In Situ AFM Study of Surface Layer Removal during Copper CMP

We used atomic force microscopy (AFM) to study the fundamentals of chemical mechanical polishing (CMP) of copper oxidized in an aqueous solution of 5 wt % peroxide and 1 wt % of glycine at varying pH levels. An AFM tip was used to mimic a single abrasive silica particle typical of those used in CMP slurry. AFM scanning removes the surface layer in different rates depending on the depth of removal and the pH of the solution. Oxide removal happens considerably faster than the CMP copper removal. The friction forces acting between the AFM tip and surface during the polishing process were measured. The correlation between those forces and the removal rate is discussed.