Covering metal test pads of a passivated integrated circuit process intermediate wafer or completed integrated circuit chip-to-test, with a thin conductive overlayer, and then accessing the test pads through the passivation layer and conductive overlayer, by a pulsed laser to provide voltage-modulated...http://www.google.de/patents/US4786864?utm_source=gb-gplus-sharePatent US4786864 - Photon assisted tunneling testing of passivated integrated circuits
