Self referencing heterodyne reflectometer and method for implementing
US7545503B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Sep 27, 2005 |
| Grant date | Jun 9, 2009 |
| Priority date | — |
| Expiry date | Sep 27, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0675
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention is directed to a self referencing heterodyne reflectometer system and method for obtaining highly accurate phase shift information from heterodyned optical signals, without the availability of a reference wafer for calibrations. The self referencing heterodyne reflectometer rapidly alternates between a heterodyne reflectometry (HR) mode, in which an HR beam comprised of s- and p-polarized beam components at split angular frequencies of ω and ω+Δω is employed, and a self referencing (SR) mode, in which an SR beam comprised of p-polarized beam components at split angular frequencies of ω and ω+Δω is employed. When the two measurements are made in rapid succession, temperature induced noise in the detector is be assumed to be the same as for both measurements. A measured phase shift δRef/film is generated from the HR beam and a reference phase shift δRef/Sub is generated from the SR beam. The measured phase shift δRef/film generated from the beat signals of the HR beam is used for film thickness measurements. The SR beam is p-polarized and no significant reflection will result from a film surface and will not carry any phase information pertaining to the film. Th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.