Specimen distance measuring system
US4788431A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 10, 1987 |
| Grant date | Nov 29, 1988 |
| Priority date | — |
| Expiry date | Apr 10, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/24578
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A specimen distance measuring system uses a plate (36) to obstruct the flux of backscattered electrons produced by an electron beam (18), and to cast a shadow across a measurement detector (32) which is sensitive to the position of the shadow. The shadow plate (36) and measurement detector (32) are aligned at an angle of approximately 45 degrees with a substrate (14) in order to allow calibration of the distance measuring system by scanning the electron beam (18). The measuring system is particularly useful as a height sensor (10) in an electron beam lithography apparatus (12) for sensing the height of a substrate (14). The distance measuring system may also include a reference detector (34) which is positioned in order to receive backscattered electron flux without obstruction from the shadow plate (36). The use of such a reference detector (32) is advantageous in allowing compensation of the signals obtained by the measurement detector, in order to allow the height sensor to operate independently of variations in electron beam current, and variations in substrate backscatter coefficient. The reference and measurement detectors (34,32) may be aligned in a vertical or horizontal pl…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.