以電化學原子層沉積銅釕薄膜之性質

利用電化學原子層沉積 (Electrochemical Atomic Layer Deposition, ECALD) 技術製備出原子層級的薄膜，可解決填洞與步階覆蓋性問題，此技術也可用至半導體銅製程合金薄膜。本實驗在銅 (Cu)薄膜摻雜了釕 (Ru)，Ru的高熱穩定性和低電阻率及化學穩定性佳，希望可以使Cu具有更好的穩定性作為研究之動機。但以ECALD法製作Cu-Ru合金薄膜之相關文獻闕如，本實驗就針對Cu-Ru合金薄膜作分析及探討。實驗利用表面侷限氧化還原取代反應，以及欠電位沉積法來製備銅釕 (Cu-Ru)。基板以玻璃基板上先用濺鍍法鍍上金 (Au) /鈦 (Ti)，然後用鉛 (Pb) 的還原電位製出鉛鍍層，再通入Cu溶液在開路電位條件下作表面侷限取代反應，讓Pb原子被Cu原子所取代，接著通入Ru溶液，施以Ru的還原電位製出Ru鍍層，穿插在Cu鍍層之間。Cu鍍層固定50次循環數，Ru鍍層分別有：10、25、50以及100次循環數，再用快速高溫退火爐(RTA)氬+氫 (Ar+H2) 的氣氛下，加熱至400℃持續5分鐘，探討得到之Cu-Ru薄膜的性質。薄膜性質利用四點探針 (FPP) 測量電性，以薄膜厚度輪廓測量儀 (Alpha-step) 測量薄膜厚度，X-ray繞射儀 (XRD) 作相結構分析，場發射掃描式電子顯微鏡 (FE-SEM) 觀察薄膜表面及斷面的微結構，能量光譜儀 (EDS) 測量成分比例，X-ray光電子能譜儀 (XPS) 觀察原子鍵結能和成分定量分析。實驗結果顯示在溶液pH值為3.5時，溶液還原電位分別為Cu：-0.1 V、Pb：-0.54 V、Ru：-0.6 V為最佳參數設定。當Ru鍍層越多時，因為Pb在Ru鍍層上的沉積速率會變慢，導致Cu所能置換的Pb鍍層變少而使Cu鍍層越薄，加熱400℃後的薄膜，會形成金銅合金，使電阻升高，但薄膜品質更緻密。

關鍵字

電化學原子層沉積；欠電位沉積；表面侷限氧化還原取代反應；銅；釕

並列摘要

Preparation of the atomic layer films by an electrochemical atomic layer deposition (ECALD) can solve step coverage issues. This technique can also be used to prepare copper alloy films for semiconductor process. This study presents copper (Cu) films doped with ruthenium (Ru), and hopes the film have a better stability because Ru has good thermal stability and low resistivity. However, preparation of Cu-Ru films by ECALD is rarely studied. This experiment is to analyze and discuss the Cu-Ru alloy films prepared by ECALD. Cu-Ru films were deposited on Au/Ti/glass substrates by ECALD. The process using surface limited redox replacement (SLRR) and underpotential deposition (UPD) to prepare the films. Pb UPD was formed at -0.54 V versus Ag/AgCl, and in Cu solution at open circuit for 1 minute performing redox replacement of Pb UPD by Cu. After that, Ru was deposited in solution at -0.6 V versus Ag/AgCl for 1 minute. The films were deposited by repeating the above processes. After deposition, the samples were annealed at 400℃ in Ar + H2 (95%+5%) atmosphere for 5 minutes. The sheet resistance of the film was measured by four-point probes, film thickness was measured by Alpha-step, crystal structure was analyzed by XRD, surface morphology and cross-sectional images were observed by FE-SEM, atomic concentration was measured by EDS, and atomic binding energy and quantitative analysis were measured by XPS. The results showed that optimal parameters can be obtained at UPD of Cu sol. : -0.1 V, Pb sol.: -0.54 V, and Ru sol. : -0.6 V from the pH 3.5 solution. Cu deposition gradually decreased when increasing Ru deposition because deposition rate of the Pb was slowed down on the Ru film. Au-Cu alloy was formed after annealing at 400℃ for 5 minutes, which resulted in an increase in resistance and densification of the film.

並列關鍵字

Electrochemical atomic layer deposition ； Underpotential deposition ； Surface limited redox replacement ； Cu ； Ru

參考文獻

[1] J. M. Shieh, S. C. Chang, B. T. Dai, M. S. Feng, 2002, “Investigation of Superfilling and Electrical Characteristics in Low-Impurity-Incorporated Cu Metallization”, Jpn. J. Appl. Phys. Vol. 41, pp. 5104-5107.

[2] Y. Wang, M. L. Zhang, F. Cao, Y. T. Liu, L. Shao, 2011, “Interficial stability of Cu/Cu(Ru)/Si contact system for barrier-free copper metallization”, Journal of Alloys and Compounds, 509, L180-L182.

[3] J. L. Stickney, B. H. F. Jr., T. L. Wade, J. W. Garvey, M. Lay, U. Happek, 2002, “Atomic layer epitaxy of CdTe using an automated electrochemical thin-layer flow deposition reactor”, Journal of Electroanalytical Chemistry, 524-525, 273-285.

[4] İ. Şişmana, U. Demirb, 2011, “Electrochemical growth and characterization of size-quantized CdTe thin films grown by underpotential deposition”, Journal of Electroanalytical Chemistry, pp.222-227.

[5] K. Mohanraj, E. Esakkiraj, S. P. Sheik Abdul Kadhar, J. Henry, S. Kannan, S. Barathan, G. Sivakumar, 2013, “Optostructral and vibrational characteristics of Cu:CdS nanoparticles by precipitation method”, Optik - International Journal for Light and Electron Optics, pp. 5229-5231.

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以電化學原子層沉積銅釕薄膜之性質

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