초록 ▼

A light beam is directed towards a surface along a direction normal to the surface. The surface is caused to move so that the beam scans the surface along a spiral path. An ellipsoidal mirror is placed with its axis along the surface normal to collect light scattered by the surface and any anomalies

A light beam is directed towards a surface along a direction normal to the surface. The surface is caused to move so that the beam scans the surface along a spiral path. An ellipsoidal mirror is placed with its axis along the surface normal to collect light scattered by the surface and any anomalies at the surface at collection angles away from the surface normal. In some applications, a lens arrangement with its axis along the surface normal is also used to collect the light scattered by the surface and any anomalies. The light scattered by the mirror and lenses may be directed to the same or different detectors. Preferably light scattered by the surface within a first range of collection angles from the axis is detected by a first detector and light scattered by the surface within a second range of collection angles from the axis is detected by a second detector. The two ranges of collection angles are different, with one detector optimized to detect scattering from large particles and defects and the other detector optimized to detect light from small particles and defects.

대표청구항 ▼

What is claimed is: 1. An optical system for detecting contaminants and defects of a test surface comprising: a device providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; a first and a second detector; a first collector havin

What is claimed is: 1. An optical system for detecting contaminants and defects of a test surface comprising: a device providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; a first and a second detector; a first collector having an optical axis substantially along a line perpendicular to the test surface, said first collector collecting light from the polarized light beam scattered by the illuminated spot of the surface and conveying the collected light to the first detector, causing the first detector to provide a single output in response to the light collected by the first collector; and a second collector collecting light from the polarized light beam scattered by the illuminated spot of the surface and conveying the collected light to the second detector, causing the second collector to provide a single output in response to the light collected by the second collector, wherein the first and second collectors collect light scattered by the surface within different ranges of collection angles from the line. 2. An optical system for detecting contaminants and defects of a test surface comprising: a device providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; a first and a second detector; a first collector collecting light scattered by the surface and conveying the collected light to the first detector; and a second collector collecting light scattered by the surface and conveying the collected light to the second detector, wherein the first and second collectors have an optical axes substantially along a line, said first and second collector collecting light scattered by the surface within different ranges of collection angles that are away from and that do not include a line normal to the test surface, said first collector having an optical axis substantially along a line perpendicular to the test surface. 3. The system of claim 2, wherein the first collector collects light scattered from the spot within collection angles of up to 25 degrees from the line. 4. The system of claim 2, wherein the first collector collects light scattered from the spot within collection angles of about 3 to 25 degrees from the line. 5. The system of claim 2, wherein the second collector collects light scattered from the spot within collection angles of about 25 to 70 degrees. 6. The system of claim 2, said system further comprising a third detector, said three detectors located to detect light scattered by the surface within at least a first, second and third range of collection angles from the line, said first range of angles being about 3 to 25 degrees, and said second range being about 25 to 65 degrees, and said third range being about 65 to 85 degrees. 7. The system of claim 2, said system further comprising an instrument causing relative rotational and translational motion between the beam and the surface, so that the beam scans a spiral path on the surface. 8. The optical system of claim 2, wherein the device provides a linearly polarized beam. 9. An optical system for detecting contaminants and defects of a test surface comprising: a device providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; a first and a second detector; a first collector collecting light scattered by the surface within a first range of collection angles, said first collector conveying the collected light to the first detector; and a second collector collecting light scattered by the surface and conveying the collected light to the second detector, wherein the second collector collects light scattered by the surface within a second range of collection angles that are different from the first range of collection angles, at least one of said first and second ranges of collection angles being away from and do(es) not include any direction normal to the test surface, and wherein said first and second ranges of collection angles do not include any specular reflection direction of the light beam, said first collector having an optical axis substantially along a line perpendicular to the test surface. 10. The system of claim 9, wherein the first collector collects light scattered from the spot within collection angles of up to 25 degrees from the line. 11. The system of claim 9, wherein the first collector collects light scattered from the spot within collection angles of about 3 to 25 degrees from the line. 12. The system of claim 9, wherein the second collector collects light scattered from the spot within collection angles of about 25 to 70 degrees. 13. The system of claim 9, said system further comprising a third detector, said three detectors located to detect light scattered by the surface within at least a first, second and third range of collection angles from the line, said first range of angles being about 3 to 25 degrees, and said second range being about 25 to 65 degrees, and said third range being about 65 to 85 degrees. 14. The system of claim 9, said system further comprising an instrument causing relative rotational and translational motion between the beam and the surface, so that the beam scans a spiral path on the surface. 15. The optical system of claim 9, wherein the device provides a linearly polarized beam. 16. An optical method for detecting contaminants and defects of a test surface comprising: providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; collecting light from the polarized light beam scattered by the surface and conveying the collected light to a first detector; and collecting light from the polarized light beam scattered by the surface and conveying the collected light to a second detector, wherein the first and second collectors collect light scattered by the surface within different ranges of collection angles that are away from and that do not include a line normal to the test surface, said ranges of collection angles being at different elevations from the test surface, wherein said first collector having an optical axis substantially along a line perpendicular to the test surface. 17. The method of claim 16, wherein the collecting and conveying light to the first detector collects light scattered from the spot within collection angles of about 3 to 25 degrees from the line. 18. The method of claim 16, wherein the collecting and conveying light to the second detector collects light scattered from the spot within collection angles of about 25 to 70 degrees. 19. The method of claim 16, said method further comprising causing relative rotational and translational motion between the beam and the surface, so that the beam scans a spiral path on the surface. 20. The optical method of claim 16, wherein the providing provides a linearly polarized beam. 21. The method of claim 16, wherein said method detects small anomalies in the presence of large anomalies on the test surface. 22. The method of claim 16, wherein said method enables differentiation between large and small anomalies. 23. The method of claim 16, wherein said method enables differentiation, characterization and/or classification of anomalies, said anomalies comprising scratches, slip lines, crystal originated particles and particles by comparing light collected by the two detectors. 24. The method of claim 16, wherein said method enables differentiation between scratches, slip lines and crystal originated particles by comparing light collected by the two detectors. 25. The method of claim 16, wherein said method enables differentiation between different topographic features by comparing light collected by the two detectors. 26. An optical method for detecting contaminants and defects of a test surface comprising: providing a polarized light beam along a path at an oblique angle to the test surface, producing an illuminated spot thereon; collecting light from the polarized light beam scattered by the surface within a first range of collection angles by a first collector, said first collector conveying the collected light to a first detector; said first collector providing a single output in response to the light collected by it; collecting light from the polarized light beam scattered by the surface and conveying the collected light to a second detector, said second collector providing a single output in response to the light collected by it; wherein the second collector collects light scattered by the surface within a second range of collection angles that are at different elevations from the first range of collection angles, at least one of said first and second ranges of collection angles being away from and do(es) not include any direction normal to the test surface, wherein said first collector having an optical axis substantially along a line perpendicular to the test surface. 27. The method of claim 26, wherein the collecting and conveying light to the first detector collects light scattered from the spot within collection angles of up to 25 degrees from the line. 28. The method of claim 26, wherein the collecting and conveying light to the first detector collects light scattered from the spot within collection angles of about 3 to 25 degrees from the line. 29. The method of claim 26, wherein the collecting and conveying light to the second detector collects light scattered from the spot within collection angles of about 25 to 70 degrees. 30. The method of claim 26, said method further comprising causing relative rotational and translational motion between the beam and the surface, so that the beam scans a spiral path on the surface. 31. The optical method of claim 26, wherein the providing provides a linearly polarized beam. 32. The method of claim 26, wherein said method detects small anomalies in the presence of large anomalies on the test surface. 33. The method of claim 26, wherein said method enables differentiation between large and small anomalies. 34. The method of claim 26, wherein said method enables differentiation, characterization and/or classification of anomalies, said anomalies comprising scratches, slip lines, crystal originated particles and particles. 35. The method of claim 26, wherein said method enables differentiation between scratches, slip lines and crystal originated particles. 36. The method of claim 26, wherein said method enables differentiation between different topographic features. 37. An optical system for detecting anomalies of a sample, comprising: optics directing a beam of radiation along a path at an oblique angle onto a surface of the sample; at least one detector; and an optical device receiving scattered radiation from the sample surface and originating from the beam and focusing the scattered radiation to said detector, causing said at least one detector to provide an output, said device comprising a curved mirrored surface collecting the radiation from the sample surface, said curved mirrored surface having an axis of symmetry substantially coaxial with a line normal to the surface so that directional scattering information in the received scattered radiation relative to the beam is retained. 38. The system of claim 37, said mirrored surface defining an input aperture positioned proximate to the sample surface to receive scattered radiation therethrough from the sample surface. 39. The system of claim 38, said mirrored surface having a paraboloidal portion, the paraboloidal portion reflecting radiation that passes through the input aperture, said device further comprising means for focusing radiation reflected by the mirrored surface to the detector. 40. The system of claim 38, said mirrored surface being an ellipsoidal mirrored surface, the mirrored surface reflecting and focusing radiation that passes through the input aperture. 41. An optical method for detecting anomalies of a sample, comprising: directing a beam of radiation along a path at an oblique angle onto a surface of the sample; providing a curved mirrored surface to receive scattered radiation from the sample surface and originating from the beam, said curved mirrored surface having an axis of symmetry substantially coaxial with a line normal to the surface so that directional scattering information in the received scattered radiation relative to the beam is retained; and detecting the scattered radiation from the mirrored surface by at least one detector to detect anomalies of the sample. 42. The method of claim 41, further comprising focusing radiation reflected by the mirrored surface to a detector. 43. An optical system for detecting anomalies of a sample, comprising: optics directing a beam of radiation along a path at an oblique angle onto a surface of the sample; at least one detector; and an optical device receiving scattered radiation from the sample surface and originating from the beam and focusing the scattered radiation to said detector, causing said at least one detector to provide an output, said device comprising a radiation collector having an axis of symmetry substantially coaxial with a line normal to the surface so that directional scattering information in the received scattered radiation relative to the beam is retained. 44. The system of claim 43, said mirrored surface defining an input aperture positioned proximate to the sample surface to receive scattered radiation therethrough from the sample surface. 45. The system of claim 44, said mirrored surface having a paraboloidal portion, the paraboloidal portion reflecting radiation that passes through the input aperture, said device comprising means for focusing radiation reflected by the mirrored surface to the detector. 46. The system of claim 43, said mirrored surface being an ellipsoidal mirrored surface, the mirrored surface reflecting and focusing radiation that passes through the input aperture. 47. An optical method for detecting anomalies of a sample, comprising: directing a beam of radiation along a path at an oblique angle onto a surface of the sample; providing a radiation collector to receive scattered radiation from the sample surface and originating from the beam, said collector having an axis of symmetry substantially coaxial with a line normal to the surface so that directional scattering information in the received scattered radiation relative to the beam is retained; and detecting the scattered radiation from the collector by at least one detector to detect anomalies of the sample. 48. The method of claim 47, further comprising focusing radiation reflected by the mirrored surface to a detector.