Method for determining the shape of a sample tip for atom probe tomography

Patent metadata

Field	Value
Publication number	US-10746759-B2
Application number	US-201916296068-A
Country	US
Kind code	B2
Filing date	Mar 7, 2019
Priority date	Mar 8, 2018
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

The disclosed technology relates to a method and apparatus for correctly positioning a probe suitable for scanning probe microscopy (SPM). The probe is positioned relative to the apex region of a needle-shaped sample, such as a sample for atom probe tomography, in order to perform a SPM acquisition of the apex region to obtain an image of the region. In one aspect, the positioning takes place by an iterative process, starting from a position wherein one side plane of the pyramid-shaped SPM probe interacts with the sample tip. By controlled consecutive scans in two orthogonal directions, the SPM probe tip approaches and finally reaches a position wherein a tip area of the probe interacts with the sample tip's apex region.

First claim

What is claimed is:

1. A method of determining, by applying scanning probe microscopy (SPM), the shape of an apex region of a free-standing tip of a needle-shaped sample, comprising:
providing a SPM apparatus comprising:
a SPM probe mounted on a cantilever, the cantilever having a fixed end and a free end, the probe being mounted on the free end of the cantilever and being shaped as a pyramid having a base, a tip area, and at least three side planes extending between the tip area and the base;
a sample holder;
a drive mechanism for driving a movement of the probe relative to the sample holder; and
detection, control and representation tools for acquiring and representing an image of a surface scanned in two dimensions by the probe;

mounting the sample on the sample holder, the sample tip being pointed toward the cantilever and the probe;
positioning the SPM probe in a first position wherein the tip of the sample interacts with a first point on a first side plane of the pyramid-shaped probe, and wherein in the first position of the SPM probe the first plane is oriented at a non-zero angle relative to the longitudinal axis of the sample;
from the first position, performing a scan movement of the probe in a first direction transverse to the first plane, thereby generating an increase of the distance between the base of the probe and the sample tip, while maintaining the interaction between the probe and the sample tip;
detecting an instance at which the sample tip crosses a rib between the first plane of the pyramid-shaped SPM probe and a plane adjacent thereto;
stopping the scan in the first direction;
initiating a scan in a second direction transversal to the first direction, thereby bringing the sample tip back into contact with the first plane;
continuing the second scan to reach a position wherein the sample tip interacts with a second point on the first plane;
from this second point, repeating the above first and second scan one or more times, until reaching a position wherein the tip area of the probe interacts with the apex region of the sample tip; and
from this position, performing a SPM acquisition scan, thereby obtaining an image of the shape of the apex region.

2. The method according to claim 1 , wherein the positioning the SPM probe in the first position is performed by:
aligning the longitudinal axis of the sample with the footprint of the first plane, with reference to the direction of the longitudinal axis; and
decreasing the distance between the base of the pyramid-shaped probe and the sample until the sample tip interacts with the first plane.

3. The method according to claim 1 , wherein the first side plane faces the fixed end of the cantilever.

4. The method according to claim 1 , wherein the inclination angle of the first plane relative to the cantilever is larger than the inclination angle of the remaining side planes.

5. The method according to claim 1 , wherein the probe is shaped as a pyramid with three side planes.

6. The method according to claim 1 , wherein the sample tip reaches the second point on the first plane by:
executing the scan in the second direction until the sample tip crosses a second rib between the first plane and a second plane adjacent thereto; and
reversing the scan in the second direction until the sample tip reaches the second point on the first plane.

7. The method according to claim 1 , wherein the SPM apparatus is an apparatus for atomic force microscopy.

8. The method according to claim 1 , wherein the sample is a sample for atomic force microscopy.

9. The SPM apparatus for performing the method according to claim 1 , wherein the SPM apparatus is configured to automatically perform the method in a consecutive order, starting from the positioning the SPM probe at the first position, until reaching a point on the apex region of the sample tip.

10. The method according to claim 2 , wherein the first side plane faces the fixed end of the cantilever.

11. The method according to claim 2 , wherein the inclination angle of the first plane relative to the cantilever is larger than the inclination angle of the remaining side planes.

12. The method according to claim 3 , wherein the inclination angle of the first plane relative to the cantilever is larger than the inclination angle of the remaining side planes.

13. The method according to claim 2 , wherein the probe is shaped as a pyramid with three side planes.

14. The method according to claim 3 , wherein the probe is shaped as a pyramid with three side planes.

15. The method according to claim 2 , wherein the sample tip reaches the second point on the first plane by:
executing the scan in the second direction until the sample tip crosses a second rib between the first plane and a second plane adjacent thereto; and
reversing the scan in the second direction until the sample tip reaches the second point on the first plane.

16. The method according to claim 3 , wherein the sample tip reaches the second point on the first plane by:
executing the scan in the second direction until the sample tip crosses a second rib between the first plane and a second plane adjacent thereto; and
reversing the scan in the second direction until the sample tip reaches the second point on the first plane.

17. The method according to claim 2 , wherein the SPM apparatus is an apparatus for atomic force microscopy.

18. The method according to claim 3 , wherein the SPM apparatus is an apparatus for atomic force microscopy.

19. The method according to claim 2 , wherein the sample is a sample for atom force microscopy.

20. The SPM apparatus for performing the method according to claim 2 , wherein the SPM apparatus is configured to automatically perform the method in a consecutive order, starting from the positioning the SPM probe at the first position, until reaching a point on the apex region of the sample tip.

Assignees

• Imec Vzw

Inventors

• Paredis Kristof
• Fleischmann Claudia
• Vandervorst Wilfried

Classifications

• H01J2237/2818

  Scanning tunnelling microscopes · CPC title

• H01J37/285

  Emission microscopes, e.g. field-emission microscopes · CPC title

• H01J2237/282

  Determination of microscope properties · CPC title

• G01Q10/06 Primary

  Circuits or algorithms therefor · CPC title

• G01Q30/20

  Sample handling devices or methods · CPC title