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Continuous and modulated discharges, fed with divinyltetramethyldisiloxane mixed with oxygen and argon, were used to deposit carbon-doped silica-like ͑SiCOH͒ low-k to ultralow-k films. The effect of various process parameters on the dielectrical and thermal properties of films as well as on their chemical composition were investigated. As deposited, the SiCOH films exhibited dielectric constants from 4.45 to 2.70. Thermal annealing in the 400-450°C temperature range was found to be necessary to reach ultralow-permittivity values, but the temperature must be controlled in order to prevent an excessive collapse of the silicate matrix, which leads to poor thermal stability and mechanical properties. Lowering the oxygen content in the discharge allowed for a continuous decrease in k values down to 2.32 when low radio frequency power was used, with a limited film thickness loss upon annealing of 11%. Fourier transform infrared spectra of ultralow-k film exhibited intense absorptions from C-containing moieties, like CH x and Si͑CH 3 ͒ x . Upon annealing at 400°C, the organic content considerably decreases, though the loss of Si͑CH 3 ͒ x groups is quite limited. Thermogravimetric analysis coupled with mass spectrometry revealed that during thermal treatment, siliconcontaining fragments were lost from the matrix along with hydrocarbon ones.

Thin films with a dielectric constant in the range of 1.9–4.5 have been deposited under different experimental conditions from allyltrimethylsilane (ATMS) and oxygen fed glow discharges. The thermal stability of the coatings is evaluated from thickness loss during the annealing process at 400 and 450 °C. Extremely low values of dielectric constant can be obtained at low input power and oxygen flow rate. However, control over the annealing temperature must be gained in order to avoid excessive film matrix collapse with subsequent deterioration of dielectric properties. For the lowest dielectric constant of 1.9, thickness shrinkage of 11% has been detected. Deposition temperature is also found to strongly affect film dielectric constant and chemical composition while input power modulation does not improve the dielectric properties of the films.

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