INSITU SCANNING ELECTRON-MICROSCOPY OBSERVATION OF THE DYNAMIC BEHAVIOR OF ELECTROMIGRATION VOIDS IN PASSIVATED ALUMINUM LINES

The dynamic behavior of electromigration (EM) voids has been studied in situ using a field-emission scanning electron microscope fitted with a Robinson backscatter detector. A high-temperature stage has been used to minimize the temperature gradients associated with Joule heating and to allow independent control of temperature and current density. No evidence of pre-existing voids was found. The formation, growth, and motion of electromigration voids were observed and recorded photographically. The voids moved dynamically against the electron wind. No correlation between void size and void velocity was found. The static growth of EM voids was observed in some instances; however, this did not precede void motion nor did it lead to failure. Moving voids formed late in the test dominated final failure. Comparison of experimental results with void motion models reveals that the models for dynamic void motion are not consistent with experimental observations.