nanodroplets is then used as a mask for MACE, after the etching process, we use SEM to observe the resulting Si nanopore structure. The Si nanopore structure is then used as the sensing layer of EGISFET. Lastly, pH sensitivity for each device is measured. The sensitivity improvements of the device are mainly contributed by the effect of electrical double layer and site-binding effect at the surface of sensing membrane. According to the result of our research, we are able to produce a pH sensing EGISFET with sensitivity higher than typical EGISFET device, in some cases, even exceeding the Nernst limit.

並列關鍵字

pH sensitivity ； Extended-gate ion-sensitive field effect transistor (EGISFET) ； silicon nanopore ； solid-state dewetting ； metal-assisted chemical etching (MACE) ； Electrical double layer (EDL) ； site-binding

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