Scanning Electron Microscope

Patent metadata

Field	Value
Publication number	US-2016148782-A1
Application number	US-201414899795-A
Country	US
Kind code	A1
Filing date	Jul 11, 2014
Priority date	Aug 2, 2013
Publication date	May 26, 2016
Grant date	—

Abstract

This scanning electron microscope is provided with: a deceleration means that decelerates an electron beam ( 5 ) when the electron beam is passing through an objective lens; and a first detector ( 8 ) and a second detector ( 7 ) that are disposed between the electron beam and the objective lens and have a sensitive surface having an axially symmetric shape with respect to the optical axis of the electron beam. The first detector is provided at the sample side with respect to the second detector, and exclusively detects the signal electrons having a high energy that have passed through a retarding field energy filter ( 9 A). When the distance between the tip ( 13 ) at the sample side of the objective lens and the sensitive surface of the first detector is L 1 and the distance between the tip at the sample side of the objective lens and the sensitive surface of the second detector is L 2 , then L 1 /L 2 ≦5/9. As a result, when performing low-acceleration observation using a deceleration method by means of a scanning electron microscope, it is possible to detect signal electrons without the effect of shading in a magnification range of a low magnification on the order of hundreds of times to a high magnification of at least 100,000×. Also, it is possible to highly efficiently detect backscattered electrons, of which the amount generated is less than that of secondary electrons.

First claim

1 . A scanning electron microscope comprising:
an electron source configured to generate an electronic beam acting as a probe; an aperture configured to limit a diameter of the electronic beam; a sample stand mounted with a sample to which the electronic beam is irradiated; an electron lens including an objective lens configured to converge the electronic beam to a surface of the sample; a deceleration means configured to decelerate the electronic beam having passed the objective lens as the electronic beam nears the sample; a deflector configured to scan the electronic beam on a sample; and at least two detectors configured to detect only a signal electron, the signal electron having passed through an objective lens, of all signal electrons released from the sample, wherein the two detectors are arranged between the electron source and the objective lens, the two sensitive surface are shaped to be axisymmetrical with reference to an optical axis, when one of the detectors is a first detector disposed to constantly detect a high-energy signal electron having passed through a retarding field energy filter and another of the detectors, which is different from the first detector, is a second detector, the first detector is installed closer to a sample side than the second detector is, and L 1 /L 2 ≦5/9 holds true where L 1 denotes a distance between a top end portion on the sample side of the objective lens and a sensitive surface of the first detector and L 2 denotes a distance between the top end portion on the sample side of the objective lens and a sensitive surface of the second detector.

2 . The scanning electron microscope according to claim 1 further comprising:
a signal processing circuit configured to perform linear addition of output signals from the first detector and the second detector.

3 . The scanning electron microscope according to claim 1 , wherein
the first detector detects a backscattered electron, and the second detector detects a secondary electron.

4 . The scanning electron microscope according to claim 1 , wherein
the retarding field energy filter is provided as a unit separate from the first detector.

5 . The scanning electron microscope according to claim 1 , wherein
the retarding field energy filter is provided as a unit integrated with the first detector.

6 . The scanning electron microscope according to claim 1 , wherein
a retarding field energy filter is installed on the sample side with respect to the sensitive surface of the second detector, and a high-energy electron having passed through the deceleration electric field energy filter is detected by each of the first detector and the second detector.

7 . The scanning electron microscope according to claim 1 , wherein
a detection solid angle of a first detector facing a top end portion of an objective lens is greater than a detection solid angle of a second detector.

8 . The scanning electron microscope according to claim 1 , wherein
a detector used as a first detector or a second detector is: a semiconductor detector; a detector employing an avalanche diode, a micro channel plate, or a scintillator material as a constituent element; or a combination of the aforementioned detectors.

9 . A scanning electron microscope comprising:
an electron source configured to generate an electronic beam acting as a probe; an aperture configured to limit a diameter of the electronic beam; a sample stand mounted with a sample to which the electronic beam is irradiated; an electron lens including an objective lens configured to converge the electronic beam to a surface of the sample; a deceleration means configured to decelerate the electronic beam having passed the objective lens as the electronic beam nears the sample; a deflector configured to scan the electronic beam on a sample; and at least two conversion plates configured to be collided with only a signal electron, the signal electron having passed through an objective lens, of all signal electrons released from the sample, wherein the two conversion plates are arranged between the electron source and the objective lens, collision surfaces of the two conversion plates are shaped to be axisymmetrical with reference to an optical axis, when one of the conversion plates is a first conversion plate disposed to be constantly collided with a high-energy signal electron having passed through a retarding field energy filter and another of the conversion plates, which is different from the first conversion plate, is a second conversion plate, the first conversion plate is disposed closer to a sample side than the second conversion plate is, and L 1 /L 2 ≦5/9 holds true where L 1 denotes a distance between a top end portion on the sample side of the objective lens and a collision surface of the first conversion plate and L 2 denotes a distance between the top end portion on the sample side of the objective lens and a collision surface of the second conversion plate.

10 . The scanning electron microscope according to claim 9 further comprising:
first and second detectors including sensitive surfaces configured to detect a conversion electron released from the collision surface to the sample side by a signal electron having collided with the first conversion plate, wherein the first and second detectors are arranged outside of the optical axis and axisymmetrical with reference to the optical axis; and
third and fourth detectors including sensitive surfaces configured to detect a conversion electron released from the collision surface to the sample side by a signal electron having collided with the second conversion plate, wherein the third and fourth detectors are arranged outside of the optical axis and axisymmetrical with reference to the optical axis.

11 . The scanning electron microscope according to claim 10 further comprising:
a signal processing circuit configured to perform linear addition of output signals from the first, second, third, and fourth detectors.

12 . The scanning electron microscope according to claim 9 , wherein
a conversion electron generated by collision of a backscattered electron with the first conversion plate is detected, and a conversion electron generated by collision of a secondary electron with the second conversion plate is detected.

13 . The scanning electron microscope according to claim 9 , wherein
the retarding field energy filter is provided as a unit separate from the first conversion plate.

14 . The scanning electron microscope according to claim 9 , wherein
the retarding field energy filter is provided as a unit integrated with the first conversion plate.

15 . The scanning electron microscope according to claim 9 , wherein
a retarding field energy filter is installed on the sample side with respect to the collision surface of the second conversion plate, and a high-energy electron having passed through the deceleration electric field energy filter collides with each of the first conversion plate and the second conversion plate.

16 . The scanning electron microscope according to claim 9 , wherein
a collision solid angle of a first conversion plate facing a top end portion of an objective lens is greater than a collision solid angle of a second conversion plate.

17 . The scanning electron microscope according to claim 9 , wherein
a detector used in first, second, third, or fourth detector is a detector employing a scintillator material as a constituent element or a combination of the aforementioned detectors.

18 . The s

Assignees

• Hitachi High Tech Corp

Inventors

• Agemura Toshihide
• Morishita Hideo

Classifications

• H01J2237/24475

  Scattered electron detectors · CPC title

• H01J2237/103

  characterised by lens type · CPC title

• H01J37/28

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title

• H01J37/244 Primary

  Detectors; Associated components or circuits therefor · CPC title

• H01J2237/1534

  Aberrations · CPC title