Cu/low- k dielectric TDDB reliability issues for advanced CMOS technologies

Abstract

With the wide application of low- k and ultra-low- k dielectric materials at the 90 nm technology node and beyond, the long-term reliability of such materials is rapidly becoming a critical challenge for technology qualification. Low- k time-dependent dielectric breakdown (TDDB) is usually considered as one of the most important reliability issues during Cu/low- k technology development because low- k materials generally have weaker intrinsic breakdown strength than traditional SiO 2 dielectrics. This problem is further exacerbated by the aggressive shrinking of the interconnect pitch size due to continuous technology scaling. In this paper, three critical issues of low- k TDDB characteristics during low- k development and qualification will be reviewed. In the first part, a low- k TDDB field acceleration model and its determination will be discussed. In the second part, low- k dielectric time-to-breakdown ( t BD) statistical distribution and TDDB area scaling law for reliability projection will be examined. In the last part, as low- k TDDB has been found to be sensitive to all aspects of integration, the effects of process variations on low- k TDDB degradation will be demonstrated. Some key aspects which need to be carefully addressed to control overall low- k TDDB performance from process and integration side will be discussed.