Abstract:
A magnetic sensor having a first sensor stack portion that includes a free layer, non-magnetic spacer or barrier layer and a portion of a pinned layer structure. The sensor has second sensor stack portion formed over the first sensor stack portion. The second sensor stack portion include includes a second portion of the pinned layer structure and a layer of antiferromagnetic material formed over the. The first sensor stack portion is configured with a width and stripe height that define the functional width and strip height of the sensor, whereas the upper portion can be made wider and deeper without affecting sensor performance. Because the patterning of the first sensor stack portion is performed on a thinner structure than would be necessary to pattern the entire sensor stack, the patterning can be performed with smaller dimensions and increased resolution.

Description:
FIELD OF THE INVENTION 
     The present invention relates to magnetic data recording and more particularly to a magnetic read sensor having a track-width defined by a bottom deposited free layer structure and having a pinned layer structure deposited over the free layer structure. 
     BACKGROUND 
     The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions. 
     The write head includes at least one coil, a write pole and one or more return poles. When a current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the write pole, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic disk, thereby recording a bit of data. The write field, then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head. 
     A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresisive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the adjacent magnetic media. 
     As the need for data density increases there is an ever present need to decrease the gap spacing of the magnetic sensor in order to decrease bit size and thereby increase linear data density. However, the thickness of the sensor layers can only be reduced so much without adversely affecting sensor performance and stability. Therefore, there remains a need for a magnetic sensor design that can provide robust sensor performance while also reducing gap spacing. 
     SUMMARY 
     The present invention provides a magnetic sensor that includes a sensor stack having a first portion and a second portion formed over the first portion. The first portion has a width that defines a sensor track-width and the second portion has a width that extends beyond the sensor track-width. The first portion of the sensor stack includes: a magnetic free layer; a non-magnetic layer; and a first portion of a first magnetic pinned layer. The non-magnetic layer is sandwiched between the magnetic free layer and the first portion of the first magnetic pinned layer. The second portion of the sensor stack includes: a second portion of the first magnetic pinned layer; a second magnetic pinned layer; a non-magnetic anti-parallel coupling layer sandwiched between the first magnetic pinned layer and the second magnetic pinned layer; and a layer of anti-ferromagnetic material exchange coupled with the second magnetic pinned layer. 
     The sensor can be formed by a process that includes, depositing a first sensor stack portion that includes: a magnetic free layer; a non-magnetic layer deposited over the magnetic free layer; and a first portion of a first magnetic pinned layer deposited over the non-magnetic layer. The track-width and back edge of the first sensor stack portion are then defined. A second sensor stack portion is then deposited over the first sensor stack portion. The second sensor stack portion includes: a second portion of the first magnetic pinned layer; a non-magnetic anti-parallel coupling layer deposited over the second portion of the first magnetic pinned layer; a second magnetic pinned layer deposited over the non-magnetic anti-parallel coupling layer; and a layer of antiferromagnetic material deposited over the second magnetic pinned layer. 
     Because the functional track-width and stripe height of the sensor are patterned and defined on the first sensor portion, smaller dimensions and finer resolution of sensor can be achieved than would be possible if the entire sensor stack were to be patterned. This improves sensor dimension resolution and allows for decreased track-width for increased data density. 
     In addition, a portion the antiferromagnetic material can be removed near the air bearing surface and the resulting space refilled with a magnetic material that can be stitched to an upper magnetic shield. This removes the thickness of the antiferromagnetic material from the total gap thickness thereby resulting in substantially reduced magnetic spacing. 
     These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the figures in which like reference numerals indicate like elements throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale. 
         FIG. 1  is a is a schematic illustration of a disk drive system in which the invention might be embodied; 
         FIG. 2  is an ABS view of a slider illustrating the location of a magnetic head thereon; 
         FIG. 3  is an ABS view of a magnetic read sensor as might be formed on a slider of a magnetic data recording system; 
         FIG. 4  is side, cross sectional view of the magnetic sensor of  FIG. 3  as seen from line  4 - 4  of  FIG. 3 ; and 
         FIGS. 5-25  are views of a magnetic sensor in various intermediate stages of manufacture, illustrating a method of manufacturing a magnetic sensor according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein. 
     Referring now to  FIG. 1 , there is shown a disk drive  100  embodying this invention. As shown in  FIG. 1 , at least one rotatable magnetic disk  112  is supported on a spindle  114  and rotated by a disk drive motor  118 , all of which are mounted within a housing  101 . The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk  112 . 
     At least one slider  113  is positioned near the magnetic disk  112 , each slider  113  supporting one or more magnetic head assemblies  121 . As the magnetic disk rotates, slider  113  moves radially in and out over the disk surface  122  so that the magnetic head assembly  121  can access different tracks of the magnetic disk where desired data are written. Each slider  113  is attached to an actuator arm  119  by way of a suspension  115 . The suspension  115  provides a slight spring force which biases slider  113  against the disk surface  122 . Each actuator arm  119  is attached to an actuator means  127 . The actuator means  127  as shown in  FIG. 1  may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller  129 . 
     During operation of the disk storage system, the rotation of the magnetic disk  112  generates an air bearing between the slider  113  and the disk surface  122  which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension  115  and supports slider  113  off and slightly above the disk surface by a small, substantially constant spacing during normal operation. 
     The various components of the disk storage system are controlled in operation by control signals generated by control unit  129 , such as access control signals and internal clock signals. Typically, the control unit  129  comprises logic control circuits, storage means and a microprocessor. The control unit  129  generates control signals to control various system operations such as drive motor control signals on line  123  and head position and seek control signals on line  128 . The control signals on line  128  provide the desired current profiles to optimally move and position slider  113  to the desired data track on disk  112 . Write and read signals are communicated to and from write and read heads  121  by way of recording channel  125 . 
     With reference to  FIG. 2 , the orientation of the magnetic head  121  in a slider  113  can be seen in more detail.  FIG. 2  is an ABS view of the slider  113 , and as can be seen the magnetic head including an inductive write head and a read sensor, is located at a trailing edge of the slider. The above description of a typical magnetic disk storage system and the accompanying illustration of  FIG. 1  are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders. 
       FIGS. 3 and 4  show a schematic view of a magnetic read head  300 .  FIG. 3  is a view of the sensor  300  as seen from the air bearing surface (ABS), and  FIG. 4  is a side cross sectional view as seen from line  4 - 4  of  FIG. 3 . The magnetic read head  300  includes a sensor stack  302  that is sandwiched between upper and lower magnetic shields  304 ,  306  that can be constructed of an electrically conductive, magnetic material such as NiFe so that they can function as electrical leads as well as magnetic shields. 
     The sensor stack  302  includes a first sensor stack portion (lower portion)  308  and a second sensor stack portion (upper portion)  310 . As shown in  FIG. 3 , the lower portion  308  has a width that defines a sensor track-width TW, whereas the upper portion  310  can be much wider. 
     The lower sensor portion  308  can include a magnetic free layer  312  that can be formed on a seed layer  314 . The magnetic free layer  312  can include materials such as NiFe, CoFe and/or a Heusler alloy. A non-magnetic spacer or barrier layer  316  can be formed over the magnetic free layer  312 . The non-magnetic spacer layer  316  can be a magnetically insulating material such as MgO, if the sensor  300  is a tunnel junction sensor or can be an electrically conductive spacer layer such as AgSn if the sensor  300  is a giant magnetoresistive (GMR) sensor. The lower sensor portion  308  also includes a first portion of a first magnetic pinned layer (AP1 first portion)  318   a , which can be constructed of a magnetic material such as NiFe or CoFe. The layer  318   a  will be discussed in greater detail herein below. 
     The sensor stack  302  includes a pinned layer structure  320  that include a first pinned magnetic layer (AP1)  318  and second pinned magnetic layer  322  and an antiparallel coupling layer  324  sandwiched between the AP1 layer  318  and AP2 layer  322 . The antiparallel coupling layer  324  can be formed of a material such as Ru. As seen in  FIG. 3 , the AP1 layer  318  is formed as two magnetic layers, a first layer  318   a  and a second layer  318   b . The first layer  318   a  is part of the lower sensor stack portion  308 , while the second layer  318   b  is part of the upper sensor stack portion  310 . Also, it can be seen that the first layer  318   a  has a width that is within the track-width TW, whereas the second layer  318   b  extends laterally beyond the track-width TW. A method for manufacturing such pinned layer structure  320  with the novel bi-layer AP1 layer  318  will be described in greater detail herein below. Both the AP1 and AP2 layers can be constructed of one or more magnetic materials such as CoFe, NiFe or combinations of these. 
     With reference to  FIG. 4 , the upper sensor stack portion  310  includes layer of antiferromagnetic material AFM layer  326  that is formed over the pinned layer structure  320 , opposite the free layer  312 . As seen in  FIG. 4 , the AFM layer  326  is recessed from the ABS, and a magnetic pedestal  402  is disposed between the AFM layer  326  and the ABS and also between the AP2 layer  322  and the upper shield  306 . The AFM layer  326  can be a material such as IrMn or PtMn and is exchange coupled with the AP2 layer  322 . The exchange coupling between the AFM layer  326  and the AP2 layer  322  pins the magnetization of the AP2 layer in a direction that is perpendicular to the ABS. The antiparallel coupling between the AP1 layer  318  and AP2 layer  322  pins the magnetization of the AP1 layer  318  in a direction that is also perpendicular to the ABS and that is opposite to that of the AP2 layer  322 . A capping layer  328  can be formed over the AFM layer  326  to protect the underlying layers during manufacture and to magnetically decouple the sensor stack  302  from the upper shield  306 . The space behind the first sensor stack portion  308  can be filled with a non-magnetic, electrically insulating fill layer such as alumina  404 . 
     The magnetic pedestal  402  can be constructed of a material similar to that of the upper shield  306 , such as NiFe. The magnetic pedestal  402  can be magnetically coupled with the magnetic shield  306  so that it functions as part of the magnetic shield. As a result, the AFM layer  326  and capping layer  328  advantageously do not contribute to the read gap, resulting in increased data density. Therefore, the read gap G is the distance between the top of the lower shield  304  and the bottom of the pedestal  402  as shown  FIG. 4 . 
     With reference again to  FIG. 3 , the sensor  300  can include magnetic bias layers  330 ,  332  at either side of the sensor stack  302 . The bias layers  330 ,  332  provide a magnetic bias field that biases the magnetization of the magnetic free layer  312  in a direction parallel with the air bearing surface (ABS). The bias layers  330 ,  332  can be separated from the sensor stack  302  and bottom shield by a thin, non-magnetic, electrically insulating material such as alumina  334 . The magnetic bias structures  330 ,  332  can be constructed of a high coercivity, hard magnetic material that keeps its magnetization as a result of its intrinsic hard magnetic properties. Alternatively, the bias layers  330 ,  332  can be constructed of a soft magnetic material. In that case, the magnetization of the bias structure can be maintained by an exchange coupled layer of antiferromagnetic material formed there-under. For example, a layer of nonmagnetic material such as Ru  336 , a layer of antiferromagnetic material such as IrMn  338  formed over the nonmagnetic material  336  and a magnetic layer  340  formed over the layer of antiferromagnetic material  338 . The non-magnetic layer  336  magnetically decouples the layer  338  from the bottom shield  304 . The antiferromagnetic layer  338  is exchange coupled with the magnetic layer  340  to pin its magnetization. This pinned magnetization of the layer  340  then maintains the magnetization of the bias layers  330 ,  332  in a desired direction parallel with the air bearing surface. 
       FIGS. 5-25  illustrate a method for manufacturing a magnetic sensor such as the sensor  300 , and further illustrate the advantages provided by such a sensor structure. With particular reference to  FIG. 5 , a bottom magnetic shield  502  is formed of a material such as NiFe. Then, an optional series of layers can be deposited to maintain magnetization of a yet to be formed bias structure. These layers can include: a non-magnetic decoupling layer such as Ru  504  deposited onto the bottom shield; a layer of antiferromagnetic material  506  deposited over the decoupling layer  504 ; and a layer of magnetic material such as NiFe  508  deposited over the layer of antiferromagnetic material  506 . 
     After depositing the optional layers  504 ,  506 ,  508 , a first series of sensor layers  510  is deposited. This first series of sensor layers  510  can correspond to the bottom sensor stack portion  308  described above with reference to  FIG. 3 . The first series of sensor layers  510  can include: a seed layer  512 ; a magnetic free layer  514  formed over the seed layer  512 , a non-magnetic barrier or spacer layer  516  deposited over the magnetic free layer  514  and a first portion of a magnetic first pinned layer (first portion of an AP1 layer)  518  formed over the non-magnetic spacer or barrier layer  516 . 
     Then, a first mask structure  520  is formed over the first series of sensor layers. The configuration of the mask  520  can be better understood with reference to  FIG. 6  which shows a top down view as seen from line  6 - 6  of  FIG. 5 . As can be seen in  FIG. 6  the mask  520  extends over an air bearing surface plane denoted ABS and extends to a back edge  522  that is configured to define a lower sensor stack stripe height. 
     With reference now to  FIG. 7 , a first ion milling is performed to remove layers not protected by the mask  520 . The ion milling can be performed until the bottom shield  502  has been reached. Then, a non-magnetic, electrically insulating fill layer such as alumina  802  is deposited and a planarization process performed, leaving a structure as shown in  FIG. 8 . The planarization can include performing a chemical mechanical polishing and may include a mask liftoff process. 
     As can be seen from the above, the masking and milling process that defines the track-width TW is performed on a much thinner structure (the series of sensor layers  510 ) than would be the case if rest of the pinned layer structure and antiferromagnetic pinning layer were to be included. This advantageously allows the masking and ion milling to define a much smaller track with than would otherwise be possible. 
     With reference now to  FIGS. 9 and 10 , a second mask structure  902  is formed.  FIG. 10  is a top down view as seen from line  10 - 10  of  FIG. 9 . The mask  902  has an opening  904  that is configured to define a stripe height of a lower sensor stack portion. Then, with reference to  FIG. 11 , a second ion milling is performed to remove material not protected by the mask  902 . This ion milling can be terminated prior to removal of layers  504 ,  506 ,  508  as shown in  FIG. 11 . With reference to  FIG. 12 , a thin, nonmagnetic, electrically insulating layer  1202  is deposited. The layer  1202  can be a material such as SiN and is preferably deposited by a conformal deposition process such as atomic layer deposition or ion beam deposition. 
     Then, with reference to  FIG. 13 , a directional material removal process such as ion milling is performed in such a manner to remove horizontally disposed portions of the insulation layer  1202  leaving vertical insulation side walls as shown in  FIG. 13 . Then, with reference to  FIG. 14 , a magnetic bias material  1402  is deposited followed by a CMP stop layer/bias capping layer  1404 . The bias material  1402  can be NiFe and the capping layer can be carbon or diamond like carbon. The insulation side walls  1202  passivate the sensor layers  510 , while leaving the magnetic layer  508  exposed to exchange couple with the magnetic bias layer  1402 . Then, a chemical mechanical polishing (CMP) can be performed to planarize the structure and remove the second mask  902 , leaving a structure as shown in  FIG. 15 . 
     With reference now to  FIG. 16 , a glancing angle mill, such as at an angle of 50 degrees-75 degrees is performed to expose layer  518  then a second series of sensor layers  1602  is deposited. These layers  1602  can correspond with the upper sensor stack portion  310  described above with reference to  FIGS. 3 and 4 . The series of sensor layers include a magnetic layer  1604  that forms a second portion of the AP1 layer. An anti-parallel coupling layer such as Ru  1606  is deposited over the magnetic layer  1604 . Another magnetic layer (AP2) layer  1608  is deposited over the anti-parallel coupling layer  1606 . A layer of antiferromagnetic material (AFM layer) such as IrMn or PtMn  1610  is deposited over the AP2 layer  1608 , and a capping layer  1612  is deposited over the AFM layer  1610 . The capping layer can include one or more of Ta and Ru. 
     Then, with reference to  FIG. 17 , a third mask structure  1702  is formed over the second series of sensor layers  1602 . The configuration of the mask  1702  can be seen more clearly with reference to  FIG. 18 , which shows a top-down view as seen from line  18 - 18  of  FIG. 17 . The mask  1702  defines the outer boundaries (stripe height and width) of the second series of sensor layers  1602 . Then, with reference to  FIG. 19 , a third ion milling is performed to remove material not protected by the third mask  1702 . The third ion milling can be performed until the bottom shield  502  has been reached. Then, an electrically insulating, nonmagnetic fill layer  2002  is deposited and a planarization process such as chemical mechanical polishing is performed, leaving a structure as shown in  FIG. 20 . 
     With reference now to  FIGS. 21 and 22 , a fourth mask structure  2101  is formed having an opening  2104  located in a region at the air bearing surface.  FIG. 22  is a side cross sectional view as seen from line  22 - 22  of  FIG. 21 . With reference to  FIG. 23 , an ion milling is performed just sufficiently to remove portions of the capping layer  1612  and AFM layer  1610  that are not protected by the mask  2102 , stopping at the AP2 layer  1608 . Then, a magnetic material  2402  is deposited and a planarization process such as chemical mechanical polishing is performed, leaving a structure as shown in  FIG. 24  with the magnetic material  2402  forming a pedestal. Then, with reference to  FIG. 25 , an upper magnetic shield  2502  is formed, such as by electroplating. The upper magnetic shield  2502  is stitched to and magnetically connected with the magnetic pedestal.  2402 . 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.