Post Plasma Etch Residue Removal Using CO2-Based Mixtures: Mechanistic Considerations

Abstract

High-pressure -based fluids have recently been proposed for post plasma etch residue removal as an environmentally benign alternative to current liquid-based methods. Specifically, -tetramethylammonium bicarbonate methanol mixtures have been used to remove photoresist residues from a CORAL low-dielectric constant film. In this work, detailed studies are performed to improve the understanding of the residue removal mechanism using these mixtures. Attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and interferometry are used for in situ and ex situ monitoring during the cleaning process; model residue films are used to facilitate interpretation of results from these studies. The role of and the additives in the mixture is also delineated. The primary cleaning mechanism appears to be attack of the interface between the residue and the capping layer by ions generated by dissociation of . Methanol promotes dissociation of the bicarbonate, while the role of is to promote diffusion of the additives to the interface.