APPARATUS AND METHOD FOR PERFORMING MICRODIFFRACTION ANALYSIS

• US 20140252226A1
• Filed: 10/08/2012
• Published: 09/11/2014
• Est. Priority Date: 10/06/2011
• Status: Active Grant

• Current Assignee: Oxford Instruments Nanotechnology Tools Limited (Oxford Instruments PLC)
• Original Assignee: Oxford Instruments Nanotechnology Tools Limited (Oxford Instruments PLC)
• Inventors: Statham, Peter J., Bewick, Angus
• Granted Patent: US 8,890,065 B2
• Time in Patent Office: Days
• US Class Current: 250/307
• CPC Class Codes: G01N 23/20058 Measuring diffraction of electrons, e.g. low energy electron diffraction [LEED] method or reflection high energy electron diffraction [RHEED] method
• CPC Class Codes: G01N 23/203 Measuring back scattering
• CPC Class Codes: H01J 37/29 Reflection microscopes

Abstract

An apparatus for detecting one or each of Kikuchi and Kossel diffraction patterns is provided. The apparatus comprises an electron column adapted in use to provide an electron beam (101) directed to wards a sample (102), the electron beam (101) having an energy in the range 2 keV to 50 keV, and a particle detector (111) for receiving and counting particles (103) from the sample (102) due to interaction of the electron beam (101) with the sample (102), the detector comprising an array of pixels (109) and having a count rate capability of at least 1000 particles per second for each pixel. The particle detector (111) is further adapted to provide electronic energy filtering of the received particles in order to count the received particles which are representative of the said diffraction pattern.

Claims

1. Apparatus for detecting one or each of Kikuchi and Kossel diffraction patterns, the apparatus comprising:

an electron column adapted in use to provide an electron beam directed towards a sample, the electron beam having an energy in the range 2 keV to 50 keV, and;

a particle detector for receiving and counting particles from the sample due to interaction of the electron beam with the sample, the detector comprising an array of pixels and having a count rate capability of at least 1000 particles per second for each pixel, and wherein;

the particle detector is adapted to provide electronic energy filtering of the received particles in order to count the received particles which are representative of the said diffraction pattern.

2. The apparatus of claim 1, wherein the detector generates an output signal in accordance with the energy of each received particle.

3. The apparatus of claim 1, wherein the received particles have a range of energies including energies representative of the said diffraction pattern and energies representative of a background.

4. The apparatus of claim 1, wherein the detector has a count rate capability, for each pixel, of at least 10000 particles per second.

5. The apparatus of claim 1, wherein the particle detector is adapted to provide electronic energy filtering with respect to at least one adjustable energy threshold.

6. The apparatus of claim 1, wherein the electronic energy filtering is adapted to distinguish between received particles having an energy representative of the said diffraction pattern and received particles having an energy representative of a background.

7. The apparatus of claim 1, wherein the particle detector is adapted to convert the energy of each received particle directly into an electronic signal, and said electronic energy filtering acts on said electronic signals.

8. The apparatus of claim 1, wherein the detector comprises at least one particle counter.

9. The apparatus of claim 8, wherein the array of pixels and the at least one particle counter are a unitary member.

10. The apparatus of claim 8, wherein each pixel comprises a semiconductor substrate for sensing particles.

11. The apparatus of claim 8, wherein each pixel has a corresponding particle counter.

12. The apparatus of claim 11, wherein each particle counter has a count rate capability of at least 1000 particles per second.

13. The apparatus of claim 11, wherein each particle counter has a count rate capability of at least 10000 particles per second.

14. The apparatus of claim 11, wherein the detector comprises an array of particle counters corresponding to the array of pixels.

15. The apparatus of claim 8, wherein each particle counter produces an individual output signal in accordance with the energy of each received particle.

16. The apparatus of claim 8, wherein each particle counter is adapted to provide electronic energy filtering with respect to at least one adjustable energy threshold.

17. The apparatus of claim 16, wherein each particle counter is adapted to provide electronic energy filtering, with respect to at least one adjustable energy threshold, acting as a high-pass filter.

18. The apparatus of claim 16, wherein each particle counter is adapted to provide electronic energy filtering, with respect to at least one adjustable energy threshold, acting as a band-pass filter.

19. The apparatus of claim 16, wherein each particle counter is adapted to provide electronic energy filtering, with respect to at least one adjustable energy threshold, acting as a low-pass filter.

20. The apparatus of claim 5, further comprising a control device operable, in use, to adjust the at least one adjustable energy threshold between a first setting and a second setting.

21. The apparatus of claim 20, wherein at the first setting each particle counter is adapted to provide electronic energy filtering, with respect to at least one adjustable energy threshold, acting as a band-pass filter;

and at the second setting each particle counter is adapted to provide electronic energy filtering, with respect to at least one adjustable energy threshold, acting as a high-pass filter.

22. The apparatus of claim 1, wherein the electron column is a part of a scanning electron microscope.

23. The apparatus of claim 1, further comprising an image processing unit adapted to generate image data from the detector.

24. The apparatus of claim 1, wherein the detector is a direct detector.

25. A method for detecting one or each of Kossel and Kikuchi diffraction patterns, the method comprising:

operating an electron column such that an electron beam having an energy in the range 2 keV to 50 keV impinges upon a sample;

receiving, at a particle detector, particles from the sample due to interaction of the electron beam with the sample, the particle detector comprising an array of pixels and having a count rate capability of at least 1000 particles per second;

electronically filtering, at the particle detector, the energy of each received particle; and

counting, at the particle detector and based on the electronic filtering, the received particles representative of the said diffraction pattern.

26. The method of claim 25, wherein the steps of electronically filtering and counting are carried out for each of the array of pixels simultaneously.

27. The method of claim 25, wherein the energy threshold is adjustable and wherein the method further comprises the step of adjusting the adjustable energy threshold between a first setting and a second setting.

28. The method of claim 27, further comprising the step of adjusting the energy threshold between a plurality of settings and at each setting generating an output signal from the detector.

29. A method of detecting Kossel and Kikuchi diffraction patterns, comprising the method of claim 27, wherein when detecting a Kassel diffraction pattern the adjustable energy threshold is set to a first setting, and when detecting a Kikuchi diffraction pattern the adjustable energy threshold is set to a second setting.

30. The method of claim 29, wherein the first setting is a band-pass filter and the second setting is a high-pass filter.