NORM GITIS AND RAGHU MUDHIVARTHI
INTRODUCTIONStudies of mechanical and chemical-mechanical surface finishing treatments have long been a part of tribology, a science of friction and wear (material removal). During chemical-mechanical polishing or planarization (CMP), surfaces of both the object being treated (e.g., the semiconductor wafer) and the finishing tool (e.g., the polishing pad), together with the polishing slurry between them, constitute a rather classical tribological system. This is sometimes referred to as a three-body interface [1-3], because it includes two solids in relative motion and the slurry containing abrasive particles at the interface. Modern CMP machines may have an abrasive pad conditioner rubbing the pad during wafer polishing, which keeps one of the surfaces in a state of constant change. A tribological system is typically characterized by classical parameters of the coefficient of friction between the surfaces and by their wear rate.The field of tribology has seen a number of theoretical models for various materials and interfaces [4]. Based on these models, the formulas for the calculation of both friction and wear have been derived. Unfortunately, these equations cannot be used directly by process and equipment design engineers unless the coefficient is known. Indeed, friction and wear properties of a tribological interface depend on macro-, micro-, and nanogeometry of the Microelectronic Applications of Chemical Mechanical Planarization, Edited by Yuzhuo Li