A technique using an electron-beam to inspect wafers with Cu interconnects was developed. It can detect defects such as voids or incomplete contact failures with resistances of more than 10(7) V by utilizing the voltage contrast of a secondary electron image. The technique is performed by controlling the charging voltage of the interconnect while the electron-beam is irradiating the wafer. The charging voltage was found to depend on the conditions of the incident electron-beam, including the incident energy. To investigate the generation of voltage contrast in a Cu via chain, the electronic characteristics of detected defects were measured with probes. It was found that the resistance of a defect measured during electron irradiation and that measured with probes agree well. The contrast of a secondary electron image depends on the resistance of the differential voltage between the ends of a defect during electron-beam irradiation. To detect voids with high sensitivity, the differential voltage between the ends of a defect should be kept between 1 and 2 V, because the resistance of the defect suddenly decreases when the differential voltage is increased beyond a certain point. (C) 2004 The Electrochemical Society.