Hard-mask-through UV-light-induced damage to low-k film during plasma process for dual damascene

Plasma irradiation impact on a SiO₂-hardmask/SiOCH low-k film stacked structure was investigated in detail. The plasma irradiation induces damage to the low-k film although it is covered by a hard mask. The hard-mask-through UV-light-induced damage showed plasma source gas dependence. The damage is determined by the UV light wavelength and photon energy. It was also found that a high substrate temperature accelerates the hard-mask-through UV-light-induced damage. The hard-mask-through UV-light-induced damage was hardly seen for the hard masks thicker than 115nm in the O₂- irradiation experiment. Conversely, an actual SiO₂ film deposition process by plasma-enhanced chemical vapor deposition (PE-CVD) induces damage during deposition. The PE-CVD process induces heavier damage to the low-k film than the O₂-plasma experiment. Higher process temperature accelerates the hard-mask-through UV-light-induced damage in the hard mask SiO₂ deposition process.