Leakage and breakdown mechanisms in Cu damascene with a bilayer-structured /spl alpha/-SiCN//spl alpha/-SiC dielectric barrier

Abstract

This work investigates the leakage and breakdown mechanisms in the Cu damascene structure with a carbon-doped low-k PECVD organosilicate glass (OSG, k=3) as the intermetal dielectric (IMD) and an /spl alpha/-SiCN(k=5)//spl alpha/-SiC(k=4) bilayer-structured dielectric film as the Cu-cap barrier. It is found that the leakage mechanism between Cu lines is dependent on the thickness ratio of the /spl alpha/-SiCN//spl alpha/-SiC bilayer barrier in the Cu damascene structure. In the Cu damascene using an /spl alpha/-SiCN//spl alpha/-SiC bilayer barrier of 40 nm/10 nm or 30 nm/20 nm bilayer thickness, the large leakage current (Frenkel-Poole emission) between Cu lines is attributed to the plenty of interfacial defects, such as cracks, voids, traps or dangling bonds at the /spl alpha/-SiC/OSG interface, which are generated by the larger tensile force of the thicker /spl alpha/-SiC film. On the other hand, the breakdown field and TDDB (time-dependent-dielectric-breakdown) lifetime of the Cu damascene reveal little dependence on the thickness ratio of the /spl alpha/-SiCN//spl alpha/-SiC bilayer barrier, and the observed breakdown of the Cu damascene structure is presumably due to dielectric breakdown of the bulk OSG layer.