ON THE BAMBOO STRUCTURE AS THE SALVATION OF THIN-FILM METALLIZATION FOR DEEP-SUBMICRON DEVICE TECHNOLOGIES

The recently proposed Dreyer-Fu-Varker (DFV) model [J. Appl. Phys. 73, 4894 (1993) and 1993 Int. Rel. Phys. Proc. 304 (1993)] for predicting electromigration lifetime has been extended to include the shape factor (normally referred to as the standard deviation). An experiment has been conducted to verify the validity of this extension. Excellent agreement between the model prediction and the experimental data has been obtained. It is found that a significant portion of the increase in the shape factor with the decrease in line width can be attributed to the increase in the temperature standard deviation for nar-rower lines. Based on this newly expanded DFV model coupled with the experimental observations it is shown that the maximum allowable current density, for meeting the reliability specification of electromigration, suffers a steep drop with line width in the deep submicron region. As a result, the bamboo structure cannot salvage thin film metallization from electromigration susceptibility for deep submicron microchip technologies.