Abstract:
A write element for perpendicular recording in a data storage system is fabricated to maintain the thickness of a side shield at both edges of a pole P 3 , and to form the pole P 3  in a trapezoidal shape. Forming a side shield around the pole P 3  removes stray fields, creating a quiet, noise-free write element and preventing side erasure. The fabrication method utilizes a magnetic buffer layer to protect a shield gap during trim of the pole P 3 , and thus to provide the shield gap with a uniform thickness. The magnetic buffer layer also protects the shield gap and pole P 3  when the top hard mask is removed. Consequently, the write field is made uniform across the track width. The fabrication method uses a metal in the shield gap to improve the pole geometry after pole trim and to provide a uniform edge to the pole P 3.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to data storage systems such as disk drives, and it particularly relates to a recording element for use in such data storage systems. More specifically, the present invention relates to a method of fabricating write element comprising a shield, a shield gap, and a pole P 3 , for perpendicular recording in a data storage system. 
   BACKGROUND OF THE INVENTION 
   Conventional magnetic storage systems comprise a thin film magnetic element with an inductive recording element mounted on a slider. The magnetic element is coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning magnetic disk. In operation, a lift force is generated by the aerodynamic interaction between the magnetic element and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk. 
   An exemplary recording element comprises a thin film write element with a bottom pole P 1  and a top pole P 2 . The pole P 1  and pole P 2  have a pole tip height dimension commonly referenced as “throat height”. In a finished write element, the throat height is measured between an air bearing surface (ABS) and a zero throat level where the pole tip of the write element transitions to a back region. The air-bearing surface is formed by lapping and polishing the pole tip. A pole tip region is defined as the region between the ABS and the zero throat level. The pole P 1  and pole P 2  each have a pole tip located in the pole tip region. The tip regions of the pole P 1  and pole P 2  are separated by a magnetic recording gap, which is a thin layer of insulation material. 
   The current trend in data storage systems strives for higher storage densities. Recording densities are increasing to meet the requirements to store large amounts of information. At higher recording densities (i.e., above 100 Gb/in 2 ), perpendicular recording elements are utilized. Perpendicular recording elements can support higher recording densities because of a smaller demagnetization field in the recorded bits. 
   One typical perpendicular recording element utilizes three poles, P 1 , P 2 , and P 3 . Magnetic flux emanates from the pole P 3  into the recording media and returns to the poles. Writing occurs at the pole P 3 . The recording resolution depends on the size and shape of the pole P 3  rather than the gap length. In the perpendicular recording element, the gap between pole P 1  and pole P 3  is larger than allowed by longitudinal recording element designs, eliminating the need for a pole P 1  pedestal. 
   As recording density increases, track distance decreases. For small track distances, a pole P 3  may introduce adjacent track erasing if the pole P 3  tip is shaped as a square. What is needed is a single pole element formed in a trapezoidal shape to eliminate the adjacent track erasing. In addition, the linear recording density can be further improved when a shield is added adjacent to the pole P 3 . The shielded perpendicular writer also provides a higher write-field gradient and reduced transition region in the recorded bits, improving linear density and reducing media noise. 
   The shielded perpendicular recording element presents distinct advantages for high-density recording. However, the fabrication of the shield and shield gap required by pole P 3  may damage pole P 3 , or may create a shield gap at that is thinner at both edges of pole P 3 . Field leakage occurs through the thin gap region, resulting in reduced recording element efficiency. 
   What is therefore needed is a method for fabricating a shield and shield gap for the perpendicular recording element that maintains a uniform thickness of the shield gap without damaging the pole P 3  during fabrication. The need for such a fabrication method and resulting write element has heretofore remained unsatisfied. 
   SUMMARY OF THE INVENTION 
   The present invention satisfies this need, and presents a fabrication method (referred to herein as “the method” or “the present method”) for fabricating write element for perpendicular recording in a data storage system that maintains the uniformity of the thickness of the side shield at both edges of pole P 3 , and that further allows pole P 3  to be formed in a desired shape, preferably a trapezoidal shape. Forming the side shield around pole P 3  removes the stray field from around pole P 3 , creating a quiet, noise-free write element and preventing or significantly minimizing side erasure. 
   The present method utilizes a magnetic buffer layer to protect the shield gap during trim of pole P 3 , to provide a shield gap with a uniform thickness. The magnetic buffer layer also protects the shield gap and P 3  pole when a top hard mask is removed. Consequently, the write field is uniform across the track width. 
   A hard mask placed above the shield gap and a magnetic buffer layer allows the formation of the trapezoidal shape of pole P 3 . The present method uses a metallic material in the shield gap to improve the pole geometry after pole trim and to provide a uniform edge to pole P 3 . This distinctive step distinguishes over the use of a non-metallic material, such as alumina, as a shield gap, which results in a non-uniform edge to pole P 3  because of the smaller mill rate between the pole materials and gap materials. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary perspective view of a data storage system in which a write element of the present invention can be used; 
       FIG. 2  is a perspective view of a head gimbal assembly comprised of a suspension, and a slider to which the write element of the present invention is secured, for use in a head stack assembly; 
       FIG. 3  is a cross-section view of a thin film recording element forming part of the recording element of  FIGS. 1 and 2 , and made according to the present invention; 
       FIG. 4  is an ABS view of the recording head in which the write element of the present invention may be used; 
       FIG. 5  is comprised of  FIGS. 5A and 5B  and represents a process flow chart illustrating a method of fabrication of the write element of  FIGS. 1 ,  2 ,  3 , and  4 ; 
       FIG. 6  is a side cross-sectional view illustrating a fabrication step of the write element after application of a pole P 3 , a shield gap, a magnetic buffer layer, and a hard mask; 
       FIG. 7  is an ABS view illustrating a fabrication step of the write element after application of a layer of photoresist; 
       FIG. 8  is an ABS view illustrating a fabrication step of the write element after etching of the hard mask, the magnetic buffer layer, the shield gap, and the pole P 3 ; 
       FIG. 9  is an ABS view illustrating a fabrication step of the write element after moving the layer of photoresist; 
       FIG. 10  is an ABS view illustrating a fabrication step of the write element after moving the hard mask; 
       FIG. 11  is an ABS view illustrating a fabrication step of the write element after application of a layer of side gap material; 
       FIG. 12  is an ABS view illustrating a fabrication step of the write element after moving a portion of the side gap material to form side gaps on either side of the pole P 3 ; 
       FIG. 13  is a cross-section view illustrating a fabrication step of the write element as shown in  FIG. 12 ; 
       FIG. 14  is an ABS view illustrating a fabrication step of the write element after application of a third shield layer; 
       FIG. 15  is a cross-section view illustrating a fabrication step of the write element after a portion of the third shield layer and the magnetic buffer layer have been removed; and 
       FIG. 16  is a cross-section view illustrating a fabrication step of the write element after a substrate layer has been added behind the third shield layer and the magnetic buffer layer. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a hard disk drive  100  in which an embodiment of the present invention may be used. An enclosure of the hard disk drive  100  comprises a base  104  and a cover  102 . The enclosure is suitably sealed to provide a relatively contaminant-free interior for a head disk assembly (HDA) portion of the hard disk drive  100 . The hard disk drive  100  also comprises a printed circuit board assembly (not shown) that is attached to base  104  and further comprises the circuitry for processing signals and controlling operations of the hard disk drive  100 . 
   Within its interior, the hard disk drive  100  comprises a magnetic disk  126  having a recording surface typically on each side of the disk, and comprises a magnetic head or slider which may suitably be a magneto-resistive (“MR”) head such as a GMR head having an MR element for reading stored data on a recording surface and an inductive element for writing data on the recording surface. The exemplary embodiment of the hard disk drive  100  illustrated in  FIG. 1  comprises three disks  126 ,  128 , and  130  providing six recording surfaces, and further comprises six magnetic heads. 
   Disk spacers such as spacers  134  and  136  are positioned between disks  126 .  128 ,  130 . A disk clamp  132  is used to clamp disks  125 ,  138 ,  130  on a spindle motor  124 . In alternative embodiments, the hard disk drive  100  may comprise a different number of disks, such as one disk, two disks, and four disks and a corresponding number of magnetic heads for each embodiment. The hard disk drive  100  further comprises a magnetic latch  10  and a rotary actuator arrangement. The rotary actuator arrangement generally comprises a head stack assembly  1112  and voice coil magnet (“VCM”) assemblies  106  and  108 . The spindle motor  124  causes each disk  126 . 128 ,  130  positioned on the spindle motor  124  to spin, preferably at a constant angular velocity. 
   A rotary actuator arrangement provides for positioning a magnetic head over a selected area of a recording surface of a disk. Such a rotary actuator arrangement comprises a permanent-magnet arrangement generally including VCM assemblies  106 ,  108 , and head stack assembly  112  coupled to base  104 . A pivot bearing cartridge is installed in a bore of the head stack assembly  112  and comprises a stationary shaft secured to the enclosure to define an axis of rotation for the rotary actuator arrangement. The head stack assembly  112  comprises a flex circuit assembly and a flex bracket  122 . The head stack assembly  112  further comprises an actuator body  114 , a plurality of actuator arms  116  cantilevered from the actuator body  114 , a plurality of head gimbal assemblies  118  each respectively attached to an actuator arm  116 , and a coil portion  120 . The number of actuator arms  116  and head gimbal assemblies  118  is generally a function of the number of disks in a given hard disk drive  100 . 
   The head gimbal assembly (HGA)  118  is secured to each of the actuator arms  116 . As illustrated in  FIG. 2 , HGA  118  is comprised of a suspension  205  and a read/write head  210 . The suspension  205  comprises a resilient load beam  215  and a flexure  220  to which the head  210  is secured. 
   The head  210  is formed of a slider  225  secured to the free end of the load beam  215  by means of the flexure  220  and a recording element  230  supported by the slider  225 . In the example illustrated in  FIG. 2 , the recording element  230  is secured to the trailing edge  235  of the slider  225 . The slider  225  can be any conventional or available slider. 
     FIG. 3  is a cross-sectional view of the recording element  230 . The recording element  230  integrates a write element  302  and a read element  304 . The read element  304  is formed of a first shield layer (shield  1 )  306  that is formed on a substrate layer  308 . The substrate layer  308  is made of alumina (Al 2 O 3 ). 
   The first shield layer  306  is made of a material that is both magnetically and electrically conductive. As an example, the first shield layer  306  can have a nickel iron (NiFe) composition, such as Permalloy, or a ferromagnetic composition with high permeability. The thickness of the first shield layer  306  can be in the range of approximately 0.5 micron to approximately 20 microns. 
   An insulation layer  310  is formed over substantially the entire surface of the first shield layer  306  to define a non-magnetic, transducing read gap  312 . The insulation layer  310  can be made of any suitable material, for example alumina (Al 2 O 3 ), aluminum oxide, or silicon nitride. 
   The read element  304  also comprises a read sensor  314  ( FIG. 4 ) formed within the insulation layer  310 . The read sensor  314  can be any suitable sensor, including but not limited to a magnetoresistive (MR) element, a giant magnetoresistive (GMR) element, a spin valve, a current-in-the-plane mode (CIP) sensor, a tunneling magnetoresistive (TMR) element, or a current-perpendicular-to-the-plane mode (CPP) sensor. 
   The read element  304  further comprises a second shield layer (shield  2 )  316  that is made of an electrically and magnetically conductive material that may be similar or equivalent to that of the first shield layer  306 . The second shield layer  316  is formed over substantially the entire surface of the insulating layer  310  and has a thickness that can be substantially similar or equivalent to that of the first shield layer  306 . 
   A piggyback gap  318  is formed on the second shield layer  316  to separate the second shield S 2  and the first pole P 1 . The piggyback gap  318  may be made of any suitable non-magnetic material such as alumina. 
   The write element  302  is comprised of a first pole or pole layer (P 1 )  320  that extends, for example, integrally from the piggyback gap  318 . The first pole P 1  is made of a magnetically conductive material. 
   A first coil layer  322  comprises conductive coil elements (or conductors) represented by conductors  324 ,  326 ,  328 . The first coil layer  322  also forms part of the write element  302 , and is formed within an insulating layer (I 2 )  330 . The first coil layer  322  may comprise a single layer of, for example, 1 to 30 turns, though a different number of turns can alternatively be selected depending on the application or design. The insulating layer  330  is covered by a substrate layer  332  comprised of, for example. 
   A second pole or pole layer (P 2 )  334  is made of a magnetically conductive material, and may be, for example, similar to that of the first shield layer  306  and the first pole P 1 . The second pole layer  334  is recessed from the air-bearing surface by a block  336  that is made, for example, of non-magnetic material such as alumina. Block  336  and substrate layer  332  may be formed of the same material. The thickness of the second pole layer  334  can be substantially the same as, or similar to, that of the first shield layer  306 . 
   A third pole or pole layer (P 3 )  338  is made of a hard magnetic material with a high saturation magnetic moment Bs. In a preferred embodiment, the saturation magnetic moment Bs is equal to or greater than 2.0 teslas. The third pole layer  338  can be made, for example, of CoFeN, CoFeNi, CoFe. 
   A shield gap  340  can be made, for example, of alumina, NiCr, Ta. A magnetic buffer layer  342  is applied to the shield gap  340 . A third shield layer (shield  3 )  344  is formed on the magnetic buffer layer  342 . A substrate layer  346  that is made, for example, of alumina, is formed on the third pole layer  338  to the same level as that of the third shield layer  344 . 
   A second coil layer  348  comprises conductive coil elements (or conductors) represented by conductors  350 ,  352 ,  354 . The second coil layer  348  forms part of the read element  304 , and is formed within an insulating layer (I 3 )  356 . The second coil layer  348  may comprise a single layer of, for example, 1 to 30 turns, though a different number of turns can alternatively be selected depending on the application or design. The insulating layer  356  is covered by a fourth shield layer (shield  4 ) that is also referred to as upper shield  358 . 
   Referring now to  FIG. 4 , it illustrates the air-bearing surface of the recording element  220 , and shows two side gaps  405 ,  410 , one on each side of the third pole  338 . Side gaps  405 ,  410  are made for example of SiN, SiO 2 , or Si. 
   A method  500  of fabricating the write element  302  is illustrated by the process flow chart of  FIG. 5  ( FIGS. 5A ,  5 B), with further reference to  FIGS. 6 through 16 . As illustrated by the cross-sectional view of  FIG. 6 , the third pole layer P 3   338  is deposited on the second pole layer P 2   334  and block  336 , at step  505 . 
   Second pole P 2   334  is recessed from the ABS, and is formed behind block  336 . Third pole P 3   338  is made of a hard magnetic material such as, for example, CoFeN, CoFeNi, CoFe, or any high magnetic moment material. The shield gap  340  that is made for example of NiCr, Al 2 O 3 , Ta, NiNb, and NiFeCr, or any other non-magnetic metallic material or dielectric material, is deposited on the third pole P 3   338 . 
   A magnetic buffer layer  342  is deposited on the shield gap  340  and a hard mask  605  is deposited on top of the magnetic buffer layer  342 . The magnetic buffer layer  342  may be comprised of, for example, NiFe, CoFe, CoFeN, and CoNiFe, or any other soft magnetic material. The hard mask  605  may be comprised of, for example, alumina or diamond-like carbon (DLC). In an embodiment, P 3   338 , the shield gap  340 , and the magnetic buffer layer  342  are deposited by sputtering or ion beam deposition. The hard mask  605  may be deposited by sputtering, reactive sputtering, ion beam deposition, or atomic layer deposition. The hard mask  605  will be removed later, with a portion of the magnetic buffer layer  342  being left to form part of the third shield layer  344 . 
   As illustrated in the ABS view of  FIG. 7 , photoresist  705  is deposited and patterned using, for example, photolithography to form a mask for definition of the third pole P 3   338  (step  510 ). 
   At step  515  of  FIG. 5A , the shape of the third pole P 3   338  is defined using, for example, ion beam etch or reactive ion beam etch ( FIG. 8 ). The hard mask  605  is used to form an inclination angle  805  between a side  841  of the third pole P 3   338  relative to a reference plane  839  (which is shown in this illustration in the horizontal plane). 
   The inclination angle  805  preferably varies between approximately 75 degrees and 90 degrees, and contributes to the creation of the generally trapezoidal shape of the third pole P 3   338 . Shaping the third pole P 3   338  in a generally trapezoidal shape prevents, or significantly minimizes erasure of, or writing on side tracks when recording on the media  20 . In one embodiment, the trapezoidal shape is such that the wider top  817  of the trapezoid is located in proximity to the shield gap  340 , while the narrower base  822  is located in proximity to the block  336 . 
   With further reference to  FIG. 9 , the photoresist  705  is removed at step  520 . At step  520 , the hard mask  605  is also removed using, for example, reactive ion etch or ion beam etch ( FIG. 10 ). In one embodiment, the hard mask  605  is removed after side gaps  405 ,  410  are defined. 
   As illustrated in  FIG. 1 , a side gap material  1105  is deposited at step  525 . The side gap material  1105  may be comprised of, for example, Si 3 N 4 , SiO 2 , or Si. In one embodiment, the side gap material  1105  is deposited using PECVD. In another embodiment, the side gap material  1105  is deposited using sputtering, ion beam deposition, or inductively coupled plasma (ICP) chemical deposition. The side gap material  1105  uniformly covers the magnetic buffer layer  344 , the shield gap  340 , P 3   338 , block  336 , and the recessed second pole P 2   334  ( FIG. 4 ). 
   The side gaps  405 ,  410  are defined at step  530  ( FIG. 12 ) using, for example, an ion mill, reactive ion beam etch, or ICP etch. Since the etch rate is different depending on the incident angle of ions, the etch rate on top of the third pole P 3   338  is faster than the side of the third pole P 3   338 . Consequently, a certain amount of side gap material remains after the side gap material  1105  is removed from the magnetic buffer layer  342 , to form the side gaps  405 ,  410 . The thickness and shape of the side gaps  405 ,  410  can be controlled by the varying the etch process conditions. 
   A cross-sectional view of the writing element  302  formed thus far is illustrated in  FIG. 13 . The second pole P 2   334  is recessed from the ABS by block  336 . At this stage, the third pole P 3   338  has been deposited on P 2   334  and block  336 . The shield gap  340  is deposited on the third pole P 3 . The magnetic buffer layer  342  is deposited on the shield gap  340 . 
   The third shield layer  344  is fabricated at step  535  using seed deposition, photolithography, and plating, as illustrated in  FIG. 14 . The third shield layer  344  covers the magnetic buffer layer  342 , the side gaps  405 ,  420 , the block  336 , and the second pole P 2   334  ( FIG. 3 ). The third shield layer  344  may be comprised, for example, of NiFe. 
   In one embodiment, the third shield layer  344  is comprised of the same material as the magnetic buffer layer  342 . A seed that is made for example of NiFe, is deposited on the wafer comprising the third pole P 3   338  of the writing element  302 . 
   The third shield layer  344  is defined using photoresist and lithography, and then plated. Plating the third shield layer  344  also precisely defines a throat  345  and the corresponding throat height. The fabrication control of step  535  is important because precision in the throat height is required. Though in a preferred embodiment the shield gap  340  is shown in  FIG. 3  to extend to the back of the third shield layer  344 , the shield gap  340  could alternatively extend to the back as shown in  FIG. 15 . 
   At step  540  ( FIG. 5B ), all unnecessary portions of the third shield layer  344  and magnetic buffer layer  342  are removed as illustrated in  FIG. 15 . As illustrated in  FIG. 16 , substrate layer  346  is deposited on the shield gap  340 , the side gaps  405 ,  410 , the second pole P 2   334 , and a portion of block  336  (step  545 ). The third shield layer  344  and the substrate layer  346  are then planarized to the same level. 
   The recording element  230  is then completed as shown in  FIGS. 3 and 4 , by applying the second coil layer  348  on top of substrate layer  346  (step  550 ). An on layer  13   356  that is made for example of photoresist, is applied on top of the coil layer  348  at step  555 . 
   The fourth shield layer  358  is formed on the insulation layer  13   356  and the third shield layer  344  using photolithography and plating (step  560 ). In one embodiment, the fourth shield layer  358  and the third shield layer  344  are made of the same material. In another embodiment, the fourth shield layer  358  and the third shield layer  344  are made of different materials.