Paper EM-TuP11
The Effect of Vacuum-Ultraviolet Irradiation on Copper Diffusion into Low-k Dielectrics

Tuesday, November 11, 2014, 6:30 pm, Room Hall D

Cu diffusion into low-k dielectrics can cause serious reliability issues in on-chip interconnect systems. A considerable attention in the research community had been devoted to understanding the effect of Cu diffusion in the electrical breakdown properties of low-k dielectrics, while Cu-induced diffusion from vacuum-ultraviolet (VUV) irradiated low-k dielectrics has received only minimal attention. This work is aimed at determining the nature of copper interactions with VUV irradiated low-k dielectrics in integrated circuits. The effects of VUV irradiation on the Cu diffusion into low-k organosilicate glass (SiCOH) dielectric films were investigated. X-ray photoelectron spectroscopy depth profiling was used to assess Cu diffusion in the dielectric in the presence of a bias-temperature stress. After 12-eV photon irradiation under bias-temperature stressing at 3.5 MV/cm and 225^oC respectively, Cu penetrates farther into the SiCOH, compared to that of an unirradiated sample. Further examination of the VUV photon-exposed SiCOH shows that the Cu distribution profile in the dielectric after bias-temperature stressing is different from the profile after the same temperature annealing but without electrical bias. In addition, no such enhanced phenomenon was observed in unexposed dielectrics, suggesting that Cu ion drift can occur in VUV-irradiated SiCOH. The implication of these findings on time-dependent dielectric breakdown in Cu/VUV irradiated low-k dielectrics is discussed.

This work has been supported by the Semiconductor Research Corporation under Contract No. 2008-KJ-1871 and the National Science Foundation under Grant No. CBET-1066231.