CMP interfacial fluid pressure and modeling

This work represents our research of the interfacial fluid pressure measurement and modeling during CMP (chemical mechanical polishing), which includes pad surface profile and compression analysis, measurement of the interfacial fluid pressure and shear force during sliding, and modeling. For most CMP applications, the interfacial fluid pressure exhibits a sub-ambient value at the leading two-thirds of the contact and a positive value at the trailing third, and the resulting (suction) force of the average interfacial fluid pressure can be of the order of up to 50-100% of the applied normal load [1]. The effects of process variables on this interfacial fluid pressure were studied, including fluid viscosity, pad structure and modulus, velocity, normal load, pad surface roughness, and wafer surface curvature. A model, based on contact stress analysis, interfacial fluid film estimation, and the fluid mechanics, can explain the pressure dependence of those process variables and predict the fluid pressure reasonably well.