초록 ▼

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

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.

대표청구항 ▼

[What is claimed is:] [1.]first optics directing a first beam of radiation along a first path onto a first spot on a surface of the sample;second optics directing a second beam of radiation along a second path onto a second spot on a surface of the sample, said first and second paths being at differ

[What is claimed is:] [1.]first optics directing a first beam of radiation along a first path onto a first spot on a surface of the sample;second optics directing a second beam of radiation along a second path onto a second spot on a surface of the sample, said first and second paths being at different angles of incidence to said surface of the sample;a first detector;collection optics including a curved mirrored surface receiving scattered radiation from the first or the second spot on the sample surface and originating from the first or second beam and focusing the scattered radiation to said first detector, said first detector providing a single output value in response to the radiation focused onto it by said curved mirrored surface; andan instrument causing relative motion between the two beams and the sample so that the spots are scanned across the surface of the sample.