铜抛光液的电化学行为研究

为分析用于超大规模集成电路(ULSI)中铜化学机械抛光(CMP)所使用抛光液的添加剂对铜硅片的氧化、溶解和腐蚀抑制行为,以双氧水为氧化剂,柠檬酸为络合剂,苯丙三唑(BTA)为腐蚀抑制剂,在pH5的条件下进行抛光液的电化学行为研究.测试了铜在抛光液中的极化曲线、交流阻抗谱以及静腐蚀量.试验结果表明:添加络合剂柠檬酸降低了原来处于钝化状态下的铜抛光液系统的阻抗;加入缓蚀剂BTA后,Cu-H2O2-Citric acid-BTA系统的交流阻抗值增大.测试到的Cu-H2O2-Citric acid系统由于存在铜的不可逆氧化过程,导致了Warburg阻抗的存在;添加BTA后,在铜的表面生成了CuBTA的缓蚀膜,抑制了铜的腐蚀并改变了铜在Cu-H2O2-Citric acid系统中的电化学反应过程.

Electrochemical behavior of slurries used for copper

To analyze the effects of additives in the slurry on the oxidation, dissolution and corrosive inhibition of copper wafer for copper chemical-mechanical polishing(CMP), the electrochemical behavior of slurry(pH5) was studied with the peroxide as an oxidant, the citric acid as a complexing reagent and the benzotriazole(BTA) as an inhibitor. The potentiodynamic polarization curves, the electrochemical impedance spectroscopy (EIS) and the static etching rate of copper were tested. It is observed that the impedance of copper in 5wt% peroxide solution existing in passivation can be greatly decreased by adding the citric acid as a complexing reagent. And the impedance of copper in the solution containing peroxide and citric acid can be increased by the addition of BTA. Because the oxidation process of copper in the slurry containing peroxide and citric acid is nonreversible, the Warburg impendence is produced. The formed CuBTA film in the presence of inhibitor BTA restrains the corrosion of copper and changes the process of Cu-H2O2-Citric acid reaction system.