Self-referencing and self-calibrating interference pattern overlay measurement
US11231654B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 14, 2020 |
| Grant date | Jan 25, 2022 |
| Priority date | — |
| Expiry date | Jun 4, 2040 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70216
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Two pairs of alignment targets (one aligned, one misaligned by a bias distance) are formed on different masks to produce a first pair of conjugated interference patterns. Other pairs of alignment targets are also formed on the masks to produce a second pair of conjugated interference patterns that are inverted the first. Misalignment of the dark and light regions of the first interference patterns and the second interference patterns in both pairs of conjugated interference patterns is determined when patterns formed using the masks are overlaid. A magnification factor (of the interference pattern misalignment to the target misalignment) is calculated as a ratio of the difference of misalignment of the relatively dark and relatively light regions in the pairs of interference patterns, over twice the bias distance. The interference pattern misalignment is divided by the magnification factor to produce a self-referenced and self-calibrated target misalignment amount, which is then output.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.