Interfacial fluid mechanics and pressure prediction in chemical mechanicalpolishing

This paper reports on the measurement of fluid (water) pressure distributio n at a soft (polyurethane) pad/steel interface. The distribution of the int erfacial 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 tha t, for most cases, the leading two-thirds of the fixture exhibits a subambi ent pressure, and the trailing third a positive pressure. The average press ure is sub-ambient and may be of the order of 50 similar to 100% of the nor mal load applied. An analytical model has been developed to predict the mag nitude 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].