Experimental validation and molecular dynamics simulation of removal of PO residue on Co surface by alkaline cleaning solution with different functional groups

Abstract

Potassium oleate (PO) is a promising inhibitor for cobalt wiring chemical mechanical polishing (CMP) of integrated circuit (IC) to replace benzotriazole (BTA). The insoluble Co-PO complex formed on cobalt surface in the process of CMP become the main organic residues object of post CMP cleaning. In this paper, tetramethylammonium hydroxide (TMAH) and three complexing agents with different functional groups were used to form alkaline cleaning solution to remove the organic residue of Co-PO complex on cobalt surface. The cleaning effect was characterized by contact angle, electrochemistry, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Furthermore, the cleaning mechanism was revealed by molecular dynamics simulation based on density functional theory (DFT). The results show that the carboxyl group in Ethylenediamine tetraacetic acid (EDTA) is more easily to chelate with Co(II), which could break the Co-PO complex to remove PO on the cobalt surface. The mechanism of removing corrosion inhibitors by complexing agents will be helpful to the post-CMP cleaning of new generation Cobalt wiring.