Abstract:
A method for manufacturing a magnetic write head having a stepped trailing shield. The stepped trailing shield is formed by forming a non-magnetic bump over a write pole prior to electroplating a wrap-around magnetic shield. This bump is formed by constructing a mask having an opening configured to define the non-magnetic bump. A magnetic material is then sputter deposited. In order to decrease deposition of the magnetic material on the sides of the mask, a collimator is used to align the deposited material along a plane substantially parallel with an air bearing surface plane. This collimation of the deposited magnetic material greatly facilitates liftoff, and more importantly prevents the formation of fences which would otherwise have to be removed by a harsh, aggressive process.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to perpendicular magnetic recording and more particularly to a method for manufacturing a magnetic write head having a stepped trailing shield structure for improved magnetic performance. 
       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 increase the write field gradient for better data error rate performance. One way to do this is to place a trailing shield adjacent to the trailing edge of the write pole. However, manufacturing limitations and design limitations have limited the performance of such a trailing shields, resulting in less than optimal write field and transition curvature. Therefore, there is a strong felt need for a write head design that can provide optimal write head performance, including optimal trailing shield performance. There is also a strong felt need for a practical method for manufacturing such a write pole having such an optimal design. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a method for manufacturing a magnetic write head having a stepped trailing shield. The stepped trailing shield is formed by forming a non-magnetic bump over a write pole prior to electroplating a wrap-around magnetic shield. This bump is formed by constructing a mask having an opening configured to define the non-magnetic bump. A magnetic material is then sputter deposited. In order to decrease deposition of the non-magnetic material on the sides of the mask, a collimator is used to align the deposited material along a plane substantially parallel with an air bearing surface plane. 
         [0010]    This collimation of the deposited non-magnetic material greatly facilitates liftoff by preventing the sides of the mask structure from being completely covered by the deposited non-magnetic material. 
         [0011]    The collimation of the deposited material also advantageously prevents the formation of non-magnetic fences which would otherwise have to be removed by a harsh, aggressive process. If such fences were allowed to form, the aggressive processes used to remove them could damage the write pole and other important structures of the write head. 
         [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 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. 
         [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 it does not erase the data bit recorded by the write head  314 . 
         [0028]    In order to increase write field gradient, and therefore, increase the speed with which the write head  306  can write data, a trailing magnetic shield  338  can be provided. The trailing 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  314 . This canting of the write field increases the speed with which write-field polarity can be switched by increasing the field gradient. 
         [0029]    With reference still to  FIG. 3 , the trailing shield  338  has a step  341  formed at its back edge away from the ABS. This step  341  is formed by a non-magnetic bump  343  that is strategically located between a portion of the trailing shield  338  and the trailing gap layer  339  and write pole  314 . This step  341  improves the performance enhancing effects of the trailing shield by achieving better write field strength due to less flux shunting to the back of trailing shield  338  while also preventing magnetic saturation of the trailing shield. This step  341  and a method for manufacturing such a step will be discussed in greater detail below. 
         [0030]    With reference now to  FIGS. 4-15  a method is described for manufacturing a write head with a bump  343  and step  341 . This method allows the front edge of the bump  343  (and therefore the step  341 ) to be accurately located relative to the back edge of the shield  338 , as will be seen. With particular reference to  FIG. 4 , a substrate  404  is provided. The substrate  404  may include the insulation layer  326  and a portion of the shaping layer  320  described above with reference to  FIG. 3 . A magnetic write pole material  406  is deposited over the substrate  404 . The magnetic write pole material  406  is preferably a lamination of magnetic layers separated by thin non-magnetic layers. A mask structure  402 , constructed of a series of mask layers is deposited over the magnetic write pole material. The mask structure  402  includes a first hard mask layer  408 , which is preferably alumina, deposited over the magnetic write pole material. This hard mask layer  408  is preferably deposited to a thickness that will define a trailing gap in the finished head. A second hard mask layer  410  is deposited over the first hard mask layer. The second hard mask layer is constructed of a material that can be removed by Reactive Ion Etching (RIE) such materials being referred to herein as “RIEable” materials. An image transfer layer  411  can be deposited over the RIEable second hard mask layer  410 . The image transfer layer can be constructed of a soluble polyimide material such as DURAMIDE®. A third hard mask layer  412 , such as SiO 2 , may also be deposited over the image transfer layer  411 . A photoresist layer  414  is then deposited over the other underlying mask layers  408 - 412 , and is photolithographically patterned to define a write pole shape, which is shown in cross section in  FIG. 4 . 
         [0031]    With reference now to  FIG. 5 , a reactive ion etching (RIE) is performed to transfer the image of the photoresist mask  414  onto the underlying mask layers  408 - 412  by removing portions of the layers  408 - 412  that are not protected by the mask  414 . Then, an ion milling operation is performed to remove portions of the magnetic write pole material  406  that are not protected by the mask structure. The ion milling can be performed at one or more angles relative to normal in order to form a write pole  406  having a trapezoidal shape as shown in  FIG. 6 . Also, as shown in  FIG. 6 , a portion of the mask structure  402  will be consumed by the ion milling process, leaving the first and second hard mask layers  408 ,  410  and possibly a portion of the image transfer layer  412 . 
         [0032]    With reference now to  FIG. 7 , a layer of non-magnetic sidewall material  702  is deposited. The non-magnetic side wall material  702  is preferably alumina and is preferably deposited by a conformal deposition process such as atomic layer deposition or chemical vapor deposition. Then a material removal process is performed to preferentially remove horizontally disposed portions of the non-magnetic gap layer  702  leaving vertical, non-magnetic side gap walls  702  at either side of the write pole  406  as shown in  FIG. 8 . The material removal process can be, for example, reactive ion milling (RIM) or could include refilling with a RIEable fill layer, performing a chemical mechanical polishing process and then performing a reactive ion etching to remove the RIEable fill layer. Then, a reactive ion etching can be performed to remove the RIEable hard mask layer  410 , leaving a structure as shown in  FIG. 9 . 
         [0033]    With reference now to  FIG. 10 , a bi-layer photoresist mask  1002  is formed to cover a region where the write pole  406  is, but leaving a region open where an electrical lapping guide (ELG) will be formed. A non-magnetic metal  1004  is then deposited full film. The non-magnetic metal  1004  can be, for example, Ru, Au, Ir, Rh, etc. The bi-layer mask  1002  can then be lifted off. The bi-layer shape of the mask  1002  facilitates liftoff, when the mask has been covered with the non-magnetic metal  1004 . 
         [0034]    With reference now to  FIG. 11 , a bi-layer mask structure  1102  is formed. The bi-layer mask  1102  can include a liftoff layer  1104 , constructed of a soluble polyimide material such as polymethylglutarimide and a photolithographically patterned photoresist layer  1106 . The mask  1102  has first and second openings  1108 ,  1110 . The first opening  1108  is formed over the write pole  406  and defines a non-magnetic bump structure (e.g. non-magnetic bump  343  in  FIG. 3 ). The second opening  1110  is formed in an electrical lapping guide region, away from the write head  406  and defines an electrical lapping guide. A possible configuration of the openings  1108 ,  1110  can be seen more clearly with reference to  FIG. 12 , which shows a top down view as viewed from line  12 - 12  of  FIG. 11 . With reference again to  FIG. 11 , a non-magnetic material  1112  is deposited, such as by sputter deposition so that it covers the mask  1102  and is also deposited into the openings  1108 ,  1110 . The non-magnetic material can be alumina, TaO or some other non-magnetic material. After deposition of the non-magnetic material  1112 , the mask structure  1102  can be lifted off. The bi-layer structure of the mask  1102  facilitates this lift off. It should be pointed out that the top-down view shown in  FIG. 12 , is shown prior to deposition of the non-magnetic material in order to more clearly show the openings  1108 ,  1110  in the mask structure  1102 . The deposition of the non-magnetic material  1112  will be described in greater detail below. 
         [0035]    With reference to  FIG. 12 , it can be seen that the second opening  1110  has a back edge  1202  that is aligned relative to a front edge  1204  of the first opening  1108 . The second opening  1110  defines an electrical lapping guide, and the first opening defines a non-magnetic bump. Therefore, the electrical lapping guide defined by the second opening  1110  will be useful for accurately locating the front edge of the non-magnetic bump  1204 , as will be seen below. 
         [0036]    During deposition of the non-magnetic material  1112  it is desirable that the non-magnetic material be deposited on the sides and top of the write pole  406  trailing gap layer  408  and side gaps  702 . However, it is not desirable for the non-magnetic material to deposit excessively on the sides of the mask structure  1102 , as this will make liftoff of the mask more difficult and will result in the formation of non-magnetic fences which will have to be later removed. The present invention, as described below, deposits this magnetic material in a manner that avoids deposition of the non-magnetic material  1112  on the sides of the mask  1102 , thereby facilitating mask liftoff and avoiding fence formation. 
         [0037]    With reference now to  FIGS. 13   a  and  13   b , the non-magnetic bump material  1112  ( FIG. 11 ) is deposited in a sputter deposition tool  1302 . The sputter deposition tool  1302  can include a chamber  1304 , in which is mounted a chuck  1306 . The chuck supports a wafer  1308 , on which many thousands of write heads will be formed. A target  1310  is held within the chamber, the target  1310  being constructed of the material that is to be deposited onto the wafer. For example, the target  1310  could be aluminum, aluminum oxide, tantalum or tantalum oxide. As can be seen, the atoms  1316  being dislodged from the target are initially oriented in a random manner scattering in all directions. The collimator  1318  aligns the direction of travel of the dislodged ions  1316  so that they travel primarily along a desired plane.  FIG. 13   a  shows a view of the wafer perpendicular to the air bearing surface (ABS) as indicated by arrow head symbol ABS, and  FIG. 13   b  shows a view of the wafer with the ABS surface oriented parallel with the page as indicated by double headed arrow symbol ABS. As can be seen, then, the collimator aligns the deposited atoms  1316  so that they are substantially vertical in a plane perpendicular to the ABS, while they are free to scatter in a plane parallel with the ABS. 
         [0038]    This can be seen more clearly with reference to  FIG. 14 , which shows an enlarged perspective view of the collimator  1318  and wafer  1308 . The orientation of the desired ABS plane (i.e. the direction of orientation of the rows of sliders) is indicated by line  1402 . As can be seen, the collimator orients the dislodged ions  1316  so that they travel primarily along a plane oriented parallel with the direction of the desired ABS plane and parallel with the orientation of the rows of sliders. 
         [0039]    Referring back to  FIG. 11 , it can be seen that the sides of the write pole  406  and side gap layers  702  are oriented substantially perpendicular to the air bearing surface plane (ABS).  FIG. 11  is a cross sectional view of a portion of a wafer, with the cross section being in a plane parallel with the ABS. Therefore, the use of a collimator  1318  ( FIG. 13 ) facilitates the deposition of the non-magnetic bump material  1112  on the top and sides of the write pole  406 , side gaps  702  and trailing gap while minimizing deposition on the side edges of the mask openings  1108  such as side edge  1204 , which can be seen more clearly with reference to  FIG. 12 . 
         [0040]    After the deposition of the non-magnetic bump material  1112 , the mask structure  1102  can be lifted off. As mentioned above, the use of the collimator  1318  ( FIG. 13 ) during deposition facilitates liftoff and avoids the formation of fences which would otherwise have to be removed by an aggressive material removal process that could damage other components of the write head. 
         [0041]    With reference now to  FIG. 15 , a side cross sectional view shows the write pole  406  and trailing magnetic gap layer  408 . As can be seen, the above process forms a non-magnetic bump  1112  having a front edge  1502  defined by the mask structure  1102  ( FIG. 1204 . In order to form a trailing magnetic shield, a seed layer  1504  is deposited and an electroplating frame mask  1506  is formed. A magnetic material  1508  such as NiFe or CoFe is then deposited by electroplating to form the magnetic trailing shield  338  described above with reference to  FIG. 3 . 
         [0042]    Also, after lifting off the mask  1102  a material removal process such as ion milling can be performed to remove portions of the non-magnetic metal  1004  that are not protected by the non magnetic material  1112 , thereby using the non-magnetic material  1112  as a mask to define an electrical lapping guide (ELG) from the non-magnetic metal  1004 . 
         [0043]    After the write head been completed, the wafer  1308  ( FIG. 14 ) will be cut into rows of sliders, and a lapping operation will be performed to remove material from the direction indicated by arrow  1510  in  FIG. 15 . The amount of material removed during this lapping process determines the location of the front edge  1502  of the bump  1112  from the air bearing surface (ABS). The location of the intended air bearing surface plane is indicated by the dashed line denote “ABS”. With reference to  FIG. 12 , the electrical lapping guide  1110  can be used to accurately determine the amount by which lapping has progressed and to indicate when lapping should be terminated. As the lapping process removes material from the front edge of the electrical lapping guide  1110  the electrical resistance of the lapping guide  1110  increases. This increase in resistance, therefore, corresponds to the lapping progress. Because the lapping guide  1110  was defined and formed in the same manufacturing processes used to define the non-magnetic bump  1112 , the lapping guide  1110  provides an accurate indication of the distance between the ABS and the front edge  1502  of the bump  1112 . 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.