Overlay key with a plurality of crossings and method of measuring overlay accuracy using the same
US7236245B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 29, 2004 |
| Grant date | Jun 26, 2007 |
| Priority date | — |
| Expiry date | Oct 1, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7076
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An overlay key includes a main scale and a vernier scale, which traverse each other forming a plurality of crossings. The main scale includes a first main sub-scale and a second main sub-scale, which are separated from each other or at least partially overlap each other. The first and second main sub-scales extend in different directions such that they are not parallel to each other. The vernier scale includes a first vernier sub-scale and a second vernier sub-scale, which are separated from each other or at least partially overlap each other. The first and second vernier sub-scales extend in different directions such that they are not parallel to each other. Two measured crossings are obtained when the main scale and the vernier scale cross each other in a measured position. Then, overlay accuracy is measured from coordinate differences between reference crossings and the measured crossings.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.