Apparatus and methods for measuring wavefront aberrations of a microlithography projection lens
US5898501A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 1997 |
| Grant date | Apr 27, 1999 |
| Priority date | — |
| Expiry date | Jul 24, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/706
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus and methods are disclosed for measuring wavefront aberrations microlithography projection lenses such as i-line or excimer laser projection lenses. The apparatus comprises an argon-ion laser irradiating a Fizeau surface that reflects reference light and transmits test light. The test light is reflected by a spherical reflecting surface to pass twice through the test lens and the Fizeau surface, to interfere with the reference light. A piezoelectric element changes the fringes slightly. An image-pickup device receives the interference fringes and outputs data to a processor that calculates corresponding wavefront aberrations of the test lens. For testing an i-line lens, the argon laser can be a single-mode, 363.8 nm laser. For testing a lens used with a KrF excimer laser, the argon laser can emit second-harmonic light at 248.25 nm.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.