Effects of substrate materials and deposition parameters on film stress

An on-line thin film stress measuring system based on Hartmann-Shack sensor technique is introduced to measure the film stress of SiO, TiO, TaO, AlO and ITO films at different thickness which are prepared by ion assisted deposition, and the effects of substrate materials and preparation parameters on the stresses of SiO and TiO are investigated in details. The results show that the film stress as a function of the film thickness is linear in the initial stage of coating, and the film stress tends to be a stable value when the film thickness reaches a certain value. The thermal stress which resulted from the different coefficients of thermal between substrates and thin films can be diminished by choosing suitable substrates. In terms of TiO films, the thermal stress plays a major role when the substrate temperature is below 150°C, but the compressive stress which resulted from the dense structure of films is dominant while the substrate temperature is above 150°C. However, the thermal stress in SiO films is always dominant at different deposition temperatures. The tensile stress in SiO films is mainly caused by the effects of ion assisted sputtering when the chamber pressure is below 1.7×10 Pa, and the tensile stress in SiO films increases with the vacuum chamber's pressure increasing when it is above 1.7×10 Pa, but the refractive index decreases.