Chemical mechanical polishing (CMP) is a method used in semiconductor fabrication for planarizing the top surface of a wafer or other substrate by the selective removal of topography-generating features. This process combines mechanical and chemical polishing in order to produce a clean, flat surface. It works, as indicated by its name, with chemicals that weaken the desired material to be removed, so it works much faster and more effectively than other material removal techniques. At the same time, it uses an abrasive action in order to speed up the process and remove the reacted materials from the surface of the wafer. This creates a smooth, quick process, removing even the smallest of ridges or bumps.

The chemicals used in chemical mechanical polishing are contained in a corrosive chemical slurry that works with a polishing pad as well as a retaining ring to smoothen the topography of the given wafer or substrate. The polishing pad and the wafer are pressed together at high pressure by a dynamic polishing head and held in place due to the retaining ring. The dynamic polishing head moves in non-concentric circles and flattens the surface of the wafer. This process is useful as it is the best known method of planarization in existence.

A few elements must be kept in check in order to make sure that chemical mechanical polishing takes place effectively:

1. The amount of pressure on the wafer.
2. The speed of rotation of the wafer.
3. The temperature at which CMP takes place.
4. The type of slurry used and the rate at which it is dispensed.
5. The condition and type of polishing pad used.

Chemical mechanical polishing is a key component in yielding faster as well as smaller integrated circuits made from copper due to its unique techniques of removing material in a planar and uniform fashion. CMP can also be used for polishing tungsten, silicon dioxide, and carbon nanotubes as well as copper and aluminum. It is a fairly recent technique but is quite popular due to recent improvements in technology.