| 摘要 |
PURPOSE:To minimize a damage on a target field due to irradiation of an electron ray, by limiting the irradiation of the elecdton ray toward the target field in a test specimen only to the field searching and the photographing tasks. CONSTITUTION:A switching circuit 16 is charged over with a switch 17a on, such a current as lowering an electron ray density on a test specimen 4 is supplied to a focusing lens 3, and, under this condition, a target field is selected with a horizontal moving mechanism 18. Then, making a switch 17b on and shifting the center of the electron ray from an optical axis by deflection coil 20, focusing or astigmatism correction is done in an area other than the target field in the test specimen 4 by focusing the electron ray in high density. After that, making a switch 17c on and positioning on the optical axis the center of the electron ray focused in low dentiy, the target field shall be photographed. Accordingly, a photograph of high resolution can be taken with remarkable reduction of the damage on the test specimen due to the irradiation of the electron ray. |
