Metrology method and inspection apparatus, lithographic system and device manufacturing method
US9946167B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 12, 2015 |
| Grant date | Apr 17, 2018 |
| Priority date | — |
| Expiry date | Sep 18, 2036 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06N20/00
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Methods are disclosed for measuring target structures formed by a lithographic process on a substrate. A grating structure within the target is smaller than an illumination spot and field of view of a measurement optical system. The optical system has a first branch leading to a pupil plane imaging sensor and a second branch leading to a substrate plane imaging sensor. A spatial light modulator is arranged in an intermediate pupil plane of the second branch of the optical system. The SLM imparts a programmable pattern of attenuation that may be used to correct for asymmetries between the first and second modes of illumination or imaging. By use of specific target designs and machine-learning processes, the attenuation patterns may also be programmed to act as filter functions, enhancing sensitivity to specific parameters of interest, such as focus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.