Ion implantation to alter etch rate

Patent metadata

Field	Value
Publication number	US-10325754-B2
Application number	US-201414759158-A
Country	US
Kind code	B2
Filing date	Jan 10, 2014
Priority date	Jan 11, 2013
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

Implanting a material in a pattern hardens the material in the pattern for subsequent etching. When the region is etched, by ion beam sputtering, chemically enhanced charged particle beam etching, or chemical etching, a thicker structure remains because of the reduced etch rate of the hardened pattern. The invention is particularly useful for the preparation of thin lamella for viewing on a transmission electron microscope.

First claim

We claim as follow:

1. A method for preparing a thin, reinforced lamellar structure using a charged particle beam system, comprising:
forming a lamella from a sample material;
applying to the lamella a hardening material in a pattern corresponding to a reinforcing structure by directing a focused beam of ions onto a face of the lamella to implant ions into the face according to the pattern; and
thinning the lamella by milling, wherein a region of the lamella corresponding to the reinforcing structure is milled at a slower rate than a region of the lamella without the hardening material, leaving the reinforcing structure where the hardening material was applied to mechanically strengthen the lamella.

2. The method of claim 1 in which:
the focused beam of ions is a first beam;
thinning the lamella comprises milling the lamella with a second beam; and
the second beam mills a region of the lamella implanted with ions at a rate that is at least 20% lower than a rate at which the second beam mills a region of the lamella not implanted with ions.

3. The method of claim 1 in which directing a focused ion beam toward the lamella to implant ions includes directing Be + , Ga + , Xe + , Ar + , O + , In + , Si + , Kr + , or Bi + ions.

4. The method of claim 3 in which directing a focused ion beam toward the lamella to implant ions includes directing a beam of beryllium ions towards the lamella.

5. The method of claim 1 in which directing a focused ion beam toward the lamella to implant ions into the lamella includes providing an ion dose of between 0.1-1.0 nC/μm 2 .

6. The method of claim 1 in which applying a hardening material and milling the lamella are performed by a single focusing column in the charged particle beam system.

7. The method of claim 6 in which the single focusing column comprises of a liquid metal alloy source or a plasma ion source and a mass filter to select the ions.

8. The method of claim 1 in which the lamella has a final thickness of less than 20 nm.

9. The method of claim 1 , wherein thinning the lamella by milling comprises:
milling the lamella with a focused ion beam comprising ions different than the ions implanted into the lamella; or
milling the lamella with a focused ion beam having a beam energy different than the focused beam of ions used for implanting ions into the lamella.

10. The method of claim 1 wherein applying to the lamella a hardening material by directing a focused beam of ions toward the lamella to implant ions into the lamella comprises applying a hardening material without beam-induced deposition.

11. The method of claim 1 wherein applying to the lamella a hardening material in a pattern corresponding to a reinforcing structure by directing a focused beam of ions toward the lamella to implant ions into the lamella comprises implanting ions into an implanted area and wherein thinning the lamella by milling comprises milling a milled area and wherein the milled area is larger than the implanted area.

12. The method of claim 1 wherein the reinforcing structure reduces bending of the lamella.

13. A method, comprising:
forming a lamella from a bulk sample;
directing a first focused ion beam into a face of the lamella such that ions are implanted into the face in a pattern, the ions implanted being of a species that hardens the material of the lamella where implanted; and
thinning the lamella using a second focused ion beam, wherein the second focused ion beam thins a region of the lamella implanted with the ions at a slower rate than a region of the lamella not implanted with the ions, thereby exposing a raised structure that corresponds to the pattern and mechanically reinforces the lamella.

14. The method of claim 13 , further comprising observing a feature in the lamella using a transmission electron microscope.

Assignees

• Fei Co

Inventors

• Foord David
• Rue Chad

Classifications

• G01N1/32

  Polishing; Etching · CPC title

• H01J37/3171

  for ion implantation · CPC title

• H01J2237/31749

  Focused ion beam · CPC title

• H01J37/3056 Primary

  for microworking, e. g. etching of gratings or trimming of electrical components · CPC title

• Y10T428/24479

  including variation in thickness · CPC title