Abstract:
A method for reducing thin film media layer thickness while maintaining adequate magnetic recording performance includes providing a substrate comprising a rigid support structure, depositing a soft underlayer on top of the substrate, depositing an interlayer on top of the soft underlayer and depositing a exchange break layer on top of the interlayer, wherein the exchange break layer comprises a flash layer of RuTi and a seed layer of Ru. The flash layer is deposited in place of a pure Ru layer, thereby reducing the amount of Ru deposited as well as decreasing the thickness of the overall intermediate layer. The magnetic performance of the media is maintained with the substitution of a RuTi flash layer for a pure Ru layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to perpendicular magnetic recording media, including continuous and patterned recording media, and more particularly to apparatus and methods for reducing the thickness and cost of an exchange break layer of perpendicular magnetic recording media. 
         [0003]    2. Description of the Related Art 
         [0004]    Hard-disk drives provide data storage for data processing systems in computers and servers, and are becoming increasingly pervasive in media players, digital recorders, and other personal devices. Advances in hard-disk drive technology have made it possible for a user to store an immense amount of digital information on an increasingly small disk, and to selectively retrieve and alter portions of such information almost instantaneously. Particularly, recent developments have simplified hard-disk drive manufacture while yielding increased track densities, thus promoting increased data storage capabilities at reduced costs. 
         [0005]    In a hard-disk drive, rotating high precision aluminum or glass disks are coated on both sides with a special thin film media designed to store information in the form of magnetic patterns. Electromagnetic read/write heads suspended or floating only fractions of micro inches above the disk are used to either record information onto the thin film media, or read information from it. 
         [0006]    A read/write head may write information to the disk by creating an electromagnetic field to orient a cluster of magnetic grains, known as a bit, in one direction or the other. In longitudinal magnetic recording media applications, a magnetic recording layer has a magnetic c-axis (or easy axis) parallel to the disk plane. As the Hard-Drive industry is transitioning to perpendicular recording technology, adjustments are being made to adapt the disk media so that the magnetic c-axis of the Cobalt alloy grows perpendicular to the disk plane. Hexagonal Close Packed (HCP) cobalt alloys are typically used as a magnetic recording layer for perpendicular recording. Most media manufacturers now rely on a Cobalt alloy with the incorporation of an oxide segregant to promote the formation of small and uniform grains. 
         [0007]    To read information, magnetic patterns detected by the read/write head are converted into a series of pulses which are sent to the logic circuits to be converted to binary data and processed by the rest of the system. To write information, a write element located on the read/write head generates a magnetic write field that travels vertically through the magnetic recording layer and returns to the write element through a soft underlayer. In this manner, the write element magnetizes vertical regions, or bits, in the magnetic recording layer. Because of the easy axis orientation, each of these bits has a magnetization that points in a direction substantially perpendicular to the media surface. To increase the capacity of disk drives, manufacturers are continually striving to reduce the size of bits and the grains that comprise the bits. 
         [0008]    The ability of individual magnetic grains to be magnetized in one direction or the other, however, poses problems where grains are extremely small. The superparamagnetic effect results when the product of a grain&#39;s volume (V) and its anisotropy energy (K u ) fall below a certain value such that the magnetization of that grain may flip spontaneously due to thermal excitations. Where this occurs, data stored on the disk is corrupted. Thus, while it is desirable to make smaller grains to support higher density recording with less noise, grain miniaturization is inherently limited by the superparamagnetic effect. To maintain thermal stability of the magnetic grains, material with high K u  may be used for the magnetic layer. However, material with a high K u  requires a stronger magnetic field to reverse the magnetic moment. Thus, the ability of the write head to write on magnetic material may be reduced where the magnetic layer has a high K u  value. 
         [0009]    The perpendicular magnetic recording medium is generally formed with a substrate, a soft magnetic underlayer (SUL), an interlayer, an exchange break layer, a perpendicular magnetic recording layer, and a protective layer for protecting the surface of the perpendicular magnetic recording layer. The exchange break layer and the interlayer comprise a plurality of Ruthenium layers which serve to control the size and orientation of the magnetic crystal grains in the magnetic recording layer. The exchange break layer and the interlayer also serve to magnetically de-couple the SUL and the perpendicular magnetic recording layer. Ruthenium is a rare material and therefore adds substantially to the overall cost involved with creating the perpendicular recording medium. 
         [0010]    Accordingly, a need exists for a practical, attainable apparatus, system, and method for reducing thin film media layer thickness. Beneficially, such an apparatus, system and method would reduce the amount of Ruthenium used in the layers on a thin film media. Such apparatuses, systems and methods are disclosed and claimed herein. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available apparatus, systems and methods. Accordingly, the present invention has been developed to provide apparatus, system and methods for reducing thin film media layer thickness while simultaneously reducing the use of Ruthenium in the layers on a thin film media. 
         [0012]    In one embodiment in accordance with the invention, a recording medium for perpendicular recording applications includes a soft magnetic underlayer deposited on a nonmagnetic substrate and a perpendicular magnetic recording layer deposited below an overcoat layer. A flash layer is deposited between the soft magnetic underlayer and the perpendicular magnetic recording layer. The perpendicular magnetic recording layer has an axis of magnetic anisotropy substantially perpendicular to the surface thereof. The flash layer comprises a RuTi alloy. 
         [0013]    In certain embodiments, the concentration of Ti in the RuTi alloy is in the range of about 5 to about 20 atomic percent. In select embodiments, the concentration of Ti is about 10 atomic percent. In certain embodiments the thickness of the flash layer is in the range of about 5 to about 20 angstroms. 
         [0014]    In another embodiment in accordance with the invention, a recording medium for perpendicular recording applications includes a substrate comprising a rigid support structure for depositing a plurality of layers thereon, an overcoat layer comprising a protective coating, a soft magnetic underlayer disposed between the overcoat layer and the substrate, an interlayer deposited on the soft magnetic underlayer, an exchange break layer disposed on the interlayer, and a perpendicular magnetic recording layer disposed between the exchange break layer and the overcoat layer. The soft underlayer comprises a cobalt containing alloy and the exchange break layer comprises a flash layer and a seed layer. The flash layer comprises a RuTi alloy wherein the concentration of Ti is in the range of about 5 to about 20 atomic percent. The seed layer comprises Ru. The perpendicular magnetic recording layer has a coercivity and an axis of magnetic anisotropy substantially perpendicular to the surface thereof. 
         [0015]    In certain embodiments the crystal structure of the flash layer comprises a hexagonal-close-packed structure that orients the c-axis of the grains of the perpendicular magnetic recording layer perpendicular to the flash layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
           [0017]      FIG. 1  is a top view of a hard-disk drive; 
           [0018]      FIG. 2  is a cross-section view of the layers of a perpendicular recording media in accordance with one embodiment of the present invention; 
           [0019]      FIG. 3  is a cross-section view of the layers of a perpendicular recording media showing a read/write head disposed above the media in accordance with one embodiment of the present invention; 
           [0020]      FIGS. 4A-4D  are cross-section views illustrating several embodiments of the interlayer in accordance with the present invention; 
           [0021]      FIGS. 5A and 5B  are cross-section views illustrating two embodiments of the exchange break layer in accordance with the present invention; 
           [0022]      FIG. 6  is a flowchart showing a method for fabricating a perpendicular recording medium according to one embodiment in accordance with the present invention; 
           [0023]      FIG. 7  is a flowchart showing a method for fabricating a perpendicular recording medium according to one embodiment in accordance with the present invention; 
           [0024]      FIG. 8  is a flowchart showing a method for fabricating a perpendicular recording medium according to one embodiment in accordance with the present invention; 
           [0025]      FIG. 9  illustrates a comparison of rocking angles (c-axis dispersion angle) for an exchange break layer without a RuTi flash layer versus an exchange break layer with a RuTi flash layer according to one embodiment of the current invention; 
           [0026]      FIG. 10  is a table illustrating performance values for media with a RuTi flash layer versus media without a RuTi flash layer according to one embodiment of the current invention; 
           [0027]      FIG. 11A  is a graph illustrating a change in coercivity as a function of a RuTi flash layer thickness in accordance with one embodiment of the current invention; 
           [0028]      FIG. 11B  is a graph illustrating soft error rate of magnetic performance as a function of a RuTi flash layer thickness in accordance with one embodiment of the current invention; and 
           [0029]      FIG. 12  is a graph illustrating the change in coercivity as a function of layer thickness according to one embodiment of the current invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
         [0031]    Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are disclosed to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0032]    Referring now to  FIG. 1 , a diagram of a conventional hard-disk drive assembly  100  is shown. A hard-disk drive assembly  100  generally comprises a plurality of hard disks comprising a perpendicular magnetic recording media  102 , rotated at high speeds by a spindle motor (not shown) during operation. The perpendicular magnetic recording media  102  will be more fully described herein. Concentric data tracks  104  formed on either or both disk surfaces receive and store magnetic information. 
         [0033]    A read/write head  110  may be moved across the disk surface by an actuator assembly  106 , allowing the head  110  to read or write magnetic data to a particular track  104 . The actuator assembly  106  may pivot on a pivot  114 . The actuator assembly  106  may form part of a closed loop feedback system, known as servo control, which dynamically positions the read/write head  110  to compensate for thermal expansion of the perpendicular magnetic recording media  102  as well as vibrations and other disturbances. Also involved in the servo control system is a complex computational algorithm executed by a microprocessor, digital signal processor, or analog signal processor  116  that receives data address information from an associated computer, converts it to a location on the perpendicular magnetic recording media  102 , and moves the read/write head  110  accordingly. 
         [0034]    Specifically, read/write heads  110  periodically reference servo patterns recorded on the disk to ensure accurate head  110  positioning. Servo patterns may be used to ensure a read/write head  110  follows a particular track accurately, and to control and monitor transition of the head  110  from one track  104  to another. Upon referencing a servo pattern, the read/write head  110  obtains head position information that enables the control circuitry  116  to subsequently re-align the head  110  to correct any detected error. 
         [0035]    Servo patterns may be contained in engineered servo sectors  112  embedded within a plurality of data tracks  104  to allow frequent sampling of the servo patterns for optimum disk drive performance. In a typical perpendicular magnetic recording media  102 , embedded servo sectors  112  extend substantially radially from the perpendicular magnetic recording media  102  center, like spokes from the center of a wheel. Unlike spokes however, servo sectors  112  form a subtly arc-shaped path calibrated to substantially match the range of motion of the read/write head  110 . 
         [0036]      FIG. 2  is a cross-sectional view of one possible embodiment of the perpendicular magnetic recording media  102 . The layers shown in  FIG. 2  may be deposited on a substrate  202  or on an adhesion layer  204  previously deposited on the substrate  202 . The layers may include a plurality of soft underlayers  206  and  208  separated by an antiferromagnetic coupling layer  210 , an intermediate layer  212  comprising an interlayer  214  and an exchange break layer  216 , a perpendicular magnetic recording layer  218 , a capping layer  220  and an overcoat  222 . The perpendicular magnetic recording media  102  may include other layers not shown in  FIG. 2 . Similarly, one skilled in the art will recognize that some of the layers illustrated in  FIG. 2  may be omitted in certain embodiments. 
         [0037]    The platter or substrate  202  may comprise an AlMg or glass platter which provides a rigid support structure upon which the recording media is deposited. In certain embodiments ion beam deposition or magnetron sputtering may be utilized to deposit the various layers comprising the perpendicular magnetic recording media  102 . 
         [0038]    In one embodiment, the first layer deposited on substrate  202  is an adhesion layer  204 . The adhesion layer  204  may comprise an AlTi layer to aid in the adhesion of subsequent layers. In certain embodiments the adhesion layer  204  may be omitted and a soft underlayer  206  may be deposited directly on the substrate  202 . 
         [0039]    The material comprising the soft underlayers  206  and  208  is a soft, magnetic, cobalt containing alloy located under the interlayer  214 . In certain embodiments the material comprising the soft underlayers  206  and  208  may be CoFeTaZr. 
         [0040]    An antiferromagnetic coupling layer  210  may be disposed between the soft underlayers  206  and  208  to couple the two soft underlayers  206  and  208 . The antiferromagnetic coupling layer  210  may be used to reduce magnetic signals originating from the soft underlayers  206  and  208  where such signals are undesirable in the perpendicular magnetic recording media  102 . 
         [0041]    The magnetic recording medium  102  may include a magnetic recording layer  218 , to store data. The magnetic recording layer  218  may comprise a plurality of magnetic grains  224  each having a magnetic easy axis substantially perpendicular to the media surface, thereby allowing the grains  224  to be vertically magnetized. The magnetic grains  224  may comprise a magnetic material such as CoPt or CoPtCr. To maintain a highly segregated magnetic layer  218 , one or more segregants may be added to the magnetic material. 
         [0042]    Referring now to  FIG. 3 , when writing, the write head  110  generates a magnetic write field  302  that travels vertically through the magnetic recording layer  218  and returns to the write head  110  through the soft underlayer  206  and  208 . In this manner, the write head  110  magnetizes vertical regions  304 , or bits  304 , in the magnetic recording layer  218 . Because of the easy axis orientation, each of these bits  304  has a magnetization  306  that points in a direction substantially perpendicular to the media surface. 
         [0043]    Because of the ability to utilize soft underlayers  206  and  208  in the perpendicular geometry, write fields generated by the perpendicular write head  110  may be substantially larger than conventional longitudinal recording write fields. This allows use of media  102  having a higher coercivity (Hc) and anisotropy energy (Ku), which is more thermally stable. Furthermore, unlike longitudinal recording, where the magnetic fields between two adjacent bits have a destabilizing effect, the magnetic fields of magnetization  306  of bits in perpendicular recording media  102  stabilize each other, enhancing the overall stability of perpendicular magnetic recording media even further. This allows for closer bit packing. 
         [0044]    Capping layer  220  is deposited on top of the perpendicular magnetic recording layer  218  which may comprise a Co alloy. Capping layer  220  serves to improve writeability of the media and to planarize the media to create a smooth surface upon which overcoat layer  222  is disposed. The Overcoat layer  222  may comprise a plurality of carbon layers to protect the perpendicular magnetic recording layer  218  and capping layer  220  against damage. 
         [0045]    An intermediate layer  212  may comprise a nonmagnetic layer disposed between the soft underlayer  208  and the perpendicular magnetic recording layer  218 . The intermediate layer  212  may comprise an interlayer  214  and an exchange break layer  216 . The intermediate layer  212  may serve to prevent the soft underlayer  208  from magnetically coupling with the perpendicular magnetic recording layer  218 . The intermediate layer  212  may also comprise a hexagonal-close-packed (HCP) crystalline structure to orient the magnetic grains  224  on the perpendicular magnetic recording layer  218  such that the magnetic c-axis or easy axis is parallel to the disk plane. 
         [0046]    Turning now to  FIG. 4A through 4D , the interlayer  214  may comprise a plurality of Cr containing layers. The material comprising the interlayer  214  may be a material with a HCP crystalline structure to act as a foundation to help align the magnetic grains  224  of the magnetic layer  218  perpendicular to the disk surface. In the embodiment illustrated in  FIG. 4A  a Cr layer may be deposited on a NiWCr layer. In another embodiment, illustrated in  FIG. 4B  the NiWCr layer may be deposited on a CrTi layer. In other embodiments, the pure Cr layer may be omitted as illustrated in  FIG. 4C . In another embodiment, illustrated in  FIG. 4D , NiWCr may be the only layer comprising the interlayer  214 . In another embodiment, not illustrated, the interlayer may be omitted and the exchange break layer  216  may be deposited directly on the soft underlayer  208 . Use of a Cr containing interlayer  214  permits a thinner Ru containing exchange break layer  216 . 
         [0047]      FIG. 5A  and  FIG. 5B  illustrate embodiments of the exchange break layer  216 . A flash layer  502  comprising a RuTi alloy may be deposited on a seed layer  504 . In certain embodiments the concentration of Ti in the flash layer  502  may be between about 5 to about 20 atomic percent. In one embodiment the concentration of Ti in the flash layer  502  may be about 10 atomic percent. The flash layer  502  may be about 5 angstroms to about 20 angstroms thick. The seed layer  504  may comprise pure Ru to orient the magnetic grains  224  of the perpendicular magnetic recording layer  218 . In the embodiment illustrated in  FIG. 5B  the seed layer  504  may be deposited on the flash layer  502 . 
         [0048]      FIG. 6  is a flow chart diagram depicting one embodiment of a method  600  for fabricating perpendicular recording medium  102  in accordance with the present invention. As depicted, the material for interlayer  214  may be deposited 602 first. The interlayer  214  may be deposited on a substrate  202  or on other layers as previously described. The interlayer may comprise pure Cr, a Cr containing alloy or layers of both pure Cr and Cr containing alloys. In step  604 , material for an exchange break layer  216  may be deposited on the interlayer  214 . The material for the exchange break layer may comprise a RuTi containing alloy. In step  606 , material for a perpendicular magnetic recording layer  218  may be deposited on the exchange break layer  216 . The material for the perpendicular magnetic recording layer  218  may comprise CoPtCr—SiOx or another similar material. There may be additional layers of material deposited than those described in method  600 . 
         [0049]      FIG. 7  is a flow chart of another possible method  700  of fabricating perpendicular magnetic recording medium  102 . In step  702 , material for a soft magnetic underlayer  206  is deposited on a substrate  202 . In step  704 , material for an antiferromagnetic coupling layer  210  is deposited on the soft magnetic underlayer  206 . In step  706 , material for another soft magnetic underlayer  208  is deposited on the antiferromagnetic coupling layer  210 . In step  708 , material for an interlayer  214  is deposited on the soft magnetic underlayer  208 . In step  710 , material for an exchange break layer  216  is deposited on the interlayer  214 . In step  712 , material for a perpendicular magnetic recording layer  218  is deposited on the exchange break layer  216 . There may be other layers of material deposited than those described in method  700 . 
         [0050]      FIG. 8  is a flow chart of another possible method  800  of fabricating perpendicular magnetic recording medium  102 . In step  802 , material for an adhesion layer  204  is deposited on a substrate  202 . In step  804 , material for a first soft magnetic underlayer  206  is deposited on adhesion layer  204 . In step  806 , material for an antiferromagnetic coupling layer  210  is deposited on the first soft magnetic underlayer layer  206 . In step  808 , material for a second soft magnetic underlayer  208  is deposited on the antiferromagnetic coupling layer  210 . In step  810 , material for an interlayer  214  is deposited on the second soft magnetic underlayer  208 . In step  812 , material for an exchange break layer  216  is deposited on the interlayer  214 . In step  814 , material for a perpendicular magnetic recording layer  218  is deposited on the exchange break layer  216 . In step  816 , material for a capping layer  220  is deposited on the perpendicular magnetic recording layer  218 . In step  818 , overcoat layer  222  is deposited on the capping layer  220 . There may be other layers of material deposited than those described in method  800 . 
         [0051]      FIG. 9  illustrates a comparison of rocking angles (c-axis dispersion angle) for a first exchange break layer  902  without a RuTi flash layer  502  versus a second exchange break layer  902  with a RuTi flash layer  502  according to one embodiment of the current invention. An interlayer  902  comprising a NiWCr layer, a Cr layer and a Ru layer was compared with an interlayer  904  comprising NiWCr layer, a Cr layer, a RuTi  10  layer and a Ru layer. The resulting data is illustrated a table  906  in  FIG. 9 . As can be seen in  FIG. 9 , when a flash layer  502  containing RuTi is incorporated into the exchange break layer  904 , the rocking angle  908  of the perpendicular magnetic recording layer  218  is not increased. Thus, there is no deterioration of the crystallographic texture with the addition of a RuTi flash layer  502 . 
         [0052]      FIG. 10  is a table  1000  illustrating performance values for media with a RuTi flash layer  502  in the second column  1002  and media without a RuTi flash layer  504  in the third column  1004  according to one embodiment of the current invention. The Byte/Bit Error Rate  1006  for media with a RuTi flash layer  502  is substantially the same as the Byte/Bit Error Rate  1006  for media without a RuTi flash layer  502 . Similarly, the magnetic core width  1008  may remain substantially the same for media with a RuTi flash layer  502  as the magnetic core width  1008  for media without a RuTi flash layer  502 . Thus, according to one embodiment of the current invention, the addition of a RuTi flash layer  502  may result in media with substantially the same performance characteristics as media without a RuTi flash layer. Further, the writeability  1010  for media with a RuTi flash layer  502  is greater than for media without a RuTi flash layer  502 . As a result, a magnetic material with a higher magnetic anisotropy (K u ) may be used for magnetic recording layer  218 . 
         [0053]    With reference to  FIG. 11A  and  FIG. 11B , an optimum RuTi flash layer  502  thickness may provide the highest magnetic coercive field required to reverse the magnetization of magnetic grains  224  as illustrated in  FIG. 11A . In one embodiment, the optimum thickness of the flash layer  502  may be in the range of about 5 angstroms to about 20 angstroms to provide the highest magnetic coercive field. Similarly, the optimum RuTi flash layer  503  thickness may provide the lowest soft error rate as illustrated in  FIG. 11B . In certain embodiments, the optimum thickness of the flash layer  502  to provide the lowest soft error rate may be in the range of about 5 angstroms to about 20 angstroms. In one embodiment the optimum thickness of the RuTi flash layer  503  may be the same to produce both the highest coercivity level as wells as the lowest soft error rate. 
         [0054]      FIG. 12  is a graph illustrating the change in coercivity as a function of layer thickness according to one embodiment of the current invention. As can be seen, a RuTi flash layer  502  may provide an optimum  1202  intermediate layer  212  thickness which is much smaller than media  102  without a RuTi flash layer  502  as illustrated by line  1204 . In certain embodiments the optimum  1202  thickness of the RuTi flash layer  502  is about 5 angstroms to about 20 angstroms. 
         [0055]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.