Scanning electron microscope and its analogous device

• US 5,894,124 A
• Filed: 05/30/1997
• Issued: 04/13/1999
• Est. Priority Date: 03/17/1995
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sato, Mitsugu, Ose, Yoichi, Iwabuchi, Yuko
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/866,304
• Time in Patent Office: 683 Days
• Field of Search: 250/310, 250/396 R, 250/396 ML, 250/397
• US Class Current: 250/310
• CPC Class Codes: H01J 2237/15 Means for deflecting or directing discharge
• CPC Class Codes: H01J 37/244 Detectors; Associated components or circuits therefor
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

The device of the present invention enables high resolution observation even when a sample is tilted. A deflecting electrode device for generating an electric field having a component in the direction perpendicular to the center axis (optical axis) of an objective lens is provided between the objective lens and the sample. A voltage applied to the deflecting electrode device is controlled in accordance with the tilting of a sample stage. A lateral electric field component generated on the optical axis when the sample stage is tilted is corrected by a deflected electric field generated by the deflecting electrode device. This is effective to suppress generation of astigmatism, and to allows effective arrival of an secondary electron at a secondary electron detector disposed at a position nearer the electron source side than the objective lens.

Claims

1. A scanning electron microscope comprising:

an electron gun for generating an electron beam;

an objective lens for converging the electron beam to a sample so as to allow emission of the electron beam on the sample;

a deflector for deflecting the electron beam so as to allow the electron beam to scan the sample;

a detector for detecting an information signal, peculiar to the sample, generated from the sample by irradiation of the electron beam;

an orthogonal electric field/magnetic field generator for generating an electric field and a magnetic field orthogonal to each other with respect to said electron beam, wherein deflecting actions of said electric field and said magnetic field are controlled to cancel each other for said electron beam and to be exerted on said detector side for said information signal;

a means for tilting the sample with respect to the electron beam; and

a means for correcting a nonaxiallysymmetric property, due to the tilting of the sample, of an electric field applied to the electron beam to be emitted on the sample;

wherein the nonaxiallysymmetric property correcting means includes a deflecting electrode means to which a variable voltage is applied for generating an electric field having a component in the direction perpendicular to an optical axis of the electron beam.

2. A scanning electron microscope according to claim 1, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, wherein said detector is positioned in the vicinity of said electrode.

3. A scanning electron microscope according to claim 2, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, and

said orthogonal electric field/magnetic field generator for generating an electric field and a magnetic field which are orthogonal to each other with respect to said electron beam being disposed in the vicinity of said electrode made of a material having a function of generating a secondary electron.

4. A scanning electron microscope according to claim 2, wherein said electrode made of a material having a function of generating a secondary electron is disposed directly under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

5. A scanning electron microscope according to claim 1, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over said objective lens.

6. A scanning electron microscope according to claim 5, wherein said electrode for generating a light or electric signal when an electron collides therewith is disposed under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

7. A scanning electron microscope according to claim 1, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over an scanning electrode for scanning said electron beam, and a means for converting said light or electric signal into an image signal.

8. A scanning electron microscope comprising:

an electron gun for generating an electron beam;

an objective lens for converging the electron beam to a sample so as to allow emission of the electron beam on the sample;

a deflector for deflecting the electron beam so as to allow the electron beam to scan the sample;

a detector for detecting an information signal, peculiar to the sample, generated from the sample by irradiation of the electron beam;

a means for tilting the sample with respect to the electron beam; and

a means for correcting a nonaxisymmetric property, due to the tilting of the sample, of an electric field applied to the electron beam to be emitted on the sample;

wherein the nonaxisymmetric property correcting means includes a deflecting electrode means to which a variable voltage is applied for generating an electric field having a component in the direction perpendicular to an optical axis of the electron beam; and

a control unit for controlling, when a negative voltage is applied to said sample, a voltage applied to said deflecting electrode to be larger than a voltage applied to said deflecting electrode in the case where no negative voltage is applied to said sample.

9. A scanning electron microscope according to claim 8, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, wherein said detector is positioned in the vicinity of said electrode.

10. A scanning electron microscope according to claim 9, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, and

an orthogonal electric field/magnetic field generator for generating an electric field and a magnetic field which are orthogonal to each other with respect to said electron beam, said generator being disposed in the vicinity of said electrode made of a material having a function of generating a secondary electron.

11. A scanning electron microscope according to claim 9, wherein said electrode made of a material having a function of generating a secondary electron is disposed directly under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

12. A scanning electron microscope according to claim 8, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over said objective lens.

13. A scanning electron microscope according to claim 12, wherein said electrode for generating a light or electric signal when an electron collides therewith is disposed under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

14. A scanning electron microscope according to claim 8, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over an scanning electrode for scanning said electron beam, and a means for converting said light or electric signal into an image signal.

15. A scanning electron microscope comprising:

an electron gun for generating an electron beam;

an objective lens for converging the electron beam to a sample so as to allow emission of the electron beam on the sample;

a deflector for deflecting the electron beam so as to allow the electron beam to scan the sample;

a detector for detecting an information signal, peculiar to the sample, generated from the sample by irradiation of the electron beam;

a means for tilting the sample with respect to the electron beam; and

a means for correcting a nonaxiallysymmetric property, due to the tilting of the sample, of an electric field applied to the electron beam to be emitted on the sample;

wherein the nonaxiallysymmetric property correcting means includes a deflecting electrode means to which a variable voltage is applied for generating an electric field having a component in the direction perpendicular to an optical axis of the electron beam; and

a control means for controlling, when a positive voltage is applied to said electrode, a voltage applied to said deflecting electrode to be larger than a voltage applied to said deflecting electrode in the case where no positive voltage is applied to said electrode.

16. A scanning electron microscope according to claim 15 further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, wherein said detector is positioned in the vicinity of said electrode.

17. A scanning electron microscope according to claim 16, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, and

an orthogonal electric field/magnetic field generator for generating an electric field and a magnetic field which are orthogonal to each other with respect to said electron beam, said generator being disposed in the vicinity of said electrode made of a material having a function of generating a secondary electron.

18. A scanning electron microscope according to claim 16, wherein said electrode made of a material having a function of generating a secondary electron is disposed directly under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

19. A scanning electron microscope according to claim 15, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over said objective lens.

20. A scanning electron microscope according to claim 19, wherein said electrode for generating a light or electric signal when an electron collides therewith is disposed under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

21. A scanning electron microscope according to claim 15, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over an scanning electrode for scanning said electron beam, and a means for converting said light or electric signal into an image signal.

22. A scanning electron microscope comprising:

an electron gun for generating an electron beam;

an objective lens for converging the electron beam to a sample so as to allow emission of the electron beam on the sample;

a deflector for deflecting the electron beam so as to allow the electron beam to scan the sample said deflector;

a detector for detecting an information signal, peculiar to the sample, generated from the sample by irradiation of the electron beam;

a means for tilting the sample with respect to the electron beam; and

a means for correcting a nonaxiallysymmetric property, due to the tilting of the sample, of an electric field applied to the electron beam to be emitted on the sample;

wherein the nonaxiallysymmetric property correcting means includes a deflecting electrode means, made of a member having a function of generating a light or electric signal when an electron collides therewith, to which a variable voltage is applied for generating an electric field having a component in the direction perpendicular to an optical axis of the electron beam; and

a means for converting said light or electric signal into an image signal.

23. A scanning electron microscope according to claim 22, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, wherein said detector is positioned in the vicinity of said electrode.

24. A scanning electron microscope according to claim 23, further comprising an electrode made of a material having a function of generating a secondary electron when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam, and

an orthogonal electric field/magnetic field generator for generating an electric field and a magnetic field which are orthogonal to each other with respect to said electron beam, said generator being disposed in the vicinity of said electrode made of a material having a function of generating a secondary electron.

25. A scanning electron microscope according to claim 23, wherein said electrode made of a material having a function of generating a secondary electron is disposed directly under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

26. A scanning electron microscope according to claim 22, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over said objective lens.

27. A scanning electron microscope according to claim 26, wherein said electrode for generating a light or electric signal when an electron collides therewith is disposed under a scanning electrode for scanning said electron beam and includes a moving mechanism for moving said electrode in the direction perpendicular to the optical axis of said electron beam.

28. A scanning electron microscope according to claim 22, further comprising an electrode for generating a light or electric signal when an electron collides therewith, said electrode being disposed in the vicinity of the optical axis of said electron beam and over an scanning electrode for scanning said electron beam, and a means for converting said light or electric signal into an image signal.