Residual stress stability in fiber textured stoichiometric AlN film grown using rf magnetron sputtering

The authors report on the stability of mechanical stress with aging and thermal cycling for columnar structured stoichiometric and homogeneous aluminum nitride thin films grown using radio frequency magnetron sputtering technique. The set of deposition parameters were optimized for the best possible orientation of crystallites in the c axis of compositionally stoichiometric films. The as-grown stress in the slightly nitrogen-rich film does not change when exposed to the atmosphere following deposition, while that in the nitrogen-deficient film, it changes due to oxidation. Additionally, the magnitude of as-grown stress has been found to depend on the substrate material in addition to the deposition parameters. The stress in the film grown on a Si(001) substrate was more tensile than in the film grown on a semi-insulating (si) GaAs(001) substrate for a given set of deposition parameters. Furthermore, the stress in the film grown on Si decreased with temperature, while that on si GaAs increased, indicating the thermally induced stress component to be the major component in the residual stress. Upon subsequent cooling the stress changes in both substrates followed the same path as of heating, thus exhibiting no hysteresis with thermal cycles between room temperature and 400 degrees C.