鉑矽化物奈米線生物感測器之製造與應用研究

Abstract

近年來一維奈米結構材料廣泛的被研究利用來當作高靈敏度的分子感測器，能夠偵測的多種微小物質，例如:離子、蛋白質、DNA以及氣體分子等等。在實驗室裡，雖然奈米碳管或者矽奈米線可能達到單分子偵測的能力，但是其製作卻難以與現代的半導體製程相容。為了改善這個缺點，在本論文中利用標準的半導體製程技術，製造出經濟又大量的鉑矽化物奈米線感測元件。 首先，我們利用電子束微影技術(Electron-Beam Lithography)以及濕式蝕刻的方法，製作出50-60nm的多晶矽奈米線。在多晶矽奈米線表面沉積金屬鉑之後，進行400℃、450℃、500℃、550℃及600℃快速退火，利用王水在75℃的溫度下將未參與反應的鉑蝕刻掉，能夠得到40nm的鉑矽化物奈米線。再者，我們在鉑矽化物奈米線表面修飾上APTMS，當作奈米線與DNA之間的Linker，讓我們能夠將單股DNA固定在奈米線表面，並偵測另一股特定序列的單股DNA。利用鉑矽化物奈米線表面電荷的不同會影響奈米線本身導電性的結果，來偵測特定序列的DNA。並且在實驗過程中利用DNA的螢光標定結果顯示，證明鉑矽化物奈米線確實是一良好的DNA感測元件。

One-dimensional nanostructures are good candidates for use in many applications as ultrasensitive, miniaturized molecule sensors for monitoring, for example, ions, proteins, DNA, and gases. Carbon nanotubes and silicon nanowires can behave as single-molecule biosensors, but the fabrication methods that been used to create such devices are not compatible with modern semiconductor manufacturing techniques, and large-scale integration is problematic. In this Thesis, we demonstrate the detection of DNA molecules, based on their intrinsic charge, by using a cheap polysilicon nanowire fabricated through standard “top-down” semiconductor processes. First, we fabricated the 80-nm polysilicon nanowire through direct e-beam writing and shrank the width of the nanowire to 50–60 nm through wet etching. After depositing a thin platinum film using a sputtering system, we used rapid isothermal annealing technology to form the platinum silicide at temperatures ranging from 400 to 600 °C. The resulting wafers were immersed in a solution of HNO3/HCl/H2O (1:3:4) at 75 °C to remove any unreacted platinum. After this step, we obtained platinum silicide grain nanowires having final line widths that had shrunk to 40 nm; we determined the temperature at which they were most sensitive toward the intrinsic charge of DNA. Next, we modified the nanowires’ surfaces for the goal of using them for biosensing. The platinum silicide surface was modified using APTMS to present amino groups and then single-stranded DNA was immobilized through these groups to allow the detection of its complementary single-stranded gene sequence. In a control experiment, we prepared a fluorescently labeled single-strand DNA so that we could observe, using fluorescence microscopy, that it did reside on the platinum silicide nanowire. Finally, we used a semiconductor analyzer to measure the conductance of the nanowires at each step of the modification process. We fabricated this nanowire-based DNA device through a successful combination of top-down and bottom-up processes; this approach highlights the possibilities of fabricating sensor arrays at high density and directly integrating them into silicon-based circuitry.