Removal of HF/CO2 post-etch residues from pattern wafers using water-in-carbon dioxide microemulsions

We have investigated different methods for removing the HF/CO₂ post-etch residues from blanket and patterned wafers of borophosphosilicate glass. The use of co-solvents, rinsing the residues with DI water followed by CO₂-based drying process, and the use of water-in-CO₂ (W/C) microemulsions were explored as possible methods to remove the etch residues. It was found that the addition of co-solvents were ineffective for quantitative removal of residues, whereas rinsing the etch residues with DI water followed by the surfactant-aided scCO₂ drying was found to be effective. To eliminate the pure water rinsing step, W/C microemulsions formed with different surfactants were directly treated with residues. While ionic surfactants such as ammonium carboxylate perfluoropolyether and sodium salt of bis (1H,1H,2H,2H-tridecafluoro-octyl)-2-sulfosuccinate did not produce stable microemulsions in the presence of HF, due to protonation effect, the reverse micelles formed with an amphiphilic block copolymeric surfactant, poly(ethylene oxide-b-perfluorooctylmethacrylate), was found to be highly efficient as clean and residue-free images were observed by microscopic analysis.