Phase shifted test pattern for monitoring focus and aberrations in optical projection systems
US6842237B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 28, 2001 |
| Grant date | Jan 11, 2005 |
| Priority date | — |
| Expiry date | Nov 28, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01M11/0264
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method is described for determining lens aberrations using a test reticle and a standard metrology tool. The method provides test patterns, preferably in the form of standard overlay metrology test patterns, that include blazed gratings having orientation and pitch selected to sample desired portions of the lens pupil. The method measures relative shifts in the imaged test patterns using standard metrology tools to provide both magnitude and sign of the aberrations. The metrology tools need not be modified if standard test patterns are used, but can be adapted to obtain additional information. The test reticles may be formed with multiple test patterns having a range of orientations and pitch in order to compute any desired order of lens aberration. Alternatively, single test patterns may be used to determine both the magnitude and sign of lower order lens aberrations, such as defocus or coma.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.