JP2011210368A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium (patterned medium) that removes process damage to prevent deterioration in magnetic property.SOLUTION: The magnetic recording medium includes: protruding patterns of magnetic recording layers, patterns of nonmagnetic layers formed by deactivating magnetism of the magnetic recording layer and formed between the protruding patterns of the magnetic recording layers with a height lower than the height of the protruding patterns of the magnetic recording layers, and carbon protection films formed on the protruding patterns of the magnetic recording layers and patterns of the nonmagnetic layers. The surfaces of the patterns of the nonmagnetic layer are formed in porous shapes.

Description

  The present invention relates to a magnetic recording medium.

  In recent years, in magnetic recording media incorporated in hard disk drives (HDD), the problem that improvement in track density is hindered due to interference between adjacent tracks has become apparent. In particular, reduction of writing blur due to the fringe effect of the recording head magnetic field is an important technical issue.

  In order to solve such a problem, a discrete track medium (DTR medium) that physically separates recording tracks has been proposed. In the DTR medium, since the side erase phenomenon of erasing information on adjacent tracks during recording and the side read phenomenon of reading information on adjacent tracks during reproduction can be reduced, the track density can be increased. Therefore, the DTR medium is expected as a magnetic recording medium that can provide a high recording density. In addition, a bit patterned medium (BPM) that performs recording / reproduction using a single magnetic dot as a single recording bit is expected as a next-generation technology capable of realizing higher density. Hereinafter, DTR media and BPM are collectively referred to as patterned media.

  The method for producing a patterned medium includes a step of peeling the mask layer after etching the magnetic recording layer using, for example, a mask layer made of carbon as a mask. To etch the magnetic recording layer, ion beam etching is performed by accelerating the electric field of ions generated by gasifying Ar or the like in vacuum, or reactive ion etching (RIE) is performed by plasmaizing reactive gas. To go. In order to remove the mask layer made of carbon, RIE is performed by converting oxygen gas into plasma.

  Since the method for manufacturing a patterned medium includes many steps, it is preferable to prevent deterioration of magnetic characteristics by suppressing process damage as much as possible in each step. In order to suppress the process damage of ion beam etching, it is conceivable to reduce the electric field acceleration of ions. However, if the electric field acceleration is small, the etching rate is slow, which is not preferable from the viewpoint of mass productivity. In RIE, since the surface of the sample to be processed is directly exposed to plasma, it is essentially difficult to suppress process damage.

  Conventionally, there has been proposed a method for manufacturing a patterned medium in which a process for removing an oxidizing gas is added after a magnetic recording layer is processed to prevent deterioration of magnetic characteristics (Patent Document 1). In this method, the cleaning gas containing hydrogen is turned into plasma and dry cleaning is performed to remove the oxidizing gas.

  However, this method has two problems. The first problem is that the process of dry-cleaning hydrogen gas into plasma itself damages the sample. In order to turn a gas into a plasma, it is generally necessary to apply high energy of several hundred to several thousand watts. In addition to fearing damage due to heat, the ionized gas collides with the sample surface and damages it. give. The second problem is that a light gas such as hydrogen is extremely difficult to turn into plasma. If the plasma is unstable, the effect of dry cleaning will also be unstable, and the process tolerance will be extremely poor. In order to stably convert hydrogen gas into plasma, it is conceivable to increase the applied power, but the damage of heat and hydrogen ions is further increased. In order to stabilize the plasma, nitrogen gas or argon gas is also mixed with hydrogen gas. However, since nitrogen gas and argon gas are also converted into plasma, damage due to these ions is unavoidable.

Japanese Patent No. 4191096

  An object of the present invention is to provide a magnetic recording medium (patterned medium) that can eliminate process damage and prevent deterioration of magnetic characteristics.

  According to the embodiment, the magnetic recording layer formed between the convex pattern of the magnetic recording layer and the convex pattern of the magnetic recording layer is lower than the height of the convex pattern of the magnetic recording layer. It has a magnetic layer pattern and a carbon protective film formed on the convex pattern of the magnetic recording layer and the pattern of the nonmagnetic layer, and the surface of the nonmagnetic layer has a porous shape A magnetic recording medium is provided.

  In the magnetic recording medium of the present invention, the concave / convex pattern of the magnetic recording layer is processed using a reducing gas that has not been converted into plasma (non-ionized). Damage can be removed to prevent deterioration of magnetic properties.

The top view which follows the circumferential direction of the DTR medium which concerns on one Embodiment of this invention. The top view which follows the circumferential direction of the discrete bit type | mold patterned medium which concerns on other embodiment of this invention. Sectional drawing which shows the manufacturing method of the magnetic-recording medium based on embodiment of this invention. The block diagram which shows the manufacturing apparatus for enforcing the method of this invention. The schematic diagram of the plane TEM image of the boundary area | region of a magnetic-recording layer and a nonmagnetic layer, and the perspective view of the crystal grain contained in a nonmagnetic layer. FIG. 3 is a cross-sectional view showing a surface state of a magnetic recording layer in Example 1. 9 is a graph showing the relationship between process pressure and process time in Example 2. FIG. 10 is a plan view showing the shape of a recording bit observed with MFM for the BPM manufactured in Example 6;

  As described above, conventionally, in order to remove the oxidizing gas after processing the magnetic recording layer and prevent the deterioration of the magnetic characteristics, it is considered necessary to convert the hydrogen gas into plasma and use it. It was. On the other hand, the present inventors have found that even when a non-ionizing reducing gas that has not been converted to plasma is used, the process damage that the concavo-convex pattern of the magnetic recording layer has received before can be removed. In the step using the non-ionizing reducing gas, the sample is not damaged by heat or collision of the ionized gas with the sample surface as in the case of using the plasma process. For this reason, it is possible to prevent the magnetic characteristics of the magnetic recording medium from deteriorating.

In the present invention, as the reducing gas, for example, hydrogen (H ₂ ), forming gas (mixed gas of N ₂ and H ₂ : a gas obtained by diluting H ₂ with N ₂ so as to be below the explosion limit, Are H ₂ concentration of 5% or less), ammonia (NH ₃ ), and carbon monoxide (CO).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a plan view of a discrete track medium (DTR medium) 1 along the circumferential direction. As shown in FIG. 1, servo areas 10 and data areas 20 are alternately formed along the circumferential direction of the medium 1. The servo area 10 includes a preamble part 11, an address part 12, and a burst part 13. The data area 20 includes discrete tracks 21 that are separated from each other.

  FIG. 2 shows a plan view of the bit patterned medium (BPM) 2 along the circumferential direction. As shown in FIG. 2, the servo area 10 has a configuration similar to that of FIG. The data area 20 includes recording bits 22 that are separated from each other.

  In the present invention, a master master having a pattern corresponding to the recording track or recording bit of the data area of the DTR medium shown in FIG. 1 or the data area of the BPM shown in FIG. A Ni stamper and a UV imprint mold (resin stamper) are produced.

  First, a UV imprint mold (resin stamper) is produced as follows. An electron beam (EB) resist (ZEP-520A manufactured by Nippon Zeon Co., Ltd.) is spin-coated on a 6-inch Si substrate, and then pre-baked at 200 ° C. for 3 minutes to form a resist layer having a thickness of about 50 nm. The pattern shown in FIG. 1 is directly drawn on the resist on the Si substrate using an EB drawing apparatus. The resist is developed by immersing in a developer (manufactured by Zeon Corporation, ZED-50N) for 90 seconds to prepare a master master. A Ni conductive film is formed on the master master by sputtering. This master master is immersed in nickel sulfamate plating solution (manufactured by Showa Chemical Co., Ltd., NS-160) and electroformed for 90 minutes to deposit a Ni layer. After electroforming, the Ni layer is peeled off, and the EB resist adhering to the surface is removed by oxygen RIE to obtain a Ni stamper. This Ni stamper is set in an injection molding machine, and a resin stamper is produced by injection molding. As the molding material, ZEON's cyclic olefin polymer ZEONOR 1060R, Teijin Kasei's polycarbonate AD5503, or the like can be used.

  Next, a method for manufacturing a magnetic recording medium (patterned medium) according to the present invention will be described with reference to FIGS.

As shown in FIG. 3A, on a glass substrate 51, a soft magnetic underlayer made of CoZrNb with a thickness of 120 nm, an orientation control underlayer made of Ru with a thickness of 20 nm, and CoCrPt—SiO _{2 with} a thickness of 15 nm. A ferromagnetic layer 52, an etching protective layer 53 made of carbon (C) having a thickness of 15 nm, and an adhesion layer 54 made of Cu having a thickness of 3 to 5 nm are sequentially formed. Here, for simplicity, the soft magnetic underlayer and the orientation control layer are not shown. The adhesion layer 54 has a function of closely adhering the UV curable resin applied thereon. Examples of the material for the adhesion layer include Cu, CoPt, Al, NiTa, Ta, Ti, Si, Cr, and NiNbZrTi.

  A resist 55 made of a UV curable resin is spin-coated on the adhesion layer 54 so as to have a thickness of 50 nm. The UV curable resin contains a monomer, an oligomer, and a polymerization initiator. Examples of the UV curable resin include those containing 85% isobornyl acrylate (IBOA) as a monomer, 10% polyurethane diacrylate (PUDA) as an oligomer, and 5% polymerization initiator (Darocur 1173).

  As shown in FIG. 3B, after the resin stamper 61 is pressed against the resist 55, UV imprinting is performed by irradiating the resin stamper 61 with ultraviolet rays to cure the resist 55, and the concavo-convex pattern of the resin stamper 61 is resisted. Transfer to 55. Thereafter, the resin stamper 61 is removed.

  As shown in FIG. 3C, the imprint residue remaining in the concave portion of the resist 55 is removed by oxygen plasma or Ar ion beam, and a part of the surface of the adhesion layer 54 is exposed. For example, using an RIE apparatus, oxygen is introduced to set the chamber pressure to 2 mTorr, oxygen plasma is generated at an input power of 100 W, and etching is performed for 15 seconds.

As shown in FIG. 3D, the adhesion layer 54 is etched using the resist 55 pattern as a mask to form a pattern of the adhesion layer 54, and a part of the surface of the etching protective film 53 is exposed. When Cu is used for the adhesion layer, ion beam etching using Ar gas is performed. When Si is used for the adhesion layer, RIE using a fluorine-based gas such as CF ₄ or CHF ₃ is performed. Since the UV curable resin can use RIE using a fluorine-based gas, when the adhesion layer is Si, the removal of the imprint residue and the etching of the adhesion layer can be performed collectively by RIE using a fluorine-based gas.

  As shown in FIG. 3E, using the pattern of the resist 55 and the adhesion layer 54 as a mask, the etching protective film 53 is etched by oxygen plasma to form a pattern of the etching protective film 53, and a part of the magnetic recording layer 52 is formed. Expose the surface. Further, the pattern of the resist 55 is removed simultaneously with the etching of the etching protective film 53. For example, using an RIE apparatus, oxygen is introduced to set the chamber pressure to 2 mTorr, oxygen plasma is generated at an input power of 100 W, and etching is performed for 30 seconds.

As shown in FIG. 3F, the magnetic recording layer 52 is ion beam etched by He + N ₂ (mixing ratio 1: 1) using the pattern of the etching protective film 53 as a mask. For example, using ECR (electron cyclotron resonance), etching is performed at a microwave power of 800 W and an acceleration voltage of 1000 V for 20 seconds to form a recess having a depth of 10 nm in the magnetic recording layer 52 having a thickness of 15 nm. At this time, a nonmagnetic layer 52a having a thickness of 5 nm is formed on the bottom of the concave portion of the magnetic recording layer 52. The nonmagnetic layer 52a is made of a magnetic recording layer that has been deactivated by exposure to He + N ₂ mixed gas plasma. Simultaneously with the etching of the magnetic recording layer 52, the pattern of the adhesion layer (for example, Cu) is removed. This is because if the adhesion layer pattern remains, the etching protective film cannot be removed in the next step.

  As shown in FIG. 3G, the pattern of the etching protective film 53 is peeled off by oxygen plasma. For example, using an RIE apparatus, oxygen is introduced to set the chamber pressure to 100 mTorr, oxygen plasma is generated at an input power of 100 W, and etching is performed for 30 seconds.

As shown in FIG. 3H, the uneven pattern of the magnetic recording layer 52 is exposed to a non-ionizing reducing gas. For example, the sample is transferred into a vacuum chamber maintained at 1.0 × 10 ⁻⁴ Pa or less, hydrogen gas is flowed at a flow rate of 100 sccm, the chamber pressure is set to 1 Pa, and the chamber is held for 30 seconds. At this time, hydrogen gas is allowed to flow without being converted into plasma.

As for the sample, as shown in FIG. 3 (h), oxygen plasma in the (c) step, Ar ion beam in the (d) step, oxygen plasma in the (e) step, He + N ₂ mixed gas plasma in the (f) step, (g) Each is exposed to oxygen plasma in the process. By exposing to a non-ionizing reducing gas in the step of FIG. 3 (h), the process damage accumulated in these steps can be removed. In particular, the oxide film on the sample surface formed by exposure to oxygen plasma in the step (g) can be reduced and removed.

  As shown in FIG. 3I, a surface protective film 56 made of carbon having a thickness of 4 nm is formed on the entire surface by CVD (chemical vapor deposition). A patterned medium according to an embodiment of the present invention is manufactured by applying a lubricant (not shown) on the surface protective film 56.

FIG. 4 shows an example of a manufacturing apparatus used for manufacturing a patterned medium according to the present invention. The sample that has passed through the UV imprint process of FIG. 3B is loaded from the load chamber 101. The sample is placed on a carrier and moved to each chamber in a consistent vacuum to perform a predetermined process. In the RIE chamber 102, the resist residue is removed by oxygen plasma in step (c). In the IBE chamber 103, the adhesion layer is etched with an Ar ion beam in step (d). In the RIE chamber 104, the etching protection film is etched by oxygen plasma in the step (e). In the IBE chamber 105, the magnetic recording layer is etched and deactivated by He + N ₂ mixed gas plasma in step (f). In the RIE chamber 106, the etching protective film pattern is removed by oxygen plasma in the step (g). In the gas flow chamber 107, process damage removal by the non-ionizing reducing gas in the step (h) is performed. Since the gas flow chamber 107 does not need to generate plasma, the gas flow chamber 107 includes only a mass flow controller for introducing gas and a turbo pump for performing vacuuming. In the heat chamber 108, the sample is preheated before being transferred to the next CVD chamber. In the CVD chamber 109, a surface protective film is formed. The sample that has completed each step in this manner is unloaded from the unload chamber 110. The reason why the blank chamber is provided between the chambers is to prevent the process gas from flowing from one chamber to the adjacent chamber.

  By the way, in an HDD apparatus incorporating a patterned medium and a recording / reproducing head, the recording / reproducing head operates with a flying height of about 10 nm. In order to stably float the recording / reproducing head, it is desirable that the unevenness of the surface of the patterned medium is 10 nm or less. In view of this, a nonmagnetic material is embedded in a recess between physically separated recording tracks or recording bits, and the surface is flattened by etching back. The nonmagnetic material is embedded by, for example, bias sputtering. In bias sputtering, since bias power is directly applied to the patterned medium, the sample may be damaged by heat. Planarization by etch back is performed by, for example, ion beam etching. For this reason, if the steps of non-magnetic material embedding and planarization are added, further process damage is accumulated.

On the other hand, as in the above-described embodiment, by ion beam etching using a He + N ₂ mixed gas, for example, etching is performed so that a part of the thickness of the magnetic recording layer having a thickness of 15 nm remains, for example, a recess having a depth of 10 nm. When a nonmagnetic layer having a thickness of 5 nm is formed by deactivating a part of the magnetic recording layer remaining in the recesses, the physical recess depth is 10 nm, but the magnetic recess depth is Is 15 nm. Therefore, it is possible to manufacture a patterned medium that can suppress the side erase phenomenon and the side lead phenomenon while ensuring the flying property of the recording / reproducing head without embedding and flattening the nonmagnetic material.

However, a magnetic recording layer which is not exposed to the ion beam of the He + N ₂ mixed gas, different surface properties in the magnetic recording layer with the He + N ₂ mixed exposed to the ion beam of the gas non-magnetic layer formed by demagnetization, It has been found that the film quality of the carbon film formed on each layer is also different.

A carbon film formed by CVD on the magnetic recording layer and a carbon film formed by CVD on the nonmagnetic layer formed by exposing the magnetic recording layer to an ion beam of a He + N ₂ mixed gas to deactivate the magnetism Were compared by Raman spectroscopy. Raman spectra were obtained with a peak intensity Id of D-band near 1390 cm ^-1, the ratio Id / Ig of the peak intensity Ig of G-band near 1555cm ^-1. Since D-band is a peak due to structural disorder, the larger Id / Ig is, the more disturbed the structure of the carbon film is and the lower the density.

As a result, the Id / Ig was slightly larger in the carbon film formed on the nonmagnetic layer than in the carbon film formed on the magnetic recording layer. This means that the density of the carbon film on the nonmagnetic layer formed by exposing to an ion beam of a He + N ₂ mixed gas and deactivating the magnetism is small and the durability is inferior. Incidentally, the carbon film formed on the nonmagnetic layer formed in the concave portion of the magnetic recording layer does not directly contact the recording / reproducing head, and therefore there is no problem in normal use. However, from the viewpoint of ensuring long-term reliability in a high-temperature and high-humidity environment, it is desirable that the carbon film formed on the nonmagnetic layer is also large and strong.

As in the above embodiment, after forming a nonmagnetic layer by ion beam etching and magnetic deactivation of the magnetic recording layer with a He + N ₂ mixed gas, it is preferable to expose it to a nonionized hydrogen gas and then form a carbon film. It was found that a carbon film was obtained. This is considered due to the following reasons.

Figure 5 (a) shows a schematic view of a planar TEM image of a boundary region between the non-magnetic layer exposed to the ion beam in the magnetic recording layer and the He + N ₂ mixed gas which have not been exposed to the ion beam of the He + N ₂ mixed gas. FIG. 5B shows a perspective view of crystal grains contained in the nonmagnetic layer. As shown in FIGS. 5A and 5B, the surface of the nonmagnetic layer exposed to the ion beam of the He + N ₂ mixed gas has a porous shape in which the pores 72 are formed in the columnar particles 71. I found out. It is considered that the nonmagnetic layer having a large surface area with a porous shape is likely to adsorb hydrogen when exposed to nonionized hydrogen gas. When a carbon film is formed by CVD on the nonmagnetic layer thus adsorbing hydrogen, a so-called hydrogenated carbon film is formed. Hydrogenated carbon films are known to have high hardness. Therefore, in the above embodiment, the carbon film formed on the nonmagnetic layer is also strong and excellent in long-term reliability.

  Next, preferred materials used in the embodiments of the present invention and details of individual processes will be described.

[substrate]
As the substrate, for example, a glass substrate, an Al alloy substrate, a ceramic substrate, a carbon substrate, a Si single crystal substrate having an oxidized surface, or the like can be used. As the glass substrate, amorphous glass or crystallized glass is used. Examples of the amorphous glass include general-purpose soda lime glass and aluminosilicate glass. Examples of crystallized glass include lithium-based crystallized glass. Examples of the ceramic substrate include sintered bodies mainly composed of general-purpose aluminum oxide, aluminum nitride, silicon nitride, etc., and fiber reinforced products thereof. As the substrate, a substrate in which a NiP layer is formed on the surface of the above-described metal substrate or non-metal substrate using a plating method or a sputtering method can also be used.

[Soft magnetic underlayer]
The soft magnetic underlayer (SUL) has a part of the head function of passing a recording magnetic field from a single pole head for magnetizing the perpendicular magnetic recording layer in the horizontal direction and returning it to the head side. A steep and sufficient vertical magnetic field is applied to the recording layer of the magnetic field to improve the recording / reproducing efficiency. For the soft magnetic underlayer, a material containing Fe, Ni, or Co can be used. Examples of such materials include FeCo alloys such as FeCo and FeCoV, FeNi alloys such as FeNi, FeNiMo, FeNiCr, and FeNiSi, FeAl alloys, FeSi alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, and FeAlO. Examples thereof include FeTa, FeTaC, and FeTaN, and FeZr alloys such as FeZrN. It is also possible to use a material having a fine structure such as FeAlO, FeMgO, FeTaN, FeZrN or the like having a granular structure in which fine crystal particles are dispersed in a matrix containing Fe of 60 at% or more. As another material of the soft magnetic underlayer, a Co alloy containing Co and at least one of Zr, Hf, Nb, Ta, Ti, and Y can be used. The Co alloy preferably contains 80 at% or more of Co. In such a Co alloy, an amorphous layer is easily formed when it is formed by sputtering. Since the amorphous soft magnetic material does not have magnetocrystalline anisotropy, crystal defects, and grain boundaries, it exhibits very excellent soft magnetism and can reduce the noise of the medium. Examples of suitable amorphous soft magnetic materials include CoZr, CoZrNb, and CoZrTa-based alloys.

  An underlayer may be further provided under the soft magnetic underlayer in order to improve the crystallinity of the soft magnetic underlayer or the adhesion to the substrate. As a material for such an underlayer, Ti, Ta, W, Cr, Pt, alloys containing these, or oxides or nitrides thereof can be used. An intermediate layer made of a nonmagnetic material may be provided between the soft magnetic underlayer and the recording layer. The intermediate layer has two functions of blocking the exchange coupling interaction between the soft magnetic underlayer and the recording layer and controlling the crystallinity of the recording layer. As the material for the intermediate layer, Ru, Pt, Pd, W, Ti, Ta, Cr, Si, alloys containing these, or oxides or nitrides thereof can be used.

  In order to prevent spike noise, the soft magnetic underlayer may be divided into a plurality of layers and antiferromagnetically coupled by inserting Ru of 0.5 to 1.5 nm. Further, a hard magnetic film having in-plane anisotropy such as CoCrPt, SmCo, or FePt, or a pinned layer made of an antiferromagnetic material such as IrMn or PtMn may be exchange-coupled with the soft magnetic layer. In order to control the exchange coupling force, a magnetic film (for example, Co) or a nonmagnetic film (for example, Pt) may be stacked on and under the Ru layer.

[Magnetic recording layer]
As the perpendicular magnetic recording layer, it is preferable to use a material mainly containing Co, containing at least Pt, and further containing an oxide. The perpendicular magnetic recording layer may contain Cr as necessary. As the oxide, silicon oxide and titanium oxide are particularly preferable. In the perpendicular magnetic recording layer, magnetic particles (crystal grains having magnetism) are preferably dispersed in the layer. The magnetic particles preferably have a columnar structure penetrating the perpendicular magnetic recording layer vertically. By forming such a structure, the orientation and crystallinity of the magnetic particles in the perpendicular magnetic recording layer are improved, and as a result, a signal noise ratio (SN ratio) suitable for high density recording can be obtained. In order to obtain such a structure, the amount of oxide to be contained is important.

  The oxide content of the perpendicular magnetic recording layer is preferably 3 mol% or more and 12 mol% or less, and more preferably 5 mol% or more and 10 mol% or less with respect to the total amount of Co, Cr, and Pt. The above range is preferable as the oxide content of the perpendicular magnetic recording layer because, when the perpendicular magnetic recording layer is formed, oxide is deposited around the magnetic particles, and the magnetic particles can be separated and refined. It is. When the oxide content exceeds the above range, the oxide remains in the magnetic particles, and the orientation and crystallinity of the magnetic particles are impaired. This is not preferable because a columnar structure in which magnetic particles penetrate vertically through the perpendicular magnetic recording layer is not formed. When the oxide content is less than the above range, separation and refinement of magnetic particles are insufficient, resulting in increased noise during recording and reproduction, and a signal-to-noise ratio (SN ratio) suitable for high-density recording. Since it cannot be obtained, it is not preferable.

  The Cr content of the perpendicular magnetic recording layer is preferably 0 at% or more and 16 at% or less, and more preferably 10 at% or more and 14 at% or less. The above range is preferable as the Cr content because the uniaxial crystal magnetic anisotropy constant Ku of the magnetic particles is not lowered too much, and high magnetization is maintained, resulting in recording / reproduction characteristics suitable for high-density recording and sufficient heat. This is because fluctuation characteristics can be obtained. When the Cr content exceeds the above range, Ku of the magnetic particles becomes small, so the thermal fluctuation characteristics deteriorate, and the crystallinity and orientation of the magnetic particles deteriorate, resulting in poor recording / reproducing characteristics. Therefore, it is not preferable.

  The Pt content in the perpendicular magnetic recording layer is preferably 10 at% or more and 25 at% or less. The above range for the Pt content is preferable because Ku required for the perpendicular magnetic layer is obtained, and the crystallinity and orientation of the magnetic particles are good. As a result, thermal fluctuation characteristics suitable for high-density recording, recording / reproduction This is because characteristics can be obtained. When the Pt content exceeds the above range, a layer having an fcc structure is formed in the magnetic particles, and crystallinity and orientation may be impaired. When the Pt content is less than the above range, it is not preferable because sufficient Ku for thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  The perpendicular magnetic recording layer contains at least one element selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxide. Can do. By including the above elements, it is possible to promote miniaturization of magnetic particles or improve crystallinity and orientation, and to obtain recording / reproducing characteristics and thermal fluctuation characteristics suitable for higher density recording. The total content of the above elements is preferably 8 at% or less. If it exceeds 8 at%, phases other than the hcp phase are formed in the magnetic particles, so that the crystallinity and orientation of the magnetic particles are disturbed, resulting in recording / reproduction characteristics and thermal fluctuation characteristics suitable for high-density recording. Since it is not possible, it is not preferable.

  The perpendicular magnetic recording layer is composed mainly of at least one selected from the group consisting of CoPt alloys, CoCr alloys, CoPtCr alloys, CoPtO, CoPtCrO, CoPtSi, CoPtCrSi, and Pt, Pd, Rh, and Ru. A multilayer structure of an alloy and Co, and CoCr / PtCr, CoB / PdB, CoO / RhO, etc., to which Cr, B, and O are added can also be used.

  The thickness of the perpendicular magnetic recording layer is preferably 5 to 60 nm, more preferably 10 to 40 nm. Within this range, a magnetic recording / reproducing apparatus suitable for a higher recording density can be produced. If the thickness of the perpendicular magnetic recording layer is less than 5 nm, the reproduction output tends to be too low and the noise component tends to be higher. If the thickness of the perpendicular magnetic recording layer exceeds 40 nm, the reproduction output tends to be too high and the waveform tends to be distorted. The coercive force of the perpendicular magnetic recording layer is preferably 237000 A / m (3000 Oe) or more. When the coercive force is less than 237000 A / m (3000 Oe), the thermal fluctuation resistance tends to be inferior. The perpendicular squareness ratio of the perpendicular magnetic recording layer is preferably 0.8 or more. When the vertical squareness ratio is less than 0.8, the thermal fluctuation resistance tends to be inferior.

[Adhesion layer]
The adhesion layer is a layer for adhering the UV curable resin. The adhesion layer is preferably a metal that is resistant to O ₂ or O ₃ gas and is mainly composed of Al, Ag, Au, Co, Cr, Cu, Ni, Pd, Pt, Si, Ta, Ti, etc. Is preferably 1 to 15 nm.

[UV curable resin]
The UV curable resin (2P agent) is a composition containing a monomer, an oligomer and a polymerization initiator, and does not contain a solvent.

  The following are used as monomers.

・ Acrylates Bisphenol A ・ Ethylene oxide modified diacrylate (BPEDA)
Dipentaerythritol hexa (penta) acrylate (DPEHA)
Dipentaerythritol monohydroxypentaacrylate (DPEHPA)
Dipropylene glycol diacrylate (DPGDA)
Ethoxylated trimethylolpropane triacrylate (ETMPTA)
Glycerin propoxytriacrylate (GPTA)
4-hydroxybutyl acrylate (HBA)
1,6-hexanediol diacrylate (HDDA)
2-hydroxyethyl acrylate (HEA)
2-hydroxypropyl acrylate (HPA)
Isobornyl acrylate (IBOA)
Polyethylene glycol diacrylate (PEDA)
Pentaerythritol triacrylate (PETA)
Tetrahydrofurfuryl acrylate (THFA)
Trimethylolpropane triacrylate (TMPTA)
Tripropylene glycol diacrylate (TPGDA)
・ Methacrylates Tetraethylene glycol dimethacrylate (4EDMA)
Alkyl methacrylate (AKMA)
Allyl methacrylate (AMA)
1,3-butylene glycol dimethacrylate (BDMA)
n-Butyl methacrylate (BMA)
Benzyl methacrylate (BZMA)
Cyclohexyl methacrylate (CHMA)
Diethylene glycol dimethacrylate (DEGDMA)
2-Ethylhexyl methacrylate (EHMA)
Glycidyl methacrylate (GMA)
1,6-hexanediol dimethacrylate (HDDMA)
2-Hydroxyethyl methacrylate (2-HEMA)
Isobornyl methacrylate (IBMA)
Lauryl methacrylate (LMA)
Phenoxyethyl methacrylate (PEMA)
t-Butyl methacrylate (TBMA)
Tetrahydrofurfuryl methacrylate (THFMA)
Trimethylolpropane trimethacrylate (TMPMA)
In particular, isobornyl acrylate (IBOA), tripropylene glycol diacrylate (TPGDA), 1,6-hexanediol diacrylate (HDDA), dipropylene glycol diacrylate (DPGDA), neopentyl glycol diacrylate (NPDA), ethoxy Isocyanuric acid triacrylate (TITA) and the like are good because the viscosity can be reduced to 10 cP or less.

  Examples of the oligomer include urethane acrylate materials such as polyurethane diacrylate (PUDA) and polyurethane hexaacrylate (PUHA), polymethyl methacrylate (PMMA), fluorinated polymethyl methacrylate (PMMA-F), polycarbonate diacrylate, fluoride. Polycarbonate methyl methacrylate (PMMA-PC-F) or the like is used.

  As the polymerization initiator, Ciba Geigy's Irgacure 184, Ciba Geigy's Darocur 1173 and the like are used.

[Residue removal]
Residues remaining at the bottom of the recesses of the resist are removed by RIE (reactive ion etching). The plasma source is preferably ICP (inductively coupled plasma) capable of generating high-density plasma at a low pressure, but ECR (electron cyclotron resonance) plasma or a general parallel plate RIE apparatus may be used. Oxygen gas is preferably used to remove the residue of the resist made of UV curable resin (2P agent).

[Magnetic deactivation etching]
Considering the flying characteristics of the recording / reproducing head, it is preferable to set the depth of the unevenness to 10 nm or less, but the thickness of the magnetic recording layer is required to be about 15 nm in order to ensure signal output. Therefore, if 10 nm of the magnetic recording layer having a thickness of 15 nm is physically removed and the remaining 5 nm is magnetically deactivated, side erasure and side read can be suppressed while ensuring the flying characteristics of the recording head. As a result, DTR media and BPM can be manufactured. As a method of magnetically deactivating a 5 nm thick magnetic recording layer, a method of exposing He or N ₂ ions is used. When He ions are exposed, Hc (coercive force) decreases while maintaining the square shape of the hysteresis loop according to the exposure time, and eventually hysteresis disappears (magnetic deactivation). In this case, if the exposure time of He gas is insufficient, a hysteresis with good squareness (with Hn (inverted nucleation magnetic field)) is maintained. However, this means that the magnetic layer at the bottom of the recess has a recording capability, and the advantages of the DTR medium or BPM are lost. On the other hand, when N ₂ ions are exposed, the square shape of the hysteresis loop deteriorates according to the exposure time, and eventually the hysteresis disappears. In this case, Hn deteriorates rapidly, but Hc hardly decreases. However, if the N ₂ gas exposure time is insufficient, a magnetic layer having a large Hc remains at the bottom of the recess, and the advantages of the DTR medium or BPM are lost. Therefore, paying attention to the difference in the behavior of magnetic deactivation by He gas and magnetic deactivation by N ₂ gas, by using a He + N ₂ mixed gas, the magnetic recording layer at the bottom of the concave portion can be efficiently etched while etching the magnetic recording layer. Can deactivate the magnetism.

[Etching protective film peeling]
After deactivating the magnetism of the magnetic recording layer, the etching protective film made of carbon is peeled off. The etching protective film can be easily peeled off by performing oxygen plasma treatment.

[Formation of surface protective film and post-treatment]
The surface protective film made of carbon is preferably formed by CVD in order to improve the coverage to unevenness, but may be formed by sputtering or vacuum evaporation. According to the CVD method, a DLC film containing a large amount of sp ³ bonded carbon is formed. If the thickness of the surface protective film is less than 2 nm, the coverage is poor, and if it exceeds 10 nm, the magnetic spacing between the head and the medium increases and the SNR decreases, which is not preferable.

  As the lubricant applied on the surface protective film, for example, perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid, or the like can be used.

[Example 1]
A DTR medium was manufactured by the method shown in FIGS. The step of exposing to non-ionized hydrogen gas is 30 by setting the chamber pressure to 1 Pa by flowing hydrogen gas at 100 sccm into a vacuum chamber that is transported and held at a high vacuum of 1.0 × 10 ⁻⁴ Pa or less. For a second.

  The manufactured DTR medium was installed in a drive and the on-track BER (bit error rate) was evaluated to be -7. This means that an error occurs once every 10000000 times. On the other hand, the BER of a DTR medium manufactured by a normal method that does not perform the step of exposing to non-ionized hydrogen gas was -6. Thus, it was found that the BER is improved by about one digit by performing the step of exposing to non-ionized hydrogen gas. The drive was operated for 720 hours in an environment of high temperature and high humidity (65 ° C., humidity 80%), but no BER degradation was observed.

  Next, the presence of oxygen was confirmed by EELS (electron energy loss spectrum) for the DTR medium used for drive evaluation.

  In a DTR medium manufactured by a normal method that does not perform the step of exposing to non-ionized hydrogen gas, oxygen is detected on the surface and side walls of the magnetic recording layer 52. As shown in FIG. It was found that the oxide film 81 was formed on the surface of the layer 52.

  In the DTR medium manufactured by the method of the present invention including the step of exposing to non-ionized hydrogen gas, oxygen is not detected, and no oxide film is formed on the surface of the magnetic recording layer 52 as shown in FIG. I understood. As described above, the reason why the DTR medium manufactured by the method of the present invention including the step of exposing to non-ionized hydrogen gas exhibits a good BER is that the oxidative damage on the surface of the magnetic recording layer 52 is removed, so that the magnetic This is thought to be due to the prevention of deterioration of characteristics.

[Example 2]
The chamber pressure (process pressure) and the process time were examined as conditions in the step of exposing to non-ionized hydrogen gas.

  FIG. 7 shows the result of examining the time in which the oxygen peak on the surface of the magnetic recording layer disappears by XPS (X-ray photoelectron spectroscopy), that is, the process time that can remove the oxidative damage, in a non-ionized hydrogen gas atmosphere at a predetermined chamber pressure Indicates.

  It was found that the process time required to remove oxidative damage was 600 seconds when the chamber pressure was 0.02 Pa, and 30 seconds or less when the chamber pressure was 1 Pa or more. This indicates that the higher the chamber pressure, the higher the hydrogen atom concentration, and thus the higher the effect of removing oxygen damage.

  A DTR medium manufactured with a chamber pressure of 0.02 Pa and a process time of 600 seconds was installed in a drive, and the BER was evaluated to be −6.5. It was found that the BER is improved by about 0.5 orders of magnitude because the BER of a DTR medium manufactured by a conventional method without performing the step of exposing to non-ionized hydrogen gas is −6. The BER of the DTR medium manufactured at a chamber pressure of 0.05 Pa or higher and the process time shown in FIG. When the chamber pressure is 0.02 Pa, since the absolute number of hydrogen atoms in the chamber is small, the penetration of hydrogen into the magnetic recording layer is limited, and the reduction inside the magnetic recording layer does not proceed. In consideration of mass productivity, one step is preferably 5 minutes (300 seconds) or less, and therefore the step of exposing to non-ionized hydrogen gas is preferably performed at a chamber pressure of 0.05 Pa or more.

  On the other hand, when the step of exposing to non-ionized hydrogen gas at a chamber pressure exceeding 10 Pa is performed, excessive hydrogen atoms adhere to the surface of the magnetic recording layer, and the surface protective film formed in the next step is applied with lubrication. It was found that the bond rate of the agent was high.

  Here, the lubricant applied to the surface protective film is divided into a bonding layer attached to the surface protective film and a free layer not attached to the surface protective film. The proportion of the bonding layer in the total amount of lubricant is called the bond rate. The higher the bond rate, the smaller the ratio of the free layer to the total amount of the lubricant. The bond rate is expressed as a ratio between the thickness of the lubricant as it is applied and the thickness of the lubricant after the free layer is washed away with a solvent.

  In a general DTR medium, a bond ratio in the range of 70 to 80%, for example, about 75% is preferable from the viewpoint of reliability. When the bond rate is less than 70%, the ratio of the free layer is large, but the ratio of the bonding layer is small. Therefore, the coverage of the medium surface with the lubricant becomes insufficient, and the reliability of the drive is lowered. When the pound rate exceeds 80%, the ratio of the free layer to the total amount of the lubricant becomes small, and when the head comes into contact with the medium and the lubricant is lost from the surface of the medium, the lubricant supplied from other areas is lost. Since the volume is reduced, the reliability of the drive is reduced.

  The relationship between the chamber pressure in the step of exposing the magnetic recording layer to non-ionized hydrogen gas and the bond ratio of the lubricant applied on the surface protective film formed on the magnetic recording layer is that the chamber pressure is 10 Pa or less. In some cases, it was about 75%, and when the chamber pressure exceeded 10 Pa, the bond rate was about 85%. Thus, when the chamber pressure exceeds 10 Pa, the bond ratio of the lubricant applied on the surface protective film becomes too high, and the reliability of the drive is lowered.

  Considering the above results, the chamber pressure in the step of exposing to non-ionized hydrogen gas is preferably 0.05 Pa or more and 10 Pa or less.

[Example 3]
The hydrogen gas flow rate was examined as a condition in the process of exposure to non-ionized hydrogen gas.

  The chamber pressure was set to 0.05 Pa with a hydrogen gas flow rate of 1 sccm, and 25 DTR media were manufactured in the same manner as in Example 2. As a result of observing the oxygen peak on the surface of the DTR medium by XPS, no oxygen peak was observed in all 25 media.

  The chamber pressure was adjusted to 0.05 Pa with a hydrogen gas flow rate of 0.5 sccm, and 25 DTR media were manufactured in the same manner as in Example 2. As a result of observing the oxygen peak on the surface of the DTR medium by XPS, oxygen peaks were observed in the three media. This is believed to be due to process instability. The chamber pressure (process pressure) is controlled by adjusting the hydrogen gas flow rate and the exhaust capacity of the vacuum pump. In order to set the chamber pressure to 0.05 Pa at a hydrogen gas flow rate of less than 1 sccm, the evacuation capacity of the vacuum pump is lowered by fine adjustment in the direction of closing the conductance valve, so the atmosphere becomes unstable. Therefore, when the hydrogen gas flow rate is as low as less than 1 sccm, the process becomes unstable and defective products are generated.

  A hydrogen gas flow rate of over 200 sccm was adjusted to a chamber pressure of 0.05 Pa, and 25 DTR media were produced in the same manner as in Example 2. As a result of observing the oxygen peak on the surface of the DTR medium by XPS, no oxygen peak was observed in all 25 media. When the bond ratio of the lubricant applied on the surface protective film was measured, it was 85%. As described in the second embodiment, if the bond rate is too high, the reliability is lowered, which is not preferable.

  In a DTR medium manufactured by adjusting the chamber pressure to 0.05 Pa with a hydrogen gas flow rate of 200 sccm or less, the bond ratio of the lubricant applied on the surface protective film is 75%, which is desirable in terms of reliability.

  Considering the above results, the hydrogen gas flow rate in the step of exposing to non-ionized hydrogen gas is preferably 1 sccm or more and 200 sccm or less.

[Example 4]
In the step of exposing to a non-ionizing reducing gas, a DTR medium was formed using forming gas, carbon monoxide (CO), or ammonia (NH ₃ ) instead of hydrogen gas.

The manufactured DTR medium was installed in a drive, and the on-track BER was evaluated. The drive was operated for 720 hours in an environment of high temperature and high humidity (65 ° C., humidity 80%), but no BER degradation was observed. The presence of oxygen was confirmed by EELS on the DTR medium used for drive evaluation, but oxygen was not detected. Thus, it has been found that even when forming gas, CO, or NH ₃ is used as the reducing gas, the same effect as that obtained when hydrogen gas is used can be obtained.

The forming gas is a gas obtained by diluting H ₂ with N ₂ so as to be below the explosive limit (H ₂ concentration is 5% or less), and since it is highly safe, it is often used as a substitute for hydrogen gas. However, for example, when used in place of hydrogen gas in the plasma process described in Japanese Patent No. 4191096, N ₂ gas is also ionized by plasma, so that active N ₂ ions react with the medium surface and cause damage.

In the present invention, even when forming gas is used as the reducing gas, it is not converted to plasma, so that N ₂ gas stays in the process chamber while being inactive and does not damage the medium surface. Thus, the process using the non-ionized reducing gas in the present invention has an advantage in terms of safety because a forming gas that causes a problem in the conventional method can be used.

Since CO and NH ₃ are toxic, when these reducing gases are used, an abatement apparatus is provided in the manufacturing apparatus. Moreover, since there is danger if there is residual gas on the surface of the medium, a water washing step is performed to completely remove the residual gas.

[Example 5]
In order to investigate the durability of the surface protective film on the nonmagnetic layer, the magnetic recording layer was magnetically deactivated on the entire surface of the substrate as follows without patterning the magnetic recording layer formed on the substrate. A sample having a nonmagnetic layer was prepared, and a sliding test with a recording / reproducing head was performed. Since the sliding test is performed by rubbing the head against the sample surface, it becomes an index for evaluating the hardness and abrasion resistance of the surface protective film.

A magnetic recording layer was formed on the substrate, irradiated with an ion beam of a He + N ₂ mixed gas, and exposed to oxygen plasma in the same manner as the etching protective film peeling step. The sample was transported into a vacuum chamber maintained at 1.0 × 10 ⁻⁴ Pa or less, hydrogen gas was flowed at a flow rate of 100 sccm, the chamber pressure was set to 1 Pa, and the sample was held for 30 seconds. Thereafter, a surface protective film was formed. When a sliding test was performed on the prepared sample, no scratch was generated on the sample surface even after 720 hours.

  For comparison, a sample of a comparative example was prepared in the same manner as described above except that the step of exposing to non-ionized hydrogen gas was not performed. When the sliding test was performed on the manufactured sample of the comparative example, the surface of the sample was scratched after 600 hours.

A general perpendicular magnetic recording medium does not cause scratches in a 720 hour sliding test. Since the sample of the comparative example, which was not subjected to the step of exposing to the non-ionized hydrogen gas after being exposed to the ion beam with the He + N ₂ mixed gas, was damaged in 600 hours, the hardness and abrasion resistance of the surface protective film were slightly It turns out that it is inferior. On the other hand, the sample subjected to the step of exposure to non-ionized hydrogen gas after being exposed to an ion beam with a He + N ₂ mixed gas was able to withstand a sliding test of 720 hours. It can be seen that the deterioration of wear resistance is suppressed.

In the case of a patterned medium, the region where the nonmagnetic layer is formed by exposure to an ion beam of He + N ₂ mixed gas is the bottom of the concave portion of the magnetic recording layer. The recording / reproducing head does not collide. For this reason, it can be said that there is no problem even if the quality of the surface protection film formed on the nonmagnetic layer is slightly deteriorated. However, in order to ensure reliability in a harsh environment of high temperature and high humidity, the step of exposing to non-ionized hydrogen gas is useful.

[Example 6]
BPM was produced in the same manner as in Example 1. The bit size of the manufactured BPM was 60 nm × 20 nm. Since BPM cannot define BER, the signal amplitude intensity was examined. When a medium having a magnetic recording layer magnetized in one direction was installed in a drive and the reproduction waveform was observed, a signal amplitude intensity of 200 mV was obtained. The positioning accuracy of the recording / reproducing head was 6 nm. Thus, it was found that BPM can also be produced by the production method of the present invention. When the manufactured BPM was observed with an MFM (magnetic force microscope), a rectangular recording bit was seen as shown in FIG.

  For comparison, BPM was produced without performing the step of exposing to non-ionized hydrogen gas. When the manufactured BPM of the comparative example was observed with an MFM (magnetic force microscope), an elliptical recording bit was seen as shown in FIG. 8B. This is because the shape of the recording bit is physically rectangular, but the magnetism of the corner of the recording bit is lost due to oxidation damage, and the shape of the magnetic recording bit appears to be elliptical. It is done.

  By performing the step of exposure to non-ionized hydrogen gas, the oxidative damage of the recording bit is reduced, and the physical shape and the magnetic shape are matched as shown in FIG. That is, the oxidation damage of the recording bit can be canceled by performing the step of exposing to non-ionized hydrogen gas.

  DESCRIPTION OF SYMBOLS 1 ... DTR medium, 2 ... BPM, 10 ... Servo area, 11 ... Preamble part, 12 ... Address part, 13 ... Burst part, 20 ... Data area, 21 ... Discrete track, 22 ... Recording bit, 51 ... Glass substrate, 52 ... magnetic recording layer, 52a ... non-recording layer, 53 ... etching protective layer, 54 ... adhesion layer, 55 ... resist, 56 ... surface protective film, 61 ... resin mold, 71 ... particle, 72 ... hole, 81 ... oxide film 91 ... Recording bit 101 ... Load chamber 102 ... RIE chamber 103 ... IBE chamber 104 ... RIE chamber 105 ... IBE chamber 106 ... RIE chamber 107 ... Gas flow chamber 108 ... Heat chamber 109 ... CVD Chamber, 110 ... unload chamber.

Claims (3)

A convex pattern of the magnetic recording layer;
A pattern of a non-magnetic layer formed between the convex patterns of the magnetic recording layer lower than the height of the convex pattern of the magnetic recording layer and the magnetic recording layer being magnetically deactivated;
A magnetic recording medium comprising a convex pattern of the magnetic recording layer and a carbon film formed on the pattern of the nonmagnetic layer, wherein the pattern of the nonmagnetic layer has a porous surface .   When the ratio of the peak intensity Id of D-band and the peak intensity Ig of G-band in the Raman spectrum of the carbon film is Id / Ig, the carbon film is more on the nonmagnetic layer pattern than the magnetic recording layer. The magnetic recording medium according to claim 1, wherein Id / Ig is larger than that of the convex pattern.   The magnetic recording medium according to claim 1, wherein an oxide film is not included between the convex pattern of the magnetic recording layer and the carbon film.

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