Stress Evolution In Sputtered Fcc Metal Multilayers

Abstract

During growth of Cu/Pd multilayers the apparent stress in the Cu layers changes from compressive to tensile during the growth of a single Cu layer. The apparent stress in the Pd layers is initially either tensile or compressive depending on the thickness of the underlying Cu layer. It has been speculated that this stress behaviour may be either a result of island growth of Cu on Pd or alloying at the Cu/Pd interface[I]. We have observed that the stress behavior is similar in Cu/Pd and Pd/Pt multilayers and continue to study these systems to better understand the origins of stress in metal multilayers. Stress evolution during growth is monitored by in-situ substrate curvature measurement using a multiple parallel laser beam technique. High angle superlattice spectra for the multilayers are found from symmetric x-ray diffraction scans in order to determine crystallographic texture. Information about interfacial disorder and alloying in the layers is obtained from simulation of the superlattice diffraction patterns. Stress behaviour is correlated with possible modes of growth of the layers, and with atomic peening and coherency effects.