Study on Stiffness and Conditioning Effects of CMP Pad Based on Physical Die-Level CMP Model

Abstract

Chemical mechanical planarization (CMP) pad stiffness and conditioning effects were evaluated based on a physical die-level CMP model, with pad effective modulus and asperity height as parameters. In one study, patterned dielectric wafers were polished using polymeric pads of different stiffnesses. In a second study, wafers were polished by standard pads using different conditioning disks. Polishing experimental data (dielectric thickness and step height) were fitted by the physical model, enabling the extraction of the pad effective modulus and asperity height model parameters. A higher pad stiffness gives better within-die uniformity, and the conditioning disk with blocky diamonds achieves up-area only polishing for longer times. Polishing simulations using the physical model reflect a clear pattern density dependence.