Detection method for use in charged-particle microscopy

Patent metadata

Field	Value
Publication number	US-9153416-B2
Application number	US-201414286811-A
Country	US
Kind code	B2
Filing date	May 23, 2014
Priority date	Feb 14, 2011
Publication date	Oct 6, 2015
Grant date	Oct 6, 2015

Abstract

A method of investigating a sample using a charged-particle microscope is disclosed. By directing an imaging beam of charged particles at a sample, a resulting flux of output radiation is detected from the sample. At least a portion of the output radiation is examined using a detector, the detector comprising a Solid State Photo-Multiplier. The Solid State Photo-Multiplier is biased so that its gain is matched to the magnitude of output radiation flux.

First claim

We claim as follows:

1. A detector for a charged-particle beam system, the detector comprising:
a scintillator for receiving a charged particle and emitting one or more photons in response to the impact of the charged particle;
a voltage source for providing a voltage to the scintillator to attract charged particles;
a multi-pixel photon counter for detecting light from the scintillator and providing an electric signal corresponding to the detected light; and
a light guide composed of an electrically-insulating and optically-transparent material for conducting light from the scintillator to the multi-pixel photon counter and electrically insulating the multi-pixel photon counter from the voltage applied to the scintillator, the light guide partially matching the refractive indices of the scintillator and the multi-pixel photon counter.

2. The detector of claim 1 in which the light guide comprises glass.

3. The detector of claim 1 in which the multi-pixel photon counter comprises a Solid State Photo-Multiplier, (SSPM), a Silicon Photo-Multiplier, (SiPM), or an on-chip pixelated Avalanche Photodiode, (APD), array.

4. The detector of claim 1 in which the scintillator, light guide, and multi-pixel photon counter are sandwiched in a stacked structure and are partially encapsulated in a jacket of electrically-insulating material, leaving at least a portion of the scintillator exposed.

5. The detector of claim 1 in which the multi-pixel photon counter comprises a SSPM, and further comprising a power supply providing an adjustable electrical bias for the SSPM, the adjustable bias allowing the detector to operate in a pulse-counter mode, an avalanche-photodiode mode, or in photodiode mode.

6. A charged-particle beam system, comprising:
a source of charged particles;
a focusing column for focusing the particles into a beam and directing the beam toward a sample; and
a detector in for detecting particles ejected from the sample, the detector comprising:
a scintillator for receiving a charged particle and emitting one or more photons in response to the impact of the charged particle;
a voltage source for providing a voltage to the scintillator to attract charged particles;
a multi-pixel photon counter for detecting light from the scintillator and providing an electric signal corresponding to the detected light; and
a light guide composed of an electrically-insulating and optically-transparent material for conducting light from the scintillator to the multi-pixel photon counter and electrically insulating the multi-pixel photon counter from the voltage applied to the scintillator, the light guide partially matching the refractive indices of the scintillator and the multi-pixel photon counter.

7. The charged-particle beam system of claim 6 in which the detector is positioned in the focusing column.

8. The charged-particle beam system of claim 6 in which the charged-particle beam system comprises any of a scanning electron microscope, a transmission electron microscope, a scanning transmission electron microscope, a focused ion beam tool, an electron-beam-induced deposition tool, an ion-beam-induced deposition tool, a dual-beam charged-particle microscope, a critical dimension microscope, a lithography tool, or hybrids thereof.

9. A method of investigating a sample using a charged-particle microscope, comprising:
providing a charged-particle microscope having a particle-optical column;
using the particle-optical column to direct an imaging beam of charged particles at the sample, as a result of which a flux of output charged particles is caused to emanate from the sample;
providing an electrical potential on a scintillator to cause the charged particles to impact the scintillator;
directing light from the scintillator through a transparent and electrically-insulating light guide toward a multi-pixel photon counter, the multi-pixel photon counter maintained at a lower voltage than the scintillator, and the light guide insulating the multi-pixel photon counter from the electrical potential on the scintillator; and
detecting the light with the multi-pixel photon counter and converting the light to an electronic signal.

10. The method of claim 9 in which directing the light from the scintillator through a transparent and electrically-insulating light guide includes directing the light through a glass light guide.

11. The method of claim 9 in which directing the light toward a multi-pixel photon counter includes directing the light to a SSPM, a SiPM, or an on-chip pixelated APD array.

12. The method of claim 9 in which the scintillator, light guide, and multi-pixel photon counter are sandwiched in a stacked structure and partially encapsulated in a jacket of electrically-insulating material, leaving at least a portion of the scintillator exposed.

13. The method of claim 9 in which the detector comprises a SSPM operating with a bias below its saturation threshold.

14. The method of claim 9 in which the detector comprises a SSPM operating with a bias above its saturation threshold.

15. The method of claim 9 in which the detector comprises a SSPM, and the method further comprising adjusting a bias so as to adjust a gain value of the SSPM to match the gain value to the magnitude of the flux.

16. The method of claim 9 in which detecting the light includes using a detector comprising a spatially-distributed structure.

17. The method of claim 16 in which the spatially-distributed structure comprise a plurality of SSPMs disposed about a point of intersection of the imaging beam and the sample.

18. The method of claim 9 in which detecting the light includes using a detector located within the particle-optical column.

19. The method of claim 9 in which the sample is positioned within an electromagnetic field of the particle-optical column.

20. The method of claim 9 in which said charged-particle microscope is selected from the group comprising a scanning electron microscope, a transmission electron microscope, a scanning transmission electron microscope, a focused ion beam tool, an electron-beam-induced deposition tool, an ion-beam-induced deposition tool, a dual-beam charged-particle microscope, a critical dimension microscope, a lithography tool, and hybrids thereof.

Assignees

• Fei Co

Inventors

• Hlavenka Petr
• Uncovsky Marek

Classifications

• G01N21/6447

  by visual observation · CPC title

• H01J2237/2443

  Scintillation detectors · CPC title

• H01J37/226

  Optical arrangements for illuminating the object; optical arrangements for collecting light from the object · CPC title

• H01J37/28

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

• H01J2237/2445

  Photon detectors for X-rays, light, e.g. photomultipliers · CPC title