US 7,119,897 B2 · Sample inspection system

Abstract

A curved mirrored surface is used to collect radiation scattered by a sample surface and originating from a normal illumination beam and an oblique illumination beam. The collected radiation is focused to a detector. Scattered radiation originating from the normal and oblique illumination beams may be distinguished by employing radiation at two different wavelengths, by intentionally introducing an offset between the spots illuminated by the two beams or by switching the normal and oblique illumination beams on and off alternately. Beam position error caused by change in sample height may be corrected by detecting specular reflection of an oblique illumination beam and changing the direction of illumination in response thereto. Butterfly-shaped spatial filters may be used in conjunction with curved mirror radiation collectors to restrict detection to certain azimuthal angles.

Claims31

Dependent claims

An optical system for detecting anomalies of a sample, comprising:

a source supplying a first beam at a first wavelength along a first path and a second beam at a second wavelength along a second path onto a surface of the sample, said two paths being at different incidence angles to the sample surface;
one or more detector(s) detecting radiation at the first and second wavelengths;
and
an optical device receiving scattered radiation from the sample surface and originating from the first and second beams and focusing the scattered radiation to said detector(s), said device receiving radiation scattered by the sample surface irrespective of polarization state of such radiation, said optical device comprising a curved reflective surface and has an axis of symmetry substantially coaxial with the first path, defining an input aperture positioned proximate to the sample surface to receive scattered radiation therethrough from the sample surface.

1 more element

Dependencies are inferred from the claim text.

Sample inspection system

Life of this patent

Sample inspection system

Life of this patent

Abstract

Claims31