JP2009235553A - Nanohole structure and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nanohole structure in which the packed states of nanoholes can be controlled so that the nanohole formed in a zone positioned on an electrode layer is kept in a packed state and the nanohole formed in a zone positioned on an insulating layer is kept in an unpacked state, and to provide a method for manufacturing the nanohole structure. <P>SOLUTION: The method for manufacturing the nanohole structure includes: an electrode layer formation step of forming the electrode layer on a substrate; an insulating layer formation step of forming the insulating layer on a part of the electrode layer; a base material formation step of forming a base material for covering the electrode layer and the insulating layer; a nanohole formation step of forming nanoholes on the base material; and a metal packing step of packing a metal in the nanohole formed in the zone positioned on the electrode layer by an electroplating method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nanohole structure applicable to a magnetic recording medium, a photonic crystal, a biochip, and the like, and a manufacturing method thereof.

  Anodized alumina produced by anodizing metallic aluminum 1) The pitch and diameter of the generated nanoholes can be controlled to some extent depending on the anodizing conditions. 2) The origin (formation) of nanohole generation on the surface of metallic aluminum before anodizing By forming shallow depressions (starting points) (texturing process), it is possible to obtain an ideal arrangement of nanoholes. 3) Various metals (metals in general, magnetic materials, living organisms) in the formed nanoholes. Affinity materials) can be filled by plating, and application to magnetic recording media, photonic crystals, biochips and the like is expected.

  In examining the application of an alumina / metal composite medium in which nanoholes are filled with metal in anodized alumina, the technology of filling an arbitrary metal into ideally arranged nanoholes is not sufficient. In other words, for example, for dielectric constant modulation in photonic crystals, servo pattern production in magnetic recording media, etc., development of patterning technology that fills any nanohole with metal (does not fill any nanohole with metal) is required.

  Conventionally, as a method for controlling a metal filling region for nanoholes formed in anodized alumina produced from bulk aluminum, it is known to perform plating after patterning anodized alumina by photolithography (see FIG. For example, Patent Document 1). However, when the nanohole pitch (nanohole pattern) is miniaturized and the anodized alumina is made of thinned aluminum, the following problems occur.

  In order to perform photolithography using a resist, it is necessary to dry the alumina prepared by the wet process and to perform a hydrophobization process in order to ensure adhesion of the resist. As a result, the thickness of the insulating layer (generally referred to as a barrier layer) at the bottom of the nanohole increases, resulting in a problem of high resistance and poor plating. Further, when the nanohole is miniaturized, it is difficult to completely remove the resist that has entered the nanohole, and the resist remaining in the nanohole causes a plating defect.

  In addition, in order to avoid plating defects due to an increase in the thickness of the insulating layer at the bottom of the nanohole, when the insulating layer is etched by performing an acid treatment before plating, the diameter of the alumina nanohole is also enlarged (in general, pore widening, There is a problem that the degree of freedom of characteristics for application is reduced.

  In addition, in order to avoid plating defects due to an increase in the thickness of the insulating layer at the bottom of the nanohole, if the plating voltage is increased to secure the plating current, stress is concentrated on the interface when using thin film aluminum, and alumina is used. There was a problem that the film easily peeled off.

  Furthermore, the following method has been proposed as another method for controlling the filling region and the non-filling region. First, the pitch of the recesses that are the starting points of the nanoholes and the pitch determined by the anodizing conditions are shifted by a specific magnification to induce and generate nanoholes at a specific position between the recesses and the recesses. The induced nanoholes are filled with metal only in the nanoholes starting from the depressions by utilizing the fact that the growth rate is slower than the nanoholes starting from the depressions (for example, Patent Document 2). However, the size of the unfilled region is at most several times the pitch of the depressions that are the starting point, and there is a problem that it is not possible to produce an unfilled region having an area necessary for application to a servo pattern or a photonic crystal. It was.

JP-A-53-093803 JP 2003-323708 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the nanoholes formed in the region located on the electrode layer can be filled, and the nanoholes formed in the region located on the insulating layer can be unfilled, thereby controlling the nanohole filling state. It is an object to provide a nanohole structure that can be manufactured and a method for manufacturing the same.

Means for solving the problems are as follows. That is,
The method for producing a nanohole structure of the present invention includes an electrode layer forming step of forming an electrode layer on a substrate, an insulating layer forming step of forming an insulating layer on a part of the electrode layer, the electrode layer, A base material forming step of forming a base material covering the insulating layer, a nano hole forming step of forming nano holes in the base material, and a metal by electroplating in the nano holes formed in the region located on the electrode layer And a metal filling step of filling.
In the method for producing a nanohole structure, an electrode layer is formed on a substrate in the electrode layer forming step, an insulating layer is formed on a part of the electrode layer in the insulating layer forming step, and the base material In the forming step, a base material covering the electrode layer and the insulating layer is formed, in the nanohole forming step, nanoholes are formed in the base material, and in the metal filling step, formed in a region located on the electrode layer The filled nanoholes are filled with metal by electroplating.
When a patterned insulating layer is provided between the electrode layer formed on the substrate and the base material and the base material is anodized, nanoholes formed in the base material grow from the base material surface toward the substrate. Here, the nanohole formed in the region located on the insulating layer has a high resistance when the lower barrier layer comes into contact with the insulating layer, and the current supply beyond that stops and the growth stops. On the other hand, nanoholes formed in a region located on the electrode layer film continue to grow up to the electrode layer. Furthermore, when electroplating is performed, metal is filled in the nanoholes formed in the region located on the electrode layer film. However, since the nanoholes formed in the region located on the insulating layer have high resistance, Not filled.

The nanohole structure of the present invention covers a substrate, an electrode layer formed on the substrate, an insulating layer formed on a part of the electrode layer, the electrode layer and the insulating layer, and the electrode The substrate has a first nanohole formed in a region located on the layer and a second nanohole formed in a region located on the insulating layer.
In the nanohole structure, the first nanohole is formed in the region located on the electrode layer, and the second nanohole is formed in the region located on the insulating layer. Nanoholes can be unfilled, and the filling state of nanoholes can be controlled.

  According to the present invention, the conventional problems can be solved, and nanoholes formed in a region located on the electrode layer are filled, and nanoholes formed in a region located on the insulating layer are unfilled. Therefore, it is possible to provide a nanohole structure that can control the filling state of the nanohole and a method for manufacturing the nanohole structure.

(Nanohole structure)
The nanohole structure is not particularly limited except that it has a substrate, an electrode layer, an insulating layer, and a base material, and further has other layers as necessary, and its shape, structure, size The thickness and the like can be appropriately selected according to the purpose.

There is no restriction | limiting in particular as said shape, According to the objective, it can select suitably, For example, plate shape, disk shape (disk shape), etc. are mentioned suitably. Among these, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, a disk shape (disk shape) is preferable.
In addition, when the said shape is the said plate shape, disk shape, etc., the said nanohole (pore) is formed in the direction substantially orthogonal to these one exposed surface (plate surface).

  There is no restriction | limiting in particular as said structure, According to the objective, it can select suitably.

  The size is not particularly limited and can be appropriately selected according to the purpose. For example, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, the size of an existing hard disk or the like is not limited. The size corresponding to the size of an existing DNA chip or the like is preferable when the nanohole structure is applied to a DNA chip or the like.

-Board-
The shape, structure, size, material and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. For example, the shape of the substrate is a magnetic disk such as a hard disk. In this case, it is disc-shaped, and the structure may be a single-layer structure or a laminated structure, and the material may be appropriately selected from known materials. Examples thereof include aluminum, glass, silicon, quartz, and SiO ₂ / Si formed by forming a thermal oxide film on the silicon surface. These board | substrate materials may be used individually by 1 type, and may use 2 or more types together. Further, as the substrate, an n ++ or P ++ Si substrate as a conductive substrate integrated with an electrode layer described later may be used.
In addition, the said board | substrate may be manufactured suitably and a commercial item may be used.

-Electrode layer-
The electrode layer can be appropriately selected according to the purpose with respect to its shape, structure, material, etc., except that it is formed on the substrate.

  There is no restriction | limiting in particular as a material of the said electrode layer, According to the objective, it can select suitably, For example, Cr, Co, Pt, Cu, Ir, Rh, these alloys, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. The electrode layer may contain W, Nb, Ti, Ta, Si, O, etc. in addition to these materials. Further, as the electrode layer, a permalloy film or an n ++ Si substrate as a conductive substrate integrated with the substrate may be used.

There is no restriction | limiting in particular as thickness of the said electrode layer, According to the objective, it can select suitably. One electrode layer may be provided, or two or more electrode layers may be provided.
The formation of the electrode layer is not particularly limited and can be performed according to a known method. For example, the electrode layer can be formed by a sputtering method, a vapor deposition method, or the like.

−Insulating layer−
As the insulating layer, except that it is formed on a part of the electrode layer, its shape, structure, material, and the like can be appropriately selected according to the purpose. For example, the insulating layer is formed by a plasma CVD method. Examples thereof include SiO ₂ films, insulating oxides such as SiON, SiOx, SiO, CeO ₂ , and alumina formed by vapor deposition or sputtering, and nitrides.
Further, the resist itself can be used as an insulating layer.
By forming the insulating layer in an arbitrary pattern, the filled region and the non-filled region can be arbitrarily set.

-Base material-
The base material covers the electrode layer and the insulating layer, except that a first nanohole is formed in a region located on the electrode layer, and a second nanohole is formed in a region located on the insulating layer. The shape, structure, material and the like can be appropriately selected according to the purpose. Examples of the material include simple metals, oxides thereof, nitrides, alloys, and the like. Among them, for example, aluminum, alumina (aluminum oxide), titanium oxide, silicon, and the like are particularly preferable.

--- Nanohole--
The nanohole includes a first nanohole formed in a region located on the electrode layer and a second nanohole formed in a region located on the insulating layer. The nanoholes are formed in the base material and grow from the base material surface toward the substrate. Here, the second nanohole formed in the region located on the insulating layer has a high resistance when the lower barrier layer contacts the insulating layer, and the current supply beyond that is stopped to stop the growth. On the other hand, the first nanohole formed in the region located on the electrode layer film continues to grow up to the electrode layer. That is, the second nanohole is shallower than the first nanohole.
Furthermore, when electroplating is performed, the first nanohole formed in the region located on the electrode layer film is filled with metal, but the second nanohole formed on the insulating layer has high resistance, so Not filled. The second nanohole that is not filled with the metal may be filled with an insulating material.

The arrangement of the nanoholes is not particularly limited and can be appropriately selected depending on the purpose.For example, the nanoholes may be arranged in parallel in one direction, or arranged in at least one of concentric and spiral shapes. It may be. The former arrangement is preferable when the nanohole structure is applied to a DNA chip or the like, and the latter arrangement is preferable when the nanohole structure is applied to the magnetic recording medium such as a hard disk or a video disk. In the case of use, a concentric shape is preferable from the viewpoint of easy access, and in the case of video disk use, a spiral shape is preferable from the viewpoint of easy continuous reproduction.
When the nanohole structure is suitable for the magnetic recording medium such as a hard disk, it is preferable that the nanoholes in adjacent nanohole arrays are arranged in the radial direction. In this case, the magnetic recording medium is capable of high-density recording and high-speed recording without increasing the write current of the magnetic head, has a large capacity, has excellent overwrite characteristics, and has uniform characteristics. There is no problem of light etc. and it is extremely high quality.

  The width of the nanohole array is not particularly limited and can be appropriately selected according to the purpose. For example, when the nanohole structure is suitable for the magnetic recording medium such as a hard disk, the recording density is increased. Therefore, it is necessary to make it narrower. Specifically, at a recording density of about 250 GB / in, the width of the array is preferably 50 to 100 nm, for example, and the width of the array corresponding to 1 TB / in is preferably 25 to 50 nm, for example.

  The arrangement pattern of the nanoholes in the arrangement of the nanoholes is not particularly limited and can be appropriately selected according to the purpose. However, at least one of the adjacent arrangements is most closely arranged in a hexagonal close-packed lattice shape. A dense pattern is preferable. Since the hexagonal close-packed lattice is the most stable pattern in alumina nanoholes, fluctuations in the pattern other than the intentionally introduced pattern change can be minimized.

The opening diameter in the nanohole is not particularly limited and may be appropriately selected depending on the purpose. For example, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, the ferromagnetic layer serving as the recording layer The layer (hard magnetic layer) is preferably large enough to have a single magnetic domain. Specifically, it is preferably 2/3 or less of the pitch of the nanoholes, more preferably 1/3 to 2/5. For example, when the pitch of the nanoholes is 30 nm, 20 nm or less is preferable, and 10 to 12 nm is more preferable.
If the aperture diameter in the nanohole exceeds 2/3 of the nanohole pitch, for example, 20 nm when the pitch is 30 nm, the magnetic recording medium to which the nanohole structure is applied may not have a single domain structure.

The pitch of the nanoholes is appropriately determined depending on the voltage in the anodizing treatment, and is approximately 2.5 times (nm) of the anodizing voltage (V). Therefore, the voltage in the anodizing treatment is not particularly limited, but is preferably 3 to 40 V, and more preferably 3 to 10 V, for example.
When the voltage is 3 to 40 V, the recording medium can be densified. When the voltage is 3 to 10 V, the pitch of the nanoholes can be 7 to 25 nm. This is particularly advantageous in that the density of the medium can be further increased.
In addition, there is no restriction | limiting in particular as a kind, density | concentration, temperature, time, etc. of the electrolyte solution in the said anodizing process, According to the number of nanoholes to form, a magnitude | size, an aspect-ratio, etc., it can select suitably. For example, preferable examples of the electrolyte include a diluted phosphoric acid solution, a diluted oxalic acid solution, and a diluted sulfuric acid solution. In any case, the adjustment of the aspect ratio of the nanohole can be performed by increasing the diameter of the nanohole (alumina pore) by immersing in a phosphoric acid solution after the anodizing treatment.

The metal filled in the nanoholes formed in the region located on the insulating layer is not particularly limited and can be appropriately selected according to the purpose. For example, magnetic materials, noble metals, conductive transparent Examples thereof include oxides and metals having high biocompatibility.
When the magnetic material is filled in the nanohole, the magnetic material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a hard magnetic material and a soft magnetic material. Here, when the inside of the nanohole is filled with a hard magnetic material and a soft magnetic material to form a multilayer structure, a soft magnetic layer and a hard magnetic layer may be laminated in this order from the substrate side, and further, the hard hole A nonmagnetic layer (intermediate layer) may be formed between the magnetic layer and the soft magnetic layer.

In the perpendicular magnetic recording medium, the hard magnetic layer functions as a recording layer and constitutes a multilayer magnetic layer together with the soft magnetic layer.
The material of the hard magnetic layer is not particularly limited and can be appropriately selected from known materials according to the purpose. For example, Fe, Co, Ni, FeCo, FeNi, CoNi, CoNiP, FePt, CoPt And at least one selected from NiPt is preferable. These may be used individually by 1 type and may use 2 or more types together.
The hard magnetic layer, the not particularly limited as long as it is formed as a perpendicular magnetization film of a material, can be appropriately selected depending on the intended purpose, for example, a Ll ₀ ordered structure, wherein the C-axis substrate Or those having an fcc structure or bcc structure and having the C-axis aligned in the direction perpendicular to the substrate, or simply obtaining perpendicular magnetization characteristics by shape anisotropy, etc. Preferably mentioned.

The thickness of the hard magnetic layer is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the linear recording density used at the time of recording. For example, (1) the soft magnetism An aspect that is equal to or less than the thickness of the layer, (2) an aspect that is 1/3 to 3 times the minimum bit length determined by the linear recording density used during recording, and (3) the thickness of the soft magnetic layer and the underlayer The aspect etc. which are below the total are preferable, for example, usually about 5 to 100 nm is preferable, 5 to 50 nm is more preferable, and when performing magnetic recording with a linear recording density of 1,500 kBPI targeting 1 Tb / in ² , 50 nm The following is preferable (about 20 nm).
Here, the thickness of the “hard magnetic layer” is such that the hard magnetic layer is a laminated structure or a structure divided into a plurality of layers (for example, a continuous layer divided by an intermediate layer such as a nonmagnetic layer). In other words, the total thickness of each hard magnetic layer is meant. Further, the thickness of the “soft magnetic layer” is such that the soft magnetic layer is a laminated structure or a structure divided into a plurality of layers (for example, a structure that is not divided into an intermediate layer such as a nonmagnetic layer to form a continuous layer). Means the total thickness of each soft magnetic layer. In addition, the “total thickness of the soft magnetic layer and the underlayer” refers to a structure in which at least one of the soft magnetic layer and the underlayer is divided into a laminated structure or a plurality of layers (for example, a nonmagnetic layer or the like). In the case of having a structure that is divided by the intermediate layer and is not a continuous layer, it means the total thickness of each soft magnetic layer and the underlayer.

In the case of a magnetic recording medium having the hard magnetic layer and the soft magnetic layer, the distance between the single magnetic pole head used for magnetic recording and the soft magnetic layer is set to the substrate (porous material) on which the nanoholes are formed. Layer) is shorter than the thickness of the hard magnetic layer and can be substantially equal to the thickness of the hard magnetic layer, so that only the thickness of the hard magnetic layer, regardless of the thickness of the substrate (porous layer) on which the nanoholes are formed, It is possible to control the concentration of magnetic flux from the single magnetic pole head, the optimum magnetic recording / reproducing characteristics at the recording density used, and the like. As a result, in the magnetic recording medium, compared with the conventional magnetic recording medium, the writing efficiency is greatly improved, the writing current is reduced, and the overwrite characteristic can be remarkably improved.
The formation of the hard magnetic layer is not particularly limited and can be performed according to a known method, for example, an electroplating method or the like.
Specifically, by immersing the base material (porous layer) on which the nanoholes are formed in a plating solution, and applying a voltage using the electrode layer as an electrode, the magnetic material is deposited or deposited. ,It can be carried out.

  The soft magnetic layer is not particularly limited and can be appropriately selected from known materials according to the purpose. For example, at least one selected from Ni, NiFe, FeSiAl, FeC, FeCoB, FeCoNiB, and CoZrNb can be selected. A seed etc. are mentioned suitably. These may be used individually by 1 type and may use 2 or more types together.

  The thickness of the soft magnetic layer is not particularly limited as long as the effects of the present invention are not impaired, and the depth of the nanoholes in the substrate (porous layer) on which the nanoholes are formed, the thickness of the hard magnetic layer, and the like. For example, (1) an aspect in which the thickness of the hard magnetic layer exceeds the thickness, and (2) an aspect in which the sum of the thickness of the underlayer exceeds the thickness of the hard magnetic layer, etc. Is mentioned.

The soft magnetic layer is advantageous in that the magnetic flux from the magnetic head used for magnetic recording can be effectively converged on the hard magnetic layer, and the perpendicular component of the magnetic field of the magnetic head can be increased. . The soft magnetic layer is preferably capable of forming a magnetic circuit of a recording magnetic field input from the magnetic head together with the magnetic head together with an underlayer.
The soft magnetic layer preferably has an easy magnetization axis in a direction substantially perpendicular to the substrate surface. In this case, when recording is performed with the perpendicular magnetic recording head, it is possible to control the concentration of magnetic flux from the perpendicular magnetic recording head, the optimum magnetic recording / reproducing characteristics at the recording density used, and the like. As a result of concentrating on the layers, the write efficiency is greatly improved, the write current is reduced, and the overwrite characteristics are remarkably improved as compared with the conventional magnetic recording apparatus.
The formation of the soft magnetic layer is not particularly limited and can be performed according to a known method. For example, the soft magnetic layer can be formed by an electroplating method or the like.
Specifically, the soft magnetic material is deposited or deposited by immersing the base material (porous layer) in which the nanoholes are formed in a plating solution and then applying a voltage using the electrode layer as an electrode. This can be done.

The nanohole in the nanohole structure (porous layer) may have a nonmagnetic layer (intermediate layer) between the hard magnetic layer and the soft magnetic layer. If the non-magnetic layer (intermediate layer) is present, the effect of the exchange coupling force between the hard magnetic layer and the soft magnetic layer is weakened. Can be controlled to a desired reproduction characteristic.
The material of the nonmagnetic layer is not particularly limited and can be appropriately selected from known materials. For example, the material is selected from Cu, Al, Cr, Pt, W, Nb, Ru, Ta, and Ti. There are at least one kind. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as thickness of the said nonmagnetic layer, According to the objective, it can select suitably.
The formation of the nonmagnetic layer is not particularly limited and can be performed according to a known method. For example, it can be performed by electrodeposition (electrodeposition method) or the like.

-Other layers-
There is no restriction | limiting in particular as said other layer, Although it can select suitably according to the objective, For example, a protective layer, an adhesion layer, an oxidation stop layer, etc. are mentioned.

--Protective layer--
The protective layer is a layer having a function of protecting the hard magnetic layer, and is provided on the surface or above the hard magnetic layer. The protective layer may be provided in only one layer, may be provided in two or more layers, may have a single layer structure, or may have a laminated structure.
There is no restriction | limiting in particular as a material of the said protective layer, According to the objective, it can select suitably, For example, DLC (diamond-like carbon) etc. are mentioned.

There is no restriction | limiting in particular as thickness of the said protective layer, According to the objective, it can select suitably.
The formation of the protective layer is not particularly limited, and can be performed according to a known method according to the purpose. For example, it can be performed by a plasma CVD method, a coating method, or the like.

-Adhesion layer-
The adhesion layer is a layer having a function of closely contacting the substrate and the electrode layer or a function of closely contacting the electrode layer and the insulating layer. The material of the adhesion layer is not particularly limited and can be appropriately selected according to the purpose. For example, Ta, Nb, Ti, Mb, etc., an insulating oxide film that is stable in an anodizing bath is formed. Metals referred to as so-called valve metals can be used.
The formation of the adhesion layer is not particularly limited and can be performed by a sputtering method or the like.

--- Oxidation stop layer--
The oxidation stop layer is a layer having a function of stopping the oxidation of the base material. There is no restriction | limiting in particular as a material of the said oxidation stop layer, According to the objective, it can select suitably, For example, stable insulating oxide films, such as Ta, Nb, Ti, Mb, are formed in an anodic oxidation bath A so-called valve metal can be used.
The formation of the oxidation stop layer is not particularly limited, and can be performed by a sputtering method or the like.

(Manufacturing method of nanohole structure)
The method for producing a nanohole structure of the present invention includes at least an electrode layer forming step, an insulating layer forming step, a base material forming step, a nanohole forming step, and a metal filling step, and further appropriately selected as necessary. Including other processes.

-Electrode layer formation process-
The electrode layer forming step is a step of forming an electrode layer on the substrate.
Examples of the substrate and the electrode layer include those described above.
The electrode layer can be formed according to a known method, but can be suitably performed by, for example, a sputtering method (sputtering), a vapor deposition method, or the like. There is no restriction | limiting in particular as formation conditions of this electrode layer, According to the objective, it can select suitably.
The electrode layer formed in the electrode layer forming step is used as an electrode when a nanohole is filled with metal by electroplating (electrodeposition).

-Insulating layer formation process-
The insulating layer forming step is a step of forming an insulating layer on a part of the electrode layer.
Examples of the insulating layer include those described above.
The insulating layer can be formed according to a known method such as a plasma CVD method. There is no restriction | limiting in particular as formation conditions of this insulating layer, According to the objective, it can select suitably.
In the insulating layer formation step, for example, the insulating layer is partially formed on the electrode layer by partially removing the insulating layer. For example, by applying a resist on the insulating film, performing a thermal imprint process using a mold, and etching, the insulating layer is partially removed to form a pattern. Further, instead of the thermal imprint process, a pattern may be formed by a photoimprint method using a combination of a photocurable resist and a transparent quartz mold, and a normal photolithography process is used. A pattern may be formed.

-Base material formation process-
The base material forming step is a step of forming a base material that covers the electrode layer and the insulating layer. In the base material forming step, for example, a metal layer is laminated on the electrode layer and the insulating layer, and the base material is formed by oxidizing the metal layer (FIG. 1A).
Examples of the substrate include those described above.
The material of the metal layer is not particularly limited as long as it is a metal material capable of forming nanoholes, and can be appropriately selected according to the purpose. For example, a simple metal, its oxide, nitride, alloy, etc. Of these, among these, for example, aluminum, aluminum alloys, and oxides thereof are preferable.

-Nanohole formation process-
The nanohole forming step is a step of forming nanoholes in the base material. In the nanohole forming step, the nanoholes are formed in the substrate by, for example, anodic oxidation (FIGS. 1C, 2A, and 3A).

  The formation of the substrate on which the nanoholes are formed is not particularly limited, and can be performed according to a known method. For example, after forming a metal material layer (metal layer) by sputtering, vapor deposition, or the like, the anode This can be done by forming the nanoholes by oxidation treatment. Anodization treatment of aluminum or the like is preferable in that a large number of nanoholes can be formed evenly at almost equal intervals.

  Note that nanoholes formed by anodizing treatment are usually randomly arranged, but a pattern for forming a plurality of regular arrays of nanoholes on the metal layer (desired depressions) before the anodizing treatment. Is preferably formed in advance (FIG. 1B). In this case, the anodizing treatment is advantageous in that the nanoholes can be efficiently formed only on the pattern.

  The method for forming the pattern is not particularly limited and may be appropriately selected depending on the intended purpose. For example, (1) circular convex portions arranged in a pattern (for example, a hexagonal close-packed lattice) A stamper having, as a surface shape, a pattern in which a plurality of regular arrays (when the nanohole structure is applied to a magnetic disk or the like, the regular array of convex portions is concentrically or spirally arranged) is formed. Imprint transfer onto the surface of a layer (for example, alumina, aluminum, etc.) and form a pattern in which a plurality of circles are regularly arranged in a hexagonal close-packed lattice, (2) a resin layer or a photoresist layer on the metal layer After the formation, patterning is performed on the surface of the metal layer by patterning these by an ordinary photo process or an imprint method using a stamper, and performing an etching process or the like ( A method in which a plurality of regularly arranged in example, if formed by arranging in a hexagonal close-packed lattice pattern) recess to form the formed pattern is preferably exemplified.

  The stamper is not particularly limited and may be appropriately selected depending on the purpose. From the viewpoint that it is most widely used as a material for producing a fine structure in the semiconductor field, silicon, a silicon oxide film, and the like. From the viewpoint of continuous use durability, a silicon carbide substrate and the like, and a Ni stamper used for molding an optical disk and the like are also included. The stamper can be used multiple times. There is no restriction | limiting in particular as the method of the said imprint transfer, According to the objective, it can select suitably from well-known methods. The resist material for the photoresist layer includes an electron beam resist material and the like in addition to the photoresist material. There is no restriction | limiting in particular as said photoresist material, It can select suitably from well-known materials in the semiconductor field | area etc., For example, the material etc. which can utilize near-ultraviolet light, near-field light, etc. are mentioned.

-Metal filling process-
The metal filling step is a step of filling a metal into a nanohole formed in a region located on the electrode layer by electroplating (FIGS. 1D, 2B, and 3B).
Examples of the substrate include those described above.
After the substrate (porous layer) on which the nanoholes are formed is immersed in a plating solution, a voltage is applied using the electrode layer as an electrode, thereby depositing or depositing the metal.

-Other processes-
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, an insulating substance filling process, a base layer formation process, a grinding | polishing process (surface treatment process), etc. are mentioned.

--Insulating material filling process--
The insulating material filling step is a step of filling the insulating material into the nanoholes selected in accordance with the necessity and formed in the region located on the insulating layer.
Examples of the insulating material include a photocurable resin. After the metal filling process, the substrate is dried and subjected to a hydrophobizing process such as by a steam process of a silane coupling agent. After applying a low-viscosity photocurable resin, it is cured by ultraviolet treatment. If the excess resin is removed by ashing, polishing or the like, only the nanoholes formed on the insulating film can be filled with the insulator.

--- Underlayer formation process--
The base layer forming step is a step of selecting a base layer as necessary and forming a base layer on the substrate.
Examples of the substrate include those described above.
The underlayer can be formed according to a known method. For example, the underlayer may be formed by a sputtering method (sputtering), a vacuum film-forming method such as a vapor deposition method, or electrodeposition (electrodeposition method). Alternatively, it may be formed by electroless plating.
The foundation layer having a desired thickness is formed on the substrate by the foundation layer forming step.

-Polishing process (flattening process)-
The polishing step is a step of polishing and planarizing the surface of the nanohole structure (porous layer) after the metal filling step.
There is no restriction | limiting in particular as the grinding | polishing method in the said grinding | polishing process, It can carry out according to a well-known method, For example, CMP process etc. are mentioned. When the surface of the magnetic recording medium is smoothed by the polishing step, a magnetic head such as a perpendicular magnetic recording head can be stably levitated, and both high density recording and low reliability can be achieved by low levitating. This is advantageous in that

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
-Fabrication of nanohole structures-
Example 1 shows a case where a metal / alumina composite medium patterned on a Si substrate is produced.
First, an n ++ Si substrate was used as a conductive substrate (substrate and electrode layer), and a Ta film having a thickness of 50 nm was formed on the Si substrate as an adhesion layer / oxidation stop layer by a sputtering method.

Next, a 20 nm-thick SiO ₂ film (insulating layer) was formed on the Ta film by plasma CVD using tetraethoxysilane (TEOS) as a raw material at a substrate temperature of 300 ° C. The deposition conditions for the SiO ₂ film were a substrate temperature of 300 ° C., a pressure of 1 Torr, a carrier gas Ar flow rate of 50 sccm, an oxygen flow rate of 50 sccm, an applied power of 200 W, and a deposition time of 60 seconds.

Next, a polymethyl methacrylate (PMMA) resist was applied to a thickness of 50 nm by a spin coating method (1,500 rotations, 30 seconds), and pattern transfer of the PMMA resist was performed by a thermal imprint method as follows.
First, after removing the solvent in the PMMA resist by pre-baking at a temperature of 90 ° C. for 30 minutes, the Ni mold was pressed under the conditions of a substrate temperature of 125 ° C., a pressure of 50 kgf / cm ² , and a holding time of 10 seconds to perform a thermal imprint process. Went. Note that an inversion pattern having a height of 50 nm is formed on the Ni mold. Then, after cooling to the temperature below the glass transition point of PMMA, the mold was peeled from the substrate. Furthermore, in order to remove the residue remaining in the mold recess, oxygen plasma ashing was performed for 1 minute under the conditions of an O ₂ pressure of 0.4 Torr and an applied power of 100 W.

Next, the substrate was moved into an RIE apparatus, and the SiO ₂ film was etched by the RIE method using CF ₄ as a process gas. The etching conditions were CF _{4 10} sccm, H ₂ 20 sccm, applied power 50 W, pressure 0.1 Torr, and 30 seconds. Etching was performed in an over-etched manner, and an excessive oxide film formed on the surface of the Ta film was removed at the same time as the SiO ₂ film was formed.

Next, the PMMA resist was removed by oxygen ashing. Thereby, the pattern of the SiO ₂ film (insulating layer) was formed.

  Next, an Al film (base material) having a film thickness of 300 nm was formed using a sputtering method, and a planarization process (CMP process) was performed in order to reduce surface irregularities.

Next, a thermal imprint process using PMMA as a resist is performed, and further, O ₂ dry etching and dry etching with CCl ₄ (texturing process) are performed, whereby a 60 nm pitch triangular lattice pattern having a depth of 10 nm is formed on the Al film. Was transcribed.

  Next, an anodization of the Al film was performed using an 0.3M sulfuric acid bath at an oxidation voltage of 25V. This is an anodic oxidation condition corresponding to a 60 nm pitch triangular lattice pattern.

  Next, Ni was filled into the alumina nanoholes using an Ni plating bath of an aqueous solution containing Ni sulfate at a concentration of 30 g / L and boric acid at a concentration of 30 g / L. Metal was plated inside the nanohole by AC 50 Hz, 15 V AC, constant voltage AC plating for 5 minutes, and excess Ni overflowed from the nanohole opening.

  The overflowed Ni was flattened to the alumina surface by Ar ion milling from an oblique direction, and the surface was observed. As a result, the portion corresponding to the buried insulating layer was not filled with metal, and a metal filled portion and a non-filled portion could be produced arbitrarily.

  In Example 1, Ta was used as the adhesion layer / oxidation stop layer. However, the present invention is not limited to this. In addition to Ta, Nb, Ti, Mb, etc., an insulating oxide film that is stable in an anodizing bath. Metals called so-called valve metals can be used.

  In Example 1, an n ++ Si substrate was used as the conductive substrate (substrate and electrode layer). However, the present invention is not limited to this, and other conductive substrates may be used. A sufficiently thick conductive electrode layer may be formed on an insulating substrate such as sapphire or plastic and below the adhesion layer / oxidation stop layer.

  In Example 1, in order to improve the alignment and verticality of the alumina nanoholes, the Al film before the anodic oxidation was planarized and textured, but the present invention is not limited to this. If the size is sufficiently large with respect to the Al film thickness or the pitch of the nanoholes, and the nanohole arrangement and the vertical disorder may be ignored, these steps can be omitted.

In Example 1, a SiO ₂ film formed by the plasma CVD method was used as the buried insulating layer. However, the present invention is not limited to this, and SiON, SiO, SiO formed by vapor deposition or sputtering is used. Insulating oxides and nitrides such as _{X 2} , CeO ₂ and alumina can also be used, and the resist itself can also be used as an insulating layer.

An example in which the resist itself is used as an insulating layer will be shown below.
First, a PMMA film having a glass transition point of 105 ° C. was applied to a film thickness of 50 nm on a substrate with a conductor film or a conductor substrate by spin coating. The spin coating was performed at a rotation speed of 1,500 rotations and a time of 30 seconds. After removing the solvent by pre-baking at a temperature of 90 ° C. for 30 minutes, a Ni-made mold was pressed to perform a thermal imprint process under the conditions of a substrate temperature of 125 ° C., a pressure of 50 kgf / cm ² , and a holding time of 10 seconds. At this time, an inverted pattern having a height of 50 nm is formed on the Ni mold.
After cooling to a temperature below the glass transition point of PMMA, the mold was peeled from the substrate. In order to remove the residue remaining in the mold recess, oxygen plasma ashing was performed for 1 minute under conditions of an O ₂ pressure of 0.4 Torr and an applied power of 100 W. Thereby, the pattern by insulator PMMA was formed on the board | substrate with a conductor film, or a conductor board | substrate.

  In Example 1, Ni inside the alumina nanohole was filled using a Ni plating bath. However, the present invention is not limited to this, and Co, Pd can be used in addition to Ni by changing the plating bath. Various metals such as Cu, Au and the like can be filled.

  In Example 1, a pattern was formed by a thermal imprint method using a PMMA resist, but this is not a limitation. By using a combination of a photo-curable resist and a transparent quartz mold, A pattern may be formed by an imprint method. Further, depending on the size of the pattern, the pattern may be formed using a normal photolithography process.

(Example 2)
Example 2 shows an example in which a servo pattern for alumina nanohole patterned media is formed.

  First, on a 2.5-type crystallized glass substrate for a hard disk drive, a Ta film with a thickness of 50 nm as an adhesion layer and a permalloy film with a thickness of 50 nm as an underlayer soft magnetic layer (electrode layer) by sputtering are used. A 5 nm Ta film as a stop layer and a 10 nm thick SiOx film as an insulating layer were formed in this order from the substrate side.

Next, a servo pattern was patterned on the SiOx film using nanoimprint and dry etching using CF ₄ . Since this servo pattern uses 2 dots of a 20 nm pitch square lattice as one bit, the pattern is formed on the basis of L / S of 40 nm pitch.

Further, an Al film having a film thickness of 70 nm was formed by sputtering. After the surface is flattened by CMP processing, thermal imprint processing using PMMA as a resist is performed, and O ₂ dry etching and dry etching with CCl ₄ are performed, whereby a 20 nm pitch square having a depth of 3 nm or less is formed on the Al film. The lattice pattern was subjected to texturing. The square lattice pattern is arranged on a circumference centering on the center of the substrate. Anodization was performed at a voltage of 7 V using a 0.3 M sulfuric acid bath. As a result, alumina nanoholes were formed in a square lattice arrangement on the circumference with a pitch of 20 nm.

  Next, using a Co plating bath of an aqueous solution containing Co sulfate at a concentration of 50 g / L and boric acid at a concentration of 20 g / L, the magnetic material Co was filled into the alumina nanoholes. Metal was plated inside the alumina nanohole by AC 50 Hz, 6 V AC, constant voltage AC plating for 10 minutes, and excess Co overflowed from the nanohole opening.

  Next, excess Co was removed by CMP treatment, and a DLC protective film having a film thickness of 5 nm was applied by sputtering, and a fluorine-based lubricant was applied by dipping. The portion embedded with the insulating film was not filled with magnetic material, and nanohole patterned media with a servo pattern was realized (FIG. 4).

  In Example 2, Co was used as the magnetic material, but the present invention is not limited to this. For example, in addition to the Co material, Fe-based materials, FePt, CoPt-based alloy-based magnetic materials, and FeNi / Co-based soft materials are used. A magnetic / hard magnetic stack structure can be used. Further, an alumina nanohole medium having a random arrangement can be produced by omitting the texturing process on the Al surface.

(Example 3)
Example 3 shows an example applied to refractive index modulation of a photonic crystal.

First, an Nb film having a film thickness of 50 nm is formed on a flat glass substrate as a base electrode and an oxidation stop film using a sputtering method, and a film thickness of 10 nm is formed on the Nb film using a plasma CVD method as an insulating layer. A SiO ₂ film was formed. Using a normal photolithography and dry etching, a line pattern having a width of 200 nm and a length of 2,400 nm serving as a waveguide pattern and a circular pattern having a diameter of 200 nm serving as a light emission hole adjacent thereto were formed.

  Next, an Al film having a thickness of 300 nm was formed by a sputtering method, and a CMP process was performed to planarize the surface. The patterning by the normal photolithographic method and dry etching were used to perform a texturing process of a triangular lattice pattern with a pitch of 200 nm and a depth of 10 nm on the surface of the Al film. Anodization was performed at a voltage of 80 V using an oxalic acid 0.3 M bath to produce alumina nanoholes with a pitch of 200 nm.

  Next, Ni was filled into the alumina nanoholes using an Ni plating bath of an aqueous solution containing Ni sulfate at a concentration of 30 g / L and boric acid at a concentration of 30 g / L. Ni was filled into the alumina nanoholes by the plating process of AC 50 Hz, 25 V AC and 15 minutes, and overflowed on the surface. When the overflowing Ni was removed by the CMP process, the portion with the buried insulating layer was not filled and could remain as nanoholes (FIG. 5).

  When light was introduced into the fabricated sample, it was detected that the light confined only in the unfilled part that deviated from the periodic refractive index modulation was extracted from the emission hole, and it was confirmed that it operates as a photonic crystal. .

  In the third embodiment, the filling portion is defined as a photonic crystal main body, and the non-filling portion is defined as a waveguide defect. However, the arrangement may be reversed.

  Further, in Example 3, Ni was used as the metal to be filled, but the present invention is not limited to this, and the dielectric of alumina such as noble metals such as Au and Pt, conductive transparent oxides such as TiOx, SnOx, and InOx, etc. Any material may be used as long as it has a difference from the rate and can be filled by plating.

Example 4
Example 4 shows an example applied to the production of a biochip.
First, an Nb film having a film thickness of 50 nm is formed on a flat glass substrate as a base electrode and an oxidation stop film using a sputtering method, and a film thickness of 10 nm is formed on the Nb film using a plasma CVD method as an insulating layer. A SiO ₂ film was formed. A pattern for biochip was formed on the SiO ₂ film by a combination of a normal photolithography method and a dry etching method. Although various shapes can be considered for the pattern, here, as an example, a square checkered pattern (FIG. 6B) having a pitch of 2 μm is patterned in a 1 cm square patterning region.

  Next, after an Al film having a thickness of 100 nm was formed by sputtering, a triangular lattice pattern with a 300 nm pitch was subjected to texturing by a normal photolithography method and a dry etching method.

  Next, anodization was performed at a voltage of 120 V using a phosphoric acid 0.3 M bath to obtain an alumina nanohole film having a pitch of 300 nm.

  Next, using an alkaline gold plating bath containing potassium gold cyanide at a concentration of 1 g / L, potassium cyanide at a concentration of 70 g / L, and dipotassium hydrogen phosphate at a concentration of 10 g / L, alumina is used. The inside of the nanohole was filled with Au. The inside of the alumina nanohole was filled by the plating process of AC 50 Hz, 30 V AC and 5 minutes, and overflowed the surface.

  The overflowing Au was removed by the CMP method to obtain a biochip formed with a fine Au pattern (FIGS. 6A, 6B, and 6C).

  In Example 4, Au was used as a metal to be filled, but the present invention is not limited to this. As a metal to be filled in a nanohole, a metal (such as Pt or TiOx) having high biocompatibility and capable of electroplating (conductive). As long as it is a sexual substance).

  In Example 4, Au was filled from the bottom. However, the present invention is not limited to this. For example, the lower layer is made of Ni and the surface layer is made of Au. It may be reduced. In this case, the surface metal can be formed by electroless plating instead of electroplating by using the base metal as a catalyst.

The preferred embodiments of the present invention are as follows.
(Appendix 1) An electrode layer forming step of forming an electrode layer on a substrate, an insulating layer forming step of forming an insulating layer on a part of the electrode layer, and a base material covering the electrode layer and the insulating layer A base material forming step for forming, a nano hole forming step for forming nano holes in the base material, and a metal filling step for filling a metal into the nano holes formed in a region located on the electrode layer by electroplating. A method for producing a nanohole structure, comprising:
(Additional remark 2) The manufacturing method of the nanohole structure of Additional remark 1 which forms the said insulating layer in a part on said electrode layer by removing the said insulating layer partially in the said insulating layer formation process.
(Supplementary note 3) The nanohole structure according to supplementary note 1, wherein in the base material forming step, a metal layer is formed on the electrode layer and the insulating layer, and the base material is formed by oxidizing the metal layer. Method.
(Additional remark 4) The manufacturing method of the nanohole structure of Additional remark 3 which forms the said base material by oxidizing the said metal layer by anodic oxidation, and forms the said nanohole in this base material.
(Supplementary Note 5) A substrate, an electrode layer formed on the substrate, an insulating layer formed on a part of the electrode layer, and the electrode layer and the insulating layer are covered and positioned on the electrode layer And a base material in which a second nanohole is formed in a region located on the insulating layer.
(Supplementary note 6) The nanohole structure according to supplementary note 5, wherein the second nanohole is shallower than the first nanohole.
(Supplementary note 7) The nanohole structure according to supplementary note 5 or 6, wherein the first nanohole is filled with a metal and the second nanohole is filled with an insulating material.

The nanohole structure of the present invention can be suitably used in various fields such as magnetic recording media, DNA chips, diagnostic devices, detection sensors, catalyst substrates, field emission displays, and the like. It can be suitably used for crystals, biochips and the like.
The method for producing a nanohole structure of the present invention can be suitably used for producing the nanohole structure of the present invention.

FIG. 1A is a drawing for explaining a method for producing a nanohole structure according to the present invention (part 1). FIG. 1B is a drawing for explaining the method for producing a nanohole structure of the present invention (No. 2). FIG. 1C is a drawing for explaining a method for producing a nanohole structure according to the present invention (part 3). FIG. 1D is a drawing for explaining a method for producing a nanohole structure according to the present invention (part 4). FIG. 2: A is a figure for demonstrating the manufacturing method of the nanohole structure of this invention (the 5). FIG. 2B is a drawing for explaining the method for producing a nanohole structure according to the present invention (No. 6). FIG. 3: A is a figure for demonstrating the manufacturing method of the nanohole structure of this invention (the 7). FIG. 3B is a drawing for explaining the method for producing a nanohole structure according to the present invention (# 8). FIG. 4 is a diagram for explaining nanohole patterned media. FIG. 5 is a diagram for explaining the dielectric constant control of the photonic crystal. FIG. 6A is a diagram for explaining a biochip. 6B is an enlarged view of a portion X in FIG. 6A. FIG. 6C is an enlarged view of a Y portion in FIG. 6B.

Claims (7)

An electrode layer forming step of forming an electrode layer on the substrate;
An insulating layer forming step of forming an insulating layer on a part of the electrode layer;
A base material forming step of forming a base material covering the electrode layer and the insulating layer;
A nanohole forming step of forming nanoholes in the substrate;
And a metal filling step of filling a metal into a nanohole formed in a region located on the electrode layer by an electroplating method.   2. The method of manufacturing a nanohole structure according to claim 1, wherein in the insulating layer forming step, the insulating layer is partially formed on the electrode layer by partially removing the insulating layer.   The method for producing a nanohole structure according to claim 1, wherein in the base material forming step, a metal layer is formed on the electrode layer and the insulating layer, and the base material is formed by oxidizing the metal layer.   The method for producing a nanohole structure according to claim 3, wherein the metal layer is oxidized by anodic oxidation to form the base material, and the nanohole is formed in the base material. A substrate,
An electrode layer formed on the substrate;
An insulating layer formed in part on the electrode layer;
A base material covering the electrode layer and the insulating layer, wherein a first nanohole is formed in a region located on the electrode layer, and a second nanohole is formed in a region located on the insulating layer. Nanohole structure.   The nanohole structure according to claim 5, wherein the second nanohole is shallower than the first nanohole.   The nanohole structure according to claim 5 or 6, wherein the first nanohole is filled with a metal, and the second nanohole is filled with an insulating material.