Intrinsic stress fracture energy measurements for PECVD thin films in the SiOxCyNz:H system

The fracture energies of a series of tensile plasma-enhanced chemical vapor deposited low dielectric constant (low-k) SiO_xC_y:H, SiO_xN_y:H and SiN_x:H thin films were calculated by determining the critical thickness at which spontaneous cracking occurred. The fracture energies determined for the SiO_xC_y:H films were in the range of 2-3 J/m², whereas for the SiO_xN_y:H and SiN_x:H films, the calculated fracture energies were higher and ranged from 5 to 14 J/m². For the SiO_xN_y:H and SiN_x:H films, the addition of nitrogen was not found to significantly increase the fracture energy of the SiON films relative to pure SiO₂. The fracture toughness, however, was improved due to the increase in modulus from the addition of nitrogen. Overall, the fracture energies determined by this method were found to be consistent with those determined by other techniques.