Novel method to visualize Preston’s coefficient distribution for chemical mechanical polishing process

Abstract

Preston’s law is widely used in polishing simulations in which the distribution of Preston’s coefficients on an entire wafer surface is generally assumed to be uniform. However, it is more likely that the distribution is not uniform and depends on several factors. To clarify Preston’s coefficient distribution in chemical mechanical polishing (CMP), we propose a novel experimental technique. In the proposed method, the unique experimental approach “stop polishing,” where the wafer does not rotate, and thus the circumferential variation of the coefficient is not averaged, is applied. Oxide-CMP experiments verified the uneven Preston’s coefficient distribution depending on the distance from the pad rotation center. Furthermore, we investigated the influence of slurry supply position on Preston’s coefficient distribution, and clarified that the distribution depends on slurry flow condition. Therefore, the proposed method is expected to be a novel tool for analyzing the CMP process from the perspective of Preston’s coefficient distribution.