在酸性硫酸溶液中各種填加劑對銅電化學沉積之效應

Abstract

酸性硫酸銅電鍍系統因環保性較佳，且成本較低，加入添加劑能使鍍層品質均勻性較一致，因此印刷電路板產業、IC 基板及半導體產業使用的銅電鍍以酸性硫酸銅電解液系統為主。本研究以酸性硫酸銅水溶液為核心，進行一系列探討，實驗含二部分，第一部分：銅電沉積效率計算及擴散係數量測；第二部分：探討再填加氯離子及各種高分子添加劑對銅的電沉積效應。於酸性硫酸銅水溶液，進行定電流密度銅電沉積，以法拉第定律計算，得到此實驗系統沉積效率約為99％。進行量測銅離子在各種不同濃度下的擴散係數，其值範圍在 3.82× 10^−10到 6.00× 10^−10 m2/s。 氯離子與聚合物作為添加劑，探討對銅電沉積帶來的影響，聚合物種類為三種，聚乙二醇 (PEG600, PEG8000)、聚乙二醇單甲醚 (MPEG2200)、EO-PO 嵌段共聚物 (BT50H1600, MEP49)。氯離子加入陰極極化曲線電流密度大幅提升，明顯呈現去極化作用，推測形成氯化亞銅吸附於電極表面穩定一價亞銅離子，之後還原成銅金屬。只添加聚合物於酸性硫酸銅水溶液，陰極極化曲線大致無明顯電流密度減小趨勢，證實聚合物需要與氯離子共同添加，才會產生極化作用，抑制 電流密度。在添加氯離子的情況下，比較同為聚乙二醇，但分子量不同的 PEG600與 PEG8000，發現分子量較大者，其極化作用較顯著，並且抑制電流密度範圍較廣，而且鍍層品質較佳。在添加氯離子的情況下，比較同為 EO-PO 嵌段共聚物的 BT50H1600 與 MEP49，進行定電流電鍍下，BT50H1600 的銅層品質不佳，量測極化曲線發現於特定電位範圍才產生極化作用，若超過此範圍則電流密度快速上升，失去抑制電流密度的效果。於酸性硫酸銅水溶液中添加 50 ppm 氯離子與 200ppm PEG8000 進行電鍍，所沉積的銅鍍層光澤度最佳並且平坦。

Acidic copper electroplating is eco-friendly, relatively inexpensive, and produces deposits of good uniformity with additives. So, acidic copper electroplating is the mainstream in the manufacturing of printed circuit boards, IC boards industry and semiconductor industry. This study will be focused on the additive effects of acidic copper sulphate solutions. The experimental work contains the two parts：One is for the copper deposition efficiency and diffusion coefficient measurements, the other is the effects of chloride ion and gycol polymers employed in copper deposition. We measured and calculated the copper deposition efficiency at constant current density, the deposition efficiency was found to be 99% for the copper electrodeposition. The diffusion coefficients of the copper ions in various concentrations of the acidic copper sulphate solutions have been measured and found to be in the range of 3.82×10^(-10) to 6.00×10^(-10) m2/s. In the second part of this study, chloride ion and polymers have been investigated for the additive effect of copper electrodeposition. The polymers are polyethylene glycol (PEG600, PEG8000), methyl polyethylene glycol (MPEG2000), and EO-PO copolymer (BT50H1600, MEP49). The current densities of the cathodic polarization curves in the acidic copper sulphate solutions containing 50ppm chloride are higher than those without chloride, so the depolarization effect due to chloride presence is obvious. The solutions containing glycol polymers only, but without chloride, show no polarization effect. So, it can be figured out that the glycol polymer additives need to be added together with chloride to produce polarization effect. The acidic copper sulphate solutions containing 50 ppm chloride and 200 ppm PEG8000 produce the best electroplating quality among the five additive employed in this study.