In-situ and real time room temperature oxidation studies of fcc TiN thin films

In-situ and real time ellipsometry was used to study the oxidation process of thin fee TINx films. The films were grown by DC reactive magnetron sputtering at various negative bias voltages (V-b) in order to deposit TiNx with different stoichiometries and then exposed to several gases and to air at room temperature. The oxidation rate was found to depend strongly on the V-b. High oxidation is observed at low V-b, where the nitrogen is weakly bonded to Ti and thus more easily can be replaced. By analysing the spectroscopic ellipsometry (SE) data, it was found that oxidation takes place in the bulk of the film and can proceed up to a 10% transformation of titanium nitride into oxide. From the SE results and those obtained from stress measurements during exposure to air, it is concluded that the fastest and most important mechanism for the film oxidation is through grain boundary diffusion and reaction of oxygen with the weakly bonded Ti-N.