CMP slurry stability

Chemical-mechanical polishing (CMP), is a technique used in semiconductor fabrication for planarizing a wafer or other substrates. This removes material and tends to even out any irregular topography, making the wafer flat or planar at the Angstrom level. Cerium(IV) oxide, also known as ceria, is an oxide of the rare earth metal cerium. It is known to have a high polishing efficiency for oxide film, but also it has an unfavourable reputation for problems linked to its quick sedimentation and agglomeration of particles, which can alter significantly the CMP process, leaving unwanted defects. Therefore it is necessary to tailor the ceria slurry in order to reach the right stability requirements for CMP applications. Polymeric dispersants are typically used to stabilise ceria particles, via steric stabilisation. Hence, the molecular weight of the dispersant plays a key role in the stability efficiency.