WO2012128657A1

WO2012128657A1 - Method for producing three-dimensional nano-metric metallic structures and device for carrying out said method

Info

Publication number: WO2012128657A1
Application number: PCT/RU2011/000181
Authority: WO
Inventors: Михаил Александрович ЮДАКОВ; Юрий Петрович ВОЛКОВ; Алексей Олегович МАНТУРОВ
Original assignee: Общество С Ограниченной Ответственностью Центр Инновационных Технологий-Нано
Priority date: 2011-03-24
Filing date: 2011-03-24
Publication date: 2012-09-27
Also published as: DE212011100203U1; RU151072U1

Abstract

The invention relates to the nano-technology field and can be used for manufacturing holographic optical elements, nano-sized electromechanical instruments, UHF transceivers and optical X-ray structures, and in the development and manufacturing of storage media and large-capacity information readers. The technical result consists in increasing the resolution to several nm, producing high metallic structures (height to diameter ratio greater than 10), and the possibility of producing structures not only with vertical walls. The nano-structures are formed by electrolytic deposition from the point of a cantilever arm of a scanning-probe microscope, which point is formed from solid electrolyte (super-ionic conductors).

Description

METHOD FOR CREATING THREE-DIMENSIONAL NANOMETER METAL STRUCTURES AND A DEVICE FOR ITS IMPLEMENTATION

Technical field

The invention relates to the field of nanotechnology and can be used for the manufacture of holographic optical elements, nanoscale electromechanical devices, microwave transceivers, X-ray ^! optical structures, in the design and manufacture of storage media and high-capacity information readers, etc.

State of the art

The lithographic process (negative or positive) is known, which consists in applying a photosensitive material to a metal layer, followed by exposure through a mask, removing an unlit or illuminated resist (for a negative / positive process) and etching a metal layer of an unprotected remaining resist. Thus, it is possible to form metal structures with dimensions up to several tens of nm having vertical walls (without taking into account the etching phenomenon). The radiation used to illuminate the photoresist is optical radiation (visible or UV), x-ray radiation, or charged particle beams (electrons, ions) (see, for example, RF patents 2072644, Н05КЗ / 06, 2164707, 2164706, G03F7 / 00, and CN1776527 , G03F1 / 16).

The disadvantages include the high complexity and multi-stage process, the need to manufacture special precision masks with high resolution, the need for complex and expensive special projection equipment (cost is hundreds of millions of dollars), the restriction on the size of the resulting structures (not less than 30-50 nm), the impossibility of obtaining high metal structures (the ratio of height to diameter is greater than 5) and structures with non-vertical walls.

The well-known LIGA process (Lithographie, Galvanoformung, Abformung) by which the formation of high cylindrical metal structures is possible. In this process, a thick dielectric layer (for example, an Ilsan film) acting as a photoresist is deposited on a metal substrate. A mask of metal is placed on the surface of the dielectric, through which the dielectric is exposed to a parallel beam of hard radiation (gamma rays) generated by the accelerator or nuclear reactor. Exposed dielectric changes its characteristics and can be removed later by etching in special solutions. Thus, holes are formed in the dielectric film repeating the shape of the windows in the mask. After that, the conductive substrate with a dielectric film is placed in a plating bath and a metal layer (for example, nickel) is deposited on the substrate, which repeats the shape of the holes in the dielectric film. Next, the film is completely etched, exposing the formed metal structures. Advantages - high resolution and high height of metal structures (the ratio of height to diameter is more than 10) (see, for example, RF patents 2350996, 2350995, G 03 F 7/00, as well as EP2182096, C25D1 / 00).

Disadvantages - the need to use unique equipment

(accelerators, nuclear reactors), which makes this technology inaccessible to most laboratories, the need to manufacture special high-resolution metal masks, the inability to create structures with non-vertical walls. To simplify the ball process, a modification of the method was developed using hard ultraviolet radiation for irradiation. Advantages - wider availability, disadvantages - in addition to the above, lower resolution (determined by the wavelength and not exceeding 100 nm).

Ion etching is known by surface treatment with a focused ion beam, which allows you to create arbitrary metal and dielectric structures of nanometer size in the absence of special masks, while the formation of structures is carried out according to the program under the control of a computer.

Disadvantages - the high cost of unique equipment, making it inaccessible to most laboratories.

It is possible to form nanoscale elements using a tunneling microscope. Using the tunneling current flowing between the tip of the microscope and the conductive substrate, metals can be deposited from organometallic gases, local oxidation followed by chemical etching of the oxide (for example, for a silicon surface), modification of a special photoresist with its subsequent chemical treatment. The advantage is the simplicity and low cost of equipment, the ability to create nanoscale structures, the ability to form elements of arbitrary shape under computer control. The disadvantages are the impossibility of forming high elements (the height does not exceed several nm) and the need to use non-oxidizing conductive substrates (noble metals, for example, gold, platinum) or work in ultrahigh vacuum.

A known probe method for forming nanoelements, including obtaining a conductive layer on a substrate, placing it in a chamber, forming charged particles zones near the substrate, creating a potential difference between the probe and the conductive layer, bringing the probe to the conductive layer, the occurrence of an electric field between the probe and the conductive layer the flow of charged particles and the formation on the surface of the conductive layer of nanoelements, characterized in that the substrate with the conductive layer is placed in a vacuum chamber and before By creating a potential difference between the probe and the conductive layer, a vacuum is created, after which a plasma is formed in the region of the probe above the substrate surface, and potentials are applied to the probe and the conductive layer, thereby controlling the interaction of the plasma with the probe and the conductive layer, after which the reaction products are removed from the region between the probe and the conductive layer (see RF application Ne 2005135747, IPC V82VZ / 00) 7

Disadvantages - the need to use a vacuum chamber and special pumping equipment (vacuum pumps), low resolution not exceeding 100 nm, due to the slow (according to linear law) decrease in current with increasing distance from the tip in a plasma discharge.

The scanning force microscope also allows you to create nanoscale structures by nanofilling (scratching the surface), applying ink using a tip previously coated with a layer of ink (followed by chemical surface treatment), modifying a photoresist with an electric current passing through a conducting tip (followed by etching of the photoresist) ( Handbook of nanotechnology. Springer, 2007, 950c). Advantages are the availability and low cost of equipment, the simplicity of the technology for forming nanostructures, the ability to programmatically set the shape and size of the created nanostructures, the absence of the need to create special masks, the high resolution of the formed elements (tens of nanometers).

Disadvantages - the inability to form high metal structures (the height does not exceed a few nm) and the need to use complex technological process consisting of several stages for the formation of nanostructures.

Closest to the proposed solution is a method and device _(the formation of nanoscale objects described in RF patent 2329945, IPC В82ВЗ / 00. The method of forming metal nanoscale objects includes layer-by-layer deposition of metal on a conductive substrate according to a given program by applying current pulses between the tip of the cantilever of a scanning probe microscope and substrate

The device for forming nano-sized objects contains a working chamber, an object stage and a measuring head for a scanning probe microscope, including a cantilever, a source of electric influence on the cantilever / sample system, piezoscanners with a compensator for thermal deformations and temperature drifts, vibration-proof devices, a digital electronic control system for the scanning head probe microscope and analog-to-digital information processing system, source of electrical influence on the cantilever / sample topic is made in the form of an electronic current control device both in a direct current mode and in a pulsed current mode, including a mode with variable polarity, while the device is additionally equipped with an electronic system for controlling the voltage amplitude and its derivative throughout the entire process of object formation, a system of independent adjustment and stabilization of the temperature of the sample and chamber, sources of reagents and their evaporators, as well as a system for bubbling, control, adjustment and stabilization of water by means of a system for evacuating the gas medium from the working volume of the chamber, which is decoupled from the working chamber by vibration noise, a gate and a bypass system.

The disadvantages are low resolution, not exceeding 100 nm, due to the slow (linearly) decreasing current with increasing distance from the tip in the discharge, the need for a chamber with a controlled environment and temperature, the use of special equipment for pumping and filling gas, the use of special and often toxic metal-containing gases by decomposition of which metal nanostructures are formed.

The objective of the present invention is the formation of metal nanoscale three-dimensional structures (objects) by electrolytic deposition. Disclosure of invention

The technical result consists in simplifying the design while expanding the functionality - increasing the resolution to several nm, creating high metal structures (height to diameter ratio of more than 10), the possibility of creating structures not only with vertical walls (tapering pyramidal walls are possible). It is possible to create metal nanostructures from various metals, as well as chemical surface modification (oxidation, fluorination) of the created nanostructures.

The method of forming metal nanoscale objects (nanostructures) involves layer-by-layer deposition of metal on a conductive substrate according to a predetermined program by applying current pulses between the tip of a cantilever of a scanning probe microscope and a substrate, according to the invention, the deposition is carried out by electrolytic deposition of metal from a tip made of solid electrolyte (superionic conductor), providing the transfer of metal ions.

After the formation of the object, chemical Ϊ modification is additionally carried out in the specified areas by exposure to current pulses between the tip of the cantilever and the substrate, while the tip of the cantelever is made of solid electrolyte, which ensures the transfer of gas ions.

The device for forming metal nanoscale objects contains a conducting stage and a measuring head for a scanning probe microscope, including a cantilever, a source of electrical influence on the cantilever / sample system as an electronic current control device, piezoscanners with a compensator for thermal deformations and temperature drifts, a vibration-proof device, a digital electronic control system for the scanning head ^" probe microscope, with the tip of the cantilever made of solid ele ctrolite, providing the transfer of metal ions.The cantilever is interchangeable.

As a solid electrolyte for the formation of nanoscale objects, an electrolyte with silver ions, for example, RbAg 4! $, Was chosen.

An electrolyte with oxygen or fluorine ions was selected as a solid electrolyte for modification.

The invention is illustrated in the drawing, which shows a block diagram of the proposed device, where 1 is a piezoscanner with a compensator for thermal deformations and temperature drifts, 2- conductive stage, 3- vibration protection device, 4- conductive cantilever, 5- solid electrolyte tip, 6- manufactured sample, 7-laser, 8- photodetector, 9- source of electrical influence on the cantilever / sample system, 10-digital electronic control system, 1 1 - computer.

The device contains a piezoscanner with a compensator for thermal deformations and temperature drifts 1, at one end of which a conductive stage is mounted 2 with the fabricated sample 6, and the other end of the piezoscanner 1 is mounted on a vibration-proof device 3. The pressing force of the conductive cantilever 4 with a tip of solid electrolyte 5 is controlled by value deflection of the cantilever 4 using an optical system consisting of a laser 7 and a photo detector 8. A digital electronic control system 10 is electrically connected to a piezoscanner 1 and a photodetector the detector 8, and the source of electrical influence on the cantilever / sample system 9 is connected to the cantilever 4 and the conductive stage 2. Computer 1] connected to the digital electronic control system 10 and the source of electrical influence on the cantilever / sample 9 controls the formation of sample 6.

The device operates as follows. Under the control of the computer 1 1, the digital electronic control circuit 10 moves using a piezoscanner 1 a conducting object stage 2 with sample 9 relative to the tip 5 to a point with programmed coordinates for forming a nanoscale metal island on sample 9. In this case, the pressing force of the tip 5 to the sample 9 is controlled by an electronic control circuit 1 0 by the deflection of the cantilever 4 measured using an optical circuit consisting of a laser 7 illuminating the surface of the cantilever 4 and a two-quadrant detector 8 recording the position of the beam reflected from the surface of the cantilever 4. After the tip 5 is installed at a point on sample 5 with programmed coordinates, computer 1 1 forms a metal island on sample 5 by applying a voltage pulse to the tip relative to the conductive stage 2 from the source of electrical exposure 9. In this case, metal ions passing along the tip from a solid electrolyte are deposited on the surface of sample 9 in the form of metal islands. Thus, in the places specified by the program, the tip of the solid electrolyte forms metal islands, the size of which is determined by the radius of curvature of the tip 5, by the force of pressing the tip to the nanostructure (minimum the diameter of the islands is 10 nm) and the magnitude and duration of the current pulse flowing through the tip (can be units of nm). After the formation of islands in the first layer is completed, the device proceeds to the formation of islands of the second layer located on the surface of the islands of the first layer, etc. Thus, nanostructures of a given shape and size are formed in layers from the deposited metal islands on the surface of sample 9. Using this device, it is possible to form nanostructures with both vertical walls and a pyramidal shape (tapering with distance from the base).

Depending on the tip material used (solid electrolyte), various metals are deposited (for example, silver for AgJ, RbAg ₄ I ₅ , silver for copper, CuBr, copper, etc.). Using cantilevers with various solid electrolytes, the formation of nanostructures from several different metals is possible. Chemical modification (oxidation, fluorination) of the surface of the created nanostructure is also possible using the corresponding solid electrolytes (for example, (В1 ₂ 0 ₃ ) _0> 8 (8гО) о, 2-For oxidation, Sro _{, 8} La _0j2 F _2j 2- for fluorination etc.), which leads to the formation of sections with different conductivities (dielectrics, semiconductors).

An example of practical implementation.

As a device for the formation of three-dimensional metal structures, a scanning force microscope (CCM) is used, for example, similar to that made by the authors (Bayburin V. B., Volkov Yu.P., Konnov NP, Multifunctional complex scanning probe microscopy and its application. Part 1 // Publishing house of the Saratov State University, 1998, - 122 pp.) Which includes a cylindrical piezoscanner (PAXY 0035 from Physical Instruments Germany), on which a conductive aluminum table is installed, a semiconductor laser (ML1016R from Mitsubishi), and a photodetector ctor (KDFM-4-03, Russia), digital electronic control unit of our own manufacture (V. B. Baiburin, A. Semenov, Yu.P. Volkov Universal Scanning Probe Microscope Complex / Uzavodskaya Laboratory, 2000, M> 12, s .17-23), a control computer (RSA6751, Advantech) vibration protection device (Thorlabs USA). The conductive cantilever is made of a piece of tungsten wire with a diameter of 60 μm and a length of 1 mm on which a light-reflecting mirror is attached (glass measuring 0.5x0.5 mm, thickness 0.1 mm coated with A1 by spraying in vacuum), and to which is attached a conductive silver-containing glue (SilverPrint) a tip from a single crystal of solid electrolyte RbAg I ₅ . The crystal has a length of 3 mm and a diameter of 0.5 mm, and the diameter decreases to its apex to sizes of 5-10 nm (the assessment was carried out according to electron microscopy). A circuit consisting of a digital-to-analog converter controlled by a computer and an amplifier providing current through the tip up to 100 mA is used as a source of electrical exposure. When a current pulse of 10 mA lasting 10 mA is applied to the tip (plus a tip), an island of silver 10 nm thick is deposited.

The scanning force microscope operates in a constant force mode, the value of which is selected equal to 10 ^"6 N. As a substrate, mica is used coated with a metal layer (for example, silver 30-50 nm thick) on the surface of which nanostructures are formed. It is also possible to form nanostructures on the crystal surface a conductor, for example, pyrolytic graphite.

Claims

Claim

1. The method of forming metal nanoscale objects, including layer-by-layer deposition of metal on a conductive substrate according to a predetermined program by applying current pulses between the tip of a cantilever of a scanning probe microscope and a substrate, characterized in that the deposition is carried out by electrolytic deposition of metal from a tip made of solid electrolyte, which provides metal ion transport.

2. The method according to p. 1, characterized in that after the formation of the object, chemical modification is additionally carried out in predetermined areas by exposure to current pulses between the tip of the cantilever and the substrate, while the tip of the cantelever is made of a solid electrolyte that ensures the transfer of gas ions.

3. A device for the formation of metal nanoscale objects containing a conducting object stage and the measuring head of a scanning probe microscope, including a cantilever, a source of electrical influence on the cantilever / sample system as an electronic current control device, piezoscanners with a compensator for thermal deformations and temperature drifts, a vibration-proof device, and a digital electronic system control head of a scanning probe microscope, characterized in that the tip of the cantilever is made from a solid electrolyte that provides the transfer of metal ions.

4. The device according to p. 1, characterized in that the cantilever is removable.

5. The device according to p. 1, characterized in that as a solid ¹ electrolyte selected electrolyte with silver ions, for example, RbAg ₄ 1 ₅ .

6. The device according to claim 1, characterized in that an electrolyte with oxygen or fluorine ions is selected as a solid electrolyte.