Patent Grant
8315018
The present invention relates to an improvement in a magnetic recording medium used for, for example, a magnetic recording/reproducing apparatus (hard disk drive), a method of manufacturing a magnetic recording medium, and a magnetic recording/reproducing apparatus.
Priority is claimed on Japanese Patent Application No. 2008-047630, filed Feb. 28, 2008, the content of which is incorporated herein by reference.
In recent years, the application range of, for example, magnetic recording/reproducing apparatuses, flexible disk apparatuses, and magnetic tape apparatuses, has increased remarkably, and the importance thereof has increased. Therefore, a technique has been developed for significantly improving the recording density of magnetic recording media used in these apparatuses. In particular, the introduction of an MR head and a PRML technique has significantly increased surface recording density. In recent years, with the development of GMR heads and TMR heads, the recording density of magnetic recording media has increased at a rate of about 100% per year. There is a demand for a further increase in the recording density of magnetic recording media. In order to meet such demand, it is necessary to improve the coercivity, signal-to-noise ratio (SNR), and resolution of the magnetic recording layer. In addition, in recent years, there has been an attempt to increase track density in addition to linear recording density, thereby improving surface recording density.
The latest magnetic recording/reproducing apparatus has a track density of 110 kTPI. However, when the track density increases, interference occurs between the magnetic recording information items of adjacent tracks, and a magnetization transition region, which is a boundary region therebetween, acts as a source of noise, which may cause a reduction in SNR. When the SNR is reduced, bit error rates deteriorate, which prevents improvements in recording density.
In order to improve the surface recording density, it is necessary to further reduce the size of each recording bit on the magnetic recording medium and maximize the magnetic film thickness and saturation magnetization for each recording bit. However, when the size of the recording bit is reduced, the minimum magnetization volume per bit is reduced, and recording data is erased due to magnetization reversal caused by heat fluctuation.
When the distance between the tracks is reduced, the magnetic recording/reproducing apparatus requires a very accurate track servo technique. In general, a method has been used which performs recording with a large track width and performs reproduction with a track width smaller than that during recording to minimize the influence of adjacent tracks. However, in this method, it is possible to minimize the influence between the tracks, but it is difficult to obtain a sufficient reproduction output. Therefore, it is difficult to ensure a sufficient SNR.
In order to solve the problem of heat fluctuation and ensure a sufficient SNR and a sufficient output, the following method has been proposed in which concave and convex portions are formed on the surface of a recording medium along the tracks to physically separate the recording tracks, thereby improving track density. Hereinafter, such a technique is referred to as a discrete track method, and a magnetic recording medium manufactured by the discrete track method is referred to as a discrete track medium. In addition, there has also been an attempt to manufacture so-called patterned media in which a data region in the same track is further divided.
As an example of discrete track media, a magnetic recording medium has been known in which a magnetic layer is formed on a non-magnetic substrate having an uneven pattern formed on the surface thereof so as to form magnetic recording tracks and servo signal patterns that are physically separated from each other (for example, Patent Document 1).
In the magnetic recording medium, a ferromagnetic layer is formed on the surface of a substrate on which a plurality of concave and convex portions is formed, with a soft magnetic layer interposed therebetween, and a protective film is formed on the surface of the ferromagnetic layer. In the magnetic recording medium, a magnetic recording region that is physically separated from its surroundings is formed in a convex region. According to the magnetic recording medium, it is possible to prevent the formation of domain walls in the soft magnetic layer. Therefore, it is possible to prevent an adverse effect by heat fluctuation and there is no interference between adjacent signals. As a result, it is possible to provide a high-density magnetic recording medium with less noise.
Examples of the discrete track method include a method of forming a magnetic recording layer including a number of thin films and physically forming tracks on the magnetic recording layer and a method of forming an uneven pattern on the surface of a substrate and forming a thin magnetic recording layer on the substrate (for example, Patent Documents 2 and 3).
In addition, a method has been proposed in which nitrogen or oxygen ions are implanted into a region between the magnetic tracks of a magnetic layer that has been formed in advance in the discrete track medium, or a laser beam is radiated onto the region to change the magnetic characteristics of the region (Patent Documents 4 to 6).
[Patent Document 1] JP-A-2004-164692
[Patent Document 2] JP-A-2004-178793
[Patent Document 3] JP-A-2004-178794
[Patent Document 4] JP-A-5-205257
[Patent Document 5] JP-A-2006-209952
[Patent Document 6] JP-A-2006-309841
As described above, in a process of manufacturing so-called discrete track media or patterned media including a magnetically separated magnetic recording pattern, in some cases, the magnetic layer is exposed to reactive plasma or reactive ions using oxygen or a halogen to form a magnetic recording pattern, or the magnetic layer is processed by, for example, ion milling so as to have a magnetic recording pattern. These manufacturing methods include a process of forming a mask layer on the surface of the magnetic layer and patterning the mask layer using a photolithography technique. As another method of patterning the mask layer, there is a nanoimprint technique using a stamp having an uneven shape in the surface thereof. In this case, a resist layer is provided on a mask layer, an uneven pattern is transferred to the resist layer by the nanoimprint technique, and for example, ion milling is performed on the mask layer using the transferred uneven pattern.
Then, a resist is applied onto the mask layer 103 to form a resist layer 104. In this case, since the resist is generally a liquid, a foreign material 111 is likely to permeate into the resist layer, as shown in
Then, the magnetic recording pattern is transferred to the resist layer 104. However, when the resist layer 104 is patterned by the nanoimprint technique, as shown in
Then, as shown in
As such, when the foreign material 111 hinders the process of the magnetic layer 102, a defective sector occurs in the magnetic recording medium. However, it is possible to use the magnetic recording medium including the defective sector in a hard disk drive while avoiding the defective sector. However, as shown in
The invention has been made in order to solve the above-mentioned problems, and an object of the invention is to provide a method of manufacturing a magnetic recording medium, a magnetic recording medium manufactured by the manufacturing method, and a magnetic recording/reproducing apparatus including the magnetic recording medium that are capable of effectively and reliably removing foreign materials on the surface of the magnetic recording medium, preventing a mask layer from remaining on the surface of the magnetic recording medium, and forming the pattern of a magnetic layer with high productivity.
In order to solve the above-mentioned problems, the inventors conducted diligent studies. As a result, the invention was achieved. That is, the invention is as follows.
According to a first aspect of the invention, there is provided a method of manufacturing a magnetic recording medium including a magnetically separated magnetic recording pattern. The method includes: a step of forming at least a magnetic layer on a non-magnetic substrate; a step of forming a mask layer on the magnetic layer; a step of patterning the mask layer to form a mask pattern; a step of forming the magnetic recording pattern on the magnetic layer using the mask pattern; a step of burnishing the surface of the mask pattern with an abrasive; and a step of removing the mask pattern.
According to a second aspect of the invention, in the method of manufacturing a magnetic recording medium according to the first aspect, in the step of burnishing the surface of the mask pattern with the abrasive, a tape including the abrasive may be pressed against the mask pattern to abrade the mask pattern.
According to a third aspect of the invention, in the method of manufacturing a magnetic recording medium according to the first or second aspect, before the surface of the mask pattern is burnished by the abrasive, a lubricant may be applied onto the surface of the mask pattern.
According to a fourth aspect of the invention, in the method of manufacturing a magnetic recording medium according to the third aspect, the lubricant may be applied with a thickness of 1 Å or more.
According to a fifth aspect of the invention, in the method of manufacturing a magnetic recording medium according to any one of the first to fourth aspects, in the process of forming the magnetic recording pattern on the magnetic layer using the mask pattern, a region of the magnetic layer that is not covered with the mask pattern may be exposed to reactive plasma or a reactive ion atmosphere such that the magnetic characteristics of the region of the magnetic layer are changed.
According to a sixth aspect of the invention, there is provided a magnetic recording medium manufactured by the method of manufacturing a magnetic recording medium according to any one of the first to fifth aspects.
According to a seventh aspect of the invention, a magnetic recording/reproducing apparatus includes: the magnetic recording medium according to the sixth aspect; a driving unit that drives the magnetic recording medium in a recording direction; a magnetic head including a recording unit and a reproducing unit; a unit that moves the magnetic head relative to the magnetic recording medium; and a recording/reproduction signal processing unit that inputs signals to the magnetic head and reproduces signals output from the magnetic head.
According to the invention, it is possible to form the pattern of the magnetic layer with high efficiency. That is, it is possible to improve the yield of forming the pattern of the magnetic layer and accurately form the pattern. Therefore, it is possible to provide a method of manufacturing a magnetic recording medium having high electromagnetic conversion characteristics and recording density with high productivity. In addition, according to the invention, it is possible to provide a magnetic recording/reproducing apparatus including a magnetic recording medium having high electromagnetic conversion characteristics and recording density.
Hereinafter, an embodiment of the invention will be described in detail with reference to the accompanying drawings.
<Method of Manufacturing Magnetic Recording Medium>
First, a method of manufacturing a magnetic recording medium according to an embodiment of the invention will be described.
The method of manufacturing the magnetic recording medium according to this embodiment is a method of manufacturing a magnetic recording medium having a magnetically separated magnetic recording pattern and includes a process of forming at least a magnetic layer on a non-magnetic substrate, a process of forming a mask layer on the magnetic layer, a process of patterning the mask layer to form a mask pattern, a process of forming a magnetic recording pattern on the magnetic layer using the mask pattern, a process of burnishing the surface of the mask pattern with an abrasive, and a process of removing the mask pattern.
Next, each of the processes of the method of manufacturing the magnetic recording medium of this embodiment will be described in detail together with the magnetic recording medium and the surface treatment apparatus (burnishing device).
(Magnetic Recording Medium)
The magnetic recording medium according to this embodiment has, for example, a structure in which a soft magnetic layer, an intermediate layer, a magnetic layer having a magnetic pattern formed thereon, and a protective film are formed on the surface of a non-magnetic substrate and a lubricant film is formed on the outer surface. As shown in
(Process of Forming Magnetic Layer)
First, the process of forming at least the magnetic layer on the non-magnetic substrate will be described. The magnetic layer is formed by a general thin film forming method, such as a sputtering method. In this way, as shown in
Non-magnetic Substrate
As the non-magnetic substrate 1, any of the following non-magnetic substrates may be used: an Al alloy substrate made of, for example, an Al—Mg alloy having Al as a main component; a general soda glass substrate; an aluminosilicate-based glass substrate; a crystallized glass substrate; a silicon substrate; a titanium substrate; a ceramic substrate; and substrates made of various kinds of resins. Among the substrates, it is preferable to use an Al alloy substrate, a glass-based substrate, such as a crystallized glass substrate, or a silicon substrate. The average surface roughness (Ra) of the non-magnetic substrate 1 is preferably equal to or less than 1 nm, more preferably equal to or less than 0.5 nm, and most preferably equal to or less than 0.1 nm.
Magnetic Layer
It is preferable that the magnetic layer 2 be made of an alloy including Co as a main component. For example, the magnetic layer 2 may be made of an alloy obtained by adding an oxide to CoCr, CoCrPt, CoCrPtB, CoCrPtB—X, or CoCrPtB—X—Y or a Co-based alloy, such as CoCrPt—O, CoCrPt—SiO2, CoCrPt—Cr2O3, CoCrPt—TiO2, CoCrPt—ZrO2, CoCrPt—Nb2O5, CoCrPt—Ta2O5, CoCrPt—Al2O3, CoCrPt—B2O3, CoCrPt—WO2, or CoCrPt—WO3. In the constituent materials, X indicates, for example, Ru or W and Y indicates, for example, Cu or Mg. It is preferable that the magnetic layer 2 includes 0.5 at % to 6 at % of oxide.
The thickness of the magnetic layer 2 is preferably equal to or more than 3 nm and equal to or less than 20 nm and more preferably equal to or more than 5 nm and equal to or less than 15 nm. The magnetic layer 2 may be formed according to the kind of magnetic alloy used and the laminated structure such that a sufficient head output is obtained. Therefore, the thickness of the magnetic layer 2 needs to be equal to or more than a given value in order to obtain a predetermined output or more during reproduction. In general, various parameters indicating recording/reproduction characteristics deteriorate with an increase in output. Therefore, it is necessary to set the thickness of the magnetic layer 2 to an optimal value.
(Process of Forming Mask Layer)
Next, the process of forming the mask layer on the magnetic layer will be described. The mask layer is formed of a general thin film forming method, such as a sputtering method. In this way, as shown in
Mask Layer
The mask layer 3 may be made of a material including one or more elements selected from the group of Ta, W, Ta nitride, W nitride, Si, SiO2, Ta2O5, Re, Mo, Ti, V, Nb, Sn, Ga, Ge, As, and Ni. The use of the materials makes it possible to improve the shielding of the mask layer 3 with respect to a milling ion 6, which will be described below. In addition, it is possible to improve the formation characteristics of a magnetic recording pattern 2A, which will be described below, by the mask layer 3. The materials facilitate dry etching using a reactive gas. Therefore, the use of the materials makes it possible to reduce the amount of residue and thus reduce the contamination of the surface of the magnetic recording medium 10 in an inert gas radiation process (see
In the method of manufacturing the magnetic recording medium according to this embodiment of the invention, among the above-mentioned materials, the mask layer 3 is preferably made of As, Ge, Sn, or Ga, more preferably Ni, Ti, V, or Nb, and most preferably Mo, Ta, or W. In addition, in general, it is preferable that the thickness of the mask layer 3 be in the range of 1 nm to 20 nm.
(Process of Forming Mask Pattern)
Next, the process of patterning the mask layer to form the mask pattern will be described.
In the process of forming the mask pattern, first, as shown in
Then, a negative pattern (having concave portions corresponding to recording tracks that are formed in the resist layer in order to separate the recording tracks) of the magnetic recording pattern is transferred to the resist layer 4 to form a resist pattern. It is preferable that the resist pattern be formed by a nanoimprint method using a stamp 5, as shown in
It is preferable that the thickness of a concave portion 4b of the resist layer 4 after the resist pattern 4a is formed be in the range of 0 nm to 10 nm. When the thickness of the concave portion 4b of the resist layer 4 is within the above-mentioned range, it is possible to prevent the sagging of the edge of the mask layer 3 in the process of etching the mask layer 3 shown in
The radioactive rays radiated to the resist layer 4 may include a wide range of electromagnetic waves, such as heat rays, visible light, ultraviolet rays, X-rays, and gamma rays. In this embodiment, the radioactive rays are radiated with the stamp 5 being pressed against the resist layer 4, but the invention is not limited thereto. For example, after the pattern is transferred to the resist layer 4 and the stamp 5 is separated from the resist layer 4, the radioactive rays may be radiated. A method of radiating the radioactive rays to the resist layer 4 is not particularly limited, but for example, any of the following methods may be appropriately selected: a method of radiating the radioactive rays from a side opposite to the stamp 5, that is, from the substrate 1; a method of radiating the radioactive rays from the stamp 5 made of a material capable of transmitting the radioactive rays; a method of radiating the radioactive rays from the side surface of the stamp 5; and a method of radiating radioactive rays with high conductivity with respect to a solid, such as heat rays, using heat transferred from the stamp 5 or the substrate 1. As such, the use of the nanoimprint method makes it possible to accurately transfer the shape of the negative pattern formed in the stamp 5 to the resist layer 4, thereby forming the resist pattern 4a.
Resist Layer
The resist layer 4 may be made of a radiation-curable resist material. Examples of the radiation-curable material include a thermosetting resin that is cured by heat rays and an ultraviolet-curable resist resin that is cured by ultraviolet rays. In this embodiment, it is preferable that a novolac-based resin, an acrylic acid ester-based ultraviolet-curable resin, or an alicyclic epoxy-based ultraviolet-curable resin be used as the resist material.
Stamp
It is preferable that a stamp material forming the stamp 5 be glass or resin with high ultraviolet transmittance. In this way, even though ultraviolet rays are radiated with the stamp 5 being pressed against the resist layer 4, the stamp 5 can transmit the ultraviolet rays, and it is possible to effectively radiate the ultraviolet rays to the resist layer 4. In addition, the stamp 5 transmitting the ultraviolet rays may be manufactured by a mother stamper. A mother stamper which may be used is that obtained by forming a fine track pattern in a metal plate using, for example, an electron beam drawing method, and a material forming the mother stamper needs to have rigidity and durability resistant to a process. For example, the mother stamper may be made of Ni. However, the mother stamper may be any material as long as the material is suitable for the above-mentioned purpose. Servo signal patterns, such as a burst pattern, a gray code pattern, and a preamble pattern, in addition to general tracks for recording data may be formed in the mother stamper. In addition, the negative pattern of the magnetic recording pattern may be formed in the stamp 5.
Then, as shown in
(Process of Forming Magnetic Recording Pattern)
Next, the process of forming the magnetic recording pattern in the magnetic layer using the mask pattern will be described. In the process of forming the magnetic recording pattern, first, it is preferable that a portion of the outer layer of the magnetic layer 2 be removed by, for example, ion milling. When a portion of the outer layer of the magnetic layer 2 is removed, it is preferable that the magnetic layer 2 be exposed to reactive plasma or a reactive ion atmosphere to modify the magnetic characteristics. In this case, it is possible to improve the contrast of the magnetic recording pattern 2A, as compared to the structure in which a portion of the magnetic layer 2 is not removed. In addition, it is possible to improve the S/N ratio of the magnetic recording medium 10 shown in
Specifically, as shown in
Then, the region of the magnetic layer 2 that is not covered with the mask pattern 3a is exposed to reactive plasma or a reactive ion atmosphere to change the magnetic characteristics of the region of the magnetic layer 2. Specifically, for example, the formed magnetic layer 2 is exposed to reactive plasma or reactive ions to change (reduce the magnetic characteristics) the magnetic characteristics of the region that magnetically separates a magnetic recording track from a servo signal pattern portion in the magnetic layer 2. A method of exposing the formed magnetic layer 2 to reactive plasma or reactive ions to make the magnetic layer 2 amorphous may be given as an example of the method of modifying the region that magnetically separates the magnetic recording track from the servo signal pattern portion. In addition, the change in the magnetic characteristics of the magnetic layer 2 in this embodiment includes a change in the crystal structure of the magnetic layer.
In this embodiment, making the magnetic layer 2 amorphous means changing the atomic arrangement of the magnetic layer 2 into an irregular atomic arrangement without a long-distance order, specifically, the random arrangement of fine crystal grains with a diameter of less than 2 nm. When the atomic arrangement (amorphous state) is checked by an analysis method, a peak waveform indicating a crystal plane is not found in X-ray diffraction or electron beam diffraction, but only a halo waveform is found.
Inductively coupled plasma (ICP) or reactive ion plasma (RIE) may be given as an example of the reactive plasma. For example, the reactive ions may include reactive ions in the inductively coupled plasma or the reactive ion plasma.
The inductively coupled plasma is high-temperature plasma obtained by applying a high voltage to air to ionize the air into plasma and generating Joule heat in the plasma due to an eddy current caused by a high-frequency variable magnetic field. The inductively coupled plasma has high electron density and can change the magnetic characteristics in the magnetic layer 2 having a large area with high efficiency, as compared to the related art that manufactures discrete track media using ion beams. The reactive ion plasma is highly reactive plasma obtained by adding a reactive gas, such as O2, SF6, CHF3, CF4, or CCl4 to plasma. In this embodiment, since the plasma is used as reactive plasma, it is possible to change the magnetic characteristics of the magnetic layer 2 with high efficiency.
In this embodiment, it is preferable that the reactive plasma or the reactive ions include halogen ions. It is preferable that the halogen ions be formed by introducing one or more kinds of halogenated gases selected from the group of CF4, SF6, CHF3, CCl4, and KBr. In this way, it is possible to improve the reactivity between the magnetic layer 2 and plasma and sharpen the magnetic layer pattern. The detailed reason is not clear, but it is conceivable that foreign materials adhered to the surface of the magnetic layer 2 are etched by halogen atoms in the reactive plasma and the surface of the magnetic layer 2 is cleaned by etching, resulting in an increase in the reaction of the magnetic layer 2. In addition, it is considered that the cleaned surface of the magnetic layer 2 reacts with the halogen atoms with high efficiency.
In this embodiment, the formed magnetic layer 2 is exposed to the reactive plasma in order to modify the magnetic layer 2. However, it is preferable that the magnetic layer 2 be modified by the reaction between the magnetic metal forming the magnetic layer 2 and atoms or ions in the reactive plasma. The reaction includes a variation in the crystal structure of the magnetic metal, a variation in the composition of the magnetic metal, oxidation of the magnetic metal, nitridation of the magnetic metal, and silicidation of the magnetic metal due to the infiltration of atoms in the reactive plasma into the magnetic metal. In this way, the magnetic recording pattern 2A is formed.
In this embodiment, it is preferable to perform the ion milling process as described above before the region of the magnetic layer 2 that is not covered with the mask pattern 3a is exposed to the reactive plasma or the reactive ion atmosphere. However, the ion milling process may not be performed. In this case, the region of the magnetic layer 2 that is not covered with the mask pattern 3a is exposed to the reactive plasma or the reactive ions.
In this embodiment, the magnetic characteristics of the magnetic layer 2 are partially changed to form the magnetic recording pattern 2A. However, a portion of the magnetic layer 2 may be physically removed without using the above-mentioned process and the removed portion may be filled with a non-magnetic material to form the magnetic recording pattern 2A in the magnetic layer 2.
Magnetic Recording Pattern
In this embodiment, the magnetically separated magnetic recording pattern 2A means that the magnetic layer 2 is separated by a non-magnetic region 21 in a top view of the magnetic recording medium, as shown in
As described above, in this embodiment, it is preferable that the magnetically separated magnetic recording pattern 2A be applied to a so-called discrete magnetic recording medium, which is a magnetic recording track and a servo signal pattern, in order to simplify the manufacturing process. In this embodiment, the modification of the magnetic layer 2 for forming the magnetic recording pattern 2A includes partially changing, for example, the coercivity and the remnant magnetization of the magnetic layer in addition to making the magnetic layer non-magnetic, in order to pattern the magnetic layer. The change in the coercivity and the remnant magnetization of the magnetic layer includes, for example, a reduction in the coercivity and a reduction in the remnant magnetization.
(Burnishing Process)
Next, the process of burnishing the surface of the mask pattern with an abrasive will be described.
In the burnishing process, a surface treatment apparatus 30 shown in
Surface Treatment Apparatus
As shown in
The base of the polishing tape 32 is made of a resin, such as PET. For example, alumina, silicon carbide, or diamond is used as abrasive grains adhered to one surface of the polishing tape 32.
The pad 33 is a member having a function of pressing the polishing tape 32 to contact the magnetic recording medium 8 and is made of a resin or fabric cloth. The member may be a rubber roller (which is also referred to as a backing rubber roller). In the example shown in
In this embodiment, the surface treatment apparatus 30 is used to burnish the surface of the mask pattern 3a or the resist pattern 4a with an abrasive. Therefore, it is possible to effectively remove the foreign material remaining on the mask layer 3 or the foreign material which has worked its way into the mask layer 3 without damaging the patterned magnetic layer 2. In this embodiment, before the burnishing process, when the mask pattern 3a or the resist pattern 4a remains, it is preferable that a lubricant be applied onto the surface of the resist pattern 4a. When the lubricant is applied to, for example, the surface of the mask pattern 3a, it is possible to further reduce the scratching of the magnetic layer 2 in the burnishing process and stably remove the foreign material from, for example, the surface of the mask layer 3 (mask pattern 3a). For example, a fluorine-based lubricant, a hydrocarbon-based lubricant, and a mixture thereof may be used as the lubricant according to this embodiment. It is preferable that the lubricant be applied with an average film thickness of 1 Å or more. When the applied lubricant is thin, the lubricant is not applied onto the surface as a continuous film. The lubricant applied according to the invention is effective even though it is applied onto the surface in an island shape in which the lubricant is not a continuous film. In this case, the thickness of the lubricant is represented by an average film thickness.
In this embodiment, as shown in
(Process of Removing Mask Pattern)
Next, the process of removing the mask pattern will be described. In the process of removing the mask pattern, as shown in
(Process of Radiating Inert Gas)
Next, in this embodiment, as shown in
Inert Gas
It is preferable that one or more gases selected from the group of Ar, He, and Xe be used as the inert gas. This is because these elements are stable and can effectively prevent the migration of the magnetic particles. It is preferable that any one selected from the group of a method using an ion gun, ICP, and RIE be used as the method of emitting the inert gas. In particular, it is preferable to use ICP and RIE since a large amount of inert gas is emitted in ICP and RIE. ICP and RIE have been described above.
(Process of Forming Protective Layer)
Finally, as shown in
Protective Film
The protective layer 9 may be made of a carbon material, such as carbon (C), hydrogenated carbon (HxC), nitrogenated carbon (CN), amorphous carbon, or silicon carbide (SiC), or a material that is generally used for a protective layer, such as SiO2, Zr2O3, or TiN. The protective layer 9 may be a laminate of two or more layers. The thickness of the protective layer 9 needs to be less than 10 nm. If the thickness of the protective layer 9 is more than 10 nm, the distance between the head and the magnetic layer is increased. As a result, the intensity of input/output signals is insufficient, which is not preferable. It is preferable to form a lubrication layer on the protective layer 9. A fluorine-based lubricant, a hydrocarbon-based lubricant, or a mixture thereof is given as an example of the lubricant used for the lubrication layer. It is preferable that the lubrication layer be generally formed with a thickness of 1 nm to 4 nm.
In this way, the magnetic recording medium 10 is manufactured as shown in
As described above, in the method of manufacturing the magnetic recording medium according to this embodiment, after the magnetic layer 2 is patterned using the mask pattern 3a, the surface of the mask pattern 3a is burnished by an abrasive. Therefore, it is possible to remove the foreign material remaining on the surface of the magnetic recording medium. Thereafter, the mask pattern 3a is removed and the foreign material is effectively and reliably removed. As a result, the foreign material does not remain on the surface of the magnetic recording medium, or the mask layer in a shade portion of the foreign material does not remain. Therefore, the use of the above-mentioned processes makes it possible to form the pattern of the magnetic layer with high efficiency and high productivity.
According to the manufacturing method of this embodiment, it is possible to provide a magnetic recording medium 10 with high surface recording density without any writing blur during magnetic recording by reducing the magnetic characteristics of the region between the magnetic tracks (the region separating the magnetic layers), for example, reducing coercivity and remnant magnetization to the utmost limit.
As such, according to the method of manufacturing the magnetic recording medium of this embodiment, it is possible to provide the magnetic recording medium 10 and a method of manufacturing the magnetic recording medium 10 capable of effectively and reliably removing the foreign material on the surface of the magnetic recording medium 10, preventing the mask layer 3 from remaining on the magnetic recording medium 10, and forming the pattern of the magnetic layer 2 with high productivity.
<Magnetic Recording/Reproducing Apparatus>
Next, a magnetic recording/reproducing apparatus according to an embodiment of the invention will be described.
As shown in
In addition, the reproducing unit of the magnetic head 27 is a GMR head or a TMR head. Therefore, it is possible to obtain sufficient signal intensity even at high recording density and thus achieve the magnetic recording/reproducing apparatus 20 with high recording density. When the flying height of the magnetic head 27 is in the range of 0.005 μm to 0.020 μm which is less than that in the related art, the output is improved and a high SNR is obtained. Therefore, it is possible to provide the magnetic recording/reproducing apparatus 20 with high capacity and high reliability. When a signal processing circuit using a maximum-likelihood decoding method is incorporated, it is possible to further improve recording density. For example, a sufficient SNR is obtained even when recording and reproduction are performed at a track density of 100 k tracks/inch or more, a linear recording density of 1000 kbits/inch or more, and a recording density of 100 Gbits per square inch or more.
As described above, according to the magnetic recording/reproducing apparatus 20 of this embodiment, it is possible to provide the magnetic recording/reproducing apparatus 20 including the magnetic recording medium 10 with good electromagnetic conversion characteristics and high recording density.
Next, the invention will be described in detail with reference to examples, but the invention is not limited to the examples.
Magnetic recording media according to Examples 1 to 9 and Comparative Examples 1 and 2 of the invention were manufactured as follows. First, a vacuum chamber with a glass substrate for an HD set therein was evacuated to 1.0×10−5 Pa or less. The glass substrate used in the examples was made of crystallized glass including Li2Si2O5, Al2O3—K2O, Al2O3—K2O, MgO—P2O5, Sb2O3—ZnO as a constituent component. The glass substrate had an outside diameter of 65 mm, an inside diameter of 20 mm and an average surface roughness (Ra) of 2 Å.
Then, a soft magnetic layer made of 65Fe-30Co-5B, an intermediate layer made of Ru, and a vertically-aligned magnetic layer with a granular structure were formed on the glass substrate using a DC sputtering method. The magnetic layer had an alloy composition of Co-10Cr-20Pt-8(SiO2) (mole ratio) and had a thickness of 150 Å. The FeCoB soft magnetic layer had a thickness of 600 Å and the Ru intermediate layer had a thickness of 100 Å. Then, a mask layer was formed on the magnetic layer by a sputtering method. The mask layer was made of Ta with a thickness of 60 nm. A resist was coated on the mask layer by a spin coating method to form a resist layer. The resist was made of a novolac resin which was an ultraviolet-curable resin. The thickness of the resist layer was 100 nm.
Then, a stamp which was made of glass and had the negative pattern of the magnetic recording pattern was pressed against the resist layer at a pressure of 1 MPa (about 8.8 kgf/cm2). In this case, the stamp made of glass with an ultraviolet transmittance of 95% or more was used. With the stamp being pressed against the resist layer, ultraviolet rays with a wavelength of 250 nm were radiated for 10 seconds from the upper side of the stamp to cure the resist. The stamp was then separated from the resist layer to transfer the magnetic recording pattern to the resist layer, thereby forming a resist pattern. In the resist pattern, a convex portion of the resist had a circular shape with a width of 120 nm, and a concave portion of the resist had a circular shape with a width of 60 nm. The resist layer had a thickness of 80 nm, and the concave portion of the resist layer had a thickness of about 5 nm. The angle of the concave portion of the resist layer with respect to the substrate surface was substantially 90 degrees.
The bottom of the concave portion of the resist pattern and a Ta layer, which was the mask layer, were removed by dry etching to form a mask pattern. The dry etching was performed on the resist layer under the etching conditions of an O2 gas flow rate of 40 sccm, a pressure of 0.3 Pa, a high-frequency plasma power of 300 W, a DC bias of 30 W, and an etching time of 10 seconds. The dry etching was performed on the Ta layer, which was the mask layer, under the etching conditions of a CF4 gas flow rate of 50 sccm, a pressure of 0.6 Pa, a high-frequency plasma power of 500 W, a DC bias of 60 W, and an etching time of 30 seconds.
Then, the surface of a region of the magnetic layer that was not covered with the mask pattern was removed by ion milling. Ar ions were used in the ion milling. The ion milling was performed under the conditions of a high-frequency discharge power of 800 W, an acceleration voltage of 500 V, a pressure of 0.014 Pa, an Ar flow rate of 5 sccm, a process time of 40 seconds, and a current density of 0.4 mA/cm2. Then, the surface subjected to the ion milling was exposed to a reactive plasma atmosphere to change the magnetic characteristics of the region of the magnetic layer that is not covered with the mask pattern. The reactive plasma process was performed using an inductively coupled plasma apparatus NE550 manufactured by ULVAC, Inc. In the reactive plasma, the flow rate of CF4 gas was 90 cc/min. In addition, the reactive plasma process conditions were a plasma generating input power of 200 W, an internal pressure of 0.5 Pa, and a process time of 300 seconds. Then, the gas was changed from CF4 to O2, and the magnetic layer was processed for 50 seconds.
Then, in Examples 1 to 5, 8, and 9 and Comparative Example 1, a lubricant was applied onto the surface of the substrate. Z-dol 2000, which is a fluorine-based lubricant, was used as the lubricant. In addition, the thickness of the lubrication film was in the range of 5 Å to 20 Å. The lubricant application conditions are shown in Table 1.
In Examples 1 to 9, the surface of the mask layer (mask pattern) and the surface of the resist layer (resist pattern) were burnished by a polishing tape. Model number DQ3 using Al2O3 with a particle diameter of 0.3 μm as an abrasive, which was manufactured by Sumitomo Ltd., was used as the polishing tape. The burnishing conditions of Examples 1 to 9 are shown in Table 1.
In Examples 1 to 9 and Comparative Examples 1 and 2, the resist layer (resist pattern) and the mask layer (mask pattern) were removed by dry etching. The dry etching was performed under the process conditions of a SF6 gas flow rate of 100 sccm, a pressure of 2.0 Pa, a high-frequency plasma power of 400 W, and a process time of 300 seconds. Then, inert gas plasma was emitted to the magnetic layer. The inert gas plasma was emitted under the conditions of an Ar gas (inert gas) flow rate of 5 sccm, a pressure of 0.014 Pa, an acceleration voltage of 300 V, a current density of 0.4 mA/cm2, and a process time of 15 seconds. Finally, a carbon (DLC: diamond-like carbon) protective film was formed with a thickness of 4 nm on the surface of the magnetic layer by a CVD method. Then, as a lubricant, Z-dol 2000 was applied with a thickness of 20 Å. In this way, the magnetic recording media according to Examples 1 to 7 and Comparative Examples 1 and 2 were manufactured.
A glide test was performed on the magnetic recording media according to Examples 1 to 9 and Comparative Examples 1 and 2. In the glide test, a head slider with a shock sensor was levitated at a height of 6 nm from the surface of the magnetic recording medium to scan the surface of the magnetic recording medium surface, and the number of impact objects detected by the sensor was counted. The results are shown in Table 1.
As shown in Table 1, in Comparative Examples 1 and 2 in which the burnishing process was not performed before the dry etching process, which was the process of removing the mask layer, the number of impact objects detected was 500 or more regardless of whether a lubricant was applied.
In contrast, in Examples 1 to 9 in which the burnishing process was performed before the dry etching process, the number of impact objects on the surface of the magnetic recording medium was 112 or less. In Examples 1 to 5, 8, and 9 in which the lubricant was applied before the burnishing process, the number of impact objects was 12 or less.
As such, according to the method of manufacturing the magnetic recording medium of the invention, it was possible to effectively remove the foreign material on the surface of the magnetic recording medium and prevent the mask layer from remaining on the surface of the magnetic recording medium.
According to the invention, it is possible to provide a magnetic recording medium with high recording density and high productivity, and thus improve the industrial applicability thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-047630 | Feb 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/052505 | 2/16/2009 | WO | 00 | 8/23/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/107496 | 9/3/2009 | WO | A |
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