TDDB reliability improvement in Cu damascene by using a bilayer-structured PECVD SiC dielectric barrier

Abstract

This work investigates the thermal stability and barrier characteristics of two species of silicon carbide dielectric films, alpha-SiCN with a dielectric constant of 4.9 and alpha-SiC with a dielectric constant of 3.8. The TDDB lifetime of Cu damascene metallization structure is greatly improved by using a alpha-SiCN/alpha-SiC bilayer dielectric stack as the etching stop layer (ESL). This improvement is presumably due to the alpha-SiC dielectric's lower leakage current, absence of nitridation on Cu surface, and better adhesion on Cu as well as OSG intermetal dielectric (IMD), though the alpha-SiC film has a very slow deposition rate. We believe that the alpha-SiCN/alpha-SiC bilayer dielectric is a favorable combination for the ESL because alpha-SiCN can protect alpha-SiC from plasma attack during the photoresist stripping.