3699 - DERIVATION OF FILM CHRACTERISTIC CONSTANTS BY USING GOVERNING PARAMETER FOR ELECTROMIGRATION DAMAGE IN PASSIVATED BAMBOO LINE

The governing parameter for electromigration damage in the passivated bamboo lines, called AFDli, was recently formulated by considering the divergence of atomic flux due to electromigration. The formulation was based on the parameter AFDli previously introduced in our studies. The parameter AFDli has been identified as the governing parameter for electromigration damage in unpassivated bamboo lines through experimental verification process. On the other hand, metal lines used in integrated-circuit (IC) products are covered with passivation or dielectric layer. A mechanical stress (atomic density) distribution induced by electromigration appears in such lines and plays an important role in the electromigration mechanism. The parameter, AFDli , was formulated by adding the effect of the atomic density gradient to AFDli. By the way, it is known that the displacement of line edge appears at the cathode end of via-connected line as a result of electromigration. So far, the velocity of the edge displacement, the so-called drift velocity, was expressed by using AFDli to construct an AFDli-based method for determination of film characteristics. In this study, the film characteristic constants in AFDli are experimentally determined from the measurement of the drift velocity, where two kinds of metal lines with different line-lengths are treated. Some of the unknown film characteristics do not depend on the line-length and others depend on the length. The film characteristic constants included in AFDli are obtained for two metal lines so that the drift velocity calculated by AFDli agrees with measured one. Through the discussion on the validity of the obtained constants, it is shown that the AFDli-based method can determine both the film characteristics independent of the line-length and another constant depending on the line-length appropriately.