It is of importance to understand cracking behavior in low dielectric constant, low modulus materials. Nanoindentation method is presented as a tool to estimate the critical film thickness, thickness above which spontaneous cracking could occur, for ILD films used in the BEOL. The critical film thickness was then used to calculate cohesive energies and fracture toughness of the films. Materials were investigated using nanoindentation combined with AFM imaging. The results were compared to data acquired by four point bend methods.