The effect of thermal cycling on a-C:F,H low dielectric constant films deposited by ECR plasma enhanced chemical vapor deposition

Thin films of a-C:F,H have been investigated to understand the effect of post-deposition annealing on density, dielectric constant, and composition. Although the initial dielectric constant value for the films was 3.2, the value decreased to about 2.4, and the loss tangent decreased from 0.12 to 0.03 after heating to 400°C. Correspondingly, the film density decreased on the order of 10%, and an increase in the C=C content of the infrared spectra was observed. Most of these measured properties reached at least 75% of their final value within 5 minutes annealing. These results suggest that a more open film network is the basis of the lower dielectric constant