Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
A PARTICLE BEAM GENERATING DEVICE
Document Type and Number:
WIPO Patent Application WO/2006/040559
Kind Code:
A1
Abstract:
A particle beam generating device formed from a substrate having a planar surface. The planar surface having an etched rebate portion (2), with a base surface and at least one wall surface, which defines a raised peripheral region. The device further comprising a particle extractor comprising a conductive layer, disposed on the wall surface, and an extracting aperture extending therethrough, to extract particles from a particle source. The particle extractor also having electrical contact means for providing a voltage thereto. The device further comprising a particle accelerator (4) comprising an accelerating passageway, in communication and extending concentrically with the extracting aperture, and extending from the wall surface and through the opposite surface of the raised peripheral region to provide a particle accelerator for particles extracted from a suitable particle source disposed on said base surface of said rebate. The device may further comprise focussing means (5, 6).

More Like This:
JP2016131137ELECTRON GUN
JP6460501Electron beam device
Inventors:
Eastham, Derek Anthony (58 Vincent Drive, Chester, Cheshire CH4 7RL, GB)
Application Number:
PCT/GB2005/003935
Publication Date:
April 20, 2006
Filing Date:
October 13, 2005
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
NFAB LIMITED (Optic Technium, Ffordd William Morgan St Asaph Business Park, St Asaph LL17 0JD, GB)
Eastham, Derek Anthony (58 Vincent Drive, Chester, Cheshire CH4 7RL, GB)
International Classes:
H01J37/065; H01J37/26; H01J37/28; H01J37/317; H01J3/02
Foreign References:
GB2259184A
US5786658A
US5729244A
Attorney, Agent or Firm:
Denmark, James Christopher (Harrison Goddard Foote, Orlando House 11c Compstall Roa, Marple Bridge Stockport SK6 5HH, GB)
Download PDF:
Claims:
CLAIMS
1. A particle beam generating device comprising a substrate having a planar surface, the planar surface comprising an etched rebate portion, having a base surface and at least one wall surface, which defines a raised peripheral region, a particle extractor comprising a conductive layer, disposed on the wall surface, and an extracting aperture extending therethrough, electrical contact means for providing a voltage to the conductive layer of the particle extractor, and a particle accelerator comprising an accelerating passageway, in communication and extending concentrically with the extracting aperture, and extending from the wall surface and through the opposite surface of the raised peripheral region to provide a particle accelerator for particles extracted from a suitable particle source disposed on said base surface of said rebate.
2. A particle beam generating device as claimed in claim 1, comprising a conductive layer disposed on the base surface and a nanotip particle source formed thereon.
3. A particle beam generating device as claimed in claim 2, wherein the nanotip particle source is formed of an insulating layer disposed on the base surface conducting layer and a particle source conducting layer disposed on the insulating layer, wherein the insulating layer is of a depth to raise said particle source conducting layer such that a particle beam emanating therefrom is level with the extracting aperture.
4. A particle beam generating device as claimed in claim 3, wherein particle source conducting layer comprises gold.
5. A particle beam generating device as claimed in claim 2, wherein the nanotip particle source is formed of an insulating layer disposed on the base surface conducting layer and a particle source magnetic material layer disposed on the insulating layer, wherein the insulating layer is of a depth to raise said particle source magnetic material layer such that a particle beam emanating therefrom is level with the extracting aperture.
6. A particle beam generating device as claimed in claim 5 wherein the magnetic material comprises cobalt.
7. A particle beam generating device as claimed in any of the preceding claims wherein the device further comprises beam collimating means.
8. A particle beam generating device as claimed in claim 7, wherein the beam collimating means are disposed on at least one end of the particle accelerator.
9. A particle beam generating device as claimed in any of the preceding claims wherein the device further comprises beam focusing means comprising alternative layers of conducting and insulating films, disposed on the opposite side of the peripheral raised region, and a focusing aperture, in communication and extending coaxially with the extracting aperture and the accelerating aperture through the alternative layers of conducting and insulating films.
10. A method of making a particle beam generating device on a substrate comprises: etching the surface to form a rebate in the substrate defined by base surface and at least one wall surface depositing a layer of conductive material on the wall surface of the rebate and forming an aperture through said layer of conductive material to provide a particle extractor forming a passageway through that portion of the substrate which remains behind said wall surface and is disposed above the base surface of the rebate after etching, said passageway extending behind said aperture to provide a particle accelerator for particles extarcted from a suitable particle source disposed on said base surface of said rebate.
Description:
A Particle Beam Generating Device

The present invention relates to particle beam generators and particularly to electron and ion beam generators for use in, for example, microscopy, such as, for example, scanning electron microscopy (SEM), and nanotechnology, such as, for example, nanolithography in the production of nanostrauctures and nanostructured surfaces by direct write techniques such as ion beam milling (sputtering), in the case of focussed ion beams (FIB), and surface modification methods, such as polymerisation or oxidation, in the case of electron beams.

Patent document PCT/GB03/02560 describes a particle beam generator and methods for focussing electron and ion beams. The generator described therein and methods associated therewith make it possible to focus electrons, in particular, down to atomic dimensions. In particular, the particle beam generator described therein and the focal lengths associated therewith are in the micrometer size range. The source of the ions or electrons is a nanotip which is positioned over a nanoscale conducting aperture. A nanoscale accelerating column follows this aperture which is used to accelerate the beam and prevent it expanding. A microscale einzel lens (or lenses) is used to focus the final beam. Also, nanoscale collimators are used to minimise the stray scattering and reduce the beam emittance.

The previous application described some methods of embodying these principles in practical designs. This application extends these concepts to a more realistic one-piece design which can be made by state-of-the-art MEMS (microelectromechanical systems) technology.

The device is a one piece design which is built into a microtip. A microtip is a piece of material usually silicon which is tapered down to a size in the micron range and forms the body of the microscope. This tapering is such that the whole assembly can be held on a vertical or horizontal cantilever such that the tip can be placed in close proximity to the surface, in this case down to one micron distant from the surface. This tapering is also such that when it is held close to the surface then electrons emitted from the end and scattered from the surface can be observed in a detector

placed above the surface. One can think of this as a device of a millimetre sized micro chip which tapers down to micron sized microtip at one end.

The particle beam generator may form part of a microscope which is may be built into such a microtip (or the end of the device body which corresponds to then tip of the whole device) by using MEMS technology including FIB (focussed ion beam) millers. In this way the microtip which produces a highly focussed electron or ion beam at a typical distance of 5 μm can be scanned over the surface in the same way as a nanoprobe in a near field instrument. Measurement of the variation in the scattered electrons can then be use to image the surface from which the electrons are scattered.

There is a desire in the industry for there to be such a particle beam generator and microscope form on a chip.

According to the present invention there is provided a particle beam generating device comprising a substrate having a planar surface, the planar surface comprising an etched rebate portion, having a base surface and at least one wall surface, which defines a raised peripheral region, a particle extractor comprising a conductive layer, disposed on the wall surface, and an extracting aperture extending therethrough, electrical contact means for providing a voltage to the conductive layer of the particle extractor, and a particle accelerator comprising an accelerating passageway, in communication and extending coaxially with the extracting aperture, and extending from the wall surface and through the opposite surface of the raised peripheral region to provide a particle accelerator for particles emanating from a suitable particle source disposed on said base surface of said rebate.

Also according to the present invention there is provided a method of making a particle beam generating device on a substrate comprises: etching the surface to form a rebate in the substrate defined by base surface and at least one wall surface; depositing a layer of conductive material on the wall surface of the rebate and forming an aperture through said layer of conductive material to provide a particle extractor; forming a passageway through that portion of the substrate which remains behind said wall surface and is disposed above the base surface of the rebate after etching, said passageway extending coaxially behind said aperture to provide a particle accelerator

for particles emanating from a suitable particle source disposed on said base surface of said rebate.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view of the planar surface of a particle beam generator device according to the present invention;

Figure 2 is a schematic sectional view of the particle beam generating device of Figure 1 ;

Figure 3 is a schematic end view of the particle beam generating device of Figures 1 and 2;

Figure 4 is a schematic view of a particle accelerating region of a particle beam generating device of Figures 1 to 3;

Referring to Figures 1 to 4, a body, 1, is made from a single piece of material but one surface is dry etched such that there is a rebate, 2, in the material on the planar surface. The preferred material is doped silicon (single crystal) with a relatively high resistance and the whole of the rebate, apart from the particle accelerating portion, 4, is coated, by vacuum deposition, with a gold (or another conducting) layer, 3, nanometers thick. On the end of the device is focussing means are formed comprising a multilayer of alternate conducting, 5, and insulating films, 6. These layers which are of micron(s) thickness are folded around the end, as shown, and continue up the back of the whole device chip (on the left of fig. 1). The end or corner may be rounded to facilitate the formation of continuous layers. This makes it possible to apply a voltage to the centre element of the multilayer whilst keeping the outer two elements at earth potential. The preferred conducting material is gold and the preferred insulator is silica or intrinsic silicon.

A micron sized passageway, 7, is formed in the three layers from the end B. This passageway stops, not at the particle accelerator region, but about lOOnm before the particle accelerating region. A much smaller concentric passageway, 8, around 50nm diameter is drilled or etched into the accelerator region, 4. By careful control of the dry etching or FIB (focussed ion beam) drilling it is possible to produce a tapered 50nm diameter hole in the lOOnm thick remaining conducting gold film layer 5 before

the entrance to the accelerator region. Using the passageway from the focusing means as a guide, a passageway, such as a slot, 9, greater than lOOnm is drilled into the planar surface of the accelerating region using a FIB or dry etched at a depth larger than the position of the original 50nm hole. An exit nanocollimator, 8, of around 50nm diameter and nanometers thick is thus formed at the end of the accelerating section adjacent to the multilayer einzel lens. The other end of the accelerating section is covered with a conductive layer, preferably a thin gold layer. By drilling or dry etching from the end, B, a 50nm diameter entrance collimator, 10, can be formed in this layer. This process ensures that the nanocollimators and passageways are all concentric. The conductive layer having an aperture forms a particle extractor.

An alternative to using high pressure gas discharge to form the aperture in the particle extractor is to generate an ion field from a nanotip 12 which sputters through the conductive layer to form an aperture exactly in the desired position. This method is particularly advantageous because it forms the aperture in exactly the desired position, that is, aligned with the nanotip. To generate the ion field the nanotip is disposed approximately 30nm from the conductive layer in Xe gas at a pressure of 10 "2 Torr.

The planar nanotip, 12, is formed by producing an insulating layer, 13, of the required thickness such that a covering conducting (metal) layer is level with the aperture of the particle extractor or nanocollimator, 10. The nanotip conductive layer will have a thickness of approximately 10 nm. The slot, 14, is then formed in these two layers such that the particle extractor is approximately 30nm from the entrance to the accelerator. Finally the shape of the nanotip is formed using a FIB or by dry etching so that the tip has a diameter of around IOnm and is adjacent to the aperture of the particle extractor or entrance of the nanocollimator.

It will be appreciated by the skilled reader that the particle beam generator according to the present invention may be used without the focussing means or alternatively with the focussing means, for example, as a microscope.

Operation of the device, or microscope, is achieved by applying a voltage of around -320 volts to the nanotip, 12, around -300 volts to the conducting layer, 3, and, if being used as a microscope, earthing the two outer elements of the focussing means

(einzel lens) whilst applying a focussing voltage to the central element. Each voltage is applied to a contact on the back or the planar surface of the chip as shown on the left in fig.l. The latter voltage should be sufficient to produce a focussed beam, 15, (fig. 1) about 5 μm from the end of the microtip.

An important alternative device is made when the nanotip, 12, is made from a magnetic material such as cobalt. This can be achieved by producing a single crystal lOnm thick film by epitaxial growth. The electrons field emitted from the tip will then be polarized and the scattering from a surface will be sensitive to the surface magnetization. A polycrystalline film of magnetic material will also function in this way because the nanotip will only contain a single crystal.

The final one-piece design therefore incorporates all of the essential features which are listed previously. It may be possible to produce this geometry in several ways including making each section separately and then aligning them with nanopositioners before fixing their positions. This latter method of production would allow one to use a more conventional nanotip rather than the planar tip shown in the figures.