Optical interferometry for surface measurements of CMP pads
Optical interferometry was used to quantitatively characterize the surface of chemical-mechanical polishing (CMP) pads used to polish oxide films. We discuss the optical interferometry technique, including a description of the parameters necessary to compare pad samples. Flat, mesa-like structures formed on the pad during the first 5 min polish when conditioning was not used. The data from the optical interferometer indicated that the surface topography did not change with subsequent polishing, even though the thermal oxide removal rate continued to decrease. We found conditioning roughened the pad surface. Rougher pad surfaces removed more oxide during a single 5 min polish than comparatively smooth pad surfaces. Data indicates that conditioning increases and stabilizes pad surface roughness.