JP2009245535A - Magnetic recording medium and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium where a magnetic recording layer of a high recording density is kept to be high in a quality by eliminating contamination of an orientated base layer surface due to solution treatment and eliminating influence of planar lowering of the bottom surface of the recessed portion of a substrate caused by etching, and to provide a method of manufacturing the magnetic recording medium capable of forming a simply pattern-formed magnetic recording layer on the substrate. <P>SOLUTION: The method of manufacturing the magnetic recording medium comprises: a resin layer forming step; an imprint step of pressing a mold structure having recessed and projecting portions on a surface to the surface of a resin layer to transfer the recessed and projecting portions to the resin layer; a residual film removal step of removing the a resin film remaining on the bottom surfaces of the recessed portions in the recessed and projecting portions formed in the resin layer by dry etching so as to expose the surface of the substrate corresponding to the recessed portions to leave only the projecting-portion resin layer on the substrate; a magnetic recording layer forming step of forming a magnetic recording layer on the surface of the substrate corresponding to the recessed portions so as to be half or less in thickness of the height of the projecting portions of the projecting-portion resin layer; and a projecting resin layer removal step of removing the projecting-portion resin layer to which the magnetic recording layer adheres. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium having a patterned magnetic recording layer and a method for manufacturing the magnetic recording medium.

  In the field of recording media, the rise of semiconductor memory becomes remarkable, and further improvement in recording density is expected for magnetic recording media. In recent years, the recording density has been improved by increasing the recording density by realizing the perpendicular recording system as a recording medium, increasing the sensitivity of the magnetic head, and improving the recording density by reducing the clearance. Improvement has been studied so far. One of the methods for further improving the recording density of magnetic recording media is to use patterned media aimed at increasing the recording density in perpendicular magnetic recording media by further isolating the recording magnetic domains to reduce side fringes and crosstalk. The method by is proposed. The production method of such patterned media has been a problem, and it is desired to provide a method that achieves both performance and productivity.

  As a method for producing the patterned media, for example, a method using a hard mask layer has been proposed as a method for processing a magnetic recording layer by dry etching (see Patent Documents 1 and 2). However, in these proposed methods, the process becomes complicated, and costs and productivity become problems. In addition, a method that does not use a hard mask has been studied. However, developing a resist material that has a sufficient selectivity in dry etching with respect to a magnetic layer, which is a difficult-to-etch material, is a major problem at present.

  As another patterning method for the magnetic recording layer, a fine patterning method using a lift-off method is proposed instead of fine processing by etching. For example, a method of forming a patterned magnetic recording layer by forming a resist pattern on a substrate, forming a magnetic recording layer in a recess of the resist pattern, and then lifting off the resist pattern with a solvent or the like has been proposed. (See Patent Document 3). However, when this proposed method is applied to the area of microfabrication required by the current patterned media, residues such as amine salts remaining on the substrate surface after resist pattern formation adhere to the substrate surface. There is a problem that it remains. In particular, in the patterned media of perpendicular magnetic recording media aimed at increasing the capacity, the magnetic recording quality deteriorates due to the decrease in the orientation of the easy axis of the magnetic recording layer, making it impossible to achieve the desired high recording density. End up. In addition, it is difficult to make the patterning quality uniform within the magnetic recording medium surface because it is technically difficult to form a photoresist layer on a disk-shaped substrate with a good film thickness distribution. Further, the method of patterning the magnetic recording layer by photolithography using EB drawing has a problem that productivity is low.

  Further, as another method, after forming a resist pattern on the substrate and forming a groove (concave portion) on the substrate surface by etching, a magnetic recording layer is laminated on the concave portion to form a magnetic film in the concave portion. A method of removing the resist by lift-off after forming the recording layer has been proposed (see Patent Document 4). When this proposed method is applied to a patterned media application of a perpendicular magnetic recording medium aimed at increasing the capacity, Ru, Co, or Cr that is an orientation layer below the perpendicular magnetic recording layer that is a recording layer The magnetic recording layer is laminated after etching the underlayer and the soft magnetic layer under the underlayer, or after etching the substrate itself, the soft magnetic layer, the underlayer, and the magnetic recording layer are formed in the recess. Need to be stacked.

  However, in the former method, since it is necessary to dry-etch difficult-to-etch materials such as Ru and soft magnetic materials, there is a high demand for the resist etching resistance and it is likely to be technically difficult. Moreover, since there is a high possibility that the resist pattern shape will be greatly broken by etching, it is difficult to obtain a laminate having the expected pattern shape. On the other hand, in the latter method, it is difficult to form the laminated magnetic recording layer horizontally with respect to the substrate due to the surface shape and inclination of the bottom surface of the recess, so the orientation of the perpendicular magnetic recording layer is insufficient. This leads to deterioration of magnetic recording quality.

  Furthermore, since the resist pattern is also etched during the dry etching of the non-magnetic layer, the shape becomes smooth, and in particular, the accuracy of forming a fine pattern of several tens of nm or less required for patterned media is reduced. There is a problem that the lift-off becomes difficult due to excessively small.

JP-A-9-97419 Japanese Patent No. 3844755 JP-A-3-222111 JP 2001-110050 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention does not contaminate the alignment underlayer surface due to solution processing, does not affect the surface condition of the bottom surface of the concave portion of the substrate due to etching, and can maintain a high recording density magnetic recording layer with high quality. It is an object of the present invention to provide a method of manufacturing a magnetic recording medium that can form a medium and a magnetic recording layer that is simply patterned on a substrate.

As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, the concave portions of the resist layer formed by patterning by removing the residual resist layer of the concave portion of the imprint pattern by imprinting and RIE after imprinting are formed on the substrate. It was found that a high-quality perpendicular magnetic recording layer having a desired pattern can be formed on a substrate by removing the resist layer with a solvent after forming the magnetic recording layer in a state where the easy axis of magnetization has a high degree of orientation. .
In addition, according to the method for manufacturing a magnetic recording medium of the present invention, there is no contamination of the alignment underlayer surface due to solution processing, and there is no influence of the surface condition of the bottom surface of the concave portion of the substrate due to etching, and a high recording density magnetic field. It has been found that the recording layer can be formed efficiently.

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 resin layer forming step of forming a resin layer on the substrate;
An imprint process in which a mold structure having an uneven portion on the surface is pressed against the surface of the resin layer to transfer the uneven portion to the resin layer;
Removing the resin film remaining on the bottom surface of the recess in the concavo-convex portion formed on the resin layer by dry etching, exposing the substrate surface corresponding to the recess and leaving only the convex resin layer on the substrate; and
A magnetic recording layer forming step of forming a magnetic recording layer on the substrate surface corresponding to the recess so as to have a thickness of half or less of the height of the protrusion of the protrusion resin layer;
And a protruding resin layer removing step of removing the protruding resin layer to which the magnetic recording layer is attached.
<2> The method for producing a magnetic recording medium according to <1>, wherein the substrate has a disk shape and has a base layer, a soft magnetic layer, and an adhesion layer in this order on a base material.
<3> The method for producing a magnetic recording medium according to any one of <1> to <2>, wherein the resin layer is formed on the substrate by either a vacuum film forming method or an ink jet method.
<4> After forming the resin layer on the substrate under low pressure by the vacuum film-forming method, pressing the uneven portion of the mold against the surface of the resin layer while maintaining the low pressure, The method for producing a magnetic recording medium according to <3>, wherein the uneven portion is transferred to the resin layer.
<5> The method for producing a magnetic recording medium according to any one of <1> to <4>, wherein the resin layer is made of a photocurable resin material, and the uneven portion transferred to the resin layer by a mold is cured by UV irradiation. It is.
<6> The method for producing a magnetic recording medium according to any one of <1> to <5>, wherein the convex resin layer removing step is a step of removing the convex resin layer with a solvent.
<7> A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to any one of <1> to <6>.

  According to the present invention, conventional problems can be solved, there is no contamination of the alignment underlayer surface due to solution processing, there is no influence of the surface deterioration of the bottom surface of the concave portion of the substrate due to etching, and high recording density magnetic recording It is possible to provide a magnetic recording medium capable of maintaining a high quality layer and a method for manufacturing a magnetic recording medium capable of forming a simply patterned magnetic recording layer on a substrate.

(Magnetic recording medium manufacturing method and magnetic recording medium)
The method for producing a magnetic recording medium of the present invention includes at least a resin layer forming step, an imprinting step, a residual film removing step, a magnetic recording layer forming step, and a convex resin layer removing step, and further if necessary. And other steps such as a flattening step of the magnetic recording layer, a protective layer forming step, and a lubricant layer forming step.
The magnetic recording medium of the present invention is manufactured by the magnetic recording medium manufacturing method of the present invention.
As a layer structure of a perpendicular magnetic recording medium suitably used as the magnetic recording medium and a method for forming each layer, conventionally known methods can be used. For example, JP 2007-335034 A and JP 2005-285275 A. The methods described in Japanese Patent Laid-Open No. 2008-10088 and the like can be used as appropriate.

  The layer structure of the patterned medium of the perpendicular magnetic recording medium will be described. The patterned medium is preferably composed of a recording portion and a non-recording portion in which at least the magnetic recording layer is patterned into a concavo-convex structure among the layer structure of the perpendicular magnetic recording medium.

In the method of manufacturing a magnetic recording medium according to the present invention, the soft magnetic layer is not patterned for the purpose of making the function of the SUL layer made of the soft magnetic layer, which is a feature of the perpendicular magnetic recording medium, sufficiently effective. It is preferable to pattern only the underlayer, the adhesion layer, and the magnetic recording layer. In addition, in order to make the orientation of the magnetic recording layer uniform in the plane of the magnetic recording medium, the constituent elements such as the underlayer, the adhesion layer, and the soft magnetic layer under the magnetic recording layer are not patterned, More preferably, only the magnetic recording layer is patterned.
Hereinafter, the details of the magnetic recording medium of the present invention will be clarified through the description of the method of manufacturing the magnetic recording medium of the present invention.

<Resin layer forming step>
The resin layer forming step is a step of forming a resin layer on the substrate.
-Board-
The shape, structure, size, material and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. For example, the shape is a disk in the case of an information recording medium. Is. The structure may be a single layer structure or a laminated structure. The material is at least a nonmagnetic support. The nonmagnetic support is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a metal substrate made of a metal material such as aluminum or an aluminum alloy; glass, ceramic, silicon, silicon carbide, carbon, and the like. Can be mentioned.

The substrate is disk-shaped, and preferably has an underlayer, a soft magnetic layer, and an adhesion layer in this order on a base material. As the substrate, the nonmagnetic support is used.
In this case, it is preferable to include at least one soft magnetic layer as viewed from the base material side. When two or more soft magnetic layers are included, it is preferable that an adhesive layer is formed between the two layers. Further, it is more preferable that the base layer of the magnetic recording layer is formed on the surface side of the soft magnetic layer. In this case, the base layer is arranged on the outermost surface side of the substrate.

The underlayer is for controlling the orientation and grain size of the magnetic recording layer (perpendicular magnetic recording layer), and the material is Ru, Ru alloy, CotoCr and non-magnetic material between crystal grains containing noble metal. A granular nonmagnetic layer containing particles is preferred.
A seed layer for further improving the orientation of the underlayer to the magnetic recording layer (perpendicular magnetic recording layer) can be formed between the base layer and the base material. The seed layer is made of, for example, a Ni alloy such as Ta, Nb, or NiP, a Co alloy such as CoCr, a nonmagnetic layer containing Ta or Ti, or Pd.

-Resin layer-
There is no restriction | limiting in particular as a formation method of the said resin layer, According to the objective, it can select suitably, For example, a spin coat method, a dip method, an inkjet method, a vacuum film-forming method etc. are mentioned. Among these, the ink jet method and the vacuum film forming method are particularly preferable from the viewpoint of coating uniformity on the disk-shaped substrate.
In the vacuum film forming method, after forming a resin layer on a substrate under a low pressure, pressing the uneven portion of the mold against the surface of the resin layer while maintaining the low pressure, and then increasing the pressure to atmospheric pressure or higher, the uneven portion Is transferred to the resin layer.
The thickness of the resin layer is preferably 10 nm to 100 nm, and more preferably 15 nm to 60 nm.

The material of the resin layer is not particularly limited, and may be a polymer material, or may be a low molecular material having a molecular weight of 2000 or less having one or more crosslinking reactive groups or polymerization reactive groups. It is good and both may be included. When using the said low molecular weight material, it is preferable to use a photoinitiator or a thermal polymerization initiator etc. together as a polymerization initiator.
As the low molecular weight material, a material having a photocurable group is preferable, and a UV curable material is more preferable from the viewpoint of easy process. For example, a (meth) acrylate monomer, a monomer having an allyl group or a vinyl group, Monomers having an acetyl group, glycidyl esters, glycidyl ethers, urethane epoxy compounds, compounds having an oxirane ring such as epoxidized polybutadienes; melamine resins, monomers having an isocyanate group, oxetane compounds, and the like. In these monomers, the crosslinkable group may be monofunctional or polyfunctional, and may have two or more types of crosslinkable groups simultaneously. Moreover, although you may have an aliphatic group as a side chain, it is preferable to have an alicyclic structure or an aromatic ring structure from a heat resistant viewpoint in the below-mentioned magnetic body film forming process.

  There is no restriction | limiting in particular as said polymeric material, According to the objective, it can select suitably, For example, polyethylene resins, such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC) resin, polymethacryl (Meth) acrylic resins such as methyl acid (PMMA); novolak resins; polystyrene resins such as parahydroxystyrene; cycloolefin polymers such as norbornene resins; celluloses such as triacetylcellulose (TAC); Etc.

<Imprint process>
The imprint process is a process in which a mold structure having a concavo-convex portion is pressed against the surface of the resin layer to transfer the concavo-convex portion to the resin layer.

In the present invention, an imprint method can be used as a patterning method for the resin layer.
In the imprint method, the pattern side of a mold having a pattern having a concavo-convex portion opposite to the concavo-convex portion of the pattern to be formed is pressed against the resin layer to form a concavo-convex portion of a desired pattern on the resin layer It is a forming method, and a UV-type imprint method or a thermal-type imprint method can be appropriately used.
In the UV imprint method, a polymerizable / crosslinkable material is used as a resin material, and the shape can be fixed by UV irradiation.
In the thermal imprint method, a polymer material is used as a resin material, a pattern shape is formed at a temperature higher than the glass transition point (Tg) of the polymer material, and then the temperature is set to a temperature equal to or lower than Tg. The shape can be fixed by heating or by a heat crosslinkable material.
Among these, the UV imprint method is particularly preferable from the viewpoint of the patterning property of a fine pattern required for patterned media.

<Residual film removal process>
In the residual film removing step, the resin film remaining on the bottom surface of the concave portion in the concave and convex portion formed in the resin layer is removed by dry etching, the substrate surface corresponding to the concave portion is exposed, and only the convex resin layer is formed on the substrate. It is a process to leave.

In the present invention, it is necessary to completely remove the resin film (residual film) remaining on the bottom surface of the recess in the uneven portion after imprinting to expose the substrate surface corresponding to the recess. For this reason, a dry etching method is used as a method for removing the remaining film for the purpose of leaving no residue after removal.
There is no restriction | limiting in particular as said dry etching method, According to the objective, it can select suitably, For example, an ion milling method and RIE method can be used suitably. Note that the etching condition is preferably a condition with high etching anisotropy.
As the ion milling method, for example, a method using Ar ions can be appropriately used.
As the RIE method, for example, a CF gas system, an O ₂ gas system, or the like can be used as appropriate.

<Magnetic recording layer formation process>
The magnetic recording layer forming step is a step of forming the magnetic recording layer on the substrate surface corresponding to the concave portion so as to have a thickness not more than half the height of the convex portion of the convex resin layer. When the magnetic recording layer is formed on the substrate surface corresponding to the concave portion, the magnetic recording layer is also formed on the convex resin layer surface.
If the thickness of the magnetic recording layer exceeds half of the height of the convex portion of the convex resin layer, the magnetic material adheres to the wall portion of the convex portion of the resin concavo-convex structure when the magnetic layer is formed, and lift-off occurs. It may be insufficient.

The material of the magnetic recording layer is not particularly limited and may be appropriately selected depending on the purpose. For example, Co (cobalt), Co alloy (CoPtCr, CoCr, CoPtCrTa, CoPtCrNbTa, CoCrB, CoNi, etc.), Co alloy -SiO _2, Co alloy -TiO _2, Fe, Fe alloy (FeCo, FePt, FeCoNi, etc.), and the like.
These materials have a large magnetic flux density and have perpendicular magnetic anisotropy by adjusting film forming conditions and composition.

In the present invention, a magnetic recording layer (ferromagnetic layer) is formed on the substrate surface corresponding to the concave portion of the concavo-convex structure of the resist pattern on the substrate formed by the imprint method and the dry etching method.
A method for forming the magnetic recording layer is not particularly limited, and a conventionally known method can be used. For example, JP 2007-335034 A, JP 2005-285275 A, and JP 2008-10088 A. For example, the method described in the gazettes.
The thickness of the magnetic recording layer is preferably 5 nm to 50 nm, and more preferably 10 nm to 40 nm.

<Protrusion resin layer removal step>
The convex resin layer removing step is a step of removing the convex resin layer to which the magnetic recording layer is attached.
As a method for removing the convex resin layer, for example, a lift-off method such as solvent removal or water removal can be used as appropriate. Among these, solvent removal is particularly preferable.
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; ester solvents such as ethyl acetate; ether solvents such as PGMEA and PGME; Etc.

<Other processes>
-Flattening process of magnetic recording layer-
In the present invention, a conventionally known method can be used for the purpose of flattening the surface of the magnetic recording layer having a patterned uneven structure. Specifically, for example, a method of filling holes between patterns with high flatness by, for example, bias sputtering (see Japanese Patent No. 3844755), or after forming a nonmagnetic layer on the pattern surface side, planarization is performed by ion beam etching. Method (refer to Japanese Patent Application Laid-Open No. 2005-235356) A method of flattening the surface in the CMP polishing step after forming the nonmagnetic layer on the pattern surface side by the damascene method can be appropriately used.

-Protective layer formation process-
The magnetic recording layer is formed for the purpose of improving the corrosion resistance and durability, and suppressing the damage caused by contact with the head, and is preferably, for example, a diamond-like carbon film (DLC (Diamond Like Carbon)) or sputtered carbon.
The thickness of the protective layer is preferably 1 nm or more and 5 nm or less because the distance between the head and the magnetic recording medium can be reduced, which is desirable from the viewpoint of high recording density.

-Lubricant layer formation process-
There is no restriction | limiting in particular as a material of the said lubricant layer, According to the objective, it can select suitably, For example, the material which has fluorine-containing chains, such as a perfluoro preether, can be used suitably. In addition, from the viewpoint of the stability of the lubricant layer, it can have an alcohol group, a carboxylic acid group, an ether group, a thioether group, or the like as a functional group having excellent adsorptivity to the protective layer on the substrate.
There is no restriction | limiting in particular as the film forming method of the said lubricant layer, According to the objective, it can select suitably, For example, a dip method, a vapor deposition method, etc. can be mentioned.

Here, FIG. 1 is a process diagram showing an example of a method for producing a magnetic recording medium of the present invention.
First, as shown in FIG. 1A, a resin layer 2 is formed on a substrate 1. As a method for forming the resin, either a vacuum film forming method or an ink jet method is preferable.
Next, as shown in FIG. 1B, a mold structure 3 having an uneven portion on the surface is pressed against the surface of the resin layer 2.
Next, as shown in C of FIG. 1, the uneven portion is transferred to the resin layer 2.
Next, as shown in FIG. 1D, the resin film remaining on the bottom surface of the concave portion in the concave and convex portion formed on the resin layer 2 is removed by dry etching, and the substrate surface corresponding to the concave portion is exposed to expose the convex portion resin. Only layer 2a is left on the substrate.
Next, as shown in FIG. 1E, the magnetic recording layer 4 is formed on the surface of the substrate corresponding to the concave portion so as to have a thickness not more than half the height of the convex portion of the convex resin layer 2a.
Next, as shown in F of FIG. 1, the convex resin layer 2a to which the magnetic recording layer is attached is removed. As described above, a magnetic recording medium having the patterned magnetic recording layer 4a can be manufactured.

  The magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium of the present invention has good SNR and can be expected to have a higher recording density, and is particularly suitable as a patterned media type magnetic recording medium.

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

Example 1
<Preparation of mold structure 1>
An electron beam resist (FEP171, manufactured by FUJIFILM Electronics Materials Co., Ltd.) was applied to a thickness of 100 nm on a disk-shaped quartz substrate having a diameter of 8 inches by using a spin coating method.
Then, the said electron beam resist which has an uneven | corrugated pattern was formed on the quartz substrate by exposing and developing a desired pattern with a rotary electron beam exposure apparatus.
Using the electron beam resist having a concavo-convex pattern as a mask, the quartz substrate was subjected to a reactive ion etching treatment with a CHF ₃ gas to form a concavo-convex shape on the quartz substrate.
The remaining electron beam resist was removed by washing with a soluble solvent, and after drying, a mold structure 1 was produced.

Here, the uneven pattern is roughly classified into an uneven pattern in the data area and an uneven pattern in the servo area.
The data region was a concavo-convex pattern with a convex width: 60 nm and a concave width: 90 nm (track pitch = 150 nm).
Regarding the servo area, the reference signal length is 90 nm, the total number of sectors is 240, and it is composed of a preamble part (45 bits), a SAM part (10 bits), a SectorCode part (8 bits), a CylinderCode part (32 bits), and a Burst part. Yes.

The SAM portion is “0000101011”, and the concavo-convex pattern in the SectorCode portion is formed using binary conversion, and the concavo-convex pattern in the cylinder code portion is formed using gray conversion.
The uneven pattern in the Burst portion is a general 4 bursts (each burst is 16 bits).
Based on the formed uneven resist pattern, a mold structure was obtained by RIE using CHF ₃ as an etchant. The concavo-convex structure was evaluated by AFM, and the data region was a concavo-convex pattern having a convex portion width: 50 nm, a concave portion width: 100 nm (track pitch = 150 nm), and a pattern depth uniformly of 100 nm.

<Preparation of magnetic recording medium>
Each layer was formed on a 2.5-inch glass substrate by the following procedure to produce a magnetic recording medium.
The produced magnetic recording medium includes an adhesion layer, a first soft magnetic layer, an adhesion layer, a second soft magnetic layer, a first nonmagnetic alignment layer, a second nonmagnetic alignment layer, a magnetic recording layer, and a protective layer. Are sequentially formed.
Note that the first soft magnetic film, the adhesion layer, the second soft magnetic layer, the first nonmagnetic alignment layer, the second nonmagnetic alignment layer, the magnetic recording layer, and the protective layer were formed by a sputtering method.

-Formation of adhesion layer-
On the cleaned glass substrate, a layer made of CrTi was formed as an adhesion layer with a thickness of 10 nm.

-Formation of first soft magnetic layer, adhesion layer, and second soft magnetic layer-
A layer made of CoZrNb with a thickness of 45 nm is formed as the first soft magnetic layer, a layer made of Ru as the adhesion layer is 0.9 nm, and a layer made of CoZrNb is made the thickness of 45 nm as the second soft magnetic layer. Formed.
Specifically, the glass substrate with the adhesion layer was placed facing the CoZrNb target, Ar gas was introduced at a pressure of 0.6 Pa, and a film was formed at DC 1,500 W. Furthermore, it was installed facing the Ru target, Ar gas was introduced to a pressure of 0.6 Pa, and a film was formed at DC 1,000 W. Further, the glass substrate was placed facing the CoZrNb target, Ar gas was introduced to a pressure of 0.6 Pa, and a film was formed at DC 1,500 W.

-Formation of first nonmagnetic alignment layer-
A Ti layer having a thickness of 5 nm was formed as the first nonmagnetic alignment layer.
Specifically, the first nonmagnetic alignment layer is placed opposite to the Ti target, Ar gas is introduced at a pressure of 0.5 Pa, discharge is performed at DC 1,000 W, and the thickness is 5 nm. A Ti seed layer was formed.

-Formation of second nonmagnetic alignment layer-
Thereafter, a Ru layer having a thickness of 16 nm was formed as a second nonmagnetic alignment layer.
After forming the first nonmagnetic alignment layer, it is placed opposite to the Ru target, Ar gas is introduced to a pressure of 0.8 Pa, discharged at DC 900 W, and the second thickness is 6 nm. As a nonmagnetic alignment layer, a Ru layer was formed.

-Formation of resist layer-
A resist layer was formed to a thickness of 100 nm on the second nonmagnetic alignment layer.
As the resist, the following R-01 solution was used, laminated on the second nonmagnetic alignment layer by the ink jet method, and further baked at 100 ° C. for 2 minutes to prepare an uncured film of the resist. .
-Preparation of R-01 solution-
・ Hydroxybenzyl acrylate 8.0g
・ Tripropylene glycol diacrylate ・ ・ ・ 1.0g
・ Trimethylolpropane triacrylate ・ ・ ・ 1.0g
・ Irgacure 907 (Ciba Specialty Chemicals) ... 0.3g
・ Polyfox 6320 (Omnova)-0.03g
・ Propylene glycol monomethyl ether acetate 50g

<Pattern patterning by imprint>
After the surface side of the produced uncured resist layer and the patterned surface of the produced mold structure 1 are combined, the resist layer and the mold are brought into close contact with each other by creating a reduced-pressure atmosphere in the chamber. .
Furthermore, after the mold is pressed against the adhered resist layer by setting the atmosphere at room temperature to atmospheric pressure or higher with respect to the medium with the resist layer and the mold in close contact, UV is applied from the outside of the mold by a halogen lamp. Irradiation was performed at an intensity of 200 mj / cm ² to cure the resist layer, and then the mold was removed from the resist layer to prepare a patterned resist layer.
Separately, a patterned resist layer prepared in the same manner was evaluated by AFM and SEM, and a resist pattern having the same shape as the mold was formed in terms of pattern shape, width, height, etc. The film thickness (residual film thickness) of the resist layer concave portion corresponding to the convex pattern on the body was 8 nm.

<Residual film removal from resist layer>
Dry etching was performed for the purpose of removing the resist layer on the bottom surface of the concave portion of the patterned resist layer thus produced, and the resist layer on the bottom surface of the pattern concave portion was removed to expose the surface of the second nonmagnetic alignment layer on the bottom surface of the concave portion.
Specifically, the ICP method (Inductively Coupled Plasma) is used to flow the Ar gas and the O ₂ gas at the same flow rate so that the pressure is 0.5 pa, and the ICP voltage is 120 W and the Bias voltage. Dry etching was performed under conditions of 10 W to remove the remaining film, and the remaining film could be completely removed. The pattern height was 100 nm, and the variation in pattern width was 3.6 nm.

<Formation of magnetic recording layer>
Thereafter, a CoCrPtO layer having a thickness of 18 nm was formed as a magnetic recording layer.
Specifically, it was placed facing the CoPtCr target, Ar gas containing 0.06% O _{2 was} introduced at a pressure of 14 Pa, and discharged at DC 290 W to form a magnetic recording layer.

<Removal of resist layer on pattern protrusion>
The convex portion of the resist layer of the sample on which the magnetic recording layer was formed was removed by solvent cleaning.
Specifically, on the spin coater, MEK was placed on the upper surface of the pattern, left for 5 minutes, and then the solvent was shaken off three times.

<Formation of protective layer>
After the magnetic recording layer was formed, it was placed facing the C target, Ar gas was introduced so that the pressure was 0.5 Pa, and discharge was performed at DC 1,000 W, and the C protective layer was formed with a thickness of 4 nm. .

<Formation of lubricant layer>
From the protective layer, TETRAOL (manufactured by Solvay) having a plurality of perfluoropolyether chains and alcohol groups was used as a lubricant, and a lubricant layer was formed by a dip coating method.
Thus, a patterned magnetic recording medium of Example 1 was produced.

(Example 2)
In Example 1, the following R-02 solution was used as a resist solution to be used, and as an imprint condition, the resist layer and the mold were brought into close contact, and then left at 120 ° C. for 2 minutes while being pressurized at a pressure of 3 MPa. Then, after returning to room temperature and normal pressure, a patterned magnetic recording medium of Example 2 was produced in the same manner as in Example 1 except that the conditions for peeling the mold from the resist layer were used.

-R-02 solution-
-Copolymer A (copolymer of benzyl acrylate and methyl methacrylate, copolymerization ratio 1/1, mass average molecular weight 30000) ... 0.5 g
・ Propylene glycol monomethyl ether acetate 50g
・ Polyfox 6320 (Omnova)-0.03g

(Example 3)
In Example 1, an adhesion layer, a first soft magnetic layer, an adhesion layer, and a second soft magnetic layer were sequentially laminated on a 2.5 inch glass substrate, and then a resist layer was formed by the same method as in Example 1. The first nonmagnetic alignment layer, the second nonmagnetic alignment layer, and the magnetic recording layer are stacked by the same method as in Example 1, After removing the resist layer, a protective layer and a lubricant layer were formed, and the patterned magnetic recording medium of Example 3 was produced.

Example 4
In Example 1, an adhesion layer, a first soft magnetic layer, an adhesion layer, a second soft magnetic layer, a first nonmagnetic orientation layer, and a second nonmagnetic orientation layer on a 2.5 inch glass substrate Then, a resist layer is deposited by vapor deposition while maintaining a reduced pressure state. Further, after the mold structure 1 is brought into close contact with the resist layer in a vacuum vessel, imprinting and resist are performed in the same manner as in Example 1. After removing the remaining film, further laminating the magnetic recording layer, and further removing the resist layer, a protective layer and a lubricant layer were formed, and the patterned magnetic recording medium of Example 4 was produced. .

(Example 5)
<Preparation of mold structure 2>
An electron beam resist (FEP171, manufactured by FUJIFILM Electronics Materials Co., Ltd.) was applied to a thickness of 100 nm on a disk-shaped quartz substrate having a diameter of 8 inches by using a spin coating method.
Then, the said electron beam resist which has an uneven | corrugated pattern was formed on the quartz substrate by exposing and developing a desired pattern with a rotary electron beam exposure apparatus.
Using the electron beam resist having a concavo-convex pattern as a mask, the quartz substrate was subjected to a reactive ion etching treatment with a CHF ₃ gas to form a concavo-convex shape on the quartz substrate.
The remaining electron beam resist was removed by washing with a soluble solvent, and after drying, a mold structure 2 was produced.

Here, the uneven pattern is roughly classified into an uneven pattern in the data area and an uneven pattern in the servo area.
The data region was a concavo-convex pattern with a convex width: 40 nm and a concave width: 40 nm (track pitch = 80 nm).
Regarding the servo area, the reference signal length is 90 nm, the total number of sectors is 240, and it is composed of a preamble part (45 bits), a SAM part (10 bits), a SectorCode part (8 bits), a CylinderCode part (32 bits), and a Burst part. Yes.
The SAM portion is “0000101011”, and the concavo-convex pattern in the SectorCode portion is formed using binary conversion, and the concavo-convex pattern in the cylinder code portion is formed using gray conversion.
The uneven pattern in the Burst portion is a general 4 bursts (each burst is 16 bits).
Based on the formed uneven resist pattern, a mold structure was obtained by RIE using CHF ₃ as an etchant. The concavo-convex structure was evaluated by AFM, and the data region was a concavo-convex pattern having a convex portion width: 30 nm, a concave portion width: 50 nm (track pitch = 150 nm), and a pattern depth uniformly of 100 nm.

  Next, a patterned magnetic recording medium of Example 5 was produced in the same manner as in Example 1 except that the mold structure 1 was replaced with the mold structure 2.

(Comparative Example 1)
-Fabrication of patterned media using patterns by photolithography-
<Preparation of magnetic recording medium>
In the same manner as in Example 1, on the 2.5-inch glass substrate, the adhesion layer, the first soft magnetic layer, the adhesion layer, the second soft magnetic layer, the first nonmagnetic orientation layer, and the second non-magnetic orientation layer are formed. After forming the magnetic alignment layer, an electron beam resist (FEP171, manufactured by Fuji Film Electronics Materials Co., Ltd.) was applied to a thickness of 100 nm using a spin coating method.
Then, the said electron beam resist which has an uneven | corrugated pattern was formed on the quartz substrate by exposing and developing a desired pattern with a rotary electron beam exposure apparatus. Here, the concavo-convex pattern formed was a pattern in which the concavo-convex pattern on the quartz substrate formed in Example 1 was exactly reversed.

<Formation of magnetic recording layer>
Thereafter, a CoCrPtO layer having a thickness of 18 nm was formed as a magnetic recording layer.
Specifically, it was placed facing the CoPtCr target, Ar gas containing 0.06% O _{2 was} introduced at a pressure of 14 Pa, and discharged at DC 290 W to form a magnetic recording layer.

<Removal of resist layer on pattern protrusion>
The convex portion of the resist layer of the sample on which the magnetic recording layer was formed was removed by solvent cleaning.
Specifically, on the spin coater, acetone was placed on the upper surface of the pattern, left for 5 minutes, and then the solvent was shaken off three times.

<Formation of protective layer>
After the formation of the magnetic layer, it was placed facing the C target, Ar gas was introduced so that the pressure was 0.5 Pa, discharged at DC 1,000 W, and the C protective layer was formed with a thickness of 4 nm.

<Formation of lubricant layer>
From the protective layer, TETRAOL (manufactured by Solvay) having a plurality of perfluoropolyether chains and alcohol groups was used as a lubricant, and a lubricant layer was formed by a dip coating method.
Thus, the patterned magnetic recording medium of Comparative Example 1 was produced.

(Comparative Example 2)
-Method of forming a magnetic recording layer after first etching the substrate-
<Etching substrate>
After a 150 nm resist layer was laminated on a 2.5 inch glass substrate in the same manner as described in Example 1, the resist layer was patterned by an imprint method, and the remaining film of the patterned resist layer was removed by etching. Reactive ion etching treatment was performed with a CHF ₃ gas, and uneven patterning was performed on the glass substrate. The pattern depth was 130 nm, the resist protrusions remained at a height of 60 nm, and the pattern width was reduced by 20 nm.
The mold structure used in the imprint method has the same pattern as in Example 1, and the thickness of the electron beam resist layer and the quartz etching conditions were changed so that the pattern depth was 150 nm. The mold structure 3 was used.

<Formation of magnetic recording layer from adhesive layer>
From the top surface of the formed concavo-convex glass substrate and resist protrusion, the adhesion layer, the first soft magnetic layer, the adhesion layer, the second soft magnetic layer, the first nonmagnetic orientation layer, and the second nonmagnetic orientation The layer and the recording layer were sequentially laminated by the same method as described in Example 1.

<Removal of resist layer on pattern protrusion>
The convex portion of the resist layer of the sample on which the magnetic recording layer was formed was removed by solvent cleaning.
Specifically, on the spin coater, acetone was placed on the upper surface of the pattern, left for 5 minutes, and then the solvent was shaken off three times.

<Formation of protective layer>
After the formation of the magnetic layer, it was placed facing the C target, Ar gas was introduced so that the pressure was 0.5 Pa, discharged at DC 1,000 W, and the C protective layer was formed with a thickness of 4 nm.

<Formation of lubricant layer>
From the protective layer, TETRAOL (manufactured by Solvay) having a plurality of perfluoropolyether chains and alcohol groups was used as a lubricant, and a lubricant layer was formed by a dip coating method.
Thus, a patterned magnetic recording medium of Comparative Example 2 was produced.

(Comparative Example 3)
<Preparation of magnetic recording medium>
An adhesion layer, a first soft magnetic layer, an adhesion layer, a second soft magnetic layer, a first nonmagnetic orientation layer, a second nonmagnetic orientation layer, and a magnetic recording layer are formed on a 2.5 inch glass substrate. After sequentially laminating, an electron beam resist (FEP171, manufactured by FUJIFILM Electronics Materials) was applied to a thickness of 100 nm using a spin coating method.
Then, the said electron beam resist which has an uneven | corrugated pattern was formed on the quartz substrate by exposing and developing a desired pattern with a rotary electron beam exposure apparatus. Here, the concavo-convex pattern formed was a pattern in which the concavo-convex pattern on the quartz substrate formed in Example 1 was exactly reversed.

The magnetic recording layer was processed by dry etching from the upper surface of the produced patterned electron beam resist layer by an ICP method (Inductively Coupled Plasma) using Ar gas. In addition, it processed by controlling the sample surface temperature at the time of an etching to become 100 degrees C or less.
Thereafter, a protective layer and a lubricant layer were formed by the same method as described in Example 1.
Thus, a patterned magnetic recording medium of Comparative Example 3 was produced.

  Next, for the magnetic recording media of Examples 1 to 5 and Comparative Examples 1 to 3, signal evaluation was performed as follows. The results are shown in Table 1.

<Signal (SNR) evaluation>
With respect to each of the patterned magnetic recording media thus produced, read / write characteristics of magnetic recording were evaluated using a spin stand (manufactured by Eyemes) using a negative pressure pico-slider (3-pad type) as a head. Specifically, when a 40 MHz signal was written and S: 40 MHz ± 1 MHz and N: 0.5 MHz to 80 MHz, the value of 20 * log 10 (S / N−S) was set as SNR.

表１の結果から、本発明の磁気記録媒体の製造方法によりパターニングされた磁気記録媒体を作製することにより、ＳＮＲが良好であり、更なる高記録密度が期待できることが分かった。
これに対し、比較例１のようにインプリント法の変わりに従来のフォトリソグラフィー法を使用した方法では、磁気記録層のＳＮＲが十分ではなく、磁気記録層の磁化容易軸の配向均一性が不十分であることが推定される。
また、比較例２のようにガラス基板よりパターニングして凹部を形成した後に磁気記録層を積層する場合でも、ＳＮＲが十分ではなく、凹部底面の平面性の影響により磁気記録層の磁化容易軸の配向均一性が不十分であることが推定される。また、パターン幅の変化量も大きく、更なる高記録密度化を狙ったパターンの微細化領域での性能確保が大きく懸念される。
また、比較例３のように磁気記録層を直接エッチングする方法では、パターン凸部のエッジ部にバリが発生してしまっているため、ヘッドの走査性を良好に確保することができなかった。

From the results in Table 1, it was found that by producing a magnetic recording medium patterned by the method of manufacturing a magnetic recording medium of the present invention, the SNR was good and a higher recording density could be expected.
On the other hand, in the method using the conventional photolithography method instead of the imprint method as in Comparative Example 1, the SNR of the magnetic recording layer is not sufficient, and the orientation uniformity of the easy axis of the magnetic recording layer is not satisfactory. It is estimated that it is sufficient.
Further, even when the magnetic recording layer is stacked after patterning from the glass substrate by patterning from the glass substrate as in Comparative Example 2, the SNR is not sufficient and the easy axis of magnetization of the magnetic recording layer is affected by the planarity of the bottom surface of the recess. It is estimated that the alignment uniformity is insufficient. In addition, the amount of change in the pattern width is large, and there is a great concern about securing performance in a pattern miniaturization area aiming at further higher recording density.
Further, in the method of directly etching the magnetic recording layer as in Comparative Example 3, since the burrs are generated at the edge portions of the pattern convex portions, the head scanability cannot be ensured satisfactorily.

  The method for producing a magnetic recording medium of the present invention is free from contamination of the alignment underlayer surface due to solution processing, is not affected by the surface condition of the bottom surface of the concave portion of the substrate due to etching, and has a high quality magnetic recording layer. Therefore, it is particularly suitable for manufacturing a patterned media type magnetic recording medium.

FIG. 1 is a process diagram showing an example of a method for producing a magnetic recording medium of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Resin layer 2a Protrusion resin layer 3 Mold structure 4 Magnetic recording layer 4a Patterned magnetic recording layer

Claims (7)

A resin layer forming step of forming a resin layer on the substrate;
An imprint process in which a mold structure having an uneven portion on the surface is pressed against the surface of the resin layer to transfer the uneven portion to the resin layer;
Removing the resin film remaining on the bottom surface of the recess in the concavo-convex portion formed on the resin layer by dry etching, exposing the substrate surface corresponding to the recess and leaving only the convex resin layer on the substrate; and
A magnetic recording layer forming step of forming a magnetic recording layer on the substrate surface corresponding to the recess so as to have a thickness of half or less of the height of the protrusion of the protrusion resin layer;
And a convex resin layer removing step of removing the convex resin layer to which the magnetic recording layer is attached.   The method of manufacturing a magnetic recording medium according to claim 1, wherein the substrate is disk-shaped and has a base layer, a soft magnetic layer, and an adhesion layer in this order on the base material.   The method for producing a magnetic recording medium according to claim 1, wherein the resin layer is formed on the substrate by a vacuum film forming method or an ink jet method.   After forming the resin layer on the substrate under a low pressure by a vacuum film-forming method, press the uneven portion of the mold against the surface of the resin layer while maintaining the low pressure, and then pressurize the uneven portion by increasing the pressure above atmospheric pressure. The method for producing a magnetic recording medium according to claim 3, wherein the magnetic recording medium is transferred to a resin layer.   The method for producing a magnetic recording medium according to claim 1, wherein the resin layer is made of a photocurable resin material, and the uneven portions transferred to the resin layer by a mold are cured by UV irradiation.   6. The method of manufacturing a magnetic recording medium according to claim 1, wherein the convex resin layer removing step is a step of removing the convex resin layer with a solvent.   A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to claim 1.

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