Automatic focusing method for scanning electron microscopy
US5302829A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 12, 1993 |
| Grant date | Apr 12, 1994 |
| Priority date | — |
| Expiry date | Jan 12, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/21
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An automatic focusing method for scanning electron microscopy. A scanning electron microscope is set in a low magnification mode to detect a taper portion of an object to be observed. The beam scanning whose direction is perpendicular to the taper portion is effected whenever objective lens control condition is changed at a first pitch, and the secondary electron signals obtained under these conditions are converted into video signals. The video signals are differential smoothed to calculate a sum of video signal absolute values. On the basis of the sum of the absolute values, an optimum objective lens control condition in the low magnification mode can be obtained. Sequentially, the microscope is set to a high magnification mode, and the objective lens control condition is further changed at a second pitch within a predetermined range with the optimum control condition in the low magnification mode as the center of the range. The beam scanning whose direction is perpendicular to the taper portion is effected. In the same way as in the low magnification mode, the secondary electrons signal obtained under these conditions are converted into video signals to obtain the optimum object…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.