硅片表面多金属污染的交流阻抗表征

在接近氢氟酸实际应用浓度条件下, 利用交流阻抗技术研究了硅片表面金属微观污染行为, 在氢氟酸溶液中分别加入0.5和1 mg/g的铜、铁、镍、钙四种金属离子, 获得了硅片在单金属溶液中的特征交流阻抗谱, 并在此基础上研究了三种金属及四种金属共存时的特征交流阻抗谱, 通过等效电路的拟合估算了硅/氢氟酸界面电化学反应的动力学参数, 并结合扫描电镜形貌图探讨了不同类型的单金属和多金属对硅电化学行为的影响. 结果表明, 多金属微观污染是各种单金属协同作用的结果, 铜在硅片上发生电化学沉积, 直接导致硅片表面粗糙化. 铁对硅片表面的破坏严重, 同时影响铜的沉积. 镍的存在使硅片表面更容易氧化. 而钙通过在硅片表面形成氟化钙沉淀物可以钝化表面, 减缓铜在硅片表面的沉积.

Multi-metal Microcontamination of Silicon Wafer Surface Characterized by Electrochemical Impedence Spectroscopy

The multi-metal microcontamination of silicon wafer surface was studied by electrochemical impedance spectroscopy (EIS) under the metallic impurity concentrations close to the practical applications (μg/g level) based on the one-metal microcontamination effect. The characteristic EIS spectra were measured in the HF solutions containing one and three or four different metals simultaneously at the levels of 0.5 and 1 μg/g, respectively. The kinetic parameters of electrochemical reactions at the Si/HF interface were evaluated by the equivalent circuit. The cffects of single or multi-metal types on the electrochemical behaviors of silicon were also investigated in combination with SEM observations. Silicon surface became rougher by copper deposition, which is directly accelerated in the presence of iron and nickel by corroding the Si surface and by increasing the charge density of Si surface, respectively, while reduced by calcium due to the formation of CaF2, which acts as a passivated surface to delay copper deposition.