ELECTRON-BEAM TESTING OF INTEGRATED-CIRCUITS WITH MULTILEVEL METAL

The use of voltage contrast techniques on passivated devices with multilevel metallization is discussed. The electric field distribution within a multilevel metal device is calculated using finite difference methods. This is used to determine the voltage coupled to the surface of a passivated device at points accessible to an electron beam probe. Additionally, a planar electrostatic grid is used to create an extraction field above the surface of the device. This extraction field is shown to dominate the surface charge buildup due to alterations in the secondary electron trajectories; thus allowing low energy electrons to be redirected to the device surface. This effect is compared with the effects of the field strength on the equipotential distribution; especially at the device surface.