| Author | John A. Tichy, Christopher J. Clutz and Timothy S. Cale |
|---|---|
| Title | CMP Pad Displacement and Slurry Flow Characteristics: Finite Element Analysis |
| Year | 1999 |
| Pages | - - |
| Editor | - - |
| Abstract | This paper reports on a fully three-dimensional finite element analysis of the stress and deformation field of a porous compliant polishing pad of finite thickness in contact with a rigid wafer; coupled to a FEM flow analysis of the slurry. The pad deformation is governed by the classical linear elasticity equations. The porous nature of the pad is accounted for by the Reynolds equation of hydrodynamic lubrication for thin film flow. The linkage between the solid contact stress and the effective fluid film is through a model that relates the contact pressure of the pad asperities and the effective surface separation distance. The pressure predictions of this model fit experimental results reasonably well. For most conditions, the average fluid pressure at the silicon/pad interface is sub-ambient. The overall fluid pressure can be on the order of 50-100% of the applied normal load. Contact pressure with friction causes skewed normal stress distribution with greater contact stress at the leading edge. Greater contact pressure causes a thinner film at the leading edge. Such a net diverging fluid film causes negative fluid pressures. |