Study on electromigration and time dependent dielectric breakdown reliabilities of ruthenium and molybdenum for next-generation interconnection

Abstract

Copper, which is currently widely used as an interconnect material in the industry, suffers from increased resistivity and reliability problems in width of less than 10 nm. Accordingly, in the back end of line (BEOL) region, there is a need for a next generation interconnect material with better resistivity and reliability characteristics. Therefore, in this study, I would like to evaluate the reliability of barrier-less next-generation interconnect candidate materials such as ruthenium and molybdenum, especially electromigration (EM) and time dependent dielectric breakdown (TDDB). In order to analyze the EM characteristics of Ru and Mo, an accelerated life test (ALT) was conducted by applying constant current stress (CCS) at several high temperatures. Through this, the activation energy of the Black’s equation was extracted, and it was confirmed that Mo has poor characteristics compared to Cu, and Ru has much better EM performance than Cu. In addition, as a result of identifying EM characteristic tendencies according to surrounding dielectric materials, it was confirmed that Ru had higher EM resistance in the surrounding environment of a dielectric having higher thermal diffusivity. Meanwhile, in order to analyze the TDDB characteristics of Ru and Mo, constant voltage stress (CVS) was applied at high temperatures to conduct an ALT. Through this, the TDDB reliability decreased rapidly at high temperature of molybdenum without barrier, and relatively high TDDB reliability was confirmed through the TDDB modeling and field acceleration factor extraction of Ru without barrier. Therefore, this study confirmed the necessity of application of Ru as a next-generation interconnect material through quantitative evaluation of the reliability and analysis of material properties of Ru and Mo without a diffusion barrier.