PURPOSE: To determine the presence or absence of a disconnection and the like of a net, by a method wherein an electron beam obtained by switching an acceleration voltage alternately is applied, a phase delay of an alternating current detected from a conducting plate is measured, and an electrostatic capacity value thus obtained is compared with an intrinsic electrostatic capacity value.
CONSTITUTION: A vacuum vessel 1, a sample table 2 for setting a board 3 to be inspected, an electron gun 4 for applying an electron beam 14 to a specified pad on the board 3, an electronic lens 5, an electrostatic deflector 6, and an acceleration voltage control circuit 9 controlling an acceleration voltage for the beam 14, are provided. Besides, an electronic lens control circuit 10 for adjusting the focus of the beam 14 onto the board 3 and a deflection control circuit 11 connected to the deflector 6 giving deflection to the beam 14 are provided. From design information on the board 3 stored beforehand in a computer 13, the beam 14 making an alternating current generated is applied to a specified pad on the board 3, and an electrostatic capacity between a net and the conducting plate, which can be preestimated from a phase delay to an acceleration voltage of a current detected 16 through the conducting plate 15, is compared with an electrostatic capacity obtained from the design information. The presence or absence of a short circuit and the like of the net can be determined therefrom.
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