Applications of Raman spectroscopy in Cu CMP: In-situ detection of chemical species in the slurry

Slurries used for copper CMP have a rich chemistry, which may change during the course of polishing due to consumption and decomposition of molecular species. Various aspects, such as small layer thickness (<50 μm), continuous flow of the slurry, and dynamics of the film removal process pose great challenge to the monitoring of slurry components between the pad and the wafer. The slurry constituents such as oxidants and corrosion inhibitors have unique signatures that can be detected using spectroscopic techniques. In this paper, work carried out to explore the use of Raman spectroscopy to detect and quantitate chemical species such as hydroxylamine, benzotriazole and hydrogen peroxide in-situ will be presented. More detailed study pertaining to the protonation of hydroxylamine with respect to the pH will also be presented. An abrasion cell integrated with a Raman spectrometer was used to make the measurements.