A liposome-containing slurry for tungsten chemical mechanical polishing

Chemical mechanical planarization (CMP) has become an essential process in the manufacturing of advanced semiconductor devices found in cell phones, computers, and other everyday electronics. The three major applications of CMP involve the planarization of structures and films made of copper, tungsten, and silicon dioxide at wafer level. While CMP of silicon dioxide or interlayer dielectric materials represents the earliest application of CMP and copper CMP has become an enabling and fast-growing segment of CMP, tungsten CMP remains steady in production volume and growth. The yield of a CMP process is heavily dependant upon the performance of its corresponding slurry, a stable colloidal aqueous dispersion of abrasive particles and various chemical additives. It is generally true that, other than the dispersed abrasive particles, all other chemical additives are homogenously dissolved in a single aqueous phase. In this paper, we report the design and performance of a liposome-containing slurry for tungsten CMP. More specifically, in addition to the abrasive particles and other chemical additives commonly found in a metal CMP slurry, this new slurry contains a model catalyst that is encapsulated inside of liposome. The caged catalyst does not interact with the oxidizer outside until the polish. The purpose of encapsulating a catalyst is to increase the pot lifetime of the slurry and reduce the static etch caused by the reaction between the catalyst and the oxidizer if they are exposed to each other directly. In this study, we demonstrated that, by caging the catalyst, the static etch rate is significantly reduced and the pot lifetime is significantly increased. The material removal rate remains high. In this paper, the basic design of such slurry is first introduced. The evidence for the encapsulation of a representative catalyst is presented. The performance of such slurry on the polish of blanket and patterned wafers is discussed. (c) 2007 The Electrochemical Society. All rights reserved.