Abstract:
A magnetic write head for perpendicular magnetic recording having a thin wrap-around magnetic shield. The small thickness and forming method of the thin wrap-around magnetic shield allow it to be electroplated using a thin photoresist frame mask. The thin photoresist frame mask has better critical dimension and straight wall control than a thicker mask, which allows the wrap-around magnetic shield to be constructed with much more straight and uniform back edge for shield throat height control than is possible when forming a thicker (i.e. taller) shield. The thin wrap-around magnetic shield can be stitched to a trailing return pole to avoid magnetic saturation of the wrap-around shield.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to perpendicular magnetic recording and more particularly to a magnetic write head having a thin wrap-around shield for improved wrap-around shield throat height control. 
       BACKGROUND OF THE INVENTION 
       [0002]    The heart of a computer&#39;s long term memory 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 toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed, for writing magnetic transitions to and reading magnetic transitions 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. 
         [0003]    The write head has traditionally included a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write head and the pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic flux in the pole pieces which causes a magnetic field to fringe out at a write gap at the ABS for the purpose of writing the aforementioned magnetic transitions in tracks on the moving media, such as in circular tracks on the aforementioned rotating disk. 
         [0004]    In recent read head designs, a GMR or TMR sensor has been employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, or barrier layer, sandwiched between first and second ferromagnetic layers, referred to as a pinned layer and a free layer. First and second leads are connected to the sensor for conducting a sense current therethrough. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer. 
         [0005]    The thickness of the spacer layer is chosen to be less than the mean free path of conduction electrons through the sensor. With this arrangement, a portion of the conduction electrons is scattered by the interfaces of the spacer layer with each of the pinned and free layers. When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering is minimal and when the magnetizations of the pinned and free layer are antiparallel, scattering is maximized. Changes in scattering alter the resistance of the spin valve sensor in proportion to cos Θ, where Θ is the angle between the magnetizations of the pinned and free layers. In a read mode the resistance of the spin valve sensor changes proportionally to the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals. 
         [0006]    In order to meet the ever increasing demand for improved data rate and data capacity, researchers have recently been focusing their efforts on the development of perpendicular recording systems. A traditional longitudinal recording system, such as one that incorporates the write head described above, stores data as magnetic bits oriented longitudinally along a track in the plane of the surface of the magnetic disk. This longitudinal data bit is recorded by a fringing field that forms between the pair of magnetic poles separated by a write gap. 
         [0007]    A perpendicular recording system, by contrast, records data as magnetizations oriented perpendicular to the plane of the magnetic disk. The magnetic disk has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole. 
         [0008]    Although such perpendicular magnetic recording heads have the potential to increase data density over longitudinal recording system, the ever increasing demand for increased data rate and data density requires even further improvement in write head design. For example it is desirable to have a wrap-around shield surrounding the write pole including a trailing shield (TS) separated from the write pole by a nonmagnetic top gap layer and a pair of side shields separated from the write pole by a nonmagnetic side gap layer. The trailing shield improves the down track write tiled gradient for better writing and data error rate performance. The side shields control the write width and eliminate adjacent track erasure. The dimension of wrap-around shield back edge to ABS called the shield throat height is critical and must be very well controlled for writing performances. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a magnetic write head having a thin wrap-around magnetic shield. The write head includes a write pole formed on a substrate and having a non-magnetic trailing gap layer formed at a trailing edge of the write pole and having first and second non-magnetic side gap layers formed at either side of the write pole. A thin wrap around magnetic shield is formed conformally over the write pole and trailing and side gap layers. The thin wrap-around shield has a thickness of 0.5 um from electroplating through 1.5 um height of photoresist frame, compared with prior art wrap-around shield of final 1.0 um height of trailing shied and 2.0 um height of side shields from CMP after 3.0 um height of electroplating through 4.0 um height of photoresist frame. 
         [0010]    The small thickness and forming method of the thin wrap-around trailing shield allows the trailing and side shields to advantageously be constructed using a thin electroplating photoresist frame. Such a thin electroplating photoresist frame is much less prone to having edge deformities that could lead to back edge non-uniformity of the wrap around shield. Therefore, the small thickness of the wrap-around shield and small thickness of the photoresist frame electroplating mask, allows the wrap around magnetic shield to he constructed with a very uniform straight back edge. This resulting back edge uniformity avoids some shield portion lap-though and shield throat height control problems that have been experienced with prior art wrap-around shields. 
         [0011]    In order to avoid magnetic saturation of the thin wrap around shield, a trailing magnetic return pole can be stitched to the wrap around shield. Connection of the trailing magnetic return pole with the wrap around shield can be in a region removed from the write pole (such as at either side of the write pole) or can also be made at a location above the write pole (near the trailing edge of the write pole) 
         [0012]    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 
         [0013]    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. 
           [0014]      FIG. 1  is a schematic illustration of a disk drive system in which the invention might be embodied; 
           [0015]      FIG. 2  is an ABS view of a slider, taken from line  2 - 2  of  FIG. 1 , illustrating the location of a magnetic head thereon; 
           [0016]      FIG. 3  is a cross sectional view of a magnetic head, taken from line  3 - 3  of  FIG. 2  and rotated 90 degrees counterclockwise, of a magnetic write head according to an embodiment of the present invention; 
           [0017]      FIG. 4  is an ABS view of a portion of the write head of  FIG. 3 ; and 
           [0018]      FIGS. 5-15  are views of a write head, in various intermediate stages of manufacture illustrating method for manufacturing a write head according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    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. 
         [0020]    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 . The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk  112 . 
         [0021]    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  may 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 . 
         [0022]    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 die slider. The air bearing thus counter-balances die 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. 
         [0023]    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 . 
         [0024]    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. 
         [0025]    With reference now to  FIG. 3 , the invention can be embodied in a magnetic head  302 . The magnetic head  302  includes a read head  304  and a write head  306 . The read head  304  includes a magnetoresistive sensor  308 , which can be a GMR, TMR, or some other type of sensor. The magnetoresistive sensor  308  is located between first and second magnetic shields  310 ,  312 . 
         [0026]    The write head  306  includes a magnetic write pole  314  and a magnetic return pole  316 . The write pole  314  can be formed upon a magnetic shaping layer  320 , and a magnetic back gap layer  318  magnetically connects the write pole  314  and shaping layer  320  with the return pole  316  in a region removed from the air bearing surface (ABS). A write coil  322  (shown in cross section in  FIG. 3 ) passes between the write pole and shaping layer  314 ,  320  and the return pole  316 , and may also pass above the write pole  314  and shaping layer  320 . The write coil can be a helical coil or can be one or more pancake coils. The write coil  322  can be formed upon an insulation layer  324  and can be embedded in a coil insulation layer  326  such as alumina and or hard baked photoresist. 
         [0027]    In operation, when an electrical current flows through the write coil  322 , a resulting magnetic field causes a magnetic flux to flow through the return pole  316 , back gap  318 , shaping layer  320  and write pole  314 . This causes a magnetic write field to be emitted from the tip of the write pole  314  toward a magnetic medium  332 . The write pole  314  has a cross section at the ABS that is much smaller than the cross section of the return pole  316  at the ABS. Therefore, the magnetic field emitting from the write pole  314  is sufficiently dense and strong that it can write a data bit to a magnetically hard top layer  330  of the magnetic medium  332 . The magnetic flux then flows through a magnetically softer under-layer  334 , and returns back to the return pole  316 , where it is sufficiently spread out and week that if does not erase the data bit recorded by the write head  314 . 
         [0028]    In order to increase write field gradient and eliminate adjacent track erasure, a wrap-around magnetic shield  338  is provided. The wrap-around magnetic shield  338  is separated from the write pole by a non-magnetic write gap  339 , and may be connected with the shaping layer  320  and/or back gap  318  by a trailing return pole  340 . The trailing shield  338  attracts the magnetic field from the write pole  314 , which slightly cants the angle of the magnetic field emitting from the write pole. This canting of the write field increases the speed with which write field polarity can be switched on the magnetic medium by increasing the field gradient. The return pole  340  can be stitched to a magnetic trailing return pole connector  342  that can magnetically connect the trailing return pole  340  with the back portion of the write head  302 . 
         [0029]    With reference to  FIG. 4 , the connection of the wrap-around shield  338  with the trailing return pole  340  can be more clearly understood.  FIG. 4  shows an enlarged view of the write pole  314  as viewed from the air bearing surface. As can be seen, the wrap-around shield  338  conforms to the write pole  314 , and is formed very thin as compared with prior art wrap-around shields. The write pole has a leading edge  408  and a trailing edge  410  the distance between which defines a write pole height. The thin wrap-around magnetic shield  338  has a thickness T measured parallel with the air bearing surface (ABS) that is less than the write pole height, and which is preferably 0.2-0.8 um or about 0.5 um. 
         [0030]    The wrap-around magnetic shield  338  is separated from the sides of the write pole by first and second non-magnetic side gap layers  402 ,  404  that can be constructed of alumina or some other material. The wrap-around shield  338  is also partially surrounded by a non-magnetic fill layer  406  that also can be alumina. The trailing return pole  340  is stitched to the thin wrap-around shield  338  in a region slightly removed front the write pole  314 . 
         [0031]    As can be seen, in the embodiment shown in  FIG. 4 , the fill layer  406  extends over the wrap-around shield in a region above the write pole  314 , thereby separating the trailing return pole  340  from the trailing shield  338  in the region above the write pole  314 . However, the write head could be constructed so that the trailing return pole  340  contacts the thin wrap-around shield  338  in this region above the write pole  314 . Such a construction will be described below with regard to a method of manufacturing an alternate possible embodiment of the invention. 
         [0032]      FIGS. 5-12  illustrate a method for manufacturing a write head such as that described above. With particular reference to  FIG. 5 , a substrate  502  is provided. The substrate  502  can be the alumina fill layer  326  and may include a portion of the shaping layer described above with reference to  FIG. 3 . A magnetic write pole material  504  is deposited over the substrate. This magnetic write pole material  504  can be a lamination of magnetic layers separated by thin non-magnetic layers. A hard mask layer  506  such as a thin alumina layer is deposited over the magnet write pole material  504 . A mask structure  508  is formed over the hard mask layer  506 . The mask structure  508  includes a photoresist layer that has been patterned to define a write pole structure, and may include other layers such as a DURMIDE® image transfer layer, second hard mask layer, etc. 
         [0033]    An ion milling is then performed to remove portions of the magnetic write pole material  504  that are not protected by the mask layer  508 . This ion milling can be performed at one or more angles to construct a trapezoidal write pole  504  as shown in  FIG. 6 . The mask; layer  508  ( FIG. 5 ) may be consumed by the ion milling process. The remaining hard mask layer  506  can be left intact to provide a trailing gap layer, as will be seen. 
         [0034]    With reference now to  FIG. 7 , a non-magnetic side gap material (preferably alumina)  702  is deposited. The non-magnetic side gap material  702  is preferably deposited by a conformal deposition method such as atomic layer deposition (ALD) or chemical vapor deposition (CVD). A reactive ion milling (or some other suitable process) is then performed to preferentially remove horizontally disposed portions of the non-magnetic side gap layer, resulting in non-magnetic side walls  702  as shown in  FIG. 8 . 
         [0035]    With reference now to  FIG. 9 , a photoresist frame  904  is constructed and a thin, conformal wrap-around magnetic shield  902  is electroplated around the write pole  314 . The wrap-around trailing shield, is electroplated thin as compared with prior art trailing shield. Prior art wrap-around shields were plated to a thickness far greater than thin wrap-around shields. This however required the use of a very thick electroplating photoresist frame. However such thick masks suffer from poor side wall definition on topography, resulting in intolerable variations in the back edge of the wrap around shield. By making the wrap around shield  902  thin, the electroplating photoresist frame mask (not shown) used to define the shape of the wrap-around shield can be formed with excellent back wall conformity. To this end, the wrap-around magnetic shield  902  preferably has a thickness T of 0.2-0.8 um (or about 0.5 um), and can be electroplated through 1.5 um height of photoresist frame, as compared with prior art wrap-around shields that were greater than 1.0 um in trailing direction and with 2.0 um side shield portions before CMP, requiring a 3.0 um after electroplating through a 4.0 um height of photoresist frame. 
         [0036]    With reference now to  FIG. 10 , a fill layer  1002  is deposited. The fill layer  1002  is preferably alumina, but could be some other material. A chemical mechanical polishing process can be performed to form the fill layer  1002  with a planar surface  1004  as shown in  FIG. 10 . 
         [0037]    Then, with reference to  FIG. 11 , a mask structure  1102  is formed over the fill layer  1002 . The mask structure  1102  has openings at areas at either side of the write pole  504 . A material removal process such as reactive ion milling process (RIM) is then performed to remove material not protected by the mask structure  1102 , thereby forming trenches in the fill layer  1002 . The RIM is performed sufficiently to expose the underlying wrap-around magnetic shield  902 . The mask layer  1102  is removed after trench formed. 
         [0038]    Then, with reference to  FIG. 12 , a magnetic trailing return pole is electroplated, so that it extends into the trenches formed in the fill layer  1002 , so that the trailing magnetic return pole structure  1202  contacts the wrap-around shield  902  in these trenches. 
         [0039]    With reference to  FIGS. 13-15 , a method for manufacturing a write head according to an alternate embodiment of the invention is described. Starting with a structure as shown in  FIG. 9  with the photoresist frame  904  lifted off, a fill layer  1302  such as alumina is deposited. A material removal process such as chemical mechanical polishing (CMP) is performed sufficiently to expose the wrap-around magnetic shield  902  in a region over the write pole  504 . This results in a planar surface across the fill layer  1302 , and wrap-around trailing magnetic shield  902 . With reference to  FIG. 14 , a mask structure  1402  is formed having openings at either side of the write pole  504 , and a material removal process such as reactive ion milling (RIM) is performed to remove portions of the fill layer that are not protected by the mask  1402 . As with the above described embodiment, the RIM is performed sufficiently to expose the underlying wrap around shield  902  within the trench. The mask layer  1402  is removed after trench formed. 
         [0040]    Then, with reference to  FIG. 15 , a trailing magnetic return pole structure  1502  is formed by electroplating. The trailing magnetic return pole structure  1502  is formed so that it extends into the openings in the fill layer  1302  to contact the wrap-around shield  902  within these openings. However, with this embodiment, as can be seen, the trailing return pole structure  1502  also contacts the wrap-around shield  902  the region above the write pole  504 , where the wrap-around shield  902  is exposed through the fill layer  1302 . This embodiment provides improved protection against magnetic saturation of the wrap-around shield  902 . However, because chemical mechanical polishing is a difficult procedure to control with great accuracy, this method also presents greater manufacturing challenges over the previously described embodiment. Because the wrap around trailing shield  902  is so thin, if the chemical mechanical polishing process proceeds too far the portion of the wrap around shield  902  extending over the write pole could be removed completely. Therefore, careful control of the chemical mechanical polishing process must be exercised. 
         [0041]    While various embodiments have been described, 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.