ABSTRACT
Nanotopography is the surface topography of wafers placed on a flat stage without chucking or clamping. It has been known as the waviness visually represented with an optical tool called a magic mirror, which provides images that are qualitative pictures of topography variations on the frontside surface of wafers. Moreover, nanotopography differs from front-referenced site flatness in that for nanotopography the wafer is measured in a free state, while for flatness it is referenced to a flat chuck. A wafer may have perfect flatness yet have nanotopography. Nanotopography bridges the gap between roughness and flatness in the topology map of wafer surface irregularities in spatial frequency. Nanotopography is measured by two techniques: light scattering and interferometry. Nanotopography of the silicon wafer is dictated to a large extent by the polishing process. In addition to Chemical-mechanical planarization process optimization, better silicon wafers are required to solve the nanotopography problem.
