| 摘要 |
PURPOSE:To evade erroneous measurement due to the contrast of a material difference by generating a symmetrical signal which corresponds to a secondary electron from a sample by a couple of detectors which are arranged symmetrically. CONSTITUTION:The deflector 3 of an electron beam lens barrel part 1 is controlled by a deflection signal generator 9 and a polarized light amplifier 10 which react to a control part 11 to scan an electron beam on the sample. Consequently, the secondary electron generated by the sample 4 is detected by the signal detectors 5a and 5b which are arranged symmetrically, their detection outputs are processed by dividers 12a and 12b to calculate the ratio and inverse ratio of both signals, and both ratios are added together by an adder 13 to extract a signal corresponding to only the contrast due to the shape with good symmetry while contrast due to the material difference is eliminated. This signal is compared with a reference value by a comparator 14 to control a counter 17 which counts pulses from oscillators 16 and an address corresponding to the counted value is determined to evade erroneous measurement due to the contrast of the material difference by a control part 11 through a memory 18, thereby measuring the shape with high accuracy.
|
