Comparison of novel cleaning solutions with various chelating agents for post-CMP cleaning on poly-Si film

In this study, various cleaning solutions containing chelating agents with carboxyl acid group (-COOH), such as ethylenediaminetetraacetic acid, citric acid and oxalic acid, were developed for post-poly-Si CMP cleaning. The chelating agent and tetramethylammonium hydroxide (TMAH) were simultaneously added into 2% ammonium hydroxide alkaline solution to promote the removal efficiency on particles and metallic impurities. The effectiveness of various cleaning recipes and their interaction mechanism with the poly-Si surface were studied. We could explain the surface behavior of various cleaning solutions by the different molecular size and charge of chelating agents. Based on the mechanism, the behavior of surface particle and metallic impurity can be realized. The co-existence of TMAH with citric acid or oxalic acid in the alkaline cleaning solutions can significantly enhance the electrical properties of capacitors.