Optical height meter, surface-inspection device provided with such a height meter, and lithographic apparatus provided with the inspection device
US6166808A · kind A · utility
19Cited by
7References
8Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Dec 4, 1997 |
| Grant date | Dec 26, 2000 |
| Priority date | — |
| Expiry date | Dec 4, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0608
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A height meter for measuring the height of a first surface of a transparent object is described, which height meter comprises a radiation source for supplying a converging measuring beam whose chief ray extends at an angle to the normal on the surface, and a radiation-sensitive detection unit for detecting a radiation beam reflected by the surface to be measured. Since a diaphragm is arranged in the path of this beam, it is prevented that radiation reflected by a second surface situated opposite the first surface can reach the detection unit. The height meter is notably suitable for an inspection device for a lithographic mask.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.