Effect of Pad Groove Designs on the Frictional and Removal Rate Characteristics of ILD CMP

Abstract

Real-time coefficient of friction (COF) analysis was used to determine the extent of normal and shear forces during chemical mechanical planarization (CMP) and identify the lubrication mechanism of the process. Experiments were done on a scaled polisher using IC-1000 pads with various surface textures, and Fujimi’s PL-4217 fumed silica slurry over a wide range of applied pressures and relative pad-wafer velocities. Stribeck curves showed that pad texture dictated the overall lubrication mechanism of the system. Average COF results yielded valuable information regarding the overall range of frictional forces associated with each type of surface texture. The linear correlation between COF data and interlayer dielectric (ILD) removal rate was consistent with previously published correlation graphs involving a variety of conventional pad textures and fumed silica concentrations. Spectral analysis of real-time friction data was used to elucidate the lubrication mechanism of the process in terms of the stick-slip phenomena and to quantify the total amount of hydrodynamic chattering as a function of various pad surface textures. For a given lubrication mechanism, analysis of the spectra for various textures indicated significant differences that were attributed to the amount of slurry present in the pad-wafer interface. © 2004 The Electrochemical Society. All rights reserved.