Analytical investigation on polishing pressure distribution by utilizing three-dimensional process simulation

This paper presents analytical investigation on polishing pressure distribution in Chemical Mechanical Polishing (CMP) process. In general, the polishing pressure is distributed unevenly around a wafer edge. This uneven distribution is essentially due to discontinuous contact of a wafer against a polishing pad. An edge profile of the wafer and nonlinear viscoelastic properties of the polishing pad affect the polishing pressure distribution significantly. The compression by a retainer ring against the polishing pad also has an indirect effect on the polishing pressure distribution. These phenomena are empirically known in industry. In order to quantify the influence of these factors, a series of analytical investigations on the polishing pressure distribution are conducted in the present study. The simulator developed by authors is utilized. Arbitrary Lagrangian-Eulerian (ALE) Finite Element Method (FEM) is employed in dynamic nonlinear analysis. In a series of process simulations, material properties, i.e., Young's modulus, Poisson's ratio and proportional damping factor, of the polishing pad and geometries of the wafer and the retainer ring are changed, respectively. The calculated results indicated that the polishing pressure distribution around the wafer edge varies considerably depending on the parameters.