JP4946500B2 - Nanohole structure and manufacturing method thereof, and magnetic recording medium and manufacturing method thereof - Google Patents

Description

  The present invention is suitable for a nanohole structure suitable for a magnetic recording medium or the like and an efficient manufacturing method thereof, an external storage device for a computer, a hard disk device widely used as a consumer video recording device, etc. The present invention relates to a magnetic recording medium capable of high-capacity and high-speed recording and an efficient and low-cost manufacturing method thereof.

In recent years, along with technological innovation in the IT industry and the like, research and development for increasing the capacity, speed, and cost of magnetic recording media has been actively conducted. In order to increase the capacity, speed, and cost of the magnetic recording medium, it is essential to improve the recording density of the magnetic recording medium.
Therefore, the magnetic film in the magnetic recording medium is not a continuous film, but has a pattern such as dots, bars, pillars, etc. As a new magnetic recording medium that combines a recording method using media (see Non-Patent Document 1) and a recording method using perpendicular recording (see Patent Document 1), a magnetic material in which pores of anodized alumina pores are filled with a magnetic metal. A recording medium has been proposed (see Patent Document 2). As shown in FIG. 1, the magnetic recording medium has a base electrode layer 120 and an anodized alumina layer 130 in this order on a substrate 110. The anodized alumina layer 130 has a large number of alumina pores in an ordered arrangement. A ferromagnetic layer 140 is formed by filling the alumina pores with a ferromagnetic metal.

  The magnetic recording medium in which the magnetic material is filled in the anodized alumina pore is easy to be magnetized in the vertical direction because the anodized alumina pore is elongated in the direction perpendicular to the exposed surface (with a high aspect ratio). The shape anisotropy of the filled magnetic material has the advantage of being resistant to thermal fluctuations. In addition, since the anodized alumina pores are normally generated in a honeycomb-type hexagonal close-packed lattice in a self-organized manner, it can be manufactured at a lower cost than a method of forming dots one by one by lithography. There are advantages.

  However, since the anodized alumina pores are two-dimensionally arrayed, such as a hexagonal close-packed lattice, from the viewpoint of magnetic recording, it is impossible to provide a gap between adjacent bit strings. There is. That is, in the patterned medium, it is ideal to record 1 bit per dot, but since dots exist in the radial direction at the same pitch as the linear direction (circumferential direction) There is a fatal problem that a cross light or a croread is generated. Therefore, for example, as shown in FIGS. 2A and 2B, one bit (63 in FIG. 2B) must be changed from several to several tens or more dots (61 in FIGS. 2A and 2B). However, even in this case, there still remains a problem that the cross write or cross read occurs. Therefore, a magnetic recording medium is desired in which the anodized alumina pores filled with a magnetic material are arranged in a row and a nonmagnetic region is provided between the rows.

  Therefore, before the anodic oxidation, the surface of the aluminum layer is formed with irregularities that will be the starting point of the anodic alumina pores (hereinafter, sometimes referred to as “texture treatment”), whereby the alumina pores to be formed are formed. By arranging regularly in one row, it is possible to control the arrangement of magnetic bits, and by controlling the oxidation voltage at the time of anodization, the density of the alumina pores, that is, the recording density is adjusted, and ultra-high density recording is performed. An actual magnetic recording medium has been proposed by the present inventors (see Patent Document 3).

By the way, as a method of performing a texture treatment on the surface of the aluminum layer, (1) a method of drawing a concavo-convex pattern using electron beam lithography, and (2) a mold having a concavo-convex pattern formed on the surface is directly applied to the aluminum layer. A direct hard imprint method in which the surface is pressed with a high pressure, (3) a polymer layer is formed on the aluminum layer, and the mold pattern is transferred to the polymer layer to transfer the uneven pattern, thereby forming the uneven pattern There is known a soft imprint method for etching the surface of the aluminum layer using, for example.
However, in the method using the electron beam lithography described in (1), as the pattern size becomes as fine as the nm order, it takes a long time to draw the concavo-convex pattern over the entire surface of the disk, and the cost is increased due to poor throughput. And cannot withstand mass production of the magnetic recording medium.
Further, in the direct hard imprint method described in (2), the pressure required for transferring the uneven pattern is large, for example, several hundred kg / cm ² at a pitch of 100 nm, and several tens of tons even for a one-inch substrate. Unit. Furthermore, the necessary pressure increases as the pitch becomes finer. With a 2.5-inch substrate that is practically required, if the uneven pattern having a pitch of 25 nm or less is to be transferred, a pressure exceeding several hundred tons is required. Realistic.
For this reason, from the viewpoint of realizing high-density recording and mass productivity improvement, there is a tendency to shift to the soft imprint method described in (3) above, and further research and development are being carried out.

However, even when the soft imprint method is used, the following problems occur as the target pitch decreases. That is, the imprint process alone cannot basically form unevenness in the aluminum layer that is deeper than the unevenness formed in the mold, and the unevenness of the mold also has an aspect ratio (recess depth and depth). The ratio with the pitch of the unevenness is limited to less than about 1.
Here, as a method for producing the mold, a resist pattern is formed using electron beam lithography, a metal such as Ni is thickly plated on the resist pattern, and the resist pattern is formed on a substrate (for example, using an etching process). , Ni, Si, SiO ₂ , quartz glass, and the like). However, according to the former, the aspect ratio of the unevenness in the mold is limited by the unevenness formed in the resist pattern, and when an attempt is made to produce a structure having an aspect ratio of 1 or more, resist collapse occurs. is there. On the other hand, according to the latter, for example, it is possible to produce a structure having an aspect ratio of 1 or more by using a process such as a two-layer resist, but the durability when imprinting is actually performed. When considered, the use of high aspect ratio molds is impractical. Therefore, in practice, the aspect ratio of the unevenness that can be directly transferred by the soft imprint method is limited to less than 1.

  As described above, in the conventional soft imprint method, since the aspect ratio of the unevenness in the uneven pattern is limited to less than 1, unevenness having a sufficient depth cannot be formed as the starting point of the anodized alumina pore. The uneven pattern cannot be accurately transferred. For this reason, in the subsequent anodic oxidation treatment, there arises a problem that the anodic alumina pores cannot be regularly arranged and formed. In particular, this problem becomes apparent as the pitch of the unevenness to be formed becomes finer.

S. Y. Chou Proc. IEEE 85 (4), 652 (1997) Japanese Patent Laid-Open No. 6-180834 JP 2002-175621 A JP 2005-305634 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, it is widely used as a nanohole structure suitable for various fields such as magnetic recording media, DNA chips, catalyst substrates, etc., and its efficient manufacturing method, as well as external storage devices for computers, consumer video recording devices, etc. It is suitable for hard disk drives, etc., which can perform 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. An object of the present invention is to provide an extremely high-quality magnetic recording medium free from problems such as writing, and an efficient and low-cost manufacturing method thereof.

Means for solving the problems are as follows. That is,
The method for producing a nanohole structure according to the present invention includes forming a metal layer on a substrate and then smoothing the surface of the metal layer, and forming the nanohole on the smoothed metal layer. A starting point forming step for forming a starting point, and a porous layer forming step for forming a porous layer in which a plurality of nanoholes are formed in a direction substantially perpendicular to the base material by performing a nanohole forming process. And
In the nanohole structure manufacturing method, in the smoothing treatment step, after the metal layer is formed on the substrate, the surface of the metal layer is smoothed. In the starting point forming step, starting points for forming nanoholes are formed in the smoothed metal layer. In the porous layer forming step, a nanohole forming process is performed to form a porous layer in which a plurality of nanoholes are formed in a direction substantially orthogonal to the base material. As a result, a nanohole structure in which nanohole arrays in which nanoholes are regularly arranged is arranged at regular intervals is easily and efficiently manufactured.

The nanohole structure according to the present invention is manufactured by the method for manufacturing a nanohole structure according to the present invention, and a nanohole array in which nanoholes are regularly arrayed is arranged on a substrate at regular intervals. .
The nanohole structure can be used as a magnetic recording medium such as a hard disk device if the nanohole is filled with a magnetic material, and can be used as a DNA chip if DNA or the like is arranged in the nanohole. If an antibody or the like is arranged in the nanohole, it can be used as a protein detection device, a diagnostic device, or the like. If the nanohole is filled with a catalyst metal for forming carbon nanotubes, for example, carbon can be obtained. A formation substrate such as a nanotube, a field emission device, or the like can be used.

The method for producing a magnetic recording medium of the present invention comprises a smoothing step of smoothing the surface of the metal layer after forming a metal layer on the substrate, and a starting point for forming nanoholes in the smoothed metal layer. Forming a starting point; forming a nanohole structure by forming a plurality of nanoholes in a direction substantially perpendicular to the substrate surface by performing a nanohole forming process; and forming a magnetic field inside the nanohole. And a magnetic material filling step for filling the material.
In the method of manufacturing the magnetic recording medium, after the metal layer is formed in the smoothing process, the surface of the metal layer is smoothed. In the starting point forming step, starting points for forming nanoholes are formed in the smoothed metal layer. In the nanohole structure forming step, by performing the nanohole forming process, a plurality of nanoholes are formed in a direction substantially orthogonal to the substrate surface to form a nanohole structure. In the magnetic material filling step, the magnetic material is filled into the nanoholes. As a result, the magnetic recording medium of the present invention is manufactured efficiently and at low cost.

The magnetic recording medium of the present invention is produced by the method for producing a magnetic recording medium of the present invention, and has a nanohole structure in which a plurality of nanoholes are formed on a substrate in a direction substantially perpendicular to the substrate surface, It is characterized by having a magnetic material inside the nanohole.
In the magnetic recording medium, nanohole arrays in which nanoholes filled with the magnetic material are regularly arranged are arranged at regular intervals, so that high-density recording and high-speed recording can be performed without increasing the write current of the magnetic head. It has a large capacity, excellent overwrite characteristics, uniform characteristics, and is extremely high quality without any problems such as cross-reading and cross-writing. The magnetic recording medium is suitable for an external storage device of a computer, a hard disk device widely used as a consumer video recording device and the like.
In the case where the magnetic recording medium has a soft magnetic layer and a ferromagnetic layer in this order from the substrate side inside the nanohole, and the thickness of the ferromagnetic layer is equal to or less than the thickness of the soft magnetic layer. The ferromagnetic layer is laminated on the soft magnetic layer formed inside the nanohole in the nanohole structure, and is thinner than the nanohole structure. Therefore, when performing magnetic recording on the magnetic recording medium using a single magnetic pole head, the distance between the single magnetic pole head and the soft magnetic layer is shorter than the thickness of the nanohole structure, Since the thickness of the ferromagnetic layer is substantially equal to the thickness of the ferromagnetic layer, the magnetic flux concentration from the single-pole head and the optimum magnetic density at the used recording density are determined only by the thickness of the ferromagnetic layer regardless of the thickness of the nanohole structure. Recording / reproduction characteristics and the like can be controlled, and as shown in FIGS. 3 and 4, the magnetic flux from the single pole head (write / read head 100) is concentrated on the ferromagnetic layer (perpendicular magnetization film) 30. As a result, in the magnetic recording medium, the writing efficiency is greatly improved, the writing current is reduced, and the overwrite characteristic is remarkably improved as compared with the conventional magnetic recording medium.

  According to the present invention, conventional problems can be solved, and a nanohole structure suitable for various fields such as a magnetic recording medium, a DNA chip, and a catalyst substrate, an efficient manufacturing method thereof, and an external storage of a computer Suitable for hard disk drives that are widely used as video recorders and consumer video recorders, etc., capable of high-density recording and high-speed recording without increasing the write current of the magnetic head, high capacity, and excellent overwrite characteristics Therefore, it is possible to provide an extremely high quality magnetic recording medium having a uniform characteristic and having no problems such as cross read and cross write, and an efficient and low cost manufacturing method thereof.

(Manufacturing method of nanohole structure)
The method for producing a nanohole structure of the present invention includes at least a smoothing treatment step, a starting point formation step, and a porous layer formation step, and further includes other steps appropriately selected as necessary.

<Smoothing process>
The said smoothing process process is a process of smoothing the surface of this metal layer, after forming a metal layer on a base material.

-Base material-
There is no restriction | limiting in particular about the material, a shape, a structure, a magnitude | size, etc. as said base material, According to the objective, it can select suitably.
The material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include glass, silicon, quartz, and SiO ₂ / Si formed by forming a thermal oxide film on the silicon surface. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular as said shape, Although it can select suitably according to the objective, 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.

-Metal layer-
The metal layer is not particularly limited as long as it is formed using a metal material, and the metal material may be, for example, a single metal, an oxide thereof, a nitride, or an alloy, Among these, for example, alumina (aluminum oxide), aluminum, and the like are preferably exemplified, and among these, aluminum is particularly preferable.
The metal layer can be formed according to a known method, but can be suitably performed by, for example, a sputtering method (sputtering) or a vapor deposition method. There is no restriction | limiting in particular as formation conditions of this metal layer, According to the objective, it can select suitably. In the case of the sputtering method, sputtering can be performed using a target formed of the metal material. The target used in this case preferably has a high purity, and when the metal material is aluminum, the target is preferably 99.990% or more.

The method for smoothing the surface of the metal layer (smoothing treatment) is not particularly limited and may be appropriately selected depending on the intended purpose. However, the CMP (chemical mechanical polishing) treatment may be performed on the surface of the metal layer. Suitable examples include milling (oblique milling) and etch back performed at an angle.
The conditions for the smoothing treatment and the like are not particularly limited and can be appropriately selected depending on the purpose. For example, when the metal layer is an aluminum layer, an alumina-based slurry is used for the CMP treatment. can do.

The size of the irregularities (depth or height: surface roughness) on the surface of the metal layer after the smoothing treatment step is not particularly limited and may be appropriately selected depending on the intended purpose, but is 3 nm or less. Is preferable, and 1 nm or less is more preferable.
When the size (depth or height) of the unevenness is 3 nm or less, the starting point for forming nanoholes can be formed in the starting point forming step described later, where the recessed portion is deep (for example, about 10 nm).

Through the above steps, after the metal layer is formed on the substrate, the surface of the metal layer is smoothed.
In the case where the metal layer is formed by sputtering using aluminum, for example, the surface of the metal layer has irregularities with a depth of several tens of nm due to grain growth. When forming the nanohole formation starting point (uneven pattern), it is necessary to form a recess having a depth equal to or greater than the depth of the recess originally present on the surface of the metal layer. When the pitch of the concave / convex pattern is reduced, it becomes difficult to form a concave / convex pattern with sufficiently deep concave portions. That is, for example, FIG. 5A shows an AFM image on the surface of an aluminum layer having a thickness of 100 nm formed by sputtering, and FIG. 5B shows a graph showing the cross-sectional height shape of the surface. Since aluminum has a low melting point and is likely to cause granular growth during film formation, at this point, irregularities of 30 nm or more are already formed on the surface (see FIG. 5B). For example, when using direct hard imprinting, the unevenness can be physically crushed because a high pressure is applied, but with soft imprinting, the unevenness remains because the applied pressure is low. To do.
However, when the smoothing process is performed, the unevenness formed on the surface of the aluminum layer during the film formation is removed, and in the subsequent starting point forming step, the unevenness pattern (starting point for forming nanoholes) having a deep recess is formed. Can be formed.

<Starting point formation process>
The starting point forming step is a step of forming a starting point for forming nanoholes in the smoothed metal layer.
The starting point for forming nanoholes means what functions as a starting point for forming nanoholes, and examples of the starting point for forming nanoholes include a concavo-convex pattern having regularly arranged fine recesses.

The starting point forming step preferably includes imprint transfer of the uneven pattern of the mold having the uneven pattern corresponding to the array pattern of nanoholes to be formed onto the polymer layer formed on the metal layer.
The mold (material) or the like is not particularly limited as the mold, and can be appropriately selected according to the purpose. However, from the viewpoint that it is most widely used as a microstructure manufacturing material in the semiconductor field. , Silicon, silicon oxide films, combinations of these, and the like. From the viewpoint of continuous use durability, silicon carbide and the like, and Ni used for molding optical disks and the like can be mentioned. The mold can be used multiple times.

The convex / concave pattern in the mold is not particularly limited as long as it has convex portions and concave portions respectively corresponding to the concave portions and convex portions at the starting point for forming nanoholes to be formed, and can be appropriately selected according to the purpose. The dot pattern is preferably a circular shape.
In addition, the arrangement pattern of the convex portions is not particularly limited as long as the convex portions are arranged at regular intervals, and can be appropriately selected according to the purpose. For example, a triangular lattice arrangement, a square lattice arrangement, and the like Can be mentioned. For example, when the convex portions are arranged in a triangular lattice pattern, when the concave / convex pattern in the mold is imprinted onto the metal layer, circular concave portions are triangular at regular intervals on the surface of the metal layer. When a concavo-convex pattern (starting point for forming a nanohole) arranged in a lattice shape is formed and a nanohole is formed in the recess, a nanohole structure in which the nanohole is arranged in a triangular lattice shape is obtained.
Further, the convex portions are preferably arranged concentrically or in a spiral shape. In particular, in the case of a hard disk application, a concentric shape is preferable from the viewpoint of easy access, and in the case of a video disk application, continuous reproduction is preferable. From the viewpoint of easiness, a spiral shape is preferable. When the convex portions are arranged concentrically or spirally, the nanoholes to be formed can be arranged concentrically or spirally.

There is no restriction | limiting in particular as the height of the convex part in the said uneven pattern, Although it can select suitably according to the objective, For example, 10 nm or more is preferable and 20-100 nm is more preferable.
When the height of the convex portion is less than 10 nm, the origin of the nanoholes is easily defined at the time of transfer onto the surface of the aluminum layer, and the resulting nanohole arrangement may be disturbed. On the other hand, when the ratio (aspect ratio) between the height of the convex portion and the interval between the convex portions is too large, deformation or breakage of the mold convex portion is likely to occur during transfer. Therefore, it is preferable that the aspect ratio is approximately 1 or less, that is, when the uneven pitch is 10 to 50 nm, the height of the convex portion is 10 to 50 nm.

The imprint transfer method is not particularly limited and may be appropriately selected from known methods according to the purpose. However, when the nanohole structure is applied to a magnetic recording medium, high-density recording is possible. From the viewpoint of realizing mass productivity improvement, soft imprint is preferable.
As the soft imprint, for example, a thermal imprint is preferably exemplified. The transfer of the uneven pattern by the thermal imprint applies, for example, heat to a polymer layer formed on the metal layer, and This can be done by pressing the mold.
The material for the polymer layer is not particularly limited and may be appropriately selected depending on the purpose. In the case of the thermal imprint, for example, a known resist material, a thermoplastic polymer such as polymethyl methacrylate (PMMA), or the like. Etc.

The starting point forming step includes forming a protective metal layer and a polymer layer on the metal layer in this order from the metal layer, and then imprinting the uneven pattern in the mold onto the polymer layer, thereby forming the unevenness. After the protective metal layer is etched using a pattern, the metal layer is preferably etched using the remaining protective metal layer as a mask.
The etching can be performed using a known etching apparatus such as an ICP-RIE (Inductive Coupled Plasma Reactive Ion Etching) apparatus or an ion milling apparatus.
By forming and etching the protective metal layer between the base material and the polymer layer, forming a recess having a depth that can sufficiently function as a starting point for forming the nanoholes in the metal layer. it can.

  Generally, a resist material used for soft imprint has a low etching resistance to chlorine-based RIE (reactive ion etching) used to etch aluminum as the material of the metal layer, and the nanohole. A recess having a depth that can sufficiently function as a starting point for formation cannot be formed. For example, FIG. 6 shows the etching rate of PMMA when etching is performed by chlorine-based RIE on PMMA as a resist material usually used for thermal imprinting. Further, the etching rate of Al when Al (aluminum) is etched under the same conditions is also shown in FIG. As shown in FIG. 6, when etching with chlorine-based RIE for Al, etching is not started until the strong natural oxide film formed on the Al surface is reduced and the surface of pure Al is exposed. There is a so-called “dead time”. On the other hand, since the dead time does not exist in PMMA, if PMMA is equal to or less than a certain film thickness, a region where no Al etching is performed occurs. As described above, since the aspect ratio of the concavo-convex pattern that can be transferred to the PMMA by the imprint method is less than 1, for example, if the concavo-convex pattern has a pitch of 200 nm, the height of the ridge formed on the PMMA is 200 nm. A concave portion having a depth of about 100 nm can be formed on the Al surface. However, if the concave and convex portions have a pitch of 100 nm, the concave and convex pattern cannot be transferred to Al at all, and a starting point for forming nanoholes is formed. In other words, the nanoholes cannot be regularly arranged.

Next, PMMA, Ta, and Al were prepared as materials for the polymer layer, the protective metal layer, and the metal layer, and these were etched by CF RIE using the ICP-RIE apparatus. The respective etching rates are shown in FIG. 7A. The etching conditions are chamber pressure = 1.5 Pa, CF ₄ = 20 sccm, Ar = 20 sccm, source power = 200 W, and BIAS power = 20 W.
FIG. 7A shows that Al is not etched at all in CF-based RIE. On the other hand, the etching rate ratio of Ta to PMMA is about 0.5, but the dead time does not exist in Ta, and when PMMA is etched by 100 nm, Ta can be etched by 30 nm under the same conditions.
In contrast, FIG. 7B shows an etching rate when etching is performed by CO-ammonia RIE. Etching conditions are: chamber pressure = 0.2 Pa, NH ₃ = 70 sccm, CO = 30 sccm, source power = 700 W, and BIAS power = 200 W.
From FIG. 7B, in CO-ammonia-based RIE, the etching rate of PMMA is very large and PMMA cannot be used as a mask, but Ta can take a rate ratio more than twice that of Al. It can be seen that Al can be etched using Ta as a mask.

  As described above, the material, thickness and the like of the protective metal layer are not particularly limited and can be appropriately selected depending on the purpose. However, when the metal layer is an aluminum layer, Preferred examples of the material include Ta and Ti in relation to the etching rate of aluminum. In this case, the protective metal layer is preferably etched by CF RIE (reactive ion etching) (see FIG. 7A), and the metal layer is etched by CO-ammonia RIE. (See FIG. 7B).

  Further, in the starting point forming step, after the polymer layer is formed on the metal layer, an uneven pattern in the mold is imprinted on the polymer layer to form an uneven pattern, which is formed on the surface of the polymer layer. After removing the polymer layer located on the bottom surface of the recessed portion by etching, forming a protective metal layer by applying a protective metal to the metal layer and the polymer layer exposed in the recessed portion, It is preferable to etch the protective metal layer located in the recess formed in the polymer layer and the surface of the metal layer located under the protective metal layer, and further remove the remaining polymer layer and the residue of the protective metal layer. . In this case, the starting point for forming the nanohole can be produced more efficiently.

  The protective metal in the starting point formation step in this case is not particularly limited and can be appropriately selected depending on the purpose, but since it is directly applied to the surface of the metal layer, it is the same kind as the material of the metal layer. It is preferable that it is a metal, and when the said metal layer is an aluminum layer, it is preferable that the said protective metal is also aluminum.

The method for applying the protective metal is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include sputtering, MBE (Molecular Beam Epitaxy), and vapor deposition.
Specifically, for example, after the PMMA layer as the polymer layer is formed on the Al layer as the metal layer, the uneven pattern in the mold is thermally imprinted on the PMMA layer. Transfer to form a concavo-convex pattern. Next, the polymer layer located on the bottom surface of the recess formed on the surface of the PMMA layer is removed by oxygen-based RIE. Then, an Al film as the protective metal is deposited on the PMMA layer by sputtering to form a protective metal layer. At this time, due to the uneven shadowing effect, the Al layer formed on the bottom surface of the concave portion in the PMMA layer is thinner than the Al layer formed on the surface of the convex portion of the PMMA layer. Then, the protective metal layer (Al layer) located in the recess from which the PMMA layer has been removed and the Al layer as the metal layer located under the protective metal layer are etched, and the remaining PMMA layer and When the residue of the protective metal layer is removed, a concavo-convex pattern as a starting point for nanohole formation is formed on the surface of the Al layer as the metal layer.

  The method for etching the protective metal layer located on the bottom surface of the recess formed in the polymer layer and the metal layer located under the protective metal layer is not particularly limited and may be appropriately selected according to the purpose. However, ion milling is preferred. When the protective metal layer and the metal layer are made of aluminum, an oxide film is formed on the aluminum surface. Therefore, in the chemical etching such as RIE, the dead time exists (see FIG. 6), but ion milling is physically performed. This is advantageous because the dead time does not occur and etching can be performed efficiently.

There is no restriction | limiting in particular as said ion milling, Although it can select suitably according to the objective, Ar ion milling is mentioned suitably.
In the ion milling, it is preferable to irradiate the ion beam from a direction inclined with respect to the vertical direction with respect to the substrate surface. In this case, the etching rate ratio (PMMA / Al) between the polymer layer (PMMA layer) and the metal layer (Al layer) can be reduced, and the etching rate of the polymer layer can be made relatively slow. Can do. As a result, a recess having a depth that can sufficiently function as the starting point for forming the nanohole can be formed in the metal layer while the polymer remains.

  In the starting point forming step, after the polymer layer is formed on the metal layer, an uneven pattern in the mold is imprinted on the polymer layer to form an uneven pattern, and the substrate surface and the polymer are formed. A protective metal layer is formed by applying a protective metal to the polymer layer from a direction inclined with respect to the vertical direction with respect to the layer surface, and the polymer layer is located on the bottom surface of the recess formed in the polymer layer. May be performed by etching the metal layer surface from which the polymer layer has been removed, and further removing the polymer layer together with the protective metal layer.

In this case, the protective metal in the starting point forming step is not particularly limited and may be appropriately selected depending on the intended purpose. Fe, Ni, Co, and the like are preferable. These may be used individually by 1 type and may use 2 or more types together.
Here, FIG. 8A shows etching rates of PMMA, Al, and Fe when etching is performed by chlorine-based RIE. Etching conditions are: chamber pressure = 0.2 Pa, Cl ₂ = 20 sccm, BCl ₂ = 20 sccm, Ar = 10 sccm, source power = 400 W, and BIAS power = 20 W.
FIG. 8B shows etching rates of PMMA, Al, and Fe when etching is performed by chlorine-based dry etching. Etching conditions are chamber pressure = 0.2 Pa, BCl ₃ = 40 sccm, Ar = 5 sccm, source power = 400 W, and BIAS power = 20 W.
8A and 8B show that Fe is not etched at all in chlorine-based RIE and chlorine-based dry etching. Therefore, it is possible to etch Al using Fe as the protective metal and using Fe as a mask. Similarly, magnetic materials such as Ni and Co can be used as well.

The method for applying the protective metal is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a highly anisotropic film forming method, such as sputtering, MBE (Molecular Beam Epitaxy). ), Vapor deposition and the like are preferable.
The direction in which the protective metal is applied, i.e., the angle at which the protective metal is inclined with respect to the vertical direction with respect to the substrate surface and the polymer layer surface (inclination angle) is not particularly limited. Although it can select suitably according to it, 10 degrees or more are preferable and 60 degrees or more are more preferable.
Specifically, for example, as shown in FIG. 9, after the formation of the PMMA layer as the polymer layer on the Al layer as the metal layer, the PMMA layer is provided with unevenness in the mold. The pattern is transferred by thermal imprinting to form an uneven pattern. Next, Fe as the protective metal is deposited on the PMMA layer by sputtering from the direction inclined with respect to the vertical direction with respect to the PMMA layer. At this time, due to the uneven shadowing effect, the Fe layer (the protective metal layer) is not formed on the bottom surface of the recess in the PMMA layer. Then, using the Fe layer as a mask (shadow mask), the PMMA layer located in the concave portion is removed by oxygen-based RIE, and the Al layer located under the PMMA layer is etched by chlorine-based RIE, and the PMMA layer together with the Fe layer is etched. When removed, a concavo-convex pattern as a starting point for forming nanoholes is formed on the surface of the Al layer.

A magnetic recording medium in which nanoholes are arranged one-dimensionally when an anodization process is performed after forming an uneven pattern (starting point for forming nanoholes) on the surface of an Al layer using a mold having a line and space pattern on the surface. It has been reported by the present inventors that a magnetic recording medium that can be suitably used for the above is obtained (see JP-A-2005-305634).
When forming the starting point for forming nanoholes using a mold having a line and space pattern formed in a disk shape, as shown in FIG. 14A, the line is formed as shown in FIG. 14A. Since the disk is disk-shaped, there is a portion where the incident direction of the protective metal particles (Fe as the protective metal) and the positional relationship between the lines are parallel. In this case, the protective metal Fe enters the bottom of the concave portion 260A in the concavo-convex pattern formed on the surface of the PMMA layer (polymer layer 260), and a protective metal layer (Fe layer) is formed. The starting point for forming nanoholes cannot be formed uniformly.

Therefore, when the line & space pattern is used as the starting point for forming the nanohole, it is preferable to form the protective metal layer (Fe layer) using a protective metal layer manufacturing apparatus shown in FIG. 14B, for example.
A protective metal layer manufacturing apparatus 400 shown in FIG. 14B is an ultra-high vacuum type vapor deposition apparatus, and is a vapor deposition source (k-cell, EB-vapor deposition source, etc.) disposed away from the base material (glass substrate) 200. ) 410, a cone 420 having a function of limiting the film formation range and increasing the parallelism of the vapor deposition particles (protective metal particles), and the substrate 200 can be tilted and rotated, and the substrate stage 430 can be rotated. And have. In order to keep the base material 200 at a low temperature, the substrate stage 430 preferably has a cooling mechanism.
When the protective metal layer (Fe) is vapor-deposited using such a protective metal layer manufacturing apparatus 400, the protective metal particles and the line direction are always obtained even if the uneven pattern in the mold is a line & space pattern. Since the protective metal layer can be formed while maintaining the positional relationship so as to be orthogonal, a starting point for forming nanoholes having a uniform line arrangement can be formed on a disk-shaped substrate.

The method for removing the polymer layer and the protective metal layer (residue of the protective metal layer) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, lift-off treatment using an organic solvent is performed. Preferably mentioned.
There is no restriction | limiting in particular as said organic solvent, According to the objective, it can select suitably, For example, acetone, resist stripping solution, xylene, methyl ethyl ketone, etc. are mentioned.

  Through the above steps, the uneven pattern in the mold is transferred to the smoothed metal layer to form an uneven pattern. The concavo-convex pattern functions as a starting point for forming nanoholes, and in the porous layer forming step described later, nanoholes are formed in the concave portions in the concavo-convex pattern, and a porous layer is formed in which the nanoholes are regularly arranged. The

<Porous layer forming step>
The porous layer forming step is a step of forming a porous layer in which a plurality of nanoholes are formed in a direction substantially orthogonal to the substrate by performing a nanohole forming process.

There is no restriction | limiting in particular as said nanohole formation process, Although it can select suitably according to the objective, It is preferable to anodize with respect to the said metal layer after the said origin formation process.
There is no restriction | limiting in particular as a voltage in the said anodizing process, According to the objective, it can select suitably.
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, as the type of the electrolytic solution, when the interval (pitch) between adjacent nanohole rows is 150 to 500 nm, a diluted phosphoric acid solution is preferably used, and when it is 80 to 200 nm, the diluted oxalic acid solution is used. Is preferable, and when it is 10 to 150 nm, a diluted sulfuric acid solution is preferably used. 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.

By the above process, a porous layer (nanohole structure) in which a plurality of nanoholes are formed in a direction substantially orthogonal to the substrate is formed.
According to the method for producing a nanohole structure of the present invention, it is possible to easily form a concavo-convex pattern with a narrow pitch (starting point for nanohole formation) by soft imprinting, and to easily form the nanohole structure of the present invention described later. It can be mass-produced efficiently.

(Nanohole structure)
The nanohole structure of the present invention is produced by the method for producing a nanohole structure of the present invention, and in particular, a nanohole array in which nanoholes are regularly arranged on a substrate is arranged at regular intervals. There is no restriction | limiting, According to the objective, the shape, a structure, a magnitude | size, etc. can be selected suitably.
In addition, about the said base material, it is as having explained in full detail in description of the manufacturing method of the said nanohole structure.

There is no restriction | limiting in particular as said shape, Although it can select suitably according to the objective, 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.
When the shape is a plate shape, a disk shape, or the like, the nanoholes (pores) are formed in a direction substantially orthogonal to the one exposed surface (plate surface). The nanohole may be formed as a hole penetrating the nanohole structure, or may be formed as a hole (dent) without penetrating the nanohole structure. For example, the nanohole structure Is used as the magnetic recording medium, the nanohole is preferably formed as a through hole penetrating the nanohole structure.

There is no restriction | limiting in particular as said structure, According to the objective, it can select suitably, A single layer structure may be sufficient and a laminated structure may be sufficient.
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. When the nanohole structure is applied to a DNA chip or the like, the size corresponding to the size of an existing DNA chip or the like is preferable. When applied to a catalyst substrate such as a nanotube, a size corresponding to the field emission device is preferable.

The arrangement of the nanohole array is not particularly limited and may be appropriately selected depending on the purpose. For example, the nanohole array may be arranged in parallel in one direction, or arranged in at least one of concentric and spiral shapes. You may do it. 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 interval between adjacent nanohole rows is not particularly limited and may be appropriately selected depending on the purpose. For example, when the nanohole structure is suitable for the magnetic recording medium such as a hard disk, the interval is 5 to 500 nm. Preferably, 10 to 200 nm is more preferable.
If the spacing is less than 5 nm, it is difficult to form nanoholes, and if it exceeds 500 nm, regular arrangement of nanoholes is difficult.

The ratio (interval / width) between the spacing between adjacent nanohole rows and the width of the nanohole rows is not particularly limited and may be appropriately selected depending on the intended purpose. For example, 1.1 to 1.9 Preferably, 1.2 to 1.8 is more preferable.
If the ratio (interval / width) is less than 1.1, adjacent nanoholes may be fused together, so that independent nanoholes may not be obtained. In addition, nanoholes may be formed in portions other than the concave line portion.

The width of the nanohole array is not particularly limited and may be appropriately selected depending on the purpose.For example, when the nanohole structure is suitable for the magnetic recording medium such as a hard disk, the width is preferably 5 to 450 nm. 8 to 200 nm is more preferable.
If the width of the nanohole array is less than 5 nm, it is difficult to form nanoholes, and if it exceeds 450 nm, regular arrangement of nanoholes is difficult.

The opening diameter in the nanohole is not particularly limited and may be appropriately selected depending on the intended purpose.For example, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, the ferromagnetic layer has a single magnetic domain. The specific size is preferably 200 nm or less, and more preferably 5 to 100 nm.
When the aperture diameter in the nanohole exceeds 200 nm, the magnetic recording medium to which the nanohole structure is applied may not have a single domain structure.

The aspect ratio (depth / opening diameter) between the depth and the opening diameter in the nanohole is not particularly limited and can be appropriately selected according to the purpose. It is preferable in that it can be increased and the holding power of the magnetic recording medium can be improved. For example, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, the number is preferably 2 or more, and 3 to 15 Is more preferable.
If the aspect ratio is less than 2, the holding power of the magnetic recording medium may not be sufficiently improved.

The thickness of the nanohole structure is not particularly limited and may be appropriately selected depending on the intended purpose. For example, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, the thickness is preferably 500 nm or less, and 300 nm. The following is more preferable, and 20 to 200 nm is particularly preferable.
When the thickness of the nanohole structure exceeds 500 nm, when the nanohole structure is applied to a magnetic recording medium such as a hard disk, high-density recording is performed even if the soft magnetic underlayer is provided on the magnetic recording medium. In some cases, it is necessary to polish the nanohole structure. In this case, time is required and the cost is high, which may cause quality degradation.

  The nanohole structure according to the present invention is suitable for various fields such as magnetic recording media, DNA chips, catalyst substrates, etc., and is used in hard disk devices widely used as computer external storage devices, consumer video recording devices, etc. It can be preferably used.

(Method of manufacturing magnetic recording medium)
The method for producing a magnetic recording medium of the present invention includes a smoothing treatment step, a starting point formation step, a nanohole structure formation step (porous layer formation step), and a magnetic material filling step, and further as necessary. The selected process includes other processes such as a soft magnetic underlayer forming process, an electrode layer forming process, a nonmagnetic layer forming process, a polishing process, and a protective layer forming process.

The smoothing treatment step is a step of smoothing the surface of the metal layer after forming the metal layer on the substrate, and is performed in the same manner as the smoothing treatment step in the method for producing a nanohole structure. preferable.
The starting point forming step is a step of forming a starting point for forming nanoholes in the smoothed metal layer, and is preferably performed in the same manner as the starting point forming step in the method for manufacturing a nanohole structure.
The details of the smoothing process and the starting point forming process are as described above.
The shape, structure, size, material and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. As the shape, the magnetic recording medium is a magnetic disk such as a hard disk. In some cases, it is disk-shaped, and the structure may be a single-layer structure or a laminated structure, and the material is the same as that of the substrate described above. Things.
The said board | substrate may be manufactured suitably and a commercial item may be used.

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

The electrode layer forming step is a step of forming an electrode layer between the nanohole structure and the soft magnetic underlayer.
The electrode layer can be formed according to a known method, but can be suitably performed by, for example, a sputtering method (sputtering) or a vapor deposition method. 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 forming at least one of a soft magnetic layer, a nonmagnetic layer, and a ferromagnetic layer by electrodeposition.

The nanohole structure forming step (porous layer forming step) includes a nanohole structure (on the soft magnetic underlayer when the soft magnetic underlayer is formed by the soft magnetic underlayer forming step) ( After forming a metal layer made of a metal material that forms a porous layer), nanohole formation processing (for example, anodic oxidation treatment is preferable) is performed on the metal layer, whereby nanoholes are formed in a direction substantially orthogonal to the substrate surface. Are formed to form a nanohole structure (porous layer).
The nanohole structure forming step can be performed in the same manner as the porous layer forming step in the nanohole structure manufacturing method.

  There is no restriction | limiting in particular as said nanohole formation process, Although it can select suitably according to the objective, For example, an anodizing process, an etching process, etc. are mentioned suitably. Among these, anodizing treatment is particularly preferable in that a large number of nanoholes can be formed in the metal layer in a direction substantially orthogonal to the substrate surface at substantially equal intervals.

  In the case of the anodic oxidation treatment, it can be carried out by electrolytic etching in an aqueous solution of sulfuric acid, phosphoric acid or oxalic acid, using the electrode in contact with the metal layer as an anode. Examples of the electrode include the soft magnetic underlayer and the electrode layer formed prior to forming the metal layer.

  In the present invention, as described above with respect to the method for manufacturing a nanohole structure, an uneven pattern for forming the nanohole array is formed in advance on the metal layer before the anodizing treatment. is required. In this case, the anodizing treatment is advantageous in that the nanoholes can be efficiently formed only in the recesses in the uneven pattern.

When the nanohole structure forming step (porous layer forming step) is performed by the anodic oxidation treatment, a number of nanoholes can be formed in the metal layer, but a barrier layer is formed below the nanoholes. However, the barrier layer can be easily removed by performing a known etching process using a known etching solution such as phosphoric acid.
As described above, a large number of the nanoholes exposing the soft magnetic underlayer or the substrate can be formed in the metal layer in a direction substantially perpendicular to the substrate surface.
By the nanohole structure forming step (porous layer forming step), the nanohole structure (porous layer) is formed on the substrate or the soft magnetic underlayer.

  The magnetic material filling step is a step of filling the nanohole formed in the nanohole structure (porous layer) with a magnetic material, and a step of forming a ferromagnetic layer that fills the nanohole with the ferromagnetic material. It may include at least a soft magnetic layer forming step for filling the nanoholes with the soft magnetic material.

The soft magnetic layer forming step is a step of forming a soft magnetic layer inside the nanohole.
The soft magnetic layer can be formed by depositing or filling a material of the soft magnetic layer, which will be described later, into the nanoholes by electrodeposition or the like.
The electrodeposition method, conditions, etc. are not particularly limited and may be appropriately selected according to the purpose. For example, the electrodeposition material includes the soft magnetic underlayer or the electrode layer as an electrode. Preferred examples include a method of depositing or depositing on the electrode by applying one or more kinds of solutions and applying a voltage.
By the soft magnetic layer forming step, the soft magnetic layer is formed inside the nanohole in the porous layer, on the substrate, on the soft magnetic underlayer, or on the electrode layer.

The ferromagnetic layer forming step is a step of forming a ferromagnetic layer on the soft magnetic layer (or on the nonmagnetic layer when the nonmagnetic layer is formed on the soft magnetic layer).
The ferromagnetic layer can be formed by depositing or filling a material of a ferromagnetic layer, which will be described later, on the soft magnetic layer formed inside the nanohole by electrodeposition or the like.
The electrodeposition method, conditions, and the like are not particularly limited and can be appropriately selected depending on the purpose. For example, the ferromagnetic layer can be formed using the soft magnetic underlayer or the electrode layer (seed layer) as an electrode. Preferred examples include a method of depositing or depositing in the nanohole by applying one or more kinds of solutions containing these materials and applying a voltage.
By the ferromagnetic layer forming step, the ferromagnetic layer is formed inside the nanohole in the porous layer and on the soft magnetic layer or the nonmagnetic layer.

The nonmagnetic layer forming step is a step of forming a nonmagnetic layer on the soft magnetic layer.
The nonmagnetic layer can be formed by depositing or filling a nonmagnetic layer material, which will be described later, on the soft magnetic layer formed inside the nanohole by electrodeposition or the like.
The electrodeposition method, conditions, and the like are not particularly limited and can be appropriately selected depending on the purpose. For example, the electrodeposition layer includes the soft magnetic underlayer or the electrode layer as an electrode, and includes the material of the nonmagnetic layer. A method of depositing or depositing in a nanohole by applying one or more kinds of solutions and applying a voltage is preferable.
By the nonmagnetic layer forming step, the nonmagnetic layer is formed inside the nanohole in the porous layer and on the soft magnetic layer or the like.

The polishing step is a step of polishing and planarizing the surface of the nanohole structure (porous layer). If the surface of the nanohole structure is removed with a certain thickness by the polishing step, higher density recording / high speed recording can be ensured, and if the surface of the magnetic recording medium is smoothed, perpendicular magnetic recording This is advantageous in that a magnetic head such as a head can be stably levitated, and both high density recording and reliability can be achieved by low levitating.
The polishing step is preferably performed after the magnetic layer forming step (including the ferromagnetic layer forming step and the soft magnetic layer forming step). If the polishing treatment is performed before the magnetic layer forming step, the nanohole structure may be destroyed, and the nanoholes may be filled with slurry, shavings, or the like, resulting in poor plating.

The polishing amount in the polishing step is preferably 15 nm or more, more preferably 40 nm or more in terms of the thickness from the outermost surface of the nanohole structure (porous layer).
When the polishing amount is 15 nm or more, the layer having surplus nanoholes (alumina pores) present in the vicinity of the surface of the nanohole structure and having a disorder in the arrangement interval of the alumina pores can be removed. Nanohole arrays in which nanoholes are regularly arranged can be formed on the surface of the nanohole structure at regular intervals.
There is no restriction | limiting in particular as the grinding | polishing method in the said grinding | polishing process, Although it can carry out according to a well-known method, CMP, ion milling etc. are mentioned suitably, for example.

  By the method for producing a magnetic recording medium of the present invention, the magnetic recording medium of the present invention described later can be produced efficiently and at low cost.

(Magnetic recording medium)
The magnetic recording medium of the present invention is manufactured by the method for manufacturing a magnetic recording medium of the present invention, and a nanohole structure (porous layer) in which a plurality of nanoholes are formed on a substrate in a direction substantially orthogonal to the substrate surface. And has a magnetic material inside the nanohole.

As said nanohole structure, the said nanohole structure of this invention is mentioned suitably, for example. The details of the nanohole structure are as described above.
There is no restriction | limiting in particular as thickness of the said porous layer, Although it can select suitably according to the objective, For example, 500 nm or less is preferable and 5-200 nm is more preferable.
When the thickness of the porous layer exceeds 500 nm, it may be difficult to fill the nanohole with the magnetic material.

  The nanohole in the porous layer (nanohole structure) may be formed as a through hole through the porous layer or may be formed as a hole without penetrating, but the nanohole is magnetic. In consideration of a case where a magnetic layer is formed by filling a material and a magnetic layer is further formed thereunder, the nanoholes are preferably formed as through holes.

The nanohole is preferably filled with a magnetic material to form a magnetic layer.
There is no restriction | limiting in particular as said magnetic layer, Although it can select suitably according to the objective, For example, a ferromagnetic layer, a soft magnetic layer, etc. are mentioned. In the present invention, it is sufficient that at least the ferromagnetic layer is formed inside the nanohole, and if necessary, the soft magnetic layer is formed between the substrate and the ferromagnetic layer. Further, a nonmagnetic layer (intermediate layer) may be formed between the ferromagnetic layer and the soft magnetic layer.

The ferromagnetic layer functions as a recording layer in the magnetic recording medium and constitutes a magnetic layer together with the soft magnetic layer.
The material of the ferromagnetic layer is not particularly limited and may 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 are preferred. These may be used individually by 1 type and may use 2 or more types together.
The ferromagnetic layer is not particularly limited as long as it is formed as a perpendicular magnetization film by the material, can be appropriately selected depending on the intended purpose, for example, a Ll ₀ ordered structure, wherein the C-axis substrate And those having an fcc structure or a bcc structure and having the C-axis aligned in the direction perpendicular to the substrate.

The thickness of the ferromagnetic layer is not particularly limited as long as the effect of the present invention is 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 soft magnetic layer and the soft magnetic underlayer For example, in the case where magnetic recording is performed at a linear recording density of 1,500 kBPI targeting 1 Tb / in ² , typically, about 5 to 100 nm is preferable, and 5 to 50 nm is more preferable. Is preferably 50 nm or less (about 20 nm).
Here, the thickness of the “ferromagnetic layer” is such that the ferromagnetic 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). (Non-structure) means the total thickness of each ferromagnetic layer. 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 soft magnetic underlayer” refers to a structure in which at least one of the soft magnetic layer and the soft magnetic under layer is laminated or divided into a plurality of layers (for example, non- In the case of having a structure which is divided by an intermediate layer such as a magnetic layer and is not a continuous layer, it means the total thickness of each soft magnetic layer and soft magnetic underlayer.

In the case of a magnetic recording medium having the ferromagnetic layer and the soft magnetic layer, the distance between the single pole head used for magnetic recording and the soft magnetic layer is shorter than the thickness of the porous layer, Since the thickness of the ferromagnetic layer can be made substantially equal, regardless of the thickness of the porous layer, only the thickness of the ferromagnetic layer can be used to concentrate the magnetic flux from the single pole head and to optimize the recording density used. It is possible to control various magnetic recording / reproducing characteristics. 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 ferromagnetic 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.

  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 NiFe, FeSiAl, FeC, FeCoB, FeCoNiB and CoZrNb, Etc. are preferable. 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 can be appropriately selected according to the depth of the nanoholes in the porous layer, the thickness of the ferromagnetic layer, and the like. Examples include (1) an aspect in which the thickness of the ferromagnetic layer exceeds the thickness, and (2) an aspect in which the sum of the thickness of the soft magnetic underlayer exceeds the thickness of the ferromagnetic layer.

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 ferromagnetic layer, and the perpendicular component of the magnetic field of the magnetic head can be increased. . Preferably, the soft magnetic layer can form a magnetic circuit of a recording magnetic field input from the magnetic head together with the magnetic head together with the soft magnetic 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, the concentration of magnetic flux from the perpendicular magnetic recording head, the optimum magnetic recording / reproducing characteristics at the recording density to be used, and the like can be controlled. 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, it can be performed by electrodeposition (electrodeposition method) or the like.

The nanohole in the porous layer may have a nonmagnetic layer (intermediate layer) between the ferromagnetic layer and the soft magnetic layer. If the non-magnetic layer (intermediate layer) is present, the effect of the exchange coupling force between the ferromagnetic 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. At least one of them. 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.

In the magnetic recording medium of the present invention, a soft magnetic underlayer may be provided between the substrate and the porous layer.
There is no restriction | limiting in particular as a material of the said soft-magnetic underlayer, Although it can select suitably from well-known things, For example, what was mentioned above as a material of the said soft-magnetic layer is mentioned suitably. These materials may be used individually by 1 type, may use 2 or more types together, and may mutually be the same as the material of the said soft-magnetic layer, and may differ.

The soft magnetic underlayer preferably has an easy axis of magnetization in the in-plane direction of the substrate surface. In this case, a magnetic circuit in which the magnetic flux from the magnetic head used for magnetic recording is effectively closed can be formed, and the vertical component of the magnetic field of the magnetic head can be increased. The soft magnetic underlayer is also effective in single domain recording with a bit size (opening diameter of the nanohole) of 100 nm or less.
The formation of the soft magnetic underlayer is not particularly limited and can be performed according to a known method. For example, it can be performed by electrodeposition (electrodeposition method), electroless plating, or the like.

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

The electrode layer is a layer that functions as an electrode when the magnetic layer (the ferromagnetic layer and the soft magnetic layer) is formed by electrodeposition or the like, and is generally on the substrate and below the ferromagnetic layer. Provided. When the magnetic layer is formed by electrodeposition, the electrode layer may be used as an electrode, but the soft magnetic underlayer or the like may be used as an electrode.
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 further contain W, Nb, Ti, Ta, Si, O, etc. in addition to these materials.

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.

The protective layer is a layer having a function of protecting the ferromagnetic layer, and is provided on the surface or above the ferromagnetic 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.

The magnetic recording medium of the present invention can be used for various types of magnetic recording using a magnetic head, but can be suitably used for magnetic recording using a single pole head. It can be particularly suitably used for the recording method.
The magnetic recording medium of the present invention 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, uniform characteristics, and high quality. For this reason, the magnetic recording medium can be designed and used as various magnetic recording media. For example, the magnetic recording medium is designed for a hard disk device widely used as an external storage device of a computer, a consumer video recording device, or the like. It can be used, and can be particularly suitably designed and used for a magnetic disk such as a hard disk.

(Magnetic recording apparatus and magnetic recording method)
The magnetic recording apparatus of the present invention comprises the magnetic recording medium of the present invention and a perpendicular magnetic recording head, and further comprises other means or members appropriately selected as necessary.
The magnetic recording method of the present invention includes recording on the magnetic recording medium of the present invention using a perpendicular magnetic recording head, and further includes other processes or steps appropriately selected as necessary. The magnetic recording method of the present invention can be preferably carried out using the magnetic recording apparatus of the present invention. The other processes or steps can be performed by the other means or members. Hereinafter, the magnetic recording method of the present invention will be described together with the description of the magnetic recording apparatus of the present invention.

  The perpendicular magnetic recording head is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a single magnetic pole head or the like is preferable. The perpendicular magnetic recording head may be dedicated for writing, or may be for writing and reading integrated with a reading head such as a GMR head.

In the magnetic recording by the magnetic recording apparatus of the present invention or the magnetic recording by the magnetic recording method of the present invention, since the magnetic recording medium of the present invention is used, when the ferromagnetic layer and the soft magnetic layer are provided, Since the distance between the perpendicular magnetic recording head and the soft magnetic layer in the magnetic recording medium is shorter than the thickness of the porous layer and substantially equal to the thickness of the ferromagnetic layer, the thickness of the porous layer Regardless of the thickness of the ferromagnetic layer, 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. For this reason, as shown in FIG. 3, the magnetic flux from the perpendicular magnetic recording head (write / read head) 100 is concentrated on the ferromagnetic layer (perpendicular magnetization film) 30. In comparison, the write efficiency is greatly improved, the write current is reduced, and the overwrite characteristic is remarkably improved.
It is preferable that the soft magnetic underlayer is formed on the magnetic recording medium because a magnetic circuit is formed between the perpendicular magnetic recording head and the soft magnetic underlayer. This is advantageous in that high density recording is possible.

In the magnetic recording by the magnetic recording apparatus of the present invention or the magnetic recording by the magnetic recording method of the present invention, the magnetic flux from the perpendicular magnetic recording head is applied to the ferromagnetic layer of the magnetic recording medium by the lower surface of the ferromagnetic layer. That is, even in the vicinity of the interface with the soft magnetic layer or the non-magnetic layer, it does not diffuse while being concentrated, so that a small bit can be written.
The degree of convergence (degree of diffusion) of the magnetic flux in the ferromagnetic layer is not particularly limited as long as the effect of the present invention is not impaired, and can be appropriately selected according to the purpose.

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

Example 1
-Production of nanohole structures and production of magnetic recording media-
As shown in FIG. 10A, an adhesion layer 210 is formed by depositing Ta with a thickness of 20 nm on a glass substrate 200 for hard disk (1 inch in diameter) using a sputtering method, and then an electrode during anodization. As the layer and soft magnetic layer, permalloy is formed to a thickness of 100 nm to form a permalloy layer 220, and Ta is formed to a thickness of 5 nm on the permalloy layer 220 to form an oxidation stop layer 230. An aluminum layer 240 was formed by depositing Al with a thickness of 200 nm.
Next, as shown in FIG. 10B, the surface of the aluminum layer 240 was polished by about 50 nm by CMP using an alumina-based slurry, and the surface of the aluminum layer 240 was smoothed. The above is the smoothing process. An AFM image of the surface of the aluminum layer 240 after the smoothing treatment step is shown in FIG. 16A, and a cross-sectional height shape is shown in FIG. 16B. From FIG. 16A and FIG. 16B, the unevenness | corrugation of the surface resulting from a grain growth was removed, and the largest unevenness | corrugation was also 3 nm or less.

Next, as shown in FIG. 10C, a protective metal layer 250 is formed on the surface of the smoothed aluminum layer 240 by sputtering to form a protective metal layer 250 so as to have a film thickness of 15 nm, as shown in FIG. 10D. As described above, PMMA having a concentration of 5 mass% was applied on the protective metal layer 250 by spin coating at 1,200 rpm, and the polymer layer 260 was formed by forming a film having a thickness of 100 nm. PMMA has a glass softening point of 112 ° C. and is a polymer that softens at a low temperature.
Next, as shown in FIG. 10E, using a thermal imprint apparatus, an uneven pattern in which the uneven pitch is 100 nm, the height of the protrusion is 100 nm, the diameter of the protrusion is 50 nm, and the protrusions are arranged in a triangular lattice pattern An imprint process was performed for 1 minute at a substrate temperature of 120 ° C. and a pressure of 50 kg / cm ² using a Ni mold 300 on the surface.
Next, as shown in FIG. 10F, in the concavo-convex pattern transferred to the polymer layer 260, in order to remove the residue existing at the bottom of the concave portion 260A, an ashing device is used to perform oxygen plasma under conditions of 200 Pa and 20 W. For 1 minute. As shown in FIG. 10G, the glass substrate 200 is introduced into the ICP-RIE chamber, and the chamber pressure = 1.5 Pa, CF ₄ = 20 sccm, Ar = 20 sccm, source power = 200 W, BIAS power = 20 W for 15 seconds. After etching the protective metal layer 250, as shown in FIG. 10H, using the protective metal layer 250 as a mask, chamber pressure = 0.2 Pa, NH ₃ = 70 sccm, CO = 30 sccm, source power = 700 W, BIAS power = The aluminum layer 240 was etched for 12 seconds under the condition of 200W. Here, overetching of 60% and 50% was performed on the protective metal layer 250 and the aluminum layer 240 corresponding to 10 nm, respectively.
Furthermore, as shown in FIG. 10I, the remaining protective metal is obtained by performing etching for 10 seconds under the conditions of chamber pressure = 1.5 Pa, CF ₄ = 20 sccm, Ar = 20 sccm, source power = 200 W, BIAS power = 20 W. Layer 250 was removed. As a result, a concavo-convex pattern P as a starting point for forming nanoholes was formed on the surface of the aluminum layer 240. The above is the starting point forming step.
FIG. 11A shows an AFM image of the surface of the aluminum layer 240 after the starting point forming step, and FIG. 11B shows a graph showing the cross-sectional height shape of the surface. From FIG. 11A, it was confirmed that the uneven | corrugated pattern (starting point for nanohole formation) in which the recessed part was arranged in the triangular lattice form was formed in the surface of the aluminum layer 240. FIG.

  Next, as shown in FIG. 10J, anodization of the aluminum layer 240 was performed at a voltage of 40 V using a 0.3 M / l oxalic acid bath. As a result, a porous layer 270 in which a plurality of alumina nanoholes 270A were formed in a direction substantially orthogonal to the glass substrate 200 was formed. The above is the porous layer forming step (the nanohole structure forming step). Thus, a nanohole structure was produced. FIG. 11C shows an SEM photograph of the surface of the porous layer 270 in the nanohole structure of Example 1, and FIG. 11D shows the porosity when the porous layer forming step is performed without performing the starting point forming step. The SEM photograph of the surface of a layer is shown. From FIG. 11C, when the starting point forming step is performed, alumina nanoholes are regularly arranged, and compared with the case where the starting point forming step shown in FIG. It turns out that the regularity is improving.

  Next, as shown in FIG. 10K, in the alumina nanohole 270A, using a Co plating bath containing 50 g of cobalt sulfate (Co) and an aqueous solution of boric acid 20 g / l, an alternating current of 50 Hz, 12 VAC, Cobalt (Co) 280 as the ferromagnetic material was filled by low voltage AC plating, and a ferromagnetic layer was formed in the alumina nanohole 270A. At this time, the inside of the alumina nanohole 270A was plated with cobalt (Co) 280, and cobalt (Co) 280 overflowed from the surface of the alumina nanohole 270A. The above is the magnetic material filling step.

  Next, as shown in FIG. 10L, the surface of the porous layer 270 was polished to remove cobalt (Co) 280 overflowing from the surface of the alumina nanohole 270A. The above is the polishing step. Furthermore, as shown in FIG. 10M, a carbon protective film 290 having a thickness of 1 nm was formed by sputtering, and then a fluorine-based lubricant was applied. The above is the protective layer forming step. Thus, a magnetic disk was manufactured.

(Example 2)
-Production of nanohole structures and production of magnetic recording media-
In Example 1, a nanohole structure was produced and a magnetic recording medium was produced in the same manner as in Example 1 except that the starting point forming step was performed by the following method.

  Similarly to Example 1, as shown in FIG. 10A, an adhesion layer 210, a permalloy layer 220, an oxidation stop layer 230, and an aluminum layer 240 are formed on a glass substrate 200 for a hard disk (1 inch in diameter). After forming in this order from the side, the surface of the aluminum layer 240 was smoothed as shown in FIG. 10B. The above is the smoothing process.

Next, as shown in FIG. 12A, PMMA having a concentration of 5% by mass is applied onto the smoothed aluminum layer 240 at 1,200 rpm by a spin coating method to form a film having a thickness of 100 nm. Layer 260 was formed.
Next, as shown in FIG. 12B, using a thermal imprint apparatus, an uneven pattern in which the uneven pitch is 100 nm, the height of the protrusions is 100 nm, the diameter of the protrusions is 50 nm, and the protrusions are arranged in a triangular lattice pattern. An imprint process was performed for 1 minute at a substrate temperature of 120 ° C. and a pressure of 50 kg / cm ² using a Ni mold 300 on the surface. A partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240 after the imprint process is shown in FIG. 12C.
Next, the glass substrate 200 is introduced into the ICP-RIE chamber, and the oxygen system is used for 10 seconds under the conditions of chamber pressure = 1.5 Pa, O ₂ = 5 sccm, N ₂ = 95 sccm, source power = 400 W, BIAS power = 40 W. Residual etching of the polymer layer 260 existing at the bottom of the concave portion 260A in the concave / convex pattern transferred to the polymer layer 260 was performed by RIE. Here, FIG. 17A shows a partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240.
Next, as shown in FIG. 17B, Al was used as the protective metal, and a protective metal layer (Al film) 330 was formed. In addition, the thickness of the protective metal layer 330 located in the recessed part 260A formed in the polymer layer 260 was 7 nm.

Next, as shown in FIG. 17C, the glass substrate 200 is introduced into an Ar ion milling chamber, and the chamber pressure = 4 × 10 ⁻⁴ Torr and the applied voltage of 700 V are applied for 150 seconds with respect to the vertical direction of the substrate 200. The protective metal layer (Al film) 330 located in the recess 260A formed in the polymer layer 260 and the metal layer (aluminum layer) 240 located therebelow were etched by Ar ion milling at a 45 ° angle. .

Here, as a sample, a PMMA layer and an Al layer were prepared, Ar ion milling was performed at angles of 0 ° and 45 ° with respect to the vertical direction of each layer, and the milling amount and etching time of PMMA and Al were determined. It was measured. The results are shown in Table 1 and FIG. 18A.
From FIG. 18A, it was found that according to Ar ion milling, the amount of milling is almost proportional to time, and there is no dead time generated during etching by RIE, so that etching can be performed efficiently. . In addition, it was found that when the ion beam is irradiated with an inclination with respect to the vertical direction of each layer (at an angle of 45 °), the amount of milling increases as compared with the case where the ion beam is not inclined (when the angle is 0 °). .

Further, Ar ion milling was performed at angles of 0 ° and 45 ° with respect to the vertical directions of the PMMA layer and the Al layer, the etching rates of PMMA and Al were measured, and the etching rate ratio was calculated. The results are shown in Table 2 and FIG. 18B.
From FIG. 18B, when the ion beam is irradiated with an inclination (at an angle of 45 °) with respect to the vertical direction of each of the PMMA layer and the Al layer, both of the etching rates are compared with the case where the ion beam is not inclined (when the angle is 0 °). However, from Table 2, the PMMA / Al etching rate ratio (PMMA / Al) is reduced from about 2.4 times to about 1.6 times, and the etching rate of PMMA is relatively slow. I understood. For this reason, according to Ar ion milling, a recess having a depth that can sufficiently function as a starting point for forming nanoholes can be formed in the aluminum layer 240 while the polymer layer 260 remains.

  Furthermore, the remaining polymer layer 260 was removed together with the residue of the protective metal layer 330 by a lift-off process using acetone ultrasonic waves. As a result, as shown in FIG. 12K, a concavo-convex pattern P as a starting point for forming nanoholes was formed on the surface of the aluminum layer 240. The above is the starting point forming step.

  Thereafter, in the same manner as in Example 1, the porous layer forming step was performed by anodizing treatment to produce a nanohole structure. In FIG. 19, the SEM photograph of the surface of the porous layer in the nanohole structure of Example 2 is shown. From FIG. 19, it was found that when the starting point forming step was performed, alumina nanoholes were completely regularly arranged.

  Further, in the same manner as in Example 1, the magnetic recording medium was manufactured by performing the magnetic material filling step, the polishing step, and the protective layer forming step.

(Example 3)
-Production of nanohole structures and production of magnetic recording media-
In Example 1, a nanohole structure was produced and a magnetic recording medium was produced in the same manner as in Example 1 except that the starting point forming step was performed by the following method.

  Similarly to Example 1, as shown in FIG. 10A, an adhesion layer 210, a permalloy layer 220, an oxidation stop layer 230, and an aluminum layer 240 are formed on a glass substrate 200 for a hard disk (1 inch in diameter). After forming in this order from the side, the surface of the aluminum layer 240 was smoothed as shown in FIG. 10B. The above is the smoothing process.

Next, as shown in FIG. 12A, PMMA having a concentration of 5% by mass is applied onto the smoothed aluminum layer 240 at 1,200 rpm by a spin coating method to form a film having a thickness of 100 nm. Layer 260 was formed.
Next, as shown in FIG. 12B, using a thermal imprint apparatus, an uneven pattern in which the uneven pitch is 100 nm, the height of the protrusions is 100 nm, the diameter of the protrusions is 50 nm, and the protrusions are arranged in a triangular lattice pattern. An imprint process was performed for 1 minute at a substrate temperature of 120 ° C. and a pressure of 50 kg / cm ² using a Ni mold 300 on the surface. A partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240 after the imprint process is shown in FIG. 12C.
Next, as shown in FIG. 12D, a glass substrate 200 is installed obliquely in the sputtering apparatus, Fe is used as the protective metal, and a film is formed from an oblique direction of 30 °, and a protective metal layer equivalent to a film thickness of 3 nm ( Fe film) 310 was formed. Here, a partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240 is shown in FIG. 12E. As shown in FIG. 12E, the glass substrate 200 is tilted by 30 ° so that Fe is applied from the direction tilted with respect to the vertical direction with respect to the surface of the polymer layer 260. A protective substrate layer 310 was formed by disposing a dummy substrate 320 for blocking the above.
FIGS. 13A and 13B show SEM photographs of the surface of the polymer layer 260 when protective metal layers (Fe films) 310 corresponding to 10 nm and 3 nm are formed, respectively. From FIG. 13B, a concave / convex pattern in which concave portions 260A are arranged in a triangular lattice pattern is clearly seen on the surface of the polymer layer 260 when the protective metal layer 310 is formed to have a thickness equivalent to 3 nm. The surface of the polymer layer 260 when 310 was formed corresponding to 10 nm was covered with Fe, and the uneven pattern could not be confirmed.

Next, as shown in FIG. 12F, the glass substrate 200 is introduced into the ICP-RIE chamber, and the chamber pressure = 0.2 Pa, O ₂ = 5 sccm, N ₂ = 45 sccm, source power = 400 W, BIAS power = 20 W. Then, residual etching of the polymer layer 260 was performed by oxygen-based RIE for 90 seconds. Here, a partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240 is shown in FIG. 12G. As shown in FIG. 12G, when etching was performed by oxygen-based RIE, the aluminum layer 240 and the protective metal layer 310 were not affected at all even when the polymer layer 260 was over-etched by 100% or more.
Further, as shown in FIG. 12H, chlorine-based RIE is performed for 90 seconds under conditions of chamber pressure = 0.2 Pa, Cl ₂ = 20 sccm, BCl ₂ = 20 sccm, Ar = 10 sccm, source power = 400 W, BIAS power = 20 W. The aluminum layer 240 was etched. Here, a partially enlarged view of the surface of the polymer layer 260 formed on the aluminum layer 240 is shown in FIG. As shown in FIG. 12I, when etching was performed by chlorine-based RIE, the protective metal layer 310 was not affected at all even if the aluminum layer 240 was over-etched by 100% or more.
Furthermore, as shown in FIG. 12J, the polymer layer 260 was removed together with the protective metal layer 310 by a lift-off process using acetone ultrasonic waves. As a result, as shown in FIG. 12K, a concavo-convex pattern P as a starting point for forming nanoholes was formed on the surface of the aluminum layer 240. The above is the starting point forming step.
FIG. 13C shows an AFM image of the surface of the aluminum layer 240 after the starting point forming step, and FIG. 13D shows a graph showing the cross-sectional height shape of the surface. From FIG. 13C, it is confirmed that a concave / convex pattern (starting point for nanohole formation) in which concave portions are arranged in a triangular lattice pattern is formed on the surface of the aluminum layer 240, and etching is performed by a very thin protective metal layer 310 having a thickness of 3 nm. It has been found that a non-resistant polymer (PMMA) layer 260 can be protected.

  Thereafter, in the same manner as in Example 1, the porous layer forming step was performed by anodizing treatment to produce a nanohole structure. FIG. 13E shows an SEM photograph of the surface of the porous layer in the nanohole structure of Example 3, and FIG. 13F shows the porous layer when the porous layer forming step is performed without performing the starting point forming step. The SEM photograph of the surface of is shown. From FIG. 13E, when the starting point forming step is performed, alumina nanoholes are regularly arranged, and compared with the case where the starting point forming step shown in FIG. It turns out that the regularity is improving.

  Further, in the same manner as in Example 1, the magnetic recording medium was manufactured by performing the magnetic material filling step, the polishing step, and the protective layer forming step.

The magnetic recording disk (the magnetic recording medium) obtained in Example 1, Example 2 and Example 3 was provided with a single pole head as a magnetic head for writing and a GMR head as a magnetic head for reading. Using a recording apparatus, writing by the single magnetic pole head and magnetic recording by reading from the GMR head were performed, and the recording / reproducing characteristics were evaluated.
First, the magnetic recording disk was magnetized by a permanent magnet in one direction perpendicular to the substrate surface, and then the magnetic disk sample was rotated to float the magnetic head, and magnetic signals were recorded and reproduced. As a result, a regular signal corresponding to the array of nanoholes arranged circumferentially was observed.

Example 4
-Fabrication of nanohole structures-
In Example 3, a nanohole structure was produced in the same manner as in Example 3 except that the uneven pattern on the surface of the mold 300 was changed from a dot pattern to a line & space pattern.
In addition, when a concavo-convex pattern (starting point for forming nanoholes) is formed on the surface of the aluminum layer using a mold having a line and space pattern on the surface, anodization is performed, and then magnetic recording in which alumina nanoholes are arranged one-dimensionally. It has been reported by the present inventors that a magnetic recording medium that can be suitably used as a medium is obtained (see Japanese Patent Application Laid-Open No. 2005-305634).

  When forming the starting point for forming nanoholes using a mold having a line and space pattern, the line is disk-shaped as shown in FIG. A region where the positional relationship between the incident direction of the particle and the line is parallel is generated. In this case, the protective metal enters the bottom of the concave portion 260A in the concave / convex pattern formed on the surface of the polymer layer 260, and the protective metal layer is formed, so that the starting points for forming nanoholes are uniformly formed on the entire surface of the disk. I can't.

Therefore, in the starting point formation step in Example 4, the protective metal layer was formed using the protective metal layer manufacturing apparatus shown in FIG. 14B.
A protective metal layer manufacturing apparatus 400 shown in FIG. 14B is an ultra-high vacuum type deposition apparatus, and a deposition source (k-cell, EB-deposition source, etc.) 410 disposed away from the glass substrate 200, The cone 420 has a function of limiting the film range and increasing the parallelism of the vapor deposition particles (protective metal particles), and the substrate stage 430 capable of tilting and rotating the glass substrate 200. In order to keep the glass substrate 200 at a low temperature, the substrate stage 430 preferably has a cooling mechanism.
When the protective metal layer (Fe) is vapor-deposited using such a protective metal layer manufacturing apparatus 400, the protective metal particles and the line direction are always obtained even if the uneven pattern in the mold is a line & space pattern. Since the protective metal layer can be formed while maintaining the positional relationship so as to be orthogonal, a starting point for forming nanoholes having a uniform line arrangement can be formed on a disk-shaped substrate.

FIG. 15 shows an example of the arrangement of nanoholes in the nanohole structure of the present invention produced by performing the starting point formation process and the nanohole structure produced by the conventional process.
As shown in FIG. 15, it was found that the nanoholes in the nanohole structure of the present invention are regularly arranged one-dimensionally. On the other hand, a conventional nanohole structure in which a mold surface shape (pattern) is transferred to a polymer layer by a conventional soft imprint method, an aluminum layer is etched using the polymer layer as a mask, and nanoholes are formed by anodization Then, it was found that even when the pattern was transferred to the surface of the polymer layer, the surface of the aluminum layer was not etched at all, so that the nanohole arrangement was random.

The preferred embodiments of the present invention are as follows.
(Additional remark 1) After forming a metal layer on a base material, the smoothing process process which smoothes the surface of this metal layer, and the starting point formation process which forms the starting point for nanohole formation in the said smoothed metal layer And a porous layer forming step of forming a porous layer in which a plurality of nanoholes are formed in a direction substantially perpendicular to the base material by performing a nanohole forming process, Method.
(Additional remark 2) The manufacturing method of the nanohole structure of Additional remark 1 whose metal layer consists of aluminum.
(Additional remark 3) The manufacturing method of the nanohole structure in any one of Additional remark 1 to 2 with which a smoothing process process is performed by CMP (chemical mechanical polishing) process.
(Additional remark 4) The manufacturing method of the nanohole structure in any one of Additional remark 1 to 3 whose unevenness | corrugation of the metal layer surface after a smoothing process process is 3 nm or less.
(Supplementary Note 5) From Supplementary Note 1, the starting point formation step includes imprint transfer of the concave / convex pattern of the mold having a convex / concave pattern corresponding to the array pattern of nanoholes to be formed onto a polymer layer formed on the metal layer. 5. The method for producing a nanohole structure according to any one of 4 above.
(Additional remark 6) The manufacturing method of the nanohole structure of Additional remark 5 with which the uneven | corrugated pattern in a mold arrange | positions circular convex part at a regular interval in the shape of a triangular lattice.
(Supplementary Note 7) After the starting point forming step forms the protective metal layer and the polymer layer on the metal layer in this order from the metal layer, the uneven pattern in the mold is imprinted and transferred to the polymer layer. The method for producing a nanohole structure according to any one of appendices 5 to 6, wherein the metal layer is etched using the remaining protective metal layer as a mask after the protective metal layer is etched using a pattern.
(Supplementary Note 8) The metal layer is an aluminum layer, the protective metal layer is either a Ta layer or a Ti layer, and the protective metal layer is etched by CF-based RIE, and the metal layer is etched by CO- The method for producing a nanohole structure according to appendix 7, which is performed by ammonia-based RIE.
(Supplementary Note 9) After the starting point forming step forms a polymer layer on the metal layer, a concave / convex pattern in the mold is imprinted on the polymer layer to form a concave / convex pattern, and the concave portion formed on the surface of the polymer layer After removing the polymer layer located on the bottom surface of the substrate by etching, a protective metal layer is formed by applying a protective metal to the metal layer and the polymer layer exposed in the recess, and the polymer layer The protective metal layer located in the recess formed in the substrate and the surface of the metal layer located under the protective metal layer are etched, and the polymer layer and the residue of the protective metal layer remaining are removed. The manufacturing method of the nanohole structure in any one.
(Supplementary note 10) The method for producing a nanohole structure according to supplementary note 9, wherein the protective metal is aluminum.
(Supplementary note 11) The method for producing a nanohole structure according to any one of supplementary notes 9 to 10, wherein the protective metal is applied by any one of sputtering, MBE, and EB vapor deposition.
(Supplementary note 12) The metal layer is an aluminum layer, and the etching of the polymer layer located on the bottom surface of the recess formed on the surface of the polymer layer is performed by oxygen-based RIE, and the etching of the surface of the metal layer is performed by ion milling. The method for producing a nanohole structure according to any one of appendices 9 to 11, which is performed.
(Additional remark 13) After an origin formation process forms a polymer layer on a metal layer, the uneven | corrugated pattern in a mold is imprint-transferred to this polymer layer, an uneven | corrugated pattern is formed, and with respect to the base-material surface and the said polymer layer surface A protective metal layer is formed by applying a protective metal to the polymer layer from a direction inclined with respect to the vertical direction, and the polymer layer located on the bottom surface of the recess formed on the surface of the polymer layer The method for producing a nanohole structure according to any one of appendices 5 to 6, wherein after removing by etching, the surface of the metal layer from which the polymer layer has been removed is etched, and the polymer layer is removed together with the protective metal layer.
(Supplementary note 14) The method for producing a nanohole structure according to supplementary note 13, wherein the protective metal is at least one selected from Fe, Ni, and Co.
(Supplementary note 15) The method for producing a nanohole structure according to any one of supplementary notes 13 to 14, wherein the protective metal is applied by any one of sputtering, MBE, and EB deposition.
(Supplementary note 16) The nanohole structure according to any one of supplementary notes 13 to 15, wherein the metal layer is an aluminum layer, the polymer layer is etched by oxygen-based RIE, and the metal layer surface is etched by chlorine-based RIE. Body manufacturing method.
(Supplementary note 17) The method for producing a nanohole structure according to any one of supplementary notes 13 to 16, wherein the polymer layer and the protective metal layer are removed by lift-off treatment using an organic solvent.
(Supplementary note 18) A nanohole structure manufactured by the method for producing a nanohole structure according to any one of supplementary notes 1 to 17, wherein a nanohole array in which nanoholes are regularly arranged is arranged on a substrate at regular intervals. Nanohole structure.
(Additional remark 19) After forming a metal layer on a board | substrate, the smoothing process process which smoothes the surface of this metal layer, The starting point formation process which forms the starting point for nanohole formation in the said smoothed metal layer, A nanohole structure forming step of forming a nanohole structure by forming a plurality of nanoholes in a direction substantially orthogonal to the substrate surface by performing a nanohole formation process, and a magnetic material that fills the inside of the nanohole with a magnetic material A method of manufacturing a magnetic recording medium, comprising: a filling step.
(Supplementary note 20) Manufactured by the method for producing a magnetic recording medium according to supplementary note 19,
A magnetic recording medium comprising a nanohole structure in which a plurality of nanoholes are formed in a direction substantially perpendicular to the substrate surface on a substrate, and having a magnetic material inside the nanoholes.

The method for producing a nanohole structure of the present invention can be suitably used for producing the nanohole structure of the present invention.
The nanohole structure of the present invention can be suitably used in various fields such as a magnetic recording medium, a DNA chip, a diagnostic device, a detection sensor, a catalyst substrate, a field emission display, and in particular, an external storage device of a computer, It can be suitably used for a hard disk device or the like widely used as a consumer video recording device or the like.
The method for producing a magnetic recording medium of the present invention can be suitably used for producing the magnetic recording medium of the present invention.
The magnetic recording medium of the present invention can be suitably used for hard disk drives and the like that are widely used as external storage devices for computers, consumer video recording devices, and the like.
The magnetic recording device of the present invention can be suitably used as a hard disk device or the like widely used as an external storage device of a computer, a consumer video recording device or the like.
The magnetic recording method of the present invention 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. Therefore, it can be suitably used for extremely high quality recording.

FIG. 1 is a schematic explanatory view showing an example of a magnetic recording medium obtained by filling a pore of an anodized alumina pore with a magnetic metal and combining a patterned medium and a perpendicular recording system. FIG. 2A is a schematic explanatory view showing an example of a magnetic recording medium formed by filling a two-dimensionally arrayed anodized alumina pore with a magnetic metal. 2B is a cross-sectional view taken along the line B-B ′ of FIG. 2A. FIG. 3 is a conceptual diagram for explaining an example of a state in which the magnetic flux is concentrated without being diffused during the magnetic recording by the perpendicular recording method. FIG. 4 is a partial cross-sectional schematic explanatory view showing an example of a state in which magnetic recording is performed on a magnetic recording medium by a perpendicular magnetic recording method using a single magnetic pole head. FIG. 5A is an AFM image showing an example of the surface of an aluminum layer formed by a sputtering method. FIG. 5B is a graph showing an example of the cross-sectional height distribution of the surface of the aluminum layer formed by sputtering. FIG. 6 is a graph showing an example of etching rates of PMMA and Al when etching is performed by chlorine-based RIE. FIG. 7A is a graph showing an example of etching rates of Ta and Al when etching is performed by CF-based RIE. FIG. 7B is a graph showing an example of etching rates of PMMA, Ta, and Al when etching is performed by CO-ammonia RIE. FIG. 8A is a graph showing an example of etching rates of PMMA, Al, and Fe when etching is performed by chlorine-based RIE. FIG. 8B is a graph showing an example of etching rates of PMMA, Al, and Fe when etching is performed by chlorine-based dry etching. FIG. 9 is a schematic explanatory view showing an example of a method for forming a protective metal layer on the surface of the PMMA layer. FIG. 10A is a process diagram (No. 1) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10B is a process diagram (part 2) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10C is a process diagram (part 3) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10D is a process diagram (No. 4) for explaining a process of the method of producing the nanohole structure of the invention and the magnetic recording medium of the invention. FIG. 10E is a process diagram (part 5) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10F is a process diagram (No. 6) for explaining a process of the method of producing the nanohole structure of the invention and the magnetic recording medium of the invention. FIG. 10G is a process diagram (No. 7) for explaining a process of the method of producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10H is a process diagram (part 8) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10I is a process diagram (part 9) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10J is a process diagram (part 10) for explaining a process of the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 10K is a process diagram (part 11) for explaining a process of the method of manufacturing the magnetic recording medium according to the present invention. FIG. 10L is a process diagram (part 12) for describing a process of the method of manufacturing the magnetic recording medium according to the present invention. FIG. 10M is a process diagram (part 13) for describing a process of the method of manufacturing the magnetic recording medium according to the present invention. FIG. 11A is an AFM image showing an example of the surface of the aluminum layer after the starting point formation step. FIG. 11B is a graph showing an example of the cross-sectional height shape of the surface of the aluminum layer after the starting point forming step. FIG. 11C is an SEM photograph showing the surface of the porous layer in the nanohole structure of Example 1. FIG. 11D is an SEM photograph showing the surface of the porous layer formed without performing the starting point forming step. FIG. 12A is a process diagram (part 1) for explaining an example of a starting point formation process in the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12B is a process diagram (part 2) for explaining an example of the starting point formation process in the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12C is a partially enlarged view of the surface of the polymer layer formed on the aluminum layer shown in FIG. 12B. FIG. 12D is a process diagram (part 3) for explaining an example of the starting point formation process in the method of manufacturing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12E is a partially enlarged view of the surface of the polymer layer formed on the aluminum layer shown in FIG. 12D. FIG. 12F is a process diagram (part 4) for explaining an example of the starting point formation process in the method for manufacturing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12G is a partially enlarged view of the surface of the polymer layer formed on the aluminum layer shown in FIG. 12F. FIG. 12H is a process diagram (part 5) for explaining an example of the starting point formation process in the method of manufacturing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12I is a partially enlarged view of the surface of the polymer layer formed on the aluminum layer shown in FIG. 12H. FIG. 12J is a process diagram (part 6) for explaining an example of the starting point formation process in the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 12K is a partially enlarged view of the surface of the polymer layer formed on the aluminum layer shown in FIG. 12J. FIG. 13A is an SEM photograph of the surface of the polymer layer when the protective metal layer is formed with a thickness equivalent to 10 nm in the starting point formation step in Example 3. FIG. 13B is an SEM photograph of the surface of the polymer layer when the protective metal layer is formed with a thickness equivalent to 3 nm in the starting point formation step in Example 3. FIG. 13C is an AFM image showing an example of the surface of the aluminum layer after the starting point formation step in Example 3. FIG. 13D is a graph showing an example of a cross-sectional height shape of the surface of the aluminum layer after the starting point formation step in Example 3. FIG. 13E is an SEM photograph of the surface of the porous layer in the nanohole structure of Example 3. FIG. 13F is an SEM photograph of the surface of the porous layer in an example of the nanohole structure manufactured without performing the starting point formation step. FIG. 14A is a schematic explanatory diagram for explaining a problem when a starting point for forming nanoholes is formed on a disk-shaped substrate using a mold having a line and space pattern on the surface. FIG. 14B shows a starting point forming step in the manufacturing method of the nanohole structure of the present invention and the magnetic recording medium of the present invention, in which a nanohole forming starting point is formed on a disk-shaped substrate using a mold having a line and space pattern on the surface. It is a schematic explanatory drawing for demonstrating an example. FIG. 15 is a photograph showing an example of the arrangement of nanoholes in the nanohole structure of the present invention and the nanohole structure produced by a conventional process. 16A is an AMF image showing an example of the surface of the aluminum layer after the smoothing process of Example 1. FIG. FIG. 16B is a graph showing an example of a cross-sectional height shape of the surface of the aluminum layer after the smoothing process of Example 1. FIG. 17A is a process diagram (No. 1) for explaining another example of the starting point forming process in the manufacturing method of the nanohole structure of the present invention and the magnetic recording medium of the present invention, and shows the next step of FIG. 12C. . FIG. 17B is a process diagram (part 2) for explaining another example of the starting point formation process in the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 17C is a process diagram (part 3) for explaining another example of the starting point formation process in the method for producing the nanohole structure of the present invention and the magnetic recording medium of the present invention. FIG. 18A is a graph showing the relationship (time dependence) between the milling amounts of PMMA and Al and the etching time. FIG. 18B is a graph showing the relationship (angle dependency) between the etching rate of PMMA and Al and the irradiation angle of the ion beam. FIG. 19 is an SEM photograph of the surface of the porous layer in the nanohole structure of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Soft magnetic layer 30 Recording layer 100 Writing / reading head (single pole head)
DESCRIPTION OF SYMBOLS 110 Substrate 120 Base electrode layer 130 Anodized alumina layer 140 Ferromagnetic layer 200 Glass substrate 210 Adhesion layer 220 Permalloy layer 230 Oxidation stop layer 240 Aluminum layer 250 Protective metal layer 260 Polymer layer (PMMA layer)
260A Concave portion 270 Porous layer (nanohole structure)
270A Alumina nanohole 280 Ferromagnetic material (cobalt)
290 Carbon protective layer 300 Mold 310 Protective metal layer (Fe film)
320 Dummy substrate 330 Protective metal layer (Al film)
400 Protective metal layer manufacturing apparatus 410 Vapor deposition source 420 Cone 430 Substrate stage P Concavity and convexity pattern (starting point for nanohole formation)

Claims (5)

After forming a metal layer on the substrate, a smoothing process for smoothing the surface of the metal layer, a starting point forming step for forming a starting point for forming nanoholes in the smoothed metal layer, and nanohole formation A porous layer forming step of forming a porous layer in which a plurality of nanoholes are formed in a direction substantially orthogonal to the substrate by performing an anodizing treatment as a treatment,
The starting point forming step forms a protective metal layer and a polymer layer on the metal layer in this order from the metal layer, and then imprints the uneven pattern in the mold onto the polymer layer, and forms the formed uneven pattern. A first starting point forming step of etching the metal layer using the remaining protective metal layer as a mask after etching the protective metal layer using, after forming a polymer layer on the metal layer, An uneven pattern in the mold is imprinted to form an uneven pattern, and after the polymer layer located on the bottom surface of the recess formed on the surface of the polymer layer is removed by etching, the metal exposed in the recess the protective metal layer is formed by applying a protective metal to the layer and the polymer layer, inclined with respect to the vertical direction with respect to the substrate surface The metal layer surface located in the lower layer of the protective metal layer and the protective metal layer located in a recess formed in said polymer layer by ion milling for irradiating the ion beam from the direction was etched, the polymer was further left A second starting point forming step of removing the residue of the layer and the protective metal layer, and after forming a polymer layer on the metal layer, the uneven pattern in the mold is imprinted and transferred to the polymer layer. A protective metal layer is formed by applying a protective metal to the polymer layer from a direction inclined with respect to the substrate surface and the vertical direction with respect to the polymer layer surface, and formed on the surface of the polymer layer. After removing the polymer layer located on the bottom surface of the recessed portion by etching, the metal layer surface from which the polymer layer has been removed is removed. Etching, and method of manufacturing a nanohole structure, characterized in that the polymer layer is either a third start point forming step is removed together with the protective metal layer.   In the first starting point forming step, the metal layer is an aluminum layer, the protective metal layer is one of a Ta layer and a Ti layer, and the protective metal layer is etched by CF-based RIE. The method for producing a nanohole structure according to claim 1, wherein the etching is performed by CO-ammonia RIE. 2. The nanohole according to claim 1, wherein in the second starting point forming step, the metal layer is an aluminum layer, and the etching of the polymer layer located on the bottom surface of the recess formed on the surface of the polymer layer is performed by oxygen-based RIE. Manufacturing method of structure.   The nanohole structure according to claim 1, wherein in the third starting point forming step, the metal layer is an aluminum layer, the etching of the polymer layer is performed by oxygen-based RIE, and the etching of the surface of the metal layer is performed by chlorine-based RIE. Body manufacturing method. After a metal layer is formed on the substrate, a smoothing process for smoothing the surface of the metal layer, a starting point forming process for forming a starting point for forming nanoholes in the smoothed metal layer, and a nanohole forming process The nanohole structure forming step of forming a nanohole structure by forming a plurality of nanoholes in a direction substantially orthogonal to the substrate surface by performing an anodizing treatment as described above, and a magnetic material that fills the inside of the nanohole with a magnetic material Including a material filling step,
The starting point forming step forms a protective metal layer and a polymer layer on the metal layer in this order from the metal layer, and then imprints the uneven pattern in the mold onto the polymer layer, and forms the formed uneven pattern. A first starting point forming step of etching the metal layer using the remaining protective metal layer as a mask after etching the protective metal layer using, after forming a polymer layer on the metal layer, An uneven pattern in the mold is imprinted to form an uneven pattern, and after the polymer layer located on the bottom surface of the recess formed on the surface of the polymer layer is removed by etching, the metal exposed in the recess the protective metal layer is formed by applying a protective metal to the layer and the polymer layer, inclined with respect to the vertical direction with respect to the substrate surface The metal layer surface located in the lower layer of the protective metal layer and the protective metal layer located in a recess formed in said polymer layer by ion milling for irradiating the ion beam from the direction was etched, the polymer was further left A second starting point forming step of removing the residue of the layer and the protective metal layer, and after forming a polymer layer on the metal layer, the uneven pattern in the mold is imprinted and transferred to the polymer layer. Forming a protective metal layer by applying a protective metal to the polymer layer from a direction inclined with respect to the substrate surface and the direction perpendicular to the polymer layer surface, and formed on the surface of the polymer layer. After removing the polymer layer located on the bottom surface of the recessed portion by etching, the metal layer surface from which the polymer layer has been removed is removed. Etching, and further method of manufacturing a magnetic recording medium, characterized in that the polymer layer is either a third start point forming step is removed together with the protective metal layer.