Method and apparatus for determining an overlay error
US8908147B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 13, 2011 |
| Grant date | Dec 9, 2014 |
| Priority date | — |
| Expiry date | Jan 27, 2033 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70633
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method of determining an overlay error. Measuring an overlay target having process-induced asymmetry. Constructing a model of the target. Modifying the model, e.g., by moving one of the structures to compensate for the asymmetry. Calculating an asymmetry-induced overlay error using the modified model. Determining an overlay error in a production target by subtracting the asymmetry-induced overlay error from a measured overlay error. In one example, the model is modified by varying asymmetry p(n′), p(n″) and the calculating an asymmetry-induced overlay error is repeated for a plurality of scatterometer measurement recipes and the step of determining an overlay error in a production target uses the calculated asymmetry-induced overlay errors to select an optimum scatterometer measurement recipe used to measure the production target.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.