Patent Number: 6,169,601

Title: Method and apparatus for distinguishing particles from subsurface defects on a substrate using polarized light

Abstract: Particles are distinguished from pits, voids, scratches, and other subsurface defects in a surface of a substrate by impinging the defect with polarized light and integrating light scattered by the defect over a wide angular range to produce a total integrated response. Using a P-polarized incident light beam, particles are distinguished from subsurface defects by comparing the total integrated responses, which vary with changes in the incident angle. Alternatively, the defect is impinged with a P-polarized incident beam at a defined incident angle, and is then impinged with an S-polarized beam at the same incident angle. Total integrated responses are measured for both beams and a P-to-S ratio of the responses is calculated. Particles are distinguished from subsurface defects by comparing the P-to-S ratio to a predetermined threshold value which separates particles from subsurface defects.

Inventors: Eremin; Yuri A. (Moscow, RU), Stover; John C. (Charlotte, NC), Scheer; Craig A. (Charlotte, NC)

Assignee: ADE Optical Systems

International Classification: G01N 21/94 (20060101); G01N 21/88 (20060101); G01N 021/00 ()

Expiration Date: 01/02/2018