IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
|
출원번호 |
US-0007729
(2004-12-07)
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발명자
/ 주소 |
- Vaez Iravani,Mehdi
- Stokowski,Stanley
- Zhao,Guoheng
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출원인 / 주소 |
- KLA Tencor Technologies Corporation
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
11 인용 특허 :
50 |
초록
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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
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The invention claimed is: 1. 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 incid
The invention claimed is: 1. 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. 2. The system of claim 1, further comprising an instrument that causes relative motion between the two beams and the surface of the sample so that the beams scan spiral scan(s) on the surface. 3. The system of claim 1, said curved surface comprising a paraboloidal or ellipsoidal mirrored surface. 4. The system of claim 1, said first path being not more than about 10 degrees angle from a nonnal direction to the sample surface. 5. The system of claim 3, said first path being substantially normal to the sample surface. 6. The system of claim 3, said second path being at an angle within a range of about 45 to 85 degrees to a normal direction to the sample surface. 7. The system of claim 1, said first and second beams producing a first and a second illuminated spot on the sample surface, said first and second illuminated spots substantially coinciding. 8. The system of claim 1, said source comprising a radiation source supplying a radiation beam and means for converting the radiation beam supplied by the source into said first and second beams. 9. The system of claim 8, said converting means including a switch that causes the radiation beam from the source to be transmitted alternately along the two paths towards the sample surface. 10. The system of claim 9, said system further comprising means for acquiring data from the detector at a data rate, said switch operating at a frequency of at least about three times that of the data rate. 11. The system of claim 9, said system further comprising means for acquiring data from the detector at a data rate, said switch operating at a frequency of at least about five times that of the data rate. 12. The system of claim 9, said switch including an eleetro-optic modulator or Bragg modulator. 13. The system of claim 1, said system comprising a first detector detecting radiation of the first wavelength and a second detector for detecting radiation of the second wavelength. 14. The system of claim 1, the sample having a smooth surface, wherein the second path is at an oblique angle to the sample surface, and the second beam is P or S polarized with respect to the sample surface. 15. The system of claim 1, the sample having a rough surface, wherein the second path is at an oblique angle to the sample surface, and the second beam is S polarized with respect to the sample surface. 16. The system of claim 1, further comprising means for comparing detected scattered radiation originating from the first beam and that originating from the second beam to distinguish between particles and COPs. 17. An optical method for detecting anomalies of a sample, comprising: directing onto a surface of the sample a first beam of radiation at a first wavelength along a first path and a second beam at a second wavelength along a second path, said two paths being at different incidence angles to the sample surface; detecting radiation at the first and second wavelengths by means of one or more detectors; and receiving scattered radiation from the sample surface and originating from the first and second beams and focusing the scattered radiation to said detector(s), wherein said receiving receives said scattered radiation from the sample surface by means of a curved reflective surface that 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. 18. The method of claim 17, further comprising causing relative motion between the two beams and the surface of the sample so tat the beams scan spiral scan(s) on the surface. 19. The method of claim 17, said first pat being not more than about 10 degrees angle from a normal direction to the sample surface. 20. The method of claim 17, said first path being substantially normal to the sample surface. 21. The method of claim 17, said second path being at an angle within a range of about 45 to 85 degrees to a normal direction to the sample surface. 22. The method of claim 17, said first and second beams producing a first and a second illuminated spot on the sample surface, said first and second illuminated spots substantially coinciding. 23. The method of claim 17, said first and second beam directing comprising: providing a source supplying a radiation beam; and converting the radiation beam supplied by the source into said first and second beams. 24. The method of claim 23, said source supplying radiation of a first and a second wavelength, wherein said detecting detects radiation of the first wavelength by means of a first detector and radiation of the second wavelength by means of a second detector. 25. The method of claim 23, said converting including switching the radiation beam from the source alternately between the two paths towards the sample surface. 26. The method of claim 25, said method further comprising acquiring data from the first detector at a data rate, wherein said switching is at a frequency of at least about three times that of the data rate. 27. The method of claim 25, said method further comprising acquiring data from the first detector at a data rate, wherein said switching is at a frequency of at least about five times that of the data rate. 28. The method of claim 25, the sample having a smooth surface, wherein the second path is at an oblique angle to the sample surface, and the directing directs a second beam that is S or P polarized with respect to the sample surface. 29. The method of claim 28, the sample having a rough surface, wherein the second pat is at an oblique angle to the sample surface, and the directing directs a second beam that is S polarized with respect to the sample surface. 30. The method of claim 28, further comprising scanning sequentially the first and second beams across the same portion of the sample surface, wherein the first but not the second beam is directed to said surface while it is being scanned in a cycle, and the second but not the first beam is directed to said surface while it is being scanned in a subsequent cycle. 31. The method of claim 17, further comprising comparing detected scattered radiation originating from the first beam and that originating from the second beam to distinguish between particles and COPs.
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