Mathematical image assembly in a scanning-type microscope

• US 9,620,330 B2
• Filed: 06/18/2015
• Issued: 04/11/2017
• Est. Priority Date: 06/18/2014
• Status: Active Grant

• Current Assignee: FEI Company (Thermo Fisher Scientific Incorporated)
• Original Assignee: FEI Company (Thermo Fisher Scientific Incorporated)
• Inventors: Poto{hacek over (c)}ek, Pavel, Kooijman, Cornelis Sander, Slingerland, Hendrik Nicolaas, van Veen, Gerard Nicolaas Anne, Boughorbel, Faysal
• Primary Examiner(s): STOFFA, WYATT A
• Application Number:
  US14/743,780
• Publication Number:
  US 20150371815A1
• Time in Patent Office: 663 Days
• CPC Class Codes: G02B 21/0024 Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
• CPC Class Codes: G02B 21/0048 scanning mirrors, e.g. rotating or galvanomirrors, MEMS mirrors
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control
• CPC Class Codes: H01J 2237/226 Image reconstruction
• CPC Class Codes: H01J 2237/28 Scanning microscopes
• CPC Class Codes: H01J 2237/2811 Large objects
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube image data processing or generation, in general G06T
• CPC Class Codes: H01J 37/226 Optical arrangements for illuminating the object; optical arrangements for collecting light from the object
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

A method and apparatus for imaging a specimen using a scanning-type microscope, by irradiating a specimen with a beam of radiation using a scanning motion, and detecting a flux of radiation emanating from the specimen in response to the irradiation, in the first sampling session {S₁} of a set {S_n}, gathering data from a first collection of sparsely distributed sampling points {P₁} of set {P_n}. A mathematical registration correction is made to compensate for drift mismatches between different members of the set {P_n}, and an image of the specimen is assembled using the set {P_n} as input to an integrative mathematical reconstruction procedure.

Claims

1. A method of accumulating an image of a specimen using a scanning-type microscope, comprising the following steps:

providing a beam of radiation that is directed from a source through an illuminator so as to irradiate the specimen;

providing a detector for detecting a flux of radiation emanating from the specimen in response to said irradiation;

causing said beam to undergo scanning motion relative to a surface of the specimen, and recording an output of the detector as a function of scan position,

in a first sampling session S₁, gathering detector data from a first collection P₁ of sampling points distributed sparsely across the specimen, the collection P₁ comprising fewer than all the sampling points in a sampling grid;

repeating this the procedure of gathering detector data from subsequent collections of sampling points so as to accumulate a set {P_n} of such collections, gathered during an associated set {S_n} of sampling sessions, each set with a cardinality N>

1;

assembling an image of the specimen by using the set {P_n} as input to an integrative mathematical reconstruction procedure,

wherein, as part of said assembly process, a mathematical registration correction is made to compensate for drift mismatches between different members of the set {P_n}.

2. A method according to claim 1, wherein:

each member P_n of the set {P_n} is used to mathematically reconstruct a corresponding sub-image I_n;

said mathematical registration correction is used to align the members of the sub-image set {I_n};

a combined image is mathematically composed from said aligned sub-image set.

3. A method according to claim 1, wherein:

prior to reconstruction, said mathematical registration correction is used to align the members of the collection set {P_n};

a composite image is mathematically reconstructed from said aligned collection set.

4. A method according to claim 1, wherein different members of the set {P_n} have different associated sparse distributions of sampling points across the specimen.

5. A method according claim 1, wherein at least one member P_n of the set {P_n} comprises a sparse distribution of sampling points that is not arranged on a regular grid.

6. A method according to claim 1, wherein correction is made for lower-order drift mismatches selected from the group consisting of displacement, rotation, and combinations hereof.

7. A method according to claim 1, wherein correction is made for higher-order drift mismatches selected from the group consisting of skew, shear, scaling, and combinations hereof.

8. A method according to claim 1, wherein the positions of sampling points in at least one given collection P_n are at least partially elected on the basis of an analysis of at least some scan information obtained from at least one previous sampling sessions S_n.

9. A method according to claim 8, wherein;

in a given sampling session S_n, sampling points in the associated collection P_n. are visited sequentially while scanning out a line-by-line pattern on the specimen;

along a given line L_j in said line-by-line pattern, the positions of sampling points are elected using detection results obtained in scanning a previous line L_i in said line-by-line pattern.

10. A method according to claim 1, wherein, in at least one sampling session S_n, at least some of the sampling points in the associated collection P_n are located below said surface of the specimen.

11. A method according to claim 1, wherein the set {P_n} is accumulated using a plurality of beams of radiation.

12. A method according to claim 1, wherein said radiation comprises charged particles and said microscope comprises a charged-particle microscope.

13. A method according to claim 12, wherein said charged-particle microscope is selected from the group consisting of a Scanning Electron Microscope and a Scanning Transmission Electron Microscope.

14. A method according to claim 1, wherein said radiation comprises photons and said microscope comprises a confocal microscope.

15. A scanning-type microscope, comprising:

a specimen holder, for holding a specimen;

a source, for producing a beam of radiation;

an illuminator, for directing said beam so as to irradiate said specimen;

a detector, for detecting a flux of radiation emanating from the specimen in response to said irradiation;

beam deflectors, for causing said beam to undergo scanning motion relative to a surface of the specimen;

a controller, for recording an output of said detector as a function of scan position, wherein the controller stores instructions which can be invoked to execute the following steps;

in a first sampling session S₁, gathering detector data from a first collection P₁ of sampling points distributed sparsely across the specimen, the collection P₁ comprising fewer than all the sampling points in a sampling grid;

repeating the procedure of gathering detector data from subsequent collections of sampling points so as to accumulate a set {P_n} of such collections, gathered during an associated set {S_n} of sampling sessions, each set with a cardinality N>

1;

assembling an image of the specimen by using the set {P_n} as input to an integrative mathematical reconstruction procedure; and

as part of said assembly process, making a mathematical registration correction to compensate for drift mismatches between different members of the set {P_n}.

16. The scanning-type microscope of claim 15 wherein the stored instructions include instructions for correction of lower-order drift mismatches selected from the group consisting of displacement, rotation, and combinations hereof.

17. The scanning-type microscope of claim 15 wherein the stored instructions include instructions for correction of higher-order drift mismatches selected from the group consisting of skew, shear, scaling, and combinations hereof.

18. The scanning-type microscope of claim 15, wherein said radiation comprises charged particles and said microscope comprises a charged-particle microscope.

19. The scanning-type microscope of claim 15, wherein said radiation comprises photons and said microscope comprises a confocal microscope.

20. The scanning-type microscope of claim 15 wherein the stored instructions include instructions for, in at least one sampling session S_n, at least some of the sampling points in the associated collection P_n are located below said surface of the specimen.