Effects of deposition temperature on the structure and thermal stability of a-C:F films with low dielectric constant

Fluorinated amorphous carbon films (a-C:F) with low dielectric constant were prepared at different temperatures by electron cyclotron resonance chemical vapor deposition (ECR-CVD) using CHF3 and C2H2 as precursors. The changes of structures, chemical compositions, and dielectric properties with deposition temperature were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and capacitance-voltage characteristics. We found that a-C:F films prepared at high deposition temperature of 300 °C remained amorphous, but the dielectric constant increased from 2.2 for the films deposited at room temperature to 2.75 while F/C composition ratio in the films decreased from 2.3 to 1.5. In order to study the thermal stability the samples were annealed up to 500 °C in vacuum ambience. The films deposited at high substrate temperature have lower F/C, less CF3, CF2 bonding and more cross-linking structures, and thereby lead to better thermal stability.