Stress development during deposition of CNx thin films

We have investigated the influence of deposition parameters on stress generation in CNx (0.3<x <0.5) thin films deposited onto Si(001) substrates by reactive magnetron sputtering of C in pure N-2 discharges. Film stress, sigma, which in all cases is compressive, decreases with an increase in the N-2 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 sigma is also a function of the film growth temperature, T-s, and exhibits a maximum value of similar to 5 GPa at 350 degrees C. Under these conditions, the films have a distorted microstructure consisting of a three-dimensional, primarily sp(2) bonded, network. In contrast, films deposited at T-s<200 degrees C with a low stress are amorphous. At 350 degrees C<T-s<600 degrees C, sigma gradually decreases as T-s is increased and the microstructure becomes mon graphitic and contains fewer defects. Nanoindentation measurements show that the films grown at 350 degrees C exhibit the highest hardness and elasticity. (C) 1998 American Institute of Physics. [S0003-6951(98)01320-5].