Study of stress evolution of boron nitride films prepared by ion assisted deposition

The evolution of the stress during N/Ar ion assisted deposition of boron nitride films on Si(001) substrates was measured in situ by a very sensitive capacity technique in dependence on the ion energy, temperature during deposition, and the ion to atom arrival rate. The relative amount of c-BN in the films was determined by Fourier-transform infrared spectrometry and the layered structure of these films was studied by spectroscopic ellipsometry and high resolution cross-section transmission electron microscopy. The stress evolution in dependence on the layer thickness is characterized by a high tensile stress in the initial stage of the film growth, followed by a transition from the tensile to the compressive stress state and the saturation or weak relaxation of the compressive stress. The existence of the c-BN phase corresponds to a compressive stress of about 2 GPa. For a compressive stress ⩾3.5 GPa boron nitride films with a c-BN content ⩾80% were obtained. The influence of the ion energy, the temperature during the deposition, and the ion to atom arrival ratio on the development of the stress is discussed.