Abstract:
A method for manufacturing a write pole for a perpendicular magnetic write head. The method employs a damascene process to construct the write pole with a very accurately controlled track width. The method includes depositing a layer of material that can be readily removed by reactive ion etching. This material can be referred to as a RIEable material. A mask is formed over the RIEable material and a reactive ion etching is performed to form a tapered trench in the RIEAble material. A CMP stop layer can the be deposited, and a write pole plated into the trench. A CMP can then be performed to define the trailing edge of the write pole. Another masking, etching and plating step can be performed to form a trailing, wrap-around magnetic shield.

Description:
FIELD OF THE INVENTION 
     The present invention relates to perpendicular magnetic recording and more particularly to damascene method for manufacturing a write pole and wrap-around trailing shield of a write head. 
     BACKGROUND OF THE INVENTION 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method for manufacturing a magnetic write head. The method includes providing a substrate and then depositing a RIEable material on the substrate. A first mask structure is formed over the RIEable material, the first mask structure having an opening configured to define a write pole. Then, a reactive ion etching is performed to remove portions of the RIEable material that are not protected by the first mask structure. A CMP stop layer is then deposited, and a first magnetic material is deposited to form the write pole material. A chemical mechanical polishing process is then performed to define the trailing edge of the write pole. A second mask structure is then performed to cover an area over the trench, leaving side areas uncovered. Then, a material removal process such as a reactive ion milling (RIM) or a second reactive ion etching (RIE) is performed to remove material not protected by the second mask structure, at the sides of the write pole. The second mask structure can then be removed and a second magnetic material can be deposited to form a trailing, wrap-around magnetic shield. 
     The write pole width (track width) and write pole bevel angle can be controlled by the photolithographic process used to define the first mask structure or by the manner in which the reactive ion etching process is performed. 
     The write pole ion milling process can advantageously be eliminated, thereby avoiding damage to the write pole. Also, a method according to the present invention allows for better control of critical dimensions, such as track width. 
     The write pole can be deposited by electroplating, but can also be deposited by another method such as sputter deposition. The write pole material can be, for example, CoFe, CoFeB, CoNiFe or NiFe. 
     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, taken from line  2 - 2  of  FIG. 1 , illustrating the location of a magnetic head thereon; 
         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; 
         FIG. 4  is an enlarged, air bearing surface view of a portion of a magnetic write head, as seen from line  4 - 4  of  FIG. 3 ; 
         FIGS. 5-14  are illustrations of a portion of a write head in various intermediate stages of manufacture, illustrating a method of manufacturing a write head according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     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 . 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  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 . 
     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. 
     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 . 
     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. 
     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 . A magnetic pedestal  336  can be provided at the ABS, and attached to the leading return pole  316  to act as a magnetic shield to prevent stray field from the write coil  322  from inadvertently reaching the magnetic media  332 . 
     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. The non-magnetic trailing gap layer  339  can be constructed of a material such as Rh, Ir or Ta. 
       FIG. 4 , shows an enlarged, air bearing surface view of a portion of the head  302  as taken from line  4 - 4  of  FIG. 3 . As can be seen, the write pole  314  has a trapezoidal cross section as viewed from the air bearing surface. Also, the shield  338  wraps around the sides of the write pole  314  to form a wrap-around shield. Therefore, the shield  338  has a trailing portion  404 , and first and second side shield portions  406 ,  408 . The trailing portion  404  is separated from the trailing edge  410  of the write pole  314  by a non-magnetic trailing gap layer  412 , that preferably extends beyond the write pole as shown. The reason for this will become clearer below where a method for manufacturing the write head will be described. 
     The side portions  406 ,  408  of the write shield  334  are separated from the sides of the write pole  314  by a non-magnetic gap SG that can include several layers such as the layer  310  described above, as well as a layer of RIEable material  414  and CMP stop layer  416  both of which will be described in greater detail below. 
     With reference now to  FIGS. 5-14 , a method for manufacturing a write head according to an embodiment of the invention will be described. With particular reference to  FIG. 5 , a layer of material that can be readily removed by reactive ion etching (RIEable layer)  504  is deposited over a substrate  502 . The substrate  502  can include the insulation layer  326 , and all or a portion of the shaping layer  320  described above with reference to  FIG. 3 . The RIEable material  504  can be a material such as alumina, SiC, SiO x , Ta or TaO x , although other materials could also be used. The mask structure  506  can be constructed of a photolithographically patterned photoresist, and may also include other layers such as one or more hard mask layers and/or an antireflective layer (not shown). The mask  506  is formed with an opening  508  that is configured to define a desired shape of a write pole. 
     With reference now to  FIG. 6 , a reactive ion etching (RIE) is performed to remove portions of the RIEable material layer  504  that are not protected by the mask  506 . This forms an opening or trench in the RIEable layer  504 . The RIE is preferably performed in such a manner that the trench in the RIEable layer is formed with tapered sidewalls  602  such that the trench is narrower at the bottom than at the top, as shown in  FIG. 6 . Therefore, the width of the trench at the top of the trench is defined by the photolithographic process used to pattern the mask  506 , while the bevel angle is controlled by the RIE. In order to form the tapered side walls  602 , RIE chemistries, such as Chlorine, Fluorine and Argon, are used. Specific RIE process conditions are also required for different type of RIEable materials. After the RIE has been performed, the mask  506  can be lifted off. By way of example, for if the RIEable layer  504  is alumina, the RIE process can be performed using a chemistry such as BC13/C12, with a chemical ratio, process pressure and top/bottom RF power chosen to provide a desired taper angle of the side wall  602 . 
     With reference now to  FIG. 7 , a layer of material  702  that can function as both a seed layer and a CMP stop layer is deposited. The layer  702  is, therefore, a material that is resistant to chemical mechanical polishing while also preferably being electrically conductive and non-magnetic. To this end, the layer  702  can be Rh, Ru, Ir or Cr, and is most preferably Rh. 
     Thereafter, with reference to  FIG. 8  a magnetic material  802  is electroplated to a sufficient thickness to completely fill the trench as shown in  FIG. 8 . This magnetic material can be, CoFe, CoFeB, CoNiFe or NiFe. In addition, as an alternative to electroplating, the magnetic material  802  can be sputter deposited, but cannot be laminated. 
     With reference now to  FIG. 9 , after the magnetic material  802  has been deposited, a chemical mechanical polishing process (CMP) is performed. The CMP is performed until the CMP stop layer  702  has been reached. As can be seen, this forms a smooth upper surface  902  on the magnetic layer  802  that is parallel with the top of the CMP stop layer  702 . This upper surface  902  will form the trailing edge  412  of the write pole  314  that was described above with reference to  FIG. 4 . 
     With reference now to  FIG. 10 , a second mask  1002  is formed. This mask has a desired width W that will affect the width of side gaps of a yet to be formed shield, as will become apparent below. After forming the mask, a material removal process such as reactive ion etching (RIE) or reactive ion milling (RIM) is performed to remove portions of the CMP stop layer  702  and RIEable layer  504  that are not protected by the second mask  1002 . This results in a structure such as that shown in  FIG. 11 . Because of the bevel angle formed by the previous RIE (described above with reference to  FIG. 6 ) a portion of the RIEable material  504  may remain as shown in  FIG. 11 . This remaining portion of the RIEable layer  504  may have a substantially triangular cross section with a vertical side wall  1102  as shown in  FIG. 11 . After this material removal process (i.e. second RIM or second RIE) has been performed, the second mask structure  1002  can be lifted off, resulting in a structure such as that shown in  FIG. 12 . 
     With reference to  FIG. 13 , a layer of material  1302  can be deposited. The material  1302  can be an electrically conductive, non-magnetic material that can function as both an electroplating seed and as a non-magnetic shield gap, as will be seen. Then, with reference to  FIG. 14 , after depositing the seed gap layer  1302 , a frame mask  1402  is constructed having an opening  1404  configured to define a trailing wrap-around magnetic shield structure. A magnetic material  1406  is then deposited into the opening. The magnetic material  1406  can be, for example, CoFe or NiFe. The magnetic material is preferably deposited by electroplating, using the seed layer  1302  as an electroplating seed. However, the magnetic material  1406  could also be deposited by a process such as sputter deposition, in which case an electrically conductive seed layer would not be needed. In that case, the layer  1302  would not need to be electrically conductive. After the magnetic material  1406  has been deposited, the frame mask  1402  can be removed. 
     As can be seen then, the above process provides a method for manufacturing a write head with a write pole and trailing, wrap-around magnetic shield, wherein the write pole has a very well controlled track width. As a result of the above described process, the magnetic material  802 , forms the write pole  314  described above with reference to  FIG. 4 , and the magnetic material  1406  forms the shield  338  also described above with reference to  FIG. 4 . In addition, the RIEable material  504  of  FIG. 14  corresponds to material layer  414  of  FIG. 4 , layer  702  of  FIG. 14  corresponds to layer  416  of  FIG. 4  and layer  1302  of  FIG. 14  corresponds to layer  412  of  FIG. 4 . 
     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.