JP2006326723A - Method for manufacturing nano-structure and nano-structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a nano-structure having projections of uniform lengths and the nano-structure. <P>SOLUTION: This method has a step for forming laminated bodies 23 and 24 having two or more layers made of materials formed with holes by anodic oxidation on substrates 21 or substrate layers 22, a step for forming through holes 25 by performing anodic oxidation for the laminated bodies 23 and 24, a step for filling contents 26 in the holes 25, and a step for forming the projections 27 made of the contents 26 by selectively removing upper layers 24 of the laminated bodies 23 and 24. This nano-structure is utilized in a field emission type electronic source, a mold for nano imprint, a probe for a probe microscope and a magnetic recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nanostructure having a protrusion perpendicular or nearly perpendicular to a film surface and the nanostructure, and more particularly, a method for manufacturing a nanostructure having a uniform height of the protrusion and the nanostructure It relates to nanostructures.

  The nanostructure can be used in a wide range as a functional material such as an electronic device or a microdevice, a structural material, or the like. In particular, it can be applied as a field emission electron source, a nanoimprint mold, a probe for a probe microscope, and the like.

  Furthermore, the present invention provides a method for producing a nanostructure excellent in planarity and film thickness controllability by selectively removing a protruding portion protruding upward with respect to the film surface and the nanostructure. Yes, it can be applied to magnetic recording media.

  As a method for forming metal and semiconductor nanowires perpendicular to the film surface, a method using an anodic oxidation method is known. The anodic oxidation method referred to here is to apply a voltage (anodic oxidation) in an acidic solution using the workpiece as an anode, and it is known that nano-scale pores are produced particularly in the anodic oxidation of Al. It has been. Using this pore as a template, various nanowires can be created.

  The anodizing method will be described in more detail. When the Al substrate is anodized in an acidic electrolyte such as sulfuric acid, oxalic acid, phosphoric acid, a porous anodic oxide film is formed (see, for example, Non-Patent Document 1). This porous film is characterized by a unique geometrical feature that extremely fine cylindrical pores (alumina nanoholes) with a diameter of several nanometers to several hundred nanometers are arranged in parallel at intervals of several tens of nanometers to several hundred nanometers. It has a structure. And this cylindrical pore has a high aspect ratio, and is excellent also in the uniformity of the diameter of a cross section.

  Further, the structure of the porous film can be controlled to some extent by changing the anodizing conditions. For example, it is known that the pore interval can be controlled to some extent by pore widening, and the pore diameter can be controlled to some extent by pore widening treatment. Here, the pore-wide treatment is an etching treatment of alumina, and a wet etching treatment with ordinary phosphoric acid is used.

  In addition, in order to improve the verticality, linearity and independence of the pores of the porous film, a method of performing two-step anodization is known. That is, a method has been proposed in which a porous film formed by performing anodic oxidation is once removed and then anodized again to produce a porous film having pores having better verticality, linearity, and independence. (For example, refer nonpatent literature 2 grade | etc.,). Here, this method uses that the depression of the Al substrate formed when the anodic oxide film formed by the first anodic oxidation is removed becomes the starting point of pore formation of the second anodic oxidation.

  Furthermore, in order to form pores arranged in a highly regular pattern in a desired pattern, a method using a stamper having protrusions is known (see, for example, Patent Document 1 and Non-Patent Document 3). In these methods, the stamper is pressed against the surface of the Al substrate, and the protrusions of the stamper are transferred as depressions on the surface of the Al substrate, thereby creating the pore formation starting point for anodic oxidation.

  The nanostructures that are naturally formed as described above, that is, self-regularly formed, are finer and special-purpose than conventional artificial nanostructure technologies such as photolithography, electron beam exposure, and X-ray exposure. There is a possibility that the structure can be realized, and in recent years, it has attracted much attention.

Thus, the nanostructure which has the pore formed in the self-regularity has proposed the application method which utilized the characteristic of the structure itself. Various application proposals including coloring, magnetic recording media, EL light emitting elements, electrochromic elements, optical elements, solar cells, gas sensors, etc. by filling the pores with magnetic materials, dielectrics, optical functional materials, etc. Has been made. It is also possible to produce a nanostructure having an upwardly protruding protrusion by using the pore body as a template.
JP-A-10-121292 R. C. Furneaux, W.M. R. Rigby & A. P. Davidson “NATURE” Vol. 337, p. 147 (1989) “Japan Journal of Applied Physics” Vol. 35, p. 126-129 (1996) Masuda “Solid Physics” 31, p. 493 (1996)

  As shown in the background art, the pores formed in a self-ordered manner by using an anodic oxidation method are filled with metal and semiconductor, and then the surrounding anodic oxide film is removed to form an upwardly protruding protrusion. There is a way to create. However, the joint portion of such protrusions is only the base, and is inferior in adhesion. In particular, in the case of a projection having a high aspect, the strength is weak and there is a problem in applying it to a device or the like. In addition, leaving a part of the anodized film solves the problem of strength accompanied by adhesion, but the upper surface of the anodized film becomes non-uniform, so the length of the protrusion relative to the upper surface of the anodized film is It becomes non-uniform.

  The present invention provides a method for producing a nanostructure having a protrusion having a uniform length and a nanostructure, and a field emission electron source, a nanoimprint mold, and a probe microscope using the nanostructure. A probe is provided.

  In addition, the present invention provides a nanostructure manufacturing method and structure excellent in flatness and film thickness controllability by selectively removing the above-mentioned protrusions, and uses this structure. The magnetic recording medium is provided.

The above problems can be solved by the following manufacturing method and configuration of the present invention.
That is, the present invention is a method for producing a nanostructure, comprising a step of laminating two or more layers made of a material in which holes are formed by anodic oxidation on a substrate or a base to form a laminate, A step of anodizing the laminate to form a through-hole, a step of filling the inclusions in the holes, and a protrusion made of inclusions by selectively removing the upper layer of the anodized laminate And a step of forming an object.

It is preferable to have a step of flattening the surface after the step of filling the inclusions in the holes.
Further, the present invention is a method for producing a nanostructure, comprising a step of laminating two or more layers made of a material in which holes are formed by anodic oxidation on a substrate or a base to form a laminate, A step of anodizing the laminate to form a through-hole, a step of filling the inclusions in the holes, and a protrusion made of inclusions by selectively removing the upper layer of the anodized laminate A method of manufacturing a nanostructure, comprising: a step of forming an object; and a step of selectively removing protrusions appearing in an upper layer portion of the laminate.

The material in which the holes are formed by the anodic oxidation is preferably a metal or alloy containing Al in the range of 50 atomic% to 100 atomic%.
It is preferable that the material in which the holes are formed by the anodic oxidation contains at least one of Ti, Zr, Hf, Nb, Ta, Mo, W, and Cr.

Moreover, this invention is the nanostructure produced by said manufacturing method.
The present invention also provides an electron source, a nanoimprint mold, and a probe microscope probe using the nanostructure produced by the manufacturing method described above.

  The present invention is also a magnetic recording medium using a nanostructure produced by the above manufacturing method.

  According to the manufacturing method of the present invention, a nanostructure having a protrusion having a desired length and a uniform length can be easily formed. The nanostructure of the present invention can be applied to a field emission electron source with little emission current variation, a nanoimprint mold, a probe for a probe microscope, and the like. Furthermore, by selectively removing the above protrusions, a nanostructure with excellent film thickness controllability can be produced and applied to a magnetic recording medium.

Hereinafter, the present invention will be described in detail.
The method for producing a nanostructure of the present invention comprises a step of forming a laminate by laminating two or more layers made of a material capable of forming holes by anodization on a substrate or a base, and anodizing the laminate. Forming a through hole, filling the inclusion into the hole, and selectively removing the upper layer of the anodized laminate to form a protrusion made of inclusion It is characterized by having.

  Furthermore, after filling the above-mentioned inclusions in the through-holes, the upper surface is flattened, and then the uppermost layer of the anodized film is selectively removed, so that the inclusions with uniform planarization accuracy and length can be obtained. A nanostructure having a protrusion is formed.

  On the other hand, after filling the inclusions in the above-described through holes, after selectively removing the uppermost layer of the anodic oxide film, the protrusions that are the inclusions in the upper layer part are removed. A nanostructure having excellent flatness in which the height of the lower layer of the anodized film is equal to the height of the inclusion and the height is controlled is prepared.

A nanostructure is provided by using the manufacturing method described above.
An electron gun, a nanoimprint stamper, and a probe microscope tip, which are produced by the above-described method and have convex protrusions, are provided.

Furthermore, a magnetic recording medium with excellent film thickness controllability is provided by the method described above.
Hereinafter, embodiments of the present invention will be described.
<Nanostructure with protrusions>
FIG. 1 is a perspective view of a nanostructure having a protrusion according to the present invention. In FIG. 1, 11 is a columnar structure having protrusions, 14 is an embedding portion of the columnar structure, and 15 is a protrusion of the columnar structure. 12 is a matrix of an anodic oxide film region of Al or Al alloy surrounding the lower part of the columnar structure, and 13 is a substrate.

  FIG. 2 is a process diagram showing an example of a method for producing a nanostructure in the present invention. Two or more Al or Al alloy layers (23, 24) are formed on the substrate 21 or the base layer 22, and the pores 25 are formed by anodic oxidation. After that, the inclusions 26 of metal, semiconductor, oxide, etc. are filled in the pores, and only the upper layer 24 of the anodic oxide film is selectively removed, thereby having nanowires with a uniform length of the protrusions 27. Nanostructures can be obtained.

  The Al alloy production method includes various sputtering methods such as a simultaneous sputtering method using an Al target and a valve metal target, a sputtering method in which a valve metal tip 33 is disposed on the Al target 34 shown in FIG. 3, and a sputtering method using a fired alloy target. Although there are methods, the method is not particularly limited to these methods. Of course, a film forming method other than the sputtering method may be used.

  At this time, the valve metal M (M = at least one of Ti, Zr, Hf, Nb, Ta, Mo, W, and Cr) is added to Al, but when the alloy is in an amorphous phase region, It becomes difficult to obtain a porous film similar to the anodized film of the Al film with good reproducibility because the verticality and linearity of the pores formed by anodization are lowered. Therefore, it is preferable to add the valve metal in a range of approximately 5 to 50 atomic%, although it depends on the type of the valve metal to be added.

  In the Al alloy and Al thus produced, the pore diameter varies depending on the anodizing conditions and the pore-wide treatment after the anodizing. The pore wide treatment is an etching treatment of alumina, and a wet etching treatment with phosphoric acid is usually used. Although it depends on the amount of acid solution used and the amount of valve metal to be added, the Al alloy added with Mo, W, Cr, etc. has high solubility in acid, and the Al alloy added with Hf, Ti, Zr, etc. has solubility in acid. Is low. For this reason, it is possible to control the pore diameter and selectively remove the anodic oxide film which is easily dissolved by utilizing the difference in solubility in acid. The greater the difference in solubility, the higher the selective solubility. However, by selecting various conditions such as the temperature and concentration of the acidic solution used as the etching solution, one anodic oxide film can be selectively removed even in a film with a small solubility difference. It is possible to do.

  On the other hand, in these Al and Al alloys, the pore interval of the pores formed by anodization depends only on the anodization conditions regardless of the material. For example, the perpendicularity of pores formed when several layers of Al and Al alloy films are anodized and the interval between the pores are kept constant.

  After anodization, the material filling the pores can be arbitrarily selected depending on the intended nanowire. Depending on the pore diameter and aspect of the pore, the filling method may be a vapor phase method using a physical method (PVD) such as a vapor deposition method or a sputtering method, a vapor phase method using a chemical method (CVD), or a liquid phase method such as plating. Further, it is possible to use a solid phase method such as a sol-gel, and it is also possible to grow carbon nanotubes or the like in the pores. In particular, when pores having a high aspect are used, a plating method that is a liquid phase method is preferable.

  In the plating method, not only metals and various alloys but also oxides such as ZnO can be filled. The plating method may be electroplating or electroless plating. When the electroplating method is used, a conductive material that becomes an electrode at the time of plating is required for the substrate or the underlayer. Further, when Cu or a noble metal layer is provided under the anodized film as the electrode layer, it is possible to form pores penetrating the electrode with good reproducibility. When the electroless plating method is used, it is necessary to form a catalyst layer on the underlayer. Hereinafter, in the present invention, electroplating and electroless plating are described without distinction.

By making use of the above-described features, it is possible to form a nanostructure having nanowires with uniform length by the manufacturing method as described below.
The first layer of Al or Al alloy layer is formed on the substrate or the base, and the second layer is formed with an Al and Al alloy layer that is more easily dissolved in acid than the first layer, and anodized to form pores. The desired material is filled by plating. Here, by selectively removing the second layer of the anodic oxide film using an acidic solution, the lower part of the nanowire is covered with the oxide film of the first layer of Al or Al alloy, and the oxide film It is possible to form a nanostructure having nanowires of uniform length from the top surface. Here, in order to selectively remove the anodic oxide film of the second layer, it is necessary to use an acidic solution such as phosphoric acid with various conditions of concentration and temperature selected.

  In addition, after filling the inclusions into the pores by plating or the like, and the inclusions grow unevenly and the length is not constant, after filling the inclusions, the surface such as CMP (Chemical Mechanical Polish) By performing the planarization process, it is possible to make the lengths of the nanowires that are inclusions uniform with the same accuracy as the polishing accuracy. In general, since the RMS (root mean square) of the sample surface can be suppressed to 1 nm or less by CMP, nanowires with the same accuracy can be formed.

  The pore diameter and interval formed by anodization can be controlled by certain anodizing conditions (bath type, bath temperature, applied voltage, etc.) called self-ordering conditions. The pore diameter can be increased by controlling the wet etching time by immersing in a pore wide treatment after anodization, for example, in an aqueous phosphoric acid solution.

  In the anodic oxidation of Al and Al alloys, the pores are naturally regularly arranged under self-ordering conditions, but it is not possible to obtain nanoholes with a large area that are completely ordered. For this purpose, there is a method (nanoimprint method) in which a depression is formed on the Al surface using a mold having protrusions and the like and anodized. In the method for producing a nanostructure of the present invention, by applying a nanoimprint method before anodic oxidation, the pore diameter and the pore spacing can be ordered. Therefore, the nanowire filled with inclusions in the ordered pores is It becomes an assembly of three-dimensionally ordered nanowires all having a uniform aperture, interval, and length.

  In the present invention, the produced nanostructure having nanowires is used as an electron source such as a field emission display (FED), a cathode ray tube (CRT), a flat lamp, and an electron gun. It is possible to do.

In an electron source such as an electron gun, it is necessary to ensure uniformity of electron emission. The field emission current density is represented by j = [(Aβ ² V ² ) / φ] exp [(− Bφ ^3/2 ) / βV] in the Fowler-Nordheim equation (φ is a work function, A, B Is a constant, V is a voltage, and β is an electric field concentration factor. Therefore, j increases as β increases. Here, in the case of an electron source using nanowires as an emitter, the electric field concentration factor β is β∝h / rd (where h is the length of the emitter, r is the radius of the tip of the emitter, and d is the distance between the emitter and the extraction electrode). Become. In order to suppress variations in electron emission, it is necessary to suppress variations in β, and it is necessary to make the curvature radius and length of the tip of the thin wire serving as the emitter uniform.

  A schematic diagram of a field emission electron gun which is cold cathode electron emission is shown in FIG. On the base 41 of the support substrate, electron emission regions 42 divided and arranged in a desired size are integrated. The emitters in the individual gate openings of the electron emission region 42 are formed in a gate insulating layer 45 sandwiched between the cathode wiring 43 and the gate electrode wiring 44 formed in an XY array.

  FIG. 5 shows a schematic cross-sectional view of the emitter portion. A cathode wiring 52 is formed on a base 51 serving as a substrate. As the cathode wiring material, Au, Ag, Cu, Pt, Al, Pb, Cr or the like is used. The nanowire 54 is made of Pt filled in pores formed by anodizing a two-layer film made of Al or an Al alloy layer. The upper anodic oxide film is selectively etched. As the nanowire material that emits electrons, it is preferable to use a material having a low work function, carbon nanotubes, or the like. The gate insulating film 55 is made of an insulating material such as SiO 2, and a gate electrode 56 is formed on the gate insulating film 55 from Cr or the like. In such an electron source, Pt thin wires having a uniform length and diameter are vertically aligned and accumulated on a desired pattern, and the electron source is suppressed from variation in the amount of emission current.

  The present invention can also be applied to producing a minute hole on another substrate by a transfer method using a nanostructure having nanowires produced in the present invention. That is, as shown in FIG. 6, by using the nanostructure obtained in the present invention as a mold 61 and pressing the resist 62 formed on the substrate 63, transfer holes 64 are formed on the resist surface.

  The mold 61 will be described with reference to the process flow of FIG. In the inclusion filling step of FIG. 2D, Ni is filled by a plating method. Further, when the surface is flattened by CMP after plating for use as a mold, the height of the projections of the mold is made more uniform and functions as a good mold. The mold thus prepared is covered with an anodized film made of Al or Al alloy in the first layer and has a high strength. Further, the length of the Ni fine wire projection can be arbitrarily selected by controlling the thickness of the second layer (upper layer) anodic oxide film to be dissolved. When transferring, it is effective to put a release agent on the mold.

Further, the nanowire produced in the present invention can be used as a probe for STM or AFM. A uniform probe having an arbitrary length can be created.
<Nanostructures with excellent film thickness controllability>
FIG. 7 is a process diagram showing a method for producing a nanostructure excellent in flatness and film thickness controllability according to the present invention. Two or more Al or Al alloy layers (73, 74) are formed on the substrate 71 or the base layer 72 of the nanostructure in the present invention (FIG. 7B), and the pores 75 are formed by anodic oxidation ( FIG. 7 (c)). Thereafter, inclusions 76 of metal, semiconductor, oxide, etc. are filled into the pores (FIG. 7 (d)), and only the upper layer of the anodic oxide film is selectively removed (FIG. 7 (e)). By selectively removing only the protrusions that are convex, a nanostructure having excellent flatness and film thickness controllability is formed (FIG. 7 (f)).

  A polishing method is particularly useful for removing the protrusions. In general, when a desired film thickness is obtained by polishing, the layer to be polished is selectively removed using a difference in polishing rate between a layer to be polished (material to be polished) and a structure manufactured after polishing. Alternatively, by sandwiching a material that is difficult to be polished, called a barrier layer, polishing is completed in the barrier layer. However, there are problems such as narrowing of choices of materials to be used and a barrier layer remaining as a remaining film.

  The present invention is a structure in which various inclusions are filled in a matrix of aluminum oxide and aluminum alloy oxide as shown in FIG. When directly polishing a structure (Fig. 7 (d)) filled with inclusions in an alumina anodic oxide film with a through-hole, the end point in polishing tends to be unclear, and a nanostructure with a desired film thickness is created. It is difficult to do. On the other hand, the upwardly protruding protrusion has a structural feature and is easily polished, and only the protruding portion can be selectively removed regardless of the material forming the protrusion. By setting the required film thickness to Al or Al alloy layer 1 (73 in FIG. 7) in advance, it becomes easy to obtain a structure having a desired film thickness.

  The method for producing a nanostructure of the present invention can be applied to a method for producing a patterned medium that is considered promising as a next-generation magnetic recording medium. Among patterned media, a magnetic recording medium has been devised in which pores formed of anodized alumina are filled with a magnetic material. In the case of a magnetic recording medium, accurately controlling the thickness of the magnetic layer is indispensable for improving recording characteristics and reliability. The aluminum or aluminum alloy layer 1 (73 in FIG. 7) shown in FIG. 7 can obtain an accurate film thickness by using a dry process such as a sputtering method. For this reason, by using the manufacturing method of the present invention, only the protrusions made of a magnetic material convex upward with the aluminum or aluminum alloy layer 1 (73 in FIG. 7) as the upper surface can be selectively removed by a polishing process. Thus, the film thickness of the magnetic recording layer can be controlled.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
FIG. 8 is a process diagram showing one embodiment of a method for producing a nanostructure in the present invention.

Process (1)
A Si substrate 81 was used as the substrate. A Pt thin film 82 having a film thickness of 30 nm was formed on the Si substrate 81 by magnetron sputtering. The Pt thin film 82 is an electrode layer for the plating process described below.

Process (2)
On the Pt layer, an AlZr alloy film 83 in which Zr was added to Al was formed to a thickness of 500 nm. Here, a sample was prepared with the configuration shown in FIG. Film formation was performed by a sputtering method, and the AlZr alloy was formed by placing a 20 mm square Zr chip on an Al target having a diameter of 4 inches (101.6 mm). At this time, the composition ratio of Zr to Al can be changed by changing the number of Zr chips. When the composition ratio of Zr to Al was examined by XRF (fluorescence X-ray) analysis, it was Zr10 atomic%. Further, an Al film 84 having a thickness of 1.5 μm was formed on the AlZr alloy film 83.

Process (3)
The Al alloy / Al bilayer film produced in the step (2) was anodized at an applied voltage of 40 V in an aqueous solution of 0.3 mol / L oxalic acid at a bath temperature of 16 ° C. Further, after anodization, a pore-wide treatment (here, immersion in a 5 wt% phosphoric acid aqueous solution for 30 minutes at room temperature) was performed. When the sample was also observed with the FE-SEM, the fine pores 85 having good straightness were divided and formed by the partition walls.

Process (4)
This sample was filled with Pt fine wires 86 in the pores by electroplating using a plating bath made of platinum diaminonitrite Pt (NO ₂ ) ₂ (NH ₃ ) ₂ . By controlling the film formation rate in plating, the pores were uniformly filled with Pt.

Step (5)
When this sample was immersed in a 2 wt% phosphoric acid aqueous solution at room temperature, the upper Al anodic oxide film 87 was selectively dissolved, and a uniform Pt with a length protruding upward from the surface of the AlZr anodic oxide film 88 was obtained. A nanostructure 89 having fine wires could be formed.

Example 2
After step (4) of Example 1, CMP (Chemical Mechanical Polish) was performed to smooth the surface. Surface smoothness was measured with an AFM (atomic force microscope). The RMS (root mean square) was 1 nm or less. Here, it is suitable for the case where the plating growth is not uniform in the plating step in the step (4) of Example 1, or when the length of the obtained Pt thin wire is made more uniform.

  When the upper anodic oxide film 1 was removed by the same process as in step (5) of Example 1, the length of the Pt fine line was a Pt fine line having the same uniformity as the polishing accuracy of CMP. Further, the higher the controllability of the plating growth in the step (4) of Example 1, the smaller the amount of polishing in CMP can be suppressed, and a Pt fine wire having a desired length is easily obtained.

Example 3
In step (5) of Example 1, it was shown that the upper anodic oxide layer was selectively dissolved. Here, Al and an Al alloy having a constant film thickness were prepared, and after anodizing at an applied voltage of 40 V in an aqueous solution of 0.3 mol / L oxalic acid at a bath temperature of 16 ° C., 2 wt% at room temperature. The difference in solubility when immersed in an aqueous phosphoric acid solution was investigated.

The prepared samples are as follows.
Sample (A): Al (100 atomic)
Sample (B): Al (95 atomic%)-Zr (5 atomic%)
Sample (C): Al (90 atomic%)-Zr (10 atomic%) Sample (D): Al (85 atomic%)-Zr (15 atomic%) Sample (E): Al (85 atomic%)-Hf (15 atomic%) Sample ( F): Al (95 atomic%)-Nb (5 atomic%)
Sample (G): Al (95 atomic%)-W (5 atomic%)
Sample (H): Al (95 atomic%)-Mo (5 atomic%)
When arranged in descending order of solubility, sample H> sample G> sample A> sample F> sample B> sample C> sample D> sample E.

  In addition, when a similar experiment was performed on an Al alloy containing 5 atomic% of Ti, Zr, Hf, Nb, Ta, Mo, W, and Cr, the Hf · Zr · When Ti was added, it was difficult to dissolve, when Nb · Ta was added, it was slightly difficult to dissolve, and when W · Mo · Cr was added, the result was easy to dissolve.

In addition, it turned out that the anodic oxide film of the said sample has a highly perpendicular | vertical pore, and a pore space | interval does not depend on a sample, but is dependent on the anodizing conditions uniquely.
Here, as Al or Al alloy laminated in Step 2 shown in Example 1, a film added with Zr.Hf or the like which is difficult to dissolve in the lower layer is adopted as shown in this Example. It has been found that it is possible to stack a film that is easier to dissolve than the lower layer in accordance with the results. In addition, when films having close acid resistance are laminated, it is difficult to selectively remove the upper oxide film.

  In the case of using Al and Al alloy having a close etching rate, the present invention is achieved by sandwiching a thin layer of Al alloy that is difficult to be etched, such as sample C, as an intermediate layer between an upper layer that is selectively dissolved and a lower layer that is not dissolved. It is possible to produce the target nanostructure. An Al alloy thin film that is difficult to be etched as an intermediate layer functions as a stopper layer. This indicates that a highly soluble material can be used as the lower layer by using the stopper thin film in the intermediate layer.

Example 4
An electron source to be a cold cathode was created by applying the method for producing a nanostructure having nanowires having a uniform length shown in Example 1. A schematic diagram of the field emission electron gun is shown in FIG. 4, and a schematic diagram of the emitter portion is shown in FIG.

  FIG. 9 shows a process chart of the method of manufacturing an electron source according to the present invention. As shown in step (1), 1 μm of copper to be the cathode wiring (underlayer film) 92 was formed on the substrate 91 by screen printing by screen printing. In step (2), a 200 nm AlZr alloy layer 93 and a 3 μm Al film 94 were deposited. By using electron beam drawing, depressions arranged at intervals of 25 nm were created at necessary locations on the Al film serving as the gate opening 97 of the electron source.

  As shown in the step (3), anodization was performed at an applied voltage of 10 V in a 0.3 mol / L sulfuric acid aqueous solution having a bath temperature of 16 ° C., and pore-wide treatment was further performed with a 5 wt% phosphoric acid aqueous solution. On the entire surface, almost uniform pores with a spacing of 25 nm are formed, and in particular, pores 95 with regular pore diameters and pore spacings are formed in the gate opening portion where electron beam drawing is performed as a pixel portion. ing. As shown in step (4), Pt fine wires 96 were filled in the pores by plating using the base film 92 as a cathode electrode as an electrode layer.

As shown in step (5), after SiO ₂ was deposited, surface planarization was performed by CMP to polish the anodized Al film. In step (6), the gate opening 97 having an inner diameter of 1 μm was masked by photolithography, and the anodized film of the Al film 94 was removed by etching until the anodized film of the first AlZr alloy layer 93 appeared. Here, there is no problem even if over-etching is performed.

Subsequently, as shown in step (7), 3.5 μm of SiO _{2 serving} as the gate insulating layer 98 is deposited in the etched region, and further, an arrayed gate electrode 99 is formed by photolithography to form Cr ₂ on the SiO ₂ by plating. Was deposited by 0.5 μm. Thereafter, as shown in step (8), the second layer of the Al anodic oxide film 94 covering the periphery of the filled Pt was selectively etched with a 5 wt% phosphoric acid aqueous solution. Through such a process, an electron source having Pt fine wires having a uniform length, radius, and spacing from the surface of the AlZr anodized film 93 was produced. This electron source became a cold cathode electron source in which variations in emission current amount were suppressed.

Example 5
A mold for producing minute holes on another substrate by a transfer method was produced by applying the method for producing nanostructures having uniform nanowires of the length shown in Example 1 (61 in FIG. 6).

The manufacturing method is almost the same as in FIG.
Step (1) is the same as in Example 1.
In step (2), the AlZr alloy film was 5 μm and the Al film was 80 nm on the base.

  Prior to step (3), a stamper having protrusions on the surface was pressed to transfer the protrusions of the stamper to the sample surface. The stamper had protrusions with a height of 30 nm arranged in a honeycomb shape at intervals of 100 nm, and was produced by exposing SiC to an electron beam.

Step (3) is the same as in Example 1.
In the plating step of step (4), the following Ni plating was performed. An aqueous solution of nickel (II) sulfate heptahydrate and boric acid was used at 24 ° C., and Ni was plated at a voltage of −1.5 V using Ag / AgCl as a reference electrode, so that Ni was formed in the pores. Filled.

Here, as shown in Example 2, the surface was planarized by CMP.
Step (5) is the same as in Example 1.
As shown in FIG. 6, the resist 62 formed on the substrate 63 was pressed using a nanostructure having nanowires produced after the completion of all the processes as a mold. As a result, transfer holes 64 were formed on the surface. .

Example 6
The nanowire having a uniform length shown in Example 1 was a uniform probe having an arbitrary length in an STM or AFM probe.

Example 7
FIG. 10 shows a manufacturing process diagram of a magnetic recording medium using the method for manufacturing a nanostructure in the present invention.

Process (1)
In this embodiment, the substrate 101 and the underlayer are formed by forming a 100 nm backing soft magnetic layer (NiFeNb) on a glass substrate by sputtering and forming an intermediate layer MgO thin film thereon. A Pt thin film of the electrode layer 102 having a thickness of 10 nm was formed on the base layer 101 by magnetron sputtering.

Here, not only the glass substrate but also various substrates can be used for the underlayer. Further, the backing layer and the intermediate layer may be other than the above materials.
Step (2)
On the electrode layer, an AlZr alloy film 103 in which Zr was added to Al was formed to a thickness of 20 nm. Here, a sample was prepared with the configuration shown in FIG. Film formation was performed by a sputtering method, and the AlZr alloy was formed by placing a 20 mm square Zr chip on an Al target having a diameter of 4 inches (101.6 mm). At this time, the composition ratio of Zr to Al can be changed by changing the number of Zr chips. When the composition ratio of Zr to Al was examined by XRF (fluorescence X-ray) analysis, it was Zr10 atomic%. Further, an Al film 104 was formed to 300 nm on the AlZr alloy film 103.

Process (3)
The Al alloy / Al bilayer film produced in the step (2) was anodized at an applied voltage of 40 V in an aqueous solution of 0.3 mol / L oxalic acid at a bath temperature of 16 ° C. Further, after anodization, a pore-wide treatment (here, immersion in a 5 wt% phosphoric acid aqueous solution for 30 minutes at room temperature) was performed. When the sample was also observed with the FE-SEM, the fine holes 105 having good straightness were divided and formed by the partition walls.
Moreover, the starting point of the anodic oxidation was created with a mold having a regular pattern before the anodic oxidation. The pores had a regular arrangement.

Step (4)
This sample was filled with FePt magnetic material 106 in the pores by electroplating using a FePt plating bath mainly composed of chloroplatinic acid and iron chloride.

Step (5)
When this sample was immersed in a 2 wt% phosphoric acid aqueous solution at room temperature, the upper Al anodic oxide film 107 was selectively dissolved, and a uniform FePt having a convex length upward from the surface of the AlZr anodic oxide film 108. Thus, a nanostructure 109 having a protrusion made of can be formed.

Step (6)
The 109 nanostructures were polished using a polishing liquid containing colloidal silica as a slurry, thereby selectively removing the protrusions to form a magnetic recording layer having a thickness of the AlZr alloy 103.

After polishing, a magnetic recording medium 110 was manufactured by applying a protective layer made of DLC (diamond carbon) and a lubricating layer of perfluorocarbon through a cleaning process.
When the cross section of the magnetic recording medium was observed with an SEM (scanning electron microscope), the magnetic layer had a thickness of 20 nm, and a recording layer having a desired thickness could be produced.

  According to the method for producing a nanostructure of the present invention, a nanostructure having a protrusion having a desired length and a uniform length can be easily formed. The present invention can be used for a field emission electron source with a small amount, a nanoimprint mold, a probe for a probe microscope, a magnetic recording medium, and the like.

It is a perspective view which shows the nanostructure which has the protrusion obtained by the manufacturing method of this invention. It is process drawing which shows an example of the manufacturing method of the nanostructure which has a protrusion of this invention. It is the schematic which shows the manufacturing method of Al alloy. It is the schematic which shows the field emission type | mold electron gun using the nanostructure which has a protrusion. It is the schematic which shows the emitter part of a field emission type electron gun. It is the schematic which shows the nanoimprint method using the nanostructure which has a protrusion. It is process drawing which shows the manufacturing method of the nanostructure excellent in the film thickness controllability of this invention. It is process drawing which shows the other example of the manufacturing method of the nanostructure which has a protrusion of this invention. It is process drawing which shows an example of the manufacturing method of the field emission type electron source using the nanostructure which has the protrusion of this invention. It is process drawing which shows the manufacturing method of the magnetic-recording medium using the nanostructure excellent in the film thickness controllability of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Columnar structure 12 Matrix 13 Board | substrate 14 Embedded part of columnar structure 15 Projection part (projection) of columnar structure
21 Substrate 22 Underlayer 23 Al or Al alloy layer 1
24 Al or Al alloy 25 Pore 26 Inclusion 27 Projection 31 Substrate 32 Ar plasma 33 Valve metal 34 Al target 41 Base 42 Electron emission region 43 Cathode electrode wiring 44 Gate electrode wiring 45 Insulating layer 51 Base 52 Cathode 53 Anodized film 54 Nanowire 55 Gate Insulating Layer 56 Gate Electrode 61 Mold 62 Resist 63 Substrate 64 Transfer Hole 71 Substrate 72 Underlayer 73 Al or Al Alloy Layer 1
74 Al or Al alloy 75 Pore 76 Inclusion 81 Si substrate 82 Pt film 83 AlZr alloy 84 Al film 85 Pore 86 Pt fine wire 87 Al anodic oxide film 88 AlZr anodic oxide film 91 Substrate 92 Underlayer film 93 AlZr film 94 Al film 95 Pore 96 Pt fine wire 97 Gate opening 98 Gate insulating layer 99 Gate electrode 101 Substrate + underlayer 102 Electrode layer 103 AlZr alloy 104 Al film 105 Pore 106 Magnetic body 107 Al anodized film 108 AlZr anodized Film 109 Nanostructure 110 Magnetic recording medium

Claims (10)

  A method for producing a nanostructure, comprising a step of laminating two or more layers made of a material capable of forming a hole by anodization on a substrate or a base to form a laminate, and anodizing the laminate. Forming a hole penetrating through, filling the inclusion into the hole, selectively removing the upper layer of the anodized laminate, and forming a protrusion made of inclusion The manufacturing method of the nanostructure characterized by having.   The method for producing a nanostructure according to claim 1, further comprising a step of flattening a surface after the step of filling the inclusions in the holes.   A method for producing a nanostructure, comprising a step of laminating two or more layers made of a material capable of forming a hole by anodization on a substrate or a base to form a laminate, and anodizing the laminate. Forming a hole penetrating through, filling the inclusion into the hole, selectively removing the upper layer of the anodized laminate, and forming a protrusion made of inclusion And a step of selectively removing protrusions appearing in the upper layer portion of the laminate.   The material for forming a hole by the anodic oxidation is a metal or an alloy containing Al in an amount of 50 atomic% to 100 atomic%. Method.   5. The material according to claim 1, wherein the material in which holes are formed by anodization contains at least one of Ti, Zr, Hf, Nb, Ta, Mo, W, and Cr. A method for producing a nanostructure according to the item.   A nanostructure produced by the production method according to claim 1.   An electron source using a nanostructure produced by the manufacturing method according to claim 1, claim 2, or claim 4.   A mold for nanoimprinting using a nanostructure produced by the manufacturing method according to claim 1, claim 2, or claim 4.   A probe for a probe microscope using a nanostructure produced by the manufacturing method according to any one of claims 1, 2, and 4 to 6.   A magnetic recording medium using a nanostructure produced by the manufacturing method according to claim 3.

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