Chemical mechanical planarization or chemical mechanical polishing CMP is a process that can remove topography from silicon oxide, poly silicon and metal surfaces. It is used to planarize oxide, poly silicon or metal layers in order to prepare them for the following lithographic step, avoiding depth focus problems during illumination of photosensitive layers. It is the preferred planarization step utilized in deep sub-micron IC manufacturing.u
CMP replaced technologies like boron phosposilicate glass BPSG deposition, followed by an BPSG anneal step to reflow the low melting doped glass, or spin-on-glass (SOG) technology. The deposited silica material reflows on the silicon surface and has to be SOG cured then to remove the remaining solvent and organic components. The smaller the requested resolution of the structure, the higher is the request for planarity of the surface. BPSG and SOG do not planarize the layer completely. There is a local height variation between chip areas of different pattern densities. CMP is the only technique that performs global planarization of the wafer.
Several materials can be planarized by chemical mechanical polishing technologies