Apparatus for detecting or collecting secondary electrons, charged-particle beam exposure apparatus comprising same, and related methods
US5981947A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 3, 1998 |
| Grant date | Nov 9, 1999 |
| Priority date | — |
| Expiry date | Feb 3, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/2448
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Apparatus and methods are disclosed for performing highly precise mark detection by obtaining a large signal as a result of the efficient capture of secondary electrons (SEs) emitted from a surface of a specimen. A charged-particle beam is directed at a location (e.g., a mark) on the specimen (e.g., reticle or wafer). SEs emitted from the location are detected using one or more secondary-electron collectors or detectors. To guide the SEs toward the secondary-electron collectors or detectors, a magnetic flux is created that extends radially outward in the vicinity of the surface of the specimen. E.g., an objective lens is situated above the specimen adjacent the specimen surface, and an electromagnetic lens is placed below the specimen adjacent the lower surface of the specimen. The magnetic fields produced by these lenses can be mutually repulsive to form a resultant magnetic flux near the upper surface of the specimen that extends radially outward parallel with the upper surface of the specimen. Thus, electrons can escape only radially outward parallel to the sample surface to the secondary-electron collectors or detectors. The apparatus provides a stable charged-particle beam wit…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.