JP2004303302A - Recording medium, recording/reproducing device, apparatus and method for manufacturing recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately perform servo control over a patterned medium of a high recording density. <P>SOLUTION: A recording medium 1 is provided with a recording area 2 in which recording tracks 21 constituted by arraying ferromagnetic dots 2101 or ferromagnetic dot groups magnetically separated from one another in a first direction 41 are arrayed in a second direction 42, and a control area 3 placed adjacently to the recording area 2 in the first direction 41 to hold servo information. In the control area 3, a first part 301 constituted by arraying ferromagnetic dots 3101 magnetically separated from one another and a second part 302 in which no ferromagnetic dots 3101 are present are alternately arrayed in the second direction. In the first part 301, at least one of the ferromagnetic dots 3101 in contact with a boundary between the first and second parts 301, 302 has a shape in which a part of the boundary side is lacked from the shape of the ferromagnetic dot 3101 positioned apart from the boundary. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording medium, a recording / reproducing apparatus, a recording medium manufacturing apparatus, and a recording medium manufacturing method.
[0002]
[Prior art]
With the development of multimedia in recent years, information such as images, videos, and sounds handled by each user is increasing more and more. Therefore, the database system is required to have a large capacity and a high speed.
[0003]
Against this background, the areal recording density of a magnetic recording medium has been improved in order to increase the recording capacity of a hard disk drive (HDD), and the size of each recording mark corresponding to one bit is currently increasing. It is extremely fine, about several tens of nm. In order to obtain a large reproduction output from a fine recording mark as described above, it is necessary to ensure as large a saturation magnetization and a film thickness as possible for each recording mark. However, when the size of the recording mark is reduced, the amount of magnetization is reduced, so that there is a problem that magnetization reversal occurs due to “thermal fluctuation”, that is, magnetization information is lost.
[0004]
As a medium for solving the problem caused by the thermal fluctuation, a magnetic recording medium called “patterned medium” has been attracting attention (for example, see Patent Document 1 below). Patterned media allows one bit of information to be recorded on one or more of ferromagnetic dots magnetically separated from each other, typically ferromagnetic dots magnetically separated from each other by a nonmagnetic layer. Magnetic recording medium.
[0005]
When the ferromagnetic layer is formed in the form of a continuous film, the position of the edge of the recording mark is equal to the position of the grain boundary of the crystal grains (or domains) constituting the ferromagnetic layer. Therefore, in order to ensure a high signal-to-noise (S / N) ratio, the crystal grains must be made as small as possible. Therefore, the minimum unit volume V of magnetization must be reduced.
[0006]
On the other hand, in the patterned media, since the position of the edge of the recording mark is defined by the contour of the ferromagnetic dot, it is not necessary to reduce the minimum magnetization unit volume V to realize a high S / N ratio. Therefore, the problem of thermal fluctuation can be avoided.
[0007]
Further, in a patterned medium, interference between ferromagnetic dots hardly occurs. Therefore, the information recorded on a certain recording mark is suppressed from disappearing due to interference from an adjacent recording mark, and the adjacent recording mark is prevented from acting as noise when reading the information recorded on a certain recording mark. can do. Furthermore, patterned media have high domain wall displacement resistance and can be expected to have excellent magnetic properties.
[0008]
By the way, when the recording density of the recording medium is increased, more precise servo control is required. However, when performing the present invention, the present inventors cannot perform servo control with sufficiently high accuracy on a patterned medium having a high recording density by a method generally adopted in an HDD or the like. I have found that.
[0009]
[Patent Document 1]
JP 2001-176049 A
[0010]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to enable servo control to be performed with sufficiently high accuracy on a patterned medium having an increased recording density.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, a recording track formed by arranging ferromagnetic dots or a group of ferromagnetic dots magnetically separated from each other in a first direction is arranged in a second direction intersecting the first direction. A recording area, and a control area adjacent to the recording area in the first direction and holding servo information. In the control area, ferromagnetic dots magnetically separated from each other are arranged. The first portion and the second portion where the ferromagnetic dots are not present are alternately arranged in the second direction, and the first portion is in contact with a boundary between the first and second portions. At least one of the ferromagnetic dots has a shape in which a part of the boundary side is omitted from the shape of the ferromagnetic dot located away from the boundary. Is done.
[0012]
According to a second aspect of the present invention, a recording medium according to the first aspect, a recording / reproducing head capable of facing the recording medium, and a drive mechanism for relatively moving the recording / reproducing head with respect to the recording medium are provided. There is provided a recording / reproducing apparatus characterized by comprising:
[0013]
According to a third aspect of the present invention, a recording area transfer unit in which dot-shaped recesses or dot-shaped recess groups are arranged in a first direction is arranged in a second direction intersecting the first direction. And a control area transfer surface adjacent to the recording area transfer surface in the first direction with respect to the recording area transfer surface, wherein the control area transfer surface has a first transfer portion in which dot-shaped concave portions are arranged. The second transfer portions in which the dot-shaped concave portions are not present are alternately arranged in the second direction, and the dot-shaped concave portions contact the boundary between the first and second transfer portions in the first transfer portion. At least one of the above has a shape in which a part of the boundary side is missing from the shape of the dot-shaped concave portion located away from the boundary. .
[0014]
According to a fourth aspect of the present invention, a step of forming a base having a dot-shaped convex portion corresponding to the dot-shaped concave portion on a surface using the manufacturing apparatus according to the third aspect as a mold; Forming a layer containing a ferromagnetic material on the surface provided with the dot-shaped protrusions.
[0015]
According to a fifth aspect of the present invention, a step of forming a layer containing a ferromagnetic material on a base, a step of forming a resist layer on the layer containing the ferromagnetic material, and a manufacturing apparatus according to the third aspect Forming a dot-like convex portion corresponding to the dot-like concave portion on the surface of the resist layer by an imprinting method using a stamper as a stamper; and forming the resist using the resist layer with the dot-like convex portion formed as a mask. And a step of etching the magnetic layer.
[0016]
The recording area and the control area may include a base provided with the dot-shaped protrusions, and a layer provided on the base and having a form of a continuous film and containing a ferromagnetic material. In this case, the ferromagnetic dots in the recording region and the control region may be portions located on the upper surfaces of the dot-shaped protrusions of the layer containing the ferromagnetic material. In this case, the layer containing the ferromagnetic material may be located deeper in the second portion than in the first portion and the ferromagnetic dots arranged in the recording area.
[0017]
Alternatively, the ferromagnetic dots in the recording area and the control area may be provided on a flat base, and may be separated from each other via a nonmagnetic layer.
Further, the first and second portions may be arranged in a checkered pattern.
[0018]
Here, the term “first direction” includes a linear direction, a circumferential direction, and the like. The term “second direction” typically means a radial direction when the “first direction” is a circumferential direction, and typically means a radial direction when the “first direction” is a linear direction. Specifically, it means a direction orthogonal to the “first direction”. Further, in the following description, the “layer containing a ferromagnetic material” is abbreviated as “ferromagnetic layer”.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings, components having the same or similar functions are denoted by the same reference numerals, and redundant description will be omitted.
[0020]
FIG. 1 is a plan view schematically showing a part of a recording medium according to an embodiment of the present invention. A recording medium 1 shown in FIG. 1 is a patterned medium, and has a structure in which a recording area 2 and a control area 3 are provided on one main surface of a substrate (not shown). In the drawing, a double arrow 41 indicates a first direction which is a track direction, and a double arrow 42 indicates a second direction (here, a direction perpendicular to the first direction 41) crossing the first direction 41. I have.
[0021]
The recording area 2 includes a plurality of recording tracks 21 arranged in the second direction 42. These recording tracks 21 have the same width, and each recording track 21 includes a plurality of ferromagnetic dots (recording cells) 2101. In the drawing, a broken line 51 indicates a boundary between the recording tracks 21.
[0022]
The ferromagnetic dots 2101 are separated from each other and magnetically separated from each other. These ferromagnetic dots 2101 are regularly arranged along the first direction 41 in each recording track 21. For example, the ferromagnetic dots 2101 are arranged so as to form an equilateral triangle when their centers are connected with a straight line. In each recording track 21, one or a plurality of ferromagnetic dots 2101 correspond to one piece of binary information, that is, information “0” or “1”. FIG. 1 illustrates a case where a plurality of ferromagnetic dots 2101 correspond to one piece of binary information.
[0023]
The control area 3 is adjacent to the data area 2 in the first direction 41. The control region 3 includes, for example, an AGC (Automatic Gain Control) unit, an address unit, a burst unit, and a pad unit. FIG. 1 shows only the burst section 31 and the pad section 32 in the control area 3. Further, in the example shown in FIG. 1, at the time of writing and reading of information, the recording medium 1 is relatively moved leftward with respect to a recording / reproducing head (not shown). Therefore, the AGC section (not shown), the address section (not shown), the pad section (not shown), the burst section 31, and the pad section 32 are sequentially arranged from left to right in the figure. .
[0024]
The AGC unit outputs a signal that can be used as a reference for amplifying a signal from the address unit, the burst unit 31, the recording track 21, or the like to an appropriate size, for example, a high-level signal. The AGC section is continuous in the second direction 42, and is configured to output a signal of a constant intensity when the recording / reproducing head is moved in any direction indicated by the double arrow 42. The AGC section is not necessarily provided. However, if the AGC section is provided, the gain of the recording / reproducing apparatus may be adjusted according to the signal strength from the AGC section when amplifying the signal from the address section, the burst section 31, the recording track 21, or the like. Can be changed. Therefore, writing and reading of information can be performed with higher accuracy.
[0025]
The address section holds address information corresponding to each recording track 21. Each portion of the address portion corresponding to each recording track 21 has, for example, a structure in which a portion outputting a high-level signal and a portion outputting a low-level signal are arranged along the first direction 41. These arrangement patterns are determined corresponding to the address information.
[0026]
It is not always necessary to provide a pad section between the address section and the burst section 31, but providing a pad section is advantageous in separating signals from the address section and signals from the burst section 31. Similarly, the pad section 32 is not necessarily provided between the burst section 31 and the recording area 2, but when the pad section 32 is provided, the signal from the burst section 31 and the signal from the recording track 21 are separated. This is advantageous.
[0027]
The burst section 31 gives information on the relative position between the recording / reproducing head and the selected recording track 21 in the second direction 42. The burst unit 31 includes a first part 301 and a second part 302 that output signals of different levels, for example, a first part 301 that outputs a high-level signal and a second part 302 that outputs a low-level signal. It is composed of an array.
[0028]
In the first portion 301, a plurality of ferromagnetic dots 3101 are arranged almost regularly. For example, the ferromagnetic dots 3101 are arranged so as to form an equilateral triangle when their centers are connected with a straight line. The ferromagnetic dots 3101 are separated from each other and magnetically separated from each other. The recording states (magnetization directions) of the ferromagnetic dots 3101 are equal to each other in each first portion 301, and the recording states (magnetization directions) of the ferromagnetic dots 3101 are equal to each other between the first portions 301. Therefore, each first portion 301 outputs a signal of the same level as each other.
[0029]
Now, in the present embodiment, the first portion 301 of the burst portion 31 is constituted by the ferromagnetic dots 3101, and the ferromagnetic dots 3101 are not present in the second portion 302. In addition, in the recording medium 1 according to the present embodiment, among the ferromagnetic dots 3101 in the first portion 301, those that are in contact with the boundary between the first portion 301 and the second portion 302 that are adjacent in the second direction 42. At least a portion has a shape in which a portion on the boundary side is removed from a portion located away from the boundary. By employing such a structure, servo control can be performed with sufficiently high accuracy even when the recording density is increased.
[0030]
2A and 2B are enlarged plan views showing the burst section 31 of the recording medium 1 shown in FIG. 3 to 5 are enlarged plan views showing a burst portion of the recording medium according to the reference example.
[0031]
As shown in FIG. 3, when a ferromagnetic layer having a granular structure of a ferromagnetic phase and a non-magnetic phase is formed in the form of a continuous film in the burst portion 31 and a burst pattern is written as magnetic information therein, The position of the boundary between the first part 301 and the second part 302 is limited to the position of the grain boundary of the ferromagnetic crystal grains 3102. In FIG. 3, the crystal grains 3102 forming the burst pattern are distinguished from other crystal grains 3102 by hatching.
[0032]
If the first and second portions 301 and 302 are sufficiently larger than the size of the crystal grains 3102, or if the number of crystal grains 3102 included in the first and second portions 301 and 302 is sufficiently large (for example, (About 1000), and the boundary between the first portion 301 and the second portion 302 can be substantially matched with the broken line 52.
[0033]
However, when the first and second parts 301 and 302 are made smaller, the position of the boundary between the first part 301 and the second part 302 is greatly shifted from the broken line 52 as shown in FIG. Therefore, servo control cannot be performed with sufficiently high accuracy.
[0034]
In addition, when the crystal grains 3102 are also made smaller as the first and second parts 301 and 302 are made smaller, the minimum unit volume V of magnetization becomes smaller. Therefore, in this case, the problem that the recorded information is lost due to the thermal fluctuation is likely to occur.
[0035]
Thus, in the structure shown in FIG. 3, the accuracy of the servo control is limited by the size of the crystal grain 3102 (about 30 nm). That is, in the structure shown in FIG. 3, a positioning accuracy lower than this cannot be expected.
[0036]
The positioning accuracy (error) required when the recording density is 200 kTPI (Track Per Inch) is considered to be 6 nm or less, and the positioning accuracy required when the recording density is 400 kTPI is 3 nm or less. Have been. Therefore, in the structure shown in FIG. 3, the positioning accuracy becomes insufficient even when the recording density is set to 200 kTPI.
[0037]
As shown in FIG. 4, a ferromagnetic layer having a granular structure of a ferromagnetic phase and a non-magnetic phase is formed in the burst portion 31 in the form of a continuous film, and the ferromagnetic layer corresponds to the second portion 302 thereof. When the removed portion is removed, a positioning accuracy of about 5 nm can be realized. That is, if this structure is adopted, the required positioning accuracy can be realized when the recording density is 200 kTPI.
[0038]
However, even when this structure is employed, the boundary position between the first portion 301 and the second portion 302 is affected by the grain boundary position of the crystal grains, though not as much as the structure in FIG. In addition, since this structure is obtained by removing a part of the ferromagnetic layer, the underlayer of the ferromagnetic layer is damaged, which affects the shape of the first portion 301. In particular, in the method of removing a part of the continuous film, the area to be removed is very large, and the shape of the ferromagnetic layer is affected at all boundaries between the first portion 301 and the second portion 302. It will be. Therefore, with this structure, it is difficult to achieve the required positioning accuracy when the recording density is 400 kTPI. Further, even in this structure, if the crystal grain 3102 is made small in order to increase the positioning accuracy, a problem that recorded information is lost due to thermal fluctuation is likely to occur.
[0039]
As shown in FIG. 5, when the entire burst portion 31 is formed of ferromagnetic dots 3101 and a burst pattern is written therein, the position of the boundary between the first portion 301 and the second portion 302 is The position is limited to the position of the body dot 3101. In FIG. 5, the ferromagnetic dots 3101 constituting the burst pattern are distinguished from other ferromagnetic dots 3101 by hatching.
[0040]
In this structure, it is ideal that the ferromagnetic dots 3101 are not located on the broken line 52, but actually, some ferromagnetic dots 3101 are located. Therefore, the position of the boundary between the first part 301 and the second part 302 is shifted from the broken line 52. That is, in this structure, the positioning accuracy is limited to the diameter of the ferromagnetic dots 3101 (for example, about 10 nm), and a higher positioning accuracy cannot be realized. Therefore, in the structure shown in FIG. 5, the positioning accuracy becomes insufficient even when the recording density is set to 200 kTPI.
[0041]
On the other hand, in the present embodiment, as shown in FIGS. 2A and 2B, the first portion 301 of the burst portion 31 is formed of ferromagnetic dots 3101 and the second portion 302 is formed of a ferromagnetic dot 3101. The body dot 3101 does not exist. In addition, in the present embodiment, as shown in FIGS. 2A and 2B, of the ferromagnetic dots 3101 in the first portion 301, the ferromagnetic dots 3101 contact the boundary between the first portion 301 and the second portion 302. In this case, the first portion 301 has a shape in which a part on the boundary side is omitted so as to form a burst pattern having a contour as designed. Moreover, the shape of the ferromagnetic dots 3101 in contact with the boundary between the first portion 301 and the second portion 302 is controlled with high precision by a method using electron beam (EB) drawing or the like, as will be described in detail later. be able to. Further, in this embodiment, as shown in FIGS. 2A and 2B, even if the arrangement direction of the ferromagnetic dots 3101 with respect to the first and second directions 41 and 42 is slightly varied, the variation is the same. The position and shape of the boundary between the first portion 301 and the second portion 302 are not affected.
[0042]
Therefore, according to the present embodiment, even if the recording density is increased, servo control can be performed with sufficiently high accuracy. For example, when the size of the ferromagnetic dot 3101 in contact with the boundary between the first portion 301 and the second portion 302 can be controlled with an accuracy of about 1 nm, even if the recording density is 400 kTPI, sufficient positioning accuracy is obtained. Can be realized.
[0043]
In the present embodiment, only the ferromagnetic dots 3101 in the first portion 301 that are in contact with the boundary between the first portion 301 and the second portion 302 have a shape in which a part on the boundary side is omitted. . Therefore, the size of the other ferromagnetic dots 3101 can be made sufficiently large. In the present embodiment, the thickness of the ferromagnetic dot 3101 is not limited, and a sufficiently large magnetization minimum unit volume V is maintained even in the ferromagnetic dot 3101 in which a part of the boundary side is omitted. can do. Therefore, according to the present embodiment, the problem of thermal fluctuation can be avoided.
[0044]
Further, as shown in FIG. 3, when a ferromagnetic layer is formed on the entire burst section 31 and a burst pattern is recorded thereon as magnetic information, the burst pattern may be lost due to a malfunction of the recording / reproducing head. On the other hand, in the present embodiment, as described above, the first portion 301 of the burst portion 31 is configured by the ferromagnetic dots 3101, and the ferromagnetic dots 3101 are not present in the second portion 302. According to such a structure, a coercive force of, for example, about twice or more as compared with the structure in FIG. 3 is obtained, and a much higher coercive force as compared with the structures in FIGS. 4 and 5. Therefore, higher reliability can be realized.
[0045]
In the present embodiment, a part of the ferromagnetic dots 3101 in the first portion 301 that is in contact with the boundary between the first portion 301 and the second portion 302 adjacent in the second direction 42 is partially omitted on the boundary side. The shape may be a curved shape. Alternatively, of the ferromagnetic dots 3101 in the first portion 301, those that are in contact with the boundary between the first portion 301 and the second portion 302 adjacent in the first direction 41 and the first portion 301 that is adjacent in the second direction 42 Both of the portions that are in contact with the boundary between the second portion 302 and the second portion 302 may have a shape in which a part of the boundary is missing. What is important for the positioning accuracy is the boundary position between the first part 301 and the second part 302 adjacent to the second direction 42, and the boundary between the first part 301 and the second part 302 adjacent to the first direction 41. This is because the position does not greatly affect the positioning accuracy.
[0046]
The above-described recording medium 1 can be manufactured, for example, by the following method. Here, a method using a stamper will be described.
[0047]
6A to 6F are cross-sectional views schematically showing an example of a method of manufacturing a stamper that can be used in the method of manufacturing the recording medium 1 shown in FIG.
In this method, first, as shown in FIG. 6A, a substrate 61 such as a silicon substrate or a quartz substrate is prepared. Here, a quartz substrate is used as the substrate 61.
[0048]
Next, a resist is applied on the quartz substrate 61, and the resist layer is light-cured. Next, a self-assembling material such as PS-PMMA (Polystyrene-polymethylmethacrylate) diblock copolymer is applied on the resist layer by a spin coating method or the like, and this is annealed. Then, nanoholes corresponding to the self-assembly pattern of PMMA are formed by selectively removing only PMMA using oxygen RIE (Reactive Ion Etching). These nanoholes are filled with SOG (Spin On Glass) and then subjected to oxygen RIE to obtain a high aspect ratio mask whose outermost surface is made of SOG. Furthermore, CF ₄ The surface region of the quartz substrate 61 exposed from the mask is removed by the RIE method using a fluorocarbon-based gas. Thereafter, the structure shown in FIG. 6B is obtained by removing the mask and the like from the quartz substrate 61.
[0049]
In the surface of the quartz substrate 61 shown in FIG. 6B, a plurality of dot-shaped protrusions are regularly arranged. The dimensions and arrangement structure of these projections can be controlled, for example, by appropriately setting the molecular weight of the diblock polymer. Further, when the self-organization is used as described above, the manufacturing process can be simplified as compared with the case where the convex portions are formed using the EB drawing.
[0050]
Next, a resist layer is formed on the surface of the quartz substrate 61 on which the dot-shaped convex portions are formed, to a thickness such that the surface becomes flat. Next, a burst pattern or the like is written in the resist layer using an EB drawing method or the like, and thereafter, the resist layer is subjected to a development process or the like. As described above, as shown in FIG. 6C, a resist pattern 62 having an opening at a position corresponding to the second portion 302 and the like is obtained.
[0051]
In forming the resist pattern 62, a method other than EB drawing may be used. For example, various pattern drawing methods such as ordinary photolithography using ultraviolet light, X-ray lithography, near-field light lithography, nanoprinting lithography, interference exposure, and FIB (Focused Ion Beam) processing can be used. According to these methods, the opening of the resist pattern 62 is extremely high regardless of whether or not a part of the dot-shaped projection provided on the quartz substrate 61 exists below the side wall of the opening provided on the resist pattern 62. A concave portion having a shape that matches with precision can be formed on the surface of the quartz substrate 61.
[0052]
Then, for example, CF ₄ The surface area of the quartz substrate 61 exposed from the resist pattern 62 is removed by RIE using a fluorocarbon-based gas. Thereafter, the resist pattern 62 is removed from the quartz substrate 61 by oxygen ashing or a treatment using sulfuric acid and a hydrogen peroxide solution. Thereby, the structure shown in FIG. 6D is obtained.
[0053]
Next, as shown in FIG. 6E, the stamper 101 is formed by performing Ni electroforming using the quartz substrate 61 as a mold. Then, the structure shown in FIG. 6F is obtained by removing the quartz substrate 61 from the stamper 101. As described above, the stamper 101 in which the concavo-convex pattern corresponding to the burst pattern or the like is formed with high accuracy is obtained.
[0054]
FIG. 7 is a plan view schematically showing an example of the stamper 101 that can be manufactured by the method shown in FIGS.
[0055]
The stamper 101 shown in FIG. 7 includes a recording area transfer surface 102 and a control area transfer surface 103 corresponding to the recording area 2 and the control area 3 of the recording medium 1.
[0056]
A dot-shaped concave portion 12101 is provided on the recording area transfer surface 102. These dot-shaped concave portions 12101 have a size and a shape corresponding to the ferromagnetic dots 2101 of the recording medium 1, and form the same arrangement structure as the ferromagnetic dots 2101. That is, on the recording area transfer surface 102, the recording track transfer portions 121 in which the dot-shaped concave portions 12101 are arranged in the first direction 141 are arranged in the second direction 142 intersecting with the first direction 141. In the drawing, a broken line 151 indicates a boundary between the recording track transfer sections 121.
[0057]
On the other hand, the control area transfer surface 103 corresponds to an AGC portion, an address portion, a pad portion, a burst portion 31, and a pad portion 32 of the recording medium 1, and includes an AGC portion transfer portion (not shown) and an address portion. It includes a transfer section (not shown), a pad section transfer section (not shown), a burst section transfer section 131, and a pad section transfer section 132.
[0058]
The transfer portion 131 for the burst portion is configured by an arrangement of a first transfer portion 1301 and a second transfer portion 1302. In the first transfer portion 1301, the dot-shaped concave portions 13101 are arranged substantially regularly in correspondence with the ferromagnetic dots 3101 of the recording medium 1.
[0059]
The second transfer portion 1302 is a convex portion based on a portion between the dot-shaped concave portions 13101 of the first transfer portion 1301. That is, the height of the portion between the dot-shaped concave portions 13101 of the first transfer portion 1301 is between the bottom surface of the dot-shaped concave portion 13101 and the surface of the second transfer portion 1302.
[0060]
Although various structures can be adopted for the pad transfer section 132, the surface of the pad transfer section 132 and the surface of the second transfer section 1302 have the same height.
[0061]
8A to 8D are cross-sectional views schematically showing an example of a method for manufacturing the recording medium 1 shown in FIG.
In this method, first, a stamper 101 shown in FIG. 6F is attached to an injection molding device (not shown), and a resin is supplied to this. Note that glass can be used instead of resin, but here, for example, resin is used.
[0062]
Next, as shown in FIG. 8A, a predetermined amount of resin is injected onto the stamper 101, and the stamper 101 is cooled to solidify the resin. Thereby, the substrate 11 is obtained.
[0063]
Thereafter, the substrate 11 is removed from the stamper 101 as shown in FIG. On one main surface of the substrate 11, dot-shaped protrusions are provided at positions corresponding to the ferromagnetic dots 2101 and 3101. At positions corresponding to the second portions 302 and the like, the dot-shaped protrusions are provided. A concave portion deeper than a concave portion defined as a portion between the convex portions is provided.
[0064]
Next, as shown in FIG. 8C, a ferromagnetic material is deposited on the surface of the substrate 11 on which the protrusions and recesses are provided by a sputtering method or the like. Thus, the ferromagnetic layer 12 is formed.
[0065]
The portions of the ferromagnetic layer 12 located on the upper surface of the dot-shaped protrusions may be physically separated, or may not be physically separated. As described below, even in the latter case, the portions located on the upper surfaces of the dot-shaped protrusions of the ferromagnetic layer 12 are magnetically separated from each other.
[0066]
As described above, the base of the magnetic layer 12 is provided with protrusions and recesses corresponding to the ferromagnetic dots 2101, 3101, the second portion 302, and the like. The magnetic layer 12 has a convex portion and a concave portion corresponding to the surface shape of the base.
[0067]
In such a structure, a portion of the ferromagnetic layer 12 formed of a metal artificial lattice or the like located on the upper surface of the dot-shaped convex portion forms a good laminated structure exhibiting ferromagnetic characteristics, but has a dot-shaped convex structure. The portions located on the side walls and the bottom surface of the concave portion, which are defined as the portions located between the portions, do not form a good laminated structure, and the magnetic properties are significantly deteriorated. That is, only the portion of the ferromagnetic layer 12 that exhibits ferromagnetic properties is located on the upper surface of the dot-shaped protrusion, and the other portions are non-magnetic. Therefore, portions located on the upper surfaces of the dot-shaped protrusions of the ferromagnetic layer 12 obtained by the above method are magnetically separated from each other even if they are not physically separated.
[0068]
Next, if necessary, as shown in FIG. 8D, a nonmagnetic layer 13 is formed on the surface of the substrate 11 on which the ferromagnetic layer 12 has been formed. Thus, the recess provided on one main surface of the substrate 11 is filled with the nonmagnetic layer 13. The recording medium 1 is obtained as described above.
[0069]
The non-magnetic layer 13 is made of, for example, SiO 2 on the ferromagnetic layer 12. ₂ And the like are deposited by a sputtering method or the like to such a thickness that the concave portions are completely buried, and then the surface is flattened using a CMP (Chemical Mechanical Polishing) method. However, in the CMP method, it is generally difficult to control the thickness on the order of nm, and the cost is high. Therefore, it is desirable to form the nonmagnetic layer 13 by another method.
[0070]
For example, the nonmagnetic layer 13 may be formed by applying SOG on the ferromagnetic layer 12, firing the SOG film obtained as necessary, and then etching back the SOG film. Since SOG used in this method is a liquid agent obtained by dissolving a glass material in a solvent, a uniform surface can be formed by embedding fine concave portions on the substrate surface by a simple method such as spin coating. Further, the solvent evaporates from the SOG film obtained in a few seconds after spin coating, so that the SOG film quickly changes to a solid. Therefore, according to this method, low cost and high thickness controllability can be realized. The SOG film does not need to be fired, but if heat treatment is performed at a temperature of 450 ° C. or more, more stable SiO ₂ Can be transformed into
[0071]
As described above, in this method, the unevenness corresponding to the burst pattern or the like is formed on one main surface of the substrate 11 using the stamper 101, and the ferromagnetic layer 12 is formed thereon. In addition, in the recording medium 1 obtained by this method, the portions located on the upper surfaces of the dot-shaped protrusions of the ferromagnetic layer 12 are magnetically separated from each other, so that they can be used as the ferromagnetic dots 2101 and 3101. is there. Therefore, unlike a case where a burst pattern is written as magnetic information on a ferromagnetic layer formed as a continuous film, the boundary position between the first portion 301 and the second portion 302 due to the irregularity of the position of the crystal grain boundary. Does not significantly deviate from the design position.
[0072]
Further, as described above, the concavo-convex pattern corresponding to the burst pattern or the like is formed on the stamper 101 with high accuracy. Further, in this method, since the injection molding method is used, the concavo-convex pattern formed on the stamper 101 is transferred onto the surface of the substrate 11 with high accuracy. Therefore, according to this method, not only the positions of the ferromagnetic dots 2101 and 3101 but also the shape and dimensions can be controlled with high accuracy.
[0073]
Further, in this method, the substrate 11 having the uneven surface is formed by the injection molding method, and the patterning of the ferromagnetic layer 12 is not performed. Moreover, according to this method, the nonmagnetic layer 13 having excellent flatness can be formed without using the CMP method. Therefore, according to this method, the process can be greatly simplified, and excellent mass productivity can be realized.
[0074]
Further, in this method, since patterning of the ferromagnetic layer 12 is unnecessary, there is no damage on the processed surface due to physical etching such as ion milling. Therefore, generation of noise due to etching damage can be prevented, and magnetic characteristics can be further improved.
[0075]
When the method described with reference to FIGS. 8A to 8D is used, the ferromagnetic layer 12 is formed over the entire recording region 2 and the control region 3. In addition, if this method is used, at least a part of the ferromagnetic layer 12 in the control region 3 can be positioned deeper than the ferromagnetic dots 2101, 3101 or the ferromagnetic layer 12 in the recording region 2. . Such a structure is extremely useful in the following applications.
[0076]
In the ferromagnetic layer 12 located deeper than the ferromagnetic dots 2101 and 3101, the distance from the recording head is too large, so that information cannot be recorded by a normal recording head. The obtained information can be read out by an ordinary reproducing head by appropriately setting a gain and the like as necessary. That is, information recorded in the ferromagnetic layer 12 located deeper than the ferromagnetic dots 2101 and 3101 cannot be falsified even if it can be read out by a normal reproducing head. Therefore, if a part of the servo information is recorded therein, it is possible to prevent the information from being lost due to a malfunction. That is, reliability can be improved. Also, a security signal or the like may be written in advance in the ferromagnetic layer 12 located deeper than the ferromagnetic dots 2101 and 3101. The effect described here can be obtained even when the structure shown in FIGS. 2A and 2B is not used in the burst section 31.
[0077]
As described above, the method described with reference to FIGS. 8A to 8D is excellent in mass productivity, but forms a soft magnetic layer that is essential when using a single-pole type recording head in perpendicular magnetic recording. I can't. On the other hand, when the imprinting method is used as described below, the soft magnetic layer can be formed, although the mass productivity is slightly inferior to the method described with reference to FIGS. 8A to 8D. Can be.
[0078]
9A to 9D are cross-sectional views schematically showing another example of the method for manufacturing the recording medium 1 shown in FIG.
In this method, first, as shown in FIG. 9A, a ferromagnetic layer 12 and a resist layer 63 are sequentially formed on one main surface of a nonmagnetic substrate 11. Here, a ferromagnetic layer having a soft magnetic layer as a backing layer is formed as the ferromagnetic layer 12.
[0079]
Next, as shown in FIG. 9B, the stamper 101 shown in FIG. 6F is pressed against the resist layer 63. As a result, the concavo-convex pattern provided on one main surface of the stamper 101 is transferred to the resist layer 63.
[0080]
Next, as shown in FIG. 9C, the stamper 101 is removed from the resist layer 63. The resist layer 63 is a resist pattern to which a concavo-convex pattern provided on one main surface of the stamper 101 is transferred. That is, the resist pattern 63 has dot-shaped protrusions at positions corresponding to the ferromagnetic dots 2101 and 3101, and a portion between the dot-shaped protrusions at a position corresponding to the second portion 302 or the like. The recess is further provided than the recess defined as.
[0081]
Next, using this resist pattern 63 as a mask, Ar ion milling or CO + NH ₃ Gas or Cl ₂ RIE using gas is performed. Then, the structure shown in FIG. 9D is obtained by removing the resist pattern 63 from the substrate 11.
[0082]
Further, the nonmagnetic layer 13 is formed by the same method as described with reference to FIG. As described above, the structure shown in FIG. 9E is obtained.
[0083]
As described above, in this method, the resist pattern 63 corresponding to the burst pattern is formed using the stamper 101, and the ferromagnetic layer 12 is patterned using the resist pattern 63 as a mask. Therefore, unlike a case where a burst pattern is written as magnetic information on a ferromagnetic layer formed as a continuous film, the boundary position between the first portion 301 and the second portion 302 due to the irregularity of the position of the crystal grain boundary. Does not significantly deviate from the design position.
[0084]
Further, as described above, the concavo-convex pattern corresponding to the burst pattern or the like is formed on the stamper 101 with high accuracy. Further, in this method, the concavo-convex pattern formed on the stamper 101 is transferred to the resist pattern 63 with high accuracy. Therefore, according to this method, not only the positions of the ferromagnetic dots 2101 and 3101 but also the shape and dimensions can be controlled with high accuracy.
[0085]
However, the method described with reference to FIGS. 9A to 9E requires etching of the ferromagnetic layer 12, and is therefore compared to the method described with reference to FIGS. 8A to 8D. If this is the case, the mass productivity is somewhat inferior. Further, the ferromagnetic layer 12 and the like may be damaged by the etching.
[0086]
However, in perpendicular recording using a single-pole recording head, the signal intensity increases about twice when the soft magnetic layer is provided, as compared with the case where the soft magnetic layer is not provided. That is, when the temporary layer is provided, the S / N ratio can be significantly improved. In the method described with reference to FIGS. 9A to 9E, damage to the ferromagnetic layer 12 and the like can be suppressed by optimizing the etching conditions. Therefore, according to this method, a high S / N ratio can be realized.
[0087]
Further, according to the method described with reference to FIGS. 9A to 9E, the first portion 301 of the burst portion 31 is formed of the ferromagnetic dots 3101 while the second portion 302 is formed of a strong portion. There is no magnetic dot 3101. Therefore, as in the structure shown in FIG. 5, both the first portion 301 and the second portion 302 include the ferromagnetic dots 3101 and the magnetization directions of the ferromagnetic dots 3101 must be different between them. Unlike the case in which the magnetic information does not need to be written, writing of magnetic information to the burst section 31 can be performed collectively. That is, magnetic information can be written to the burst section 31 in a very short time.
[0088]
As described above, in the method described with reference to FIGS. 8A to 8D and 9A to 9E, the formation of the ferromagnetic dots 2101 and the formation of the burst pattern and the like are performed simultaneously. For this reason, the recording medium 1 can be manufactured in a shorter time than when they are formed in separate steps. If these operations are performed at the same time, there is no need to align the ferromagnetic dots 2101 with a burst pattern or the like. Therefore, extremely high positional accuracy can be realized.
[0089]
Next, materials that can be used for the recording medium 1 will be described.
The substrate 11 may be a non-magnetic substrate, and may be made of, for example, resin or glass. Examples of resins that can be used for the substrate 11 include polycarbonate, polystyrene, styrene-based polymer alloy, polyolefin, polyethylene, polypropylene, amorphous polyolefin, acrylic resin (for example, polymethyl methacrylate), polyvinyl chloride, and thermoplastic. Examples include polyurethane, polyester, and nylon. In addition, thermosetting resins such as thermosetting polyurethane, epoxy resin, unsaturated acrylic resin, acrylic urethane resin, unsaturated polyester, and diethylene glycol bisallyl carbonate resin can also be used. In addition, a resin obtained by curing a resin liquid containing urethane-containing poly (meth) acrylate, polycarbonate di (meth) acrylate, acetal glycol diacrylate, or the like as a main component can also be used. When a thermosetting resin is used, a curing catalyst or a curing agent may be contained in the resin. Further, an ultraviolet curable resin can also be used. In this case, a photosensitizer is used as a curing catalyst. Representative photosensitizers include acetophenones, benzoin alkyl ethers, propiophenones, ketones, anthraquinones, and thioxanthones. These may be used alone or in combination. In particular, ketone-based 1-hydroxycyclohexyl phenyl ketone and the like are suitable in terms of transfer performance, mold release performance, and quality stability. Alternatively, glass, especially low-melting glass, may be used instead of the resin. However, it is preferable to use injection-molded polycarbonate from the viewpoint of productivity, cost, moisture absorption resistance, and the like, and it is preferable to use amorphous polyolefin from the viewpoint of chemical resistance and moisture absorption resistance.
[0090]
For the ferromagnetic layer 12 such as the ferromagnetic dots 2101 and 3101, a ferromagnetic material generally used in current magnetic recording media can be used. As the material of the ferromagnetic layer 12, a material having a large saturation magnetization Is and a large magnetic anisotropy is suitable. From this viewpoint, for example, Co, Pt, Sm, Fe, Ni, Cr, Mn, Bi, It is desirable to use at least one selected from the group consisting of Al and alloys of these metals. Among these, Co alloys and Fe alloys having large crystal magnetic anisotropy, particularly those based on CoPt, SmCo, and CoCr, and ordered alloys such as FePt and CoPt are more preferable. For example, Co-Cr, Co-Pt, Co-Cr-Ta, Co-Cr-Pt, Co-Cr-Ta-Pt, Fe ₅₀ Pt ₅₀ , Co ₅₀ Pt ₅₀ , Fe ₅₀ Pd ₅₀ , Co ₇₅ Pt ₂₅ It is desirable to use such as. In addition to these, Tb-Fe, Tb-Fe-Co, Tb-Co, Gd-Tb-Fe-Co, Gd-Dy-Fe-Co, Nd-Fe-Co, Nd-Tb-Fe- Rare earth-transition metal alloys such as Co, multilayer films of magnetic layers and noble metal layers (artificial lattice: Co / Pt, Co / Pd, etc.), semimetals such as PtMnSb, magnetic oxides such as Co ferrite, Ba ferrite, etc. You can choose.
[0091]
For the purpose of controlling the magnetic properties of the ferromagnetic layer 12, an alloy of the above-described magnetic material and at least one element selected from the magnetic elements Fe and Ni may be used as the ferromagnetic layer. . Additives for improving magnetic properties, such as Cr, Nb, V, Ta, Mo, Ti, W, Hf, Cr, V, In, Zn, Al, Mg, Si, are added to these metals or alloys. B or the like, or a compound of these elements and at least one element selected from oxygen, nitrogen, carbon, and hydrogen may be added.
[0092]
The ferromagnetic layer 12 is preferably a composite material composed of magnetic particles and a non-magnetic substance existing therebetween. This is because high-density magnetic recording using magnetic particles as a reversal unit becomes possible. However, when patterning the recording area, the presence of a non-magnetic material is not always necessary, and a continuous amorphous magnetic material such as a rare earth-transition metal alloy may be used.
[0093]
Regarding the magnetic anisotropy of the ferromagnetic layer 12, an in-plane magnetic anisotropy component may be present as long as the perpendicular magnetic anisotropy component is main. The thickness of the ferromagnetic layer 12 is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 20 nm or less in consideration of high-density recording. If the thickness of the ferromagnetic layer 12 is 0.1 nm or less, it may be difficult to form a continuous film.
[0094]
When the structure shown in FIG. 8D is employed, it is preferable that the ferromagnetic layer 12 be a multilayer film in which Co and Pt or Pd are alternately laminated, that is, a metal artificial lattice. As described above, since the characteristics of the metal artificial lattice are affected by the state of the lamination interface, the portions of the ferromagnetic layer 12 located on the side surfaces of the projections and on the side walls and the bottom surface of the depressions have beautiful laminations. The structure cannot be obtained, and the magnetic properties are significantly deteriorated. Therefore, portions of the ferromagnetic layer 12 located on the upper surface of the convex portion can be magnetically separated by portions located on the side surface of the convex portion and the side wall and the bottom surface of the concave portion. That is, when a metal artificial lattice is used, the ferromagnetic dots 2101 and the ferromagnetic dots 3101 can be more reliably magnetically separated from each other.
[0095]
When the method described with reference to FIGS. 8A to 8D is adopted, the ferromagnetic layer 12 should be thinner than the depth of the concave portion and the height of the convex portion, and the thickness of the ferromagnetic layer 12 should be smaller than that of the concave portion. It is desirable that the height be not more than half of the depth or the height of the projection. In this case, the ferromagnetic dots 2101 and the ferromagnetic dots 3101 can be magnetically separated from each other more reliably.
[0096]
When the method described with reference to FIGS. 8A to 8D is employed, the area between the ferromagnetic dots 2101 and between the ferromagnetic dots 3101 is reduced by reducing the area of the upper surface of the convex portion. A single magnetic domain state in which the directions of magnetization are aligned without real interaction can be realized. For example, in order to make each of the ferromagnetic dots 2101 and each of the ferromagnetic dots 3101 into a single magnetic domain state, it is desirable that their dimensions be 100 nm square or less, more preferably 80 nm or less. Note that this is the same even when the method described with reference to FIGS. 9A to 9E is adopted.
[0097]
The ferromagnetic dots 2101 and 3101 are typically circular, but their shape is not particularly limited. For example, the ferromagnetic dots 2101 and 3101 may be rectangular or elliptical.
[0098]
There is no particular limitation on the arrangement structure of the ferromagnetic dots 2101, 3101 as long as they are arranged sufficiently regularly. For example, the ferromagnetic dots 2101 and 3101 may be arranged in a square lattice, or may be arranged in a hexagonal lattice.
[0099]
In the present embodiment, the number of ferromagnetic dots 3101 in each recording track 21 in the second direction 42 is two or more. On the other hand, there is no particular limitation as long as the number of ferromagnetic dots 2101 in each recording track 21 in the second direction 42 is one or more. That is, one ferromagnetic dot 2101 may correspond to one piece of binary information, or a plurality of ferromagnetic dots 2101 may correspond to one piece of binary information.
[0100]
Although the ferromagnetic layer 12 has been described mainly with respect to the portion located in the recording region 2 and the burst portion 31, various structures are adopted for the ferromagnetic layer 12 in portions other than the burst portion 31 in the control region 3. be able to. For example, in an AGC portion, an address portion, a pad portion, or the like, the ferromagnetic layer 12 may be a continuous film provided on a flat base, or may be a ferromagnetic layer like the first portion 301 or the recording region 2. It may be a body dot. When the form of ferromagnetic dots is used for the ferromagnetic layer 12 in the address section, ferromagnetic dots may be arranged in the entire address section, and address information may be magnetically written there. Alternatively, as in the burst section 31, the first section 301 in which the ferromagnetic dots 3101 are arranged and the second section 302 in which no ferromagnetic dots are present are arranged in the address section, whereby the address is changed. Information may be held.
[0101]
Further, in the recording medium 1 shown in FIG. 1, a burst pattern formed by arranging rectangular first and second portions 301 and 302 in a checkered pattern is employed for the burst section 31. Various deformations are possible.
[0102]
FIG. 10 is a plan view schematically showing an example of a burst pattern that can be employed in the recording medium 1 of FIG. In the structure shown in FIG. 10, both the first portion 301 and the second portion 302 are wedge-shaped. For example, even when such a structure is employed in the burst section 31, the same effects as described above can be obtained.
[0103]
When the method described with reference to FIGS. 9A to 9E is adopted, as described above, a soft magnetic layer necessary for perpendicular magnetic recording is provided on the non-magnetic substrate 11. You may. The soft magnetic layer only needs to have a coercive force such that the magnetic direction (spin direction) is changed by the magnetic field of the single-pole head during recording and reproduction, and a closed magnetic loop is formed. Generally, the coercive force of the soft magnetic layer is preferably several kOe or less, more preferably 1 kOe or less, and even more preferably 50 Oe or less.
[0104]
Examples of the soft magnetic material that can be used for the soft magnetic layer include soft magnetic materials containing any of Fe, Ni, and Co, such as CoFe, NiFe, CoZrNb, ferrite, silicon iron, and carbon iron. Can be mentioned.
[0105]
When the fine structure of the soft magnetic layer is similar to that of the ferromagnetic layer, it is advantageous in terms of crystallinity and fine structure control. However, when giving priority to the magnetic characteristics, another structure can be adopted as the fine structure of the soft magnetic layer. For example, an amorphous soft magnetic layer and a crystalline ferromagnetic layer may be combined, or a crystalline soft magnetic layer and an amorphous ferromagnetic layer may be combined. The soft magnetic layer may be a layer in which soft magnetic fine particles are present in a nonmagnetic matrix, that is, a layer having a granular structure, or a plurality of layers having different magnetic properties (for example, a soft magnetic layer). / Multilayer film of non-magnetic layer).
[0106]
The direction of the magnetic anisotropy of the soft magnetic layer other than during recording / reproduction may be perpendicular to the film surface, may be in the in-plane circumferential direction, may be in the in-plane radial direction, or These may be synthesized.
[0107]
The material of the nonmagnetic layer 13 is not particularly limited as long as it is a nonmagnetic material, but is typically an insulator. The insulator usable for the non-magnetic layer 13 is, for example, SiO 2 ₂ , Al ₂ O ₃ , TiO ₃ Oxides such as Si ₃ N ₄ , AlN, nitrides such as TiN, carbides such as TiC, and borides such as BN.
[0108]
The recording medium 1 described above can be mounted on, for example, the following recording / reproducing device.
[0109]
FIG. 11 is a perspective view schematically showing an example of a recording and reproducing apparatus equipped with the recording medium 1 of FIG.
[0110]
The recording / reproducing apparatus 200 shown in FIG. 11 is a magnetic recording / reproducing apparatus, and has a magnetic disk as the recording medium 1.
[0111]
The magnetic disk 1 is rotatably supported by a spindle 201. The spindle 201 is connected to a motor (not shown) that operates according to a control signal from a control circuit included in a control unit (not shown). I have. In the recording / reproducing apparatus 200 shown in FIG. 11, this makes it possible to control the rotation of the magnetic disk 1 and the like.
[0112]
A fixed shaft 202 is disposed near the circumference of the magnetic disk 1, and the fixed shaft 202 swings the magnetic head assembly 203 via ball bearings (not shown) disposed at two positions above and below the fixed shaft 202. We support as much as possible. A coil (not shown) is wound around the bobbin portion of the magnetic head assembly 203. The coil, the permanent magnet and the opposing yoke, which are opposed to each other with the coil interposed therebetween, form a magnetic circuit and a voice coil. The motor 204 is configured. The voice coil motor 204 is also connected to the control unit, so that the head slider 2032 at the tip of the magnetic head assembly 203 can be positioned on a desired recording track 21 of the magnetic disk 1.
[0113]
The magnetic head assembly 203 has an actuator arm 2030 provided with, for example, a bobbin for holding a drive coil. One end of a suspension 2031 is attached to the actuator arm 2030, and a head slider 2032 is attached to the other end of the suspension 2031. A recording / reproducing head is incorporated in the head slider 2032. Note that a piezo element for performing minute position control is installed at the tip of the actuator arm 2030.
[0114]
Lead wires (not shown) for writing and reading signals are formed on the suspension 2031. These lead wires are electrically connected to electrodes of a recording / reproducing head incorporated in the head slider 2032, respectively. I have. In the magnetic recording / reproducing apparatus 200, recording and reproduction of information are performed in a state where the magnetic disk 1 is rotated and the head slider 2032 is floated from the magnetic disk 1 by an air flow generated thereby. In the magnetic recording / reproducing apparatus 200 shown in FIG. 11, a motor connected to the spindle 201 and a voice coil motor 204 constitute a driving mechanism, and a signal from the control area 3 is provided inside the magnetic recording / reproducing apparatus 200. A microprocessor for generating a tracking signal based on the control signal.
[0115]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements in an implementation stage without departing from the scope of the invention. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.
[0116]
【Example】
Hereinafter, examples of the present invention will be described.
[0117]
(Example 1)
In this example, the stamper 101 shown in FIG. 7 was manufactured by the following method.
[0118]
First, as shown in FIG. 6A, a silicon substrate 61 having a 200-nm-thick thermal oxide film formed on one main surface was prepared. Next, a photoresist was applied on the silicon substrate 61 by a spin coating method to form a resist layer having a thickness of 100 nm.
[0119]
After photo-curing the resist layer, a PS-PMMA diblock copolymer having a molecular weight ratio of PS and PMMA of 170,000: 42,000 diluted with a resist thinner (PGMEA) was applied on the resist layer by spin coating. This coating film was annealed at 200 ° C. for 20 hours to obtain a structure in which PMMA particles having a diameter of 40 nm were arranged in a hexagonal lattice at a pitch of 80 nm.
[0120]
Thereafter, only PMMA was selectively removed by oxygen RIE. As a result, nanoholes having a diameter of 40 nm and a depth of 20 nm corresponding to the self-assembly pattern of PMMA were formed.
[0121]
Next, these nano holes were filled with SOG (trade name “OCD type 2” manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then, oxygen RIE was performed to obtain a structure in which pillars having a diameter of 40 nm and a height of 100 nm were arranged in a hexagonal lattice at a pitch of 80 nm on the thermal oxide film. Then, CF ₄ RIE using gas is carried out, and SiO having a diameter of 40 nm and a height of 50 nm is used. ₂ A structure was obtained in which pillars (dot-shaped protrusions) were arranged in a hexagonal lattice at a pitch of 80 nm.
[0122]
After obtaining the structure shown in FIG. 6B as described above, an EB resist is applied by spin coating to the surface of the substrate 61 on which the dot-shaped convex portions are formed, and a resist layer having a thickness of 400 nm is formed. Formed. Next, a burst pattern similar to that shown in FIG. 1 was written in this resist layer by using the EB drawing method. Here, writing was performed such that the size of the first transfer portion 1301 was 200 nm × 200 nm, and the width of the second transfer portion 302 interposed between the first transfer portions 1301 was 200 nm. Thereafter, the resist layer is subjected to a development process or the like to form a resist pattern 62 having an opening at a position corresponding to a portion other than the first transfer portion 1301 of the control region transfer surface 103 as shown in FIG. 6C. Obtained.
[0123]
Then, CF ₄ The surface region of the substrate 61 exposed from the resist pattern 62 was removed by RIE using gas. Thereafter, the resist pattern 62 was removed from the substrate 61 by oxygen ashing. Thus, the structure shown in FIG. 6D was obtained.
[0124]
Next, a 20-nm-thick Ni layer was formed on the surface of the substrate 61 on which the dot-shaped convex portions were formed by a sputtering method. Next, as shown in FIG. 6E, the stamper 101 was formed by performing Ni electroforming using this Ni layer as a conductive base. Then, the structure shown in FIG. 6F was obtained by removing the substrate 61 from the stamper 101.
[0125]
Next, as shown in FIG. 8A, a polycarbonate substrate 11 was manufactured by an injection molding method using the stamper 101 as a mold. That is, a polycarbonate material (trade name “AD5503” manufactured by Teijin Limited) is supplied to a hopper of an injection molding apparatus, and the temperature of the stamper 101 is set to 125 ° C., the resin temperature is set to 340 ° C., the injection pressure is set to 30 t, and the cycle time is set to 12 seconds. Injection molding was performed under the following conditions.
[0126]
Thereafter, the substrate 11 was removed from the stamper 101 as shown in FIG. The substrate 11 thus obtained had a dot-like convex portion having a height of 40 nm.
[0127]
Subsequently, as shown in FIG. 8C, an artificial lattice formed by alternately stacking Co layers and Pd layers was formed as the ferromagnetic layer 12 by using a sputtering method. Here, the thickness of the Co layer was 0.3 nm, the thickness of the Pd layer was 0.7 nm, and the number of layers was 10 layers. The magnetic properties of the obtained patterned media were a squareness ratio of 0.9 and a coercive force of 4500 Oe.
[0128]
Thereafter, as shown in FIG. 8D, an SOG layer is formed on the ferromagnetic layer 12, the surface is flattened, and a C protective film is formed to a thickness of 10 nm by a sputtering method. Was applied. After the recording medium 1 thus obtained is magnetized in one direction at 20 kOe in the direction perpendicular to the disk surface by a magnet, a pulse-like signal generated from a projection portion sometimes generated under the condition of a disc rotation speed of 4200 rpm disappears. After burnishing to the extent, an R / W test was performed.
[0129]
FIG. 12 is a plan view schematically showing a burst pattern of the recording medium 1 manufactured in this example. FIG. 13 is a graph schematically showing an example of a signal obtained from the burst pattern shown in FIG. In FIG. 12, for the sake of simplicity, the shapes of the ferromagnetic dots 3101 are all drawn substantially equally circular, but in this example, as shown in FIGS. 1 and 2A and 2B, Of the ferromagnetic dots 3101 in the first part 301, those that straddle the boundary between the first part 301 and the second part 302 have a shape in which a part on the boundary side is omitted. Also, in FIG. 12, reference numeral 55 indicates a trajectory formed by the overlap between the detection section of the recording / reproducing head and the burst pattern, and FIG. 5 shows a signal waveform obtained when the recording medium 1 is moved relative to the recording medium 1.
[0130]
In this example, under the condition that the maximum amplitude of the signal waveform shown in FIG. 13 is 20 mA, the recording / reproducing head is finely moved using a piezo element so that the signal strength of the burst C and the signal strength of the burst D become equal. In this way, servo control was performed. As a result, servo control could be performed with sufficiently high accuracy.
[0131]
In this example, as described above, the length of the first portion 301 and the second portion 302 in the second direction 42 is 200 nm. That is, the recording density of the recording medium 1 manufactured in this example is about 130 kTPI.
[0132]
(Example 2)
In this example, first, as the PS-PMMA diblock copolymer, the one having a molecular weight ratio of PS and PMMA of 65,000: 13000 instead of the molecular weight ratio of PS and PMMA of 170,000: 42,000 is used, and the first transfer is performed. The stamper 101 is manufactured by the same method as described in Embodiment 1, except that the size of the portion 1301 is 60 nm × 60 nm and the width of the second transfer portion 1302 interposed between the first transfer portions 1301 is 60 nm. did.
[0133]
That is, first, in Example 1, a PS-PMMA diblock copolymer having a molecular weight ratio of PS and PMMA of 65,000: 13000 instead of a molecular weight ratio of PS and PMMA of 170,000: 42,000 was used. According to the same method as described, a structure in which PMMA particles having a diameter of 15 nm were arranged in a hexagonal lattice at a pitch of 30 nm was obtained.
[0134]
Next, nanoholes are formed by the same method as described in Example 1, and these nanoholes are filled with SOG, and then oxygen RIE and CF are performed. ₄ RIE using gas was sequentially performed. This results in a 15 nm diameter and 15 nm height SiO ₂ A structure was obtained in which pillars (dot-shaped protrusions) were arranged in a hexagonal lattice at a pitch of 30 nm.
[0135]
Further, the same method as that described in Embodiment 1 is used, except that the size of the first transfer portion 1301 is set to 60 nm × 60 nm and the width of the second transfer portion 1302 interposed between the first transfer portions 1301 is set to 60 nm. A stamper 101 was formed.
[0136]
After that, the recording medium 1 was manufactured by the same method as that described in Example 1 except that the stamper 101 was used. In this example, as shown in FIGS. 1 and 2A and 2B, of the ferromagnetic dots 3101 in the first portion 301, the boundary between the first portion 301 and the second portion 302 is formed. The straddle has a shape in which a part of the boundary side is omitted.
[0137]
This recording medium 1 is also magnetized in one direction at 20 kOe in the direction perpendicular to the disk surface by a magnet, and under a condition of a disc rotation speed of 4200 rpm, a pulse-like signal generated from a projection part which sometimes occurs is eliminated. After burnishing, an R / W test was performed. As a result, also in this example, a signal waveform similar to that shown in FIG. 13 was obtained, and servo control could be performed with sufficiently high accuracy.
[0138]
In this example, as described above, the length of the first portion 301 and the second portion 302 in the second direction 42 is 60 nm. That is, the recording density of the recording medium 1 manufactured in this example is about 400 kTPI.
[0139]
(Reference Example 1)
In this example, the recording medium 1 is manufactured by the same method as that described in the second embodiment, except that the structure shown in FIG. 5 is employed for the burst section 31 and a burst pattern is written therein using a servo track writer. did. That is, first, in the present example, the second transfer portion 1302 is added to the second transfer portion 1302 by the same method as that described in Example 2 except that the steps described with reference to FIGS. 6C and 6D are omitted. The stamper 101 having the same structure as the one transfer portion 1301 was manufactured. Next, a recording medium 1 was manufactured by the same method as that described in Example 2 except that the stamper 101 was used. After that, the ferromagnetic layer 12 was magnetized under the same conditions as in Example 2, and a burst pattern similar to that in Example 2 was written using a servo track writer.
[0140]
This recording medium 1 was also subjected to the same R / W test as in Example 2. As a result, in this example, a signal waveform similar to that shown in FIG. 13 was not obtained, and servo control could not be performed.
[0141]
(Example 3)
In this example, first, the stamper 101 shown in FIG. 7 was manufactured by the following method. In this example, the dot-shaped concave portions 12101 and 13101 are rectangular instead of circular.
[0142]
That is, first, as shown in FIG. 6A, a silicon substrate 61 having a 200-nm-thick thermal oxide film formed on one main surface was prepared. Next, an EB resist was applied on the thermal oxide film of the silicon substrate by a spin coating method to form a resist layer.
[0143]
Next, a burst pattern similar to that shown in FIG. 12 was written to the resist layer by using the EB drawing method, and further subjected to processing such as development to form a resist pattern. Here, the writing was performed such that the size of the first transfer portion 1301 was 200 nm × 200 nm, and the width of the second transfer portion 1302 interposed between the first transfer portions 1301 was 200 nm. Here, writing was performed such that the dot-shaped concave portions 12101 and 13101 had a rectangular shape of 50 nm × 50 nm and were arranged at a pitch of 50 nm.
[0144]
Then, CF ₄ The surface region exposed from the resist pattern of the substrate 61 was removed by RIE using gas. Thereafter, the resist pattern was removed from the substrate 61 by oxygen ashing. Thus, the structure shown in FIG. 6B was obtained.
[0145]
Subsequently, the same steps as described with reference to FIGS. 6C to 6F in Example 1 were performed. The stamper 101 was manufactured by the above method.
[0146]
After that, the recording medium 1 was manufactured by the same method as that described in Example 1 except that the stamper 101 was used. In this example, as shown in FIGS. 1 and 2A and 2B, of the ferromagnetic dots 3101 in the first portion 301, the boundary between the first portion 301 and the second portion 302 is formed. The straddle has a shape in which a part of the boundary side is omitted.
[0147]
This recording medium 1 is also magnetized in one direction at 20 kOe in the direction perpendicular to the disk surface by a magnet, and under a condition of a disc rotation speed of 4200 rpm, a pulse-like signal generated from a projection part which sometimes occurs is eliminated. After burnishing, an R / W test was performed. As a result, also in this example, a signal waveform similar to that shown in FIG. 13 was obtained, and servo control could be performed with sufficiently high accuracy.
[0148]
(Example 4)
In this example, first, the structure shown in FIG. 9A was formed. That is, first, a soft magnetic layer (not shown) made of CoZrNb and having a thickness of 200 nm was formed on one main surface of the glass substrate 11 by a sputtering method. Next, a 15-nm thick ferromagnetic layer 12 made of a CoCrPt alloy was formed on the soft magnetic layer. Subsequently, a resist layer 63 having a thickness of 40 nm was formed on the ferromagnetic layer 12.
[0149]
Next, as shown in FIG. 9B, the stamper 101 manufactured in Example 2 was pressed against the resist layer 63. Thereby, as shown in FIG. 9C, the concavo-convex pattern of the stamper 101 was transferred to the resist layer 63.
[0150]
Next, the ferromagnetic layer 12 was patterned by the Ar ion milling method using the resist layer 63 to which the concavo-convex pattern of the stamper 101 was transferred as a mask. Thus, the structure shown in FIG. 9D was obtained. The magnetization curve (Ker hysteresis loop) of the patterned medium thus obtained was measured using the magneto-optical Kerr effect, and the coercive force was 4000 Oe.
[0151]
Thereafter, as shown in FIG. 9E, an SOG layer 13 is formed on the ferromagnetic layer 12, the surface is flattened, and a C protective film is formed to a thickness of 10 nm by a sputtering method. Material was applied. In this example, as shown in FIGS. 1 and 2A and 2B, of the ferromagnetic dots 3101 in the first portion 301, the boundary between the first portion 301 and the second portion 302 is formed. The straddle has a shape in which a part of the boundary side is omitted.
[0152]
After the recording medium 1 thus obtained is magnetized in one direction at 20 kOe in the direction perpendicular to the disk surface by a magnet, a pulse-like signal generated from a projection portion sometimes generated under the condition of a disc rotation speed of 4200 rpm disappears. After burnishing to the extent, an R / W test was performed. As a result, also in this example, a signal waveform similar to that shown in FIG. 13 was obtained, and servo control could be performed with sufficiently high accuracy.
[0153]
In the present example, the length of the first portion 301 and the second portion 302 in the second direction 42 is 60 nm. That is, the recording density of the recording medium 1 manufactured in this example is about 400 kTPI.
[0154]
(Example 5)
In this example, first, the recording medium 1 was manufactured by the same method as that described in Example 1. The recording medium 1 is magnetized in one direction at 20 kOe in the direction perpendicular to the disk surface by a magnet, and then burnish under a condition of a disc rotation speed of 4200 rpm until a pulse-like signal generated from a projection portion generated occasionally disappears. Then, an R / W test was performed.
[0155]
Next, information was written to a part of the pad section 32. Since the pad section 32 is located deeper than the ferromagnetic dots 2101 and 3101, information cannot be written by a recording / reproducing head mounted on a general recording / reproducing apparatus. Therefore, here, a 300 kFCI signal was written to a part of the pad section 32 using a high-output recording head for research and development.
[0156]
Next, using a recording / reproducing head mounted on a general recording / reproducing apparatus, a signal written to the pad section 32 was read. As a result, a reproduction signal of 300 kFCI could be detected.
[0157]
Next, using a recording / reproducing head mounted on a general recording / reproducing apparatus, overwriting was performed at recording frequencies of 100 k, 300 k, and 600 kFCI. As a result, a signal could be written in the recording area 2, but a signal could not be written in the pad section 32.
[0158]
Subsequently, DC degaussing was performed using a recording / reproducing head mounted on a general recording / reproducing apparatus. As a result, the signal written to the pad section 32 was not erased.
[0159]
(Example 6)
In the recording medium 1 shown in FIG. 1, the recording area 2 and the control area 3 are mixed, and it is impossible to measure their magnetic properties individually. Therefore, the magnetic characteristics of the recording area 2 and the control area 3 were examined by performing an LLG simulation.
[0160]
For the recording area 2, an LLG simulation was performed assuming a model in which ferromagnetic dots 2101 were arranged in a hexagonal lattice on a plane having an infinite width. Here, the ferromagnetic dot 2101 has a diameter of 40 nm, a height of 40 nm, an arrangement pitch of 80 nm, a saturation magnetization intensity of 620 emu / cc, and a magnetic illegality constant Ku of 2.10. 0x10 ⁶ erg / cc. As a result, a coercive force of 4900 Oe was obtained.
[0161]
For the control region 3, the LLG simulation was performed only on the first portion 301 in the burst section 31. Here, it is assumed that the size of the first portion 301 is 300 nm × 300 nm, and the other parameters are the same as those described above for the recording area 2. Here, as shown in FIGS. 1 and 2A and 2B, of the ferromagnetic dots 3101 in the first portion 301, the ferromagnetic dots 3101 straddle the boundary between the first portion 301 and the second portion 302. The thing was simulated as a shape in which a part of the boundary side was omitted. As a result, a coercive force of 5100 Oe was obtained.
[0162]
Thus, according to the structure shown in FIG. 1, the coercive force of the burst portion 31 is larger than the coercive force of the recording area 2. That is, in the structure shown in FIG. 1, the stability of the information held by the burst unit 31 is high. Also, from this result, the stability of the information held by the burst unit 31 when the structure of FIGS. 1 and 2A and 2B is adopted for the burst unit 31 is compared to the case where the structure of FIG. It turns out that becomes high. That is, when the structure shown in FIGS. 1 and 2A and 2B is adopted for the burst section 31, a higher S / N ratio can be realized as compared with the case where the structure shown in FIG. 5 is adopted.
[0163]
(Reference Example 2)
An LLG simulation was performed under the same conditions as described in the sixth embodiment when the structure of FIG. As a result, a coercive force of 2000 Oe was obtained.
[0164]
The coercive force 5100 Oe obtained in the sixth embodiment is an extremely effective value for preventing information recorded in the burst section 31 from being erased due to a malfunction. However, the coercive force of 2000 Oe obtained in this example is less than half of the coercive force of 5100 Oe obtained in Example 6, so that not only a high-output recording head but also a recording and reproducing device mounted on a general recording and reproducing apparatus is used. Even when a reproducing head is used, the information recorded in the burst section 31 may be erased due to the malfunction.
[0165]
【The invention's effect】
As described above, according to the present invention, servo control can be performed with sufficiently high precision on a patterned medium having an increased recording density.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing a part of a recording medium according to an embodiment of the present invention.
2A and 2B are enlarged plan views showing a burst portion of the recording medium shown in FIG. 1;
FIG. 3 is an enlarged plan view showing a burst portion of a recording medium according to a reference example.
FIG. 4 is an enlarged plan view showing a burst portion of a recording medium according to a reference example.
FIG. 5 is an enlarged plan view showing a burst portion of a recording medium according to a reference example.
6A to 6F are cross-sectional views schematically illustrating an example of a method of manufacturing a stamper that can be used in the method of manufacturing the recording medium illustrated in FIG.
FIG. 7 is a plan view schematically showing an example of a stamper that can be manufactured by the method shown in FIGS. 6 (a) to 6 (f).
8A to 8D are cross-sectional views schematically showing an example of a method for manufacturing the recording medium shown in FIG.
9A to 9D are cross-sectional views schematically showing another example of a method for manufacturing the recording medium shown in FIG.
FIG. 10 is a plan view schematically showing an example of a burst pattern that can be employed in the recording medium of FIG. 1;
11 is a perspective view schematically showing an example of a recording / reproducing apparatus on which the recording medium of FIG. 1 is mounted.
FIG. 12 is a plan view schematically showing a burst pattern of the recording medium manufactured in Example 1.
13 is a graph schematically showing an example of a signal obtained from the burst pattern shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Recording area, 3 ... Control area, 11 ... Substrate, 12 ... Ferromagnetic layer, 13 ... Non-magnetic layer, 21 ... Recording track, 31 ... Burst part, 32 ... Pad part, 41 ... No. 1 direction, 42 second direction, 51 broken line, 52 broken line, 61 substrate, 62 resist pattern, 63 resist layer, 301 first portion, 302 second portion, 101 stamper, 102 recording Area transfer surface, 103: Control area transfer surface, 121: Recording track transfer unit, 131: Burst transfer unit, 132: Pad transfer unit, 141: First direction, 142: Second direction, 151 Dashed line, 200 recording / reproducing device, 201 spindle, 202 fixed shaft, 203 magnetic head assembly, 204 voice coil motor, 1301 first transfer portion, 1302 second transfer portion, 2030 Effectuator eta arm, 2031 ... suspension, 2032 ... head slider, 2101 ... ferromagnetic dots, 3101 ... ferromagnetic dot, 12101 ... dot-like recesses, 13101 ... dot-like recesses.

Claims (9)

A recording area in which a recording track in which ferromagnetic dots or a group of ferromagnetic dots magnetically separated from each other are arranged in a first direction is arranged in a second direction intersecting the first direction; A control area adjacent to the first direction and holding servo information,
In the control region, a first portion in which ferromagnetic dots magnetically separated from each other are arranged and a second portion in which the ferromagnetic dots are not present are alternately arranged in the second direction,
In the first portion, at least one of the ferromagnetic dots that is in contact with the boundary between the first and second portions is one of the ferromagnetic dots located away from the boundary and one of the ferromagnetic dots on the boundary side. A recording medium having a shape in which a portion is missing. The recording region and the control region include a base provided with dot-shaped protrusions, and a layer provided on the base and having a form of a continuous film and containing a ferromagnetic material. The recording medium according to claim 1, wherein the recording medium is a portion located on an upper surface of the dot-shaped convex portion of a layer containing a material. The recording device according to claim 2, wherein the layer containing the ferromagnetic material is located deeper in the second portion than the ferromagnetic dots arranged in the first portion and the recording region. Medium. The recording medium according to claim 1, wherein the ferromagnetic dots in the recording area and the control area are provided on a flat base, and are separated from each other via a nonmagnetic layer. The recording medium according to claim 1, wherein the first and second portions are arranged in a checkered pattern. A recording medium according to any one of claims 1 to 5,
A recording / reproducing head capable of facing the recording medium,
A drive mechanism for moving the recording / reproducing head relative to the recording medium. A recording area transfer surface in which dot-shaped recesses or a group of dot-shaped recesses are arranged in a first direction is arranged in a second direction intersecting the first direction. And a control area transfer surface adjacent to the first direction in the first direction.
On the transfer surface for the control region, a first transfer portion formed by arranging dot-shaped recesses and a second transfer portion having no dot-shaped recesses are alternately arranged in the second direction,
In the first transfer portion, at least one of the dot-shaped recesses that is in contact with a boundary between the first and second transfer portions is different from the shape of the dot-shaped recess located away from the boundary from one of the boundaries. An apparatus for manufacturing a recording medium, wherein the apparatus has a shape in which a portion is missing. A step of forming a base having a dot-shaped convex portion corresponding to the dot-shaped concave portion on a surface by using the manufacturing apparatus according to claim 7 as a mold;
Forming a layer containing a ferromagnetic material on the surface of the base on which the dot-shaped protrusions are provided. Forming a layer containing a ferromagnetic material on the underground;
Forming a resist layer on the layer containing the ferromagnetic material,
Forming a dot-like convex portion corresponding to the dot-like concave portion on the surface of the resist layer by an imprinting method using the manufacturing apparatus according to claim 7 as a stamper;
Etching the ferromagnetic layer using the resist layer having the dot-shaped protrusions as a mask.

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