Abstract:
A magnetic sensor having improved pinned layer robustness for improved reliability and having improved side shielding for improved track resolution at very high data densities. The sensor has a pinned layer structure with laterally extending wing portions that become thicker with increasing distance from the air bearing surface and has a side shield structure has a thickness that decreases with increasing distance from the air bearing surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates to magnetic data recording and more particularly to a magnetic read sensor with a side shield and extended pinned layer design that improves side shielding while also improving pinned layer pinning. 
     BACKGROUND 
     A magnetoresistance effect magnetic head is a part used as a sensor to reproduce magnetic information recorded on a magnetic recording medium in a magnetic recording device of high recording density, primarily a hard disk, and largely governs the performance of magnetic recording technology. 
     Magnetic reproducing heads utilizing the magnetoresistance effect of a multilayer film having ferromagnetic metal layers laminated with a nonmagnetic intermediary layer in between, or so-called giant magnetoresistance effect (hereafter, GMR), or the like, have been used in recent years. The GMR head initially used was a CIP (current-in-plane) head, in which an electric signal is charged parallel within the film surface. To improve recording density, TMR (tunneling magnetoresistance effect) heads and a CPP-GMR (current perpendicular to plane-giant magnetoresistance effect) heads were developed, which appeared to be useful for obtaining high output by narrowing the track width and narrowing the gap. The TMR head has become the mainstream in magnetic reproducing heads today. The TMR head and the CPP-GMR head, unlike the conventional GMR head, greatly differ from CIP heads in that the sense current travels in a direction perpendicular to the planes of the sensor layers, rather than parallel. 
     Refining the effective track width of a magnetoresistive sensor and obtaining a high S/N ratio are required to respond to the demand in recent years for even higher density recording. Although there is a phenomenon of information being read in the width direction of reproduction tracks from an adjacent or nearby track, or so-called side reading, this phenomenon can be suppressed by forming a side shield structure of a soft magnetic material arranged to the left and right of the sensor. 
     SUMMARY 
     The present invention provides a magnetic sensor that includes, a magnetic pinned layer structure having a center portion extending to an air bearing surface and first and second laterally extending wing portions having a tapered front surface that is recessed from the air bearing surface. The sensor also has a magnetic free layer structure having first and second sides, and a non-magnetic layer sandwiched between the magnetic free layer structure and the magnetic pinned layer structure. The sensor further includes first and second magnetic side shield structures extending laterally from the first and second sides of the magnetic free layer structure, the magnetic side shield structures each having a back edge that is tapered to follow the taper of the tapered front surface of the laterally extending wing portions of the magnetic pinned layer structure. 
     The sensor can be manufactured by a process that includes, depositing a magnetic pinned layer structure, depositing a non-magnetic layer over the magnetic pinned layer structure, and depositing a magnetic free layer structure over the magnetic pinned layer structure. A mask is formed over the pinned layer structure, non-magnetic layer and magnetic free layer structure, the mask having a track-width defining portion extending to an air bearing surface and having laterally extending wing portions that are recessed from an air bearing surface plane. Then, an ion milling is performed in such a manner to form the magnetic pinned layer structure with laterally extending wing portions that have a tapered front surface. 
     After this masking and ion milling process has been performed to form the novel pinned layer shape, an insulation layer and magnetic side shield layer can be deposited. This can form a novel side shield structure having a tapered back edge that conforms with the tapered front edge of the pinned layer structure. 
     The novel pinned layer shape and side shield shape optimizes magnetic side shield effectiveness for improved data track resolution at very high data densities. At the same time, the novel pinned layer shape improves magnetic pinning of the pinned layer structure, thereby improving sensor reliability and robustness. 
     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 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 air bearing surface view of a magnetic sensor; 
         FIG. 4  is a side cross sectional view as seen from line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a side cross sectional view as seen from line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a perspective view of a portion of the sensor of  FIGS. 3-6 ; and 
         FIGS. 7-19  are views of a magnetic sensor shown in various intermediate stages of manufacture in order to illustrate a method for manufacturing a magnetic sensor. 
     
    
    
     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. The disk drive  100  includes a housing  101 . At least one rotatable magnetic disk  112  is supported on a spindle  114  and rotated by a disk drive motor  118 . 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 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. 
       FIG. 3  shows a magnetic sensor  300  that includes a sensor stack  302  that is sandwiched between a leading magnetic shield  304  and a trailing magnetic shield  306 . The leading and trailing magnetic shields can be constructed of an electrically conductive, magnetic material such as NiFe so that they can function as electrically conductive leads as well as magnetic shields. The sensor also includes magnetic first and second magnetic side shields  308  at either side of the sensor stack  302 . The first and second magnetic side shields are separated from the sensor stack  302  and from the bottom shield  304  by a non-magnetic, electrically insulating layer  312  in order to prevent sense current from being shunted through the sensor side shields  308 . 
     The sensor stack includes a pinned layer structure  314 , a magnetic free layer  316  and a non-magnetic barrier or spacer layer  318  sandwiched there-between. If the sensor  300  is a giant magnetoresistive sensor (GMR), then the layer  318  is a non-magnetic, electrically conductive spacer layer. On the other hand, if the sensor  300  is a tunnel junction magnetoresistive sensor (TMR), then the layer  318  is a thin, non-magnetic, electrically insulating barrier layer such as MgO. 
     The magnetic free layer  316  can be constructed of one or more magnetic materials and has a magnetization that is biased in a direction generally parallel with the air bearing surface (ABS) of the sensor, but which is free to move in response to a magnetic field, such as from a magnetic media. The magnetic free layer  316  can be formed of, for example, 5 nm of CoFeB and 2 nm of NiFe. The pinned layer structure  314  can be an anti-parallel coupled structure including first and second magnetic layers  320 ,  322  that are anti-parallel coupled across a non-magnetic anti-parallel coupling layer such as Ru,  324 . The magnetic layers  320 ,  322  can be formed of, for example, CoFeB. The first magnetic layer  320  can be exchange coupled with a layer of anti-ferromagnetic material (AFM layer)  326 . This exchange coupling pins the magnetization of the first magnetic layer  320  in a first direction that is perpendicular to the air bearing surface (ABS). The anti-parallel coupling between the first and second magnetic layers  320 ,  322 , then, pins the magnetization of the second magnetic layer  322  in a second direction that is perpendicular to the air bearing surface and anti-parallel with the first direction. In addition to the pinned layer  314 , free layer  316  and spacer/barrier layer  318 , the sensor stack can also include a seed layer  328 , such as Ta, at its bottom to induce a desired grains structure in the above deposited layers, and a capping layer  330  at its top to prevent damage to the underlying sensor layers during manufacture. 
     In order to increase data density, it is necessary to improve signal resolution by preventing reading of adjacent tracks. This allows data tracks to be spaced closer together, thereby increasing the number of data tracks the can be recorded and read in a given area of magnetic media. In addition, it becomes necessary to make the sensor ever smaller. However, as the sensor becomes smaller, the pinning strength of the pinned layer structure can suffer. The sensor structure disclosed herein provides improvement in both of these areas, providing strong robust pinning and improving data track resolution. 
     With reference to  FIGS. 4 and 5 , a novel pinned layer structure  314  and novel side magnetic shield structure  308  can be better understood.  FIG. 4  shows a side cross sectional view of a plane that is perpendicular to the air bearing surface at a location within the central portion of the sensors stack  302  as taken from line  4 - 4  of  FIG. 3 .  FIG. 5  on the other hand shows a side cross sectional view of a plane that is perpendicular to the air bearing surface at an outer region within the side shield  308  as seen from line  5 - 5  of  FIG. 3 . 
     With reference now to  FIG. 4  it can be seen that the free layer  316  extends to a first stripe height SH1, whereas the pinned layer structure  314  extends beyond this first stripe height to a second stripe height SH2. The space behind the free layer structure  316  can be filled with a non-magnetic, electrically insulating fill layer such as alumina  402 . The first stripe height SH1 is a functional stripe height for purposes of sensor performance and resolution, however, extending the pinned layer beyond the first stripe height SH1 to the second stripe height SH2 improves pinning strength, thereby making the magnetic pinning of the magnetic pinned layer structure robust even at very small sensor sized. 
     With reference now to  FIG. 5 , which shows a side, cross sectional view of the sensor  300  in an outer region at the location of the side shield  308 , it can be seen that the pinned layer structure  314  (as well as the AFM  326 ) and the magnetic side shield  308  taper in such a manner that the recessed portion of the pinned layer structure  314  becomes thinner as it moves toward the air bearing surface (ABS), whereas the magnetic side shield  308 , becomes thinner as it moves away from the air bearing surface (ABS). The pinned layer structure  314  and AFM  326 , therefore, have a tapered surface  502  that defines an angle  1504  relative to the plane of the sensor layers (e.g. parallel to the plane of the layers  320 ,  322 ,  324  or horizontal in  FIG. 5 ). The angle  1504  is preferably 15-60 degrees and more preferably about 25 degrees. Another way to describe the tapered surface  502  is that it defines an angle of 75 to 30 degrees or more preferably about 65 degrees relative to the air bearing surface ABS. 
     The shape and configuration of the free layer and pinned layer structure can be understood more clearly with reference to  FIG. 6 , which shows a perspective view of the sensor with only the pinned layer  314 , free layer  316  and barrier layer  318  shown, the shields  304 ,  306  and side shields  308  having been removed. In  FIG. 6  it can be seen that the pinned layer structure  314  has laterally extending wing portions  602 ,  604  at a region removed from the air bearing surface ABS. These wing portions are tapered as described above, such that they taper to a point, terminating at a location that is recessed from the air bearing surface. That is, the wing portions do not extend to the air bearing surface (ABS), or alternatively can terminate to a point at the air bearing surface. 
       FIGS. 6-19  show a magnetic sensor in various intermediate stages of manufacture in order to illustrate a method of manufacturing a magnetic sensor. With particular reference to  FIG. 7 , a bottom shield  304  is formed, and a series of sensor layers  302  are deposited over the shield  304 . The sensor layers can include: a seed layer  328 ; an AFM layer  326 ; a pinned layer structure  314  with layers  320 ,  322 ,  324  as described above; a spacer/barrier layer  318 ; a free layer  316 ; and a capping layer  330 . A stripe height defining mask  702  is then formed over the sensor layers  302 . The stripe height defining mask has a back edge  704  that is located a desired distance from an air bearing surface plane (ABS) in order to define a stripe height of the free layer  316 . The mask  702  can include a photoresist layer that has been photolithographically patterned, and can also include other layers as well, such as one or more hard mask layers an image transfer layer a bottom anti-reflective coating, etc. 
     Then, with reference to  FIG. 8  and ion milling is performed to remove portions of the free layer  316  and capping layer  330  that are not protected by the mask  702 . The ion milling can be terminated when the barrier/spacer layer  318  has been reached or at some point within the barrier/spacer layer  318 . Then, with reference to  FIG. 9  a non-magnetic, electrically insulating fill layer such as alumina  402  is deposited to about the thickness of the free layer  316  and capping layer  330 . A mask liftoff process and chemical mechanical polishing can then be performed, leaving a structure as shown in  FIG. 10 . 
     With reference now to  FIG. 11 , a second mask structure  1102  is formed over the sensor layers  302 . This mask  1102  is configured to define a track-width of the sensor as well as defining a pinned layer/side shield layer taper. The configuration of the mask  1102  can be seen more clearly with reference to  FIG. 12  which shows a top down view as seen from line  12 - 12  of  FIG. 11 . With reference to both  FIGS. 11 and 12 , it can be seen that the mask  1102  has a centrally located track-width defining portion  1102   a  that extends over the free layer  316  and capping layer  330 , and has a pinned layer taper defining portion  1102   b  formed as outward extending wings at a location recessed from the ABS plane. The transition between portions  1102   a  and  1102   b  is indicated by a dashed line  1104  in  FIG. 11 . 
       FIG. 13  shows a cross sectional view parallel with the ABS and shows how the track-width defining portion of the mask  1102   a  has a width that is configured to define a track-width of the sensor as seen from line  13 - 13  of  FIG. 12 . With the mask  1102  formed as described above, an ion milling is performed to remove material not protected by the mask  1102 . The ion milling is preferably performed at an angle relative to normal and in a sweeping manner.  FIG. 14  shows how this sweeping, angled ion milling forms the sensor with at track width in the location of where the free layer  316  remains. On the other hand,  FIG. 15  shows a cross sectional view of a plane perpendicular with the air bearing surface at the location of line  15 - 15  of  FIG. 12 . In  FIG. 15  it can be seen that the angled, sweeping ion milling forms a tapered surface  1502  as a result of shadowing from the mask  1102   b.    
     The surface  1502  defines an angle  1504  relative to the as deposited plane of the layers  326 ,  320 ,  324 ,  322 ,  318 , or relative to horizontal. The angle  1504  of the surface  1502  can be controlled by adjusting the height of the mask  1102   b  and by adjusting the angle at which the ion milling is performed and adjusting the sweep angle of the ion milling. The masking and ion milling process is preferably performed in such a manner as to result in the surface  1502  having an angle  1504  of 15-60 degrees, and more preferably about 25 degrees. In order to achieve this angle  1504 , the ion milling is preferably performed at an angle of 5-60 degrees relative to normal, or more preferably about 30 degrees relative to normal. 
     With reference now to  FIG. 16 , a thin, insulation layer  312  is deposited followed by a magnetic shield material  308 . The insulation layer can be a non-magnetic, electrically insulating material such as alumina deposited by a conformal deposition process such as chemical vapor deposition or atomic layer deposition. The magnetic shield material can be a magnetic material having a relatively low coercivity, such as NiFe.  FIG. 17  shows a side cross sectional view at the location of  FIG. 15  after deposition of the insulation and magnetic shield material  312 ,  308 . A mask liftoff process and chemical mechanical polishing can then be performed, leaving a structure as shown in  FIGS. 18 and 19 . After formation of the sensor as outlined above, an upper magnetic shield  306  can be formed by a process such as electroplating, leaving a sensor  300  as described above with reference to  FIGS. 3 ,  4  and  5 . 
     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.