Apparatus and method for correcting arrayed astigmatism in a multi-column scanning electron microscopy system

Patent metadata

Field	Value
Publication number	US-10497536-B2
Application number	US-201715645863-A
Country	US
Kind code	B2
Filing date	Jul 10, 2017
Priority date	Sep 8, 2016
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

A multi-beam scanning electron microscopy (SEM) system is disclosed. The system includes an electron beam source configured to generate a source electron beam. The system includes a set of electron-optical elements configured to generate a flood electron beam from the source electron beam. The system includes a multi-beam lens array with a plurality of electron-optical pathways configured to split the flood electron beam into a plurality of primary electron beams, and a plurality of electrically-charged array layers configured to adjust at least some of the plurality of primary electron beams. The system includes a set of electron-optical elements configured to direct at least some of the plurality of primary electron beams onto a surface of a sample secured by a stage. The system includes a detector array configured to detect a plurality of electrons emanated from the surface of the sample in response to the plurality of primary electron beams.

First claim

What is claimed:

1. A multi-beam scanning electron microscopy (SEM) system, comprising:
an electron beam source configured to generate a source electron beam;
a first set of electron-optical elements configured to generate a flood electron beam from the source electron beam;
a multi-beam lens array, comprising:
a plurality of electron-optical pathways configured to split the flood electron beam into a plurality of primary electron beams; and
a plurality of electrically-chargeable array layers configured to adjust at least some of the plurality of primary electron beams, wherein the plurality of electrically-chargeable array layers comprise:
a set of common voltage plates including a first common voltage plate with a first set of apertures and a second common voltage plate with a second set of apertures, wherein at least one of an aperture of the first set of apertures or an aperture of the second set of apertures includes a first radius and a second radius, wherein the first radius and the second radius are different;
a focusing voltage plate including a third set of apertures; and
one or more multi-pole beam deflectors configured to adjust astigmatism within the multi-beam lens array,
wherein at least one of a voltage of the focusing voltage plate or a voltage of the one or more multi-pole beam deflectors is independently adjustable relative to a voltage of the set of common voltage plates;

a second set of electron-optical elements configured to direct at least some of the plurality of primary electron beams onto a surface of a sample;
a stage configured to secure the sample; and
a detector array configured to detect a plurality of electrons emanated from the surface of the sample in response to the plurality of primary electron beams.

2. The system in claim 1 , wherein the electron beam source comprises:
an electron emitter, an extractor, and an anode.

3. The system in claim 1 , wherein the first set of electron-optical elements is configured to direct the flood electron beam to the multi-beam lens array.

4. The system in claim 1 , wherein an electron-optical pathway of the plurality of electron-optical pathways includes an aperture of the first set of apertures, an aperture of the second set of apertures, a multi-pole beam deflector of the one or more multi-pole beam deflectors, and an aperture of the third set of apertures.

5. The system in claim 1 , wherein a difference between the first radius and the second radius introduces the astigmatism into the electron-optical pathway.

6. The system in claim 5 , wherein the multi-pole beam deflector reduces the astigmatism introduced into the electron-optical pathway by adjusting the primary electron beam.

7. The system in claim 1 , wherein the one or more multi-pole beam deflectors are positioned between the focusing voltage plate and the second common voltage plate.

8. The system in claim 1 , wherein the one or more multi-pole beam deflectors include at least one of one or more quadrupole beam deflectors or one or more octupole beam deflectors.

9. The system in claim 1 , wherein the one or more emanated electrons include one or more secondary electrons, wherein the detector array includes one or more secondary electron detector assemblies.

10. The system in claim 9 , further comprising:
a deflector assembly configured to deflect the one or more secondary electrons to the detector array via a third set of electron-optical elements.

11. An apparatus for correcting arrayed astigmatism in a multi-beam scanning electron microscopy (SEM) system, comprising:
a plurality of electron-optical pathways configured to split a flood electron beam to generate a plurality of primary electron beams, wherein the flood electron beam is generated via a first set of electron-optical elements from a source electron beam, wherein the source electron beam is generated via an electron beam source; and
a plurality of electrically-chargeable array layers configured to adjust at least some of the plurality of primary electron beams, wherein the plurality of electrically-chargeable array layers comprise:
a set of common voltage plates including a first common voltage plate with a first set of apertures and a second common voltage plate with a second set of apertures, wherein at least one of an aperture of the first set of apertures or an aperture of the second set of apertures includes a first radius and a second radius, wherein the first radius and the second radius are different;
a focusing voltage plate including a third set of apertures; and
one or more multi-pole beam deflectors configured to adjust astigmatism within the multi-beam lens array,
wherein at least one of a voltage of the focusing voltage plate or a voltage of the one or more multi-pole beam deflectors is independently adjustable relative to a voltage of the set of common voltage plates,

wherein at least some of the plurality of primary electron beams are directed onto a surface of a sample via a second set of electron-optical elements, wherein a plurality of electrons emanate from the surface of the sample in response to the plurality of primary electron beams, wherein the plurality of electrons are detected by a detector array.

12. A method, comprising:
generating a source electron beam;
generating a flood electron beam from the source electron beam via a first set of electron-optical elements;
splitting the flood electron beam to generate a plurality of primary electron beams via a multi-beam lens array;
adjusting at least some of the plurality of primary electron beams via the multi-beam lens array, wherein the multi-beam lens array includes a plurality of electrically-chargeable array layers configured to adjust at least some of the plurality of primary electron beams, wherein the plurality of electrically-chargeable array layers comprise:
a set of common voltage plates including a first common voltage plate with a first set of apertures and a second common voltage plate with a second set of apertures;
a focusing voltage plate including a third set of apertures; and
one or more multi-pole beam deflectors configured to adjust astigmatism within the multi-beam lens array,
wherein at least one of a voltage of the focusing voltage plate or a voltage of the one or more multi-pole beam deflectors is independently adjustable relative to a voltage of the set of common voltage plates;

directing at least some of the plurality of primary electron beams through a second set of electron-optical elements onto a surface of a sample; and
detecting a plurality of electrons emanated from the surface of the sample in response to the plurality of primary electron beams.

Assignees

• Kla Tencor Corp
• Rockwell Collins Inc

Inventors

• Brodie Alan D

Classifications

• H01J2237/1532

  Astigmatism · CPC title

• H01J37/28 Primary

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

• H01J37/153 Primary

  Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators · CPC title

• H01J2237/2813

  characterised by the application · CPC title

• G01N23/2251 Primary

  using incident electron beams, e.g. scanning electron microscopy [SEM] · CPC title