Structural changes of plasma deposited SiOxCyHz thin films attained by thermal annealing

The objective of the Present work was to investigate the influence of thermal annealing on the optical and mechanical properties as well as on the chemical structure of plasma deposited SiOxCyHz, films. The films were prepared by PECVD from HMDSO/oxygen mixtures under a wide range of deposition conditions. Their optical and mechanical properties were studied by spectroscopic ellipsometry and depth sensing indentation technique, respectively. The atomic composition was determined by RBS and ERDA measurements. FTIR analysis was used to find the densities of particular chemical bonds in the films. The annealed films exhibited changes of the refractive index and extinction coefficient. The refractive index always decreased with increasing annealing temperature. The observed increase in hardness and elastic modulus after annealing was probably correlated with dehydration of the films and an increase of Si-O-Si bonds with increasing annealing temperature.