Depletion of charge produced during plasma exposure in aluminum oxide by vacuum ultraviolet radiation

A temporary increase in the conductivity of aluminum oxide sputter deposited on the surface of aluminum wafers was made by exposure to vacuum ultraviolet (VUV) radiation produced by a synchrotron light source. The oxide was charged, either positively or negatively, by exposure to a nonreactive inductively coupled plasma, under typical plasma processing conditions. We show the dependence of the conductivity on the energy of the incoming radiation, and conclude that only those photons whose energy is above the band gap of the oxide are capable of producing a temporary increase in the conductivity. By exposing localized regions of precharged oxide samples to the vacuum ultraviolet radiation, we produce regions of charge depletion in and around the exposed areas. We conclude that VUV radiation may be used to significantly decrease plasma-induced surface charging of dielectrics.