Process robust overlay metrology based on optical scatterometry
US10732516B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 4, 2018 |
| Grant date | Aug 4, 2020 |
| Priority date | — |
| Expiry date | Jan 4, 2038 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30148
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Methods and systems for robust overlay error measurement based on a trained measurement model are described herein. The measurement model is trained from raw scatterometry data collected from Design of Experiments (DOE) wafers by a scatterometry based overlay metrology system. Each measurement site includes one or more metrology targets fabricated with programmed overlay variations and known process variations. Each measurement site is measured with known metrology system variations. In this manner, the measurement model is trained to separate actual overlay from process variations and metrology system variations which affect the overlay measurement. As a result, an estimate of actual overlay by the trained measurement model is robust to process variations and metrology system variations. The measurement model is trained based on scatterometry data collected from the same metrology system used to perform measurements. Thus, the measurement model is not sensitive to systematic errors, aysmmetries, etc.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.