Effect of Pad Surface Micro-Texture on Tribological, Thermal and Kinetic Characterizations during Copper Chemical Mechanical Planarization

Abstract

This study investigated the effect of different pad surface micro-textures on the tribological, thermal and kinetic attributes during copper chemical mechanical planarization (CMP). Different micro-textures were generated by two different chemical vapor deposited (CVD) diamond-coated conditioner discs (i.e. Disc A and Disc B). Results showed that while pad temperature and removal rate increased with polishing pressure and sliding velocity on both discs, Disc B generated consistently lower removal rates and coefficients of friction (COF) than Disc A. To fundamentally elucidate the cause(s) of such differences, pad surface contact area and topography were analyzed using laser confocal microscopy. The comparison of the pad surface micro-texture analysis indicated that Disc A generated a surface having a smaller abruptness (λ) and much more solid contact area which resulted in a higher removal rate. In contrast, Disc B generated less contact areas and COF. A two-step modified Langmuir–Hinshelwood model was employed to simulate copper removal rates as well as chemical and mechanical rate constants. The simulated chemical to mechanical constant ratios indicated that Disc A produced a more mechanically limited process under all of the polishing conditions tested.