Effect of Dielectric Capping Layer on TDDB Lifetime of Cu Interconnects in SiOF

Abstract

In this study, intralevel dielectric breakdown is studied for copper interconnects in an SiOF dielectric, capped with either SiN or SiCN. The leakage current is higher and the failure time of dielectric breakdown is shorter for an SiCN capping layer compared to an SiN capping layer. It is proposed that the dielectric breakdown of the integrated structure is limited by the interface between the capping layer and the SiOF dielectric. Lower lifetime for dielectric breakdown is observed for structures with an SiCN cap compared to structures with an SiN cap, due to higher leakage current in the SiCN. The higher leakage for an SiCN cap is consistent with results from planar metal-insulator-semiconductor capacitors.

The effects of plasma exposure and vacuum ultraviolet irradiation on photopatternable low-k dielectric materials

“…7 In particular, the slope of the IV characteristics has been found to be related to the Weibull statistics slope of TDDB characteristics in low-k dielectrics. 8,9 Additionally, photons of sufficient energy, particularly in the VUV range, have been shown to cause a number of unwanted effects, including differential charging of patterned structures 10 and the creation of bulk and interfacial trap states that contribute to damage induced by leakage currents. 11…”