Mechanical characterization of low-k and barrier dielectric thin films

The integration of low-k organo-silicate glass interlayer dielectrics is accompanied by an increase in mechanical reliability risks. New characterization techniques must be developed, particularly for measuring thermo-mechanical properties. This paper presents and compares the use of two mechanical characterization techniques: Brillouin light scattering technique and nano-indentation, for determining Young's modulus, Poisson's ratio and hardness of low-k films and dielectric barrier layers. The obtained values of the elastic constants are then used to evaluate the coefficient of thermal expansion from substrate curvature measurement during thermal cycling. The low-k film studied is a carbon-doped silicon oxide (SiOC:H, k = 3.0) and the dielectric barrier is an hydrogenated nitrogen silicon carbide film (SiCN:H, k = 5.0), both deposited by plasma enhanced chemical vapor deposition (PECVD).