MULTIPLE-BEAM SYSTEM FOR HIGH-SPEED ELECTRON-BEAM INSPECTION

• US 20120241606A1
• Filed: 04/27/2011
• Published: 09/27/2012
• Est. Priority Date: 03/23/2011
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Han, Liqun, Jiang, Xinrong, Greene, John D.
• Granted Patent: US 8,362,425 B2
• Time in Patent Office: Days
• US Class Current: 250/307
• CPC Class Codes: G01N 2223/102 beta or electrons
• CPC Class Codes: G01N 2223/611 patterned objects; electronic devices
• CPC Class Codes: G01N 23/2251 using incident electron beams, e.g. scanning electron microscopy [SEM]
• CPC Class Codes: H01J 2237/0435 Multi-aperture
• CPC Class Codes: H01J 2237/04926 combined
• CPC Class Codes: H01J 2237/1205 Microlenses
• CPC Class Codes: H01J 2237/15 Means for deflecting or directing discharge
• CPC Class Codes: H01J 2237/2446 Position sensitive detectors
• CPC Class Codes: H01J 37/04 Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement H01J37/32009, H01J37/32623, H01J37/3266, H01J37/32697 take precedence; electron or ion-optical systems for localised treatment of objects H01J37/3007
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

One embodiment disclosed relates to a multiple-beamlet electron beam imaging apparatus for imaging a surface of a target substrate. A beam splitter lens array is configured to split the illumination beam to form a primary beamlet array, and a scanning system is configured to scan the primary beamlet array over an area of the surface of the target substrate. In addition, a detection system configured to detect individual secondary electron beamlets. Another embodiment disclosed relates to a method of imaging a surface of a target substrate using a multiple-beamlet electron beam column. Other features and embodiments are also disclosed.

Claims

1. A multiple-beamlet electron beam imaging apparatus for imaging a surface of a target substrate, the apparatus comprising:

an electron source configured to emit electrons;

a condensor electron lens configured to focus the emitted electrons from the electron source into an illumination beam;

a beam splitter lens array configured to split the illumination beam to form a primary beamlet array, wherein the beam splitter lens array comprises a multiple-layer electrostatic lens array stack;

an objective electron lens configured to focus the primary beamlet array onto the surface of the target substrate so as to produce a secondary electron beamlet array;

a scanning system configured to scan the primary beamlet array over an area of the surface of the target substrate; and

a detection system configured to detect individual secondary electron beamlets of the secondary electron beamlet array.

2. The apparatus of claim 1, further comprising:

transfer electron-optics arranged between the beam splitter lens array and the objective electron lens.

3. The apparatus of claim 2, wherein the transfer electron-optics is configured to focus the primary beamlet array onto a back-focal plane of the objective electron lens.

4. The apparatus of claim 2, wherein the scanning system includes a pre-scanner arranged above the transfer electron-optics and a main scanner arranged below the transfer electron-optics.

5. The apparatus of claim 1, wherein the detection system includes secondary electron adjustment optics.

6. The apparatus of claim 5, wherein the secondary electron adjustment optics includes a focus adjustment electron lens, a rotation adjustment electron lens, and a magnification adjustment electron lens.

7. The apparatus of claim 6, wherein the secondary electron adjustment optics further includes an array of detector cells.

8. The apparatus of claim 7, wherein the array of detector cells has a number of cells which is equal to a number of secondary electron beamlets in the secondary electron beamlet array.

10. The apparatus of claim 1, wherein the electrostatic lens array stack comprises alternating electrically-grounded and electrically-floating electrode plates.

11. The apparatus of claim 10, wherein said electrode plates are perforated with a plurality of beamlet-forming columnar openings which are aligned from plate to plate so as to extend through the electrostatic lens array stack.

12. The apparatus of claim 1, wherein the objective electron lens is configured to focus the primary beamlet array such that the primary beamlet array lands normal to the surface of the target substrate.

13. The apparatus of claim 1, wherein the scanning system is configured to scan each primary beamlet of the primary beamlet array in a raster pattern such that said primary beamlet covers a corresponding sub-area of a framed surface area.

14. The apparatus of claim 1, further comprising a translatable stage which holds the target substrate, wherein the scanning system is configured to scan each primary beamlet of the primary beamlet array in a first dimension while the target substrate is translated under the primary beamlet array in a second dimension which is perpendicular to the first dimension.

9. (canceled)

15. A method of imaging a surface of a target substrate using a multiple-beamlet electron beam column, the method comprising:

emitting electrons into a vacuum chamber;

focusing the emitted electrons from the electron source into an illumination beam;

splitting the illumination beam using a multiple-layer electrostatic lens array stack to form a primary beamlet array;

focusing the primary beamlet array onto the surface of the target substrate using an objective electron-lens so as to produce a secondary electron beamlet array;

scanning the primary beamlet array over an area of the surface of the target substrate; and

detecting individual secondary electron beamlets of the secondary electron beamlet array.

16. The method of claim 15, further comprising:

focusing the primary beamlet array onto a back-focal plane of the objective electron lens using transfer electron-optics.

17. The method of claim 15, further comprising adjusting the focus, rotation, and magnification of the secondary electron beamlet array prior to detecting the individual secondary electron beamlets.

18. The method of claim 15, wherein each primary beamlet of the primary beamlet array is scanned in a raster pattern such that said primary beamlet covers a corresponding sub-area of a framed surface area.

19. The method of claim 15, wherein each primary beamlet of the primary beamlet array is scanned in a first dimension while the target substrate is translated under the primary beamlet array in a second dimension which is perpendicular to the first dimension.

20. An automated inspection system for inspecting a surface of a target substrate using a multiple-beamlet electron beam column, the automated inspection system comprising:

an electron source configured to emit electrons;

a condensor electron lens configured to focus the emitted electrons from the electron source into an illumination beam;

a beam splitter lens array configured to split the illumination beam to form a primary beamlet array, wherein the beam splitter lens array comprises a multiple-layer electrostatic lens array stack;

an objective electron lens configured to focus the primary beamlet array onto the surface of the target substrate so as to produce a secondary electron beamlet array;

a scanning system configured to scan the primary beamlet array over an area of the surface of the target substrate; and

a detection system configured to detect individual secondary electron beamlets of the secondary electron beamlet array.