Effects of Thin-Film Properties on Pattern Transfer Mechanism of Direct Metal Imprint

直接奈米壓印應用於金屬薄膜性質及其成型機制之研究

姚中翰(Chung-Han Yao)

指導教授 ： 宋震國

國立清華大學/工學院/動力機械工程學系/博士(2009年)

摘要

In this study, we experimentally investigated the effects of metallic thin-film properties on pattern formation using a direct nanoimprint process. Instead of the methods being commonly used to form nanostructures on polymers, direct nanoimprint process was used for the fabrication of subwavelength structures on aluminum thin films. We focused on determining mechanical properties such as grain size, defects, fabrication processes and substrate materials. Aluminum thin films were used as transfer materials, the grain size and microstructures of which were controlled using different deposition process and parameters. The mechanical properties of thin films were determined by nanoindentation experiments. Formation height was applied to analyze the formation qualities in the nanoimprint process and was measured by atomic force microscopy. Scanning electron microscopy and transmission electron microscopy were utilized to analyze the surface topography, grain size, microstructure, and internal defect of thin films. From the experimental results, the following phenomena were observed. With a larger line width to pitch ratio (LPR) of the mold, the formation height ratio is higher. Different pile-up mechanisms lead to transferred patterns with dual peaks or a single peak. For aluminum films of the same thickness, hardness decreases when grain size increases, a phenomenon called the Hall–Petch effect. When the grain size of the thin films increases, formation height increases because hardness decreases. For the same formation height, the imprinting force decreases with the softer substrates. In this study, the relationships between grain size, hardness and formation height for different fabrication methods and different substrates were determined. The formability of the metallic thin films was improved through suitable parameter control.

關鍵字

奈米直壓 ； 製程參數 ； 金屬結構 ； 晶粒大小 ； 奈米壓痕實驗

並列摘要

不同於一般壓印於高分子，本文研究採用本實驗室所提出之直接壓印製程，將次波長奈米結構直接轉印至金屬薄膜。文中主要針對薄膜機械性質，包括晶粒大小、微結構缺陷、濺鍍製程與基材種類，討論對於奈米壓印成型性的影響。薄膜材料使用鋁金屬，藉由改變薄膜濺鍍製程與參數來達到改變晶粒大小與顯微結構不同，並利用奈米壓痕實驗來確認材料機械性質。原子力顯微鏡(AFM)用來量測壓印實驗後之成型高度，並以此做為判斷鋁薄膜成型品質的依據。掃描式顯微鏡(SEM)與穿透式電子顯微鏡(TEM)則用來分析薄膜材料的表面形貌、晶粒大小、顯微結構與缺陷觀察。由實驗結果可以觀察到下列現象：隨著模具的線寬節距比(LPR)越大，成型高度比也越好，同時可觀察到不同的堆積情形而呈現出單峰或雙峰現象；在相同薄膜厚度下，硬度隨著晶粒大小增大而降低，符合Hall-Petch效應。當薄膜中的晶粒增大，因硬度降低會使成型高度提高；相同成型高度下，壓印力隨著基材越軟而越小。依據本文，可得到晶粒大小、硬度、成型高度相對於不同濺鍍製程與不同基材的關係。藉由適當的控制製程參數，壓印成型高度可獲得足夠的改善。

並列關鍵字

Direct nanoimprint ； Process parameters ； Metallic pattern ； Grain size ； Nanoindenter

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