Metrology method, patterning device, apparatus and computer program
US11385553B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 3, 2021 |
| Grant date | Jul 12, 2022 |
| Priority date | — |
| Expiry date | May 3, 2041 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7076
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method of measuring overlay uses a plurality of asymmetry measurements from locations (LOI) on a pair of sub-targets (1032, 1034) formed on a substrate (W). For each sub-target, the plurality of asymmetry measurements are fitted to at least one expected relationship (1502, 1504) between asymmetry and overlay, based on a known bias variation deigned into the sub-targets. Continuous bias variation in one example is provided by varying the pitch of top and bottom gratings (P1/P2). Bias variations between the sub-targets of the pair are equal and opposite (P2/P1). Overlay (OV) is calculated based on a relative shift (xs) between the fitted relationships for the two sub-targets. The step of fitting asymmetry measurements to at least one expected relationship includes wholly or partially discounting measurements (1506, 1508, 1510) that deviate from the expected relationship and/or fall outside a particular segment of the fitted relationship.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.