What is a CMP process?
CMP (Chemical Mechanical Polishing/Planarization) is a highly precise polishing process. It combines two specific actions. Firstly, the process modifies chemical properties of the substrate by chemical agents. Meanwhile, highly designed abrasive particles are performing the mechanical treatment.
Properties of the process
Experts recommend chemical mechanical planarazing for highly demanding semiconductor applications. Indeed, the process brings remarkable properties:

High precision: the more data we achieve to store on a device, the more precise the design becomes. Storage devices are often produced by successive layers deposit. Those layers are very thin and must be fully flat with a perfect surface finish. Several means help measuring the surface finish, for example the Peak-to-Valley. Indeed, PV is the measurement of the height difference between the highest point and the lowest point on the surface polished. The latest technologies of semiconductors require PV down to Angstrom levels (10 ^-10m).

Fast use: CMP is a multi-step process related to several substrates polishing. The objective is to optimize the duration of each step. However, keeping a high precision polishing process is still essential. Each step is already lasting less than a minute!