Method and apparatus for inspecting defects in a patterned specimen

• US 6,621,571 B1
• Filed: 10/30/2000
• Issued: 09/16/2003
• Est. Priority Date: 10/29/1999
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Uto, Sachio, Yoshida, Minoru, Yoshida, Atsushi, Nakata, Toshihiko, Maeda, Shunji, Shishido, Hiroaki, Shibata, Yukihiro
• Primary Examiner(s): Stafira, Michael P.
• Assistant Examiner(s): Barth, Vincent P.
• Application Number:
  US09/698,167
• Time in Patent Office: 1,051 Days
• Field of Search: 356/237.1, 356/237--23, 356/239.7, 356/239.8, 356/600, 356/243.7, 356/394, 250/559.44
• US Class Current: 356/237.5
• CPC Class Codes: G01N 2021/95615 with stored comparision signal
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/95607 using a comparative method

Abstract

In a method and apparatus for detecting pattern defects, a UV laser is focused on a pupil of an objective lens and scanned; the focused and scanned UV lens illuminates a specimen on which patterns are formed; the specimen illuminated by the UV laser is imaged: and the resulting image of the specimen is compared with a previously stored reference image. The specimen illuminated by UV light is imaged using an anti-blooming time delay integration image sensor or a back-illumination time delay integration image sensor; and the resulting specimen image is compared with a previously stored reference image.

Claims

1. An apparatus for inspecting defects in a patterned specimen, comprising:

laser light source means for emitting a laser;

coherency reducing means for reducing coherency of said laser emitted from said laser light source means;

illuminating weans for illuminating a specimen with a laser of which a coherency thereof is reduced by said coherency reducing means;

image detecting weans for detecting an image of said specimen illuminated by said laser from said illuminating means; and

defect detecting means for detecting pattern defects formed on said specimen based on information relating to said image of said specimen detected by said image detecting means;

wherein said illuminating means includes an objective lens module, a focusing optical system which focuses said laser onto a pupil of said objective lens, and a scanning module which scans said laser on the pupil of said objective lens.

2. An apparatus according to the claim 1, wherein said scanning module scans said laser on said pupil using a mirror.

3. An apparatus according to the claim 1, wherein said image detecting means detects images with a storage-type image sensor, and said scanning module effects scanning of the laser on the pupil in synchronism with a storage time of the image sensor.

4. An apparatus according to the claim 1, wherein said defect detecting means includes a storage module storing a reference image signal and a pattern detection module detecting defects in patterns formed on said specimen by comparing an image signal of said specimen output from said image detecting means with a reference image signal stored in said storage module.

30. An apparatus according to claim 2, wherein said mirror is a galvano-mirror.

5. An apparatus for inspecting defects in a patterned specimen, comprising:

a laser light source which emits a UV laser;

a coherency reducer which reduces coherency of said UV laser emitted from said laser light source;

an illuminator which illuminates a specimen with said UV laser of which a coherency thereof is reduced by said coherency reducer;

a polarizing means which adjusts polarization states of said UV laser;

an image detector which detects an image of said specimen formed by diffracted light by the illumination of said UV laser from said illuminator and in which a polarization condition of said diffracted light is adjusted by said polarizing means; and

a defect detector which detects defects of a pattern formed on said specimen based on information relating to said image of said specimen detected by said image detector.

6. An apparatus according to the claim 5, wherein said polarizing means includes a quarter-wave plate or a half-wave plate and a quarter-wave plate disposed in an optical path connecting said laser light source and said specimen, and an analyzer disposed in an optical path connecting said specimen and said image detector.

7. An apparatus according to the claim 6, wherein at least one of said half-wave plate, said quarter-wave plate, and said analyzer is rotatable.

8. An apparatus according to the claim 6, wherein said image detecting means includes time delay integration (TDI) image sensor means that is sensitive to UV light.

9. An apparatus according to the claim 8, wherein said TDI image sensor is an anti-blooming TDI sensor.

10. An apparatus according to the claim 8, wherein said TDI image sensor is at back-illumination TDI sensor.

11. An apparatus according to the claim 5, wherein said defect inspecting means includes a storage module storing a reference signal and a defect detection module detecting defects in patterns formed on said specimen by comparing an image signal of said specimen output from said image detecting means with a reference image signal stored in said storage module.

12. An apparatus according to the claim 5, wherein said coherency reducer includes an optical path section formed from a plurality of glass rod lenses or a plurality of cylindrical lens arrays and a focus lens;

wherein said laser emitted from said laser light source means is passed through said optical path section formed from said plurality of glass rod lenses or said plurality of cylindrical lens arrays and said focus lens and exits from another end toward an objective lens of said illuminator; and

wherein said laser is scanned on a pupil of said objective lens.

13. An apparatus according to the claim 5, wherein said defect detecting means outputs information relating to positions and dimensions of detected defects in said pattern.

14. An apparatus for inspecting a defect, comprising:

a laser light source which emits a laser;

a coherency reducer which reduces coherency of said laser emitted by said laser light source means;

an illuminator which illuminates a specimen with said laser of which a coherency thereof is reduced by said coherency reducer;

an analyzer which adjusts polarization states of light diffracted from the specimen illuminated by the illuminator;

an image detector which detects an image of said specimen formed by diffracted light from said specimen and passed through said analyzer; and

an image processor which processes an image of said specimen detected by said image detector;

wherein said apparatus processes said-specimen having a diameter on the order of 200 mm at a speed corresponding to a throughput of three units per hour, and detects defects in the order of 100 nm on said patterns formed on said specimen.

15. A method of inspecting a defect of a pattern, comprising the steps of:

illuminating with a UV laser a specimen on which a pattern is formed;

imaging said specimen illuminated with said UV laser; and

detecting defects on said pattern by comparing an image of said specimen obtained by said imaging step with a previously stored reference image;

wherein said image of said specimen obtained by said imaging step is formed by light from said specimen of which a polarization state thereof is adjusted.

16. A method of inspecting a defect of a pattern, comprising the steps of:

focussing and scanning a UV laser on a pupil of an objective lens;

illuminating a specimen on which a pattern is formed with said focused and scanned UV laser;

imaging said specimen illuminated by said UV laser; and

detecting defects on said pattern by comparing an image of said specimen obtained by said imaging step with a previously stored reference image.

17. A method of inspecting a defect, comprising the steps of:

illuminating a specimen on which a pattern is formed with UV light;

imaging said specimen illuminated by UV light;

correcting a difference in brightness between an image of said specimen obtained by said imaging step and a previously stored reference image so that brightnesses are roughly identical; and

detecting defects on said pattern by comparing said image of said specimen and said reference image which have been corrected for brightness.

18. A method according to the claim 17, wherein said UV light illuminating said specimen is emitted from a laser light source and is a UV light in which laser coherence has been reduced.

19. A method of inspecting a defect, comprising the steps of:

reducing coherence of a laser emitted from a laser light source;

illuminating a surface of a specimen on which a pattern is forced via an objective lens using said laser with reduced coherence while varying the direction of illumination over time;

imaging said specimen illuminated by said laser; and

detecting defects on said pattern by comparing paid image of said specimen obtained in said imaging step and a previously stored reference image;

wherein said image of said specimen obtained in said imaging step is formed by light from said specimen of which a polarization state thereof is adjusted.

20. A method according to the claim 19, wherein said image of said specimen obtained in said imaging step is an image obtained by taking an image of said specimen illuminated by said laser and changing the polarization state using an analyzer.

21. A method of inspecting a defect, comprising the steps of:

illuminating a surface of a specimen through an object lens using UV light;

obtaining an image signal with an image sensor by imaging said surface of said specimen illuminated by said UV light;

detecting defects of no greater than 100 nm on said specimen by processing said image signal; and

outputting information relating to positions on said specimen of detected defects of 100 nm and less;

wherein in the step of illuminating, said UV light is scanned on a pupil of said object lens in synchronism with operation of said image sensor.

22. A method according to the claim 21, wherein said UV light illuminating said surface of said specimen is emitted from a laser light source and is a UV light with reduced laser coherence.

23. A method according to the claim 21, wherein said specimen is imaged using a time delay integration (TDI) image sensor.

24. A method according to the claim 21, wherein said specimen is imaged using an anti-blooming time delay integration (TDI) image sensor.

25. A method according to the claim 21, wherein said specimen is imaged using a back-illumination type time delay integration (TDI) image sensor.

26. A method according to the claim 21, wherein information relating to positions and dimensions of said detected defects are output.

27. A method according to the claim 21, wherein said UV light illuminates said specimen through an objective lens having an NA of at least 0.75.

28. A method according to the claim 21, wherein an image signal is obtained by imaging, in synchronization with movements of said specimen, said surface of said specimen using a time delay integration image sensor, said image signal being compared to a previously stored reference image signal to detect defects on said specimen.

29. A method of inspecting a defect, comprising the steps of:

illuminating UV light on a wafer with a diameter that is at least on the order of 200 mm;

detecting an image of said wafer by imaging said wafer illuminated by said UV light;

detecting defects of no greater than 100 mm on patterns formed on said wafer by processing said detected images of said wafer illuminated by said UV light, said detection being performed at a throughput of at least three wafers with said 200 mm diameter per hour;

wherein in the step of detecting, said image is detected by at least one of (a) a back-illumination type time delay integration (TDI) image sensor, (b) a TDI image sensor having anti-blooming characteristics, and (c) a TDI image sensor coated with an organic thin-film.