Method and apparatus for measuring reflectance in two wavelength bands to enable determination of thin film thickness
US5486701A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 1994 |
| Grant date | Jan 23, 1996 |
| Priority date | — |
| Expiry date | Mar 28, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70483
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and system for performing reflectance measurements of a sample using radiation having UV frequency components (preferably in a broad UV band) and visible frequency components (preferably in a broad band). Preferably, two detectors simultaneously receive a sample beam reflected from the sample surface. One detector generates a signal indicative of the sample beam components in the UV band and the other detector generates a signal indicative of the sample beam components in the visible band. By processing these two signals, the invention enables accurate measurement of the thickness of a very thin film on the sample. Preferably, the system determines a single effective wavelength for the UV radiation incident on the first detector and a single effective wavelength for the visible radiation incident on the second detector. Embodiments of the system can also measure reflectance spectra and refractive indices, and can determine lithographic exposure times. Preferred embodiments include an objective lens assembly having a pupil stop with an entrance portion with one or more relatively large apertures therethrough and an exit portion with one or more relatively small apertures th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.