Optical system with a frustrated isotropic block
US10162087B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 10, 2017 |
| Grant date | Dec 25, 2018 |
| Priority date | — |
| Expiry date | Apr 10, 2037 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B27/4233
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An optical system configured as part of optical metrology unit used to assess the operational status of a workpiece and, in a specific case, configured as an encoder head of a lithographic exposure tool. The optical system is devoid of a stand-alone optical corner-cubes and includes, instead, a single, imperfect or frustrated cuboid of optically-isotropic material that, in operation with the diffraction grating of the workpiece, simultaneously forms four interferometric signals for measuring x-, y, and z-positions of the workpiece grating relative to the optical system. Proposed system and method solve problems of (i) structural complexity of a conventional metrology unit for use in an exposure tool, (ii) burdensome alignment of the multitude of optical prisms in the process of forming such metrology unit, and (iii) cyclic non-linear errors associated with measurements involving conventional corner-cubes-based metrology units.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.