Tribological Behavior in chemical-mechanical planarization

Chemical-Mechanical Planarization (CMP) has been used as the primary method of semiconductor wafers for last two decades due to its high-quality nano-scale finishing capability([1-6]). The CMP process is a synergistic interaction of the CMP components. Considering the CMP as a tribocheical process, it involves a simultaneous interaction between a polishing slurry, a semiconductor wafer, and a polishing pad. 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. The CMP mechanisms have remained elusive due to its dynamic nature. The removal of materials takes place at a fine scale while the planarization requirement is global. It is difficult to clearly separate the roles of various participating components. In slurry, for example. the flow rate, chemistry, particle concentration, nanostructure, and additives are considered affecting CMP results. Others such as wafer surface films, pad surface and bulk structure, as well as fluid dynamics are important issues. To integrate all these mentioned factors together, this paper focuses on the synergistic interactions using a tribological approach. The narnabrasive particle size and surface film are the examples as case studies to discuss the basic wear mechanisms during CMP.