We know that CMP is used for planarization of interconnects in IC fabrication and surface micromachining in MEMS processes. Yet, I am not able to ascertain the role of chemicals in slurry passed during the process. What is its composition and how does it etch the metals? Also, what is role of abrasives in it?
I worked with chemical, mechanical and chemical mechanical polishing of silicon. The chemical mechanical process is the best concerning the planarity of the polished surfaces and at the same time the removal of the damaged layer from the surface of the material. Therefore the CMP became a standard planarization process in the integrated circuits applications. Normally the polishing material consists of an etching solution in which a very fine powder is suspended. Without the mechanical motion and pressure on the wafers during the polishing process the etch rate is very small. So, the mechanical motion with pressure result in friction which increases the surface temperature of the wafer. This activates the etch process and speeds up the reaction. At the same time the higher surface areas with higher pressure will be etched with higher speed leading to surface planarization.
The fine powder is made normally from alumina. While the etch solution varies according to the material to be polished.
You can find more useful information on CMP following the link:
www.entrepix.com/docs/papers-and.../051909_ENTR_ECS_GB+RR.pdf
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