Novel method of predicting lot polish time for high-volume oxide chemical mechanical polishing

Abstract

Determining the required polish time in oxide chemical mechanical polishing (CMP) is more challenging than in metal CMP, where the metal is polished until a polish stop is reached. In oxide CMP, the objective is to remove topography caused by depositing an oxide layer over metal lines, stopping at a target thickness. It is important that this target thickness be maintained for subsequent process steps. Because of the device and layer dependence of oxide CMP and the drift in the flat film polish rate with time it is helpful to use a pilot polish time calculation algorithm which considers these effects. An algorithm of this type and its use with computer integrated manufacturing has been described. The implementation of this algorithm has produced a substantial decrease in the frequency of touch polishing pilot wafers and has essentially eliminated the need for second pilot wafers, and may eventually eliminate the need for flat film rate qualification. This system has proven beneficial in reducing manufacturing errors and has improved tool availability.