WO2004096699A1 - Method of manufacturing a nanoscale conductive device - Google Patents

Method of manufacturing a nanoscale conductive device Download PDF

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Publication number
WO2004096699A1
WO2004096699A1 PCT/SE2004/000658 SE2004000658W WO2004096699A1 WO 2004096699 A1 WO2004096699 A1 WO 2004096699A1 SE 2004000658 W SE2004000658 W SE 2004000658W WO 2004096699 A1 WO2004096699 A1 WO 2004096699A1
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Prior art keywords
nanoconductor
force
elongated
substrate
surface irregularity
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PCT/SE2004/000658
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French (fr)
Inventor
Mohammad Shafiqul Kabir
Eleanor E. B. Campbell
Per Delsing
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Chalmers Intellectual Property Rights Ab
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Publication of WO2004096699A1 publication Critical patent/WO2004096699A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H01L29/0657—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body
    • H01L29/0665—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body the shape of the body defining a nanostructure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H01L29/0657—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body
    • H01L29/0665—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body the shape of the body defining a nanostructure
    • H01L29/0669—Nanowires or nanotubes
    • H01L29/0673—Nanowires or nanotubes oriented parallel to a substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/84—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of applied mechanical force, e.g. of pressure

Definitions

  • This invention relates to a method of manufacturing a nanoscale conductive device, for example to be used in nano-size electronic components.
  • Nanotechnology is predicted to be of major importance in the field of electronics in the future, as the state of the art silicon technology starts to reach its physical limits.
  • thin conductors such as carbon nanotubes, have been developed, which are predicted to be of great importance in future electronics.
  • a carbon nanotube has a single dimension quantum line structure, i.e. constitutes a one-dimensional quantum wire, and exhibits excellent mechanical, chemical and electronic and electromechanical properties. Moreover, depending on the atomic structure, the carbon nanotube is semiconducting or metallic. It has also been shown that, by inducing mechanical changes on the nanotube structure electrical properties thereof may be changed. One example .of this is disclosed in the article "AFM manipulation of carbon nanotubes: realisation of ultra-fine nanoelectrodes; C. Thelander, L.
  • a nanoelectrode is generated by positioning a carbon nanotube on a plane substrate, and thereafter inducing mechanical changes on the structure by manipulating the carbon nanotube in a direction parallel to the substrate by means of an atomic force microscope, so that kinks are generated on the nanotube lying on the substrate surface.
  • an object of this invention is to overcome the above described problems with the prior art.
  • the above and other objects are at least in part achieved by a method according to claim 1.
  • a method of manufacturing a nanoscale conductive device comprising the steps of providing a substrate, having a top surface provided with at least one surface irregularity, providing an elongated nanoconductor across said at least one surface irregularity, applying a force on said elongated nanoconductor by means of a force application means, at least one component of the force being directed essentially perpendicular to the surface of the substrate, in order to induce a change in an electrical property of said elongated nanoconductor.
  • the topography of the substrate is used, together with the applied force, to alter the electrical properties of the nanoconductor, and thereby the method facilitates easy and reproducible manufacture of the conductive nano-scale device.
  • the inventive method it is possible to introduce one or more artificial defect centres along the nano-conductor at selected positions, in a reproducible manner.
  • the effect of the applied force is significantly increased by the irregularities of the surface.
  • the step of applying a force on said elongated nanoconductor results in a deformation of said elongated nanoconductor, such as a bending of said elongated nanoconductor.
  • said deformation is suitably permanent, enabling further processing of the device .
  • said nanoconductor is one of a nanotube, such as a carbon nanotube or a silicon carbide nanotube, a nanowire, such as a carbon nanowire or a silicon nanowire, or a nanowhisker.
  • a nanotube such as a carbon nanotube or a silicon carbide nanotube
  • a nanowire such as a carbon nanowire or a silicon nanowire, or a nanowhisker.
  • Carbon nanotubes have many advantageous properties, and may be single-walled or multi-walled. Since different nanoconductors, having different mechanical, chemical, optical and electrical properties may be used, a plurality of different components, having different properties may be achieved.
  • the surface irregularity can be a protrusion or a recess.
  • the dimensions and shape of the surface irregularity may be altered in order to achieve different effects when applying a force on the nanoconductor, and also define the positions for manipulation on the nanoconductor.
  • a protrusion can be singular (i.e. a pillar) or elongated (i.e. a ridge)
  • a recess can be singular (i.e. a pit) or elongated (i.e. a trench).
  • the method further comprising the step of providing said surface irregularity by means of etching or nanoprinting on said top surface of said substrate.
  • the surface irregularities may either be formed directly in a solid bulk substrate, or in a special layer, applied on the top of a substrate.
  • the applied force can be mechanical, and can be applied by scanning along said nanoconductor over said surface irregularity by means of a scanning probe microscope, such as an atomic force microscope in tapping mode, hence accomplishing said induced change of the electrical property of the elongated nanoconductor.
  • the applied force can be electrodynamical, and can be applied by applying an electrical field over the substrate and the nanoconductor, the applied electrical field causing said induced change of the electrical property of the elongated nanoconductor.
  • the method further comprises the step of evaporating an electrode onto the nanoconductor on at least one side of said surface irregularity.
  • electrodes are evaporated onto the nanoconductor on both sides of the surface irregularity, hence facilitating electrical contact with the nano-scale device.
  • One of the electrodes may in some application be referred to as a drain, and the other one as a source.
  • said substrate is suitably manufactured from an electrically insulating material, such as Si0 2 .
  • Fig la-lf discloses a cross-section of a device under manufacturing in accordance with a first embodiment of the invention.
  • Fig 2a-2e discloses a cross-section of a device under manufacturing in accordance with a second embodiment of the invention.
  • Fig 3 discloses a cross-section of a device according to a third embodiment of this invention.
  • a first schematic embodiment of this invention is disclosed in fig la-lf.
  • a substrate 2 is arranged, comprising an expose layer 11 and a spin resist layer 12.
  • the resist layer 12 is developed.
  • the substrate 2 is subjected to dry etching, resulting in a surface irregularity 3, here an elongated recess, i.e. a trench 9, having a width x, typically about 30-400 nm and a depth y, typically about 10-50 nm.
  • a fourth step the resist is removed, and an elongated nanoconductor 4, such as a carbon nanotube, is positioned across the trench, so that it rests on both sides of the trench.
  • a force is applied on the nanoconductor, over said trench by means of a force application means 5.
  • the force should have at least one component directed essentially perpendicular to the surface 6 of the substrate 2.
  • the force may be applied by an atomic force microscope in tapping mode (also referred to as nano- hammering) .
  • the force applied to the nanoconductor may be directed in an angle towards the substrate surface. In other words, apart from a force component directed essentially perpendicular to the substrate surface 6, there will also be a component directed along the surface 6.
  • a nanotube is attached to the tip of the AFM, thereby resulting in a more narrow area of interaction, and possibly a more controlled direction of the force.
  • the microscope is scanned across the nanotube about 5-10 times.
  • the nanoconductor 4 is forced down into the trench 9, and the force application causes a deformation, in this case a bending, of said nanoconductor, which induces a change in the electrical properties of the non-conductor.
  • a deformation in this case a bending
  • single or multiple quantum walls and/or quantum islands may be induced in the nanoconductor as a result of the above deformation.
  • the amount of bending may be adjusted, so that desired properties of the nanoconductor are achieved.
  • electrodes 7, 8 are evaporated onto the nanoconductor on each side of the trench, which electrodes in some applications may be used as a drain and a source, respectively.
  • a second preferred embodiment of this invention is disclosed in fig 2a-2e.
  • a substrate 2 is arranged, comprising an expose layer 11 and a spin resist layer 12.
  • the spin resist layer 12 is in this case a spin double resist layer.
  • the resist layer 12 is patterned by using a mask, a nanoimprinter or an electron beam irradiation development.
  • a surface irregularity 3 in the form of a protrusion here an elongated ridge 10 of a metal or an insulator is deposited on the substrate 2, the ridge having a width x and a height y.
  • the ridge may or may not be covered with an insulating layer, which may be achieved either by oxidation or by evaporation.
  • This insulating layer facilitates that the pillar may be used as a centre for a manipulated nanoconductor and/or as a gate in a three-terminal device, such as a transistor.
  • an elongated nanoconductor 4 such as a carbon nanotube, is positioned across the ridge 10, so that it rests on the ridge. Thereafter, a force is applied on the nanoconductor, over said pillar by means of a force application means 5.
  • the force may be applied by an atomic force microscope in tapping mode (also referred to as nano- hammering) , in a similar way as was described above.
  • the nanoconductor 4 is forced to bend over the ridge, so that the ends come of the nanoconductor comes into contact with the substrate surface 6.
  • the force application causes a deformation, in this case a bending, of said nanoconductor, which induces a change in the electrical properties of the non-conductor. For example, single or multiple quantum walls and/or quantum islands may be induced in the nanoconductor as a result of the above deformation.
  • the amount of bending may be adjusted, so that desired properties of the nanoconductor are achieved.
  • a fifth step electrodes 7, 8 are evaporated onto the nanoconductor on each side of the trench, which electrodes in some applications may be used as a drain and a source, respectively.
  • the ridge 10 described above has a height and a width in the nanoscale region, i.e. about the same dimensions as the trench 9 mentioned above.
  • One advantage with this embodiment is that, as indicated above, the material of the ridge may be altered so that the pillar may be used as a gate, thereby enabling a transistor structure.
  • One alternative embodiment is disclosed in fig 3.
  • the ridge 10 has a triangular cross-section shape, enabling a close contact between the nanoconductor and the substrate, which may by advantageous for certain applications.
  • a substrate 2 of Si0 2 was provided.
  • a droplet of sonicated nanotube solution was dispersed on the prepared substrate, and a tapping mode atomic force microscope was used to image the deposited nanotubes.
  • a single nanotube was selected, and was suspended across one of the above trenches. Initially, the nanotube will have a slight dip (about 2.5 nm) in the centre of the trench, due to the tendency of the nanotube to follow the trench wall.
  • the nanotube is pushed further down in the middle of the trench, resulting in an irreversible bending of the nanotube, enabling further processing of the device.
  • the trench was 100 nm wide and 30 nm deep.
  • the scanning speed was about 0.29 Hz with a force constant of 40 N/m and a tip with ⁇ 10 nm diameter was used.
  • a cross-section analysis revealed that the nanotube was bent from its initial position to a central depth of about 22 nm after six AFM scanning cycles. It was also found that the bending angle ⁇ of the nanotube with respect to the substrate was quite symmetric at both edges of the trench. Moreover, it was found that the induced changes of the nanotube was permanent, enabling further processing of the device.
  • a source electrode 8 and a drain electrode 7 (5 nm/10 nm Ti/Au) was evaporated onto the nanotube, at both sides of the trench.
  • the electrodes 7, 8 was spaced by about 600-900 nm.
  • the current/voltage characteristics were measured as a function of temperature, by scanning the voltage on the source electrode 8 while keeping the drain electrode 7 at ground potential.
  • the nanotube showed a metallic behaviour with a linear current-voltage behaviour down to the lowest investigated temperature 20 K and a resistance of about 40 ⁇ at room temperature.
  • a nonlinear current-voltage behaviour was exhibited over the entire range of investigated temperatures (20 K-300 K) .
  • a second device was produced in the same way as described under example 1 above, but the nanotube was suspended over a narrower and shallower trench (30 nm and ⁇ 10 nm, respectively) .
  • the resistance was measured for this second device, and for the corresponding first device of example 1, and the resistance change as a function of the amount of bending was analysed. It was noted that for a less bent nanotubes, the resistance change was smaller.
  • the inventive method is hence based on the formation of an irregularity and the shaping of a nanoconductor positioned over said irregularity, the shaping being made by means of force application. Since the above processes are controllable to a high level, the inventive method enables production of nano-scale electrical components with a high grade of reproducibility and accuracy, and is therefore suitable for mass production. Depending on the force applied and the geometry of the surface irregularity over which the nanoconductor is suspended, it is possible to fabricate single or coupled multiple quantum islands within a single nanotube. Moreover, the inventive method may be used to manufacture various electronic components, such as transistors, sensors, actuators, and may hence also be used to produce logic gates, memory, and even nano-processors .

Abstract

A method of manufacturing a nanoscale conductive device (1), comprising the steps of providing a substrate (2), having a top surface (6) provided with at least one surface irregularity (3), providing an elongated nanoconductor (4) across said at least one surface irregularity (3), and applying a force on said elongated nanoconductor (4), at least one component of the force being directed essentially perpendicular to the surface of the substrate (3). The topography of the substrate is thus used together with the applied force to alter the electrical properties of the nanoconductor. The method facilitates easy and reproducible manufacturing of a conductive nano-scale device.

Description

METHOD OF MANUFACTURING A NANOSCALE CONDUCTIVE DEVICE
Technical field of the invention
This invention relates to a method of manufacturing a nanoscale conductive device, for example to be used in nano-size electronic components.
Background of the invention
Integrated circuits are becoming smaller and smaller, and consequently, the importance of nano-size solutions is increasing. Nanotechnology is predicted to be of major importance in the field of electronics in the future, as the state of the art silicon technology starts to reach its physical limits. For example, thin conductors, such as carbon nanotubes, have been developed, which are predicted to be of great importance in future electronics.
A carbon nanotube has a single dimension quantum line structure, i.e. constitutes a one-dimensional quantum wire, and exhibits excellent mechanical, chemical and electronic and electromechanical properties. Moreover, depending on the atomic structure, the carbon nanotube is semiconducting or metallic. It has also been shown that, by inducing mechanical changes on the nanotube structure electrical properties thereof may be changed. One example .of this is disclosed in the article "AFM manipulation of carbon nanotubes: realisation of ultra-fine nanoelectrodes; C. Thelander, L. Samuelsson; Nanotechnology 13 (2002) 108-113." In this article a nanoelectrode is generated by positioning a carbon nanotube on a plane substrate, and thereafter inducing mechanical changes on the structure by manipulating the carbon nanotube in a direction parallel to the substrate by means of an atomic force microscope, so that kinks are generated on the nanotube lying on the substrate surface.
However, a problem with this technology is that it is difficult to reproduce, so that two devices has the same properties. Hence, this method is less suitable for mass production.
The article "In situ resistance measurements of strained carbon nanotubes", S. Paulson et al, Applied Physics letter, Volume 75, No. 19, 8 November 1999, pp 2936 - 2938, also relates to application of force to nanotubes. Again, the nanotube is arranged on a plane surface, and a force directed along the surface is applied to the nanotube by the tip of an atomic force microscope. The article also mentions applying a force normal to the surface.
Summary of the invention
Hence, an object of this invention is to overcome the above described problems with the prior art. The above and other objects are at least in part achieved by a method according to claim 1. According to this invention, a method of manufacturing a nanoscale conductive device is provided, the method comprising the steps of providing a substrate, having a top surface provided with at least one surface irregularity, providing an elongated nanoconductor across said at least one surface irregularity, applying a force on said elongated nanoconductor by means of a force application means, at least one component of the force being directed essentially perpendicular to the surface of the substrate, in order to induce a change in an electrical property of said elongated nanoconductor.
Hence, the topography of the substrate is used, together with the applied force, to alter the electrical properties of the nanoconductor, and thereby the method facilitates easy and reproducible manufacture of the conductive nano-scale device. By the inventive method, it is possible to introduce one or more artificial defect centres along the nano-conductor at selected positions, in a reproducible manner.
Compared to the discussed prior art, the effect of the applied force is significantly increased by the irregularities of the surface.
Suitably, the step of applying a force on said elongated nanoconductor results in a deformation of said elongated nanoconductor, such as a bending of said elongated nanoconductor. Moreover, said deformation is suitably permanent, enabling further processing of the device .
Suitably, said nanoconductor is one of a nanotube, such as a carbon nanotube or a silicon carbide nanotube, a nanowire, such as a carbon nanowire or a silicon nanowire, or a nanowhisker. Carbon nanotubes have many advantageous properties, and may be single-walled or multi-walled. Since different nanoconductors, having different mechanical, chemical, optical and electrical properties may be used, a plurality of different components, having different properties may be achieved.
The surface irregularity can be a protrusion or a recess. The dimensions and shape of the surface irregularity may be altered in order to achieve different effects when applying a force on the nanoconductor, and also define the positions for manipulation on the nanoconductor. Thus, a protrusion can be singular (i.e. a pillar) or elongated (i.e. a ridge), and a recess can be singular (i.e. a pit) or elongated (i.e. a trench). Suitably, the method further comprising the step of providing said surface irregularity by means of etching or nanoprinting on said top surface of said substrate. Hence, the surface irregularities may either be formed directly in a solid bulk substrate, or in a special layer, applied on the top of a substrate.
The applied force can be mechanical, and can be applied by scanning along said nanoconductor over said surface irregularity by means of a scanning probe microscope, such as an atomic force microscope in tapping mode, hence accomplishing said induced change of the electrical property of the elongated nanoconductor. Alternatively, the applied force can be electrodynamical, and can be applied by applying an electrical field over the substrate and the nanoconductor, the applied electrical field causing said induced change of the electrical property of the elongated nanoconductor.
As yet an alternative, the above two methods of applying a force on the nano-conductor may be combined.
According to an embodiment of this invention, the method further comprises the step of evaporating an electrode onto the nanoconductor on at least one side of said surface irregularity. Most often, electrodes are evaporated onto the nanoconductor on both sides of the surface irregularity, hence facilitating electrical contact with the nano-scale device. One of the electrodes may in some application be referred to as a drain, and the other one as a source. Moreover, said substrate is suitably manufactured from an electrically insulating material, such as Si02.
The above and other objects are also at least in part achieved by a nanoscale conductive device manufactured by a method as described above.
Brief description of the drawings
The present invention will hereinafter be described in closer detail by means of preferred embodiments thereof, with reference to the accompanying drawings. Fig la-lf discloses a cross-section of a device under manufacturing in accordance with a first embodiment of the invention. Fig 2a-2e discloses a cross-section of a device under manufacturing in accordance with a second embodiment of the invention. Fig 3 discloses a cross-section of a device according to a third embodiment of this invention.
Description of preferred embodiments of the invention A first schematic embodiment of this invention is disclosed in fig la-lf. According to fig la, in a first step of the inventive method, a substrate 2 is arranged, comprising an expose layer 11 and a spin resist layer 12. In the second step (fig lb) , the resist layer 12 is developed. In the third step (fig lc) the substrate 2 is subjected to dry etching, resulting in a surface irregularity 3, here an elongated recess, i.e. a trench 9, having a width x, typically about 30-400 nm and a depth y, typically about 10-50 nm. Thereafter, in a fourth step (fig Id) the resist is removed, and an elongated nanoconductor 4, such as a carbon nanotube, is positioned across the trench, so that it rests on both sides of the trench. In a fifth step (fig le) , a force is applied on the nanoconductor, over said trench by means of a force application means 5. In order to accomplish the desired deformation, the force should have at least one component directed essentially perpendicular to the surface 6 of the substrate 2.
The force may be applied by an atomic force microscope in tapping mode (also referred to as nano- hammering) . As the tip of an AFM typically is much wider than a nanoconductor, the force applied to the nanoconductor may be directed in an angle towards the substrate surface. In other words, apart from a force component directed essentially perpendicular to the substrate surface 6, there will also be a component directed along the surface 6. According to one embodiment, a nanotube is attached to the tip of the AFM, thereby resulting in a more narrow area of interaction, and possibly a more controlled direction of the force.
Preferably, the microscope is scanned across the nanotube about 5-10 times. In this way, the nanoconductor 4 is forced down into the trench 9, and the force application causes a deformation, in this case a bending, of said nanoconductor, which induces a change in the electrical properties of the non-conductor. For example, single or multiple quantum walls and/or quantum islands may be induced in the nanoconductor as a result of the above deformation. Depending on the applied force, the amount of bending may be adjusted, so that desired properties of the nanoconductor are achieved. Moreover, the shape and dimensions of the surface irregularity 3 affects the properties. The above process enables a good reproducibility .
Thereafter, in a sixth step (fig If) electrodes 7, 8 are evaporated onto the nanoconductor on each side of the trench, which electrodes in some applications may be used as a drain and a source, respectively. An advantage with this embodiment is that, given that a certain distance is maintained between the nanoconductor and the bottom of the trench 9, the interaction between the substrate and the nanoconductor in this region may be held at a low level .
A second preferred embodiment of this invention is disclosed in fig 2a-2e. According to fig 2a, in a first step of the inventive method according to this embodiment, a substrate 2 is arranged, comprising an expose layer 11 and a spin resist layer 12. The spin resist layer 12 is in this case a spin double resist layer. In the second step (fig lb), the resist layer 12 is patterned by using a mask, a nanoimprinter or an electron beam irradiation development. In the third step (fig lc) , a surface irregularity 3 in the form of a protrusion, here an elongated ridge 10 of a metal or an insulator is deposited on the substrate 2, the ridge having a width x and a height y. The ridge may or may not be covered with an insulating layer, which may be achieved either by oxidation or by evaporation. This insulating layer facilitates that the pillar may be used as a centre for a manipulated nanoconductor and/or as a gate in a three-terminal device, such as a transistor. In fig 2d, an elongated nanoconductor 4, such as a carbon nanotube, is positioned across the ridge 10, so that it rests on the ridge. Thereafter, a force is applied on the nanoconductor, over said pillar by means of a force application means 5.
The force may be applied by an atomic force microscope in tapping mode (also referred to as nano- hammering) , in a similar way as was described above. In this way, the nanoconductor 4 is forced to bend over the ridge, so that the ends come of the nanoconductor comes into contact with the substrate surface 6. The force application causes a deformation, in this case a bending, of said nanoconductor, which induces a change in the electrical properties of the non-conductor. For example, single or multiple quantum walls and/or quantum islands may be induced in the nanoconductor as a result of the above deformation. Depending on the applied force, the amount of bending may be adjusted, so that desired properties of the nanoconductor are achieved. Moreover, the shape and dimensions of the ridge 10 affects the properties. The above process enables a good reproducibility .
Thereafter, in a fifth step (fig le) electrodes 7, 8 are evaporated onto the nanoconductor on each side of the trench, which electrodes in some applications may be used as a drain and a source, respectively. The ridge 10 described above has a height and a width in the nanoscale region, i.e. about the same dimensions as the trench 9 mentioned above. One advantage with this embodiment is that, as indicated above, the material of the ridge may be altered so that the pillar may be used as a gate, thereby enabling a transistor structure. One alternative embodiment is disclosed in fig 3. Here, the ridge 10 has a triangular cross-section shape, enabling a close contact between the nanoconductor and the substrate, which may by advantageous for certain applications.
EXAMPLE 1
A substrate 2 of Si02 was provided. A plurality of shallow trenches, having a depth of 10-50 nm, was fabricated with different widths, from 30 nm to 400 nm. A droplet of sonicated nanotube solution was dispersed on the prepared substrate, and a tapping mode atomic force microscope was used to image the deposited nanotubes. A single nanotube was selected, and was suspended across one of the above trenches. Initially, the nanotube will have a slight dip (about 2.5 nm) in the centre of the trench, due to the tendency of the nanotube to follow the trench wall. However, by scanning along the nanotube above the trench, by means of an atomic force microscope (AFM) in tapping mode, the nanotube is pushed further down in the middle of the trench, resulting in an irreversible bending of the nanotube, enabling further processing of the device. In example 1, the trench was 100 nm wide and 30 nm deep. The scanning speed was about 0.29 Hz with a force constant of 40 N/m and a tip with <10 nm diameter was used. A cross-section analysis revealed that the nanotube was bent from its initial position to a central depth of about 22 nm after six AFM scanning cycles. It was also found that the bending angle θ of the nanotube with respect to the substrate was quite symmetric at both edges of the trench. Moreover, it was found that the induced changes of the nanotube was permanent, enabling further processing of the device.
After the AFM manipulation described above, a source electrode 8 and a drain electrode 7 (5 nm/10 nm Ti/Au) was evaporated onto the nanotube, at both sides of the trench. The electrodes 7, 8 was spaced by about 600-900 nm. The current/voltage characteristics were measured as a function of temperature, by scanning the voltage on the source electrode 8 while keeping the drain electrode 7 at ground potential. Without the above AFM manipulation, the nanotube showed a metallic behaviour with a linear current-voltage behaviour down to the lowest investigated temperature 20 K and a resistance of about 40 Ω at room temperature. However, with the above manipulation, a nonlinear current-voltage behaviour was exhibited over the entire range of investigated temperatures (20 K-300 K) .
EXAMPLE 2
A second device was produced in the same way as described under example 1 above, but the nanotube was suspended over a narrower and shallower trench (30 nm and ~10 nm, respectively) . The resistance was measured for this second device, and for the corresponding first device of example 1, and the resistance change as a function of the amount of bending was analysed. It was noted that for a less bent nanotubes, the resistance change was smaller.
The inventive method is hence based on the formation of an irregularity and the shaping of a nanoconductor positioned over said irregularity, the shaping being made by means of force application. Since the above processes are controllable to a high level, the inventive method enables production of nano-scale electrical components with a high grade of reproducibility and accuracy, and is therefore suitable for mass production. Depending on the force applied and the geometry of the surface irregularity over which the nanoconductor is suspended, it is possible to fabricate single or coupled multiple quantum islands within a single nanotube. Moreover, the inventive method may be used to manufacture various electronic components, such as transistors, sensors, actuators, and may hence also be used to produce logic gates, memory, and even nano-processors . By altering the dimensions and shape of the irregularity, as well as the force applied on the nanoconductor, different electrical , properties may be achieved. In the examples above, it has been possible to achieve active device areas as low as 5x5 nm, which enables fabrication of highly dense and compact circuitries, based on electrical components manufactured according to the invention. Hence, with the present invention, very robust, reproducible, cost effective, high dense and small circuits may be achieved. Also, the effective length and shape of the nanoconductor is well-defined, resulting in well-defined electrical properties of the component.
It is to be understood that the above-described embodiments of the invention are only given for illustrative purposes, and that many embodiments are possible without departing from the spirit and scope of this invention as defined by the appended claims.

Claims

Claims
1. A method of manufacturing a nanoscale conductive device (1), comprising the steps of: providing a substrate (2), having a top surface (6) provided with at least one surface irregularity (3) , providing an elongated nanoconductor (4) across said at least one surface irregularity (3) , and applying a force on said elongated nanoconductor (4) by means of a force application means (5) , at least one component of the force being directed essentially perpendicular to the surface of the substrate (3) , in order to induce a change in an electrical property of said elongated nanoconductor (4).
2. A method according to claim 1, the step of applying a force on said elongated nanoconductor (4) results in a deformation of said elongated nanoconductor (4), such as a bending of said elongated nanoconductor (4) .
3. A method according to claim 2, wherein said deformation is permanent.
4. A method according to any one of the preceding claims, wherein said nanoconductor (4) is one of a nanotube, a nanowire or a nanowhisker.
5. A method according to any one of the preceding claims, wherein said surface irregularity (3) is one of a protrusion (10) or a recess (9).
6. A method according to claim 3, further comprising the step of providing said surface irregularity (3) by means of etching or nanoprinting on said top surface (6) of said substrate (2) .
7. A method according to any one of the preceding claims, wherein the step of applying a force on said elongated nanoconductor (4) comprises the step of scanning along said nanoconductor (4) over said surface irregularity (3) by means of a scanning probe microscope, such as an atomic force microscope in tapping mode.
8. A method according to any one of the claims 1- 6, wherein the step of applying a force on said elongated nanoconductor (4) comprises the step of applying an electrical field over the substrate (2) and the nanoconductor (4).
9. A method according to claim 1, further comprising the step of evaporating an electrode (7, 8) onto the nanoconductor (4) on at least one side of said surface irregularity (3) .
10. A method according to claim 1, wherein said substrate (2) is manufactured from an electrically insulating material, such as Si02.
11. A nanoscale conductive device manufactured by a method according to any one of the claims 1-10.
PCT/SE2004/000658 2003-04-28 2004-04-28 Method of manufacturing a nanoscale conductive device WO2004096699A1 (en)

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DE102005012689B3 (en) * 2005-03-18 2006-11-23 Siemens Ag Method of making a tape
US7687876B2 (en) 2005-04-25 2010-03-30 Smoltek Ab Controlled growth of a nanostructure on a substrate
US7977761B2 (en) 2005-04-25 2011-07-12 Smoltek Ab Controlled growth of a nanostructure on a substrate, and electron emission devices based on the same
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US8183659B2 (en) 2005-08-26 2012-05-22 Smoltek Ab Integrated circuits having interconnects and heat dissipators based on nanostructures
US8415787B2 (en) 2005-08-26 2013-04-09 Smoltek Ab Integrated circuits having interconnects and heat dissipators based on nanostructures
US9535063B2 (en) 2006-11-22 2017-01-03 President And Fellows Of Harvard College High-sensitivity nanoscale wire sensors
US8815332B2 (en) 2007-09-12 2014-08-26 Smoltek Ab Connecting and bonding adjacent layers with nanostructures
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US8866307B2 (en) 2008-02-25 2014-10-21 Smoltek Ab Deposition and selective removal of conducting helplayer for nanostructure processing
US9114993B2 (en) 2008-02-25 2015-08-25 Smoltek Ab Deposition and selective removal of conducting helplayer for nanostructure processing
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WO2011038228A1 (en) * 2009-09-24 2011-03-31 President And Fellows Of Harvard College Bent nanowires and related probing of species

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