USE OF ZETA POTENTIAL DURING CHEMICAL MECHANICAL POLISHING FOR END POINT DETECTION

摘要

A technique for utilizing a sensor to monitor fluid pressure from a fluid bearing located under a polishing pad to detect a polishing end point. A sensor is located at the leading edge of a fluid bearing of a linear polisher, which is utilized to perform chemical-mechanical polishing on a semiconductor wafer. The sensor monitors the fluid pressure to detect a change in the fluid pressure during polishing, which change corresponds to a change in the shear force when the polishing transitions from one material layer to the next. In order to ensure that there is a noticeable difference in the shear force variation at the polishing end point, a slurry having a particular pH level is selected. The pH level ensures that the zeta potential changes noticeably from one material to the next, so as to induce a change in the shear force, which is detected by a change in the fluid pressure.