Abstract
For oxide-CMP process in semiconductor manufacturing, which requires high precision, Run-to-Run control has been developed. The Run-to-Run control is a kind of repetitive control to adjust polishing time at every start of lot work in a work sequence. Film-thickness is controlled based on a process model, which expresses the relation between polishing time and polished thickness. In this paper, process model for oxide-film CMP with ceria slurry and the Run-to-Run control method in high volume manufacturing is described. In this CMP, relationship between polished thickness and polishing time is nonlinear. Control calculation is found to be concise by using a variable, which is film-thickness before CMP divided by removal-rate, for polishing-time correction. Parameters in the model are estimated with two steps to evaluate controllability. Run-to-Run control simulation is applied in order to determine the best parameter set, which achieves the largest process capability index Cpk. A result of high-precision film-thickness, whose Cpk is 1.39, is obtained.
