Fluorocarbon polymer deposited on a checkerboard wafer composed of low-k dielectrics and TiN dies (2×2 cm squares) was used as a model polymer for wet removal experiments. The model polymer and the polymer residues generated on sidewalls of patterned dielectric structure were characterized using ellipsometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and angle-resolved X-ray photoelectron spectroscopy, respectively. Both types of samples showed that while wet cleans using a mixture of dimethylsulfoxide and monoethanolamine or a commercial solvent mixture only removed partially the polymer, a short irradiation of the polymer with UV (λ∼254 nm, dose ≥3 J/cm 2 ) followed by an immersion in the same solvent mixture led to substantial improvement of polymer removal. Mechanisms of modification of the polymer structure under the effect of UV radiation have been proposed. The improvement of removal was explained by a mechanism involving chain scissioning of the polymer backbone under UV irradiation.In back-end of line (BEOL) processing, fluorocarbon-containing plasma is commonly used to pattern silica-based dielectric layers. During the patterning process, fluoropolymers (CFx) are intentionally deposited on the created dielectric sidewalls 1, 2 to ensure etching anisotropy, profile control and prevent/minimize dielectric degradation. These polymers need to be removed in later process steps to achieve high adhesion and good coverage of materials deposited in the etched features. 2-4 These residues are typically removed by a combination of dry photoresist strip and a wet clean. However, strip plasmas based on oxygen, fluoro-oxygen, and hydrogen induce damage to the porous dielectric in the stack. A possible way to minimize low-k damage is using a metallic hard mask, e.g. TaN or TiN hard mask, for the patterning of low-k dielectrics thanks to its high selectivity toward low-k materials. In this case, the photoresist layer is stripped just after the hard mask opening thereby minimizing damage to the low-k material. Typically, using fluorocarbon plasma (Ar/CF 4 ) for patterning of a TiN hard mask/porous low-k stack, the dielectric sidewall was found to be composed of silicon (15%), oxygen (19%), carbon (17%), titanium (1%), and fluorine (49%). 5 This result clearly indicated the presence of a highly fluorinated layer and a negligible amount of TiN-based etch by-products deposited on the trench sidewalls during the plasma etch.With regard to wet clean, diluted aqueous solutions (e.g. HF-based) are not efficient for polymer removal without etching the dielectric to lift-off the polymer, leading to unacceptable dimension loss. Other cleaning solutions that contain hydroxylamine were not compatible with certain low-k materials and Cu. 6 A cleaning approach based on reductive chemistry using radical anions was proposed, showing significant defluorination of post-etch photoresist and etch residues. 7, 8 Another alternative process by means of super critical carbon dioxide and additives mixture also ...