30 - Chemical Mechanical Polishing: Role of Polymeric Additives and Composite Particles in Slurries

Abstract

Publisher Summary This chapter highlights the role of polymeric additives in the slurry and the use of novel composite abrasive particles incorporating polymers as promising alternatives to traditional inorganic oxide nanoparticles. Polymeric additives are of fundamental importance to the planarization process as they can control the aggregation, dispersion, surface hardness, and stability of the inorganic oxide nanoparticles. Abrasive composites range from simple inorganic particles surface decorated with organic moieties to compressible polymeric microspheres that incorporate inorganic oxide nanoparticles. Typically, slurries used in mechanical polishing/planarization (CMP) consist of a liquid solvent and a solid dispersant. The liquid phase is generally deionized water with additives like oxidizers, complexing agents inhibitors, and surfactants. The solid phase consists of abrasives, which are typically metal oxides such as alumina (Al2O 3 ), silica (SiO 2 ), and ceria (CeO 2 ). While silica and alumina particles are commonly used for polishing copper and tungsten, silica and ceria are used to polish SiO 2 , poly-Si, and silicon nitride. The stability of the abrasive particles is an important criterion for CMP as particle sedimentation or aggregation often leads to the formation of scratches on the wafer surface after polishing. The CMP process draws upon a broad base of knowledge from the fields of science and engineering, which range across colloidal science, surface and interfacial phenomena, polymer physics and chemistry, tribology, fluid mechanics and dynamics, and surface metrology.