使用原子層沉積與聚焦離子束技術應用於奈米微結構之製作與奈米電漿子之研究

Abstract

離子束微影技術在奈米結構，穿透式電子顯微鏡(Transmission Electron microscope)樣品製備和奈米結構沉積等等多種領域得到了廣泛的應用。離子束微影技術有很多優點，如無需光阻，特定區域上的離子佈質，較少的背向散射(和電子束微影相比)等。原子層沉積(Atomic Layer Deposition, ALD)是另一種在奈米結構製造中很有前景的方法，ALD可提供大面積上的良好保形性(conformality)，良好的再現性和高均勻性使其成為光電元件製作的重要技術。在本論文中，展示了結合離子束微影技術和ALD技術可以製造小於10nm的奈米結構以及其在表面電漿子方面的應用。 首先，我提出了一個叫自我微縮介電光罩(Self-Shrinking Dielectric Mask, SDM)的技術。SDM主要的原理來自於離子照射期間的再沉積效應和因為被離子照射加熱後介電層的溶融狀態變形，將其收縮到想要的奈米尺度。甚至可以透過這種技術製造小於3nm的結構。利用SDM的概念，可以在奈米尺度上任意地作出奈米結構。因此，SDM可以在下一代微影中扮演重要的角色。此外，透過調整氧化鋁陣列的初始深度，也可以做出小於10奈米的氧化鋁奈米柱。 另一方面，具有氧化鋁覆蓋層的表面電漿增強晶片可以透過ALD和熱蒸鍍系統的配合來製造。有氧化鋁覆蓋的晶片可以耐環境污染，有利於重複測量。極薄層的氧化鋁透過ALD的沉積可以均勻的包覆在銀的奈米顆粒外，ALD製程的高溫也可以使得奈米銀顆粒變得更圓。在氧化鋁包覆的狀態下，甚至也可以達到106的拉曼散射增強。 最後，我提出了透過氦離子束的金屬沉積與ALD的選擇性成長來製造高質量純化金屬結構的方法。在這篇研究中，我們選擇氦離子束，因為借由它所做出的ALD選擇性成長可以做到對基板的零破壞(damage-free)與十奈米的解析度。在此方法中的ALD金屬將僅沉積在預先由氦離子束寫入的種子層上來達到選擇性沉積。 小於10nm的微影對於半導體製程和高品質的表面電漿增強晶片是很重要的。而透過ALD和離子束系統的組合，可以做到小於五奈米的奈米結構，也可以做到對基板零破壞的選擇性成長同時保有十奈米的解析度，讓這兩個技術的結合在未來有更多的應用。

Ion beam lithography has been widely used and shown a great promise in a variety of fields such as nanostructures fabrication, TEM sample milling, or nanostructure deposition. There are a lot of advantages of the ion beam lithography technique, such as resistless lithography, ion implantation on specific area, less back scattering occurring as comparing to electron beam lithography, etc. Atomic layer deposition (ALD) is another promising technique to act a role in nanostructure fabrication. Several advantages such as good conformality, good reproducibility, and high uniformity over a large area make it an important technique in electrical and optical devices. In this dissertation, the combination of the ion beam lithography and ALD technique to fabricate sub-10nm nanostructures and their applications in plasmonics are demonstrated. First, a technique called Self-shrinking dielectric mask (SDM) was demonstrated. SDM method relies on a hard dielectric mask which will automatically shrink the critical dimension of nanopatterns thanks to the thermally induced reflow and the redeposition effect during the ion irradiation. Even sub-3nm patterns can be fabricated by this technique. With the concept of SDM, nanopatterns can be manipulated arbitrarily small on the nanometer scale. Hence SDM has paved a promising way towards the next-generation lithography in a variety of applications. Moreover, nanopillar can also be made by adjusting the initial patterns of the alumina array. On the other hand, plasmonic chips with alumina covered layer can be fabricated by the combination of ALD and thermal evaporation system. The alumina covered chips are resistant to detrimental environment which is advantageous to the repetition of the chemical detections. Furthermore, ultra-thin and comformal Al2O3 layer is covered on the Ag nanoparticles and the high temperature of the ALD process for the alumina growth reform the Ag particles on the plasmonic substrate. A 106 times Raman enhancement factor is measured even with the Al2O3 cover. Finally, a method based on a combination of the helium ion beam induced deposition and the area-selective ALD to fabricate high quality and purified metal structures was demonstrated. In this study, helium ion beam induced deposition was selected to deposit the seed layer owing to its abilities to do the damage-free seed layer deposition together with a 10 nm resolution. By this method, the ALD metal will only be deposited on the seed layer which was previously written by the helium ion beam. Sub-10nm lithography is critical and important to semiconductor process and high quality SERS substrate. By the combination of the ALD and the ion beam system, sub-5nm structures can be fabricated and the damage-free, high resolution metal deposition can be realized, which gives this combination promising possibilities.