矽奈米線元件於分子感測之最佳化研究

Abstract

當帶電生物分子鍵結於奈米線表面時，半導體奈米線中載子如電子和電洞會受到帶電生物分子的影響，形成累積和空乏及反轉的現象。當奈米線表面鍵結量達飽和時，由於表面原子數與體原子數比例(ratio)極大。帶電生物分子將主導奈米線輸出電流電荷特性，在不同生物分子溶液濃度下將有不同輸出電流特性變化；且觀察電流特性變化的方向可知道生物分子帶電的極性；更進一步地可以用Dip-pen Nanolithography(DPN)的方式在奈米線上進行區域選擇性沉積生物分子。 由於元件本體對奈米線周圍環境濃度變化極為敏感，因此我們將元件電流特性變化用於生物物質感測上，驗證了奈米導線元件於生物感測上的應用性。吾人使用ISE-TCAD軟體來模擬當帶電生物分子吸附在奈米線場效電晶體上時，在那些操作的條件下，可以獲得較好的敏感度；以及藉由閘極電壓的變化，可以求出帶電生物分子吸附的密度。

Binding of charged biological molecules on the surface of silicon nanowires (SiNWs) causes the carriers accumulation and depletion or inversion in conduction channel so that conductivity of nanowire changed. Moreover, the shift in current-voltage characteristics is linearly dependent to the binding density and the charge polarities. By judging the shift direction, the polarity of biological molecules can be easily identified. And, by manipulating the bias of the bottom gate, the charge density of binding molecules can be estimated. The thesis also emphasizes on the optimization of operation parameters so that the highest sensitivity achieved. To understand the detection limits using silicon nanowire devices in molecule detection and to mimic the molecules anchoring using dip-pen nanolithography, nanometer scale top gate was simulated. Finally, instead of developing a home-made program, a commercial simulation tool, ISE-TCAD, was adopted to simulate the SiNW devices for biosensing so that the devices can incorporate with the modern IC process smoothly.