Effect of UV Irradiation on Modification and Subsequent Wet Removal of Model and Post-Etch Fluorocarbon Residues

Abstract

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 Jcm 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. © 2011 The Electrochemical Society.