Yield improvement in chemical mechanical polishing process investigation of wafer scale

Chemical mechanical polishing (CMP) is a planarization process that produces high quality surfaces both locally and globally. It is one of the key process steps during the fabrication of very large scale integrated (VLSI) chips in integrated circuit (IC) manufacturing. CMP consists of a chemical process and a mechanical process being performed together to reduce height variation across a wafer. High and reliable wafer yield, which is dependent upon uniformity of the material removal rate across the entire wafer, is of critical importance in the CMP process. In this thesis, the wafer pad contact is modeled as the indentation of a rigid indenter on an elastic half-space. The model predictions are first verified against experimental observations. Simulation results for wafer yield under open loop processing conditions are presented. Wafer curvature is identified as a key design variable influencing the spatial distribution of the material removal rate. The load control, the curvature control, the combined curvature and load strategies are investigated for improving the wafer yield. It utilizes an objective function based on minimizing a moment function that represents the wafer curvature and the height of the oxide layer left for material removal. Simulation results indicate that curvature control can improve wafer yield significantly, and is more effective that just the load control