Charged particle beam apparatus

Patent metadata

Field	Value
Publication number	US-11430630-B2
Application number	US-201716641035-A
Country	US
Kind code	B2
Filing date	Sep 4, 2017
Priority date	Sep 4, 2017
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

The present invention realizes a composite charged particle beam apparatus capable of suppressing a leakage magnetic field from a pole piece forming an objective lens of an SEM with a simple structure. The charged particle beam apparatus according to the present invention obtains an ion beam observation image while passing a current to a first coil constituting the objective lens, and performs an operation of reducing the image shift by passing a current to a second coil with a plurality of current values, and determines a current to be passed to the second coil based on a difference between the operations.

First claim

The invention claimed is:

1. A charged particle beam apparatus for irradiating a specimen with a charged particle beam, the apparatus comprising:
an ion beam irradiation unit that emits a focused ion beam to the specimen;
an electron beam irradiation unit that emits an electron beam to the specimen;
an objective lens for focusing the electron beam on the specimen; and
a control unit that controls the objective lens,
wherein the objective lens includes
a first magnetic pole piece,
a second magnetic pole piece that is disposed at a position further away from the electron beam path with respect to the first magnetic pole piece, and
a first coil that is disposed between the first magnetic pole piece and the second magnetic pole piece,
the charged particle beam apparatus further includes
a second coil that is disposed at a position further away from the electron beam path with respect to the second magnetic pole piece,
the control unit performs
a first operation of acquiring an observation image of the specimen by the focused ion beam while passing a first current to the first coil, and
a second operation of acquiring the observation image of the specimen by the focused ion beam while passing a second current to the first coil after disposing a position of the specimen at the same position as the first operation,
the control unit passes a correction current to the second coil to generate a magnetic field that reduces a positional shift of the observation image caused by passing a current to the first coil, and
the control unit determines the correction current based on a difference between the first operation and the second operation.

2. The charged particle beam apparatus according to claim 1 , wherein
the control unit acquires a first shift amount between the first observation image of the specimen when the first current is passed to the first coil and the second observation image of the specimen when the second current is passed to the first coil, as the difference, and
the control unit determines the correction current based on the first shift amount.

3. The charged particle beam apparatus according to claim 2 , wherein
the control unit estimates a first correspondence between the current to be passed to the first coil and the first shift amount, based on the first current, the second current, and the first shift amount, and
the control unit determines the correction current corresponding to the current to be passed to the first coil according to the estimated first correspondence.

4. The charged particle beam apparatus according to claim 2 , wherein
the control unit acquires a second shift amount between a third observation image of the specimen when a third current is passed to the second coil and a fourth observation image of the specimen when a fourth current is passed to the second coil,
the control unit estimates a second correspondence between the current to be passed to the second coil and the second shift amount, based on the third current, the fourth current, and the second shift amount, and
the control unit determines the correction current so as to reduce the first shift amount according to the estimated second correspondence.

5. The charged particle beam apparatus according to claim 2 , wherein
the control unit passes a plurality of different currents to the first coil, and acquires an observation image of the specimen by the focused ion beam while passing each of the currents,
the control unit estimates a correspondence between a current to be passed to the first coil and a shift amount of the observation image, and
the control unit determines the correction current corresponding to a current to be passed to the first coil in according to the estimated correspondence.

6. The charged particle beam apparatus according to claim 1 , wherein
the control unit reduces a positional shift of an observation image of the specimen acquired by the focused ion beam while passing the first current to the first coil by passing a first correction current to the second coil,
the control unit reduces a positional shift of an observation image of the specimen acquired by the focused ion beam while passing the second current to the first coil by passing a second correction current to the second coil,
the control unit acquires a third shift amount between the first correction current and the second correction current, as the difference, and
the control unit determines the correction current corresponding to a current to be passed to the first coil, based on the third shift amount.

7. The charged particle beam apparatus according to claim 6 , wherein
the control unit estimates a third correspondence between a current to be passed to the first coil and the correction current, based on the first current, the second current, and the third shift amount, and
the control unit determines the correction current corresponding to the current to be passed to the first coil according to the estimated third correspondence.

8. The charged particle beam apparatus according to claim 1 , wherein
when an acceleration voltage used when the electron beam irradiation unit emits the electron beam is changed, the control unit determines a current to be passed to the first coil under the changed acceleration voltage, and
the control unit determines the correction current corresponding to a current to be passed to the first coil under the changed acceleration voltage.

9. The charged particle beam apparatus according to claim 1 , further comprising:
a third coil that is disposed at a position away from the electron beam path with respect to the second magnetic pole piece, wherein
the control unit passes a third correction current to the third coil to generate a magnetic field that reduces a positional shift of the observation image caused by passing a current to the first coil, and
the control unit determines the third correction current based on a difference between the first operation and the second operation.

10. The charged particle beam apparatus according to claim 9 , further comprising:
a third magnetic pole piece that is disposed at a position away from the electron beam path with respect to the second coil,
wherein the second magnetic pole piece and the third magnetic pole piece form a magnetic path surrounding the second coil.

11. The charged particle beam apparatus according to claim 1 ,
wherein at least one of the first coil and the second coil is formed by a plurality of coils.

12. The charged particle beam apparatus according to claim 9 , wherein
the number of turns of the second coil is equal to or greater than the number of turns of the first coil, and
the number of turns of the first coil is equal to or greater than the number of turns of the third coil.

13. The charged particle beam apparatus according to claim 1 ,
wherein the number of turns of the first coil is equal to or greater than the number of turns of the second coil.

Assignees

• Hitachi High Tech Corp

Inventors

• Hirano Ryo
• Nomaguchi Tsunenori
• Kamiya Chisato
• Katane Junichi

Classifications

• H01J2237/28

  Scanning microscopes · CPC title

• H01J37/09 Primary

  Diaphragms; Shields associated with electron or ion-optical arrangements; Compensation of disturbing fields · CPC title

• H01J2237/0266

  electromagnetic · CPC title

• H01J2237/141

  Coils · CPC title

• H01J37/3005

  Observing the objects or the point of impact on the object · CPC title