Damage and etching of ultra low-k materials in fluorocarbon plasma at lowered temperatures

SiOCH ULK films with k-value from 2.5 to 2.1 and porosity from 24 to 40% were etched in CHF₃, CHF₃  +  Ar, CF₄ and CF₄  +  Ar plasmas at  +15…−120 °C with and without bias being applied. It was shown that the presence of Ar in gas mixture can significantly increase the damage of unetched ultra low-k (ULK) material (at sidewalls) due to the removal of  −CH₃ groups from the film by VUV photons. It was also shown that etching and damage of the sidewalls by F atoms can be partially prevented by lowering the temperature of the sample. (paper)