Interfacial fluid mechanics and pressure prediction in chemical mechanical polishing

This paper reports on the measurement of fluid (water) pressure distribution at a soft (polyurethane) pad/steel interface. The distribution of the interfacial fluid pressure has been measured with a specially-designed fixture over the typical range of normal loads and velocities used in the chemical mechanical polishing/planarization of silicon wafers. The results show that, for most cases, the leading two-thirds of the fixture exhibits a subambient pressure, and the trailing third a positive pressure. The average pressure is sub-ambient and may be of the order of 50 similar to 100% of the normal load applied. An analytical model has been developed to predict the magnitude and distribution of the interfacial fluid pressure. The predictions of this model fit the experimental results reasonably well, especially for low sliding velocities. [S0742-4787(00)00902-4].