Microscopy imaging method and system

• US 10,586,680 B2
• Filed: 10/13/2017
• Issued: 03/10/2020
• Est. Priority Date: 05/13/2011
• Status: Active Grant

• Current Assignee: Fibics Incorporated
• Original Assignee: Fibics Incorporated
• Inventors: Phaneuf, Michael William, Lagarec, Ken Guillaume
• Primary Examiner(s): Habib, Irfan
• Application Number:
  US15/783,054
• Publication Number:
  US 20180053627A1
• Time in Patent Office: 879 Days
• CPC Class Codes: G06T 2207/10061 from scanning electron microscope
• CPC Class Codes: H01J 2237/226 Image reconstruction
• CPC Class Codes: H01J 2237/2811 Large objects
• CPC Class Codes: H01J 2237/3174 Etching microareas
• CPC Class Codes: H01J 2237/31749 Focused ion beam
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube
• CPC Class Codes: H01J 37/26 Electron or ion microscopes; Electron or ion diffraction tubes
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence
• CPC Class Codes: H01J 37/3005 Observing the objects or the point of impact on the object
• CPC Class Codes: H01J 37/304 Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
• CPC Class Codes: H01J 37/3045 Object or beam position registration
• CPC Class Codes: H01J 37/3056 for microworking, e. g. etching of gratings or trimming of electrical components

Abstract

Notches or chevrons with known angles relative to each other are formed on a surface of the sample, where each branch of a chevron appears in a cross-sectional face of the sample as a distinct structure. Therefore, when imaging the cross-section face during the cross-sectioning operation, the distance between the identified structures allows unique identification of the position of the cross-section plane along the Z axis. Then a direct measurement of the actual position of each slice can be calculated, allowing for dynamic repositioning to account for drift in the plane of the sample and also dynamic adjustment of the forward advancement rate of the FIB to account for variations in the sample, microscope, microscope environment, etc. that contributes to drift. An additional result of this approach is the ability to dynamically calculate the actual thickness of each acquired slice as it is acquired.

Claims

1. A sample for cross sectioning, comprising:

a substrate containing a feature of interest;

a first protective layer formed over the substrate by deposition using a first charged particle beam from a first gas precursor, the first protective layer having a first property including any one of average atomic number and density; and

a second protective layer formed on the first protective layer by deposition using a second charged particle beam from a second gas precursor different from the first gas precursor, one of the first gas precursor and the second gas precursor including metallic material and the other of the first gas precursor and the second gas precursor including only non-metallic material, the second protective layer having a second property including any one of average atomic number and density, where the average atomic number or density of the first protective layer is different from the average atomic number or density of the second protective layer, and the cross-sectioning of the sample concurrently exposes the substrate, the first protective layer and the second protective layer in a cross-sectioned face.

2. The sample of claim 1, wherein the second protective layer covers the entire first protective layer.

3. The sample of claim 1, wherein the second protective layer covers selected areas of the first protective layer.

4. The sample of claim 1, including at least one fiducial which can be imaged in the cross-sectioned face.

5. The sample of claim 4, wherein the first protective layer is formed using the first gas precursor with an ion beam as the first charged particle beam, and the second protective layer is formed using the second gas precursor with an electron beam as the second charged particle beam.

6. The sample of claim 4, wherein each of the at least one fiducial includes a set of structures.

7. The sample of claim 6, wherein the set of structures includes notches formed in the first protective layer and at least partially filled by the second protective layer.

8. The sample of claim 4, wherein the at least one fiducial is located over the feature of interest in the substrate.

9. The sample of claim 4, wherein the at least one fiducial is located in another cross-sectioned face of the sample.

10. The sample of claim 1, wherein the first charged particle beam and the second charged particle beam are the same.

11. A method for preparing a sample for cross sectioning, comprising:

depositing a first protective layer over a surface of the sample by deposition using a first charged particle beam from a first gas precursor, the first protective layer having a first property including any one of average atomic number and density; and

depositing a second protective layer on the first protective layer by deposition using a second charged particle beam from a second gas precursor different from the first gas precursor, one of the first gas precursor and the second gas precursor including metallic material and the other of the first gas precursor and the second gas precursor including only non-metallic material, the second protective layer having a second property including any one of average atomic number and density, where the average atomic number or density of the first protective layer is different from the average atomic number or density of the second protective layer, and the cross-sectioning of the sample concurrently exposes the substrate, the first protective layer and the second protective layer in a cross-sectioned face.

12. The method of claim 11, further including nanofabricating notches on a surface of the first protective layer prior to depositing the second protective layer that at least partially fills the notches.

13. The method of claim 11, further including nanofabricating at least one fiducial which can be imaged in the cross-sectioned face.

14. The method of claim 13, wherein the first protective layer is formed using the first gas precursor with an ion beam as the first charged particle beam, and the second protective layer is formed using the second gas precursor with an electron beam as the second charged particle beam.

15. The method of claim 11, wherein the first charged particle beam and the second charged particle beam are the same.