High accuracy measurement system for focusing and leveling
US9846373B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 15, 2016 |
| Grant date | Dec 19, 2017 |
| Priority date | — |
| Expiry date | Feb 14, 2036 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7026
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The present disclosure provides a high accuracy measurement system for focusing and leveling. The system determines an off-focus distance in the perpendicular direction within the exposure field and an inclination in the horizontal direction by measuring heights of four detection points on a substrate by using a four-channel detection method, thereby achieving focusing and leveling of the substrate. The detection of the substrate heights is implemented by a focusing method based on dual-channel light intensity modulation. Two superposed grating fringes are formed with phase difference of π/2. The shift can be resolved by the phase variation of corresponding fringes. According to the method, the off-focus distance can be derived. The present disclosure effectively eliminates the error due to the intensity changes caused by the fluctuations of the source or the reflectance of the substrate surface. The apparatus for focusing and leveling is easy to be implemented and has an accuracy of nanoscale.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.