Tuning the Removal Rate of Carbon Doped Oxide during Chemical Mechanical Polishing

Abstract

Most integration schemes require CMP barrier slurries to have high SiO 2 and tunable carbon doped oxide (CDO) removal rates (RR). An additive, T, is able to enhance the SiO 2 rate at low pH, but greatly suppressed the CDO RR at the concentration providing maximum SiO 2 RR. With the addition of another additive, Z or P, the CDO rate could be tuned upward while not affecting the SiO 2 RR substantially. Additives Z and P are anionic surfactants with short to intermediate chain length. They are effective only in the presence of T, which suggests a synergistic effect between the additives. Contact angle studies and SIMS analysis indicate that in the presence of T, Z was adsorbed only on SiO 2 , but not on CDO. Without T in the slurry, Z could not be adsorbed on either film. It was proposed that the adsorption of Z onto silica abrasive made the colloidal silica particle more hydrophobic, leading to greatly enhanced impact on the hydrophobic CDO surface.