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

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