Current leakage relaxation and charge trapping in ultra-porous low-k materials

摘要

Time dependent dielectric failure has become a pivotal aspect of interconnect design as industry pursues integration of sub-22 nm process-technology nodes. Literature has provided key information about the role played by individual species such as electrons, holes, ions, and neutral impurity atoms. However, no mechanism has been shown to describe how such species interact and influence failure. Current leakage relaxation in low-k dielectrics was studied using bipolar field experiments to gain insight into how charge carrier flow becomes impeded by defects within the dielectric matrix. Leakage current decay was correlated to injection and trapping of electrons. We show that current relaxation upon inversion of the applied field can be described by the stretched exponential function. The kinetics of charge trapping events are consistent with a time-dependent reaction rate constant, k=k0⋅(t+1)β−1, where 0 < β < 1. Such dynamics have previously been observed in studies of charge trapping reactions in amorphous solids by W. H. Hamill and K. Funabashi, Phys. Rev. B 16, 5523–5527 (1977). We explain the relaxation process in charge trapping events by introducing a nonlinear charge trapping model. This model provides a description on the manner in which the transport of mobile defects affects the long-tail current relaxation processes in low-k films.