分子動力學模擬於大馬士革製程中銅沉積與微結構之研究

Study on Trench-Filling and Microstructure of Copper Damascene Process via Molecular Dynamics Simulation

洪榮泰(Rong-Tai Hong)

指導教授 ： 黃美嬌

共同指導教授 ： 楊照彥

國立臺灣大學/工學院/機械工程學研究所/博士(2006年)

https://doi.org/10.6342/NTU.2006.01246

摘要

本論文以平行分子動力學模擬，模擬在物理氣相沉積下， 銅金屬原子以濺鍍法方式沉積在導線凹槽內之銅大馬士格製程。 分別研究大馬士格製程中銅金屬沉積在凹槽的形貌及微結構之變化。 所探討之凹槽內擴散阻絕層結構分別為: 鈦單晶六面密堆疊表面指數(0001)， 以及鉭單晶體心面之表面指數(100)、 (110)及(111)。在形貌方面 ， 主要探討基板溫度、 入射動能及凹槽之展弦比參數下， 對不同阻絕層之材料下之覆蓋百分比。 在微結構方面， 對鉭擴散
阻絕層不同的晶格表面下， 分析銅對鉭擴散阻絕層之沉積紋路及銅原子與擴散阻絕層混合情形。
在分子動力學模擬中 ， 所使用之原子間勢能函數為Johnson的解析鄰近嵌入式原子方法。 基於勢能函數轉換不變性的理論下， 來處理本文銅原子與擴散阻絕層材料Cu/Ta及Cu/Ti之合金勢能之計算。 由結果可知 ， 增加基材溫度及入射銅原子之動能 ，可提昇覆蓋程度。由於鉭相對於鈦具有較佳熱穩定性及較深的勢能井，銅原子之沉積覆蓋相對較高於以鈦為主之擴散阻絕層。此外 ， 鈦之合金的形成相較於鉭為主來得嚴重。 對鉭不同表面指標下，具有表面開口結構之(100)鉭晶格下， 其覆蓋程度相對較差， 這對在高展弦比下所形成之效果更為明顯。對於沉積紋路所形成方向 ， 在較高表面能量之擴散阻絕層下， 所形成之紋路較傾向水平，反之則以垂直纖維形成。 此外 ， 基材溫度也會影響沉積紋路之方向。
本文使用叢集電腦環境來發展凹槽沉積平行分子動力學模擬:空間分割及原子分割法之平行程式碼， 比較上述平行算則，在不同的叢集電腦系統之適用性及效能。由本文結果， 由於空間分割法在資料交換的次數較低， 其效能大於原子分割法。

關鍵字

大馬士革製程 ； 擴散阻絕層 ； 平行分子動力學模擬

並列摘要

The trench filling and microstructures of depositing copper atoms on the titanium and tantalum diffusion barrier layers in a damascene process have been studied using parallel molecular dynamics simulation with the embedded atom method (EAM) as interaction potential for the present alloy metal system which is based on the invariance transformation of alloy system. The effects of different process parameters including incident energies of depositing atoms, substrate temperature, the different surface indices of tantalum and the aspect ratio of trench were investigated. The surface indices of tantalum layer considered were (100), (110) and (111) and the aspect ratios were 1, 1.5 and 2, respectively.
The coverage of trench filling is improved as increasing the substrate temperature and incident copper atoms energy. Comparing with titanium and tantalum diffusion barrier layers under the same process parameters, it is found that due to a better thermal stability significant improvement in coverage percentage can be obtained using the tantalum barrier layer, especially at higher substrate temperatures. The enhancement of trench filling is studied in case of (110) and (111) crystal structure of tantalum because there are fewer open structures in sidewall of diffusion barrier layers. In microstructure of trench filling, the alloy formation is serious in the case of titanium than that of tantalum diffusion barrier layers. The orientations of textures are changed with different surface energies and the deposited copper within trench has fiber structure with lower surface energy.
To treat a larger system, parallel molecular dynamics simulation is also implemented and we compare the efficiency of different PC cluster computing environments including homogeneous and heterogeneous computer systems. The clarification of the suitability is studied between such systems. In this work, the different parallel schemes are developed including atomic and spatial decomposition methods. Comparing the efficiencies between the two schemes, the spatial decomposition performs better in this work.

並列關鍵字

Damascene process ； diffusion barrier layer ； parallel molecular dynamics simulation

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