Method for sample orientation for TEM lamella preparation

Patent metadata

Field	Value
Publication number	US-10504689-B2
Application number	US-201715851632-A
Country	US
Kind code	B2
Filing date	Dec 21, 2017
Priority date	Dec 21, 2017
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

A substrate is alignable for ion beam milling or other inspection or processing by obtaining an electron channeling pattern (ECP) or other electron beam backscatter pattern from the substrate based on electron beam backscatter from the substrate. The ECP is a function of substrate crystal orientation and tilt angles associated with ECP pattern values at or near a maximum, minimum, or midpoint are used to determine substrate tilt. Such tilt is then compensated or eliminated using a tilt stage coupled the substrate, or by adjusting an ion beam axis. In typical examples, circuit substrate “chunks” are aligned for ion beam milling to reveal circuit features for evaluation of circuit processing.

First claim

We claim:

1. A method, comprising:
directing an electron beam to a substrate at a plurality of angles of incidence and detecting portions of the electron beam returned from the substrate;
producing, based on the detected portions of the electron beam and the plurality of angles, an electron backscatter pattern; and
aligning the substrate with respect to an ion beam axis based on the electron backscatter pattern.

2. The method of claim 1 , wherein the substrate is aligned with the ion beam axis by applying a tilt to the substrate.

3. The method of claim 1 , wherein the substrate is aligned with the ion beam axis by adjusting the ion beam axis.

4. The method of claim 1 , wherein the substrate is aligned with the ion beam axis by applying a tilt to the substrate and adjusting the ion beam axis.

5. The method of claim 1 , wherein the substrate is aligned with respect to the ion beam axis so that a substrate surface facing the ion beam axis is perpendicular to the ion beam axis.

6. The method of claim 1 , wherein the substrate is aligned based on a maximum or minimum in the electron channeling pattern.

7. The method of claim 6 , wherein the substrate is secured to a tilt stage and the electron beam is directed to the substrate at the plurality of angles of incidence by varying a substrate tilt with the tilt stage.

8. The method of claim 6 , wherein the electron beam is directed to the substrate at the plurality of angles of incidence by varying an axis of the electron beam.

9. The method of claim 1 , further comprising ion beam milling the aligned substrate.

10. An apparatus, comprising:
a tilt stage;
a specimen mount coupled to the tilt stage and situated to secure a specimen;
an electron beam source situated to direct an electron beam to the specimen;
an electron beam detector situated to receive portions of the electron beam backscattered from the specimen; and
a controller coupled to at least one of the tilt stage or the electron beam source so as to:
vary an angle of incidence of the electron beam with respect to the specimen,
process the detected portions of the electron beam to produce an electron channeling pattern, and
determine a tilt of the specimen based on the electron channeling pattern.

11. The apparatus of claim 10 , further comprising an ion beam source, wherein the controller is further configured to adjust at least one of an ion beam axis and a specimen tilt based on the determined specimen tilt.

12. The apparatus of claim 10 , wherein the ion beam source includes an ion beam deflector, wherein the specimen tilt with respect to the ion beam is adjusted based on a beam deflection of the ion beam.

13. The apparatus of claim 10 , wherein the controller is coupled to the tilt stage to align a substrate surface to be perpendicular to the ion beam axis.

14. The apparatus of claim 10 , wherein the controller is coupled to the tilt stage to vary a specimen tilt about two orthogonal axes and receive signals associated with the corresponding backscattered portions of the electron beam.

15. The apparatus of claim 14 , wherein the ion beam source is a focused ion beam source.

16. The apparatus of claim 10 , wherein the controller determines the tilt of the specimen based on a portion of the electron channeling pattern as a function of a tilt angle about a single axis.

17. The apparatus of claim 10 , wherein the controller determines the tilt of the specimen based on a portion of the electron channeling pattern as a function of a tilt angle about two axes.

18. The apparatus of claim 16 , wherein the controller determines the tilt of the specimen based on a maximum backscattered electron beam intensity in the single axis portion of the electron channeling pattern.

19. One or more computer readable media having defined therein processor-executable instructions for performing a method comprising:
directing an electron beam to a substrate so as to be incident to the substrate at a plurality of plurality of angles of incidence and obtaining associated backscattered electron beam intensities;
processing the backscattered electron beam intensities to produce an electron channeling pattern (ECP); and
based on the ECP, aligning the substrate with respect to an ion beam axis.

20. The one or more computer readable media of claim 19 , wherein the method further comprising controlling an ion beam source to direct an ion beam along the ion beam axis to thin the aligned substrate.

Assignees

• Fei Co

Inventors

• Vystav{Hacek Over (E)}L Tomá{Hacek Over (S)}
• Strako{Hacek Over (S)} Libor
• Prokhodtseva Anna
• Va{Hacek Over (N)}Hara Jaromir
• Stárek Jaroslav

Classifications

• H01J2237/30455

  Correction during exposure · CPC title

• H01J2237/1501

  Beam alignment means or procedures · CPC title

• H01J37/3045 Primary

  Object or beam position registration · 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

  Detectors; Associated components or circuits therefor · CPC title