請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/4618
標題: | 利用飛秒聲學量測原子級界面層之彈性性質 Probing Elastic Properties of Atomically-thin Interfacial Layer by Femtosecond Acoustics |
作者: | Hui-Yuan Chen 陳薈元 |
指導教授: | 孫啟光(Chi-Kuang Sun) |
關鍵字: | 飛秒聲學,界面層,彈性係數,聲學阻抗,聲子,熱傳導, interfacial layer,elastic property,femtosecond acoustics,phonon,thermal management, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 隨著現今高科技半導體製程持續朝著微縮的方向發展,各種先進製程設計出更複雜的堆疊結構、更稠密的材料組合,以期達到最高空間利用而增進元件整體的效能。在這樣的趨勢下,材料與材料間的界面數量相較以往大幅增加;然而,很多證據都顯示,在兩個異質材料間往往會有一層接近原子層級厚度(約0~3奈米)的界面層產生。我們認為此界面層之存在可能會改變兩兩材料間的熱傳導,進而影響元件的效能與可靠度;由於熱效應會隨元件尺寸愈小而愈發彰顯,此界面層的存在對於元件散熱的潛在影響更是不容忽視,因此成了我們主要研究的對象。
在半導體材料中,熱主要是藉由聲學聲子之運動而傳遞。由於聲學聲子本質上就是固體材料中的彈性波,因此元件材料的彈性性質(如:聲阻抗、彈性係數等)便是了解聲子在材料中傳遞行為的關鍵,也成了處理元件散熱問題的重要資訊。然而,據我們所知,常見用於量測極薄材料之彈性性質的技術如:奈米壓痕技術、雷射表面聲波技術、表面布里淵散射技術等,都無法量測前述如此薄之界面層之彈性性質。而在此論文中,我們提出並示範飛秒聲學是一個有效量測此原子級厚度的界面層彈性性質的技術。 我們首先設計並建立了一個界面層模型系統(其結構為:氮化鎵/界面層/氧化鋁),經由電子顯微鏡確認,其中的界面層約為5~6層原子層,厚度為1.85奈米。接著,我們利用飛秒超聲學技術的高空間與時間解析力,成功量測出此界面層的兩項彈性參數:聲阻抗與彈性係數。最後,我們簡單探討了此界面層之存在可能對於兩材料間熱能傳遞上的影響,以呼應我們的研究初衷。 從我們的研究可顯示,飛秒聲學技術是一種合適的方式來偵測原子級薄的界面層之彈性性質,提供了研究熱傳導所需的材料參數,對於為未來解決奈米元件散熱問題可說是重要的一步。 While the developing trend of modern electronic devices is toward scaling down, heat removal is a critical issue since thermal effect becomes seriously significant as dimensions shrink. Besides, many complex and denser structures such as 3D integrated circuits or FinFET were designed to exploit the limited space and optimize the overall device performance, which is a trend well-characterized by Moore’s law. However, it is well-known that an interfacial layer (IL) is usually formed between two adjacent heterogeneous materials. The existence of this unavoidable interfacial layer might hinder the heat conduction in those fabricated devices, and thus certainly diminishes their operational lifetime. Since heat is mainly carried by acoustic phonons, elastic property of materials is among the essential information for thermal management. Unfortunately, a proper technology to probe the elastic property of this atomically-thin interfacial layer has not yet been documented. In this thesis, we designed an interfacial layer (IL) model system between bulk GaN and Al2O3 film, and conducted femtosecond acoustic measurement to obtain the elastic properties of the IL. The acoustic impedance, mass density and a cross-plane elastic constant of the IL were successfully obtained. We further evaluated a 16% reduction in thermal energy transmission owing to the IL from a theoretical calculation. With the capability of probing the elastic properties across layers of only several atoms thick, our demonstration could be deemed as the first step to deal with heat dissipation issue stemming from the ILs. Hopefully, our approach will provide a better thermal management for nano-scaled devices in the future. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/4618 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 光電工程學研究所 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-104-1.pdf | 2 MB | Adobe PDF | 檢視/開啟 |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。