System for imaging a secondary charged particle beam with adaptive secondary charged particle optics

Patent metadata

Field	Value
Publication number	US-9953805-B2
Application number	US-201615364060-A
Country	US
Kind code	B2
Filing date	Nov 29, 2016
Priority date	Jul 2, 2015
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A secondary charged particle imaging system for imaging a secondary charged particle beam emanating from a sample by impingement of a primary charged particle beam is provided. The system includes a detector arrangement, and an adaptive secondary charged particle optics. The detector arrangement comprises a first detection element for detecting a first secondary charged particle sub-beam of the secondary charged particle beam, and a second detection element for detecting a second secondary charged particle sub-beam of the secondary charged particle beam. The adaptive secondary charged particle optics comprises an aperture plate including a first opening for letting the first secondary charged particle sub-beam pass through and a second opening for letting the second secondary charged particle sub-beam pass through; a lens system for mapping the secondary charged particle beam onto the aperture plate, the lens system comprising a first lens and a second lens; and a controller for controlling the excitation of the first lens and the excitation of the second lens. The controller is configured to independently control the excitation of the first lens and of the second lens to map the secondary charged particle beam onto the aperture plate so that the first secondary charged particle sub-beam passes through the first opening and the second secondary charged particle sub-beam passes through the second opening independent of a variation of at least one first operating parameter selected from a group comprising: landing energy of the primary charged particle beam on the sample, extraction field strength for the secondary charged particle beam at the sample, magnetic field strength of an objective lens that focuses the primary charged particle beam onto the sample, and working distance of the objective lens from the sample.

First claim

The invention claimed is:

1. A secondary charged particle imaging system for imaging a secondary charged particle beam emanating from a sample by impingement of a primary charged particle beam, the system comprising:
a detector arrangement comprising:
a first detection element for detecting a first secondary charged particle sub-beam of the secondary charged particle beam in a topography detection mode, and
a second detection element for detecting a second secondary charged particle sub-beam of the secondary charged particle beam in the topography detection mode, the first detection element and the second detection element being separated from each other;

the secondary charged particle imaging system further comprising:
adaptive secondary charged particle optics comprising:
an aperture plate including a first opening for letting the first secondary charged particle sub-beam pass through and a second opening for letting the second secondary charged particle sub-beam pass through;
a lens system for mapping the secondary charged particle beam onto the aperture plate, the lens system comprising a first lens and a second lens; and
a controller for controlling the excitation of the first lens and the excitation of the second lens,
wherein, with respect to a propagation of the secondary charged particle beam, the aperture plate is arranged upstream of the detector arrangement, the first lens is arranged upstream of the aperture plate, and the second lens is arranged upstream of the first lens,
wherein the controller is configured to independently control the excitation of the first lens and of the second lens to map the secondary charged particle beam onto the aperture plate so that the first secondary charged particle sub-beam passes through the first opening and the second secondary charged particle sub-beam passes through the second opening in the topography detection mode independent of a variation of at least one first operating parameter selected from a group comprising: landing energy of the primary charged particle beam on the sample, extraction field strength for the secondary charged particle beam at the sample, magnetic field strength of an objective lens that focuses the primary charged particle beam onto the sample, and working distance of the objective lens from the sample, and
wherein at least one of the first lens or the second lens comprises a magnetic lens portion for rotating the secondary charged particle beam to compensate a Larmor rotation of the objective lens.

2. The secondary charged particle imaging system according to claim 1 , wherein the aperture plate defines an optical axis, and wherein the first lens and the second lens are aligned to the optical axis of the aperture plate.

3. The secondary charged particle imaging system according to claim 1 , wherein the aperture plate defines an optical axis, wherein:
the detector arrangement further comprises a central detection element through which the optical axis passes, wherein the first detection element and the second detection element are arranged radially outward from the optical axis;
the aperture plate further comprises a central opening through which the optical axis passes, wherein the first opening and the second opening are located radially outward from the optical axis; and
the controller is configured to independently control the excitation of the first lens and of the second lens to map the secondary charged particle beam onto the aperture plate so that a third secondary charged particle sub-beam of the secondary charged particle beam passes through the central opening in the topography detection mode.

4. The secondary charged particle imaging system according to claim 3 , wherein:
the controller is configured to independently control the excitation of the first lens and of the second lens to map the secondary charged particle beam onto the aperture plate so that the secondary charged particle beam passes entirely through the central opening in a bright field detection mode independent of a variation of at least one second operating parameter selected from a group comprising: landing energy of the primary charged particle beam on the sample, extraction field strength for the secondary charged particle beam at the sample, magnetic field strength of an objective lens that focuses the primary charged particle beam onto the sample, and working distance of the objective lens from the sample; and
the controller is configured to switch between the topography detection mode and the bright field detection mode by adapting the excitations of the first lens and of the second lens.

5. The secondary charged particle imaging system according to claim 4 , wherein the at least one first operating parameter and the at least one second operating parameter are the same at least one operating parameter.

6. The secondary charged particle imaging system according to claim 1 , wherein the aperture plate defines an optical axis, wherein:
the detector arrangement comprises an integer number N of further detection elements, the integer number N either being zero or being larger than zero,
the aperture plate comprises the same integer number N of further openings, wherein the first opening, the second opening and the N further openings are located around the optical axis of the aperture plate such that the aperture plate has an N+2-fold rotational symmetry with respect to the optical axis of the aperture plate.

7. The secondary charged particle imaging system according to claim 1 , wherein the controller is configured to control the excitation of the magnetic lens portion to map the secondary charged particle beam onto the aperture plate so that the first secondary charged particle sub-beam passes through the first opening and the second secondary charged particle sub-beam passes through the second opening in the topography detection mode independent of a variation in the magnetic field strength of the objective lens.

8. The secondary charged particle imaging system according to claim 1 , further comprising a beam bender acting on the secondary charged particle beam and being arranged, with respect to the propagation of the secondary charged particle beam, upstream of the second lens.

9. The secondary charged particle imaging system according to claim 8 , wherein the distance between the beam bender and the second lens is 60 mm or below.

10. The secondary charged particle imaging system according to claim 8 , wherein the distance between the beam bender and the first lens is 50 mm or above.

11. The secondary charged particle imaging system according to claim 1 , wherein the aperture plate comprises a separation electrode adapted for separating the secondary charged particle beam into secondary charged particle sub-beams.

12. The secondary charged particle imaging system according to claim 1 , wherein the distance between the first lens and the second lens is in the range from 40 to 200 mm.

13. The secondary charged particle imaging system according to claim 1 , wherein the first lens and/or the second lens is a compound lens including an electrostatic lens portion and a magnetic lens portion.

14. The secondary charged particle imaging system according to claim 1 , wherein the first lens and the second lens are adapted for adjusting an opening angle of the secondary charged particle beam.

15. A charged particle beam device, comprising:
an emitter for emitting a primary charged particle beam;
an objective lens for focusing the primary charged particle beam onto a sample;
a beam separator for separating the primary charged particle beam from a seconda

Assignees

• Ict Integrated Circuit Testing Ges Fuer Halbleiterprueftechnik Mhh
• Ict Integrated Circuit Testing Ges Fuer Halbleiterprueftechnik Mbh

Inventors

• Firnkes Matthias
• Lanio Stefan
• Winkler Dieter

Classifications

• H01J2237/0453

  multiple apertures · CPC title

• H01J2237/1202

  Associated circuits · CPC title

• H01J37/12

  electrostatic · CPC title

• G01N2223/6116

  semiconductor wafer · CPC title

• H01J37/222

  Image processing arrangements associated with the tube · CPC title