Lamella creation method and device using fixed-angle beam and rotating sample stage

Patent metadata

Field	Value
Publication number	US-9733164-B2
Application number	US-201213493735-A
Country	US
Kind code	B2
Filing date	Jun 11, 2012
Priority date	Jun 11, 2012
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A system for creating a substantially planar face in a substrate, the system including directing one or more beams at a first surface of a substrate to remove material from a first location, the beam being offset from a normal to the first surface by a curtaining angle; sweeping the one or more beams in a plane that is perpendicular to the first surface to mill one or more initial cuts, the initial cuts exposing a second surface that is substantially perpendicular to the first surface; rotating the substrate about an axis other than an axis normal to the first beam or parallel to the first beam; directing the first beam at the second surface to remove additional material from the substrate without changing the curtaining angle; and scanning the one or more beams in across the second surface to mill one or more finishing cuts.

First claim

We claim as follows:

1. A method of creating a sample lamella for observation by a transmission electron microscope, the method comprising forming a first substantially planar face of the sample lamella by:
directing a first beam at a first surface of a substrate positioned on a sample stage to remove material from a first location in the substrate, the first beam being offset from a normal to the first surface by a first nonzero curtaining angle;
sweeping the first beam in a plane that is perpendicular to the first surface to mill one or more first initial cuts in the substrate, the first initial cuts exposing a second surface that is tapered but substantially perpendicular to the first surface;
determining a nonzero rotation angle according to the equation:

θ
r

=

sin

-
1

⁡

[

tan
⁡

(

θ
m

)

tan
⁡

(

θ
c

)

]

,

where θ r is the nonzero rotation angle, θ m is a desired milling angle, and θ c is the nonzero curtaining angle;
rotating the substrate without tilting the sample stage with respect to the first beam and through the nonzero rotation angle about an axis other than an axis that is normal to the first beam or parallel to the first beam;
directing the first beam at the second surface to remove additional material from the substrate without changing the first nonzero curtaining angle; and
scanning the first beam in a pattern across the second surface to mill one or more first finishing cuts in the substrate, the one or more first finishing cuts substantially removing the taper of the second surface,
wherein rotating the substrate occurs after milling the one or more first initial cuts and before milling the one or more first finishing cuts.

2. The method of claim 1 , further comprising forming a second substantially planar face of the sample lamella by:
directing a second beam at the first surface of the substrate to remove material from a second location in the substrate, the second beam being offset from a normal to the first surface by a second nonzero curtaining angle, the second location in the substrate disposed sufficiently proximal to the first location in the substrate to form a lamella of a desired thickness;
sweeping the second beam in a plane that is perpendicular to the first surface to mill one or more second initial cuts in the substrate, the second initial cuts exposing a third surface that is tapered but substantially perpendicular to the first surface and substantially parallel to the second surface;
rotating the substrate without tilting the sample stage with respect to the second beam and through a nonzero rotation angle about an axis other than an axis that is normal to the second beam or parallel to the second beam;
directing the second beam at the third surface to remove additional material from the substrate without changing the second nonzero curtaining angle; and
scanning the second beam in a pattern across the third surface to mill one or more second finishing cuts in the substrate, the one or more second finishing cuts substantially removing the taper of the third surface,
wherein rotating the substrate without tilting the sample stage with respect to the second beam and through the nonzero rotation angle about the axis other than the axis that is normal to the second beam or parallel to the second beam occurs after milling the one or more second initial cuts and before the one or more second finishing cuts.

3. The method of claim 1 , further comprising rotating the substrate through a nonzero rotation angle about an axis perpendicular to the first surface.

4. The method of claim 1 , in which the first beam is selected from a group comprising: a focused ion beam, an electron beam, a laser beam, and a water jet from a water jet cutter.

5. The method of claim 2 , in which the second beam is selected from a group comprising: a focused ion beam, an electron beam, a laser beam, and a water jet from a water jet cutter.

6. The method of claim 1 , further comprising imaging the substrate with a scanning electron microscope during milling.

7. The method of claim 1 , in which the first nonzero curtaining angle is the angle between the beam and a normal to the first surface of the substrate.

8. The method of claim 1 , in which the nonzero rotation angle is the angle between a plane including the beam and the axis about which the substrate is rotated and a plane including the second surface of the substrate.

9. The method of claim 2 , in which the directing of said first beam and the directing of said second beam occurs time-sequentially, and wherein said first beam and said second beam are the same beam.

10. The method of claim 2 , in which the directing of said first beam and the directing of said second beam occurs generally concurrently, and wherein said first beam and said second beam are different beams.

11. The method of claim 1 , in which the one or more first finishing cuts removes material that is redeposited on and/or flows onto the second surface during and/or after milling the one or more first initial cuts.

12. The method of claim 1 , in which the one or more first finishing cuts remove material on the second surface that has been made amorphous during milling of the one or more first initial cuts.

13. The method of claim 2 , in which the one or more first finishing cuts and the one or more second finishing cuts substantially remove variations in thickness between the top and the bottom of the lamella.

14. The method of claim 2 , in which the one or more first finishing cuts and the one or more second finishing cuts separate the lamella from the substrate.

15. The method of claim 2 , further comprising directing a first beam and second beam at the substrate to increase throughput, the first beam removing material from the first location in the substrate, and the second beam removing material from the second location in the substrate.

16. The method of claim 2 , in which the method is performed automatically without manual intervention from an operator.

17. The method of claim 15 , further comprising directing the first beam at the second surface to remove additional material from the substrate, and directing the second beam at the third surface to remove additional material from the substrate.

18. A method for creating a substantially planar face in a substrate comprising:
directing a first

Assignees

• Wells Andrew B
• Parker N William
• Chandler Clive D
• Utlaut Mark W
• Fei Co

Inventors

• Wells Andrew B
• Parker N William
• Chandler Clive D
• Utlaut Mark W

Classifications

• H01J2237/31745

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

• G01N1/32 Primary

  Polishing; Etching · CPC title

• H01J37/3056

  for microworking, e. g. etching of gratings or trimming of electrical components · CPC title

• H01J37/3023

  Program control · CPC title