Photocurrent spectroscopy of low- k dielectric materials: Barrier heights and trap densities

Abstract

Measurements of photoinduced current have been performed on thin films of porous low- k dielectric materials comprised of carbon-doped oxides. The dielectric films were deposited on silicon surfaces and prepared with a thin gold counterelectrode. From the spectral dependence of the photoinduced current, barrier heights for the dielectricsilicon and dielectricgold interface were deduced. Transient currents were also found to flow after the photoexcitation was abruptly stopped. An estimate of the density of shallow electron traps within the low- k material was obtained from the measurement of the net charge transported from this detrapping current. A density of traps in the range of 6× 1016 traps cm3 was inferred for the low- k films, far exceeding that observed by the same technique for reference dielectric films of pure Si O2. This behavior was also compatible with photocurrent I-V measurements on the low- k dielectric films and Si O2 reference sample. © 2008 American Institute of Physics.