NONDESTRUCTIVE SAMPLE IMAGING

• US 20190311881A1
• Filed: 04/10/2018
• Published: 10/10/2019
• Est. Priority Date: 04/10/2018
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Lavely, Eugene M., Marcinuk, Adam J., Masurkar, Amrita V., Moffitt, Paul R., Richman, Michael S., Takahashi, Jonathan R., Tong, Jonathan K., Willis, Chris L.
• Granted Patent: US 10,468,230 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 2223/072 combination of measurements, 2 kinds of secondary emission
• CPC Class Codes: G01N 2223/076 X-ray fluorescence
• CPC Class Codes: G01N 2223/079 incident electron beam and measuring excited X-rays
• CPC Class Codes: G01N 2223/611 patterned objects; electronic devices
• CPC Class Codes: G01N 23/2251 using incident electron beams, e.g. scanning electron microscopy [SEM]
• CPC Class Codes: H01J 2237/20214 Rotation
• CPC Class Codes: H01J 2237/20221 Translation
• CPC Class Codes: H01J 2237/20278 Motorised movement
• CPC Class Codes: H01J 2237/20292 Means for position and/or orientation registration
• CPC Class Codes: H01J 2237/226 Image reconstruction
• CPC Class Codes: H01J 2237/2445 Photon detectors for X-rays, light, e.g. photomultipliers
• CPC Class Codes: H01J 2237/24475 Scattered electron detectors
• CPC Class Codes: H01J 2237/2448 Secondary particle detectors
• CPC Class Codes: H01J 2237/2505 characterised by their application
• CPC Class Codes: H01J 2237/2611 Stereoscopic measurements and/or imaging
• CPC Class Codes: H01J 2237/2804 Scattered primary beam
• CPC Class Codes: H01J 2237/2806 Secondary charged particle
• CPC Class Codes: H01J 2237/2807 X-rays
• CPC Class Codes: H01J 37/20 Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support introducing the objects H01J37/18
• 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 37/244 : Detectors; Associated components or circuits therefor
• CPC Class Codes: H01J 37/256 : using scanning beams
• CPC Class Codes: H01J 37/28 : with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

A system and method for imaging a sample having a complex structure (such as an integrated circuit) implements two modes of operation utilizing a common electron beam generator that produces an electron beam within a chamber. In the first mode, the electron beam interacts directly with the sample, and backscattered electrons, secondary electrons, and backward propagating fluorescent X-rays are measured. In the second mode, the electron beam interrogates the sample via X-rays generated by the electron beam within a target that is positioned between the electron beam generator and the sample. Transmitted X-rays are measured by a detector within the vacuum chamber. The sample is placed on a movable platform to precisely position the sample with respect to the electron beam. Interferometric and/or capacitive sensors are used to measure the position of the sample and movable platform to provide high accuracy metadata for performing high resolution three-dimensional sample reconstruction.

Claims

1. A system for imaging an integrated circuit (IC) sample, the system comprising:

a sample holder configured to secure the IC sample;

an electron beam generator configured to produce an electron beam within a vacuum chamber;

an electron detector configured to measure electrons that have interacted with the IC sample;

a spectral X-ray detector configured to measure first X-rays resulting from the electron beam interacting with the IC sample and second X-rays transmitted through the IC sample, the second X-rays resulting from the electron beam interacting with a target that is positioned between the electron beam generator and the sample holder; and

a memory device configured to store data generated by the electron detector and the spectral X-ray detector.

2. The system of claim 1, further comprising a processor configured to reconstruct the IC sample using the data stored in the memory device.

3. The system of claim 1, further comprising a processor configured to perform a three-dimensional reconstruction of the IC sample.

4. The system of claim 1, wherein the electron detector comprises at least one of:

a backscattered electron detector configured to measure backscattered electrons resulting from the electron beam interacting with the IC sample; and

a secondary electron detector configured to measure secondary electrons resulting from the electron beam interacting with the IC sample.

5. The system of claim 1, further comprising a movable platform that supports the sample holder.

6. The system of claim 5, wherein the movable platform provides translational and rotational movement of the IC sample.

7. The system of claim 5, further comprising an interferometric tower and at least one interferometric sensor positioned on the movable platform, wherein data collected by the at least one interferometric sensor enables a position estimation of the movable platform to be performed.

8. The system of claim 5, further comprising one or more capacitive sensors on the movable platform, wherein data collected by the one or more capacitive sensors enables a position estimation of the movable platform to be performed.

9. The system of claim 5, further comprising a motor configured to provide translational and rotational movement of the movable platform.

10. The system of claim 1, wherein the spectral X-ray detector comprises a silicon drift detector that positioned adjacent to the electron beam generator.

11. The system of claim 1, wherein the spectral X-ray detector comprises a transition edge sensor camera.

12. The system of claim 1, wherein the electron beam generator that produces the electron beam is a scanning electron microscope.

13. A system for imaging a sample, the system comprising:

a sample holder configured to secure the sample;

an electron beam generator configured to produce an electron beam within a vacuum chamber;

a first spectral X-ray detector, positioned adjacent to the electron beam generator, that is configured to measure first X-rays resulting from the electron beam interacting with the sample;

a second spectral X-ray detector, spaced apart from the electron beam generator and the first spectral X-ray detector, that is configured to measure second X-rays resulting from the electron beam interacting with a target that is positioned between the electron beam generator and the sample holder; and

a processor configured to receive data generated by the first spectral X-ray detector and the second spectral X-ray detector, and further configured to perform a three-dimensional reconstruction of the sample.

14. The system of claim 13, further comprising:

a backscattered electron detector configured to measure backscattered electrons resulting from the electron beam interacting with the sample; and

a secondary electron detector configured to measure secondary electrons resulting from the electron beam interacting with the sample.

15. The system of claim 13, further comprising a movable platform that supports the sample holder, and that provides translational and rotational movement of the sample.

16. The system of claim 15, further comprising:

an optical light source within the vacuum chamber; and

at least one interferometric sensor positioned on the movable platform, wherein data collected by the at least one interferometric sensor enables a position estimation of the movable platform to be performed.

17. The system of claim 16, further comprising one or more capacitive sensors, wherein data collected by the one or more capacitive sensors enables a supplemental position estimation of the movable platform to be performed.

18. The system of claim 15, further comprising a motor configured to provide translational and rotational movement of the movable platform.

19. The system of claim 13, wherein the first spectral X-ray detector and the second spectral X-ray detector each comprise a detector selected from a group consisting of a transition edge sensor camera and a silicon drift detector.

20. A method for imaging a sample using a system having an electron beam generator that produces an electron beam that interacts with the sample, the method comprising:

acquiring first data over a first area of the sample in a first mode of operation by measuring backscattered electrons at two electron detectors, the backscattered electrons resulting from the electron beam interacting with the sample;

acquiring second data over a second area of the in a second mode of operation by photon counting of X-rays with a forward direction of travel that is away from the electron beam generator, wherein the counted X-rays result from the electron beam interacting with a target positioned between the electron beam generator and the sample, and wherein a spectral X-ray detector is used to acquire the second data;

performing an inversion on the first data and the second data;

acquiring one or more model priors for the sample; and

generating a reconstruction of the sample using the one or more model priors and the inverted first and second data.

21. The method of claim 20, wherein generating the reconstruction of the sample comprises generating a three-dimensional reconstruction of the sample.

22. The method of claim 20, further comprising:

comparing the reconstruction of the sample with a trusted standard; and

making a determination that discrepancies exist between the reconstruction of the sample and the trusted standard.

23. The method of claim 20, wherein:

the spectral X-ray detector is selected from a transition edge sensor camera array and a silicon drift detector; and

acquiring the first data in the first mode of operation comprises collecting secondary electrons at a secondary electron detector and collecting the backscattered electrons at the secondary electron detector and a backscattered electron detector.

24. The method of claim 20, wherein:

the spectral X-ray detector comprises a transition edge sensor (TES) camera; and

acquiring the second data in the second mode of operation comprises collecting the X-rays at the TES camera and collecting metadata about the target using the TES camera.

25. The method of claim 20, further comprising :

defining an optimal data acquisition strategy by assessing output from the inversion and identifying regions of the sample where convergence has not been met;

acquiring third data in the second mode of operation using a multiresolution sampling strategy at the spectral X-ray detector, wherein the third data comprises X-ray transmission spectra corresponding to pixels of the spectral X-ray detector; and

performing multiscale inversions on the X-ray transmission spectra.

26. The method of claim 20, wherein:

the sample is an integrated circuit (IC) sample;

generating the reconstruction of the sample comprises generating a three-dimensional reconstruction of the IC sample; and

the method further comprises converting the three-dimensional reconstruction of the IC sample into a GDSII binary format.