Electron beam inspection method and electron beam inspection apparatus

• US 20080315093A1
• Filed: 05/02/2008
• Published: 12/25/2008
• Est. Priority Date: 06/19/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohta, Hiroya, Hasegawa, Masaki
• Granted Patent: US 7,863,565 B2
• Time in Patent Office: Days
• US Class Current: 250/310
• CPC Class Codes: G01N 23/225 using electron or ion
• CPC Class Codes: H01J 2237/0047 using electromagnetic radiations, e.g. UV, X-rays, light
• CPC Class Codes: H01J 2237/221 Image processing
• CPC Class Codes: H01J 2237/2446 Position sensitive detectors
• CPC Class Codes: H01J 2237/24495 Signal processing, e.g. mixing of two or more signals
• CPC Class Codes: H01J 2237/2482 Optical means
• CPC Class Codes: H01J 2237/2855 Photo-emission
• CPC Class Codes: H01J 37/026 Means for avoiding or neutralising unwanted electrical charges on tube components
• CPC Class Codes: H01J 37/285 Emission microscopes, e.g. field-emission microscopes
• CPC Class Codes: H01J 37/29 Reflection microscopes

Abstract

An electron beam inspection apparatus images reflected electrons and cancels negative charging derived from electron-beam irradiation. Ultraviolet rays are irradiated and an irradiated area of ultraviolet rays is displayed as a photoelectron image. The photoelectron image and a reflected-electron image are displayed on a monitor while being superposed on each other, to easily grasp the positional relationship between the images and the difference in size between them. Specifically, the shape of the irradiated area of an electron beam includes the shape of the irradiated area of ultraviolet rays on a display screen. The intensity of the ultraviolet rays in the irradiated area of the electron beam is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained. Moreover, an amount-of-ultraviolet ray adjustment mechanism is controlled on the monitor so that an amount of the ultraviolet rays is adjusted while observing a reflected-electron image obtained during ultraviolet irradiation.

Claims

1. An electron beam inspection apparatus including:

an electron optical system that irradiates an electron beam, which is emitted from an electron source, to a range covering a field of view on a sample;

means for applying a voltage to the sample;

electron beam imaging means for converging electrons, which are reflected from the sample due to the irradiated electron beam, so as to acquire a reflected-electron image;

means that has the sample mounted thereon and moves the sample with respect to the irradiated electron beam;

means that uses the reflected-electron beam to extract a foreign matter or defect on the sample, and records the position of the foreign matter or defect or an image thereof; and

an ultraviolet irradiation system that irradiates ultraviolet rays to the sample, comprising;

means for adjusting so that the shape of the irradiated area of the electron beam includes the shape of the irradiated area of the ultraviolet rays; and

means for adjusting the intensity of the ultraviolet rays in the irradiated area of the electron beam while sustaining the reflected-electron imaging conditions for the reflected-electron image.

2. The electron beam inspection apparatus according to claim 1, comprising means that uses the electron-beam imaging means to converge photoelectrons, which are generated from the sample due to the irradiation of the ultraviolet rays, so as to acquire a photoelectron image, and displays the irradiated area of the ultraviolet rays.

3. The electron beam inspection apparatus according to claim 2, comprising means that adjusts the position and size of the irradiated area of the ultraviolet rays so that the contour of the photoelectron image will be limited in the contour of the reflected-electron image.

4. The electron beam inspection apparatus according to claim 1, wherein the ultraviolet rays and electron beam are irradiated simultaneously, the intensity of the ultraviolet rays is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained, and negative charging in the irradiated area of the electron beam derived from the irradiated electron beam is neutralized.

5. The electron beam inspection apparatus according to claim 1, wherein the ultraviolet irradiation system includes an ultraviolet light source and a reflecting surface that changes the advancing direction of the ultraviolet rays from one to another so as to irradiate the ultraviolet rays to the sample.

6. The electron beam inspection apparatus according to claim 5, wherein the reflecting surface is located in the middle of the electron optical system, and has an opening through which the electron beam passes and which is intended to align the direction in which the electron beam is irradiated to the sample with the direction in which the ultraviolet rays are irradiated to the sample.

7. The electron beam inspection apparatus according to claim 1, wherein the ultraviolet irradiation system has means, which adjusts an amount of ultraviolet rays, and a pinhole interposed between the ultraviolet light source and the reflecting surface.

8. The electron beam inspection apparatus according to claim 7, wherein a diaphragm for limiting a field of view is mounted on the optical path of the electron optical system, and the diaphragm and pinhole are used to limit the shape and size of the irradiated area of the ultraviolet rays in the shape and size of the irradiated area of the electron beam.

9. An electron beam inspection apparatus including:

an electron optical system that shapes an electron beam, which is emitted from an electron source, into a planar electron beam, and irradiates the planar electron beam to a range covering a field of view on a sample;

means for applying a negative voltage to the sample;

an electron-beam imaging means that converges electrons, which are reflected from the sample due to the irradiated electron beam, so as to acquire a reflected-electron image;

means that has the sample mounted thereon and moves the sample with respect to the irradiated electron beam;

means that uses the reflected-electron image to extract a foreign matter or defect on the sample, and records the position of the foreign matter or defect or an image thereof; and

an ultraviolet irradiation system that irradiates ultraviolet rays to the sample, comprising;

means for adjusting so that the shape of the irradiated area of the electron beam includes the shape of the irradiated area of the ultraviolet rays; and

means for adjusting the intensity of the ultraviolet rays in the irradiated area of the electron beam while sustaining the reflected-electron imaging conditions for the reflected-electron image,

wherein negative charging in the irradiated area of the electron beam derived from the irradiated electron beam is neutralized.

10. An electron beam inspection method including:

a step of irradiating an electron beam to a range covering a field of view on a sample, to which a voltage is applied, through an electron optical system;

a step of converging electrons, which are reflected from the sample due to the irradiation of the electron beam, so as to acquire a reflected-electron image;

a step of extracting a foreign matter or defect on the sample using the reflected-electron image, and recording and displaying the position of the foreign matter or defect or an image thereof; and

a step of alleviating negative charging on the sample, which is derived from the electron-beam irradiation, by irradiating ultraviolet rays, comprising the steps of;

limiting the shape of the irradiated area of the electron beam in the shape of the irradiated area of the ultraviolet rays; and

adjusting an amount of ultraviolet rays in the irradiated area of the electron beam while sustaining the reflected-electron imaging conditions for the reflected-electron image.

11. The electron beam inspection method according to claim 10, comprising a step of converging photoelectrons, which are generated from the sample due to the irradiation of the ultraviolet rays, so as to acquire a photoelectron image.

12. The electron beam inspection method according to claim 11, wherein the position and size of the irradiated area of the ultraviolet rays are adjusted so that the contour of the photoelectron image will be limited in the contour of the reflected-electron image.

13. The electron beam inspection method according to claim 10, wherein the ultraviolet rays and electron beam are irradiated simultaneously, the intensity of the ultraviolet rays is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained, and negative charging on the sample surface in the irradiated area of the electron beam derived from the irradiated electron beams is neutralized.

14. The electron beam inspection method according to claim 11, wherein the ultraviolet rays and electron beam are irradiated simultaneously, the intensity of the ultraviolet rays is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained, and negative charging on the sample surface in the irradiated area of the electron beam derived from the irradiated electron beams is neutralized.

15. The electron beam inspection method according to claim 12, wherein the ultraviolet rays and electron beam are irradiated simultaneously, the intensity of the ultraviolet rays is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained, and negative charging on the sample surface in the irradiated area of the electron beam derived from the irradiated electron beams is neutralized.