KR100937167B1 - Fabrication method of nanostructure using nanopore array - Google Patents

Abstract

The present invention relates to a method for manufacturing a nanostructure, specifically, the step of forming a conductive layer and an anodizing layer on the substrate in order; Anodizing the anodic oxide layer to form a plurality of nanopores; Removing an oxide of the anodization layer formed under the nanopores to expose an oxide of the conductive layer formed between an oxide bottom of the anodization layer and a surface of the conductive layer; And removing the oxide of the exposed conductive layer to expose the conductive layer under the nanopores. According to the present invention, only the oxide of the conductive layer under the nano-pores can be selectively removed, so that the conductivity between the material grown inside the nano-pores and the lower electrode can be kept excellent, thereby improving functionality as an element.

Nano structure, nano pore, anodization layer, conductive layer, lower electrode, oxide, etching solution

Description

Manufacturing method of nano structure using nano pore array {FABRICATION METHOD OF NANOSTRUCTURE USING NANOPORE ARRAY}

1A to 1E are conceptual views illustrating a method of manufacturing a nanostructure using a nanopore array according to an embodiment of the present invention.

Figure 2a to 2f is a SEM image of the TiO ₂ etching pattern in the nanostructure production according to the present invention.

3A to 3C are SEM photographs according to Test Example 1. FIG.

4A to 4C are graphs 4b and 4c illustrating a conceptual diagram 4a of a structure for measuring resistance according to Test Example 2 and a measurement result.

5A to 5E are conceptual views illustrating a method of manufacturing a nanostructure using a nanopore array according to another embodiment of the present invention.

The present invention relates to a method of manufacturing a nanostructure using a nano-pore array formed through the anodization of the material, in particular nano that can exhibit excellent conductivity by selectively removing the oxide generated from the conductive layer, the lower electrode of the lower portion of the nano-pore A method of manufacturing a nanostructure having a pore array.

Materials such as aluminum, titanium, tantalum, niobium, silicon, and zirconium are oxidized to form fine porous structures, that is, nanopore arrays, and are used in various fields. As such, nanostructured pores that can be produced from oxidation of certain materials are very large, have an adjustable aspect ratio, and can be prepared in the form of pore arrays ranging in diameter from several hundreds to hundreds of nanometers. By growing a desired material in a variety of ways, it has been spotlighted as a template of nanostructures such as nanotubes or nanowires. As an example, the most common one is anodized aluminum, which refers to an oxide film in which pores having a nano structure regularly arranged vertically on a surface obtained by anodizing an aluminum thin film are formed.

In particular, in recent years, as research on various devices using nanostructures such as nanowires has been actively conducted, many attempts have been reported to implement nanopore arrays of anodized aluminum having regular vertically arranged structures on wafers.

In general, however, nanostructured pores obtainable from anodized aluminum are characterized by the formation of a continuous layer of aluminum oxide, several tens to hundreds of nanometers thick, with aluminum that has not yet been oxidized. In other words, when fabricating a nano-pore array of anodized aluminum, a continuous aluminum oxide layer remains between the substrate and the pore array even after all of the aluminum is oxidized and the anodization is completed. Corresponding to or more than half the thickness is difficult to selectively remove it.

When various materials are grown in the nanopores and used as devices, such a continuous oxide layer may be present between the pore array and the electrodes on the substrate to increase the contact resistance between the materials in the nanopores, thereby causing the material to be exposed to external stimuli. It may cause a problem such as inhibiting the sensitivity or increasing the operating voltage of the device in measuring the electrical signal generated from the. In addition, there are cases where a catalyst layer is needed to grow a specific material in the nanopores. Most catalyst materials are metals such as Au, Co, Ni, Fe, and the like. It can be formed in advance. In this case, the continuous oxide layer should be removed because it prevents the exposure of the catalyst layer and prevents contact with the catalyst layer and the causative agent of the specific material to be grown.

In order to more easily remove the continuous oxide layer, it has been suggested to use a conductive film made of a specific metal between the aluminum thin film and the substrate. In this case, the conductive film may serve as a lower electrode with the role of removing the continuous aluminum oxide layer, and is required to oxidize aluminum in all parts when the thickness of aluminum is not constant. When the conductive film is inserted, a smaller pore or pore between the continuous oxide layer and the conductive film is maintained by the conductive film when the anodization of aluminum ends, that is, when the anodized aluminum reaches the conductive film. It is observed that a void is formed. When such smaller pores or pores are generated, even if the etching process is not necessary or necessary, the thickness of the continuous oxide layer becomes thinner and the etching solution penetrates into the smaller pores or pores to penetrate the continuous oxide layer in both directions. Etching allows selective etching, which can be removed more easily.

When the conductive film is inserted between the aluminum thin film and the substrate, the current change when the anodization of aluminum is finished depends on the type of conductive film to be inserted. According to the current change, the material forming the conductive film can be classified into three groups. In the first group, the current rapidly decreases when all aluminum is oxidized, and Ti, Zr, Nb, Ta, Mo, etc. For example. While the first group material is easy to determine when to stop the anodization reaction through a change in current, the inserted first group material itself is also anodized to form an oxide layer on the lower electrode surface to form a continuous aluminum oxide layer. Even after removal, there is a problem that another oxide layer exists under the pore.

In the case of the second group, for example, Pt, Au, and the like, and the current increases rapidly with severe bubble generation at the time when all of the aluminum is oxidized. Since the material belonging to the second group has a very low tendency to oxidize, it is very unlikely that anodization reaction will continue after all the aluminum is oxidized, but the anodic oxidation is stopped due to the rapid rise of the current with severe bubbles generated by the electrolyte. It is difficult to determine the timing point, which causes a problem that the nano-pore array is detached from the substrate.

In the third group, when the aluminum is all oxidized, the current decreases and then increases, and then decreases again, and examples thereof include Ru and ITO. Since the material belonging to the third group has bubbles, but the oxide itself has good conductivity, it is possible to secure the conductivity under the nanopores by stopping the anodization at a suitable time. However, there is a problem that the interface is damaged and the nano-pore array is desorbed if it does not properly stop the anodic oxidation because it has a property to dissolve in the electrolyte through the anodization reaction.

Therefore, when the conductive film is inserted between the aluminum thin film and the substrate to facilitate the continuous removal of the aluminum oxide layer, the material to be inserted must maintain stable interfacial adhesion between the substrate and the nanopore array and ensure the conductivity of the lower portion of the pore. In order to expose the lower catalyst layer, it is necessary to clarify the time when the anodic oxidation is stopped due to a decrease in current due to the slowing of the oxidation reaction while preventing an abrupt bubble generation. It can be said that it is suitable.

As an example of manufacturing a nanopore array by inserting a conductive film as described above, in International Patent Publication No. 03/046265, a conductive film of Ti or Pt is formed on a Si substrate, and aluminum is deposited and then anodized to form a nanopore. After formation, it is described to remove the barrier layer, which is a continuous oxide layer, generated by cathodic polarization. However, although the barrier layer, that is, the continuous oxide layer can be removed by the above method, there is a problem that TiO _{2, which} is an oxide of the conductive film, is generated or the nanopore array can be detached from the substrate.

In addition, U.S. Patent No. 6,628,053 discloses that when a conductive layer is inserted into a substrate and anodized aluminum deposited thereon, a number of narrow holes are formed in the alumina film, in particular, Ti, Zr, Nb, Ta. When the conductive layer is formed of a material such as Mo, Cu, or Zn, it is disclosed that a bridge-shaped path connecting the lower portion of the narrow hole and the surface of the conductive layer can be formed. In this case, the oxides of the materials are stable and not easily dissolved in the electrolyte so that alumina remains in the form of the passage, so that the conductivity can be improved by annealing and reducing it under hydrogen gas, inert gas or hydrogen and inert gas atmosphere. It is described as. However, according to the above document, rather than removing the continuous aluminum oxide layer itself, the conductivity is secured through a very narrow passage formed in the alumina film, so that a desired level of conductivity cannot be obtained, and the material inserted into the conductive layer as well as the aluminum oxide layer. Since oxides are also generated from the above, they have the same problems as described above.

As such, when the nanopore array is manufactured by anodizing the material, when the material belonging to the first group is inserted into the conductive film, the anodization of the upper material layer aluminum is finished and the anodizing of the conductive film proceeds. It is stable without bubble generation or rapid rise of current, and is easy to prevent desorption of the alumina film. In addition, as the anodization of the lower conductive film proceeds, dissolution of the upper continuous aluminum oxide film is continued, and the oxide of the lower conductive film generated as a result of the anodic oxidation can take the place of the continuous aluminum oxide film. If the oxide of the lower conductive layer formed as described above can be selectively removed, the lower electrode can be exposed to secure conductivity and may be revealed when the catalyst layer is inserted. Therefore, in the case of inserting a material belonging to the first group into the conductive film in manufacturing the nano-pore array through the anodization of the material, a method for selectively removing the oxide generated from the conductive film is required.

The present invention has been made to solve this problem, and relates to a method for manufacturing a nanostructure using a nano-pore array by the anodization of the material, in particular to selectively remove only the oxide of the conductive layer formed under the nanopore It relates to a method for producing a nanostructure containing.

As a result of intensive studies of the present inventors in order to solve the above problems, the etching can be selectively etched only the oxide generated from the conductive layer inserted into the lower electrode when manufacturing the nanostructure using the nano-pore array by the anodization of the material By selectively removing only the oxide using a solution, the lower electrode or the catalyst layer is exposed to the lower portion of the nanopores to secure the conductivity of the lower portion of the nanopores, and suitable nanowires can be grown inside the nanopores using the exposed catalyst. It was found that the present invention was completed.

The present invention comprises the steps of sequentially forming a conductive layer and an anodizing layer on the substrate; Anodizing the anodic oxide layer to form a plurality of nanopores; Removing an oxide of the anodization layer formed under the nanopores to expose an oxide of the conductive layer formed between an oxide bottom of the anodization layer and a surface of the conductive layer; And removing the oxide of the exposed conductive layer to expose the conductive layer under the nanopores.

In addition, the present invention comprises the steps of sequentially forming a catalyst layer, a conductive layer and an anodizing layer on a substrate; Anodizing the anodic oxide layer to form a plurality of nanopores; Removing an oxide of the anodization layer formed under the nanopores to expose an oxide of the conductive layer formed between an oxide bottom of the anodization layer and a surface of the conductive layer; And removing the oxide of the exposed conductive layer to expose the catalyst layer under the nanopores.

In addition, the present invention relates to a method of manufacturing a nanostructure further comprising the step of growing a nanotube or nanowires inside the nano-pores exposed conductive layer or catalyst layer on the bottom as described above.

The removing of the oxide of the conductive layer may be performed by using an etching solution for selectively etching only the oxide of the conductive layer with respect to the oxide of the anodizing layer.

Hereinafter, a method of manufacturing a nanostructure according to the present invention will be described in detail.

In the present invention, in the fabrication of nanostructures using nanopore arrays by anodization, a conductive layer and an anodizing layer serving as a lower electrode are formed on a substrate, and the anodization process is performed to generate a lower portion of the nanopores. By selectively removing not only the oxide of the anodization layer but also the oxide of the conductive layer, the nanowires can be grown inside the nanopores to exhibit excellent electrical characteristics, thereby maximizing functionality as a device. It features.

In order to manufacture the nanostructure according to the present invention, a conductive layer and an anodizing layer are sequentially formed on a substrate.

The substrate may be selected from the group consisting of silicon, sapphire, silicon carbide, silicon oxide, quartz, plastic, ceramic, and gallium arsenide, but is not limited thereto.

An oxide film, for example, a silicon oxide film, may be formed before the conductive layer is formed on the substrate. The silicon oxide layer protects the substrate and may serve to prevent an additional reaction of the material forming the substrate. Specifically, during the aluminum anodization process, a potential of several to several tens of volts is applied to aluminum, so that when the substrate is sensitive to an electric field, a sufficient thickness is obtained by doping a silicon wafer or a substrate used to protect the substrate. It is necessary to form a silicon oxide film. In addition, when silicon is exposed to electrolyte during the process, there is a possibility that an additional reaction such as unwanted silicon oxidation may occur, so that such additional reaction can be prevented by forming a silicon oxide film. The thickness of the silicon oxide film is generally about 100 nm, but is not limited thereto. In addition, it is already known to those skilled in the art that the oxide film that plays the above role may be different depending on the type of the substrate in addition to the silicon oxide film, and an appropriate oxide film may be formed according to the substrate.

A conductive layer is formed on the substrate. Such a conductive layer serves as efficient removal of a continuous aluminum oxide layer formed during anodization, such as aluminum, performs a uniform oxidation reaction when the aluminum thickness is not constant, and serves as a lower electrode, also referred to as a conductive film. In the present invention, the conductive layer is preferably a nitride of a metal, particularly preferably a nitride of a metal having a specific resistance in the range of 100 to 300 mPa cm. Examples of particularly preferred conductive layers in the present invention include, but are not limited to, those selected from titanium nitride, tantalum nitride and tungsten nitride.

As described above, when the nitride of the metal is inserted into the conductive layer, when the anodic oxide layer formed on the top is anodized, the current decreases rapidly at the time when all of the anodized oxide layer is oxidized to stop the anodization reaction. The timing can be easily determined, and the process is stable without the occurrence of gas bubbles or rapid current rise, so that it is easy to prevent desorption of the formed oxide film. In addition, it is not necessary to etch the barrier layer, which is an oxide of the anodizing layer under the nanopore formed by the anodization, or the barrier layer is thin and can be easily etched in both directions so as to be easily etched. do.

The thickness of the conductive layer may be appropriately selected according to need, and may be used as a lower electrode after removing the oxide generated from the conductive layer in a later step, so that a thickness sufficient to serve as an electrode may be secured. It can be formed. For example, when TiN is used as the conductive layer, a thickness of about 50 nm is preferable, but is not limited thereto. In the case of forming the catalyst layer as described below, the conductive layer under the pore is oxidized by anodization, and the catalyst layer can be formed to a thickness such that it is not oxidized. For example, when TiN is used as the conductive layer, a thickness of about 10 to 50 nm is preferable, but is not limited thereto. If less than the above range, anodization may proceed to the catalyst layer after all of the conductive layer under the pore is oxidized, and if it exceeds the above range, all of the conductive layer may not be oxidized.

An anodized layer to be anodized is formed on the conductive layer formed as described above. The anodization layer is not particularly limited as long as it is a material capable of forming a porous structure, that is, a nano-pore array through anodization, and for example, a material selected from the group consisting of aluminum, tantalum, niobium, silicon, and zirconium is used. Aluminum, which is generally used for the production of microporous structures by anodization, is particularly preferred.

The thickness of the anodization layer may be appropriately selected as necessary, for example, may have a range of about 100 nm to several μm, but is not limited thereto.

The conductive layer and the anodic oxide layer may be formed by a general method known to those skilled in the art, for example, electrolytic deposition, atomic layer deposition, chemical vapor deposition, and the like, but is not limited thereto.

In this way, the conductive layer and the anodic oxide layer are formed on the substrate and then anodized. The anodic oxidation process can be carried out according to a method known to those skilled in the art, and is generally performed by flowing a direct current using an anodized layer as an anode in an electrolyte solution and a separate carbon electrode as a cathode. When anodization is performed, the anodic oxide layer is oxidized by the ionic species containing oxygen diffused by the applied electric field, and is converted into an oxide having a plurality of nanopores. and Depending on the distribution of the electric field, the conductive layer below the nanopores is first oxidized and then oxidized as it extends to the periphery. In the present invention, the anodic oxidation is an oxide having a nano-pore array by oxidizing all the anodizing layer, and a portion of the conductive layer under the nano-pore is also oxidized to form an oxide generated from the conductive layer on the lower portion of the pore and the surface of the conductive layer. Is going to be.

After the anodization proceeds as described above, the oxide of the anodization layer formed on the lower portion of the nanopores is removed and formed on the lower portion (ie, between the oxide lower portion of the anodization layer formed on the lower portion of the nanopores and the surface of the conductive layer). The oxide of the conductive layer is exposed. That is, in the present invention, in order to efficiently remove the oxide of the conductive layer formed on the lower portion of the nano-pores, the oxide of the anodic oxide layer remaining on the upper portion is removed. Oxide removal of the anodic oxide layer can be used a suitable known method, for example, it is possible to remove the oxide of the anodic oxide layer by etching with a suitable acid solution according to the anodization layer used. Examples of acid solutions that can be used include those selected from the group consisting of a phosphoric acid solution, a sulfuric acid solution, a chromic acid solution, a hydroxyl solution and a mixed solution thereof, but is not limited thereto. Specifically, when aluminum is used as the anodizing layer, alumina, an oxide of the anodizing layer generated under the nanopores, may contain a solution containing phosphoric acid, preferably a mixed solution of 6 wt% phosphoric acid and 1.8 wt% chromic acid. Can be selectively etched and removed.

Etch times and temperatures are known to those skilled in the art and may be selected and used as appropriate for the respective materials and conditions. For example, when aluminum is used as the anodization layer, the alumina, which is the generated oxide, is generally etched at a temperature of 30 to 60 ° C., and depending on the etching rate, the time may proceed from several minutes to several hours. For example, to control the pore diameter of the alumina, the etching rate is low, so it is preferable to etch for 5 to 15 minutes at 30 ℃, to quickly remove the alumina under the pore can be etched for more than 15 minutes at 50 ℃.

When the oxide of the anodic oxide layer formed on the lower portion of the nano-pores is removed as described above, the oxide generated from the conductive layer formed between the anodized oxide layer on the lower portion of the nano-pore and the surface of the conductive layer is exposed to the lower portion of the nano-pores. As such, when only the oxide of the conductive layer exposed to the lower portion of the nano-pores is selectively removed, the conductive layer serving as the lower electrode of the lower portion or the catalyst layer to be described later may be exposed. Excellent conductivity and functionality can be secured. In the present invention, it is characterized in that only the oxide of the exposed conductive layer is selectively removed without removing the oxide of the anodizing layer forming the wall between the nano-pores, specifically, with respect to the oxide of the anodizing layer Only an oxide of the conductive layer may be selectively removed by using an etching solution for etching only the oxide of the conductive layer.

That is, according to the prior art, only the oxide of the anodized layer is removed, and the oxide of the conductive layer remains as it is, or the interface is damaged, so that the nanopore array is desorbed from the substrate. Likewise, by using an etching solution capable of selectively etching the oxide of the conductive layer exposed to the lower part of the nanopore with respect to the oxide of the anodizing layer forming the wall between the nanopores, the conduction generated on the surface of the conductive layer below the nanopore. Only oxides of the layer can be selectively removed.

When TiN is used as the conductive layer and aluminum is used as the anodizing layer, only TiO _2, which is an oxide of the conductive layer, is selectively removed from the alumina, which is an oxide of aluminum, using a mixed aqueous solution of ammonia and hydrogen peroxide as an etching solution. The mixing ratio of the aqueous ammonia solution and the hydrogen peroxide mixed aqueous solution is preferably NH ₄ OH: H ₂ O ₂ : H ₂ O in the range of 0.5: 1.0: 5.0 to 1.0: 1.0: 10.0, and particularly preferably 1: 1: 5 When the etching solution is etched, the alumina forming the walls between the nanopores may be selectively etched and removed without removing the TiO ₂ oxide of the conductive layer formed on the surface of the conductive layer under the nanopores.

Etching temperature and time may be appropriately selected according to what is known to those skilled in the art, for example, may be made for 1 to 30 minutes at 20 ~ 100 ℃ but is not limited thereto.

As described above, only the oxide of the conductive layer exposed to the lower portion of the nano-pores is selectively etched and removed, thereby growing conductivity of the nanowires in the nano-pores to secure conductivity between the nanowires and the lower electrode inside the nano-pores. can do. Therefore, when used as an element, it is possible to solve problems such as sensitivity degradation due to deterioration of electrical characteristics due to an increase in resistance, thereby contributing to performance improvement of the element.

After the oxide of the conductive layer is selectively removed as described above, the oxide of the anod oxide layer forming the wall between the nanopores may be etched as needed before the desired material is grown in the nanopores, thereby controlling the size of the nanopores. have. As described above, the anode oxide layer oxide may be etched using a suitable acid solution as described above. For example, when aluminum is used as the anodization layer, alumina forming a wall between nanopores generated by anodization may be etched using a mixed solution of phosphoric acid and chromic acid.

The nanostructures may be manufactured by growing a desired nanotube or nanowire using an appropriate method in the nanopores thus formed. At this time, the method of growing the nanotube or nanowire in the nano-pores can be appropriately selected from methods known to those skilled in the art, for example, from the group consisting of electrolytic deposition, atomic layer deposition, chemical vapor deposition and pulse laser deposition Depending on the method chosen.

It will be described in more detail with reference to FIG. As shown in FIG. 1A, after the silicon oxide film 12 is formed on the silicon substrate 11, the TiN 13 as a conductive layer and the aluminum 14 as an anodized layer are sequentially formed, anodization is performed. As shown in FIG. 1B, aluminum is oxidized into alumina 14B having a plurality of nanopores 14A, and a part of the TiN layer 13 below is also oxidized to alumina layer under the nanopores 14A. Between the surface 14B and the TiN layer 13, a TiO ₂ layer 13A, which is an oxide of the conductive layer, is formed. Subsequently, the alumina layer 14B formed under the nanopores 14A is removed by etching using a mixed solution of phosphoric acid and chromic acid to expose the TiO ₂ layer 13A formed thereunder (FIG. 1C). When the exposed TiO ₂ layer 13A is etched and removed using a mixed aqueous solution of ammonia and hydrogen peroxide, the TiN layer 13 is exposed under the nanopores 14A as shown in FIG. 1D. Thereafter, the nanostructures may be manufactured by growing the nanowires 15 in the nanopores 14A.

According to another aspect of the present invention, when the catalyst layer is required for growth of a specific material inside the nano-pores, except that the catalyst layer is formed between the substrate and the conductive layer, and the thickness of the conductive layer is made thinner. Nanostructures are prepared by a similar method.

At this time, the material used for the catalyst layer can be used by appropriately selecting a known material according to the nanowires or nanotubes to be grown. Examples of the material usable as the catalyst layer include, but are not limited to, metals such as Au, Co, Ni, Fe, and the like.

Specifically, the catalyst layer, the conductive layer, and the anodizing layer are sequentially formed on the substrate, and then the anodizing layer is anodized. The anodization process in the case of the catalyst layer is an oxide oxide layer is oxidized to an oxide having a nano-pore, the conductive layer below the nano-pore is oxidized to form an oxide, the catalyst layer is not oxidized. That is, the oxide of the anodizing layer, the oxide of the conductive layer, and the catalyst layer are sequentially disposed under the nanopores formed by the anodization process. By removing the oxide of the anode oxide layer formed on the lower portion of the nano-pores, exposing the oxide of the conductive layer to the lower portion of the nano-pores, and selectively removed by using an etching solution for etching only the oxide of the exposed conductive layer It goes through the process of exposing the catalyst layer. Thereafter, the nanostructure may be manufactured by growing an appropriate nanowire or nanotube inside the nanopores where the catalyst layer is exposed.

This will be described in more detail with reference to FIG. 5. As shown in FIG. 5A, after the silicon oxide film 52, the catalyst layer 53, the TiN 54 as a conductive layer, and the aluminum 55 as an anodized layer are sequentially formed on the silicon substrate 51, When anodization is performed, as shown in FIG. 1B, aluminum is oxidized to change into alumina 55B having a plurality of nanopores 55A, and the TiN layer 54 is also oxidized to lower the nanopores 55A. A TiO ₂ layer 54A, which is an oxide of the conductive layer, is formed between the lower portion of the alumina layer 55B and the catalyst layer 53. Subsequently, the alumina layer 55B formed under the nanopores 55A is removed by etching using the phosphoric acid and chromic acid mixed solution to expose the TiO ₂ layer 54A formed under the nanopore 55A (FIG. 5C). When the exposed TiO ₂ layer 54A is etched and removed using an aqueous mixed solution of ammonia and hydrogen peroxide, the catalyst layer 53 is exposed under the nanopores 55A as shown in FIG. 5D. Thereafter, the nanostructure 56 may be manufactured by growing the nanowires 56 (FIG. 5E) in the nanopores 55A using the catalyst layer 53.

When nanowires and the like are grown in the nanopores according to the method of the present invention, the conductive layer oxide under the nanopores is removed, so that the grown nanowires come into good contact with the conductive layer under the nanopores, that is, the lower electrode. That is, when the resistance measurement as shown in Test Example 2 to be described later, it can be confirmed that the current shows a linear behavior with respect to the voltage. Therefore, the material such as nanowires grown in the nanopores according to the present invention and the lower electrode (conductive layer) exhibit ohmic contact characteristics, and thus have good electrical conductivity and can maintain excellent characteristics as devices. It can be seen.

In addition, when the catalyst layer necessary for nanowire growth is formed, the catalyst layer is exposed on the lower portion of the nanopores to remove elements that interfere with contact with the causative agent of the nanowires, thereby efficiently growing the desired nanowires using the catalyst layer. You can do it.

Hereinafter, with reference to the embodiments and the accompanying drawings will be described the present invention in more detail.

Example 1

As shown in FIG. 1A, after forming a silicon oxide film (SiO ₂ ) 12 on the silicon wafer 11, a TiN layer 13 is formed as a conductive layer on the silicon oxide film 12, and the TiN An aluminum thin film 14 was formed on the layer 13.

The silicon wafer prepared as described above was immersed in an electrolyte solution (0.3 M oxalic acid solution) and anodized. At this time, a potential of 40 V is applied to the aluminum thin film 14 as an anode in the electrolyte solution and a carbon electrode (not shown) as the cathode. Drift the current.

As a result, as shown in FIG. 1B, the aluminum thin film 14 is changed into an alumina layer 14B having a plurality of nanopores 14A, and the TiN layer (a conductive layer) and the alumina 14B under the pores 14A are formed. 13) TiO ₂ (13A) was formed as an oxide thereof.

After exposing the lower TiO ₂ (13A) by etching the alumina 14B under the nanopores 14A for 5 minutes in 6 wt% phosphoric acid and 1.8 wt% chromic acid mixed solution maintained at 30 ° C (FIG. 1C), 30 The exposed TiO ₂ (13A) was removed by etching for 5 minutes with a mixture of aqueous ammonia and hydrogen peroxide solution (NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 5) maintained at ℃.

If necessary, the pores may be sized by etching alumina in a mixed solution of 6 wt% phosphoric acid and 1.8 wt% chromic acid maintained at 30 ° C. for 1-5 minutes. As a result of this process, as shown in FIG. 1D, a conductive layer, that is, a nanopore array in which the lower electrode is exposed is formed. Thereafter, the desired nanowires or nanotubes 15 were grown in the nanopores 14A by electrolytic deposition, atomic layer deposition, chemical vapor deposition, or the like (FIG. 1e).

SEM pictures of TiO ₂ etching patterns are shown in FIGS. 2A to 2F. FIG. 2A is a planar photograph after etching TiO ₂ for 4 minutes after removing the alumina under the nanopore, and FIG. 2B is a cross-sectional view showing the interface removed by etching TiO ₂ for 4 minutes after removing the alumina under the nanopore. . FIG. 2C is a planar photograph after etching for 5 minutes, FIG. 2D is a cross-sectional photograph when etching for 5 minutes, FIG. 2E is a planar photograph when etching for 6 minutes, and FIG. 2F is a cross-sectional photograph when etching for 6 minutes . The white spots in the planar image are TiO ₂ , and when removed for 5 minutes, it can be confirmed that they are well removed.

Example 2

As shown in Figs. 5A to 5E, the thickness of the TiN layer 54, which is a conductive layer, is reduced, and the nano-to be grown in the nanopores between the silicon oxide film 52 and the TiN layer 54 formed on the silicon substrate 51. Nanopore arrays were prepared in the same manner as in Example 1 except that the catalyst layer 53 for promoting wire growth was inserted.

That is, as illustrated in FIG. 5A, the silicon substrate 51, the silicon oxide film 52, the catalyst layer 53, the TiN layer 54, and the aluminum thin film layer 55 are stacked in this order, followed by anodizing. As shown in FIG. 5B, the aluminum thin film 55 is oxidized to alumina having a plurality of nanopores 55A, and a TiO ₂ layer (between the surfaces of the alumina 55B and the TiN layer 54 below the pore 55A). 54A) was formed. After alumina (55B) was etched in a mixed solution of 6 wt% phosphoric acid and 1.8 wt% chromic acid maintained at 30 ° C. for 5 minutes to expose TiO ₂ (54A) at the bottom (FIG. 5C), ammonia water and hydrogen peroxide maintained at 30 ° C. The catalyst layer 53 was exposed by etching for 5 minutes with an aqueous mixed solution (NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 5) to remove TiO ₂ (54A) under the nanopores 55A. (FIG. 5D).

The exposed catalyst layer 53 was used to grow an appropriate nanowire or nanotube 56 inside the nanopores 55A (FIG. 5E).

Test Example

In this test example, in the nanostructure manufactured in Example 1, after depositing Ru in the nano-pores by atomic layer deposition method, to check the contact state of Ru and TiN, to evaluate the electrical properties of the lower electrode Evaluation was performed. As a control, a specimen in which Ru was deposited on a nanostructure in which TiO ₂ was not removed was used.

Test Example 1

3A-3C show SEM images of the deposited Ru layer. Figure 3a is a planar picture of the Ru layer deposited inside the nano-pores, since the Ru layer is deposited from the surface of the nano-pores it can be seen that there is an empty space in the center of the pore after the deposition is completed. FIG. 3b is a cross-sectional photograph of a sample on which Ru is deposited after removing the TiO ₂ from the lower portion of the nanopores through a selective etching process according to Example 1, and FIG. 3c is a control, that is, Ru is deposited without removing TiO ₂ . A cross section of the specimen. Comparing FIGS. 3B and 3C, in FIG. 3B, Ru and TiN are in good contact with each other without a separate layer between Ru and TiN. In FIG. 3C, a separate layer, that is, a TiO ₂ layer, is present between Ru and TiN. You can see that.

From this, according to the present invention it can be seen that the oxide generated from the conductive layer, that is, the lower electrode layer is selectively removed, so that the material grown in the nanopores and the lower electrode can be in good contact.

Test Example 2

Results of measuring the resistance using Ru deposited in the nanopores as described above are shown in FIGS. 4A to 4C. 4A is a schematic diagram of a structure for resistance measurement. After depositing Ru, about 500 nm of aluminum was deposited in a region having a diameter of 2 mm using a sputter. Then, Ru is removed from the region where aluminum is not deposited through dry etching, and the resistance between the two pads is measured. The results are shown in FIGS. 4B and 4C.

FIG. 4B is a result of measuring the resistance between the aluminum pads of the specimen selectively removed TiO ₂ according to Example 1, and FIG. 4C is a result of measuring the resistance between the aluminum pads of the specimen without TiO ₂ removed. Comparing Figures 4b and 4c, when TiO ₂ is removed (Figure 4b), it exhibits a typical ohmic contact characteristic, which shows a linear behavior of current with respect to voltage, while TiO ₂ is not removed. 4c, it can be seen that the typical schottky contact characteristic that the current rapidly increases with increasing voltage.

From this, according to the present invention, the oxide layer generated from the conductive layer, which is the lower electrode layer, may be selectively removed to ensure conductivity between the material grown in the nanopores and the lower electrode. It can be seen that it does not occur.

Although the present invention has been described with reference to various embodiments, it is merely exemplary, and therefore, the scope of the present invention should be defined by the technical spirit described in the claims.

According to the present invention, when the nanostructure having nanopores obtained by oxidizing various materials such as aluminum, only the oxides generated from the lower electrode, which is a conductive layer under the nanopore, are selectively removed, so that the conductive layer is suitable for the nanopore bottom. Since the lower electrode or the catalyst layer for nanowire growth can be exposed, it can be used to form nanostructures in which nanowires are selectively grown on nanopore arrays.

The nanostructure in which a desired material is grown therein using the nanopore array manufactured by the present invention maintains excellent contact between the material inside the pore and the lower electrode, thereby ensuring high electrical conductivity.

Therefore, when the nanowires are grown on the nanostructures according to the present invention to fabricate nanodevices using the same, the nanowires grown therein are highly sensitive when measuring electrical signals generated from external stimuli, and smooth operation of the devices is achieved. It can be usefully used as a nano-sensor and so on.

Claims (17)

Sequentially forming a titanium nitride layer and an aluminum layer on the substrate; Anodizing the aluminum layer to form a plurality of nanopores; Removing the aluminum oxide formed under the nanopores to expose the titanium oxide formed between the lower portion of the aluminum oxide and the surface of the titanium nitride layer; And Removing the titanium oxide, exposing the titanium nitride layer under the nanopore; The step of removing the titanium oxide is ammonia water and hydrogen peroxide water in which the ratio of NH ₄ OH: H ₂ O ₂ : H ₂ O selectively etching only titanium oxide with respect to aluminum oxide 0.5: 1.0: 5.0 to 1.0: 1.0: 10.0 Etched Using Mixed Aqueous Solution Method for producing a nanostructure. Sequentially forming a catalyst layer, a titanium nitride layer, and an aluminum layer on the substrate; Anodizing the aluminum layer to form a plurality of nanopores; Removing the aluminum oxide formed under the nanopores to expose the titanium oxide formed between the lower portion of the aluminum oxide and the surface of the titanium nitride layer; And Removing the exposed titanium oxide, exposing the catalyst layer under the nanopores, The step of removing the titanium oxide is ammonia water and hydrogen peroxide water in which the ratio of NH ₄ OH: H ₂ O ₂ : H ₂ O selectively etching only titanium oxide with respect to aluminum oxide 0.5: 1.0: 5.0 to 1.0: 1.0: 10.0 Etched Using Mixed Aqueous Solution Method for producing a nanostructure. The method according to claim 1 or 2, The substrate is characterized in that selected from the group consisting of silicon, sapphire, silicon carbide, quartz, plastics, ceramics, gallium arsenide and silicon oxide Method for producing a nanostructure. The method of claim 1, After exposing the titanium nitride layer under the nanopores, further comprising growing nanotubes or nanowires inside the nanopores. Method for producing a nanostructure. The method of claim 4, wherein The growth is characterized by the method selected from the group consisting of electrolytic deposition, atomic layer deposition, chemical vapor deposition and pulse laser deposition. Method for producing a nanostructure. The method according to claim 1 or 2, And forming an oxide film before forming the titanium nitride layer on the substrate. Method for producing a nanostructure. The method of claim 6, The oxide film is characterized in that the silicon oxide film Method for producing a nanostructure. The method of claim 1, The anodization is characterized in that the aluminum layer is oxidized to aluminum oxide having a plurality of nano-pores, a portion of the titanium nitride layer below the nano-pores is oxidized to form titanium oxide. Method for producing a nanostructure. The method of claim 2, The anodization is characterized in that the aluminum layer is oxidized to aluminum oxide having a plurality of nano pores, the titanium nitride layer under the nano-pore is oxidized to form titanium oxide, the catalyst layer is not oxidized Method for producing a nanostructure. The method according to claim 1 or 2, After removing the titanium oxide, by etching the aluminum oxide forming a wall between the nano-pores, further comprising adjusting the size of the nano-pores Method for producing a nanostructure. Nanostructure made by the method according to claim 4, wherein nanowires or nanotubes are formed in the nanopores. The method of claim 2, After exposing the catalyst layer under the nanopores, further comprising growing nanotubes or nanowires inside the nanopores. Method for producing a nanostructure. The method of claim 12, The growth is characterized by the method selected from the group consisting of electrolytic deposition, atomic layer deposition, chemical vapor deposition and pulse laser deposition. Method for producing a nanostructure. The nanostructure produced by the method according to claim 12, wherein the nanowires or nanotubes are formed in the nanopores. delete delete delete

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