JP5592646B2 - Magnetic recording medium and method for manufacturing the same - Google Patents

Description

  The present invention is a magnetic recording medium mounted on an HDD (hard disk drive) or the like, and a magnetic recording area for recording and reproducing magnetic information and a non-recording area for magnetically separating the magnetic recording area The present invention relates to a magnetic recording medium having a magnetic recording layer arranged in the in-plane direction of the substrate and provided with a data area and a servo area, and a method for manufacturing the same, and more particularly to a magnetic recording medium with improved servo signal output.

  With the increase in information processing capacity and downsizing of equipment, there is an increasing demand for high surface recording density and downsizing of magnetic disks used in HDDs. As one means, a perpendicular magnetic recording system has been proposed and put into practical use. Compared with the conventional in-plane recording method, the perpendicular magnetic recording method suppresses a so-called thermal fluctuation phenomenon (a phenomenon in which the thermal stability of the recording signal is lost due to the superparamagnetic phenomenon and the recording signal disappears). Therefore, it is suitable for increasing the recording density.

  In order to further improve the surface recording density, it is required to improve the linear recording density and the track density to narrow the 1-bit recording width. As a means for this, DTM (discrete track media) that patterns the magnetic track (recording area) for recording and the nonmagnetic track (non-recording area) in parallel to prevent interference between adjacent recording areas, or an arbitrary pattern can be used. There are magnetic recording media such as BPM (bit pattern media) that are artificially arranged regularly (hereinafter also referred to as patterned media).

  As a method of manufacturing such a magnetic recording medium, after forming a magnetic recording layer on a nonmagnetic substrate, the magnetic recording layer is partially irradiated with ions, and the ion irradiated region is softened or made nonmagnetic. Techniques for forming a magnetically separated pattern by making it amorphous (for example, Patent Documents 1, 2, and 3) have been proposed.

  The manufacturing method is described in Patent Document 2 and Patent Document 3, for example. That is, a magnetic recording layer is formed on a nonmagnetic substrate, a resist is formed thereon, and a desired uneven pattern is formed. Thereafter, ions are irradiated from the surface. Ions are shielded by the convex portions of the resist, but the resist concave portions have a thin resist film thickness, so that the ions reach the magnetic recording layer below the resist, weakening the magnetic property of the magnetic material and becoming non-recording regions. Thereafter, the resist is peeled to obtain a patterned medium in which a magnetic recording area and a non-recording area as recording portions are arranged in the plane. That is, this resist plays a role of a mask in ion irradiation, and a layer formed by this resist is called a resist mask layer.

  The method of weakening the magnetism of the irradiated part by ion irradiation to make it a non-recording area (hereinafter also referred to as ion irradiation method) has simple process control and is advantageous in terms of cost. The benefits are great.

  Incidentally, a servo pattern as shown in FIG. 1 is written on a magnetic recording medium used in the HDD. The magnetic head of the HDD is positioned on the data track by servo control according to the position information by the servo pattern magnetically recorded on the magnetic recording medium.

  Conventionally, the servo pattern is written using an STW (servo track writer) after manufacturing the magnetic recording medium.

  On the other hand, in the patterned medium, it is possible to process and form a highly accurate servo pattern simultaneously with the process of magnetically separating the data tracks. Therefore, unlike the prior art, it is possible to form a highly accurate servo pattern at low cost without requiring a servo pattern writing operation by STW after the manufacture of the magnetic recording medium.

  FIG. 2 schematically shows the reproduction signal output of the preamble portion of the servo pattern. In the STW, since the servo signal is magnetically written, the magnetization direction of the servo pattern is upward (+1) or downward (−1) as shown in FIG.

  On the other hand, in the case of a patterned medium, the servo pattern is physically formed and the magnetism of the groove is lost. Therefore, even in an ideal state, the magnetization directions are the signal part (+1) and the groove part (0) as shown in FIG. Since the magnetic head outputs a larger signal as the change in the magnetization direction is larger, the servo signal output of the patterned medium is ½ that of the medium on which the servo pattern is written by the STW.

  In addition, when a high TPI (Track Per Inch) is performed on a patterned medium, the interval (track pitch) of the magnetic recording area is reduced, and at the same time, the size and interval of the servo pattern are reduced. That is, the servo signal output tends to decrease. Generally, when the servo signal output decreases, the positioning accuracy decreases.

  In particular, in a magnetic recording medium manufactured in an ion irradiation method in which a non-recording region is provided by ion irradiation and magnetically separated, as shown in FIG. 2C, the magnetization of the non-recording region into which ions are implanted is completely zero. Since the magnetic layer is physically removed by an etching method or the like and the magnetic recording medium in which the magnetic property of the non-recording area is completely eliminated is generated, there is a problem that the servo signal output is further reduced.

  Patent Document 4 discloses a magnetic recording medium manufactured by an etching method and improved in magnetic pattern separation performance in a magnetic recording area and excellent in high recording density characteristics.

JP 2008-226428 A JP 2008-77788 A JP 2008-135092 A JP 2009-170040 A

  As the recording density increases, the interval between magnetic recording areas becomes narrower, so the positioning accuracy requirement by the servo pattern is higher than the conventional one. Servo pattern output has decreased and positioning accuracy has deteriorated. Therefore, in order to improve the positioning accuracy by the servo pattern in the magnetic recording medium, it is necessary to positively increase the output of the servo pattern. In particular, the magnetic recording medium is manufactured by an ion irradiation method having a great merit compared to other methods. Improving the output of servo signals in magnetic recording media is a very important issue.

  An object of the present invention is to improve the output of a servo signal in a magnetic recording medium manufactured by an ion irradiation method.

  As a result of intensive studies to solve the above problems, the inventors of the present invention reduced the height of the non-recording area compared to the magnetic recording area in the magnetic recording medium manufactured by the ion irradiation method, If the distance is increased, the effect of spacing loss reduces the influence on the magnetic head even if the magnetization remains in the groove. As a result, the magnetization of the groove approaches (0) and the servo signal output increases. I found out that

  The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) A magnetic recording area for recording / reproducing magnetic information and a non-recording area for magnetically separating the magnetic recording area on at least one surface of the substrate in the in-plane direction of the substrate A magnetic recording medium having regularly arranged magnetic recording layers,
The non-recording area has a magnetic permeability of 2H / m or more and 100H / m or less,
Further, the surface of the non-recording area has a recess with respect to the surface of the magnetic recording area, and the depth of the recess is not less than 0.5 nm and not more than 2.0 nm.

This is because, on at least one surface of the substrate, a magnetic recording region for recording and reproducing magnetic information and a non-recording region for magnetically separating the magnetic recording region are arranged in the in-plane direction of the substrate. A magnetic recording medium having a magnetic recording layer that is regularly arranged and divided into a data area and a servo area in a plane,
The non-recording area has semi-hard magnetism,
Furthermore, the non-recording area may be a magnetic recording medium in which a recess having a depth of 1.0 nm or more and 5.0 nm or less is formed on the surface of the magnetic recording area.

  Here, the non-recording area may have a relative magnetic permeability of 2 or more and 100 or less.

(2) A method of manufacturing the magnetic recording medium of (1),
A release layer forming step of forming a release layer mainly composed of carbon on the magnetic recording layer;
A resist mask layer forming step of forming a resist mask layer made of SOG (spin-on-glass) on the release layer after the release layer forming step;
After the resist mask layer film forming step, a patterning step of partially changing the thickness of the resist mask layer to form convex portions and concave portions of a predetermined pattern;
After the patterning step, a bottoming step of removing the resist mask layer by dry etching until the release layer is exposed in the concave portion;
After the bottoming step, an etching step for removing a part of the magnetic recording layer in the recess,
An ion irradiation step of irradiating ions from above the resist mask layer after the etching step to form the non-recording region;
Removing the resist mask layer with an alkaline solvent after the ion irradiation step, and a resist mask layer removing step;
After the resist mask layer removing step, the peeling layer is removed to expose the surface of the magnetic recording layer by removing the peeling layer;
A method of manufacturing a magnetic recording medium, comprising a protective layer forming step of forming a protective layer on the magnetic recording layer after the release layer removing step.

(3) A method of manufacturing the magnetic recording medium of (1),
A protective layer forming step of forming a protective layer mainly composed of carbon on the magnetic recording layer;
A resist mask layer forming step of forming a resist mask layer made of SOG (spin-on-glass) on the protective layer after the protective layer forming step;
After the resist mask layer forming step, the resist mask layer has a predetermined pattern of a convex portion having a thickness that does not transmit ions when irradiated with the ions, and a thickness that is thin enough to transmit ions. A patterning step for forming a recess;
An ion irradiation step of irradiating ions from above the resist mask layer after the patterning step to form the non-recording region;
After the ion irradiation step, the resist mask layer is removed with an alkaline solvent, and the non-recording area is formed so as to form a recess having a depth of 1.0 nm or more and 5.0 nm or less with respect to the surface of the magnetic recording area. A method of manufacturing a magnetic recording medium, comprising a step of forming a recess to dissolve a recording area.

(4) The ion irradiation in the ion irradiation step includes B, P, Si, F, C, In, Bi, Kr, Ar, Xe, W, As, Ge, Mo, Sn, N ₂ , O ₂ , Ne, Irradiation with one or more non-magnetic ions selected from He and H ₂ at an irradiation energy of 1 keV to 50 keV and a dose of 1 × 10 ¹⁵ atoms / cm ² to 1 × 10 ¹⁷ atoms / cm ² The method for producing a magnetic recording medium according to (2) or (3), wherein:

  (5) The magnetic recording medium according to any one of (2) to (4), wherein in the patterning step, a convex portion and a concave portion having a predetermined pattern are formed on the resist mask layer by a nanoimprint method. Method.

  (6) The method for manufacturing a magnetic recording medium according to any one of (2) to (5), further comprising a lubricating layer forming step of forming a lubricating layer on the protective layer.

  According to the present invention, the servo signal output can be increased in a magnetic recording medium in which a servo pattern is formed in advance by ion irradiation.

It is a figure which shows the outline of a servo track. (A) It is a figure which shows the servo signal output written by STW. (B) It is a figure which shows the servo signal output of an ideal patterned medium. (C) It is a figure which shows the servo signal output of the patterned medium manufactured by the ion irradiation system by a prior art. The figure which shows the outline of the surface of the magnetic-recording layer of the magnetic recording medium of this invention. The figure which shows the outline of the manufacturing method of the magnetic-recording medium based on this invention. It is a figure which shows the outline of the surface change in the recessed part formation process in the other manufacturing method of the magnetic-recording medium based on this invention. It is a figure which shows the result of having measured the magnetic recording medium manufactured with the method of this invention with the magnetic force microscope. It is a figure which shows the relationship between the depth of the recessed part of the surface of a non-recording area | region, and a servo signal output in Example 1 of this invention. It is a figure which shows the relationship between the depth of the recessed part of the surface of a non-recording area | region, and a servo signal output in Example 2 of this invention.

  Hereinafter, the structure of the magnetic recording medium of the present invention will be described with reference to FIG.

  FIG. 3 is a diagram showing the concept of the cross-sectional structure of the magnetic recording medium of the present invention. The magnetic recording medium of the present invention is configured by stacking each layer in the order of a soft magnetic layer 32, an intermediate layer 33, a magnetic recording layer 34, and a protective layer 36 on a disk-shaped glass substrate 31. A lubricating layer may be further provided on the protective layer.

  A non-recording area 35 having semi-hard magnetism is formed in the magnetic recording layer by ion irradiation, and the magnetic recording layer is magnetically separated into a magnetic recording area and a non-recording area. The non-recording area 35 may have a relative permeability in the range of 2-100.

  Each layer below the magnetic recording layer 34 is subdivided into several layers. In the present invention, the subdivided layer structure is not particularly limited. Each of these layers is formed by depositing a material necessary for each layer by a CVD method, a PVD method, a magnetron sputtering method, or the like.

  Usually, glass or aluminum is used as a non-magnetic substrate material. The material for the glass substrate is not particularly limited. Examples thereof include glass ceramics such as aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, and crystallized glass. These glass and aluminum are processed into a disk shape and subjected to surface polishing or the like, and the glass is subjected to treatment such as chemical strengthening and used as a non-magnetic substrate.

  The soft magnetic layer 32 is a layer for temporarily forming a magnetic circuit during recording in order to allow magnetic flux to pass through the magnetic recording layer in the perpendicular direction in the perpendicular magnetic recording method. As the material of the magnetic layer, for example, a cobalt-based alloy such as CoTaZr, or a Co—Fe-based alloy such as CoFeTaZr or CoCrFeB is used.

  The intermediate layer 33 is a layer that blocks material interference between the lower soft magnetic layer 32 and the upper magnetic recording layer 34. Further, it has a so-called base function for controlling the grain size, grain size dispersion, and crystal orientation of the upper magnetic recording layer 34. If the intermediate layer is further divided into an upper layer and a lower layer, it is preferable for simultaneously controlling the crystal orientation and the grain size of the magnetic recording layer. For example, for the lower layer of the intermediate layer, a simple metal such as Ni, Cu, Pt, Pd, Zr, Hf, or Nb, or an alloy obtained by adding W, Cr, V, Ta, Mo or the like to them can be used. Further, for controlling the crystal orientation of the magnetic recording layer 34, for example, an hcp or fcc crystal material such as Ru, Re, Pd, or Pt, or an alloy such as RuCr or RuCo can be used for the upper layer of the intermediate layer. . In particular, Ru is effective in improving the crystal orientation of Co because it has a lattice constant close to that of Co, which is the main component of the magnetic grains of the magnetic recording layer 34, and has the same crystal structure.

  The magnetic recording layer 34 becomes a part for recording information which is a main function of the magnetic recording medium. The magnetic recording layer is composed of at least two layers. The first magnetic recording layer has a granular structure in which magnetic grains of a ferromagnetic material having a columnar structure are surrounded by a grain boundary made of a nonmagnetic material. As a material of the granular structure magnetic recording layer, for example, a composite material obtained by adding an oxide or carbon to a Co-based alloy or Fe-based alloy is used. A columnar granular structure can be suitably obtained by depositing this material on the intermediate layer and epitaxially growing it.

  Further, as the second magnetic recording layer, a second magnetic recording layer having magnetically continuous properties is provided on the columnar granular structure film. The second magnetic recording layer is made of, for example, a Co-based alloy.

  In the magnetic recording medium of the present invention, the non-recording area 35 is regularly arranged in the in-plane direction of the substrate in the magnetic recording layer 34, so that the magnetic recording area and the non-recording area are separated. Not only the data area but also the servo area is formed in the same manner. The medium surface above the non-recording area 35 forms a recess with respect to the medium surface above the magnetic recording area.

  The protective layer 36 can be formed by forming a thin film mainly made of carbon, such as DLC (diamond-like carbon), by the CVD method. The protective layer 36 has a role of protecting the magnetic recording layer 34 from the impact of the magnetic head and increasing the reliability by suppressing the corrosion of the magnetic recording layer. In general, carbon formed by the CVD method is denser and has a higher film hardness than that formed by the sputtering method, so that the reliability can be further improved.

  The lubricating layer is usually a finished product of a magnetic recording medium and is formed on the protective layer 36, and is for preventing damage or loss of the protective layer 36 when the magnetic head comes into contact. The lubricating layer can be formed of PFPE (perfluoropolyether) by dip coating.

  Next, a method for manufacturing a magnetic recording medium according to the present invention will be described with reference to FIG. In the manufacturing process according to the present invention, an intermediate body of a magnetic recording medium in which a soft magnetic layer, an intermediate layer, and a magnetic recording layer are laminated on a substrate, a release layer forming process, a resist mask layer forming process, a patterning process, an ion The completed magnetic recording medium is obtained by passing the irradiation process, resist mask layer removing process, release layer removing process, and protective layer film forming process in this order. FIG. 4 shows a layer above the magnetic recording layer.

  FIG. 4A shows a release layer film forming process. The release layer film forming step is a step of forming the release layer 37 on the intermediate layer laminated up to the magnetic recording layer, and is a method of forming a carbon film by the CVD method. The film thickness is about several nm, and a uniform film forming technique is required.

  FIG. 4B shows a resist mask layer forming process. The resist mask layer forming step is a step of forming a resist mask layer 41 for subsequent patterning on the peeling layer 37. As the resist, a resist suitable for the subsequent patterning method is selected. Here, a case where patterning is performed by the nanoimprint method will be described as an example. Of course, the patterning method is not limited to the nanoimprint method, and a lithography method or the like used in the semiconductor manufacturing process can also be used.

  The room temperature nanoimprint resist is suitable for pressing a stamper, taking a mold as it is, and releasing the mold. It is a very simple process because it simply presses the stamper. However, since the pressing pressure of the stamper is high, it is necessary to develop a device for that purpose. However, it is easy to handle and the equipment configuration is not complicated.

  A room temperature nanoimprint resist is a liquid material in which a silicon (Si) compound and additives (diffusion impurities, glassy forming agent, organic binder, etc.) are dissolved in an organic solvent (alcohol, ester, ketone, etc.). There are glass, hydrogenated silsesquioxane polymer (HSQ), hydrogenated alkylsiloxane polymer (HOSP), alkylsiloxane polymer, alkylsilsesquioxane polymer (MSQ), etc., which are called SOG (spin-on-glass) ing. In the resist mask layer forming step, SOG is applied on the release layer by spin coating to form a film. The thickness is preferably about 50 to 60 nm although it depends on patterning. The resist mask layer has a role of resist and a role of mask in the ion irradiation process.

  In the present invention, a room temperature nanoimprint resist is used as a nanoimprint resist for nanoimprint.

  FIG. 4C shows a patterning process. As shown in FIG. 4C, the pattern is transferred (imprinted) by pressing the stamper 42. The stamper 42 has a concavo-convex pattern corresponding to each pattern of a track portion as a recording region to be transferred and a non-track portion which is a non-recording region, that is, an ion transmission region and an ion shielding (mask) region. At this time, if a release agent is applied to the pattern surface of the stamper, the stamper can be easily released later.

  At the time of ion irradiation, a portion through which ions are transmitted becomes a concave portion of the resist mask layer, and a portion that blocks ions becomes a convex portion of the resist mask layer. That is, the unevenness of the stamper 52 is reversed.

  In other words, the thickness of the convex portion of the resist mask layer has at least a thickness that does not transmit ions when ion irradiation is performed, and the thickness of the concave portion is sufficiently thin to allow ions to pass therethrough. For example, the thickness of the concave portion of the resist mask layer is desirably 30 nm or less. Moreover, although the thickness of the convex part of a resist mask layer is based on ion irradiation energy, if it is the thickness which remains 50 nm or more after ion irradiation, since there is no permeation | transmission of ion and sufficient mask effect is obtained, it is preferable.

  After the magnetic recording track pattern is transferred by the stamper 42, the stamper is released (released) from the resist mask layer 41, thereby forming a desired uneven pattern in the resist mask layer 41.

  FIG. 4D shows a bottoming process and an etching process. First, following the patterning step, the resist mask layer and the release layer in the pattern recess are etched to expose the magnetic film. The resist mask layer and the release layer can be removed by dry etching such as RIE (Reactive Ion Etching).

  Further, following the bottoming process, a part of the magnetic recording layer in the pattern recess is etched. The magnetic recording layer can be removed by a dry process such as IBE (Ion Beam Etching) or RIE.

  FIG. 4E shows an ion irradiation process. The intermediate whose surface is covered with the resist mask layer is irradiated with ions 43, and ions are implanted into the medium. At this time, the convex portion of the resist mask layer 41 is shielded because the resist mask layer is thick and the ions 43 do not pass through the resist mask layer. On the other hand, since the recess has been removed up to a part of the magnetic recording layer as described above, ions are directly implanted into the magnetic recording layer.

  When ions are implanted into the magnetic recording layer, the magnetism of the region into which ions are implanted in the magnetic recording layer is weakened. As a result, the magnetic layer is much weaker than the ferromagnetic layer into which ions are not implanted, and a non-recording region is formed. At this time, the non-recording area is preferably formed to be semi-hard magnetic. Moreover, you may form so that a relative magnetic permeability may exist in the range of 2-100. Since the ion beam is highly linear, a non-recording area can be formed in accordance with the shape of the recess in the resist mask layer. Thus, the magnetic recording layer is separated into a magnetic recording area and a non-recording area, and a data area and a servo area can be formed by forming a pattern in the stamper 42 in advance.

  The present invention is effective for a magnetic recording medium in which the non-recording area has semi-hard magnetism or the non-recording area has a relative magnetic permeability of 2 or more and 100 or less. This is because if the non-permeability of the non-recording area is less than 2, the separation of the magnetic recording area is insufficient in the first place, and if it exceeds 100, the output of the servo signal increases to some extent and the effect of the present invention is not great.

Although ions are not particularly limited to irradiation, typically, B, P, Si, F , C, In, Bi, Kr, Ar, Xe, W, As, Ge, Mo, Sn, N 2, O 2, Ne , He, or H ₂ is irradiated with any one or more non-magnetic ions selected from the group consisting of: The valences of the above ions are all +1. Among the above ions, Ar, N ₂ , O ₂ , Kr, Xe, Ne, He, and H ₂ are preferably used from the viewpoint of ease of handling. Furthermore, from the viewpoint of cost, it is more preferable to use Ar, N ₂ , or O ₂ .

In the ion irradiation, it is preferable to select energy so that the ion density implanted at the center depth of the magnetic recording layer is maximized. The ion irradiation energy is preferably 1 to 50 keV, and the dose is preferably 1 × 10 ¹⁵ to 1 × 10 ¹⁷ atoms / cm ² .

  FIG. 4F shows a resist mask layer removing process. After the ion irradiation step, the resist mask layer can be removed by wet etching. In the case where the resist mask layer is SOG, an organic solvent can be used. However, since the etching rate is remarkably reduced, an alkaline solution is preferably used as the solvent. As the alkaline solution, a KOH-containing solution, a NaOH-containing solution, or the like is usually used, but is not particularly limited to these solutions, and may be appropriately selected depending on the type of SOG.

FIG. 4G shows a peeling layer removing step and a protective layer forming step. After the resist mask layer, the peeling layer is removed by ashing. The release layer is a film mainly composed of carbon, and can be removed, for example, by burning and decomposing carbon with oxygen (ashing). As the ashing gas, N ₂ , H ₂ , H ₂ O, CF ₄ , NH ₃ , Ne, and the like can be used in addition to O ₂ , and any gas can be removed by reacting with carbon. In addition, since the magnetic recording layer is not ashed, the surface of the magnetic recording layer is not damaged by suitably controlling the material gas and the process conditions.

  After removing the release layer once, a protective layer is formed on the exposed surface of the magnetic recording layer. When the peeling layer is removed, the resist mask layer remaining without being etched is removed, so that deterioration of the surface flatness due to the remaining resist can be avoided.

  Thereafter, if necessary, a lubricant application step and a baking step can be performed in the same manner as in a normal magnetic recording medium.

  In the magnetic recording medium of the present invention, the depth of the concave portion formed by the non-recording region with respect to the surface of the magnetic recording layer is preferably 1.0 nm or more and 5.0 nm or less. If the depth of the recess is 1.0 nm or less, the effect of increasing the output of the servo signal cannot be obtained sufficiently. On the other hand, if the magnetic recording medium of the present invention is used as a magnetic disk of an HDD, the head cannot float above 5.0 nm.

  The depth of the recess can be changed, for example, by adjusting a processing time such as IBE in the etching process.

  The magnetic recording medium of the present invention can also be produced by the following method.

  First, a protective layer is formed in place of the peeling layer by the same method as the manufacturing method described above, and after forming a resist mask layer, a desired uneven pattern is formed on the resist mask layer 41 using the stamper 42. Then, ion irradiation is performed (FIG. 5A).

  In this manufacturing method, it is not necessary to remove the resist mask layer in the recesses after the concavo-convex pattern is formed and before the ion irradiation, but the SOG and DLC in the pattern recesses are etched by using the RIE process apparatus. May be exposed.

  After ion irradiation, the resist mask layer is removed by wet etching (FIG. 5B).

  At this time, the resist mask layer is completely removed by being immersed in an alkaline solvent for a certain period of time or more, and then a recess is formed on the surface. This is presumably because the magnetic atoms were dissolved in the solvent through the protective layer 36 above the portion that was a recess in FIG. 5A, which was irradiated with ions (FIG. 5C).

  As the magnetic atoms in the region irradiated with ions, that is, the non-recording region melt, the non-recording region forms a recess with respect to the surface of the magnetic recording region. The depth of the recess can be changed by adjusting the immersion time in the alkaline solvent.

  Thereafter, if necessary, a lubricant application step and a baking step can be performed in the same manner as in a normal magnetic recording medium.

  As described above, according to the present invention, it is possible to obtain a magnetic recording medium having good servo signal output characteristics in which the surface of the non-recording area is formed with a recess with respect to the surface of the magnetic recording area.

  Hereinafter, an embodiment in which a magnetic recording medium having a servo area is manufactured by the method of the present invention will be described.

  An adhesion layer (CrTi), a soft magnetic layer (FeCoTaZr), a lower intermediate layer (NiW), an upper intermediate layer (Ru), and a magnetic recording layer are formed on a glass substrate, and a DLC release layer is formed to a thickness of 3 nm. Then, SOG was spin-coated with a thickness of 50 nm thereon to form a resist mask layer.

The magnetic recording layer is a two-layer structure having different compositions, the first magnetic recording layer closer to the glass substrate, the composition and 90 (70Co-14Cr-16Pt) -10SiO 2, the second magnetic recording layer thereon, a composition It was set to 62Co-18Cr-15Pt-5B. The thickness of the first magnetic recording layer was 14 nm, and the thickness of the second magnetic recording layer was 7 nm.

  Patterning was performed by a nanoimprint method, and a mold (120 nm track pitch, recording area width: 65 nm, non-recording area width: 55 nm) was pressed, the pressing pressure was 100 MPa, and the pressing time was 10 seconds.

  Next, using a RIE process apparatus, the SOG and DLC in the pattern recess were etched to expose the magnetic film, and a part of the magnetic film in the pattern recess was etched using the IBE apparatus.

Next, an ion beam was irradiated on the intermediate body of the magnetic recording medium after the etching to perform ion implantation. In the ion irradiation, nitrogen (N ₂ ) ions are irradiated at 8 KeV so that the ion density implanted at the center depth of the magnetic recording layer in the pattern concave portion is maximized, and the dose amount is 2 × 10 ¹⁶ atoms / cm ^2. It was.

  The intermediate after ion implantation was immersed in a KOH solution for 20 minutes to remove the resist mask layer. Thereafter, the release layer made of DLC was removed by ashing, and then a DLC film having a thickness of 5 nm was formed as a protective layer.

  After the formation of the protective layer, the lubricant was applied and baked in the same manner as in the production of a normal magnetic recording medium.

  In this example, five types of magnetic recording media having different recess depths were manufactured by changing the IBE processing time.

  FIG. 6 shows the result of measuring the manufactured magnetic recording medium by MFM (Magnetic Force Microscopy). It was confirmed that the magnetic recording area and the non-recording area were clearly separated magnetically.

  In addition, after the DC erase process was performed on the entire surface of the medium, a head read / write tester equipped with a perpendicular magnetic recording system magnetic head (read element width 80 nm) was checked and the servo reproduction signal output was measured. It was.

  Table 1 shows the depth of the recesses on the surface of the non-recording area, whether the head can float, and the servo signal output, as measured by AFM (Atomic Force Microscope). Here, the servo reproduction signal output is a signal output of the preamble portion. The preamble part is selected because the pattern is continuous and the signal output can be obtained more stably than other pattern parts. FIG. 7 shows the relationship between the depth of the recess and the servo signal output.

  As shown in Table 1, in the magnetic recording medium (Nos. 2 to 4) in which the surface of the non-recording area forms the recesses defined in the present invention with respect to the magnetic recording area, there is no problem in the head flying, Servo output signal was also high.

  The magnetic recording medium (No. 1) in which the concave portion is not formed has insufficient servo signal output, and the magnetic recording medium (No. 5) having a concave portion depth of 6.0 nm cannot pass the head and fails. became.

  After forming the magnetic recording layer by the same method as in Example 1, a protective layer film forming step is performed instead of the release layer film forming step, and then from resist mask layer formation to ion irradiation by the same method as in Example 1. went. However, after forming the resist mask layer and before ion irradiation, the resist mask layer in the concave portion was not removed, and the energy of ion irradiation was 12 keV. Thereafter, a magnetic recording medium was produced by the following method.

  After the ion irradiation, the intermediate is immersed in a KOH solution having a concentration of 10% and a temperature of 50 ° C. to completely peel off the SOG resist mask. Further, the surface of the non-recorded area irradiated with the ion is opposite to the surface of the magnetic recording area. A recess was formed.

  Thereafter, a lubricant was applied and baked in the same manner as in the production of a normal magnetic recording medium.

  In this example, five types of magnetic recording media having different recess depths were manufactured by appropriately changing the immersion time in the KOH solution.

  As a result of measuring the manufactured magnetic recording medium by MFM, it was confirmed that the magnetic recording area and the non-recording area were magnetically clearly separated as in Example 1.

  Further, similarly to Example 1, confirmation of whether or not the head was allowed to fly and measurement of servo reproduction signal output were performed.

  Table 2 shows the results. FIG. 8 shows the relationship between the depth of the recess and the servo signal output.

  As shown in Table 2, in the magnetic recording medium (Nos. 7 to 9) in which the surface of the non-recording area is formed with the recesses defined in the present invention with respect to the magnetic recording area, there is no problem in flying the head. The servo output signal also showed a high value.

  The magnetic recording medium (No. 6) in which the concave portion is not formed has insufficient servo signal output, and the magnetic recording medium (No. 10) having the concave portion depth of 5.8 nm cannot pass the head and is rejected. became.

  As described above, it has been confirmed that the magnetic recording medium manufactured by the method according to the present invention can obtain a very good servo signal output and can perform high-density magnetic recording functionally.

  The present invention can be used for manufacturing a high-density magnetic recording medium manufactured by an ion irradiation method. Particularly, since the servo signal output can be increased, the positioning accuracy by the servo pattern can be improved, and the present invention can be applied to a high-density small-sized magnetic disk or the like that will be demanded in the future.

DESCRIPTION OF SYMBOLS 10 Magnetic recording medium 11 Data area 12 Servo area 13 Servo pattern 31 Glass substrate 32 Soft magnetic layer 33 Intermediate layer 34 Magnetic recording layer 35 Non-recording area 36 Protective layer 37 Release layer 41 Resist mask layer 41a Shield ion of resist mask layer 41b Part to transmit ion of resist mask layer 42 Stamper 43 Ion 71 Non-recording area (semi-hard magnetic area)
72 Magnetic recording area

Claims (4)

On at least one surface of the substrate, a magnetic recording area for recording / reproducing magnetic information and a non-recording area for magnetically separating the magnetic recording area are regularly arranged in the in-plane direction of the substrate. A magnetic recording medium having an arranged magnetic recording layer, wherein the non-recording area has a magnetic permeability of 2 H / m or more and 100 H / m or less, and the surface of the non-recording area is formed of the magnetic recording area. A method of manufacturing a magnetic recording medium in which a recess is formed on a surface, and the depth of the recess is 0.5 nm or more and 2.0 nm or less ,
A protective layer forming step of forming a protective layer mainly composed of carbon on the magnetic recording layer;
A resist mask layer forming step of forming a resist mask layer made of SOG (spin-on-glass) on the protective layer after the protective layer forming step;
After the resist mask layer forming step, the resist mask layer has a predetermined pattern of a convex portion having a thickness that does not transmit ions when irradiated with the ions, and a thickness that is thin enough to transmit ions. A patterning step for forming a recess;
An ion irradiation step of irradiating ions from above the resist mask layer after the patterning step to form the non-recording region;
After the ion irradiation step, the resist mask layer is removed with an alkaline solvent, and the non-recording area is formed so as to form a recess having a depth of 1.0 nm or more and 5.0 nm or less with respect to the surface of the magnetic recording area. A method of manufacturing a magnetic recording medium, comprising a step of forming a recess to dissolve a recording area. Said ion irradiation in the ion irradiation step, B, P, Si, F , C, In, Bi, Kr, Ar, Xe, W, As, Ge, Mo, Sn, N 2, O 2, Ne, He, H Irradiating at least one nonmagnetic ion selected from ₂ with an irradiation energy of 1 keV to 50 keV and a dose of 1 × 10 ¹⁵ atoms / cm ² to 1 × 10 ¹⁷ atoms / cm ² A method for manufacturing a magnetic recording medium according to claim 1 . Wherein in the patterning step, at a nanoimprint method, a method of manufacturing a magnetic recording medium according to claim 1 or 2, characterized in that to form the projections and recesses of a predetermined pattern to the resist mask layer. Further, the production method of the magnetic recording medium according to any one of claims 1 to 3, characterized in that it has a lubricating layer forming step of forming a lubricating layer on the protective layer.