1.1.4 Chemical Mechanical Polishing

Due to the fact that several process steps which modify the topography of the wafer surface (etching, deposition, oxidation) are necessary to generate an IC, the surface becomes severely non-planar. This creates several problems especially for the lithography process, because non-planar surfaces require a high depth of focus which is incompatible with the requirement of a high numerical aperture of the imaging systems, which is necessary to guarantee a small minimum feature size.

Chemical mechanical polishing CMP is used as a planarization technique. A chemical slurry with etchant agents and abrasives is applied to the wafer surface.