Variable axis immersion lens electron beam projection system
US4544846A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 28, 1983 |
| Grant date | Oct 1, 1985 |
| Priority date | — |
| Expiry date | Jun 28, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/141
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A variable axis immersion lens electron beam projection system shifts the electron beam while eliminating rapidly changing fields, eddy currents and stray magnetic fields in the target area. The electron beam projection system includes an electron beam source and a deflection means. A variable axes immersion lens for focusing the electron beam includes an upper pole piece, and a lower pole piece having a non-zero bore section, a zero bore section and an opening therebetween for inserting the target into the lens. The variable axis immersion lens provides an axial magnetic projection field which has zero first derivative in the vicinity of the target area. A magnetic compensation yoke, positioned within the bore of the upper pole piece produces a magnetic compensation field which is proportional to the first derivative of the axial magnetic projection field. The magnetic compensation field is approximately zero in the target area to thereby eliminate eddy currents in the target holder, target handler and target stepper table. Stray magnetic fields are accordingly eliminated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.