Effects of Polishing Parameters on Evolution of Different Wafer Patterns During Cu CMP

Chemical mechanical polishing (CMP) has been widely used in the IC industry. To specify proper polishing parameters for Cu CMP is a very important and difficult task. In this paper, by using the linear system method modeling the relationship between the contact pressure and topography of wafer, the evolutions of the wafer patterns under different polishing parameters are simulated and compared with experimental data. The wafer patterns contain square-wave features with different pitches and pattern densities. The effects and tradeoffs between different polishing parameters on the evolution of different wafer patterns are studied. It is found that high selectivity ratio can achieve small dishing, while small selectivity ratio can help to achieve small erosion and small differences among different patterns. Small down force and large Young's modulus of pad can achieve a good planar surface. Large Preston coefficient will have small erosion during one-material polishing, while small Preston coefficient will have small erosion in two-material polishing. Time point of changing polishing parameters is important to achieve an efficient polishing process and a planar surface.