電化學機械研磨金屬銅與其電化學特性的研究

The Study on Electromechanical Polishing of Cu Metal and Its Electrochemical Charateristics

吳君薇(Jiun-Wei Wu)

指導教授 ： 顏溪成

國立臺灣大學/工學院/化學工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.03264

摘要

有別於傳統的化學機械研磨(CMP)，電化學機械研磨(ECMP)可以使用較小的施加應力(< 0.5 psi)，不至於傷害到微孔結構的低介電常數介電物質層，更因為外加電場可有效的提高導線銅的移除速率；此外ECMP可以使用不含研磨粒子的研磨液，可避免傳統CMP必須後清洗與金屬表面殘留研磨粒子造成各種缺陷的困擾。本研究著重在銅電化學機械研磨效能的影響，並探討在H3PO4-based電化學機械研磨時的施加電壓、下壓力、相對轉速等操作參數對於電化學機械研磨金屬銅的影響以及其腐蝕動力學的現象探討；另外更探討了Cu在不同研磨粒子磷酸研磨液中與抑制劑聚乙二醇的添加之電化學特性，及其對研磨速率的影響。利用直流極化曲線與開環電位等電化學量測，探討了包括表面鈍化、腐蝕溶解等反應以及其與機械作用間的關係，再利用交流阻抗技術分析Cu在施加電位的磷酸研磨液中的反應機制。原子力學顯微鏡(AFM)則被採用作為研磨前後表面平坦度和組成成分的分析。實驗結果顯示，施加電壓是影響Cu ECMP的最主要參數。而當施加電壓0.1V增加到0.8V，會造成研磨速率變快，而使Cu表面的鈍化層變薄，且銅片研磨後的表面粗糙度由12.63nm大幅上升至57.54nm，顯示其表面粗糙度有大幅上升的趨勢。此外，在Cu ECMP研究上添加研磨粒子的不一定能輔助機械磨損作用增加移除速率外，並會造成研磨後Cu表面平坦度大幅降低，因此在ECMP研磨機制下添加研磨粒子並非提升Cu研磨移除效能與改善磨後平坦度的有效方法。另外抑制劑PEG的添加在磷酸研磨液中會造成PEG與Cu表面有以類似吸附作用附著於表面改變其表面狀態，並有效阻礙了Cu與研磨液中的腐蝕作用，增加了Cu氧化層生成的時間，藉此以提高Cu ECMP的研磨後平坦度，藉以得到較佳的研磨效能。

關鍵字

電化學機械研磨 ； 抑制劑 ； 研磨粒子 ； 銅 ； 電化學量測

並列摘要

Unlike conventional chemical mechanical polishing (CMP), electrochemical mechanical polishing (ECMP) enables virtually zero downforce (< 0.5 psi), which can manage the weak mechanical strength of low-k dielectrics. In addition, in this new voltage-induced ECMP technology, we can use slurries without abrasives, which can not only evade the procedure of post-cleaning but also avoid the defect caused by abrasives. In this study, we focus on the efficacy and corrosion kinetics during Cu ECMP in H3PO4-based slurries by operating parameters of applied potential, downforce, and rotated speed. Also, we discuss the electrochemical effect of adding abrasives or adding inhibitor of PEG. By performing electrochemical measurements such as polarization curves and open-circuit potentials, we investigate the relationship between electrochemical corrosion and mechanical abrasion during Cu ECMP. Furthermore, surface morphological analysis after ECMP was carried out by atomic force microscopy (AFM) to acquire the roughness of Cu surface before and after ECMP process. The experimental results show that applied potential is the main operation parameter during Cu ECMP. As applied potential increases from 0.1V to 0.8V, it would increase the removal rates of Cu, causing thinner passive film, and the roughness of Cu surface would also increase from 12.63 nm to 57.54 nm, lowering the planarity or the polished Cu surfaces. Besides, on the research of adding abrasives, the outcome shows that adding abrasives may not support mechanical abrasion and therefore it is not a effective way to improve the planarity after Cu ECMP. Moreover, we confer the viscosity effect and the change after adding PEG 600. The experimental results indicate that inhibitor of PEG would be adsorbed on the Cu surface, causing denser Cu oxide layer. Adding inhibitor in H3PO4 slurries effectually hinder the corrosion reaction, attaining high planarity and polishing performances.

並列關鍵字

ECMP ； Inhibitor ； abrasives ； Copper ； Electrochemical measurement

參考文獻

陳怡秀，化學機械研磨阻障層鉭與其電化學特性的研究，台大化工所碩士學位論文 (2010)。

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