System and method for measuring overlay alignment using diffraction gratings
US7289214B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 23, 2004 |
| Grant date | Oct 30, 2007 |
| Priority date | — |
| Expiry date | Oct 31, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70633
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A system and method for optical offset measurement is provided. An offset between two grating layers in a compound grating is measured by illuminating the gratings with light having a plane of incidence that is neither parallel with nor perpendicular to the grating lines. This non-symmetrical optical illumination allows determination of the sign and magnitude of the offset. Two measurements are performed at azimuthal angles separated by 180°, and a difference of these measurements is calculated. Measurement of this difference allows determination of the offset (e.g., with a calibration curve). Alternatively, two compound gratings having a predetermined non-zero offset difference can be employed. This arrangement permits determination of the offsets without the need for a calibration curve (or for additional compound gratings), based on a linear approximation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.