# US 2023/0273136 A1 · Sample preparation method and apparatus

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- Number: US 2023/0273136 A1
- Document ID: US20230273136A1
- Status: Published application
- Kind: A1
- Application number: 18/023,692
- Filed: 2021-08-26
- Published: 2023-08-31
- Earliest claimed: 2020-08-28
- Assignees: Oxford Instruments Nanotechnology Tools Limited
- Applicants: Oxford Instruments Nanotechnology Tools Limited
- Inventors: John Lindsay; Patrick Trimby; Peter Statham; Niels-Henrik Schmidt; Knud Thomsen
- Web page: https://patentgrep.com/patent/US20230273136A1

## CPC

- G01N 1/28: Preparing specimens for investigation {including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q}(mounting specimens on microscopic slides G02B21/34; means for supporting the objects or the materials to be analysed in electron microscopes H01J37/20 {; laboratory gas handling apparatus B01L5/00})
- G01N 1/32: Polishing; Etching
- G01N 1/286: {involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising (microtomes G01N1/06; pulverising in general B02C; mixing in general B01F)}
- G01N 2223/03: by transmission
- G01N 2223/102: beta or electrons
- H01J 2237/2802: Transmission microscopes
- H01J 2237/31745: for preparing specimen to be viewed in microscopes or analyzed in microanalysers
- H01J 2237/31749: Focused ion beam
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 2)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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.

### Claim 8 (depends on 7)

The method of claim 7 wherein the step of collecting a signal comprises:
collecting scattered electrons from the electron transparent sample layer with an electron detector.

### Claim 9 (depends on 7)

The method of claims 7 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.

### Claim 10 (depends on 7)

The method of claim 7 wherein collecting a signal comprises:
collecting X-rays generated in the electron transparent sample layer with an X-ray detector.

### Claim 11 (depends on 10)

The method of claim 10 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.

### Claim 12 (depends on 1)

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

### Claim 13 (depends on 12)

The method of claim 12 wherein the polycrystalline surface layer comprises a thickness of less than 100 nm and/or comprises nanocrystalline structures with dimensions less than 100 nm

### Claim 14 (depends on 1)

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

### Claim 15 (depends on 1)

The method of claim 1 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.

### Claim 16 (depends on 1)

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.

### Claim 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.

### Claim 18 (depends on 17)

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.

### Claim 19 (depends on 18)

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.

### Claim 20 (depends on 18)

The apparatus of claim 18 further comprising:
a processing unit configured to analyse the electron intensity image to identify one or more Kikuchi bands within the signal.

### Claim 21 (depends on 20)

The apparatus of claim 20 wherein the processing unit is configured to:
measure the distance of the identified Kikuchi band to the pattern centre; apply a correction to the determined width of the Kikuchi band to mitigate the effect of gnomonic distortion based on the measured distance.

### Claim 22 (depends on 20)

The apparatus of claim 20 wherein the processing unit is configured to:
calculate a minimum and/or maximum Kikuchi band width based on the lattice spacings of one or more candidate phases;
disregard the identified Kikuchi band if the determined width is below the calculated minimum Kikuchi band width and/or above the maximum Kikuchi band width.

### Claim 23 (depends on 17)

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.

### Claim 24 (depends on 23)

The apparatus of claim 23 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.

### Claim 25 (depends on 17)

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;
an X-ray detector configured to collect X-rays emitted from the electron transparent surface layer to provide an X-ray energy spectrum; and
a sample holder configured to move the sample relative to the electron beam system, electron imaging detector and X-ray detector 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 and the X-ray detector are directed at the surface region of interest on the first face of the sample.

### Claim 26 (depends on 1, 17)

The apparatus of claim 17 further comprising:
a memory holding computer-readable instructions, that when executed, cause the apparatus to perform the method steps of claim 1.