Inspection method and apparatus using electron beam

• US 6,265,719 B1
• Filed: 10/30/1998
• Issued: 07/24/2001
• Est. Priority Date: 10/31/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Nagai, Takamitsu, Yamazaki, Yuichiro, Miyoshi, Motosuke
• Primary Examiner(s): Anderson, Bruce C.
• Application Number:
  US09/182,415
• Time in Patent Office: 998 Days
• Field of Search: 250/310, 250/397, 250/492.2
• US Class Current: 250/310
• CPC Class Codes: H01J 2237/1506 Tilting or rocking beam around an axis substantially at an angle to optical axis
• 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

An inspection apparatus using an electron beam according to this invention has an electron beam irradiation unit (1-10) for irradiating a sample (11) with an electron beam (31), a projection optical unit (16-21) for forming a one- and/or two-dimensional image or images of secondary and reflected electrons (32) projected in accordance with changes in shape, material, and electrical potential of the sample surface, an electron beam detection unit (22-27) for outputting a detection signal on the basis of the one- and/or two-dimensional image or images, an image display unit (30) for displaying the one- and/or two-dimensional image or images of the sample surface upon receiving the detection signal, and an electron beam deflection unit (27, 43-44) for changing the incident angle of the electron beam coming from the electron beam irradiation unit onto the sample, and guiding the received secondary and reflected electrons to the mapping projection optical unit. With this apparatus, problems of the conventional apparatus (i.e., being unable to inspect defects present on the pattern side wall and difficulties in attaining optical axis adjustment due to the electron beam striking the sample surface at an oblique angle can be solved.

Claims

1. An electron beam inspection apparatus comprising:

an electron beam irradiation unit configured to irradiate a sample with an electron beam;

a mapping projection optical unit configured to form at least one of one-dimensional and two-dimensional images of secondary and reflected electrons produced in accordance with a sample surface of the sample upon irradiating the sample with the electron beam by said electron beam irradiation unit;

an electron beam detection unit configured to output a detection signal based on the at least one of one-dimensional and two-dimensional images of the secondary and reflected electrons formed on said electron beam detection unit by said mapping projection optical unit;

an image display unit configured to receive the detection signal output from said electron beam detection unit and display the at least one of one-dimensional and two-dimensional images of the sample surface; and

an electron beam deflection unit configured to deflect the electron beam received from said electron beam irradiation unit onto the sample and allow said mapping projection optical unit to capture the secondary and reflected electrons received from the sample;

wherein said electron beam deflection unit receives the electron beam from said electron beam irradiation unit at an angle of 10°

to 40°

from an axis running perpendicular to the sample and changes an angle of the electron beam to make the electron beam be incident on the sample at 90°

±

5°

.

2. An apparatus according to claim 1, wherein the electron beam from said electron beam irradiation unit has a cross-section which is at least one of linear, rectangular and elliptic in shape.

3. An apparatus according to claim 1, wherein a difference between an incident angle of the electron beam irradiated by said electron beam irradiation unit and deflected by said electron beam deflection unit, and the capturing angle of the secondary and reflected electrons produced from the sample by said mapping projection optical unit via said electron beam deflection unit falls within the range of −

5°

to +5°

.

4. An apparatus according to claim 1, wherein said electron beam deflection unit comprises means for deflecting the electron beam by forming a field in which an electric field and a magnetic field intersect each other in a plane perpendicular to an optical axis of said mapping projection optical unit.

5. An apparatus according to claim 1, wherein said electron beam irradiation unit has an electron optical lens system including at least one multi-pole lens.

6. An apparatus according to claim 5, wherein said electron optical lens system of said electron beam irradiation unit includes a plurality of quadrupole lenses as the at least one multi-pole lens.

7. An apparatus according to claim 1, wherein said electron beam irradiation unit is positioned obliquely above the sample surface.

8. An apparatus according to claim 1, wherein said electron beam deflection unit comprises a deflection device configured to deflect the electron beam by forming a field in which an electric field and a magnetic field intersect each other in a plane perpendicular to an optical axis of said mapping projection optical unit.

9. An electron beam inspection apparatus comprising:

electron beam irradiation means for irradiating a sample with an electron beam;

mapping projection optical means for forming at least one of one-dimensional and two-dimensional images of secondary and reflected electrons produced in accordance with a sample surface of the sample upon irradiating the sample with the electron beam by said electron beam irradiation means;

electron beam detection means for outputting a detection signal based on the at least one of one-dimensional and two-dimensional images of the secondary and reflected electrons formed on said electron beam detection means by said mapping projection optical means;

image display means for receiving the detection signal output from said electron beam detection means and displaying the at least one of one-dimensional and two-dimensional images of the sample surface; and

electron beam deflection means for deflecting the electron beam irradiated from said electron beam irradiation means toward the sample and allowing said mapping projection optical means to capture the secondary and reflected electrons received from the sample;

wherein said electron beam deflection means receives the electron beam from said electron beam irradiation means at an angle of 10°

to 40°

with respect to an axis running perpendicular to the sample and deflects the electron beam to be incident on the sample at 90°

±

5°

with respect to the sample.

10. An apparatus according to claim 9, wherein the electron beam from said electron beam irradiation means has a cross-section which is at least one of linear, rectangular and elliptic in shape.

11. An apparatus according to claim 9, wherein a difference between an incident angle of the electron beam deflected by said electron beam deflection means with respect to the sample and a capturing angle of the secondary and reflected electrons produced from the sample with respect to said mapping projection optical means via said electron beam deflection means falls within the range of −

5°

to +5°

.

12. An apparatus according to claim 9, wherein said electron beam deflection means deflects the electron beam by forming a field in which an electric field and a magnetic field intersect each other in a plane perpendicular to an optical axis of said mapping projection optical means.

13. An apparatus according to claim 9, wherein said electron beam irradiation means includes an electron optical lens system including at least one multi-pole lens.

14. An apparatus according to claim 13, wherein said electron optical lens system of said electron beam irradiation means comprises a plurality of quadruple lenses.

15. An apparatus according to claim 9, wherein said electron beam irradiation means is positioned obliquely above the sample surface.