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 115 nm 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.

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A serious issue affecting metal–oxide–semiconductor field-effect transistors is plasma-induced charging damage caused by the spreading current during plasma-enhanced chemical vapor deposition of dielectric films. This current is studied in detail by direct measurement of the plasma-induced vacuum ultraviolet photocurrent through a deposited SiO2 film. The current increased with increasing antenna-wiring spacing, which spreads the electric field over a greater area. Furthermore, the photocurrent showed a parabolic dependence on film thickness. A finite element method simulation demonstrated that the current through a deposited SiO2 film increased when the spreading effect was dominant and decreased when the resistance increase was dominant.