Cryogenic etching processes applied to porous low-k materials using SF6/C4F8 plasmas

摘要

Cryogenic etching processes in SF6 and SF6/C4F8 plasmas were successfully applied to porous organosilicate glasses. Such materials are low-k candidates for advanced interconnects. Their integration is very challenging because of plasma induced damage. These two chemistries (SF6 and SF6/C4F8) have demonstrated a promising capability of significantly reducing the damage caused by plasma etching. Desorbed species were analyzed during the wafer warm-up from cryogenic to room temperature by in situ mass spectrometry. An equivalent damage layer (EDL) was evaluated by ex situ Fourier transform infrared (FTIR) spectroscopy and in situ ellipsometry. An anneal step at 350 degrees C seems efficient to completely desorb the remaining CFx species. Anisotropic profiles were obtained using both chemistries. The selectivity is enhanced using SF6/C4F8 process at low temperature.