Positioning two elements using an alignment target with a designed offset
US7046361B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 4, 2002 |
| Grant date | May 16, 2006 |
| Priority date | — |
| Expiry date | May 8, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7076
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An alignment system for aligning two elements includes an alignment target with periodic patterns on each element. The alignment target includes two locations, at least one of which has a designed in offset. If desired, both locations may have designed in offsets of the same magnitude but in opposite directions. The diffraction patterns produced at the two locations are compared. If the difference between the patterns is at a minimum, the elements are properly aligned. When an alignment error is introduced, however, the calculated difference can be used to determine the error. In another embodiment, bands in the moiré fringes from the different locations may be compared to determine the alignment error. The two elements may then be moved relative to each other to minimize the alignment error. Thus, the alignment target may advantageously be used in any alignment system, such as an exposure tool.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.