CHARGED-PARTICLE MICROSCOPE WITH IN SITU DEPOSITION FUNCTIONALITY

Abstract

A charged-particle microscope, comprising a vacuum chamber in which are provided: A specimen holder for holding a specimen in an irradiation position; A particle-optical column, for producing a charged particle beam and directing it so as to irradiate the specimen; A detector, for detecting a flux of radiation emanating from the specimen in response to irradiation by said beam,
wherein: Said vacuum chamber comprises an in situ magnetron sputter deposition module, comprising a magnetron sputter source for producing a vapor stream of target material; A stage is configured to move a sample comprising at least part of said specimen between said irradiation position and a separate deposition position at said deposition module; Said deposition module is configured to deposit a layer of said target material onto said sample when held at said deposition position.

Claims

1. A charged-particle microscope, comprising a vacuum chamber in which are provided: a specimen holder for holding a specimen in an irradiation position; a particle-optical column, for producing a charged particle beam and directing it so as to irradiate the specimen; and a detector, for detecting a flux of radiation emanating from the specimen in response to irradiation by said beam, wherein: said vacuum chamber comprises an in situ magnetron sputter deposition module, comprising a magnetron sputter source for producing a vapor stream of target material; a stage is configured to move a sample comprising at least part of said specimen between said irradiation position and a separate deposition position at said deposition module; and said deposition module is configured to deposit a layer of said target material onto said sample when held at said deposition position.

2. A microscope according to claim 1, wherein said deposition module comprises a limiting aperture, disposed between said sputter source and said deposition position, for limiting a footprint of said vapor stream presented at said deposition position.

3. A microscope according to claim 1, wherein said deposition module comprises a skirt around a perimeter of said deposition position, for curtailing migration of said vapor stream into said vacuum chamber.

4. A microscope according to claim 1, wherein said deposition module comprises a tubular member configured such that: sputter source is disposed proximal a first end of said tubular member; and deposition position is disposed proximal a second, opposite end of said tubular member.

5. A microscope according to claim 1, which is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen.

6. A microscope according to claim 1, wherein said deposition module is configured to be retractable when not in use.

7. A method of using a charged-particle microscope, comprising a vacuum chamber in which are provided: a specimen holder for holding a specimen in an irradiation position; a particle-optical column, for producing a charged-particle beam and directing it so as to irradiate the specimen; and a detector, for detecting a flux of radiation emanating from the specimen in response to irradiation by said beam, in which method the charged-particle beam is used to irradiate the specimen at said irradiation position, wherein the method comprises: providing in said vacuum chamber an in situ magnetron sputter deposition module, comprising a magnetron sputter source for producing a vapor stream of target material; using a stage to move a sample comprising at least part of said specimen from said irradiation position to a separate deposition position at said deposition module; and using said deposition module to deposit a layer of said target material onto said sample.

8. A method according to claim 7 wherein, after said target material has been deposited on said sample, said stage is used to move the sample back to said irradiation position, for inspection of the sample.

9. A method according to claim 7, wherein the microscope is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen, which method comprises the following actions performed at said irradiation position: using said electron beam to form an image of said specimen; and using said ion beam to cut a sample out of said specimen, which sample is subsequently moved by said stage to said deposition position.

10. A method according to claim 7, wherein a sputter gas is administered specifically to the vicinity of the sputter source in the deposition module.

11. A method according to claim 7, wherein a sputter gas is administered generically to an interior of the vacuum chamber.

12. A microscope according to claim 2, wherein said deposition module comprises a skirt around a perimeter of said deposition position, for curtailing migration of said vapor stream into said vacuum chamber.

13. A microscope according to claim 2, wherein said deposition module comprises a tubular member configured such that: said sputter source is disposed proximal a first end of said tubular member; said deposition position is disposed proximal a second, opposite end of said tubular member.

14. A microscope according to claim 3, wherein said deposition module comprises a tubular member configured such that: said sputter source is disposed proximal a first end of said tubular member; and said deposition position is disposed proximal a second, opposite end of said tubular member.

15. A microscope according to claim 2, which is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen.

16. A microscope according to claim 3, which is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen.

17. A microscope according to claim 4, which is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen.

18. A method according to claim 8, wherein the microscope is a dual-beam microscope comprising: an electron-optical column, for producing an electron beam and directing it so as to irradiate the specimen; and an ion-optical column, for producing an ion beam and directing it so as to irradiate the specimen, which method comprises the following actions performed at said irradiation position: said electron beam to form an image of said specimen; and said ion beam to cut a sample out of said specimen, which sample is subsequently moved by said stage to said deposition position.

19. A method according to claim 8, wherein a sputter gas is administered specifically to the vicinity of the sputter source in the deposition module.

20. A method of depositing material within a charged particle microscope, comprising: moving a sample from an irradiation position to a separate deposition position using a stage, the deposition position being located proximal to a deposition module including an in-situ magnetron sputter source for producing a vapor stream of target material, both positions being within a vacuum chamber of the charged particle microscope; and producing from the deposition module a vapor stream of target material from the magnetron sputter source; and directing the vapor stream of target material toward the sample to deposit a layer of the target material onto the sample.

Description

[0051] The invention will now be elucidated in more detail on the basis of exemplary embodiments and the accompanying schematic drawings, in which:

[0052] FIG. 1 renders a longitudinal cross-sectional view of an embodiment of a CPM in which the present invention is implemented.

[0053] FIG. 2 renders a longitudinal cross-sectional view of an alternative CPM in which the present invention is implemented.

[0054] In the Figures, where pertinent, corresponding parts may be indicated using corresponding reference symbols.

EMBODIMENT 1

[0055] FIG. 1 is a highly schematic depiction of an embodiment of a CPM in which the present invention is implemented; more specifically, it shows an embodiment of a microscope M, which, in this case, is a SEM (though, in the context of the current invention, it could just as validly be a (S)TEM, or an ion-based microscope, for example). The microscope M comprises a particle-optical column (illuminator) 1, which produces a beam 3 of input charged particles (in this case, an electron beam) that propagates along a particle-optical axis 3′. The column 1 is mounted on a vacuum chamber 5, which comprises a specimen holder 7 and associated actuator(s) 7′ for holding/positioning a specimen S. The vacuum chamber 5 is evacuated using vacuum pumps (not depicted). With the aid of voltage supply 17, the specimen holder 7, or at least the specimen S, may, if desired, be biased (floated) to an electrical potential with respect to ground.

[0056] The column 1 (in the present case) comprises an electron source 9 (such as a Schottky gun, for example), lenses 11, 13 to focus the electron beam 3 onto the specimen S, and a deflection unit 15 (to perform beam steering/scanning of the beam 3). The microscope M further comprises a controller/computer processing apparatus 25 for controlling inter alia the deflection unit 15, lenses 11, 13 and detectors 19, 21, and displaying information gathered from the detectors 19, 21 on a display unit 27.

[0057] The detectors 19, 21 are chosen from a variety of possible detector types that can be used to examine different types of emergent radiation E emanating from the specimen S in response to irradiation by the input beam 3. In the apparatus depicted here, the following (non-limiting) detector choices have been made: [0058] Detector 19 is a solid state detector (such as a photodiode) that is used to detect cathodoluminescence emanating from the specimen S. It could alternatively be an X-ray detector, such as Silicon Drift Detector (SDD) or Silicon Lithium (Si(Li)) detector, for example. [0059] Detector 21 is a segmented silicon electron detector, comprising a plurality of independent detection segments (e.g. quadrants) disposed in annular configuration about a central aperture 23 (allowing passage of the primary beam 3). Such a detector can, for example, be used to investigate the angular dependence of a flux of emergent backscattered electrons emanating from the specimen S. It will typically be biased to a positive potential, so as to attract electrons emitted from the specimen S.
The skilled artisan will understand that many different types of detector can be chosen in a set-up such as that depicted.

[0060] By scanning the input beam 3 over the specimen S, emergent radiation—comprising, for example, X-rays, infrared/visible/ultraviolet light, secondary electrons (SEs) and/or backscattered electrons (BSEs)—emanates from the specimen S. Since such emergent radiation is position-sensitive (due to said scanning motion), the information obtained from the detectors 19, 21 will also be position-dependent. This fact allows (for instance) the signal from detector 21 to be used to produce a BSE image of (part of) the specimen S, which image is basically a map of said signal as a function of scan-path position on the specimen S.

[0061] The signals from the detectors 19, 21 pass along control lines (buses) 25′, are processed by the controller 25, and displayed on display unit 27. Such processing may include operations such as combining, integrating, subtracting, false colouring, edge enhancing, and other processing known to the skilled artisan. In addition, automated recognition processes (e.g. as used for particle analysis) may be included in such processing.

[0062] It should be noted that many refinements and alternatives of such a set-up will be known to the skilled artisan, including, but not limited to: [0063] The use of dual beams—for example an electron beam 3 for imaging and an ion beam 33 for machining (or, in some cases, imaging) the specimen S—see FIG. 2, for example; [0064] The use of a controlled environment at the specimen S—for example, maintaining a pressure of several mbar (as used in a so-called Environmental SEM) or by admitting gases, such as etching or precursor gases, etc.

[0065] In the specific context of the current invention, the vacuum chamber 5 comprises an in situ magnetron sputter deposition module D, which is here located to the right side of the axis 3′ (but could also be located elsewhere within the chamber 5). This module D comprises a magnetron sputter source D1 for producing a vapor stream of target material, and, in the present embodiment, a limiting aperture D2 is located in the path of this stream, so as to perform appropriate shaping/sizing of the cross-section/footprint of this stream. As here depicted, the source D1 is located at one end (upper end) of a tubular member D3, whose other end (lower end) is flared so as to form a skirt, beneath/within which a sample can be held during a visit to module D. To this end, a stage (in the present case, items 7′/7) is configured to move (substantially in an XY plane) a sample—comprising at least part of specimen S—between an irradiation position Pi beneath column 1 (along axis 3′) and a separate(d) deposition position Pd beneath deposition module D. While the sample is held at this deposition position Pd, the module D can be invoked to deposit a layer of the target material (e.g. a metal such as gold) onto a presented face of the sample.

EMBODIMENT 2

[0066] FIG. 2 shows a variant of the CPM in FIG. 1—in this case a so-called FIB-SEM. This is largely identical to the apparatus of FIG. 1, except in that it comprises an ion-optical column 31 in addition to the aforementioned electron-optical column 1. In analogy to the electron column 1, the ion column 31 comprises an ion source 39 (such as a Knudsen cell, for example) and imaging optics 32, and these produce/direct an ion beam 33 along an ion-optical axis 33′. To facilitate easy axis to a specimen on holder 7, the ion axis 33′ is canted relative to the electron axis 3′.

[0067] As hereabove described, such an ion (FIB) column 31 can be used inter alia to cut from a “bulk” specimen S a small sample, such as a thin lamella (flake/sliver), by performing a plurality of (angled) incisions that serve to liberate the sample (along its perimeter) from the surrounding specimen. In the current embodiment, a stage comprising a (needle-like) manipulator arm A, which can be actuated in various degrees of freedom by actuator system A′, can then be used to transfer such a sample between the irradiation position P, where it was created (˜intersection of axes 3′ and 33′) and a deposition position Pd facing (a mouth of) in situ magnetron sputter deposition module D, where it can be coated with (for example) a metallic later. Note in the present case that D is canted somewhat toward Pi, though this need not necessarily be the case. When the sample has been coated at module D, it can, if desired, be moved back to position Pi (using stage A/A′), where it can be inspected and/or further machined using electron column 1 and/or ion column 31. This procedure can, if desired/required, be performed in multiple iterations.

EMBODIMENT 3

[0068] In a specific example of TEM lamella preparation using the in situ magnetron sputter deposition module of the present invention, a (particular face of a) bulk specimen is first coated with about 1-10 nm of metal (e.g. Cr or Au), so as to improve imaging (contrast enhancement and anti-charging layer). Once a suitable image of said face is obtained, a lamella is excised from the face, using a FIB. In order to suppress charging effects, a further 1-5 nm of metal is deposited onto the lamella. Such deposition can, for example, be performed at a deposition rate of the order of about 1-10 nm per minute (typically), though this is discretionary. Sputter gas pressure in the deposition module is usually in a range of ca. 0.1-100 Pa, whereby a typical process gas is Argon. Plasma generation voltages are usually in a range of ca. 20-2000 V, with typical currents in a range of ca. 1-1000 mA. The magnetron can be cooled if needed, so as to control heating.

EMBODIMENT 4

[0069] The following is a non-exhaustive list of various exemplary situations in which the in situ magnetron sputter deposition module of the present invention can be employed: [0070] For an insulating wafer sample, deposition of ca. 2-5 nm of Cr can suppress charging effects and give good backscatter images. [0071] In the case of cryogenic samples (e.g. vitrified biological samples) which are prone to ice contamination, metal coatings of thickness ca. 1-10 nm improve imaging performance. [0072] One can deposit a passivation layer, to shield and protect a delicate air-sensitive lamella/sample from oxidation/corrosion. [0073] In photonics samples, the invention can be used for in situ deposition of a photoactive layer. [0074] Organic materials can be sputtered, e.g. to create nanopolymer films. [0075] Inorganic materials can be sputtered, e.g. to create a ceramic or glass layer. [0076] A thin seed layer can be deposited on a device to promote better deposition of other layers. [0077] The invention provides an in situ fabrication method for multilayer samples, allowing high-quality low-temperature depositions for constructing nanolayer stacks.