Leakage and breakdown mechanisms in cu damascene with a bilayer-structured a-SiCN/a-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 alpha-SiCN(k=5)/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 alpha-SiCN/alpha-SiC bilayer barrier in the Cu damascene structure. In the Cu damascene using an alpha-SiCN/alpha-SiC bilayer barrier of 40nm/10nm or 30nm/20nm 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 alpha-SiC/OSG interface, which are generated by the larger tensile force of the thicker 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 alpha-SiCN/alpha-SiC bilayer barrier, and the observed breakdown of the Cu damascene structure is presumably due to dielectric breakdown of the bulk OSG layer.