Stress development during deposition of CN_x thin films

We have investigated the influence of deposition parameters on stress generation in CN_x (0.3≪x≪0.5) thin films deposited onto Si(001) substrates by reactive magnetron sputtering of C in pure N₂ discharges. Film stress, σ, which in all cases is compressive, decreases with an increase in the N₂ pressure, P_N2, due to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. The film stress σ is also a function of the film growth temperature, T_s, and exhibits a maximum value of ∼5 GPa at 350 °C. Under these conditions, the films have a distorted microstructure consisting of a three-dimensional, primarily sp² bonded, network. In contrast, films deposited at T_s≪200 °C with a low stress are amorphous. At 350 °C≪T_s≪600 °C, σ gradually decreases as T_s is increased and the microstructure becomes more graphitic and contains fewer defects. Nanoindentation measurements show that the films grown at 350 °C exhibit the highest hardness and elasticity. © 1998 American Institute of Physics.