Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/0006—Electron-beam welding or cutting specially adapted for particular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/0013—Positioning or observing workpieces, e.g. with respect to the impact; Aligning, aiming or focusing electronbeams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/002—Devices involving relative movement between electronbeam and workpiece
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/0026—Auxiliary equipment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/08—Removing material, e.g. by cutting, by hole drilling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K15/00—Electron-beam welding or cutting
  • B23K15/10—Non-vacuum electron beam-welding or cutting
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/31—Electron-beam or ion-beam tubes for localised treatment of objects for cutting or drilling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/16—Bands or sheets of indefinite length

Definitions

• the invention relates to a method for the formation of nanometer- scale electrodes.
• the invention relates to a method for the formation of electrodes with which nanometer-scale elements can be detected and measured with the aid of conduction.
• electrically conductive components such as active electrical components
• making electrical contact is often problematic.
• Such nanometer -scale components which may for instance consist of particles with dimensions of one to a few nanometers and may even consist of, for instance, one single molecule, render nanometer-scale electrodes necessary, in particular electrodes with a precision from one to a few nanometers.
• a method according to the invention use is made of an electron beam to directly process an electrically conductive material, without intervention of layers which are sensitive to electrons or light layers. It has been found that, with the aid of an electron beam, atoms can be displaced, so that a groove can be formed in a strip of electrically conductive material, in particular metal, such that the electrical conduction through the strip is influenced, in particular interrupted. Thus, in a simple and particularly accurate manner, nanometer-scale electrodes can be manufactured.
• nanometer scale is at least understood to mean that, at least in a width direction and a thickness direction, the electrodes have dimensions between one nanometer and some tens to hundreds of nanometers, at least near the groove and/or a groove formed between the electrodes has a width which is so small that it can be bridged by elements with outer dimensions on a scale of small and medium -sized molecules, for instance between less than one nanometer and a few nanometers.
• a strip is at least understood to mean any type of element manufactured from electrically conductive material which has a minimum length and a minimum width which are considerably larger than the thickness of the material, measured at right angles to this longitudinal and width direction, at least at the height of the location where the at least one groove is provided.
• a groove is at least understood to mean a deformation of the surface of the strip which has a depth, viewed from the surface, and a width, while the deformation may have flat as well as singly or doubly curved or irregularly formed side surfaces which at least substantially determine the facing walls of the groove.
• the groove may have a bottom from the material of the strip but may also extend through the entire thickness of the strip.
• the material in which the groove is made is monocrystalline. This offers a greater control of the manufacturing process of the groove.
• the groove is preferably provided in a top surface of the strip, with a depth, calculated approximately at right angles to this top surface, which is at least equal to the thickness of the strip at the location of the groove, such that the strip is divided into at least two parts electrically separated from each other, which parts form the electrodes.
• the strip is provided on a support, prior to the provision of the at least one groove. This further simplifies processing.
• an opening can be provided, through which changes in the strip can be observed during the formation of the groove, at least the processing of the strip.
• an electron microscope in particular of a transmission electron microscope.
• an electron microscope an electron beam can accurately be generated and monitored, which electron beam can be focused to a spot size of, for instance, about one nanometer. Particularly small surfaces can thus be processed particularly accurately and atoms can be displaced for forming particularly narrow grooves, at least surface changes.
• use of an electron microscope offers the advantage that, during the deformation of the strip, at least the formation of the at least one groove, the changes obtained can be observed accurately and in real time, on the basis of which the electron beam can be monitored and controlled, for instance in direction, size, intensity.
• the strip may, for instance, have been or be manufactured from precious metal such as silver, gold, platinum, or from a metallic oxide.
• the material in which the groove is provided is additionally heated or cooled via an external temperature control. This can influence the formation of groove in a positive manner.
• the support is manufactured from a silicon -based material, for instance silicon nitride or silicon oxide.
• the strip is preferably manufactured by use of conventional techniques, in particular lithography, more in particular photolithography. Thus, relatively narrow, thin strips can be provided accurately and relatively simply, in a desired shape and dimension.
• the invention further relates to a set of electrodes, characterized by the measures according to claim 13.
• a set of electrodes offers the advantage that nanometer-scale elements can thereby be detected, controlled, influenced, investigated or manipulated otherwise with the aid of electric current or charge or quantities derived or to be derived therefrom.
• the first ends preferably have a slightly tapering design, such that they approach each other at a small distance only across a small width.
• the strips may, for instance, be formed from a relatively pure metal or from a metal alloy. With use of an alloy, during processing, the first ends can be enriched with one of the components from the alloy, so that the conduction can be influenced positively or negatively.
• the strip Prior to the provision of the groove, the strip preferably has a relatively small thickness and width, for instance a thickness between 2 and 20 nm and a width between 20 and 100 nm. Particularly the width may, in principle, be larger, but this causes the processing time to be relatively long.
• a strip can be used which on average has a first width and which locally has a smaller width, while the groove is provided in the part with the smaller width.
• the invention moreover relates to the use of an electron beam for the formation of electrodes by migration of atoms and to the use of an electron microscope for the formation of electrodes from a metal strip.
• the invention further relates to an apparatus for the formation of at least two electrically conductive strip parts electrically insulated from each other from a strip, in particular electrodes, characterized by the measures according to claim 18.
• FIG. 1 schematically shows an apparatus according to the invention for the manufacture of electrically conductive strips
• Fig. 2 schematically shows, in side elevational view, a set of electrodes manufactured with a method and apparatus according to the present invention, in use
• Fig. 3A schematically shows, in perspective, partially cross -sectional view, a step in a method according to the present invention
• Figs. 3B-H show images, produced with an electron microscope, of a strip during a method according to the present invention.
• Figs. 4A-F show six recordings during the manufacture of an electrode set with a method according to the present invention.
• same or corresponding parts have same or corresponding reference numerals.
• the exemplary embodiments shown are only shown and described by way of illustration of the present invention and should not be taken as being limitative in any way.
• Fig. 1 schematically shows, in a very simplified manner, an electron microscope 1 with focusing means 2, coupled with a camera 3 via a control device 4.
• the camera 3 and/or the control device 4 may also be an integral part of the electron microscope 1.
• other means can be used for generating and monitoring an electron beam.
• a highly focused electron beam can be obtained with a nanometer-scale spot size on a workpiece 5, for instance of a diameter of 2 to 10 nm or less.
• Fig. 1 schematically shows a workpiece 5, as will be described in more detail, on a very greatly magnified scale.
• This workpiece 5 comprises a support 6, comprising a base 7 and a membrane 8, on which membrane 8 a strip 9 is supported, from which, with a method according to the present invention, with the aid of an electron beam, an electrode set according to the invention will be formed, as schematically shown in more detail in Fig. 2.
• the strip 9 has a thickness D which is relatively small, for instance between 2 and 20 nm, more in particular between 5 and 15 nm and a width, at right angles with the plane of the drawing, which can be slightly larger, for instance more than 10 nm, more in particular more than 50 nm and for instance 100 to 150 nm. This will be discussed in more detail.
• At least one opening is provided next to and/or under the strip 9, at the height of the position where the strip 9 will be processed with the aid of the electron beam 2.
• the purpose of such an opening is that, with the aid of the camera 3, deformations of the strip 9 and/or of the membrane 8 can be observed, for instance in real time, with the aid of the camera 3, so that, with the aid of the control device 4, the electron microscope 1, in particular the focusing means 2, and/or displacements of the electron beam can be controlled for obtaining the desired deformation of the strip 9 by displacement of atoms, in particular diffusion of atoms in the strip 9, such that, as schematically shown in Fig.
• a groove 11 is formed which completely cuts through the strip 9 across its width B, i.e. at right angles to the plane of the drawing in Figs. 1 and 2, at least up to the membrane 8, so that, on both sides of the groove 11, an electrode 12A, 12B is formed, which electrodes are electrically separated from each other by the groove.
• Each electrode 12A, 12B has a first end 13A, 13B.
• the first ends 13A, 13B bound the groove 11 and have a mutual distance W, the width of the groove 11, on a nanometer scale.
• This width W may, for instance, be 1-2 nm, but may also be made smaller or larger, depending on, for instance, the spot size, the intensity of the electron beam, the processing time and the like.
• an element 14 can be positioned, after which, with the aid of a circuit 15 connected to the two electrodes 12A, 12B, for instance the presence of the element 14 can be established or electrical properties thereof can be determined, the element 14 can be electrically excited or be electrically influenced or manipulated in another manner, or the presence thereof can be determined.
• the circuit 15 will be closed.
• nanoclusters, nanotubes or even single molecules can be used as element 14. These can be characterized on the basis of electrical measurements with the aid of the circuit 15.
• Fig. 3A shows in perspective, partly cross -sectional view, a workpiece 5 during the carrying out of a method according to the present invention, where an electron beam 16 is schematically drawn in as an hourglass shape, while a focusing point 17 is located at the height of the membrane 8, at least the strip 9.
• the workpiece 5 comprises a strip 9 supported on a support 6.
• This support 6 comprises a base 7, an intermediate layer 18 and a membrane 8.
• the membrane is, for instance, an approximately 40 nm thick SiN membrane, while the intermediate layer is a silicon oxide layer, supported by a relatively thick layer of silicon.
• an opening 10 has been provided in a manner known per se, which widens in the direction away from the membrane 8.
• This opening 10 is, for instance, approximately rectangular and is, for instance, 400 by 400 nm.
• the strip 9 is, for instance, manufactured from a 10 nm thick exposed gold film with a bicrystalline orientation or a platinum film with an approximately equal thickness and a width B of about 150 nm.
• the width B 1 of the strip 9 has been reduced considerably, for instance to a width of about 20 or 50 nm, in order to reduce the processing time.
• Fig. 3A shows, as described hereinabove, an apparatus according to the invention
• Figs. 3B-H show images of a strip 9 according to the invention during processing with a method according to the present invention.
• Figs. 3B-D show three images of an unsuccessful manufacturing attempt
• Figs. 3E-H show a successful attempt.
• C, D, E and H in the top right-hand corner, cross sections of the workpiece are schematically shown, during the respective step.
• Fig. 3B shows a polycrystalline metal strip 9 manufactured from platinum with a width of 50 nm, in which a bridge 19 has been provided, with a width of about 50 nm. This has been obtained with the aid of an ion beam (ion beam milling). Then, as shown in Fig. 3B, with a short lighting, a small opening has been provided in the SisN4 membrane, as indicated by arrow K. Then, as shown in Fig. 3C, parts of the bridge have locally been removed by local radiation by the electron beam, so that the width of the bridge 19 has been reduced considerably, to about 1.5 nm, as shown in Fig. 3 C in the bottom right-hand corner. Then, as shown in Fig.
• the electron beam has intentionally been widened in order to be able to record the formation of the groove 11 in real time with a fast CCD camera (fast-scan CCD).
• a fast CCD camera fast-scan CCD
• Fig. 3E an image is shown, approximately halfway a manufacturing method in a second attempt.
• a cut is made in an upper part of the bridge (Fig. 3E), after which, from the bottom side (bottom side and top side are herein understood to mean the top and bottom in the different images of Figs. 3A-H and 4A-F, which means both sides of the strip 9 at the height of the bridge 19 when viewed approximately at right angles to the surface of the membrane 8), so that the width of the bridge 19 is reduced further and further.
• the changed shape of the bridge is shown in more detail, being slightly magnified.
• FIGs. 3F-H clearly show, further processing with the electron beam, which has been moved in a direction approximately at right angles to the longitudinal direction of the strip 9, relative to this strip, at least bridge 19, results in a groove 11 formed between two first ends 13A, B of two electrodes 12 formed on both sides of the groove 11.
• the narrowest groove which has thus been formed in the given embodiment has a minimum width of 0.6 nm and electrically separates the two electrodes 12 from each other.
• further processing with an electron beam leads to a further widening of the groove 11, in the example shown to a width of about 1.4 nm.
• the material in which the groove is provided can be monocrystalline.
• the temperature can be controlled, for instance by cooling or heating.
• Figs. 4A-4F six images are shown, which were taken from a film made during processing of a 10 nm thick, exposed gold film with bicrystalline orientation for the formation of a set of electrodes 12.
• a hole was made with the aid of the electron beam for the formation of an 5 approximately 20 nm wide bridge 19.
• the width of the bridge 19 was slowly reduced during the continuous observation thereof with a fast camera. As appears from Figs.
• the width of the bridge gradually decreased until a moment between 97 and 101 seconds from the outset, when the bridge 19 broke (between images 4E and 4F), after which the two 0 first ends 13A, 13B of the two electrodes 12A, 12B withdrew relatively fast (within about 0.1 second), thereby forming a groove having a width of about 2 nm.
• This width could be increased by continued electron beam lighting. From the contrast obtained of the strip, it can be concluded that the height of the two first ends 13A, 13B was approximately equal above the 5 membrane 8.
• the height of the electrodes 12A, 12B may not be equal after the formation, which could be the result of, for instance, non-isotropic, lighting-induced mechanical stress which could lead to curling up of the electrode ends 13A, 13B.
• polycrystalline metal strips, o such as gold provided on a membrane, for instance a 40 nm SiN membrane, which membrane was also locally removed during processing with the electron beam, this effect can be reduced or even be prevented.
• This local removal of the membrane has the additional advantage that, unintentionally, metal parts extending in the environment of the groove 11 5 were removed.
• the opening in the substrate under and around the groove offers high-resolution TEM inspection of molecules captured in the groove.
• Electron beam-induced changes in the strip are related to atom diffusion along surfaces and grain boundaries. Lateral atom displacements were clearly visible in the film from which the images were taken.
• the simplest cuts through polycrystalline strips 9 were made when the dimensions of any single crystalline grains were relatively small (preferably smaller than about 5 nm). However, for preserving the shape of the electrodes after processing, relatively large grains proved to be advantageous.
• the electron beam is controlled, for instance in diameter, shape and intensity of the electron beam, depending on the observed changes in the material. It is, for instance, possible, when the groove 11 is formed, to reduce the intensity in order to prevent too fast a widening of the groove 11.
• a method according to the present invention can excellently be combined with optical lithography and focused ion beam processing known per se.
• a set of electrodes according to the present invention may, for instance, be used, together with an opening therewith, for detecting, for instance, molecules which go through this opening, such as for instance use as a nanosensor, comprising a pore with electrodes therewith for being able to quickly electrically detect, for instance, DNA strands (single DNA strands).
• a lower energy can be used, for instance from 150 KeV, and/or a lower current, for instance from 2 nA.
• the invention is not limited in any way to the exemplary embodiments shown in the description and drawings. Many variations thereof are possible within the framework of the invention as set forth in the claims. Thus, other widths and/or thicknesses can be used in strips, as well as other types of supports. In addition, micropores can be manufactured with other applications.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Nanotechnology (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Composite Materials (AREA)
• Analytical Chemistry (AREA)
• Analysing Materials By The Use Of Radiation (AREA)

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Citations (4)

• 2004
  • 2004-09-01 NL NL1026942A patent/NL1026942C2/nl not_active IP Right Cessation
• 2005
  • 2005-08-31 WO PCT/NL2005/000630 patent/WO2006025737A1/en active Application Filing

Patent Citations (4)

Non-Patent Citations (2)

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