Investigation on the Material Removal Process of Copper by a Single PAD Asperity

Multilevel copper interconnection structures in integrated circuits (ICs) are generally processed by the electrochemical deposition and planarization. Chemical mechanical polishing(CMP) is almost the only way to remove the redundtant copper deposited and achieve both local and global planarized surface. As the removal of copper is affected by a combination of chemical and mechanical effects, it is of great value to further understand the mechanism of action in order to improve the performance of CMP of copper surface. In this study, a polyoxymethylene (Pom) ball was used to mimic a single pad asperity and polish a copper film surface. The effect of load and time interval between two sliding traces on material removal process is investigated. The results indicate that the section area of grooves worn by Pom ball increases nonlinearly with the load, and the variation of the cross-section area is also affected by the time interval between two adjacent scratches. In addition, the above changes are also affected by the pH value of the slurry. This study is expected to provide some insights into the mechanism of copper removal from the microscale.