雙氧水系統中銅/釕化學機械研磨之電化學特性研究

The Study of Electrochemical Characteristics of Cu/Ru CMP in Hydrogen Peroxide Systems

郭昱汝(Yu-Ru Kuo)

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(2017年)

https://doi.org/10.6342/NTU201701550

摘要

隨著積體電路中開始以銅導線製程取代鋁導線製程，為了克服銅導線容易擴散進入導線間質的缺點，使銅導線的擴散阻障層(Diffusion barrier layer)研究越來越多，釕金屬(Ru)做為擴散阻障層材料甚具潛力，其主要特色為在超薄厚度之下仍保有低阻值的效能。因此，本研究以釕作為銅導線之擴散阻障層，進行銅/釕化學機械研磨之電化學特性探討。
實驗中以定電流法將釕沉積於銅基材上，將釕視為銅之擴散阻障層進行後續化學機械研磨探討。使用鍍液組成為氯化釕（RuCl3）、鹽酸（HCl）、磺胺酸（NH2SO3H）及聚乙二醇（PEG），測試在不同鍍液溫度（40℃、50℃、60℃）和電流密度（-3 mA/cm2、-4 mA/cm2、-5 mA/cm2）條件下執行電沉積，綜合比較發現在50℃環境下配合電流密度為 -4 mA/cm2，能獲得最佳電流效率26%，再以X光電子能譜儀（XPS）和表面輪廓計證實鍍層為釕金屬與少許二氧化釕且鍍層厚度約為3.15 μm。後續化學機械研磨部分，主要探討添加檸檬酸於過氧化氫系統中，使用奈米二氧化矽研磨粒子，在低壓力約2 psi配合轉速100 rpm下，以直流極化技術分析銅與釕在各種不同組成比例的研磨液中的腐蝕電位與腐蝕電流，最後以場發射電子顯微鏡（FEG-SEM）和原子力顯微鏡（AFM）觀察銅/釕研磨前後表面形態與表面粗糙度，並以電化學分析方法探討影響磨後平坦度的主因。實驗發現在不含雙氧水之研磨液中加入1.0 wt.%的檸檬酸有較佳的銅/釕移除率比，此時，而銅和釕移除速率分別為9.87 nm/min和11.24 nm/min；又含5 wt.%的雙氧水系統中則在加入0.5 wt.%檸檬酸時能使銅/釕移除速率比最接近1，此時銅和釕移除速率分別為29.63 nm/min和27.59 nm/min，此兩組研磨液為最適合之銅/釕共同化學機械研磨的研磨液。

關鍵字

釕 ； 電沉積 ； 化學機械研磨 ； 過氧化氫系統 ； 表面粗糙度

並列摘要

The implementation of the copper metallization into semiconductor manufacturing requires a viable pattern definition process – chemical mechanical polishing (CMP) of copper and the diffusion barrier layer. In this study, ruthenium (Ru) has been chosen to be the diffusion barrier layer material, and its electrochemical characteristics has been investigated.
First, we investigated Ru electrodeposition on copper substrate at various temperatures (40℃, 50℃, 60℃) and current density (-3 mA/cm2, -4 mA/cm2, -5 mA/cm2). The chemicals for the acid-bath ruthenium electrochemical deposition were ruthenium(III) chloride (RuCl3), hydrochloric acid (HCl), sulfamic acid (NH2SO3H), and polyethylene glycol (PEG). The results showed that the optimum current efficiency was 26% with the current density of -4 mA/cm2 at 50℃, and then the X-ray photoelectron spectroscopy (XPS) and the surface profilometer showed that the coating was ruthenium with a little ruthenium dioxide and the film thickness was about 3.15 μm. In chemical mechanical polishing, the potentiodynamic polarization method was used to investigate the electrochemical characteristics of Cu/Ru. Then, copper and ruthenium corrosion mechanism were proposed, and their susceptibility with slurries were studied. The effects of hydrogen peroxide and citric acid on the metal removal rate, corrosion current and surface morphology of Cu/Ru in the slurry have been investigated. Field-emission gun scanning electron microscopy (FEG-SEM) and atomic forced microscopy (AFM) were used to observe the surface morphology and surface roughness of copper / ruthenium before and after CMP. It was found that the addition of 1.0 wt.% citric acid in the slurry without hydrogen peroxide had the best copper / ruthenium removal rate, and the removal rates of copper and ruthenium were 9.87 nm/min and 11.24 nm/min, respectively. However, for adding 0.5 wt.% citric acid in the slurry with 5 wt.% hydrogen peroxide, the removal rates of copper and ruthenium were 29.63 nm/min and 27.59 nm/min, respectively.

並列關鍵字

ruthenium ； electrodeposition ； hydrogen peroxide ； surface roughness ； chemical mechanical polishing

參考文獻

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