Silicon dioxide and low-k material sputtering in dual frequency inductive discharge by argon ions with energies from 16 to 200 eV

Abstract

Thermal and PECVD deposited silicon dioxide and organosilicate low-k materials with porosity from 24 to 44% and corresponding k values from 2.5 to 2.0 were sputtered in dual frequency inductive discharge by argon ions with energies from 16 to 200 eV. The film thickness was measured in process by laser ellipsometry and controlled before and after plasma treatment by spectroscopic ellipsometry. Sputtering rate and yield dependencies on ion energy were measured. It was shown that SiO2 sputtering threshold in plasma is significantly lower (<10 eV) than the threshold measured in ion beam sputtering experiments. This is attributed to the fact that in ion beam sputtering there can be significant charging of the material surface leading to the reduction of ion energy. For low-k sputtering it is shown that the sputtering yield can be significantly higher than that of SiO2 and also −CH3 group removal by vacuum ultraviolet photons from the discharge significantly influences material sputtering rate.