Wear phenomena in chemical mechanical polishing

Abstract

Chemical mechanical polishing (CMP) has become a primary method for planarization of semiconductor wafers. The CMP process is a tribochemical process, which involves a simultaneous interaction between a polishing slurry, a semiconductor wafer, and a polishing pad. Mechanical and chemical-assisted wear dominate the entire CMP process. The material, chemical, mechanical and lubricating properties of the three mentioned bodies determine the controllability and quality of CMP. For semiconductor wafers, the material removal rate, surface roughness, the number of defects, and the surface flatness are the benchmarks of CMP performance. In this work, we examined the polished surfaces of waters and pads, using an optical microscope, scanning electron microscope, atomic force microscope, and other surface analysis techniques. We investigated the properties vs. performance relationships of polishing pads, s;urries and wafers. We found that plastic deformation predominates the wear mechanisms of both wafer and pad materials. Wear of materials in CMP takes place over a wide range from the nanometer to micrometer scale.