前瞻性奈米探針陣列之製作與應用

Abstract

奈米科技日漸重要，朝向微觀世界發展，首先要先製作出可以量測更精細的工具。目前已製作的各類探針情況各有侷限，比如有的散亂成長，無法成長探針在指定的位置，因此我們將研究奈米探針之製作方法，未來可以運用到生化系統上，降低誤差並提高操作的精確度，量測單一神經元細胞的奈伏至微伏訊號，最終預期將成為一前瞻性研究生物細胞等級的奈米工作平台，對往後生物醫學的研究與應用有突破性發展。 本論文針對奈米探針設定目標，由於未來希望運用在生物上研究生命跡象，因此內部為導電材料，而且探針尖小於30度。先用乾蝕刻方式，之後經熱氧化和去除的過程，使探針尖小於30度。奈米探針外部必須對周遭環境絕緣，以避免電雜訊干擾。因此奈米探針上增長熱氧化物，且利用濕式蝕刻法來得到開口式的探針。可有效控制探針成長的位置。研究中發展新式的半導陣列製造技術，結果不同的微影及蝕刻製程設計，成功的製造出各種不同型態的奈米探針，並瞭解其製程探針的成形機制。另外我們也嘗試在探針上以自我對準方式來成長單一奈米碳管。針對所發展之奈米探針，其場發射特性已成功的被測定到。

Nanoscaled tips are received much attention recently due to its versatile applications such as near-field optical microscopy, scanning tunneling microscopy, flat panel displays, and high-efficiency field emission. A sharp tip can induce the stronger field enhancement effect, and therefore, increase the field emission current. Similarly, the sharp tip is also beneficial for improving the spatial resolution in scanning probe microscopy. In this thesis, well aligned nanotip arrays by combining the electron beam lithography and reactive ion etching (RIE) technology are fabricated. From the SEM observation, a nanoscaled tip with apexes of about 12 nm radius and 500 nm height is achieved. The tip-end radius can be further sharpened by a subsequent oxidization and wet etch process to achieve a very smaller apex. The etching mechanism to form the nanotips is also discussed in this thesis. We find the remained photoresist on top of the tip is gradually reduced with increasing the etching time. The photoresist serves as the purpose of shielding mask to protect the underlying silicon. As the photoresist is fully etched away at the final, a pyramid-like shape is formed at the tip-end due to the etch probability of incident ion on the sidewall. We find a pyramid shape is formed although the initial pattern is defined as cylinder. The shape conversion is at various etching times. Interestingly, the initial shape is cylinder, and will turn into pyramid with tapered sidewall after 3 min etching. The tip becomes pyramid shape with slope sidewall after 6 min etching, and become pyramid with recessed sidewall after 7 min etching. The shape of the nanotip can influence the field emission property, and more field emission results will be given in the thesis.