Reactions Between CO[sub 2] and Tetramethylammonium Hydroxide in Cleaning Solutions

Supercritical and subcritical CO 2 -based mixtures are being considered as environmentally benign media for photoresist and plasma etch residue removal in electronic device manufacture. Despite many attractive features, supercritical CO 2 has little solvating power for photoresist or inorganic materials. Addition of a basic modifier, such as tetramethylammonium hydroxide (TMAH), to CO 2 can yield a mixture suitable for residue removal. This work investigates chemical reactions between TMAH and CO 2 to gain insight into the cleaning efficiency of subcritical CO 2 mixtures containing TMAH. Results suggest that although tetramethylammonium carbonate/bicarbonate mixtures form, the cleaning ability of TMAH based mixtures in the liquid phase is not significantly affected.