Internal stress analysis in thin metallic films by combining curvature and X-ray diffraction methods

Structural and mechanical state of Cu and Mo thin films (200 nm) deposited on oxidised Si substrates have been analysed using X ray diffraction and mechanical spectroscopy. In this paper, we show the interest and the complementarity of the two methods to investigate stresses in thin films. The in plane stress values determined by the two methods in the copper films are in good agreement. In the case of molybdenum films, the values obtained indicate a very high compressive stress state, but we observed a large difference (approximate to 2 GPa) between the stress magnitude determined with the two methods : 4.5 and 2.3 GPa for X-rays and curvature methods respectively. In order to explain this stress level difference which is certainly correlated to a particular structure of the deposits, we followed the evolution of the internal friction Q(-1) and the mechanical state during thermal cycling in a temperature range 300-760 K.