THERMAL EFFECTS OF RESIDUAL MACROSTRESS AND MICROSTRAIN IN PLASMA-ASSISTED CVD TIN FILMS

The effects of both the deposition and tempering temperatures on the residual macrostress and microstrain are investigated in plasma-assisted chemical vapour deposition (PACVD) TiN films. Unlike the case of thermal CVD processes, the residual macrostress in PACVD TiN films decreases with the increase of the deposition temperature and shows a dramatic drop once the temperature is above 700-degrees-C. The residual microstrain, indicated by peak broadening and a stress-free lattice constant, exhibits the same variation with the deposition temperature. This implies that the competition for the formation of stress and strain is related to the coating process and that the macrostress in PACVD TiN film is usually of an intrinsic nature. Nevertheless, the thermal stability of macrostress behaves differently from that of microstrain. The tempering treatment tends to release residual macrostress but shows little effect on the microstrain detected by the X-ray method. Different origins may exist for the macrostress and microstrain in the film, although only those films deposited at relatively low temperatures and, bence, involved mainly with intrinsic macrostresses display a significant relaxation rate.