Aperture alignment in scatterometry metrology systems
US9726984B2 · kind B2 · utility
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28Claims
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Key dates
| Filing date | Sep 11, 2014 |
| Grant date | Aug 8, 2017 |
| Priority date | — |
| Expiry date | Sep 11, 2034 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70258
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Methods and algorithms are provided, as well as new metrics for misalignment of apertures with respect to the optical axis of a metrology system. The methods comprise aligning aperture(s) to an optical axis of a scatterometry metrology tool using correction term(s) derived by minimizing an overlay variation measure calculated with respect to overlay measurements of a periodic structure. These methods result in highly sensitive misalignment metrics, which may be used in calibration stages or on the fly to align the system's apertures, and enable reducing target size due to the resulting enhanced alignment accuracy.
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