Scanning electron beam apparatus
US4961003A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 1, 1989 |
| Grant date | Oct 2, 1990 |
| Priority date | — |
| Expiry date | Nov 1, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/141
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An apparatus for directing a scanned electron beam to a sample along an axis. An objective magnetic lens of a single-pole type focusses the scanned electron beam onto the sample. The objective magnetic lens includes a central pole portion extending along the axis and having a central end face effective to generate a magnetic field for focusing the scanned electron beam onto the sample and a peripheral sleeve portion extending along the axis and having a peripheral edge face effective to form a magnetic circuit between the central end face and the peripheral edge face, the peripheral sleeve portion having an inner radius R. A magnetic shield member is disposed to surround the sample to magnetically shield the same. The magnetic shield member has a central section spaced axially from the central end face of the pole portion a distance L which is not substantially less than R so that the magnetic shield member is not magnetically coupled to the magnetic circuit, and a peripheral section spaced from the peripheral edge face of the peripheral sleeve a spatial gap sufficient to magnetically isolate the magnetic shield member from the magnetic lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.