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

Abstract

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.