Effect of Slurry Injection Position on Slurry Mixing, Frictional Forces, Removal Rate and Process Temperature During Copper CMP

摘要

It was hypothesized that there existed a mixing phenomenon between the new injected slurry and old slurry (i.e., used slurry located on top of the polishing pad), whereby the less reactive slurry would degrade the chemical activity of the slurry with the wafer, thus reducing removal rate. Three slurry injection positions were selected to induce different extents of slurry mixing. Using a novel wafer carrier and an infrared camera, the temperature of the wafer as well as of the surface of the pad were measured in real-time. Tribological mechanism was investigated as a function of injection position to identify any potential changes in the lubrication characteristics. The role of diamond conditioner and the bow wave in slurry mixing were evaluated experimentally. Result showed that slurry injection position played a significant role in slurry mixing characteristics and slurry utilization efficiency. The slurry injection position that induced less slurry mixing significantly increased copper removal rate. This work underscored the importance of optimum slurry injection geometry and flow for obtaining environmentally benign copper CMP processes.