Particulate science and technology in the engineering of slurries for chemical mechanical planarization

Chemical Mechanical Planarization (CMP) is a process that is now routinely used to planarize metal as well dielectric films during the fabrication of integrated circuits. This process uses slurries comprised of fine abrasive particles, such as silica, ceria or alumina. The stability and performance of the slurries are influenced by the size and properties of these particles, which in turn are influenced by their synthesis route. Stability is important to improve slurry lifetime and minimize defects such as microscratching caused by particle agglomerates or large particle counts (LPC) during polishing. The rheological behavior of slurry affects the friction at the pad-particle-wafer interface and alters the material removal rate. It is, thus, necessary to carefully engineer the slurry characteristics to achieve good removal rate and planarity without causing defects. This paper reviews the published literature on the synthesis of abrasive particles used in the preparation of CMP slurries as well as stability and rheological characteristics of slurries made from these particles. A brief account of particle-film interactions and importance of LPC in wafer scratching is also provided.