Study on the Mechanism of Silicon Chemical Mechanical Polishing Employing<i>In Situ</i>Infrared Spectroscopy

Abstract

The mechanism of chemical mechanical polishing (CMP) on silicon (Si) surfaces was studied by means of in situ Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR). IR absorption spectra at 2000–2300 cm-1 arising from silicon–hydrogen (Si–H) bonds on the Si surfaces were observed during CMP using colloidal silica as a slurry. A high loading pressure which contributed to the growth of oxides on the Si surface during CMP led to a high polishing rate. On the other hand, a high revolution speed of the pad which contributed to the removal of the Si oxides also led to a high polishing rate. Thus, a balance between the pressure and the revolution speed of the pad is one of the important parameters for achieving a high polishing rate. The effect of oxidant agent addition to the slurry was also investigated. We found that the polishing rate increased with a high oxidant concentration in the slurry. Hence, the generation rate of Si oxides on the surface strongly influences the Si polishing rate since the polishing is carried out through the formation of the oxide layer on the Si surface and its subsequent removal.