Focus system for oblique optical metrology device
US11346790B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 2, 2020 |
| Grant date | May 31, 2022 |
| Priority date | — |
| Expiry date | Jan 27, 2041 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/068
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The light from an optical metrology device is focused into a measurement spot on a sample using a focusing system. The focusing system uses an image of the light reflected from the measurement spot to determine a best focal position at a desired position of the sample. The focusing system selects a characteristic of reflected light, such as polarization state or wavelengths, to use for focusing. The characteristic of the reflected light that is selected for use in determining focal position is affected different by different portions of the sample. For example, light reflected from a top surface of a sample may have a different characteristic than light reflected by an underlying layer. The selected characteristic of the reflected light is used by the focusing system to focus the measurement spot at the top surface or an underlying layer of the sample.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.