Study on diamond dressing for non-uniformity of pad surface topography in CMP process

Diamond dressing process is critical in conditioning pad surface topography before and after chemical mechanical planarization/polishing (CMP) process for integrated circuit (IC) fabrication. This paper addresses a kinematic model of diamond dressing effect on the profile of pad cutting rate (PCR) with a ring-type diamond dresser through both simulation and experiments. In this kinematic model, the cutting locus distribution, relative velocity of diamond grits on a pad surface, and sliding time have been described as significant factors for non-uniformity of pad surface topography. Moreover, the speed ratio between the diamond dresser and the polishing pad has been investigated with respect to the center distance of the pad and the diamond dresser by the developed method. The model has been verified by experiments of diamond dressing of pad. Experimental results show that the dressing marks and pad cutting rate on the pad surface follow the same trend as simulation results and the final pad surface is obtained as a concave shape. Results of this study can be applied on diamond dressing of pads used in CMP and furthermore can be extended to investigate an optimal diamond dressing process for semiconductor fabrication.