Method of examining a sample in a charged-particle microscope

Patent metadata

Field	Value
Publication number	US-9312098-B2
Application number	US-201514629387-A
Country	US
Kind code	B2
Filing date	Feb 23, 2015
Priority date	Feb 24, 2014
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

Examining a sample in a charged-particle microscope of a scanning transmission type includes:
Providing a beam of charged particles that is directed from a source through an illuminator so as to irradiate the sample; Providing a detector for detecting a flux of charged particles traversing the sample; Causing said beam to scan across a surface of the sample, and recording an output of the detector as a function of scan position, resulting in accumulation of a charged-particle image of the sample, Embodying the detector to comprise a plurality of detection segments; Combining signals from different segments of the detector so as to produce a vector output from the detector at each scan position, and compiling this data to yield a vector field; and Mathematically processing said vector field by subjecting it to a two-dimensional integration operation, thereby producing an integrated vector field image.

First claim

We claim as follows:

1. A method of examining a sample in a charged-particle microscope of a scanning transmission type, comprising:
providing a beam of charged particles that is directed from a source through an illuminator so as to irradiate the sample;
providing a detector for detecting a flux of charged particles traversing the sample;
causing said beam to scan across a surface of the sample, and recording an output of the detector as a function of scan position, resulting in accumulation of a charged-particle image of the sample,

including:
embodying the detector to comprise a plurality of detection segments;
combining signals from different segments of the detector so as to produce a vector output from the detector at each scan position, and compiling this data to yield a vector field;
mathematically processing said vector field by subjecting it to a two-dimensional integration operation, thereby producing an integrated vector field image.

2. A method according to claim 1 , wherein:
said detector is embodied to comprise four quadrants;
said vector output is produced by calculating difference signals between complementary pairs of quadrants.

3. A method according claim 2 , wherein said integrated vector field image is post-processed by subjecting it to at least one operation selected from the group comprising:
filtering;
opening Angle Correction;
deconvolution correction,
and combinations hereof.

4. A method according to claim 2 , wherein the integrated vector field image is further manipulated by subjecting it to a Laplacian operation.

5. A method according to claim 2 , wherein the integrated vector field image is further manipulated by subjecting it to a single differentiation operation.

6. A method according to claim 2 , wherein said mathematical processing of vector field {tilde over (E)} comprises finding an estimate {circumflex over (φ)} of a potential φ as a fitting problem involving functional minimization of an objective function J defined as:
J (φ)=∫∫∥(−∇φ)− {tilde over (E)}∥ 2 dxdy=∫∫∥∇φ+{tilde over (E)}∥ 2 dxdy

for Cartesian coordinates (x, y) along a scan path of said beam on the sample.

7. A method according to claim 1 , wherein:
said detector is embodied as a pixelated detector comprising an array of pixels;
said vector output is produced using a procedure comprising the following steps:
comparing pixel values to determine a location for a barycenter of said flux on the detector;
expressing a coordinate position of said barycenter on the detector.

8. A method according to claim 7 , wherein the charged particles are electrons.

9. A method according claim 7 , wherein said integrated vector field image is post-processed by subjecting it to at least one operation selected from the group comprising:
filtering;
opening Angle Correction;
deconvolution correction,

and combinations hereof.

10. A method according to claim 7 , wherein the integrated vector field image is further manipulated by subjecting it to a Laplacian operation.

11. A method according to claim 7 , wherein the integrated vector field image is further manipulated by subjecting it to a single differentiation operation.

12. A method according to claim 7 , wherein said mathematical processing of vector field {tilde over (E)} comprises finding an estimate {circumflex over (φ)} of a potential φ as a fitting problem involving functional minimization of an objective function J defined as:
J (φ)=∫∫∥(−∇φ)− {tilde over (E)}∥ 2 dxdy=∫∫∥∇φ+{tilde over (E)}∥ 2 dxdy

for Cartesian coordinates (x, y) along a scan path of said beam on the sample.

13. A method according to claim 1 , wherein the employed detector is a Position-Sensitive Detector.

14. A method according to claim 1 , wherein said integrated vector field image is post-processed by subjecting it to at least one operation selected from the group comprising:
filtering;
opening Angle Correction;
deconvolution correction,

and combinations hereof.

15. A method according to claim 1 , wherein the integrated vector field image is further manipulated by subjecting it to a Laplacian operation.

16. A method according to claim 1 , wherein the integrated vector field image is further manipulated by subjecting it to a single differentiation operation.

17. A method according to claim 1 , wherein said mathematical processing of vector field {tilde over (E)} comprises finding an estimate {circumflex over (φ)} of a potential φ as a fitting problem involving functional minimization of an objective function J defined as:
J (φ)=∫∫∥(−∇φ)− {tilde over (E)}∥ 2 dxdy=∫∫∥∇φ+{tilde over (E)}∥ 2 dxdy

for Cartesian coordinates (x, y) along a scan path of said beam on the sample.

18. A method according to claim 17 , wherein said functional minimization is achieved with the aid of at least one technique selected from the group comprising:
a Poisson solver technique;
a Basis Function reconstruction;
residual minimization using an Lp norm-based objective function;
residual minimization using an M-estimator;
anisotropic weighting;
application of a Diffusion tensor;
application of a regularization function,

and combinations hereof.

19. A method according to claim 1 , wherein the charged particles are electrons.

20. A charged-particle microscope of a scanning transmission type, comprising:
a sample holder, for holding a sample;
a source, for producing a beam of charged particles;
an illuminator, for directing said beam so as to irradiate said sample;
a detector, for detecting a flux of charged particles traversing the sample in response to said irradiation;
scanning means, for causing said beam to make a scanning motion relative to a surface of the sample;
a controller, for recording an output of said detector as a function of scan position, resulting in accumulation of a charged-particle image of the sample,

characterized in that:
said detector comprises a plurality of detection segments;
said controller is embodied to perform the following additional actions:
combine signals from different segments of the detector so as to produce a vector output from the detector at each scan position, and compile this data to yield a vector field;
mathematically process said vector field by subjecting it to a two-dimensional integration operation, thereby producing an integrated vector field image.

Assignees

• Fei Co

Inventors

• Lazic Ivan
• Bosch Eric Gerardus Theodoor
• Boughorbel Faysal
• Buijsse Bart
• Sader Kasim
• Lazar Sorin

Classifications

• H01J37/28

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title

• H01J2237/2802

  Transmission microscopes · CPC title

• H01J37/265

  Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination · CPC title

• H01J37/244 Primary

  Detectors; Associated components or circuits therefor · CPC title

• H01J2237/2446

  Position sensitive detectors · CPC title