Non-invasive charged particle beam monitor

Patent metadata

Field	Value
Publication number	US-9390887-B2
Application number	US-201414486739-A
Country	US
Kind code	B2
Filing date	Sep 15, 2014
Priority date	Sep 17, 2013
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

An electromagnetic wakefield detector placed in close proximity to a design trajectory of a non-relativistic charged particle beam produces an optical signal in response to passage of the charged particle beam without interrupting the charged particle beam. A photon detector receives the optical signal and produces a corresponding output. The wakefield detector may be based on the electro optic effect. Specifically, the detector may measure the effect of the charged particle beam a beam of radiation on the phase of radiation travelling parallel to the beam in a nearby electro optic waveguide. This abstract is provided to comply with rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

First claim

What is claimed is:

1. A system, comprising:
a) a set of one or more electro-optic (EO) materials placed in close proximity to a design trajectory of a charged particle beam; and
b) a set of one or more optical probes configured to receive a beam of electromagnetic radiation and probe a change of refractive index of the one or more EO materials resulting from passage of the charged particle from the beam due to the electro-optic effect of the charged particle's electromagnetic field; and
c) a set of one or more photon detectors coupled to the one or more optical probes, wherein each photon detector in the set is configured to produce a photon signal that corresponds to the change of refractive index of a corresponding EO material of the set of one of the one or more EO materials.

2. The system of claim 1 , wherein the set of one or more photon detectors includes a photon detector coupled to a dark port of a particular optical probe of the set of one or more optical probes.

3. The system of claim 2 , wherein the optical probe of the set of one or more optical probes is configured to direct radiation from the beam of electromagnetic radiation of a first polarization into a particular EO material of the set of one or more electro-optic (EO) materials, wherein the particular optical probe includes a polarizing beam splitter configured to receive at least a portion of the beam of electromagnetic radiation that has traveled in the particular EO material and direct radiation of a second polarization that is orthogonal to the first polarization to a particular photon detector of the set of one or more photon detectors.

4. The system of claim 1 , wherein the set of one or more optical probes includes a particular optical probe configured to couple at least a portion of the beam of electromagnetic radiation onto a waveguide structure in a particular EO material of the set of one or more EO materials, wherein the waveguide structure is configured to direct the portion of the beam of electromagnetic radiation in a direction substantially parallel to a direction of a portion of the charged particle beam beam's design trajectory that is proximate the waveguide structure.

5. The system of claim 4 , wherein the waveguide structure is configured such that a group velocity of the portion of the beam of electromagnetic radiation in the waveguide structure is approximately equal to a velocity of charged particles in the charged particle beam to within a range of adjustment of the velocity of the charged particles.

6. The system of claim 1 , further comprising a secondary particle detector configured to produce a secondary signal in response to detection of secondary particles generated by interaction between the charged particle beam and a target.

7. The system of claim 6 , further comprising a signal processor coupled to the photon detector and the secondary particle detector, wherein the signal processor is configured to use the photon signal from a photon detector in the set of photon detectors to apply a noise cancellation to the secondary signal thereby producing a processed signal.

8. The system of claim 7 , wherein the processed signal corresponds to a ratio of the secondary signal to the photon signal.

9. The system of claim 1 , wherein a signal from the photon detector provides a servo input that is used to control a property of the charged particle beam.

10. The system of claim 1 , wherein the set of one or more optical probes is configured to implement a beam position monitor that measures a position of the charged particle beam.

11. The system of claim 1 , wherein the set of one or more optical probes is configured to implement a beam profile monitor.

12. The system of claim 1 , wherein the set of one or more optical probes is configured to implement an energy spectrometer.

13. The system of claim 1 , the set of one or more optical probes is configured to implement a multi-function beam monitor.

14. The system of claim 13 , wherein the multi-function monitor implements two or more of the following functions: beam current monitoring, beam position monitoring, beam energy spectrometry, or beam profile monitoring.

15. The system of claim 1 , further comprising a charged particle beam optical column configured to produce the charged particle beam.

16. The system of claim 15 , wherein the charged particle beam is an electron beam.

17. The system of claim 16 , wherein the charged particle beam optical column is part of a scanning electron microscope.

18. The system of claim 15 , wherein a signal from the photon detector provides a servo input to a controller coupled to the charged particle beam optical column that is used to control a property of the charged particle beam.

19. A system, comprising:
a) a set of one or more electromagnetic wakefield detectors placed in close proximity to a design trajectory of a non-relativistic charged particle beam, wherein the set of one or more wakefield detectors is configured to produce one or more optical signals in response to passage of the charged particle beam without interrupting the charged particle beam; and
c) a set of one or more photon detectors configured to receive the one or more optical signals and produce one or more corresponding outputs.

20. The system of claim 19 , the set of one or more electromagnetic wakefield detectors is configured to implement a multi-function beam monitor that implements two or more of the following functions: beam current monitoring, beam position monitoring, beam energy spectrometry, or beam profile monitoring.

21. The system of claim 19 , wherein the set of one or more electromagnetic wakefield detectors includes a detector based on one or more of the following: the electro optic effect, image charge generation, radiation by an undulator, the Cerenkov effect, generation of transition radiation, generation of radiation by the Smith-Purcell effect, or Compton scattering.

Assignees

• Kla Tencor Corp

Inventors

• Plettner Thomas
• Gerling John

Classifications

• H01J2237/24507

  Intensity, dose or other characteristics of particle beams or electromagnetic radiation · CPC title

• H01J2237/24535

  Beam current · CPC title

• H01J2237/2482

  Optical means · CPC title

• H01J2237/24542

  Beam profile · CPC title

• H01J2237/24485

  Energy spectrometers · CPC title