| 摘要 |
An electron beam transversely scans a planar surface having a longitudinal structure projecting therefrom. Two Everhart-Thornley detectors are positioned on transversely opposite sides, respectively, of the structure. During a first scan, only one detector is turned ON to produce a first electric signal having a pronounced amplitude dip corresponding to the structure's bottom edge which is facing away from the ON detector. During the next scan, only the other detector is turned ON to produce a second electric signal having a pronounced amplitude dip corresponding to the structure's other bottom edge which is now facing away from the ON detector. The two signals are combined to produce a composite signal whose waveform comprises two enhanced and segmented dips corresponding precisely to the locations of the structure's two bottom edges.
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