Overlay measurement using multiple wavelengths
US11158548B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 3, 2018 |
| Grant date | Oct 26, 2021 |
| Priority date | — |
| Expiry date | Jul 14, 2039 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/08
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method of determining overlay (“OVL”) in a pattern in a semiconductor wafer manufacturing process comprises capturing images from a cell in a metrology target formed in at least two different layers in the wafer with parts of the target offset in opposing directions with respect to corresponding parts in a different layer. The images may be captured using radiation of multiple different wavelengths, each image including +1 and −1 diffraction patterns. A first and second differential signal may be determined for respective pixels in each image by subtracting opposing pixels from the +1 and −1 diffraction orders for each of the multiple wavelengths. An OVL for the respective pixels may be determined based on analyzing the differential signals from multiple wavelengths simultaneously. Then an OVL for the pattern may be determined as a weighted average of the OVL of the respective pixels.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.