銅在化學–機械拋光電解液中之電化學性質研究

Electrochemical Behavior of Copper in Chemical-Mechanical Polishing Slurries

本研究主要探討銅在檸檬酸水溶液中之電化學性質及化機－機械拋光後之表面型態。由實驗結果得知：在電化學性質方面：以雙氧水為氧化劑時，隨著雙氧水濃度的增加（0-12%），腐蝕電位由-40 mV上升至約470 mV vs. SCE。利用外差法計算極化曲線之電流密度及感應耦合電漿光譜分析顯示：當雙氧水的添加量在0-6%時，腐蝕速率會隨著雙氧水濃度的增加而增加。但添加更高濃度的雙氧水後（> 6%），腐蝕速率反而下降。在模擬化學-機械拋光的試驗結果顯示：雙氧水的添加，可以明顯提昇銅金屬在檸檬酸研磨液中的研磨速率。而AFM觀察結果也顯示，在檸檬酸研磨液中添加雙氧水可以大幅降低表面粗糙度而促進化學機械拋光的平整度。

The electrochemical behavior of copper in citric acid solution and surface morphology after CMP (Chemical-Mechanical Polishing) were investigated. The addition of hydrogen peroxide in the range of 0~12 vol.% would cause an increase in the corrosion potential of copper from -40 to 470 mV (vs SCE) in citric acid solution. The dependence of corrosion rates on the concentration of hydrogen peroxide, in terms of corrosion current density measured by Tafel extrapolation and dissolved metallic ion concentration measured by ICP were all consistent. The results showed that the corrosion rate increased with the concentration of hydrogen peroxide in the range of 0 ~ 6 vol.%, while it decreased beyond 6 vol. %. Under the conditions simulating CMP processes, the experimental results showed that the metal removal rate of copper could be greatly increased with the addition of hydrogen peroxide. Examination of surface morphology using atomic force microscope (AFM) also revealed that the presence of hydrogen peroxide could cause a significant reduction in surface roughness of copper chemical-mechanically polished in citric acid solution.