利用分子動力學研究金屬薄膜的沉積與結構變化

Micro-structure and deposition of metal thin film studied by molecular dynamics simulation

蔡卓翰(John Tsai)

指導教授 ： 蕭百沂

國立清華大學/原子科學院/工程與系統科學系/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00363

摘要

隨著製程技術的進步，薄膜應用也變的廣泛。由於薄膜的性質與薄膜的結構有關，因此深入瞭解製程參數對於薄膜結構的影響，也變得比以往重要。本文利用分子動力學模擬，討論入射能量、晶格匹配度以及基板溫度等製程參數，對於薄膜磊晶成長過程的影響，研究主題包含：(一)側向原子距離、(二)磊晶程度、(三)薄膜覆蓋率、(四)表面粗糙度。研究結果顯示：晶格匹配度是決定薄膜是否能以pseudomorphic 的方式成長的主要關鍵。對FCC的金屬而言，提高入射能量會促使薄膜生長出具有優選方向為(111)的平面，同樣的我們也發現基板溫度提高也會促使薄膜生長出具有優選方向為(111)的平面。對表面粗糙度的研究發現，提高入射能量可以降低薄膜的表面粗糙度並提高覆蓋率，但是入射能量或基板溫度的提高會有一飽和值，當溫度或入射能量超過飽和值時對於表面粗糙度與覆蓋率並沒有再進一步的變化。 透過深入研究Cu/Ni(100)的系統，我們發現薄膜的表面粗糙度與覆蓋率在基板溫度為600K或入射能量為1eV時會有大幅度的改善；進一步提高溫度與入射能量，對於系統的表面粗糙度與覆蓋率並沒有的改善。但過高的基板溫度或入射能量卻會降低具有(100)優選方向的程度，因此要在(100)的Ni基板，保持同樣具有(100)優選方向的Cu薄膜，基板溫度須約控制在300K，而入射能量則須控制在0.4eV左右，才可以得到良好品質且與基材具有同樣優選方向的薄膜。

關鍵字

分子動力學模擬 ； 金屬薄膜 ； 表面粗糙度 ； 基板溫度 ； 入射能量 ； 晶格錯位

並列摘要

Because of the improvement of processing techniques, the applications of thin film have become more and more wider spread. The properties of the material strongly depend on its structure. As we know, many processing parameters such as incident energy, temperature of substrate, and misfit between film and substrate atoms play an important role in the thin-film deposition. Understanding the relationship between those processing parameters and the structure of thin film is very important. In this article, we investigate (1) lateral distance of film atoms、(2) prefer orientation、(3) roughness、(4) coverage by means of molecular dynamics simulations with Embedded atom method potential. The result shows that the misfit is the most important factor to obtain a pseudomorphic film. The degree of prefer orientation decreases as the temperature is increased. Moreover, the roughness and the coverage of thin film are found to be improved by increasing the incident energy or the substrate temperature. We found that this improvement will saturate at some value if we continue increasing the incident energy or the temperature.
Further study of Cu/Ni(100) system shows that the roughness and the coverage are both improved at 600K substrate temperature or with incident energy of 1eV. Nevertheless, if we increase further the temperature or the incident energy there will be no significant improvement for the system. Extra high temperature or incident energy, on the other hand, degrades the degree of prefer orientation of substrate. Therefore, to obtain a pseudomorphic thin-film of Cu/Ni(100), the substrate temperature should be controlled at around 300K and the incident energy should be fixed around 0.4eV.

並列關鍵字

molecular dynamics simulation ； incident energy ； metal thin film ； misfit ； roughness ； temperature