Method and apparatus for decreasing thermal loading and roughness sensitivity in a photoacoustic film thickness measurement system
US6504618B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 2002 |
| Grant date | Jan 7, 2003 |
| Priority date | — |
| Expiry date | Mar 6, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0666
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Disclosed are methods and apparatus for reducing thermal loading of a film disposed on a surface of a sample, such as a semiconductor wafer, while obtaining a measurement of a thickness of the film in an area about a measurement site. The method includes steps of (a) bringing an optical assembly of the measurement system into focus; (b) aligning a beam spot with the measurement site; (c) turning on one of a dither EOM or a dither AOM or a piezo-electric dither assembly to sweep the beam spot in an area about the measurement site, thereby reducing the thermal loading within the measurement site; (d) making a measurement by obtaining a signal representing an average for the film under the area; (e) recording the measurement data; and (f) analyzing the measurement data to determine an average film thickness in the measurement area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.