JP2008016064A - Patterned magnetic recording medium and magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a patterned medium capable of recording/reproducing data with an existing HDD recording system without performing a synchronized recording for its strength to fluctuations in writing timing. <P>SOLUTION: The patterned magnetic recording medium is provided with: a substrate; and a recording layer formed on the substrate, having a plurality of sides with planar shapes inclined in a down track direction, a first width part of a cross track direction, and a second width part smaller than the first width part of the cross track direction, and including recording bits constituting projecting patterns. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium, and more particularly to a patterned magnetic recording medium. The present invention also relates to a magnetic recording apparatus incorporating a patterned medium.

  Research is progressing to increase the recording capacity of HDDs (hard disk drives) by improving the surface recording density of magnetic recording media. As a result, each recording bit size on the magnetic recording medium has become extremely fine, about several tens of nm. In order to obtain a reproduction output from such a fine recording bit, it is necessary to ensure as much saturation magnetization and film thickness as possible for each bit. However, the amount of magnetization per bit decreases with the miniaturization of recording bits. As the amount of magnetization per bit decreases, there is a problem that magnetization reversal due to “thermal fluctuation” easily occurs, and magnetization information is lost. That is, the magnetic anisotropy energy required to keep the magnetization direction of the magnetic particles in one direction is about the same as the thermal fluctuation energy at room temperature, and the magnetization fluctuates with time, which causes the recorded information to disappear. . In general, the smaller the value of Ku · V / kT (where Ku is the anisotropy constant, V is the minimum magnetization unit volume, k is the Boltzmann constant, and T is the absolute temperature), the greater the influence of this thermal fluctuation. From experience, it is said that when Ku · V / kT is less than 100, magnetization reversal due to “thermal fluctuation” occurs.

As a medium for solving the problem of magnetization reversal due to thermal fluctuation, a magnetic recording medium called a “patterned medium” has attracted attention (see, for example, Patent Document 1). In general, a patterned medium is a magnetic recording medium in which a plurality of magnetic material regions each serving as a recording bit unit are independently formed in a nonmagnetic material layer. However, a magnetically continuous magnetic thin film has a size of a recording magnetic domain. It can also be said to be a divided medium. In a general patterned medium, as a non-magnetic material layer, for example, oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , nitrides such as Si ₃ N ₄ , AlN, TiN, carbides such as TiC, BN, etc. Borides are used, and ferromagnetic regions are selectively formed in these nonmagnetic layers. Since the patterned medium is obtained by dividing the magnetic thin film into the size of the recording magnetic domain, the minimum magnetization unit volume V can be increased, and the problem of thermal fluctuation can be avoided.

  On the other hand, in the recent improvement in the track density of HDDs, the problem of interference with adjacent tracks has become apparent. In particular, reduction of writing blur due to the magnetic head fringe effect is an important technical issue. For example, a discrete track type patterned magnetic recording medium (DTR medium) that physically separates recording tracks described in Patent Document 2 has a side erase phenomenon during recording and information on adjacent tracks during reproduction. Therefore, the density in the cross track direction can be increased, and a high-density magnetic recording medium can be provided. The DTR medium is a form of patterned medium.

  In a conventional HDD recording system, for example, recording is performed on blank paper (continuous film). An address (servo information) is written at an arbitrary position on a blank sheet, and a record is written based on the address. Since the servo information and the recording mark are synchronized, the information is not lost. On the other hand, the patterned medium is not a blank paper but a graph paper in which addresses are written in advance. If recording is not possible in a predetermined cell (recording bit), information is lost. This is the biggest problem with patterned media technology. The positioning accuracy of the current recording / reproducing head is about 10 nm, but this is in the radial direction (cross track direction) of the medium, and the concept of positioning is not necessary with respect to the rotation direction (down track direction) of the medium. However, in the case of a patterned medium, since the recording bits are physically separated, it is necessary to write the record only in the portion where the recording bit exists in the rotation direction of the medium, that is, to perform synchronized recording. For this reason, when performing recording and writing on a conventional patterned medium, a recording error occurs if the writing timing is shifted even a little. Therefore, strict synchronized recording is required, and the current HDD recording system cannot be used as it is. This synchronized recording has become the biggest issue for the practical application of patterned media.

  Non-Patent Document 1 discusses synchronized recording on a bit patterned medium. Non-Patent Document 1 describes that in a patterned medium, magnetization reversal does not occur unless the recording head covers up to half of the bits.

Non-Patent Document 2 discusses a phenomenon in which an asymmetric structure acts as an asymmetric potential barrier when a domain wall moves with respect to a soft magnetic wire.
JP 2001-17604 A Japanese Patent Laid-Open No. 7-85406 IEEE trans. mag. Vol. 38, NO. 4, 1725 (2002) J. et al. Appl. Phys. 97, 066101 (2005)

  An object of the present invention is to provide a patterned medium that can be recorded and reproduced by an existing HDD recording system without having to perform synchronized recording because it is resistant to fluctuations in writing timing.

  Another object of the present invention is to provide a magnetic recording apparatus equipped with a patterned medium that can be recorded and reproduced by an existing HDD recording system without having to perform synchronized recording because it is resistant to fluctuations in writing timing. is there.

  A patterned magnetic recording medium according to an aspect of the present invention includes a substrate, a plurality of sides formed on the substrate, the planar shape of which is inclined with respect to the down-track direction, and a first width portion in the cross-track direction. And a recording layer including a recording bit having a convex pattern and having a second width portion narrower than the first width in the cross track direction.

  A magnetic recording / reproducing apparatus according to another aspect of the present invention includes the patterned magnetic recording medium and a recording / reproducing head.

  According to the present invention, it is possible to provide a medium that can be recorded and reproduced by an existing HDD recording system without having to perform synchronized recording because it is resistant to fluctuations in writing timing.

  Further, according to the present invention, it is possible to provide a magnetic recording apparatus equipped with a medium that can perform recording / reproduction with an existing HDD recording system without having to perform synchronized recording because it is resistant to fluctuations in write timing.

  Embodiments of the present invention will be described below. Here, the traveling direction of the recording head that performs recording on recording bits is referred to as a down-track direction, and the direction orthogonal to the down-track direction is referred to as a cross-track direction.

  FIG. 1 shows a schematic sectional view of an embodiment of the patterned medium of the present invention. In the patterned medium of FIG. 1, a base layer 2 and a recording bit 3 forming a convex pattern are formed on a substrate 1. A nonmagnetic embedded layer 7 is embedded in the recesses between the recording bits 3 forming a convex pattern, and the recording bits 3 are separated from each other via the embedded layer 7. Further, in the medium of FIG. 1, a protective film 8 is formed so as to cover the recording bit 3 and the nonmagnetic buried layer 7. A lubricant (not shown) is applied on the protective film 8.

  The pattern of the recording bit 3 is schematically shown in FIG. FIG. 2 shows a surface pattern of a discrete bit type patterned magnetic recording medium in which a data portion 11, a preamble portion 12, an address portion 13, and a burst portion 14 are formed as a pattern of a ferromagnetic recording layer.

FIG. 3A shows an enlarged plan view of the recording bit 3 of FIG. The upper arrow in FIG. 3A indicates the down track direction. The recording bit 21 in FIG. 3A has a planar shape that is parallel to the cross track direction on the downstream side in the down track direction and has a width of w ₁ and the cross track direction on the upstream side in the down track direction. Is a trapezoid having a second side having a width w ₂ (w ₂ is smaller than w ₁ ) and two sides inclined with respect to the down-track direction.

  The present inventors pay attention to the fact that the energy required for the domain wall movement in the direction toward the narrow part is lower than the energy required for the domain wall movement in the direction toward the wide part, as shown in FIG. In addition, by providing a difference in the width of the recording bit in the cross-track direction, it is possible to control the moving direction of the domain wall generated in the recording bit, and widen the timing at which recording can be performed reliably without causing a recording error. I found that I can do it.

  Recording on the recording bit is performed by reversing the magnetization of the recording bit by a recording magnetic field generated from the recording head. In the case of a patterned medium, the magnetization reversal state of the recording bit differs depending on the position of the recording head when the recording magnetic field is generated. If a recording magnetic field is generated at a timing when the recording head is positioned so as to cover the entire recording bit to be recorded when viewed from above the recording head, all portions of the recording bit in the bit are magnetized and recorded. Succeeds. However, if a recording magnetic field is generated when the timing deviates from the above-described timing, a portion where magnetization reversal occurs and a portion where reversal does not occur occur in a recording bit, and a domain wall occurs at the boundary. This state where the domain wall exists is called a multi-domain structure, and becomes unstable as the recording bit becomes smaller. Since the recording bit of the patterned medium is not large enough to have a multi-domain structure, the recording bit of the multi-domain structure is more affected by the domain wall moving either upstream or downstream in the down track direction. Transition to a stable single domain structure. Considering the moving direction of the recording head, if the domain wall moves upstream in the down-track direction, the entire recording bit is reversed and recording is successful, while if the domain wall moves downstream in the down-track direction, the recording bit is It can be seen that a recording error occurs without magnetization reversal.

  The amount of energy required for the domain wall to move depends on the width of the recording bit in the cross track direction. Therefore, in the case where the recording bit is a conventional bit having a uniform width in the cross track direction, the amount of energy required does not change between the movement of the domain wall upstream in the down track direction and the movement of the domain wall downstream. Therefore, it is probabilistic which domain wall moves, and it is probabilistic whether recording is successful.

  On the other hand, as shown in FIG. 3A, the planar shape of the recording bit of the patterned medium of this embodiment is such that the width of the side parallel to the cross track direction on the upstream side in the down track direction is downstream in the down track direction. Because the trapezoid is smaller than the width of the side parallel to the cross track direction on the side, the domain wall generated in the recording bit moves to the upstream side in the down track direction where the required energy is lower, and as a result, the magnetization of the entire recording bit is reversed. Therefore, even if the timing of writing to the recording bit is shifted, recording succeeds without causing a recording error as long as the magnetization of a part of the recording bit is reversed.

  Here, the size of the allowable range of the write timing shift of the present embodiment will be described while comparing the patterned medium of the present embodiment with a conventional patterned medium.

  FIG. 4 schematically shows the positional relationship between the recording head 20 and recording bits. The arrow described above the recording track 20 in FIG. 4A indicates the downtrack direction.

  When the recording magnetic field is generated at the timing shown in FIG. 4A, the recording magnetic field does not reach the recording bit 21 and the recording magnetic field reaches the entire recording bit 22. Therefore, if the recording magnetic field is generated at the timing of FIG. 4A, the recording bit 21 is not recorded because the magnetization reversal does not occur regardless of the shape of the recording bit. Recording is successful because the entire recording bit 22 causes magnetization reversal.

  FIG. 4B shows the positional relationship where the upstream end of the recording head 20 in the down-track direction and the upstream end of the recording bit 22 in the down-track direction overlap when viewed from above. Show. If the recording magnetic field is generated at the timing shown in FIG. 4B, the recording magnetic field reaches the entire recording bit 22 as in FIG. 4A. Therefore, the magnetization of the recording bit 22 is reversed regardless of the shape. Therefore, if the recording magnetic field is generated at the timing between FIG. 4A and FIG. 4B, recording is successful regardless of the shape of the recording bit 22.

  FIG. 4C shows the positional relationship when the recording head 20 further moves in the down track direction from the position shown in FIG. When the recording magnetic field is generated at the timing shown in FIG. 4C, a domain wall is generated in the recording bit 22. As described above, since the recording bit of the patterned medium cannot take a multi-domain structure, the recording bit 22 transitions to a single-domain state when the domain wall moves.

  5A and 5B respectively show the magnetization states of the recording bits 22 of the conventional patterned medium and the patterned medium of the present embodiment when the recording magnetic field is generated at the timing of FIG. 4C. It is the surface view represented typically. As shown in FIG. 5A, in the case of a conventional patterned medium in which the recording bit has a rectangular surface shape, the domain wall is either upstream in the down-track direction (left side) or downstream in the down-track direction (right side). It is probabilistic that a recording error will occur, and a recording error may occur. That is, for the conventional patterned medium, it can be seen that the timing of FIG. 4C cannot be said to be a timing at which reliable recording can be performed. On the other hand, in the case of the patterned medium of this embodiment in which the surface shape of the recording bit is trapezoidal, when a domain wall is generated in the recording bit 22, the domain wall is upstream in the down-track direction as shown in FIG. As a result, magnetization reversal occurs in the entire recording bit 22 as a result. That is, for the patterned medium of the present invention, it can be seen that the timing of FIG. 4C is a timing at which reliable recording can be performed.

  When the recording head 20 is further moved to generate a recording magnetic field at the timing shown in FIGS. 4D and 4E, the position where the domain wall is generated changes. 5C and 5D schematically show the magnetization states of the recording bits 22 of the conventional patterned medium and the patterned medium of the present embodiment when the recording magnetic field is generated at the timing of FIG. 4E. FIG. As shown in FIG. 5C, in the case of a conventional patterned medium in which the planar shape of the recording bits is a rectangle, it is uncertain whether the recording is successful or a recording error occurs. That is, for the conventional patterned medium, it can be said that the timing of FIG. 4E cannot be said to be a timing at which reliable recording can be performed. On the other hand, in the case of the patterned medium of this embodiment in which the surface shape of the recording bit is trapezoidal, the domain wall moves upstream in the down-track direction as shown in FIG. Magnetization reversal occurs. That is, for the patterned medium of the present invention, it can be seen that the timing of FIG. 4E is a timing at which reliable recording can be performed.

  From the above, in the patterned medium of this embodiment in which the surface shape of the recording bit is trapezoidal, the domain wall moves upstream in the down-track direction wherever the recording bit 22 occurs, and as a result, the entire bit 22 is magnetized. It turns out that it reverses. That is, when viewed from the top of the recording head 20, the positional relationship where the downstream end of the recording head 20 on the downstream side and the downstream end of the recording bit 22 in the down-track direction overlap, that is, the positional relationship of FIG. It can be seen that the recording is successful even if the recording magnetization is generated at the timing just before the time becomes. After the positional relationship shown in FIG. 4F is reached, the recording magnetic field does not reach the recording bit 22, and recording is not successful.

  Consider the above facts in terms of recording margins. Here, the recording margin is an allowable range of the write timing at which recording can be performed without a recording error, as a moving distance of the recording head. In the patterned medium, the size of the recording bits is uniform, and the recording bits are arranged at equal intervals in the medium. Hereinafter, the length of the recording bit 21 and the recording bit 22 of the present embodiment in the down-track direction is a bit length m, and the distance between the recording bit 21 and the recording bit 22 is an inter-bit spacing n.

  In the case of the patterned medium of the present embodiment in which the planar shape of the recording bit is trapezoidal, if a recording magnetic field is generated at the timings of FIGS. 4A to 4F as described above, recording can be performed without recording errors. Is possible. The moving distance of the recording head 20 from FIG. 4A to FIG. 4B corresponds to the inter-bit spacing n, and the moving distance of the recording head 20 from FIG. 4B to FIG. Corresponds to the length m. Therefore, the patterned medium of the present embodiment can have a recording margin of bit spacing n + bit length m.

  On the other hand, in the case of a conventional patterned medium in which the planar shape of the recording bit is rectangular, as described above, a recording error may occur unless a recording magnetic field is generated at the timings of FIGS. 4 (A) to 4 (B). For this reason, only the inter-bit spacing n can be taken as the recording margin.

  As described above, the patterned medium of the present embodiment can ensure a recording margin longer than the conventional patterned medium by a distance corresponding to the bit length. Therefore, the conventional patterned medium has a narrow recording margin and needs synchro recording in order to prevent a recording error. However, the patterned medium of the present embodiment can have a wide recording margin and can record without performing the synchro recording. It can be seen that errors can be suppressed.

  Next, a modification of the embodiment of the present invention described above will be described. FIG. 6 shows the surface pattern of the patterned medium of this modification. The pattern of FIG. 6 is a surface pattern of a discrete track type patterned magnetic recording medium in which the recording track 15, the preamble portion 12, the address portion 13, and the burst portion 14 are formed as a pattern of a ferromagnetic recording layer.

  Since the discrete track type patterned medium has a structure in which recording bits are connected in the down track direction, it does not require strict synchronized recording as the discrete bit type patterned medium. However, in a conventional DTR medium in which the width of the recording track in the cross-track direction is uniform, if the recording timing is shifted and a domain wall is generated in a recording bit as a recording unit, a recording error occurs because the moving direction of the domain wall is not fixed. there's a possibility that.

  On the other hand, as can be seen from FIG. 6, the patterned medium of the present modification has a recording track 15 in which the recording bits 3 of FIG. 2 having a trapezoidal plan shape are formed side by side in the down track direction. Since the shape of the recording bit 3 is the same as that of the embodiment of the present invention described above, even if a domain wall is generated in the recording bit 3 due to a recording timing shift, the entire domain of the recording bit is reversed in magnetization. It is possible to make the recording succeed for each recording bit which is each recording unit. Accordingly, the recording margin can be made wider than that of the conventional discrete track type patterned medium.

Next, another embodiment of the present invention will be described. FIG. 3B shows a schematic diagram of the planar shape of the recording bit of the patterned medium of the present embodiment. The recording bit in FIG. 3B has two sides on the upstream side and the downstream side in the down-track direction that are parallel to the cross-track direction and equal in width to w ₁ , and the width w _{2 in the} center in the cross-track direction. Has a hexagonal surface shape larger than the width w _{1 of the} two sides.

  FIG. 7 shows the magnetization state of the recording bit of the patterned medium of this embodiment when a domain wall is generated in the recording bit. FIG. 7A shows the magnetization state when the recording magnetic field is generated at the timing of FIG. 4C, and FIG. 7B shows the recording magnetic field generated at the timing immediately before FIG. 4D. The magnetization state is shown. As can be seen from FIG. 7, if the domain wall is generated in the recording bit 22 anywhere upstream from the center in the down track direction, the domain wall moves to the upstream in the down track direction where the width in the cross track direction is narrow. As a result, the magnetization of the entire recording bit 22 is reversed. Therefore, it can be seen that for the patterned medium of this embodiment, the timing between FIGS. 4A to 4D is a timing at which reliable recording can be performed without a recording error. If the bit length of the recording bits of this embodiment is m ′, the patterned medium of this embodiment can take the recording margin n + bit spacing n + half the bit length m ′ / 2. In other words, the patterned medium of the present embodiment can have a recording margin wider than the conventional patterned medium by half m ′ / 2 of the bit length, so that recording errors can be suppressed without performing synchronized recording. You can see that

Next, still another embodiment of the present invention will be described. FIG. 3C shows a schematic diagram of the planar shape of the recording bit of the patterned medium of the present embodiment. The recording bit in FIG. 3C has two sides, which are parallel to the cross track direction and equal in width w ₂ , on the upstream side and the downstream side in the down track direction, and the width w _{1 in} the center cross track direction is The surface shape is smaller than the width w _{2 of the} two sides. In the patterned medium of the present embodiment, when the bit length of the recording bit is m ″, the recording margin can be set to n−bit spacing n + half the bit length m ″ / 2. That is, the patterned medium of the present embodiment can provide a recording margin wider than the conventional patterned medium by a half bit length m ″ / 2, so that recording errors can be suppressed without performing synchronized recording. be able to.

  Hereinafter, an example of a method for producing a patterned medium of the present invention will be described with reference to the drawings. The material of each component of the patterned medium will be described later.

First, as shown in FIG. 8A, an underlayer 2 (including a soft magnetic underlayer and an orientation control underlayer), a recording bit 3 and a protective layer 4 are sequentially formed on a substrate 1. For example, on the glass substrate 1, a CoZrNb layer as a soft magnetic layer is 120 nm, Ru is 20 nm as an orientation control underlayer, and a CoCrPt—SiO ₂ layer is 20 nm as a ferromagnetic recording layer, and a protective layer is formed thereon. A C protective layer is deposited to 4 nm.

  As shown in FIG. 8B, an imprint resist layer 5 is formed on the protective layer 4 by spin coating. As the imprint resist, for example, a general novolak photoresist or spin-on-glass (SOG) can be used.

  As shown in FIG. 8C, the pattern is transferred by pressing a stamper 6 onto the imprint resist layer 5 (imprint method). The stamper 6 has a concavo-convex pattern corresponding to each pattern of a track portion, a preamble portion, an address portion, and a burst portion to be transferred. By applying a fluorine-based release agent on the surface of the stamper in advance, the stamper 6 and the imprint resist layer 5 can be peeled off favorably.

  Here, a method of manufacturing an imprint stamper for pattern transfer used for manufacturing the patterned medium of the present invention will be described with reference to FIG.

  In an ordinary imprint stamper manufacturing method, a desired pattern is formed on a stamper master using electron beam (EB) drawing. In this method, the pattern is drawn while the position of the EB is fixed and the disk-shaped master is rotated.

  In manufacturing the stamper for manufacturing the patterned medium of the present invention, the EB irradiation position is finely adjusted in the radial direction of the master, and the master is rotated by changing the radial position of the EB spot as shown in FIG. Draw while drawing. Thus, the shape of the recording bit of the patterned medium of the present invention can be drawn. At this time, since the exposure amount increases at the place where the EB spots overlap, blanking (thinning of the beam current) is performed according to the exposure amount. This makes it possible to draw with a uniform depth. By this method, a pattern of recording bits having a surface shape such as a trapezoid or a hexagon can be drawn.

  Since the pattern drawn by EB becomes a concave portion on the master, when a stamper is raised from this master, a stamper (father stamper) in which recording bits are formed by convex portions can be manufactured. By further raising the stamper from the father stamper, a mother stamper in which the recording bit is formed by the concave portion is manufactured, and this is used for imprinting.

  Further, here, pattern transfer by the imprint method will be described. Imprinting is performed using a die set. On the lower plate of the die set, the stamper 6, the substrate 1, and the buffer layer are laminated in this order, and the upper plate of the die set is installed on the die set so as to be sandwiched between the lower plate of the die set. At this time, the unevenness of the stamper 6 and the imprint resist layer 5 formed on the substrate 1 are laminated to face each other. The pressing is performed, for example, at 2000 bar for 60 seconds. 60 seconds is the movement time of the resist.

  By removing the stamper 6 after the imprint process, as shown in FIG. 8D, the substrate 1 having the imprint resist layer 5 to which the uneven pattern is transferred is obtained.

As shown in FIG. 8E, reactive ion etching (RIE) is performed to remove the resist residue remaining in the pattern recess transferred to the imprint resist layer 5. The gas used for RIE is appropriately selected according to the material of the imprint resist layer 5. When SOG is used as the imprint resist, a fluorine-based gas such as CF ₄ or SF ₆ is preferable. However, since it may react with water in the atmosphere to generate acids such as HF and H ₂ SO ₄ , Need to do. When a novolak photoresist is used as the imprint resist, RIE using oxygen gas is suitable. The plasma source is preferably an inductively coupled plasma (ICP) capable of generating a high-density plasma at a low pressure, but an electron cyclotron resonance (ECR) plasma or a general parallel plate RIE apparatus is used. You can also

As shown in FIG. 8F, magnetic material processing is performed using the imprint resist layer 5 from which the residue has been removed as an etching mask. Etching using Ar ion beam (Ar ion milling) is suitable for magnetic processing, but RIE using Cl gas or a mixed gas of CO and NH ₃ may also be used. In the case of RIE using a mixed gas of CO and NH ₃ , a hard mask such as Ti, Ta, or W must be used as an etching mask. When these magnetic bodies RIE are used, the magnetic body unevenness is not tapered. When performing magnetic processing by Ar ion milling that can etch any material, for example, etching is performed by changing the acceleration voltage 400V and the ion incident angle from 30 ° to 70 °. Milling using an ECR ion gun can be processed with a taper on the magnetic material unevenness by etching with a stationary facing type (ion incident angle of 90 °). As a result, the concave / convex pattern of the recording bit 3 is formed.

  As shown in FIG. 8G, the imprint resist layer 5 remaining on the convex portion of the recording bit 3 is removed. For removing the resist, a method similar to that for removing the resist residue can be used.

  As shown in FIG. 8H, in order to realize stable flying of the recording / reproducing head, the concave / convex pattern of the recording bit 3 is embedded by the nonmagnetic embedded layer 7. The embedding is performed by depositing a non-magnetic material by bias sputtering or normal sputtering. The bias sputtering method is a method of forming a sputtering film while applying a bias to the substrate, and can easily form a film while embedding irregularities. However, since the substrate is easily melted and sputter dust is generated by the substrate bias, it is preferable to use a normal sputtering method.

  As shown in FIG. 8I, etch back is performed until the recording bit 3 is exposed. In the etch back process, it is preferable to use Ar ion milling. Since the silicon-based buried layer is used in the method of the present invention, RIE using a fluorine-based gas can also be performed. Etching using ECR may also be used.

As shown in FIG. 8J, the C protective layer 4 is formed. The C protective layer 4 is preferably formed by a CVD method in order to improve the coverage to the unevenness, but may be a sputtering method or a vacuum evaporation method. When the C protective layer 4 is formed by the CVD method, a DLC film containing a large amount of sp ³ bonded carbon is formed. If the film thickness is 2 nm or less, the coverage is poor, and if it is 10 nm or more, the magnetic spacing between the recording / reproducing head and the medium increases and the SNR decreases, which is not preferable. A lubricant (not shown) is applied on the protective layer 3.

  Next, the configuration of the drive using the patterned medium of the present invention will be described with reference to FIG.

  FIG. 10 is an external perspective view showing one embodiment of the magnetic recording apparatus according to the present invention. The magnetic recording apparatus includes a magnetic disk 50, a magnetic head 55, a head suspension assembly (suspension and arm) 54 on which the magnetic head 55 is mounted, an actuator 53, and a circuit board 56 inside a housing. The magnetic disk 50 is attached to a spindle motor 51 and rotated, and various digital data are recorded by a perpendicular magnetic recording method. The magnetic head 55 is a so-called composite head, and a single magnetic pole structure write head and a read head using a GMR film or a TMR film are mounted on a common slider mechanism. A shield type MR reproducing element or the like is used for the read head. The head suspension assembly 54 supports the magnetic head opposite to the recording surface of the magnetic disk. The actuator 53 positions the magnetic head 53 at an arbitrary radial position of the magnetic disk 50 via a head suspension assembly 54 by a voice coil motor (VCM) 52. The circuit board 56 includes a head IC, and generates a drive signal for the actuator 53 and a control signal for performing read / write control of the magnetic head 55.

(Example)
Hereinafter, embodiments of the present invention will be described in detail.

(Example 1)
In this example, a patterned medium was manufactured according to the method shown in FIG.

First, a 120 nm CoZrNb layer as a soft magnetic layer, a 20 nm Ru layer as an orientation control underlayer, a 20 nm CoCrPt—SiO ₂ layer as a ferromagnetic recording layer, and a 4 nm carbon as a protective layer were sequentially formed on a glass substrate. .

  Thereafter, SOG as an imprint resist layer was applied on the protective film to a thickness of 100 nm by spin coating.

  Next, the imprint stamper on which the concave / convex pattern having a trapezoidal shape as shown in FIG. 11A is pressed on the SOG layer to perform imprinting, and the concave / convex pattern is transferred to the SOG layer. .

After the pattern transfer, RIE was performed in the ICP etching apparatus to remove the imprint residue in the recessed portion of the transferred uneven pattern. The RIE was performed for 30 seconds under the following conditions: process gas; CF ₄ , chamber pressure; 2 mTorr, Coil RF; 100 W, Platen RF;

  After removing the resist residue, the magnetic layer was subjected to magnetic processing by ion milling using the imprint resist as an etching mask. Ion milling was performed in the etching apparatus for 3 minutes under the following conditions: process gas; Ar, plasma source; ECR ion gun, microwave power; 800 W, acceleration voltage: 500 V. After etching by ion milling, the protective layer and the ferromagnetic recording layer were completely removed in the concave portion, and an uneven pattern with a height difference of 24 nm from the upper surface of the convex portion to the upper surface of the concave portion was formed in the magnetic layer.

After processing the magnetic material, SOG remaining on the magnetic layer protrusions was removed by RIE. RIE was performed for 1 minute under the following conditions: process gas; CF ₄ , chamber pressure; 2 mTorr, Coil RF; 100 W, Platen RF;

  After removing the resist, a nonmagnetic embedding material was embedded in the concave portion of the pattern of the magnetic layer for the purpose of stable flying of the recording / reproducing head in the sputtering apparatus. In this example, the embedding was performed by depositing 100 nm of C at 500 W and 0.5 Pa with a sputter deposition apparatus for HDD.

  Next, the nonmagnetic embedded layer was etched back. Etchback was performed by ion milling using an ECR ion gun for about 5 minutes under the following conditions: process gas; Ar, microwave power; 800 W, acceleration voltage; The end point of etch back was detected when Co on the surface of the magnetic layer was detected using a quadrupole mass spectrometer (Q-mass).

  After the etch back, a patterned medium of this example was obtained by forming a DLC protective layer on the surface by CVD (chemical vapor deposition) and applying a lubricant thereon.

  As shown in FIG. 11A, the surface shape of the recording bit of the manufactured patterned medium has a width of a side parallel to the cross track direction on the upstream side in the down track direction of 80 nm and the cross on the downstream side in the down track direction. It was a trapezoid with a side width parallel to the track direction of 120 nm and a maximum bit length of 25 nm in the down track direction. This patterned medium has a recording density equivalent to 130 Gbpsi.

When this medium was incorporated in an HDD and the bit error rate (BER) was measured, a good value of 1.0 × 10 ⁻⁶ was obtained.

(Comparative Example 1)
A patterned medium was produced in the same manner as in Example 1 except that a stamper whose surface shape of the pattern corresponding to the recording bits was rectangular in the imprint process was used.

  The shape of the recording bit of the manufactured patterned recording medium was a rectangle having a width in the cross track direction of 120 nm and a width in the down track direction (bit length) of 25 nm.

When this medium was incorporated in an HDD and the BER was measured, a value of 1.0 × 10 ⁻⁴ was obtained.

  Comparing the results of Example 1 and Comparative Example 1, it can be seen that the medium of Example 1 has a two-digit BER better than the medium of Comparative Example 1. This is because the sync recording sequence was not incorporated in the recording head, so the medium of Comparative Example 1, which is a conventional patterned medium, caused a recording error when a recording magnetic field was generated at a timing shifted from the recording bit. Therefore, it is considered that the BER has deteriorated. On the other hand, the medium according to the first embodiment has a recording margin for recording bits that is wider than the conventional medium by a bit length, that is, 25 nm, so that recording errors can be prevented without performing synchronized recording. It is thought that the BER was better than that.

(Example 2)
A patterned medium was produced in the same manner as in Example 1 except that a stamper having a hexagonal surface shape as shown in FIG.

  As shown in FIG. 11B, the surface shape of the recording bit of the manufactured patterned medium is such that the width of two sides parallel to the upstream and downstream cross-track directions in the down-track direction is 80 nm, respectively. It was a hexagon having a width of 120 nm in the cross track direction and a maximum bit length of 50 nm in the down track direction. This patterned medium has a recording density equivalent to 65 Gbpsi.

When this medium was incorporated into an HDD and the BER was measured, a good value of 1.0 × 10 ⁻⁶ was obtained.

(Example 3)
A patterned medium was produced in the same manner as in Example 1 except that a stamper whose surface shape of the pattern corresponding to the recording bit was as shown in FIG. 11C was used in the imprint process.

  As shown in FIG. 11C, the surface shape of the recording bit of the manufactured patterned medium is 120 nm in width parallel to the upstream and downstream cross track directions in the down track direction, and the width in the center cross track direction. Was 80 nm, and the maximum bit length in the down-track direction was 50 nm. This patterned medium has a recording density equivalent to 65 Gbpsi.

When this medium was incorporated into an HDD and the BER was measured, a good value of 1.0 × 10 ⁻⁶ was obtained.

  From the results of Examples 2 and 3, the recording bit surface of the medium having a hexagonal shape has a recording margin that is wider than the conventional medium by half the bit length, that is, 25 nm. Has also been found to prevent recording errors and thereby exhibit better BER than conventional media.

  The size of the first to third embodiments can be drawn by the current EB drawing. In other words, the patterned medium having the trapezoidal shape of the recording bit of Example 1 was able to confirm a recording density equivalent to 130 Gbpsi, but other bit shapes could only confirm a recording density equivalent to half of 65 Gbpsi. From this point, it can be said that a medium in which the recording bit has a trapezoidal planar shape is the best. However, if there is an EB drawing apparatus capable of further fine drawing, it is considered that if the bit plane shape is a hexagonal medium, the recording bit plane shape is equivalent to a trapezoid medium.

Example 4
In the imprint process, a patterned medium was produced in the same manner as in Example 1 except that a stamper having a recording track pattern having a surface shape shown in FIG. 12 was used instead of the pattern corresponding to the recording bit.

  As shown in FIG. 12, the surface shape of the recording track of the manufactured DTR type patterned medium has a side width of 80 nm parallel to the cross track direction on the upstream side in the down track direction, and the cross track on the downstream side in the down track direction. The trapezoids whose side width parallel to the direction is 120 nm and the maximum bit length in the down track direction is 50 nm are arranged in the down track direction without gaps.

When this DTR medium was incorporated in an HDD and the BER was measured, a good value of 1.0 × 10 ⁻⁶ was obtained.

  From the results of Example 4, it can be seen that the recording error due to the deviation of the recording timing can be suppressed by controlling the movement of the domain wall by changing the width of the recording track in the cross track direction. Since the DTR medium has a structure connected in the down-track direction, it does not require strict synchronized recording as the discrete bit type patterned medium. However, it is considered that the DTR medium of Example 4 suppresses the recording error and exhibits a good BER, which is a great advantage.

  Hereinafter, the material used for each layer of the patterned medium according to the embodiment of the present invention and the laminated structure of each layer will be described.

<Board>
As the substrate, for example, a glass substrate, an Al-based alloy substrate, ceramic, carbon, a Si single crystal substrate having an oxidized surface, and those obtained by plating such a substrate with NiP or the like can be used. As the glass substrate, there are amorphous glass and crystallized glass, and general-purpose soda lime glass and aluminosilicate glass can be used as the amorphous glass. Further, as the crystallized glass, lithium-based crystallized glass can be used. As the ceramic substrate, a sintered body mainly composed of general-purpose aluminum oxide, aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used. As the substrate, a substrate in which a NiP layer is formed on the surface of the metal substrate or the nonmetal substrate by using a plating method or a sputtering method can also be used. Further, only the sputtering method has been described below as a method for forming a thin film on the substrate, but the same effect can be obtained by a vacuum deposition method or an electrolytic plating method.

<Soft magnetic underlayer>
The soft magnetic underlayer (SUL) is one of the functions of a magnetic head that circulates a recording magnetic field from a magnetic head for magnetizing a perpendicular magnetic recording layer, for example, a single magnetic pole head, to the magnetic head side in the horizontal direction. It can play the role of applying a steep and sufficient perpendicular magnetic field to the recording layer of the magnetic field to improve the recording / reproducing efficiency.

  For the soft magnetic underlayer, a material containing Fe, Ni, and Co can be used. Examples of such materials include FeCo alloys such as FeCo and FeCoV, FeNi alloys such as FeNi, FeNiMo, FeNiCr, and FeNiSi, FeAl alloys, FeSi alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, and FeAlO. Examples thereof include FeTa, FeTaC, and FeTaN, and FeZr alloys such as FeZrN. Further, a material having a fine crystal structure such as FeAlO, FeMgO, FeTaN, FeZrN or the like containing 60 at% or more of Fe or a granular structure in which fine crystal particles are dispersed in a matrix can be used.

  As another material of the soft magnetic underlayer, a Co alloy containing Co and at least one of Zr, Hf, Nb, Ta, Ti, and Y can be used. Co is preferably contained at 80 at% or more. When such Co alloy is formed by sputtering, an amorphous layer is likely to be formed, and amorphous soft magnetic materials do not have magnetocrystalline anisotropy, crystal defects, and grain boundaries, and thus have excellent soft magnetism. Show. Further, the use of this amorphous soft magnetic material can reduce the noise of the medium. Examples of suitable amorphous soft magnetic materials include CoZr, CoZrNb, and CoZrTa-based alloys.

  Under the soft magnetic underlayer, an underlayer can be further provided in order to improve the crystallinity of the soft magnetic underlayer or the adhesion to the substrate. As the underlayer material, Ti, Ta, W, Cr, Pt, alloys containing these, oxides or nitrides thereof can be used.

  An intermediate layer made of a nonmagnetic material can be provided between the soft magnetic underlayer and the recording layer. There are two roles of the intermediate layer: blocking the exchange coupling interaction between the soft magnetic underlayer and the recording layer, and controlling the crystallinity of the recording layer. As the intermediate layer material, Ru, Pt, Pd, W, Ti, Ta, Cr, Si, alloys containing these, oxides or nitrides thereof can be used.

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

<Ferromagnetic recording layer (general structure)>
The perpendicular magnetic recording layer is preferably made of an alloy containing Co as a main component and containing Pt because high anisotropy can be achieved. The recording layer may further be made of a material containing an oxide. As this oxide, silicon oxide, titanium oxide, or an oxide of a metal constituting the magnetic recording layer is particularly suitable.

  In the perpendicular magnetic recording layer, magnetic particles (crystal grains having magnetism) are preferably dispersed in the layer. The magnetic particles preferably have a columnar structure penetrating the perpendicular magnetic recording layer vertically. By forming such a structure, the orientation and crystallinity of the magnetic particles in the perpendicular magnetic recording layer are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. it can. In order to obtain such a structure, the amount of oxide to be contained is important. The oxide content is preferably 3 mol% or more and 12 mol% or less with respect to the total amount of Co, Cr, and Pt. More preferably, it is 5 mol% or more and 10 mol% or less. The above range is preferable as the content of the oxide in the perpendicular magnetic recording layer because, when the layer is formed, the oxide is precipitated around the magnetic particles, so that the magnetic particles can be isolated and refined. It is. When the oxide content exceeds the above range, the oxide remains in the magnetic particles, and the orientation and crystallinity of the magnetic particles are impaired. This is not preferable because a columnar structure in which magnetic particles penetrate vertically through the perpendicular magnetic recording layer is not formed. Further, when the oxide content is less than the above range, separation and miniaturization of magnetic particles are insufficient, resulting in an increase in noise during recording and reproduction, and a signal / noise ratio (S) suitable for high-density recording. / N ratio) is not obtained. The content of Cr in the perpendicular magnetic recording layer is preferably 0 at% or more and 16 at% or less. More preferably, it is 10 at% or more and 14 at% or less. The Cr content is in the above range because the uniaxial crystal magnetic anisotropy constant Ku of the magnetic particles is not lowered too much, and high magnetization is maintained, resulting in recording / reproduction characteristics suitable for high-density recording and sufficient heat. This is because it is suitable for obtaining fluctuation characteristics. When the Cr content exceeds the above range, Ku of the magnetic particles becomes small, so the thermal fluctuation characteristics deteriorate, and the crystallinity and orientation of the magnetic particles deteriorate, resulting in poor recording / reproducing characteristics. Therefore, it is not preferable. The Pt content in the perpendicular magnetic recording layer is preferably 10 at% or more and 25 at% or less. The Pt content is in the above range because Ku required for the perpendicular magnetic layer is obtained, and the crystallinity and orientation of the magnetic particles are good. As a result, thermal fluctuation characteristics and recording / reproduction characteristics suitable for high-density recording. This is preferable because it is obtained. When the Pt content exceeds the above range, a layer having an fcc structure is formed in the magnetic particles, and crystallinity and orientation may be impaired. Further, when the Pt content is less than the above range, it is not preferable because Ku for obtaining thermal fluctuation characteristics suitable for high density recording cannot be obtained.

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

  In addition to the above, the perpendicular magnetic recording layer is at least selected from the group consisting of CoPt alloys, CoCr alloys, CoPtCr alloys, CoPtO, CoPtCrO, CoPtSi, CoPtCrSi, and Pt, Pd, Rh, and Ru. A multilayer structure of an alloy mainly composed of one kind and Co, and CoCr / PtCr, CoB / PdB, CoO / RhO, and the like obtained by adding Cr, B, and O to these can be used.

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

<Nonmagnetic buried layer>
Nonmagnetic materials used for the nonmagnetic buried layer include oxides such as SiO ₂ , TiO _x , and Al ₂ O ₃ , nitrides such as Si ₃ N ₄ , AlN, and TiN, carbides such as TiC, borides such as BN, A wide selection can be made from simple substances such as C and Si.

<Protective layer>
The protective layer is provided for the purpose of preventing corrosion of the perpendicular magnetic recording layer and preventing damage to the medium surface when the magnetic head comes into contact with the medium. Examples of the material include those containing C, SiO ₂ and ZrO ₂ . The thickness of the protective layer is preferably 1 to 10 nm. Thereby, the distance between the head and the medium can be reduced, which is suitable for high-density recording.

Carbon can be classified into sp ² bonded carbon (graphite) and sp ³ bonded carbon (diamond). Durability and corrosion resistance are superior to sp ³ -bonded carbon, but since it is crystalline, surface smoothness is inferior to graphite. Usually, the carbon film is formed by sputtering using a graphite target. In this method, amorphous carbon in which sp ² bonded carbon and sp ³ bonded carbon are mixed is formed. Those having a large proportion of sp ³ bonded carbon are called diamond-like carbon (DLC). Since it is excellent in durability and corrosion resistance and is excellent in surface smoothness due to being amorphous, it is used as a surface protective film of a magnetic recording medium. DLC film formation by the CVD (Chemical Vapor Deposition) method excites and decomposes the source gas in plasma and generates DLC by a chemical reaction. By adjusting the conditions, DLC richer in sp ³ bond carbon can be obtained. Can be formed.

<Lubrication layer>
Examples of the lubricant used in the lubricating layer include conventionally known materials such as perfluoropolyether, fluorinated alcohol, and fluorinated carboxylic acid.

1 is a schematic cross-sectional view of a patterned medium according to an embodiment of the present invention. The top view which shows the example of the magnetic pattern of the patterned medium of one Embodiment of this invention. The figure which shows the example of the surface shape of the recording bit of the patterned medium of this invention. The figure which shows the timing of recording with respect to the patterned medium of this invention. 4C and 4E, when the recording magnetic field is generated for the conventional recording bit having a rectangular planar shape and the recording bit of the present invention having a trapezoidal planar shape, The schematic diagram which shows a magnetization state. The top view which shows the example of the magnetic pattern of the DTR type patterned medium which is a modification of one Embodiment of this invention. FIG. 4C shows the magnetization state of a recording bit when a recording magnetic field is generated for the recording bit of the present invention having a hexagonal plane shape at the timing shown in FIG. 4C and the timing just before reaching FIG. Pattern diagram. The figure which shows an example of the manufacturing method of the patterned medium of this invention. The figure which shows an example of the manufacturing method of the imprint stamper used in an example of the manufacturing method of the patterned medium of this invention. 1 is a cross-sectional view illustrating a configuration of an example of a magnetic recording / reproducing apparatus of the present invention. The top view of the recording bit of the patterned medium produced in the Example of this invention. The top view of the recording track of the DTR type patterned medium produced in the Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Underlayer, 3 ... Ferromagnetic recording layer, 4 ... Protective layer, 7 ... SiOC buried layer, 8 ... Protective layer, 11, 21, 22 ... Recording bit, 20 ... Recording head, 55 ... Magnetic head .

Claims (5)

A substrate,
A plurality of sides formed on the substrate and having a planar shape inclined with respect to the down-track direction, a first width portion in the cross-track direction, and a second width narrower than the first width in the cross-track direction And a recording layer including a recording bit having a convex pattern, and a patterned magnetic recording medium.   The planar shape of the recording bit is such that the first width side parallel to the cross track direction on the downstream side in the down track direction and the first width side parallel to the cross track direction on the upstream side in the down track direction. 2. The patterned magnetic recording medium according to claim 1, wherein the patterned magnetic recording medium is a trapezoid having a side having a short second width and two sides inclined with respect to the down-track direction.   2. The patterned magnetic recording according to claim 1, wherein the planar shape of the recording bit is a shape having two sides parallel to the cross track direction and having the same width on the upstream side and the downstream side in the down track direction. Medium.   4. The patterned shape according to claim 3, wherein the planar shape of the recording bit is a hexagon in which the width of the center in the cross track direction is longer than two sides on the upstream side and the downstream side in the down track direction. Magnetic recording medium.   A magnetic recording / reproducing apparatus comprising the patterned magnetic recording medium according to claim 1 and a recording / reproducing head.

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