Electron beam system

• US 7,157,703 B2
• Filed: 08/29/2003
• Issued: 01/02/2007
• Est. Priority Date: 08/30/2002
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Murakami, Takeshi, Yoshikawa, Shoji, Noji, Nobuharu, Satake, Tohru, Nakasuji, Mamoru
• Primary Examiner(s): Wells; Nikita
• Assistant Examiner(s): LEYBOURNE, JAMES J
• Application Number:
  US10/651,105
• Publication Number:
  US 20040159787A1
• Time in Patent Office: 1,222 Days
• Field of Search: 250/311, 250/307, 250/397
• US Class Current: 250/311
• CPC Class Codes: H01J 2237/0492 Lens systems individual lenses H01J2237/10
• CPC Class Codes: H01J 2237/2441 Semiconductor detectors, e.g. diodes
• CPC Class Codes: H01J 2237/2446 Position sensitive detectors
• CPC Class Codes: H01J 2237/2806 Secondary charged particle
• CPC Class Codes: H01J 2237/2817 Pattern inspection
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

Provided is an electron beam system, in which an electron beam emitted from an electron gun is irradiated to a stencil mask, and the electron beam that has passed through the stencil mask is magnified by an electron lens and then detected by a detector having a plurality of pixels so as to form an image of the sample. Further provided is an electron beam system, in which a primary electron beam emitted from an electron gun is directed to a sample surface of a sample prepared as a subject to be inspected, and an electron image formed by a secondary electron beam emanated from the sample is magnified and detected, wherein an NA aperture is disposed in a path common to both of the primary electron beam and the secondary electron beam. An electron lens is disposed in the vicinity of a sample surface, and in this arrangement, a crossover produced by the electron gun, the electron lens and the NA aperture may be in conjugate relationships relative to each other with respect to the primary electron beam.

Claims

1. An electron beam system comprising:

an electron gun for emitting an electron beam and for irradiating the electron beam against a sample when the sample is positioned at an irradiation location;

an electron lens for magnifying the electron beam after having passed through the sample; and

a detector for detecting the electron beam after having been magnified so as to form an image of the sample,

wherein a crossover image of said electron gun is to be formed on or in the vicinity of a principle plane of said electrons lens.

2. The electron beam system according to claim 1, wherein

said electron gun is for irradiating the electron beam against a sample by irradiating the electron beam against a stencil mask or a mask having a pattern formed on a membrane.

3. The electron beam system according to claim 1, further comprising:

an NA aperture disposed between said electron gun and the irradiation location such that when said electron gun emits the electron beam the electron beam is passed through said NA aperture so as to allow a well-collimated electron beam to be irradiated against the sample.

4. The electron beam system according to claim 1, further comprising:

a single shaping aperture disposed between said electron gun and the irradiation location such that when said electron gun emits the electron beam the electron beam is passed through said single shaping aperture and irradiated against a surface of the sample so as to allow an image of said single shaping aperture to be formed on the surface of the sample.

5. The electron beam system according to claim 1, further comprising:

an optical axis; and

shaping apertures disposed in the vicinity of said optical axis, with an overlapping arrangement of said shaping apertures being changeable so as to make variable an area on the sample to be irradiated by the electron beam when emitted from said electron gun.

6. The electron beam system according to claim 1, wherein

said electron gun has a thermionic emission cathode and is operable under a space-charge-limited condition.

7. The electron beam system according to claim 1, further comprising:

at least a two-stage arrangement of electron lenses disposed between said detector and the irradiation location such that said detector is for detecting the electron beam after the electron beam passed through said two-stage arrangement of electron lenses.

8. The electron beam system according to claim 1, further comprising:

an entrance pupil of an irradiation lens system disposed between said electron gun and the irradiation location such that a source image is formed in said entrance pupil.

9. The electron beam system according to claim 8, further comprising:

a two-stage arrangement of lenses between said electron gun and the irradiation location,

wherein said electron lens is constructed and arranged such that by changing a focal length of said electron lens a crossover image can be formed so as to scan a sample surface of the sample with the crossover image, or by reducing an overlap between two shaping apertures the electron beam is made to have a small diameter so as to scan the sample surface of the sample with this electron beam, such that registration of the sample can be performed.

10. The electron beam system according to claim 1, further comprising:

two magnifying lenses disposed between the irradiation location and said detector, with a magnification of said two magnifying lenses being able to be made variable in response to a size of an irradiation area of the electron beam on the sample.

11. The electron beam system according to claim 1, wherein

said electron gun is for irradiating the electron beam against the sample by irradiating against the sample an electron beam having an irradiation area that is defined to be rectangular in shape, having long sides and short sides, and

said electron beam system further comprises a sample table, at the irradiation location, on which the sample is to be loaded, with said sample table being movable such that detection of the sample is performed by said detector while moving said sample table, having the sample loaded thereon, continuously in a direction of the short sides.

12. The electron beam system according to claim 1, further comprising:

a sample table carrier for controlling the electron beam so as to perform a scanning motion in a step-by-step manner or continuously.

13. The electron beam system according to claim 1, wherein said detector comprises

(i) a scintillator that is to change the electron beam to an image of light,

(ii) an optical lens for adjusting a size of the image of light as produced by said scintillator, or an optical system for projecting the image of light, and

(iii) either one of a CCD detector or a TDI detector on which the image of light, whose size has been adjusted by said optical lens, is to be formed.

14. The electron beam system according to claim 13, further comprising:

a vacuum window arranged between said scintillator and said optical lens for removing the image of light when directed to said optical lens,

wherein said scintillator is disposed in a vacuum, and said optical lens and said CCD detector or TDI detector are disposed in an atmosphere.

15. The electron beam system according to claim 13, wherein

said scintillator, said optical lens and said CCD detector or TDI detector are disposed in a vacuum.

16. The electron beam system according to claim 1, wherein

said electron gun is an electron gun having a small source and having an FE, a TFE or a Schottky cathode.

17. The electron beam system according to claim 1, wherein

said electron gun is disposed under the irradiation location, and

said detector is for detecting a defect in the sample, and is disposed above the irradiation location.

18. The electron beam system according to claim 1, further comprising:

magnifying lenses, for magnifying the electron beam, disposed between said electron gun and said detector,

wherein a magnifying lens, serving as a first one of said magnifying lenses to magnify the electron beam that has passed through the sample, is a doublet lens.

19. The electron beam system according to claim 1, further comprising:

magnifying lenses, for magnifying the electron beam, disposed between said electron gun and said detector, and

an NA aperture disposed between said magnifying lenses,

wherein said NA aperture is able to remove electron beams of a bad collimation that have been scattered by the sample.

20. The electron beam system according to claim 1, wherein

said detector comprises an image detector, with said image detector being composed of an MCP and an EB-CCD detector or an EB-CCD, or otherwise an MCP and an EB-TDI detector or an EB-TDI.

21. The electron beam system according to claim 1, further comprising:

a second detector for detecting secondary electrons or back scattering electrons, which are generated upon scanning of the sample with the electron beam, disposed between the irradiation location and said electron gun.

22. The electron beam system in accordance with claim 1, wherein

a pixel processing rate for an image of said system is set to be equal to at least 200 MHz.

23. The electron beam system according to claim 1, further comprising:

a storage unit in which reference pattern data is stored in advance; and

a control unit for comparing image data, obtained from the electron beam after having passed through the sample, to the pattern data,

wherein said control unit is to perform a defect inspection of the sample based on a comparison of the image data and the pattern data.

24. A manufacturing method of a semiconductor device, comprising:

preparing wafers;

processing said wafers by performing a lithography process by employing a stencil mask which has been inspected for any defect by using the electron beam system according to claim 1; and

assembling devices using the processed wafers.

25. An electron beam system comprising:

an electron gun for emitting a primary electron beam and irradiating the primary electron beam against a sample, when positioned at an irradiation location as a subject to be inspected, so as to form an electron image, by a transmission electron beam having passed through the sample, to be magnified and detected;

an NA aperture disposed in a path of the transmission electron beam; and

an electron lens in the vicinity of the irradiation location,

wherein a principle plane of said electron lens and said NA aperture are in a conjugate relationship with respect to each other.

26. The electron beam system according to claim 25, further comprising:

an optical axis; and

shaping apertures in the vicinity of said optical axis, with an overlapping arrangement of said shaping apertures being changeable so as to make variable an area on the sample to be irradiated by the primary electron beam when emitted from said electron gun.

27. The electron beam system according to claim 25, further comprising:

a shaping aperture in a path of the primary electron beam when emitted by said electron gun,

wherein said shaping aperture and the sample, when positioned at the irradiation location, are arranged to be in a conjugate relationship relative to each other.

28. The electron beam system according to claim 25, further comprising:

a two-stage arrangement of electron lenses in a path of the transmission electron beam, said two-stage arrangement of electron lenses including a first stage electron lens and a second stage electron lens, with said first stage electron lens to produce a magnified image that is to be focused on a certain point upstream of said second stage electron lens.

29. The electron beam system according to claim 25, further comprising:

an adjuster for adjusting a distance between the irradiation location and said electron lens when one sample is replaced by another.

30. An electron beam system comprising:

a two-stage arrangement of electron lenses for magnifying an electron image of secondary electrons emanated from a sample surface, back scattering electrons or an electron having passed through the sample so as to be detected,

wherein said two-stage arrangement of electron lenses includes a first stage electron lens and a second stage electron lens, with said first stage electron lens to produce a magnified image that is to be focused on a certain point upstream of said second stage electron lens to thereby reduce a distortion aberration or a magnification aberration.

31. The electron beam system according to claim 30, wherein

a distance between said second stage electron lens and the magnified image is a compensation parameter, and a position of the magnified image when produced by said first stage electron lens is to be set in response to the compensation parameter being optimized.

32. An electron beam system, in which a primary electron beam is irradiated to a sample, and an image of secondary electrons emanated from the sample, an image of back scattering electrons or an image of transmission electrons having passed through the sample is magnified and detected as an image, wherein

a distortion aberration in the detected image is simulated by calculation to thereby determine a difference between a third order of absolute value and a fifth order of absolute value of the distortion aberration, and a compensation parameter is optimized such that the difference is minimized or that the fifth order of absolute value is greater than the third order of absolute value by about 5 to 15%, wherein a position of a magnified image produced by a first stage electron lens is to be set in response to the optimized compensation parameter.

33. An electron beam system comprising:

an electron gun for emitting an electron beam and for irradiating the electron beam against a sample when the sample is positioned at an irradiation location;

an electron lens disposed close to the irradiation location, said electron lens for magnifying, as a transmission electron image, electrons that have passed through the sample so as to be detectable by either one of a CCD, a TDI or an EBCCD; and

an NA aperture between said electron gun and said irradiation location, with an NA aperture image to be focused on or in the vicinity of a principle plane of said electron lens,

wherein when a magnification for magnifying the electrons is to be changed, a distance between the irradiation location and said electron lens is changed.