Method and apparatus for automatic focusing of scanning electron microscope
US5130540A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 17, 1991 |
| Grant date | Jul 14, 1992 |
| Priority date | — |
| Expiry date | Jul 17, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/28
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Method and an apparatus for automatically moving the focal plane of the electron beam produced by a scanning electron microscope to the position of specimen surface. An auxiliary coreless coil of a low inductance is disposed close to the objective lens. The exciting current fed to the coil is varied to move the focal plane of the electron beam toward the optical axis. At each of discrete positions of the focal plane, a specimen is scanned with the electron beam. The resulting secondary electrons are detected by a detector. Individual output signals from the detector are compared to select the maximum signal. Then, only the objective lens is excited. The exciting current fed to the objective lens is modified to move the focal plane along the position closest to the specimen surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.