Mechano-chemical polishing of silicon wafers

Rapid progress in recent IC fabrication industry has increased the demand of tight specification of non-uniformity (NU) and surface polishing in silicon wafer planarization. Chemical–mechanical polishing (CMP) is currently the most popular method for IC wafer planarization. However, the sub-surface damage problem caused by hard abrasives and chemical waste problem of CMP have decreased the throughput and increased the cost of IC fabrication. This study is to investigate the mechano-chemical polishing (MCP) of silicon wafers by slurry of soft abrasives, BaCO3 and through experiments to verify that the solid phase chemical reaction (SPCR) is the main reaction process involved in MCP. A planarization mechanism with compliance has been designed and tested through MCP experiments. Experimental results of MCP of silicon wafers have achieved the average of surface roughness improvement ratio (SRIR) to 99% and the surface roughness Ra=0.633 nm measured by atomic force microscope (AFM). The material removal rate (MRR) has been calculated and the significant influence of slurry weight percent and polishing pressure have been found. The NU has also been estimated for evaluation of MCP parameters. The sub-surface damage of silicon wafer has not yet been found in experimental results and hence the MCP process of silicon wafers has been verified to become a green or environment-friendly technology of silicon wafer planarization.