JP5033003B2 - Mold structure, imprint method using the same, magnetic recording medium and method for manufacturing the same - Google Patents

Description

  The present invention relates to a mold structure having a concavo-convex pattern for transferring information to a magnetic recording medium, an imprint method using the mold structure, a magnetic recording medium, and a method for manufacturing the magnetic recording medium.

In recent years, hard disk drives with excellent speed and cost have been installed in portable devices such as mobile phones, small audio devices, and video cameras as the mainstay of storage devices, in order to meet the demand for further miniaturization and larger capacity. Therefore, a technique for improving the recording density is demanded.
In order to increase the recording density of a hard disk drive, high-performance magnetic recording media and narrowing the magnetic head width have been used, but the effect of magnetism between adjacent tracks by narrowing the data track interval ( (Crosstalk) and thermal fluctuations cannot be ignored, and there is a limit to the improvement of the surface recording density by narrowing the magnetic head.

  Therefore, a magnetic recording medium called a discrete track medium has been proposed as means for solving the noise caused by the crosstalk (see Patent Documents 1 and 2). In this discrete track medium, a nonmagnetic guard band region is provided between adjacent tracks to form a discrete structure in which individual tracks are magnetically separated, thereby reducing magnetic interference between adjacent tracks.

  As means for solving the demagnetization due to the thermal fluctuation, a magnetic recording medium called a patterned medium in which individual bits for signal recording are provided in a predetermined shape pattern has been proposed (see Patent Document 3). .

  When the discrete track media and the patterned media are manufactured, as disclosed in Patent Document 4, a resist pattern forming mold (hereinafter sometimes referred to as “stamper”) is used to form a magnetic surface. There is an imprint method in which a desired pattern is transferred to a resist layer formed on a magnetic recording medium substrate having a layer.

By the way, in the use of a magnetic recording medium, since it is necessary to perform nanoimprint lithography (NIL) on a fine and wide area, NIL uniformity and stability are important. Also, it is necessary to process two types of patterns: a servo signal for positioning the magnetic head and a data signal for recording actual data. The data portion is composed of a simple pattern such as a concentric circle pattern in discrete track media (DTM) and a dot pattern in bit patterned media (BPM). The servo part is composed mainly of 4 types of patterns such as preamble, servo timing mark, address (sector, cylinder), burst, etc. The address (sector, cylinder), burst pattern part is mixed with coarse signal and complicated It is a pattern array.
Since complex patterns are densely formed on the entire disk surface as described above, it is required that the uneven pattern of the mold structure be faithfully transferred to the entire imprint resist layer during NIL.

  In this imprint method, a transfer process is required many times from the viewpoint of cost reduction, and mold durability capable of transferring at least several hundred to several tens of thousands of times is required. Therefore, in order to impart mold durability, a process of imparting a mold release agent to the mold surface in a liquid phase or a gas phase has been performed. However, the release agent is depleted as the imprint process is repeated, and finally, resist clogging occurs in the uneven pattern of the mold structure.

In addition, when obtaining an information recording medium such as a hard disk or an optical disk using the imprint method, fine pattern processing can be performed by a wet etching method or a dry etching method using an organic resist pattern formed by the imprint process as a mask. Done. The wet etching method has high productivity, and by using an organic resist pattern, the magnetic layer can be selectively etched by selecting an optimum etching solution. However, the wet etching method is difficult to control the contamination and isotropically proceeds, so that it is not suitable for processing a very fine pattern.
On the other hand, in the dry etching method, contamination control is easier than in the wet etching method, and in the case of reactive ion etching, the magnetic layer can be etched by selecting an optimum reaction gas. However, from the examination so far, the reactive gas for etching the magnetic layer is limited to a process for obtaining a carbonyl-based compound such as a chlorine-based or Nakatani process (NH ₃ + CO), and for these etching processes, The organic resist mask has a low resistance and has a problem that a sufficient selectivity cannot be obtained.

  On the other hand, the argon ion milling method that has been studied in the past has excellent processing anisotropy and can also achieve a selective ratio with an organic resist mask, but has low material selectivity and a poor pattern shape after processing (for example, variability). It is said that the wall angle is difficult to control) and is not suitable for the manufacturing process of discrete track media and patterned media for which a high fine pattern is required. In particular, there is a problem that the corners of the pattern are easily etched, resulting in a rounded pattern shape.

  Therefore, a mold structure that has excellent durability and high transferability to the substrate and can form a high-definition pattern close to a square cross-section by an ion milling method and related technology have not yet been realized, and the provision thereof is What is desired is the current situation.

Japanese Patent Laid-Open No. 56-119934 JP-A-2-201730 JP-A-3-22211 JP 2004-221465 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention has excellent durability and high transferability to the substrate, and can form a high-definition pattern close to a square cross section by an ion milling method, and transfers high-quality patterns to discrete track media and patterned media. It is an object of the present invention to provide a mold structure that can be formed, an imprint method using the mold structure, a magnetic recording medium, and a method for manufacturing the magnetic recording medium.

  As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, the cross-sectional shape in the arrangement direction of the concave portions of the mold structure is made to be a substantially convex shape in which both end portions of the bottom side of the concave portion are recessed from the central portion This makes it easy for the release agent to collect in the substantially convex recess, and even when the imprint process is performed many times, the release agent stored in the substantially convex recess is supplied, and durability is improved. improves. In addition, by using a mold structure having a substantially convex cross-sectional shape, it is possible to form an organic resist mask pattern having a substantially concave shape in which both end portions of the top side of the convex portion protrude from the central portion. It becomes. As a result, in the argon ion milling process, it has been found that even if the corners of the convex portions of the resist pattern are cut and rounded, the concavo-convex pattern processing of the magnetic layer can obtain a highly fine shape close to a square cross section.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> A mold structure having a disk-shaped substrate and a concavo-convex portion formed by arranging a plurality of convex portions and concave portions on one surface of the substrate,
The mold structure is characterized in that the cross-sectional shape in the arrangement direction of the concave portions is a substantially convex shape in which both end portions of the bottom side of the concave portions are recessed from the central portion.
<2> The mold structure according to <1>, wherein the cross-sectional shape of the concave portion is a substantially convex shape in which both end portions of the bottom side of the concave portion are gradually inclined from the central portion and depressed.
<3> The ratio <(B / A) × 100] between the depth A of the recess and the height B of the substantially convex shape of the bottom of the recess is 5% to 30%. The mold structure according to any one of the above.
<4> The mold structure according to any one of <1> to <3>, which is made of any material of quartz, metal, and resin.
<5> The mold structure according to any one of <1> to <4> is pressed against an imprint resist layer made of an imprint resist composition formed on a magnetic recording medium substrate. It is an imprint method characterized by including the transfer process which transfers the uneven | corrugated pattern based on the uneven | corrugated | grooved part formed in the body at least.
<6> A method for manufacturing a magnetic recording medium, wherein the magnetic recording medium is manufactured using the imprint method according to <5>.
A method for producing a magnetic recording medium, wherein the cross-sectional shape in the arrangement direction of the convex portions of the resist pattern after being transferred and cured has a substantially concave shape in which both end portions of the top side of the convex portions protrude from the central portion It is.
<7> The method for producing a magnetic recording medium according to <6>, wherein etching is performed by an ion milling method using the concavo-convex pattern formed on the substrate as a mask.
<8> A magnetic recording medium manufactured using the method for manufacturing a magnetic recording medium according to any one of <6> to <7>.
<9> The magnetic recording medium according to <8>, wherein the magnetic recording medium is at least one of a discrete magnetic recording medium and a patterned media magnetic recording medium.

  According to the present invention, conventional problems can be solved, durability is high, transferability to a substrate is high, and a highly fine pattern close to a square cross section can be formed by an ion milling method. Discrete track media and patterned media Further, it is possible to provide a mold structure capable of transferring and forming a high-quality pattern, an imprint method using the same, a magnetic recording medium, and a method for manufacturing the magnetic recording medium.

(Mold structure)
The mold structure of the present invention has a disk-shaped substrate and a concavo-convex portion formed by arranging a plurality of convex portions and concave portions on one surface of the substrate, and further if necessary. It has other configurations.

The convex portion is provided corresponding to the servo portion and the data portion of the magnetic recording medium.
The data portion is an area in which data is recorded, having a substantially concentric convex pattern.
The servo part is composed of a plurality of types of convex patterns having different convex part areas.
The servo unit corresponds to a tracking servo control signal, and mainly includes, for example, a preamble, a servo timing mark, an address pattern, a burst pattern, and the like.
The preamble pattern is a part that generates a reference clock signal for reading various control signals from an address pattern region or the like.
The servo timing mark is a trigger signal for reading an address and a burst pattern.
The address mark is composed of sector (angle) information and track (radius) information, and indicates the absolute position (address) of the disk.
The burst pattern has a function of finely adjusting the head traveling position to achieve highly accurate positioning when the magnetic head is in an on-track state.

The cross-sectional shape in the arrangement direction of the concave portions is a substantially convex shape in which both end portions of the bottom side of the concave portions are recessed from the central portion. This makes it easy for the release agent to accumulate in the substantially convex recess, and even when the imprint process is performed many times, the release agent collected in the substantially convex recess is supplied, and transfer durability is improved. It can be improved. Moreover, the pattern of the organic resist mask which has the substantially concave shape which the both ends of the top side in the convex part protruded from the center part is formed by using the mold structure whose cross-sectional shape in the arrangement | sequence direction of the said recessed part is a substantially convex shape. It becomes possible. As a result, in the ion milling process, even if the corners of the convex portions of the resist pattern are cut and rounded, a high-definition pattern close to a square cross section can be obtained.
Moreover, it is preferable from a viewpoint of the etching workability after that that the cross-sectional shape in the arrangement | sequence direction of the said recessed part is a substantially convex shape in which the both ends of the base in this recessed part were gradually inclined from the center part. This is because the plasma density increases at the corners of the resist pattern, and the resist mask shape cannot be maintained.

There is no restriction | limiting in particular as a material of the said mold structure, Although it can select suitably according to the objective, Any material of quartz, a metal, and resin is suitable.
As said metal, various metals, such as Ni, Cu, Al, Mo, Co, Cr, Ta, Pd, Pt, Au, or these alloys can be used, for example. Among these, Ni and Ni alloys are particularly preferable.
Examples of the resin include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), low-melting fluororesin, polymethyl methacrylate (PMMA), triacetate cellulose (TAC), and the like.

Here, FIG. 1 is a partial perspective view showing a configuration of an embodiment of a mold structure according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
As shown in FIG. 1, the mold structure 1 of the present invention has a plurality of convex portions 3a and concave portions 3b on one surface 2a (hereinafter sometimes referred to as a reference surface 2a) of a substrate 2 having a disk shape. It is formed concentrically. In this case, the convex portion 3 a and the concave portion 3 b formed between the plurality of convex portions 3 a are collectively referred to as the concave and convex portion 3.
As shown in FIG. 2, the concave portion 3b has a base 4 that is substantially parallel to the reference surface 2a, and a substantially convex shape in which both end portions 4b and 4b of the base 4 are depressed more than the central portion 4a. In addition, the both ends and center part of a base means the part of every 1/3 which divided the base into 3 equal parts.
The length of the projections in the arrangement direction (the direction in which the projections are arranged, the radial direction of the disk-shaped substrate) is preferably 100 nm or less, and more preferably 70 nm or less. If the length of the convex portions in the arrangement direction exceeds 100 nm, the recording portion is reduced and the recording density may not be increased.
Moreover, it is preferable that the thickness of the board | substrate 2 is 0.5 mm or more and 10 mm or less.

Further, the ratio [(B / A) × 100] between the depth A of the concave portion and the height B of the substantially convex shape of the bottom of the concave portion is preferably 5% to 30%, more preferably 5% to 20%. . Here, as shown in FIG. 2, the depth A of the concave portion represents the distance to the deepest point of the concave portion, and the height of the substantially convex shape is substantially the same as the deepest point of the concave portion as shown in FIG. It represents the distance from the highest point of the convex shape.
When the ratio [(B / A) × 100] is less than 5%, the mold release agent supplied to the concave portion of the mold structure is depleted, resulting in a decrease in durability against multiple imprint processes. If it exceeds 30%, sharp convex shapes are formed at both ends of the resist pattern, and imperfect pattern formation may occur at the time of imprint peeling, which may reduce the concavo-convex pattern accuracy of the magnetic layer.

Moreover, the cross-sectional shape in the arrangement | sequence direction of the said recessed part 3b has comprised the rectangle, for example.
In addition, the cross-sectional shape in the arrangement direction of the concave portions 3b is not limited to a rectangle, and an arbitrary shape can be selected by controlling an etching process described later according to the purpose.
In the present invention, the “cross section (shape)” refers to a section (shape) in the arrangement direction of the recesses 3b (the direction in which the recesses 3b are arranged) unless otherwise specified.

The cross-sectional shape in the arrangement direction of the concave portions is a substantially convex shape in which both end portions of the bottom side of the concave portions are recessed from the central portion.
The shape of the substantially convex portion of the base is not particularly limited as long as both ends of the base are substantially convex indented from the central portion, and other than the shape shown in FIG. 2, those shown in FIGS. Etc. For example, FIG. 3 shows that the central portion is formed in a convex shape in FIG. FIG. 4 shows a shape in which a substantially convex shape is formed in a substantially semicircular shape. Further, FIG. 5 shows that the central part is formed in a concave shape in FIG. Moreover, FIG. 6 shows that both ends of the bottom are formed in a rectangular shape. In FIG. 7, both end portions of the base are formed in a square shape. Further, FIG. 8 shows that both ends of the base are formed in a substantially triangular shape.
There is no particular limitation on the method for forming the cross-sectional shape in the arrangement direction of the concave portions of the mold structure so that both end portions of the bottom side of the concave portion are substantially convex with respect to the central portion, and depending on the purpose. For example, a method of appropriately adjusting an etching gas and etching process conditions, a method of performing different etching processes a plurality of times, a method of appropriately adjusting an incident angle of etching ions, an electron beam (EB) drawing The method of adjusting conditions suitably etc. are mentioned.

<Method for producing mold structure>
Hereinafter, a method for producing a mold structure according to the present invention will be described with reference to FIGS.
-First embodiment-
<< Preparation of master disk >>
FIG. 9 is a cross-sectional view showing an example of production of a master in the method for producing a mold structure of the present invention.
First, as shown in FIG. 9A, a photoresist solution such as PMMA is applied on the Si substrate 10 by spin coating or the like to form a photoresist layer 21. The material of the resist layer may be either a positive resist material or a negative resist material.
Next, as shown in FIG. 9B, while rotating the Si substrate 10, a laser beam (or electron beam) modulated corresponding to at least one of the data recording track and the servo information is irradiated to form a photoresist. A predetermined pattern on the entire surface, for example, a data track pattern consisting of a substantially concentric convex pattern, a servo pattern consisting of a plurality of types of convex patterns having different convex areas, and a radial direction between the data track pattern and the servo pattern And a buffer pattern consisting of a substantially radial convex pattern connected to.
Next, as shown in FIG. 9C, the photoresist layer 21 is developed to form a desired concavo-convex pattern with the photoresist layer 21 remaining after removing the exposed portion.
Next, as shown in FIG. 9D, a concavo-convex pattern is formed on the substrate 10 by performing selective etching by RIE (Reactive Ion Etching) using the pattern of the formed photoresist layer 21 as a mask. To do.
Next, as shown in E of FIG. 9, the remaining photoresist layer 21 is removed, and the master 11 having an uneven shape is produced.

<< Production of mold structure >>
FIG. 10 is a cross-sectional view showing an example of production of a mold structure in the method for producing a mold structure of the present invention.
As shown in FIG. 10A, for example, an imprint resist layer 24 formed by applying an imprint resist solution containing a photocurable resin is formed on one surface of a quartz substrate 30 as a substrate to be processed. Then, the master 11 is pressed, and the pattern of the protrusions formed on the master 11 is transferred to the imprint resist layer 24.

<< imprint resist layer >>
The imprint resist layer includes, for example, an imprint resist composition containing at least one of a thermoplastic resin, a thermosetting resin, and a photocurable resin (hereinafter sometimes referred to as “imprint resist solution”). It is a layer formed by applying to a substrate, a magnetic recording medium or the like.
The thickness of the imprint resist layer can be measured, for example, by optical measurement using an ellipsometer or the like, contact measurement using a stylus type step gauge, an atomic force microscope (AFM), or the like.
In addition, as the imprint resist composition, those having thermoplasticity, those having photocurability, sol-gel, or the like are used. A novolak resin, an epoxy resin, an alicyclic resin, or a fluorine-based resin with good peelability having these characteristics and high dry etching resistance is suitable.

Here, the material of the substrate to be processed in the present invention is appropriately selected according to the purpose without any particular limitation as long as it is a material having optical transparency and functioning as a mold structure. , Quartz (SiO ₂ ), resin (PET, PEN, polycarbonate, low melting point fluororesin, PMMA) and the like.
Further, the “having light transmittance” specifically means that light is emitted from the other surface of the substrate to be processed so that the light is emitted from one surface on which the imprint resist layer is formed on the substrate to be processed. This means that the imprint resist is sufficiently cured when incident, and at least the light transmittance from the other surface to the one surface is 50% or more.
Further, “having the strength to function as a mold structure” means that the imprint resist layer formed on the substrate of the magnetic recording medium is pressed against the imprint resist layer under the condition that the average surface pressure is 4 kgf / cm ² . It means strength that can withstand pressure.

  Next, as shown in FIG. 10B, the transferred pattern is cured by irradiating the imprint resist layer 24 with ultraviolet rays or the like.

Thereafter, as shown in FIG. 10C, selective etching is performed by RIE or the like using the transferred pattern as a mask. As shown in FIG. 10D, the cross-sectional shape of the concave portion is centered at both ends of the bottom portion of the concave portion. A mold structure 1 having a substantially convex shape that is recessed from the portion is produced.
In the selective etching, the cross-sectional shape of the concave portion of the mold structure 1 is adjusted by a method of appropriately adjusting an etching gas and etching process conditions, a method of performing different etching processes a plurality of times, a method of appropriately adjusting an incident angle of etching ions, The cross-sectional shape shown in any of FIGS.

<< Peeling layer forming process >>
A release agent layer is formed on the irregular surface of the produced mold structure. The release agent is preferably formed on the surface of the mold structure so that it can be peeled off at the interface between the mold structure and the imprint resist layer after imprinting. The release agent material can be appropriately selected as long as it meets the purpose of being easily adhered and bonded to the mold structure and hardly adsorbed on the surface of the imprint resist layer. Among these, a fluorine-based resin is preferable in that it hardly adheres to the resist layer surface.
When the release agent layer is thick, the pattern accuracy deteriorates. Therefore, it is preferable to make the layer as thin as possible, specifically 10 nm or less, more preferably 5 nm or less.
As a means for forming the release agent layer, a coating or vapor deposition means can be used. Further, after the release agent layer is formed, a step of increasing the adsorptivity to the mold structure by means such as baking may be applied.

-Second Embodiment-
<< Preparation of master disk >>
11A to 11B are cross-sectional views illustrating a method for producing a mold structure according to the second embodiment. As shown in FIG. 11A, a master 11 having a concavo-convex pattern was produced as in the first embodiment. In addition, in FIG. 11A-FIG. 11B, the roundish shape of convex parts, such as a mold structure, is abbreviate | omitted and described.
<< Production of mold structure >>
As shown in FIG. 11B, a conductive film 22 is formed on the surface of the master 11 by a sputtering method, and the master 11 provided with the conductive film 22 is immersed in a Ni electroforming bath to perform an electroforming process. A mold structure 23 was produced.
The conductive film 22 can be formed on the concavo-convex pattern of the master 11 by using a conductive material as a vacuum film forming means such as a vacuum deposition method, a sputtering method or an ion plating method, a plating method, or the like.
The conductive material can be appropriately selected according to the post-process (electroforming), but Ni-based, Fe-based, and Co-based metal or alloy materials are preferable. The thickness of the Ni mold structure obtained by electroforming is preferably in the range of 20 to 800 μm, more preferably 40 to 400 μm.
<< Peeling layer forming process >>
As in the first embodiment, it is preferable to form a release agent layer on the surface of the Ni mold structure.

-Third embodiment-
<< Preparation of master disk >>
12A to 12B are cross-sectional views illustrating a method for producing a mold structure according to the third embodiment. As shown in FIG. 12A, a master 11 having a concavo-convex pattern was produced as in the first embodiment. In FIGS. 12A to 12B, the rounded shape of the convex portion such as a mold structure is abbreviated.
<< Production of mold structure >>
As shown in FIG. 12B, the master 11 is pressed against the thermoplastic resin sheet 31. After that, by heating to a temperature equal to or higher than the softening point of the resin, the viscosity of the resin was lowered, and the pattern of the protrusions formed on the master 11 was transferred to the resin sheet 31. Then, the pattern transferred by cooling was cured, and the resin sheet was peeled from the master, thereby producing a resin mold structure 1 having an uneven shape.
Here, the resin material is appropriately selected according to the purpose without particular limitation as long as it is a material having thermoplasticity, light transmittance, and strength that functions as a mold structure. For example, PET , PEN, polycarbonate, low melting point fluororesin, PMMA and the like.
Further, the “having light transmittance” specifically means that light is emitted from the other surface of the substrate to be processed so that the light is emitted from one surface on which the imprint resist layer is formed on the substrate to be processed. This means that the imprint resist is sufficiently cured when incident, and at least the light transmittance from the other surface to the one surface is 50% or more.
Further, “having the strength to function as a mold structure” means that the imprint resist layer formed on the substrate of the magnetic recording medium is pressed against the imprint resist layer under the condition that the average surface pressure is 4 kgf / cm ² . It means strength that can withstand pressure.
<< Peeling layer forming process >>
As in the first embodiment, it is preferable to form a release agent layer on the surface of the resin mold structure.

  The mold structure of the present invention is suitably used for an imprint method including at least a transfer step of transferring the concavo-convex pattern to the imprint resist layer with the convex and concave portions of the mold structure facing the imprint resist layer. And is particularly suitable for the method for producing a magnetic recording medium of the present invention described below.

(Method of manufacturing magnetic recording medium)
A magnetic recording medium manufacturing method of the present invention is a magnetic recording medium manufacturing method of manufacturing a magnetic recording medium using the imprint method of the present invention,
The cross-sectional shape in the arrangement direction of the convex portions of the resist pattern after being transferred and cured has a substantially concave shape in which both end portions of the top sides of the convex portions protrude from the central portion.
In this case, even if etching is performed by ion milling using the resist pattern (uneven pattern of the imprint resist layer) formed on the substrate as a mask, the protruding portions at both ends of the top side of the pattern are etched first, and the cross section A highly fine pattern close to a square shape can be obtained.
The ion milling method, also called ion beam etching, introduces an inert gas such as Ar into an ion source, generates ions, accelerates them using a grid or the like, and collides with a sample substrate for etching. Is. Examples of the ion source include a Kaufman type, a high frequency type, an electron impact type, a duoplasmatron type, a freeman type, an ECR (electron cyclotron resonance) type, and a closed drift type.

  Hereinafter, a manufacturing method (imprint method) for manufacturing a magnetic recording medium such as a discrete track medium or a patterned medium using the mold structure according to the present invention will be described with reference to the drawings.

The method for producing a magnetic recording medium of the present invention is a method for transferring a concavo-convex pattern formed on the mold structure by pressing the mold structure of the present invention against an imprint resist layer formed on a substrate of the magnetic recording medium. Process,
A curing step of curing the concavo-convex pattern transferred to the imprint resist layer and peeling the mold structure;
Using the imprint resist layer to which the concavo-convex pattern is transferred as a mask, the magnetic layer formed on the surface of the substrate of the magnetic recording medium is etched to form a magnetic pattern portion based on the concavo-convex pattern in the magnetic layer. A magnetic pattern portion forming step;
A non-magnetic pattern portion forming step of embedding a non-magnetic material in the concave portion formed on the magnetic layer, and further including other steps as necessary.

Hereinafter, an example of a method for manufacturing a magnetic recording medium such as a discrete track medium or a patterned medium will be described with reference to the drawings.
[Transfer process]
On a magnetic layer of a magnetic recording medium intermediate having a magnetic layer 50 such as Fe or Fe alloy, Co or Co alloy on a substrate such as aluminum, glass, silicon, or quartz, an inner layer such as polymethyl methacrylate (PMMA) is used. With respect to the magnetic recording medium intermediate with a resist layer in which a resist layer 24 formed by applying a print resist solution is formed, the cross-sectional shape in the arrangement direction of the recesses is substantially the same as the both ends of the bottom of the recesses are recessed from the center. The convex / concave pattern formed on the mold structure is transferred to the resist layer 24 by pressing and pressing the convex mold structure 1.

[Curing process]
-Curing by light irradiation-
When the imprint resist composition for forming the imprint resist layer contains a photocurable resin, the imprint resist layer is irradiated with an electron beam such as ultraviolet rays via the imprint mold structure 1 having transparency, The imprint resist layer will be cured.
The photocurable resin used here includes a radical polymerization type and a cationic polymerization type, and can be appropriately selected for the required pattern shape accuracy and curing speed.
―Curing by heating―
When the imprint resist composition for forming the imprint resist layer contains a thermoplastic resin, when the imprint mold structure 1 is pressed against the imprint resist layer, the system is changed to the glass transition point (Tg) of the resist solution. ), The imprint resist layer is cured by lowering the glass transition point of the resist solution after the transfer. Furthermore, the pattern may be cured by irradiating ultraviolet rays or the like as necessary.
When the imprint resist composition contains a thermosetting resin, the imprint mold structure 1 is pressed against the imprint resist layer in a state where the imprint resist composition exhibits fluidity at room temperature or after heating to transfer the concavo-convex pattern. The imprint resist layer is cured by heating to the curing temperature of the resin. The cross-sectional shape in the arrangement direction of the transferred convex portions after curing has a substantially concave shape in which both end portions of the top sides of the convex portions protrude from the central portion.

[Magnetic pattern formation process]
Next, dry etching is performed using the resist layer to which the pattern of the concavo-convex portion is transferred as a mask, thereby forming a concavo-convex shape on the magnetic layer based on the concavo-convex pattern shape formed on the resist layer.
The dry etching is not particularly limited as long as it can form a concavo-convex shape in the magnetic layer, and can be appropriately selected according to the purpose. Examples thereof include ion milling, reactive ion etching (RIE), and sputter etching. , Etc. Among these, the ion milling method is particularly preferable.
The ion milling method is also called ion beam etching. An inert gas such as Ar is introduced into an ion source to generate ions. This is accelerated through the grid and collides with the sample substrate for etching. Examples of the ion source include a Kaufman type, a high frequency type, an electron impact type, a duoplasmatron source, a Freeman type, an ECR (electron cyclotron resonance) type, and a closed drift type.
As a process gas in ion beam etching, a gas obtained by adding a trace amount of oxygen, nitrogen, or hydrogen gas to Ar can be used.

[Non-magnetic pattern part forming process]
Next, after embedding a nonmagnetic material in the formed recess and planarizing the surface, a protective film or the like can be formed as necessary to produce the magnetic recording medium 100.
Examples of the nonmagnetic material include polymers such as SiO ₂ , carbon, alumina, polymethyl methacrylate (PMMA), polystyrene (PS), and smooth oil.
As the protective film, diamond carbon (DLC), sputtered carbon or the like is preferable, and a lubricant layer may be further provided on the protective film.

  The magnetic recording medium manufactured by the magnetic recording medium manufacturing method of the present invention is preferably at least one of a discrete magnetic recording medium and a patterned media magnetic recording medium.

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

Example 1
<Manufacture of mold structure>
-Production of master-
As shown in FIG. 9A, an electron beam resist was applied on the Si substrate 10 by spin coating so as to have a thickness of 100 nm to form a resist layer. Next, by exposing and developing a desired pattern with a rotary electron beam exposure apparatus, a Si substrate with a resist layer having a concavo-convex pattern was produced.
Thereafter, using the resist pattern as a mask, the following reactive ion etching (RIE) was performed to form a concavo-convex shape on the Si substrate.
-Reactive ion etching conditions-
・ Plasma source: ICP type (Inductively Coupled Plasma)
・ Gas: CF gas and a small amount of hydrogen gas ・ Pressure: 0.5 Pa
・ Input power: ICP-300W, Bias-50W

Thereafter, the remaining resist was removed by washing with a soluble solvent and dried to produce a master.
The patterns used in this embodiment are roughly divided into a data portion and a servo portion. The data portion was a pattern having a convex width: 120 nm and a concave width: 30 nm (TP = 150 nm).
The servo section has a servo basic bit length of 90 nm at the innermost circumference, a total number of sectors of 240, a preamble (45 bits) / servo mark (10 bits) / SectorCode (8 bits), and a CylinderCode (32 bits) / Burst pattern.
The servo mark part is “0000101011”, the Sector uses Binary, and the Cylinder uses Gray conversion. The Burst part is a general phase burst signal (16 bits).

-Fabrication of mold structure-
Next, a photocurable acrylic imprint resist solution (manufactured by Toyo Gosei Co., Ltd., PAK-01) was applied on the quartz substrate by a spin coating method to form a resist layer.
Next, UV nanoimprinting was performed using the master as a mold structure. In UV nanoimprinting, pattern transfer was performed by applying pressure at 1 MPa for 5 seconds, and then pattern curing was performed by irradiation with 25 mJ / cm ² of UV light for 10 seconds.
Based on the concavo-convex resist pattern after nanoimprinting, selective etching was performed by RIE shown below to form a concavo-convex shape on the quartz substrate.
・ Plasma source: ICP type (Inductively Coupled Plasma)
・ Gas: CF gas and Ar gas are added 1: 1, a small amount of hydrogen gas is added ・ Pressure: 0.5 Pa
・ Input power: ICP-300W, Bias-60W
Thereafter, the remaining resist was removed by washing with a soluble solvent and dried to produce a quartz mold.
The concave portion of the mold structure thus obtained has a substantially convex shape in which the cross-sectional shape in the arrangement direction of the concave portion is a substantially convex shape in which both end portions of the bottom side of the concave portion are recessed from the central portion, and the depth A of the concave portion is 40 nm, The height B of the substantially convex shape was 2 nm, and the ratio [(B / A) × 100] was 5%. In addition, the depth A of the concave portion and the height B of the substantially convex shape were measured by a TEM (transmission electron microscope) by cutting out a cross section.

<Peeling layer formation>
A release agent layer was formed on the irregular surface of the produced mold structure by a wet method. F13-OTCS (Tridecafluoro-1,1,2,2-tetrahydro-OctylTriChloroSilane) (manufactured by Gelest) was used as the release agent layer material, and 0.1% by mass of stripped with Asahi Clin AK225 (manufactured by Asahi Glass Co., Ltd.) A layer solution was prepared. Using this release layer solution, 1 mm / sec. A release layer having a thickness of 5.25 nm was formed on the quartz mold at a pulling speed of.
The mold structure on which the release layer was formed was exposed to an environment of 90 ° C. and 80% RH for 5 hours to chemically adsorb the release layer material on the surface of the mold structure (chemical bonding treatment). Thus, a mold structure of Example 1 was produced.

<Preparation of magnetic recording medium intermediate>
A soft magnetic layer, a first nonmagnetic alignment layer, a second nonmagnetic alignment layer, a magnetic recording layer, and a protective layer were formed in this order on a 2.5 inch glass substrate as follows. The soft magnetic film, the first nonmagnetic alignment layer, the second nonmagnetic alignment layer, the magnetic recording layer, and the protective layer were formed by sputtering. The lubricant layer on the protective layer was formed by a dip method.
First, CoZrNb was laminated as a soft magnetic layer material so as to have a thickness of 100 nm. Specifically, the glass substrate was placed facing the CoZrNb target, Ar gas was introduced so that the pressure became 0.6 Pa, and a soft magnetic layer was formed at DC 1,500 W.
Next, Pt was laminated as the first nonmagnetic alignment layer so as to have a thickness of 5 nm. Specifically, the soft magnetic layer formed on the substrate is placed opposite to the Pt target, Ar gas is introduced so that the pressure becomes 0.5 Pa, and the first nonmagnetic orientation is discharged by DC 1,000 W. Layers were deposited.
Next, Ru was laminated as the second nonmagnetic alignment layer so as to have a thickness of 10 nm. Specifically, the first nonmagnetic alignment layer formed on the substrate is placed facing the Ru target, Ar gas is introduced so that the pressure becomes 0.5 Pa, and discharge is performed at DC 1,000 W. A second nonmagnetic alignment layer was formed.
Next, CoPtCr—SiO ₂ was laminated as a magnetic recording layer to a thickness of 15 nm. Specifically, the second nonmagnetic alignment layer formed on the substrate is placed facing the CoPtCr—SiO ₂ target, Ar gas is introduced so that the pressure becomes 1.5 Pa, and discharge is performed at DC 1000 W. A magnetic recording layer was formed.
After the magnetic recording layer is formed, the magnetic recording layer formed on the substrate is placed facing the C target, Ar gas is introduced so that the pressure is 0.5 Pa, and discharge is performed at DC 1,000 W. A 4 nm protective layer was deposited. Thus, a magnetic recording medium intermediate was produced. The coercive force of the obtained magnetic recording medium intermediate was 334 kA / m (4.2 kOe).

<Preparation of nanoimprint and discrete type perpendicular magnetic recording medium>
A photocurable acrylic imprint resist solution (manufactured by Toyo Gosei Co., Ltd .: PAK-01) is applied to the produced magnetic recording medium intermediate by spin coating to form a resist layer. did.
The above-mentioned mold structure was placed opposite to the obtained magnetic recording medium intermediate with a resist layer, and the magnetic recording medium intermediate was pressed at a pressure of 1 MPa for 5 seconds to transfer a pattern, and then 25 mJ / cm ² . The pattern was cured by irradiation with UV light for 10 seconds. Thereafter, the mold structure and the magnetic recording medium intermediate were peeled off to form a concavo-convex pattern on the resist layer on the magnetic recording medium intermediate.
Thereafter, as shown in FIG. 13C, an argon ion milling method (an ion gun manufactured by Advanced Energy, process pressure = 0.05 Pa, input power = 200W), an uneven shape based on the pattern shape of the uneven portion 3 formed on the imprint mold structure 1 is formed on the magnetic layer 50, and a nonmagnetic material 70 (SiO ₂ is formed by CVD in the recessed portion. Formation) and the surface was planarized (CMP treatment), and then a protective film was formed (a protective layer made of DLC was formed by a CVD method) to obtain the magnetic recording medium 100. Thus, the discrete type perpendicular magnetic recording medium of Example 1 was produced.

(Examples 2 to 4, Reference Example 5, Examples 6 to 8, and Comparative Examples 1 and 2)
In Example 1, as shown in Table 1, Examples 2 to 4 and Reference were made in the same manner as in Example 1 except that the etching process conditions of the master were changed to adjust the depth of the recesses and the convex shape height. Mold structures of Example 5, Examples 6 to 8, and Comparative Examples 1 and 2 were produced.
A magnetic recording medium was produced by imprinting using the produced mold structures in the same manner as in Example 1.

Example 9
A master having a concavo-convex pattern was produced in the same manner as in Example 1. However, the master was prepared in the same manner as in Example 1 except that the gas etching conditions were changed to CF gas: Ar = 1: 1 and a small amount of hydrogen gas.
Next, based on the uneven pattern on the surface of the master 11, a conductive film was formed on the surface by sputtering. The master disc on which the conductive film was formed was immersed in a Ni electroforming bath having the following composition and rotated at a rotational speed of 50 rpm to 150 rpm, and electroforming was performed to produce a 300 μm thick Ni disc. Thereafter, the Ni disc was peeled from the master disc, and the remaining resist film was removed and washed. As described above, the Ni mold structure of Example 9 was produced.
-Ni electroforming bath composition and temperature-
・ Nickel sulfamate ... 600g / L
・ Boric acid ... 40g / L
・ Surfactant (sodium lauryl sulfate) ... 0.15 g / L
・ PH = 4.0
・ Temperature = 55 ℃

  The concave portion of the mold structure thus obtained has a substantially convex shape in which the cross-sectional shape in the arrangement direction of the concave portion is a substantially convex shape in which both end portions of the bottom side of the concave portion are recessed from the central portion, and the depth A of the concave portion is 40 nm, The height B of the substantially convex shape was 2 nm, and the ratio [(B / A) × 100] was 5%. In addition, adjustment of the cross-sectional shape of the concave portion was performed in the same manner as in Example 1 under the etching process conditions of the master.

<Preparation of magnetic recording medium>
An imprint resist solution made of PMMA resin was applied by spin coating to a magnetic recording medium intermediate produced in the same manner as in Example 1 to a thickness of 100 nm to form a resist layer.
The above-described magnetic recording medium intermediate with a resist layer was placed with the above-mentioned mold structure made of Ni facing, and heated at 150 ° C. and pressurized at 3 MPa for 30 seconds to transfer the pattern, and then 60 The pattern was cured by cooling to ° C. Thereafter, the mold structure and the magnetic recording medium intermediate were peeled off to form a concavo-convex pattern on the resist layer on the magnetic recording medium intermediate.
Next, etching was performed using the formed uneven pattern as a mask to form an uneven shape on the magnetic recording layer. Thus, the perpendicular magnetic recording medium of Example 9 was produced.

(Example 10)
A master having a concavo-convex pattern was produced in the same manner as in Example 1. However, the master was prepared in the same manner as in Example 1 except that the gas etching conditions were changed to CF gas: Ar = 1: 1 and a small amount of hydrogen gas.
Next, a thermoplastic resin sheet made of PMMA was placed oppositely, and the pattern was transferred by applying pressure at 3 MPa for 30 seconds while being heated to 150 ° C., and then cooled to 60 ° C. to cure the pattern. Then, the resin mold structure 1 which has uneven | corrugated shape was obtained by peeling with a mold structure.
The concave portion of the mold structure thus obtained has a substantially convex shape in which the cross-sectional shape in the arrangement direction of the concave portion is a substantially convex shape in which both end portions of the bottom side of the concave portion are recessed from the central portion, and the depth A of the concave portion is 40 nm, The height B of the substantially convex shape was 2 nm, and the ratio [(B / A) × 100] was 5%. In addition, adjustment of the cross-sectional shape of the concave portion was performed in the same manner as in Example 1 under the etching process conditions of the master.
A magnetic recording medium was produced by imprinting using the produced resin mold structure in the same manner as in Example 1.

Next, the durability and size accuracy of each mold structure of Examples 1 to 4, Reference Example 5, Examples 6 to 10, and Comparative Examples 1 and 2 were evaluated as follows. Further, the servo characteristics of each manufactured magnetic recording medium were evaluated as follows. The results are shown in Table 1.

<Durability evaluation>
Using each of the produced mold structures, a process of transferring the uneven fine pattern onto the resin formed on the substrate side was repeated 100 times, and after that process, using an atomic force microscope (AFM) Then, four 1 μm square areas were measured every 90 ° at a radius position of 25 mm of each mold structure, and the presence or absence of clogging and pattern collapse was evaluated according to the following criteria.
〔Evaluation criteria〕
◯: There is no pattern in which the depth of the recess is less than a predetermined 40% or pattern collapse.
X: A pattern in which the depth of the recess is less than a predetermined 40%, or one or more pattern collapses exist.

<Evaluation of size accuracy>
Using each of the produced mold structures, the pattern width after the imprint process was compared with the pattern width after etching, and the size accuracy was evaluated according to the following criteria.
〔Evaluation criteria〕
◎: Change in width is 5% or less ○: Change in width is 10% or less ×: Change in width exceeds 10%

<< Evaluation of servo characteristics >>
For each of the produced magnetic recording media, the position error signal of the reproduced signal is obtained by a magnetic head tester for hard disk (manufactured by Eyemes, BitFinder Model-YS 3300) equipped with a GMR head having a reproduction track width of 0.1 μm and a reproduction gap of 0.06 μm. (PES) measurement was performed and evaluated based on the following evaluation criteria. The results are shown in Table 1.
[Evaluation criteria]
◎: Media with servo following and PES within ± 10% of track width ○: Media with servo following PES within ± 10% to ± 20% of track width ×: Unable to follow servo Medium

As shown in Table 1, the mold structures of Examples 1 to 4, Reference Example 5, and Examples 6 to 9 whose bottoms of pattern recesses are substantially convex have good size accuracy in addition to mold durability. In addition, a mold structure that can transfer and form a high-quality pattern on discrete track media or patterned media has been provided.
On the other hand, in Comparative Examples 1 and 2 in which the pattern concave portion has a substantially concave shape, neither the mold durability nor the size accuracy can satisfy the evaluation criteria, and the servo characteristics are also insufficient.

  The mold structure of the present invention and the imprint method using the mold structure are excellent in durability and transferability to the substrate, and a high-definition pattern close to a square cross section can be obtained by the ion milling method. It is suitable for manufacturing discrete media and patterned media.

FIG. 1 is a partial perspective view showing an example of a mold structure of the present invention. FIG. 2 is a schematic cross-sectional view taken along line AA in FIG. FIG. 3 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 4 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 5 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 6 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 7 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 8 is another schematic cross-sectional view of the mold structure of the present invention. FIG. 9 is a process diagram showing the production of a master in the method for producing a mold structure of the present invention. FIG. 10 is a process diagram showing the production of a mold in the method for producing a mold structure of the present invention. FIG. 11A is a process diagram illustrating another example of a method for manufacturing a mold structure. FIG. 11B is a process diagram illustrating another example of a method for manufacturing a mold structure. FIG. 12A is a process diagram illustrating still another example of a method for manufacturing a mold structure. FIG. 12B is a process diagram illustrating still another example of a method for manufacturing a mold structure. FIG. 13 is a process diagram showing a method of manufacturing a magnetic recording medium using the mold structure of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold structure 2 Substrate 3 Uneven part 3a Convex part 3b Concave part 4 Base 4a Center part 4b End part 24 Imprint resist layer 40 Magnetic recording medium substrate 50 Magnetic layer 100 Magnetic recording medium

Claims (8)

A mold structure having a disk-shaped substrate and a concavo-convex portion formed by arranging a plurality of convex portions and concave portions on one surface of the substrate,
Sectional shape in the arrangement direction of the recess, Ri substantially convex shape der both ends of the base is recessed than the central portion in the recess, the depth A of said recess, a height of approximately convex shape of the bottom side of the recess The mold structure characterized in that the ratio [B / A] × 100 to B is 5% to 30% .   2. The mold structure according to claim 1, wherein the cross-sectional shape of the concave portion is a substantially convex shape in which both end portions of the bottom side of the concave portion are gradually inclined from the central portion. The mold structure according to claim 1 , wherein the substantially convex shape is a substantially semicircular shape, or the central portion is a concave shape .   The mold structure according to any one of claims 1 to 3, wherein the mold structure is made of any one of quartz, metal, and resin.   The uneven structure formed in the said mold structure by pressing the mold structure in any one of Claim 1 to the imprint resist layer which consists of an imprint resist composition formed on the board | substrate for magnetic recording media An imprint method comprising at least a transfer step of transferring a concavo-convex pattern based on a portion. A method of manufacturing a magnetic recording medium for manufacturing a magnetic recording medium using the imprint method according to claim 5,
A method for producing a magnetic recording medium, wherein the cross-sectional shape in the arrangement direction of the convex portions of the resist pattern after being transferred and cured has a substantially concave shape in which both end portions of the top side of the convex portions protrude from the central portion .   The method for manufacturing a magnetic recording medium according to claim 6, wherein etching is performed by an ion milling method using the concave / convex pattern formed on the magnetic recording medium substrate as a mask.   A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to claim 6.