UV-induced modification of fluorocarbon for improvement of subsequent wet removal

The effect of UV irradiation was studied for its potential application for post-etch residue removal in the back-end of line. A model fluorocarbon polymer (CFx) deposited by plasma polymerization of CF"4/CH"2F"2 was used as test vehicle. This work mainly focused on investigating the effect of various UV exposure parameters including atmosphere, pressure, temperature, UV power density and dose on the magnitude of change of the polymer properties which in turn affected its cleanability by wet solution. A partial removal of CFx (x=1-3), CF?CF"2, and C?O occurred during UV irradiation in oxygen. Increasing the UV dose and oxygen pressure resulted in a more dramatic removal of the polymer. In terms of material removal in the subsequent wet clean, experimental results also showed that the UV dose and the atmosphere in which the UV pre-treatment is carried out represent the most critical parameters. The presence of a minimum concentration of reactive species such as oxygen radicals during UV treatment was necessary to allow an efficient modification that made polymer fragments more hydrophilic and led to the removal of the polymer in the subsequent wet clean. Other parameters such as the power density of the UV source and temperature appear to play a minor role in polymer removal.