利用自組裝單層膜達成區域選擇性原子層沉積技術之研究

Abstract

隨著電子元件尺寸朝向低於十奈米的發展，許多圖案化薄膜技術逐漸受到挑戰，如何降低對準的誤差也成為重要的議題。解決該問題的方案之一為透過區域選擇性原子層沉積技術，此方法為利用有機分子材料來達到區域性失活以阻擋薄膜的沉積，而在未失活的區域則能夠沉積欲成長的氧化物，因此有助於提高製程的整合度。本論文針對該方法進行研究，內容主要為透過液相及氣相兩種方式來沉積自組裝單層膜，以達到區域選擇性原子層沉積的效果。 首先，第一部分為以液相的方式，將鈷金屬基板及二氧化矽基板浸泡在配置好自組裝單層膜的溶液當中，其中的磷酸正十八酯自組裝單層膜能夠選擇性披覆在鈷金屬表面上，使表面具有較高的疏水性，在後續能夠有效屏蔽50-cycle氧化鋁的沉積，反之，在二氧化矽基板上自組裝單層膜的披覆極少，因此透過這樣的差異性，能做到一定程度的選擇性效果。接著，第二部分我們利用氣相的方式，在Savannah 100 ALD機台上沉積另一種自組裝單層膜有機分子-1H,1H,2H,2H-全氟辛基三氯矽烷作為阻擋層，由於此分子頭端基團為矽烷，與前述磷酸正十八酯自組裝單層膜所使用的磷酸根並不同，因此我們將對其在二氧化矽及矽表面兩種不同官能基結尾差異所造成不同的披覆程度，進行探討和研究。 在本論文中，我們以橢圓偏振光譜儀量測薄膜的光學性質和做為量測膜厚的方法，而接觸角量測儀能夠快速幫助我們得知表面的疏水性，作為自組裝單層膜在基板表面披覆程度的依據。在進一步的材料分析中，我們亦透過穿透式電子顯微鏡得到精確的膜厚、X射線光電子能譜學分析表面化學元素的構成，以及利用導電原子力顯微鏡來了解表面的粗糙程度和表面缺陷的分布。

With the continuous evolution of modern electronic devices, conventional lithography processes have appeared to be challenging when the feature size of nanoscale devices is aggressively scaled deep into the nanometer range. Elimination of the alignment error caused by nanopatterning processes has become a vital issue. One of the solutions is to use the area-selective atomic layer deposition (AS-ALD) technique for the improvement of process integration. The AS-ALD technique utilizes polymers for regional deactivation of the underlying surface to prevent the deposition of the thin film on the particular region, whereas the materials can be successfully deposited on the activated surface, which ultimately realizes the area selective deposition. In this thesis, the liquid- and gas- phase self-assembled monolayers (SAMs) were investigated to optimally achieve AS-ALD. In the first part, the liquid phase method was used and the substrates, containing cobalt (Co) and silicon dioxide (SiO2), were immersed in the prepared solution. The liquid-phase SAM, octadecylphosphonic acid (ODPA), can selectively cover on the surface of Co to increase its hydrophobicity. This subsequently prevents the Co surface being deposited by a layer of aluminum oxide (Al2O3) using ALD. However, Al2O3 can be deposited on top of SiO2 since it has barely been covered by ODPA. Therefore, a certain extent of selectivity can be achieved due to the difference of surface functionality. In the second part, the gas-phase SAM, tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS), incorporated in the Savannah ALD tool was adopted as the blocking layer. The details of the surface reaction and the coverage of FOTS on SiO2 and Si interface were investigated and discussed in this thesis. In the experiment, spectroscopic ellipsometry (SE) was exploited to characterize the optical properties and thickness of the thin films, including SAMs. On the other hand, water contact angle measurement was performed to probe the hydrophobicity of the surfaces, which is a strong indicator of the coverage of SAMs. Furthermore, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and conductive atomic force microscope (CAFM) measurements were carried out to extract the accurate thickness, the chemical composition, and the surface roughness and defect distribution, respectively.