Stresses arising from a solid state reaction between palladium films and Si(001) investigated by in situ combined x-ray diffraction and curvature measurements

By combining simultaneously in situ x-ray diffraction and curvature measurements, the stress evolution during silicide formation in thin Pd films deposited on Si substrates has been reliably investigated. The in-plane strain in the silicide is compressive. The combination method also permits the determination of the elastic constants and thermal expansion coefficient of Pd2Si ([001] fiber texture): Esil=86±8 GPa, νsil=0.34±0.05, and αsil=13.2×10−6 K−1. It is shown that during growth the average compressive stress increases progressively up to a maximum temperature-dependent value (−1.5 GPa at 220 °C) and then vanishes for long annealing. This behavior is in reasonable agreement with the predictions of a model by Zhang and d’Heurle [S. L. Zhang and F. M. d’Heurle, Thin Solid Films 213, 34 (1992)]. A strain gradient in the growing silicide layer, which is predicted by the model, has been shown.