Sample preparation method and apparatus

Patent metadata

Field	Value
Publication number	US-12529629-B2
Application number	US-202118023692-A
Country	US
Kind code	B2
Filing date	Aug 26, 2021
Priority date	Aug 28, 2020
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

The invention relates to a method of preparing a sample for analysis. The method comprises: providing a sample comprising a surface region of interest on a first face of the sample and a second face oriented at an angle to the first face about a common edge between the first and second faces, the second face extending between the common edge and a second edge on the opposing side of the second face of the sample; and milling the second face of the sample to provide a trench in the surface of the second face, the trench extending from a first position on the second face between the common edge and the second edge to a second position adjacent to the common edge; wherein the trench is arranged so as to provide an electron transparent sample layer comprising the surface region of interest. By milling the second face of the sample only, a surface region of interest on the first face of the sample is fully preserved and remains free of milling beam induced damage. This allows for correlative characterisation work which requires both an electron transparent sample and a fully intact sample surface to obtain surface-sensitive data.

First claim

The invention claimed is:

1 . A method of preparing a sample for analysis, the method comprising: providing a sample comprising a surface region of interest on a first face of the sample and a second face oriented at an angle to the first face about a common edge between the first and second faces, the second face extending between the common edge and a second edge on the opposing side of the second face of the sample; and
milling the second face of the sample to provide a trench in the surface of the second face, the trench extending from a first position on the second face between the common edge and the second edge to a second position adjacent to the common edge; wherein the trench is arranged so as to provide an electron transparent sample layer comprising the surface region of interest.

2 . The method of claim 1 wherein the trench in the second surface comprises a sloping trench with a deepest side adjacent to the common edge between the first and second faces.

3 . The method of claim 2 wherein the sloping trench comprises:
a first internal side parallel with the surface layer of interest, the base of the first internal side defining the deepest point of the trench; and
an angled bottom surface sloping upwards away from the base of the first internal side to meet the surface of the second face.

4 . The method of claim 2 further comprising:
milling the first face of the sample to prepare a polished surface on the surface region of interest prior to milling the sloping trench in the second face of the sample.

5 . The method of claim 1 wherein the trench is arranged such that the electron transparent sample layer is parallel to the first face of the sample.

6 . The method of claim 1 wherein milling the second face of the sample is carried out with a milling beam system and the method further comprises orienting the sample such that the milling beam is parallel with surface layer of interest.

7 . The method of claim 1 wherein the milling is performed using one or more of:
a focussed ion beam; and
a broad ion beam.

8 . The method of claim 1 further comprising:
directing a focussed electron beam through the electron transparent sample layer;
collecting a signal generated by the interaction of the focussed electron beam with the electron transparent sample layer with a detector.

9 . The method of claim 8 wherein the step of collecting a signal comprises:
collecting scattered electrons from the electron transparent sample layer with an electron detector.

10 . The method of claim 8 comprising orienting the sample to:
direct the focussed electron beam at the milled surface of the electron transparent sample layer; and
direct the electron detector at the first face of the sample, opposite to the milled surface.

11 . The method of claim 8 wherein collecting a signal comprises:
collecting X-rays generated in the electron transparent sample layer with an X-ray detector.

12 . The method of claim 11 comprising orienting the sample to:
direct the focussed electron beam at the surface region of interest on the first face of the sample:
direct the X-ray detector at the surface region of interest on the first face of the sample.

13 . The method of claim 1 wherein the first face of the sample comprises a polycrystalline surface layer.

14 . The method of claim 13 wherein the polycrystalline surface layer comprises a thickness of less than 100 nm and/or comprises nanocrystalline structures with dimensions less than 100 nm.

15 . The method of claim 1 further comprising:
preparing the first face of the sample prior to milling to produce a deformation free surface.

16 . The method of claim 1 further comprising:
analysing the surface region of interest on the first face of the sample using a surface characterisation technique.

17 . An apparatus for preparing a sample for analysis, the sample comprising a surface region of interest on a first face of the sample and a second face oriented at an angle to the first face about a common edge between the first and second faces, the second face extending between the common edge and a second edge on the opposing side of the second face of the sample, the apparatus comprising:
a milling beam system arranged to mill the second face of the sample to provide a trench in the surface of the second face, the trench extending from a first position on the second face between the common edge and the second edge to a second position adjacent to the common edge; wherein the trench is arranged so as to provide an electron transparent sample layer comprising the surface region of interest; an electron beam system arranged to direct a focussed electron beam through the electron transparent sample layer; and a detector arranged to collect a signal generated by the interaction of the focussed electron beam with the electron transparent sample layer.

18 . The apparatus of claim 17 comprising an electron detector configured to collect scattered electrons from the electron transparent sample layer to provide an electron intensity image.

19 . The apparatus of claim 18 configured to allow orientation of the sample such that:
the focussed electron beam is directed at the milled surface of the electron transparent surface layer; and
the electron detector is directed at the first face of the sample, opposite to the milled surface.

20 . The apparatus of claim 17 comprising an X-ray detector configured to collect X-rays emitted from the electron transparent surface layer to provide an X-ray energy spectrum.

21 . The apparatus of claim 20 configured to allow orientation of the sample such that:
the focussed electron beam is directed at the surface region of interest on the first face of the sample;
the X-ray detector is directed at the surface region of interest on the first face of the sample.

22 . The apparatus of claim 17 comprising:
an electron detector configured to collect scattered electrons from the electron transparent sample layer to provide an electron intensity image;
a sample holder configured to move the sample between:
a first orientation in which the focussed electron beam is directed at the milled surface of the electron transparent surface layer and the electron detector is directed at the first face of the sample, opposite to the milled surface; and a second orientation in which the focussed electron beam is directed at the surface region of interest on the first face of the sample.

Assignees

• Oxford Instruments Nanotechnology Tools Ltd

Inventors

• Lindsay John
• Trimby Patrick
• Statham Peter
• Schmidt Niels-Henrik
• Thomsen Knud

Classifications

• H01J2237/2802

  Transmission microscopes · CPC title

• H01J2237/31749

  Focused ion beam · CPC title

• H01J2237/31745

  for preparing specimen to be viewed in microscopes or analyzed in microanalysers · CPC title

• G01N2223/102

  beta or electrons · CPC title

• G01N2223/03

  by transmission · CPC title