X-ray diffraction analysis of thermally-induced stress relaxation in ZnO films deposited by magnetron sputtering on (100) Si substrates

Residual stresses in sputtered ZnO films on Si are determined and discussed. By means of X-ray diffraction, we show that as-deposited ZnO films are highly compressively stressed. Moreover, a transition of stress is observed as a function of the post-deposition annealing temperature. After an 800 °C annealing, ZnO films are tensily stressed while ZnO films encapsulated by Si3N4 are stress-free. With the aid of in-situ X-ray diffraction under ambient and argon atmosphere, we argue that this thermally activated stress relaxation may be attributed to a variation of the stoichiometry of the ZnO films.