研磨液組成及機械變數對鋁化學–機械拋光製程中電化學性質影響之研究

Effects of Slurry Composition and Mechanical Parameter on the Electrochemical Behaviors of Aluminum During CMP Process

本研究主要分析鋁在化學機械拋光（Chemical Mechanical Polishing, CMP）過程中的電化學性質，探討在靜態及研磨過程中，改變溶液的pH值及添加H2O2與否對電化學行為及化學溶解速率的影響；同時瞭解研磨壓力及研磨盤轉速對研磨速率及電化學反應的作用。實驗結果顯示，在靜態環境下鋁展現穩定的鈍化行為。降低pH值或添加H2O2皆可有效提高腐蝕電位及鈍態電流密度。不過鈍化現象在研磨狀態下則無法維持，轉而呈現活化溶解的情況。在研磨狀態下，研磨速率會隨著pH值的上升而略為下降，但電化學實驗所量測到之腐蝕電流密度（icorr）卻反而提高。H2O2的添加會影響腐蝕電位，使其提高了約500mV，對於腐蝕電流密度則影響不大。無論是改變研磨盤轉速或研磨壓力，所得到的極化曲線圖並不會有明顯的差異，顯示在本研究的實驗條件範圍內，機械變因對電化學反應的影響很小，且由研磨速率所得的結果顯示，其並未遵守Preston's equation，但隨著研磨壓力及研磨轉盤轉速的增加，研磨速率仍有上升的趨勢。由XPS之結果顯示，隨著pH值的增加，有利於反應生成Al2O3、Al (OH)3及AIPO4。

The electrochemical behaviors of Al during chemical mechanical polishing (CMP) process were investigated. The effects of pH and H2O2 on the chemical dissolution rate at static state or under polishing condition were explored. The influences of polishing pressure and platen speed on the changes of electrochemical behavior and removal rate were also studied. The experimental results showed that Al exhibited stable passivation in the slurry investigated at stress free condition. Both the corrosion potential and the current density were increased by reducing the pH and/or by adding H2O2 in the slurry. Under polishing condition, however, passivation could no longer exist. The removal rate was decreased slightly while the dissolution current density was increased by increasing the pH of the slurry. The adding of H2O2 caused an increase of corrosion potential by 500mV but without affecting the current density. The experimental results also showed that either platen speed or polishing pressure exerted no effect on the potentiodynamic polarization behavior under polishing condition, demonstrating the negligible effect of mechanical factor on the electrochemical reaction. Furthermore, the results clearly showed that though Preston’s equation was not obeyed the removal rate was still increased with increasing polishing pressure and platen speed. The XPS analyses reveal that the formations of Al2O3 and AlPO4 were prevailed when the slurry pH was increased.