The Effect of Metal Area and Line Spacing on TDDB Characteristics of 45nm Low-k SiCOH Dielectrics

Low-k time-dependent dielectric breakdown (TDDB) is rapidly becoming one of the most important reliability issues in Cu/low-k technology development and qualification. Although considerable progress has been made in recent years in addressing the electric field dependence of low-k time-to-breakdown (tBD), there has been very little comprehensive work done on the effect of metal area and line spacing on low-k TDDB. The lifetime of a product chip is typically obtained by extrapolating TDDB data from small test structures to large chip areas, and the low-k TDDB line spacing scaling rule normally should be considered for the definition of operating voltages for various technologies to assure long-term reliability. Therefore, both area scaling and line spacing scaling relations are of great importance, in order to have a robust technology qualification. In this study, a thorough investigation into the 45 nm low-k SiCOH TDDB was conducted in order to understand the breakdown failure statistics, to model the area dependence, and to explore the line spacing scaling. With the help of experimental results and computational simulations, the effect of line-to-line spacing on low-k TDDB was clearly identified and a methodology for accurate determination of Weibull shape factor is proposed.