The influence of the passivation material on stress voiding in Al-Cu alloys

Storage tests have been performed to obtain information on the influence of the passivation material and its geometry on the mechanical reliability of Al-Cu lines. During storage tests, the stress in the lines is tensile and depends on the passivation material and passivation geometry. The passivati on was either a SiO2 layer or a SiNx layer. In both cases the influence of a conformal and a planarised passivation geometry has been studied. Passiva ting the lines with a material with a higher stiffness such as SiNx will in crease the stress void density in the lines. Moreover, a conformal passivat ion layer induces less stress voids in the metal than a planarised passivat ion, deposited by a Dep/Etch method. The number of stress voids saturates w ithin 24 h at 200 degrees C. However, the voids continue to grow during lon ger storage times. When the lines are passivated with the lower stiffness m aterial SiO2, stress voids have not been observed after storage testing. (C ) 2000 Elsevier Science B.V. All rights reserved.