The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 03, 2003
Filed:
Nov. 12, 1998
Shrenik Deliwala, Brighton, MA (US);
Allen Flusberg, Newton, MA (US);
Stephen D. Swartz, Cambridge, MA (US);
Science Research Laboratory, Inc., Somerville, MA (US);
Abstract
A method and apparatus for enhancing the precision of distance or position measurements using a two-wavelength interferometer is disclosed. The invention provides for the direct measurement of air density fluctuations, thus allowing for correction of measurement errors, including those due to air turbulence and air thermal variations in a measurement path of a distance measuring interferometer. The invention can function both as a precision enhancement to an existing interferometric measuring system, or as a stand-alone system, measuring both “uncorrected” distance and air density and providing a corrected distance value. A novel measurement head design removes the constraint that a measurement and a reference component of the interferometer optical signals travel a shared path at any point in the interferometer, and thus substantially reduces errors due to polarization leakage. A novel signal processing technique reduces the cost, size and complexity of a distance or position measurement system according to the invention, and renders the invention particularly useful for lithographic integrated-circuit wafer production applications with critical dimensions below 0.1 &mgr;m.