Enhanced overlay measurement marks for overlay alignment and exposure tool condition control
US6727989B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 20, 2000 |
| Grant date | Apr 27, 2004 |
| Priority date | — |
| Expiry date | Jun 1, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70633
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
In an overlay measurement mark comprising an inner box and an outer box located at a predetermined area on a mask through which patterns are formed on a semiconductor device, the improvement of an overlay mark that extends the overlay measurement range comprising: in-focused marks means printed at an optimal or ideal focal plane level from an illumination source, and de-focused marks means located at a different focus level from the optimal focal plane to provide image placement shift of the de-focused marks larger than that of the in-focused marks means to enable measurement of the shift of de-focused marks that are not attributable to a mechanical alignment error to be determined with greater accuracy.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.