Evaluation of Silicon Wafer Polishing Pads — Rheological Behaviour of Polishing Pads and Improvement of Wafer Flatness

We have developed some new easy-to-use equipment for measuring quantitatively the rheological deformation characteristics of the polishing pads. The main results, using the measuring equipment, are as follows : (1) With the processing time, the value of th elastic deformation of the pads becomes higher at the peripheral region of the polishing table compared with the center, (2) The four-element rheology model showed good agreement with the experimental results. (3) New parameter α and β, which are drived from the four-element model and are related to the elastic modulus, were found to be significant for the wafer flatness. (4) the best pad for the flatness, is also the best pad for surface roughness.